[OpenSIPS-Users] OpenSIPS as Teams SBC

[Slava Bendersky]

Hello All, 
Microsoft is rely on approved sbc vendors, where most sbc are use VIA and headers to route traffic. That why Contact header is important, also they use from and to. 
Opensips is rely on route headers and use different way to route it. 

volga629 


From: "John Quick" <john.quick at smartvox.co.uk> 
To: "OpenSIPS users mailling list" <users at lists.opensips.org>, james at ip-sentinel.com 
Sent: Monday, May 11, 2020 6:19:50 AM 
Subject: Re: [OpenSIPS-Users] OpenSIPS as Teams SBC 

I agree completely with Ovidiu. 
The Microsoft documentation says to use a FQDN in the Contact header, but 
this is wrong when the SBC is acting as a SIP Proxy. 
The blog post on the OpenSIPS website explains that actually the 
Record-Route header needs the FQDN. 
The one exception to this is the handling of OPTIONS pings - for these, 
OpenSIPS is the end point so it must use a FQDN in Contact. 

If you change the Contact header in call setup then you risk breaking the 
path for sequential requests, such as ACK. 
If ACK does not reach its destination, the call drops at one end after about 
20 seconds - exactly what you are seeing. 

I have not yet found a good way to capture TLS encoded SIP. In theory, you 
can use sngrep with the -k option to identify the path to the private key 
file. 
It would be necessary to start sngrep first, then start (or restart) 
OpenSIPS. However, this never works for me. 
I had more success using the siptrace module to capture the packets to a DB 
table. Presenting it as a sequence diagram may be possible using the 
OpenSIPS Control Panel. 
Wireshark also has the ability to capture, decode and present TLS encrypted 
SIP. 
Another option might be to mirror the traffic to Homer in HEP format and 
then use Homer to create the sequence diagram. 

John Quick 
Smartvox Limited 


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