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
draft-ietf-sipping-presence-scaling-requirements-00.txt
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Abstract
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
[4].
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
IBM
Science Park Building 18/D
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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