[SIPForum-discussion] Regarding maddr parameter

AMIT ANAND amiit.anand at gmail.com
Wed Jan 20 22:30:11 UTC 2010


maddr gives you a multicast address where the UAS should send the
request considering it is in contact.
So i believe the behaviour would be same if it si coming in register or Invite,

Lets see if we could get some expert comments from any one in group

         if the Via header field value contains a "maddr"
         parameter, the response MUST be forwarded to the address listed
         there, using the port indicated in "sent-by", or port 5060 if
         none is present.  If the address is a multicast address, the
         response SHOULD be sent using the TTL indicated in the "ttl"
         parameter, or with a TTL of 1 if that parameter is not present.


         The maddr parameter indicates the server address
<http://rfc-ref.org/RFC-TEXTS/3261/kw-server_address.html> to be
         contacted for this user, overriding any address
<http://rfc-ref.org/RFC-TEXTS/3261/kw-address.html> derived from
         the host <http://rfc-ref.org/RFC-TEXTS/3261/kw-host.html>
field.  When an maddr parameter is present, the port
<http://rfc-ref.org/RFC-TEXTS/3261/kw-port.html>         and transport
<http://rfc-ref.org/RFC-TEXTS/3261/kw-transport.html> components of
the URI <http://rfc-ref.org/RFC-TEXTS/3261/kw-uri.html> apply to the
address <http://rfc-ref.org/RFC-TEXTS/3261/kw-address.html>
indicated in the maddr parameter value
<http://rfc-ref.org/RFC-TEXTS/3261/kw-parameter_value.html>.  [4
<http://rfc-ref.org/RFC-TEXTS/3261/chapter29.html#4>] describes the
         proper interpretation of the transport
<http://rfc-ref.org/RFC-TEXTS/3261/kw-transport.html>, maddr, and
hostport in
         order to obtain the destination address
<http://rfc-ref.org/RFC-TEXTS/3261/kw-destination_address.html>, port
<http://rfc-ref.org/RFC-TEXTS/3261/kw-port.html>, and transport
<http://rfc-ref.org/RFC-TEXTS/3261/kw-transport.html>         for
sending a request.

         The maddr field has been used as a simple form of loose source
         routing <http://rfc-ref.org/RFC-TEXTS/3261/kw-routing.html>.
It allows a URI <http://rfc-ref.org/RFC-TEXTS/3261/kw-uri.html> to
specify a proxy <http://rfc-ref.org/RFC-TEXTS/3261/kw-proxy.html> that
must be
         traversed en-route
<http://rfc-ref.org/RFC-TEXTS/3261/kw-route.html> to the destination
<http://rfc-ref.org/RFC-TEXTS/3261/kw-destination.html>.  Continuing
to use the
         maddr parameter this way is strongly discouraged (the
         mechanisms that enable it are deprecated).  Implementations
         should instead use the Route
<http://rfc-ref.org/RFC-TEXTS/3261/kw-route.html> mechanism described
in this
         document, establishing a pre-existing route
<http://rfc-ref.org/RFC-TEXTS/3261/kw-route.html> set if necessary
         (see Section  This provides a full URI
<http://rfc-ref.org/RFC-TEXTS/3261/kw-uri.html> to describe
         the node <http://rfc-ref.org/RFC-TEXTS/3261/kw-node.html> to
be traversed.

On Tue, Jan 19, 2010 at 2:50 PM, SIP Babie <sipbabie at gmail.com> wrote:

> Hi All,
> Please help me to understand the significance of parameter maddr. What
> difference it makes when maddr is used in Contact header of Register request
> in 3rd party registration & when it is used in Request URI in the INVITE
> Request.
> Regards,
> sipbabie
> _______________________________________________
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Amit Anand
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