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IETF 54 SIMPLE WG. IMSX Protocol Evaluation for Session Based IM draft-barnes-simple-imsx-prot-eval-00.txt Mary Barnes (mbarnes@nortelnetworks.com). Overview. Overview of analysis General conclusions Other Disadvantage/Advantages of IMSX Related mailing list discussions.
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IETF 54 SIMPLE WG IMSX Protocol Evaluation for Session Based IM draft-barnes-simple-imsx-prot-eval-00.txt Mary Barnes (mbarnes@nortelnetworks.com)
Overview • Overview of analysis • General conclusions • Other Disadvantage/Advantages of IMSX • Related mailing list discussions
Overview of analysis • Evaluates the suitability of the IMSX protocol as a transport for Session Based IM. • IMSX (draft-mrose-simple-exchange-01) defines a BEEP (RFC 3080) profile for exchanging CPIM messages after SIP has performed its session setup signaling. • Compares IMSX against the IMPP requirements (RFC 2779) . • Compares the ability for IMSX to interoperate with other IM systems based upon the CPIM profile (draft-ietf-impp-cpim-02). • Discusses IMSX with regards to the Guidelines for Instant Message Sessions (draft-mankin-im-session-guide-00).
General Conclusions • IMSX meets the majority of the CPIM requirements with the exception of the Network topology requirements, which were beyond the scope of the original design intent of BEEP: • Middlebox traversal (NATs and FIREWALLS) for IMSX is a requirement that is currently not specifically addressed by BEEP. However, it is deemed equivalent to and addressed by the same mechanism which would be used for TCP based SIP media. • IMSX does not address the proxy or relay requirements for support of IM. However, a solution to this requirement is not beyond the scope of BEEP. • Related to these requirements, as evaluated against the IM Session Guidelines, the IMSX/BEEP IM Session solution does not fully address intermediaries.
Additional Disadvantages of IMSX • Beyond the identified requirements, which are not fully met, additional disadvantages of IMSX as the Session IM protocol are: • BEEP does not currently support threading. • Requires the development and support of a new protocol for most existing SIP implementations.
Additional Advantages of IMSX • A user can use a single TCP connection for multiple IM Session connections to the same user. • Several channels may be multiplexed over the same TCP connection having different characteristics. • For this model of a single TCP connection, interleaving provides a fair share of the use of connection to support the multiple types of media.
Mailing List Discussion on IMSX/BEEP • One Pro IMSX/BEEP posting: “I personally lean towards the mrose approach. BEEP does a decent job of the message delivery operation. It allows standardized relay elements to be added as needed and provides for a sort of path-discovery that would appear to be beneficial in firewall traversal scenarios. It provides a nice layering distinction between "can I talk to you" and "may I talk to the network".” • One Con IMSX/BEEP posting: • “have to administer two very different types of devices, with different (and, in the case of mrose, undefined) network management.” • Doesn’t see the advantages to mrose wrt "standardized relay elements to be added as needed". What can be added there that can't be added in simple-message? • One proposal to progress IMSX as informational, with message-session being the WG document (standards track).