A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists
RFC 4662

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Network Working Group                                        A. B. Roach
Request for Comments: 4662                                   B. Campbell
Category: Standards Track                               Estacado Systems
                                                            J. Rosenberg
                                                           Cisco Systems
                                                             August 2006

   A Session Initiation Protocol (SIP) Event Notification Extension
                           for Resource Lists

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document presents an extension to the Session Initiation
   Protocol (SIP)-Specific Event Notification mechanism for subscribing
   to a homogeneous list of resources.  Instead of sending a SUBSCRIBE
   for each resource individually, the subscriber can subscribe to an
   entire list and then receive notifications when the state of any of
   the resources in the list changes.

Roach, et al.               Standards Track                     [Page 1]
RFC 4662                    SIP Event Lists                  August 2006

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Overview of Operation ...........................................4
   4. Operation of List Subscriptions .................................5
      4.1. Negotiation of Support for Resource Lists ..................6
      4.2. Subscription Duration ......................................7
      4.3. NOTIFY Bodies ..............................................7
      4.4. RLS Processing of SUBSCRIBE Requests .......................7
      4.5. RLS Generation of NOTIFY Requests ..........................7
      4.6. Subscriber Processing of NOTIFY Requests ...................9
      4.7. Handling of Forked Requests ...............................10
      4.8. Rate of Notifications .....................................10
   5. Using multipart/related to Convey Aggregate State ..............10
      5.1. XML Syntax ................................................11
      5.2. List Attributes ...........................................13
      5.3. Resource Attributes .......................................14
      5.4. Name Attributes ...........................................14
      5.5. Instance Attributes .......................................14
      5.6. Constructing Coherent Resource State ......................16
           5.6.1. Processing Full State Notifications ................17
           5.6.2. Processing Partial State Notifications .............17
   6. Example ........................................................18
   7. Security Considerations ........................................31
      7.1. Authentication ............................................31
           7.1.1. RLS and Subscriber in the Same Domain ..............31
           7.1.2. RLS and Subscriber in Different Domains ............32
      7.2. Risks of Improper Aggregation .............................33
      7.3. Signing and Sealing .......................................33
      7.4. Infinite Loops ............................................34
   8. IANA Considerations ............................................34
      8.1. New SIP Option Tag: eventlist .............................34
      8.2. New MIME type for Resource List Meta-Information ..........34
      8.3. URN Sub-Namespace .........................................35
   9. Acknowledgements ...............................................36
   10. References ....................................................36
      10.1. Normative References .....................................36
      10.2. Informative References ...................................37

Roach, et al.               Standards Track                     [Page 2]
RFC 4662                    SIP Event Lists                  August 2006

1.  Introduction

   The SIP-specific event notification mechanism [2] allows a user (the
   subscriber) to request to be notified of changes in the state of a
   particular resource.  This is accomplished by the subscriber
   generating a SUBSCRIBE request for the resource, which is processed
   by a notifier that represents the resource.

   In many cases, a subscriber has a list of resources they are
   interested in.  Without some aggregating mechanism, this will require
   the subscriber to generate a SUBSCRIBE request for each resource
   about which they want information.  For environments in which