Hi Jun, In an ongoin session ,loss of connectivity wld b detected rapidly by the absence of media packets, typically sent at a much higher rate than any signaling keep-alive mesgs could be sent. In addition, the signaling path is not needed during the conversation and may well be completely different (due to proxy and redirect servers) than the media path, so that keep-alives have a limited functionality. If it is desired to test the liveness of a signaling server, it is always possible to send either OPTIONS or (re)INVITE messages, mentioned by u as well..........
However, knowing the call state might be useful for certain applications (e.g., when billing is involved, when firewall permissions need to be set etc.). Session timer extension has been defined to solve this.... u may find draft draft-ietf-sip-session-timer-01.txt and it basically allows the servers indicate a desired refresh interval. The call is considered terminated if a re-INVITE is not received within that interval. Regards Vishal > >Hi, >To make sure the connection between two - somtimes more than two - parties, >keepalive machanism such as a "ping" is required. >I'm told that there're a couple of ways of doing this in the SIP networks. >1. OPTIONS (between Proxy Servers ?) >2. REGISTER (between Registrar and UA ?) >3. session timers >4. STUN or TCP CR/LF (Firewall case ?) >And I wonder if more ways would be there. >Which way, by the way, do you think the best ? and which one is the most >popular way in the real SIP networks ? >Thanks in advance, >Jun > *********************** FSS-Unclassified *********************** "DISCLAIMER: This message is proprietary to Flextronics Software Systems Limited (FSS) and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. FSS accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus." _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
