[SIPForum-discussion] Difference between Via header andRouteSet header

Thu Apr 19 12:07:37 UTC 2007

Hi,

6.2.28 Route
The Route header field is used to provide routing information for requests. RFC 3261 introduces two types of routing: strict and loose routing, which have similar meaning as the IP routing modes of the same name. In 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. In loose 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 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 example.com;lr>
Chapter 10 contains an example of the use of the Record-Route and Route header fields. Examples of Route header fields constructed from the example Record-Route header fields in Section 6.2.12 are:

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

     Route: <sip:139.23.1.44 ;lr>
6.1.10 Record-Route
The Record-Route header field is used to force routing through a proxy for all subsequent requests in a session between two user agents. Normally, the presence of a Contact header field allows user agents to send messages directly bypassing the proxy chain used in the initial request (which probably involved database lookups to locate the called party). A proxy inserting its address into a Record-Route header field overrides this and forces future requests to include a Route header field containing the address of the proxy that forces this proxy to be included.

A proxy, such as a firewall control proxy, wishing to implement this inserts the header field containing its own URI, or adds its URI to an already present Record-Route header field. The URI is constructed so that the URI resolves back to the proxy server. The UAS copies the Record-Route header field into the 200 OK response to the request. The header field is forwarded unchanged by proxies back to the UAC. The UAC then stores the Record-Route proxy list plus a Contact header field if present in the 200 OK for use in a Route header field in all subsequent requests. Because Record-Route is bidirectional, messages in the reverse direction will also traverse the same set of proxies. Chapter 10 contains an example of the use of the Record-Route and Route header fields. 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>
------<<SIP: Understanding the Session Initiation Protocol, Second Edition>> by Alan B. Johnston  Regards,
Xu Rui
  ----- Original Message ----- 
  From: harish T 
  To: Retesh 
  Cc: discussion at sipforum.org 
  Sent: Thursday, April 19, 2007 7:28 PM
  Subject: Re: [SIPForum-discussion] Difference between Via header andRouteSet header

  Hi Retesh,

  If that is the case ,the what is the Difference between RouteSet and Contact header..Even contact header is used to send subsequent request...

  Can any one please tell me when exactly i should use RouteSet header(I mean ,For which request RouteSet Header is Mandatory )

  On 4/19/07, Retesh <retesh.chadha at gmail.com> wrote: 
    Via header is used to send the response to a request, but route header
    is used to send a new request within the dialog.

    Regards
    Retesh

    On 4/19/07, harish T <harish0611 at gmail.com > wrote:
    > Hi Friends,
    >
    > Can any one tell me the difference between Via header and RouteSet header.
    > Both are used to send responce message ,Where exactly it differs ?
    >
    >
    > If anyone knows ,please let me know .
    >
    >
    >
    >
    > With regards
    > Harish.T
    >
    > ------------------------------------------------------
    > To accomplish great things, we must not only act, but also dream; not only 
    > plan, but also believe.
    >
    >
    >
    >
    > _______________________________________________
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    > TO UNSUBSCRIBE, or edit your delivery options, please visit 
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    >

    --
    With Regards
    Retesh Chadha

  -- 
  ------------------------------------------------------
  To accomplish great things, we must not only act, but also dream; not only plan, but also believe. 

  With regards
  Harish.T 

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