Subject: [Simple] draft-ietf-simple-message-sessions-03

From: "Orsic, Milo (Milo)" <[email-masked]>
Date: Thu, 25 Mar 2004 16:46:55 -0600

Ben,
Currently the draft-ietf-simple-message-sessions-03 specifies two message-primitives: VISIT and SEND. As the 3GPP user of the draft I would suggest that the authors consider to add an additional message-primitives, e.g. "END", that could be sent by either endpoint over the TCP connection to terminate the message exchange. The endpoint that receives the END would know that there are no messages following the END that will be received (and will have to be acknowledged). Hence, it would put the 200 OK (to END) into its outgoing  TCP buffer (behind all acknowledgements), and it would not send any new messages. Likewise, the END-sending endpoint, upon receiving the 200 OK (to END) would know that there are no messages following the 200 OK that will be received (and will have to be acknowledged). Hence, the END-sending endpoint would close the TCP connection toward its peer. Subsequently, the peer would also close the TCP connection. The message loss due to synchronization problem!
  between SIP signaling (BYE) and message sending would be eliminated. In addition, by using the END message-primitive:
1.) We would NOT violate the semantics of the BYE, as stated in RFC326 1 (15.1.1):
"The UAC MUST consider the session terminated (and therefore stop sending or listening for media) as soon as the BYE request is passed to the client transaction." The usage of BYE in the draft-ietf-simple-message-sessions-03 is "usage-specific", since -upon sending the BYE - the TCP connection is kept open and used "for a while."
2.) We could keep the dialog (and associated sessions for other media, if any) alive. Since the BYE in the draft-ietf-simple-message-sessions-03 is used to terminate the message exchange, the side effect is that the dialog (and associated sessions for other media, if any) has to be terminated.
etc.
Please consider.

Cheers,
Milo 

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