On Sat, 2019-03-30 at 19:28 +0200, Juha Heinanen wrote: > > I may have lost the point already, but Android phone notices without > much delay when its network connectivity is lost. So does Kamailio > SIP > proxy (no resoponse to TCP keepalives).
That's the key. You have to buy into the concept of TCP keepalives. I don't. I think TCP should just wait and resume my session when things come back. I want my ssh session to survive the VPN (or even Internet connection) going down and just pick up where it left off when it did disappear. TCP keepalives ruin that. > When that happens, Kamailio > automatically un-REGISTERs the SIP client. Which would indeed close the TCP session and drop the TCP queue, preventing any backlog to extend retry timers on a blocked TCP session. > And when Android phone > notices that network connection is re-established, baresip > immediately > reconnects to SIP Proxy and re-REGISTERs its account. Yeah. I get it. It just seems like more work (not for me, granted) to accomplish what UDP accomplishes without it. > I don't see how UDP would work any better in such a situation. It's just that little bit lighter and not racy in not needing to tear down the TCP session through keep-alives. If the PBX wants to INVITE the phone before a keep-alive tears down the TCP session the same problem occurs, so you still have a failure window. Cheers, b.
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