Hi Yuantao
I'm SunYongGuang, my msn is [EMAIL PROTECTED]
it is ok,
"If the initial offer is in an INVITE, the answer MUST be in a
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. "
Does that mean if "Invite" contains SDP offer, "200 OK" MUST contain SDP
answer.
"the answer MUST be in a reliable non-failure message from UAS back to UAC
which is
correlated to that INVITE" in your scenario , the 180 with 100rel is
reliable non-failure message and it includes SDP, the offer/answer is
completed, so the 200 response may include SDP or not, please refer RFC3262
2008/5/22, Yuantao Zhang <[EMAIL PROTECTED]>:
>
> Dear Sir or Madam
>
> I am an R&D engineer in Ericsson and really confused by the following
> part in RFC_3261. Could you please help us to explain it? Thank you very
> much.
> "
> 13.2.1 Creating the Initial INVITE
> .
> .
> .
> If the initial offer is in an INVITE, the answer MUST be in a
> 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.
> .
> .
> ."
>
> Let's break it into 2 parts, in part 1,
> "If the initial offer is in an INVITE, the answer MUST be in a
> 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. "
> Does that mean if "Invite" contains SDP offer, "200 OK" MUST contain SDP
> answer.
>
> In part 2,
> "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."
> Does that mean if "Invite" contains SDP offer, the answer SDP MAY be in
> "180 ring" and not in "200 OK"? I think part 1 and part 2 are
> inconsistent.
>
> The attached sequence chart is the real problem we meet. Sx1 sends "bye"
> to sx2 after the "200 OK" because there is no SDP answer in "200 OK".
> But the producer of sx2 argues that the SDP answer is in "180 ring"
> already. No need to repeat it in "200 OK". Could you please tell me who
> is right? MUST 200 OK contain SDP? Thank you very much.
>
> Sx1 xs2
> ====1 invite(SDP) ====>
> <====2 100 trying ====
> <====3 180 ringing(SDP)====
> ====4 prack ====>
> <====5 200 ack ====>
> <====6 200 OK (no SDP)====>
>
>
>
> Best Regards
> Yuantao Zhang
>
> I&V Engineer
> Broadband Networks R&D Center
> Ericsson (China) Company Ltd.
> Ericsson Tower Phone :+86 10 8476 7240
> No. 5 Lize East Street Internal:11240
> Chaoyang District Fax :+86 10 8476 7738
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> http://www.ericsson.com e-mail :[EMAIL PROTECTED]
>
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