Re: [Sip] Question regarding SDP 'M' Line

["Guangwu.He" <heguangwu at huawei.com>]

see my comments inline.

 

Thanks & Regards,

Guangwu.He


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From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On Behalf Of Jayantheesh Srimushnam
Sent: Wednesday, April 16, 2008 5:58 PM
To: sip at ietf.org
Subject: [Sip] Question regarding SDP 'M' Line

Hi All,

 

While adding a new media stream is it MUST to add a new ‘M’ line in the SDP or existing ‘M’ line can be replaced with the new one.

Please go through the below specified example and clarify me which is the correct way of implementing?

 

Example 1:

========

 

Initial INVITE:

 

m=audio 7100 RTP/AVP 0 101

a=rtcp:7101

a=sendonly

a=rtpmap:0 PCMU/8000

a=rtpmap:101 telephone-event/8000

 

Re-Invite:

 

m=image 20112 udptl t38

a=T38FaxVersion:0

a=T38MaxBitRate:1440

 

[Guangwu]:the example is wrong;RFC3264 8.1

New media streams are created by new additional media descriptions
below the existing ones, or by reusing the "slot" used by an old
media stream which had been disabled by setting its port to zero.

in you example 1,the port is not zero;

 

Example 2:

========

 

Initial INVITE:

 

m=audio 7100 RTP/AVP 0 101

a=rtcp:7101

a=sendonly

a=rtpmap:0 PCMU/8000

a=rtpmap:101 telephone-event/8000

 

Re-Invite:

 

m=audio 7100 RTP/AVP 0 101

a=rtcp:7101

a=sendonly

a=rtpmap:0 PCMU/8000

a=rtpmap:101 telephone-event/8000

m=image 5080 udptl t38

c=IN IP4 10.101.210.30

a=T38FaxVersion:0  

 

Thanks,

Jayantheesh

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