SIPPING WG                                                      A. Houri
Internet-Draft                                                       IBM
Intended status: Informational                             S. Parameswar
Expires: August 12, 2008                           Microsoft Corporation
                                                                 E. Aoki
                                                                 AOL LLC
                                                                V. Singh
                                                          H. Schulzrinne
                                                             Columbia U.
                                                        February 9, 2008

            Scaling Requirements for Presence in SIP/SIMPLE

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Copyright Notice

   Copyright (C) The IETF Trust (2008).


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

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   separate scaling analysis document.

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  . . . . . . . . . . . . . . . . . 3
     3.4.  Topology Requirements . . . . . . . . . . . . . . . . . . . 4
   4.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informational References  . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8

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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 [1].

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 [4].

3.  Suggested Requirements

   In the presence scaling draft [4], 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: It does 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 does not limit the ability for presentities
      to present different views of presence to different watchers.
   o  REQ-005: The solution does not restrict the ability of a
      presentity to obtain its list of watchers.
   o  REQ-006: The solution MUST NOT create any new or make worse any
      existing privacy holes.

3.3.  Scalability Requirements

   o  REQ-007: It is highly desirable for any presence system (intra or
      inter-domain) to scale linearly as number of watchers and
      presentities increase linearly.

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   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: It MUST support a very high level of watcher/presentity
      intersections in 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.  Conclusions

   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

   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
   a lot in network and hardware in order to create real big 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 tends not to think about 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

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   that in interdomain or even between servers in the same domain (as
   between RLSs 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 servers is connecting to another server using current protocol,
   there will be an extreme number of redundant messages due to the
   overhead of supporting UDP and to the need to send multiple presence
   documents for the same watched user due to privacy issue.  A server
   to server protocol will have to address these issues.  Some initial
   work to address these issues can be found in: [5], [6] and [7]

   Another issue that is more concerning protocol design is whether
   NOTIFY messages should not be considered as media as audio, video and
   even text messaging.  The SUBSCRIBE can be extended to do similar
   three way handshake as INVITE and negotiate where the notify messages
   should go, rate and other 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 stack for the client/server NOTIFY but make use of a
   more optimized and controllable protocol for the server-to-server
   interface.  Another possibility is to use the MSRP [2], [3]protocol
   for the notifies.

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 delagate 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.  Acknowledgments

   We would like to thank Jonathan Rosenberg, Ben Campbell, Markus
   Isomaki Piotr Boni, David Viamonte, Aki Niemi and Marc Willekens for

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   their ideas and input.

7.  References

7.1.  Normative References

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

7.2.  Informational References

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

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

   [4]  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-03 (work
        in progress), November 2007.

   [5]  Houri, A., "Scaling Optimizations for Presence in SIP/SIMPLE",
        draft-houri-simple-interdomain-scaling-optimizations-00 (work in
        progress), July 2007.

   [6]  Rosenberg, J., Donovan, S., and K. McMurry, "Optimizing
        Federated Presence with View Sharing",
        draft-rosenberg-simple-view-sharing-00 (work in progress),
        November 2007.

   [7]  Rosenberg, J., "Models for Intra-Domain Presence Federation",
        draft-rosenberg-simple-intradomain-federation-00 (work in
        progress), November 2007.

Authors' Addresses

   Avshalom Houri
   Science Park  Building 18/D


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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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