SIPPING WG                                                      A. Houri
Internet-Draft                                                       IBM
Intended status: Informational                             S. Parameswar
Expires: January 4, 2009                           Microsoft Corporation
                                                                 E. Aoki
                                                                 AOL LLC
                                                                V. Singh
                                                          H. Schulzrinne
                                                             Columbia U.
                                                            July 3, 2008

            Scaling Requirements for Presence in SIP/SIMPLE

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   The document provides a set of requirements for enabling interdomain
   scaling in presence for SIP/SIMPLE.

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Table of Contents

   1.  Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Suggested Requirements  . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Backward Compatibility Requirements . . . . . . . . . . . . 3
     3.2.  Policy, Privacy, Permissions Requirements . . . . . . . . . 3
     3.3.  Scalability Requirements  . . . . . . . . . . . . . . . . . 4
     3.4.  Topology Requirements . . . . . . . . . . . . . . . . . . . 4
   4.  Considerations for Possible Optimizations . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informational References  . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9

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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2.  Introduction

   The document lists requirements for optimizations of the SIP/SIMPLE
   protocol.  These optimizations should reduce the traffic in
   interdomain presence subscriptions.  The requirements are based on a
   separate scaling analysis document

3.  Suggested Requirements

   In the presence scaling draft
   [I-D.ietf-simple-interdomain-scaling-analysis], several areas where
   the deployment of a presence system is far from being trivial are
   described, these include network load, memory load and CPU load.  In
   this section lists an initial set of requirements for a solution that
   will optimize the interdomain presence traffic.

3.1.  Backward Compatibility Requirements

   o  REQ-001: The solution SHOULD NOT hinder the ability of existing
      SIMPLE clients and/or servers from peering with a domain or client
      implementing the solution.  No changes may be required of existing
      servers to interoperate.

   o  REQ-002: The solution SHOULD NOT constrain any existing RFC
      functional or security requirements for presence.

   o  REQ-003: Systems that are not using the new additions to the
      protocol SHOULD operate at the same level as they do today.

3.2.  Policy, Privacy, Permissions Requirements

   o  REQ-004: The solution SHOULD NOT limit the ability for
      presentities to present different views of presence to different

   o  REQ-005: The solution SHOULD NOT restrict the ability of a
      presentity to obtain its list of watchers.

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   o  REQ-006: The solution MUST NOT create any new or make worse any
      existing privacy holes.

3.3.  Scalability Requirements

   o  REQ-007: Presence systems (intra or inter-domain) SHOULD scale in
      linear proportion to the number of watchers and presentities in
      the system.

   o  REQ-008: The solution SHOULD NOT require significantly more state
      in order to implement the solution.

   o  REQ-009: It MUST be able to scale to tens of millions of
      concurrent users in each domain and in each peer domain.

   o  REQ-010: There may be various usage patterns when users of one
      domain subscribe to users from another domain.  It may be that
      only small percentage of users from each domain will subscribe to
      users from the other domain, it may be that most watchers will be
      coming from one domain while there will be few watchers form the
      other domain.  The solution MUST support high percentage of
      watcher/presentity intersections between the domains and it MUST
      support various intersection models.

   o  REQ-011: Protocol changes MUST NOT prohibit optimizations in
      different deployment models esp. where there is a high level of
      cross subscriptions between the domains.

   o  REQ-012: New functionalities and extensions to the presence
      protocol SHOULD take into account scalability with respect to the
      number of messages, state size and management and processing load.

3.4.  Topology Requirements

   o  REQ-013: The solution SHOULD allow for arbitrary federation
      topologies including direct peering and intermediary routing.

4.  Considerations for Possible Optimizations

   The document provides an initial list of requirements for a solution
   of scalability of interdomain presence systems using the SIP/SIMPLE
   protocol.  The issue of scalability was shown in a separate document

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   It is very possible that the issues that are described in this
   document are inherent to presence systems in general and not specific
   to the SIMPLE protocol.  Organizations need to be prepared to invest
   substantial resources in the form of networks and hardware in order
   to create sizable systems.  However, it is apparent that not all the
   possible optimizations were done yet and further work is needed in
   the IETF in order to provide better scalability

   Nevertheless, we should remember that SIP was originally designed for
   end to end session creation and number and size of messages are of
   secondary importance for end to end session negotiation.  For large
   scale and especially for very large scale presence the number of
   messages that are needed and the size of each message are of extreme
   importance.  It seems that we need to think about the problem in a
   different way.  We need to think about scalability as part of the
   protocol design.  The IETF sometimes does not give the right priority
   to actual deployments when designing a protocol but in this case it
   seems that if we do not think about scalability with the protocol
   design it will be very hard to scale.

   We should also consider whether using the same protocol between
   clients and servers and between servers is a good choice.  It may be
   that in interdomain or even between servers in the same domain (as
   between RLSs (Resource List Servers [RFC4662]) and presence servers)
   there is a need to have a different protocol that will be very
   optimized for the load and can assume some assumptions about the
   network (e.g. do not use unreliable protocol as UDP but only TCP).

   When a server is connecting to another server using current protocol,
   there will be an extreme number of redundant messages due to the
   overhead in the SIP protocol of supporting both TCP and UDP and due
   to the need to send multiple presence documents for the same watched
   user because of privacy issues.  A server to server protocol will
   have to address these issues.  Some initial work to address these
   issues can be found in:
   [I-D.ietf-simple-view-sharing] and

   Another issue that is more concerning protocol design is whether
   NOTIFY messages should not be considered as media just like audio,
   video and even text messaging.  The SUBSCRIBE method may be extended
   to negotiate the route and other parameters of the NOTIFY messages,
   in a similar way that the INVITE method is negotiating media
   parameters.  This way the load can be offloaded to a specialized
   NOTIFY "relays" thus not loading the control path of SIP.  One of the
   possible ideas (Marc Willekens) is to use the SIP protocol for
   client/server NOTIFY but make use of a more optimized and

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   controllable protocol for the server-to-server interface.  Another
   possibility is to use the MSRP [RFC4975], [RFC4976]protocol for the

5.  Security Considerations

   This document discusses scalability requirements for the existing
   SIP/SIMPLE presence protocol and model.  Many of the changes to the
   protocol will have security implications as mentioned in some of the
   requirements above.

   One example of possible protocol changes that may have security
   implications is sending a presence document only once between domains
   in order to optimize the number of messages and network load.  This
   possible optimization will delegate privacy protection from one
   domain to another domain and should be addressed when designing
   protocol optimizations

   Important part of work on the requirements and optimizations will be
   to make sure that all the security aspects are covered.

6.  IANA Considerations


7.  Acknowledgments

   We would like to thank Jonathan Rosenberg, Ben Campbell, Markus
   Isomaki Piotr Boni, David Viamonte, Aki Niemi, Marc Willekens Gonzalo
   Camarillo for their ideas and input.  Special thanks to Vijay K.
   Gurbani for the a detailed review.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informational References

              Houri, A., "Scaling Optimizations for Presence in SIP/

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              (work in progress), July 2007.

              Houri, A., Aoki, E., Parameswar, S., Rang, T., Singh, V.,
              and H. Schulzrinne, "Presence Interdomain Scaling Analysis
              for SIP/SIMPLE",
              draft-ietf-simple-interdomain-scaling-analysis-04 (work in
              progress), February 2008.

              Rosenberg, J. and A. Houri, "Models for Intra-Domain
              Presence Federation",
              draft-ietf-simple-intradomain-federation-00 (work in
              progress), February 2008.

              Rosenberg, J., Donovan, S., and K. McMurry, "Optimizing
              Federated Presence with View Sharing",
              draft-ietf-simple-view-sharing-00 (work in progress),
              February 2008.

   [RFC4662]  Roach, A., Campbell, B., and J. Rosenberg, "A Session
              Initiation Protocol (SIP) Event Notification Extension for
              Resource Lists", RFC 4662, August 2006.

   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message
              Session Relay Protocol (MSRP)", RFC 4975, September 2007.

   [RFC4976]  Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
              for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
              September 2007.

Authors' Addresses

   Avshalom Houri
   3 Pekris Street, Science Park


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   Sriram Parameswar
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052


   Edwin Aoki
   360 W. Caribbean  Drive
   Sunnyvale, CA  94089


   Vishal Singh
   Columbia University
   Department of Computer Science
   450 Computer  Science Building
   New York, NY  10027


   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer  Science Building
   New York, NY  10027

   Phone: +1 212 939  7004

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