[SIPForum-discussion] Regarding Route Header

Tomasz Zieleniewski tzieleniewski at gmail.com
Wed Jun 10 08:15:02 UTC 2009


Route header is used by UAC cores (initiator of the request) to force
downstream request
routing, through the provided list of intermediary nodes. For for instance
outbound SIP Proxy

The Record-Route header is inserted into the dialog creating requests by
nodes (proxies) to force future requests sent within this dialog to be
routed through this set of proxies,
so called "route set". Ofcaurse if there are no Record-Route headers route
set is empty.
Route set is established during dialog creation and it can not be changed
later on
during further dialog transactions. When UAS receives initial dialog
creating request with a list of
Record-Route headers it constructs a route set and any further request sent
within this dialog will
initially contain a list of Route headers build from the previously received
Record-Route list.
Similarly UAC but in this case UAC will receive a route set in the dialog
creating response (both early and final).
Any further request sent by UAC  within this dialog will initially contain a
specific list of Route headers.

So usage of Route header is a general behaviour compliant with RFC3261
called loose routing,
 and Record-Route mechanizm simply utilizes the Route header functionality.

Kind regards,
-Tomasz Zieleniewski

2009/6/9 SIP Babie <sipbabie at gmail.com>

> Hi All,
> I am  newbie to SIP.
> I will like to know the whats the difference between Route & Record-Route
> header?
> And also whats the significance of Route header.
> I know Record-Route header is been added by proxies, so that all the
> further SIP messaging will be passed via
> proxies after an initial INVITE. I would like to know who adds Route header
> and how Route header are been manipulated by proxies.
> Regards,
> babie
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