[Users] 408 error

[unplug]

In what case the server will issue 408 error.
An user can make call without problem.  He also can receive call but
the call will be dropped automatically around 50 seconds.  From the
log below, a 408 request timeout (line682) is created and then the
call is dropped.

http://fisher.no-ip.com/ngrep/ngrep6667871.log

>From the document, the server will create 408 when it can't produce a
response before a given time out.  But in this case, I don't know why
it creates such error only for this user and not for other user.

Could anyone can tell me why the server create such error message?

Thanks!