SIPPING WG A. Houri
Internet-Draft IBM
Intended status: Informational S. Parameswar
Expires: January 14, 2010 Microsoft Corporation
E. Aoki
AOL LLC
V. Singh
H. Schulzrinne
Columbia U.
July 13, 2009
Scaling Requirements for Presence in SIP/SIMPLE
draft-ietf-sipcore-presence-scaling-requirements-01.txt
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Abstract
The document provides a set of requirements for enabling inter-domain
scaling in presence for SIP/SIMPLE.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Backward Compatibility Requirements . . . . . . . . . . . . 4
3.2. Policy, Privacy, Permissions Requirements . . . . . . . . . 4
3.3. Scalability Requirements . . . . . . . . . . . . . . . . . 4
3.4. Topology Requirements . . . . . . . . . . . . . . . . . . . 5
4. Considerations for Possible Optimizations . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7. Changes from Previous Versions . . . . . . . . . . . . . . . . 7
7.1. Changes in version 01 . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informational References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 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 [RFC2119].
2. Introduction
The document lists requirements for optimizations of SIP/SIMPLE. See
[I-D.ietf-simple-simple] for the list of RFCs and drafts that are
considered as part of SIP/SIMPLE. These optimizations should reduce
the load on the network and the presence servers due to inter-domain
presence subscriptions. The need for the requirements is based on a
separate scaling analysis document
[I-D.ietf-simple-interdomain-scaling-analysis].
The scaling analysis document shows that the following aspects of
SIP/SIMPLE can be optimized: the number of bytes sent between two
federating domains, the number of messages processed, and the amount
of state managed by the presence server.
For example, for two peering networks that have a total of 20 million
users, we calculated that approximately 19 billion messages per 8
hours work day are exchanged between the networks for the presence
service.
For very large session peering (150 million subscriptions), we
calculated that the presence server needs to manage approximately a
terabyte of state.
It may be that very large systems require the deployment of
significant resources, but we should consider the following:
o The scaling analysis document makes moderate assumptions about the
number of presence status changes per hour and the the size of the
presence document.
o Even when applying all optimizations for presence as described by
drafts and RFCs, we still calculated around 10 billion messages
per 8 hours work day for a total of 20 million federating users.
This is better than the base case, but not enough given the
moderate assumptions and given that, when presence is deployed in
a mass market, the number of federating users will be much larger
than 20 million.
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3. Requirements
This section lists the requirements for a solution that optimizes the
inter-domain presence loads. The requirements are based on the
presence scaling draft
[I-D.ietf-simple-interdomain-scaling-analysis].
3.1. Backward Compatibility Requirements
o REQ-001: The solution SHOULD NOT deprecate existing protocol
mechanisms defined in SIP/SIMPLE.
o REQ-002: Existing SIP/SIMPLE clients SHOULD be able to communicate
with clients and servers that implement new presence scaling
features.
o REQ-003: The solution SHOULD NOT constrain any existing RFC
functional requirements for presence.
o REQ-004: The solution MUST NOT constrain any existing RFC security
requirements for presence.
o REQ-005: Systems that do not use the new additions to the protocol
SHOULD operate at the same level as they do today.
3.2. Policy, Privacy, Permissions Requirements
o REQ-006: The solution SHOULD NOT limit the ability of presentities
to present different views of presence to different watchers.
o REQ-007: The solution SHOULD NOT restrict the ability of a
presentity to obtain its list of watchers.
o REQ-008: The solution MUST NOT create any new privacy holes or
make any existing ones worse.
3.3. Scalability Requirements
o REQ-009: Presence systems (intra- or inter-domain) SHOULD scale in
linear proportion to the number of watchers and presentities in
the system.
o REQ-010: The solution SHOULD NOT require a significant increase in
the size of maintained state, compared to the current state size
required by SIP/SIMPLE.
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o REQ-011: The solution MUST allow presence systems to scale. Note:
we view scalability on the order of tens of millions of users in
each peer domain.
o REQ-012: The solution MUST support a high percentage of watcher/
presentity intersections between the domains and it MUST support
various intersection models such as either small or large
percentage of users from each domain subscribing to users from the
other domain.
o REQ-013: Protocol changes MUST NOT prohibit optimizations in
deployment models where there is a high number of inter-domain
subscriptions.
o REQ-014: New functionalities and extensions to the presence
protocol SHOULD consider scalability with respect to the number of
messages, state size, and management and processing load.
3.4. Topology Requirements
o REQ-015: The solution SHOULD allow for arbitrary federation
topologies including direct and indirect peering.
4. Considerations for Possible Optimizations
This section discusses the possible paths for optimization. One of
the most important considerations is whether SIP, which was designed
more as an end-to-end protocol, needs to be optimized for direct
interactions between presence servers.
It is very possible that the issues described here are inherent to
presence systems in general and not specific to SIP/SIMPLE.
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 additional protocol optimizations are
possible and further IETF work is needed in order to provide better
scalability of large presence systems.
We should remember that SIP was originally designed for end-to-end
session creation and that the number and size of messages are of
secondary importance for an end-to-end session negotiation protocol.
For large scale and especially for very large scale presence, the
number of messages and the size of each message are of extreme
importance. Care must be taken to address scalability during the
initial phase of protocol design; shoehorning scalability at a later
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phase will be doomed to failure.
We should also consider whether using the same protocol between
clients and servers and between servers is a good choice. It may be
that, between inter-domain servers or even intra-domain servers (such
as between RLSes [RFC4662] and presence servers), there needs to be a
different protocol that is optimized for the load and that can make
assumptions about the network (using only TCP, for example. In
[I-D.ietf-simple-interdomain-scaling-analysis], see the section that
calculates the number of bytes and messages for an imaginary,
optimized SIP).
When a presence server connects to another server using current SIP/
SIMPLE, there is an extreme number of redundant messages due to SIP's
support of both TCP and UDP and due to privacy controls that cause
the sending of multiple presence documents for the same presentity.
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
[I-D.ietf-simple-intradomain-federation] and in other (still
individual) drafts.
Another issue related to 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, similar to the
way the INVITE method negotiates media parameters. This way, the
load can be shifted to specialized NOTIFY "relays" and taken off the
control path of SIP. One of the possible ideas (Marc Willekens) is
to use SIP for client/server NOTIFY but use a more optimized and
controllable protocol for the server-to-server interface. Another
possibility is to use the MSRP [RFC4975], [RFC4976] protocol for the
notifications.
5. Security Considerations
This document discusses the scalability requirements for the existing
SIP/SIMPLE protocol and model. Many of the above-mentioned changes
to the protocol will have security implications.
For example, a potential protocol change that may have security
implications is the single sending of a presence document between
domains in order to reduce the number of messages and network load.
This possible optimization will delegate privacy protection from one
domain to the other, and this delegated protection should be
addressed during design.
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An important part of work on the requirements and optimizations will
be to ensure that all the security aspects are covered.
6. IANA Considerations
This document has no IANA actions.
7. Changes from Previous Versions
7.1. Changes in version 01
Editorial language changes.
8. Acknowledgments
We would like to thank Jonathan Rosenberg, Ben Campbell, Markus
Isomaki Piotr Boni, David Viamonte, Aki Niemi, Marc Willekens, and
Gonzalo Camarillo for their ideas and input. Special thanks to Jean-
Francois Mule, Vijay K. Gurbani and Hisham Khartabil for their a
detailed review. Very sprecial thanks A. Jean Mahoney for reviewing
this draft.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informational References
[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-07 (work in
progress), July 2009.
[I-D.ietf-simple-intradomain-federation]
Rosenberg, J., Houri, A., Smyth, C., and F. Audet, "Models
for Intra-Domain Presence and Instant Messaging (IM)
Bridging", draft-ietf-simple-intradomain-federation-03
(work in progress), March 2009.
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[I-D.ietf-simple-simple]
Rosenberg, J., "SIMPLE made Simple: An Overview of the
IETF Specifications for Instant Messaging and Presence
using the Session Initiation Protocol (SIP)",
draft-ietf-simple-simple-05 (work in progress),
March 2009.
[I-D.ietf-simple-view-sharing]
Rosenberg, J., Donovan, S., and K. McMurry, "Optimizing
Federated Presence with View Sharing",
draft-ietf-simple-view-sharing-02 (work in progress),
November 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
Sriram Parameswar
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: Sriram.Parameswar@microsoft.com
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Edwin Aoki
AOL LLC
401 Ellis St.
Mountain View, CA 94043
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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