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
draft-ietf-sipping-presence-scaling-requirements-01.txt
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Abstract
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
[I-D.ietf-simple-interdomain-scaling-analysis].
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
watchers.
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
[I-D.ietf-simple-interdomain-scaling-analysis].
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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.houri-simple-interdomain-scaling-optimizations],
[I-D.ietf-simple-view-sharing] and
[I-D.ietf-simple-intradomain-federation]
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
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 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
None.
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
[I-D.houri-simple-interdomain-scaling-optimizations]
Houri, A., "Scaling Optimizations for Presence in SIP/
SIMPLE",
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draft-houri-simple-interdomain-scaling-optimizations-00
(work in progress), July 2007.
[I-D.ietf-simple-interdomain-scaling-analysis]
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.
[I-D.ietf-simple-intradomain-federation]
Rosenberg, J. and A. Houri, "Models for Intra-Domain
Presence Federation",
draft-ietf-simple-intradomain-federation-00 (work in
progress), February 2008.
[I-D.ietf-simple-view-sharing]
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
IBM
3 Pekris Street, Science Park
Rehovot,
Israel
Email: avshalom@il.ibm.com
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Sriram Parameswar
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: Sriram.Parameswar@microsoft.com
Edwin Aoki
AOL LLC
360 W. Caribbean Drive
Sunnyvale, CA 94089
USA
Email: aoki@aol.net
Vishal Singh
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Email: vs2140@cs.columbia.edu
URI: http://www.cs.columbia.edu/~vs2140
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu/~hgs
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