P2PSIP%20Concepts%20

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P2PSIP Concepts Terminologydraft-willis-p2psip
-concepts-03

• David Bryan
• Philip Matthews
• Eunsoo Shim
• Dean WillisIETF 67

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Outline of Presentation

• 1) Tutorial review of basic concepts
• 2) Review of recent changes
• 3) Review of open issues
• Note The names associated with many of the
  concepts are still under discussion, so for now,
  please concentrate on the concepts and dont
  worry too much about the names

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Document Goal

• Define concepts and a framework within which we
  can discuss the design.
• Mention major design choices, but be neutral on
  how they will be resolved.
• For now, be general enough to reflect different
  views of what P2PSIP might be.

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P2PSIP

• A suite of communication protocols that extend
  SIP to use peer-to-peer techniques for looking up
  and reaching users and resources.

vs.
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P2PSIP Overlay

• An association of P2PSIP nodes that provides
• 1. User and resource registration (e.g., SIP
  registration)
• 2. Lookup of registration information
• 3. SIP request routing
• . . . and perhaps other functions
• using a peer-to-peer organization.
• For example, if Skype used P2PSIP, then
  skype.com would be a P2PSIP Overlay.

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Two types of Overlay nodes
P2PSIP Peer P2PSIP Client
Participates in and understands the routing topology. Uses the Overlay.
Provides storage and retrieval services to other nodes. Does NOT provide storage and retrieval services to other nodes.
Has a unique identifier in the Overlay. Does NOT have a unique identifer in the Overlay.
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Peer/Clients SIP entity

• Both Peers and Clients may be coupled with a SIP
  entity. Examples
• Peer SIP UA ( Phone)
• Peer SIP Proxy Server
• Peer SIP Registrar
• Client SIP UA ( another Phone)
• Client SIP Redirect Server
• Client Gateway

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P2PSIP Resource (User)

• An addressable user endpoint, entity, service, or
  function within a P2PSIP Overlay.
• Examples include but are not limited to
• Humans, automata, bridges, mixers, media relays,
  gateways, and media storage
• Has a unique identifier within the P2PSIP overlay
  that is presumably equivalent to an Address of
  Record.
• Still under discussion What, if anything, is the
  difference between a resource and a user? And are
  there multiple types of resources or users?

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Enrollment vs Insertion

• Enrollment Gaining a user or peer ID and
  credentials needed to access the overlay.
  One-time operation
• Insertion/Admission Connecting to an overlay and
  adding routing information to that overlay so
  that the inserting node can be found. Multiple
  times.Equivalent to SIP Registration process.

1) Enroll. 2) Insert. 3) Make or take a call.
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Peer vs. Client Protocol

• Peer Protocol Spoken between peers
• Client Protocol Spoken between a Client and a
  Peer
• Client Protocol functionality is a subset of the
  Peer Protocol functionality.
• gt Anything a Client can do, a Peer can also do.
• Client Protocol and Peer Protocol may be
  syntactically different.
• E.g., one might be SIP-based, the other XML-based.

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Protocol Comparison
Operation Peer Protocol ClientProtocol
Enroll Peer in Overlay v X
Insert Peer into Overlay v X
Enroll Resource/User in Overlay v v
Insert Resource/User in Overlay v v
Retrieve info about Resource/User from Overlay v v
There may be additional operations not shown here.
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Reference Model
SIP UA A
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Sample Message Flow
SIP Invite

• Client calling a Peer
• Client C sends a query to Peer Q for the
  location of User U.
• Messages are exchanged between peers, and User U
  is determined to reside on Peer F
• Peer Q sends response back to Client C.
• Client C sends SIP Invite message to Peer F.

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Open Issues vs. Design Questions

• Document contains both Open Issues and Design
  Questions.
• Open Issues represent problems with the document
  that we hope to fix soon.
• These are internal inconsistencies.
• Design Questions (section 4 of the document)
  represent major design choices that the WG will
  have to resolve.

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Some Design Questions

• Peer vs Client Protocol Are these the same
  things, or not? Do we really need a Client
  protocol? Are either SIP?
• How to find a media relay? Does it have to be
  network-path optimal?
• How best to arrange NAT traversal?
• Security If peers are untrusted, how do we
  protect sensitive messages flowing through them?
• Credentials. Certs from a CA? Self-signed?
• Bootstrapping. How to start from zero?

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Major changes since -00 (-00 was presented at
ad-hoc in Montreal)

• Removed most short-forms and alternative names.
  Most remaining ones changed to comparisons with
  concepts from general P2P literature. (-03)
• Split concept of P2PSIP Resource Identifier
  into P2PSIP Resource Name (human-readable) and
  P2PSIP Resource Identifier (not human-readable
  and likely a hash value). (-02)
• Added concept of P2PSIP Bootstrap Peer and
  reworked the text is a number of places to make
  the distinction clear (-03)
• Noted the design possibility that the Client
  Protocol might be just SIP and discussed some
  ramifications of this choice (-02)
• Added a discussion of the operations supported by
  the Peer protocol and the Client protocol (-03)

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Major changes (continued)

• Removed mention of "Send" operation in Client
  Protocol (-03), but added related Open Issue.
• New reference model diagram (based on suggestion
  by Spencer Dawkins) which labels every node and
  clarifies usage of Peer protocol vs Client
  protocol (-02)
• Added three message flow examples to illustrate
  expected operation (-02)
• Added four new questions (-01)
• Credential Recovery
• Overlapping Domains
• Hybrid Domains
• Admissions Control

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Major Open Issues

• What, if any, is the difference between a User
  and a Resource?
• Names for various concepts (!!)
• EKR has proposed a third design model (Clients
  are aware of the Overlay structure). How can we
  accommodate this in our framework?
• Need to rewrite certain sections with NATs in
  mind.
• Does every peer support all services? If not,
  then need the concept of searching for a peer (or
  client?) that offers the service.