Subject: RE: [Sip] SDP Query

From: "Attila Sipos" <[email-masked]>
Date: Thu, 25 Aug 2005 10:01:38 +0100

Hi Udit, 
 
Yes it is valid.  The question is what did you intend it to mean?
 
In your example, you will end up with audio with IP 224.2.17.13
and video with IP 224.2.17.12.
 
The first "c=" (is a session description "c=" since it comes before any
"m=" section) means use this IP address for all media unless the
media description says otherwise.
 
The second "c=" (is a media description "c=" because it comes after the "m=")
means for this particular media use the address I've specified here.
 
You could have, as an alternative, written your SDP like this:
 
        t=2873397496 2873404696 
        a=recvonly 
        m=audio 49170 RTP/AVP 0 
        c=IN IP4 224.2.17.13/127 
        m=video 51372 RTP/AVP 31 
        c=IN IP4 224.2.17.12/127 

In my example above, there is no session description "c=" so every
media description has to have a "c=".
 
Regards,
 
Attila Sipos
http://www.vegastream.com

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of [email-masked]
Sent: 24 August 2005 21:11
To: SIP Implementors
Cc: SIP IETF
Subject: [Sip] SDP Query

Hi, 

Just want to check if following SDP is valid: 

        c=IN IP4 224.2.17.12/127 
        t=2873397496 2873404696 
        a=recvonly 
        m=audio 49170 RTP/AVP 0 
        c=IN IP4 224.2.17.13/127 
        m=video 51372 RTP/AVP 31 

It indicates different IP address used for audio and video types. 

I thought the reason we have connection parameter in both session and media description is for handling hold cases, where you want to hold a particular set of media instead of whole session. 

Regards, 
Udit 

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