SIPPING WG A. Houri
Internet-Draft IBM
Intended status: Informational S. Parameswar
Expires: October 22, 2009 Microsoft Corporation
E. Aoki
AOL LLC
V. Singh
H. Schulzrinne
Columbia U.
April 20, 2009
Scaling Requirements for Presence in SIP/SIMPLE
draft-ietf-sipcore-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.
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 . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. 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 the SIP/SIMPLE
protocol. See [I-D.ietf-simple-simple] for the list of RFCs and
drafts that are considered as part of the SIP/SIMPLE protocol. These
optimizations should reduce the load on the network and the presence
servers in interdomain 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 have shown that there is much room for
optimizations in the SIP/SIMPLE protocol. The need for optimizations
is in the number of bytes that are sent between two federating
domains, the number of messages that need to be processed and the
amount of state that needs to be managed by the presence servers.
For example, for two peering networks that have total of 20 million
users, we got around 19 billion messages per 8 hours work day that
needs to be exchanged between the networks only for supporting the
presence service.
For very large session peering (150 million subscriptions) we got a
state close to a tera byte that needs to be managed by the server in
order to manage presence.
It may be that when deploying a very large systems big resources need
to be allocated but we should take into the considration the
following:
o The assumptions that have been used in the scaling analysis
document are very moderate from the aspect of number of presence
status changes per hour and the the size of the presence document
that was assumed.
o Even when applying all current drafted and/or RFCd optimizations
for presence we still got around 10 billion messages per 8 hours
work day for a total of 20 million fedearting users. This is good
but not enough given the moderate assumptions that we have used
and given that when presence will be deployed to a mass market the
number of federating users will be much more then 20 million
federating users.
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3. Requirements
This section lists requirements for a solution that will optimize the
interdomain 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 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-006: The solution SHOULD NOT limit the ability for
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 or make worse any
existing privacy holes.
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 state to maintain, 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: 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
from the other domain while there will be few watchers from the
same domain. The solution MUST support high percentage of
watcher/presentity intersections between the domains and it MUST
support various intersection models.
o REQ-013: Protocol changes MUST NOT prohibit optimizations in
deployment models where there is a high level of cross
subscriptions between the domains.
o REQ-014: 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-015: The solution SHOULD allow for arbitrary federation
topologies including direct and indirect peering.
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].
The following is a discussion of the various possible paths for
optimizations. One of the most important considerations is whether
there is a need to adapt SIP that was designed more as an end to end
protocol to be much more optimized when presence server interacts
directly with another presence server.
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 SIP/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
additional protocol optimizations are possible and further work is
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needed in the IETF 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 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 that are needed and the size of each message are of extreme
importance. Adequate care must be taken in addressing scalability as
part of the initial protocol design phase; Trying to to shoehorn
scalability at a later 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 in interdomain or even between servers in the same domain (as
between RLSs [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 (for example do not use
unreliable protocol as UDP but only TCP, see the section that
calculates the number of bytes and messages for imaginary very
optimized SIP).
When a presence server connects to another server using the current
SIP/SIMPLE 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
[I-D.ietf-simple-intradomain-federation] and in other (still
individual) drafts.
Another issue that is more 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,
in a similar way that the INVITE method negotiates 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 controllable protocol for the
server-to-server interface. Another possibility is to use the MSRP
[RFC4975], [RFC4976] protocol for the notifications.
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5. Security Considerations
This document discusses scalability requirements for the existing
SIP/SIMPLE 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
This document has no IANA actions.
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 Jean-Francois
Mule, Vijay K. Gurbani and Hisham Khartabil for their 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.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-05 (work in
progress), October 2008.
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[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.
[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.
[RFC3857] Rosenberg, J., "A Watcher Information Event Template-
Package for the Session Initiation Protocol (SIP)",
RFC 3857, August 2004.
[RFC3858] Rosenberg, J., "An Extensible Markup Language (XML) Based
Format for Watcher Information", RFC 3858, August 2004.
[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
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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