I think that a transaction stateful proxy should forward retransmitted INVITE as a new INVITE request. The INVITE transaction at the proxy will be later ended by retransmitted 200 OK response from the UAS or by a timer expiration.
Mitko
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Marc
Petit-Huguenin
Sent: Tuesday, April 13, 2004 10:57 AM
To: [EMAIL PROTECTED]
Subject: Re: [Sip-implementors] 200 INVITE lost
So, does someone know what should be done in this case for a transaction
stateful proxy?
Thanks.
Marc Petit-Huguenin wrote:
>
> [EMAIL PROTECTED] wrote:
>
>>> An UAC sends an INVITE to an UAS. The UAS responds with a 200 (no 1xx
>>> was sent, or the 1xx was lost), but the 200 is lost in the network.
>>> In this case the UAC will retransmit the INVITE until a 200 is
>>> received, and the UAS will retransmit the 200 until an ACK is
>>> received. What is not clear is what the UAS must do with the
>>> retransmitted INVITE received. The transaction is gone, so the INVITE
>>> is received directly by the TU. Bug654[1] says that a 500 must be
>>> sent, but it looks like a bad idea, as the 200 can still be
>>> retransmitted and received by the UAC. A better alternative would be
>>> to simply discard the INVITE that have a sequence number equals to
>>> the remote sequence number; the 200 will be retransmitted and
>>> hopefully the UAC will send an ACK to the UAS.
>>>
>>
>>
>> Discarding the INVITE is the correct thing to do.
>>
>>> Another related problem is when there is a stateful proxy between the
>>> UAC and the UAS. If the 200 is lost between the UAC and the proxy,
>>> then what the proxy must do with the retransmitted INVITE?
>>
>>
>>
>> I think here you mean the Proxy is call stateful. In this case,
>> the proxy must have a similar logic as the UA for doing
>> retransmissions of 2xx. Hence the INVITE which matches a dialog
>> but has the same Cseq can be discarded.
>
>
> Ok, but what about a transaction stateful proxy? There is no dialog to
> match, so how to discard the retransmitted INVITE?
>
>>
>>
>>> Thank you for your responses.
>>>
>>>
>>> [1] http://www.sipwg.org/sipwg/show_bug.cgi?id=654
>>
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