Re: [Sipping] About offeranswer draft:

[Eric wang <eric.wangxr@xxxxxxxxx>]

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

 

 

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