[OpenSIPS-Users] OpenSIPS as Teams SBC

[James Hogbin]

I disagree.  The blog pre assumes a MASSIVE amount of knowledge and configuration

with a pre-existing opensips.conf routing set up

Goodness knows what that is.  It isn’t the Proxy set up or the Residential set up.  I’ve tried both and neither work.

It would be really helpful if the Blog started with which config file it is based on and went from there.

With a lot of blind hacking around on the script I’ve got to the stage where

Teams outbound works fine with a
             $rd="pbx.ip-sentinel.com<http://pbx.ip-sentinel.com>";
             $rp=5081;

 However to have the Inbound accepted by MS Teams I have to modify the TO, FROM add a ROUTE AND force the CONTACT
  strip(1);
                prefix("+44");
                uac_replace_from( , "sip:$fU at sbc.ip-sentinel.com:5091");
                uac_replace_to( , "sip:$rU at sip.pstnhub.microsoft.com");
                $rd="sip.pstnhub.microsoft.com<http://sip.pstnhub.microsoft.com>";
                $rp=5061;
                record_route_preset("sbc.ip-sentinel.com:5091<http://sbc.ip-sentinel.com:5091>;transport=tls”);
And in the route
      if(check_source_address(0)){
                xlog("[INFO] FIX ACK CONTACT");
                remove_hf("Contact");
                append_hf("Contact: <sip:$fU at sbc.ip-sentinel.com:5091;transport=tls>\r\n”);
And onroute_reply
      if(check_source_address(0)){
                xlog("[INFO] FIX ACK CONTACT");
                remove_hf("Contact");
                append_hf("Contact: <sip:$fU at sbc.ip-sentinel.com:5091;transport=tls>\r\n”);

However even with that I eventually miss an ACK and the whole thing falls over.  Most frustrating!

James Hogbin
Director 
 
IP Sentinel 
t. +44 (0)20 3011 4150
m. +44 7786910895
w. https://www.ip-sentinel.com

On 11 May 2020, at 18:14, Ovidiu Sas <osas at voipembedded.com<mailto:osas at voipembedded.com>> wrote:

Microsoft’s SIP routing is RFC compliment.
There’s no special routing for approved SBCs. The routing Is based on the type of SBC: B2BUA vs proxy, which again, is rfc complient.
For OpenSiPS, which is a proxy, all the configuration steps are very well outlined in the blog. No need to mess with Via or Contact headers! Follow the loose routing rules as outlined in the rfc and all is good.

Regards,
Ovidiu Sas

On Mon, May 11, 2020 at 05:51 Slava Bendersky via Users <users at lists.opensips.org<mailto:users at lists.opensips.org>> wrote:
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<mailto:john.quick at smartvox.co.uk>>
To: "OpenSIPS users mailling list" <users at lists.opensips.org<mailto:users at lists.opensips.org>>, james at ip-sentinel.com<mailto: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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