Message Sessions by ewghwehws


									        Message Sessions

Ben Campbell (
●   We've been may places
    –   MESSAGE dialogs
    –   IMTP proposal
    –   Cpimmsg-sessions with COMEDIA (most recent)
    –   And now...MSRP
Message Session Relay Protocol
●   Attempts to solve COMEDIA related
    problems in previous drafts.
●   Design effort from Paul Kyzivat, Robert
    Sparks,Jonathan Rosenberg, and Ben
●   Builds on work from message sessions
    design team discussed in Atlanta.
Message Session Relay Protocol
●   Similar to cpim-msg approach:
    –   Congestion-safe, connection-oriented transports.
    –   Arbitrary MIME payloads (including
●   But different:
    –   No COMEDIA dependency
    –   Supports 1 and 2 NAT scenarios
    –   Supports common firewall policies
    –   Connections may carry multiple sessions.
        The Trouble with COMEDIA
●   Limited support for bidirectional connections
    –   No good way to associate an inbound
        connection with a session
    –   Cannot use source address/port to identify
        connections due to NATs.
                Relay Support
●   Explicit support for zero or one relay
●   At least one endpoint must have a pre-
    existing relationship with the relay
●   Implicit support for dual relay scenario
                 MSRP Structure
●   Primitives
    –   BIND (RELEASE) -- establishes session state at
        a relay
    –   VISIT (LEAVE) -- associates a connection with a
    –   SEND -- sends a message
●   Host/Visitor endpoint concept
    –   Visitor connects to Host...
    –   ...or to a relay operating on behalf of the Host.
                  Open Issues
●   ACK related Bug in offer/answer handling
    –   May be able to handle with UPDATE
●   Do we need a refresh mechanism for BIND
●   Race condition when tearing down a session.
                   Open Issues
●   Need to fully define MSRP: URI scheme.
●   SDP encoding mechanism requires the host
    and visitor temp URIs to share the same
    –   Probably ok, since both represent resources at
        the same host device.
                       Open Issues
●   Additional work needed for security
    –   Digest authentication on BIND not fully specified.
    –   Do we need an msrps: URI scheme?
    –   Needs more work on end-to-end security
         ●   Session key exchange using MIKEY
         ●   Fitting in S/MIME
         ●   Protection across CPIM gateways.

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