Re: About offeranswer draft:

HI Shinji,

  I noticed the chart in your mail showed ,SDP4 and SDP5 both exist in
reliable response(1xx-rel). In my mind, no matter SDP5 is offer or answer,
it shouldn't be allowed.

     UAC                   UAS
      | F1  INVITE (SDP1)   |  <-- offer
      |-------------------->|
      | F2     1xx (SDP2)   |
      |<--------------------|
      | F3     1xx (SDP3)   |
      |<--------------------|
      | F4 1xx-rel (SDP4)   |  <-- answer
      |<--------------------|
      | F5 1xx-rel (SDP5)   |
      |<--------------------|
      | F6    1xxl (SDP6)   |
      |<--------------------|
      | F7  2xx INV(SDP7)   |
      |<--------------------|
      | F8     ACK          |
      |-------------------->|
   (PRACK transactions are not shown)

Shinji: Just you said "different SDPs(compare with the answer) can
exist in non-reliable response and final 2xx response".
Eric:  I mean different SDPs may appear in non-reliable response,because
some SERVER may use 1xx with SDP
to play some announcements before foward a call, eg a charge server "HI guy,
you have only 5 minute to communicate",
or, a redirect server "the call is forwarding"!   If the server want to use
reliable response, it must use re-INVITE after
the call is established ,for the SERVER cannot send the SDP in final
response from UE-B to UE-A.But if the SERVER
use non-reliable response, the SERVER may use final response to carry SDP.

UE-A       SERVER     UE-B
| - INVITE -> |                |
 | <-18x-------- |                |
 |                  | -INVITE ->|
|                  |                |


BR

Eric

_______________________________________________
Sipping mailing list  https://www.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email protected] for questions on current sip
Use [email protected] for new developments of core SIP