I agree with Brett. I would also like to point out that changing media
and refreshing the session are not mutually exclusive - you may do both
with a single message exchange. So a UAS must not assume a request just
just one or the other.
Also, a UAC may send a reINVITE with the intent of simply refreshing the
session timer, including the same old SDP as before. But the UAS is
still free to update its SDP answer in the response. The UAC must be
prepared for this.
Paul
Brett Tate wrote:
> You can check the origin line of the SDP. If the origin line has not
> changed, the SDP has not changed. I agree it isn't very efficient; however
> you should not need to fully parse the SDP to perform the check. However
> sending a re-INVITE with a non changed SDP isn't just to refresh the
> session, the receiver still needs to check other headers to ensure nothing
> else is potentially changing.
>
> If UPDATE is supported by both devices, sending the UPDATE request is more
> efficient than sending a re-INVITE for a session refresh. The mechanism
> uses less messages and the SDP is not needed.
>
>
>
>>-----Original Message-----
>>From: [EMAIL PROTECTED]
>>[mailto:[EMAIL PROTECTED] On Behalf
>>Of Sumin Seo
>>Sent: Thursday, April 13, 2006 10:53 PM
>>To: [email protected]
>>Subject: [Sip-implementors] re-INVITE
>>
>>
>>Hi,
>>
>>
>>
>>If during a call, UAC sends re-INVITE to change the media and
>>to refresh session, how can we know re-INVITE for session
>>refreshment from re-INVITE for media change?
>>
>>If we can know the purpose of re-INVITE only by checking
>>SDP, I think that is very inefficient way because in worst
>>case, we should check every SDP of re-INVITEs for session
>>refreshment unnecessarily although we never get re-INVITE for
>>media change during a dialog.
>>
>>
>>
>>Thanks in advance for your help.
>>
>>Sumin.
>
>
>
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