draft-ietf-sipcore-rfc3265bis-02.txt   draft-ietf-sipcore-rfc3265bis-03.txt 
Network Working Group A. B. Roach Network Working Group A. B. Roach
Internet-Draft Tekelec Internet-Draft Tekelec
Obsoletes: 3265 (if approved) August 17, 2010 Obsoletes: 3265 (if approved) July 5, 2011
Updates: 4660 (if approved) Updates: 4660 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: February 18, 2011 Expires: January 6, 2012
SIP-Specific Event Notification SIP-Specific Event Notification
draft-ietf-sipcore-rfc3265bis-02 draft-ietf-sipcore-rfc3265bis-03
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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 18, 2011. This Internet-Draft will expire on January 6, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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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 . . . . . . 14 4.1.3. Receiving and Processing State Information . . . . . . 14
4.1.4. Forking of SUBSCRIBE Messages . . . . . . . . . . . . 16 4.1.4. Forking of SUBSCRIBE Requests . . . . . . . . . . . . 16
4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 16 4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 17
4.2.1. Subscription Establishment and Maintenance . . . . . . 16 4.2.1. Subscription Establishment and Maintenance . . . . . . 17
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 . . . . . . . . . . . . . . . . . . 23
4.3. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . 22 4.3. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . 23
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 . . . . . . . . . . . 24
4.4.2. Notifier Migration . . . . . . . . . . . . . . . . . . 23 4.4.2. Notifier Migration . . . . . . . . . . . . . . . . . . 24
4.4.3. Polling Resource State . . . . . . . . . . . . . . . . 24 4.4.3. Polling Resource State . . . . . . . . . . . . . . . . 25
4.4.4. Allow-Events header field usage . . . . . . . . . . . 25 4.4.4. Allow-Events header field usage . . . . . . . . . . . 26
4.5. Targeting Subscriptions at Devices . . . . . . . . . . . . 25 4.5. Targeting Subscriptions at Devices . . . . . . . . . . . . 26
4.5.1. Using GRUUs to Route to Devices . . . . . . . . . . . 26 4.5.1. Using GRUUs to Route to Devices . . . . . . . . . . . 27
4.5.2. Sharing Dialogs . . . . . . . . . . . . . . . . . . . 26 4.5.2. Sharing Dialogs . . . . . . . . . . . . . . . . . . . 27
4.6. CANCEL Requests for SUBSCRIBE and NOTIFY . . . . . . . . . 28 4.6. CANCEL Requests for SUBSCRIBE and NOTIFY Transactions . . 29
5. Event Packages . . . . . . . . . . . . . . . . . . . . . . . . 28 5. Event Packages . . . . . . . . . . . . . . . . . . . . . . . . 29
5.1. Appropriateness of Usage . . . . . . . . . . . . . . . . . 28 5.1. Appropriateness of Usage . . . . . . . . . . . . . . . . . 29
5.2. Event Template-packages . . . . . . . . . . . . . . . . . 29 5.2. Event Template-packages . . . . . . . . . . . . . . . . . 30
5.3. Amount of State to be Conveyed . . . . . . . . . . . . . . 29 5.3. Amount of State to be Conveyed . . . . . . . . . . . . . . 30
5.3.1. Complete State Information . . . . . . . . . . . . . . 30 5.3.1. Complete State Information . . . . . . . . . . . . . . 31
5.3.2. State Deltas . . . . . . . . . . . . . . . . . . . . . 30 5.3.2. State Deltas . . . . . . . . . . . . . . . . . . . . . 31
5.4. Event Package Responsibilities . . . . . . . . . . . . . . 31 5.4. Event Package Responsibilities . . . . . . . . . . . . . . 32
5.4.1. Event Package Name . . . . . . . . . . . . . . . . . . 31 5.4.1. Event Package Name . . . . . . . . . . . . . . . . . . 32
5.4.2. Event Package Parameters . . . . . . . . . . . . . . . 31 5.4.2. Event Package Parameters . . . . . . . . . . . . . . . 32
5.4.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . 31 5.4.3. SUBSCRIBE Request Bodies . . . . . . . . . . . . . . . 32
5.4.4. Subscription Duration . . . . . . . . . . . . . . . . 32 5.4.4. Subscription Duration . . . . . . . . . . . . . . . . 33
5.4.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . 32 5.4.5. NOTIFY Request Bodies . . . . . . . . . . . . . . . . 33
5.4.6. Notifier processing of SUBSCRIBE requests . . . . . . 32 5.4.6. Notifier processing of SUBSCRIBE requests . . . . . . 33
5.4.7. Notifier generation of NOTIFY requests . . . . . . . . 32 5.4.7. Notifier generation of NOTIFY requests . . . . . . . . 33
5.4.8. Subscriber processing of NOTIFY requests . . . . . . . 32 5.4.8. Subscriber processing of NOTIFY requests . . . . . . . 34
5.4.9. Handling of forked requests . . . . . . . . . . . . . 33 5.4.9. Handling of forked requests . . . . . . . . . . . . . 34
5.4.10. Rate of notifications . . . . . . . . . . . . . . . . 33 5.4.10. Rate of notifications . . . . . . . . . . . . . . . . 34
5.4.11. State Aggregation . . . . . . . . . . . . . . . . . . 33 5.4.11. State Aggregation . . . . . . . . . . . . . . . . . . 35
5.4.12. Examples . . . . . . . . . . . . . . . . . . . . . . . 34 5.4.12. Examples . . . . . . . . . . . . . . . . . . . . . . . 35
5.4.13. Use of URIs to Retrieve State . . . . . . . . . . . . 34 5.4.13. Use of URIs to Retrieve State . . . . . . . . . . . . 35
6. Security Considerations . . . . . . . . . . . . . . . . . . . 34 6. Security Considerations . . . . . . . . . . . . . . . . . . . 35
6.1. Access Control . . . . . . . . . . . . . . . . . . . . . . 34 6.1. Access Control . . . . . . . . . . . . . . . . . . . . . . 35
6.2. Notifier Privacy Mechanism . . . . . . . . . . . . . . . . 34 6.2. Notifier Privacy Mechanism . . . . . . . . . . . . . . . . 36
6.3. Denial-of-Service attacks . . . . . . . . . . . . . . . . 35 6.3. Denial-of-Service attacks . . . . . . . . . . . . . . . . 36
6.4. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 35 6.4. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 36
6.5. Man-in-the middle attacks . . . . . . . . . . . . . . . . 35 6.5. Man-in-the middle attacks . . . . . . . . . . . . . . . . 37
6.6. Confidentiality . . . . . . . . . . . . . . . . . . . . . 36 6.6. Confidentiality . . . . . . . . . . . . . . . . . . . . . 37
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
7.1. Event Packages . . . . . . . . . . . . . . . . . . . . . . 36 7.1. Event Packages . . . . . . . . . . . . . . . . . . . . . . 38
7.1.1. Registration Information . . . . . . . . . . . . . . . 37 7.1.1. Registration Information . . . . . . . . . . . . . . . 38
7.1.2. Registration Template . . . . . . . . . . . . . . . . 38 7.1.2. Registration Template . . . . . . . . . . . . . . . . 39
7.2. Reason Codes . . . . . . . . . . . . . . . . . . . . . . . 38 7.2. Reason Codes . . . . . . . . . . . . . . . . . . . . . . . 39
7.3. Header Field Names . . . . . . . . . . . . . . . . . . . . 39 7.3. Header Field Names . . . . . . . . . . . . . . . . . . . . 40
7.4. Response Codes . . . . . . . . . . . . . . . . . . . . . . 40 7.4. Response Codes . . . . . . . . . . . . . . . . . . . . . . 41
8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.1. New Methods . . . . . . . . . . . . . . . . . . . . . . . 40 8.1. New Methods . . . . . . . . . . . . . . . . . . . . . . . 41
8.1.1. SUBSCRIBE method . . . . . . . . . . . . . . . . . . . 40 8.1.1. SUBSCRIBE method . . . . . . . . . . . . . . . . . . . 41
8.1.2. NOTIFY method . . . . . . . . . . . . . . . . . . . . 40 8.1.2. NOTIFY method . . . . . . . . . . . . . . . . . . . . 41
8.2. New Header Fields . . . . . . . . . . . . . . . . . . . . 41 8.2. New Header Fields . . . . . . . . . . . . . . . . . . . . 42
8.2.1. "Event" Header Field . . . . . . . . . . . . . . . . . 41 8.2.1. "Event" Header Field . . . . . . . . . . . . . . . . . 42
8.2.2. "Allow-Events" Header Field . . . . . . . . . . . . . 41 8.2.2. "Allow-Events" Header Field . . . . . . . . . . . . . 42
8.2.3. "Subscription-State" Header Field . . . . . . . . . . 41 8.2.3. "Subscription-State" Header Field . . . . . . . . . . 42
8.3. New Response Codes . . . . . . . . . . . . . . . . . . . . 41 8.3. New Response Codes . . . . . . . . . . . . . . . . . . . . 42
8.3.1. "202 Accepted" Response Code . . . . . . . . . . . . . 41 8.3.1. "202 Accepted" Response Code . . . . . . . . . . . . . 42
8.3.2. "489 Bad Event" Response Code . . . . . . . . . . . . 42 8.3.2. "489 Bad Event" Response Code . . . . . . . . . . . . 43
8.4. Augmented BNF Definitions . . . . . . . . . . . . . . . . 42 8.4. Augmented BNF Definitions . . . . . . . . . . . . . . . . 43
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.1. Normative References . . . . . . . . . . . . . . . . . . . 43 9.1. Normative References . . . . . . . . . . . . . . . . . . . 44
9.2. Informative References . . . . . . . . . . . . . . . . . . 44 9.2. Informative References . . . . . . . . . . . . . . . . . . 45
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 45 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 46
Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 45 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 47
B.1. Changes from draft-ietf-sipcore-rfc3265bis-01 to B.1. Changes from draft-ietf-sipcore-rfc3265bis-02 to
draft-ietf-sipcore-rfc3265bis-02 . . . . . . . . . . . . . 46 draft-ietf-sipcore-rfc3265bis-03 . . . . . . . . . . . . . 47
B.2. Changes from draft-ietf-sipcore-rfc3265bis-00 to B.2. Changes from draft-ietf-sipcore-rfc3265bis-01 to
draft-ietf-sipcore-rfc3265bis-01 . . . . . . . . . . . . . 46 draft-ietf-sipcore-rfc3265bis-02 . . . . . . . . . . . . . 47
B.3. Changes from draft-roach-sipcore-rfc3265bis-00 to B.3. Changes from draft-ietf-sipcore-rfc3265bis-00 to
draft-ietf-sipcore-rfc3265bis-00 . . . . . . . . . . . . . 46 draft-ietf-sipcore-rfc3265bis-01 . . . . . . . . . . . . . 47
B.4. Changes since RFC 3265 . . . . . . . . . . . . . . . . . . 46 B.4. Changes from draft-roach-sipcore-rfc3265bis-00 to
B.4.1. Bug 666: Clarify use of expires=xxx with terminated . 46 draft-ietf-sipcore-rfc3265bis-00 . . . . . . . . . . . . . 48
B.4.2. Bug 667: Reason code for unsub/poll not clearly B.5. Changes since RFC 3265 . . . . . . . . . . . . . . . . . . 48
spelled out . . . . . . . . . . . . . . . . . . . . . 46 B.5.1. Bug 666: Clarify use of expires=xxx with terminated . 48
B.4.3. Bug 669: Clarify: SUBSCRIBE for a duration might B.5.2. Bug 667: Reason code for unsub/poll not clearly
be answered with a NOTIFY/expires=0 . . . . . . . . . 46 spelled out . . . . . . . . . . . . . . . . . . . . . 48
B.4.4. Bug 670: Dialog State Machine needs clarification . . 47 B.5.3. Bug 669: Clarify: SUBSCRIBE for a duration might
B.4.5. Bug 671: Clarify timeout-based removal of be answered with a NOTIFY/expires=0 . . . . . . . . . 48
subscriptions . . . . . . . . . . . . . . . . . . . . 47 B.5.4. Bug 670: Dialog State Machine needs clarification . . 48
B.4.6. Bug 672: Mandate expires= in NOTIFY . . . . . . . . . 47 B.5.5. Bug 671: Clarify timeout-based removal of
B.4.7. Bug 673: INVITE 481 response effect clarification . . 47 subscriptions . . . . . . . . . . . . . . . . . . . . 48
B.4.8. Bug 677: SUBSCRIBE response matching text in error . . 47 B.5.6. Bug 672: Mandate expires= in NOTIFY . . . . . . . . . 48
B.4.9. Bug 695: Document is not explicit about response B.5.7. Bug 673: INVITE 481 response effect clarification . . 49
to NOTIFY at subscription termination . . . . . . . . 47 B.5.8. Bug 677: SUBSCRIBE response matching text in error . . 49
B.4.10. Bug 696: Subscription state machine needs B.5.9. Bug 695: Document is not explicit about response
clarification . . . . . . . . . . . . . . . . . . . . 47 to NOTIFY at subscription termination . . . . . . . . 49
B.4.11. Bug 697: Unsubscription behavior could be clarified . 47 B.5.10. Bug 696: Subscription state machine needs
B.4.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh clarification . . . . . . . . . . . . . . . . . . . . 49
requests . . . . . . . . . . . . . . . . . . . . . . . 48 B.5.11. Bug 697: Unsubscription behavior could be clarified . 49
B.4.13. Bug 722: Inconsistent 423 reason phrase text . . . . . 48 B.5.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh
B.4.14. Bug 741: guidance needed on when to not include requests . . . . . . . . . . . . . . . . . . . . . . . 49
Allow-Events . . . . . . . . . . . . . . . . . . . . . 48 B.5.13. Bug 722: Inconsistent 423 reason phrase text . . . . . 49
B.4.15. Bug 744: 5xx to NOTIFY terminates a subscription, B.5.14. Bug 741: guidance needed on when to not include
but should not . . . . . . . . . . . . . . . . . . . . 48 Allow-Events . . . . . . . . . . . . . . . . . . . . . 49
B.4.16. Bug 752: Detection of forked requests is incorrect . . 48 B.5.15. Bug 744: 5xx to NOTIFY terminates a subscription,
B.4.17. Bug 773: Reason code needs IANA registry . . . . . . . 48 but should not . . . . . . . . . . . . . . . . . . . . 50
B.4.18. Bug 774: Need new reason for terminating B.5.16. Bug 752: Detection of forked requests is incorrect . . 50
subscriptions to resources that never change . . . . . 48 B.5.17. Bug 773: Reason code needs IANA registry . . . . . . . 50
B.4.19. Clarify handling of Route/Record-Route in NOTIFY . . . 48 B.5.18. Bug 774: Need new reason for terminating
B.4.20. Eliminate implicit subscriptions . . . . . . . . . . . 48 subscriptions to resources that never change . . . . . 50
B.4.21. Deprecate dialog re-use . . . . . . . . . . . . . . . 49 B.5.19. Clarify handling of Route/Record-Route in NOTIFY . . . 50
B.4.22. Rationalize dialog creation . . . . . . . . . . . . . 49 B.5.20. Eliminate implicit subscriptions . . . . . . . . . . . 50
B.4.23. Refactor behavior sections . . . . . . . . . . . . . . 49 B.5.21. Deprecate dialog re-use . . . . . . . . . . . . . . . 50
B.4.24. Clarify sections that need to be present in event B.5.22. Rationalize dialog creation . . . . . . . . . . . . . 50
packages . . . . . . . . . . . . . . . . . . . . . . . 49 B.5.23. Refactor behavior sections . . . . . . . . . . . . . . 51
B.4.25. Make CANCEL handling more explicit . . . . . . . . . . 49 B.5.24. Clarify sections that need to be present in event
B.4.26. Remove State Agent Terminology . . . . . . . . . . . . 49 packages . . . . . . . . . . . . . . . . . . . . . . . 51
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 50 B.5.25. Make CANCEL handling more explicit . . . . . . . . . . 51
B.5.26. 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 6 skipping to change at page 6, line 6
Subscriber Notifier Subscriber Notifier
|-----SUBSCRIBE---->| Request state subscription |-----SUBSCRIBE---->| Request state subscription
|<-------200--------| Acknowledge subscription |<-------200--------| Acknowledge subscription
|<------NOTIFY----- | Return current state information |<------NOTIFY----- | Return current state information
|--------200------->| |--------200------->|
|<------NOTIFY----- | Return current state information |<------NOTIFY----- | Return current state information
|--------200------->| |--------200------->|
Subscriptions are expired and must be refreshed by subsequent Subscriptions are expired and must be refreshed by subsequent
SUBSCRIBE messages. SUBSCRIBE requests.
1.2. Documentation Conventions 1.2. Documentation Conventions
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
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defines a set of state information to be reported by a notifier to defines a set of state information to be reported by a notifier to
a subscriber. Event packages also define further syntax and a subscriber. Event packages also define further syntax and
semantics based on the framework defined by this document required semantics based on the framework defined by this document required
to convey such state information. to convey such state information.
Event Template-Package: An event template-package is a special kind Event Template-Package: An event template-package is a special kind
of event package which defines a set of states which may be of event package which defines a set of states which may be
applied to all possible event packages, including itself. applied to all possible event packages, including itself.
Notification: Notification is the act of a notifier sending a NOTIFY Notification: Notification is the act of a notifier sending a NOTIFY
message to a subscriber to inform the subscriber of the state of a request to a subscriber to inform the subscriber of the state of a
resource. resource.
Notifier: A notifier is a user agent which generates NOTIFY requests Notifier: A notifier is a user agent which generates NOTIFY requests
for the purpose of notifying subscribers of the state of a for the purpose of notifying subscribers of the state of a
resource. Notifiers typically also accept SUBSCRIBE requests to resource. Notifiers typically also accept SUBSCRIBE requests to
create subscriptions. create subscriptions.
Subscriber: A subscriber is a user agent which receives NOTIFY Subscriber: A subscriber is a user agent which receives NOTIFY
requests from notifiers; these NOTIFY requests contain information requests from notifiers; these NOTIFY requests contain information
about the state of a resource in which the subscriber is about the state of a resource in which the subscriber is
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subscriptions exist in both a subscriber and a notifier. subscriptions exist in both a subscriber and a notifier.
Subscription Migration: Subscription migration is the act of moving Subscription Migration: Subscription migration is the act of moving
a subscription from one notifier to another notifier. a subscription from one notifier to another notifier.
3. SIP Methods for Event Notification 3. SIP Methods for Event Notification
3.1. SUBSCRIBE 3.1. SUBSCRIBE
The SUBSCRIBE method is used to request current state and state The SUBSCRIBE method is used to request current state and state
updates from a remote node. SUBSCRIBE is a target refresh request, updates from a remote node. SUBSCRIBE requests are target refresh
as that term is defined in SIP [RFC3261]. requests, as that term is defined in [RFC3261].
3.1.1. Subscription Duration 3.1.1. Subscription Duration
SUBSCRIBE requests SHOULD contain an "Expires" header field (defined SUBSCRIBE requests SHOULD contain an "Expires" header field (defined
in SIP [RFC3261]). This expires value indicates the duration of the in [RFC3261]). This expires value indicates the duration of the
subscription. In order to keep subscriptions effective beyond the subscription. In order to keep subscriptions effective beyond the
duration communicated in the "Expires" header field, subscribers need duration communicated in the "Expires" header field, subscribers need
to refresh subscriptions on a periodic basis using a new SUBSCRIBE to refresh subscriptions on a periodic basis using a new SUBSCRIBE
message on the same dialog as defined in SIP [RFC3261]. request on the same dialog as defined in [RFC3261].
If no "Expires" header field is present in a SUBSCRIBE request, the If no "Expires" header field is present in a SUBSCRIBE request, the
implied default is defined by the event package being used. implied default MUST be defined by the event package being used.
200-class responses to SUBSCRIBE requests also MUST contain an 200-class responses to SUBSCRIBE requests also MUST contain an
"Expires" header field. The period of time in the response MAY be "Expires" header field. The period of time in the response MAY be
shorter but MUST NOT be longer than specified in the request. The shorter but MUST NOT be longer than specified in the request. The
notifier is explicitly allowed to shorten the duration to zero. The notifier is explicitly allowed to shorten the duration to zero. The
period of time in the response is the one which defines the duration period of time in the response is the one which defines the duration
of the subscription. of the subscription.
An "expires" parameter on the "Contact" header field has no semantics An "expires" parameter on the "Contact" header field has no semantics
for SUBSCRIBE and is explicitly not equivalent to an "Expires" header for the SUBSCRIBE method and is explicitly not equivalent to an
field in a SUBSCRIBE request or response. "Expires" header field in a SUBSCRIBE request or response.
A natural consequence of this scheme is that a SUBSCRIBE with an A natural consequence of this scheme is that a SUBSCRIBE request with
"Expires" of 0 constitutes a request to unsubscribe from an event. an "Expires" of 0 constitutes a request to unsubscribe from an event.
In addition to being a request to unsubscribe, a SUBSCRIBE message In addition to being a request to unsubscribe, a SUBSCRIBE request
with "Expires" of 0 also causes a fetch of state; see with "Expires" of 0 also causes a fetch of state; see
Section 4.4.3. Section 4.4.3.
Notifiers may also wish to cancel subscriptions to events; this is Notifiers may also wish to cancel subscriptions to events; this is
useful, for example, when the resource to which a subscription refers useful, for example, when the resource to which a subscription refers
is no longer available. Further details on this mechanism are is no longer available. Further details on this mechanism are
discussed in Section 4.2.2. discussed in Section 4.2.2.
3.1.2. Identification of Subscribed Events and Event Classes 3.1.2. Identification of Subscribed Events and Event Classes
Identification of events is provided by three pieces of information: Identification of events is provided by three pieces of information:
Request URI, Event Type, and (optionally) message body. Request URI, Event Type, and (optionally) message body.
The Request URI of a SUBSCRIBE request, most importantly, contains The Request URI of a SUBSCRIBE request, most importantly, contains
enough information to route the request to the appropriate entity per enough information to route the request to the appropriate entity per
the request routing procedures outlined in SIP [RFC3261]. It also the request routing procedures outlined in [RFC3261]. It also
contains enough information to identify the resource for which event contains enough information to identify the resource for which event
notification is desired, but not necessarily enough information to notification is desired, but not necessarily enough information to
uniquely identify the nature of the event (e.g., uniquely identify the nature of the event (e.g.,
"sip:adam@example.com" would be an appropriate URI to subscribe to "sip:adam@example.com" would be an appropriate URI to subscribe to
for my presence state; it would also be an appropriate URI to for my presence state; it would also be an appropriate URI to
subscribe to the state of my voice mailbox). subscribe to the state of my voice mailbox).
Subscribers MUST include exactly one "Event" header field in Subscribers MUST include exactly one "Event" header field in
SUBSCRIBE requests, indicating to which event or class of events they SUBSCRIBE requests, indicating to which event or class of events they
are subscribing. The "Event" header field will contain a token which are subscribing. The "Event" header field will contain a token which
skipping to change at page 9, line 10 skipping to change at page 9, line 10
If the event package to which the event token corresponds defines If the event package to which the event token corresponds defines
behavior associated with the body of its SUBSCRIBE requests, those behavior associated with the body of its SUBSCRIBE requests, those
semantics apply. semantics apply.
Event packages may also define parameters for the Event header field; Event packages may also define parameters for the Event header field;
if they do so, they must define the semantics for such parameters. if they do so, they must define the semantics for such parameters.
3.1.3. Additional SUBSCRIBE Header Field Values 3.1.3. Additional SUBSCRIBE Header Field Values
Because SUBSCRIBE requests create a dialog as defined in SIP Because SUBSCRIBE requests create a dialog usage as defined in
[RFC3261], they MAY contain an "Accept" header field. This header [RFC3261], they MAY contain an "Accept" header field. This header
field, if present, indicates the body formats allowed in subsequent field, if present, indicates the body formats allowed in subsequent
NOTIFY requests. Event packages MUST define the behavior for NOTIFY requests. Event packages MUST define the behavior for
SUBSCRIBE requests without "Accept" header fields; usually, this will SUBSCRIBE requests without "Accept" header fields; usually, this will
connote a single, default body type. connote a single, default body type.
Header values not described in this document are to be interpreted as Header values not described in this document are to be interpreted as
described in SIP [RFC3261]. described in [RFC3261].
3.2. NOTIFY 3.2. NOTIFY
NOTIFY messages are sent to inform subscribers of changes in state to NOTIFY requests are sent to inform subscribers of changes in state to
which the subscriber has a subscription. Subscriptions are typically which the subscriber has a subscription. Subscriptions are created
put in place using the SUBSCRIBE method; however, it is possible that using the SUBSCRIBE method. In legacy implementations, it is
other means have been used. possible that other means of subscription creation have been used.
However, this specification does not allow the creation of
subscriptions except through SUBSCRIBE requests and (for backwards-
compatibility) REFER requests [RFC3515].
NOTIFY is a target refresh request, as that term is defined in SIP NOTIFY is a target refresh request, as that term is defined in
[RFC3261]. [RFC3261].
A NOTIFY does not terminate its corresponding subscription; in other A NOTIFY request does not terminate its corresponding subscription;
words, a single SUBSCRIBE request may trigger several NOTIFY in other words, a single SUBSCRIBE request may trigger several NOTIFY
requests. requests.
3.2.1. Identification of Reported Events, Event Classes, and Current 3.2.1. Identification of Reported Events, Event Classes, and Current
State State
Identification of events being reported in a notification is very Identification of events being reported in a notification is very
similar to that described for subscription to events (see similar to that described for subscription to events (see
Section 3.1.2). Section 3.1.2).
As in SUBSCRIBE requests, NOTIFY "Event" header fields will contain a As in SUBSCRIBE requests, NOTIFY request "Event" header fields MUST
single event package name for which a notification is being contain a single event package name for which a notification is being
generated. The package name in the "Event" header field MUST match generated. The package name in the "Event" header field MUST match
the "Event" header field in the corresponding SUBSCRIBE message. the "Event" header field in the corresponding SUBSCRIBE request.
Event packages may define semantics associated with the body of their Event packages may define semantics associated with the body of their
NOTIFY requests; if they do so, those semantics apply. NOTIFY bodies NOTIFY requests; if they do so, those semantics apply. NOTIFY
are expected to provide additional details about the nature of the request bodies are expected to provide additional details about the
event which has occurred and the resultant resource state. nature of the event which has occurred and the resultant resource
state.
When present, the body of the NOTIFY request MUST be formatted into When present, the body of the NOTIFY request MUST be formatted into
one of the body formats specified in the "Accept" header field of the one of the body formats specified in the "Accept" header field of the
corresponding SUBSCRIBE request. This body will contain either the corresponding SUBSCRIBE request. This body will contain either the
state of the subscribed resource or a pointer to such state in the state of the subscribed resource or a pointer to such state in the
form of a URI (see Section 5.4.13). form of a URI (see Section 5.4.13).
4. Node Behavior 4. Node Behavior
4.1. Subscriber Behavior 4.1. Subscriber Behavior
4.1.1. Detecting Support for SIP Events 4.1.1. Detecting Support for SIP Events
The extension described in this document does not make use of the use The extension described in this document does not make use of the use
of "Require" or "Proxy-Require" header fields; similarly, there is no of "Require" or "Proxy-Require" header fields; similarly, there is no
token defined for "Supported" header fields. Potential subscribers token defined for "Supported" header fields. Potential subscribers
may probe for the support of SIP Events using the OPTIONS request may probe for the support of SIP Events using the OPTIONS request
defined in SIP [RFC3261]. defined in [RFC3261].
The presence of "SUBSCRIBE" in the "Allow" header field of any The presence of "SUBSCRIBE" in the "Allow" header field of any
request or response indicates support for SIP Events; further, in the request or response indicates support for SIP Events; further, in the
absence of an "Allow" header field, the simple presence of an "Allow- absence of an "Allow" header field, the simple presence of an "Allow-
Events" header field is sufficient to indicate that the node that Events" header field is sufficient to indicate that the node that
sent the message is capable of acting as a notifier (see sent the message is capable of acting as a notifier (see
Section 4.4.4. Section 4.4.4.
The "methods" parameter for Contact may also be used to The "methods" parameter for Contact may also be used to
specifically announce support for SUBSCRIBE and NOTIFY messages specifically announce support for SUBSCRIBE and NOTIFY requests
when registering. (See [RFC3840] for details on the "methods" when registering. (See [RFC3840] for details on the "methods"
parameter). parameter).
4.1.2. Creating and Maintaining Subscriptions 4.1.2. Creating and Maintaining Subscriptions
From the subscriber's perspective, a subscription proceeds according From the subscriber's perspective, a subscription proceeds according
to the following state diagram: to the following state diagram:
+-------------+ +-------------+
| init |<-----------------------+ | init |<-----------------------+
skipping to change at page 11, line 22 skipping to change at page 11, line 22
+-------------+ SUBSCRIBE failure | +-------------+ SUBSCRIBE failure |
+------------| 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 || || | | Re-subscription A A ||
|| | V Timer N Fires; | | || || | V times out; | | ||
|| | +-------------+ Receive NOTIFY, | | || || | +-------------+ Receive NOTIFY, | | ||
|| | | pending |-- state=terminated; --+ | || || | | pending |-- state=terminated; --+ | ||
|| | +-------------+ or 481 response | || || | +-------------+ or 481 response | ||
|| | | to SUBSCRIBE | || || | | to SUBSCRIBE | ||
|| | Receive NOTIFY, refresh | || || | Receive NOTIFY, refresh | ||
|| | state=active | || || | state=active | ||
|| | | Timer N Fires; | || || | | Re-subscription | ||
|| | V Receive NOTIFY, | || || | V times out; | ||
|| | +-------------+ state=terminated; | || || | +-------------+ Receive NOTIFY, | ||
|| +----------->| active |-- or 481 response -------+ || || +----------->| active |-- state=terminated; -----+ ||
|| +-------------+ to SUBSCRIBE || || +-------------+ or 481 response ||
|| refresh || || to SUBSCRIBE ||
|| Subscription || || Subscription refresh ||
++=================================================================++ ++=================================================================++
In the state diagram, "Re-subscription times out" means that an
attempt to refresh or update the subscription using a new SUBSCRIBE
request does not result in a NOTIFY request before the corresponding
Timer N expires.
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
be generated as the result of a single SUBSCRIBE request (see be generated as the result of a single SUBSCRIBE request (see
Section 4.4.1). Each of these new subscriptions exists in its own Section 4.4.1). Each of these new subscriptions exists in its own
independent state machine. independent state machine, and runs its own set of timers.
4.1.2.1. Requesting a Subscription 4.1.2.1. Requesting a Subscription
SUBSCRIBE is a dialog-creating method, as described in SIP [RFC3261]. SUBSCRIBE is a dialog-creating method, as described in [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 request. If the initial SUBSCRIBE
represents a request outside of a dialog (as it typically will), its request represents a request outside of a dialog (as it typically
construction follows the procedures outlined in SIP [RFC3261] for UAC will), its construction follows the procedures outlined in [RFC3261]
request generation outside of a dialog. for UAC 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. that a NOTIFY request will be sent immediately.
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 request indicates the actual duration for which the subscription will
active (unless refreshed). remain active (unless refreshed).
Non-200 class final responses indicate that no subscription or dialog Non-200 class final responses indicate that no subscription or new
has been created, and no subsequent NOTIFY message will be sent. All dialog usage has been created, and no subsequent NOTIFY request will
non-200 class responses (with the exception of "489", described be sent. All non-200 class responses (with the exception of "489",
herein) have the same meanings and handling as described in SIP described herein) have the same meanings and handling as described in
[RFC3261]. For the sake of clarity: if a SUBSCRIBE request contains [RFC3261]. For the sake of clarity: if a SUBSCRIBE request contains
an "Accept" header field, but that field does not indicate a MIME an "Accept" header field, but that field does not indicate a MIME
type that the notifier is capable of generating in its NOTIFY type that the notifier is capable of generating in its NOTIFY
requests, then the proper error response is 406 (Not Acceptable). requests, then the proper error response is 406 (Not Acceptable).
4.1.2.2. Refreshing of Subscriptions 4.1.2.2. Refreshing of Subscriptions
At any time before a subscription expires, the subscriber may refresh At any time before a subscription expires, the subscriber may refresh
the timer on such a subscription by sending another SUBSCRIBE request the timer on such a subscription by sending another SUBSCRIBE request
on the same dialog as the existing subscription. The handling for on the same dialog as the existing subscription. The handling for
such a request is the same as for the initial creation of a such a request is the same as for the initial creation of a
subscription except as described below. subscription except as described below.
If a SUBSCRIBE request to refresh a subscription receives a 404, 405, If a SUBSCRIBE request to refresh a subscription receives a 404, 405,
410, 416, 480-485, 489, 501, or 604 response, the subscriber should 410, 416, 480-485, 489, 501, or 604 response, the subscriber MUST
consider the subscription terminated. (See [RFC5057] for further consider the subscription terminated. (See [RFC5057] for further
details and notes about the effect of error codes on dialogs and details and notes about the effect of error codes on dialogs and
usages within dialog, such as subscriptions). If the subscriber usages within dialog, such as subscriptions). If the subscriber
wishes to re-subscribe to the state, he does so by composing an wishes to re-subscribe to the state, he does so by composing an
unrelated initial SUBSCRIBE request with a freshly-generated Call-ID unrelated initial SUBSCRIBE request with a freshly-generated Call-ID
and a new, unique "From" tag (see Section 4.1.2.1.) and a new, unique "From" tag (see Section 4.1.2.1.)
If a SUBSCRIBE request to refresh a subscription fails with any error If a SUBSCRIBE request to refresh a subscription fails with any error
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 the most recent successful SUBSCRIBE
communicated by NOTIFY in the "Subscription-State" header field transaction, or as communicated by a NOTIFY request in its
"expires" parameter. "Subscription-State" header field "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. requests will be received.
When refreshing a subscription, a subscriber starts Timer N, set to When refreshing a subscription, a subscriber starts Timer N, set to
64*T1, when it sends the SUBSCRIBE message. If this Timer N expires 64*T1, when it sends the SUBSCRIBE request. If this Timer N expires
prior to the receipt of a NOTIFY message, the subscriber considers prior to the receipt of a NOTIFY request, the subscriber considers
the subscription terminated. If the subscriber receives a success the subscription terminated. If the subscriber receives a success
response to the SUBSCRIBE request that indicates that no NOTIFY will response to the SUBSCRIBE request that indicates that no NOTIFY
be generated -- such as the 204 response defined in [RFC5839] -- then request will be generated -- such as the 204 response defined for use
it MUST cancel Timer N. with the optional extension described 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 request.
The final NOTIFY may or may not contain information about the state The final NOTIFY request may or may not contain information about the
of the resource; subscribers need to be prepared to receive final state of the resource; subscribers need to be prepared to receive
NOTIFY messages both with and without state. final NOTIFY requests 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 request 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, when it sends a SUBSCRIBE. If this Timer N expires prior to 64*T1, when it sends a SUBSCRIBE request. If this Timer N expires
the receipt of a NOTIFY message, the subscriber considers the prior to the receipt of a NOTIFY request, the subscriber considers
subscription failed, and cleans up any state associated with the the subscription failed, and cleans up any state associated with the
subscription attempt. subscription attempt.
Until Timer N expires, several NOTIFY messages may arrive from Until Timer N expires, several NOTIFY requests may arrive from
different destinations (see Section 4.4.1). Each of these messages different destinations (see Section 4.4.1). Each of these requests
establish a new dialog and a new subscription. After the expiration establish a new dialog usage and a new subscription. After the
of Timer N, the subscriber SHOULD reject any such NOTIFY messages expiration of Timer N, the subscriber SHOULD reject any such NOTIFY
that would otherwise establish a new dialog with a "481" response requests that would otherwise establish a new dialog usage with a
code. "481" response code.
Until the first NOTIFY message arrives, the subscriber should Until the first NOTIFY request 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
state. Documents which define new event packages MUST define this state. Event package specifications MUST define this "neutral state"
"neutral state" in such a way that makes sense for their application in such a way that makes sense for their application (see
(see Section 5.4.7). Section 5.4.7).
Due to the potential for both out-of-order messages and forking, the Due to the potential for both out-of-order messages and forking, the
subscriber MUST be prepared to receive NOTIFY messages before the subscriber MUST be prepared to receive NOTIFY requests before the
SUBSCRIBE transaction has completed. SUBSCRIBE transaction has completed.
Except as noted above, processing of this NOTIFY is the same as in Except as noted above, processing of this NOTIFY request is the same
Section 4.1.3. as in Section 4.1.3.
4.1.3. Receiving and Processing State Information 4.1.3. Receiving and Processing State Information
Subscribers receive information about the state of a resource to Subscribers receive information about the state of a resource to
which they have subscribed in the form of NOTIFY requests. which they have subscribed in the form of NOTIFY requests.
Upon receiving a NOTIFY request, the subscriber should check that it Upon receiving a NOTIFY request, the subscriber should check that it
matches at least one of its outstanding subscriptions; if not, it matches at least one of its outstanding subscriptions; if not, it
MUST return a "481 Subscription does not exist" response unless MUST return a "481 Subscription does not exist" response unless
another 400- or 500-class response is more appropriate. The rules another 400- or 500-class response is more appropriate. The rules
for matching NOTIFY requests with subscriptions that create a new for matching NOTIFY requests with subscriptions that create a new
dialog are described in Section 4.4.1. Notifications for dialog usage are described in Section 4.4.1. Notifications for
subscriptions which were created inside an existing dialog match if subscriptions which were created inside an existing dialog match if
they are in the same dialog and the "Event" header fields match (as they are in the same dialog and the "Event" header fields match (as
described in Section 8.2.1). described in Section 8.2.1).
If, for some reason, the event package designated in the "Event" If, for some reason, the event package designated in the "Event"
header field of the NOTIFY request is not supported, the subscriber header field of the NOTIFY request is not supported, the subscriber
will respond with a "489 Bad Event" response. will respond with a "489 Bad Event" response.
To prevent spoofing of events, NOTIFY requests SHOULD be To prevent spoofing of events, NOTIFY requests SHOULD be
authenticated, using any defined SIP authentication mechanism. authenticated, using any defined SIP authentication mechanism.
skipping to change at page 14, line 47 skipping to change at page 15, line 7
If the "Subscription-State" value is "pending", the subscription has If the "Subscription-State" value is "pending", the subscription has
been received by the notifier, but there is insufficient policy been received by the notifier, but there is insufficient policy
information to grant or deny the subscription yet. If the header information to grant or deny the subscription yet. If the header
field also contains an "expires" parameter, the subscriber SHOULD field also contains an "expires" parameter, the subscriber SHOULD
take it as the authoritative subscription duration and adjust take it as the authoritative subscription duration and adjust
accordingly. No further action is necessary on the part of the accordingly. No further action is necessary on the part of the
subscriber. The "retry-after" and "reason" parameters have no subscriber. The "retry-after" and "reason" parameters have no
semantics for "pending". semantics for "pending".
If the "Subscription-State" value is "terminated", the subscriber If the "Subscription-State" value is "terminated", the subscriber
should consider the subscription terminated. The "expires" parameter MUST consider the subscription terminated. The "expires" parameter
has no semantics for "terminated" -- notifiers SHOULD NOT include an has no semantics for "terminated" -- notifiers SHOULD NOT include an
"expires" parameter on a "Subscription-State" header field with a "expires" parameter on a "Subscription-State" header field with a
value of "terminated," and subscribers MUST ignore any such value of "terminated," and subscribers MUST ignore any such
parameter, if present. If a reason code is present, the client parameter, if present. If a reason code is present, the client
should behave as described below. If no reason code or an unknown should behave as described below. If no reason code or an unknown
reason code is present, the client MAY attempt to re-subscribe at any reason code is present, the client MAY attempt to re-subscribe at any
time (unless a "retry-after" parameter is present, in which case the time (unless a "retry-after" parameter is present, in which case the
client SHOULD NOT attempt re-subscription until after the number of client SHOULD NOT attempt re-subscription until after the number of
seconds specified by the "retry-after" parameter). The reason codes seconds specified by the "retry-after" parameter). The reason codes
defined by this document are: defined by this document are:
skipping to change at page 16, line 16 skipping to change at page 16, line 30
parameter. parameter.
Other specifications may define new reason codes for use with the Other specifications may define new reason codes for use with the
"Subscription-State" header field. "Subscription-State" header field.
Once the notification is deemed acceptable to the subscriber, the Once the notification is deemed acceptable to the subscriber, the
subscriber SHOULD return a 200 response. In general, it is not subscriber SHOULD return a 200 response. In general, it is not
expected that NOTIFY responses will contain bodies; however, they expected that NOTIFY responses will contain bodies; however, they
MAY, if the NOTIFY request contained an "Accept" header field. MAY, if the NOTIFY request contained an "Accept" header field.
Other responses defined in SIP [RFC3261] may also be returned, as Other responses defined in [RFC3261] may also be returned, as
appropriate. In no case should a NOTIFY transaction extend for any appropriate. In no case should a NOTIFY transaction extend for any
longer than the time necessary for automated processing. In longer than the time necessary for automated processing. In
particular, subscribers MUST NOT wait for a user response before particular, subscribers MUST NOT wait for a user response before
returning a final response to a NOTIFY request. returning a final response to a NOTIFY request.
4.1.4. Forking of SUBSCRIBE Messages 4.1.4. Forking of SUBSCRIBE Requests
In accordance with the rules for proxying non-INVITE requests as In accordance with the rules for proxying non-INVITE requests as
defined in SIP [RFC3261], successful SUBSCRIBE requests will receive defined in [RFC3261], successful SUBSCRIBE requests will receive only
only one 200-class response; however, due to forking, the one 200-class response; however, due to forking, the subscription may
subscription may have been accepted by multiple nodes. The have been accepted by multiple nodes. The subscriber MUST therefore
subscriber MUST therefore be prepared to receive NOTIFY requests with be prepared to receive NOTIFY requests with "From:" tags which differ
"From:" tags which differ from the "To:" tag received in the from the "To:" tag received in the SUBSCRIBE 200-class response.
SUBSCRIBE 200-class response.
If multiple NOTIFY messages are received in different dialogs in If multiple NOTIFY requests are received in different dialogs in
response to a single SUBSCRIBE message, each dialog represents a response to a single SUBSCRIBE request, each dialog represents a
different destination to which the SUBSCRIBE request was forked. different destination to which the SUBSCRIBE request was forked.
Subscriber handling in such situations varies by event package; see Subscriber handling in such situations varies by event package; see
Section 5.4.9 for details. Section 5.4.9 for details.
4.2. Notifier Behavior 4.2. Notifier Behavior
4.2.1. Subscription Establishment and Maintenance 4.2.1. Subscription Establishment and Maintenance
Notifiers learn about subscription requests by receiving SUBSCRIBE Notifiers learn about subscription requests by receiving SUBSCRIBE
requests from interested parties. Notifiers MUST NOT create requests from interested parties. Notifiers MUST NOT create
subscriptions except upon receipt of a SUBSCRIBE message. However, subscriptions except upon receipt of a SUBSCRIBE request. However,
for historical reasons, the implicit creation of subscriptions as for historical reasons, the implicit creation of subscriptions as
defined in [RFC3515] is still permitted. defined in [RFC3515] is still permitted.
[RFC3265] allowed the creation of subscriptions using means other [RFC3265] allowed the creation of subscriptions using means other
than SUBSCRIBE. The only standardized use of this mechanism is than the SUBSCRIBE method. The only standardized use of this
the REFER method [RFC3515]. Implementation experience with REFER mechanism is the REFER method [RFC3515]. Implementation
has shown that the implicit creation of a subscription has a experience with REFER has shown that the implicit creation of a
number of undesirable effects, such as the inability to signal the subscription has a number of undesirable effects, such as the
success of a REFER while signaling a problem with the inability to signal the success of a REFER request while signaling
subscription; and difficulty performing one action without the a problem with the subscription; and difficulty performing one
other. Additionally, the proper exchange of dialog identifiers is action without the other. Additionally, the proper exchange of
difficult without dialog re-use (which has its own set of dialog identifiers is difficult without dialog re-use (which has
problems; see Section 4.5). its own set of problems; see Section 4.5).
4.2.1.1. Initial SUBSCRIBE Transaction Processing 4.2.1.1. Initial SUBSCRIBE Transaction Processing
In no case should a SUBSCRIBE transaction extend for any longer than In no case should a SUBSCRIBE transaction extend for any longer than
the time necessary for automated processing. In particular, the time necessary for automated processing. In particular,
notifiers MUST NOT wait for a user response before returning a final notifiers MUST NOT wait for a user response before returning a final
response to a SUBSCRIBE request. response to a SUBSCRIBE request.
This requirement is imposed primarily to prevent the non-INVITE This requirement is imposed primarily to prevent the non-INVITE
transaction timeout timer F (see [RFC3261]) from firing during the transaction timeout timer F (see [RFC3261]) from firing during the
skipping to change at page 17, line 41 skipping to change at page 17, line 51
event/event class is not understood. event/event class is not understood.
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 [RFC3261].
Once the notifier determines that it has enough information to create Once the notifier determines that it has enough information to create
the subscription (i.e., it understands the event package, the the subscription (i.e., it understands the event package, the
subscription pertains to a known resource, and there are no other subscription pertains to a known resource, and there are no other
barriers to creating the subscription), it creates the subscription barriers to creating the subscription), it creates the subscription
and a dialog, and returns a 200 (OK) response. and a dialog usage, and returns a 200 (OK) response.
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 request 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
described earlier in this section. described earlier in this section.
200-class responses to SUBSCRIBE requests will not generally contain 200-class responses to SUBSCRIBE requests will not generally contain
any useful information beyond subscription duration; their primary any useful information beyond subscription duration; their primary
purpose is to serve as a reliability mechanism. State information purpose is to serve as a reliability mechanism. State information
will be communicated via a subsequent NOTIFY request from the will be communicated via a subsequent NOTIFY request from the
notifier. notifier.
The other response codes defined in SIP [RFC3261] may be used in The other response codes defined in [RFC3261] may be used in response
response to SUBSCRIBE requests, as appropriate. to SUBSCRIBE requests, as appropriate.
4.2.1.2. Confirmation of Subscription Creation/Refreshing 4.2.1.2. Confirmation of Subscription Creation/Refreshing
Upon successfully accepting or refreshing a subscription, notifiers Upon successfully accepting or refreshing a subscription, notifiers
MUST send a NOTIFY message immediately to communicate the current MUST send a NOTIFY request immediately to communicate the current
resource state to the subscriber. This NOTIFY message is sent on the resource state to the subscriber. This NOTIFY request is sent on the
same dialog as created by the SUBSCRIBE response. If the resource same dialog as created by the SUBSCRIBE response. If the resource
has no meaningful state at the time that the SUBSCRIBE message is has no meaningful state at the time that the SUBSCRIBE request is
processed, this NOTIFY message MAY contain an empty or neutral body. processed, this NOTIFY request MAY contain an empty or neutral body.
See Section 4.2.2 for further details on NOTIFY message generation. See Section 4.2.2 for further details on NOTIFY request generation.
Note that a NOTIFY message is always sent immediately after any 200- Note that a NOTIFY request is always sent immediately after any 200-
class response to a SUBSCRIBE request, regardless of whether the class response to a SUBSCRIBE request, regardless of whether the
subscription has already been authorized. subscription has already been authorized.
4.2.1.3. Authentication/Authorization of SUBSCRIBE requests 4.2.1.3. Authentication/Authorization of SUBSCRIBE Requests
Privacy concerns may require that notifiers apply policy to determine Privacy concerns may require that notifiers apply policy to determine
whether a particular subscriber is authorized to subscribe to a whether a particular subscriber is authorized to subscribe to a
certain set of events. Such policy may be defined by mechanisms such certain set of events. Such policy may be defined by mechanisms such
as access control lists or real-time interaction with a user. In as access control lists or real-time interaction with a user. In
general, authorization of subscribers prior to authentication is not general, authorization of subscribers prior to authentication is not
particularly useful. particularly useful.
SIP authentication mechanisms are discussed in SIP [RFC3261]. Note SIP authentication mechanisms are discussed in [RFC3261]. Note that,
that, even if the notifier node typically acts as a proxy, even if the notifier node typically acts as a proxy, authentication
authentication for SUBSCRIBE requests will always be performed via a for SUBSCRIBE requests will always be performed via a "401" response,
"401" response, not a "407;" notifiers always act as a user agents not a "407;" notifiers always act as a user agents when accepting
when accepting subscriptions and sending notifications. subscriptions and sending notifications.
Of course, when acting as a proxy, a node will perform normal Of course, when acting as a proxy, a node will perform normal
proxy authentication (using 407). The foregoing explanation is a proxy authentication (using 407). The foregoing explanation is a
reminder that notifiers are always UAs, and as such perform UA reminder that notifiers are always UAs, and as such perform UA
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 200 (OK) response is returned immediately. subscription is allowed, a 200 (OK) response is returned immediately.
Note that a NOTIFY message is still formed and sent under these Note that a NOTIFY request is still formed and sent 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 request 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
subscriber is still authorized, the notifier updates the expiration subscriber is still authorized, the notifier updates the expiration
time for subscription. As with the initial subscription, the server time for subscription. As with the initial subscription, the server
MAY shorten the amount of time until expiration, but MUST NOT MAY shorten the amount of time until expiration, but MUST NOT
increase it. The final expiration time is placed in the "Expires" increase it. The final expiration time is placed in the "Expires"
header field in the response. If the duration specified in a header field in the response. If the duration specified in a
SUBSCRIBE message is unacceptably short, the notifier SHOULD respond SUBSCRIBE request is unacceptably short, the notifier SHOULD respond
with a "423 Interval Too Brief" message. with a "423 Interval Too Brief" response.
If no refresh for a notification address is received before its If no refresh for a notification address is received before its
expiration time, the subscription is removed. When removing a expiration time, the subscription is removed. When removing a
subscription, the notifier SHOULD send a NOTIFY message with a subscription, the notifier SHOULD send a NOTIFY request with a
"Subscription-State" value of "terminated" to inform it that the "Subscription-State" value of "terminated" to inform it that the
subscription is being removed. If such a message is sent, the subscription is being removed. If such a request is sent, the
"Subscription-State" header field SHOULD contain a "reason=timeout" "Subscription-State" header field SHOULD contain a "reason=timeout"
parameter. parameter.
Clients can cause a subscription to be terminated immediately by Clients can cause a subscription to be terminated immediately by
sending a SUBSCRIBE with an "Expires" header field set to '0'. sending a SUBSCRIBE request with an "Expires" header field set to
Notifiers largely treat this the same way as any other subscription '0'. Notifiers largely treat this the same way as any other
expiration: they send a NOTIFY message containing a "Subscription- subscription expiration: they send a NOTIFY request containing a
State" of "terminated", with a reason code of "timeout." For "Subscription-State" of "terminated", with a reason code of
consistency with state polling (see Section 4.4.3) and subscription "timeout." For consistency with state polling (see Section 4.4.3)
refreshes, the notifier may choose to include resource state in this and subscription refreshes, the notifier may choose to include
final NOTIFY. However, in some cases, including such state makes no resource state in this final NOTIFY request. However, in some cases,
sense. Under such circumstances, the notifier may choose to omit including such state makes no sense. Under such circumstances, the
state information from the terminal NOTIFY message. notifier may choose to omit state information from the terminal
NOTIFY request.
The sending of a NOTIFY when a subscription expires allows the The sending of a NOTIFY request when a subscription expires allows
corresponding dialog to be terminated, if appropriate. the corresponding dialog usage to be terminated, if appropriate.
4.2.2. Sending State Information to Subscribers 4.2.2. Sending State Information to Subscribers
Notifiers use the NOTIFY method to send information about the state Notifiers use the NOTIFY method to send information about the state
of a resource to subscribers. The notifier's view of a subscription of a resource to subscribers. The notifier's view of a subscription
is shown in the following state diagram: is shown in the following state diagram:
+-------------+ +-------------+
| init | | init |
+-------------+ +-------------+
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notifier SHOULD immediately construct and send a NOTIFY request, notifier SHOULD immediately construct and send a NOTIFY request,
subject to authorization, local policy, and throttling subject to authorization, local policy, and throttling
considerations. considerations.
If the NOTIFY request fails due to expiration of SIP Timer F If the NOTIFY request fails due to expiration of SIP Timer F
(transaction timeout), the notifier SHOULD remove the subscription. (transaction timeout), the notifier SHOULD remove the subscription.
This behavior prevents unnecessary transmission of state This behavior prevents unnecessary transmission of state
information for subscribers who have crashed or disappeared from information for subscribers who have crashed or disappeared from
the network. Because such transmissions will be sent multiple the network. Because such transmissions will be sent multiple
times, per the retransmission algorithm defined in SIP [RFC3261] times, per the retransmission algorithm defined in [RFC3261]
(instead of the typical single transmission for functioning (instead of the typical single transmission for functioning
clients), continuing to service them when no client is available clients), continuing to service them when no client is available
to acknowledge them could place undue strain on a network. Upon to acknowledge them could place undue strain on a network. Upon
client restart or reestablishment of a network connection, it is client restart or reestablishment of a network connection, it is
expected that clients will send SUBSCRIBE messages to refresh expected that clients will send SUBSCRIBE requests to refresh
potentially stale state information; such messages will re-install potentially stale state information; such requests will re-install
subscriptions in all relevant nodes. subscriptions in all relevant nodes.
If the NOTIFY transaction fails due to the receipt of a 404, 405, If the NOTIFY transaction fails due to the receipt of a 404, 405,
410, 416, 480-485, 489, 501, or 604 response to the NOTIFY, the 410, 416, 480-485, 489, 501, or 604 response to the NOTIFY request,
notifier MUST remove the corresponding subscription. See [RFC5057] the notifier MUST remove the corresponding subscription. See
for further details and notes about the effect of error codes on [RFC5057] for further details and notes about the effect of error
dialogs and usages within dialog (such as subscriptions). codes on dialogs and usages within dialog (such as subscriptions).
A notify error response would generally indicate that something A notify error response would generally indicate that something
has gone wrong with the subscriber or with some proxy on the way has gone wrong with the subscriber or with some proxy on the way
to the subscriber. If the subscriber is in error, it makes the to the subscriber. If the subscriber is in error, it makes the
most sense to allow the subscriber to rectify the situation (by most sense to allow the subscriber to rectify the situation (by
re-subscribing) once the error condition has been handled. If a re-subscribing) once the error condition has been handled. If a
proxy is in error, the periodic SUBSCRIBE refreshes will re- proxy is in error, the periodic sending of SUBSCRIBE requests to
install subscription state once the network problem has been refresh the expiration timer will re-install subscription state
resolved. once the network problem has been resolved.
NOTIFY requests MUST contain a "Subscription-State" header field with NOTIFY requests MUST contain a "Subscription-State" header field with
a value of "active", "pending", or "terminated". The "active" value a value of "active", "pending", or "terminated". The "active" value
indicates that the subscription has been accepted and has been indicates that the subscription has been accepted and has been
authorized (in most cases; see Section 6.2). The "pending" value authorized (in most cases; see Section 6.2). The "pending" value
indicates that the subscription has been received, but that policy indicates that the subscription has been received, but that policy
information is insufficient to accept or deny the subscription at information is insufficient to accept or deny the subscription at
this time. The "terminated" value indicates that the subscription is this time. The "terminated" value indicates that the subscription is
not active. not active.
If the value of the "Subscription-State" header field is "active" or If the value of the "Subscription-State" header field is "active" or
"pending", the notifier MUST also include in the "Subscription-State" "pending", the notifier MUST also include in the "Subscription-State"
header field an "expires" parameter which indicates the time header field an "expires" parameter which indicates the time
remaining on the subscription. The notifier MAY use this mechanism remaining on the subscription. The notifier MAY use this mechanism
to shorten a subscription; however, this mechanism MUST NOT be used to shorten a subscription; however, this mechanism MUST NOT be used
to lengthen a subscription. to lengthen a subscription.
Including expiration information for active and pending Including expiration information for active and pending
subscriptions is necessary in case the SUBSCRIBE request forks, subscriptions is necessary in case the SUBSCRIBE request forks,
since the response to a forked SUBSCRIBE may not be received by since the response to a forked SUBSCRIBE request may not be
the subscriber. [RFC3265] allowed the notifier some discretion in received by the subscriber. [RFC3265] allowed the notifier some
the inclusion of this parameter, so subscriber implementations are discretion in the inclusion of this parameter, so subscriber
warned to handle the lack of an "expires" parameter gracefully. implementations are warned to handle the lack of an "expires"
Note well that this "expires" value is a parameter on the parameter gracefully. Note well that this "expires" value is a
"Subscription-State" header field, NOT an "Expires" header field. parameter on the "Subscription-State" header field, NOT an
"Expires" header field.
The period of time for a subscription can be shortened to zero by The period of time for a subscription can be shortened to zero by
the notifier. In other words, it is perfectly valid for a the notifier. In other words, it is perfectly valid for a
SUBSCRIBE with a non-zero expires to be answered with a NOTIFY SUBSCRIBE request with a non-zero expires to be answered with a
that contains "Subscription-Status: terminated;reason=expired". NOTIFY request that contains "Subscription-Status:
This merely means that the notifier has shortened the subscription terminated;reason=expired". This merely means that the notifier
timeout to zero, and the subscription has expired instantaneously. has shortened the subscription timeout to zero, and the
The body may contain valid state, or it may contain a neutral subscription has expired instantaneously. The body may contain
state (see Section 5.4.7). valid state, or it may contain a neutral state (see
Section 5.4.7).
If the value of the "Subscription-State" header field is If the value of the "Subscription-State" header field is
"terminated", the notifier SHOULD also include a "reason" parameter. "terminated", the notifier SHOULD also include a "reason" parameter.
The notifier MAY also include a "retry-after" parameter, where The notifier MAY also include a "retry-after" parameter, where
appropriate. For details on the value and semantics of the "reason" appropriate. For details on the value and semantics of the "reason"
and "retry-after" parameters, see Section 4.1.3. and "retry-after" parameters, see Section 4.1.3.
4.2.3. PINT Compatibility 4.2.3. PINT Compatibility
The "Event" header field is considered mandatory for the purposes of The "Event" header field is considered mandatory for the purposes of
this document. However, to maintain compatibility with PINT (see this document. However, to maintain compatibility with PINT (see
[RFC2848]), notifiers MAY interpret a SUBSCRIBE request with no [RFC2848]), notifiers MAY interpret a SUBSCRIBE request with no
"Event" header field as requesting a subscription to PINT events. If "Event" header field as requesting a subscription to PINT events. If
a notifier does not support PINT, it SHOULD return "489 Bad Event" to a notifier does not support PINT, it SHOULD return "489 Bad Event" to
any SUBSCRIBE messages without an "Event" header field. any SUBSCRIBE requests without an "Event" header field.
4.3. Proxy Behavior 4.3. Proxy Behavior
Proxies need no additional behavior beyond that described in SIP Proxies need no additional behavior beyond that described in
[RFC3261] to support SUBSCRIBE and NOTIFY. If a proxy wishes to see [RFC3261] to support SUBSCRIBE and NOTIFY transactions. If a proxy
all of the SUBSCRIBE and NOTIFY requests for a given dialog, it MUST wishes to see all of the SUBSCRIBE and NOTIFY requests for a given
add a Record-Route header field to the initial SUBSCRIBE request and dialog, it MUST add a Record-Route header field to the initial
all NOTIFY requests. It MAY choose to include Record-Route in SUBSCRIBE request and all NOTIFY requests. It MAY choose to include
subsequent SUBSCRIBE messages; however, these requests cannot cause Record-Route in subsequent SUBSCRIBE requests; however, these
the dialog's route set to be modified. requests cannot cause the dialog's route set to be modified.
Proxies that did not add a Record-Route header field to the initial Proxies that did not add a Record-Route header field to the initial
SUBSCRIBE request MUST NOT add a Record-Route header field to any of SUBSCRIBE request MUST NOT add a Record-Route header field to any of
the associated NOTIFY requests. the associated NOTIFY requests.
Note that subscribers and notifiers may elect to use S/MIME Note that subscribers and notifiers may elect to use S/MIME
encryption of SUBSCRIBE and NOTIFY requests; consequently, proxies encryption of SUBSCRIBE and NOTIFY requests; consequently, proxies
cannot rely on being able to access any information that is not cannot rely on being able to access any information that is not
explicitly required to be proxy-readable by SIP [RFC3261]. explicitly required to be proxy-readable by [RFC3261].
4.4. Common Behavior 4.4. Common Behavior
4.4.1. Dialog Creation and Termination 4.4.1. Dialog Creation and Termination
Dialogs are created upon completion of a NOTIFY transaction for a new Dialogs usages are created upon completion of a NOTIFY transaction
subscription, unless the NOTIFY contains a "Subscription-State" of for a new subscription, unless the NOTIFY request contains a
"terminated." "Subscription-State" of "terminated."
Because the dialog is established by the NOTIFY request, the route Because the dialog usage is established by the NOTIFY request, the
set at the subscriber is taken from the NOTIFY request itself, as route set at the subscriber is taken from the NOTIFY request itself,
opposed to the route set present in the 200-class response to the as opposed to the route set present in the 200-class response to the
SUBSCRIBE request. SUBSCRIBE request.
NOTIFY requests are matched to such SUBSCRIBE requests if they NOTIFY requests are matched to such SUBSCRIBE requests if they
contain the same "Call-ID", a "To" header field "tag" parameter which contain the same "Call-ID", a "To" header field "tag" parameter which
matches the "From" header field "tag" parameter of the SUBSCRIBE, and matches the "From" header field "tag" parameter of the SUBSCRIBE
the same "Event" header field. Rules for comparisons of the "Event" request, and the same "Event" header field. Rules for comparisons of
header fields are described in Section 8.2.1. the "Event" header fields are described in Section 8.2.1.
A subscription is destroyed after a notifier sends a NOTIFY request A subscription is destroyed after a notifier sends a NOTIFY request
with a "Subscription-State" of "terminated." The subscriber will with a "Subscription-State" of "terminated," or in certain error
situations described elsewhere in this document. The subscriber will
generally answer such final requests with a "200 OK" response (unless generally answer such final requests with a "200 OK" response (unless
a condition warranting an alternate response has arisen). Except a condition warranting an alternate response has arisen). Except
when the mechanism described in Section 4.5.2 is used, the when the mechanism described in Section 4.5.2 is used, the
destruction of a subscription results in the termination of its destruction of a subscription results in the termination of its
associated dialog. associated dialog.
A subscriber may send a SUBSCRIBE request with an "Expires" header A subscriber may send a SUBSCRIBE request with an "Expires" header
field of 0 in order to trigger the sending of such a NOTIFY field of 0 in order to trigger the sending of such a NOTIFY
request; however, for the purposes of subscription and dialog request; however, for the purposes of subscription and dialog
lifetime, the subscription is not considered terminated until the lifetime, the subscription is not considered terminated until the
NOTIFY transaction with a "Subscription-State" of "terminated" NOTIFY transaction with a "Subscription-State" of "terminated"
completes. completes.
4.4.2. Notifier Migration 4.4.2. Notifier Migration
It is often useful to allow migration of subscriptions between It is often useful to allow migration of subscriptions between
notifiers. Such migration may be effected by sending a NOTIFY notifiers. Such migration may be effected by sending a NOTIFY
message with a "Subscription-State" header field of "terminated", and request with a "Subscription-State" header field of "terminated", and
a reason parameter of "deactivated". This NOTIFY request is a reason parameter of "deactivated". This NOTIFY request is
otherwise normal, and is formed as described in Section 4.2.2. otherwise normal, and is formed as described in Section 4.2.2.
Upon receipt of this NOTIFY message, the subscriber SHOULD attempt to Upon receipt of this NOTIFY request, the subscriber SHOULD attempt to
re-subscribe (as described in the preceding sections). Note that re-subscribe (as described in the preceding sections). Note that
this subscription is established on a new dialog, and does not re-use this subscription is established on a new dialog, and does not re-use
the route set from the previous subscription dialog. the route set from the previous subscription dialog.
The actual migration is effected by making a change to the policy The actual migration is effected by making a change to the policy
(such as routing decisions) of one or more servers to which the (such as routing decisions) of one or more servers to which the
SUBSCRIBE request will be sent in such a way that a different node SUBSCRIBE request will be sent in such a way that a different node
ends up responding to the SUBSCRIBE request. This may be as simple ends up responding to the SUBSCRIBE request. This may be as simple
as a change in the local policy in the notifier from which the as a change in the local policy in the notifier from which the
subscription is migrating so that it serves as a proxy or redirect subscription is migrating so that it serves as a proxy or redirect
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a matter of local notifier policy, and are left up to individual a matter of local notifier policy, and are left up to individual
implementations. implementations.
4.4.3. Polling Resource State 4.4.3. Polling Resource State
A natural consequence of the behavior described in the preceding A natural consequence of the behavior described in the preceding
sections is that an immediate fetch without a persistent subscription sections is that an immediate fetch without a persistent subscription
may be effected by sending a SUBSCRIBE with an "Expires" of 0. may be effected by sending a SUBSCRIBE with an "Expires" of 0.
Of course, an immediate fetch while a subscription is active may be Of course, an immediate fetch while a subscription is active may be
effected by sending a SUBSCRIBE with an "Expires" equal to the number effected by sending a SUBSCRIBE request with an "Expires" equal to
of seconds remaining in the subscription. the number of seconds remaining in the subscription.
Upon receipt of this SUBSCRIBE request, the notifier (or notifiers, Upon receipt of this SUBSCRIBE request, the notifier (or notifiers,
if the SUBSCRIBE request was forked) will send a NOTIFY request if the SUBSCRIBE request was forked) will send a NOTIFY request
containing resource state in the same dialog. containing resource state in the same dialog.
Note that the NOTIFY messages triggered by SUBSCRIBE messages with Note that the NOTIFY requests triggered by SUBSCRIBE requests with
"Expires" header fields of 0 will contain a "Subscription-State" "Expires" header fields of 0 will contain a "Subscription-State"
value of "terminated", and a "reason" parameter of "timeout". value of "terminated", and a "reason" parameter of "timeout".
Polling of event state can cause significant increases in load on the Polling of event state can cause significant increases in load on the
network and notifiers; as such, it should be used only sparingly. In network and notifiers; as such, it should be used only sparingly. In
particular, polling SHOULD NOT be used in circumstances in which it particular, polling SHOULD NOT be used in circumstances in which it
will typically result in more network messages than long-running will typically result in more network messages than long-running
subscriptions. subscriptions.
When polling is used, subscribers SHOULD attempt to cache When polling is used, subscribers SHOULD attempt to cache
authentication credentials between polls so as to reduce the number authentication credentials between polls so as to reduce the number
of messages sent. of messages sent.
Due to the requirement on notifiers to send a NOTIFY immediately Due to the requirement on notifiers to send a NOTIFY request
upon receipt of a SUBSCRIBE request, the state provided by polling immediately upon receipt of a SUBSCRIBE request, the state
is limited to the information that the notifier has immediate provided by polling is limited to the information that the
local access to when it receives the SUBSCRIBE. If, for example, notifier has immediate local access to when it receives the
the notifier generally needs to retrieve state from another SUBSCRIBE request. If, for example, the notifier generally needs
network server, then that state will be absent from the NOTIFY to retrieve state from another network server, then that state
that results from polling. will be absent from the NOTIFY request that results from polling.
4.4.4. Allow-Events header field usage 4.4.4. Allow-Events header field usage
The "Allow-Events" header field, if present, includes a list of The "Allow-Events" header field, if present, includes a list of
tokens which indicates the event packages supported by a notifier. tokens which indicates the event packages supported by a notifier.
In other words, a user agent sending an "Allow-Events" header field In other words, a user agent sending an "Allow-Events" header field
is advertising that it can process SUBSCRIBE requests and generate is advertising that it can process SUBSCRIBE requests and generate
NOTIFY requests for all of the event packages listed in that header NOTIFY requests for all of the event packages listed in that header
field. field.
Any user agent that can act as a notifier for one or more event Any user agent that can act as a notifier for one or more event
packages SHOULD include an appropriate "Allow-Events" header field packages SHOULD include an appropriate "Allow-Events" header field
indicating all supported events in all methods which initiate dialogs indicating all supported events in all methods which initiate dialogs
and their responses (such as INVITE) and OPTIONS responses. and their responses (such as INVITE) and OPTIONS responses.
This information is very useful, for example, in allowing user This information is very useful, for example, in allowing user
agents to render particular interface elements appropriately agents to render particular interface elements appropriately
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 dialog established by a NOTIFY
the only event package supported is the one associated with that request if the only event package supported is the one associated
subscription. with that 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 The "Allow-Events" header field does not include a list of the event
template packages supported by an implementation. If a subscriber template packages supported by an implementation. If a subscriber
wishes to determine which event template packages are supported by a wishes to determine which event template packages are supported by a
notifier, it can probe for such support by attempting to subscribe to notifier, it can probe for such support by attempting to subscribe to
the event template packages it wishes to use. the event template packages it wishes to use.
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to the actual event packages. Candidates include the "Target-Dialog" to the actual event packages. Candidates include the "Target-Dialog"
header field [RFC4538], 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 [RFC5627], and Notifiers MUST implement the Globally Routable User-Agent URI (GRUU)
MUST use a GRUU as their local target. This allows subscribers to extension defined in [RFC5627], and MUST use a GRUU as their local
explicitly target desired devices. target. This allows subscribers to 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 request.
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.
4.5.2. Sharing Dialogs 4.5.2. Sharing Dialogs
For compatibility with older clients, subscriber and notifier For compatibility with older clients, subscriber and notifier
implementations may choose to allow dialog sharing. The behavior of implementations may choose to allow dialog sharing. The behavior of
multiple usages within a dialog are described in [RFC5057]. multiple usages within a dialog are described in [RFC5057].
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indicate that dialog sharing is not supported. indicate that dialog sharing is not supported.
To implement dialog sharing, subscribers and notifiers perform the To implement dialog sharing, subscribers and notifiers perform the
following additional processing: following additional processing:
o When subscriptions exist in dialogs associated with INVITE-created o When subscriptions exist in dialogs associated with INVITE-created
application state and/or other subscriptions, these sets of application state and/or other subscriptions, these sets of
application state do not interact beyond the behavior described application state do not interact beyond the behavior described
for a dialog (e.g., route set handling). In particular, multiple for a dialog (e.g., route set handling). In particular, multiple
subscriptions within a dialog are expire independently, and subscriptions within a dialog are expire independently, and
require independent SUBSCRIBE refreshes. require independent subscription refreshes.
o If a subscription's destruction leaves no other application state o If a subscription's destruction leaves no other application state
associated with the dialog, the dialog terminates. The associated with the dialog, the dialog terminates. The
destruction of other application state (such as that created by an destruction of other application state (such as that created by an
INVITE) will not terminate the dialog if a subscription is still INVITE) will not terminate the dialog if a subscription is still
associated with that dialog. This means that, when dialog are re- associated with that dialog. This means that, when dialog are re-
used, then a dialog created with an INVITE does not necessarily used, then a dialog created with an INVITE does not necessarily
terminate upon receipt of a BYE. Similarly, in the case that terminate upon receipt of a BYE. Similarly, in the case that
several subscriptions are associated with a single dialog, the several subscriptions are associated with a single dialog, the
dialog does not terminate until all the subscriptions in it are dialog does not terminate until all the subscriptions in it are
destroyed. destroyed.
o Subscribers MAY include an "id" parameter in SUBSCRIBE request o Subscribers MAY include an "id" parameter in SUBSCRIBE request
"Event" header field to allow differentiation between multiple "Event" header field to allow differentiation between multiple
subscriptions in the same dialog. This "id" parameter, if subscriptions in the same dialog. This "id" parameter, if
present, contains an opaque token which identifies the specific present, contains an opaque token which identifies the specific
subscription within a dialog. An "id" parameter is only valid subscription within a dialog. An "id" parameter is only valid
within the scope of a single dialog. within the scope of a single dialog.
o If an "id" parameter is present in the SUBSCRIBE message used to o If an "id" parameter is present in the SUBSCRIBE request used to
establish a subscription, that "id" parameter MUST also be present establish a subscription, that "id" parameter MUST also be present
in all corresponding NOTIFY messages. in all corresponding NOTIFY requests.
o When a subscriber refreshes a the subscription timer, the o When a subscriber refreshes a the subscription timer, the
SUBSCRIBE MUST contain the same "Event" header field "id" SUBSCRIBE request MUST contain the same "Event" header field "id"
parameter as was present in the initial subscription. (Otherwise, parameter as was present in the SUBSCRIBE request that created the
the notifier will interpret the SUBSCRIBE message as a request for subscription. (Otherwise, the notifier will interpret the
a new subscription in the same dialog). SUBSCRIBE request as a request for a new subscription in the same
dialog).
o When a subscription is created in the notifier, it stores the any o When a subscription is created in the notifier, it stores any
"Event" header field "id" parameter as part of the subscription "Event" header field "id" parameter as part of the subscription
information (along with the event package name). information (along with the event package name).
o If an initial SUBSCRIBE is sent on a pre-existing dialog, a o If an initial SUBSCRIBE request is sent on a pre-existing dialog,
matching NOTIFY request merely creates a new subscription a matching NOTIFY request merely creates a new subscription
associated with that dialog. associated with that dialog.
4.6. CANCEL Requests for SUBSCRIBE and NOTIFY 4.6. CANCEL Requests for SUBSCRIBE and NOTIFY Transactions
Neither SUBSCRIBE nor NOTIFY messages can be canceled. If a UAS Neither SUBSCRIBE nor NOTIFY requests can be canceled. If a UAS
receives a CANCEL request that matches a known SUBSCRIBE or NOTIFY receives a CANCEL request that matches a known SUBSCRIBE or NOTIFY
transaction, it MUST respond to the CANCEL request, but otherwise transaction, it MUST respond to the CANCEL request, but otherwise
ignore it. In particular, the CANCEL request MUST NOT affect ignore it. In particular, the CANCEL request MUST NOT affect
processing of the SUBSCRIBE or NOTIFY request in any way. processing of the SUBSCRIBE or NOTIFY request in any way.
UACs SHOULD NOT send CANCEL requests for SUBSCRIBE or NOTIFY UACs SHOULD NOT send CANCEL requests for SUBSCRIBE or NOTIFY
transactions. transactions.
5. Event Packages 5. Event Packages
This section covers several issues which should be taken into This section covers several issues which should be taken into
consideration when event packages based on SUBSCRIBE and NOTIFY are consideration when event packages based on the SUBSCRIBE and NOTIFY
proposed. Event package definitions contain sections addressing each methods are proposed. Event package definitions contain sections
of these issues, ideally in the same order and with the same titles addressing each of these issues, ideally in the same order and with
as the following sections. the same titles as the following sections.
5.1. Appropriateness of Usage 5.1. Appropriateness of Usage
When designing an event package using the methods described in this When designing an event package using the methods described in this
document for event notification, it is important to consider: is SIP document for event notification, it is important to consider: is SIP
an appropriate mechanism for the problem set? Is SIP being selected an appropriate mechanism for the problem set? Is SIP being selected
because of some unique feature provided by the protocol (e.g., user because of some unique feature provided by the protocol (e.g., user
mobility), or merely because "it can be done?" If you find yourself mobility), or merely because "it can be done?" If you find yourself
defining event packages for notifications related to, for example, defining event packages for notifications related to, for example,
network management or the temperature inside your car's engine, you network management or the temperature inside your car's engine, you
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total voice messages"). This complicates implementation of total voice messages"). This complicates implementation of
subscribing entities (since they have to maintain complete state for subscribing entities (since they have to maintain complete state for
the entity to which they have subscribed), and also is particularly the entity to which they have subscribed), and also is particularly
susceptible to synchronization problems. susceptible to synchronization problems.
There are two possible solutions to this problem that event packages There are two possible solutions to this problem that event packages
may choose to implement. may choose to implement.
5.3.1. Complete State Information 5.3.1. Complete State Information
In general, event packages need to be able to convey a well-defined
and complete state, rather than just a stream of events. If it is
not possible to describe complete system state for transmission in
NOTIFY requests, then the problem set is not a good candidate for an
event package.
For packages which typically convey state information that is For packages which typically convey state information that is
reasonably small (on the order of 1 KB or so), it is suggested that reasonably small (on the order of 1 KB or so), it is suggested that
event packages are designed so as to send complete state information event packages are designed so as to send complete state information
when an event occurs. whenever an event occurs.
In some circumstances, conveying the current state alone may be In some circumstances, conveying the current state alone may be
insufficient for a particular class of events. In these cases, the insufficient for a particular class of events. In these cases, the
event packages should include complete state information along with event packages should include complete state information along with
the event that occurred. For example, conveying "no customer service the event that occurred. For example, conveying "no customer service
representatives available" may not be as useful as conveying "no representatives available" may not be as useful as conveying "no
customer service representatives available; representative customer service representatives available; representative
sip:46@cs.xyz.int just logged off". sip:46@cs.xyz.int just logged off".
5.3.2. State Deltas 5.3.2. State Deltas
In the case that the state information to be conveyed is large, the In the case that the state information to be conveyed is large, the
event package may choose to detail a scheme by which NOTIFY messages event package may choose to detail a scheme by which NOTIFY requests
contain state deltas instead of complete state. contain state deltas instead of complete state.
Such a scheme would work as follows: any NOTIFY sent in immediate Such a scheme would work as follows: any NOTIFY request sent in
response to a SUBSCRIBE contains full state information. NOTIFY immediate response to a SUBSCRIBE request contains full state
messages sent because of a state change will contain only the state information. NOTIFY requests sent because of a state change will
information that has changed; the subscriber will then merge this contain only the state information that has changed; the subscriber
information into its current knowledge about the state of the will then merge this information into its current knowledge about the
resource. state of the resource.
Any event package that supports delta changes to states MUST include Any event package that supports delta changes to states MUST include
a version number that increases by exactly one for each NOTIFY a version number that increases by exactly one for each NOTIFY
transaction in a subscription. Note that the state version number transaction in a subscription. Note that the state version number
appears in the body of the message, not in a SIP header field. appears in the body of the message, not in a SIP header field.
If a NOTIFY arrives that has a version number that is incremented by If a NOTIFY request arrives that has a version number that is
more than one, the subscriber knows that a state delta has been incremented by more than one, the subscriber knows that a state delta
missed; it ignores the NOTIFY message containing the state delta has been missed; it ignores the NOTIFY request containing the state
(except for the version number, which it retains to detect message delta (except for the version number, which it retains to detect
loss), and re-sends a SUBSCRIBE to force a NOTIFY containing a message loss), and re-sends a SUBSCRIBE request to force a NOTIFY
complete state snapshot. request containing a complete state snapshot.
5.4. Event Package Responsibilities 5.4. Event Package Responsibilities
Event packages are not required to reiterate any of the behavior Event packages are not required to reiterate any of the behavior
described in this document, although they may choose to do so for described in this document, although they may choose to do so for
clarity or emphasis. In general, though, such packages are expected clarity or emphasis. In general, though, such packages are expected
to describe only the behavior that extends or modifies the behavior to describe only the behavior that extends or modifies the behavior
described in this document. described in this document.
Note that any behavior designated with "SHOULD" or "MUST" in this Note that any behavior designated with "SHOULD" or "MUST" in this
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used to designate the event package. It MUST include the information used to designate the event package. It MUST include the information
which appears in the IANA registration of the token. For information which appears in the IANA registration of the token. For information
on registering such types, see Section 7. on registering such types, see Section 7.
5.4.2. Event Package Parameters 5.4.2. Event Package Parameters
If parameters are to be used on the "Event" header field to modify If parameters are to be used on the "Event" header field to modify
the behavior of the event package, the syntax and semantics of such the behavior of the event package, the syntax and semantics of such
header fields MUST be clearly defined. header fields MUST be clearly defined.
5.4.3. SUBSCRIBE Bodies Any "Event" header field parameters defined by an event package MUST
be registered in the "Header Field Parameters and Parameter Values"
registry defined by [RFC3968]. An "Event" header field parameter,
once registered in conjunction with an event package, MUST NOT be re-
used with any other event package. Non-event-package specifications
MAY define "Event" header field parameters that apply across all
event packages (with emphasis on "all", as opposed to "several"),
such as the "id" parameter defined in this document. The restriction
of a parameter to use with a single event package only applies to
parameters that are defined in conjunction with an event package.
5.4.3. SUBSCRIBE Request Bodies
It is expected that most, but not all, event packages will define It is expected that most, but not all, event packages will define
syntax and semantics for SUBSCRIBE method bodies; these bodies will syntax and semantics for SUBSCRIBE request bodies; these bodies will
typically modify, expand, filter, throttle, and/or set thresholds for typically modify, expand, filter, throttle, and/or set thresholds for
the class of events being requested. Designers of event packages are the class of events being requested. Designers of event packages are
strongly encouraged to re-use existing MIME types for message bodies strongly encouraged to re-use existing MIME types for message bodies
where practical. where practical.
This mandatory section of an event package defines what type or types This mandatory section of an event package defines what type or types
of event bodies are expected in SUBSCRIBE requests (or specify that of event bodies are expected in SUBSCRIBE requests (or specify that
no event bodies are expected). It should point to detailed no event bodies are expected). It should point to detailed
definitions of syntax and semantics for all referenced body types. definitions of syntax and semantics for all referenced body types.
5.4.4. Subscription Duration 5.4.4. Subscription Duration
It is RECOMMENDED that event packages give a suggested range of times It is RECOMMENDED that event packages give a suggested range of times
considered reasonable for the duration of a subscription. Such considered reasonable for the duration of a subscription. Such
packages MUST also define a default "Expires" value to be used if packages MUST also define a default "Expires" value to be used if
none is specified. none is specified.
5.4.5. NOTIFY Bodies 5.4.5. NOTIFY Request Bodies
The NOTIFY body is used to report state on the resource being The NOTIFY request body is used to report state on the resource being
monitored. Each package MUST define what type or types of event monitored. Each package MUST define what type or types of event
bodies are expected in NOTIFY requests. Such packages MUST specify bodies are expected in NOTIFY requests. Such packages MUST specify
or cite detailed specifications for the syntax and semantics or cite detailed specifications for the syntax and semantics
associated with such event body. associated with such event body.
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
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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. subscribers and authorization issues for the package.
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 request to be
to compute the state information in the NOTIFY, how to generate sent, how to compute the state information in the NOTIFY, how to
neutral or fake state information to hide authorization delays and generate neutral or fake state information to hide authorization
decisions from users, and whether state information is complete or delays and decisions from users, and whether state information is
deltas for notifications; see Section 5.3. Such a section is complete or deltas for notifications; see Section 5.3. Such a
required. section is required.
This section may optionally describe the behavior used to process the This section may optionally describe the behavior used to process the
subsequent response. subsequent response.
5.4.8. Subscriber processing of NOTIFY requests 5.4.8. Subscriber processing of NOTIFY requests
This section of an event package describes the process followed by This section of an event package describes the process followed by
the subscriber upon receipt of a NOTIFY request, including any logic the subscriber upon receipt of a NOTIFY request, including any logic
required to form a coherent resource state (if applicable). required to form a coherent resource state (if applicable).
5.4.9. Handling of forked requests 5.4.9. Handling of forked requests
Each event package MUST specify whether forked SUBSCRIBE requests are Each event package MUST specify whether forked SUBSCRIBE requests are
allowed to install multiple subscriptions. allowed to install multiple subscriptions.
If such behavior is not allowed, the first potential dialog- If such behavior is not allowed, the first potential dialog-
establishing message will create a dialog. All subsequent NOTIFY establishing message will create a dialog. All subsequent NOTIFY
messages which correspond to the SUBSCRIBE message (i.e., match "To", requests which correspond to the SUBSCRIBE request (i.e., match "To",
"From", "From" header field "tag" parameter, "Call-ID", "Event", and "From", "From" header field "tag" parameter, "Call-ID", "Event", and
"Event" header field "id" parameter) but which do not match the "Event" header field "id" parameter) but which do not match the
dialog would be rejected with a 481 response. Note that the 200- dialog would be rejected with a 481 response. Note that the 200-
class response to the SUBSCRIBE can arrive after a matching NOTIFY class response to the SUBSCRIBE request can arrive after a matching
has been received; such responses might not correlate to the same NOTIFY request has been received; such responses might not correlate
dialog established by the NOTIFY. Except as required to complete the to the same dialog established by the NOTIFY request. Except as
SUBSCRIBE transaction, such non-matching 200-class responses are required to complete the SUBSCRIBE transaction, such non-matching
ignored. 200-class responses are ignored.
If installing of multiple subscriptions by way of a single forked If installing of multiple subscriptions by way of a single forked
SUBSCRIBE is allowed, the subscriber establishes a new dialog towards SUBSCRIBE request is allowed, the subscriber establishes a new dialog
each notifier by returning a 200-class response to each NOTIFY. Each towards each notifier by returning a 200-class response to each
dialog is then handled as its own entity, and is refreshed NOTIFY request. Each dialog is then handled as its own entity, and
independent of the other dialogs. is refreshed independent of the other dialogs.
In the case that multiple subscriptions are allowed, the event In the case that multiple subscriptions are allowed, the event
package MUST specify whether merging of the notifications to form a package MUST specify whether merging of the notifications to form a
single state is required, and how such merging is to be performed. single state is required, and how such merging is to be performed.
Note that it is possible that some event packages may be defined in Note that it is possible that some event packages may be defined in
such a way that each dialog is tied to a mutually exclusive state such a way that each dialog is tied to a mutually exclusive state
which is unaffected by the other dialogs; this MUST be clearly stated which is unaffected by the other dialogs; this MUST be clearly stated
if it is the case. if it is the case.
5.4.10. Rate of notifications 5.4.10. Rate of notifications
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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 certain 4xx and 6xx responses to SUBSCRIBE The mere act of returning certain 4xx and 6xx responses to SUBSCRIBE
requests may, under certain circumstances, create privacy concerns by requests may, under certain circumstances, create privacy concerns by
revealing sensitive policy information. In these cases, the notifier revealing sensitive policy information. In these cases, the notifier
SHOULD always return a 200 (OK) response. While the subsequent SHOULD always return a 200 (OK) response. While the subsequent
NOTIFY message may not convey true state, it MUST appear to contain a NOTIFY request may not convey true state, it MUST appear to contain a
potentially correct piece of data from the point of view of the potentially correct piece of data from the point of view of the
subscriber, indistinguishable from a valid response. Information subscriber, indistinguishable from a valid response. Information
about whether a user is authorized to subscribe to the requested about whether a user is authorized to subscribe to the requested
state is never conveyed back to the original user under these state is never conveyed back to the original user under 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.
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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
amplifier node to be used in a smurf attack. amplifier node to be used in a smurf attack.
Also, the creation of state upon receipt of a SUBSCRIBE request can Also, the creation of state upon receipt of a SUBSCRIBE request can
be used by attackers to consume resources on a victim's machine, be used by attackers to consume resources on a victim's machine,
rendering it unusable. rendering it unusable.
To reduce the chances of such an attack, implementations of notifiers To reduce the chances of such an attack, implementations of notifiers
SHOULD require authentication. Authentication issues are discussed SHOULD require authentication. Authentication issues are discussed
in SIP [RFC3261]. in [RFC3261].
6.4. Replay Attacks 6.4. Replay Attacks
Replaying of either SUBSCRIBE or NOTIFY can have detrimental effects. Replaying of either SUBSCRIBE or NOTIFY requests can have detrimental
effects.
In the case of SUBSCRIBE messages, attackers may be able to install In the case of SUBSCRIBE requests, attackers may be able to install
any arbitrary subscription which it witnessed being installed at some any arbitrary subscription which it witnessed being installed at some
point in the past. Replaying of NOTIFY messages may be used to spoof point in the past. Replaying of NOTIFY requests may be used to spoof
old state information (although a good versioning mechanism in the old state information (although a good versioning mechanism in the
body of the NOTIFY messages may help mitigate such an attack). Note body of the NOTIFY requests may help mitigate such an attack). Note
that the prohibition on sending NOTIFY messages to nodes which have that the prohibition on sending NOTIFY requests to nodes which have
not subscribed to an event also aids in mitigating the effects of not subscribed to an event also aids in mitigating the effects of
such an attack. such an attack.
To prevent such attacks, implementations SHOULD require To prevent such attacks, implementations SHOULD require
authentication with anti-replay protection. Authentication issues authentication with anti-replay protection. Authentication issues
are discussed in SIP [RFC3261]. are discussed in [RFC3261].
6.5. Man-in-the middle attacks 6.5. Man-in-the middle attacks
Even with authentication, man-in-the-middle attacks using SUBSCRIBE Even with authentication, man-in-the-middle attacks using SUBSCRIBE
may be used to install arbitrary subscriptions, hijack existing requests may be used to install arbitrary subscriptions, hijack
subscriptions, terminate outstanding subscriptions, or modify the existing subscriptions, terminate outstanding subscriptions, or
resource to which a subscription is being made. To prevent such modify the resource to which a subscription is being made. To
attacks, implementations SHOULD provide integrity protection across prevent such attacks, implementations SHOULD provide integrity
"Contact", "Route", "Expires", "Event", and "To" header fields of protection across "Contact", "Route", "Expires", "Event", and "To"
SUBSCRIBE messages, at a minimum. If SUBSCRIBE bodies are used to header fields of SUBSCRIBE requests, at a minimum. If SUBSCRIBE
define further information about the state of the call, they SHOULD request bodies are used to define further information about the state
be included in the integrity protection scheme. of the call, they SHOULD be included in the integrity protection
scheme.
Man-in-the-middle attacks may also attempt to use NOTIFY messages to Man-in-the-middle attacks may also attempt to use NOTIFY requests to
spoof arbitrary state information and/or terminate outstanding spoof arbitrary state information and/or terminate outstanding
subscriptions. To prevent such attacks, implementations SHOULD subscriptions. To prevent such attacks, implementations SHOULD
provide integrity protection across the "Call-ID", "CSeq", and provide integrity protection across the "Call-ID", "CSeq", and
"Subscription-State" header fields and the bodies of NOTIFY messages. "Subscription-State" header fields and the bodies of NOTIFY requests.
Integrity protection of message header fields and bodies is discussed Integrity protection of message header fields and bodies is discussed
in SIP [RFC3261]. in [RFC3261].
6.6. Confidentiality 6.6. Confidentiality
The state information contained in a NOTIFY message has the potential The state information contained in a NOTIFY request has the potential
to contain sensitive information. Implementations MAY encrypt such to contain sensitive information. Implementations MAY encrypt such
information to ensure confidentiality. information to ensure confidentiality.
While less likely, it is also possible that the information contained While less likely, it is also possible that the information contained
in a SUBSCRIBE message contains information that users might not want in a SUBSCRIBE request contains information that users might not want
to have revealed. Implementations MAY encrypt such information to to have revealed. Implementations MAY encrypt such information to
ensure confidentiality. ensure confidentiality.
To allow the remote party to hide information it considers sensitive, To allow the remote party to hide information it considers sensitive,
all implementations SHOULD be able to handle encrypted SUBSCRIBE and all implementations SHOULD be able to handle encrypted SUBSCRIBE and
NOTIFY messages. NOTIFY requests.
The mechanisms for providing confidentiality are detailed in SIP The mechanisms for providing confidentiality are detailed in
[RFC3261]. [RFC3261].
7. IANA Considerations 7. IANA Considerations
(This section is not applicable until this document is published as (This section is not applicable until this document is published as
an RFC.) an RFC.)
7.1. Event Packages 7.1. Event Packages
This document defines an event-type namespace which requires a This document defines an event-type namespace which requires a
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 Policies for registration of SIP event packages and SIP event package
Considerations Section in RFCs" [RFC5226], normal event package templates are defined in section 4.1 of [RFC5727].
identification tokens are allocated as First Come First Served, and
event template-package identification tokens are allocated on a IETF
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
template-package. template-package.
Registered tokens to designate packages and template-packages MUST Registered tokens to designate packages and template-packages MUST
skipping to change at page 39, line 10 skipping to change at page 40, line 10
Following the policies outlined in "Guidelines for Writing an IANA Following the policies outlined in "Guidelines for Writing an IANA
Considerations Section in RFCs" [RFC5226], 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 [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
IANA registry. We include its reason code ("badfilter") in the IANA registry. We include its reason code ("badfilter") in the
initial list of reason codes to ensure a complete registry. initial list of reason codes to ensure a complete registry.
The IANA registry for reason code will be initialized with the The IANA registry for reason code will be initialized with the
following values: following values:
Reason Code Reference Reason Code Reference
----------- --------- ----------- ---------
skipping to change at page 40, line 24 skipping to change at page 41, line 24
Default Reason Phrase: Accepted Default Reason Phrase: Accepted
Response Code Number: 489 Response Code Number: 489
Default Reason Phrase: Bad Event Default Reason Phrase: Bad Event
8. Syntax 8. Syntax
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 [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.
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.
skipping to change at page 41, line 12 skipping to change at page 42, line 12
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
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 requests with SUBSCRIBE requests,
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
parameters are considered when performing a comparison. SUBSCRIBE parameters are considered when performing a comparison. SUBSCRIBE
responses are matched per the transaction handling rules in SIP responses are matched per the transaction handling rules in
[RFC3261]. [RFC3261].
Note that the forgoing text means that "Event: foo; id=1234" would Note that the forgoing text means that "Event: foo; id=1234" would
match "Event: foo; param=abcd; id=1234", but not "Event: foo" (id match "Event: foo; param=abcd; id=1234", but not "Event: foo" (id
does not match) or "Event: Foo; id=1234" (event portion does not does not match) or "Event: Foo; id=1234" (event portion does not
match). match).
This document does not define values for event-types. These values This document does not define values for event-types. These values
will be defined by individual event packages, and MUST be registered will be defined by individual event packages, and MUST be registered
with the IANA. with the IANA.
skipping to change at page 42, line 9 skipping to change at page 43, line 9
For historical purposes, the 202 (Accepted) response code is added to For historical purposes, the 202 (Accepted) response code is added to
the "Success" header field definition. the "Success" header field definition.
This document does not specify the use of the 202 response code in This document does not specify the use of the 202 response code in
conjunction with the SUBSCRIBE or NOTIFY methods. Previous versions conjunction with the SUBSCRIBE or NOTIFY methods. Previous versions
of the SIP Events Framework assigned specific semantics to the 202 of the SIP Events Framework assigned specific semantics to the 202
response code. Implementations conformant with the current response code. Implementations conformant with the current
specification MUST treat an incoming 202 response as identical to a specification MUST treat an incoming 202 response as identical to a
200 response, and MUST NOT generate 202 response codes to SUBSCRIBE 200 response, and MUST NOT generate 202 response codes to SUBSCRIBE
or NOTIFY messages. or NOTIFY requests.
This document also updates [RFC4660], which reiterates the 202-based This document also updates [RFC4660], which reiterates the 202-based
behavior in several places. Implementations compliant with the behavior in several places. Implementations compliant with the
present document MUST NOT send a 202 response to SUBSCRIBE, and will present document MUST NOT send a 202 response to a SUBSCRIBE request,
send an alternate success response (such as 200) in its stead. 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
The Augmented BNF definitions for the various new and modified syntax The Augmented BNF definitions for the various new and modified syntax
elements follows. The notation is as used in SIP [RFC3261], and any elements follows. The notation is as used in [RFC3261], and any
elements not defined in this section are as defined in SIP and the elements not defined in this section are as defined in SIP and the
documents to which it refers. documents to which it refers.
SUBSCRIBEm = %x53.55.42.53.43.52.49.42.45 ; SUBSCRIBE in caps SUBSCRIBEm = %x53.55.42.53.43.52.49.42.45 ; SUBSCRIBE in caps
NOTIFYm = %x4E.4F.54.49.46.59 ; NOTIFY in caps NOTIFYm = %x4E.4F.54.49.46.59 ; NOTIFY in caps
extension-method = SUBSCRIBEm / NOTIFYm / token extension-method = SUBSCRIBEm / NOTIFYm / token
Event = ( "Event" / "o" ) HCOLON event-type Event = ( "Event" / "o" ) HCOLON event-type
*( SEMI event-param ) *( SEMI event-param )
event-type = event-package *( "." event-template ) event-type = event-package *( "." event-template )
skipping to change at page 44, line 14 skipping to change at page 45, line 14
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.
[RFC3968] Camarillo, G., "The Internet Assigned Number Authority
(IANA) Header Field Parameter Registry for the Session
Initiation Protocol (SIP)", BCP 98, RFC 3968,
December 2004.
[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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, October 2009. (SIP)", RFC 5627, October 2009.
[RFC5727] Peterson, J., Jennings, C., and R. Sparks, "Change Process
for the Session Initiation Protocol (SIP) and the Real-
time Applications and Infrastructure Area", BCP 67,
RFC 5727, March 2010.
9.2. Informative References 9.2. Informative References
[RFC2779] Day, M., Aggarwal, S., Mohr, G., and J. Vincent, "Instant [RFC2779] Day, M., Aggarwal, S., Mohr, G., and J. Vincent, "Instant
Messaging / Presence Protocol Requirements", RFC 2779, Messaging / Presence Protocol Requirements", RFC 2779,
February 2000. 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,
skipping to change at page 46, line 5 skipping to change at page 47, line 13
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 [RFC5057]. of RFC 5057 [RFC5057].
Appendix B. 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/.
B.1. Changes from draft-ietf-sipcore-rfc3265bis-01 to B.1. Changes from draft-ietf-sipcore-rfc3265bis-02 to
draft-ietf-sipcore-rfc3265bis-03
o Clarified scope of Event header field parameters. In RFC3265, the
scope is ambiguous, which causes problems with the RFC3968
registry. The new text ensures that Event header field parameters
are unique across all event packages.
o Removed obsoleted language around IANA registration policies for
event packages. Instead, we now cite RFC5727, which supersedes
RFC3265, and is authoritative on event package registration
policy.
o Several editorial updates after input from working group,
including proper designation of "dialog usage" rather than
"dialog" where appropriate.
o Fixed left-over language that allowed implicit subscriptions (in
contradiction to text elsewhere in the document)
o Fixed subscriber state machine handling of Timer N
o Clarified two normative statements about subscription termination
by changing from plain English prose to RFC2119 language.
B.2. Changes from draft-ietf-sipcore-rfc3265bis-01 to
draft-ietf-sipcore-rfc3265bis-02 draft-ietf-sipcore-rfc3265bis-02
o Removed "Table 2" expansions, per WG consensus on how SIP table 2 o Removed "Table 2" expansions, per WG consensus on how SIP table 2
is to be handled. is to be handled.
o Removed 202 response code. o Removed 202 response code.
o Clarified that "Allow-Events" does not list event template o Clarified that "Allow-Events" does not list event template
packages. packages.
o Clarified that Timer N *does* apply to subscription refreshes. o Clarified that Timer N *does* apply to subscription refreshes.
B.2. Changes from draft-ietf-sipcore-rfc3265bis-00 to B.3. 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 unknown 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.
B.3. Changes from draft-roach-sipcore-rfc3265bis-00 to B.4. Changes from draft-roach-sipcore-rfc3265bis-00 to
draft-ietf-sipcore-rfc3265bis-00 draft-ietf-sipcore-rfc3265bis-00
None None
B.4. Changes since RFC 3265 B.5. Changes since RFC 3265
B.4.1. Bug 666: Clarify use of expires=xxx with terminated B.5.1. 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.
B.4.2. Bug 667: Reason code for unsub/poll not clearly spelled out B.5.2. 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).
B.4.3. Bug 669: Clarify: SUBSCRIBE for a duration might be answered B.5.3. 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.
B.4.4. Bug 670: Dialog State Machine needs clarification B.5.4. 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.
B.4.5. Bug 671: Clarify timeout-based removal of subscriptions B.5.5. 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).
B.4.6. Bug 672: Mandate expires= in NOTIFY B.5.6. 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.
B.4.7. Bug 673: INVITE 481 response effect clarification B.5.7. Bug 673: INVITE 481 response effect clarification
This bug was addressed in [RFC5057]. This bug was addressed in [RFC5057].
B.4.8. Bug 677: SUBSCRIBE response matching text in error B.5.8. 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.
B.4.9. Bug 695: Document is not explicit about response to NOTIFY at B.5.9. 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".
B.4.10. Bug 696: Subscription state machine needs clarification B.5.10. 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.
B.4.11. Bug 697: Unsubscription behavior could be clarified B.5.11. 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 request. 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.
B.4.12. Bug 699: NOTIFY and SUBSCRIBE are target refresh requests B.5.12. 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.
B.4.13. Bug 722: Inconsistent 423 reason phrase text B.5.13. 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].
B.4.14. Bug 741: guidance needed on when to not include Allow-Events B.5.14. 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.
B.4.15. Bug 744: 5xx to NOTIFY terminates a subscription, but should B.5.15. 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.
B.4.16. Bug 752: Detection of forked requests is incorrect B.5.16. 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.
B.4.17. Bug 773: Reason code needs IANA registry B.5.17. 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.
B.4.18. Bug 774: Need new reason for terminating subscriptions to B.5.18. 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.
B.4.19. Clarify handling of Route/Record-Route in NOTIFY B.5.19. 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 requests, and adding "MAY" level statements
for subsequent SUBSCRIBE messages. for subsequent SUBSCRIBE requests.
B.4.20. Eliminate implicit subscriptions B.5.20. 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.
B.4.21. Deprecate dialog re-use B.5.21. 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.
B.4.22. Rationalize dialog creation B.5.22. 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).
B.4.23. Refactor behavior sections B.5.23. 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.
B.4.24. Clarify sections that need to be present in event packages B.5.24. 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.
B.4.25. Make CANCEL handling more explicit B.5.25. 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].
B.4.26. Remove State Agent Terminology B.5.26. 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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