[SIPForum-discussion] Reg: SDP offer

[Roni Even]

Hi,

The cpar is specified in RFC 3407 http://tools.ietf.org/html/rfc3407 

 

Roni Even

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Ayyanar PK
Sent: Thursday, April 09, 2009 4:45 PM
To: prem ranjan
Cc: discussion
Subject: Re: [SIPForum-discussion] Reg: SDP offer

 

Hi Prem,

I have never seen such a SDP. The intention is to send fax over T.38 or G.711. I ask this because, I can see Image as well as a Re-INVITE with only G.711 code in Re-INVITE's SDP.

Also in 180 Ringing the SDP has both audio as well as image. What is the need or purpose to send T.38 information in the initial negotiation even if it is fax call. I dont understand this negotiation. Can you elobrate on this ? or can somebody elobrate on this ?

Regards,
Ayyanar


---------- Original message ----------
From:prem ranjan< prem.behera at gmail.com >
Date: 08 Apr 09 16:34:52
Subject: [SIPForum-discussion] Reg: SDP offer
To: discussion at sipforum.org

Hi,
I have the following scenario:
A calls B
A sends INVITE with the following SDP:

v=0
o=780 409699 409699 IN IP4 192.168.0..20
s=-
c=IN IP4 151.98.90.197
t=0 0
m=audio 41270 RTP/AVP 8 18 4 96
a=rtpmap:96 telephone-event/8000
a=ptime:20
a=SilenceSupp:off
a=fmtp:96 0-15
a=nortpproxy:yes


B answers the following SDP in 180 Ringing:

v=0
o=- 38000001 1239174750 IN IP4 151.98.90.196
s=SDP Data
c=IN IP4 151.98.90.196
t=0 0
m=audio 18990 RTP/AVP 8 96
a=rtpmap:96 TELEPHONE-EVENT/8000
a=ptime:20
a=sqn:0
a=cdsc:1 image udptl t38
a=cpar: a=T38FaxVersion:0
a=cpar: a=T38MaxBitRate:14400
a=cpar: a=T38FaxRateManagement:transferredTCF
a=cpar: a=T38FaxMaxBuffer:280
a=cpar: a=T38FaxMaxDatagram:260
a=cpar: a=T38FaxUdpEC:t38UDPRedundancy

After this Call is successful.
Now B wants to send a FAX. For this it creates a Re-Invite with the following SDP:

v=0
o=- 38000001 1239174761 IN IP4 151.98.90.196
s=SDP Data
c=IN IP4 151.98.90.196
t=0 0
m=audio 0 RTP/AVP 8
a=ptime:10
m=image 33815 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxBuffer:1800
a=T38FaxMaxDatagram:260
a=T38FaxUdpEC:t38UDPRedundancy

Now my question is, can we have the value "Zero" in the audio port. Is this RFC compliant???

Kind Regards,
Prem Ranjan Behra 

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