--- 1/draft-ietf-sipcore-info-events-08.txt 2010-09-28 14:12:17.000000000 +0200 +++ 2/draft-ietf-sipcore-info-events-09.txt 2010-09-28 14:12:17.000000000 +0200 @@ -1,21 +1,21 @@ SIPCORE C. Holmberg Internet-Draft Ericsson Obsoletes: 2976 (if approved) E. Burger Intended status: Standards Track NeuStar, Inc. -Expires: November 20, 2010 H. Kaplan +Expires: April 1, 2011 H. Kaplan Acme Packet - May 19, 2010 + September 28, 2010 Session Initiation Protocol (SIP) INFO Method and Package Framework - draft-ietf-sipcore-info-events-08 + draft-ietf-sipcore-info-events-09 Abstract This document defines a method, INFO, for the Session Initiation Protocol (SIP), and an Info Package mechanism. The document obsoletes RFC 2976. For backward compatibility the document also specifies a "legacy" mode of usage of the INFO method that is compatible with the usage previously defined in RFC 2976, referred to as "legacy INFO Usage" in this document. @@ -33,121 +33,110 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on November 20, 2010. + This Internet-Draft will expire on April 1, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 5 - 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . 5 - 3.2.1. INFO Request Sender . . . . . . . . . . . . . . . . . 5 - 3.2.2. INFO Request Receiver . . . . . . . . . . . . . . . . 6 - 3.2.3. SIP Proxies . . . . . . . . . . . . . . . . . . . . . 7 - 3.3. INFO Message Body . . . . . . . . . . . . . . . . . . . . 7 - 3.3.1. INFO Request Message Body . . . . . . . . . . . . . . 7 - 3.3.2. INFO Response Message Body . . . . . . . . . . . . . . 7 - 3.4. Order of Delivery . . . . . . . . . . . . . . . . . . . . 8 - 4. Info Packages . . . . . . . . . . . . . . . . . . . . . . . . 8 - 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 4.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 8 - 4.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 8 - 4.2.2. UA Procedures . . . . . . . . . . . . . . . . . . . . 8 - 4.2.3. Recv-Info header field rules . . . . . . . . . . . . . 10 - 4.2.4. Info Package fallback rules . . . . . . . . . . . . . 10 - 4.3. REGISTER Processing . . . . . . . . . . . . . . . . . . . 11 - 5. Formal INFO Method Definition . . . . . . . . . . . . . . . . 11 - 5.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 11 - 6. INFO Header Fields . . . . . . . . . . . . . . . . . . . . . . 13 - 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 6.2. Info-Package header field . . . . . . . . . . . . . . . . 14 - 6.3. Recv-Info header field . . . . . . . . . . . . . . . . . 14 - 7. Info Package Considerations . . . . . . . . . . . . . . . . . 14 + 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. Applicability and Backward Compatibility . . . . . . . . . . . 6 + 4. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 6 + 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 4.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . 6 + 4.2.1. INFO Request Sender . . . . . . . . . . . . . . . . . 7 + 4.2.2. INFO Request Receiver . . . . . . . . . . . . . . . . 8 + 4.2.3. SIP Proxies . . . . . . . . . . . . . . . . . . . . . 8 + 4.3. INFO Message Body . . . . . . . . . . . . . . . . . . . . 8 + 4.3.1. INFO Request Message Body . . . . . . . . . . . . . . 8 + 4.3.2. INFO Response Message Body . . . . . . . . . . . . . . 9 + 4.4. Order of Delivery . . . . . . . . . . . . . . . . . . . . 9 + 5. Info Packages . . . . . . . . . . . . . . . . . . . . . . . . 9 + 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 5.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 10 + 5.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 10 + 5.2.2. UA Procedures . . . . . . . . . . . . . . . . . . . . 10 + 5.2.3. Recv-Info header field rules . . . . . . . . . . . . . 11 + 5.2.4. Info Package fallback rules . . . . . . . . . . . . . 12 + 5.3. REGISTER Processing . . . . . . . . . . . . . . . . . . . 12 + 6. Formal INFO Method Definition . . . . . . . . . . . . . . . . 13 + 6.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 13 + 7. INFO Header Fields . . . . . . . . . . . . . . . . . . . . . . 14 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 7.2. Appropriateness of Info Package Usage . . . . . . . . . . 14 - 7.3. Alternative Mechanisms . . . . . . . . . . . . . . . . . 15 - 7.3.1. Alternative SIP signaling plane mechanisms . . . . . . 15 - 7.3.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 16 - 7.3.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 17 - 8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 8.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 9. Legacy INFO Usage . . . . . . . . . . . . . . . . . . . . . . 18 - 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 9.2. Problems . . . . . . . . . . . . . . . . . . . . . . . . 18 - 9.3. Co-existence with Info Package based INFO usage . . . . . 19 + 7.2. Info-Package header field . . . . . . . . . . . . . . . . 15 + 7.3. Recv-Info header field . . . . . . . . . . . . . . . . . 16 + 8. Info Package Considerations . . . . . . . . . . . . . . . . . 16 + 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 8.2. Appropriateness of Info Package Usage . . . . . . . . . . 16 + 8.3. Alternative Mechanisms . . . . . . . . . . . . . . . . . 16 + 8.3.1. Alternative SIP signaling plane mechanisms . . . . . . 16 + 8.3.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 18 + 8.3.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 19 + 9. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 9.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 19 10. Info Package Requirements . . . . . . . . . . . . . . . . . . 19 10.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19 10.2. Overall Description . . . . . . . . . . . . . . . . . . . 20 10.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 20 - 10.4. Info Package Name . . . . . . . . . . . . . . . . . . . . 20 + 10.4. Info Package Name . . . . . . . . . . . . . . . . . . . . 21 10.5. Info Package Parameters . . . . . . . . . . . . . . . . . 21 10.6. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 21 - 10.7. INFO Message Body Parts . . . . . . . . . . . . . . . . . 21 + 10.7. INFO Message Body Parts . . . . . . . . . . . . . . . . . 22 10.8. Info Package Usage Restrictions . . . . . . . . . . . . . 22 10.9. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 22 - 10.10. Info Package Security Considerations . . . . . . . . . . 22 + 10.10. Info Package Security Considerations . . . . . . . . . . 23 10.11. Implementation Details . . . . . . . . . . . . . . . . . 23 10.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . 23 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 11.1. Update to Registration of SIP INFO Method . . . . . . . . 23 11.2. Registration of the Info-Package header field . . . . . . 24 11.3. Registration of the Recv-Info header field . . . . . . . 24 11.4. Creation of the Info Packages Registry . . . . . . . . . 24 11.5. Registration of the Info-Package Content-Disposition . . 25 11.6. SIP Response Code 469 Registration . . . . . . . . . . . 25 12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 12.1. Indication for which Info Packages UAs are willing to receive INFO requests . . . . . . . . . . . . . . . . . . 25 12.1.1. Initial INVITE request . . . . . . . . . . . . . . . . 25 12.1.2. Target refresh . . . . . . . . . . . . . . . . . . . . 26 12.2. INFO request associated with Info Package . . . . . . . . 27 12.2.1. Single payload . . . . . . . . . . . . . . . . . . . . 27 - 12.2.2. Multipart INFO . . . . . . . . . . . . . . . . . . . . 27 - 13. Security Considerations . . . . . . . . . . . . . . . . . . . 30 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 - 14.1. Normative References . . . . . . . . . . . . . . . . . . 31 - 14.2. Informative References . . . . . . . . . . . . . . . . . 31 - Appendix A. Legacy INFO Usage . . . . . . . . . . . . . . . . . . 33 - A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 33 - A.2. ISUP . . . . . . . . . . . . . . . . . . . . . . . . . . 33 - A.3. QSIG . . . . . . . . . . . . . . . . . . . . . . . . . . 34 - A.4. MSCML . . . . . . . . . . . . . . . . . . . . . . . . . . 34 - A.5. MSML . . . . . . . . . . . . . . . . . . . . . . . . . . 34 - A.6. Video Fast Update . . . . . . . . . . . . . . . . . . . . 34 - A.7. DTMF . . . . . . . . . . . . . . . . . . . . . . . . . . 34 - Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 34 - Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 35 + 12.2.2. Multipart INFO . . . . . . . . . . . . . . . . . . . . 28 + 13. Security Considerations . . . . . . . . . . . . . . . . . . . 31 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32 + 14.1. Normative References . . . . . . . . . . . . . . . . . . 32 + 14.2. Informative References . . . . . . . . . . . . . . . . . 32 + Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 34 + Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38 1. Introduction This document defines a method, INFO, for the Session Initiation Protocol (SIP) [RFC3261]. The purpose of the INFO message is to carry application level information between endpoints, using the SIP dialog signaling path. Note that the INFO method is not used to update characteristics of a @@ -177,198 +166,273 @@ NOTE: A UA can use an empty Recv-Info header field (a header field without a value) to indicate that it is not willing to receive INFO requests for any Info-Package, but to inform other UAs that it still supports the Info Package mechanism. When a UA sends an INFO request, it uses the Info-Package header field to indicate which Info Package is associated with the request. One particular INFO request can only be associated with a single Info Package. -2. Applicability +2. Motivation + + A number of applications, standardized and proprietary, make use of + the INFO method as it was previously defined in RFC 2976 [RFC2976], + referred to as "legacy INFO usage". These include but are not + limited to: + + o RFC 3372 [RFC3372] specifies the encapsulation of ISDN User Part + (ISUP) in SIP message bodies. ITU-T and 3GPP have specified + similar procedures. + o [Ecma-355] specifies the encapsulation of QSIG in SIP message + bodies. + o RFC 5022 [RFC5022] specifies how INFO is used as a transport + mechanism by the Media Server Control Markup Language (MSCML) + protocol. MSCML uses an option-tag in the Require header field to + ensure that the receiver understands the INFO content. + o RFC 5707 [RFC5707] specifies how INFO us used as a transport + mechanism by the Media Server Markup Language (MSML) protocol. + o Companies have been using INFO messages in order to request fast + video update. Currently a standardized mechanism, based on RTCP, + has been specified in RFC 5168 [RFC5168]. + o Companies have been using INFO messages in order to transport DTMF + tones. All mechanisms are proprietary, and have not been + standardized. + + Some legacy INFO usages are also recognized as being shortcuts to + more appropriate and flexible mechanisms. + + Furthermore, RFC 2976 did not define mechanisms that would enable a + SIP UA to indicate (1) the types of applications and contexts in + which they support the INFO method or (2) the types of application + and context with which a specific INFO message is associated. + + Because legacy INFO usages do not have associated Info Packages, it + is not possible to use the Recv-Info and Info-Package header fields + with legacy INFO usages. That is, a UA cannot use the Recv-Info + header field to indicate for which legacy INFO usages it is willing + to receive INFO requests, and a UA cannot use the Info-Package header + field to indicate for which legacy INFO usage an INFO request is + associated with. + + Due to the problems described above, legacy INFO usages often require + static configuration about for what type of applications and contexts + UAs support the INFO method, and the way they handle application + information transported in INFO messages. That has caused + interoperability problems in the industry. + + To overcome these problems, the SIP Working Group has spent + significant discussion time over many years coming to agreement on + whether it was more appropriate to fix INFO (by defining a + registration mechanism for the ways in which it was used) or to + deprecate it altogether (with the usage described in RFC 3398 + [RFC3398] being grandfathered as the sole legitimate usage). + Although it required substantial consensus building and concessions + by those more inclined to completely deprecate INFO, the eventual + direction of the working group was to publish a framework for + registration of INFO packages as defined in this specification. + +3. Applicability and Backward Compatibility This document defines a method, INFO, for the Session Initiation Protocol (SIP) [RFC3261], and an Info Package mechanism. The - document obsoletes [RFC2976]. For backward compatibility the - document also specifies a "legacy" mode of usage of the INFO method - that is compatible with the usage previously defined in [RFC2976], - referred to as "legacy INFO Usage" in this document. + document obsoletes RFC 2976 [RFC2976]. For backward compatibility, + the document also specifies a "legacy" mode of usage of the INFO + method that is compatible with the usage previously defined in RFC + 2976, referred to as "legacy INFO Usage". -3. The INFO Method + For backward compatibility purposes, this document does not deprecate + legacy INFO usages, and does not mandate users to define Info + Packages for such usages. However: -3.1. General + 1. A UA MUST NOT insert an Info-Package header field in a legacy + INFO request (as described in Section 3, an INFO request + associated with an Info Package always contains an Info-Package + header field). + 2. It is strongly RECOMMENDED that any new usage uses the Info + Package mechanism defined in this specification, since it does + not share the issues associated with legacy INFO usage, and since + Info Packages can be registered with IANA. + 3. UAs are allowed to enable both legacy INFO usages and Info + Package usages as part of the same invite dialog usage, but UAs + SHALL NOT mix legacy INFO usages and Info Package usages in order + to transport the same application level information. If + possible, UAs SHALL prefer the usage of an Info Package. + +4. The INFO Method + +4.1. General The INFO method provides a mechanism for transporting application level information that can further enhance a SIP application. Annex A gives more details on the types of applications for which the use of INFO is appropriate. This section describes how a UA handles INFO requests and responses, as well as the message bodies included in INFO messages. -3.2. INFO Request - -3.2.1. INFO Request Sender +4.2. INFO Request +4.2.1. INFO Request Sender An INFO request can be associated with an Info Package (see - Section 4), or associated with a legacy INFO usage (see Section 9). + Section 5), or associated with a legacy INFO usage (see Section 2). The construction of the INFO request is the same as any other non- target refresh request within an existing invite dialog usage as - described in Section 12.2 of [RFC3261]. + described in Section 12.2 of RFC 3261. When a UA sends an INFO request associated with an Info Package, it MUST include an Info-Package header field that indicates which Info Package is associated with the request. A specific INFO request can be used only for a single Info Package. When a UA sends an INFO request associated with an legacy INFO usage there is no Info Package associated with the request, and the UA MUST NOT include an Info-Package header field in the request. The INFO request MUST NOT contain a Recv-Info header field. A UA can only indicate a set of Info Packages for which it is willing to receive INFO requests by using the SIP methods (and their responses) - listed in Section 4. + listed in Section 5. A UA MUST NOT send an INFO request outside an invite dialog usage and MUST NOT send an INFO request for an Info Package inside an invite dialog usage if the remote UA has not indicated willingness to receive that Info-Package within that dialog. If a UA receives a 469 (Bad Info Package) response to an INFO - request, based on [RFC5057] the response represents a Transaction - Only failure, and the UA MUST NOT terminate the invite dialog usage. + request, based on RFC 5057 the response represents a Transaction Only + failure, and the UA MUST NOT terminate the invite dialog usage. Due to the possibility of forking, the UA which sends the initial INVITE request MUST be prepared to receive INFO requests from multiple remote UAs during the early dialog phase. In addition, the UA MUST be prepared to receive different Recv-Info header field values from different remote UAs. NOTE: If the UAS (receiver of the initial INVITE request) sends an INFO request just after it has sent the response which creates the dialog, the UAS needs to be prepared that the INFO request can reach the UAC before the dialog creating response, and might therefore be rejected by the UAC. In addition, an INFO request might be rejected due to a race condition, if a UA sends the INFO request at the same time as the remote UA sends a new set of Info Packages for which it is willing to receive INFO requests. -3.2.2. INFO Request Receiver +4.2.2. INFO Request Receiver If a UA receives an INFO request associated with an Info Package that the UA has not indicated willingness to receive, the UA MUST send a 469 (Bad Info Package) response (see Section 11.6), which contains a Recv-Info header field with Info Packages for which the UA is willing to receive INFO requests. The UA MUST NOT use the response to update the set of Info Packages, but simply to indicate the current set. In the terminology of Multiple Dialog Usages [RFC5057], this represents a Transaction Only failure, and does not terminate the invite dialog usage. If a UA receives an INFO request associated with an Info Package and the message body part with Content-Disposition 'Info-Package' (see - Section 3.3.1) has a Multipurpose Internet Mail Extensions (MIME) + Section 4.3.1) has a Multipurpose Internet Mail Extensions (MIME) type that the UA supports but not in the context of that Info Package, it is RECOMMENDED that the UA send a 415 (Unsupported Media Type) response. The UA MAY send other error responses, such as Request Failure (4xx), Server Failure (5xx) and Global Failure (6xx), in accordance with the - error handling procedures in [RFC3261]. + error handling procedures defined in RFC 3261. Otherwise, if the INFO request is syntactically correct and well structured, the UA MUST send a 200 (OK) response. NOTE: If the application needs to reject the information which it received in an INFO request, that needs to be done on the application level. I.e. the application needs to trigger a new INFO request, which contains information that the previously received application data was not accepted. Individual Info Package specifications need to describe the details for such procedures. -3.2.3. SIP Proxies +4.2.3. SIP Proxies - Proxies need no additional behavior beyond that described in - [RFC3261] to support INFO. + Proxies need no additional behavior beyond that described in RFC 3261 + to support INFO. -3.3. INFO Message Body +4.3. INFO Message Body -3.3.1. INFO Request Message Body +4.3.1. INFO Request Message Body The purpose of the INFO request is to carry application level information between SIP UAs. The application information data is carried in the payload of the message body of the INFO request. NOTE: An INFO request associated with an Info Package can also include information associated with the Info Package using Info- Package header field parameters. If an INFO request associated with an Info Package contains a message body part, the body part is identified by a Content-Disposition header field 'Info-Package' value. The body part can contain a single MIME type, or it can be a multipart [RFC5621] which contains other body parts associated with the Info Package. - UAs MUST support multipart body parts in accordance with [RFC5621]. + UAs MUST support multipart body parts in accordance with RFC 5621. NOTE: An INFO request can also contain other body parts that are meaningful within the context of an invite dialog usage but are not specifically associated with the INFO method and the application concerned. When a UA supports a specific Info-Package, the UA MUST also support message body MIME types in accordance with that Info-Package. - However, in accordance with [RFC3261] the UA still indicates the + However, in accordance with RFC 3261 the UA still indicates the supported MIME types using the Accept header. -3.3.2. INFO Response Message Body +4.3.2. INFO Response Message Body A UA MUST NOT include a message body associated with an Info Package in an INFO response. Message bodies associated with Info Packages MUST only be sent in INFO requests. A UA MAY include a message body which is not associated with an Info Package in an INFO response. -3.4. Order of Delivery +4.4. Order of Delivery The Info Package mechanism does not define a delivery order mechanism. Info Packages can rely on the CSeq header field to detect if an INFO request is received out of order. If specific applications need additional mechanisms for order of delivery, those mechanisms, and related procedures, are specified as part of the associated Info Package (e.g. the use of sequence numbers within the application data). -4. Info Packages +5. Info Packages -4.1. General +5.1. General An Info Package specification defines the content and semantics of the information carried in an INFO message associated with an Info Package. The Info Package mechanism provides a way for UAs to indicate for which Info Packages they are willing to receive INFO requests, and which Info Package a specific INFO request is associated with. -4.2. User Agent Behavior +5.2. User Agent Behavior -4.2.1. General +5.2.1. General This section describes how a UA handles Info Packages, how a UA uses the Recv-Info header field, and how the UA acts in re-INVITE rollback situations. -4.2.2. UA Procedures +5.2.2. UA Procedures A UA which supports the Info Package mechanism MUST indicate, using the Recv-Info header field, the set of Info Packages for which it is willing to receive INFO requests for a specific session. A UA can list multiple Info Packages in a single Recv-Info header field, and the UA can use multiple Recv-Info header fields. A UA can use an empty Recv-Info header field, i.e. a header field without any header field values. A UA provides its set of Info Packages for which it is willing to @@ -414,38 +478,38 @@ If a UA indicates multiple Info Packages, which provide similar functionality, it is not possible to indicate a priority order of the Info Packages, or to indicate that the UA wishes to only receive INFO requests for one of the Info Packages. It is up to the application logic associated with the Info Packages, and specific Info Package specifications, to describe application behavior in such cases. For backward compatibility purpose, even if a UA indicates support of the Info Package mechanism, it is still allowed to enable legacy INFO - usages Section 9. In addition, if a UA indicates support of the INFO - method using the Allow header field [RFC3261], it does not implicitly + usages. In addition, if a UA indicates support of the INFO method + using the Allow header field [RFC3261], it does not implicitly indicate support of the Info Package mechanism. A UA MUST use the Recv-Info header field in order to indicate that it supports the Info Package mechanism. Likewise, even if a UA uses the Recv-Info header field to indicate that it supports the Info Package mechanism, in addition the UA still indicates support of the INFO method using the Allow header. This document does not define a SIP option tag [RFC3261] for the Info Package mechanism. However, an Info Package specification can define an option-tag associated with the specific Info Package, as described in Section 10.6. -4.2.3. Recv-Info header field rules +5.2.3. Recv-Info header field rules The text below defines rules on when a UA is required to include a - Recv-Info header field in SIP messages. Section 6.1 lists the SIP + Recv-Info header field in SIP messages. Section 7.1 lists the SIP methods, for which a UA can insert a Recv-Info header field in requests and responses. - The sender of an initial INVITE request MUST include a Recv-Info header field in the initial INVITE request, even if the sender is not willing to receive INFO requests associated with any Info Package. - The receiver of a request which contains a Recv-Info header field MUST include a Recv-Info header field in a reliable 18x/2xx response to the request, even if the request contains an empty Recv-Info @@ -460,56 +524,57 @@ not restricted to generate its own set of Info Packages as a subset of the Info Package set received in the Info Package header field of the request. Similar to SDP answers, the receiver can include the same Recv-Info header field value in multiple responses (18x/2xx) for the same INVITE/re-INVITE transaction, but the receiver MUST use the same Recv-Info header field value (if included) in all responses for the same transaction. -4.2.4. Info Package fallback rules +5.2.4. Info Package fallback rules If the receiver of a request which contains a Recv-Info header field rejects the request, both the sender and receiver of the request MUST roll back to the set of Info Packages which was used before the request was sent. This also applies to the case where the receiver of an INVITE/re-INVITE request has included a Recv-Info header field in a provisional response, but later rejects the request. NOTE: The dialog state rollback rules for Info Packages might differ from the rules for other types of dialog state information (SDP, target, etc). -4.3. REGISTER Processing +5.3. REGISTER Processing This document allows a UA to insert a Recv-Info header field in a REGISTER request. However, a UA SHALL NOT include a header value for a specific Info Package unless the specific Info Package specification describes how the header field value shall be interpreted and used by the registrar, e.g. in order to determine request targets. Rather than using the Recv-Info header field in order to determine request targets, it is recommended to use more appropriate - mechanisms, e.g. based on [RFC3840]. However, this document does not - define a feature tag for the Info Package mechanism, or a mechanism - to define feature tags for specific Info Packages. + mechanisms, e.g. based on RFC 3840 [RFC3840]. However, this document + does not define a feature tag for the Info Package mechanism, or a + mechanism to define feature tags for specific Info Packages. -5. Formal INFO Method Definition +6. Formal INFO Method Definition -5.1. INFO Method +6.1. INFO Method This document describes one new SIP method: INFO. This document - replaces the definition and registrations found in [RFC2976]. + replaces the definition and registrations found in RFC 2976 + [RFC2976]. - This table expands on Tables 2 and 3 in [RFC3261]. + This table expands on Tables 2 and 3 in RFC 3261 [RFC3261]. Header Where INFO ------ ----- ---- Accept R o Accept 415 o Accept-Encoding R o Accept-Encoding 2xx o Accept-Encoding 415 c Accept-Language R o Accept-Language 2xx o @@ -570,25 +635,25 @@ To c m (w/ Tag) Unsupported 420 o User-Agent o Via m Warning r o WWW-Authenticate 401 m WWW-Authenticate 407 o Figure 1: Table 1: Summary of Header Fields -6. INFO Header Fields +7. INFO Header Fields -6.1. General +7.1. General - This table expands on tables 2 and 3 in [RFC3261]. + This table expands on tables 2 and 3 in RFC 3261 [RFC3261]. Header field where proxy ACK BYE CAN INV OPT REG PRA INF MSG UPD ------------------------------------------------------------------ Info-Package R - - - - - - - m* - - Recv-Info R - - - m - o o - - o Recv-Info 2xx - - - o** - - o***- - o*** Recv-Info 1xx - - - o** - - - - - - Recv-Info 469 - - - - - - - m* - - Recv-Info r - - - o - - o - - o @@ -609,76 +674,76 @@ * Not applicable to INFO requests and responses associated with legacy INFO usages. ** Mandatory in at least one reliable 18x/2xx response, if sent, to the INVITE request, if the associated INVITE request contained a Recv-Info header field. *** Mandatory if the associated request contained a Recv-Info header field. - As defined in section 20 of RFC 3261 [RFC3261], a "mandatory" - header field MUST be present in a request, and MUST be understood - by the UAS receiving the request." + As defined in section 20 of RFC 3261, a "mandatory" header field + MUST be present in a request, and MUST be understood by the UAS + receiving the request." -6.2. Info-Package header field +7.2. Info-Package header field This document adds Info-Package to the definition of the element - "message-header" in the SIP message grammar [RFC3261]. Section 3 + "message-header" in the SIP message grammar [RFC3261]. Section 4 describes the Info-Package header field usage. For the purposes of matching Info Package types indicated in Recv- Info with those in the Info-Package header field value, one compares the Info-package-name portion of the Info-package-type portion of the Info-Package header field octet-by-octet with that of the Recv-Info header field value. That is, the Info Package name is case sensitive. Info-package-param is not part of the comparison-checking algorithm. This document does not define values for Info-Package types. Individual Info Package specifications define these values. -6.3. Recv-Info header field +7.3. Recv-Info header field This document adds Recv-Info to the definition of the element - "message-header" in the SIP message grammar [RFC3261]. Section 4 + "message-header" in the SIP message grammar [RFC3261]. Section 5 describes the Recv-Info header field usage. -7. Info Package Considerations +8. Info Package Considerations -7.1. General +8.1. General This section covers considerations to take into account when deciding whether the usage of an Info Package is appropriate for transporting of application information for a specific use-case. -7.2. Appropriateness of Info Package Usage +8.2. Appropriateness of Info Package Usage When designing an Info Package, for application level information exchange, it is important to consider: is signaling, using INFO requests, within a SIP dialog, an appropriate mechanism for the use- case? Is it because it is the most reasonable and appropriate choice, or merely because "it's easy"? Choosing an inappropriate mechanism for a specific use-case can cause negative effects in SIP networks where the mechanism is used. -7.3. Alternative Mechanisms +8.3. Alternative Mechanisms -7.3.1. Alternative SIP signaling plane mechanisms +8.3.1. Alternative SIP signaling plane mechanisms -7.3.1.1. General +8.3.1.1. General This subsection describes some alternative mechanisms for transporting application information on the SIP signaling plane, using SIP messages. -7.3.1.2. INFO Request Rate and Volume +8.3.1.2. INFO Request Rate and Volume INFO messages differ from many other sorts of SIP messages in that they carry application information, and the size and rate of the INFO message is directly determined by the application. This can cause application information traffic to interfere with other traffic on that infrastructure, or to self-interfere when data rates become too high. There is no default throttling mechanism for INFO requests. Apart from the SIP session establishment, the number of SIP messages @@ -704,21 +769,21 @@ exchange of bulk data beyond these limits, especially if the headers plus body exceed the User Datagram Protocol (UDP) MTU [RFC0768]. Appropriate mechanisms for such traffic include the Hypertext Transfer Protocol (HTTP) [RFC2616], the Message Session Relay Protocol (MSRP) [RFC4975], or other media plane data transport mechanisms. RFC 5405 [RFC5405] provides additional guidelines for applications using UDP that may be useful background reading. -7.3.1.3. SUBSCRIBE/NOTIFY +8.3.1.3. SUBSCRIBE/NOTIFY An alternative for application level interaction is to use subscription-based events [RFC3265], which uses the SIP SUBSCRIBE and NOTIFY methods. Using that mechanism, a UA requests state information, such as key pad presses from a device to an application server or key map images from an application server to a device. Event Packages [RFC3265] perform the role of disambiguating the context of a message for subscription-based events. The Info Package mechanism provides similar functionality for application information @@ -738,155 +803,88 @@ and B2BUAs, the resource impact caused by the subscription dialogs needs to be considered. The number of subscription dialogs per user also needs to be considered. As for any other SIP signaling plane based mechanism for transporting application information, the SUBSCRIBE/NOTIFY messages can put a significant burden on intermediate SIP entities which are part of the dialog route set, but do not have any interest in the application information transported between the end users. -7.3.1.4. MESSAGE +8.3.1.4. MESSAGE The MESSAGE method [RFC3428] defines one-time instant message exchange, typically for sending MIME contents for rendering to the user. -7.3.2. Media Plane Mechanisms +8.3.2. Media Plane Mechanisms -7.3.2.1. General +8.3.2.1. General In SIP, media plane channels associated with SIP dialogs are established using SIP signaling, but the data exchanged on the media plane channel does not traverse SIP signaling intermediates, so if there will be a lot of information exchanged, and there is no need for the SIP signaling intermediaries to examine the information, it is recommended to use a media plane mechanism, rather than a SIP signaling based. A low latency requirement for the exchange of information is one strong indicator for using a media channel. Exchanging information through the SIP routing network can introduce hundreds of milliseconds of latency. -7.3.2.2. MRCP +8.3.2.2. MRCP One mechanism for media plane exchange of application data is the Media Resource Control Protocol (MRCP) [I-D.ietf-speechsc-mrcpv2], where a media plane connection-oriented channel, such as a Transmission Control Protocol (TCP) [RFC0793] or Stream Control Transmission Protocol (SCTP) [RFC4960] stream is established. -7.3.2.3. MRSP +8.3.2.3. MRSP MSRP [RFC4975] defines session-based instant messaging as well as bulk file transfer and other such large-volume uses. -7.3.3. Non-SIP related mechanisms +8.3.3. Non-SIP related mechanisms Another alternative is to use a SIP-independent mechanism, such as HTTP [RFC2616]. In this model, the UA knows about a rendezvous point to direct HTTP requests to for the transfer of information. Examples include encoding of a prompt to retrieve in the SIP Request URI in [RFC4240] or the encoding of a SUBMIT target in a VoiceXML [W3C.REC- voicexml21-20070619] script. -8. Syntax +9. Syntax -8.1. General +9.1. General This section describes the syntax extensions to the ABNF syntax - defined in [RFC3261] required for the INFO method, and adds + defined in RFC 3261 required for the INFO method, and adds definitions for the Info-Package and Recv-Info header fields. The previous sections describe the semantics. The ABNF defined in this - specification is conformant to [RFC5234]. + specification is conformant to RFC 5234 [RFC5234]. -8.2. ABNF +9.2. ABNF INFOm = %x49.4E.46.4F ; INFO in caps Method =/ INFOm message-header =/ (Info-Package / Recv-Info) CRLF Info-Package = "Info-Package" HCOLON Info-package-type Recv-Info = "Recv-Info" HCOLON [Info-package-list] Info-package-list = Info-package-type *( COMMA Info-package-type ) Info-package-type = Info-package-name *( SEMI Info-package-param) Info-package-name = token Info-package-param = generic-param -9. Legacy INFO Usage - -9.1. General - - A number of applications, standardized and proprietary, make use of - the INFO method as it was previously defined in [RFC2976], referred - to as "legacy INFO usage". - - For backward compatibility purpose, this document does not deprecate - such usages, and does not mandate users to define Info Packages for - such usages. However, it is strongly RECOMMENDED that any new usage - uses the Info Package mechanism defined in this specification, since - it does not share the issues associated with legacy INFO usage, and - since Info Packages can be registered with IANA. - -9.2. Problems - - While legacy INFO usage has been widely adopted for specific - application use cases, [RFC2976] did not define a mechanism for SIP - UAs to indicate for which types of applications and contexts they - support the INFO method. In addition, [RFC2976] did not provide a - mechanism to explicitly indicate the type of application and context - for which a specific INFO message is associated. - - Example: If the Content-Type is "image/jpeg", the MIME-attached - content is a JPEG image. Still, there are many useful ways a UA can - render an image. The image could be a caller-id picture, a contact - icon, a photo for sharing, and so on. The sender does not know which - image to send to the receiver if the receiver supports an image - content type. Likewise, the receiver does not know the context of an - image the client is sending if the receiver supports receiving more - than one image content type. - - Since legacy INFO usages do not have associated Info Packages, it is - not possible to use the Recv-Info and Info-Package header fields with - legacy INFO usages. That is, a UA cannot use the Recv-Info header - field to indicate for which legacy INFO usages it is willing to - receive INFO requests, and a UA cannot use the Info-Package header - field to indicate for which legacy INFO usage an INFO request is - associated with. - - Due to the problems described above, legacy INFO usages often require - static configuration about for what type of applications and contexts - UAs support the INFO method, and the way they handle application - information transported in INFO messages. That has caused - interoperability problems in the industry. Therefore, a need for a - well defined and documented description of what the information sent - in the INFO is used for has been identified. This situation is - analogous to the context issue in Internet Mail [RFC3458]. - - Section 4.1 describes how the Info Package mechanisms solves the - issues associated with legacy INFO usages. - -9.3. Co-existence with Info Package based INFO usage - - As described in Section 3, an INFO request associated with an Info - Package always contains an Info-Package header field. A UA MUST NOT - insert an Info-Package header field in a legacy INFO request. - - UAs are allowed to enable both legacy INFO usages and Info Package - usages as part of the same invite dialog usage. However, UAs SHALL - NOT mix legacy INFO usages and Info Package usages in order to - transport the same application level information. If possible, UAs - SHALL prefer the usage of an Info Package. - - See Appendix A for examples of existing legacy INFO usages. - 10. Info Package Requirements 10.1. General This section provides guidance on how to define an Info Package, and what information needs to exist in an Info Package specification. If, for an Info Package, there is a need to extend or modify the behavior described in this document, that behavior MUST be described in the Info Package specification. It is bad practice for Info @@ -896,21 +894,21 @@ Info Package specifications MUST NOT weaken any behavior designated with "SHOULD" or "MUST" in this specification. However, Info Packages specifications MAY strengthen "SHOULD", "MAY", or "RECOMMENDED" requirements to "MUST" strength if applications associated with the Info Package require it. Info Package specifications MUST address the issues defined in the following subsections, or document why an issue is not applicable for the specific Info Package. - Section 7.3 describes alternative mechanisms, which should be + Section 8.3 describes alternative mechanisms, which should be considered as part of the process for solving a specific use-case, when there is a need for transporting application information. 10.2. Overall Description The Info Package specification MUST contain an overall description of the Info Package: what type of information are carried in INFO requests associated with the Info Package, and for what type of applications and functionalities UAs can use the Info Package. @@ -931,21 +929,21 @@ information. Annex A provides more information, and describes alternative mechanisms which one should consider for solving a specific use-case. 10.4. Info Package Name The Info Package specification MUST define an Info Package name, which UAs use as a header field value (e.g. "infoX") to identify the Info Package in the Recv-Info and Info-Package header fields. The - header field value MUST conform to the ABNF defined in Section 8.2. + header field value MUST conform to the ABNF defined in Section 9.2. The Info Package mechanism does not support package versioning. Specific Info Package message body payloads can contain version information, which is handled by the applications associated with the Info Package. However, such feature is outside the scope of the generic Info Package mechanism. NOTE: Even if an Info Package name contains version numbering (e.g. foo_v2), the Info Package mechanism does not distinguish a version number from the rest of the Info Package name. @@ -969,23 +967,23 @@ the name with parameters defined for other Info Packages, but the parameter semantics are specific to the Info Package for which they are defined. However, when choosing the name of a parameter it is RECOMMENDED to not use the same name as an existing parameter for another Info Package, if the semantics of the parameters are different. 10.6. SIP Option Tags The Info Package specification MAY define SIP option tags, which can - be used as described in [RFC3261]. + be used as described in RFC 3261. - The registration requirements for option tags are defined in + The registration requirements for option tags are defined in RFC 5727 [RFC5727]. 10.7. INFO Message Body Parts The Info Package specification MUST define which message body part MIME types are associated with the Info Package. The specification MUST either define those body parts, which include the syntax, semantics and MIME type of the each body part, or refer to other documents which define the body parts. @@ -1004,21 +1002,21 @@ Package, or whether the UA has to wait for the response for a previous INFO request associated with the same Info Package. There can also be restrictions related to whether UAs need to support and use other SIP extensions and capabilities when they use the Info Package, and if there are restrictions related to how UAs can use the Info-Package together with other Info Packages. As the SIP stack might not be aware of Info Package specific restrictions, it cannot be assumed that overlapping requests would be - rejected. As defined in Section 3.2.2, UAs will normally send a 200 + rejected. As defined in Section 4.2.2, UAs will normally send a 200 (OK) response to an INFO request. The application logic associated with the Info Package needs to handle situations where UAs do not follow restrictions associated with the Info Package. 10.9. Rate of INFO Requests If there is a maximum or minimum rate at which UAs can send INFO requests associated with the Info Package within a dialog, the Info Package specification MUST document the rate values. @@ -1111,24 +1109,25 @@ The policy for review of Info Packages is "Specification Required", as defined in [RFC5226]. This policy was selected because Info Packages re-use an existing mechanism for transport of arbitrary session-associated data within SIP, and therefore new Info Packages do not require the more extensive review required by specifications that make fundamental protocol changes. However, the reviewer is expected to verify that each Info Package registration is in fact consistent with this definition. Changes to the SIP protocol and state machine are outside of the allowable scope for an Info Package - and are governed by other procedures including [RFC5727] and its + and are governed by other procedures including RFC 5727 and its successors, if any. The following data elements populate the Info Package Registry. + o Info Package Name: The Info Package Name is a case-sensitive token. In addition, IANA shall not register multiple Info Package names that have identical case-insensitive values. o Reference: A reference to a specification which describes the Info Package. The initial population of this table shall be: Name Reference @@ -1350,26 +1347,25 @@ Content-length: 59 I am a foo-x message type, and I belong to Info Package foo --theboundary-- 13. Security Considerations By eliminating multiple usages of INFO messages without adequate community review and by eliminating the possibility for rogue SIP UAs from confusing another UA by purposely sending unrelated INFO - requests, as described in Section 9.2, we expect this document's - clarification of the use of INFO to improve the security of the - Internet. Whilst rogue UAs can still send unrelated INFO requests, - this mechanism provides mechanisms for which the UAS and other - security devices can associate INFO requests with Info Packages that - have been negotiated for a session. + requests, we expect this document's clarification of the use of INFO + to improve the security of the Internet. Whilst rogue UAs can still + send unrelated INFO requests, this mechanism provides mechanisms for + which the UAS and other security devices can associate INFO requests + with Info Packages that have been negotiated for a session. If the content of the Info Package payload is private, UAs will need to use end-to-end encryption, such as S/MIME, to prevent access to the content. This is particularly important as transport of INFO is likely not to be end-to-end, but through SIP proxies and back-to-back user agents (B2BUA's), which the user may not trust. The INFO request transports application level information. One implication of this is INFO messages may require a higher level of protection than the underlying SIP dialog signaling. In particular, @@ -1435,34 +1431,36 @@ Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. + [RFC3398] Camarillo, G., Roach, A., Peterson, J., and L. Ong, + "Integrated Services Digital Network (ISDN) User Part + (ISUP) to Session Initiation Protocol (SIP) Mapping", + RFC 3398, December 2002. + [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, August 2004. [RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol for Telephones (SIP-T): Context and Architectures", BCP 63, RFC 3372, September 2002. [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. - [RFC3458] Burger, E., Candell, E., Eliot, C., and G. Klyne, "Message - Context for Internet Mail", RFC 3458, January 2003. - [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and D. Gurle, "Session Initiation Protocol (SIP) Extension for Instant Messaging", RFC 3428, December 2002. [RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network Media Services with SIP", RFC 4240, December 2005. [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 4960, September 2007. @@ -1484,90 +1482,49 @@ November 2008. [RFC5707] Saleem, A., Xin, Y., and G. Sharratt, "Media Server Markup Language (MSML)", RFC 5707, February 2010. [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification", RFC 5751, January 2010. [W3C.REC-voicexml21-20070619] - Porter, B., Oshry, M., Bodell, M., Rehor, K., McGlashan, - S., Burke, D., Auburn, R., Candell, E., Burnett, D., - Carter, J., Baggia, P., and A. Lee, "Voice Extensible - Markup Language (VoiceXML) 2.1", World Wide Web Consortium + Rehor, K., Bodell, M., Burke, D., Baggia, P., Auburn, R., + Burnett, D., Candell, E., Carter, J., McGlashan, S., Lee, + A., Porter, B., and M. Oshry, "Voice Extensible Markup + Language (VoiceXML) 2.1", World Wide Web Consortium Recommendation REC-voicexml21-20070619, June 2007, . [I-D.ietf-speechsc-mrcpv2] - Shanmugham, S. and D. Burnett, "Media Resource Control + Burnett, D. and S. Shanmugham, "Media Resource Control Protocol Version 2 (MRCPv2)", - draft-ietf-speechsc-mrcpv2-20 (work in progress), - August 2009. + draft-ietf-speechsc-mrcpv2-21 (work in progress), + July 2010. [Ecma-355] "Standard ECMA-355 Corporate Telecommunication Networks - Tunnelling of QSIG over SIP", ECMA http:// www.ecma-international.org/publications/standards/ Ecma-355.htm, June 2008. -Appendix A. Legacy INFO Usage - -A.1. General - - This section provides examples of existing legacy INFO usages. The - section is not meant to be a comprehensive catalog of legacy INFO - usages, but it should give the reader a flavor for current legacy - INFO usages. - -A.2. ISUP - - [RFC3372] specifies the encapsulation of ISDN User Part (ISUP) in SIP - message bodies. ITU-T and 3GPP have specified similar procedures. - -A.3. QSIG - - [Ecma-355] specifies the encapsulation of QSIG in SIP message bodies. - -A.4. MSCML - - [RFC5022] specifies how INFO is used as a transport mechanism by the - Media Server Control Markup Language (MSCML) protocol. MSCML uses an - option-tag in the Require header field to ensure that the receiver - understands the INFO content. - -A.5. MSML - - [RFC5707] specifies how INFO us used as a transport mechanism by the - Media Server Markup Language (MSML) protocol. - -A.6. Video Fast Update - - Companies have been using INFO messages in order to request fast - video update. Currently a standardized mechanism, based on RTCP, has - been specified in [RFC5168] - -A.7. DTMF - - Companies have been using INFO messages in order to transport DTMF - tones. All mechanisms are proprietary, and have not been - standardized. - -Appendix B. Acknowledgements +Appendix A. Acknowledgements The work on this document was influenced by the "INFO Considered Harmful" draft (26 December 2002) written by Jonathan Rosenberg, and by the "Packaging and Negotiation of INFO Methods for the Session Initiation Protocol" draft (15 January 2003) written by Dean Willis. The following individuals have been involved in the work, and have provided input and feedback on this document: + Adam Roach, Anders Kristensen, Andrew Allen, Arun Arunachalam, Ben Campbell, Bob Penfield, Bram Verburg, Brian Stucker, Chris Boulton, Christian Stredicke, Cullen Jennings, Dale Worley, Dean Willis, Eric Rescorla, Frank Miller, Gonzalo Camarillo, Gordon Beith, Henry Sinnreich, Inaki Baz Castillo, James Jackson, James Rafferty, Jeroen van Bemmel, Joel Halpern, John Elwell, Johnathan Rosenberg, Juha Heinanen, Gordon Beith, Keith Drage, Kevin Attard Compagno, Manpreet Singh, Martin Dolly, Mary Barnes, Michael Procter, Paul Kyzivat, Peili Xu, Peter Blatherwick, Raj Jain, Rayees Khan, Robert Sparks, Roland Jesske, Roni Evan Salvatore @@ -1579,24 +1536,28 @@ Keith Drage provided comments and helped immensely with Figure 1. Arun Arunachalam, Brett Tate, John Elwell, Keith Drage and Robert Sparks provided valuable feedback during the WGLC process, in order to prepare this document for publication. Adam Roach, Dean Willis, John Elwell and Paul Kyzivat provided valuable input in order to sort out the message body part usage for Info Packages. -Appendix C. Change Log +Appendix B. Change Log [RFC EDITOR NOTE: Please remove this section when publishing] + Changes from draft-ietf-sipcore-info-events-09 + o New Motivation section added + o Old section 9 and Annex A removed + Changes from draft-ietf-sipcore-info-events-08 o Further changes based on IESG comments o Editorial changes o Section 7.3 removed o New section 7.4.1.2. added, containing text from old section 7.3 Changes from draft-ietf-sipcore-info-events-07 o Further changes based on WGLC comments o Editorial changes o IANA registry procedures clarified