[SIPForum-discussion] Invalid SDP line (no '=' delimiter) error !

Joel Gerber Joel.Gerber at corp.eastlink.ca
Thu May 28 16:26:49 UTC 2015

>From a cursory glance, I would say the issue is caused from the source.

This is what is sent out:
m=audio 5000/1 RTP/AVP 8 101

The "/1" after the "m=audio 5000" is invalid as far as I know.

Not knowing where the ws_frame4 file was grabbed from makes it hard to describe what happened, but, I would say somewhere between the w_frame52 capture and the ws_frame4 capture there is a SIP ALG, Proxy, B2BUA, or some other sort of SIP device that had an issue parsing the originally sent SDP which caused its parsing engine to generate the messed up SDP body that is seen in the ws_frame4 packet capture file.

It's a perfect illustration of the old adage: "Garbage in, garbage out" :)

Joel Gerber
Network Operations Specialist - Telephone
Joel.Gerber at corp.eastlink.ca<mailto:%20Joel.Gerber at corp.eastlink.ca>    T: 519.786.1241

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Badri Ranganathan
Sent: May-28-15 9:16 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Invalid SDP line (no '=' delimiter) error !

Hi all,

I am answering a SIP call made to my softphone. The softphone rings and also sends a 200 OK correctly. But the other end that made the call is seeing a failure in the SDP of the 200 OK packet.

This error is seen in SDP header => Invalid SDP line (no '=' delimiter) error

w.r.t w_frame4_public_ip.pcap It looks like the failure as seen in wireshark is because  line "audio 5000 RTP/AVP 8 101" should really be "m= audio 5000 RTP/AVP 8 101"
so it doesn't see the '=' delimiter.

But if you look at w_frame52_local_ip.pcap, the packets sent from the local IP has the contents correct.

It is only after passing the public IP and at the network premises, that this failure is reported by the Session Border controller.

I am not able to understand why a correctly formed packet sent out is seen "corrupted" at the network end.

Any ideas really appreciated.

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