Lun,

The registrar should create a servertransaction for the REGISTER, which 
would handle retransmissions. Upon a retransmission it would repeat the 200 
OK response that was sent

Regards,
Jeroen

Lun Tong wrote:
> In rfc3261 section 10.3, item 6
>
> 6. The registrar checks whether the request contains the Contact
>         header field.  If not, it skips to the last step.  If the
>         Contact header field is present, the registrar checks if there
>         is one Contact field value that contains the special value "*"
>         and an Expires field.  If the request has additional Contact
>         fields or an expiration time other than zero, the request is
>         invalid, and the server MUST return a 400 (Invalid Request)
>         and skip the remaining steps.
> <start here>
>         If not, the registrar checks whether
>         the Call-ID agrees with the value stored for each binding.  If
>         not, it MUST remove the binding.  If it does agree, it MUST
>         remove the binding only if the CSeq in the request is higher
>         than the value stored for that binding.  Otherwise, the update
>         MUST be aborted and the request fails.
> <end here>
>
> Reading through start to end, my understanding is: if Call-ID agrees,
> then check CSeq. If CSeq is less or equal than the value stored for
> that binding, the update MUST be aborted and the request fails.
>
> I used cisco 7960 phone. When a REGISTER was sent by that phone, the
> registrations was successful. But the 200 OK to the phone was lost.
> As the phone did not get response, it retransmited the REGISTER with
> the same CSeq. On the server side, the binding was already there and
> the retrans' CSeq was not higher. So this request failed. Then the
> phone never knows it is registed and made bunch of retrans, and
> finally display that the line is disconnected.
>
> So I just modified the server and let it accept this case.
> Hope my modification is correct.
> Thanks!
> Lun
>
>
>
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