Inline
On 3/17/12 1:44 PM, Nataraju A.B wrote:
> Hi All,
>
> Following is the excerpt from the RFCs 3261 and 6337, with respect to
> Answer being carried in Reliable-1xx and 2xx-INV
>
> <3261>
>
> o If the initial offer is in an INVITE, the answer *MUST *be in a
Note the last word above is "a", not "the first".
> reliable non-failure message from UAS back to UAC which is
> correlated to that INVITE. For this specification, that is
> only the final 2xx response to that INVITE. That same exact
> answer MAY also be placed in any provisional responses sent
> prior to the answer. The UAC MUST treat the first session
> description it receives as the answer, and MUST ignore any
> session descriptions in subsequent responses to the initial
> INVITE.
>
> </3261>
>
> <6337>
>
> In Pattern 3, the first reliable provisional response *may or may not*
> have an answer. When a reliable provisional response contains a
> session description, and is the first to do so, then that session
> description is the answer to the offer in the INVITE request. The
> answer cannot be updated, and a new offer cannot be sent in a
> subsequent reliable response for the same INVITE transaction.
>
> </6337>
>
> Looks like rfc6337 is little bit deviating from 3261's intention.
> rfc6337 - may or may not requirement for carrying answer in reliable 1xx
> rfc3261 - MUST requirement for carrying answer in 2xx/reliable
> non-failure response
>
> Am I missing something here ????
Yes.
When the offer is in the invite, the answer must be in a reliable
response, but it need not be the first reliable response. 3261 says this
and 6337 restates it in a way that is hopefully clearer.
I think you are mixing this up with the prior paragraph in 3261:
o The initial offer MUST be in either an INVITE or, if not there,
in the first reliable non-failure message from the UAS back to
the UAC. In this specification, that is the final 2xx
response.
Namely, its when there is no offer in the INVITE that it must be in the
*first* reliable response. This is covered by patterns 2 and 4 of 6337.
Thanks,
Paul
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