asterisk users - Feb 2005 - Problems with SIP invite due to long ping round trips

Hi,

I'm installing asterisk 1.0.5 for a partner in China.
Since the ping round trip takes typically 600 msec, I doubt,
whether voice quality will we satisfying, but that is currently
not my concern.

The problem is, that most SIP phones or software (e.g. SJPhone)
do resend the invite request, after approx 500 msec (measured
by ethereal).

chan_sip from asterisk seems to have a special handling for
duplicate messages (i.e. messages with the same CSeq number)
in order to ignore those messages in certain circumstances.

Unfortunately asterisk doesn't ignore that second invite message
by the client and sends an error message. (Though in the log
files those "Too late messages" are mentioned.)

Does anyone know a solution for the below shown scenery?
Thanks for any hints!
Roger.


By the way:
Registration succeeds without any problems.


Following is the invite scenery:

Client side        <- approx 300 msec ->          asterisk
(Germany)                                         (China P.R.)

Invite             ->
(CSeq=1)
                                     ->  Invite arrives
                                         (CSeq=1)
                                     <-  407: need authorization
                                         (CSeq=1)
Resend Invite      ->
(CSeq=1)
407 arrives        <-
(CSeq=1)
Ack CSeq=1         ->
Invite with auth.  ->
(CSeq=2)
                                     ->  Resent Invite arrives
                                         (without auth)
                                         (CSeq=1)
                                     <-  503: Not available
                                         (CSeq=1)
                                     ->  Ack CSeq=1 arrives
                                     ->  Invite with auth. arrives
                                         (CSeq=2)
                                     <-  407: need author.
                                         (CSeq=2)
Resent Invite w.a. ->
(CSeq=2)


...
(Repeated approx 10 times than fails.)