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Enhanced Message Session Protocol: Addressing Key Issues and Improvements

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  1. Message Session Open Issues draft-ietf-simple-message-sessions-02 Ben Campbell

  2. Relay Shutdown • Stop Accepting Connections • Reject new requests with 481 • Wait one transaction timeout period for open transactions to complete. • Should we talk about clients reconnecting when this happens?

  3. SEND Failures • When SEND requests timeout, client may re-send content as new request. This may cause duplicates. • Do we want to disallow this? • Do we want to resend with same TR-ID, and suppress duplicates based on TR-ID? • Aki suggests going to contiguous, ordered TR-IDs

  4. SEND Failures • What about cross-session duplicates? • Client has a failure on a session, creates new session, resends on new session. • TR-ID based duplicate suppression would require globally unique TR-IDs… • …and require endpoints to remember TR-IDs from past sessions for some period of time.

  5. Session Purpose • We suggest using distinct sessions for things like large content transfer. • What keeps the other end from sending IMs on the session we intended for file transfer? • Do we need a mechanism to label the session purpose? • MIME type has been suggested, but not granular enough.

  6. Session Teardown at Visiting Relay • Currently done implicitly—no “unvisit” semantic. • Visiting relay destroys session state when its host connection goes away. • Do we need an explicit operation for this?

  7. SEND for Keep Alives • Relay uses SEND requests to determine liveness of a session. • Endpoints periodically generate empty SEND requests if they have no other traffic to send. • Several people have objected to this, and prefer a separate keep alive method. • Relay does not know difference between a “real” SEND and a “keep alive” Send. Adding a new method would change this.

  8. Multiple Digest Algorithms • Currently require a separate challenge per algorithm. • This is also true of HTTP digest. • Do we want to allow multiple algorithm choices be presented for the same challenge? • Multiple challenges possible in same response.

  9. Security Considerations • Cullen wants more specification on TLS certificate usage, and has kindly offered to supply text.  • Aki suggests more discussion of interaction between authentication mechanisms, MiTM attacks on digest, etc.

  10. Clean up MIME usage • Content-type syntax needs cleaning up • Do we need to indicate MIME version? • Should content-type be part of the body? • What about other MIME headers • Content-Disposition?

  11. More Examples • Several have requested more exhaustive use cases. • Should these go in base spec, or separate document? • Suggestions so far • New offer with no change • New offer with MIME type changes • New offer from Visitor (who continues as visitor)

  12. Congestion Issues • Are we “Trashing the Commons?” • Several people have requested more discussion on the congestion aspects. • Please send text!!!

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