[SIPForum-discussion] Loose routing, strict routing

[Amit Limaye]

RFC 3261 introduces two types of routing: strict and loose routing.
Strict routing, a proxy must use the first URI in the Route header field to rewrite the Request-URI, which is then forwarded. In loose routing, a proxy does not re-write the Request-URI, but either forwards the request to the first URI in the Route header field or it may forward the request to another loose routing element.  strict routing, the request must only route through the set of
servers in the Route header field with the Request-URI being rewritten at each
hop. A proxy or UAC can tell if the next element in the route set supports loose
routing by the presence of a lr parameter. An example is:
Route: <sip:proxy at xyz.com;lr>

Route: <sip:firewall33.corporation.com;lr>,
<sip:proxy1.carrier.com;lr>
Route: <sip:139.23.1.44 ;lr>


Ioose routing, the request must route through every server in the Route list
(but may also route through other servers) before it may be routed based on the
Request-URI. In
The lr parameter is new to RFC
3261 and indicates that the proxy server supports “loose routing.” Older RFC
2543 compliant proxy servers create Record-Route URIs that instead of the
lr parameter often contain the maddr parameter with an address or host that
resolves to that proxy server.
Examples are:
Record-Route: <sip:proxy1.carrier.com;lr>,
<sip:firewall33.corporation.com;lr>
Record-Route:<sip:139.23.1.44;lr>

If you don't use the "lr" parameter, you are using
"strict routing" and the routing rules in RFC3261
do not apply.






Regards
Amit Limaye
VOIP Engineer






Raghul Prasanna <raghul82 at yahoo.co.uk> wrote: Hi All,
  
 Can anyone tell me the difference between Loose and Strict Routing please?
  
   RFC 3261 says that a proxy is said to be loose routing if it follows the procedure stated in that doc...
  
   Can somebody say what procedure the above definition means please?
  
 Also if the record route does not have lr parameter does it mean that if follows Strict routing? 
  
 Please explain.
  
 Thanks,
 Raghul
  
  
  
  

          
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