Subject: [SIP] Error response to re-INVITE.

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Wed, 17 May 2000 00:49:17 -0700

When a UAS issues a 400+ response to a re-INVITE, is it signaling that a)
the entire call has been torn down  or b) that only the re-INVITE failed but
the call is still active? I couldn't find anywhere this has been clarified.

Both scenarios have their uses and pitfalls.

The former case allows no room for correction/negotiation of the failed
message component. Problems also arise if one side or one of the
intermediate proxies assumes that the call has not been torn down.

Likewise, if the latter alternative is true, then it is easily conceivable
that a UAC might incorrectly issue an ACK instead of a BYE to the failed
re-INVITE. Now the UAC has torn down the call but the UAS has not. 

I guess you could say that this is simply another reason why the SIP Session
Timer is a good idea. 

Cheers,

Robert.

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From: [email-masked]
Date: Wed, 17 May 2000 13:41:35 +0530

Hi,

The current understanding is that if a RE-INVITE fails - its valid only for
the reinvite and not for the entire call.
i.e. the previous call parameters (and hence the call) are still active.

robert> Likewise, if the latter alternative is true, then it is easily
conceivable
robert>  that a UAC might incorrectly issue an ACK instead of a BYE to the
failed
robert>  re-INVITE. Now the UAC has torn down the call but the UAS has not.

I dont follow you here. Why is this a problem ? the usual
INVITE-FinalResponse-ACK happens here. Both parties know the RE-INVITE
failed and hence the old call proceeds.
The RE-INVITE issuing party as it is needs to send an ACK to the final
response from the other party.
And a BYE  Iguess will be sent only if the calling party decides that if
the re-INVITE fails, then he is not interested in carrying on with the old
parameters.

Regds
Arjun

--
Arjun Roychowdhury @ Hughes Software Systems

"Fairlie-Cuninghame, Robert" <[email-masked]> on 05/17/2000 01:19:17 PM

To:   IETF SIP <[email-masked]>
cc:

Subject:  [SIP] Error response to re-INVITE.

When a UAS issues a 400+ response to a re-INVITE, is it signaling that a)
the entire call has been torn down  or b) that only the re-INVITE failed
but
the call is still active? I couldn't find anywhere this has been clarified.

I guess you could say that this is simply another reason why the SIP
Session
Timer is a good idea.

Cheers,

Robert.