[SIPForum-discussion] How to use lr parameter in URI

[hemanth kumar]

Please find my answer inline
   
  Regards
  Hemanth
  

harish T <harish0611 at gmail.com> wrote:
  Thank you Hemanth,

  case 2: (Based on your explanation ,Can i conclude like this )


   if second URI contain lr parameter then 
 <sip:proxy1>,<sip:proxy2;lr>,<sip:proxy3>,<sip:proxy4>,<sip:user at remoteua>  

For 2nd hop will this request formate correct

  METHOD <sip:user at remoteua>(removing 2nd URI from Record route,and placing  end point info in Request URI )
Route: <sip:proxy3>,<sip:proxy4>,<sip:user at remoteua >

  Since Proxy1 is a strict router, It adds Proxy2's info in the Request URI and forwards it to Proxy2.
  When the message reaches Proxy2, As it finds it entry in the Request URI, It looks into the next hop in the route set.
  As Proxy3 is a strict router, It updates the Request URI with Proxy3's info and removes it from route set.
   
  So <sip:user at remoteua> would be added in the Request URI only by the last hop(Proxy4).
   
  NOTE: Strict Router does not do any checks on what is the next hop. It is only the loose router which does the evaluation.
   
  Hope this answers your question
   
For 3rd  hop will this request formate correct

METHOD <sip:proxy3>
Route: <sip:proxy4>,<sip:user at remoteua>






  On 2/15/07, hemanth kumar <cyhk007 at yahoo.com> wrote:    Hi
   
  Please find my answers inline

harish T <harish0611 at gmail.com > wrote:
  
While reading RFC 3261 i could not make out the difference between   "URI that contain   the lr parameter" and 
  "URI does not contain lr parameter"

case 1:
   if first URI doen't contain lr parameter then   
          <sip:proxy1>,<sip:proxy2>,<sip:proxy3;lr>,<sip:proxy4>  

   The request will be formed with the following Request-URI and Route
   header field:

   METHOD sip:proxy1
     Route:
 <sip:proxy2>,<sip:proxy3;lr>,<sip:proxy4>,<sip:user at remoteua  >
  If the lr parameter is absent, it means that it is a strict router. Strict router expects its entry( that it added in the Record Route of the initial Request) in the Request URI. So the UA gets the entry from the route set and puts it in the Request URI. It adds the end point's info as the last entry in the record route. 
   
  case 2: (is this correct?)


   if first URI contain lr parameter then 
          <sip:proxy1;lr>,<sip:proxy2>,<sip:proxy3>,<sip:proxy4>

   The request will be formed with the following Request-URI and Route
  
header field:

METHOD sip:proxy1
Route: <sip:proxy2>,<sip:proxy3>,<sip:proxy4>,<sip:user at remoteua>

Is this correct?...

I could not understand the lr concept ...if any one knows please explain how to use lr parameter... 
if possible please provide simple example

  If the UA finds from route set that the next hop is a loose router, It then uses the end point's info (obtained from the contact header in the initial request) in the Request URI and sends it. when it reaches the loose router, it looks for its entry in the route set and removes its entry from the route list and forwards it to the next hop. Before forwarding it checks in the route set if the next hop is a loose router or a strict router. if it is a strict router, it replaces the Request URI with the next hops entry in the route list and removes that entry in the route list. It also adds the destination's entry from the request URI to the route set as the last entry.

  Hope this answers your question

  Regards
  Hemanth




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With regards 
Harish.T _______________________________________________
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Chenji Hemanth Kumar 
Wipro Technologies
Ph: 23404007 
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-- 
------------------------------------------------------
To accomplish great things, we must not only act, but also dream; not only plan, but also believe.



With regards
Harish.T 


********************************************************************* 
Chenji Hemanth Kumar 
Wipro Technologies
Ph: 23404007 
*********************************************************************



 Send instant messages to your online friends http://uk.messenger.yahoo.com 
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