draft-ietf-sipcore-rfc3265bis-01.txt   draft-ietf-sipcore-rfc3265bis-02.txt 
Network Working Group A. B. Roach Network Working Group A. B. Roach
Internet-Draft Tekelec Internet-Draft Tekelec
Expires: August 23, 2010 February 19, 2010 Obsoletes: 3265 (if approved) August 17, 2010
Updates: 4660 (if approved)
Intended status: Standards Track
Expires: February 18, 2011
SIP-Specific Event Notification SIP-Specific Event Notification
draft-ietf-sipcore-rfc3265bis-01 draft-ietf-sipcore-rfc3265bis-02
Abstract Abstract
This document describes an extension to the Session Initiation This document describes an extension to the Session Initiation
Protocol (SIP). The purpose of this extension is to provide an Protocol (SIP). The purpose of this extension is to provide an
extensible framework by which SIP nodes can request notification from extensible framework by which SIP nodes can request notification from
remote nodes indicating that certain events have occurred. remote nodes indicating that certain events have occurred.
Note that the event notification mechanisms defined herein are NOT Note that the event notification mechanisms defined herein are NOT
intended to be a general-purpose infrastructure for all classes of intended to be a general-purpose infrastructure for all classes of
event subscription and notification. event subscription and notification.
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Overview of Operation . . . . . . . . . . . . . . . . . . 5 1.1. Overview of Operation . . . . . . . . . . . . . . . . . . 5
1.2. Documentation Conventions . . . . . . . . . . . . . . . . 6 1.2. Documentation Conventions . . . . . . . . . . . . . . . . 6
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. SIP Methods for Event Notification . . . . . . . . . . . . . . 7 3. SIP Methods for Event Notification . . . . . . . . . . . . . . 7
3.1. SUBSCRIBE . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. SUBSCRIBE . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Subscription Duration . . . . . . . . . . . . . . . . 7 3.1.1. Subscription Duration . . . . . . . . . . . . . . . . 7
3.1.2. Identification of Subscribed Events and Event 3.1.2. Identification of Subscribed Events and Event
Classes . . . . . . . . . . . . . . . . . . . . . . . 8 Classes . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.3. Additional SUBSCRIBE Header Field Values . . . . . . . 9 3.1.3. Additional SUBSCRIBE Header Field Values . . . . . . . 9
3.2. NOTIFY . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2. NOTIFY . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.1. Identification of Reported Events, Event Classes, 3.2.1. Identification of Reported Events, Event Classes,
and Current State . . . . . . . . . . . . . . . . . . 9 and Current State . . . . . . . . . . . . . . . . . . 9
4. Node Behavior . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Node Behavior . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 10 4.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 10
4.1.1. Detecting Support for SIP Events . . . . . . . . . . . 10 4.1.1. Detecting Support for SIP Events . . . . . . . . . . . 10
4.1.2. Creating and Maintaining Subscriptions . . . . . . . . 10 4.1.2. Creating and Maintaining Subscriptions . . . . . . . . 10
4.1.3. Receiving and Processing State Information . . . . . . 13 4.1.3. Receiving and Processing State Information . . . . . . 14
4.1.4. Forking of SUBSCRIBE Messages . . . . . . . . . . . . 16 4.1.4. Forking of SUBSCRIBE Messages . . . . . . . . . . . . 16
4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 16 4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 16
4.2.1. Subscription Establishment and Maintenance . . . . . . 16 4.2.1. Subscription Establishment and Maintenance . . . . . . 16
4.2.2. Sending State Information to Subscribers . . . . . . . 20 4.2.2. Sending State Information to Subscribers . . . . . . . 20
4.2.3. PINT Compatibility . . . . . . . . . . . . . . . . . . 22 4.2.3. PINT Compatibility . . . . . . . . . . . . . . . . . . 22
4.3. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . 22 4.3. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . 22
4.4. Common Behavior . . . . . . . . . . . . . . . . . . . . . 23 4.4. Common Behavior . . . . . . . . . . . . . . . . . . . . . 23
4.4.1. Dialog Creation and Termination . . . . . . . . . . . 23 4.4.1. Dialog Creation and Termination . . . . . . . . . . . 23
4.4.2. Notifier Migration . . . . . . . . . . . . . . . . . . 23 4.4.2. Notifier Migration . . . . . . . . . . . . . . . . . . 23
4.4.3. Polling Resource State . . . . . . . . . . . . . . . . 24 4.4.3. Polling Resource State . . . . . . . . . . . . . . . . 24
skipping to change at page 3, line 7 skipping to change at page 3, line 4
4.5. Targeting Subscriptions at Devices . . . . . . . . . . . . 25 4.5. Targeting Subscriptions at Devices . . . . . . . . . . . . 25
4.5.1. Using GRUUs to Route to Devices . . . . . . . . . . . 26 4.5.1. Using GRUUs to Route to Devices . . . . . . . . . . . 26
4.5.2. Sharing Dialogs . . . . . . . . . . . . . . . . . . . 26 4.5.2. Sharing Dialogs . . . . . . . . . . . . . . . . . . . 26
4.6. CANCEL Requests for SUBSCRIBE and NOTIFY . . . . . . . . . 28 4.6. CANCEL Requests for SUBSCRIBE and NOTIFY . . . . . . . . . 28
5. Event Packages . . . . . . . . . . . . . . . . . . . . . . . . 28 5. Event Packages . . . . . . . . . . . . . . . . . . . . . . . . 28
5.1. Appropriateness of Usage . . . . . . . . . . . . . . . . . 28 5.1. Appropriateness of Usage . . . . . . . . . . . . . . . . . 28
5.2. Event Template-packages . . . . . . . . . . . . . . . . . 29 5.2. Event Template-packages . . . . . . . . . . . . . . . . . 29
5.3. Amount of State to be Conveyed . . . . . . . . . . . . . . 29 5.3. Amount of State to be Conveyed . . . . . . . . . . . . . . 29
5.3.1. Complete State Information . . . . . . . . . . . . . . 30 5.3.1. Complete State Information . . . . . . . . . . . . . . 30
5.3.2. State Deltas . . . . . . . . . . . . . . . . . . . . . 30 5.3.2. State Deltas . . . . . . . . . . . . . . . . . . . . . 30
5.4. Event Package Responsibilities . . . . . . . . . . . . . . 30
5.4. Event Package Responsibilities . . . . . . . . . . . . . . 31
5.4.1. Event Package Name . . . . . . . . . . . . . . . . . . 31 5.4.1. Event Package Name . . . . . . . . . . . . . . . . . . 31
5.4.2. Event Package Parameters . . . . . . . . . . . . . . . 31 5.4.2. Event Package Parameters . . . . . . . . . . . . . . . 31
5.4.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . 31 5.4.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . 31
5.4.4. Subscription Duration . . . . . . . . . . . . . . . . 31 5.4.4. Subscription Duration . . . . . . . . . . . . . . . . 32
5.4.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . 31 5.4.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . 32
5.4.6. Notifier processing of SUBSCRIBE requests . . . . . . 32 5.4.6. Notifier processing of SUBSCRIBE requests . . . . . . 32
5.4.7. Notifier generation of NOTIFY requests . . . . . . . . 32 5.4.7. Notifier generation of NOTIFY requests . . . . . . . . 32
5.4.8. Subscriber processing of NOTIFY requests . . . . . . . 32 5.4.8. Subscriber processing of NOTIFY requests . . . . . . . 32
5.4.9. Handling of forked requests . . . . . . . . . . . . . 32 5.4.9. Handling of forked requests . . . . . . . . . . . . . 33
5.4.10. Rate of notifications . . . . . . . . . . . . . . . . 33 5.4.10. Rate of notifications . . . . . . . . . . . . . . . . 33
5.4.11. State Aggregation . . . . . . . . . . . . . . . . . . 33 5.4.11. State Aggregation . . . . . . . . . . . . . . . . . . 33
5.4.12. Examples . . . . . . . . . . . . . . . . . . . . . . . 33 5.4.12. Examples . . . . . . . . . . . . . . . . . . . . . . . 34
5.4.13. Use of URIs to Retrieve State . . . . . . . . . . . . 34 5.4.13. Use of URIs to Retrieve State . . . . . . . . . . . . 34
6. Security Considerations . . . . . . . . . . . . . . . . . . . 34 6. Security Considerations . . . . . . . . . . . . . . . . . . . 34
6.1. Access Control . . . . . . . . . . . . . . . . . . . . . . 34 6.1. Access Control . . . . . . . . . . . . . . . . . . . . . . 34
6.2. Notifier Privacy Mechanism . . . . . . . . . . . . . . . . 34 6.2. Notifier Privacy Mechanism . . . . . . . . . . . . . . . . 34
6.3. Denial-of-Service attacks . . . . . . . . . . . . . . . . 35 6.3. Denial-of-Service attacks . . . . . . . . . . . . . . . . 35
6.4. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 35 6.4. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 35
6.5. Man-in-the middle attacks . . . . . . . . . . . . . . . . 35 6.5. Man-in-the middle attacks . . . . . . . . . . . . . . . . 35
6.6. Confidentiality . . . . . . . . . . . . . . . . . . . . . 36 6.6. Confidentiality . . . . . . . . . . . . . . . . . . . . . 36
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
7.1. Event Packages . . . . . . . . . . . . . . . . . . . . . . 36 7.1. Event Packages . . . . . . . . . . . . . . . . . . . . . . 36
7.1.1. Registration Information . . . . . . . . . . . . . . . 37 7.1.1. Registration Information . . . . . . . . . . . . . . . 37
7.1.2. Registration Template . . . . . . . . . . . . . . . . 38 7.1.2. Registration Template . . . . . . . . . . . . . . . . 38
7.2. Reason Codes . . . . . . . . . . . . . . . . . . . . . . . 38 7.2. Reason Codes . . . . . . . . . . . . . . . . . . . . . . . 38
7.3. Header Field Names . . . . . . . . . . . . . . . . . . . . 39 7.3. Header Field Names . . . . . . . . . . . . . . . . . . . . 39
7.4. Response Codes . . . . . . . . . . . . . . . . . . . . . . 39 7.4. Response Codes . . . . . . . . . . . . . . . . . . . . . . 40
8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.1. New Methods . . . . . . . . . . . . . . . . . . . . . . . 40 8.1. New Methods . . . . . . . . . . . . . . . . . . . . . . . 40
8.1.1. SUBSCRIBE method . . . . . . . . . . . . . . . . . . . 41 8.1.1. SUBSCRIBE method . . . . . . . . . . . . . . . . . . . 40
8.1.2. NOTIFY method . . . . . . . . . . . . . . . . . . . . 41 8.1.2. NOTIFY method . . . . . . . . . . . . . . . . . . . . 40
8.2. New Header Fields . . . . . . . . . . . . . . . . . . . . 42 8.2. New Header Fields . . . . . . . . . . . . . . . . . . . . 41
8.2.1. "Event" Header Field . . . . . . . . . . . . . . . . . 42 8.2.1. "Event" Header Field . . . . . . . . . . . . . . . . . 41
8.2.2. "Allow-Events" Header Field . . . . . . . . . . . . . 42 8.2.2. "Allow-Events" Header Field . . . . . . . . . . . . . 41
8.2.3. "Subscription-State" Header Field . . . . . . . . . . 43 8.2.3. "Subscription-State" Header Field . . . . . . . . . . 41
8.3. New Response Codes . . . . . . . . . . . . . . . . . . . . 43 8.3. New Response Codes . . . . . . . . . . . . . . . . . . . . 41
8.3.1. "202 Accepted" Response Code . . . . . . . . . . . . . 43 8.3.1. "202 Accepted" Response Code . . . . . . . . . . . . . 41
8.3.2. "489 Bad Event" Response Code . . . . . . . . . . . . 43 8.3.2. "489 Bad Event" Response Code . . . . . . . . . . . . 42
8.4. Augmented BNF Definitions . . . . . . . . . . . . . . . . 43 8.4. Augmented BNF Definitions . . . . . . . . . . . . . . . . 42
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.1. Normative References . . . . . . . . . . . . . . . . . . . 44 9.1. Normative References . . . . . . . . . . . . . . . . . . . 43
9.2. Informative References . . . . . . . . . . . . . . . . . . 45 9.2. Informative References . . . . . . . . . . . . . . . . . . 44
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 46 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 45
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 46 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 45
B.1. Bug 711: Allow-Events can't express template support . . . 47 B.1. Changes from draft-ietf-sipcore-rfc3265bis-01 to
B.2. Remove 202 Response Code? . . . . . . . . . . . . . . . . 47 draft-ietf-sipcore-rfc3265bis-02 . . . . . . . . . . . . . 46
B.3. Timer N and Resubscribes . . . . . . . . . . . . . . . . . 47 B.2. Changes from draft-ietf-sipcore-rfc3265bis-00 to
Appendix C. Changes . . . . . . . . . . . . . . . . . . . . . . . 48 draft-ietf-sipcore-rfc3265bis-01 . . . . . . . . . . . . . 46
C.1. Changes from draft-ietf-sipcore-rfc3265bis-00 to B.3. Changes from draft-roach-sipcore-rfc3265bis-00 to
draft-ietf-sipcore-rfc3265bis-01 . . . . . . . . . . . . . 48 draft-ietf-sipcore-rfc3265bis-00 . . . . . . . . . . . . . 46
C.2. Changes from draft-roach-sipcore-rfc3265bis-00 to B.4. Changes since RFC 3265 . . . . . . . . . . . . . . . . . . 46
draft-ietf-sipcore-rfc3265bis-00 . . . . . . . . . . . . . 48 B.4.1. Bug 666: Clarify use of expires=xxx with terminated . 46
C.3. Changes since RFC 3265 . . . . . . . . . . . . . . . . . . 48 B.4.2. Bug 667: Reason code for unsub/poll not clearly
C.3.1. Bug 666: Clarify use of expires=xxx with terminated . 48 spelled out . . . . . . . . . . . . . . . . . . . . . 46
C.3.2. Bug 667: Reason code for unsub/poll not clearly B.4.3. Bug 669: Clarify: SUBSCRIBE for a duration might
spelled out . . . . . . . . . . . . . . . . . . . . . 48 be answered with a NOTIFY/expires=0 . . . . . . . . . 46
C.3.3. Bug 669: Clarify: SUBSCRIBE for a duration might B.4.4. Bug 670: Dialog State Machine needs clarification . . 47
be answered with a NOTIFY/expires=0 . . . . . . . . . 48 B.4.5. Bug 671: Clarify timeout-based removal of
C.3.4. Bug 670: Dialog State Machine needs clarification . . 48 subscriptions . . . . . . . . . . . . . . . . . . . . 47
C.3.5. Bug 671: Clarify timeout-based removal of B.4.6. Bug 672: Mandate expires= in NOTIFY . . . . . . . . . 47
subscriptions . . . . . . . . . . . . . . . . . . . . 49 B.4.7. Bug 673: INVITE 481 response effect clarification . . 47
C.3.6. Bug 672: Mandate expires= in NOTIFY . . . . . . . . . 49 B.4.8. Bug 677: SUBSCRIBE response matching text in error . . 47
C.3.7. Bug 673: INVITE 481 response effect clarification . . 49 B.4.9. Bug 695: Document is not explicit about response
C.3.8. Bug 677: SUBSCRIBE response matching text in error . . 49 to NOTIFY at subscription termination . . . . . . . . 47
C.3.9. Bug 695: Document is not explicit about response B.4.10. Bug 696: Subscription state machine needs
to NOTIFY at subscription termination . . . . . . . . 49 clarification . . . . . . . . . . . . . . . . . . . . 47
C.3.10. Bug 696: Subscription state machine needs B.4.11. Bug 697: Unsubscription behavior could be clarified . 47
clarification . . . . . . . . . . . . . . . . . . . . 49 B.4.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh
C.3.11. Bug 697: Unsubscription behavior could be clarified . 49 requests . . . . . . . . . . . . . . . . . . . . . . . 48
C.3.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh B.4.13. Bug 722: Inconsistent 423 reason phrase text . . . . . 48
requests . . . . . . . . . . . . . . . . . . . . . . . 49 B.4.14. Bug 741: guidance needed on when to not include
C.3.13. Bug 722: Inconsistent 423 reason phrase text . . . . . 50 Allow-Events . . . . . . . . . . . . . . . . . . . . . 48
C.3.14. Bug 741: guidance needed on when to not include B.4.15. Bug 744: 5xx to NOTIFY terminates a subscription,
Allow-Events . . . . . . . . . . . . . . . . . . . . . 50 but should not . . . . . . . . . . . . . . . . . . . . 48
C.3.15. Bug 744: 5xx to NOTIFY terminates a subscription, B.4.16. Bug 752: Detection of forked requests is incorrect . . 48
but should not . . . . . . . . . . . . . . . . . . . . 50 B.4.17. Bug 773: Reason code needs IANA registry . . . . . . . 48
C.3.16. Bug 752: Detection of forked requests is incorrect . . 50 B.4.18. Bug 774: Need new reason for terminating
C.3.17. Bug 773: Reason code needs IANA registry . . . . . . . 50 subscriptions to resources that never change . . . . . 48
C.3.18. Bug 774: Need new reason for terminating B.4.19. Clarify handling of Route/Record-Route in NOTIFY . . . 48
subscriptions to resources that never change . . . . . 50 B.4.20. Eliminate implicit subscriptions . . . . . . . . . . . 48
C.3.19. Clarify handling of Route/Record-Route in NOTIFY . . . 50 B.4.21. Deprecate dialog re-use . . . . . . . . . . . . . . . 49
C.3.20. Eliminate implicit subscriptions . . . . . . . . . . . 50 B.4.22. Rationalize dialog creation . . . . . . . . . . . . . 49
C.3.21. Deprecate dialog re-use . . . . . . . . . . . . . . . 51 B.4.23. Refactor behavior sections . . . . . . . . . . . . . . 49
C.3.22. Rationalize dialog creation . . . . . . . . . . . . . 51 B.4.24. Clarify sections that need to be present in event
C.3.23. Refactor behavior sections . . . . . . . . . . . . . . 51 packages . . . . . . . . . . . . . . . . . . . . . . . 49
C.3.24. Clarify sections that need to be present in event B.4.25. Make CANCEL handling more explicit . . . . . . . . . . 49
packages . . . . . . . . . . . . . . . . . . . . . . . 51 B.4.26. Remove State Agent Terminology . . . . . . . . . . . . 49
C.3.25. Make CANCEL handling more explicit . . . . . . . . . . 51 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 50
C.3.26. Remove State Agent Terminology . . . . . . . . . . . . 51
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 52
1. Introduction 1. Introduction
The ability to request asynchronous notification of events proves The ability to request asynchronous notification of events proves
useful in many types of SIP services for which cooperation between useful in many types of SIP services for which cooperation between
end-nodes is required. Examples of such services include automatic end-nodes is required. Examples of such services include automatic
callback services (based on terminal state events), buddy lists callback services (based on terminal state events), buddy lists
(based on user presence events), message waiting indications (based (based on user presence events), message waiting indications (based
on mailbox state change events), and PSTN and Internet on mailbox state change events), and PSTN and Internet
Internetworking (PINT) [RFC2848] status (based on call state events). Internetworking (PINT) [RFC2848] status (based on call state events).
skipping to change at page 6, line 20 skipping to change at page 6, line 20
There are several paragraphs throughout this document which provide There are several paragraphs throughout this document which provide
motivational or clarifying text. Such passages are non-normative, motivational or clarifying text. Such passages are non-normative,
and are provided only to assist with reader comprehension. These and are provided only to assist with reader comprehension. These
passages are set off from the remainder of the text by being indented passages are set off from the remainder of the text by being indented
thus: thus:
This is an example of non-normative explanatory text. It does not This is an example of non-normative explanatory text. It does not
form part of the specification, and is used only for form part of the specification, and is used only for
clarification. clarification.
The all-capital terms "MUST", "SHOULD", "MAY", "SHOULD NOT", "MUST The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT", and "RECOMMENDED" are used as defined in [RFC2119]. In "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
particular, implementors need to take careful note of the meaning of document are to be interpreted as described in [RFC2119].
"SHOULD" defined in RFC 2119. To rephrase: violation of SHOULD-
In particular, implementors need to take careful note of the meaning
of "SHOULD" defined in RFC 2119. To rephrase: violation of SHOULD-
strength requirements requires careful analysis and clearly strength requirements requires careful analysis and clearly
enumerable reasons. It is inappropriate to fail to comply with enumerable reasons. It is inappropriate to fail to comply with
"SHOULD"-strength requirements whimsically or for ease of "SHOULD"-strength requirements whimsically or for ease of
implementation. implementation.
The use of quotation marks next to periods and commas follows the The use of quotation marks next to periods and commas follows the
convention used by the American Mathematical Society; although convention used by the American Mathematical Society; although
contrary to traditional American English convention, this usage lends contrary to traditional American English convention, this usage lends
clarity to certain passages. clarity to certain passages.
skipping to change at page 11, line 23 skipping to change at page 11, line 23
+------------| notify_wait |-- response; --------+ | +------------| notify_wait |-- response; --------+ |
| +-------------+ or NOTIFY, | | | +-------------+ or NOTIFY, | |
| | state=terminated | | | | state=terminated | |
| | | | | | | |
++========|===================|============================|==|====++ ++========|===================|============================|==|====++
|| | | V | || || | | V | ||
|| Receive NOTIFY, Receive NOTIFY, +-------------+ || || Receive NOTIFY, Receive NOTIFY, +-------------+ ||
|| state=active state=pending | terminated | || || state=active state=pending | terminated | ||
|| | | +-------------+ || || | | +-------------+ ||
|| | | A A || || | | A A ||
|| | V Receive NOTIFY, | | || || | V Timer N Fires; | | ||
|| | +-------------+ state=terminated; | | || || | +-------------+ Receive NOTIFY, | | ||
|| | | pending |-- or 481 response ----+ | || || | | pending |-- state=terminated; --+ | ||
|| | +-------------+ to SUBSCRIBE | || || | +-------------+ or 481 response | ||
|| | | refresh | || || | | to SUBSCRIBE | ||
|| | Receive NOTIFY, | || || | Receive NOTIFY, refresh | ||
|| | state=active | || || | state=active | ||
|| | | | || || | | Timer N Fires; | ||
|| | V Receive NOTIFY, | || || | V Receive NOTIFY, | ||
|| | +-------------+ state=terminated; | || || | +-------------+ state=terminated; | ||
|| +----------->| active |-- or 481 response -------+ || || +----------->| active |-- or 481 response -------+ ||
|| +-------------+ to SUBSCRIBE || || +-------------+ to SUBSCRIBE ||
|| refresh || || refresh ||
|| Subscription || || Subscription ||
++=================================================================++ ++=================================================================++
Any transition from "notify_wait" into a "pending" or "active" state Any transition from "notify_wait" into a "pending" or "active" state
results in a new subscription. Note that multiple subscriptions can results in a new subscription. Note that multiple subscriptions can
skipping to change at page 12, line 8 skipping to change at page 12, line 8
SUBSCRIBE is a dialog-creating method, as described in SIP [RFC3261]. SUBSCRIBE is a dialog-creating method, as described in SIP [RFC3261].
When a subscriber wishes to subscribe to a particular state for a When a subscriber wishes to subscribe to a particular state for a
resource, it forms a SUBSCRIBE message. If the initial SUBSCRIBE resource, it forms a SUBSCRIBE message. If the initial SUBSCRIBE
represents a request outside of a dialog (as it typically will), its represents a request outside of a dialog (as it typically will), its
construction follows the procedures outlined in SIP [RFC3261] for UAC construction follows the procedures outlined in SIP [RFC3261] for UAC
request generation outside of a dialog. request generation outside of a dialog.
This SUBSCRIBE request will be confirmed with a final response. 200- This SUBSCRIBE request will be confirmed with a final response. 200-
class responses indicate that the subscription has been accepted, and class responses indicate that the subscription has been accepted, and
that a NOTIFY will be sent immediately. A 200 response indicates that a NOTIFY will be sent immediately.
that the subscription has been accepted and that the user is
authorized to subscribe to the requested resource. A 202 response
merely indicates that the subscription has been understood, and that
authorization may or may not have been granted.
The "Expires" header field in a 200-class response to SUBSCRIBE The "Expires" header field in a 200-class response to SUBSCRIBE
indicates the actual duration for which the subscription will remain indicates the actual duration for which the subscription will remain
active (unless refreshed). active (unless refreshed).
Non-200 class final responses indicate that no subscription or dialog Non-200 class final responses indicate that no subscription or dialog
has been created, and no subsequent NOTIFY message will be sent. All has been created, and no subsequent NOTIFY message will be sent. All
non-200 class responses (with the exception of "489", described non-200 class responses (with the exception of "489", described
herein) have the same meanings and handling as described in SIP herein) have the same meanings and handling as described in SIP
[RFC3261]. For the sake of clarity: if a SUBSCRIBE request contains [RFC3261]. For the sake of clarity: if a SUBSCRIBE request contains
skipping to change at page 13, line 9 skipping to change at page 12, line 51
code other than those listed above, the original subscription is code other than those listed above, the original subscription is
still considered valid for the duration of the most recently known still considered valid for the duration of the most recently known
"Expires" value as negotiated by SUBSCRIBE and its response, or as "Expires" value as negotiated by SUBSCRIBE and its response, or as
communicated by NOTIFY in the "Subscription-State" header field communicated by NOTIFY in the "Subscription-State" header field
"expires" parameter. "expires" parameter.
Note that many such errors indicate that there may be a problem Note that many such errors indicate that there may be a problem
with the network or the notifier such that no further NOTIFY with the network or the notifier such that no further NOTIFY
messages will be received. messages will be received.
When refreshing a subscription, a subscriber starts Timer N, set to
64*T1, when it sends the SUBSCRIBE message. If this Timer N expires
prior to the receipt of a NOTIFY message, the subscriber considers
the subscription terminated. If the subscriber receives a success
response to the SUBSCRIBE request that indicates that no NOTIFY will
be generated -- such as the 204 response defined in [RFC5839] -- then
it MUST cancel Timer N.
4.1.2.3. Unsubscribing 4.1.2.3. Unsubscribing
Unsubscribing is handled in the same way as refreshing of a Unsubscribing is handled in the same way as refreshing of a
subscription, with the "Expires" header field set to "0". Note that subscription, with the "Expires" header field set to "0". Note that
a successful unsubscription will also trigger a final NOTIFY message. a successful unsubscription will also trigger a final NOTIFY message.
The final NOTIFY may or may not contain information about the state The final NOTIFY may or may not contain information about the state
of the resource; subscribers need to be prepared to receive final of the resource; subscribers need to be prepared to receive final
NOTIFY messages both with and without state. NOTIFY messages both with and without state.
4.1.2.4. Confirmation of Subscription Creation 4.1.2.4. Confirmation of Subscription Creation
The subscriber can expect to receive a NOTIFY message from each node The subscriber can expect to receive a NOTIFY message from each node
which has processed a successful subscription or subscription which has processed a successful subscription or subscription
refresh. To ensure that subscribers do not wait indefinitely for a refresh. To ensure that subscribers do not wait indefinitely for a
subscription to be established, a subscriber starts a Timer N, set to subscription to be established, a subscriber starts a Timer N, set to
64*T1. If this Timer N expires prior to the receipt of a NOTIFY 64*T1, when it sends a SUBSCRIBE. If this Timer N expires prior to
message, the subscriber considers the subscription failed, and cleans the receipt of a NOTIFY message, the subscriber considers the
up any state associated with the subscription attempt. subscription failed, and cleans up any state associated with the
subscription attempt.
Until Timer N expires, several NOTIFY messages may arrive from Until Timer N expires, several NOTIFY messages may arrive from
different destinations (see Section 4.4.1). Each of these messages different destinations (see Section 4.4.1). Each of these messages
establish a new dialog and a new subscription. After the expiration establish a new dialog and a new subscription. After the expiration
of Timer N, the subscriber SHOULD reject any such NOTIFY messages of Timer N, the subscriber SHOULD reject any such NOTIFY messages
that would otherwise establish a new dialog with a "481" response that would otherwise establish a new dialog with a "481" response
code. code.
Until the first NOTIFY message arrives, the subscriber should Until the first NOTIFY message arrives, the subscriber should
consider the state of the subscribed resource to be in a neutral consider the state of the subscribed resource to be in a neutral
skipping to change at page 17, line 32 skipping to change at page 17, line 43
The notifier SHOULD also perform any necessary authentication and The notifier SHOULD also perform any necessary authentication and
authorization per its local policy. See Section 4.2.1.3. authorization per its local policy. See Section 4.2.1.3.
The notifier MAY also check that the duration in the "Expires" header The notifier MAY also check that the duration in the "Expires" header
field is not too small. If and only if the expiration interval is field is not too small. If and only if the expiration interval is
greater than zero AND smaller than one hour AND less than a notifier- greater than zero AND smaller than one hour AND less than a notifier-
configured minimum, the notifier MAY return a "423 Interval Too configured minimum, the notifier MAY return a "423 Interval Too
Brief" error which contains a "Min-Expires" header field field. The Brief" error which contains a "Min-Expires" header field field. The
"Min-Expires" header field is described in SIP [RFC3261]. "Min-Expires" header field is described in SIP [RFC3261].
If the notifier is able to immediately determine that it understands Once the notifier determines that it has enough information to create
the event package, that the authenticated subscriber is authorized to the subscription (i.e., it understands the event package, the
subscribe, and that there are no other barriers to creating the subscription pertains to a known resource, and there are no other
subscription, it creates the subscription and a dialog (if barriers to creating the subscription), it creates the subscription
necessary), and returns a "200 OK" response (unless doing so would and a dialog, and returns a 200 (OK) response.
reveal authorization policy in an undesirable fashion; see
Section 6.2).
If the notifier cannot immediately create the subscription (e.g., it
needs to wait for user input for authorization, or is acting for
another node which is not currently reachable), or wishes to mask
authorization policy, it will return a "202 Accepted" response. This
response indicates that the request has been received and understood,
but does not necessarily imply that the subscription has been
authorized yet.
When a subscription is created in the notifier, it stores the event When a subscription is created in the notifier, it stores the event
package name as part of the subscription information. package name as part of the subscription information.
The "Expires" values present in SUBSCRIBE 200-class responses behave The "Expires" values present in SUBSCRIBE 200-class responses behave
in the same way as they do in REGISTER responses: the server MAY in the same way as they do in REGISTER responses: the server MAY
shorten the interval, but MUST NOT lengthen it. shorten the interval, but MUST NOT lengthen it.
If the duration specified in a SUBSCRIBE message is unacceptably If the duration specified in a SUBSCRIBE message is unacceptably
short, the notifier may be able to send a 423 response, as short, the notifier may be able to send a 423 response, as
skipping to change at page 19, line 18 skipping to change at page 19, line 18
authentication. authentication.
If authorization fails based on an access list or some other If authorization fails based on an access list or some other
automated mechanism (i.e., it can be automatically authoritatively automated mechanism (i.e., it can be automatically authoritatively
determined that the subscriber is not authorized to subscribe), the determined that the subscriber is not authorized to subscribe), the
notifier SHOULD reply to the request with a "403 Forbidden" or "603 notifier SHOULD reply to the request with a "403 Forbidden" or "603
Decline" response, unless doing so might reveal information that Decline" response, unless doing so might reveal information that
should stay private; see Section 6.2. should stay private; see Section 6.2.
If the notifier owner is interactively queried to determine whether a If the notifier owner is interactively queried to determine whether a
subscription is allowed, a "202 Accept" response is returned subscription is allowed, a 200 (OK) response is returned immediately.
immediately. Note that a NOTIFY message is still formed and sent Note that a NOTIFY message is still formed and sent under these
under these circumstances, as described in the previous section. circumstances, as described in the previous section.
If subscription authorization was delayed and the notifier wishes to If subscription authorization was delayed and the notifier wishes to
convey that such authorization has been declined, it may do so by convey that such authorization has been declined, it may do so by
sending a NOTIFY message containing a "Subscription-State" header sending a NOTIFY message containing a "Subscription-State" header
field with a value of "terminated" and a reason parameter of field with a value of "terminated" and a reason parameter of
"rejected". "rejected".
4.2.1.4. Refreshing of Subscriptions 4.2.1.4. Refreshing of Subscriptions
When a notifier receives a subscription refresh, assuming that the When a notifier receives a subscription refresh, assuming that the
skipping to change at page 25, line 39 skipping to change at page 25, line 39
according to whether the events required to implement the features according to whether the events required to implement the features
they represent are supported by the appropriate nodes. they represent are supported by the appropriate nodes.
On the other hand, it doesn't necessarily make much sense to On the other hand, it doesn't necessarily make much sense to
indicate supported events inside a NOTIFY-established dialog if indicate supported events inside a NOTIFY-established dialog if
the only event package supported is the one associated with that the only event package supported is the one associated with that
subscription. subscription.
Note that "Allow-Events" header fields MUST NOT be inserted by Note that "Allow-Events" header fields MUST NOT be inserted by
proxies. proxies.
The "Allow-Events" header field does not include a list of the event
template packages supported by an implementation. If a subscriber
wishes to determine which event template packages are supported by a
notifier, it can probe for such support by attempting to subscribe to
the event template packages it wishes to use.
4.5. Targeting Subscriptions at Devices 4.5. Targeting Subscriptions at Devices
[RFC3265] defined a mechanism by which subscriptions could share [RFC3265] defined a mechanism by which subscriptions could share
dialogs with invite usages and with other subscriptions. The purpose dialogs with invite usages and with other subscriptions. The purpose
of this behavior was to allow subscribers to ensure that a of this behavior was to allow subscribers to ensure that a
subscription arrived at the same device as an established dialog. subscription arrived at the same device as an established dialog.
Unfortunately, the re-use of dialogs has proven to be exceedingly Unfortunately, the re-use of dialogs has proven to be exceedingly
confusing. [RFC5057] attempted to clarify proper behavior in a confusing. [RFC5057] attempted to clarify proper behavior in a
variety of circumstances; however, the ensuing rules remain confusing variety of circumstances; however, the ensuing rules remain confusing
and prone to implementation error. At the same time, the mechanism and prone to implementation error. At the same time, the mechanism
described in [I-D.ietf-sip-gruu] now provides a far more elegant and described in [RFC5627] now provides a far more elegant and
unambiguous means to achieve the same goal. unambiguous means to achieve the same goal.
Consequently, the dialog re-use technique described in RFC 3265 is Consequently, the dialog re-use technique described in RFC 3265 is
now deprecated. now deprecated.
This dialog-sharing technique has also historically been used as a This dialog-sharing technique has also historically been used as a
means for targeting an event package at a dialog. This usage can be means for targeting an event package at a dialog. This usage can be
seen, for example, in certain applications of the REFER method seen, for example, in certain applications of the REFER method
[RFC3515]. With the removal of dialog re-use, an alternate (and more [RFC3515]. With the removal of dialog re-use, an alternate (and more
explicit) means of targeting dialogs needs to be used for this type explicit) means of targeting dialogs needs to be used for this type
of correlation. The appropriate means of such targeting is left up of correlation. The appropriate means of such targeting is left up
to the actual event packages. Candidates include the "Target-Dialog" to the actual event packages. Candidates include the "Target-Dialog"
header field [RFC4528], the "Join" header field [RFC3911], and the header field [RFC4538], the "Join" header field [RFC3911], and the
"Replaces" header field [RFC3891], depending on the semantics "Replaces" header field [RFC3891], depending on the semantics
desired. Alternately, if the semantics of those header fields do not desired. Alternately, if the semantics of those header fields do not
match the event package's purpose for correlation, event packages can match the event package's purpose for correlation, event packages can
devise their own means of identifying dialogs. For an example of devise their own means of identifying dialogs. For an example of
this approach, see the Dialog Event Package [RFC4235]. this approach, see the Dialog Event Package [RFC4235].
4.5.1. Using GRUUs to Route to Devices 4.5.1. Using GRUUs to Route to Devices
Notifiers MUST implement the GRUU extension defined in Notifiers MUST implement the GRUU extension defined in [RFC5627], and
[I-D.ietf-sip-gruu], and MUST use a GRUU as their local target. This MUST use a GRUU as their local target. This allows subscribers to
allows subscribers to explicitly target desired devices. explicitly target desired devices.
If a subscriber wishes to subscribe to a resource on the same device If a subscriber wishes to subscribe to a resource on the same device
as an established dialog, it should check whether the remote contact as an established dialog, it should check whether the remote contact
in that dialog is a GRUU (i.e., whether it contains a "gr" URI in that dialog is a GRUU (i.e., whether it contains a "gr" URI
parameter). If so, the subscriber creates a new dialog, using the parameter). If so, the subscriber creates a new dialog, using the
GRUU as the request URI for the new SUBSCRIBE. GRUU as the request URI for the new SUBSCRIBE.
Because GRUUs are guaranteed to route to a a specific device, this Because GRUUs are guaranteed to route to a a specific device, this
ensures that the subscription will be routed to the same place as ensures that the subscription will be routed to the same place as
the established dialog. the established dialog.
skipping to change at page 32, line 18 skipping to change at page 32, line 30
Event packages also MUST define which MIME type is to be assumed if Event packages also MUST define which MIME type is to be assumed if
none are specified in the "Accept" header field of the SUBSCRIBE none are specified in the "Accept" header field of the SUBSCRIBE
request. request.
5.4.6. Notifier processing of SUBSCRIBE requests 5.4.6. Notifier processing of SUBSCRIBE requests
This section describes the processing to be performed by the notifier This section describes the processing to be performed by the notifier
upon receipt of a SUBSCRIBE request. Such a section is required. upon receipt of a SUBSCRIBE request. Such a section is required.
Information in this section includes details of how to authenticate Information in this section includes details of how to authenticate
subscribers and authorization issues for the package. Such subscribers and authorization issues for the package.
authorization issues may include, for example, whether all SUBSCRIBE
requests for this package are answered with 202 responses (see
Section 6.2).
5.4.7. Notifier generation of NOTIFY requests 5.4.7. Notifier generation of NOTIFY requests
This section of an event package describes the process by which the This section of an event package describes the process by which the
notifier generates and sends a NOTIFY request. This includes notifier generates and sends a NOTIFY request. This includes
detailed information about what events cause a NOTIFY to be sent, how detailed information about what events cause a NOTIFY to be sent, how
to compute the state information in the NOTIFY, how to generate to compute the state information in the NOTIFY, how to generate
neutral or fake state information to hide authorization delays and neutral or fake state information to hide authorization delays and
decisions from users, and whether state information is complete or decisions from users, and whether state information is complete or
deltas for notifications; see Section 5.3. Such a section is deltas for notifications; see Section 5.3. Such a section is
skipping to change at page 34, line 37 skipping to change at page 34, line 46
control of the notifier's user, since many types of events may be control of the notifier's user, since many types of events may be
considered sensitive for the purposes of privacy. Similarly, the considered sensitive for the purposes of privacy. Similarly, the
notifier should have the ability to selectively reject subscriptions notifier should have the ability to selectively reject subscriptions
based on the subscriber identity (based on access control lists), based on the subscriber identity (based on access control lists),
using standard SIP authentication mechanisms. The methods for using standard SIP authentication mechanisms. The methods for
creation and distribution of such access control lists is outside the creation and distribution of such access control lists is outside the
scope of this document. scope of this document.
6.2. Notifier Privacy Mechanism 6.2. Notifier Privacy Mechanism
The mere act of returning a 200 or certain 4xx and 6xx responses to The mere act of returning certain 4xx and 6xx responses to SUBSCRIBE
SUBSCRIBE requests may, under certain circumstances, create privacy requests may, under certain circumstances, create privacy concerns by
concerns by revealing sensitive policy information. In these cases, revealing sensitive policy information. In these cases, the notifier
the notifier SHOULD always return a 202 response. While the SHOULD always return a 200 (OK) response. While the subsequent
subsequent NOTIFY message may not convey true state, it MUST appear NOTIFY message may not convey true state, it MUST appear to contain a
to contain a potentially correct piece of data from the point of view potentially correct piece of data from the point of view of the
of the subscriber, indistinguishable from a valid response. subscriber, indistinguishable from a valid response. Information
Information about whether a user is authorized to subscribe to the about whether a user is authorized to subscribe to the requested
requested state is never conveyed back to the original user under state is never conveyed back to the original user under these
these circumstances. circumstances.
Individual packages and their related documents for which such a mode Individual packages and their related documents for which such a mode
of operation makes sense can further describe how and why to generate of operation makes sense can further describe how and why to generate
such potentially correct data. For example, such a mode of operation such potentially correct data. For example, such a mode of operation
is mandated by [RFC2779] for user presence information. is mandated by [RFC2779] for user presence information.
6.3. Denial-of-Service attacks 6.3. Denial-of-Service attacks
The current model (one SUBSCRIBE request triggers a SUBSCRIBE The current model (one SUBSCRIBE request triggers a SUBSCRIBE
response and one or more NOTIFY requests) is a classic setup for an response and one or more NOTIFY requests) is a classic setup for an
skipping to change at page 36, line 46 skipping to change at page 37, line 8
central coordinating body. The body chosen for this coordination is central coordinating body. The body chosen for this coordination is
the Internet Assigned Numbers Authority (IANA). the Internet Assigned Numbers Authority (IANA).
There are two different types of event-types: normal event packages, There are two different types of event-types: normal event packages,
and event template-packages; see Section 5.2. To avoid confusion, and event template-packages; see Section 5.2. To avoid confusion,
template-package names and package names share the same namespace; in template-package names and package names share the same namespace; in
other words, an event template-package MUST NOT share a name with a other words, an event template-package MUST NOT share a name with a
package. package.
Following the policies outlined in "Guidelines for Writing an IANA Following the policies outlined in "Guidelines for Writing an IANA
Considerations Section in RFCs" [RFC2434], normal event package Considerations Section in RFCs" [RFC5226], normal event package
identification tokens are allocated as First Come First Served, and identification tokens are allocated as First Come First Served, and
event template-package identification tokens are allocated on a IETF event template-package identification tokens are allocated on a IETF
Consensus basis. Consensus basis.
Registrations with the IANA MUST include the token being registered Registrations with the IANA MUST include the token being registered
and whether the token is a package or a template-package. Further, and whether the token is a package or a template-package. Further,
packages MUST include contact information for the party responsible packages MUST include contact information for the party responsible
for the registration and/or a published document which describes the for the registration and/or a published document which describes the
event package. Event template-package token registrations MUST event package. Event template-package token registrations MUST
include a pointer to the published RFC which defines the event include a pointer to the published RFC which defines the event
skipping to change at page 38, line 32 skipping to change at page 38, line 49
reference a specification when appropriate). reference a specification when appropriate).
Person & email address to contact for further information: Person & email address to contact for further information:
7.2. Reason Codes 7.2. Reason Codes
This document further defines "reason" codes for use in the This document further defines "reason" codes for use in the
"Subscription-State" header field (see Section 4.1.3). "Subscription-State" header field (see Section 4.1.3).
Following the policies outlined in "Guidelines for Writing an IANA Following the policies outlined in "Guidelines for Writing an IANA
Considerations Section in RFCs" [RFC2434], new reason codes require a Considerations Section in RFCs" [RFC5226], new reason codes require a
Standards Action. Standards Action.
Registrations with the IANA include the reason code being registered Registrations with the IANA include the reason code being registered
and a reference to a published document which describes the event and a reference to a published document which describes the event
package. Insertion of such values takes place as part of the RFC package. Insertion of such values takes place as part of the RFC
publication process or as the result of inter-SDO liaison activity. publication process or as the result of inter-SDO liaison activity.
New reason codes must conform to the syntax of the ABNF "token" New reason codes must conform to the syntax of the ABNF "token"
element defined in SIP [RFC3261]. element defined in SIP [RFC3261].
[RFC4660] defined a new reason code prior to the establishment of an [RFC4660] defined a new reason code prior to the establishment of an
skipping to change at page 40, line 17 skipping to change at page 40, line 31
This section describes the syntax extensions required for event This section describes the syntax extensions required for event
notification in SIP. Semantics are described in Section 4. Note notification in SIP. Semantics are described in Section 4. Note
that the formal syntax definitions described in this document are that the formal syntax definitions described in this document are
expressed in the ABNF format used in SIP [RFC3261], and contain expressed in the ABNF format used in SIP [RFC3261], and contain
references to elements defined therein. references to elements defined therein.
8.1. New Methods 8.1. New Methods
This document describes two new SIP methods: SUBSCRIBE and NOTIFY. This document describes two new SIP methods: SUBSCRIBE and NOTIFY.
This table expands on tables 2 and 3 in SIP [RFC3261].
Header Where SUB NOT
------ ----- --- ---
Accept R o o
Accept 2xx - -
Accept 415 o o
Accept-Encoding R o o
Accept-Encoding 2xx - -
Accept-Encoding 415 o o
Accept-Language R o o
Accept-Language 2xx - -
Accept-Language 415 o o
Alert-Info R - -
Alert-Info 180 - -
Allow R o o
Allow 2xx o o
Allow r o o
Allow 405 m m
Authentication-Info 2xx o o
Authorization R o o
Call-ID c m m
Call-Info R o o
Contact R m m
Contact 1xx o o
Contact 2xx m o
Contact 3xx m m
Contact 485 o o
Content-Disposition o o
Content-Encoding o o
Content-Language o o
Content-Length t t
Content-Type * *
CSeq c m m
Date o o
Error-Info 300-699 o o
Expires o -
Expires 2xx m -
From c m m
In-Reply-To R - -
Max-Forwards R m m
Min-Expires 423 m -
MIME-Version o o
Organization o -
Priority R o -
Proxy-Authenticate 407 m m
Proxy-Authorization R o o
Proxy-Require R o o
RAck R - -
Record-Route R o o
Record-Route 2xx,401,484 o o
Reply-To - -
Require o o
Retry-After 404,413,480,486 o o
Retry-After 500,503 o o
Retry-After 600,603 o o
Route R c c
RSeq 1xx o o
Server r o o
Subject R - -
Supported R o o
Supported 2xx o o
Timestamp o o
To c(1) m m
Unsupported 420 o o
User-Agent o o
Via c m m
Warning R - o
Warning r o o
WWW-Authenticate 401 m m
8.1.1. SUBSCRIBE method 8.1.1. SUBSCRIBE method
"SUBSCRIBE" is added to the definition of the element "Method" in the "SUBSCRIBE" is added to the definition of the element "Method" in the
SIP message grammar. SIP message grammar.
Like all SIP method names, the SUBSCRIBE method name is case Like all SIP method names, the SUBSCRIBE method name is case
sensitive. The SUBSCRIBE method is used to request asynchronous sensitive. The SUBSCRIBE method is used to request asynchronous
notification of an event or set of events at a later time. notification of an event or set of events at a later time.
8.1.2. NOTIFY method 8.1.2. NOTIFY method
"NOTIFY" is added to the definition of the element "Method" in the "NOTIFY" is added to the definition of the element "Method" in the
SIP message grammar. SIP message grammar.
The NOTIFY method is used to notify a SIP node that an event which The NOTIFY method is used to notify a SIP node that an event which
has been requested by an earlier SUBSCRIBE method has occurred. It has been requested by an earlier SUBSCRIBE method has occurred. It
may also provide further details about the event. may also provide further details about the event.
8.2. New Header Fields 8.2. New Header Fields
This table expands on tables 2 and 3 in SIP [RFC3261], as amended by
the changes described in Section 8.1.
Header field where proxy ACK BYE CAN INV OPT REG PRA SUB NOT
-----------------------------------------------------------------
Allow-Events R o o - o o o o o o
Allow-Events 2xx - o - o o o o o o
Allow-Events 489 - - - - - - - m m
Event R - - - - - - - m m
Subscription-State R - - - - - - - - m
8.2.1. "Event" Header Field 8.2.1. "Event" Header Field
Event is added to the definition of the element "message-header Event is added to the definition of the element "message-header
field" in the SIP message grammar. field" in the SIP message grammar.
For the purposes of matching NOTIFY messages with SUBSCRIBE messages, For the purposes of matching NOTIFY messages with SUBSCRIBE messages,
the event-type portion of the "Event" header field is compared byte- the event-type portion of the "Event" header field is compared byte-
by-byte, and the "id" parameter token (if present) is compared byte- by-byte, and the "id" parameter token (if present) is compared byte-
by-byte. An "Event" header field containing an "id" parameter never by-byte. An "Event" header field containing an "id" parameter never
matches an "Event" header field without an "id" parameter. No other matches an "Event" header field without an "id" parameter. No other
skipping to change at page 43, line 16 skipping to change at page 41, line 49
8.2.3. "Subscription-State" Header Field 8.2.3. "Subscription-State" Header Field
Subscription-State is added to the definition of the element Subscription-State is added to the definition of the element
"request-header field" in the SIP message grammar. Its usage is "request-header field" in the SIP message grammar. Its usage is
described in Section 4.1.3. described in Section 4.1.3.
8.3. New Response Codes 8.3. New Response Codes
8.3.1. "202 Accepted" Response Code 8.3.1. "202 Accepted" Response Code
The 202 response is added to the "Success" header field definition. For historical purposes, the 202 (Accepted) response code is added to
"202 Accepted" has the same meaning as that defined in HTTP/1.1 the "Success" header field definition.
[RFC2616].
This document does not specify the use of the 202 response code in
conjunction with the SUBSCRIBE or NOTIFY methods. Previous versions
of the SIP Events Framework assigned specific semantics to the 202
response code. Implementations conformant with the current
specification MUST treat an incoming 202 response as identical to a
200 response, and MUST NOT generate 202 response codes to SUBSCRIBE
or NOTIFY messages.
This document also updates [RFC4660], which reiterates the 202-based
behavior in several places. Implementations compliant with the
present document MUST NOT send a 202 response to SUBSCRIBE, and will
send an alternate success response (such as 200) in its stead.
8.3.2. "489 Bad Event" Response Code 8.3.2. "489 Bad Event" Response Code
The 489 event response is added to the "Client-Error" header field The 489 event response is added to the "Client-Error" header field
field definition. "489 Bad Event" is used to indicate that the server field definition. "489 Bad Event" is used to indicate that the server
did not understand the event package specified in a "Event" header did not understand the event package specified in a "Event" header
field. field.
8.4. Augmented BNF Definitions 8.4. Augmented BNF Definitions
skipping to change at page 44, line 50 skipping to change at page 43, line 50
/ event-reason-extension / event-reason-extension
event-reason-extension = token event-reason-extension = token
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2779] Day, M., Aggarwal, S., Mohr, G., and J. Vincent, "Instant
Messaging / Presence Protocol Requirements", RFC 2779,
February 2000.
[RFC2848] Petrack, S. and L. Conroy, "The PINT Service Protocol: [RFC2848] Petrack, S. and L. Conroy, "The PINT Service Protocol:
Extensions to SIP and SDP for IP Access to Telephone Call Extensions to SIP and SDP for IP Access to Telephone Call
Services", RFC 2848, June 2000. Services", RFC 2848, June 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002. Event Notification", RFC 3265, June 2002.
[RFC4483] Burger, E., "A Mechanism for Content Indirection in [RFC4483] Burger, E., "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", RFC 4483, Session Initiation Protocol (SIP) Messages", RFC 4483,
May 2006. May 2006.
[I-D.ietf-sip-gruu] [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
Rosenberg, J., "Obtaining and Using Globally Routable User IANA Considerations Section in RFCs", BCP 26, RFC 5226,
Agent (UA) URIs (GRUU) in the Session Initiation Protocol May 2008.
(SIP)", draft-ietf-sip-gruu-15 (work in progress),
October 2007. [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, October 2009.
9.2. Informative References 9.2. Informative References
[RFC2779] Day, M., Aggarwal, S., Mohr, G., and J. Vincent, "Instant
Messaging / Presence Protocol Requirements", RFC 2779,
February 2000.
[RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer [RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, April 2003. Method", RFC 3515, April 2003.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session "Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004. Initiation Protocol (SIP)", RFC 3840, August 2004.
[RFC3891] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation [RFC3891] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation
Protocol (SIP) "Replaces" Header", RFC 3891, Protocol (SIP) "Replaces" Header", RFC 3891,
September 2004. September 2004.
skipping to change at page 46, line 16 skipping to change at page 45, line 9
(SIP) "Join" Header", RFC 3911, October 2004. (SIP) "Join" Header", RFC 3911, October 2004.
[RFC4235] Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE- [RFC4235] Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE-
Initiated Dialog Event Package for the Session Initiation Initiated Dialog Event Package for the Session Initiation
Protocol (SIP)", RFC 4235, November 2005. Protocol (SIP)", RFC 4235, November 2005.
[RFC4485] Rosenberg, J. and H. Schulzrinne, "Guidelines for Authors [RFC4485] Rosenberg, J. and H. Schulzrinne, "Guidelines for Authors
of Extensions to the Session Initiation Protocol (SIP)", of Extensions to the Session Initiation Protocol (SIP)",
RFC 4485, May 2006. RFC 4485, May 2006.
[RFC4528] Zeilenga, K., "Lightweight Directory Access Protocol [RFC4538] Rosenberg, J., "Request Authorization through Dialog
(LDAP) Assertion Control", RFC 4528, June 2006. Identification in the Session Initiation Protocol (SIP)",
RFC 4538, June 2006.
[RFC4660] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa- [RFC4660] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
Requena, "Functional Description of Event Notification Requena, "Functional Description of Event Notification
Filtering", RFC 4660, September 2006. Filtering", RFC 4660, September 2006.
[RFC5057] Sparks, R., "Multiple Dialog Usages in the Session [RFC5057] Sparks, R., "Multiple Dialog Usages in the Session
Initiation Protocol", RFC 5057, November 2007. Initiation Protocol", RFC 5057, November 2007.
[RFC5839] Niemi, A. and D. Willis, "An Extension to Session
Initiation Protocol (SIP) Events for Conditional Event
Notification", RFC 5839, May 2010.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Thanks to the participants in the Events BOF at the 48th IETF meeting Thanks to the participants in the Events BOF at the 48th IETF meeting
in Pittsburgh, as well as those who gave ideas and suggestions on the in Pittsburgh, as well as those who gave ideas and suggestions on the
SIP Events mailing list. In particular, I wish to thank Henning SIP Events mailing list. In particular, I wish to thank Henning
Schulzrinne of Columbia University for coming up with the final Schulzrinne of Columbia University for coming up with the final
three-tiered event identification scheme, Sean Olson for three-tiered event identification scheme, Sean Olson for
miscellaneous guidance, Jonathan Rosenberg for a thorough scrubbing miscellaneous guidance, Jonathan Rosenberg for a thorough scrubbing
of the -00 draft, and the authors of the "SIP Extensions for of the -00 draft, and the authors of the "SIP Extensions for
Presence" document for their input to SUBSCRIBE and NOTIFY request Presence" document for their input to SUBSCRIBE and NOTIFY request
semantics. semantics.
I also owe a debt of gratitude to all the implementors who have I also owe a debt of gratitude to all the implementors who have
provided feedback on areas of confusion or difficulty in the original provided feedback on areas of confusion or difficulty in the original
specification. In particular, Robert Sparks' Herculean efforts specification. In particular, Robert Sparks' Herculean efforts
organizing, running, and collecting data from the SIPit events have organizing, running, and collecting data from the SIPit events have
proven invaluable in shaking out specification bugs. Robert Sparks proven invaluable in shaking out specification bugs. Robert Sparks
is also responsible for untangling the dialog usage mess, in the form is also responsible for untangling the dialog usage mess, in the form
of RFC 5057. of RFC 5057 [RFC5057].
Appendix B. Open Issues
B.1. Bug 711: Allow-Events can't express template support
OPEN ISSUE: There are several things we can do here. I have not
proposed on in particular; I would prefer to solicit initial feedback
from implementors regarding what has been developed and deployed so
far.
The key problem is that support of template event packages can't be
expressed in a complete yet bounded fashion. It would not be
reasonable, for example, to require notifiers that support winfo on
arbitrary packages to include an "Allow-Events" header field with
contents like "presence, presence.winfo, presence.winfo.winfo,
presence.winfo.winfo.winfo, presence.winfo.winfo.winfo.winfo,
presence.winfo.winfo.winfo.winfo.winfo...."
One alternative would be to list event packages and template event
packages, without explicitly indicating which templates can be
applied to which other packages. In such a case, the preceding
example would be collapsed to "Allow-Events: presence, winfo". The
notifier may have local policy that limits how they can be combined
-- but we have plenty of other places where protocol allows
something, but policy forbids it.
B.2. Remove 202 Response Code?
In practice, the 202 response code defined in RFC 3265 has proven to
be nearly useless, due to its redundancy with the "pending" state,
and its interaction with the HERFP problem. Given that 202 must be
treated as 200 if an implementation does not understand it: would
removing the 202 response code cause any issues for current
implementations?
B.3. Timer N and Resubscribes
Section 4.1.2.4 defines a new Timer N that is used upon initial
subscription to bound the amount of time that a subscriber needs to
wait for a NOTIFY. Should this also apply to resubscribes? On one
hand, the mechanism is not as necessary, since the subscriber already
has a negotiated expiration time associated with the subscription.
On the other hand, if no NOTIFY arrives in 64*T1, it is highly likely
that the notifier has gone off the rails, which means that the
subscriber can safely clean up state associated with that
subscription. The key question involved in applying Timer N to
resubscriptions is whether doing so makes subscriptions unnecessarily
brittle.
Appendix C. Changes Appendix B. Changes
This section, and all of its subsections, will be consolidated into a This section, and all of its subsections, will be consolidated into a
single "Changes Since RFC 3265" section prior to publication. Bug single "Changes Since RFC 3265" section prior to publication. Bug
numbers refer to the identifiers for the bug reports kept on file at numbers refer to the identifiers for the bug reports kept on file at
http://bugs.sipit.net/. http://bugs.sipit.net/.
C.1. Changes from draft-ietf-sipcore-rfc3265bis-00 to B.1. Changes from draft-ietf-sipcore-rfc3265bis-01 to
draft-ietf-sipcore-rfc3265bis-02
o Removed "Table 2" expansions, per WG consensus on how SIP table 2
is to be handled.
o Removed 202 response code.
o Clarified that "Allow-Events" does not list event template
packages.
o Clarified that Timer N *does* apply to subscription refreshes.
B.2. Changes from draft-ietf-sipcore-rfc3265bis-00 to
draft-ietf-sipcore-rfc3265bis-01 draft-ietf-sipcore-rfc3265bis-01
o Renamed Timer L to Timer N, to avoid a naming conflict. o Renamed Timer L to Timer N, to avoid a naming conflict.
o Added clarification about proper response when the SUBSCRIBE o Added clarification about proper response when the SUBSCRIBE
indicates an unkonwn MIME type in its Accept header field. indicates an unkonwn MIME type in its Accept header field.
o Clarification around Route and Record-Route behavior. o Clarification around Route and Record-Route behavior.
o Added non-normative warning about the limitations of state o Added non-normative warning about the limitations of state
polling. polling.
o Added information about targeting subscriptions at specific o Added information about targeting subscriptions at specific
dialogs. dialogs.
o Added "Call-Info" header field to RFC 3261 Table 2 expansion. o Added "Call-Info" header field to RFC 3261 Table 2 expansion.
C.2. Changes from draft-roach-sipcore-rfc3265bis-00 to B.3. Changes from draft-roach-sipcore-rfc3265bis-00 to
draft-ietf-sipcore-rfc3265bis-00 draft-ietf-sipcore-rfc3265bis-00
None None
C.3. Changes since RFC 3265 B.4. Changes since RFC 3265
C.3.1. Bug 666: Clarify use of expires=xxx with terminated B.4.1. Bug 666: Clarify use of expires=xxx with terminated
Strengthened language in Section 4.1.3 to clarify that expires should Strengthened language in Section 4.1.3 to clarify that expires should
not be sent with terminated, and must be ignored if received. not be sent with terminated, and must be ignored if received.
C.3.2. Bug 667: Reason code for unsub/poll not clearly spelled out B.4.2. Bug 667: Reason code for unsub/poll not clearly spelled out
Clarified description of "timeout" in Section 4.1.3. (n.b., the text Clarified description of "timeout" in Section 4.1.3. (n.b., the text
in Section 4.4.3 is actually pretty clear about this). in Section 4.4.3 is actually pretty clear about this).
C.3.3. Bug 669: Clarify: SUBSCRIBE for a duration might be answered B.4.3. Bug 669: Clarify: SUBSCRIBE for a duration might be answered
with a NOTIFY/expires=0 with a NOTIFY/expires=0
Added clarifying text to Section 4.2.2 explaining that shortening a Added clarifying text to Section 4.2.2 explaining that shortening a
subscription to zero seconds is valid. Also added sentence to subscription to zero seconds is valid. Also added sentence to
Section 3.1.1 explicitly allowing shortening to zero. Section 3.1.1 explicitly allowing shortening to zero.
C.3.4. Bug 670: Dialog State Machine needs clarification B.4.4. Bug 670: Dialog State Machine needs clarification
The issues associated with the bug deal exclusively with the handling The issues associated with the bug deal exclusively with the handling
of multiple usages with a dialog. This behavior has been deprecated of multiple usages with a dialog. This behavior has been deprecated
and moved to Section 4.5.2. This section, in turn, cites [RFC5057], and moved to Section 4.5.2. This section, in turn, cites [RFC5057],
which addresses all of the issues in Bug 670. which addresses all of the issues in Bug 670.
C.3.5. Bug 671: Clarify timeout-based removal of subscriptions B.4.5. Bug 671: Clarify timeout-based removal of subscriptions
Changed Section 4.2.2 to specifically cite Timer F (so as to avoid Changed Section 4.2.2 to specifically cite Timer F (so as to avoid
ambiguity between transaction timeouts and retransmission timeouts). ambiguity between transaction timeouts and retransmission timeouts).
C.3.6. Bug 672: Mandate expires= in NOTIFY B.4.6. Bug 672: Mandate expires= in NOTIFY
Changed strength of including of "expires" in a NOTIFY from SHOULD to Changed strength of including of "expires" in a NOTIFY from SHOULD to
MUST in Section 4.2.2. MUST in Section 4.2.2.
C.3.7. Bug 673: INVITE 481 response effect clarification B.4.7. Bug 673: INVITE 481 response effect clarification
This bug was addressed in [RFC5057]. This bug was addressed in [RFC5057].
C.3.8. Bug 677: SUBSCRIBE response matching text in error B.4.8. Bug 677: SUBSCRIBE response matching text in error
Fixed Section 8.2.1 to remove incorrect "...responses and..." -- Fixed Section 8.2.1 to remove incorrect "...responses and..." --
explicitly pointed to SIP for transaction response handling. explicitly pointed to SIP for transaction response handling.
C.3.9. Bug 695: Document is not explicit about response to NOTIFY at B.4.9. Bug 695: Document is not explicit about response to NOTIFY at
subscription termination subscription termination
Added text to Section 4.4.1 indicating that the typical response to a Added text to Section 4.4.1 indicating that the typical response to a
terminal NOTIFY is a "200 OK". terminal NOTIFY is a "200 OK".
C.3.10. Bug 696: Subscription state machine needs clarification B.4.10. Bug 696: Subscription state machine needs clarification
Added state machine diagram to Section 4.1.2 with explicit handling Added state machine diagram to Section 4.1.2 with explicit handling
of what to do when a SUBSCRIBE never shows up. Added definition of of what to do when a SUBSCRIBE never shows up. Added definition of
and handling for new Timer N to Section 4.1.2.4. Added state machine and handling for new Timer N to Section 4.1.2.4. Added state machine
to Section 4.2.2 to reinforce text. to Section 4.2.2 to reinforce text.
C.3.11. Bug 697: Unsubscription behavior could be clarified B.4.11. Bug 697: Unsubscription behavior could be clarified
Added text to Section 4.2.1.4 encouraging (but not requiring) full Added text to Section 4.2.1.4 encouraging (but not requiring) full
state in final NOTIFY message. Also added text to Section 4.1.2.3 state in final NOTIFY message. Also added text to Section 4.1.2.3
warning subscribers that full state may or may not be present in the warning subscribers that full state may or may not be present in the
final NOTIFY. final NOTIFY.
C.3.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh requests B.4.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh requests
Added text to both Section 3.1 and Section 3.2 explicitly indicating Added text to both Section 3.1 and Section 3.2 explicitly indicating
that SUBSCRIBE and NOTIFY are target refresh methods. that SUBSCRIBE and NOTIFY are target refresh methods.
C.3.13. Bug 722: Inconsistent 423 reason phrase text B.4.13. Bug 722: Inconsistent 423 reason phrase text
Changed reason code to "Interval Too Brief" in Section 4.2.1.1 and Changed reason code to "Interval Too Brief" in Section 4.2.1.1 and
Section 4.2.1.4, to match 423 reason code in SIP [RFC3261]. Section 4.2.1.4, to match 423 reason code in SIP [RFC3261].
C.3.14. Bug 741: guidance needed on when to not include Allow-Events B.4.14. Bug 741: guidance needed on when to not include Allow-Events
Added non-normative clarification to Section 4.4.4 regarding Added non-normative clarification to Section 4.4.4 regarding
inclusion of Allow-Events in a NOTIFY for the one-and-only package inclusion of Allow-Events in a NOTIFY for the one-and-only package
supported by the notifier. supported by the notifier.
C.3.15. Bug 744: 5xx to NOTIFY terminates a subscription, but should B.4.15. Bug 744: 5xx to NOTIFY terminates a subscription, but should
not not
Issue of subscription (usage) termination versus dialog termination Issue of subscription (usage) termination versus dialog termination
is handled in [RFC5057]. The text in Section 4.2.2 has been updated is handled in [RFC5057]. The text in Section 4.2.2 has been updated
to summarize the behavior described by 5057, and cites it for to summarize the behavior described by 5057, and cites it for
additional detail and rationale. additional detail and rationale.
C.3.16. Bug 752: Detection of forked requests is incorrect B.4.16. Bug 752: Detection of forked requests is incorrect
Removed erroneous "CSeq" from list of matching criteria in Removed erroneous "CSeq" from list of matching criteria in
Section 5.4.9. Section 5.4.9.
C.3.17. Bug 773: Reason code needs IANA registry B.4.17. Bug 773: Reason code needs IANA registry
Added Section 7.2 to create and populate IANA registry. Added Section 7.2 to create and populate IANA registry.
C.3.18. Bug 774: Need new reason for terminating subscriptions to B.4.18. Bug 774: Need new reason for terminating subscriptions to
resources that never change resources that never change
Added new "invariant" reason code to Section 4.1.3, ABNF syntax. Added new "invariant" reason code to Section 4.1.3, ABNF syntax.
C.3.19. Clarify handling of Route/Record-Route in NOTIFY B.4.19. Clarify handling of Route/Record-Route in NOTIFY
Changed text in Section 4.3 mandating Record-Route in initial Changed text in Section 4.3 mandating Record-Route in initial
SUBSCRIBE and all NOTIFY messages, and adding "MAY" level statements SUBSCRIBE and all NOTIFY messages, and adding "MAY" level statements
for subsequent SUBSCRIBE messages. for subsequent SUBSCRIBE messages.
C.3.20. Eliminate implicit subscriptions B.4.20. Eliminate implicit subscriptions
Added text to Section 4.2.1 explaining some of the problems Added text to Section 4.2.1 explaining some of the problems
associated with implicit subscriptions, normative language associated with implicit subscriptions, normative language
prohibiting them. Removed language from Section 3.2 describing "non- prohibiting them. Removed language from Section 3.2 describing "non-
SUBSCRIBE" mechanisms for creating subscriptions. Simplified SUBSCRIBE" mechanisms for creating subscriptions. Simplified
language in Section 4.2.2, now that the soft-state/non-soft-state language in Section 4.2.2, now that the soft-state/non-soft-state
distinction is unnecessary. distinction is unnecessary.
C.3.21. Deprecate dialog re-use B.4.21. Deprecate dialog re-use
Moved handling of dialog re-use and "id" handling to Section 4.5.2. Moved handling of dialog re-use and "id" handling to Section 4.5.2.
It is documented only for backwards-compatibility purposes. It is documented only for backwards-compatibility purposes.
C.3.22. Rationalize dialog creation B.4.22. Rationalize dialog creation
Section 4.4.1 has been updated to specify that dialogs should be Section 4.4.1 has been updated to specify that dialogs should be
created when the NOTIFY arrives. Previously, the dialog was created when the NOTIFY arrives. Previously, the dialog was
established by the SUBSCRIBE 200, or by the NOTIFY transaction. This established by the SUBSCRIBE 200, or by the NOTIFY transaction. This
was unnecessarily complicated; the newer rules are easier to was unnecessarily complicated; the newer rules are easier to
implement (and result in effectively the same behavior on the wire). implement (and result in effectively the same behavior on the wire).
C.3.23. Refactor behavior sections B.4.23. Refactor behavior sections
Reorganized Section 4 to consolidate behavior along role lines Reorganized Section 4 to consolidate behavior along role lines
(subscriber/notifier/proxy) instead of method lines. (subscriber/notifier/proxy) instead of method lines.
C.3.24. Clarify sections that need to be present in event packages B.4.24. Clarify sections that need to be present in event packages
Added sentence to Section 5 clarifying that event packages are Added sentence to Section 5 clarifying that event packages are
expected to include explicit sections covering the issues discussed expected to include explicit sections covering the issues discussed
in this section. in this section.
C.3.25. Make CANCEL handling more explicit B.4.25. Make CANCEL handling more explicit
Text in Section 4.6 now clearly calls out behavior upon receipt of a Text in Section 4.6 now clearly calls out behavior upon receipt of a
CANCEL. We also echo the "...SHOULD NOT send..." requirement from CANCEL. We also echo the "...SHOULD NOT send..." requirement from
[RFC3261]. [RFC3261].
C.3.26. Remove State Agent Terminology B.4.26. Remove State Agent Terminology
As originally planned, we anticipated a fairly large number of event As originally planned, we anticipated a fairly large number of event
packages that would move back and forth between end-user devices and packages that would move back and forth between end-user devices and
servers in the network. In practice, this has ended up not being the servers in the network. In practice, this has ended up not being the
case. Certain events, like dialog state, are inherently hosted at case. Certain events, like dialog state, are inherently hosted at
end-user devices; others, like presence, are almost always hosted in end-user devices; others, like presence, are almost always hosted in
the network (due to issues like composition, and the ability to the network (due to issues like composition, and the ability to
deliver information when user devices are offline). Further, the deliver information when user devices are offline). Further, the
concept of State Agents is the most misunderstood by event package concept of State Agents is the most misunderstood by event package
authors. In my expert review of event packages, I have yet to find authors. In my expert review of event packages, I have yet to find
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