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List:       sip-implementors
Subject:    Re: [Sip-implementors] How to determine a Session Refresh Request(re-INVITE)?
From:       Paul Kyzivat <pkyzivat () cisco ! com>
Date:       2004-10-27 18:26:03
Message-ID: 417FE83B.3050808 () cisco ! com
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Manish wrote:
>  >I think, that each re-INVITE should contain the SIP session timer
>  >parameters and, as Paul said, each of these re-INVITE's is a "session
>  >refresh". If you don't do this, you'll end up sending more re-INVITE's
>  >than is necessary
> Antilla, I agree totally on this. I am just talking about reinvites 
> which are just intended for session refresh. I just mentioned that an 
> identifier for this refresh invites will make the processing light 
> weight. It will be independent of session descriptor type. For ex for 
> SDP one might use 'o' field to reduce media descr processing. But as 
> Paul mentioned, the draft is not going to change on this, may be we have 
> to live with the little extra processing and handle inherent 
> complexities in other ways.

If your goal is just to eliminate need to parse the SDP, you can simply 
build a special pre-parser that just looks for the o-line. If that has 
not changed, then you don't have to parse the SDP - it is same as prior.

This does not mean that this request was generated as a session timer 
refresh. But it is a request that hasn't changed its offer. If you feel 
you can simply respond with the prior answer in this case then you have 
simplified things.

You do still have to check for *other* changes that might have occurred. 
For instance, the Contact address might have changed. If so you must 
deal with that.

	Paul


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