IMSX Protocol Evaluation for Session Based IM draft-barnes-simple-imsx-prot-eval-00.txt Mary Barnes IETF 54 SIMPLE WG

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt Overview  Overview of analysis  General conclusions  Other Disadvantage/Advantages of IMSX  Related mailing list discussions

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt 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).

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt 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.

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt 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.

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt 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.

July 17th, draft-barnes-simple-imsx-prot-eval-00.txt 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).