draft-ietf-pint-protocol-02.txt   draft-ietf-pint-protocol-03.txt 
INTERNET-DRAFT Scott Petrack, INTERNET-DRAFT Scott Petrack,
Internet Engineering Task Force Metatel Internet Engineering Task Force MetaTel
PINT Working Group Lawrence Conroy, PINT Working Group Lawrence Conroy,
Issued: 14 October 1999 Siemens Roke Manor Research Issued: 18 February 2000 Siemens Roke Manor Research
Expires: 18 August 2000
The PINT Service Protocol: The PINT Service Protocol:
Extensions to SIP and SDP for IP Access to Telephone Call Services Extensions to SIP and SDP for IP Access to Telephone Call Services
<draft-ietf-pint-protocol-02.txt> <draft-ietf-pint-protocol-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 10, line ? skipping to change at page 10, line ?
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright Notice Copyright Notice
Copyright (c) The Internet Society (1999). All rights reserved. Copyright (c) The Internet Society (1999). All rights reserved.
Abstract Abstract
This document contains the specification of the PINT Service Protocol 1.0, This document contains the specification of the PINT Service Protocol
which defines a protocol for invoking certain telephone services from an IP 1.0, which defines a protocol for invoking certain telephone services
network. These services include placing basic calls, sending and receiving from an IP network. These services include placing basic calls, sending
faxes, and receiving content over the telephone. The protocol is specified and receiving faxes, and receiving content over the telephone. The
as a set of enhancements and additions to the SIP 2.0 and SDP protocols. protocol is specified as a set of enhancements and additions to the SIP
2.0 and SDP protocols.
This document is intended for the PSTN-Internet Interworking (PINT) working This document is intended for the PSTN-Internet Interworking (PINT)
group of the Internet Engineering Task Force. Comments are solicited and working group of the Internet Engineering Task Force. Comments are
should be addressed to the working group's mailing list at solicited and should be addressed to the working group's mailing list at
pint@lists.research.bell-labs.com and/or the authors. pint@lists.research.bell-labs.com and/or the authors.
Petrack & Conroy [Page 1] Petrack & Conroy [Page 1]
Contents Contents
1. Introduction ......................................................... 4 1. Introduction .................................................... 4
1.1 Glossary ............................................................ 5 1.1 Glossary ....................................................... 6
2. PINT Milestone Services .............................................. 6 2. PINT Milestone Services ......................................... 6
2.1 Request to Call ................................................. 6 2.1 Request to Call ............................................ 6
2.2 Request to Fax .................................................. 6 2.2 Request to Fax ............................................. 6
2.3 Request to Hear Content ......................................... 6 2.3 Request to Hear Content .................................... 7
2.4 Relation between PINT milestone services and traditional 2.4 Relation between PINT milestone services and traditional
telephone services ............................................... 6 telephone services .......................................... 7
3. PINT Functional and Protocol Architecture ............................. 7 3. PINT Functional and Protocol Architecture ........................ 7
3.1. PINT Functional Architecture .................................... 7 3.1. PINT Functional Architecture ............................... 7
3.2. PINT Protocol Architecture ...................................... 8 3.2. PINT Protocol Architecture ................................. 8
3.2.1. SDP operation in PINT ..................................... 9 3.2.1. SDP operation in PINT ................................ 9
3.2.2. SIP Operation in PINT ..................................... 9 3.2.2. SIP Operation in PINT ............................... 10
3.3. REQUIRED and OPTIONAL elements for PINT compliance ............. 10 3.3. REQUIRED and OPTIONAL elements for PINT compliance ........ 10
3.4. PINT Extensions to SDP 2.0 ..................................... 10 3.4. PINT Extensions to SDP 2.0 ................................ 11
3.4.1. Network Type "TN" and Address Type "RFC2543" ............. 11 3.4.1. Network Type "TN" and Address Type "RFC2543" ........ 11
3.4.2. Support for Data Objects within PINT ..................... 11 3.4.2. Support for Data Objects within PINT ................ 12
3.4.2.1. Use of fmtp attributes in PINT requests ............ 13 3.4.2.1. Use of fmtp attributes in PINT requests ....... 14
3.4.2.2. Support for Remote Data Object References in PINT .. 13 3.4.2.2. Support for Remote Data Object References
3.4.2.3. Support for GSTN-based Data Objects in PINT ........ 14 in PINT .................................... 15
3.4.2.4. Session Description support for included Data Objects 15 3.4.2.3. Support for GSTN-based Data Objects in PINT.... 15
3.4.2.4. Session Description support for included Data
Objects .................................... 17
3.4.3. Attribute Tags to pass information into the Telephone 3.4.3. Attribute Tags to pass information into the Telephone
Network .................................................. 16 Network .................................... 17
3.4.3.1. The phone-context attribute ........................ 17 3.4.3.1. The phone-context attribute ................... 18
3.4.3..2. Presentation Restriction attribute ................. 19 3.4.3.2. Presentation Restriction attribute ............ 20
3.4.3.3. ITU-T CalledPartyAddress attributes parameters ..... 19 3.4.3.3. ITU-T CalledPartyAddress attributes parameters 21
3.4.4. The "require" attribute .................................. 20 3.4.4. The "require" attribute ............................. 22
3.5. PINT Extensions to SIP 2.0 ..................................... 21 3.5. PINT Extensions to SIP 2.0 ................................ 23
3.5.1. Multi-part MIME (sending data along with SIP request) .... 21 3.5.1. Multi-part MIME (sending data along with SIP request) 23
3.5.2. Warning header ........................................... 22 3.5.2. Warning header ...................................... 24
3.5.3. Mechanism to register interest in the disposition of a PINT 3.5.3. Mechanism to register interest in the disposition of
service, and to receive indications on that disposition .. 23 a PINT service, and to receive indications on that
3.5.3.1. Opening a monitoring session with a SUBSCRIBE request 23 disposition ........................................ 24
3.5.3.2. Sending Status Indications with a NOTIFY request ... 24 3.5.3.1. Opening a monitoring session with a SUBSCRIBE
request .................................... 25
3.5.3.2. Sending Status Indications with a NOTIFY
request .................................... 26
3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE 3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE
request ............................................ 25 request ....................................... 27
3.5.3.4. Timing of SUBSCRIBE requests ....................... 25 3.5.3.4. Timing of SUBSCRIBE requests .................. 28
3.5.4. The "Require:" header for PINT ........................... 26 3.5.4. The "Require:" header for PINT ...................... 28
3.5.5. PINT URLs within PINT requests ........................... 26 3.5.5. PINT URLs within PINT requests ...................... 29
3.5.5.1. PINT URLS within Request-URIs ...................... 27 3.5.5.1. PINT URLS within Request-URIs ................. 29
3.5.6. Telephony Network Parameters within PINT URLs ............ 27 3.5.6. Telephony Network Parameters within PINT URLs ....... 30
3.5.7. REGISTER requests within PINT ............................ 28 3.5.7. REGISTER requests within PINT ....................... 30
3.5.8. BYE Requests in PINT ..................................... 28 3.5.8. BYE Requests in PINT ................................ 31
4. Examples of PINT Requests and Responses .............................. 30
4.1. A request to a call centre from an anonymous user to receive a
phone call ..................................................... 30
4.2. A request from a non anonymous customer (John Jones) to receive a
phone call from a particular sales agent (Mary James) .......... 30
4.3. A request to get a fax back .................................... 31
Petrack & Conroy [Page 2] Petrack & Conroy [Page 2]
4.4. A request to have information read out over the phone .......... 32
4.5. A request to send an included text page to a friend's pager .... 32 4. Examples of PINT Requests and Responses ......................... 32
4.1. A request to a call center from an anonymous user to receive
a phone call ........................................... 32
4.2. A request from a non anonymous customer (John Jones) to
receive a phone call from a particular sales agent
(Mary James) ........................................... 33
4.3. A request to get a fax back ............................... 34
4.4. A request to have information read out over the phone ..... 34
4.5. A request to send an included text page to a friend's pager 35
4.6. A request to send an image as a fax to phone number 4.6. A request to send an image as a fax to phone number
+972-9-956-1867 ................................................ 33 +972-9-956-1867 ........................................ 35
4.7. A request to read out over the phone two pieces of content in 4.7. A request to read out over the phone two pieces of content
sequence ....................................................... 33 in sequence ............................................ 36
4.8. Request for the prices for ISDN to be sent to my fax machine ... 34 4.8. Request for the prices for ISDN to be sent to my fax
4.9. Request for a callback ......................................... 34 machine ................................................ 36
4.10.Sending a set of information in response to an enquiry ......... 35 4.9. Request for a callback .................................... 37
4.11.Sportsline "headlines" message sent to your phone/fax/pager .... 35 4.10.Sending a set of information in response to an enquiry .... 37
4.12.Automatically giving someone a fax copy of your phone bill ..... 37 4.11.Sportsline "headlines" message sent to your phone/fax/pager 38
4.12.Automatically giving someone a fax copy of your phone bill 39
5. Security Considerations .............................................. 38 5. Security Considerations ......................................... 40
5.1. Basic Principles for PINT Use ................................. 38 5.1. Basic Principles for PINT Use ............................ 40
5.1.1. Responsibility for service requests ..................... 38 5.1.1. Responsibility for service requests ................ 40
5.1.2. Authority to make requests .............................. 38 5.1.2. Authority to make requests ......................... 41
5.1.3. Privacy ................................................. 39 5.1.3. Privacy ............................................ 41
5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ................ 39 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ........... 42
5.2. Registration Procedures ....................................... 40 5.2. Registration Procedures .................................. 42
5.3. Security mechanisms and implications on PINT service .......... 40 5.3. Security mechanisms and implications on PINT service ..... 43
5.4. Summary of Security Implications .............................. 42 5.4. Summary of Security Implications ......................... 45
6. Deployment considerations and the Relationship PINT to I.N. 6. Deployment considerations and the Relationship PINT to I.N.
(Informative) ........................................................ 44 (Informative) ................................................... 47
6.1. Web Front End to PINT Infrastructure ........................... 44 6.1. Web Front End to PINT Infrastructure ...................... 47
6.2. Redirects to Multiple Gateways ................................. 44 6.2. Redirects to Multiple Gateways ............................ 47
6.3. Competing PINT Gateways REGISTERing to offer the same service .. 45 6.3. Competing PINT Gateways REGISTERing to offer the same
service ................................................ 48
6.4. Limitations on Available Information and Request Timing for 6.4. Limitations on Available Information and Request Timing for
SUBSCRIBE ...................................................... 46 SUBSCRIBE .............................................. 49
6.5. Parameters needed for invoking traditional GSTN Services within 6.5. Parameters needed for invoking traditional GSTN Services
PINT ........................................................... 47 within PINT............................................. 51
6.5.1. Service Identifier ....................................... 47 6.5.1. Service Identifier .................................. 51
6.5.2. A and B parties .......................................... 47 6.5.2. A and B parties ..................................... 51
6.5.3. Other Service Parameters ................................. 48 6.5.3. Other Service Parameters ............................ 51
6.5.4. Service Parameter Summary ................................ 48 6.5.4. Service Parameter Summary ........................... 52
6.6. Parameter Mapping to PINT Extensions............................ 49 6.6. Parameter Mapping to PINT Extensions....................... 53
7. Open Issues and Draft State .......................................... 51
7.1. Open Issues .................................................... 51
7.2. Draft State .................................................... 51
8. References ........................................................... 51
9. Acknowledgements ..................................................... 52
Appendix A: Collected ABNF for PINT Extensions .......................... 53
Appendix B: IANA Considerations ......................................... 58
Appendix C: Authors' Addresses .......................................... 60 7. Open Issues and Draft State ..................................... 55
7.1. Open Issues ............................................... 55
7.2. Draft State ............................................... 55
8. References ...................................................... 55
9. Acknowledgements ................................................ 56
Appendix A: Collected ABNF for PINT Extensions ..................... 57
Appendix B: IANA Considerations .................................... 61
Appendix C: Authors' Addresses ..................................... 63
Petrack & Conroy [Page 3] Petrack & Conroy [Page 3]
1. Introduction 1. Introduction
The desire to invoke certain telephone call services from the Internet has The desire to invoke certain telephone call services from the Internet
been identified by many different groups (users, public and private network has been identified by many different groups (users, public and private
operators, call center service providers, equipment vendors, see [7]). The network operators, call center service providers, equipment vendors, see
generic scenario is as follows (when the invocation is successful): [7]). The generic scenario is as follows (when the invocation is
successful):
1. an IP host sends a request to a server on an IP network; 1. an IP host sends a request to a server on an IP network;
2. the server relays the request into a telephone network; 2. the server relays the request into a telephone network;
3. the telephone network performs the requested call service. 3. the telephone network performs the requested call service.
As examples, consider a user who wishes to have a call placed to his/her As examples, consider a user who wishes to have a callback placed to
telephone. It may be that a customer wishes to get a call from the support his/her telephone. It may be that a customer wants someone in the
department of some business, or a user wishes to hear some remote automatic support department of some business to call them back. Similarly, a user
weather service via recorded or synthesised speech. Within a local may want to hear some announcement of a weather warning sent from a
environment such a request might result in the placement of a call between remote automatic weather service in the event of a storm.
employees over the internal PBX.
We use the term "PSTN/Internet Interworking (PINT) Service" to denote such We use the term "PSTN/Internet Interworking (PINT) Service" to denote
a complete transaction, starting with the sending of a request from an IP such a complete transaction, starting with the sending of a request from
client and including the telephone call itself. PINT services are an IP client and including the telephone call itself. PINT services are
distinguished by the fact that they always involve two separate networks: distinguished by the fact that they always involve two separate
an IP network to request the placement of a call, and the Global Switched networks:
Telephone Network (GSTN) to execute the actual call. It is understood that an IP network to request the placement of a call, and the Global
Intelligent Network systems, private PBXs, cellular phone networks, and Switched Telephone Network (GSTN) to execute the actual call. It is
the ISDN can all be used to deliver PINT services. Also, the request for understood that Intelligent Network systems, private PBXs, cellular
service might come from within a private IP network that is disconnected phone networks, and the ISDN can all be used to deliver PINT services.
from the whole Internet. Also, the request for service might come from within a private IP
network that is disconnected from the whole Internet.
The requirements for the PINT protocol were deliberately restricted to The requirements for the PINT protocol were deliberately restricted to
providing the ability to invoke a small number of fixed telephone call providing the ability to invoke a small number of fixed telephone call
services. These "Milestone PINT services" are specified in section 2. Great services. These "Milestone PINT services" are specified in section 2.
care has been taken, however, to develop a protocol that is aligned with Great care has been taken, however, to develop a protocol that is
other Internet protocols where possible, so that future extensions to PINT aligned with other Internet protocols where possible, so that future
could develop along with Internet conferencing. extensions to PINT could develop along with Internet conferencing.
Within the Internet conference architecture, establishing media calls is Within the Internet conference architecture, establishing media calls is
done via a combination of protocols. SIP [1] is used to establish the done via a combination of protocols. SIP [1] is used to establish the
association between the participants within the call (this association association between the participants within the call (this association
between participants within the call is called a "session"), and SDP [2] is between participants within the call is called a "session"), and SDP [2]
used to describe the media to be exchanged within the session. The PINT is used to describe the media to be exchanged within the session. The
protocol uses these two protocols together, providing some extensions and PINT protocol uses these two protocols together, providing some
enhancements to enable SIP clients and servers to become PINT clients and extensions and enhancements to enable SIP clients and servers to become
servers. PINT clients and servers.
A PINT user who wishes to invoke a service within the telephone network uses A PINT user who wishes to invoke a service within the telephone network
SIP to invite a remote PINT server into a session. The invitation contains uses SIP to invite a remote PINT server into a session. The invitation
an SDP description of the media session that the user would like to take contains an SDP description of the media session that the user would
place. This might be a "sending a fax session" or a "telephone call like to take place. This might be a "sending a fax session" or a
session", for example. In a PINT service execution session the media is "telephone call session", for example. In a PINT service execution
transported over the phone system, while in a SIP session the media is session the media is transported over the phone system, while in a SIP
normally transported over an internet. session the media is normally transported over an internet.
Petrack & Conroy [Page 4] Petrack & Conroy [Page 4]
When used to invoke a PINT service, SIP establishes an association between a When used to invoke a PINT service, SIP establishes an association
requesting PINT client and the PINT server that is responsible for invoking between a requesting PINT client and the PINT server that is responsible
the service within the telephone network. These two entities are not the for invoking the service within the telephone network. These two
same entities as the telephone network entities involved in the telephone entities are not the same entities as the telephone network entities
network service. The SIP messages carry within their SDP payloads a involved in the telephone network service. The SIP messages carry within
description of the telephone network media session. their SDP payloads a description of the telephone network media session.
Note that the fact that a PINT server accepts an invitation and a session is Note that the fact that a PINT server accepts an invitation and a
established is no guarantee that the media will be successfully transported. session is established is no guarantee that the media will be
(This is analogous to the fact that if a SIP invitation is accepted successfully transported. (This is analogous to the fact that if a SIP
successfully, this is no guarantee against a subsequent failure of audio invitation is accepted successfully, this is no guarantee against a
hardware). subsequent failure of audio hardware).
The particular requirements of PINT users lead to some new messages. When a The particular requirements of PINT users lead to some new messages.
PINT server agrees to send a fax to telephone B, it may be that the fax When a PINT server agrees to send a fax to telephone B, it may be that
transmission fails after part of the fax is sent. Therefore, the PINT client the fax transmission fails after part of the fax is sent. Therefore, the
may wish to receive information about the status of the actual telephone PINT client may wish to receive information about the status of the
call session that was invoked as a result of the established PINT session. actual telephone call session that was invoked as a result of the
Three new requests, SUBSCRIBE, UNSIUBSCRIBE, and NOTIFY, are added here established PINT session. Three new requests, SUBSCRIBE, UNSIUBSCRIBE,
to vanilla SIP to allow this. and NOTIFY, are added here to vanilla SIP to allow this.
The enhancements and additions specified here are not intended to alter the The enhancements and additions specified here are not intended to alter
behaviour of baseline SIP or SDP in any way. The purpose of PINT extension the behaviour of baseline SIP or SDP in any way. The purpose of PINT
is to extend the usual SIP/SDP services to the telephone world. Apart from extensions is to extend the usual SIP/SDP services to the telephone
integrating well into existing protocols and architectures, and the world. Apart from integrating well into existing protocols and
advantages of reuse, this means that the protocol specified here can handle architectures, and the advantages of reuse, this means that the protocol
a rather wider class of call services than just the Milestone services. specified here can handle a rather wider class of call services than
just the Milestone services.
The rest of this document is organised as follows: Section 2 describes the The rest of this document is organised as follows: Section 2 describes
PINT Milestone services; section 3 specifies the PINT functional the PINT Milestone services; section 3 specifies the PINT functional and
and protocol architecture; section 4 gives examples of the PINT 1.0 protocol architecture; section 4 gives examples of the PINT 1.0
extensions of SIP and SDP; section 5 contains some security considerations extensions of SIP and SDP; section 5 contains some security
for PINT. The final section contains descriptions of how the PINT protocol considerations for PINT. The final section contains descriptions of how
may be used to provide service over the GSTN. the PINT protocol may be used to provide service over the GSTN.
For a summary of the extensions to SIP and SDP specified in this
document, Section 3.2 gives an combined list, plus one each describing
the extensions to SIP and SDP respectively.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119. In addition, the document are to be interpreted as described in RFC 2119. In addition,
construct "MUST .... OR ...." implies that it is an absolute requirement of the construct "MUST .... OR ...." implies that it is an absolute
this specification to implement one of the two possibilities stated requirement of this specification to implement one of the two
(represented by dots in the above phrase). An implementation MUST be able to possibilities stated (represented by dots in the above phrase). An
interoperate with another implementation that chooses either of the two implementation MUST be able to interoperate with another implementation
possibilities. that chooses either of the two possibilities.
Petrack & Conroy [Page 5]
1.1 Glossary 1.1 Glossary
Requestor - An Internet host from which a request for service originates Requestor - An Internet host from which a request for service originates
PINT Service - A services invoked within a phone system in response to a PINT Service - A service invoked within a phone system in response to a
request received from an PINT client. request received from an PINT client.
PINT Client - An Internet host that sends requests for invocation of a PINT PINT Client - An Internet host that sends requests for invocation of a
Service, in accordance with this document. PINT Service, in accordance with this document.
PINT Gateway - An Internet host that accepts requests for PINT Service and
dispatches them onwards towards a telephone network.
Petrack & Conroy [Page 5] PINT Gateway - An Internet host that accepts requests for PINT Service
and dispatches them onwards towards a telephone network.
Executive System - A system that interfaces to a telephone network that Executive System - A system that interfaces to PINT Server and to a
executes a PINT service, and to a PINT Server. It is not directly associated telephone network that executes a PINT service. It need not be directly
with the Internet, and is represented by the PINT Server. associated with the Internet, and is represented by the PINT Server in
transactions with Internet entities.
Requesting User - The initiator of a request for service. This role may be Requesting User - The initiator of a request for service. This role may
distinct from that of the "party" to any telephone network call that results be distinct from that of the "party" to any telephone network call that
from the request. results from the request.
(Service Call) Party - A person who is involved in a telephone network call (Service Call) Party - A person who is involved in a telephone network
that results from the execution of a PINT service request, or a telephone call that results from the execution of a PINT service request, or a
network-based resource that is involved (such as an automatic Fax Sender or telephone network-based resource that is involved (such as an automatic
a Text-to-Speech Unit). Fax Sender or a Text-to-Speech Unit).
2. PINT Milestone Services 2. PINT Milestone Services
The original motivation for defining this protocol was the desire to invoke The original motivation for defining this protocol was the desire to
the following three telephone network services from within an IP network: invoke the following three telephone network services from within an IP
network:
2.1 Request to Call 2.1 Request to Call
A request is sent from an IP host that causes a phone call to be made, A request is sent from an IP host that causes a phone call to be made,
connecting party A to some remote party B. connecting party A to some remote party B.
2.2 Request to Fax 2.2 Request to Fax
A request is sent from an IP host that causes a fax to be sent to fax A request is sent from an IP host that causes a fax to be sent to fax
machine B. The request MUST contain a pointer to the fax data (that machine B. The request MUST contain a pointer to the fax data (that
could reside in the IP network or in the Telephone Network), OR could reside in the IP network or in the Telephone Network), OR the fax
fax data itself. The content of the fax MAY be text OR some other data itself. The content of the fax MAY be text OR some other more
more general image data. The details of the fax transmission are not general image data. The details of the fax transmission are not
accessible to the IP network, but remain entirely within the telephone accessible to the IP network, but remain entirely within the telephone
network. network.
The PINT Request to Fax service does not involve "Fax over IP": the IP The PINT Request to Fax service does not involve "Fax over IP": the IP
network is only used to send the request that a certain fax be sent. Of network is only used to send the request that a certain fax be sent. Of
course, it is possible that the resulting telephone network fax call happens course, it is possible that the resulting telephone network fax call
to use a real-time IP fax solution, but this is completely transparent to happens to use a real-time IP fax solution, but this is completely
the PINT transaction. transparent to the PINT transaction.
Petrack & Conroy [Page 6]
2.3 Request to Hear Content 2.3 Request to Hear Content
A request is sent from an IP host that causes a phone call to be made to A request is sent from an IP host that causes a phone call to be made to
user A, and for some sort of content to be spoken out. The request MUST user A, and for some sort of content to be spoken out. The request MUST
EITHER contain a URL pointing to the content, OR include the content itself. EITHER contain a URL pointing to the content, OR include the content
The content MAY be text OR some other more general application data. The itself. The content MAY be text OR some other more general application
details of the content transmission are not accessible to the IP network, data. The details of the content transmission are not accessible to the
but remain entirely within the telephone network. IP network, but remain entirely within the telephone network. This
service could equally be called "Request to have Content Spoken"; the
user's goal is to hear the content spoken to them. The mechanism by
which the request is formulated is outside the scope of this document;
however, an example might be that a Web page has a button that when
pressed causes a PINT request to be passed to the PSTN, resulting in the
content of the page (or other details) being spoken to the person.
2.4 Relation between PINT milestone services and traditional telephone 2.4 Relation between PINT milestone services and traditional telephone
services services
There are many different versions and variations of each telephone call There are many different versions and variations of each telephone call
service invoked by a PINT request. Consider as an example what happens when service invoked by a PINT request. Consider as an example what happens
a user requests to call 1-800-2255-287 via the PINT Request-to-Call service. when a user requests to call 1-800-2255-287 via the PINT Request-to-Call
service.
Petrack & Conroy [Page 6]
There may be thousands of agents in the call centre, and there may be any There may be thousands of agents in the call center, and there may be
number of sophisticated algorithms and equipments that are used to decide any number of sophisticated algorithms and pieces of equipment that are
exactly which agent will return the call. And once this choice is made, used to decide exactly which agent will return the call. And once this
there may be many different ways to set up the call: the agent's phone might choice is made, there may be many different ways to set up the call: the
ring first, and only then the original user will be called; or perhaps the agent's phone might ring first, and only then the original user will be
user might be called first, and hear some horrible music or pre-recorded called; or perhaps the user might be called first, and hear some
message while the agent is located. horrible music or pre-recorded message while the agent is located.
Similarly, when a PINT request causes a fax to be sent, there are hundreds Similarly, when a PINT request causes a fax to be sent, there are
of fax protocol details to be negotiated, as well as transmission details hundreds of fax protocol details to be negotiated, as well as
within the telephone networks used. transmission details within the telephone networks used.
PINT requests do not specify too precisely the exact telephone-side service. PINT requests do not specify too precisely the exact telephone-side
Operational details of individual events within the telephone network that service. Operational details of individual events within the telephone
executes the request are outside the scope of PINT. This does not preclude network that executes the request are outside the scope of PINT. This
certain high-level details of the telephone network session from being does not preclude certain high-level details of the telephone network
expressed within a PINT request. For example, it is possible to use the SDP session from being expressed within a PINT request. For example, it is
"lang" attribute to express a language preference for the possible to use the SDP "lang" attribute to express a language
Request-to-Hear-Content Service. If a particular PINT system wishes to preference for the Request-to-Hear-Content Service. If a particular
allow requests to contain details of the telephone-network-side service, it PINT system wishes to allow requests to contain details of the
uses the SDP attribute mechanism (see section 3.4.2). telephone-network-side service, it uses the SDP attribute mechanism (see
section 3.4.2).
3. PINT Functional and Protocol Architecture 3. PINT Functional and Protocol Architecture
3.1. PINT Functional Architecture 3.1. PINT Functional Architecture
Familiarity is assumed with SIP 2.0 [1] and with SDP [2]. Familiarity is assumed with SIP 2.0 [1] and with SDP [2].
PINT clients and servers are SIP clients and servers. SIP is used to carry Petrack & Conroy [Page 7]
the request over the IP network to the correct PINT server in a secure and
reliable manner, and SDP is used to describe the telephone network session
that is to be invoked or whose status is to be returned.
A PINT system uses SIP proxy servers and redirect servers for their usual PINT clients and servers are SIP clients and servers. SIP is used to
purpose, but at some point there must be a PINT server with the means to carry the request over the IP network to the correct PINT server in a
relay received requests into a telephone system and to receive secure and reliable manner, and SDP is used to describe the telephone
network session that is to be invoked or whose status is to be returned.
A PINT system uses SIP proxy servers and redirect servers for their
usual purpose, but at some point there must be a PINT server with the
means to relay received requests into a telephone system and to receive
acknowledgement of these relayed requests. A PINT server with this acknowledgement of these relayed requests. A PINT server with this
capability is called a "PINT gateway". A PINT gateway appears to a SIP capability is called a "PINT gateway". A PINT gateway appears to a SIP
system as a User Agent Server. Notice that a PINT gateway appears to the system as a User Agent Server. Notice that a PINT gateway appears to the
PINT infrastructure as if it represents a "user", while in fact it really PINT infrastructure as if it represents a "user", while in fact it
represents an entire telephone network infrastructure that can provide a really represents an entire telephone network infrastructure that can
set of telephone network services. provide a set of telephone network services.
So the PINT system might appear to an individual PINT client as follows: So the PINT system might appear to an individual PINT client as follows:
/\/\/\/\/\/\/\ /\/\/\/\/\/\/\/\ /\/\/\/\/\/\/\ /\/\/\/\/\/\/\/\
___________ \ __/___ ___\_ \ ___________ \ __/___ ___\_ \
| PINT | PINT \ PINT | PINT | |Exec| Telephone / | PINT | PINT \ PINT | PINT | |Exec| Telephone /
| client |<-------------->| server |gatewy|=====|Syst| Network \ | client |<-------------->| server |gatewy|=====|Syst| Network \
|_________| protocol / cloud |______| |____| Cloud / |_________| protocol / cloud |______| |____| Cloud /
\ \ / \ \ \ / \
/\/\/\/\/\/\/\ \/\/\/\/\/\/\/\/ /\/\/\/\/\/\/\ \/\/\/\/\/\/\/\/
Figure 1: PINT Functional Architecture Figure 1: PINT Functional Architecture
Petrack & Conroy [Page 7]
The system of PINT servers is represented as a cloud to emphasise that a The system of PINT servers is represented as a cloud to emphasise that a
single PINT request might pass through a series of location servers, proxy single PINT request might pass through a series of location servers,
servers, and redirect servers, before finally reaching the correct PINT proxy servers, and redirect servers, before finally reaching the correct
gateway that can actually process the request by passing it to the PINT gateway that can actually process the request by passing it to the
Telephone Network Cloud. Telephone Network Cloud.
The PINT gateway might have a true telephone network interface, or it might The PINT gateway might have a true telephone network interface, or it
be connected via some other protocol or API to an "Executive System" that might be connected via some other protocol or API to an "Executive
is capable of invoking services within the telephone cloud. System" that is capable of invoking services within the telephone cloud.
As an example, within an I.N. (Intelligent Network) system, the PINT gateway As an example, within an I.N. (Intelligent Network) system, the PINT
might appear to realise the Service Control Gateway Function. In an office gateway might appear to realise the Service Control Gateway Function. In
environment, it might be a server adjunct to the office PBX, connected to an office environment, it might be a server adjunct to the office PBX,
both the office LAN and the office PBX. connected to both the office LAN and the office PBX.
The Executive System that lies beyond the PINT gateway is outside the scope The Executive System that lies beyond the PINT gateway is outside the
of PINT. scope of PINT.
3.2. PINT Protocol Architecture 3.2. PINT Protocol Architecture
This section explains how SIP and SDP work in combination to convey the This section explains how SIP and SDP work in combination to convey the
information necessary to invoke telephone network sessions. information necessary to invoke telephone network sessions.
Petrack & Conroy [Page 8]
The following list summarises the extension features used in PINT 1.0. The following list summarises the extension features used in PINT 1.0.
Following on from this the features are considered separately for SDP and Following on from this the features are considered separately for SDP
then for SIP: and then for SIP:
1) Telephony URLs in SDP Contact Fields 1) Telephony URLs in SDP Contact Fields
2) Refinement of SIP/SDP Telephony URLs 2) Refinement of SIP/SDP Telephony URLs
* Inclusion of private dialling plans * Inclusion of private dialling plans
3) Specification of Telephone Service Provider (TSP) and/or 3) Specification of Telephone Service Provider (TSP) and/or
phone-context URL-parameters phone-context URL-parameters
4) Data Objects as session media 4) Data Objects as session media
4a) Protocol Transport formats to indicate the treatment of the media 4a) Protocol Transport formats to indicate the treatment of the media
within the GSTN within the GSTN
5) Implicit (Indirect) media streams and opaque arguments 5) Implicit (Indirect) media streams and opaque arguments
6) In-line data objects using multipart/mime 6) In-line data objects using multipart/mime
7) Refinement/Clarification of Opaque arguments passed onwards to Executive 7) Refinement/Clarification of Opaque arguments passed onwards to
Systems Executive Systems
* Framework for Presentation Restriction Indication * Framework for Presentation Restriction Indication
* Framework for Q.763 arguments * Framework for Q.763 arguments
8) An extension mechanism for SDP to specify strictures and force 8) An extension mechanism for SDP to specify strictures and force
failure when a recipient does NOT support the specified extensions, failure when a recipient does NOT support the specified extensions,
using "require" headers. using "require" headers.
9) Mandatory support for "Warning" headers to give more detailed 9) Mandatory support for "Warning" headers to give more detailed
information on request disposition. information on request disposition.
10) Mechanism to register interest in the disposition of a requested 10) Mechanism to register interest in the disposition of a requested
service, and to receive indications on that disposition. service, and to receive indications on that disposition.
Both PINT and SIP rely on features of MIME[4]. The use of SIP 2.0 is implied Both PINT and SIP rely on features of MIME[4]. The use of SIP 2.0 is
by PINT 1.0, and this also implies compliance with version 1.0 of MIME. implied by PINT 1.0, and this also implies compliance with version 1.0
of MIME.
Petrack & Conroy [Page 8]
3.2.1. SDP operation in PINT 3.2.1. SDP operation in PINT
The SDP payload contains a description of the particular telephone network The SDP payload contains a description of the particular telephone
session that the requestor wishes to occur in the GSTN. This information network session that the requestor wishes to occur in the GSTN. This
includes such things as the telephone network address (i.e. the "telephone information includes such things as the telephone network address (i.e.
number") of the terminal(s) involved in the call, an indication of the media the "telephone number") of the terminal(s) involved in the call, an
type to be transported (e.g. audio, text, image or application data), and an indication of the media type to be transported (e.g. audio, text, image
indication if the information is to be transported over the telephone or application data), and an indication if the information is to be
network via voice, fax, or pager transport. An indication of the content to transported over the telephone network via voice, fax, or pager
be sent to the remote telephone terminal (if there is any) is also included. transport. An indication of the content to be sent to the remote
telephone terminal (if there is any) is also included.
SDP is flexible enough to convey these parameters independently. For SDP is flexible enough to convey these parameters independently. For
example, a request to send some text via voice transport will be fulfilled example, a request to send some text via voice transport will be
by invoking some text-to-speech-over-the-phone service, and a request to fulfilled by invoking some text-to-speech-over-the-phone service, and a
send text via fax will be fulfilled by invoking some text-to-fax service. request to send text via fax will be fulfilled by invoking some
text-to-fax service.
Petrack & Conroy [Page 9]
The following is a list of PINT 1.0 enhancements and additions to SDP. The following is a list of PINT 1.0 enhancements and additions to SDP.
a. A new network type "TN" and address types "RFC2543" and "X-..." a. A new network type "TN" and address types "RFC2543" and "X-..."
(section 3.4.1) (section 3.4.1)
b. New media types "text", "image", and "application", b. New media types "text", "image", and "application",
new protocol transport keywords "voice", "fax" and new protocol transport keywords "voice", "fax" and
"pager" and the associated format types and attribute tags "pager" and the associated format types and attribute tags
(section 3.4.2) (section 3.4.2)
c. New format specific attributes for included content data c. New format specific attributes for included content data
(section 3.4.2.4) (section 3.4.2.4)
d. New attribute tags, used to pass information to the telephone d. New attribute tags, used to pass information to the telephone
network (section 3.4.3) network (section 3.4.3)
e. A new attribute tag "require", used by a client to indicate that e. A new attribute tag "require", used by a client to indicate that
some attribute is required to be supported in the server some attribute is required to be supported in the server
(section 3.4.4) (section 3.4.4)
3.2.2. SIP Operation in PINT 3.2.2. SIP Operation in PINT
SIP is used to carry the request for telephone service from the PINT client SIP is used to carry the request for telephone service from the PINT
to the PINT gateway, and may include a telephone number if needed for the client to the PINT gateway, and may include a telephone number if needed
particular service. The following is a complete list of PINT enhancements for the particular service. The following is a complete list of PINT
and additions to SIP: enhancements and additions to SIP:
f. The multipart MIME payloads (section 3.5.1) f. The multipart MIME payloads (section 3.5.1)
g. Mandatory support for "Warning:" headers (section 3.5.2) g. Mandatory support for "Warning:" headers (section 3.5.2)
h. The SUBSCRIBE and NOTIFY, and UNSUBSCRIBE requests (section 3.5.3) h. The SUBSCRIBE and NOTIFY, and UNSUBSCRIBE requests (section 3.5.3)
i. Require: headers (section 3.5.4) i. Require: headers (section 3.5.4)
j. A format for PINT URLS within a PINT request (section 3.5.5) j. A format for PINT URLS within a PINT request (section 3.5.5)
k. Telephone Network Parameters within PINT URLs (section 3.5.6) k. Telephone Network Parameters within PINT URLs (section 3.5.6)
Section 3.5.8 contains remarks about how BYE requests are used within PINT. Section 3.5.8 contains remarks about how BYE requests are used within
This is not an extension to baseline SIP; it is included here only for PINT. This is not an extension to baseline SIP; it is included here only
clarification of the semantics when used with telephone network sessions. for clarification of the semantics when used with telephone network
sessions.
Petrack & Conroy [Page 9]
3.3. REQUIRED and OPTIONAL elements for PINT compliance 3.3. REQUIRED and OPTIONAL elements for PINT compliance
Of these, only the TN network type (with its associated RFC2543 address Of these, only the TN network type (with its associated RFC2543 address
type) and the "require" attribute MUST be supported by PINT 1.0 clients type) and the "require" attribute MUST be supported by PINT 1.0 clients
and servers. In practice, most PINT service requests will use other changes, and servers. In practice, most PINT service requests will use other
of which references to Data Objects in requests are most likely to appear changes, of which references to Data Objects in requests are most likely
in PINT requests. to appear in PINT requests.
Each of the other new PINT constructs enables a different function, and a Each of the other new PINT constructs enables a different function, and
client or server that wishes to enable that particular function MUST do so a client or server that wishes to enable that particular function MUST
by the construct specified in this document. For example, building a PINT do so by the construct specified in this document. For example, building
client and server that provide only the Request-to-Call telephone call a PINT client and server that provide only the Request-to-Call telephone
service, without support for the other Milestone services, is allowed. call service, without support for the other Milestone services, is
allowed.
The "Require:" SIP header and the "require" attribute provide a mechanism The "Require:" SIP header and the "require" attribute provide a
that can be used by clients and servers to signal their need and/or mechanism that can be used by clients and servers to signal their need
ability to support specific "new" PINT protocol elements. and/or ability to support specific "new" PINT protocol elements.
It should be noted that many optional features of SIP and SDP make sense as It should be noted that many optional features of SIP and SDP make sense
specified in the PINT context. One example is the SDP a=lang: attribute, as specified in the PINT context. One example is the SDP a=lang:
which can be used to describe the preferred language of the callee. Another attribute, which can be used to describe the preferred language of the
example is the use of the "t=" parameter to indicate that the time at which callee. Another example is the use of the "t=" parameter to indicate
the PINT service is to be invoked. This is the normal use of the "t=" field. that the time at which the PINT service is to be invoked. This is the
A third example is the quality attributes. Any SIP or SDP option or normal use of the "t=" field. A third example is the quality attributes.
facility is available to PINT clients and servers without change. Any SIP or SDP option or facility is available to PINT clients and
servers without change.
Conversely, support for Data Objects within Internet Conference sessions may Conversely, support for Data Objects within Internet Conference sessions
be useful, even if the aim is not to provide a GSTN service request. In this may be useful, even if the aim is not to provide a GSTN service request.
case, the extensions covering these items may be incorporated into an In this case, the extensions covering these items may be incorporated
otherwise "plain" SIP/SDP invitation. Likewise, support for SDP "require" into an otherwise "plain" SIP/SDP invitation. Likewise, support for SDP
may be useful, as a framework for addition of features to a "traditional" "require" may be useful, as a framework for addition of features to a
SIP/SDP infrastructure. Again, these may be convenient to incorporate into "traditional" SIP/SDP infrastructure. Again, these may be convenient to
SIP/SDP implementations that would not be used for PINT service requests. incorporate into SIP/SDP implementations that would not be used for PINT
Such additions are beyond the scope of this document, however. service requests. Such additions are beyond the scope of this document,
however.
3.4. PINT Extensions to SDP 3.4. PINT Extensions to SDP
PINT 1.0 adds to SDP the possibility to describe audio, fax, and pager PINT 1.0 adds to SDP the possibility to describe audio, fax, and pager
telephone sessions. It is deliberately designed to hide the underlying telephone sessions. It is deliberately designed to hide the underlying
technical details and complexity of the telephone network. The only network technical details and complexity of the telephone network. The only
type defined for PINT is the generic "TN" (Telephone Network). More precise network type defined for PINT is the generic "TN" (Telephone Network).
tags such as "ISDN", "GSM", are not defined. Similarly, the transport More precise tags such as "ISDN", "GSM", are not defined. Similarly, the
protocols are designated simply as "fax", "voice", and "pager"; there are no transport protocols are designated simply as "fax", "voice", and
more specific identifiers for the various telephone network voice, fax, or "pager"; there are no more specific identifiers for the various
pager protocols. Similarly, the data to be transported is identified only as telephone network voice, fax, or pager protocols. Similarly, the data to
a MIME type, such as "text" data, "image" data, or some more general be transported are identified only by a MIME content type, such as
"application" data, etc. An important example of transporting "application" "text" data, "image" data, or some more general "application" data. An
data is the milestone service "Voice Access to Web Content". In this case important example of transporting "application" data is the milestone
the data to be transported is pointed to by a URI, the data type is service "Voice Access to Web Content". In this case the data to be
application/URI, and the transport protocol would be "voice". Some sort of transported are pointed to by a URI, the data content type is
speech-synthesis facility, speaking out to a Phone, will have to be invoked application/URI, and the transport protocol would be "voice". Some sort
to perform this service. of speech-synthesis facility, speaking out to a Phone, will have to be
invoked to perform this service.
This section gives details of the new SDP keywords. This section gives details of the new SDP keywords.
3.4.1. Network Type "TN" and Address Type "RFC2543" 3.4.1. Network Type "TN" and Address Type "RFC2543"
The TN ("Telephone Network") network type is used to indicate that the The TN ("Telephone Network") network type is used to indicate that the
terminal is connected to a telephone network. terminal is connected to a telephone network.
The address types allowed for network type TN are "RFC2543" and private The address types allowed for network type TN are "RFC2543" and private
address types, which MUST begin with an "X-". address types, which MUST begin with an "X-".
Address type RFC2543 is followed by a string conforming to a subset of the Address type RFC2543 is followed by a string conforming to a subset of
"telephone-subscriber" BNF specified in RFC2543, (this is specified in the "telephone-subscriber" BNF specified in figure 4 of SIP [1]).
figure 4 of SIP [1]). Note that this BNF is NOT identical to the BNF that Note that this BNF is NOT identical to the BNF that defines the
defines the "phone-number" within the "p=" field of SDP. "phone-number" within the "p=" field of SDP.
Examples: Examples:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
c= TN RFC2543 12014064090 c= TN RFC2543 12014064090
A telephone-subscriber string is of one of two types: global-phone-number or A telephone-subscriber string is of one of two types:
local-phone-number. These are distinguished by preceeding a global-phone-number or
global-phone-number with a "plus" sign ("+"). A global-phone-number is by local-phone-number.
default to be interpreted as an internationally significant E.164 Number These are distinguished by preceeding a global-phone-number with a
Plan Address, as defined by [6], whilst a local-phone-number is a number "plus" sign ("+"). A global-phone-number is by default to be interpreted
specified in the default dialling plan within the context of the recipient as an internationally significant E.164 Number Plan Address, as defined
PINT Gateway. by [6], whilst a local-phone-number is a number specified in the default
dialling plan within the context of the recipient PINT Gateway.
An implementation MAY use private addressing types, which can be useful An implementation MAY use private addressing types, which can be useful
within a local domain. These address types MUST begin with an "X-", and within a local domain. These address types MUST begin with an "X-", and
SHOULD contain a domain name after the X-, e.g. "X-mytype.mydomain.com". SHOULD contain a domain name after the X-, e.g. "X-mytype.mydomain.com".
An example of such a connection line is as follows: An example of such a connection line is as follows:
c= TN X-mytype.mydomain.com A*8-HELEN c= TN X-mytype.mydomain.com A*8-HELEN
where "X-mytype.mydomain.com" identifies this private address type, and where "X-mytype.mydomain.com" identifies this private address type, and
"A*8-HELEN" is the number in this format. Such a format is defined as an "A*8-HELEN" is the number in this format. Such a format is defined as an
"OtherAddr" in the ABNF of Appendix A. "OtherAddr" in the ABNF of Appendix A. Note that most dialable telephone
Note that most dialable telephone numbers are expressable as numbers are expressable as local-phone-numbers within address RFC2543;
local-phone-numbers within address RFC2543; new address types should only be new address types SHOULD only be used for formats which cannot be so
used for formats which cannot be so written. written.
3.4.2. Support for Data Objects within PINT 3.4.2. Support for Data Objects within PINT
One significant change over traditional SIP/SDP Internet Conference sessions One significant change over traditional SIP/SDP Internet Conference
with PINT is that a PINT service request may refer to a Data Object to be sessions with PINT is that a PINT service request may refer to a Data
used as source information in that request. For example, a PINT service Object to be used as source information in that request. For example, a
request may specify a document to be processed as part of a GSTN service by PINT service request may specify a document to be processed as part of a
which a Fax is sent. Similarly, a GSTN service may be take a Web page and GSTN service by which a Fax is sent. Similarly, a GSTN service may be
result in a vocoder processing that page and speaking the contents over a take a Web page and result in a vocoder processing that page and
telephone. speaking the contents over a telephone.
The SDP specification does not have explicit support for reference to or The SDP specification does not have explicit support for reference to or
carriage of Data Objects within requests. In order to use SDP for PINT, carriage of Data Objects within requests. In order to use SDP for PINT,
there is a need to describe such media sessions as "a telephone call to a there is a need to describe such media sessions as "a telephone call to
certain number during which such-and-such an image is sent as a fax". a certain number during which such-and-such an image is sent as a fax".
To support this, two extensions to the session description format are To support this, two extensions to the session description format are
specified. These are some new allowed values for the Media Field, specified. These are some new allowed values for the Media Field, and a
and a description of the "fmtp" parameter when used with the Media description of the "fmtp" parameter when used with the Media Field
Field values (within the context of the Contact Field Network type "TN"). values (within the context of the Contact Field Network type "TN").
An addition is also made to the SIP message format to allow the inclusion An addition is also made to the SIP message format to allow the
of data objects as sub-parts within the request message itself. inclusion of data objects as sub-parts within the request message
The original SDP syntax (from [2]) for media-field is given as: itself. The original SDP syntax (from [2]) for media-field is given as:
media-field = "m=" media space port ["/" integer] media-field = "m=" media space port ["/" integer]
space proto 1*(space fmt) CRLF space proto 1*(space fmt) CRLF
When used within PINT requests, the definition of the sub-fields is When used within PINT requests, the definition of the sub-fields is
expanded slightly. expanded slightly. The Media sub-field definition is relaxed to accept
The Media sub-field definition is relaxed to accept all of the discrete all of the discrete "top-level" media types defined in [4]. In the
"top-level" media types defined in [4]. In the milestone services the milestone services the discrete type "video" is not used, and the extra
discrete type "video" is not used, and the extra types "data" and "control" types "data" and "control" are likewise not needed. The use of these
are likewise not needed. The use of these types is not precluded, but the types is not precluded, but the behaviour expected of a PINT Gateway
behaviour expected of a PINT Gateway receiving a request including such a receiving a request including such a type is not defined here.
type is not defined here.
The Port sub-field has no meaning in PINT requests as the destination The Port sub-field has no meaning in PINT requests as the destination
terminals are specified using "TN" addressing, so the value of the port terminals are specified using "TN" addressing, so the value of the port
sub-field in PINT requests is normally set to "1". A value of "0" may sub-field in PINT requests is normally set to "1". A value of "0" may be
be used as in SDP to indicate that the terminal is not receiving media. used as in SDP to indicate that the terminal is not receiving media.
This is useful to indicate that a telephone terminal has gone "on hold" This is useful to indicate that a telephone terminal has gone "on hold"
temporarily. Likewise, the optional integer sub-field is not used in PINT. temporarily. Likewise, the optional integer sub-field is not used in
PINT.
As mentioned in [2], the Transport Protocol sub-field is specific to the As mentioned in [2], the Transport Protocol sub-field is specific to the
associated Address Type. In the case that the Address Type in the preceeding associated Address Type. In the case that the Address Type in the
Contact field is one of those defined for use with the Network Type "TN", preceeding Contact field is one of those defined for use with the
the following values are defined for the Transport Protocol sub-field: Network Type "TN", the following values are defined for the Transport
Protocol sub-field:
"voice", "fax", and "pager". "voice", "fax", and "pager".
The interpretation of this sub-field within PINT requests is the treatment The interpretation of this sub-field within PINT requests is the
or disposition of the resulting GSTN service. Thus, for transport protocol treatment or disposition of the resulting GSTN service. Thus, for
"voice", the intent is that the service will result in a GSTN voice call, transport protocol "voice", the intent is that the service will result
whilst for protocol "fax" the result will be a GSTN fax transmission, and in a GSTN voice call, whilst for protocol "fax" the result will be a
protocol "pager" will result in a pager message being sent. GSTN fax transmission, and protocol "pager" will result in a pager
message being sent.
Note that this sub-field does not necessarily dictate the media type and Note that this sub-field does not necessarily dictate the media type and
subtype of any source data; for example, one of the milestone services calls subtype of any source data; for example, one of the milestone services
for a textual source to be vocoded and spoken in a resulting telephone calls for a textual source to be vocoded and spoken in a resulting
service call. The transport protocol value in this case would be "voice", telephone service call. The transport protocol value in this case would
whilst the media type would be "text". be "voice", whilst the media type would be "text".
The Fmt sub-field is described in [2] as being transport protocol-specific. The Fmt sub-field is described in [2] as being transport
When used within PINT requests having one of the above protocol values, protocol-specific. When used within PINT requests having one of the
this sub-field consists of a list of one or more values, each of which is above protocol values, this sub-field consists of a list of one or more
a defined MIME sub-type of the associated Media sub-field value. The values, each of which is a defined MIME sub-type of the associated Media
special value "-" is allowed, meaning that there is no MIME sub-type. sub-field value. The special value "-" is allowed, meaning that there
This sub-field retains (from [2]) its meaning that the list will contain is no MIME sub-type. This sub-field retains (from [2]) its meaning that
a set of alternative sub-types, with the first being the preferred value. the list will contain a set of alternative sub-types, with the first
being the preferred value.
For experimental purposes and by mutual consent of the sender and recipient, For experimental purposes and by mutual consent of the sender and
a sub-type value may be specified as an <X-token>, i.e. a character string recipient, a sub-type value may be specified as an <X-token>, i.e. a
starting with "X-". The use of such values is discouraged, and if such a character string starting with "X-". The use of such values is
value is expected to find common use then it SHOULD be registered with IANA discouraged, and if such a value is expected to find common use then it
using the standard content type registration process (see Appendix C). SHOULD be registered with IANA using the standard content type
registration process (see Appendix C).
When the Fmt parameter is the single character "-" ( a dash ), this is When the Fmt parameter is the single character "-" ( a dash ), this is
interpreted as meaning that a unspecified or default sub-type should be used interpreted as meaning that a unspecified or default sub-type can be
for this service. Thus, the media field value "m=audio 1 voice -<CRLF>" is used for this service. Thus, the media field value "m=audio 1 voice
taken to mean that a voice call is requested, using whatever audio sub type -<CRLF>" is taken to mean that a voice call is requested, using whatever
is deemed appropriate by the Executive System. PINT service is a special audio sub type is deemed appropriate by the Executive System. PINT
case, in that the request comes from the IP network but the service call is service is a special case, in that the request comes from the IP network
provided within the GSTN. Thus the service request will not normally be able but the service call is provided within the GSTN. Thus the service
to define the particular codec used for the resulting GSTN service call. If request will not normally be able to define the particular codec used
such an intent IS required, then the quality attribute may be used (see for the resulting GSTN service call. If such an intent IS required, then
"Suggested Attributes" section of [2]). the quality attribute may be used (see "Suggested Attributes" section of
[2]).
3.4.2.1. Use of fmtp attributes in PINT requests 3.4.2.1. Use of fmtp attributes in PINT requests
For each element of the Fmt sub-field, there MUST be a following fmtp For each element of the Fmt sub-field, there MUST be a following fmtp
attribute. When used within PINT requests, the fmtp attribute has a general attribute. When used within PINT requests, the fmtp attribute has a
structure as defined here: general structure as defined here:
"a=fmtp:" <subtype> <space> resolution "a=fmtp:" <subtype> <space> resolution
*(<space> resolution) *(<space> resolution)
(<space> ";" 1(<attribute>) *(<space> <attribute>)) (<space> ";" 1(<attribute>)
*(<space> <attribute>))
where: where:
<resolution> := (<uri-ref> | <opaque-ref> | <sub-part-ref>) <resolution> := (<uri-ref> | <opaque-ref> | <sub-part-ref>)
A fmtp attribute describes the sources used with a given Fmt entry in the A fmtp attribute describes the sources used with a given Fmt entry in
Media field. The entries in a Fmt sub-field are alternatives (with the the Media field. The entries in a Fmt sub-field are alternatives (with
preferred one first in the list). Each entry will have a matching fmtp the preferred one first in the list). Each entry will have a matching
attribute. The list of resolutions in a fmtp attribute describes the set of fmtp attribute. The list of resolutions in a fmtp attribute describes
sources that resolve the matching Fmt choice; all elements of this set will the set of sources that resolve the matching Fmt choice; all elements of
be used. this set will be used.
It should be noted that, for use in PINT services, the elements in such a It should be noted that, for use in PINT services, the elements in such
set will be sent as a sequence; it is unlikely that trying to send them in a set will be sent as a sequence; it is unlikely that trying to send
parallel would be successful. them in parallel would be successful.
A fmtp attribute can contain a mixture of different kinds of element. Thus A fmtp attribute can contain a mixture of different kinds of element.
an attribute might contain a sub-part-ref to included data held in a Thus an attribute might contain a sub-part-ref indicating included data
sub-part of the current message, followed by an opaque-ref to some content held in a sub-part of the current message, followed by an opaque-ref
on the GSTN, followed by a uri-ref pointing to some data held externally on referring to some content on the GSTN, followed by a uri-ref pointing to
the IP network. some data held externally on the IP network.
To indicate which form each resolution element takes, each of them To indicate which form each resolution element takes, each of them
starts with its own literal tag. The detailed syntax of each form is starts with its own literal tag. The detailed syntax of each form is
described in the following sub-sections. described in the following sub-sections.
3.4.2.2. Support for Remote Data Object References in PINT 3.4.2.2. Support for Remote Data Object References in PINT Where data
Where data objects stored elsewhere on the IP Network are to be used as objects stored elsewhere on the IP Network are to be used as sources for
sources for processing within a PINT service, they may be referred to using processing within a PINT service, they may be referred to using the
the uri-ref form. This is simply a Uniform Resource Identifier (URI), as uri-ref form. This is simply a Uniform Resource Identifier (URI), as
described in [9]. described in [9].
Note that the reference SHOULD be an absolute URI, as there may not be Note that the reference SHOULD be an absolute URI, as there may not be
enough contextual information for the recipient server to resolve a relative enough contextual information for the recipient server to resolve a
reference; any use of relative references requires some private agreement relative reference; any use of relative references requires some private
between the sender and recipient of the message, and should be avoided agreement between the sender and recipient of the message, and SHOULD be
unless the sender can be sure that the recipient is the one intended and the avoided unless the sender can be sure that the recipient is the one
reference is unambiguous in context. intended and the reference is unambiguous in context.
This also holds for partial URIs (such as: "uri:http://aMachine/index.html") This also holds for partial URIs (such as"uri:http://aNode/index.htm")
as these will need to be resolved in the context of the eventual recipient as these will need to be resolved in the context of the eventual
of the message. recipient of the message.
The general syntax of a reference to an Internet-based external data object The general syntax of a reference to an Internet-based external data
in a fmtp line within a PINT session description is: object in a fmtp line within a PINT session description is:
<uri-ref> := ("uri:" URI-reference) <uri-ref> := ("uri:" URI-reference)
where URI-reference is as defined in Appendix A of [9] where URI-reference is as defined in Appendix A of [9]
For example: For example:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain m= text 1 fax plain
a=fmtp:plain uri:ftp://ftp.isi.edu/in-notes/rfc2468.txt a=fmtp:plain uri:ftp://ftp.isi.edu/in-notes/rfc2468.txt
or: or:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain m= text 1 fax plain
a=fmtp:plain uri:http://www.ietf.org/meetings/glance_minneapolis.txt a=fmtp:plain
uri:http://www.ietf.org/meetings/glance_minneapolis.txt
means get this data object from the Internet and use it as a source for the means get this data object from the Internet and use it as a source for
requested GSTN Fax service. the requested GSTN Fax service.
3.4.2.3. Support for GSTN-based Data Objects in PINT 3.4.2.3. Support for GSTN-based Data Objects in PINT
PINT services may refer to data that is held not on the IP Network but PINT services may refer to data that are held not on the IP Network but
instead within the GSTN. The way in which these items are indicated need instead within the GSTN. The way in which these items are indicated need
have no meaning within the context of the Requestor or the PINT Gateway; it have no meaning within the context of the Requestor or the PINT Gateway;
is merely some data that may be used by the Executive System to indicate the the reference is merely some data that may be used by the Executive
content intended as part of the request. This data forms an opaque System to indicate the content intended as part of the request. These
reference, in that it is sent "untouched" through the PINT infrastructure. data form an opaque reference, in that they are sent "untouched" through
the PINT infrastructure.
A reference to some data object held on the GSTN has the general definition: A reference to some data object held on the GSTN has the general
definition:
<opaque-ref> := ("opr:" *uric) <opaque-ref> := ("opr:" *uric)
where uric is as defined in Appendix A of [9]. where uric is as defined in Appendix A of [9].
For example: For example:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain m= text 1 fax plain
a=fmtp:plain opr:APPL.123.456 a=fmtp:plain opr:APPL.123.456
means send me the data that is indexed ON THE GSTN by the reference value means send the data that is indexed ON THE GSTN by the reference value
"APPL.123.456"; the Executive System may also take the Telephone URL held in "APPL.123.456" to the fax machine on +1-201-406-4090. The Executive
the To: field of the enclosing SIP message into account when deciding the System may also take the Telephone URL held in the To: field of the
context to be used for the data object dereference. enclosing SIP message into account when deciding the context to be used
for the data object dereference.
Of course, an opaque reference may also be used for other purposes; it Of course, an opaque reference may also be used for other purposes; it
could, for example, be needed to authorise access to a document held on the could, for example, be needed to authorise access to a document held on
GSTN rather than being required merely to disambiguate the data object. The the GSTN rather than being required merely to disambiguate the data
purpose to which an opaque reference is put, however, is out of scope for object. The purpose to which an opaque reference is put, however, is out
this document. It is merely an indicator carried within a PINT Request. of scope for this document. It is merely an indicator carried within a
PINT Request.
An opaque reference may have no value in the case where the value to be used An opaque reference may have no value in the case where the value to be
is implicit in the rest of the request. For example, suppose some company used is implicit in the rest of the request. For example, suppose some
wishes to use PINT to implement a "fax-back service". In their current company wishes to use PINT to implement a "fax-back service". In their
implementation, the image(s) to be faxed are entirely defined by the current implementation, the image(s) to be faxed are entirely defined by
telephone number dialled. Within the PINT request, this telephone number the telephone number dialled. Within the PINT request, this telephone
would appear within the "To:" field of the PINT request, and so there number would appear within the "To:" field of the PINT request, and so
is no need for an opaque reference value. there is no need for an opaque reference value.
If there are several resolutions for a PINT Service Request, and one of If there are several resolutions for a PINT Service Request, and one of
these is an opaque reference with no value, then that opaque reference MUST these is an opaque reference with no value, then that opaque reference
be included in the attribute line, but with an empty value field. MUST be included in the attribute line, but with an empty value field.
For example: For example:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain m= text 1 fax plain
a=fmtp:plain spr:<Content-ID> opr: a=fmtp:plain uri:http://www.sun.com/index.html opr:
might be used to precede some unambiguous "faxed back" data with a covering might be used to precede some data to be faxed with a covering note.
note (see next sub-section for details of the sub-part reference).
In the special case where an opaque reference is the sole resolution of a In the special case where an opaque reference is the sole resolution of
PINT Service Request, AND that reference needs no value, there is no need a PINT Service Request, AND that reference needs no value, there is no
for a Fmt list at all; the intent of the service is unambiguous without any need for a Fmt list at all; the intent of the service is unambiguous
further resolution. without any further resolution.
For example: For example:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax - m= text 1 fax -
means that there is an implied content stored on the GSTN, and that this is means that there is an implied content stored on the GSTN, and that this
uniquely identified by the combination of SIP To-URI and the Contact field is uniquely identified by the combination of SIP To-URI and the Contact
of the session description. field of the session description.
3.4.2.4. Session Description support for included Data Objects 3.4.2.4. Session Description support for included Data Objects
As an alternative to pointing to the data via a URI or an opaque reference As an alternative to pointing to the data via a URI or an opaque
to a data item held on the GSTN, it is possible to include the content data reference to a data item held on the GSTN, it is possible to include the
within the SIP request itself. This is done by using multipart MIME for the content data within the SIP request itself. This is done by using
SIP payload. The first MIME part contains the SDP description of the multipart MIME for the SIP payload. The first MIME part contains the SDP
telephone network session to be executed. The other MIME parts contain the description of the telephone network session to be executed. The other
content data to be transported. MIME parts contain the content data to be transported.
Format specific attribute lines within the session description are used to Format specific attribute lines within the session description are used
indicate which other MIME part within the request contains the content data. to indicate which other MIME part within the request contains the
Instead of a URI or opaque reference, the format-specific attribute content data. Instead of a URI or opaque reference, the format-specific
indicates the Content-ID of the MIME part of the request that contains the attribute indicates the Content-ID of the MIME part of the request that
actual data, and is defined as: contains the actual data, and is defined as:
<sub-part-ref> := ("spr:" Content-ID) <sub-part-ref> := ("spr:" Content-ID)
where Content-ID is as defined in Appendix A of [3] and in [10]). where Content-ID is as defined in Appendix A of [3] and in [10]).
For example: For example:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain m= text 1 fax plain
a=fmtp:plain spr:<Content-ID> a=fmtp:plain spr:<Content-ID>
The <Content-ID> parameter is the Content-ID of one of the MIME parts inside The <Content-ID> parameter is the Content-ID of one of the MIME parts
the message, and this fragment means that the requesting user would like the inside the message, and this fragment means that the requesting user
data object held in the sub-part of this message labelled <Content-ID> to be would like the data object held in the sub-part of this message labelled
faxed to the machine at phone number +1-201-406-4090. <Content-ID> to be faxed to the machine at phone number +1-201-406-4090.
See also section 3.5.1 for a discussion on the support needed in the See also section 3.5.1 for a discussion on the support needed in the
enclosing SIP request for included data objects. enclosing SIP request for included data objects.
3.4.3. Attribute Tags to pass information into the Telephone Network 3.4.3. Attribute Tags to pass information into the Telephone Network
It may be desired to include within the PINT request service parameters It may be desired to include within the PINT request service parameters
that can be understood only by some entity in the "Telephone Network that can be understood only by some entity in the "Telephone Network
Cloud". SDP attribute parameters are used for this purpose. They MAY appear Cloud". SDP attribute parameters are used for this purpose. They MAY
within a particular media description or outside of a media description. appear within a particular media description or outside of a media
description.
These attributes may also appear as parameters within PINT URLS (see section These attributes may also appear as parameters within PINT URLS (see
3.5.6) as part of a SIP request. section 3.5.6) as part of a SIP request.
This is necessary so that telephone terminals that require the attributes to This is necessary so that telephone terminals that require the
be defined can appear within the To: line of a PINT request as well as attributes to be defined can appear within the To: line of a PINT
within PINT session descriptions. request as well as within PINT session descriptions.
The purpose of these attributes is to allow the client to specify extra The purpose of these attributes is to allow the client to specify extra
context within which a particular telephone number is to be interpreted. context within which a particular telephone number is to be interpreted.
There are many reasons why extra context might be necessary to interpret a There are many reasons why extra context might be necessary to interpret
given telephone number: a given telephone number:
a. The telephone number might be reachable in many different ways a. The telephone number might be reachable in many different ways
(such as via competing telephone service providers), and the PINT (such as via competing telephone service providers), and the PINT
client wishes to indicate its selection of service provider. client wishes to indicate its selection of service provider.
b. The telephone number might be reachable only from a limited b. The telephone number might be reachable only from a limited
number of networks (such as an '800' freephone number). number of networks (such as an '800' freephone number).
c. The telephone number might be reachable only within a c. The telephone number might be reachable only within a
single telephone network (such as the '152' customer service single telephone network (such as the '152' customer service
number of BT). Similarly, the number might be an internal number of BT). Similarly, the number might be an internal
corporate extension reachable only within the PBX. corporate extension reachable only within the PBX.
However, as noted above, it is not usually necessary to use SDP However, as noted above, it is not usually necessary to use SDP
attributes to specify the phone context. URLs such as 152@pint.bt.co.il attributes to specify the phone context. URLs such as 152@pint.bt.co.il
within the To: and From: headers and/or Request-URI, normally offer within the To: and From: headers and/or Request-URI, normally offer
sufficient context to resolve telephone numbers. sufficient context to resolve telephone numbers.
skipping to change at page 16, line 54 skipping to change at page 18, line 16
single telephone network (such as the '152' customer service single telephone network (such as the '152' customer service
number of BT). Similarly, the number might be an internal number of BT). Similarly, the number might be an internal
corporate extension reachable only within the PBX. corporate extension reachable only within the PBX.
However, as noted above, it is not usually necessary to use SDP However, as noted above, it is not usually necessary to use SDP
attributes to specify the phone context. URLs such as 152@pint.bt.co.il attributes to specify the phone context. URLs such as 152@pint.bt.co.il
within the To: and From: headers and/or Request-URI, normally offer within the To: and From: headers and/or Request-URI, normally offer
sufficient context to resolve telephone numbers. sufficient context to resolve telephone numbers.
If the client wishes the request to fail if the attributes are not If the client wishes the request to fail if the attributes are not
supported, these attributes should be used in conjunction with the supported, these attributes SHOULD be used in conjunction with the
"require" attribute (section 3.4.4) and the "Require:org.ietf.sdp.require" "require" attribute (section 3.4.4) and the
header (section 3.5.4). "Require:org.ietf.sdp.require" header (section 3.5.4).
It is not possible to standardise every possible internal telephone network It is not possible to standardise every possible internal telephone
parameter. PINT 1.0 attributes have been chosen for specification because network parameter. PINT 1.0 attributes have been chosen for
they are common enough that many different PINT systems will want to use specification because they are common enough that many different PINT
them, and therefore interoperability will be increased by having a single systems will want to use them, and therefore interoperability will be
specification. increased by having a single specification.
Proprietary attribute "a=" lines, that by definition are not interoperable, Proprietary attribute "a=" lines, that by definition are not
may be nonetheless useful when it is necessary to transport some proprietary interoperable, may be nonetheless useful when it is necessary to
internal telephone network variables over the IP network, for example to transport some proprietary internal telephone network variables over the
identify the order in which service call legs should be made. These private IP network, for example to identify the order in which service call legs
attributes SHOULD BE, however, subject to the same IANA registration are to be be made. These private attributes SHOULD BE, however, subject
procedures mentioned in the SDP specification[2] (see also this Appendix C). to the same IANA registration procedures mentioned in the SDP
specification[2] (see also this Appendix C).
3.4.3.1. The phone-context attribute 3.4.3.1. The phone-context attribute
An attribute is specified to enable "remote local dialling". This is the An attribute is specified to enable "remote local dialling". This is the
service that allows a PINT client to reach a number from far outside the service that allows a PINT client to reach a number from far outside the
area or network that can usually reach the number. It is useful when the area or network that can usually reach the number. It is useful when the
sending or receiving address is only dialable within some local context, sending or receiving address is only dialable within some local context,
which may be remote to the origin of the PINT client. which may be remote to the origin of the PINT client.
For example, if Alice wanted to report a problem with her telephone, she For example, if Alice wanted to report a problem with her telephone, she
might then dial a "network wide" customer care number; within the British might then dial a "network wide" customer care number; within the
Telecom network in the U.K., this is "152". Note that in this case she British Telecom network in the U.K., this is "152". Note that in this
doesn't dial any trunk prefix - this is the whole dialable number. If case she doesn't dial any trunk prefix - this is the whole dialable
dialled from another operator's network, it will not connect to British number. If dialled from another operator's network, it will not connect
Telecom's Engineering Enquiries service; and dialling "+44 152" will not to British Telecom's Engineering Enquiries service; and dialling "+44
normally succeed. Such numbers are called Network-Specific Service Numbers. 152" will not normally succeed. Such numbers are called Network-Specific
Service Numbers.
Within the telephone network, the "local context" is provided by the Within the telephone network, the "local context" is provided by the
physical connection between the subscriber's terminal and the central physical connection between the subscriber's terminal and the central
office. An analogous association between the PINT client and the PINT server office. An analogous association between the PINT client and the PINT
that first receives the request may not exist, which is why it may be server that first receives the request may not exist, which is why it
necessary to supply this missing "telephone network context". may be necessary to supply this missing "telephone network context".
This attribute is defined as follows: This attribute is defined as follows:
a=phone-context: <phone-context-ident> a=phone-context: <phone-context-ident>
phone-context-ident = network-prefix / private-prefix phone-context-ident = network-prefix / private-prefix
network-prefix = intl-network-prefix / local-network-prefix network-prefix = intl-network-prefix / local-network-prefix
intl-network-prefix = "+" 1*DIGIT intl-network-prefix = "+" 1*DIGIT
local-network-prefix = 1*DIGIT local-network-prefix = 1*DIGIT
excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d)) excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d))
private-prefix = 1*excldigandplus 0*uric private-prefix = 1*excldigandplus 0*uric
An intl-network-prefix and local-network-prefix MUST be a bona fide network An intl-network-prefix and local-network-prefix MUST be a bona fide
prefix, and a network-prefix that is an intl-network-prefix MUST begin with network prefix, and a network-prefix that is an intl-network-prefix MUST
an E.164 service code ("country code"). begin with an E.164 service code ("country code").
It is possible to register new private-prefixes with IANA so as to avoid It is possible to register new private-prefixes with IANA so as to avoid
confrontation. Prefixes that are not so registered MUST begin with an "X-" collisions. Prefixes that are not so registered MUST begin with an "X-"
to indicate their private, non-standard nature (see Appendix C). to indicate their private, non-standard nature (see Appendix C).
Example 1: Example 1:
c= TN RFC2543 1-800-765-4321 c= TN RFC2543 1-800-765-4321
a=phone-context:+972 a=phone-context:+972
This describes an terminal whose address in Israel (E.164 country code 972) This describes an terminal whose address in Israel (E.164 country code
is 1-800-765-4321. 972) is 1-800-765-4321.
Example 2: Example 2:
c= TN RFC2543 1-800-765-4321 c= TN RFC2543 1-800-765-4321
a=phone-context:+1 a=phone-context:+1
This describes an terminal whose address in North America (E.164 country This describes an terminal whose address in North America (E.164 country
code 1) is 1-800-765-4321. code 1) is 1-800-765-4321.
The two telephone terminals described by examples 1 and 2 are different; in The two telephone terminals described by examples 1 and 2 are different;
fact they are located in different countries. in fact they are located in different countries.
Example 3: Example 3:
c=TN RFC2543 123 c=TN RFC2543 123
a=phone-context:+97252 a=phone-context:+97252
This describes a terminal whose address when dialled from within the network This describes a terminal whose address when dialled from within the
identified by +97252 is the string "123". It so happens that +97252 defines network identified by +97252 is the string "123". It so happens that
one of the Israeli cell phone providers, and 123 reaches customer service +97252 defines one of the Israeli cell phone providers, and 123 reaches
when dialled within that network. customer service when dialled within that network.
It may well be useful or necessary to use the SDP "require" parameter in It may well be useful or necessary to use the SDP "require" parameter in
conjunction with the phone-context attribute. conjunction with the phone-context attribute.
Example 4: Example 4:
c= TN RFC2543 321 c= TN RFC2543 321
a=phone-context:X-acme.com-23 a=phone-context:X-acme.com-23
This might describe the telephone terminal that is at extension 321 of PBX This might describe the telephone terminal that is at extension 321 of
number 23 within the acme.com private PBX network. It is expected that such PBX number 23 within the acme.com private PBX network. It is expected
a description would be understandable by the acme.com PINT server that that such a description would be understandable by the acme.com PINT
receives the request. server that receives the request.
Note that if the PINT server receiving the request is inside the acme.com Note that if the PINT server receiving the request is inside the
network, the same terminal might be addressable as follows: acme.com network, the same terminal might be addressable as follows:
c= TN RFC2543 7-23-321 c= TN RFC2543 7-23-321
(assuming that "7" is dialled in order to reach the private PBX network from (assuming that "7" is dialled in order to reach the private PBX network
within acme.com) from within acme.com)
3.4.3.2. Presentation Restriction attribute 3.4.3.2. Presentation Restriction attribute
Although it has no affect on the transport of the service request through Although it has no affect on the transport of the service request
the IP Network, there may be a requirement to allow originators of a PINT through the IP Network, there may be a requirement to allow originators
service request to indicate whether or not they wish the "B party" in of a PINT service request to indicate whether or not they wish the "B
the resulting service call to be presented with the "A party's" calling party" in the resulting service call to be presented with the "A
telephone number. It is a legal requirement in some jurisdictions that a party's" calling telephone number. It is a legal requirement in some
caller be able to select whether or not their correspondent can find out jurisdictions that a caller be able to select whether or not their
the calling telephone number (using Automatic Number Indication or Caller correspondent can find out the calling telephone number (using Automatic
Display or Calling Line Identity Presentation equipment). Thus an attribute Number Indication or Caller Display or Calling Line Identity
may be needed to indicate the originator's preference. Presentation equipment). Thus an attribute may be needed to indicate the
originator's preference.
Whether or not the default behaviour of the Executive System is to present Whether or not the default behaviour of the Executive System is to
or not present a party's telephone number to the correspondent GSTN terminal present or not present a party's telephone number to the correspondent
is not specified, and it is not mandatory in all territories for a PINT GSTN terminal is not specified, and it is not mandatory in all
Gateway or Executive System to act on this attribute. It is, however, territories for a PINT Gateway or Executive System to act on this
defined here for use where there are regulatory restrictions on GSTN attribute. It is, however, defined here for use where there are
operation, and in that case the Executive System can use it to honour the regulatory restrictions on GSTN operation, and in that case the
originator's request. Executive System can use it to honour the originator's request.
The attribute is specified as follows: The attribute is specified as follows:
a=clir:<"true" | "false"> a=clir:<"true" | "false">
This boolean value is needed within the attribute as it may be that the GSTN This boolean value is needed within the attribute as it may be that the
address is, by default, set to NOT present its identity to correspondents, GSTN address is, by default, set to NOT present its identity to
and the originator wants to do so for this particular call. It is in keeping correspondents, and the originator wants to do so for this particular
with the aim of this attribute to allow the originator to specify what call. It is in keeping with the aim of this attribute to allow the
treatment they want for the requested service call. originator to specify what treatment they want for the requested service
call.
The expected interpretation of this attribute is that, if it is present and The expected interpretation of this attribute is that, if it is present
the value is "false" then the Calling Line Identity CAN be presented to the and the value is "false" then the Calling Line Identity CAN be presented
correspondent terminal, whilst if it is "true" then it if possible the to the correspondent terminal, whilst if it is "true" then it if
Executive System is requested to NOT present the Calling Line Identity. possible the Executive System is requested to NOT present the Calling
Line Identity.
3.4.3.3. ITU-T CalledPartyAddress attributes parameters 3.4.3.3. ITU-T CalledPartyAddress attributes parameters
These attributes correspond to fields that appear within the ITU-T Q.763 These attributes correspond to fields that appear within the ITU-T Q.763
"CalledPartyAddress" field (see [8] ,section 3.9). PINT clients "CalledPartyAddress" field (see [8] ,section 3.9). PINT clients use
use these attributes in order to specify further parameters relating to these attributes in order to specify further parameters relating to
Terminal Addresses, in the case when the address indicates a Terminal Addresses, in the case when the address indicates a
"local-phone-number". In the case that the PINT request contains a "local-phone-number". In the case that the PINT request contains a
reference to a GSTN terminal, the parameters may be required to correctly reference to a GSTN terminal, the parameters may be required to
identify that remote terminal. correctly identify that remote terminal.
The general form of this attribute is "a=Q763-<token>((":" <value>) |"")". The general form of this attribute is:
Three of the possible elements and their use in SDP attributes are described "a=Q763-<token>((":" <value>) |"")".
here. Where other Q763 elements are to be used, then these should be the Three of the possible elements and their use in SDP attributes are
subject of further specification to define the syntax of the attribute described here. Where other Q763 elements are to be used, then these
mapping. It is recommended that any such specification maintains the value should be the subject of further specification to define the syntax of
sets shown in Q.763. the attribute mapping. It is recommended that any such specification
maintains the value sets shown in Q.763.
The defined attributes are: The defined attributes are:
a=Q763-nature: - indicates the "nature of address indicator". a=Q763-nature: - indicates the "nature of address indicator".
The value MAY be any number between 0 and 127. The value MAY be any number between 0 and 127.
The following values are specified: The following values are specified:
"1" a subscriber number "1" a subscriber number
"2" unknown "2" unknown
"3" a nationally significant number "3" a nationally significant number
skipping to change at page 20, line 28 skipping to change at page 21, line 46
expansion of Q.763. expansion of Q.763.
a=Q763-plan: - indicates the numbering plan to which the address a=Q763-plan: - indicates the numbering plan to which the address
belongs. The value MAY be any number between 0 and belongs. The value MAY be any number between 0 and
7. The following values are specified: 7. The following values are specified:
"1" Telephone numbering plan (ITU-T E.164) "1" Telephone numbering plan (ITU-T E.164)
"3" Data numbering plan (ITU-T X.121) "3" Data numbering plan (ITU-T X.121)
"4" Telex numbering plan (ITU-T F.69) "4" Telex numbering plan (ITU-T F.69)
The values have been chosen to coincide with the values in Q.763. The values have been chosen to coincide with the values in Q.763. Other
Other values are allowed, according to national rules or future values are allowed, according to national rules or future expansion of
expansion of Q.763. Q.763.
a=Q763-INN - indicates if routing to the Internal Network Number a=Q763-INN - indicates if routing to the Internal Network Number
is allowed. The value MUST be ONE of: is allowed. The value MUST be ONE of:
"0" routing to internal network number allowed "0" routing to internal network number allowed
"1" routing to internal network number not "1" routing to internal network number not
allowed allowed
The values have been chosen to coincide with the values in Q.763. The values have been chosen to coincide with the values in Q.763.
Note that it is possible to use a local-phone-number and indicate via Note that it is possible to use a local-phone-number and indicate via
attributes that the number is in fact an internationally significant attributes that the number is in fact an internationally significant
E.164 number. Normally this SHOULD NOT be done; an internationally E.164 number. Normally this SHOULD NOT be done; an internationally
significant E.164 number is indicated by using a "global-phone-number" significant E.164 number is indicated by using a "global-phone-number"
for the address string. for the address string.
3.4.4. The "require" attribute 3.4.4. The "require" attribute
According to the SDP specification, a PINT server is allowed simply to According to the SDP specification, a PINT server is allowed simply to
ignore attribute parameters that it does not understand. In order to force a ignore attribute parameters that it does not understand. In order to
server to fail a request if it does not understand one of the PINT force a server to decline a request if it does not understand one of the
attributes, a client should use the "require" attribute, specified as PINT attributes, a client SHOULD use the "require" attribute, specified
follows: as follows:
a=require:<attribute-list> a=require:<attribute-list>
where the attribute-list is a comma-separated list of attributes that appear where the attribute-list is a comma-separated list of attributes that
elsewhere in the session description. appear elsewhere in the session description.
In order to process the request successfully the PINT server must BOTH In order to process the request successfully the PINT server must BOTH
understand the attribute AND ALSO fulfil the request implied by the presence understand the attribute AND ALSO fulfil the request implied by the
of the attribute, for each attribute appearing within the attribute-list of presence of the attribute, for each attribute appearing within the
the require attribute. attribute-list of the require attribute.
If the server does not recognise the attribute listed, the PINT server MUST If the server does not recognise the attribute listed, the PINT server
return an error status code (such as 420 (Bad Extension) or 400 (Bad MUST return an error status code (such as 420 (Bad Extension) or 400
Request)), and SHOULD return suitable Warning: lines explaining the problem (Bad Request)), and SHOULD return suitable Warning: lines explaining the
or an Unsupported: header containing the attribute it does not understand. problem or an Unsupported: header containing the attribute it does not
If the server recognizes the attribute listed, but cannot fulfil the understand. If the server recognizes the attribute listed, but cannot
request implied by the presence of the attribute, the request MUST fail fulfil the request implied by the presence of the attribute, the request
with a status code of (606 Not Acceptable), along with a suitable MUST be rejected with a status code of (606 Not Acceptable), along with
Unsupported: header or Warning: line. a suitable Unsupported: header or Warning: line.
The "require" attribute may appear anywhere in the session description, and The "require" attribute may appear anywhere in the session description,
any number of times, but it MUST appear before the use of the attribute and any number of times, but it MUST appear before the use of the
marked as required. attribute marked as required.
Since the "require" attribute is itself an attribute, the SIP specification Since the "require" attribute is itself an attribute, the SIP
allows a server that does not understand the require attribute to ignore specification allows a server that does not understand the require
it. In order to ensure that the PINT server will comply with the "require" attribute to ignore it. In order to ensure that the PINT server will
attribute, a PINT client should include a Require: header with the tag comply with the "require" attribute, a PINT client SHOULD include a
"ietf.org.sdp.require" (section 3.5.4) Require: header with the tag "ietf.org.sdp.require" (section 3.5.4)
Note that the majority of the PINT extensions are "tagged" and these tags Note that the majority of the PINT extensions are "tagged" and these
can be included in Require strictures. The exception is the use of phone tags can be included in Require strictures. The exception is the use of
numbers in SDP parts. However, these are defined as a new network and phone numbers in SDP parts. However, these are defined as a new network
address type, so that a receiving SIP/SDP server should be able to detect and address type, so that a receiving SIP/SDP server should be able to
whether or not it supports these forms. The default behaviour for any SDP detect whether or not it supports these forms. The default behaviour for
recipient is that it will fail a PINT request if it does not recognise or any SDP recipient is that it will fail a PINT request if it does not
support the TN and RFC2543 or X-token network and address types, as without recognise or support the TN and RFC2543 or X-token network and address
the contents being recognised no media session could be created. Thus a types, as without the contents being recognised no media session could
separate stricture is not required in this case. be created. Thus a separate stricture is not required in this case.
3.5. PINT Extensions to SIP 2.0 3.5. PINT Extensions to SIP 2.0
PINT requests are SIP requests; Many of the specifications within this PINT requests are SIP requests; Many of the specifications within this
document merely explain how to use existing SIP facilities for the purposes document merely explain how to use existing SIP facilities for the
of PINT. purposes of PINT.
3.5.1. Multi-part MIME (sending data along with SIP request) 3.5.1. Multi-part MIME (sending data along with SIP request)
A PINT request can contain a payload which is multipart MIME. In this case A PINT request can contain a payload which is multipart MIME. In this
the first part MUST contain an SDP session description that includes at case the first part MUST contain an SDP session description that
least one of the format specific attribute tags for "included content data" includes at least one of the format specific attribute tags for
specified above in section 3.4.3. All subsequent parts contain content data "included content data" specified above in section 3.4.3. Subsequent
that is to be transferred to the requested Telephone Call Service. As parts contain content data that may be transferred to the requested
discussed earlier, within a single PINT request, some of the data MAY be Telephone Call Service. As discussed earlier, within a single PINT
pointed to by a URI within the request, and some of the data MAY be included request, some of the data MAY be pointed to by a URI within the request,
within the request. and some of the data MAY be included within the request.
Where included data is carried within a PINT service request, the Content Where included data is carried within a PINT service request, the
Type entity header of the enclosing SIP message MUST indicate this. To do Content Type entity header of the enclosing SIP message MUST indicate
so, the media type value within this entity header MUST be set to a value of this. To do so, the media type value within this entity header MUST be
"multipart". set to a value of "multipart". There is a content sub-type that is
intended for situations like this in which sub-parts are to be handled
together. This is the multipart/related type (defined in [19]), and it's
use is recommended.
The enclosed body parts SHOULD include the part-specific Content Type The enclosed body parts SHOULD include the part-specific Content Type
headers as appropriate ("application/sdp" for the first body part holding headers as appropriate ("application/sdp" for the first body part
the session description, with an appropriate content type for each of the holding the session description, with an appropriate content type for
subsequent, "included data object" parts). This matches the standard syntax each of the subsequent, "included data object" parts). This matches the
of MIME multipart messages as defined in [4]. standard syntax of MIME multipart messages as defined in [4].
For example, in a multipart message where the string "------next-------" is For example, in a multipart message where the string "------next-------"
the boundary, the first two parts might be as follows: is the boundary, the first two parts might be as follows:
------next------- ------next-------
Content-Type: application/sdp Content-Type: application/sdp
.... ....
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
m= text 1 pager plain m= text 1 pager plain
a=fmtp:plain spr:17@mymessage.acme.com a=fmtp:plain spr:17@mymessage.acme.com
----------next------- ----------next-------
Content-Type: text/plain Content-Type: text/plain
Content-ID: 17@mymessage.acme.com Content-ID: 17@mymessage.acme.com
This is the text that is to be paged to +1-201-406-4090 This is the text that is to be paged to +1-201-406-4090
----------next----------- ----------next-----------
The ability to indicate different alternatives for the content to be The ability to indicate different alternatives for the content to be
transported is useful, even when the alternatives are included within the transported is useful, even when the alternatives are included within
request. For example, a request to send a short message to a pager might the request. For example, a request to send a short message to a pager
include the message in Unicode [5] and an alternative version of the same might include the message in Unicode [5] and an alternative version of
content in text/plain, should the PINT server or telephone network not be the same content in text/plain, should the PINT server or telephone
able to process the unicode. network not be able to process the unicode.
PINT clients should be extremely careful when sending included data within a PINT clients should be extremely careful when sending included data
PINT request. Such requests SHOULD be sent via TCP, to avoid fragmentation within a PINT request. Such requests SHOULD be sent via TCP, to avoid
and to transmit the data reliably. It is possible that the PINT server is a fragmentation and to transmit the data reliably. It is possible that the
proxy server that will replicate and fork the request, which could be PINT server is a proxy server that will replicate and fork the request,
disastrous if the request contains a large amount of application data. PINT which could be disastrous if the request contains a large amount of
proxy servers should be careful not to create many copies of a request with application data. PINT proxy servers should be careful not to create
large amounts of data in it. If the client does not know the actual location many copies of a request with large amounts of data in it. If the client
of the PINT gateway, and is using the SIP location services to find it, and does not know the actual location of the PINT gateway, and is using the
the included data makes the PINT request likely to be transported in several SIP location services to find it, and the included data makes the PINT
IP datagrams, it is RECOMMENDED that the initial PINT request not include request likely to be transported in several IP datagrams, it is
the data but instead hold a reference to it. RECOMMENDED that the initial PINT request not include the data object
but instead hold a reference to it.
3.5.2. Warning header 3.5.2. Warning header
A PINT server MUST support the SIP "Warning:" header so that it can signal A PINT server MUST support the SIP "Warning:" header so that it can
lack of support for individual PINT features. As an example, suppose the signal lack of support for individual PINT features. As an example,
PINT request is to send a jpeg picture to a fax machine, but the server suppose the PINT request is to send a jpeg picture to a fax machine, but
cannot retrieve and/or translate jpeg pictures from the Internet into fax the server cannot retrieve and/or translate jpeg pictures from the
transmissions. Internet into fax transmissions.
In such a case the server fails the request and includes a In such a case the server fails the request and includes a Warning such
Warning such as the following: as the following:
Warning: 305 pint.acme.com Incompatible media format: jpeg Warning: 305 pint.acme.com Incompatible media format: jpeg
SIP servers that do not understand the PINT extensions at all are strongly SIP servers that do not understand the PINT extensions at all are
encouraged to implement Warning: headers to indicate that PINT extensions strongly encouraged to implement Warning: headers to indicate that PINT
are not understood. extensions are not understood.
Also, Warning: headers may be included within NOTIFY requests if it is Also, Warning: headers may be included within NOTIFY requests if it is
necessary to notify the client about some condition concerning the necessary to notify the client about some condition concerning the
invocation of the PINT service (see next). invocation of the PINT service (see next).
3.5.3. Mechanism to register interest in the disposition of a PINT service, 3.5.3. Mechanism to register interest in the disposition of a PINT
and to receive indications on that disposition service, and to receive indications on that disposition
It can be very useful to find out whether or not a requested service has It can be very useful to find out whether or not a requested service has
completed, and if so whether or not it was successful. This is especially completed, and if so whether or not it was successful. This is
true for PINT service, where the person requesting the service is not especially true for PINT service, where the person requesting the
(necessarily) a party to it, and so may not have an easy way of finding out service is not (necessarily) a party to it, and so may not have an easy
the disposition of that service. Equally, it may be useful to indicate when way of finding out the disposition of that service. Equally, it may be
the service has changed state, for example when the service call has useful to indicate when the service has changed state, for example when
started. the service call has started.
Arranging a flexible system to provide extensive monitoring and control Arranging a flexible system to provide extensive monitoring and control
during a service is non-trivial (see section 6.4 for some issues); PINT 1.0 during a service is non-trivial (see section 6.4 for some issues); PINT
uses a simple scheme that should nevertheless provide useful information. It 1.0 uses a simple scheme that should nevertheless provide useful
is possible to expand the scheme in a "backwards compatible" manner, so if information. It is possible to expand the scheme in a "backwards
required it can be enhanced at a later date. Such enhancement would be compatible" manner, so if required it can be enhanced at a later date.
expected to be the subject of a separate document. Such enhancement would be expected to be the subject of a separate
document.
The PINT 1.0 status registration and indication scheme uses three new The PINT 1.0 status registration and indication scheme uses three new
methods; SUBSCRIBE, UNSUBSCRIBE, and NOTIFY. These are used to allow a PINT methods; SUBSCRIBE, UNSUBSCRIBE, and NOTIFY. These are used to allow a
Requesting entity to register an interest in (or "subscribe" to) the status PINT Requesting entity to register an interest in (or "subscribe" to)
of a service request, to indicate that this monitoring session is over, the status of a service request, to indicate that a prior interest has
and for the gateway to return service indications. All of these messages lapsed (i.e "unsubscribe" from the status), and for the gateway to
follow the same procedure as used for all the SIP requests other than return service indications. All of these messages follow the same
INVITE; the recipient MUST acknowledge the request with a final response procedure as used for all the SIP requests other than INVITE; the
message, otherwise the request will be repeated. recipient MUST acknowledge the request with a final response message,
otherwise the request will be repeated.
3.5.3.1. Opening a monitoring session with a SUBSCRIBE request 3.5.3.1. Opening a monitoring session with a SUBSCRIBE request
The SUBSCRIBE request indicates that a user wishes to receive information
about the status of a session. The request identifies the session of
interest normally by including the original session description along
with the request. Where the subscription is being made by the user who
initiated the original service request, the Call-ID may be used as it
will be known to the receiver to refer to a previously established
session. (When the request comes from a user other than the original
requesting user, the request constitutes a new SIP call leg, so the
Call-ID should not be used; instead the origin-field of the session
description enclosed within the original service request must be used).
The request MUST NOT include whatever content was present in the original
request other than the session description, and a server MUST ignore
whatever content is included within a SUBSCRIBE request with the sole
exception of the enclosed session description.
The request MAY contain a "Contact:" header, specifying the PINT User Agent When a SUBSCRIBE request is sent to a PINT Server, it indicates that a
Server to which such information should be sent. In addition, it SHOULD user wishes to receive information about the status of a service
contain an Expires: header, which indicates for how long the PINT Requestor session. The request identifies the session of interest by including the
wishes to receive notification of the session status. See section 5.1.4. original session description along with the request, using the SDP
global-session-id that forms part of the origin-field to identify the
service session uniquely.
The SUBSCRIBE request (like any other SIP request about an ongoing
session) is sent to the same server as was sent the original INVITE,
or to a server which was specified in the Contact: field within a
subsequent response (this might well be the PINT gateway for the
session).
Whilst there are situations in which re-use of the Call-ID used in the
original INVITE that initiated the session of interest is possible,
there are other situations in which it is not. In detail, where the
subscription is being made by the user who initiated the original
service request, the Call-ID may be used as it will be known to the
receiver to refer to a previously established session. However, when the
request comes from a user other than the original requesting user, the
SUBSCRIBE request constitutes a new SIP call leg, so the Call-ID SHOULD
NOT be used; the only common identifier is the origin-field of the
session description enclosed within the original service request, and so
this MUST be used.
Rather than have two different methods of identifying the "session of
interest" the choice is to use the origin-field of the SDP sub-part
included both in the original INVITE and in this SUBSCRIBE request.
Note that the request MUST NOT include any sub-parts other than the
session description, even if these others were present in the original
INVITE request. A server MUST ignore whatever sub-parts are included
within a SUBSCRIBE request with the sole exception of the enclosed
session description.
The request MAY contain a "Contact:" header, specifying the PINT User
Agent Server to which such information should be sent.
In addition, it SHOULD contain an Expires: header, which indicates for
how long the PINT Requestor wishes to receive notification of the
session status. We refer to the period of time before the expiration of
the SUBSCRIBE request as the "subscription period". See section 5.1.4.
for security considerations, particularly privacy implications. for security considerations, particularly privacy implications.
A value of 0 within the Expires: header indicates a desire to receive one A value of 0 within the Expires: header indicates a desire to receive
single immediate response (i.e. the request expires immediately). We refer one single immediate response (i.e. the request expires immediately). It
to the period of time before the expiration of the SUBSCRIBE request as the is possible for a sequence of monitoring sessions to be opened, exist,
"subscription period". and complete, all relating to the same service session.
A successful response to the SUBSCRIBE request includes the session A successful response to the SUBSCRIBE request includes the session
description, according to the Gateway. Normally this will be identical to description, according to the Gateway. Normally this will be identical
the last cached response that the Gateway returned to any request concerning to the last cached response that the Gateway returned to any request
the same SDP global session id (see [2], section 6, o= field). The t= line concerning the same SDP global session id (see [2], section 6, o=
may be altered to indicate the actual start or stop time, however. The field). The t= line may be altered to indicate the actual start or stop
Gateway might add an i= line to the session description to indicate such time, however. The Gateway might add an i= line to the session
information as how many fax pages were sent. The Gateway SHOULD include an description to indicate such information as how many fax pages were
Expires: header indicating how long it is willing to maintain the monitoring sent. The Gateway SHOULD include an Expires: header indicating how long
session. If this is unacceptable to the PINT Requestor, then it can close it is willing to maintain the monitoring session. If this is
the session by sending an immediate BYE (see 3.5.3.3). unacceptable to the PINT Requestor, then it can close the session by
sending an immediate UNSUBSCRIBE message (see 3.5.3.3).
In principle, a user might send a SUBSCRIBE request after the telephone In principle, a user might send a SUBSCRIBE request after the telephone
network service has completed. This allows, for example, checking up "the network service has completed. This allows, for example, checking up
morning after" to see if the fax was successfully transmitted. However, a "the morning after" to see if the fax was successfully transmitted.
PINT gateway is only required to keep state about a call for as long as it However, a PINT gateway is only required to keep state about a call for
indicated previously in a Expires: header within the response to the as long as it indicated previously in an Expires: header sent within the
original INVITE message that triggered the service session, within the response to the original INVITE message that triggered the service
response to the SUBSCRIBE message, within the response to the BYE session, within the response to the SUBSCRIBE message, within the
message, or within its own BYE message (but see section 3.5.8, point 3). response to any UNSUBSCRIBE message, or within its own UNSUBSCRIBE
message (but see section 3.5.8, point 3).
If the Server no longer has a record of the session to which a Requestor has If the Server no longer has a record of the session to which a Requestor
SUBSCRIBEd, it returns "606 Not Acceptable", along with the appropriate has SUBSCRIBEd, it returns "606 Not Acceptable", along with the
Warning: 307 header indicating that the SDP session ID is no longer valid. appropriate Warning: 307 header indicating that the SDP session ID is no
This means that a requesting Client that knows that it will want information longer valid. This means that a requesting Client that knows that it
about the status of a session after the session terminates SHOULD send a will want information about the status of a session after the session
SUBSCRIBE request before the session terminates. terminates SHOULD send a SUBSCRIBE request before the session
terminates.
3.5.3.2. Sending Status Indications with a NOTIFY request 3.5.3.2. Sending Status Indications with a NOTIFY request
During the subscription period, the Gateway may, from time to time, send a
spontaneous NOTIFY request to the entity indicated in the Contact: header of
the "opening" SUBSCRIBE request. Normally this will happen as a result of
any change in the status of the service session for which the Requestor has
subscribed.
The receiving user agent server MUST acknowledge this by returning a final During the subscription period, the Gateway may, from time to time, send
response (normally a "200 OK"). In this version of the PINT extensions, the a spontaneous NOTIFY request to the entity indicated in the Contact:
Gateway is not required to support redirects (3xx codes), and so may treat header of the "opening" SUBSCRIBE request. Normally this will happen as
them as a failure. Thus, if the response code class is above 2xx then this a result of any change in the status of the service session for which
may be treated by the Gateway as a failure of the monitoring session, and in the Requestor has subscribed.
that situation it will immediately attempt to close the session (see next).
The NOTIFY request contains the modified session description. For example, The receiving user agent server MUST acknowledge this by returning a
the Gateway may be able to indicate a more accurate start or stop time. final response (normally a "200 OK"). In this version of the PINT
extensions, the Gateway is not required to support redirects (3xx
codes), and so may treat them as a failure.
The Gateway may include a Warning: header to describe some problem with the Thus, if the response code class is above 2xx then this may be treated
invocation of the service, and may indicate within an i= line some by the Gateway as a failure of the monitoring session, and in that
situation it will immediately attempt to close the session (see next).
The NOTIFY request contains the modified session description. For
example, the Gateway may be able to indicate a more accurate start or
stop time.
The Gateway may include a Warning: header to describe some problem with
the invocation of the service, and may indicate within an i= line some
information about the telephone network session itself. information about the telephone network session itself.
Example: Example:
NOTIFY sip:petrack@pager.com SIP/2.0 NOTIFY sip:petrack@pager.com SIP/2.0
To: sip:petrack@pager.com To: sip:petrack@pager.com
From: sip:R2F.pint.com@service.com From: sip:R2F.pint.com@service.com
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4711 SUBSCRIBE CSeq: 4711 SUBSCRIBE
Warning: xxx fax aborted, will try for the next hour. Warning: xxx fax aborted, will try for the next hour.
Content-Type:application/sdp Content-Type:application/sdp
c=... c=...
i=3 pages of 5 sent i=3 pages of 5 sent
t=... t=...
3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE request 3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE request
At some point, either the Client's representative User Agent Server or the
Gateway may decide to terminate the monitoring session. This is achieved At some point, either the Client's representative User Agent Server or
by sending an UNSUBSCRIBE request to the correspondent server. Such a the Gateway may decide to terminate the monitoring session. This is
request indicates that the sender intends to close the monitoring session achieved by sending an UNSUBSCRIBE request to the correspondent server.
immediately, and, on receipt of the final response from the receiving Such a request indicates that the sender intends to close the monitoring
server, the session is deemed over. session immediately, and, on receipt of the final response from the
receiving server, the session is deemed over.
Note that unlike the SUBSCRIBE request, which is never sent by a PINT
gateway, an UNSUBSCRIBE request can be sent by a PINT gateway to the
User Agent Server to indicate that the monitoring session is closed.
(This is analogous to the fact that a gateway never sends an INVITE,
although it can send a BYE to indicate that a telephone call has ended.)
If the Gateway initiates closure of the monitoring session by sending an If the Gateway initiates closure of the monitoring session by sending an
UNSUBSCRIBE message, it SHOULD include an "Expires:" header showing for UNSUBSCRIBE message, it SHOULD include an "Expires:" header showing for
how much longer after this monitoring session is closed it is willing to how much longer after this monitoring session is closed it is willing to
store information on the service session. This acts as a minimum time store information on the service session. This acts as a minimum time
within which the Client can send a new SUBSCRIBE message to open another within which the Client can send a new SUBSCRIBE message to open another
monitoring session; after the time indicated in the Expires: header the monitoring session; after the time indicated in the Expires: header the
Gateway is free to dispose of any record of the service session, so that Gateway is free to dispose of any record of the service session, so that
subsequent SUBSCRIBE requests can be rejected with a "606" response. subsequent SUBSCRIBE requests can be rejected with a "606" response.
If the subscription period specified by the Client has expired, then the If the subscription period specified by the Client has expired, then the
Gateway may send an immediate UNSUBSCRIBE request to the Client's Gateway may send an immediate UNSUBSCRIBE request to the Client's
representative User Agent Server. This ensures that the monitoring session representative User Agent Server. This ensures that the monitoring
always completes with a UNSUBSCRIBE/response exchange, and that the session always completes with a UNSUBSCRIBE/response exchange, and that
representative User Agent Server can avoid maintaining state in certain the representative User Agent Server can avoid maintaining state in
circumstances. certain circumstances.
3.5.3.4. Timing of SUBSCRIBE requests 3.5.3.4. Timing of SUBSCRIBE requests
As it relies on the Gateway having a copy of the INVITEd session As it relies on the Gateway having a copy of the INVITEd session
description, the SUBSCRIBE message is limited in when it can be issued. The description, the SUBSCRIBE message is limited in when it can be issued.
Gateway must have received the service request to which this monitoring The Gateway must have received the service request to which this
session is to be associated, which from the Client's perspective happens as monitoring session is to be associated, which from the Client's
soon as the Gateway has sent a 1xx response back to it. perspective happens as soon as the Gateway has sent a 1xx response back
to it.
However, once this has been done, there is no reason why the Client should However, once this has been done, there is no reason why the Client
not send a monitoring request. It does not have to wait for the final should not send a monitoring request. It does not have to wait for the
response from the Gateway, and it can certainly send the SUBSCRIBE request final response from the Gateway, and it can certainly send the SUBSCRIBE
before sending the ACK for the Service request final response. Beyond this request before sending the ACK for the Service request final response.
point, the Client is free to send a SUBSCRIBE request when it decides, Beyond this point, the Client is free to send a SUBSCRIBE request when
unless the Gateway's final response to the initial service request indicated it decides, unless the Gateway's final response to the initial service
a short Expires: time. request indicated a short Expires: time.
However, there are good reasons (see 6.4) why it may be appropriate to start However, there are good reasons (see 6.4) why it may be appropriate to
a monitoring session immediately before the service is confirmed by the PINT start a monitoring session immediately before the service is confirmed
Client sending an ACK. At this point the Gateway will have decided whether by the PINT Client sending an ACK. At this point the Gateway will have
or not it can handle the service request, but will not have passed the decided whether or not it can handle the service request, but will not
request on to the Executive System. It is therefore in a good position to have passed the request on to the Executive System. It is therefore in a
ask the Executive System to enable monitoring when it sends the service good position to ask the Executive System to enable monitoring when it
request onwards. In practical implementations, it is likely that more sends the service request onwards. In practical implementations, it is
information on transient service status will be available if this is likely that more information on transient service status will be
indicated as being important BEFORE or AS the service execution phase available if this is indicated as being important BEFORE or AS the
starts; once execution has begun the level of information that can be service execution phase starts; once execution has begun the level of
returned may be difficult to change. information that can be returned may be difficult to change.
Thus, whilst it is free to send a SUBSCRIBE request at any point after Thus, whilst it is free to send a SUBSCRIBE request at any point after
receiving an Interim response from the Gateway to its service request, it is receiving an Interim response from the Gateway to its service request,
recommended that the Client should send such a monitoring request it is recommended that the Client should send such a monitoring request
immediately prior to sending an ACK message confirming the service if it is immediately prior to sending an ACK message confirming the service if it
interested in transient service status messages. is interested in transient service status messages.
3.5.4. The "Require:" header for PINT 3.5.4. The "Require:" header for PINT
PINT clients use the Require: header to signal to the PINT server that a PINT clients use the Require: header to signal to the PINT server that a
certain PINT extension of SIP is required. PINT 1.0 defines two strings that certain PINT extension of SIP is required. PINT 1.0 defines two strings
can go into the Require header: that can go into the Require header:
org.ietf.sip.subscribe -- the server can fulfill SUBSCRIBE requests org.ietf.sip.subscribe -- the server can fulfill SUBSCRIBE requests
and associated methods (see section 3.5.3) and associated methods (see section 3.5.3)
org.ietf.sdp.require -- the PINT server (or the SDP parser associated org.ietf.sdp.require -- the PINT server (or the SDP parser associated
to it) understands the "require" attribute to it) understands the "require" attribute
defined in (section 3.4.4) defined in (section 3.4.4)
Example: Example:
Require:org.ietf.sip.subscribe,org.ietf.sdp.require Require:org.ietf.sip.subscribe,org.ietf.sdp.require
A client should only include a Require: header where it truly requires the A client SHOULD only include a Require: header where it truly requires
server to fail the request if the option is not supported. the server to reject the request if the option is not supported.
3.5.5. PINT URLs within PINT requests 3.5.5. PINT URLs within PINT requests
Normally the hostnames and domain names that appear in the PINT URLs are the Normally the hostnames and domain names that appear in the PINT URLs are
internal affair of each individual PINT system. A client uses the the internal affair of each individual PINT system. A client uses the
appropriate SDP payload to indicate the particular service it wishes to appropriate SDP payload to indicate the particular service it wishes to
invoke; it is not necessary to use a particular URL to identify the service. invoke; it is not necessary to use a particular URL to identify the
service.
A PINT URL is used in two different ways within PINT requests: within the A PINT URL is used in two different ways within PINT requests: within
Request-URI, and within the To: and From: headers. Use within the the Request-URI, and within the To: and From: headers. Use within the
Request-URI requires clarification in order to ensure smooth interworking Request-URI requires clarification in order to ensure smooth
with the Telephone Network serviced by the PINT infrastructure, and this interworking with the Telephone Network serviced by the PINT
is covered next. infrastructure, and this is covered next.
3.5.5.1. PINT URLS within Request-URIs 3.5.5.1. PINT URLS within Request-URIs
There are some occasions when it may be useful to indicate service There are some occasions when it may be useful to indicate service
information within the URL in a standardized way: information within the URL in a standardized way:
a. it may not be possible to use SDP information to route the request if a. it may not be possible to use SDP information to route the request
it is encrypted; if it is encrypted;
b. it allows implementation that make use of I.N. "service indicators"; b. it allows implementation that make use of I.N. "service
c. It enables multiple competing PINT gateways to REGISTER with a single indicators";
"broker" server (proxy or redirect) (see section 6.3) c. It enables multiple competing PINT gateways to REGISTER with a
single "broker" server (proxy or redirect) (see section 6.3)
For these reasons, the following conventions for URLs are offered for use For these reasons, the following conventions for URLs are offered for
in PINT requests: use in PINT requests:
1. The user portion of a sip URL indicates the service to be requested. At 1. The user portion of a sip URL indicates the service to be requested.
present the following services are defined: At present the following services are defined:
R2C (for Request-to-Call) R2C (for Request-to-Call)
R2F (for Request-to-Fax) R2F (for Request-to-Fax)
R2HC (for Request-to-Hear-Content) R2HC (for Request-to-Hear-Content)
The user portions "R2C", "R2F", and "R2HC" are reserved for the PINT The user portions "R2C", "R2F", and "R2HC" are reserved for the PINT
milestone services. Other user portions MUST be used in case the requested milestone services. Other user portions MUST be used in case the
service is not one of the Milestone services. See section 6.2 for some requested service is not one of the Milestone services. See section 6.2
related considerations concerning registrations by competing PINT systems to for some related considerations concerning registrations by competing
a single PINT proxy server acting as a service broker. PINT systems to a single PINT proxy server acting as a service broker.
2. The host portion of a sip URL contains the domain name of the PINT 2. The host portion of a sip URL contains the domain name of the PINT
service provider. service provider.
3. A new url-parameter is defined to be "tsp" (for "telephone service 3. A new url-parameter is defined to be "tsp" (for "telephone service
provider"). This can be used to indicate the actual telephone network provider"). This can be used to indicate the actual telephone network
provider to be used to fulfil the PINT request. provider to be used to fulfil the PINT request.
Thus, for example:- Thus, for example:-
INVITE sip:R2C@pint.pintservice.com SIP/2.0 INVITE sip:R2C@pint.pintservice.com SIP/2.0
skipping to change at page 27, line 40 skipping to change at page 29, line 55
2. The host portion of a sip URL contains the domain name of the PINT 2. The host portion of a sip URL contains the domain name of the PINT
service provider. service provider.
3. A new url-parameter is defined to be "tsp" (for "telephone service 3. A new url-parameter is defined to be "tsp" (for "telephone service
provider"). This can be used to indicate the actual telephone network provider"). This can be used to indicate the actual telephone network
provider to be used to fulfil the PINT request. provider to be used to fulfil the PINT request.
Thus, for example:- Thus, for example:-
INVITE sip:R2C@pint.pintservice.com SIP/2.0 INVITE sip:R2C@pint.pintservice.com SIP/2.0
INVITE sip:R2F@pint.pintservice.com;tsp=telco.com SIP/2.0 INVITE sip:R2F@pint.pintservice.com;tsp=telco.com SIP/2.0
INVITE sip:R2HC@pint.mycom.com;tsp=pbx23.mycom.com SIP/2.0 INVITE sip:R2HC@pint.mycom.com;tsp=pbx23.mycom.com SIP/2.0
INVITE sip:13@pint.telco.com SIP/2.0 INVITE sip:13@pint.telco.com SIP/2.0
3.5.6. Telephony Network Parameters within PINT URLs 3.5.6. Telephony Network Parameters within PINT URLs
Any legal SIP URL can appear as a PINT URL within the Request-URI or To: Any legal SIP URL can appear as a PINT URL within the Request-URI or To:
header of a PINT request. But if the address is a telephone address, we header of a PINT request. But if the address is a telephone address, we
indicated in section 3.4.3 that it may be necessary to include more indicated in section 3.4.3 that it may be necessary to include more
information in order correctly to identify the remote telephone terminal or information in order correctly to identify the remote telephone terminal
service. PINT clients MAY include these attribute tags within PINT URLs if or service. PINT clients MAY include these attribute tags within PINT
they are necessary or a useful complement to the telephone number within the URLs if they are necessary or a useful complement to the telephone
SIP URL. These attribute tags MUST be included as URL parameters as defined number within the SIP URL. These attribute tags MUST be included as URL
in [1] (i.e. in the semi-colon separated manner). parameters as defined in [1] (i.e. in the semi-colon separated manner).
The following is an example of a PINT URL containing extra attribute tags: The following is an example of a PINT URL containing extra attribute
tags:
sip:+9725228808@pint.br.com;user=phone;require=Q763-plan;a=Q763-plan:4 sip:+9725228808@pint.br.com;user=phone;require=Q763-plan;a=Q763-plan:4
As we noted in section 3.4.3, these extra attribute parameters will not As we noted in section 3.4.3, these extra attribute parameters will not
normally be needed within a URL, because there is a great deal of context normally be needed within a URL, because there is a great deal of
available to the help the server interpret the phone number correctly. In context available to the help the server interpret the phone number
particular, there is the SIP URL within the To: header, and there is also correctly. In particular, there is the SIP URL within the To: header,
the Request-URI. In most cases this provides sufficient information for the and there is also the Request-URI. In most cases this provides
telephone network. sufficient information for the telephone network.
The SDP attributes defined in section 3 above will normally only be used The SDP attributes defined in section 3 above will normally only be used
when they are needed to supply necessary context to identify a telephone when they are needed to supply necessary context to identify a telephone
terminal. terminal.
3.5.7. REGISTER requests within PINT 3.5.7. REGISTER requests within PINT
A PINT gateway is a SIP user agent server. A User Agent Server uses the A PINT gateway is a SIP user agent server. A User Agent Server uses the
REGISTER request to tell a proxy or redirect server that it is available to REGISTER request to tell a proxy or redirect server that it is available
"receive calls" (i.e. to service requests). Thus a PINT Gateway registers to "receive calls" (i.e. to service requests). Thus a PINT Gateway
with a proxy or redirect server the service that is accessible via itself, registers with a proxy or redirect server the service that is accessible
whilst in SIP, a user is registering his/her presence at a particular SIP via itself, whilst in SIP, a user is registering his/her presence at a
Server. particular SIP Server.
There may be competing PINT servers that can offer the same PINT service There may be competing PINT servers that can offer the same PINT service
trying to register at a single PINT server. The PINT server might act as a trying to register at a single PINT server. The PINT server might act as
"broker" among the various PINT gateways that can fulfil a request. A a "broker" among the various PINT gateways that can fulfil a request. A
format for PINT URLs was specified in section 3.5.5 that enables independent format for PINT URLs was specified in section 3.5.5 that enables
PINT systems to REGISTER an offer to provide the same service. The registrar independent PINT systems to REGISTER an offer to provide the same
can apply its own mechanisms and policies to decide how to respond to service. The registrar can apply its own mechanisms and policies to
INVITEs from clients seeking service (See section 6.3 for some possible decide how to respond to INVITEs from clients seeking service (See
deployment options). There is no change between SIP and PINT REGISTER section 6.3 for some possible deployment options). There is no change
semantics or syntax. between SIP and PINT REGISTER semantics or syntax.
Of course, the information in the PINT URLs within the REGISTER request may Of course, the information in the PINT URLs within the REGISTER request
not be sufficient to completely define the service that a gateway can offer. may not be sufficient to completely define the service that a gateway
The use of SIP and SDP within PINT REGISTER requests to enable a gateway to can offer. The use of SIP and SDP within PINT REGISTER requests to
specify in more detail the services it can offer is the subject of future enable a gateway to specify in more detail the services it can offer is
study. the subject of future study.
3.5.8. BYE Requests in PINT 3.5.8. BYE Requests in PINT
The semantics of BYE requests within PINT requires some extra precision. One The semantics of BYE requests within PINT requires some extra precision.
issue concerns conferences that "cannot be left", and the other concerns One issue concerns conferences that "cannot be left", and the other
keeping call state after the BYE. concerns keeping call state after the BYE.
The BYE request [1] is normally used to indicate that the originating entity The BYE request [1] is normally used to indicate that the originating
no longer wishes to be involved in the specified call. The request entity no longer wishes to be involved in the specified call. The
terminates the call and the media session. Applying this model to PINT, if a request terminates the call and the media session. Applying this model
PINT client makes a request that results in invocation of a telephone call to PINT, if a PINT client makes a request that results in invocation of
from A to B, a BYE request from the client, if accepted, should result in a a telephone call from A to B, a BYE request from the client, if
termination of the phone call. accepted, should result in a termination of the phone call.
A question arises when the telephone call might not have even started at the One might expect this to be the case if the telephone call has not
time when the BYE request is received. For example, if a request to fax is started when the BYE request is received. For example, if a request to
sent with a t= line indicating that the fax is to be sent tomorrow at 4 AM, fax is sent with a t= line indicating that the fax is to be sent
the requestor might wish to cancel the request before the specified time. tomorrow at 4 AM, the requestor might wish to cancel the request before
the specified time.
Even if the call has yet to start, it may not be possible to terminate the However, even if the call has yet to start, it may not be possible to
media session on the telephone system side. For example, the fax call may terminate the media session on the telephone system side. For example,
be in progress when the BYE arrives, and perhaps it is just not possible to the fax call may be in progress when the BYE arrives, and perhaps it is
cancel the fax in session. Another possibility is that the entire just not possible to cancel the fax in session. Another possibility is
telephone-side service might be completed before the BYE is received. In the that the entire telephone-side service might be completed before the BYE
above Request-to-Fax example, the BYE might be sent the following morning, is received. In the above Request-to-Fax example, the BYE might be sent
and the entire fax has been sent before the BYE was received. It is too late the following morning, and the entire fax has been sent before the BYE
to send the BYE. was received. It is too late to send the BYE.
In the case where the telephone network cannot terminate the call, the In the case where the telephone network cannot terminate the call, the
server MUST return a "606 Not Acceptable" response to the BYE, along with a server MUST return a "606 Not Acceptable" response to the BYE, along
session description that indicates the telephone network session that is with a session description that indicates the telephone network session
causing the problem. that is causing the problem.
Thus, in PINT, a "Not Acceptable" response can be returned to INVITE or Thus, in PINT, a "Not Acceptable" response MAY be returned both to
BYE requests. It indicates that some aspect of the session description makes INVITE and BYE requests. It indicates that some aspect of the session
the request unacceptable. description makes the request unacceptable.
By allowing a server to return a "Not Acceptable" response to BYE requests, By allowing a server to return a "Not Acceptable" response to BYE
we are not changing its semantics, just enlarging its use. requests, we are not changing its semantics, just enlarging its use.
A combination of Warning: headers and i= lines within the session A combination of Warning: headers and i= lines within the session
description can be used to indicate the precise nature of the problem. description can be used to indicate the precise nature of the problem.
Example: Example:
SIP/2.0 606 Not Acceptable SIP/2.0 606 Not Acceptable
From: ... From: ...
To: ....... To: .......
..... .....
Warning: 399 pint.mycom.com Fax in progress, service cannot be aborted Warning: 399 pint.mycom.com Fax in progress, service cannot be
aborted
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: ... Content-Length: ...
v=0 v=0
... ...
... ...
i=3 of 5 pages sent OK i=3 of 5 pages sent OK
c=TN RFC2543 +12014064090 c=TN RFC2543 +12014064090
m=image 1 fax tif m=image 1 fax tif
a=fmtp:tif uri:http://tifsRus.com/yyyyyy.tif a=fmtp:tif uri:http://tifsRus.com/yyyyyy.tif
Note that the server may return an updated session description within a Note that the server might return an updated session description within
successful response to a BYE as well. This can be used, for example, to a successful response to a BYE as well. This can be used, for example,
indicate the actual start times and stop times of the telephone session, or to indicate the actual start times and stop times of the telephone
how many pages were sent in the fax transmission. session, or how many pages were sent in the fax transmission.
The second issue concerns how long must a server keep call state after The second issue concerns how long must a server keep call state after
receiving a BYE. A question arises because other clients might still wish to receiving a BYE. A question arises because other clients might still
send queries about the telephone network session that was the subject of wish to send queries about the telephone network session that was the
the PINT transaction. Ordinary SIP semantics have three important subject of the PINT transaction. Ordinary SIP semantics have three
implications for this situation: important implications for this situation:
1. A BYE indicates that the requesting client will clear out all call state 1. A BYE indicates that the requesting client will clear out all call
as soon as it receives a successful response. A client SHOULD NOT send a state as soon as it receives a successful response. A client SHOULD NOT
SUBSCRIBE request after it has sent a BYE. send a SUBSCRIBE request after it has sent a BYE.
2. A server may return an Expires: header within a successful response to a 2. A server may return an Expires: header within a successful response
BYE request. This indicates for how long the server will retain session to a BYE request. This indicates for how long the server will retain
state about the telephone network session. At any point during this time, a session state about the telephone network session. At any point during
client may send a SUBSCRIBE request to the server to learn about the session this time, a client may send a SUBSCRIBE request to the server to learn
state. about the session state (although as explained in the previous paragraph,
a client that has sent a BYE will not normally send a SUBSCRIBE).
3. When engaged in a SUBSCRIBE/NOTIFY monitoring session, PINT servers that 3. When engaged in a SUBSCRIBE/NOTIFY monitoring session, PINT servers
send BYE to a URL listed in the Contact: header of a client request SHOULD that send UNSUBSCRIBE to a URL listed in the Contact: header of a client
not clear session state until after the successful response to the BYE is request SHOULD not clear session state until after the successful
received. For example, it may be that the requesting client host is turned response to the UNSUBSCRIBE message is received. For example, it may be
off when the telephone service is executed (and is therefore not available that the requesting client host is turned off (or in a low power mode)
at the location previously specified in the Contact: attribute) to receive when the telephone service is executed (and is therefore not available
the PINT server's BYE. Of course, it is possible that the BYE request will at the location previously specified in the Contact: attribute) to
simply time out. receive the PINT server's UNSUBSCRIBE. Of course, it is possible that
the UNSUBSCRIBE request will simply time out.
4. Examples of PINT Requests and Responses 4. Examples of PINT Requests and Responses
4.1. A request to a call centre from an anonymous user to receive a phone 4.1. A request to a call center from an anonymous user to receive a
call. phone call.
C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0 C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:anon-1827631872@chinet.net From: sip:anon-1827631872@chinet.net
To: sip:+1-201-456-7890@iron.org;user=phone To: sip:+1-201-456-7890@iron.org;user=phone
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4711 INVITE CSeq: 4711 INVITE
Subject: Sale on Ironing Boards Subject: Sale on Ironing Boards
Content-type: application/sdp Content-type: application/sdp
Content-Length: 174 Content-Length: 174
skipping to change at page 30, line 38 skipping to change at page 33, line 4
C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0 C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:anon-1827631872@chinet.net From: sip:anon-1827631872@chinet.net
To: sip:+1-201-456-7890@iron.org;user=phone To: sip:+1-201-456-7890@iron.org;user=phone
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4711 INVITE CSeq: 4711 INVITE
Subject: Sale on Ironing Boards Subject: Sale on Ironing Boards
Content-type: application/sdp Content-type: application/sdp
Content-Length: 174 Content-Length: 174
v=0 v=0
o=- 2353687637 2353687637 IN IP4 128.3.4.5 o=- 2353687637 2353687637 IN IP4 128.3.4.5
s=R2C s=R2C
i=Ironing Board Promotion i=Ironing Board Promotion
e=anon-1827631872@chinet.net e=anon-1827631872@chinet.net
t=2353687637 0 t=2353687637 0
m=audio 1 voice - m=audio 1 voice -
c=TN RFC2543 +1-201-406-4090 c=TN RFC2543 +1-201-406-4090
In this example, the context that is required to interpret the To: address In this example, the context that is required to interpret the To:
as a telephone number is not given explicitly; it is implicitly known to the address as a telephone number is not given explicitly; it is implicitly
R2C@pint.mailorder.com server. But the telephone of the person who wishes to known to the R2C@pint.mailorder.com server. But the telephone of the
receive the call is explicitly identified as an internationally significant person who wishes to receive the call is explicitly identified as an
E.164 number that falls within the North American numbering plan internationally significant E.164 number that falls within the North
(because of the "+1" within the c= line). American numbering plan (because of the "+1" within the c= line).
4.2. A request from a non anonymous customer (John Jones) to receive a phone 4.2. A request from a non anonymous customer (John Jones) to receive a
call from a particular sales agent (Mary James) concerning the defective phone call from a particular sales agent (Mary James) concerning the
ironing board that was purchased defective ironing board that was purchased
C->S: INVITE sip:marketing@pint.mailorder.com SIP/2.0 C->S: INVITE sip:marketing@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:mary.james@mailorder.com To: sip:mary.james@mailorder.com
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4712 INVITE CSeq: 4712 INVITE
Subject: Defective Ironing Board - want refund Subject: Defective Ironing Board - want refund
Content-type: application/sdp Content-type: application/sdp
Content-Length: 150 Content-Length: 150
v=0 v=0
o=- 2353687640 2353687640 IN IP4 128.3.4.5 o=- 2353687640 2353687640 IN IP4 128.3.4.5
s=marketing s=marketing
e=john.jones.3@chinet.net e=john.jones.3@chinet.net
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
t=2353687640 0 t=2353687640 0
m=audio 1 voice - m=audio 1 voice -
The To: line might include the Mary James's phone number instead of a The To: line might include the Mary James's phone number instead of a
email-like address. An implementation that cannot accept email-like URLs in email-like address. An implementation that cannot accept email-like URLs
the "To:" header must fail the request with a 606 Not Acceptable. in the "To:" header must decline the request with a 606 Not Acceptable.
Note that the sending PINT client "knows" that the PINT Gateway contacted Note that the sending PINT client "knows" that the PINT Gateway
with the "marketing@pint.mailorder.com" Request-URI is capable of processing contacted with the "marketing@pint.mailorder.com" Request-URI is capable
the client request as expected. (see 3.5.5.1 for a discussion on this). of processing the client request as expected. (see 3.5.5.1 for a
discussion on this).
Note also that such a telephone call service could be implemented on the Note also that such a telephone call service could be implemented on the
phone side with different details. For example, it might be that first the phone side with different details. For example, it might be that first
agent's phone rings, and then the customer's phone rings, or it might be the agent's phone rings, and then the customer's phone rings, or it
that first the customer's phone rings and he hears silly music until the might be that first the customer's phone rings and he hears silly music
agent comes on line. If necessary, such service parameter details might be until the agent comes on line. If necessary, such service parameter
indicated in "a=" attribute lines within the session description. The details might be indicated in "a=" attribute lines within the session
specification of such attribute lines for service consistency is beyond the description. The specification of such attribute lines for service
scope of the PINT 1.0 specifications. consistency is beyond the scope of the PINT 1.0 specifications.
4.3. A request from the same user to get a fax back on how to assemble the 4.3. A request from the same user to get a fax back on how to assemble
Ironing Board the Ironing Board
C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:1-800-3292225K@steam.edu;user=phone;phone-context=+1 To: sip:1-800-3292225K@steam.edu;user=phone;phone-context=+1
Call-ID: 19971205T234505.66.79@chinet.net Call-ID: 19971205T234505.66.79@chinet.net
CSeq: 4713 INVITE CSeq: 4713 INVITE
Content-type: application/sdp Content-type: application/sdp
Content-Length: 218 Content-Length: 218
skipping to change at page 32, line 8 skipping to change at page 34, line 29
s=faxback s=faxback
e=john.jones.3@chinet.net e=john.jones.3@chinet.net
t=2353687660 0 t=2353687660 0
m=application 1 fax URI m=application 1 fax URI
c=TN RFC2543 1-201-406-4091 c=TN RFC2543 1-201-406-4091
a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html
In this example, the fax to be sent is stored on some local server In this example, the fax to be sent is stored on some local server
(localstore), whose name may be only resolvable, or that may only be (localstore), whose name may be only resolvable, or that may only be
reachable, from within the IP network on which the PINT server sits. The reachable, from within the IP network on which the PINT server sits. The
phone number to be dialled is a "local phone number" as well. There is no phone number to be dialled is a "local phone number" as well. There is
"phone-context" attribute, so the context (in this case, for which nation no "phone-context" attribute, so the context (in this case, for which
the number is "nationally significant") must be supplied by the nation the number is "nationally significant") must be supplied by the
faxback@pint.mailorder.com PINT server. faxback@pint.mailorder.com PINT server.
If the server that receives does not understand the number, it should fail If the server that receives it does not understand the number, it SHOULD
the request with and include a "Network Address Not Understood" warning. decline the request and include a "Network Address Not Understood" warning.
Note that no "require" attribute was used here, since it is very likely Note that no "require" attribute was used here, since it is very likely
that the request can be serviced even by a server that does not support that the request can be serviced even by a server that does not support
the "require" attribute. the "require" attribute.
4.4. A request from same user to have that same information read out over 4.4. A request from same user to have that same information read out
the phone over the phone
C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1 To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1
Call-ID: 19971205T234505.66.79@chinet.net Call-ID: 19971205T234505.66.79@chinet.net
CSeq: 4713 INVITE CSeq: 4713 INVITE
Content-type: application/sdp Content-type: application/sdp
Content-Length: 220 Content-Length: 220
v=0 v=0
skipping to change at page 32, line 47 skipping to change at page 35, line 13
a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html
4.5. A request to send an included text page to a friend's pager. 4.5. A request to send an included text page to a friend's pager.
In this example, the text to be paged out is included in the request. In this example, the text to be paged out is included in the request.
C->S: INVITE sip:R2F@pint.pager.com SIP/2.0 C->S: INVITE sip:R2F@pint.pager.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:scott.petrack@chinet.net From: sip:scott.petrack@chinet.net
To: sip:R2F@pint.pager.com To: sip:R2F@pint.pager.com
Call-ID: 19974505.66.79@chinet.net Call-ID: 19974505.66.79@chinet.net
CSeq: 4714 INVITE CSeq: 4714 INVITE
Content-Type: multipart/mixed; boundary=--next Content-Type: multipart/related; boundary=--next
----next ----next
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: 236 Content-Length: 236
v=0 v=0
o=- 2353687680 2353687680 IN IP4 128.3.4.5 o=- 2353687680 2353687680 IN IP4 128.3.4.5
s=R2F s=R2F
e=scott.petrack@chinet.net e=scott.petrack@chinet.net
t=2353687680 0 t=2353687680 0
m=text 1 pager plain m=text 1 pager plain
skipping to change at page 33, line 34 skipping to change at page 36, line 5
v=0 v=0
o=- 2353687700 2353687700 IN IP4 128.3.4.5 o=- 2353687700 2353687700 IN IP4 128.3.4.5
s=faxserver s=faxserver
e=scott.petrack@chinet.net e=scott.petrack@chinet.net
t=2353687700 0 t=2353687700 0
m=image 1 fax tif gif m=image 1 fax tif gif
c= TN RFC2543 +972-9-956-1867 c= TN RFC2543 +972-9-956-1867
a=fmtp:tif uri:http://petrack/images/tif/picture1.tif a=fmtp:tif uri:http://petrack/images/tif/picture1.tif
a=fmtp:gif uri:http://petrack/images/gif/picture1.gif a=fmtp:gif uri:http://petrack/images/gif/picture1.gif
The image is available as tif or as gif. The tif is the preferred format. The image is available as tif or as gif. The tif is the preferred
Note that the http server where the pictures reside is local, and the PINT format. Note that the http server where the pictures reside is local,
server is also local (because it can resolve machine name "petrack") and the PINT server is also local (because it can resolve machine name
"petrack")
4.7. A request to read out over the phone two pieces of content in sequence. 4.7. A request to read out over the phone two pieces of content in
First some included text is read out by text-to-speech. Then some text that sequence.
is stored at some URI on the internet is read out. First some included text is read out by text-to-speech. Then some text
that is stored at some URI on the internet is read out.
C->S: INVITE sip:R2HC@pint.acme.com SIP/2.0 C->S: INVITE sip:R2HC@pint.acme.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:scott.petrack@chinet.net From: sip:scott.petrack@chinet.net
To: sip:R2HC@pint.acme.com To: sip:R2HC@pint.acme.com
Call-ID: 19974505.66.79@chinet.net Call-ID: 19974505.66.79@chinet.net
CSeq: 4716 INVITE CSeq: 4716 INVITE
Content-Type: multipart/mixed; boundary=next Content-Type: multipart/related; boundary=next
--next --next
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: 316 Content-Length: 316
v=0 v=0
o=- 2353687720 2353687720 IN IP4 128.3.4.5 o=- 2353687720 2353687720 IN IP4 128.3.4.5
s=R2HC s=R2HC
e=scott.petrack@chinet.net e=scott.petrack@chinet.net
c= TN RFC2543 +1-201-406-4091 c= TN RFC2543 +1-201-406-4091
t=2353687720 0 t=2353687720 0
m=text 1 voice plain m=text 1 voice plain
a=fmtp:plain spr:2@53655768 a=fmtp:plain spr:2@53655768
m=text 1 voice plain m=text 1 voice plain
a=fmtp:plain uri:http://www.your.com/texts/stuff.doc a=fmtp:plain uri:http://www.your.com/texts/stuff.doc
--next --next
Content-Type: text/plain Content-Type: text/plain
Content-ID: 2@53655768 Content-ID: 2@53655768
skipping to change at page 35, line 14 skipping to change at page 37, line 42
4.10.Sending a set of information in response to an enquiry 4.10.Sending a set of information in response to an enquiry
INVITE sip:R2FB@pint.bt.co.uk SIP/2.0 INVITE sip:R2FB@pint.bt.co.uk SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44 To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44
From: sip:colin.masterton@sales.hh.bt.co.uk From: sip:colin.masterton@sales.hh.bt.co.uk
Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk
CSeq: 1147 INVITE CSeq: 1147 INVITE
Subject: Price Info, as requested Subject: Price Info, as requested
Content-Type: multipart/mixed; boundary=next Content-Type: multipart/related; boundary=next
--next --next
Content-type: application/sdp Content-type: application/sdp
Content-Length: 325 Content-Length: 325
v=0 v=0
o=- 2353687780 2353687780 IN IP4 128.3.4.5 o=- 2353687780 2353687780 IN IP4 128.3.4.5
s=R2FB s=R2FB
i=Your documents i=Your documents
e=colin.masterton@sales.hh.bt.co.uk e=colin.masterton@sales.hh.bt.co.uk
t=2353687780 0 t=2353687780 0
skipping to change at page 35, line 29 skipping to change at page 38, line 4
v=0 v=0
o=- 2353687780 2353687780 IN IP4 128.3.4.5 o=- 2353687780 2353687780 IN IP4 128.3.4.5
s=R2FB s=R2FB
i=Your documents i=Your documents
e=colin.masterton@sales.hh.bt.co.uk e=colin.masterton@sales.hh.bt.co.uk
t=2353687780 0 t=2353687780 0
m=application 1 fax octet-stream m=application 1 fax octet-stream
c=TN RFC2543 +44-1794-8331010 c=TN RFC2543 +44-1794-8331010
a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr: a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr:
spr:2@53655768 spr:2@53655768
--next --next
Content-Type: text/plain Content-Type: text/plain
Content-ID: 2@53655768 Content-ID: 2@53655768
Content-Length: 352 Content-Length: 352
Dear Sir, Dear Sir,
Thank you for your enquiry. I have checked availability in your Thank you for your enquiry. I have checked availability in your
area, and we can provide service to your cottage. I enclose a quote area, and we can provide service to your cottage. I enclose a
for the costs of installation, together with the ongoing rental quote for the costs of installation, together with the ongoing
costs for the line. If you want to proceed with this, please quote rental costs for the line. If you want to proceed with this,
job reference isdn/hh/123.45.9901. please quote job reference isdn/hh/123.45.9901.
Yours Sincerely, Yours Sincerely,
Colin Masterton Colin Masterton
--next-- --next--
Note that the "implicit" faxback content is given by an EMPTY opaque Note that the "implicit" faxback content is given by an EMPTY opaque
reference in the middle of the fmtp line in this example. reference in the middle of the fmtp line in this example.
4.11.Sportsline "headlines" message sent to your phone/pager/fax 4.11.Sportsline "headlines" message sent to your phone/pager/fax
(i) phone (i) phone
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1 To:
sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1
From: sip:fred.football.fan@skynet.com From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4721 INVITE CSeq: 4721 INVITE
Subject: Wonderful World Of Sports NFL Final Scores Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp Content-type: application/sdp
Content-Length: 220 Content-Length: 220
v=0 v=0
o=- 2353687800 2353687800 IN IP4 128.3.4.5 o=- 2353687800 2353687800 IN IP4 128.3.4.5
s=R2FB s=R2FB
i=NFL Final Scores i=NFL Final Scores
e=fred.football.fan@skynet.com e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331013 c=TN RFC2543 +44-1794-8331013
t=2353687800 0 t=2353687800 0
m=audio 1 voice x-pay m=audio 1 voice x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature> a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
skipping to change at page 36, line 17 skipping to change at page 38, line 48
i=NFL Final Scores i=NFL Final Scores
e=fred.football.fan@skynet.com e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331013 c=TN RFC2543 +44-1794-8331013
t=2353687800 0 t=2353687800 0
m=audio 1 voice x-pay m=audio 1 voice x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature> a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
(ii) fax (ii) fax
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1 To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;
phone-context=+1
From: sip:fred.football.fan@skynet.com From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4722 INVITE CSeq: 4722 INVITE
Subject: Wonderful World Of Sports NFL Final Scores Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp Content-type: application/sdp
Content-Length: 217 Content-Length: 217
v=0 v=0
o=- 2353687820 2353687820 IN IP4 128.3.4.5 o=- 2353687820 2353687820 IN IP4 128.3.4.5
s=R2FB s=R2FB
i=NFL Final Scores i=NFL Final Scores
e=fred.football.fan@skynet.com e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331010 c=TN RFC2543 +44-1794-8331010
t=2353687820 0 t=2353687820 0
m=text 1 fax x-pay m=text 1 fax x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature> a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
skipping to change at page 36, line 38 skipping to change at page 39, line 17
i=NFL Final Scores i=NFL Final Scores
e=fred.football.fan@skynet.com e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331010 c=TN RFC2543 +44-1794-8331010
t=2353687820 0 t=2353687820 0
m=text 1 fax x-pay m=text 1 fax x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature> a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
(iii) pager (iii) pager
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1 To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;
phone-context=+1
From: sip:fred.football.fan@skynet.com From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4723 INVITE CSeq: 4723 INVITE
Subject: Wonderful World Of Sports NFL Final Scores Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp Content-type: application/sdp
Content-Length: 219 Content-Length: 219
v=0 v=0
o=- 2353687840 2353687840 IN IP4 128.3.4.5 o=- 2353687840 2353687840 IN IP4 128.3.4.5
s=R2FB s=R2FB
skipping to change at page 37, line 27 skipping to change at page 40, line 14
v=0 v=0
o=- 2353687860 2353687860 IN IP4 128.3.4.5 o=- 2353687860 2353687860 IN IP4 128.3.4.5
s=BillsRUs s=BillsRUs
i=Joe Pendleton's Phone Bill i=Joe Pendleton's Phone Bill
e=agent.mulder@fbi.gov e=agent.mulder@fbi.gov
c=TN RFC2543 +1-202-833-1010 c=TN RFC2543 +1-202-833-1010
t=2353687860 0 t=2353687860 0
m=text 1 fax x-files-id m=text 1 fax x-files-id
a=fmtp:x-files-id opr:fbi.gov/jdcn-123@45:3des;base64,<signature> a=fmtp:x-files-id opr:fbi.gov/jdcn-123@45:3des;base64,<signature>
Note: in this case the opaque reference is data used to convince the Note: in this case the opaque reference is a collection of data used to
Executive System that the requester has the right to get this information, convince the Executive System that the requester has the right to get
rather than selecting the particular content (the A party in the To: field this information, rather than selecting the particular content (the A
of the SIP "wrapper" does that alone). party in the To: field of the SIP "wrapper" does that alone).
5. Security Considerations 5. Security Considerations
5.1. Basic Principles for PINT Use 5.1. Basic Principles for PINT Use
A PINT Gateway, and the Executive System(s) with which that Gateway is A PINT Gateway, and the Executive System(s) with which that Gateway is
associated, exist to provide service to PINT Requestors. The aim of the PINT associated, exist to provide service to PINT Requestors. The aim of the
protocol is to pass requests from those users on to a PINT Gateway so an PINT protocol is to pass requests from those users on to a PINT Gateway
associated Executive System can service those requests. so an associated Executive System can service those requests.
5.1.1. Responsibility for service requests 5.1.1. Responsibility for service requests
The facility of making a GSTN-based call to numbers specified in the PINT
request, however, comes with some risks. The request can specify an incorrect
telephone of fax number. It is also possible that the Requestor has purposely
entered the telephone number of an innocent third party. Finally, the request
may have been intercepted on its way through any intervening PINT or SIP
infrastructure, and the request may have been altered.
In any of these cases, the result may be that a call is placed incorrectly. The facility of making a GSTN-based call to numbers specified in the
Where there is intent or negligence, this may be construed as harrasment of PINT request, however, comes with some risks. The request can specify an
the person incorrectly receiving the call. Whilst the regulatory framework for incorrect telephone of fax number. It is also possible that the
misuse of Internet connections differs throughout the world and is not always Requestor has purposely entered the telephone number of an innocent
mature, the rules under which GSTN calls are made are much more settled. third party. Finally, the request may have been intercepted on its way
Someone may be liable for mistaken or incorrect calls. through any intervening PINT or SIP infrastructure, and the request may
have been altered.
Understandably, the GSTN Operators would prefer that this someone is not them, In any of these cases, the result may be that a call is placed
so they will need to ensure that any PINT Gateway and Executive System incorrectly. Where there is intent or negligence, this may be construed
combination does not generate incorrect calls through some error in the as harrasment of the person incorrectly receiving the call. Whilst the
Gateway or Executive system implementation or GSTN-internal communications regulatory framework for misuse of Internet connections differs
fault. Equally, it is important that the Operator can show that they act only throughout the world and is not always mature, the rules under which
on requests that they have good reason to believe are correct. This means that GSTN calls are made are much more settled. Someone may be liable for
the Gateway must not pass on requests unless it is sure that they have not mistaken or incorrect calls.
been corrupted in transit from the Requestor.
If a request can be shown to have come from a particular Requestor and to have Understandably, the GSTN Operators would prefer that this someone is not
been acted on in good faith by the PINT service provider, then responsibility them, so they will need to ensure that any PINT Gateway and Executive
for making requests may well fall to the Requestor rather than the Operator System combination does not generate incorrect calls through some error
who executed these requests. in the Gateway or Executive system implementation or GSTN-internal
communications fault. Equally, it is important that the Operator can
show that they act only on requests that they have good reason to
believe are correct. This means that the Gateway must not pass on
requests unless it is sure that they have not been corrupted in transit
from the Requestor.
Finally, it may be important for the PINT service provider to be able to show If a request can be shown to have come from a particular Requestor and
that they act only on requests for which they have some degree of assurance of to have been acted on in good faith by the PINT service provider, then
origin. In many jurisdictions, it is a requirement on GSTN Operators that they responsibility for making requests may well fall to the Requestor rather
place calls only when they can, if required, identify the parties to the call than the Operator who executed these requests.
(such as when required to carry out a Malicious Call Trace). It is at least
likely that the provider of PINT services will have a similar responsibility
placed on them.
It follows that the PINT service provider may require that the identity of the Finally, it may be important for the PINT service provider to be able to
Requestor be confirmed. If such confirmation is not available, then they may show that they act only on requests for which they have some degree of
be forced (or choose) not to provide service. This identification will require assurance of origin. In many jurisdictions, it is a requirement on GSTN
personal authentication of the Requesting User. Operators that they place calls only when they can, if required,
identify the parties to the call (such as when required to carry out a
Malicious Call Trace). It is at least likely that the provider of PINT
services will have a similar responsibility placed on them.
It follows that the PINT service provider may require that the identity
of the Requestor be confirmed. If such confirmation is not available,
then they may be forced (or choose) not to provide service. This
identification may require personal authentication of the Requesting
User.
5.1.2. Authority to make requests 5.1.2. Authority to make requests
Where GSTN resources are used to provide a PINT service, it is at least Where GSTN resources are used to provide a PINT service, it is at least
possible that someone will have to pay for it. This person may not be the possible that someone will have to pay for it. This person may not be
Requestor, as, for example, in the case of existing GSTN split-charging the Requestor, as, for example, in the case of existing GSTN
services like free phone in which the recipient of a call rather than the split-charging services like free phone in which the recipient of a call
originator is responsible for the call cost. rather than the originator is responsible for the call cost.
This is not, of course, the only possibility; for example, PINT service may be This is not, of course, the only possibility; for example, PINT service
provided on a subscription basis, and there are a number of other models. may be provided on a subscription basis, and there are a number of other
However, whichever model is chosen, there may be a requirement that the models. However, whichever model is chosen, there may be a requirement
authority of a Requestor to make a PINT request is confirmed. that the authority of a Requestor to make a PINT request is confirmed.
If such confirmation is not available, then, again, the PINT Gateway and If such confirmation is not available, then, again, the PINT Gateway and
associated Executive System may choose not to provide service. associated Executive System may choose not to provide service.
5.1.3. Privacy 5.1.3. Privacy
Even if the identity of the Requesting User and the Authority under which they Even if the identity of the Requesting User and the Authority under
make their request is known, there remains the possibility that the request is which they make their request is known, there remains the possibility
either corrupted, maliciously altered, or even replaced whilst in transit that the request is either corrupted, maliciously altered, or even
between the Requestor and the PINT Gateway. replaced whilst in transit between the Requestor and the PINT Gateway.
Similarly, information on the Authority under which a request is made may well Similarly, information on the Authority under which a request is made
be carried within that request. This can be sensitive information, as an may well be carried within that request. This can be sensitive
eavesdropper might steal this and use it within their own requests. Such information, as an eavesdropper might steal this and use it within their
authority should be treated as if it were financial information (such as a own requests. Such authority SHOULD be treated as if it were financial
credit card number or PIN). information (such as a credit card number or PIN).
The data authorizing a Requesting User to make a PINT request should be known The data authorizing a Requesting User to make a PINT request should be
only to them and the service provider. However, this information may be in a known only to them and the service provider. However, this information
form that does not match the schemes normally used within the Internet. For may be in a form that does not match the schemes normally used within
example, X.509 certificates[14] are commonly used for secured transactions on the Internet. For example, X.509 certificates[14] are commonly used for
the Internet both in the IP Security Architecture[12] and in the TLS secured transactions on the Internet both in the IP Security
protocol[13], but the GSTN provider may only store an account code and PIN Architecture[12] and in the TLS protocol[13], but the GSTN provider may
(i.e. a fixed string of numbers). only store an account code and PIN (i.e. a fixed string of numbers).
A Requesting User has a reasonable expectation that their requests for service A Requesting User has a reasonable expectation that their requests for
are confidential. For some PINT services, no content data is carried over the service are confidential. For some PINT services, no content is carried
Internet; however, the telephone or fax numbers of the parties to a resulting over the Internet; however, the telephone or fax numbers of the parties
service calls may be considered sensitive. As a result, it is likely that the to a resulting service calls may be considered sensitive. As a result,
Requestor (and their PINT service provider) will require that any request that it is likely that the Requestor (and their PINT service provider) will
is sent across the Internet be protected against eavesdroppers; in short, the require that any request that is sent across the Internet be protected
requests should to be encrypted. against eavesdroppers; in short, the requests SHOULD to be encrypted.
5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY
Some special considerations relate to monitoring sessions using the SUBSCRIBE Some special considerations relate to monitoring sessions using the
and NOTIFY messages. The SUBSCRIBE message that is used to register an SUBSCRIBE and NOTIFY messages. The SUBSCRIBE message that is used to
interest in the disposition of a PINT service transaction uses the original register an interest in the disposition of a PINT service transaction
Session Description carried in the related INVITE message. This current uses the original Session Description carried in the related INVITE
specification does not restrict the source of such a SUBSCRIBE message, so it message. This current specification does not restrict the source of such
is possible for an eavesdropper to capture an unprotected session description a SUBSCRIBE message, so it is possible for an eavesdropper to capture an
and use this in a subsequent SUBSCRIBE request. In this way it is possible to unprotected session description and use this in a subsequent SUBSCRIBE
find out details on that transaction that may well be considered sensitive. request. In this way it is possible to find out details on that
transaction that may well be considered sensitive.
The initial solution to this risk is to recommend that a session description The initial solution to this risk is to recommend that a session
that may be used within a subsequent SUBSCRIBE message SHOULD be protected. description that may be used within a subsequent SUBSCRIBE message
SHOULD be protected.
However, there is a further risk; if the origin-field used is "guessable" then However, there is a further risk; if the origin-field used is
it might be possible for an attacker to reconstruct the session description "guessable" then it might be possible for an attacker to reconstruct the
and use this reconstruction within a SUBSCRIBE message. session description and use this reconstruction within a SUBSCRIBE
message.
SDP (see section 6 of [2], "o=" field) does not specify the mechansim used to SDP (see section 6 of [2], "o=" field) does not specify the mechansim
generate the sess-id field, and suggests that a method based on timestamps used to generate the sess-id field, and suggests that a method based on
produced by Network Time Protocol [16] can be used. This is sufficient to timestamps produced by Network Time Protocol [16] can be used. This is
guarantee uniqueness, but may allow the value to be guessed, particularly if sufficient to guarantee uniqueness, but may allow the value to be
other unprotected requests from the same originator are available. guessed, particularly if other unprotected requests from the same
originator are available.
Thus, to ensure that the session identifier is not guessable the techniques Thus, to ensure that the session identifier is not guessable the
described in section 6.3 of [17] can be used when generating the origin-field techniques described in section 6.3 of [17] can be used when generating
for a session description to be used inside a PINT INVITE message. If all the origin-field for a session description to be used inside a PINT
requests from (and responses to) a particular PINT requesting entity are INVITE message. If all requests from (and responses to) a particular
protected, then this is not needed. Where such a situation is not assured, AND PINT requesting entity are protected, then this is not needed. Where
where session monitoring is supported, then a method by which an origin-field such a situation is not assured, AND where session monitoring is
within a session description is not guessable SHOULD be used. supported, then a method by which an origin-field within a session
description is not guessable SHOULD be used.
5.2. Registration Procedures 5.2. Registration Procedures
Any number of PINT Gateways may register to provide the same service; this is Any number of PINT Gateways may register to provide the same service;
indicated by the Gateways specifying the same "userinfo" part in the To: this is indicated by the Gateways specifying the same "userinfo" part in
header field of the REGISTER request. Whilst such ambiguity would be unlikely the To: header field of the REGISTER request. Whilst such ambiguity
to occur with the scenarios covered by "core" SIP, it is very likely for PINT; would be unlikely to occur with the scenarios covered by "core" SIP, it
there could be any number of service providers all willing to support a is very likely for PINT; there could be any number of service providers
"Request-To-Fax" service, for example. Unless a request specifies the Gateway all willing to support a "Request-To-Fax" service, for example.
name explicitly, an intervening Proxy that acts on a registration database to
which several Gateways have all registered is in a position to select from the Unless a request specifies the Gateway name explicitly, an intervening
registrands using whatever algorithm it chooses; in principle, any Gateway Proxy that acts on a registration database to which several Gateways
that has registered as "R2F" would be appropriate. have all registered is in a position to select from the registrands
using whatever algorithm it chooses; in principle, any Gateway that has
registered as "R2F" would be appropriate.
However, this opens up an avenue for attack, and this is one in which a However, this opens up an avenue for attack, and this is one in which a
"rogue" Gateway operator stands to make a significant gain. The standard SIP "rogue" Gateway operator stands to make a significant gain. The standard
procedure for releasing a registration is to send a REGISTER request with a SIP procedure for releasing a registration is to send a REGISTER request
Contact field having a wildcard value and an expires parameter with a value of with a Contact field having a wildcard value and an expires parameter
0. It is important that a PINT Registrar uses authentication of the with a value of 0. It is important that a PINT Registrar uses
Registrand, as otherwise one PINT service provider would be able to "spoof" authentication of the Registrand, as otherwise one PINT service provider
another and remove their registration. As this would stop the Proxy passing would be able to "spoof" another and remove their registration. As this
any requests to that provider, this would both increase requests being sent to would stop the Proxy passing any requests to that provider, this would
the rogue and stop requests going to the victim. both increase requests being sent to the rogue and stop requests going
to the victim.
Another variant on this attack would be to register a Gateway using a name Another variant on this attack would be to register a Gateway using a
that has been registered by another provider; thus a rogue Operator might name that has been registered by another provider; thus a rogue Operator
register its Gateway as "R2C@pint.att.com", thereby hijacking requests. might register its Gateway as "R2C@pint.att.com", thereby hijacking
requests.
The solution is the same; all registrations by PINT Gateways MUST be The solution is the same; all registrations by PINT Gateways MUST be
authenticated; this includes both new or apparent replacement registrations, authenticated; this includes both new or apparent replacement
and any cancellation of current registrations. This recommendation is also registrations, and any cancellation of current registrations. This
made in the SIP specification, but for the correct operation of PINT, it is recommendation is also made in the SIP specification, but for the
very important indeed. correct operation of PINT, it is very important indeed.
5.3. Security mechanisms and implications on PINT service 5.3. Security mechanisms and implications on PINT service
PINT is a set of extensions to SIP[1] and SDP[2], and will use the security PINT is a set of extensions to SIP[1] and SDP[2], and will use the
procedures described in SIP. There are several implications of this, and these security procedures described in SIP. There are several implications of
are covered here. this, and these are covered here.
For several of the PINT services, the To: header field of SIP is used to For several of the PINT services, the To: header field of SIP is used to
identify one of the parties to the resulting service call. The PINT identify one of the parties to the resulting service call. The PINT
Request-To-Call service is an example. As mentioned in the SIP specification, Request-To-Call service is an example. As mentioned in the SIP
this field is used to route SIP messages through an infrastructure of Redirect specification, this field is used to route SIP messages through an
and Proxy server between the corresponding User Agent Servers, and so cannot infrastructure of Redirect and Proxy server between the corresponding
be encrypted. This means that, although the majority of personal or sensitive User Agent Servers, and so cannot be encrypted. This means that,
data can be protected whilst in transit, the telephone (or fax) number of one although the majority of personal or sensitive data can be protected
of the parties to a PINT service call cannot, and will be "visible" to any whilst in transit, the telephone (or fax) number of one of the parties
interception. For the PINT milestone services this may be acceptable, since to a PINT service call cannot, and will be "visible" to any
the caller named in the To: service is typically a "well known" provider interception. For the PINT milestone services this may be acceptable,
address, such as a Call Centre. since the caller named in the To: service is typically a "well known"
provider address, such as a Call Center.
Another aspect of this is that, even if the Requesting User does not consider Another aspect of this is that, even if the Requesting User does not
the telephone or fax numbers of the parties to a PINT service to be private, consider the telephone or fax numbers of the parties to a PINT service
those parties might. Where PINT servers have reason to believe this might be to be private, those parties might. Where PINT servers have reason to
the case they SHOULD encrypt the request, even if the Requestor has not done believe this might be the case they SHOULD encrypt the request, even if
so. This could happen, for example, if a Requesting User within a company the Requestor has not done so. This could happen, for example, if a
placed a PINT request and this was carried via the company's Intranet to their Requesting User within a company placed a PINT request and this was
Proxy/firewall and thence over the Internet to a PINT Gateway at another carried via the company's Intranet to their Proxy/firewall and thence
location. over the Internet to a PINT Gateway at another location.
If a request carries data that can be reused by an eavesdropper either to If a request carries data that can be reused by an eavesdropper either
"spoof" the Requestor or to obtain PINT service by inserting the Requestor's to "spoof" the Requestor or to obtain PINT service by inserting the
authorization token into an eavesdropper's request, then this data MUST be Requestor's authorization token into an eavesdropper's request, then
protected. This is particularly important if the authorization token consists this data MUST be protected. This is particularly important if the
of static text (such as an account code and/or PIN). authorization token consists of static text (such as an account code
and/or PIN).
One approach is to encrypt the whole of the request, using the methods One approach is to encrypt the whole of the request, using the methods
described in the SIP specification. As an alternative, it may be acceptable described in the SIP specification. As an alternative, it may be
for the authorization token to be held as an opaque reference (see section acceptable for the authorization token to be held as an opaque reference
3.4.2.3 and examples 4.11 and 4.12), using some proprietary scheme agreed (see section 3.4.2.3 and examples 4.11 and 4.12), using some proprietary
between the Requestor and the PINT service provider, as long as this is scheme agreed between the Requestor and the PINT service provider, as
resistant to interception and re-use. Also, it may be that the authorization long as this is resistant to interception and re-use. Also, it may be
token cannot be used outside of a request cryptographically signed by the that the authorization token cannot be used outside of a request
Requestor; if so then this requirement can be relaxed, as in this case the cryptographically signed by the Requestor; if so then this requirement
token cannot be re-used by another. However, unless both the Requestor and the can be relaxed, as in this case the token cannot be re-used by another.
Gateway are assured that this is the case, any authorization token MUST be However, unless both the Requestor and the Gateway are assured that this
treated as sensitive, and so MUST be encrypted. is the case, any authorization token MUST be treated as sensitive, and
so MUST be encrypted.
A PINT request may contain data within the SDP message body that can be used A PINT request may contain data within the SDP message body that can be
more efficiently to route that request. For example, it may be that one used more efficiently to route that request. For example, it may be that
Gateway and Executive System combination cannot handle a request that one Gateway and Executive System combination cannot handle a request
specifies one of the parties as a pager, whilst another can. Both gateways may that specifies one of the parties as a pager, whilst another can. Both
have registered with a PINT/SIP Registrar, and this information may be gateways may have registered with a PINT/SIP Registrar, and this
available to intervening PINT/SIP Proxies. However, if the message body is information may be available to intervening PINT/SIP Proxies. However,
encrypted, then the request cannot be decoded at the Proxy server, and so if the message body is encrypted, then the request cannot be decoded at
Gateway selection based on contained information cannot be made there. the Proxy server, and so Gateway selection based on contained
information cannot be made there.
The result is that the Proxy may deliver the request to a Gateway that cannot The result is that the Proxy may deliver the request to a Gateway that
handle it; the implication is that a PINT/SIP Proxy SHOULD consider its choice cannot handle it; the implication is that a PINT/SIP Proxy SHOULD
for the appropriate Gateway subject to correction, and, on receiving a 501 or consider its choice for the appropriate Gateway subject to correction,
415 rejection from the first gateway chosen, try another. In this way, the and, on receiving a 501 or 415 rejection from the first gateway chosen,
request will succeed if at all possible, even though it may be delayed (and try another. In this way, the request will succeed if at all possible,
tie up resources in the inappropriate Gateways). even though it may be delayed (and tie up resources in the inappropriate
Gateways).
This opens up an interesting avenue for Denial Of Service; sending a valid This opens up an interesting avenue for Denial Of Service; sending a
request that appears to be suitable for a number of different Gateways, and valid request that appears to be suitable for a number of different
simply occupying those Gateways in decrypting a message requesting a service Gateways, and simply occupying those Gateways in decrypting a message
they cannot provide. As mentioned in section 3.5.5.1, the choice of service requesting a service they cannot provide. As mentioned in section
name to be passed in the userinfo portion of the SIP Request-URI is flexible, 3.5.5.1, the choice of service name to be passed in the userinfo portion
and it is RECOMMENDED that names be chosen that allow a Proxy to select an of the SIP Request-URI is flexible, and it is RECOMMENDED that names be
appropriate Gateway without having to examine the SDP body part. Thus, in the chosen that allow a Proxy to select an appropriate Gateway without
example given here, the service might be called "Request-To-Page" or "R2P" having to examine the SDP body part. Thus, in the example given here,
rather than the more general use of "R2F", if there is a possibility of the the service might be called "Request-To-Page" or "R2P" rather than the
SDP body part being protected during transit. more general use of "R2F", if there is a possibility of the SDP body
part being protected during transit.
A variation on this attack is to provide a request that is syntactically A variation on this attack is to provide a request that is syntactically
invalid but that, due to the encryption, cannot be detected without expending invalid but that, due to the encryption, cannot be detected without
resources in decoding it. The effects of this form of attack can be minimised expending resources in decoding it. The effects of this form of attack
in the same way as for any SIP Invitation; the Proxy should detect the 400 can be minimised in the same way as for any SIP Invitation; the Proxy
rejection returned from the initial Gateway, and not pass the request onwards should detect the 400 rejection returned from the initial Gateway, and
to another. not pass the request onwards to another.
Finally, note that the Requesting User may not have a prior relationship with Finally, note that the Requesting User may not have a prior relationship
a PINT Gateway, whilst still having a prior relationship with the Operator of with a PINT Gateway, whilst still having a prior relationship with the
the Executive System that fulfils their request. Thus there may be two levels Operator of the Executive System that fulfils their request. Thus there
of authentication and authorization; one carried out using the techniques may be two levels of authentication and authorization; one carried out
described in the SIP specification (for use between the Requestor and the using the techniques described in the SIP specification (for use between
Gateway), with another being used between the Requesting User or the Requestor the Requestor and the Gateway), with another being used between the
and the Executive System. Requesting User or the Requestor and the Executive System.
For example, the Requesting User may have an account with the PINT service For example, the Requesting User may have an account with the PINT
provider. That provider might require that requests include this identity service provider. That provider might require that requests include this
before they will be convinced to provide service. In addition, to counter identity before they will be convinced to provide service. In addition,
attacks on the request whilst it is in transit across the Internet, the to counter attacks on the request whilst it is in transit across the
Gateway may require a separate X.509-based certification of the request. These Internet, the Gateway may require a separate X.509-based certification
are two separate procedures, and data needed for the former would normally be of the request. These are two separate procedures, and data needed for
expected to be held in opaque references inside the SDP body part of the the former would normally be expected to be held in opaque references
request. inside the SDP body part of the request.
The detailed operation of this mechanism is, by definition, outside the scope The detailed operation of this mechanism is, by definition, outside the
of an Internet Protocol, and so must be considered a private matter. However, scope of an Internet Protocol, and so must be considered a private
one approach to indicating to the Requestor that such "second level" matter. However, one approach to indicating to the Requestor that such
authentication or authorization is required by their Service Provider would be "second level" authentication or authorization is required by their
to ask for this inside the textual description carried with a 401 response Service Provider would be to ask for this inside the textual description
returned from the PINT Gateway. carried with a 401 response returned from the PINT Gateway.
5.4. Summary of Security Implications 5.4. Summary of Security Implications
>From the above discussion, PINT always carries data items that are sensitive,
and there may be financial considerations as well as the more normal privacy
concerns. As a result, the transactions MUST be protected from interception,
modification and replay in transit.
PINT is based on SIP and SDP, and can use the security procedures outlined in From the above discussion, PINT always carries data items that are
[1] (sections 13 and 15). However, in the case of PINT, the SIP recommendation sensitive, and there may be financial considerations as well as the more
that requests and responses MAY be protected is not enough. PINT messages MUST normal privacy concerns. As a result, the transactions MUST be protected
be protected, so PINT Implementations MUST support SIP Security (as described from interception, modification and replay in transit.
in [1], sections 13 & 15), and be capable of handling such received messages.
In some configurations, PINT Clients, Servers, and Gateways can be sure that PINT is based on SIP and SDP, and can use the security procedures
they operate using the services of network level security [13], transport outlined in [1] (sections 13 and 15). However, in the case of PINT, the
layer security [12], or physical security for all communications between them. SIP recommendation that requests and responses MAY be protected is not
In these cases messages MAY be exchanged without SIP security, since all enough. PINT messages MUST be protected, so PINT Implementations MUST
traffic is protected already. Clients and servers SHOULD support manual support SIP Security (as described in [1], sections 13 & 15), and be
configuration to use such lower layer security facilities. capable of handling such received messages.
In some configurations, PINT Clients, Servers, and Gateways can be sure
that they operate using the services of network level security [13],
transport layer security [12], or physical security for all
communications between them. In these cases messages MAY be exchanged
without SIP security, since all traffic is protected already. Clients
and servers SHOULD support manual configuration to use such lower layer
security facilities.
When using network layer security [13], the Security Policy Database When using network layer security [13], the Security Policy Database
MUST be configured to provide appropriate protection to PINT traffic. MUST be configured to provide appropriate protection to PINT traffic.
When using TLS, a port configured MUST NOT also When using TLS, a port configured MUST NOT also be configured for
be configured for non-TLS traffic. When TLS is used, basic authentication non-TLS traffic. When TLS is used, basic authentication MUST be
MUST be supported, and client-side certificates MAY be supported. supported, and client-side certificates MAY be supported.
Authentication of the Client making the request is required, however, so Authentication of the Client making the request is required, however, so
if this is not provided by the underlying mechanism used, then it MUST be if this is not provided by the underlying mechanism used, then it MUST
included within the PINT messages using SIP authentication techniques. In be included within the PINT messages using SIP authentication
contrast with SIP, PINT requests are often sent to parties with which a techniques. In contrast with SIP, PINT requests are often sent to
prior communications relationship exists (such as a Telephone Carrier). In parties with which a prior communications relationship exists (such as a
this case, there may be a shared secret between the client and the PINT Telephone Carrier). In this case, there may be a shared secret between
Gateway. Such PINT systems MAY use authentication based on shared secrets, the client and the PINT Gateway. Such PINT systems MAY use
with HTTP "basic authentication". When this is done, the message integrity authentication based on shared secrets, with HTTP "basic
and privacy must be guaranteed by some lower layer mechanism. authentication". When this is done, the message integrity and privacy
must be guaranteed by some lower layer mechanism.
There are implications on the operation of PINT here though. If a PINT proxy There are implications on the operation of PINT here though. If a PINT
or redirect server is used, then it must be able to examine the contents of proxy or redirect server is used, then it must be able to examine the
the IP datagrams carried. It follows that an end-to-end approach using contents of the IP datagrams carried. It follows that an end-to-end
network-layer security between the PINT Client and a PINT Gateway precludes approach using network-layer security between the PINT Client and a PINT
the use of an intervening proxy; communication between the Client and Gateway Gateway precludes the use of an intervening proxy; communication between
is carried via a tunnel to which any intervening entity cannot gain access, the Client and Gateway is carried via a tunnel to which any intervening
even if the IP datagrams are carried via this node. Conversely, if a entity cannot gain access, even if the IP datagrams are carried via this
"hop-by-hop" approach is used, then any intervening PINT proxies (or redirect node. Conversely, if a "hop-by-hop" approach is used, then any
servers) are, by implication, trusted entities. intervening PINT proxies (or redirect servers) are, by implication,
trusted entities.
However, if there is any doubt that there is an underlying network or However, if there is any doubt that there is an underlying network or
transport layer security association in place, then the players in a PINT transport layer security association in place, then the players in a
protocol exchange MUST use encryption and authentication techniques within the PINT protocol exchange MUST use encryption and authentication techniques
protocol itself. The techniques described in section 15 of RFC2543 MUST be within the protocol itself. The techniques described in section 15 of
used, unless there is an alternative protection scheme that is agreed between RFC2543 MUST be used, unless there is an alternative protection scheme
the parties. In either case, the content of any message body (or bodies) that is agreed between the parties. In either case, the content of any
carried within a PINT request or response MUST be protected; this has message body (or bodies) carried within a PINT request or response MUST
implications on the options for routing requests via Proxies (see 5.3). be protected; this has implications on the options for routing requests
via Proxies (see 5.3).
Using SIP techniques for protection, the Request-URI and To: fields headers Using SIP techniques for protection, the Request-URI and To: fields
within PINT requests cannot be protected. In the baseline PINT services these headers within PINT requests cannot be protected. In the baseline PINT
fields may contain sensitive information. This is a consideration, and if services these fields may contain sensitive information. This is a
these data ARE considered sensitive, then this will preclude the sole use of consideration, and if these data ARE considered sensitive, then this
SIP techniques; in such a situation, transport [12] or network layer [13] will preclude the sole use of SIP techniques; in such a situation,
protection mechanisms MUST be used. transport [12] or network layer [13] protection mechanisms MUST be used.
As a final point, this choice will in turn have an influence on the choice of As a final point, this choice will in turn have an influence on the
transport layer protocol that can be used; if a TLS association is available choice of transport layer protocol that can be used; if a TLS
between two nodes, then TCP will have to be used. This is different from association is available between two nodes, then TCP will have to be
the default behaviour of SIP (try UDP, then try TCP if that fails). used. This is different from the default behaviour of SIP (try UDP, then
try TCP if that fails).
6. Deployment considerations and the Relationship PINT to I.N. (Informative) 6. Deployment considerations and the Relationship PINT to I.N.
(Informative)
6.1. Web Front End to PINT Infrastructure 6.1. Web Front End to PINT Infrastructure
It is possible that some other protocol may be used to communicate a It is possible that some other protocol may be used to communicate a
Requesting User's requirements. Due to the high numbers of available Web Requesting User's requirements. Due to the high numbers of available Web
Browsers and servers it seems likely that some PINT systems will use Browsers and servers it seems likely that some PINT systems will use
HTML/HTTP as a "front end". In this scenario, HTTP will be used over a HTML/HTTP as a "front end". In this scenario, HTTP will be used over a
connection from the Requesting User's Web Browser (WC) to an Intermediate connection from the Requesting User's Web Browser (WC) to an
Web Server (WS). This will be closely associated with a PINT Client (using Intermediate Web Server (WS). This will be closely associated with a
some unspecified mechanism to transfer the data from the Web Server to the PINT Client (using some unspecified mechanism to transfer the data from
PINT Client). The PINT Client will represent the Requesting User to the PINT the Web Server to the PINT Client). The PINT Client will represent the
Gateway, and thus to the Executive System that carries out the required Requesting User to the PINT Gateway, and thus to the Executive System
action. that carries out the required action.
[WC]------[WS] [WC]------[WS]
[PC] [PC]
\ \
\ \
[PG] [PG]
[XS] [XS]
Figure 2: Basic "Web-fronted" Configuration Figure 2: Basic "Web-fronted" Configuration
6.2. Redirects to Multiple Gateways 6.2. Redirects to Multiple Gateways
It is quite possible that a given PINT Gateway is associated with an It is quite possible that a given PINT Gateway is associated with an
Executive System (or systems) that can connect to the GSTN at different Executive System (or systems) that can connect to the GSTN at different
places. Equally, if there is a chain of PINT Servers, then each of these places. Equally, if there is a chain of PINT Servers, then each of these
intermediate or proxy servers (PP) may be able to route PINT requests to intermediate or proxy servers (PP) may be able to route PINT requests to
Executive Systems that connect at specific points to the GSTN. The result of Executive Systems that connect at specific points to the GSTN. The
this is that there may be more than one PINT Gateway or Executive System that result of this is that there may be more than one PINT Gateway or
can deal with a given request. The mechanisms by which the choice on where Executive System that can deal with a given request. The mechanisms by
to deliver a request are outside the scope of this document. which the choice on where to deliver a request are outside the scope of
this document.
[WC]------[WS] [WC]------[WS] [WC]------[WS] [WC]------[WS]
[PC] [PC] [PC] [PC]
\ \ \ \
\ \ \ \
[PG] [PP] [PG] [PP]
.........[XS]......... / \ .........[XS]......... / \
: : / \ : : / \
[PG] [PG] [PG] [PG]
[XS] [XS] [XS] [XS]
skipping to change at page 44, line 48 skipping to change at page 48, line 14
[WC]------[WS] [WC]------[WS] [WC]------[WS] [WC]------[WS]
[PC] [PC] [PC] [PC]
\ \ \ \
\ \ \ \
[PG] [PP] [PG] [PP]
.........[XS]......... / \ .........[XS]......... / \
: : / \ : : / \
[PG] [PG] [PG] [PG]
[XS] [XS] [XS] [XS]
Figure 3: Multiple Access Configurations Figure 3: Multiple Access Configurations
However, there do seem to be two approaches. Either a Server that acts as a However, there do seem to be two approaches. Either a Server that acts
proxy or redirect will select the appropriate Gateway itself and will cause as a proxy or redirect will select the appropriate Gateway itself and
the request to be sent on accordingly, or a list of possible Locations will will cause the request to be sent on accordingly, or a list of possible
be returned to the Requesting User from which they can select their choice. Locations will be returned to the Requesting User from which they can
select their choice.
In SIP, the implication is that, if a proxy cannot resolve to a single In SIP, the implication is that, if a proxy cannot resolve to a single
unique match for a request destination, then a response containing a list of unique match for a request destination, then a response containing a
the choices should be returned to the Requesting User for selection. This is list of the choices should be returned to the Requesting User for
not too likely a scenario within the normal use of SIP. selection. This is not too likely a scenario within the normal use of
SIP.
However, within PINT, such ambiguity may be quite common; it implies that However, within PINT, such ambiguity may be quite common; it implies
there are a number of possible providers of a given service. that there are a number of possible providers of a given service.
6.3. Competing PINT Gateways REGISTERing to offer the same service 6.3. Competing PINT Gateways REGISTERing to offer the same service
With PINT, the registration is not for an individual but instead for a With PINT, the registration is not for an individual but instead for a
service that can be handled by a service provider. Thus, one can envisage a service that can be handled by a service provider. Thus, one can
registration by the PINT Server of the domain telcoA.com of its ability to envisage a registration by the PINT Server of the domain telcoA.com of
support the service R2C as "R2C@telcoA.com", sent to an intermediary server its ability to support the service R2C as "R2C@telcoA.com", sent to an
that acts as registrar for the "broker.telcos.com" domain from intermediary server that acts as registrar for the "broker.telcos.com"
"R2C@pint.telcoA.com" as follows: domain from "R2C@pint.telcoA.com" as follows:
REGISTER sip:registrar@broker.telcos.com SIP/2.0 REGISTER sip:registrar@broker.telcos.com SIP/2.0
To: sip:R2C@pint.telcoA.com To: sip:R2C@pint.telcoA.com
From: sip:R2C@pint.telcoA.com From: sip:R2C@pint.telcoA.com
... ...
This is the standard SIP registration service. This is the standard SIP registration service.
However, what happens if there are a number of different Service Providers, However, what happens if there are a number of different Service
all of whom support the "R2C" service? Suppose there is a PINT system at Providers, all of whom support the "R2C" service? Suppose there is a
domain "broker.com". PINT clients requesting a Request-to-Call service from PINT system at domain "broker.com". PINT clients requesting a
broker.com might be very willing to be redirected or proxied to any one of Request-to-Call service from broker.com might be very willing to be
the various service providers that had previously registered with the redirected or proxied to any one of the various service providers that
registrar. PINT servers might also be interested in providing service for had previously registered with the registrar. PINT servers might also be
requests that did not specify the service provider explicitly, as well as interested in providing service for requests that did not specify the
those requests that were directed "at them". service provider explicitly, as well as those requests that were
directed "at them".
To enable such service, PINT servers would REGISTER at the broker PINT To enable such service, PINT servers would REGISTER at the broker PINT
server registrations of the form: server registrations of the form:
REGISTER sip:registrar@broker.com SIP/2.0 REGISTER sip:registrar@broker.com SIP/2.0
To: sip:R2C@broker.com To: sip:R2C@broker.com
From: sip:R2C@pint.telcoA.com From: sip:R2C@pint.telcoA.com
When several such REGISTER messages appear at the registrar, each differing When several such REGISTER messages appear at the registrar, each
only in the URL in the From: line, the registrar has many possibilities, differing only in the URL in the From: line, the registrar has many
e.g.: possibilities, e.g.:
(i) it overwrites the prior registration for "R2C@broker.telcos.com" (i) it overwrites the prior registration for "R2C@broker.telcos.com"
when the next comes in; when the next comes in;
(ii) it rejects the subsequent registration for "R2C@broker.telcos.com"; (ii) it rejects the subsequent registration for
"R2C@broker.telcos.com";
(iii) it maintains all such registrations. (iii) it maintains all such registrations.
In this last case, on receiving an Invitation for the "general" service, In this last case, on receiving an Invitation for the "general" service,
either: either:
(iii.1) it passes on the invitation to all registered service (iii.1) it passes on the invitation to all registered service
providers, returning a collated response with all providers, returning a collated response with all
acceptances, using multiple Location: headers, acceptances, using multiple Location: headers,
or or
(iii.2) it silently selects one of the registrations (using, for (iii.2) it silently selects one of the registrations (using, for
example, a "round robin" approach) and routes the Invitation example, a "round robin" approach) and routes the Invitation
and response onwards without further comment. and response onwards without further comment.
As an alternative to all of the above approaches, it: As an alternative to all of the above approaches, it:
(iv) may choose to not allow registrations for the "general" service, (iv) may choose to not allow registrations for the "general" service,
rejecting all such REGISTER requests. rejecting all such REGISTER requests.
The algorithm by which such a choice is made will be The algorithm by which such a choice is made will be
implementation-dependent, and is outside the scope of PINT. Where a implementation-dependent, and is outside the scope of PINT. Where a
behaviour is to be defined by requesting users, then some sort of call behaviour is to be defined by requesting users, then some sort of call
processing language might be used to allow those clients, as a pre-service processing language might be used to allow those clients, as a
operation, to download the behaviour they expect to the server making such pre-service operation, to download the behaviour they expect to the
decisions. This, however, is a topic for other protocols, not for PINT. server making such decisions. This, however, is a topic for other
protocols, not for PINT.
6.4. Limitations on Available Information and Request Timing for SUBSCRIBE 6.4. Limitations on Available Information and Request Timing for
SUBSCRIBE
A reference configuration for PINT is that service requests are sent, via a A reference configuration for PINT is that service requests are sent,
PINT Gateway, to an Executive System that fulfils the Service Control via a PINT Gateway, to an Executive System that fulfils the Service
Function (SCF) of an Intelligent Network (see [11]). The success or failure Control Function (SCF) of an Intelligent Network (see [11]). The success
of the resulting service call may be information available to the SCF and so or failure of the resulting service call may be information available to
may potentially be made available to the PINT Gateway. In terms of the SCF and so may potentially be made available to the PINT Gateway. In
historical record of whether or not a service succeeded, a large SCF may be terms of historical record of whether or not a service succeeded, a
dealing with a million call attempts per hour. Given that volume of service large SCF may be dealing with a million call attempts per hour. Given
transactions, there are finite limits beyond which it cannot store service that volume of service transactions, there are finite limits beyond
disposition records; expecting to find out if a Fax was sent last month from which it cannot store service disposition records; expecting to find out
a busy SCF is unrealistic. if a Fax was sent last month from a busy SCF is unrealistic.
Other status changes, such as that on completion of a successful service Other status changes, such as that on completion of a successful service
call, require the SCF to arrange monitoring of the service call in a way call, require the SCF to arrange monitoring of the service call in a way
that the service may not do normally, for performance reasons. In most that the service may not do normally, for performance reasons. In most
implementations, it is difficult efficiently to interrupt a service to implementations, it is difficult efficiently to interrupt a service to
change it once it has begun execution, so it may be necessary to have two change it once it has begun execution, so it may be necessary to have
different services; one that sets GSTN resources to monitor service call two different services; one that sets GSTN resources to monitor service
termination, and one that doesn't. It is unlikely to be possible to decide call termination, and one that doesn't. It is unlikely to be possible to
that monitoring is required once the service has started. decide that monitoring is required once the service has started.
These factors can have implications both on the information that is These factors can have implications both on the information that is
potentially available at the PINT Gateway, and when a request to register potentially available at the PINT Gateway, and when a request to
interest in the status of a PINT service can succeed. The alternative to register interest in the status of a PINT service can succeed. The
using a general SCF is to provide a dedicated Service Node just for PINT alternative to using a general SCF is to provide a dedicated Service
services. As this node is involved in placing all service calls, it is in a Node just for PINT services. As this node is involved in placing all
position to collect the information needed. However, it may well still not service calls, it is in a position to collect the information needed.
be able to respond successfully to a registration of interest in call state However, it may well still not be able to respond successfully to a
changes once a service logic program instance is running. registration of interest in call state changes once a service logic
program instance is running.
Thus, although a Requesting User may register an interest in the status of a Thus, although a Requesting User may register an interest in the status
service request, the PINT Gateway may not be in a position to comply with of a service request, the PINT Gateway may not be in a position to
that request. Although this does not affect the protocol used between the comply with that request. Although this does not affect the protocol
Requestor and the PINT Gateway, it may influence the response returned. used between the Requestor and the PINT Gateway, it may influence the
To avoid the problem of changing service logic once running, any response returned. To avoid the problem of changing service logic once
registration of interest in status changes should be made at or before the running, any registration of interest in status changes should be made
time at which the service request is made. at or before the time at which the service request is made.
Conversely, if a historical request is made on the disposition of a service, Conversely, if a historical request is made on the disposition of a
this should be done within a short time after the service has completed; the service, this should be done within a short time after the service has
Executive System is unlikely to store the results of service requests for completed; the Executive System is unlikely to store the results of
service requests for
long; these will have been processed as AMA (Automatic Message Accounting) long; these will have been processed as AMA (Automatic Message
records quickly, after which the Executive System has no reason to keep Accounting) records quickly, after which the Executive System has no
them, and so they may be discarded. reason to keep them, and so they may be discarded.
Where the PINT Gateway and the Executive System are intimately linked, the Where the PINT Gateway and the Executive System are intimately linked,
Gateway can respond to status subscription requests that occur while a the Gateway can respond to status subscription requests that occur while
service is running. It may accept these requests and simply not even try to a service is running. It may accept these requests and simply not even
query the Executive System until it has information that a service has try to query the Executive System until it has information that a
completed, merely returning the final status. Thus the PINT Requestor may be service has completed, merely returning the final status. Thus the PINT
in what it believes is a monitoring state, whilst the PINT Gateway has not Requestor may be in what it believes is a monitoring state, whilst the
even informed the Executive System that a request has been made. This will PINT Gateway has not even informed the Executive System that a request
increase the internal complexity of the PINT Gateway in that it will have a has been made. This will increase the internal complexity of the PINT
complex set of interlocking state machines, but does mean that status Gateway in that it will have a complex set of interlocking state
registration and indication CAN be provided in conjunction with an I.N. machines, but does mean that status registration and indication CAN be
system. provided in conjunction with an I.N. system.
6.5. Parameters needed for invoking traditional GSTN Services within PINT 6.5. Parameters needed for invoking traditional GSTN Services within
PINT
This section describes how parameters needed to specify certain traditional This section describes how parameters needed to specify certain
GSTN services can be carried within PINT requests. traditional GSTN services can be carried within PINT requests.
6.5.1. Service Identifier 6.5.1. Service Identifier
When a Requesting User asks for a service to be performed, he or she will, When a Requesting User asks for a service to be performed, he or she
of course, have to specify in some way which service. This can be done will, of course, have to specify in some way which service. This can be
in the URLs within the To: header and the Request-URI (see section 3.5.5.1). done in the URLs within the To: header and the Request-URI (see section
3.5.5.1).
6.5.2. A and B parties 6.5.2. A and B parties
With the Request-to-Call service, they will also need to specify the A and B With the Request-to-Call service, they will also need to specify the A
parties they want to be engaged in the resulting service call. The A party and B parties they want to be engaged in the resulting service call. The
could identify, for example, the Call Centre from which they want a call A party could identify, for example, the Call Center from which they
back, whilst the B party is their telephone number (i.e. who the Call Centre want a call back, whilst the B party is their telephone number (i.e. who
agent is to call). the Call Center agent is to call).
The Request-to-Fax and Request-to-Hear-Content services require the B party The Request-to-Fax and Request-to-Hear-Content services require the B
to be specified (respectively the telephone number of the destination Fax party to be specified (respectively the telephone number of the
machine or the telephone to which spoken content is to be delivered), but destination Fax machine or the telephone to which spoken content is to
the A party is a Telephone Network based resource (either a Fax or speech be delivered), but the A party is a Telephone Network based resource
transcoder/sender), and is implicit; the Requesting User does not (and (either a Fax or speech transcoder/sender), and is implicit; the
cannot) specify it. Requesting User does not (and cannot) specify it.
With the "Fax-Back" variant of the Request-to-Fax service, (i.e. where the With the "Fax-Back" variant of the Request-to-Fax service, (i.e. where
content to be delivered resides on the GSTN) they will also have specify two the content to be delivered resides on the GSTN) they will also have
parties. As before, the B party is the telephone number of the fax machine specify two parties. As before, the B party is the telephone number of
to which they want a fax to be sent. However, within this variant the A the fax machine to which they want a fax to be sent. However, within
party identifies the "document context" for the GSTN-based document store this variant the A party identifies the "document context" for the
from which a particular document is to be retrieved; the analogy here is to GSTN-based document store from which a particular document is to be
a GSTN user dialling a particular telephone number and then entering the retrieved; the analogy here is to a GSTN user dialling a particular
document number to be returned using "touch tone" digits. The telephone telephone number and then entering the document number to be returned
number they dial is that of the document store or A party, with the "touch using "touch tone" digits. The telephone number they dial is that of the
tone" digits selecting the document within that store. document store or A party, with the "touch tone" digits selecting the
document within that store.
6.5.3. Other Service Parameters 6.5.3. Other Service Parameters
In terms of the extra parameters to the request, the services again differ. In terms of the extra parameters to the request, the services again
The Request-to-Call service needs only the A and B parties. Also it is differ. The Request-to-Call service needs only the A and B parties. Also
convenient to assert that the resulting service call will carry voice, as it is convenient to assert that the resulting service call will carry
the Executive System within the destination GSTN may be able to check that voice, as the Executive System within the destination GSTN may be able
assertion against the A and B party numbers specified and may treat the call to check that assertion against the A and B party numbers specified and
differently. may treat the call differently.
With the Request-to-Fax and Request-to-Hear-Content services, the source With the Request-to-Fax and Request-to-Hear-Content services, the source
information to be transcoded is held on the Internet. That means either that information to be transcoded is held on the Internet. That means either
this information is carried along with the request itself, or that a that this information is carried along with the request itself, or that
reference to the source of this information is given. In addition, it is a reference to the source of this information is given.
convenient to assert that the service call will carry fax or voice, and,
where possible, to specify the format for the source information.
The GSTN-based content or "Fax-Back" variant of the Request-to-Fax service In addition, it is convenient to assert that the service call will carry
needs to specify the Document Store number and the Fax machine number to fax or voice, and, where possible, to specify the format for the source
which the information is to be delivered. It is convenient to assert that information.
the call will carry Fax data, as the destination Executive System may be
able to check that assertion against the document store number and that of
the destination Fax machine.
In addition, the document number may also need to be sent. This parameter is The GSTN-based content or "Fax-Back" variant of the Request-to-Fax
an opaque reference that is carried through the Internet but has service needs to specify the Document Store number and the Fax machine
significance only within the GSTN. The document store number and document number to which the information is to be delivered. It is convenient to
number together uniquely specify the actual content to be faxed. assert that the call will carry Fax data, as the destination Executive
System may be able to check that assertion against the document store
number and that of the destination Fax machine.
In addition, the document number may also need to be sent. This
parameter is an opaque reference that is carried through the Internet
but has significance only within the GSTN. The document store number and
document number together uniquely specify the actual content to be
faxed.
6.5.4. Service Parameter Summary 6.5.4. Service Parameter Summary
The following table summarises the information needed in order to specify The following table summarises the information needed in order to
fully the intent of a GSTN service request. Note that it excludes any other specify fully the intent of a GSTN service request. Note that it
parameters (such as authentication or authorisation tokens, or Expires: or excludes any other parameters (such as authentication or authorisation
CallId: headers) that may be used in a request. tokens, or Expires: or CallId: headers) that may be used in a request.
Service ServiceID AParty BParty CallFmt Source SourceFmt Service ServiceID AParty BParty CallFmt Source SourceFmt
------- --------- ------ ------ ------- ------ ------- ------- --------- ------ ------ ------- ------ -------
R2C x x x voice - - R2C x x x voice - -
R2F x - x fax URI/IL ISF/ILSF R2F x - x fax URI/IL ISF/ILSF
R2FB x x x fax OR - R2FB x x x fax OR -
R2HC x - x voice URI/IL ISF/ILSF R2HC x - x voice URI/IL ISF/ILSF
In this table, "x" means that the parameter is required, whilst "-" means In this table, "x" means that the parameter is required, whilst "-"
that the parameter is not required. means that the parameter is not required.
The Services listed are Request-to-Call (R2C), Request-to-Fax (R2F), the The Services listed are Request-to-Call (R2C), Request-to-Fax (R2F), the
GSTN-based content or "Fax-back" Variant of Request-to-Fax (R2FB), and GSTN-based content or "Fax-back" Variant of Request-to-Fax (R2FB), and
Request-to-Hear-Content (R2HC). Request-to-Hear-Content (R2HC).
The Call Format parameter values "voice" or "fax" indicate the kind of The Call Format parameter values "voice" or "fax" indicate the kind of
service call that results. service call that results.
The Source Indicator "URI/IL" implies either that the data is either an The Source Indicator "URI/IL" implies either that the information is
Internet source reference (a Universal Resource Identifier, or URI) or is either an Internet source reference (a Universal Resource Identifier, or
URI) or is carried "in-line" with the message. The Source indicator "OR"
carried "in-line" with the message. The Source indicator "OR" means that means that the value passed is an Opaque Reference that should be
the value passed is an Opaque Reference that should be carried along carried along with the rest of the message but is to be interpreted only
with the rest of the message but is to be interpreted only within the within the destination (GSTN) context. As an alternative, it could be
destination (GSTN) context. As an alternative, it could be given as a given as a "local" reference with the "file" style, or even using a
"local" reference with the "file" style, or even using a partial reference partial reference with the "http" style. However, the way in which such
with the "http" style. However, the way in which such a reference is a reference is interpreted is a matter for the receiving PINT Server and
interpreted is a matter for the receiving PINT Server and Executive System; Executive System; it remains, in effect, an opaque reference.
it remains, in effect, an opaque reference.
The Source Format value "ISF/ILSF" means that the format of the source is The Source Format value "ISF/ILSF" means that the format of the source
specified either in terms of the URI or that it is carried "in-line". Note is specified either in terms of the URI or that it is carried "in-line".
that, for some data, the format either can be detected by inspection or, if Note that, for some data, the format either can be detected by
all else fails, can be assumed from the URI (for example, by assuming that inspection or, if all else fails, can be assumed from the URI (for
the file extension part of a URL indicates the data type). For an opaque example, by assuming that the file extension part of a URL indicates the
reference, the Source Format is not available on the Internet, and so is not data type). For an opaque reference, the Source Format is not available
given. on the Internet, and so is not given.
6.6. Parameter Mapping to PINT Extensions 6.6. Parameter Mapping to PINT Extensions
This section describes the way in which the parameters needed to specify a This section describes the way in which the parameters needed to specify
GSTN service request fully might be carried within a "PINT extended" message. a GSTN service request fully might be carried within a "PINT extended"
There are other choices, and these are not precluded. However, in order to message. There are other choices, and these are not precluded. However,
ensure that the Requesting User receives the service that they expect, it is in order to ensure that the Requesting User receives the service that
necessary to have some shared understanding of the parameters passed and the they expect, it is necessary to have some shared understanding of the
behaviour expected of the PINT Server and its attendant Executive System. parameters passed and the behaviour expected of the PINT Server and its
attendant Executive System.
The Service Identifier can be sent as the userinfo element of the The Service Identifier can be sent as the userinfo element of the
Request-URI. Thus, the first line of a PINT Invitation would be of the form: Request-URI. Thus, the first line of a PINT Invitation would be of the
form:
INVITE <serviceID>@<pint-server>.<domain> SIP/2.0 INVITE <serviceID>@<pint-server>.<domain> SIP/2.0
The A Party for the Request-to-Call and "Fax-back" variant of Request-to-Fax The A Party for the Request-to-Call and "Fax-back" variant of
service can be held in the "To:" header field. In this case the "To:" header Request-to-Fax service can be held in the "To:" header field. In this
value will be different from the Request-URI. In the services where the A case the "To:" header value will be different from the Request-URI. In
party is not specified, the "To:" field is free to repeat the value held in the services where the A party is not specified, the "To:" field is free
the Request-URI. This is the case for Request-to-Fax and to repeat the value held in the Request-URI. This is the case for
Request-to-Hear-Content services. Request-to-Fax and Request-to-Hear-Content services.
The B party is needed in all these milestone services, and can be held in The B party is needed in all these milestone services, and can be held
the enclosed SDP sub-part, as the value of the "c=" field. in the enclosed SDP sub-part, as the value of the "c=" field.
The call format parameter can be held as part of the "m=" field value. It The call format parameter can be held as part of the "m=" field value.
maps to the "transport protocol" element as described in section 3.4.2 of It maps to the "transport protocol" element as described in section
this document. 3.4.2 of this document.
..--
The source format specifier is held in the "m=", as a type and either "-" The source format specifier is held in the "m=", as a type and either
or sub-type. The latter is normally required for all services except "-" or sub-type. The latter is normally required for all services except
Request-to-Call or "Faxback", where the "-" form may be used. As shown Request-to-Call or "Faxback", where the "-" form may be used. As shown
earlier, the source format and source are not always required when earlier, the source format and source are not always required when
generating requests for services. However, the inclusion in all requests generating requests for services. However, the inclusion in all requests
of a source format specifier can make parsing the request simpler and of a source format specifier can make parsing the request simpler and
allows for other services to be specified in the future, and so values allows for other services to be specified in the future, and so values
are always given. The source format parameter is covered in section 3.4.2 are always given. The source format parameter is covered in section
as the "media type" element. 3.4.2 as the "media type" element.
The source itself is identified by an "a=fmtp:" field value, where needed. The source itself is identified by an "a=fmtp:" field value, where
With the exception of the Request-to-Call service, all invitations will needed. With the exception of the Request-to-Call service, all
normally include such a field. From the perspective of the SDP extensions, invitations will normally include such a field. From the perspective of
it can be considered as qualifying the media sub-type, as if to say, the SDP extensions, it can be considered as qualifying the media
for example, "when I say jpeg, what I mean is the following". sub-type, as if to say, for example, "when I say jpeg, what I mean is
the following".
In summary, the parameters needed by the different services are carried in In summary, the parameters needed by the different services are carried
fields as shown in the following table: in fields as shown in the following table:
Service Svc Param PINT/SIP or SDP field used Example value Service Svc Param PINT/SIP or SDP field used Example value
------- --------- -------------------------- ------------- ------- --------- -------------------------- -------------
R2C R2C
ServiceID: <SIP Request-URI userinfo> R2C ServiceID: <SIP Request-URI userinfo> R2C
BParty: <SIP To: field> sip:123@p.com BParty: <SIP To: field> sip:123@p.com
AParty: <SDP c= field> TN RFC2543 4567 AParty: <SDP c= field> TN RFC2543 4567
CallFormat: <SDP transport protocol CallFormat: <SDP transport protocol
sub-field of m= field> voice sub-field of m= field> voice
skipping to change at page 51, line 50 skipping to change at page 55, line 51
"Multipurpose Internet Mail Extensions (MIME) "Multipurpose Internet Mail Extensions (MIME)
Part Two: Media Types", Part Two: Media Types",
RFC2046, November 1996. RFC2046, November 1996.
[5] The Unicode Consortium, [5] The Unicode Consortium,
"The Unicode Standard -- Version 2.0", "The Unicode Standard -- Version 2.0",
Addison-Wesley, 1996. Addison-Wesley, 1996.
[6] ITU-T Study Group 2, [6] ITU-T Study Group 2,
"E.164 - The International Public Network Numbering Plan", "E.164 - The International Public Network Numbering Plan",
ITU-T, June 1997. ITU-T, June 1997.
[7] H. Lu et al, [7] H. Lu et al,
"Toward the PSTN/Internet Inter-Networking--Pre-PINT Implementations", "Toward the PSTN/Internet Inter-Networking--Pre-PINT
Informational RFC2458, Internet Engineering Task Force, Nov 1998. Implementations", Informational RFC2458,
Internet Engineering Task Force, Nov 1998.
[8] ITU-T Study Group XI, [8] ITU-T Study Group XI,
"Q.763 - Formats and Codes for the ISDN User Part of SS No7" "Q.763 - Formats and Codes for the ISDN User Part of SS No7"
ITU-T, August 1994. ITU-T, August 1994.
[9] T. Berners-Lee, R. Fielding, & L. Masinter, [9] T. Berners-Lee, R. Fielding, & L. Masinter,
"Uniform Resource Identifiers (URI): Generic Syntax", RFC2396, "Uniform Resource Identifiers (URI): Generic Syntax", RFC2396,
Internet Engineering Task Force, August 1998. Internet Engineering Task Force, August 1998.
[10] D. Crocker, [10] D. Crocker,
"Standard for the format of ARPA Internet text messages",RFC822, "Standard for the format of ARPA Internet text messages",RFC822,
Internet Engineering Task Force, August 1982. Internet Engineering Task Force, August 1982.
[11] ITU-T Study Group XI, [11] ITU-T Study Group XI,
"Q.1204 - IN Distributed Functional Plane Architecture", "Q.1204 - IN Distributed Functional Plane Architecture",
ITU-T, February 1994. ITU-T, February 1994.
[12] T. Dierks & C. Allen, [12] T. Dierks & C. Allen,
"The TLS Protocol Version 1.0", RFC2246, "The TLS Protocol Version 1.0", RFC2246,
Internet Engineering Task Force, January 1999. Internet Engineering Task Force, January 1999.
[13] S. Kent, R. Atkinson, [13] S. Kent, R. Atkinson,
skipping to change at page 52, line 18 skipping to change at page 56, line 21
[11] ITU-T Study Group XI, [11] ITU-T Study Group XI,
"Q.1204 - IN Distributed Functional Plane Architecture", "Q.1204 - IN Distributed Functional Plane Architecture",
ITU-T, February 1994. ITU-T, February 1994.
[12] T. Dierks & C. Allen, [12] T. Dierks & C. Allen,
"The TLS Protocol Version 1.0", RFC2246, "The TLS Protocol Version 1.0", RFC2246,
Internet Engineering Task Force, January 1999. Internet Engineering Task Force, January 1999.
[13] S. Kent, R. Atkinson, [13] S. Kent, R. Atkinson,
"Security Architecture for the Internet Protocol", RFC2401, "Security Architecture for the Internet Protocol", RFC2401,
Internet Engineering Task Force, November 1998. Internet Engineering Task Force, November 1998.
[14] R. Housley, W. Ford, W. Polk & D. Solo, [14] R. Housley, W. Ford, W. Polk & D. Solo,
"Internet X.509 Public Key Infrastructure Certificate and CRL Profile", "Internet X.509 Public Key Infrastructure Certificate and CRL
RFC2459, Internet Engineering Task Force, January 1999. Profile", RFC2459,
Internet Engineering Task Force, January 1999.
[15] D. Crocker & P. Overall, [15] D. Crocker & P. Overall,
"Augmented BNF for Syntax Specifications: ABNF", RFC2234, "Augmented BNF for Syntax Specifications: ABNF", RFC2234,
Internet Engineering Task Force, November 1997. Internet Engineering Task Force, November 1997.
[16] D. Mills, "Network Time Protocol (version 3) specification and [16] D. Mills, "Network Time Protocol (version 3) specification and
implementation", RFC1305, Internet Engineering Task Force, March 1992. implementation", RFC1305, Internet Engineering Task Force,
March 1992.
[17] D. Eastlake, S. Crocker & J.Schiller, [17] D. Eastlake, S. Crocker & J.Schiller,
"Randomness Recommendations for Security", Informational RFC 1305, "Randomness Recommendations for Security", Informational RFC 1305,
Internet Engineering Task Force, March 1992. Internet Engineering Task Force, March 1992.
[18] P. Mockapetris, [18] P. Mockapetris,
"Domain Names - Implementation and Specification" RFC 1035, "Domain Names - Implementation and Specification" RFC 1035,
Inernet Engineering Task Force November 1987. Inernet Engineering Task Force November 1987.
[19] E. Levinson,
"The MIME Multipart/Related Content-type" RFC 2387,
Inernet Engineering Task Force August 1998.
9. Acknowledgements 9. Acknowledgements
The authors wish to thank the members of the PINT working group for The authors wish to thank the members of the PINT working group for
comments that were helpful to the preparation of this specification. comments that were helpful to the preparation of this specification. Ian
Ian Elz's comments were extremely useful to our understanding of internal Elz's comments were extremely useful to our understanding of internal
PSTN operations. The SUBSCRIBE and NOTIFY requests were first suggested PSTN operations. The SUBSCRIBE and NOTIFY requests were first suggested
by Henning Schulzrinne and Jonathan Rosenberg. Finally, thanks to Bernie by Henning Schulzrinne and Jonathan Rosenberg. The suggestion to use
an audio port of 0 to express that the phone is "on hold" (i.e. not
receiving voice) is due to Ray Zibman. Finally, thanks to Bernie
Hoeneisen for his close proofreading. Hoeneisen for his close proofreading.
Appendix A: Collected ABNF for PINT Extensions Appendix A: Collected ABNF for PINT Extensions
;; --(ABNF is specified in RFC 2234 [15]) ;; --(ABNF is specified in RFC 2234 [15])
;; --Variations on SDP definitions ;; --Variations on SDP definitions
connection-field = ["c=" nettype space addrtype space connection-field = ["c=" nettype space addrtype space
connection-address CRLF] connection-address CRLF]
; -- this is the original definition from SDP, included for completeness ; -- this is the original definition from SDP, included for completeness
skipping to change at page 54, line 23 skipping to change at page 58, line 23
INProto = 1* (<alpha-numeric>) INProto = 1* (<alpha-numeric>)
; -- this is the "classic" SDP protocol, defined if nettype == "IN" ; -- this is the "classic" SDP protocol, defined if nettype == "IN"
; -- alpha-numeric is as defined in SDP ; -- alpha-numeric is as defined in SDP
..-- ..--
TNProto = ("voice"/"fax"/"pager") TNProto = ("voice"/"fax"/"pager")
; -- this is the PINT protocol, defined if nettype == "TN" ; -- this is the PINT protocol, defined if nettype == "TN"
fmt = (<subtype> / "-") fmt = (<subtype> / "-")
; -- NOTE redefined as a subset of the original SDP definition ; -- NOTE redefined as a subset of the original SDP definition
; -- subtype as defined in RFC2046, or "-". MUST be a subtype of type held ; -- subtype as defined in RFC2046, or "-". MUST be a subtype of type
held
; -- in associated media sub-field or the special value "-". ; -- in associated media sub-field or the special value "-".
attribute-fields = *("a=" attribute-list <CRLF>) attribute-fields = *("a=" attribute-list <CRLF>)
; -- redefined as a superset of the definition given in SDP ; -- redefined as a superset of the definition given in SDP
; -- CRLF is as defined in SDP ; -- CRLF is as defined in SDP
attribute-list = 1(PINT-attribute / <attribute>) attribute-list = 1(PINT-attribute / <attribute>)
; -- attribute is as defined in SDP ; -- attribute is as defined in SDP
PINT-attribute = (clir-attribute / q763-nature-attribute / PINT-attribute = (clir-attribute / q763-nature-attribute /
skipping to change at page 55, line 40 skipping to change at page 59, line 37
tsp-attribute = tsp-tag "=" provider-domainname tsp-attribute = tsp-tag "=" provider-domainname
tsp-tag = "tsp" tsp-tag = "tsp"
provider-domainname = <domain> provider-domainname = <domain>
; -- domain is defined in RFC1035 ; -- domain is defined in RFC1035
; -- NOTE the following is redefined relative to the normal use in SDP ; -- NOTE the following is redefined relative to the normal use in SDP
pint-fmtp-attribute = "fmtp:" <subtype> <space> resolution pint-fmtp-attribute = "fmtp:" <subtype> <space> resolution
*(<space> resolution) *(<space> resolution)
(<space> ";" 1(<attribute>) *(<space> <attribute>)) (<space> ";" 1(<attribute>) *(<space>
<attribute>))
; -- subtype as defined in RFC2046. ; -- subtype as defined in RFC2046.
; -- NOTE that this value MUST match a fmt on the ultimately preceeding ; -- NOTE that this value MUST match a fmt on the ultimately preceeding
; -- media-field ; -- media-field
; -- attribute is as defined in SDP ; -- attribute is as defined in SDP
resolution = (uri-ref / opaque-ref / sub-part-ref) resolution = (uri-ref / opaque-ref / sub-part-ref)
uri-ref = uri-tag ":" <URI-Reference> uri-ref = uri-tag ":" <URI-Reference>
; -- URI-Reference defined in RFC2396 ; -- URI-Reference defined in RFC2396
skipping to change at page 58, line 9 skipping to change at page 61, line 9
; -- NOTE this is redefined as a subset of the SIP definition ; -- NOTE this is redefined as a subset of the SIP definition
; -- (from RFC2543/section 6.30) ; -- (from RFC2543/section 6.30)
required-extensions = ("org.ietf.sip.subscribe" / required-extensions = ("org.ietf.sip.subscribe" /
"org.ietf.sdp.require") "org.ietf.sdp.require")
Appendix B: IANA Considerations Appendix B: IANA Considerations
There are three kinds of identifier used in PINT extensions that SHOULD There are three kinds of identifier used in PINT extensions that SHOULD
be registered with IANA, if a new value is specified. These are: be registered with IANA, if a new value is specified. These are:
* Media Format sub-types, as described in section 3.4.2 of this document. * Media Format sub-types, as described in section 3.4.2 of this
document.
* Private Attributes as mentioned in section 3.4.3 * Private Attributes as mentioned in section 3.4.3
* Private Phone Context values, as described in section 3.4.3.1. * Private Phone Context values, as described in section 3.4.3.1.
It should be noted that private Address Types (in section 3.4.1) have been It should be noted that private Address Types (in section 3.4.1) have
explicitly excluded from this process, as they must be in the form of been explicitly excluded from this process, as they must be in the form
an X-Token. of an X-Token.
B.1. Media Format Sub-types B.1. Media Format Sub-types
Taking these in turn, the media format sub-types are used within the PINT Taking these in turn, the media format sub-types are used within the
extensions to SDP to specify the attribute line that holds the data source PINT extensions to SDP to specify the attribute line that holds the data
definitions. In normal use, the values in this field are sub-types of MIME source definitions. In normal use, the values in this field are
discrete types[4]. If a value other than an IANA-registered sub-type is to sub-types of MIME discrete types[4]. If a value other than an
be used, then it should either be an X-Token (i.e. start with "X-") or it IANA-registered sub-type is to be used, then it should either be an
should be registered with IANA. if the intention is to describe a new MIME X-Token (i.e. start with "X-") or it should be registered with IANA. if
sub-type, then the procedures specified in RFC 2048 should be used. It is the intention is to describe a new MIME sub-type, then the procedures
ASSUMED that any new MIME sub-type would follow the syntactic rules for specified in RFC 2048 should be used. It is ASSUMED that any new MIME
interpretation of associated PINT fmtp lines defined in this document. sub-type would follow the syntactic rules for interpretation of
associated PINT fmtp lines defined in this document.
Note that, in keeping with the SDP description, such registrations SHOULD Note that, in keeping with the SDP description, such registrations
include the "proto" field values within which they are defined; however, it SHOULD include the "proto" field values within which they are defined;
is appropriate to specify only that they can be used with "all values of however, it is appropriate to specify only that they can be used with
TNProto". "all values of TNProto".
Conversely, if the intent is to define a new way of including data source Conversely, if the intent is to define a new way of including data
definitions within PINT, then it will be necessary to specify, in the source definitions within PINT, then it will be necessary to specify, in
documentation supporting any such new "PINT Media Format Sub-type" the documentation supporting any such new "PINT Media Format Sub-type"
registration, the syntax of the associated "fmtp" attribute line, as registration, the syntax of the associated "fmtp" attribute line, as the
the identifier serves to indicate the interpretation that should be made identifier serves to indicate the interpretation that should be made of
of format specific attribute lines "tagged" with with such a sub-type. format specific attribute lines "tagged" with with such a sub-type.
If the fmtp interpretation follows the PINT default, then it is adequate If the fmtp interpretation follows the PINT default, then it is adequate
to mention this in the defining document rather than repeating the syntax to mention this in the defining document rather than repeating the
definition given here (although, in this case, it is unclear why such a new syntax definition given here (although, in this case, it is unclear why
registration would be required). As before, the Media Format sub-type SHOULD such a new registration would be required). As before, the Media Format
specify the values of "proto" field within which it is defined, but this can sub-type SHOULD specify the values of "proto" field within which it is
be "all values of TNProto". defined, but this can be "all values of TNProto".
B.2. Private Attributes B.2. Private Attributes
Any proprietary attribute lines that are added may be registered with IANA Any proprietary attribute lines that are added may be registered with
using the procedures mentioned in [2]; the mechanism is the same as that IANA using the procedures mentioned in [2]; the mechanism is the same as
used in SDP. If the attribute is defined for use only within PINT, then it that used in SDP. If the attribute is defined for use only within PINT,
may be approapriate to mention this in the supporting documentation. Note then it may be approapriate to mention this in the supporting
that, in the PINT 1.0 specification covered here, there is no mechanism to documentation. Note that, in the PINT 1.0 specification covered here,
add such freshly registered attribute lines to a "require:" clause. there is no mechanism to add such freshly registered attribute lines to
a "require:" clause.
B.3. Private phone-contexts B.3. Private phone-contexts
Within the session description used for PINT requests, a phone-context Within the session description used for PINT requests, a phone-context
attribute may be used to specify the prefix or context within which an attribute may be used to specify the prefix or context within which an
associated telephone-number (in a connextion line) should be interpreted. associated telephone-number (in a connextion line) should be
interpreted.
For "public" phone contexts the prefix to be used MUST start with either For "public" phone contexts the prefix to be used MUST start with either
a DIGIT or a "+". Private phone contexts may be registered with IANA that a DIGIT or a "+". Private phone contexts may be registered with IANA
do NOT start with either of these characters. Such a prefix may be useful that do NOT start with either of these characters. Such a prefix may be
to identify a private network, potentially with an associated numeric ID useful to identify a private network, potentially with an associated
(see example 4 in section 3.4.3.1). In the example, the prefix acts as numeric ID (see example 4 in section 3.4.3.1). In the example, the
the context for X-acme.com's private network numbering plan. prefix acts as the context for X-acme.com's private network numbering
plan.
It is recommended that any private context to be registered have the general It is recommended that any private context to be registered have the
form of a token including a domain name, optionally followed by a digit string general form of a token including a domain name, optionally followed by
or other token. The appropriate form of the initial token name space will be a digit string or other token. The appropriate form of the initial token
similar to that used for private or vendor registrations for sub-types name space will be similar to that used for private or vendor
(e.g. vnd.acme.com). However, note that the registration will be used to registrations for sub-types (e.g. vnd.acme.com). However, note that the
specify a customer's private network numbering plan format rather than being registration will be used to specify a customer's private network
used generally for all of their equipment vendor's customer's; thus, fbi.gov numbering plan format rather than being used generally for all of their
would be appropriate, but lucent.com would not (unless the private network equipment vendor's customer's; thus, fbi.gov would be appropriate, but
were to be that used by Lucent internally). lucent.com would not (unless the private network were to be that used by
Lucent internally).
In addition, the supporting documentation MUST either declare that there is In addition, the supporting documentation MUST either declare that there
no associated token, or define the syntax by which that token can be parsed is no associated token, or define the syntax by which that token can be
(e.g. vnd.fbi.gov <space> 1*DIGIT). Note that the registration describes a parsed (e.g. vnd.fbi.gov <space> 1*DIGIT). Note that the registration
format, not a value range; it is sufficient that the private context can be describes a format, not a value range; it is sufficient that the private
parsed, without the value being interpreted. context can be parsed, without the value being interpreted.
In detail, the registration request should include: In detail, the registration request SHOULD include:
* Kind of registration (i.e. private phone-context attribute to be used * Kind of registration (i.e. private phone-context attribute to be
within the service description of PINT service requests) used within the service description of PINT service requests)
* Contact details for the person responsible for the registration request * Contact details for the person responsible for the registration
(name, organisation, e-mail address, public telephone number) request (name, organisation, e-mail address, public telephone
number)
* Private Prefix initial token name (e.g. vnd.fbi.gov) * Private Prefix initial token name (e.g. vnd.fbi.gov)
* syntax for private context (e.g. "vnd.fbi.gov" <space> 1*DIGIT, or * syntax for private context (e.g. "vnd.fbi.gov" <space> 1*DIGIT, or
"vnd.gtn.gov.uk") "vnd.gtn.gov.uk")
* Description of use (e.g. "This phone context declares an associated * Description of use (e.g. "This phone context declares an associated
telephone number to be within the 'government telecommunications telephone number to be within the 'government telecommunications
network'; the number is in an internal or private number plan form) network'; the number is in an internal or private number plan form)
* Network Type and Address Type with which this private context is * Network Type and Address Type with which this private context is
associated; If the "normal" telephone types (as specified in this associated; If the "normal" telephone types (as specified in this
document) are used, then the values would be shown as: document) are used, then the values would be shown as:
"nettype=TN" , addrtype="RFC2543Addr". If, however, this context were "nettype=TN" , addrtype="RFC2543Addr". If, however, this context
to be used with another address type, then a reference to that were to be used with another address type, then a reference to that
address type name and the syntax of that address value would be required. address type name and the syntax of that address value would be
required.
In short, this context is the telephone equivalent of a "Net 10" address In short, this context is the telephone equivalent of a "Net 10" address
space behind a NAT, and the initial name (and contact information) shows space behind a NAT, and the initial name (and contact information) shows
the context within which that address is valid. It also specifies the format the context within which that address is valid. It also specifies the
for the network and address types (and address value syntax) with which this format for the network and address types (and address value syntax) with
context is associated. which this context is associated.
Of course, IANA may refer the requested registration to the IESG or an Of course, IANA may refer the requested registration to the IESG or an
appropriate IETF working group for review, and may require revisions to be appropriate IETF working group for review, and may require revisions to
made before the registration is accepted. be made before the registration is accepted.
Appendix C: Author's Addresses Appendix C: Author's Addresses
Scott Petrack Scott Petrack
MetaTel, Inc. MetaTel, Inc.
284 North Ave. 35 Rumford Avd.
Weston, MA 02493 Waltham, MA 02453
scott.petrack@metatel.com scott.petrack@metatel.com
+1 (781)-891-9000 +1 (781)-891-9000
Lawrence Conroy Lawrence Conroy
Siemens Roke Manor Research Siemens Roke Manor Research
Roke Manor Roke Manor
Old Salisbury Lane Old Salisbury Lane
Romsey, Hampshire Romsey, Hampshire
U.K. SO51 0ZN U.K. SO51 0ZN
lwc@roke.co.uk lwc@roke.co.uk
+44 (1794) 833666 +44 (1794) 833666
Petrack & Conroy [Page 63]
 End of changes. 344 change blocks. 
1451 lines changed or deleted 1619 lines changed or added

This html diff was produced by rfcdiff 1.34. The latest version is available from http://tools.ietf.org/tools/rfcdiff/