--- 1/draft-ietf-pint-protocol-01.txt 2007-12-18 18:55:00.000000000 +0100 +++ 2/draft-ietf-pint-protocol-02.txt 2007-12-18 18:55:00.000000000 +0100 @@ -1,20 +1,18 @@ INTERNET-DRAFT Scott Petrack, Internet Engineering Task Force Metatel PINT Working Group Lawrence Conroy, -Issued: 3 August 1999 Siemens Roke Manor Research -Expires: 14 January 2000 - +Issued: 14 October 1999 Siemens Roke Manor Research The PINT Service Protocol: Extensions to SIP and SDP for IP Access to Telephone Call Services - + Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. @@ -35,21 +33,21 @@ Copyright Notice Copyright (c) The Internet Society (1999). All rights reserved. Abstract This document contains the specification of the PINT Service Protocol 1.0, which defines a protocol for invoking certain telephone services from an IP network. These services include placing basic calls, sending and receiving faxes, and receiving content over the telephone. The protocol is specified -as a set of enhancements and additions to the SIP 2.0 and SDP 2.0 protocols. +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 group of the Internet Engineering Task Force. Comments are solicited and should be addressed to the working group's mailing list at pint@lists.research.bell-labs.com and/or the authors. Petrack & Conroy [Page 1] Contents @@ -72,31 +70,32 @@ 3.4. PINT Extensions to SDP 2.0 ..................................... 10 3.4.1. Network Type "TN" and Address Type "RFC2543" ............. 11 3.4.2. Support for Data Objects within PINT ..................... 11 3.4.2.1. Use of fmtp attributes in PINT requests ............ 13 3.4.2.2. Support for Remote Data Object References in PINT .. 13 3.4.2.3. Support for GSTN-based Data Objects in PINT ........ 14 3.4.2.4. Session Description support for included Data Objects 15 3.4.3. Attribute Tags to pass information into the Telephone Network .................................................. 16 3.4.3.1. The phone-context attribute ........................ 17 - 3.4.3.2. Presentation Restriction attribute ................. 19 + 3.4.3..2. Presentation Restriction attribute ................. 19 3.4.3.3. ITU-T CalledPartyAddress attributes parameters ..... 19 3.4.4. The "require" attribute .................................. 20 3.5. PINT Extensions to SIP 2.0 ..................................... 21 3.5.1. Multi-part MIME (sending data along with SIP request) .... 21 3.5.2. Warning header ........................................... 22 3.5.3. Mechanism to register interest in the disposition of a PINT service, and to receive indications on that disposition .. 23 3.5.3.1. Opening a monitoring session with a SUBSCRIBE request 23 3.5.3.2. Sending Status Indications with a NOTIFY request ... 24 - 3.5.3.3. Closing a monitoring session with a BYE request .... 25 + 3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE + request ............................................ 25 3.5.3.4. Timing of SUBSCRIBE requests ....................... 25 3.5.4. The "Require:" header for PINT ........................... 26 3.5.5. PINT URLs within PINT requests ........................... 26 3.5.5.1. PINT URLS within Request-URIs ...................... 27 3.5.6. Telephony Network Parameters within PINT URLs ............ 27 3.5.7. REGISTER requests within PINT ............................ 28 3.5.8. BYE Requests in PINT ..................................... 28 4. Examples of PINT Requests and Responses .............................. 30 4.1. A request to a call centre from an anonymous user to receive a @@ -107,62 +106,62 @@ 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 4.6. A request to send an image as a fax to phone number +972-9-956-1867 ................................................ 33 4.7. A request to read out over the phone two pieces of content in sequence ....................................................... 33 4.8. Request for the prices for ISDN to be sent to my fax machine ... 34 4.9. Request for a callback ......................................... 34 - 4.10.Sending a set of information in response to an enquiry ......... 34 + 4.10.Sending a set of information in response to an enquiry ......... 35 4.11.Sportsline "headlines" message sent to your phone/fax/pager .... 35 - 4.12.Automatically giving someone a fax copy of your phone bill ..... 36 + 4.12.Automatically giving someone a fax copy of your phone bill ..... 37 -5. Security Considerations .............................................. 37 - 5.1. Basic Principles for PINT Use ................................. 37 - 5.1.1. Responsibility for service requests ..................... 37 - 5.1.2. Authority to make requests .............................. 37 - 5.1.3. Privacy ................................................. 38 - 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ................ 38 - 5.2. Registration Procedures ....................................... 39 - 5.3. Security mechanisms and implications on PINT service .......... 39 - 5.4. Summary of Security Implications .............................. 41 +5. Security Considerations .............................................. 38 + 5.1. Basic Principles for PINT Use ................................. 38 + 5.1.1. Responsibility for service requests ..................... 38 + 5.1.2. Authority to make requests .............................. 38 + 5.1.3. Privacy ................................................. 39 + 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ................ 39 + 5.2. Registration Procedures ....................................... 40 + 5.3. Security mechanisms and implications on PINT service .......... 40 + 5.4. Summary of Security Implications .............................. 42 6. Deployment considerations and the Relationship PINT to I.N. - (Informative) ........................................................ 43 - 6.1. Web Front End to PINT Infrastructure ........................... 43 - 6.2. Redirects to Multiple Gateways ................................. 43 - 6.3. Competing PINT Gateways REGISTERing to offer the same service .. 44 + (Informative) ........................................................ 44 + 6.1. Web Front End to PINT Infrastructure ........................... 44 + 6.2. Redirects to Multiple Gateways ................................. 44 + 6.3. Competing PINT Gateways REGISTERing to offer the same service .. 45 6.4. Limitations on Available Information and Request Timing for - SUBSCRIBE ...................................................... 45 - 6.5. Parameters needed for invoking traditional PSTN Services within - PINT ........................................................... 46 - 6.5.1. Service Identifier ....................................... 46 - 6.5.2. A and B parties .......................................... 46 - 6.5.3. Other Service Parameters ................................. 47 - 6.5.4. Service Parameter Summary ................................ 47 - 6.6. Parameter Mapping to PINT Extensions............................ 48 + SUBSCRIBE ...................................................... 46 + 6.5. Parameters needed for invoking traditional GSTN Services within + PINT ........................................................... 47 + 6.5.1. Service Identifier ....................................... 47 + 6.5.2. A and B parties .......................................... 47 + 6.5.3. Other Service Parameters ................................. 48 + 6.5.4. Service Parameter Summary ................................ 48 + 6.6. Parameter Mapping to PINT Extensions............................ 49 -7. Open Issues and Draft State .......................................... 50 - 7.1. Open Issues .................................................... 50 - 7.2. Draft State .................................................... 50 +7. Open Issues and Draft State .......................................... 51 + 7.1. Open Issues .................................................... 51 + 7.2. Draft State .................................................... 51 -8. References ........................................................... 52 +8. References ........................................................... 51 -9. Acknowledgements ..................................................... 53 +9. Acknowledgements ..................................................... 52 -Appendix A: Collected ABNF for PINT Extensions .......................... 54 +Appendix A: Collected ABNF for PINT Extensions .......................... 53 -Appendix B: IANA Considerations ......................................... 59 +Appendix B: IANA Considerations ......................................... 58 -Appendix C: Authors' Addresses .......................................... 61 +Appendix C: Authors' Addresses .......................................... 60 Petrack & Conroy [Page 3] 1. Introduction The desire to invoke certain telephone call services from the Internet has been identified by many different groups (users, public and private network operators, call center service providers, equipment vendors, see [7]). The generic scenario is as follows (when the invocation is successful): @@ -170,31 +169,31 @@ 2. the server relays the request into a telephone network; 3. the telephone network performs the requested call service. As examples, consider a user who wishes to have a call placed to his/her telephone. It may be that a customer wishes to get a call from the support department of some business, or a user wishes to hear some remote automatic weather service via recorded or synthesised speech. Within a local environment such a request might result in the placement of a call between employees over the internal PBX. -We use the term "PSTN/Internet Interworking (PINT) Service" to denote such a -complete transaction, starting with the sending of a request from an IP +We use the term "PSTN/Internet Interworking (PINT) Service" to denote such +a complete transaction, starting with the sending of a request from an IP client and including the telephone call itself. PINT services are -distinguished by the fact that they always involve two separate networks: an -IP network to request the placement of a call, and a telephone network to -execute the actual call. It is understood that Intelligent Network systems, -private PBXs, cellular phone networks, and the ISDN can all be used to -deliver PINT services. Also, the request for service might come from within -a private IP network that is disconnected from the whole Internet. +distinguished by the fact that they always involve two separate networks: +an IP network to request the placement of a call, and the Global Switched +Telephone Network (GSTN) to execute the actual call. It is understood that +Intelligent Network systems, private PBXs, cellular phone networks, and +the ISDN can all be used to deliver PINT services. 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 providing the ability to invoke a small number of fixed telephone call services. These "Milestone PINT services" are specified in section 2. Great care has been taken, however, to develop a protocol that is aligned with other Internet protocols where possible, so that future extensions to PINT could develop along with Internet conferencing. Within the Internet conference architecture, establishing media calls is done via a combination of protocols. SIP [1] is used to establish the association between the participants within the call (this association @@ -225,22 +224,22 @@ established is no guarantee that the media will be successfully transported. (This is analogous to the fact that if a SIP invitation is accepted successfully, this is no guarantee against a subsequent failure of audio hardware). The particular requirements of PINT users lead to some new messages. When a PINT server agrees to send a fax to telephone B, it may be that the fax transmission fails after part of the fax is sent. Therefore, the PINT client may wish to receive information about the status of the actual telephone call session that was invoked as a result of the established PINT session. -Two new requests, SUBSCRIBE and NOTIFY, are added here to vanilla SIP to -allow this. +Three new requests, SUBSCRIBE, UNSIUBSCRIBE, and NOTIFY, are added here +to vanilla SIP to allow this. The enhancements and additions specified here are not intended to alter the behaviour of baseline SIP or SDP in any way. The purpose of PINT extension is to extend the usual SIP/SDP services to the telephone world. Apart from integrating well into existing protocols and architectures, and the advantages of reuse, this means that the protocol 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 PINT Milestone services; section 3 specifies the PINT functional @@ -348,22 +347,22 @@ expressed within a PINT request. For example, it is possible to use the SDP "lang" attribute to express a language preference for the Request-to-Hear-Content Service. If a particular PINT system wishes to allow requests to contain details of the telephone-network-side service, it uses the SDP attribute mechanism (see section 3.4.2). 3. PINT Functional and Protocol Architecture 3.1. PINT Functional Architecture -Familiarity is assumed with SIP 2.0 [1] and with SDP 2.0 [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 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 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 capability is called a "PINT gateway". A PINT gateway appears to a SIP @@ -402,145 +401,138 @@ both the office LAN and the office PBX. The Executive System that lies beyond the PINT gateway is outside the scope of PINT. 3.2. PINT Protocol Architecture This section explains how SIP and SDP work in combination to convey the information necessary to invoke telephone network sessions. -*-*- -.-. The following list summarises the extension features used in PINT 1.0. Following on from this the features are considered separately for SDP and then for SIP: 1) Telephony URLs in SDP Contact Fields 2) Refinement of SIP/SDP Telephony URLs * Inclusion of private dialling plans 3) Specification of Telephone Service Provider (TSP) and/or phone-context URL-parameters 4) Data Objects as session media 4a) Protocol Transport formats to indicate the treatment of the media - within the PSTN + within the GSTN 5) Implicit (Indirect) media streams and opaque arguments 6) In-line data objects using multipart/mime 7) Refinement/Clarification of Opaque arguments passed onwards to Executive Systems * Framework for Presentation Restriction Indication * Framework for Q.763 arguments 8) An extension mechanism for SDP to specify strictures and force failure when a recipient does NOT support the specified extensions, using "require" headers. 9) Mandatory support for "Warning" headers to give more detailed information on request disposition. 10) Mechanism to register interest in the disposition of a requested 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 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 The SDP payload contains a description of the particular telephone network -session that the requestor wishes to occur in the PSTN. This information +session that the requestor wishes to occur in the GSTN. This information includes such things as the telephone network address (i.e. the "telephone number") of the terminal(s) involved in the call, an indication of the media type to be transported (e.g. audio, text, image or application data), and an indication if the information is to be transported over the telephone network via voice, fax, or pager 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 example, a request to send some text via voice transport will be fulfilled by invoking some text-to-speech-over-the-phone service, and a request to send text via fax will be fulfilled by invoking some text-to-fax service. 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-..." (section 3.4.1) b. New media types "text", "image", and "application", new protocol transport keywords "voice", "fax" and "pager" and the associated format types and attribute tags (section 3.4.2) c. New format specific attributes for included content data (section 3.4.2.4) d. New attribute tags, used to pass information to the telephone network (section 3.4.3) e. A new attribute tag "require", used by a client to indicate that some attribute is required to be supported in the server (section 3.4.4) -*-*- 3.2.2. SIP Operation in PINT SIP is used to carry the request for telephone service from the PINT client to the PINT gateway, and may include a telephone number if needed for the particular service. The following is a complete list of PINT enhancements and additions to SIP: f. The multipart MIME payloads (section 3.5.1) g. Mandatory support for "Warning:" headers (section 3.5.2) - h. The SUBSCRIBE and NOTIFY requests (section 3.5.3) + h. The SUBSCRIBE and NOTIFY, and UNSUBSCRIBE requests (section 3.5.3) i. Require: headers (section 3.5.4) 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) -*-*- Section 3.5.8 contains remarks about how BYE requests are used within PINT. This is not an extension to baseline SIP; it is included here only for clarification of the semantics when used with telephone network sessions. Petrack & Conroy [Page 9] 3.3. REQUIRED and OPTIONAL elements for PINT compliance -*-*- 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 and servers. In practice, most PINT service requests will use other changes, of which references to Data Objects in requests are most likely to appear in PINT requests. Each of the other new PINT constructs enables a different function, and a client or server that wishes to enable that particular function MUST do so by the construct specified in this document. For example, building a PINT client and server that provide only the Request-to-Call telephone call service, without support for the other Milestone services, is allowed. --.-. + The "Require:" SIP header and the "require" attribute provide a mechanism that can be used by clients and servers to signal their need 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 specified in the PINT context. One example is the SDP a=lang: attribute, which can be used to describe the preferred language of the callee. Another example is the use of the "t=" parameter to indicate that the time at which the PINT service is to be invoked. This is the normal use of the "t=" field. A third example is the quality attributes. 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 -be useful, even if the aim is not to provide a PSTN service request. In this +be useful, even if the aim is not to provide a GSTN service request. In this case, the extensions covering these items may be incorporated into an otherwise "plain" SIP/SDP invitation. Likewise, support for SDP "require" may be useful, as a framework for addition of features to a "traditional" SIP/SDP infrastructure. Again, these may be convenient to incorporate into SIP/SDP implementations that would not be used for PINT service requests. Such additions are beyond the scope of this document, however. -3.4. PINT Extensions to SDP 2.0 +3.4. PINT Extensions to SDP PINT 1.0 adds to SDP the possibility to describe audio, fax, and pager telephone sessions. It is deliberately designed to hide the underlying technical details and complexity of the telephone network. The only network type defined for PINT is the generic "TN" (Telephone Network). More precise tags such as "ISDN", "GSM", are not defined. Similarly, the transport protocols are designated simply as "fax", "voice", and "pager"; there are no more specific identifiers for the various telephone network voice, fax, or pager protocols. Similarly, the data to be transported is identified only as a MIME type, such as "text" data, "image" data, or some more general @@ -553,33 +545,32 @@ This section gives details of the new SDP keywords. 3.4.1. Network Type "TN" and Address Type "RFC2543" The TN ("Telephone Network") network type is used to indicate that the terminal is connected to a telephone network. The address types allowed for network type TN are "RFC2543" and private address types, which MUST begin with an "X-". --.-. + Address type RFC2543 is followed by a string conforming to a subset of the "telephone-subscriber" BNF specified in RFC2543, (this is specified in figure 4 of SIP [1]). Note that this BNF is NOT identical to the BNF that defines the "phone-number" within the "p=" field of SDP. Examples: c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 12014064090 -*-*- A telephone-subscriber string is of one of two types: global-phone-number or local-phone-number. These are distinguished by preceeding a global-phone-number with a "plus" sign ("+"). A global-phone-number is by default to be interpreted as an internationally significant E.164 Number Plan Address, as defined 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 within a local domain. These address types MUST begin with an "X-", and @@ -588,21 +579,20 @@ c= TN X-mytype.mydomain.com A*8-HELEN 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 "OtherAddr" in the ABNF of Appendix A. Note that most dialable telephone numbers are expressable as local-phone-numbers within address RFC2543; new address types should only be used for formats which cannot be so written. -*-*- 3.4.2. Support for Data Objects within PINT One significant change over traditional SIP/SDP Internet Conference sessions with PINT is that a PINT service request may refer to a Data Object to be used as source information in that request. For example, a PINT service request may specify a document to be processed as part of a GSTN service by which a Fax is sent. Similarly, a GSTN service may be take a Web page and result in a vocoder processing that page and speaking the contents over a telephone. @@ -622,21 +612,21 @@ media-field = "m=" media space port ["/" integer] space proto 1*(space fmt) CRLF When used within PINT requests, the definition of the sub-fields is expanded slightly. The Media sub-field definition is relaxed to accept all of the discrete "top-level" media types defined in [4]. In the milestone services the discrete type "video" is not used, and the extra types "data" and "control" are likewise not needed. The use of these types is not precluded, but the behaviour expected of a PINT Gateway receiving a request including such a type is not defined here. --.-. + 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 sub-field in PINT requests is normally set to "1". A value of "0" may be 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" 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 associated Address Type. In the case that the Address Type in the preceeding Contact field is one of those defined for use with the Network Type "TN", @@ -647,36 +637,35 @@ or disposition of the resulting GSTN service. Thus, for transport protocol "voice", the intent is that the service will result in a GSTN voice call, whilst for protocol "fax" the result will be a 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 subtype of any source data; for example, one of the milestone services calls for a textual source to be vocoded and spoken in a resulting telephone service call. The transport protocol value in this case would be "voice", whilst the media type would be "text". --.-. + The Fmt sub-field is described in [2] as being transport protocol-specific. When used within PINT requests having one of the above protocol values, this sub-field consists of a list of one or more values, each of which is a defined MIME sub-type of the associated Media sub-field value. The special value "-" is allowed, meaning that there is no MIME sub-type. This sub-field retains (from [2]) its meaning that 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, a sub-type value may be specified as an , i.e. a character string starting with "X-". The use of such values is discouraged, and if such a value is expected to find common use then it 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 interpreted as meaning that a unspecified or default sub-type should be used for this service. Thus, the media field value "m=audio 1 voice -" is taken to mean that a voice call is requested, using whatever audio sub type is deemed appropriate by the Executive System. PINT service is a special case, in that the request comes from the IP network but the service call is provided within the GSTN. Thus the service request will not normally be able to define the particular codec used for the resulting GSTN service call. If such an intent IS required, then the quality attribute may be used (see "Suggested Attributes" section of [2]). @@ -776,21 +765,21 @@ could, for example, be needed to authorise access to a document held on the GSTN rather than being required merely to disambiguate the data object. The purpose to which an opaque reference is put, however, is out 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 is implicit in the rest of the request. For example, suppose some company wishes to use PINT to implement a "fax-back service". In their current implementation, the image(s) to be faxed are entirely defined by the telephone number dialled. Within the PINT request, this telephone number -would appear within the "to:" field of the PINT request, and so there +would appear within the "To:" field of the PINT request, and so there is no need for an opaque reference value. 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 be included in the attribute line, but with an empty value field. For example: c= TN RFC2543 +1-201-406-4090 m= text 1 fax plain a=fmtp:plain spr: opr: @@ -804,21 +793,20 @@ further resolution. For example: c= TN RFC2543 +1-201-406-4090 m= text 1 fax - means that there is an implied content stored on the GSTN, and that this is uniquely identified by the combination of SIP To-URI and the Contact field of the session description. -*-*- 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 to a data item held on the GSTN, it is possible to include the content data within the SIP request itself. This is done by using multipart MIME for the SIP payload. The first MIME part contains the SDP description of the telephone network session to be executed. The other MIME parts contain the content data to be transported. Format specific attribute lines within the session description are used to @@ -827,33 +815,31 @@ indicates the Content-ID of the MIME part of the request that contains the actual data, and is defined as: := ("spr:" Content-ID) where Content-ID is as defined in Appendix A of [3] and in [10]). For example: c= TN RFC2543 +1-201-406-4090 m= text 1 fax plain a=fmtp:plain spr: -*-*- + The parameter is the Content-ID of one of the MIME parts inside the message, and this fragment means that the requesting user would like the data object held in the sub-part of this message labelled 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 enclosing SIP request for included data objects. 3.4.3. Attribute Tags to pass information into the Telephone Network -*-*- It may be desired to include within the PINT request service parameters that can be understood only by some entity in the "Telephone Network Cloud". SDP attribute parameters are used for this purpose. They MAY appear within a particular media description or outside of a media description. These attributes may also appear as parameters within PINT URLS (see section 3.5.6) as part of a SIP request. This is necessary so that telephone terminals that require the attributes to be defined can appear within the To: line of a PINT request as well as @@ -870,33 +856,32 @@ number of networks (such as an '800' freephone number). c. The telephone number might be reachable only within a single telephone network (such as the '152' customer service number of BT). Similarly, the number might be an internal corporate extension reachable only within the PBX. 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 within the To: and From: headers and/or Request-URI, normally offer sufficient context to resolve telephone numbers. --.-. + If the client wishes the request to fail if the attributes are not supported, these attributes should be used in conjunction with the "require" attribute (section 3.4.4) and the "Require:org.ietf.sdp.require" header (section 3.5.4). It is not possible to standardise every possible internal telephone network parameter. PINT 1.0 attributes have been chosen for specification because they are common enough that many different PINT systems will want to use them, and therefore interoperability will be increased by having a single specification. -*-*- Proprietary attribute "a=" lines, that by definition are not interoperable, may be nonetheless useful when it is necessary to transport some proprietary internal telephone network variables over the IP network, for example to identify the order in which service call legs should be made. These private attributes SHOULD BE, however, subject 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 An attribute is specified to enable "remote local dialling". This is the @@ -951,53 +936,50 @@ c= TN RFC2543 1-800-765-4321 a=phone-context:+1 This describes an terminal whose address in North America (E.164 country code 1) is 1-800-765-4321. The two telephone terminals described by examples 1 and 2 are different; in fact they are located in different countries. Example 3: --.-. + c=TN RFC2543 123 a=phone-context:+97252 --.-. + This describes a terminal whose address when dialled from within the network identified by +97252 is the string "123". It so happens that +97252 defines one of the Israeli cell phone providers, and 123 reaches customer service when dialled within that network. --.-. + It may well be useful or necessary to use the SDP "require" parameter in conjunction with the phone-context attribute. Example 4: 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 number 23 within the acme.com private PBX network. It is expected that such a description would be understandable by the acme.com PINT server that receives the request. Note that if the PINT server receiving the request is inside the acme.com network, the same terminal might be addressable as follows: c= TN RFC2543 7-23-321 (assuming that "7" is dialled in order to reach the private PBX network from within acme.com) -*-*- - -*-*- 3.4.3.2. Presentation Restriction attribute Although it has no affect on the transport of the service request through the IP Network, there may be a requirement to allow originators of a PINT service request to indicate whether or not they wish the "B party" in the resulting service call to be presented with the "A party's" calling telephone number. It is a legal requirement in some jurisdictions that a caller be able to select whether or not their correspondent can find out the calling telephone number (using Automatic Number Indication or Caller Display or Calling Line Identity Presentation equipment). Thus an attribute @@ -1018,32 +1000,30 @@ address is, by default, set to NOT present its identity to correspondents, and the originator wants to do so for this particular call. It is in keeping with the aim of this attribute to allow the 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 value is "false" then the Calling Line Identity CAN be presented to the correspondent terminal, whilst if it is "true" then it if possible the Executive System is requested to NOT present the Calling Line Identity. -*-*- 3.4.3.3. ITU-T CalledPartyAddress attributes parameters These attributes correspond to fields that appear within the ITU-T Q.763 "CalledPartyAddress" field (see [8] ,section 3.9). PINT clients use these attributes in order to specify further parameters relating to Terminal Addresses, in the case when the address indicates a "local-phone-number". In the case that the PINT request contains a -reference to a PSTN terminal, the parameters may be required to correctly +reference to a GSTN terminal, the parameters may be required to correctly identify that remote terminal. -*-*- The general form of this attribute is "a=Q763-((":" ) |"")". Three of the possible elements and their use in SDP attributes are described here. Where other Q763 elements are to be used, then these should be the subject of further specification to define the syntax of the attribute mapping. It is recommended that any such specification maintains the value sets shown in Q.763. The defined attributes are: a=Q763-nature: - indicates the "nature of address indicator". @@ -1078,90 +1058,85 @@ "1" routing to internal network number not allowed 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 attributes that the number is in fact an internationally significant E.164 number. Normally this SHOULD NOT be done; an internationally significant E.164 number is indicated by using a "global-phone-number" for the address string. --.-. + 3.4.4. The "require" attribute --.-. + 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 server to fail a request if it does not understand one of the PINT attributes, a client should use the "require" attribute, specified as follows: --.-. + a=require: where the attribute-list is a comma-separated list of attributes that appear elsewhere in the session description. --.-. In order to process the request successfully the PINT server must BOTH understand the attribute AND ALSO fulfil the request implied by the presence of the attribute, for each attribute appearing within the attribute-list of the require attribute. If the server does not recognise the attribute listed, the PINT server MUST return an error status code (such as 420 (Bad Extension) or 400 (Bad -Request)), -and SHOULD return suitable Warning: lines explaining the problem or an -Unsupported: header containing the attribute it does not understand. If the -server recognizes the attribute listed, but cannot fulfil the request implied -by the presence of the attribute, the request MUST fail with a status code -of (606 Not Acceptable), along with a suitable Unsupported: header or -Warning: line. --.-. +Request)), and SHOULD return suitable Warning: lines explaining the problem +or an Unsupported: header containing the attribute it does not understand. +If the server recognizes the attribute listed, but cannot fulfil the +request implied by the presence of the attribute, the request MUST fail +with a status code of (606 Not Acceptable), along with a suitable +Unsupported: header or Warning: line. + The "require" attribute may appear anywhere in the session description, and any number of times, but it MUST appear before the use of the attribute marked as required. --.-. + Since the "require" attribute is itself an attribute, the SIP specification allows a server that does not understand the require attribute to ignore it. In order to ensure that the PINT server will comply with the "require" attribute, a PINT client should include a 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 can be included in Require strictures. The exception is the use of phone numbers in SDP parts. However, these are defined as a new network and address type, so that a receiving SIP/SDP server should be able to detect whether or not it supports these forms. The default behaviour for any SDP recipient is that it will fail a PINT request if it does not recognise or support the TN and RFC2543 or X-token network and address types, as without the contents being recognised no media session could be created. Thus a separate stricture is not required in this case. 3.5. PINT Extensions to SIP 2.0 PINT requests are SIP requests; Many of the specifications within this document merely explain how to use existing SIP facilities for the purposes of PINT. -*-*- 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 the first part MUST contain an SDP session description that includes at least one of the format specific attribute tags for "included content data" specified above in section 3.4.3. All subsequent parts contain content data that is to be transferred to the requested Telephone Call Service. As discussed earlier, within a single PINT request, some of the data MAY be pointed to by a URI 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 Type entity header of the enclosing SIP message MUST indicate this. To do so, the media type value within this entity header MUST be set to a value of "multipart". The enclosed body parts SHOULD include the part-specific Content Type headers as appropriate ("application/sdp" for the first body part holding the session description, with an appropriate content type for each of the subsequent, "included data object" parts). This matches the standard syntax of MIME multipart messages as defined in [4]. @@ -1217,63 +1191,63 @@ Warning: 305 pint.acme.com Incompatible media format: jpeg SIP servers that do not understand the PINT extensions at all are strongly encouraged to implement Warning: headers to indicate that PINT extensions are not understood. Also, Warning: headers may be included within NOTIFY requests if it is necessary to notify the client about some condition concerning the invocation of the PINT service (see next). -*-*- 3.5.3. Mechanism to register interest in the disposition of a PINT service, and to receive indications on that disposition 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 true for PINT service, where the person requesting the service is not (necessarily) a party to it, and so may not have an easy way of finding out the disposition of that service. Equally, it may be useful to indicate when the service has changed state, for example when the service call has started. 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 uses a simple scheme that should nevertheless provide useful information. It is possible to expand the scheme in a "backwards compatible" manner, so if required it can be enhanced at a later date. Such enhancement would be expected to be the subject of a separate document. -The PINT 1.0 status registration and indication scheme uses two new methods; -SUBSCRIBE and NOTIFY. These are used to allow a PINT Requesting entity to -register an interest in (or "subscribe" to) the status of a service request, -and for the gateway to return service indications. Both of these messages +The PINT 1.0 status registration and indication scheme uses three new +methods; SUBSCRIBE, UNSUBSCRIBE, and NOTIFY. These are used to allow a PINT +Requesting entity to register an interest in (or "subscribe" to) the status +of a service request, to indicate that this monitoring session is over, +and for the gateway to return service indications. All of these messages follow the same procedure as used for all the SIP requests other than INVITE; the 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 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 -call, so the Call-ID should not be used; instead the origin-field of the -session description enclosed within the original service request is used). +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 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. See section 5.1.4. for security considerations, particularly privacy implications. A value of 0 within the Expires: header indicates a desire to receive one single immediate response (i.e. the request expires immediately). We refer to the period of time before the expiration of the SUBSCRIBE request as the "subscription period". @@ -1288,22 +1262,22 @@ Expires: header indicating how long it is willing to maintain the monitoring session. If this is unacceptable to the PINT Requestor, then it can close the session by sending an immediate BYE (see 3.5.3.3). In principle, a user might send a SUBSCRIBE request after the telephone network service has completed. This allows, for example, checking up "the morning after" to see if the fax was successfully transmitted. However, a PINT gateway is only required to keep state about a call for as long as it indicated previously in a Expires: header within the response to the original INVITE message that triggered the service session, within the -response to the SUBSCRIBE message, or within its BYE message (but see -section 3.5.8, point 3). +response to the SUBSCRIBE message, within the response to the BYE +message, or within its own BYE 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 SUBSCRIBEd, it returns "606 Not Acceptable", along with the appropriate Warning: 307 header indicating that the SDP session ID is no longer valid. This means that a requesting Client that knows that it will want information about the status of a session after the session terminates SHOULD send a SUBSCRIBE request before the session terminates. 3.5.3.2. Sending Status Indications with a NOTIFY request During the subscription period, the Gateway may, from time to time, send a @@ -1320,57 +1294,57 @@ 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. Example: - NOTIFY sip:petrack@pager.com SIP/2.0 To:sip:petrack@pager.com From:sip:R2F.pint.com@service.com + Call-ID: 19971205T234505.56.78@pager.com + CSeq: 4711 SUBSCRIBE Warning: xxx fax aborted, will try for the next hour. Content-Type:application/sdp c=... i=3 pages of 5 sent t=... -3..5.3.3. Closing a monitoring session with a BYE 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 by -sending a BYE request to the correspondent server. Such a request indicates -that the sender intends to close the monitoring session immediately, and, on -receipt of the final response from the receiving server, the session is -deemed over. +Gateway may decide to terminate the monitoring session. This is achieved +by sending an UNSUBSCRIBE request to the correspondent server. Such a +request indicates that the sender intends to close the monitoring session +immediately, and, on receipt of the final response from the receiving +server, the session is deemed over. -If the Gateway initiates closure of the monitoring session by sending a BYE -message, it SHOULD include an "Expires:" header showing for 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 within which the Client -can send a new SUBSCRIBE message to open another 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 subsequent SUBSCRIBE requests can -be rejected with a "606" response. +If the Gateway initiates closure of the monitoring session by sending an +UNSUBSCRIBE message, it SHOULD include an "Expires:" header showing for +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 +within which the Client can send a new SUBSCRIBE message to open another +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 +subsequent SUBSCRIBE requests can be rejected with a "606" response. If the subscription period specified by the Client has expired, then the -Gateway may send an immediate BYE request to the Client's representative -User Agent Server. This ensures that the monitoring session always completes -with a BYE/response exchange, and that the representative User Agent Server -can avoid maintaining state in certain circumstances. +Gateway may send an immediate UNSUBSCRIBE request to the Client's +representative User Agent Server. This ensures that the monitoring session +always completes with a UNSUBSCRIBE/response exchange, and that the +representative User Agent Server can avoid maintaining state in certain +circumstances. 3.5.3.4. Timing of SUBSCRIBE requests - 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 Gateway must have received the service request to which this monitoring session is to be associated, which from the Client's 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 not send a monitoring request. It does not have to wait for the final response from the Gateway, and it can certainly send the SUBSCRIBE request before sending the ACK for the Service request final response. Beyond this @@ -1396,28 +1370,28 @@ immediately prior to sending an ACK message confirming the service if it is interested in transient service status messages. 3.5.4. The "Require:" header for PINT 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 can go into the Require header: org.ietf.sip.subscribe -- the server can fulfill SUBSCRIBE requests - (section 3.5.3) --.-. + and associated methods (see section 3.5.3) + org.ietf.sdp.require -- the PINT server (or the SDP parser associated to it) understands the "require" attribute defined in (section 3.4.4) Example: --.-. + Require:org.ietf.sip.subscribe,org.ietf.sdp.require A client should only include a Require: header where it truly requires the server to fail the request if the option is not supported. 3.5.5. PINT URLs within PINT requests Normally the hostnames and domain names that appear in the PINT URLs are the internal affair of each individual PINT system. A client uses the appropriate SDP payload to indicate the particular service it wishes to @@ -1444,21 +1418,21 @@ 1. The user portion of a sip URL indicates the service to be requested. At present the following services are defined: R2C (for Request-to-Call) R2F (for Request-to-Fax) R2HC (for Request-to-Hear-Content) The user portions "R2C", "R2F", and "R2HC" are reserved for the PINT milestone services. Other user portions MUST be used in case the requested -service is not one of the Milestone services. See section 3.5.8 for some +service is not one of the Milestone services. See section 6.2 for some related considerations concerning registrations by competing 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 service provider. 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 to be used to fulfil the PINT request. @@ -1475,37 +1449,36 @@ 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 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 service. PINT clients MAY include these attribute tags within PINT URLs if they are necessary or a useful complement to the telephone number within the SIP URL. These attribute tags MUST be included as URL 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: --.-. + 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 normally be needed within a URL, because there is a great deal of context available to the help the server interpret the phone number correctly. In particular, there is the SIP URL within the To: header, and there is also the Request-URI. In most cases this provides sufficient information for the telephone network. 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 terminal. 3.5.7. REGISTER requests within PINT -*-*- 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 "receive calls" (i.e. to service requests). Thus a PINT Gateway registers with a proxy or redirect server the service that is accessible via itself, whilst in SIP, a user is registering his/her presence at a particular SIP Server. 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 "broker" among the various PINT gateways that can fulfil a request. A @@ -1565,23 +1538,25 @@ description can be used to indicate the precise nature of the problem. Example: SIP/2.0 606 Not Acceptable From: ... To: ....... ..... Warning: 399 pint.mycom.com Fax in progress, service cannot be aborted Content-Type: application/sdp - Content-Length: 50 + Content-Length: ... v=0 + ... + ... i=3 of 5 pages sent OK c=TN RFC2543 +12014064090 m=image 1 fax tif a=fmtp:tif uri:http://tifsRus.com/yyyyyy.tif Note that the server may return an updated session description within a successful response to a BYE as well. This can be used, for example, to indicate the actual start times and stop times of the telephone session, or how many pages were sent in the fax transmission. @@ -1612,56 +1587,63 @@ 4. Examples of PINT Requests and Responses 4.1. A request to a call centre from an anonymous user to receive a phone call. C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 From: sip:anon-1827631872@chinet.net To: sip:+1-201-456-7890@iron.org;user=phone - Call-ID: 19971205T234505.56.78@chinet.net + Call-ID: 19971205T234505.56.78@pager.com + CSeq: 4711 INVITE Subject: Sale on Ironing Boards Content-type: application/sdp - Content-Length: ... + Content-Length: 174 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687637 2353687637 IN IP4 128.3.4.5 + s=R2C i=Ironing Board Promotion - c= TN RFC2543 +1-201-406-4090 + e=anon-1827631872@chinet.net + t=2353687637 0 m=audio 1 voice - + c=TN RFC2543 +1-201-406-4090 --.-. In this example, the context that is required to interpret the To: address as a telephone number is not given explicitly; it is implicitly known to the R2C@pint.mailorder.com server. But the telephone of the person who wishes to receive the call is explicitly identified as an internationally significant E.164 number that falls within the North 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 call from a particular sales agent (Mary James) concerning the defective ironing board that was purchased C->S: INVITE sip:marketing@pint.mailorder.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 From: sip:john.jones.3@chinet.net To: sip:mary.james@mailorder.com - Call-ID: 19971205T234505.56.79@chinet.net + Call-ID: 19971205T234505.56.78@pager.com + CSeq: 4712 INVITE Subject: Defective Ironing Board - want refund Content-type: application/sdp - Content-Length: ... + Content-Length: 150 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687640 2353687640 IN IP4 128.3.4.5 + s=marketing + e=john.jones.3@chinet.net c= TN RFC2543 +1-201-406-4090 - m=audio 1 voice + t=2353687640 0 + m=audio 1 voice - 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 the "To:" header must fail the request with a 606 Not Acceptable. Note that the sending PINT client "knows" that the PINT Gateway contacted with the "marketing@pint.mailorder.com" Request-URI is capable 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 phone side with different details. For example, it might be that first the @@ -1671,201 +1653,225 @@ indicated in "a=" attribute lines within the session description. The specification of such attribute lines for service 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 Ironing Board C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 From: sip:john.jones.3@chinet.net - To: sip:1-800-FAXBACK@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 + CSeq: 4713 INVITE Content-type: application/sdp - Content-Length: ... + Content-Length: 218 v=0 - o=- 53655768 2353687637 IN IP4 128.3.4.5 - c= TN RFC2543 1-201-406-4091 + o=- 2353687660 2353687660 IN IP4 128.3.4.5 + s=faxback + e=john.jones.3@chinet.net + t=2353687660 0 m=application 1 fax URI + c=TN RFC2543 1-201-406-4091 a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html 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 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-context" attribute, so the context (in this case, for which nation the number is "nationally significant") must be supplied by the faxback@pint.mailorder.com PINT server. --.-. If the server that receives does not understand the number, it should fail the request with and include a "Network Address Not Understood" warning. 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 the "require" attribute. 4.4. A request from same user to have that same information read out over the phone - C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - From: john.jones.3@chinet.net - To: sip:1-800-FAXBACK@steam.edu;user=phone;phone-context=+1 + From: sip:john.jones.3@chinet.net + To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1 Call-ID: 19971205T234505.66.79@chinet.net + CSeq: 4713 INVITE Content-type: application/sdp - Content-Length: ... + Content-Length: 220 v=0 - o=- 53655768 2353687637 IN IP4 128.3.4.5 - c= TN RFC2543 +1-201-406-4090 + o=- 2353687660 2353687660 IN IP4 128.3.4.5 + s=faxback + e=john.jones.3@chinet.net + t=2353687660 0 m=application 1 voice URI + c=TN RFC2543 1-201-406-4090 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. - 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 Via: SIP/2.0/UDP 169.130.12.5 - From: scott.petrack@chinet.net + From: sip:scott.petrack@chinet.net To: sip:R2F@pint.pager.com Call-ID: 19974505.66.79@chinet.net + CSeq: 4714 INVITE Content-Type: multipart/mixed; boundary=--next ----next Content-Type: application/sdp - Content-Length: ... + Content-Length: 236 v=0 - o=- 53655768 2353687637 IN IP4 128.3.4.5 - c= TN RFC2543 +972-9-956-1867 + o=- 2353687680 2353687680 IN IP4 128.3.4.5 + s=R2F + e=scott.petrack@chinet.net + t=2353687680 0 m=text 1 pager plain + c= TN RFC2543 +972-9-956-1867 a=fmtp:plain spr:2@53655768 - ----next Content-Type: text/plain Content-ID: 2@53655768 - Content-Length:... + Content-Length:50 Hi Joe! Please call me asap at 555-1234. ----next-- 4.6. A request to send an image as a fax to phone number +972-9-956-1867 C->S: INVITE sip:faxserver@pint.vocaltec.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - From: scott.petrack@chinet.net + From: sip:scott.petrack@chinet.net To: sip:faxserver@pint.vocaltec.com Call-ID: 19971205T234505.66.79@chinet.net + CSeq: 4715 INVITE Content-type: application/sdp - Content-Length: ... + Content-Length: 267 v=0 - o=- 53655768 2353687637 IN IP4 128.3.4.5 - c= TN RFC2543 +972-9-956-1867 + o=- 2353687700 2353687700 IN IP4 128.3.4.5 + s=faxserver + e=scott.petrack@chinet.net + t=2353687700 0 m=image 1 fax tif gif + c= TN RFC2543 +972-9-956-1867 a=fmtp:tif uri:http://petrack/images/tif/picture1.tif 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. Note that the http server where the pictures reside is local, 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. - 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 Via: SIP/2.0/UDP 169.130.12.5 - From: scott.petrack@chinet.net + From: sip:scott.petrack@chinet.net To: sip:R2HC@pint.acme.com Call-ID: 19974505.66.79@chinet.net + CSeq: 4716 INVITE Content-Type: multipart/mixed; boundary=next --next Content-Type: application/sdp - Content-Length: ... + Content-Length: 316 v=0 - o=- 53655768 2353687637 IN IP4 128.3.4.5 + o=- 2353687720 2353687720 IN IP4 128.3.4.5 + s=R2HC + e=scott.petrack@chinet.net c= TN RFC2543 +1-201-406-4091 + t=2353687720 0 m=text 1 voice plain a=fmtp:plain spr:2@53655768 m=text 1 voice plain a=fmtp:plain uri:http://www.your.com/texts/stuff.doc --next Content-Type: text/plain Content-ID: 2@53655768 - Content-Length: ... + Content-Length: 172 Hello!! I am about to read out to you the document you requested, "uri:http://www.your.com/texts/stuff.doc". We hope you like acme.com's new speech synthesis server. --next-- -*-*- 4.8. Request for the prices for ISDN to be sent to my fax machine - INVITE sip:R2FB@pint.bt.co.uk SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:0345-12347-01;user=phone;phone-context=+44 + To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44 From: sip:hank.wangford@newts.demon.co.uk Call-ID: 19981204T201505.56.78@demon.co.uk + CSeq: 4716 INVITE Subject: Price List Content-type: application/sdp - Content-Length: 116 + Content-Length: 169 v=0 - o=-53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687740 2353687740 IN IP4 128.3.4.5 + s=R2FB i=ISDN Price List - c=TN RFC2543 +44-1794-8331010 + e=hank.wangford@newts.demon.co.uk + t=2353687740 0 m=text 1 fax - + c=TN RFC2543 +44-1794-8331010 4.9. Request for a callback - INVITE sip:R2C@pint.bt.co.uk SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:0345-123456;user=phone;phone-context=+44 + To: sip:0345-123456@pint.bt.co.uk;user=phone;phone-context=+44 From: sip:hank.wangford@newts.demon.co.uk Call-ID: 19981204T234505.56.78@demon.co.uk + CSeq: 4717 INVITE Subject: It costs HOW much? Content-type: application/sdp - Content-Length: 123 + Content-Length: 176 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687760 2353687760 IN IP4 128.3.4.5 + s=R2C i=ISDN pre-sales query + e=hank.wangford@newts.demon.co.uk c= TN RFC2543 +44-1794-8331013 + t=2353687760 0 m=audio 1 voice - 4.10.Sending a set of information in response to an enquiry INVITE sip:R2FB@pint.bt.co.uk SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:0345-12347-01;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 Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk + CSeq: 1147 INVITE Subject: Price Info, as requested Content-Type: multipart/mixed; boundary=next --next Content-type: application/sdp - Content-Length: 211 + Content-Length: 325 v=0 - o=-53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687780 2353687780 IN IP4 128.3.4.5 + s=R2FB i=Your documents - c=TN RFC2543 +44-1794-8331010 + e=colin.masterton@sales.hh.bt.co.uk + t=2353687780 0 m=application 1 fax octet-stream + c=TN RFC2543 +44-1794-8331010 a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr: spr:2@53655768 + --next Content-Type: text/plain Content-ID: 2@53655768 Content-Length: 352 Dear Sir, Thank you for your enquiry. I have checked availability in your area, and we can provide service to your cottage. I enclose a quote for the costs of installation, together with the ongoing rental costs for the line. If you want to proceed with this, please quote @@ -1872,149 +1878,163 @@ job reference isdn/hh/123.45.9901. Yours Sincerely, Colin Masterton --next-- Note that the "implicit" faxback content is given by an EMPTY opaque reference in the middle of the fmtp line in this example. 4.11.Sportsline "headlines" message sent to your phone/pager/fax (i) phone - INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:1-900-123-456-7;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 Call-ID: 19971205T234505.56.78@chinet.net + CSeq: 4721 INVITE Subject: Wonderful World Of Sports NFL Final Scores Content-type: application/sdp - Content-Length: 174 - + Content-Length: 220 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687800 2353687800 IN IP4 128.3.4.5 + s=R2FB i=NFL Final Scores + e=fred.football.fan@skynet.com c= TN RFC2543 +44-1794-8331013 + t=2353687800 0 m=audio 1 voice x-pay a=fmtp:x-pay opr:mci.com/md5: (ii) fax INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:1-900-123-456-7;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 Call-ID: 19971205T234505.56.78@chinet.net + CSeq: 4722 INVITE Subject: Wonderful World Of Sports NFL Final Scores Content-type: application/sdp - Content-Length: 173 + Content-Length: 217 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687820 2353687820 IN IP4 128.3.4.5 + s=R2FB i=NFL Final Scores + e=fred.football.fan@skynet.com c= TN RFC2543 +44-1794-8331010 + t=2353687820 0 m=text 1 fax x-pay a=fmtp:x-pay opr:mci.com/md5: (iii) pager INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:1-900-123-456-7;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 Call-ID: 19971205T234505.56.78@chinet.net + CSeq: 4723 INVITE Subject: Wonderful World Of Sports NFL Final Scores Content-type: application/sdp - Content-Length: 173 + Content-Length: 219 v=0 - o=- 53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687840 2353687840 IN IP4 128.3.4.5 + s=R2FB i=NFL Final Scores + e=fred.football.fan@skynet.com c= TN RFC2543 +44-1794-8331015 + t=2353687840 0 m=text 1 pager x-pay a=fmtp:x-pay opr:mci.com/md5: Note that these are all VERY similar. 4.12.Automatically giving someone a fax copy of your phone bill INVITE sip:BillsRUs@pint.sprint.com SIP/2.0 Via: SIP/2.0/UDP 169.130.12.5 - To:+1-555-888-1234;user=phone + To: sip:+1-555-888-1234@fbi.gov;user=phone From: sip:agent.mulder@fbi.gov Call-ID: 19991231T234505.56.78@fbi.gov + CSeq: 911 INVITE Subject: Itemised Bill for January 98 Content-type: application/sdp - Content-Length: 117 + Content-Length: 247 v=0 - o=-53655765 2353687637 IN IP4 128.3.4.5 + o=- 2353687860 2353687860 IN IP4 128.3.4.5 + s=BillsRUs i=Joe Pendleton's Phone Bill + e=agent.mulder@fbi.gov c=TN RFC2543 +1-202-833-1010 + t=2353687860 0 m=text 1 fax x-files-id a=fmtp:x-files-id opr:fbi.gov/jdcn-123@45:3des;base64, Note: in this case the opaque reference is data used to convince the Executive System that the requester has the right to get this information, rather than selecting the particular content (the A party in the To: field of the SIP "wrapper" does that alone). 5. Security Considerations 5.1. Basic Principles for PINT Use 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 protocol is to pass requests from those users on to a PINT Gateway so an associated Executive System can service those requests. 5.1.1. Responsibility for service requests -The facility of making a PSTN-based call to numbers specified in the PINT +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. Where there is intent or negligence, this may be construed as harrasment of the person incorrectly receiving the call. Whilst the regulatory framework for misuse of Internet connections differs throughout the world and is not always -mature, the rules under which PSTN calls are made are much more settled. +mature, the rules under which GSTN calls are made are much more settled. Someone may be liable for mistaken or incorrect calls. -Understandably, the PSTN Operators would prefer that this someone is not them, +Understandably, the GSTN Operators would prefer that this someone is not them, so they will need to ensure that any PINT Gateway and Executive System combination does not generate incorrect calls through some error in the -Gateway or Executive system implementation or PSTN-internal communications +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. If a request can be shown to have come from a particular Requestor and to have been acted on in good faith by the PINT service provider, then responsibility for making requests may well fall to the Requestor rather than the Operator who executed these requests. Finally, it may be important for the PINT service provider to be able to show that they act only on requests for which they have some degree of assurance of -origin. In many jurisdictions, it is a requirement on PSTN Operators that they +origin. In many jurisdictions, it is a requirement on GSTN 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 will require personal authentication of the Requesting User. 5.1.2. Authority to make requests -Where PSTN 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 -Requestor, as, for example, in the case of existing PSTN split-charging +Requestor, as, for example, in the case of existing GSTN split-charging services like free phone in which the recipient of a call rather than the originator is responsible for the call cost. This is not, of course, the only possibility; for example, PINT service may be provided on a subscription basis, and there are a number of other models. However, whichever model is chosen, there may be a requirement 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 associated Executive System may choose not to provide service. @@ -2029,40 +2049,38 @@ be carried within that request. This can be sensitive information, as an eavesdropper might steal this and use it within their own requests. Such authority should be treated as if it were financial information (such as a credit card number or PIN). The data authorizing a Requesting User to make a PINT request should be known only to them and the service provider. However, this information may be in a form that does not match the schemes normally used within the Internet. For example, X.509 certificates[14] are commonly used for secured transactions on the Internet both in the IP Security Architecture[12] and in the TLS -protocol[13], but the PSTN provider may only store an account code and PIN +protocol[13], but the GSTN provider may 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 are confidential. For some PINT services, no content data is carried over the Internet; however, the telephone or fax numbers of the parties to a resulting service calls may be considered sensitive. As a result, it is likely that the Requestor (and their PINT service provider) will require that any request that is sent across the Internet be protected against eavesdroppers; in short, the requests should to be encrypted. --.-. 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY Some special considerations relate to monitoring sessions using the SUBSCRIBE and NOTIFY messages. The SUBSCRIBE message that is used to register an interest in the disposition of a PINT service transaction uses the original Session Description carried in the related INVITE message. This current specification does not restrict the source of such a SUBSCRIBE message, so it -is possible for an eavesdropper to capture an unprotected sesssion description +is possible for an eavesdropper to capture an unprotected session description and use this in a subsequent SUBSCRIBE 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 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 it might be possible for an attacker to reconstruct the session description and use this reconstruction within a SUBSCRIBE message. @@ -2100,21 +2118,20 @@ 0. It is important that a PINT Registrar uses authentication of the Registrand, as otherwise one PINT service provider would be able to "spoof" another and remove their registration. As this would stop the Proxy passing any requests to that provider, this would 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 that has been registered by another provider; thus a rogue Operator might register its Gateway as "R2C@pint.att.com", thereby hijacking requests. --.-. The solution is the same; all registrations by PINT Gateways MUST be authenticated; this includes both new or apparent replacement registrations, and any cancellation of current registrations. This recommendation is also made in the SIP specification, but for the correct operation of PINT, it is very important indeed. 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 procedures described in SIP. There are several implications of this, and these @@ -2133,27 +2150,27 @@ address, such as a Call Centre. Another aspect of this is that, even if the Requesting User does not consider the telephone or fax numbers of the parties to a PINT service to be private, those parties might. Where PINT servers have reason to believe this might be the case they SHOULD encrypt the request, even if the Requestor has not done so. This could happen, for example, if a Requesting User within a company placed a PINT request and this was carried via the company's Intranet to their Proxy/firewall and thence over the Internet to a PINT Gateway at another location. --.-. + If a request carries data that can be reused by an eavesdropper either to "spoof" the Requestor or to obtain PINT service by inserting the Requestor's authorization token into an eavesdropper's request, then this data MUST be protected. This is particularly important if the 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 described in the SIP specification. As an alternative, it may be acceptable for the authorization token to be held as an opaque reference (see section 3.4.2.3 and examples 4.11 and 4.12), using some proprietary scheme agreed between the Requestor and the PINT service provider, as long as this is resistant to interception and re-use. Also, it may be that the authorization token cannot be used outside of a request cryptographically signed by the Requestor; if so then this requirement can be relaxed, as in this case the token cannot be re-used by another. However, unless both the Requestor and the Gateway are assured that this is the case, any authorization token MUST be @@ -2210,41 +2227,38 @@ expected to be held in opaque references inside the SDP body part of the request. The detailed operation of this mechanism is, by definition, outside the scope of an Internet Protocol, and so must be considered a private matter. However, one approach to indicating to the Requestor that such "second level" authentication or authorization is required by their Service Provider would be to ask for this inside the textual description carried with a 401 response returned from the PINT Gateway. --..- 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 [1] (sections 13 and 15). However, in the case of PINT, the SIP recommendation that requests and responses MAY be protected is not enough. PINT messages MUST be protected, so PINT Implementations MUST support SIP Security (as described 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 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. +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 MUST be configured to provide appropriate protection to PINT traffic. When using TLS, a port configured MUST NOT also be configured for non-TLS traffic. When TLS is used, basic authentication MUST be supported, and client-side certificates MAY be supported. 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 included within the PINT messages using SIP authentication techniques. In @@ -2348,21 +2362,21 @@ 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 registration by the PINT Server of the domain telcoA.com of its ability to support the service R2C as "R2C@telcoA.com", sent to an intermediary server that acts as registrar for the "broker.telcos.com" domain from "R2C@pint.telcoA.com" as follows: REGISTER sip:registrar@broker.telcos.com SIP/2.0 To:sip:R2C@pint.telcoA.com - From:R2C@pint.telcoA.com + From: sip:R2C@pint.telcoA.com ... This is the standard SIP registration service. However, what happens if there are a number of different Service Providers, all of whom support the "R2C" service? Suppose there is a PINT system at domain "broker.com". PINT clients requesting a Request-to-Call service from broker.com might be very willing to be redirected or proxied to any one of the various service providers that had previously registered with the registrar. PINT servers might also be interested in providing service for @@ -2399,21 +2413,20 @@ (iv) may choose to not allow registrations for the "general" service, rejecting all such REGISTER requests. The algorithm by which such a choice is made will be implementation-dependent, and is outside the scope of PINT. Where a 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 operation, to download the behaviour they expect to the 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 A reference configuration for PINT is that service requests are sent, via a PINT Gateway, to an Executive System that fulfils the Service Control Function (SCF) of an Intelligent Network (see [11]). The success or failure of the resulting service call may be information available to the SCF and so may potentially be made available to the PINT Gateway. In terms of historical record of whether or not a service succeeded, a large SCF may be dealing with a million call attempts per hour. Given that volume of service transactions, there are finite limits beyond which it cannot store service @@ -2459,104 +2472,104 @@ service is running. It may accept these requests and simply not even try to query the Executive System until it has information that a service has completed, merely returning the final status. Thus the PINT Requestor may be in what it believes is a monitoring state, whilst the PINT Gateway has not even informed the Executive System that a request has been made. This will increase the internal complexity of the PINT Gateway in that it will have a complex set of interlocking state machines, but does mean that status registration and indication CAN be provided in conjunction with an I.N. system. -6.5. Parameters needed for invoking traditional PSTN Services within PINT +6.5. Parameters needed for invoking traditional GSTN Services within PINT This section describes how parameters needed to specify certain traditional -PSTN services can be carried within PINT requests. +GSTN services can be carried within PINT requests. 6.5.1. Service Identifier When a Requesting User asks for a service to be performed, he or she will, of course, have to specify in some way which service. This can be 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 -With the Request-to-Talk 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 and B parties they want to be engaged in the resulting service call. The A party could identify, for example, the Call Centre from which they want a call back, whilst the B party is their telephone number (i.e. who the Call Centre agent is to call). The Request-to-Fax and Request-to-Hear-Content services require the B party to be specified (respectively the telephone number of the destination Fax machine or the telephone to which spoken content is to be delivered), but the A party is a Telephone Network based resource (either a Fax or speech transcoder/sender), and is implicit; the Requesting User does not (and cannot) specify it. With the "Fax-Back" variant of the Request-to-Fax service, (i.e. where the content to be delivered resides on the GSTN) they will also have specify two parties. As before, the B party is the telephone number of the fax machine to which they want a fax to be sent. However, within this variant the A -party identifies the "document context" for the PSTN-based document store +party identifies the "document context" for the GSTN-based document store from which a particular document is to be retrieved; the analogy here is to -a PSTN user dialling a particular telephone number and then entering the +a GSTN user dialling a particular telephone number and then entering the document number to be returned using "touch tone" digits. The telephone number they dial is that of the document store or A party, with the "touch tone" digits selecting the document within that store. 6.5.3. Other Service Parameters In terms of the extra parameters to the request, the services again differ. -The Request-to-Talk service needs only the A and B parties. Also it is +The Request-to-Call service needs only the A and B parties. Also it is convenient to assert that the resulting service call will carry voice, as the Executive System within the destination GSTN may be able to check that assertion against the A and B party numbers specified and may treat the call differently. 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 this information is carried along with the request itself, or that a reference to the source of this information is given. In addition, it is convenient to assert that the service call will carry fax or voice, and, where possible, to specify the format for the source information. -The PSTN-based content or "Fax-Back" variant of the Request-to-Fax service +The GSTN-based content or "Fax-Back" variant of the Request-to-Fax service needs to specify the Document Store number and the Fax machine number to which the information is to be delivered. It is convenient to 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 The following table summarises the information needed in order to specify -fully the intent of a PSTN service request. Note that it excludes any other +fully the intent of a GSTN service request. Note that it excludes any other parameters (such as authentication or authorisation tokens, or Expires: or CallId: headers) that may be used in a request. Service ServiceID AParty BParty CallFmt Source SourceFmt ------- --------- ------ ------ ------- ------ ------- R2C x x x voice - - R2F x - x fax URI/IL ISF/ILSF R2FB x x x fax OR - R2HC x - x voice URI/IL ISF/ILSF In this table, "x" means that the parameter is required, whilst "-" means that the parameter is not required. -The Services listed are Request to Talk (R2C), Request to Fax (R2F), the -PSTN-based content or "Fax-back" Variant of Request-to-Fax (R2FB), and +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 Request-to-Hear-Content (R2HC). The Call Format parameter values "voice" or "fax" indicate the kind of service call that results. The Source Indicator "URI/IL" implies either that the data is either an Internet source reference (a Universal Resource Identifier, or URI) or is carried "in-line" with the message. The Source indicator "OR" means that the value passed is an Opaque Reference that should be carried along @@ -2571,56 +2584,57 @@ specified either in terms of the URI or that it is carried "in-line". Note that, for some data, the format either can be detected by inspection or, if all else fails, can be assumed from the URI (for example, by assuming that the file extension part of a URL indicates the data type). For an opaque reference, the Source Format is not available on the Internet, and so is not given. 6.6. Parameter Mapping to PINT Extensions This section describes the way in which the parameters needed to specify a -PSTN service request fully might be carried within a "PINT extended" message. +GSTN service request fully might be carried within a "PINT extended" message. There are other choices, and these are not precluded. However, in order to ensure that the Requesting User receives the service that they expect, it is necessary to have some shared understanding of the 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 Request-URI. Thus, the first line of a PINT Invitation would be of the form: INVITE @. SIP/2.0 -The A Party for the Request-to-Talk and "Fax-back" variant of Request-to-Fax +The A Party for the Request-to-Call and "Fax-back" variant of Request-to-Fax service can be held in the "To:" header field. In this case the "To:" header value will be different from the Request-URI. In the services where the A party is not specified, the "To:" field is free to repeat the value held in the Request-URI. This is the case for 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 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 maps to the "transport protocol" element as described in section 3.4.2 of this document. - -The source format specifier is held in the "m=", as a type and optional -sub-type. The latter is normally required for all services except -Request-to-Talk. As shown earlier, the source format and source are not -always required when generating requests for services. However, the inclusion -in all requests 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 are always given. The source format parameter is covered in section -3.4.2 as the "media type" element. +..-- +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 +Request-to-Call or "Faxback", where the "-" form may be used. As shown +earlier, the source format and source are not always required when +generating requests for services. However, the inclusion in all requests +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 +are always given. The source format parameter is covered in section 3.4.2 +as the "media type" element. The source itself is identified by an "a=fmtp:" field value, where needed. -With the exception of the Request-to-Talk service, all invitations will +With the exception of the Request-to-Call service, all invitations will normally include such a field. From the perspective of the SDP extensions, it can be considered as qualifying the media 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 fields as shown in the following table: Service Svc Param PINT/SIP or SDP field used Example value ------- --------- -------------------------- ------------- @@ -2675,168 +2689,27 @@ preceding m= field> a=fmtp:html 7. Open Issues and Draft State 7.1. Open Issues Thre are no current technical open issues. 7.2. Draft State -Please note that changes are cumulative. - -Changes from version 00: - -* Removed References to Q763 parameters. - It is difficult to see how these prameters could be passed to an Intelligent - Network System, and in many potential configurations this information would - not be accepted, as it did not come from a "trusted" source. -* Removed references to ITU and other standardisation efforts. - A PINT standards-track RFC cannot really refer to standards that are in - progress. The set of IETF references are to documents that are on the - Standards Track. Standardisation efforts in other organisations are subject - to change and so these references are not appropriate. - -Changes from version 01 to previous interim version: - -* Corrected a few typos, orphaned internal references, and some of the - examples. -* Made a few corrections and added some comments on changes to be expected - in the next draft. These were highlighted by **** before the affected - paragraphs. -* Removed references to the Telephony URL draft that has expired. It seems - likely that the SIP draft will reach RFC status first. - -Changes from interim version to profile version 03: - -* removed previous change marks -* New changes are indicated by *-*- in the text above the change -* Corrected a few more typos, and re-visited the examples - (thanks to Francois for the MIME comments!) -* removed refs to out of date Internet Conference Architecture draft - from "Introduction" -* Corrected a few more typos, and re-visited the examples - -* added initial summary list for new PINT features - in "PINT Protocol Architecture" -* added a comment on the MIME version implied by PINT 1.0 - in "PINT Protocol Architecture" -* added sub-section number for SDP description in "PINT Protocol - Architecture" -* added sub-section number for SIP description in "PINT Protocol - Architecture" -* removed reference to Security mechanisms in "SIP Operation in PINT" -* added strictures as MUST and split into separate paras for clarity in - "REQUIRED and OPTIONAL elements for PINT compliance" -* added comment that PINT features may be useful for SIP/SDP in "REQUIRED - and OPTIONAL elements for PINT compliance" -* changed E.164 number -> N.P.A., and added local dialling plan number - in " Network Type "TN" and Address Type "RFC2543" -* added an introductory section on data object support in PINT & rewrote - section in "Support for Data Objects within PINT" -* added section on opaque references in "Support for Data Objects within - PINT" -* changed section number and reworked text in "Session Description - support for included Data Objects" -* removed ref to former (non-tagged) method of checking resolution type - in "Session Description support for included Data Objects" -* moved last part of section to the SIP description, leaving a ref. in - "Session Description support for included Data Objects" -* highlighted that attributes may appear as PINT URL parameters in SIP in - "Attribute Tags to pass information into the Telephone Network" -* moved para from end of "phone-context attribute" to main body of - "Attribute Tags to pass information into the Telephone Network" -* added sub-section added (by request) on "Presentation Restriction - attribute" -* Re-introduced sub-section on "CalledPartyAddress attributes parameters" - (Q763 parameters), also by request -* added comment on the general form of Q763 attributes to the original - content of this section -* added a comment that all PINT extensions can be covered by Strictures - to "The "strict" attribute" -* moved some orphaned text from "Session Description support for included - Data Objects" into "Multi-part MIME" -* removed sub-section on " PINT URLS within To: headers" and comments on - "1-800-FLOWERS" style telephony URLs -* removed references to wildcards in REGISTER messages within " REGISTER - requests within PINT" -* replaced example 4.8 with new examples 4.8 - 4.12 -* added section on "Limitations on Available Information and Request - Timing for SUBSCRIBE" -* added a few references that were missing -* added "Collected ABNF" Appendix. - -Changes from profile version 3 to verion 4: - -* New changes are indicated by a -*-* mark on the line before the change -* added a Security Considerations Section -* really added the comment on PINT/SIP implying MIME 1.0 this time! - -* added ABNF definition for the use of PINT attributes as URL parameters -* added ABNF definition of tsp URL parameter -* added a statement that there are no current technical open issues -* corrected boilerplate -* added reference to SIP RFC number. +This draft reflects all changes resulting from the WG "last call" phase. -Changes from profile version 4 to this version (indicated by -.-.) -* In section 4.1, changed wording to emphasize that a "+1" number falls - within the N.A.N.P. region. -* Changed Ordering of Authors. -* Changed incorrect reference to SIP in 3.4.4 - should be SDP -* CHANGED! "strict:" SDP attribute to "require:" throughout -* Corrected typos in 3.1 and 4.6 and 3.4.3.1, clarified text in 3.4.1 -* Changed title (repl. "profile" with more appropriate terms throughout) -* CHANGED! SHOULD to MUST in 5.2 and also in 5.3 -* Added section on privacy implications of identifying the associated - requst within SUBSCRIBE (section 5.1.4) -* Added IANA Considerations Appendix -* CHANGED! specification of Port value to "1" for PINT in 3.4.2 and ABNF -* CHANGED! spec of "defaulted" media sub-type; uses "-" rather than empty -ABNF CHANGES: -* throughout, changed "|" to "/" as per RFC2234 (oops). -* changed use of "<" and ">" throughout. these now imply a definition - in another document (except for the initial connection-field - definition that is merely copied to the PINT ABNF for completeness). -* re-ordered rules to have refinements follow from dependent rules -* added comments to show which rule names are redefinitions of SDP/SIP - names. Where the redefinitions are not pure supersets, comment is - preceded with "NOTE". -* removed stray "media " from the pint-fmtp definition. -* added space separators within PINT variant of fmtp attribute to - deleniate the resolution items, if there's more than one. -* changed definition of PINT variant of fmtp attribute to allow existing - SDP attributes to be appended. Note that this allows zero or more sets - of one or more attributes, with a semi-colon preceeding each set, and - with spaces separating each attribute from its neighbours. -* comma-separated values for require-header and strict-attribute. -* added terminals for each of the tags used in attributes/parameters. -* corrected mistaken ABNF definition of strict/require attribute - - it should include just the field tags, not complete attributes! -* changed the tag value of the strict attribute to "require" for - consistency with the equivalent(ish) require-header, as per request. - Note that they now share the same tag value ("require:"). -* added strict-attribute to the list of PINT/SDP attributes (duh!) -* added some extra rule names for common elements (for q763xx) -* added the fmtp explicit source type tags (uri, spr, and opr) to the - list of items that may be specified in a strict-attribute. For PINT, - the expected behaviour on the part of a recipient (as mentioned in the - body text) is that it should fail an Invitation including one of these - constructs that it doesn't support. However, including these in a - strict-attribute allows them to be used in the wider SIP/SDP context - (e.g. as part of an OPTIONS message exchange). -Changes from "protocol" version 00 to this version (indicated by -..-) -* Security summary section 5.4 clarified and improved 8. References + [1] M. Handley, E. Schooler, H. Schulzrinne, & J. Rosenberg, "SIP: Session Initiation Protocol", RFC2543, Internet Engineering Task Force, March 1999. - [2] M. Handley & V. Jacobsen, "SDP: Session Description Protocol", RFC2327, Internet Engineering Task Force, April 1998. [3] N. Freed & N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC2045, November 1996. [4] N. Freed & N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", @@ -2872,27 +2746,32 @@ "Internet X.509 Public Key Infrastructure Certificate and CRL Profile", RFC2459, Internet Engineering Task Force, January 1999. [15] D. Crocker & P. Overall, "Augmented BNF for Syntax Specifications: ABNF", RFC2234, Internet Engineering Task Force, November 1997. [16] D. Mills, "Network Time Protocol (version 3) specification and implementation", RFC1305, Internet Engineering Task Force, March 1992. [17] D. Eastlake, S. Crocker & J.Schiller, "Randomness Recommendations for Security", Informational RFC 1305, Internet Engineering Task Force, March 1992. +[18] P. Mockapetris, + "Domain Names - Implementation and Specification" RFC 1035, + Inernet Engineering Task Force November 1987. 9. Acknowledgements -The authors wish to thank the members of the PINT working group for comments -that were helpful to the preparation of this specification. Ian Elz's -comments were extremely useful to our understanding of internal PSTN -operations. The SUBSCRIBE and NOTIFY requests were first suggested by -Henning Schulzrinne and Jonathan Rosenberg. + +The authors wish to thank the members of the PINT working group for +comments that were helpful to the preparation of this specification. +Ian Elz's comments were extremely useful to our understanding of internal +PSTN operations. The SUBSCRIBE and NOTIFY requests were first suggested +by Henning Schulzrinne and Jonathan Rosenberg. Finally, thanks to Bernie +Hoeneisen for his close proofreading. Appendix A: Collected ABNF for PINT Extensions ;; --(ABNF is specified in RFC 2234 [15]) ;; --Variations on SDP definitions connection-field = ["c=" nettype space addrtype space connection-address CRLF] ; -- this is the original definition from SDP, included for completeness ; -- the following are PINT interpretations and modifications @@ -2944,187 +2823,158 @@ ; -- 0 retains usual sdp meaning of "temporarily no media" ; -- (i.e. "line is on hold") ; -- (1 means there is media) proto = (INProto/TNProto) ; -- redefined as a superset of the original SDP definition INProto = 1* () ; -- this is the "classic" SDP protocol, defined if nettype == "IN" ; -- alpha-numeric is as defined in SDP - -TNProto = ("phone"/"fax"/"pager") +..-- +TNProto = ("voice"/"fax"/"pager") ; -- this is the PINT protocol, defined if nettype == "TN" fmt = ( / "-") ; -- NOTE redefined as a subset of the original SDP definition ; -- subtype as defined in RFC2046, or "-". MUST be a subtype of type held ; -- in associated media sub-field or the special value "-". --.-. attribute-fields = *("a=" attribute-list ) ; -- redefined as a superset of the definition given in SDP ; -- CRLF is as defined in SDP attribute-list = 1(PINT-attribute / ) ; -- attribute is as defined in SDP --.-. PINT-attribute = (clir-attribute / q763-nature-attribute / q763plan-attribute / q763-INN-attribute / - phone-context-attribute / + phone-context-attribute / tsp-attribute / pint-fmtp-attribute / strict-attribute) --.-. + clir-attribute = clir-tag ":" ("true" / "false") --.-. clir-tag = "clir" --.-. q763-nature-attribute = Q763-nature-tag ":" q763-natures --.-. q763-nature-tag = "Q763-nature" --.-. q763-natures = ("1" / "2" / "3" / "4") --.-. q763-plan-attribute = Q763-plan-tag ":" q763-plans --.-. q763-plan-tag = "Q763-plan" --.-. q763-plans = ("1" / "2" / "3" / "4" / "5" / "6" / "7") ; -- of these, the meanings of 1, 3, and 4 are defined in the text --.-. q763-INN-attribute = Q763-INN-tag ":" q763-INNs --.-. q763-INN-tag = "Q763-INN" --.-. q763-INNs = ("0" / "1") --.-. phone-context-attribute = phone-context-tag ":" phone-context-ident --.-. + phone-context-tag = "phone-context" phone-context-ident = network-prefix / private-prefix network-prefix = intl-network-prefix / local-network-prefix intl-network-prefix = "+" 1* local-network-prefix = 1* private-prefix = 1*excldigandplus 0* excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d)) +..-- +tsp-attribute = tsp-tag "=" provider-domainname + +tsp-tag = "tsp" + +provider-domainname = +; -- domain is defined in RFC1035 --.-. ; -- NOTE the following is redefined relative to the normal use in SDP pint-fmtp-attribute = "fmtp:" resolution *( resolution) ( ";" 1() *( )) ; -- subtype as defined in RFC2046. ; -- NOTE that this value MUST match a fmt on the ultimately preceeding ; -- media-field ; -- attribute is as defined in SDP --.-. resolution = (uri-ref / opaque-ref / sub-part-ref) --.-. uri-ref = uri-tag ":" ; -- URI-Reference defined in RFC2396 --.-. + uritag = "uri" --.-. opaque-ref = opr-tag ":" 0* --.-. opr-tag = "opr" --.-. sub-part-ref = spr-tag ":" ; -- Content-ID is as defined in RFC2046 and RFC822 --.-. spr-tag = "spr" --.-. strict-attribute = "require:" att-tag-list --.-. att-tag-list = 1(PINT-att-tag-list / / pint-fmtp-tag-list) *("," (PINT-att-tag-list / / pint-fmtp-tag-list) ) ; -- att-field as defined in SDP --.-. PINT-att-tag-list = (phone-context-tag / clir-tag / q763-nature-tag / q763-plan-tag / q763-INN-tag) --.-. pint-fmtp-tag-list = (uri-tag / opr-tag / spr-tag) ;; --Variations on SIP definitions --.-. clir-parameter = clir-tag "=" ("true" / "false") --.-. q763-nature-parameter = Q763-nature-tag "=" Q763-natures --.-. q763plan-parameter = Q763-plan-tag "=" q763plans --.-. q763-INN-parameter = Q763-INN-tag "=" q763-INNs --.-. -tsp-parameter = tsp-tag "=" -; -- hostname is as defined in SIP - --.-. -tsp-tag = "tsp" +tsp-parameter = tsp-tag "=" provider-domainname --.-. phone-context-parameter = phone-context-tag "=" phone-context-ident SIP-param = ( / / / / / ) ; -- the values in this list are all as defined in SIP PINT-param = ( clir-parameter / q763-nature-parameter / q763plan-parameter / q763-INN-parameter/ tsp-parameter / phone-context-parameter ) URL-parameter = (SIP-param / PINT-param) ; -- redefined SIP's URL-parameter to include ones defined in PINT --.-. Require-header = "require:" 1(required-extensions) *("," required-extensions) ; -- NOTE this is redefined as a subset of the SIP definition ; -- (from RFC2543/section 6.30) --.-. required-extensions = ("org.ietf.sip.subscribe" / "org.ietf.sdp.require") Appendix B: IANA Considerations There are three kinds of identifier used in PINT extensions that SHOULD 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. * Private Attributes as mentioned in section 3.4.3 * Private Phone Context values, as described in section 3.4.3.1.