[Serusers] SER losing SIP registrations

[Jan Janak]

On 22-06-2005 17:57, Juan Carlos Castro y Castro wrote:
> Our company has a call center implementation on a client with up to 100
> support personnel using X-Lite version 1050 softphones running under
> Windows 98. Until a few days ago, the softphones were logged in directly
> on our PBXs. Now, they log onto a separate SER 0.8.14 box and the PBXs
> forward calls to SER. That was needed to unify queue management.
> 
> It works. But some softphones are being randomly kicked out of SER, it
> seems SER isn't receiving the refresh REGISTER messages from the
> softphones. The re-register timeout is set to 500 seconds on the
> softphones. There's a lot of "removing spare zombie" and "Binding
> '<user>','<url>' has expired" messages in /var/log/messages.

  The message means that SER did not receive REGISTER re-fresh and is
  thus removing the contact from the user location database.

  Pick one user agent that has this problem and install ngrep monitor on
  the server to monitor all REGISTER messages from that user agent. This
  way you could find out if the problem is in the user agent or network
  (in this case you will not see REGISTER refresh messages on the
  server) or in SER (in that case you will see them but SER probably
  fails to process them).

  Also make sure that SER is not configured to shorten the registration
  period. When registrar receives a REGISTER message, it is free to use
  shorter expires value for the Contac than what was suggested by the
  user agent in the request. In this case the real expires value of the
  contact will be in 200 OK and user agents are suppose to pick it up
  from there and update the refresh interval accordingly. This may not
  work in the case when Contact IP address is rewritten by the server
  for the purpose of NAT traversal. In this case the user agent will be
  unable to find its contact (because it has been rewritten) and will
  not update the refresh interval (resulting in expired registrations).

> For now, we're instructing the client to increase the timeout to 10
> hours on the softphones in which the problem happens most often. I don't
> know if that's really the right thing to do, I think we should somehow
> make sure the re-registers are done in a timely fashion and retried, but
> I could not find ant SER configuration option related to that. What
> should I do?

  You can configure the maximum allowed expires value in SER, if a user
  agent tries to REGISTER a contact with longer expires value than it
  will be automatically updated by registrar to the value of max_expires
  parameter.

  There is also min_expires parameter in registrar module but that one
  should not be used because the current implementation violates
  RFC3261.

  If you are using any of the two parameter than it might be a good idea
  to retry without them (to see if the problem persists).

    Jan.
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