Subject: Re: [Sip] Significance of port in maddr parameter.

From: "Sreerekha Shenoy (sresheno)" <[email-masked]>
Date: Wed, 23 Dec 2009 12:48:26 +0530

Hi Vineet,
As per RFC 3261, I don't see a placeholder for port number in the
maddr-param.
The ABNF syntax for maddr goes as follows:

maddr-param       =  "maddr=" host
host             =  hostname / IPv4address / IPv6reference

please explain on what do you mean by 'port in maddr param'

Thanks,
Best Regards,
Rekha

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Today's Topics:

   1. Significance of port in maddr parameter. (Vineet Gupta)

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Message: 1
Date: Tue, 22 Dec 2009 17:27:40 +0530
From: Vineet Gupta <[email-masked]>
Subject: [Sip] Significance of port in maddr parameter.
To: [email-masked]
Message-ID:
	<[email-masked]>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

Can someone let me know why exactly following statement is present in
RFC
3261:

*"The maddr parameter indicates the server address to be contacted for
this
user, overriding any address derived from the host field.  When an maddr
parameter is present, the port and transport components of the URI apply
to
the address indicated in the maddr parameter value"*

To be specific:
a) What exactly can go wrong on using the port in maddr parameter?
b) In what are situations where port present in Req-URI should be used
rather than port present in maddr parameter?
c) And in what situation port in maddr parameter should be used?

Regards,
Vineet.
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From: aayush bhatnagar <[email-masked]>
Date: Wed, 23 Dec 2009 08:25:02 +0030

Vineet,

The maddr parameter can be present in the Via header and in the request URI.

If present in the Via header, it signifies that the client is sending
the request to a multicast receiver. Refer to section 18.1.1 of 3261
for this.

It may be present in the Request URI...which means that the entry of
the request uri is added as the only entry in the target set for the
request.

As for the port, it is not present in the maddr paramater. It is
present in the sent-by parameter, or defaults to 5060 in case the
sent-by parameter is absent.

Hope this helps. For more info of maddr parameter usage, read sections
16.4, 16.5, 18.1.1, 18.1.2 and 19.1.1 of RFC 3261.

-- 
aayush
http://in.linkedin.com/in/abhatnagar19
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