Revised November 3, 2006

Peer-to-Peer Session Initiation Protocol (P2PSIP)

Chairs: TBD

RAI Area Director(s): Cullen Jennings and Jon Peterson

RAI Area Advisor: Cullen Jennings

Mailing Lists: General Discussion: p2p-sip@cs.columbia.edu 
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Archive at: http://lists.cs.columbia.edu/pipermail/p2p-sip/

Description of the Working Group:

The Peer-to-Peer (P2P) Session Initiation Protocol working group
(P2PSIP WG) is chartered to develop protocols and mechanisms for the
use of the Session Initiation Protocol (SIP) in settings where the
service of establishing and managing sessions is principally handled
by a collection of intelligent endpoints,rather than centralized
servers as in SIP as currently deployed. A number of cases where such
an architecture is desirable have been documented in [1].

The terminology and concepts draft [2] explains the terms and concepts
used here. The work focuses on collections of nodes called "P2PSIP
peers" and "P2PSIP clients". P2PSIP peers manifest a distributed
namespace in which overlay users are identified and provides
mechanisms for locating users or resources within the P2PSIP
overlay. P2PSIP clients and peers use the resolution services of the
peers as an alternative to the SIP discovery process of RFC
3263. Session management, messaging, and presence functions are
performed using traditional SIP.

This group's primary tasks are to produce:

1. An overview document explaining concepts, terminology, rationale,
   and illustrative use cases for the remaining work.
 
2. A proposed standard defining a P2PSIP Peer Protocol. This protocol
   is used between P2PSIP overlay peers, some of which may be behind
   NATs. This protocol will define how the P2PSIP peers collectively
   provide for user and resource location in a SIP environment with no
   or minimal centralized servers. This protocol may or may not be
   syntactically based on SIP, a decision to be made by the WG. The
   group will identify and require one base P2P algorithm (likely a
   particular Distributed Hash Table (DHT) algorithm), while allowing
   for additional optional algorithms in the future.

3. A proposed standard defining a P2PSIP Client Protocol for use by
   P2PSIP clients, some of which may be behind NATs. This protocol
   will define how the P2PSIP clients query and/or modify, the
   resource location information of the overlay. While clearly a
   logical subset of the P2PSIP Protocol, the WG will determine if the
   client protocol is a syntactic subset of the peer protocol, and
   whether the client protocol builds on the SIP protocol.

4. An applicability statement. This document will address how the
   protocols defined above, along with existing IETF protocols, can be
   used to produce systems to locate a user, identify appropriate
   resources to facilitate communications (for example media relays),
   and establish communications between the users, without relying on
   centralized servers.

The work planned for the P2PSIP working group is distinct from, but
requires close participation with other IETF WGs, particularly SIP,
SIPPING, SIMPLE, BEHAVE and MMUSIC. The group cannot modify the
baseline SIP behavior, define a new version of SIP, or attempt to
produce a parallel protocol for session establishment. If the group
determines that any capabilities requiring an extension to SIP are
needed, the group will seek to define such extensions within the SIP
working group using the SIP change process (RFC 3427). Similarly,
existing tools developed in the BEHAVE and MMUSIC groups will be used
for NAT traversal, with extensions or changes desired to support
P2PSIP created in these groups.

The working group takes it as a fact that NATs and firewalls exist in
the Internet, and will ensure that the protocols produced work in
their presence as much as possible. Similarly, the group will attempt
not to make design decisions that preclude anonymous communications
systems from being crafted using the protocols defined by this WG.

The following topics are excluded from the Working Group's scope:

1. Issues specific to applications other than locating users and
   resources for SIP-based communications and presence.

2. Solving "research" type questions related to P2PSIP or P2P in
   general. The WG will instead forward such work to the IRTF P2PRG or
   other RG as appropriate. Examples include fully distributed schemes
   for assuring unique user identities and the development of
   P2P-based replacements for DNS.

3. Locating resources based on something other than URIs. In other
   words, arbitrary search of attributes is out of scope, but locating
   resources based on their URIs is in scope. Using URIs need not
   imply using the DNS or having a record in the DNS for the URI.

4. Multicast and dynamic DNS based approaches as the core lookup
   mechanism locating users and resources. These techniques may be
   in-scope for locating bootstrap peers/servers or for interoperation
   with traditional SIP.

Goals and Milestones

Sep 2007 Submit P2PSIP overview document to the IESG (Informational)

Sep 2008 Submit P2PSIP overlay client protocol document to the IESG
(Standards track)

Sep 2008 Submit P2PSIP overlay peer protocol document to the IESG
(Standards track)

May 2009 Submit P2PSIP applicability statement to the IESG (Standards
track)


References

[1] D. Bryan, E. Shim, B. B. Lowekamp, "Use Cases for Peer-to-Peer
    Session Initiation Protocol (P2PSIP)",
    draft-bryan-sipping-p2p-usecases (work-in-progress)

[2] D. Willis, D. Bryan, P. Matthews, E. Shim, "Concepts and
    Terminology for Peer to Peer SIP,"
    draft-willis-p2psip-concepts (work-in-progress)