--- 1/draft-ietf-pint-protocol-00.txt 2007-12-18 18:54:58.000000000 +0100 +++ 2/draft-ietf-pint-protocol-01.txt 2007-12-18 18:54:58.000000000 +0100 @@ -1,20 +1,20 @@ INTERNET-DRAFT Scott Petrack, Internet Engineering Task Force Metatel PINT Working Group Lawrence Conroy, -Issued: 18th June 1999 Siemens Roke Manor Research -Expires: 18th December 1999 +Issued: 3 August 1999 Siemens Roke Manor Research +Expires: 14 January 2000 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. @@ -44,22 +44,20 @@ 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. 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] - PSP: Extensions to SIP and SDP June, 1999 - Contents 1. Introduction ......................................................... 4 1.1 Glossary ............................................................ 5 2. PINT Milestone Services .............................................. 6 2.1 Request to Call ................................................. 6 2.2 Request to Fax .................................................. 6 2.3 Request to Hear Content ......................................... 6 2.4 Relation between PINT milestone services and traditional @@ -101,23 +99,20 @@ 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 phone call ..................................................... 30 4.2. A request from a non anonymous customer (John Jones) to receive a phone call from a particular sales agent (Mary James) .......... 30 4.3. A request to get a fax back .................................... 31 Petrack & Conroy [Page 2] - - PSP: Extensions to SIP and SDP June, 1999 - 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 4.11.Sportsline "headlines" message sent to your phone/fax/pager .... 35 @@ -157,22 +152,20 @@ 9. Acknowledgements ..................................................... 53 Appendix A: Collected ABNF for PINT Extensions .......................... 54 Appendix B: IANA Considerations ......................................... 59 Appendix C: Authors' Addresses .......................................... 61 Petrack & Conroy [Page 3] - PSP: Extensions to SIP and SDP June, 1999 - 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): 1. an IP host sends a request to a server on an IP network; 2. the server relays the request into a telephone network; 3. the telephone network performs the requested call service. @@ -214,21 +207,20 @@ A PINT user who wishes to invoke a service within the telephone network uses SIP to invite a remote PINT server into a session. The invitation contains an SDP description of the media session that the user would like to take place. This might be a "sending a fax session" or a "telephone call session", for example. In a PINT service execution session the media is transported over the phone system, while in a SIP session the media is normally transported over an internet. Petrack & Conroy [Page 4] - PSP: Extensions to SIP and SDP June, 1999 When used to invoke a PINT service, SIP establishes an association between a requesting PINT client and the PINT server that is responsible for invoking the service within the telephone network. These two entities are not the same entities as the telephone network entities involved in the telephone network service. The SIP messages carry within their SDP payloads a description of the telephone network media session. Note that the fact that a PINT server accepts an invitation and a session is established is no guarantee that the media will be successfully transported. (This is analogous to the fact that if a SIP invitation is accepted @@ -273,22 +265,20 @@ request received from an PINT client. PINT Client - An Internet host that sends requests for invocation of a PINT Service, in accordance with this document. PINT Gateway - An Internet host that accepts requests for PINT Service and dispatches them onwards towards a telephone network. Petrack & Conroy [Page 5] - PSP: Extensions to SIP and SDP June, 1999 - Executive System - A system that interfaces to a telephone network that executes a PINT service, and to a PINT Server. It is not directly associated with the Internet, and is represented by the PINT Server. Requesting User - The initiator of a request for service. This role may be distinct from that of the "party" to any telephone network call that results from the request. (Service Call) Party - A person who is involved in a telephone network call that results from the execution of a PINT service request, or a telephone @@ -332,22 +322,20 @@ 2.4 Relation between PINT milestone services and traditional telephone services There are many different versions and variations of each telephone call service invoked by a PINT request. Consider as an example what happens when a user requests to call 1-800-2255-287 via the PINT Request-to-Call service. Petrack & Conroy [Page 6] - PSP: Extensions to SIP and SDP June, 1999 - There may be thousands of agents in the call centre, and there may be any number of sophisticated algorithms and equipments that are used to decide exactly which agent will return the call. And once this choice is made, there may be many different ways to set up the call: the agent's phone might ring first, and only then the original user will be called; or perhaps the user might be called first, and hear some horrible music or pre-recorded message while the agent is located. Similarly, when a PINT request causes a fax to be sent, there are hundreds of fax protocol details to be negotiated, as well as transmission details @@ -391,22 +379,20 @@ | PINT | PINT \ PINT | PINT | |Exec| Telephone / | client |<-------------->| server |gatewy|=====|Syst| Network \ |_________| protocol / cloud |______| |____| Cloud / \ \ / \ /\/\/\/\/\/\/\ \/\/\/\/\/\/\/\/ Figure 1: PINT Functional Architecture Petrack & Conroy [Page 7] - PSP: Extensions to SIP and SDP June, 1999 - The system of PINT servers is represented as a cloud to emphasise that a single PINT request might pass through a series of location servers, proxy servers, and redirect servers, before finally reaching the correct PINT gateway that can actually process the request by passing it to the Telephone Network Cloud. The PINT gateway might have a true telephone network interface, or it might be connected via some other protocol or API to an "Executive System" that is capable of invoking services within the telephone cloud. @@ -448,22 +434,20 @@ 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] - PSP: Extensions to SIP and SDP June, 1999 - *-*- 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 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 @@ -505,22 +489,20 @@ 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] - PSP: Extensions to SIP and SDP June, 1999 - 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 @@ -562,22 +544,20 @@ 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 "application" data, etc. An important example of transporting "application" data is the milestone service "Voice Access to Web Content". In this case the data to be transported is pointed to by a URI, the data type is application/URI, and the transport protocol would be "voice". Some sort of speech-synthesis facility, speaking out to a Phone, will have to be invoked to perform this service. - PSP: Extensions to SIP and SDP June, 1999 - 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-". -.-. @@ -619,21 +599,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 The SDP specification does not have explicit support for reference to or carriage of Data Objects within requests. In order to use SDP for PINT, there is a need to describe such media sessions as "a telephone call to a certain number during which such-and-such an image is sent as a fax". To support this, two extensions to the session description format are specified. These are some new allowed values for the Media Field, and a description of the "fmtp" parameter when used with the Media Field values (within the context of the Contact Field Network type "TN"). @@ -677,21 +656,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 -.-. 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 @@ -734,22 +712,20 @@ To indicate which form each resolution element takes, each of them starts with its own literal tag. The detailed syntax of each form is described in the following sub-sections. 3.4.2.2. Support for Remote Data Object References in PINT Where data objects stored elsewhere on the IP Network are to be used as sources for processing within a PINT service, they may be referred to using the uri-ref form. This is simply a Uniform Resource Identifier (URI), as described in [9]. - PSP: Extensions to SIP and SDP June, 1999 - Note that the reference SHOULD be an absolute URI, as there may not be enough contextual information for the recipient server to resolve a relative reference; any use of relative references requires some private agreement between the sender and recipient of the message, and should be avoided unless the sender can be sure that the recipient is the one intended and the reference is unambiguous in context. This also holds for partial URIs (such as: "uri:http://aMachine/index.html") as these will need to be resolved in the context of the eventual recipient of the message. @@ -789,22 +765,20 @@ For example: c= TN RFC2543 +1-201-406-4090 m= text 1 fax plain a=fmtp:plain opr:APPL.123.456 means send me the data that is indexed ON THE GSTN by the reference value "APPL.123.456"; the Executive System may also take the Telephone URL held in the To: field of the enclosing SIP message into account when deciding the context to be used for the data object dereference. - PSP: Extensions to SIP and SDP June, 1999 - Of course, an opaque reference may also be used for other purposes; it could, for example, be needed to authorise access to a document held on the 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 @@ -824,21 +798,21 @@ might be used to precede some unambiguous "faxed back" data with a covering note (see next sub-section for details of the sub-part reference). In the special case where an opaque reference is the sole resolution of a PINT Service Request, AND that reference needs no value, there is no need for a Fmt list at all; the intent of the service is unambiguous without any further resolution. For example: c= TN RFC2543 +1-201-406-4090 - m= text 1 fax + m= text 1 fax - means that there is an implied content stored on the GSTN, and that this is 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 @@ -847,22 +821,20 @@ 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 indicate which other MIME part within the request contains the content data. Instead of a URI or opaque reference, the format-specific attribute indicates the Content-ID of the MIME part of the request that contains the actual data, and is defined as: := ("spr:" Content-ID) - PSP: Extensions to SIP and SDP June, 1999 - 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 @@ -904,22 +876,20 @@ 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). - PSP: Extensions to SIP and SDP June, 1999 - 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 @@ -961,22 +931,20 @@ private-prefix = 1*excldigandplus 0*uric An intl-network-prefix and local-network-prefix MUST be a bona fide network prefix, and a network-prefix that is an intl-network-prefix MUST begin with an E.164 service code ("country code"). It is possible to register new private-prefixes with IANA so as to avoid confrontation. Prefixes that are not so registered MUST begin with an "X-" to indicate their private, non-standard nature (see Appendix C). - PSP: Extensions to SIP and SDP June, 1999 - Example 1: c= TN RFC2543 1-800-765-4321 a=phone-context:+972 This describes an terminal whose address in Israel (E.164 country code 972) is 1-800-765-4321. Example 2: @@ -1015,22 +983,20 @@ 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) *-*- - PSP: Extensions to SIP and SDP June, 1999 - *-*- 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 @@ -1071,22 +1037,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 - The defined attributes are: a=Q763-nature: - indicates the "nature of address indicator". The value MAY be any number between 0 and 127. The following values are specified: "1" a subscriber number "2" unknown "3" a nationally significant number "4" an internationally significant number @@ -1128,22 +1092,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 - -.-. 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 @@ -1185,21 +1147,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 *-*- 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 @@ -1243,22 +1204,20 @@ the data but instead hold a reference to it. 3.5.2. Warning header A PINT server MUST support the SIP "Warning:" header so that it can signal lack of support for individual PINT features. As an example, suppose the PINT request is to send a jpeg picture to a fax machine, but the server cannot retrieve and/or translate jpeg pictures from the Internet into fax transmissions. - PSP: Extensions to SIP and SDP June, 1999 - In such a case the server fails the request and includes a Warning such as the following: 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 @@ -1300,21 +1259,20 @@ 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). 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. - PSP: Extensions to SIP and SDP June, 1999 -.-. 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 @@ -1357,21 +1315,20 @@ The receiving user agent server MUST acknowledge this by returning a final response (normally a "200 OK"). In this version of the PINT extensions, the Gateway is not required to support redirects (3xx codes), and so may treat them as a failure. Thus, if the response code class is above 2xx then this may be treated by the Gateway as a failure of the monitoring session, and in that situation it will immediately attempt to close the session (see next). The NOTIFY request contains the modified session description. For example, the Gateway may be able to indicate a more accurate start or stop time. - PSP: Extensions to SIP and SDP June, 1999 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 Warning: xxx fax aborted, will try for the next hour. @@ -1414,22 +1371,20 @@ 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 point, the Client is free to send a SUBSCRIBE request when it decides, unless the Gateway's final response to the initial service request indicated a short Expires: time. - PSP: Extensions to SIP and SDP June, 1999 - However, there are good reasons (see 6.4) why it may be appropriate to start a monitoring session immediately before the service is confirmed by the PINT Client sending an ACK. At this point the Gateway will have decided whether or not it can handle the service request, but will not have passed the request on to the Executive System. It is therefore in a good position to ask the Executive System to enable monitoring when it sends the service request onwards. In practical implementations, it is likely that more information on transient service status will be available if this is indicated as being important BEFORE or AS the service execution phase starts; once execution has begun the level of information that can be @@ -1467,21 +1422,20 @@ internal affair of each individual PINT system. A client uses the appropriate SDP payload to indicate the particular service it wishes to invoke; it is not necessary to use a particular URL to identify the service. A PINT URL is used in two different ways within PINT requests: within the Request-URI, and within the To: and From: headers. Use within the Request-URI requires clarification in order to ensure smooth interworking with the Telephone Network serviced by the PINT infrastructure, and this is covered next. - PSP: Extensions to SIP and SDP June, 1999 3.5.5.1. PINT URLS within Request-URIs There are some occasions when it may be useful to indicate service information within the URL in a standardized way: a. it may not be possible to use SDP information to route the request if it is encrypted; b. it allows implementation that make use of I.N. "service indicators"; c. It enables multiple competing PINT gateways to REGISTER with a single "broker" server (proxy or redirect) (see section 6.3) @@ -1524,22 +1478,20 @@ 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 - PSP: Extensions to SIP and SDP June, 1999 - 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. @@ -1581,22 +1533,20 @@ terminates the call and the media session. Applying this model to PINT, if a PINT client makes a request that results in invocation of a telephone call from A to B, a BYE request from the client, if accepted, should result in a termination of the phone call. A question arises when the telephone call might not have even started at the time when the BYE request is received. For example, if a request to fax is sent with a t= line indicating that the fax is to be sent tomorrow at 4 AM, the requestor might wish to cancel the request before the specified time. - PSP: Extensions to SIP and SDP June, 1999 - Even if the call has yet to start, it may not be possible to terminate the media session on the telephone system side. For example, the fax call may be in progress when the BYE arrives, and perhaps it is just not possible to cancel the fax in session. Another possibility is that the entire telephone-side service might be completed before the BYE is received. In the above Request-to-Fax example, the BYE might be sent the following morning, and the entire fax has been sent before the BYE was received. It is too late to send the BYE. In the case where the telephone network cannot terminate the call, the @@ -1638,22 +1588,20 @@ The second issue concerns how long must a server keep call state after receiving a BYE. A question arises because other clients might still wish to send queries about the telephone network session that was the subject of the PINT transaction. Ordinary SIP semantics have three important implications for this situation: 1. A BYE indicates that the requesting client will clear out all call state as soon as it receives a successful response. A client SHOULD NOT send a SUBSCRIBE request after it has sent a BYE. - PSP: Extensions to SIP and SDP June, 1999 - 2. A server may return an Expires: header within a successful response to a BYE request. This indicates for how long the server will retain session state about the telephone network session. At any point during this time, a client may send a SUBSCRIBE request to the server to learn about the session state. 3. When engaged in a SUBSCRIBE/NOTIFY monitoring session, PINT servers that send BYE to a URL listed in the Contact: header of a client request SHOULD not clear session state until after the successful response to the BYE is received. For example, it may be that the requesting client host is turned @@ -1673,36 +1621,34 @@ To: sip:+1-201-456-7890@iron.org;user=phone Call-ID: 19971205T234505.56.78@chinet.net Subject: Sale on Ironing Boards Content-type: application/sdp Content-Length: ... v=0 o=- 53655765 2353687637 IN IP4 128.3.4.5 i=Ironing Board Promotion c= TN RFC2543 +1-201-406-4090 - m=audio 1 voice + m=audio 1 voice - -.-. 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 - PSP: Extensions to SIP and SDP June, 1999 - 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 Subject: Defective Ironing Board - want refund Content-type: application/sdp Content-Length: ... v=0 @@ -1744,21 +1690,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 -.-. 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 @@ -1798,22 +1743,20 @@ ----next Content-Type: text/plain Content-ID: 2@53655768 Content-Length:... Hi Joe! Please call me asap at 555-1234. ----next-- - PSP: Extensions to SIP and SDP June, 1999 - 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 To: sip:faxserver@pint.vocaltec.com Call-ID: 19971205T234505.66.79@chinet.net Content-type: application/sdp Content-Length: ... @@ -1854,55 +1797,54 @@ --next Content-Type: text/plain Content-ID: 2@53655768 Content-Length: ... 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-- - PSP: Extensions to SIP and SDP June, 1999 *-*- 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 From: sip:hank.wangford@newts.demon.co.uk Call-ID: 19981204T201505.56.78@demon.co.uk Subject: Price List Content-type: application/sdp Content-Length: 116 v=0 o=-53655765 2353687637 IN IP4 128.3.4.5 i=ISDN Price List c=TN RFC2543 +44-1794-8331010 - m=text 1 fax + m=text 1 fax - 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 From: sip:hank.wangford@newts.demon.co.uk Call-ID: 19981204T234505.56.78@demon.co.uk Subject: It costs HOW much? Content-type: application/sdp Content-Length: 123 v=0 o=- 53655765 2353687637 IN IP4 128.3.4.5 i=ISDN pre-sales query c= TN RFC2543 +44-1794-8331013 - m=audio 1 voice + 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 From: sip:colin.masterton@sales.hh.bt.co.uk Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk Subject: Price Info, as requested Content-Type: multipart/mixed; boundary=next @@ -1910,23 +1852,20 @@ --next Content-type: application/sdp Content-Length: 211 v=0 o=-53655765 2353687637 IN IP4 128.3.4.5 i=Your documents c=TN RFC2543 +44-1794-8331010 m=application 1 fax octet-stream a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr: spr:2@53655768 - - PSP: Extensions to SIP and SDP June, 1999 - --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 @@ -1967,22 +1906,20 @@ Content-type: application/sdp Content-Length: 173 v=0 o=- 53655765 2353687637 IN IP4 128.3.4.5 i=NFL Final Scores c= TN RFC2543 +44-1794-8331010 m=text 1 fax x-pay a=fmtp:x-pay opr:mci.com/md5: - PSP: Extensions to SIP and SDP June, 1999 - (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 From: sip:fred.football.fan@skynet.com Call-ID: 19971205T234505.56.78@chinet.net Subject: Wonderful World Of Sports NFL Final Scores Content-type: application/sdp Content-Length: 173 @@ -2011,21 +1948,20 @@ i=Joe Pendleton's Phone Bill c=TN RFC2543 +1-202-833-1010 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). - PSP: Extensions to SIP and SDP June, 1999 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 request, however, comes with some risks. The request can specify an incorrect @@ -2068,22 +2004,20 @@ 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 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 services like free phone in which the recipient of a call rather than the originator is responsible for the call cost. - PSP: Extensions to SIP and SDP June, 1999 - 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. 5.1.3. Privacy Even if the identity of the Requesting User and the Authority under which they @@ -2125,22 +2059,20 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 - SDP (see section 6 of [2], "o=" field) does not specify the mechansim used to generate the sess-id field, and suggests that a method based on timestamps produced by Network Time Protocol [16] can be used. This is sufficient to guarantee uniqueness, but may allow the value to be guessed, particularly if other unprotected requests from the same originator are available. Thus, to ensure that the session identifier is not guessable the techniques described in section 6.3 of [17] can be used when generating the origin-field for a session description to be used inside a PINT INVITE message. If all requests from (and responses to) a particular PINT requesting entity are @@ -2181,22 +2113,20 @@ 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 are covered here. - PSP: Extensions to SIP and SDP June, 1999 - For several of the PINT services, the To: header field of SIP is used to identify one of the parties to the resulting service call. The PINT Request-To-Call service is an example. As mentioned in the SIP specification, this field is used to route SIP messages through an infrastructure of Redirect and Proxy server between the corresponding User Agent Servers, and so cannot be encrypted. This means that, although the majority of personal or sensitive data can be protected whilst in transit, the telephone (or fax) number of one of the parties to a PINT service call cannot, and will be "visible" to any interception. For the PINT milestone services this may be acceptable, since the caller named in the To: service is typically a "well known" provider @@ -2238,21 +2168,20 @@ encrypted, then the request cannot be decoded at the Proxy server, and so Gateway selection based on contained information cannot be made there. The result is that the Proxy may deliver the request to a Gateway that cannot handle it; the implication is that a PINT/SIP Proxy SHOULD consider its choice for the appropriate Gateway subject to correction, and, on receiving a 501 or 415 rejection from the first gateway chosen, try another. In this way, the request will succeed if at all possible, even though it may be delayed (and tie up resources in the inappropriate Gateways). - PSP: Extensions to SIP and SDP June, 1999 This opens up an interesting avenue for Denial Of Service; sending a valid request that appears to be suitable for a number of different Gateways, and simply occupying those Gateways in decrypting a message requesting a service they cannot provide. As mentioned in section 3.5.5.1, the choice of service name to be passed in the userinfo portion of the SIP Request-URI is flexible, and it is RECOMMENDED that names be chosen that allow a Proxy to select an appropriate Gateway without having to examine the SDP body part. Thus, in the example given here, the service might be called "Request-To-Page" or "R2P" rather than the more general use of "R2F", if there is a possibility of the SDP body part being protected during transit. @@ -2281,94 +2210,88 @@ 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] for ALL -communications between them. In this case, PINT messages need not be - PSP: Extensions to SIP and SDP June, 1999 -protected using the procedures described in SIP; all traffic is protected -already. The initiating entity can instead send the request "in plain". +In some configurations, PINT Clients, Servers, and Gateways can be sure that +they operate using the services of network level security [13], transport +layer security [12], or physical security for all +communications between them. In these cases messages MAY be exchanged +without SIP security, since all traffic is protected already. Clients + +and servers SHOULD support manual configuration to use such lower +layer security facilities. + +When using network layer security [13], the Security Policy Database +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 contrast with SIP, PINT requests are often sent to parties with which a prior communications relationship exists (such as a Telephone Carrier). In this case, there may be a shared secret between the client and the PINT Gateway. Such PINT systems MAY use authentication based on shared secrets, with HTTP "basic authentication". When this is done, the message integrity -must be guaranteed by some lower layer mechanism. +and privacy must be guaranteed by some lower layer mechanism. There are implications on the operation of PINT here though. If a PINT proxy or redirect server is used, then it must be able to examine the contents of the IP datagrams carried. It follows that an end-to-end approach using network-layer security between the PINT Client and a PINT Gateway precludes the use of an intervening proxy; communication between the Client and Gateway is carried via a tunnel to which any intervening entity cannot gain access, even if the IP datagrams are carried via this node. Conversely, if a "hop-by-hop" approach is used, then any intervening PINT proxies (or redirect servers) are, by implication, trusted entities. -If using TCP for underlying transport of PINT messages, then transport layer -security mechanisms (SSL or TLS [12]) may be used as an alternative. Again, -all PINT players MUST be sure that TLS is in operation if they wish to avoid -using SIP Security, and if mutual authentication is not available, then SIP -authentication techniques MUST be used. - -In any case, TLS is required for HTTP traffic, in those configurations that -use a "Web" front-end "prior" to any PINT protocol transactions; there is no -point in protecting the PINT transactions if the data used to construct -requests via HTTP requests is passed "in clear". - However, if there is any doubt that there is an underlying network or transport layer security association in place, then the players in a PINT protocol exchange MUST use encryption and authentication techniques within the protocol itself. The techniques described in section 15 of RFC2543 MUST be used, unless there is an alternative protection scheme that is agreed between the parties. In either case, the content of any message body (or bodies) carried within a PINT request or response MUST be protected; this has implications on the options for routing requests via Proxies (see 5.3). Using SIP techniques for protection, the Request-URI and To: fields headers within PINT requests cannot be protected. In the baseline PINT services these fields may contain sensitive information. This is a consideration, and if -these data ARE considered sensitive, then this will preclude the use of the +these data ARE considered sensitive, then this will preclude the sole use of SIP techniques; in such a situation, transport [12] or network layer [13] protection mechanisms MUST be used. -Choice of mechanism is by mutual agreement between the PINT entities. As a final point, this choice will in turn have an influence on the choice of transport layer protocol that can be used; if a TLS association is available -between two nodes, then TCP will have to be used. This means that the default -behaviour of SIP entities (try UDP, then try TCP if that fails) may be -modified in such a situation. - - PSP: Extensions to SIP and SDP June, 1999 +between two nodes, then TCP will have to be used. This is different from +the default behaviour of SIP (try UDP, then try TCP if that fails). 6. Deployment considerations and the Relationship PINT to I.N. (Informative) 6.1. Web Front End to PINT Infrastructure It is possible that some other protocol may be used to communicate a Requesting User's requirements. Due to the high numbers of available Web Browsers and servers it seems likely that some PINT systems will use HTML/HTTP as a "front end". In this scenario, HTTP will be used over a connection from the Requesting User's Web Browser (WC) to an Intermediate @@ -2411,22 +2334,20 @@ However, there do seem to be two approaches. Either a Server that acts as a proxy or redirect will select the appropriate Gateway itself and will cause the request to be sent on accordingly, or a list of possible Locations will be returned to the Requesting User from which they can select their choice. In SIP, the implication is that, if a proxy cannot resolve to a single unique match for a request destination, then a response containing a list of the choices should be returned to the Requesting User for selection. This is not too likely a scenario within the normal use of SIP. - PSP: Extensions to SIP and SDP June, 1999 - However, within PINT, such ambiguity may be quite common; it implies that there are a number of possible providers of a given service. 6.3. Competing PINT Gateways REGISTERing to offer the same service With PINT, the registration is not for an individual but instead for a 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 @@ -2467,22 +2388,20 @@ In this last case, on receiving an Invitation for the "general" service, either: (iii.1) it passes on the invitation to all registered service providers, returning a collated response with all acceptances, using multiple Location: headers, or (iii.2) it silently selects one of the registrations (using, for example, a "round robin" approach) and routes the Invitation and response onwards without further comment. - PSP: Extensions to SIP and SDP June, 1999 - As an alternative to all of the above approaches, it: (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. @@ -2524,22 +2443,20 @@ that request. Although this does not affect the protocol used between the Requestor and the PINT Gateway, it may influence the response returned. To avoid the problem of changing service logic once running, any registration of interest in status changes should be made at or before the time at which the service request is made. Conversely, if a historical request is made on the disposition of a service, this should be done within a short time after the service has completed; the Executive System is unlikely to store the results of service requests for - PSP: Extensions to SIP and SDP June, 1999 - long; these will have been processed as AMA (Automatic Message Accounting) records quickly, after which the Executive System has no reason to keep them, and so they may be discarded. Where the PINT Gateway and the Executive System are intimately linked, the Gateway can respond to status subscription requests that occur while a 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 @@ -2579,22 +2496,20 @@ 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 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 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. - PSP: Extensions to SIP and SDP June, 1999 - 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 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 @@ -2636,22 +2551,20 @@ 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 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 - PSP: Extensions to SIP and SDP June, 1999 - carried "in-line" with the message. The Source indicator "OR" means that the value passed is an Opaque Reference that should be carried along with the rest of the message but is to be interpreted only within the destination (GSTN) context. As an alternative, it could be given as a "local" reference with the "file" style, or even using a partial reference with the "http" style. However, the way in which such a reference is interpreted is a matter for the receiving PINT Server and Executive System; it remains, in effect, an opaque reference. The Source Format value "ISF/ILSF" means that the format of the source is @@ -2692,43 +2605,41 @@ 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. - PSP: Extensions to SIP and SDP June, 1999 - 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 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 ------- --------- -------------------------- ------------- R2C ServiceID: R2C BParty: sip:123@p.com AParty: TN RFC2543 4567 CallFormat: voice SourceFmt: audio - (--- No media sub-type + (--- only "-" sub-type sub-field value used) --- Source: (--- No source specified) --- R2F ServiceID: R2F BParty: (--- SIP To: field not used) sip:R2F@pint.xxx.net AParty: TN RFCxxx +441213553 CallFormat: fax SourceFmt: sip:1-730-1234@p.com AParty: TN RFCxxx +441213553 CallFormat: fax SourceFmt: image jpeg Source: a=fmtp:jpeg opr:1234 - - PSP: Extensions to SIP and SDP June, 1999 - R2HC ServiceID: R2HC BParty: (--- SIP To: field not used) sip:R2HC@pint.ita.il AParty: TN RFCxxx +441213554 CallFormat: voice SourceFmt: text html @@ -2791,32 +2699,30 @@ 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 version 03: +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 - PSP: Extensions to SIP and SDP June, 1999 - * 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 @@ -2852,34 +2758,33 @@ * 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 version 3 to verion 4: +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! - PSP: Extensions to SIP and SDP June, 1999 * 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. -Changes from version 4 to this version (indicated by -.-.) +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) @@ -2911,26 +2816,27 @@ 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. - PSP: Extensions to SIP and SDP June, 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", @@ -2952,44 +2858,42 @@ Internet Engineering Task Force, August 1998. [10] D. Crocker, "Standard for the format of ARPA Internet text messages",RFC822, Internet Engineering Task Force, August 1982. [11] ITU-T Study Group XI, "Q.1204 - IN Distributed Functional Plane Architecture", ITU-T, February 1994. [12] T. Dierks & C. Allen, "The TLS Protocol Version 1.0", RFC2246, Internet Engineering Task Force, January 1999. -[13] R. Thayer, N. Doraswamy & R. Glenn, - "IP Security Document Roadmap", Informational RFC2411, +[13] S. Kent, R. Atkinson, + "Security Architecture for the Internet Protocol", RFC2401, Internet Engineering Task Force, November 1998. [14] R. Housley, W. Ford, W. Polk & D. Solo, "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. 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. - PSP: Extensions to SIP and SDP June, 1999 - 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 @@ -3019,51 +2923,49 @@ INPAddr = "+" 0*(("-" )/) ; -- POS-DIGIT and DIGIT as defined in SDP LDPAddr = 0*(("-" )/) OtherAddr = 1* ; -- OtherAdd defined in the context of OtherAddrType ; -- uric is as defined in RFC2396 media-field = "m=" media port proto - 0*( fmt) + 1*( fmt) ; -- NOTE redefined as subset/relaxation of original SDP definition ; -- space and CRLF as defined in SDP media = ("application"/"audio"/"image"/"text") ; -- NOTE redefined as a subset of the original SDP definition ; -- This could be any MIME discrete type; Only those listed are ; -- used in PINT 1.0 - PSP: Extensions to SIP and SDP June, 1999 - port = ("0" / "1") ; -- NOTE redefined from the original SDP definition; ; -- 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") ; -- this is the PINT protocol, defined if nettype == "TN" -fmt = +fmt = ( / "-") ; -- NOTE redefined as a subset of the original SDP definition -; -- subtype as defined in RFC2046. MUST be a subtype of type held -; -- in associated media sub-field +; -- 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 -.-. @@ -3085,22 +2987,20 @@ -.-. q763-natures = ("1" / "2" / "3" / "4") -.-. q763-plan-attribute = Q763-plan-tag ":" q763-plans -.-. q763-plan-tag = "Q763-plan" - PSP: Extensions to SIP and SDP June, 1999 - -.-. 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" @@ -3142,22 +3042,20 @@ ; -- URI-Reference defined in RFC2396 -.-. uritag = "uri" -.-. opaque-ref = opr-tag ":" 0* -.-. opr-tag = "opr" - PSP: Extensions to SIP and SDP June, 1999 - -.-. sub-part-ref = spr-tag ":" ; -- Content-ID is as defined in RFC2046 and RFC822 -.-. spr-tag = "spr" -.-. strict-attribute = "require:" att-tag-list @@ -3199,41 +3097,37 @@ -.-. tsp-tag = "tsp" -.-. phone-context-parameter = phone-context-tag "=" phone-context-ident SIP-param = ( / / / / / ) ; -- the values in this list are all as defined in SIP - PSP: Extensions to SIP and SDP June, 1999 - 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") - PSP: Extensions to SIP and SDP June, 1999 - 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. It should be noted that private Address Types (in section 3.4.1) have been explicitly excluded from this process, as they must be in the form of @@ -3270,21 +3164,20 @@ be "all values of TNProto". B.2. Private Attributes Any proprietary attribute lines that are added may be registered with IANA using the procedures mentioned in [2]; the mechanism is the same as that used in SDP. If the attribute is defined for use only within PINT, then it may be approapriate to mention this in the supporting documentation. Note that, in the PINT 1.0 specification covered here, there is no mechanism to add such freshly registered attribute lines to a "require:" clause. - PSP: Extensions to SIP and SDP June, 1999 B.3. Private phone-contexts Within the session description used for PINT requests, a phone-context attribute may be used to specify the prefix or context within which an associated telephone-number (in a connextion line) should be interpreted. For "public" phone contexts the prefix to be used MUST start with either a DIGIT or a "+". Private phone contexts may be registered with IANA that do NOT start with either of these characters. Such a prefix may be useful to identify a private network, potentially with an associated numeric ID (see example 4 in section 3.4.3.1). In the example, the prefix acts as @@ -3327,22 +3220,20 @@ In short, this context is the telephone equivalent of a "Net 10" address space behind a NAT, and the initial name (and contact information) shows the context within which that address is valid. It also specifies the format for the network and address types (and address value syntax) with which this context is associated. Of course, IANA may refer the requested registration to the IESG or an appropriate IETF working group for review, and may require revisions to be made before the registration is accepted. - PSP: Extensions to SIP and SDP June, 1999 - Appendix C: Author's Addresses Scott Petrack MetaTel, Inc. 284 North Ave. Weston, MA 02493 scott.petrack@metatel.com +1 (781)-891-9000 Lawrence Conroy