Re: [Sip] two questions for route information preprocessing of initial INVITE with Route headers

["Scott Lawrence" <scott.lawrence at nortel.com>]

On Fri, 2009-09-18 at 13:46 +0800, ding.xuexin at zte.com.cn wrote:

> I have two questions for route information preprocessing of initial INVITE
> with Route headers

These questions would be more appropriate on the sip-implementors
<sip-implementors at lists.cs.columbia.edu> mailing list.

> first question:
> 
> UA(or B2BUA) receives an initial INVITE with Route headers, assuming UA's
> host is example.com
> 
> if the sip entity which sends the INVITE is a loose router, the INVITE may
> be like this:
> 
>    INVITE sip:bob at example.com
>    Route: <sip:xx at example.com;lr>
> 
> if the sip entity which sends the INVITE is a strict router, the INVITE may
> be like this:
> 
>    INVITE sip:xx at example.com
>    Route: <sip:bob at example.com>
> 
> we cannot distinguish those two scenarioes because Requet-URIs in two
> scenarioes are similar.
> if we do route information preprocessing according RFC3261 section 16.4, we
> will get two different
> results. And there is no desciption for UA route information preprocessing
> in RFC3261, RFC3261
> section 16.4 just describes proxy behavior.
> 
> How to processing route information of initial INVITE with Route headers
> for UA?
> 
> 
> second question:
> 
> as RFC3261 section 16.4 descibed, proxy must check whether the request-uri
> was placed by the
> proxy previously. But the request-uri in initial INVITE must not be placed
> by the proxy previously.
> 
> Is something wrong with RFC3261 section 16.4?