Dale,
You are right and I found example from RFC3621
16.12.1 Examples
16.12.1.1 Basic SIP Trapezoid
.....
U1 sends:
INVITE sip:[email protected] SIP/2.0
Contact: sip:[email protected]
..............
Since all the route set elements contain the lr parameter, U1
constructs the following BYE request:
BYE sip:[email protected] SIP/2.0
Route: <sip:p1.example.com;lr>,<sip:p2.domain.com;lr>
....................
*Thanks a lot!
Frank*
On Wed, Jul 25, 2012 at 11:06 AM, Worley, Dale R (Dale)
<[email protected]>wrote:
> On Wed, 2012-07-25 at 10:43 -0500, fuliang yuan wrote:
> > I assume that it is legit for Proxy or UAS to add R-R of other nodes
> in
> > Response based on your comments.
>
> I am not sure exactly what you mean. The proper pattern of Record-Route
> header usage is:
>
> 1. The UAC generates the request without any Record-Route headers.
>
> 2. As the request passes through proxies, the proxies add Record-Route
> headers if they desire to do so.
>
> 3. The UAS receives the request and saves a copy of the Record-Route
> headers. It copies the Record-Route headers into any responses it
> generates.
>
> 4. The responses pass through the proxies back to the UAC. The
> Record-Route headers in the response are usually not modified, and in
> particular, no proxy adds a Record-Route to a *response* (although the
> response may be carrying a Record-Route header that is a copy of one
> that the proxy added to the *request*).
>
> 5. The UAC receives the response and saves a copy of the Record-Route
> headers.
>
> There are some complications:
>
> Because the actual UAs may contain "internal" proxies, the UAC may send
> a request that already contains Record-Route headers. Similarly, the
> UAS may add Record-Route headers to a request that it receives before
> carrying out step (3).
>
> Similarly, a proxy may add two or more (necessarily consecutive)
> Record-Route headers to a request during a single pass of the request
> through the proxy. In principle, this is modeling the proxy as a series
> of proxies.
>
> In some circumstances, a proxy may need to change the value of a
> Record-Route header in a response, when the Record-Route header is a
> copy of one that the proxy added to the request. This is called
> "Record-Route rewriting" and is discussed in RFC 3261 section 16.12.1.3.
>
> Since a request may pass through the same proxy more than once during
> its journey to the UAS, one proxy may add several (not necessarily
> consecutive) Record-Route headers to a request.
>
> To summarize:
>
> The UAS adds Record-Routes to the response, but those headers are always
> a copy of the Record-Routes received in the request.
>
> A proxy never adds Record-Routes to a response, although the response
> may contain a copy of a Record-Route that the proxy added to the
> request.
>
> Dale
>
>
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