[SIPForum-discussion] Need Help for SDP Specification - c=*

[Mohit Soni]

Hi Anil,

 

The C=* parameter is mandatory in the SDP body.

 

However, there is a flexibility to mention it at the session level or at the
media description level as per required.

 

When it is mentioned at the session level, then it is applicable for all the
media descriptions exists in the SDP body.

When it is mentioned at the media description level, then it is applicable
for that particular media description only.

 

 

Example-1:

Consider that there are two separate Media Servers  deployed in the Service
Provider's network. One is to deal with normal RTP and second is to deal
with secure RTP.

 

Some UA has subscribed for Secure RTP and some UA has not subscribed for
secure RTP.

 

Now, in this case, during SDP offer-answer, the Service Provider's server
can include two separate "m" lines in the SDP body, one with credentials of
SRTP and second with normal RTP.

For the "m" line of the SRTP, it will mention "c" line with the IP Address
of the Media Server capable to deal with SRTP and for "m" line of normal RTP
it will mention "c" line with the IP Address of the Media Server capable to
deal with normal RTP.

 

Example-2:

In same deployment mentioned in Example-1, the Service Provider's server can
include single "m" line with either SRTP or with normal RTP if Server is
taking decision based on whether subscriber has subscribed for SRTP or not.

 

So, in case of subscriber has subscribed for SRTP then it can include "c"
line at the session level rather than in the media description and include
single "m" line with having SRTP credentials and similar way it will create
SDP body for Subscribers who has not subscribed for SRTP.

 

 

For brief, refer section 5 in RFC4566.

 

 

Regards,

Mohit Soni

 

 

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Anil Patil
Sent: Monday, November 04, 2013 10:04 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Need Help for SDP Specification - c=*

 

Hi All,

 

Why c=* parameter in not a mandatory parameter in SDP

 

C= (connection information -- not required if included in all media)

 

Can any once explain with real time example so it will easy to understand.

 

 

thanks 

  <https://mail.google.com/mail/u/0/images/cleardot.gif> 

 

Anil....

 

 

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