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List:       sip-implementors
Subject:    Re: [Sip-implementors] 100Rel from UAS
From:       "Dale Worley" <dworley () nortel ! com>
Date:       2009-06-24 19:14:13
Message-ID: 1245870853.3748.37.camel () victoria-pingtel-com ! us ! nortel ! com
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On Wed, 2009-06-17 at 17:10 +0400, Kashin Mihail wrote:
> Hi, everybody!
> 
> Is it legitimate for UAS to request reliable provisional response
> option after receiving INVITE without Required or Supported headers.
> 
> In my case the flow is like this
> 
>  
> 
> Inv (no 100Rel*)->
> 
> <-100 Trying
> 
> <- 180 Trying (no 100Rel)
> 
> **
> 
> <-INFO (Required:100Rel)
> 
> 200OK(no 100Rel)
> 
> ............
> 
>  
> 
> *   - Means no 100Rel indication in the message
> 
> ** - At this moment UAS (which is actually a B2BUA) establishes a
> session with another proxy where it uses 100Rel and now it is trying
> to "back-enable" 100Rel in our call leg.
> 
>  
> 
> So is it OK for UAC to answer 200OK to INFO without 100Rel indication?
> Or should it send 200OK with Req:100Rel and then initiate reliable
> prov. Response procedure?

First, there is no reason to consider 100rel to be a feature of the
dialog or call leg.  In principle, it is applied to each request
individually.

In practice, the only requests that get provisional responses (other
than 100) will be INVITEs that establish dialogs.  So there is no reason
to consider 100rel except in the context of an initial INVITE.

Dale



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