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Nortel CS 2000


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We are experiencing failed calls when interacting with a certain upstream GW. Nortels CS2000 is responding to INVITES with a 183 with an SDP that is either to a new standard release or not supported by PBXnSIP.


Here is the following and please help me understand my course of action.


PBXnSIP <--> Ditech C100 SBC <--> Nortel CS2000


PBXnSIP INVITE with the following SDP payload.

User-Agent: pbxnsip-PBX/



o=- 25385 25385 IN IP4 10.x.x.x


c=IN IP4 10.x.x.x

t=0 0

m=audio 55350 RTP/AVP 0 8 2 3 101

a=fmtp:101 0-11

a=rtpmap:0 pcmu/8000

a=rtpmap:8 pcma/8000

a=rtpmap:2 g726-32/8000

a=rtpmap:3 gsm/8000

a=rtpmap:101 telephone-event/8000



CS200 responds with 183 Session Progress with the following SDP payload.

Server: CS2000_NGSS/8.0



o=PVG 0 841331007 IN IP4 x.x.x.x


p=+1 6135555555

c=IN IP4 x.x.x.x

t=0 0

a=cdsc: 1 audio RTP/AVP 0 8 116 18 13 101

a=cpar: a=rtpmap:116 AAL2-G726-32/8000

a=cpar: a=rtpmap:101 telephone-event/8000

a=cpar: a=fmtp:101 0-15

a=cpar: a=ptime:10

a=cpar: a=ptime:20

a=cpar: a=fmtp:18 annexb=yes

a=sqn: 0

m=audio 57802 RTP/AVP 0 8 101

a=fmtp:101 0-15


a=rtpmap:101 telephone-event/8000


Then PBXnSIP responds with a CANCEL


I see some problems with compatibility of the SDP payloads and I am reaching out for assistance in resolution.


In the list of RTP/AVP from the CS2000 CODECs 0 and 8 (which are in the PBXnSIP INVITE = match) are listed but with no corresponding a= parameter. Seems out of standard.


Does PBXnSIP support RFC 3407?


Thanks for any assistance.



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Hmmm, I was more thinking about accessing one existing account and service... If you can share login information, please send a private message to me or to support@pbxnsip.com.


Can you confirm that PBXnSIP is supporting RFC 3407?


No. But it does not have to be compatible (that's the purpose of RFC 3407). The PBX does not need to have capabilities outside of the "classical" codec set. The negotiation should work fine, there must be something else trivial in the way.

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