[SIPForum-discussion] routing of sip messages

[Paul Kyzivat]

On 7/23/14 3:02 AM, mohit gupta wrote:
> Hi,
>
> Just wondering in what scenarios can ROUTE header and RECORD-ROUTE
> header come together in a sip message, if at all ?
> Is there any other provision to change the route after it is set for a
> dialog ?

Route is used to control the path followed by the request containing it.

Record-Route is used in dialog-establishing requests and responses to 
select a Route to be used for subsequent requests within that dialog.

Yes, Route can be used to control the path of a dialog-establishing 
request, and Record-Route can be used within that to determine the Route 
to be used subsequently within the dialog.

Carrying that further, there is also Service-Route (RFC3608), which is 
similar to Record-Route but used with REGISTER rather than 
dialog-establishing requests.

So you might do your initial registration, and get a Service-Route in 
response. You would then use that Service-Route to initialize the Route 
header of subsequent out-of-dialog and dialog-establishing requests. 
Those requests in turn may yield Record-Route headers that are then used 
to initialize the Route header for in-dialog requests.

And of course you could use a Route header in the REGISTER too.

	Thanks,
	Paul