Via header "maddr" parameter question

Hi,

I'm implementing a Media Server, which is functioning as a
SIP UA and do
nothing about proxy or registration. The implementation is
compliant to RFC
3261.

Here is an INVITE request received by MS. The request is
received from
source address "10.10.0.1":

	INVITE sip:annc10.10.2.51;play=5;repeat=2 SIP/2.0 
	Via:SIP/2.0/UDP
10.10.0.1:5455;maddr=10.10.0.2;branch=z9hG4bK+222

As you can see, the Via header also contains
"maddr" parameter with a
different address "10.10.0.2". 

1) Which address should be used to send response,
"10.10.0.1" or
"10.10.0.2"?

2) As per RFC 3261 section 18.2.2, address
"10.10.0.2" (maddr) should be
used, but I'm not sure if this rule is applicable for the
MS, as the MS is a
pure SIP UA and does not support multicast. 

3) Also, if response is not sent back to source address,
what happen to the
client transaction on the UAC side? Timed-out?

Your comments are appreciated.

Thanks,
Yong


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Thanks, based on section 18.2.2 of RFC 3261, the INVITE
transaction will be
completed like this:

1) If Via with "maddr"

send-by                        MS                   maddr
    |                           |                     |
    |----------INVITE --------->|                     |
    |                           |--------100 -------->|
    |<------------------- 100 ------------------------|
    |                           |--------200 -------->|
    |<------------------- 200 ------------------------|
    |----------ACK ------------>|                     |

2) If Via without "maddr"

send-by				  MS
    |                           |
    |----------INVITE --------->|
    |<--------- 100 ----------->|
    |<--------- 200 ------------|
    |----------ACK ------------>|  

I'm wondering if there's an use case scenario that call flow
#1 is needed
and better than call flow #2.

Thanks,
Yong


-----Original Message-----
From: Sanjay Sinha (sanjsinh) [mailto:sanjsinhcisco.com] 
Sent: Thursday, May 31, 2007 2:26 PM
To: yong.xinradisys.com; Sip-implementorscs.columbia.edu
Subject: RE: [Sip-implementors] Via header "maddr"
parameter question

Pl. see section 18.2.2 of RFC 3261 about how to send
response if there is
maddr param in Via  

>-----Original Message-----
>From: sip-implementors-bouncescs.columbia.edu
>[mailto:sip-implementors-bouncescs.columbia.edu] On Behalf
Of Yong Xin
>Sent: Thursday, May 31, 2007 3:43 PM
>To: Sip-implementorscs.columbia.edu
>Subject: [Sip-implementors] Via header "maddr"
parameter question
>
>Hi,
>
>I'm implementing a Media Server, which is functioning as
a SIP UA and 
>do nothing about proxy or registration. The
implementation is compliant 
>to RFC 3261.
>
>Here is an INVITE request received by MS. The request is
received from 
>source address "10.10.0.1":
>
>	INVITE sip:annc10.10.2.51;play=5;repeat=2 SIP/2.0 
>	Via:SIP/2.0/UDP
>10.10.0.1:5455;maddr=10.10.0.2;branch=z9hG4bK+222
>
>As you can see, the Via header also contains
"maddr" parameter with a 
>different address "10.10.0.2".
>
>1) Which address should be used to send response,
"10.10.0.1" 
>or "10.10.0.2"?
>
>2) As per RFC 3261 section 18.2.2, address
"10.10.0.2" (maddr) should 
>be used, but I'm not sure if this rule is applicable for
the MS, as the 
>MS is a pure SIP UA and does not support multicast.
>
>3) Also, if response is not sent back to source address,
what happen to 
>the client transaction on the UAC side? Timed-out?
>
>Your comments are appreciated.
>
>Thanks,
>Yong
>
>
>_______________________________________________
>Sip-implementors mailing list
>Sip-implementorscs.columbia.edu
>https://lists.cs.columbia.edu/cucslists/listinf
o/sip-implementors
>


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