Hi,
>
> I guess it depends on whether sending an early-session SDP offer
> "fulfills" the requirement to send an SDP offer in the first
> reliable response.
It's OK if the first reliable 18x with early media fulfill the requirement.
>
> If it does, is it then allowed to complete the whole INVITE
> transaction with only an early-session SDP offer/answer?
I think there must be normal session offer/answer exchange if the final response
is 2xx, but if the final response is 3xx-6xx as INVITE fails, an early-session
SDP offer/answer on the purpose of failure-notice is enough.
Then, if the INVITE carrys NO SDP ,the first reliable response generator must
fill the response with at least one SDP(early-session, or normal session, or both).
There must be at least one normal session offer/answer exchange if the final response
is 2xx.
Regards,
Eric
>
> Regards,
>
> Christer
>
> From: wang.libo@xxxxxxxxxx [mailto:wang.libo@xxxxxxxxxx]
> Sent: Thursday, April 02, 2009 9:25 AM
> To: Christer Holmberg
> Cc: Hisham Khartabil; Sanjay Sinha (sanjsinh); sipping@xxxxxxxx;
> sipping-bounces@xxxxxxxx
> Subject: Re: PRACK: Change MUST requirement to include SDP
> offerin first reliable provisional response
>
> Hi,
>
> Considering early-session, if the UAS receives an INVITE without SDP,
> before transmit it,the UAS wants to play a tone with early-session in order
> to inform the caller the call is ongoing.The UAS may have no rule to
> generate a normal session SDP.Unless UAS creates a fake one e.g with
> ip 0.0.0.0.
>
> UAC UAS
> |--------INVITE----->|
> |<-----183(early)----|-----INVITE-->
> |-----PRACK(early)-->|
> |<--------200--------|
>
>
> Regards
> Eric
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