[OpenSIPS-Users] OpenSIPS as Teams SBC

Sun May 10 18:10:58 EST 2020

The MS documentation should be taken with a grain of salt. For SIP proxies
there’s no need for an FQDN in the Contact header, instead an FQDN is
required in the top Record-Route header. The FQDN is required in the
Contact header of the OPTIONS ping because this is a direct message between
the proxy and MS and there are no Record-Route headers in this particular
SIP request.
Everything is covered by the blog posted on the OpenSIPS website. Each
item/step can be implemented as described there or slightly different,
based on one’s needs.

Regards,
Ovidiu Sas

On Sun, May 10, 2020 at 12:27 James Hogbin <james at ip-sentinel.com> wrote:

> OK.
>
> Thank you for the Record_Route_Preset fix.  I had followed the example
> without understanding what it was doing.  It always seemed odd to put the
> 5060 port after the TLS port.  I understand why now. And more importantly
> why not to do it.
>
> Adding a * to the listen port caused an error in the script. I’m running
> 3.0.2 if that matters?
>
> However the routing is still not working correctly
>
>         if (is_method("INVITE") && !has_totag() &&
> check_source_address(0)) {
>                 xlog("[ROUTE]Incoming call to MS: RURI=$ruri, SI=$si,
> M=$rm\n");
>                 strip(1);
>                 prefix("+44");
>                 uac_replace_from( , "sip:$fU at sbc.ip-sentinel.com:5091");
>
> $rd="sip.pstnhub.microsoft.com";
>                 $rp=5061;
>
>                 $var(ct) = $ct;
>                 xlog("[INFO] Old Contact = $var(ct)\n”);
>
>                 remove_hf("Contact");
>                 append_hf("Contact: <
> sip:$fU at sbc.ip-sentinel.com:5091;transport=tls>\r\n");
>
>                 record_route_preset("sbc.ip-sentinel.com:5091
> ;transport=tls");
>
>                 route(relay);
>
>
> This routes the call from Zoiper -> Freeswich -> OpenSIPS -> Teams and I
> get ringing.
>
> If I pick up the call In Teams the Zopier client knows it has been
> accepted.
> I can hang up the call from Zoiper and Teams hangs up
>
> I don’t get Audio from Zoiper -> Teams but I do get Audio from Teams back
> to Teams with a slight delay
> Teams then hangs up the call after 20 seconds but the call remains open on
> Zoiper
>
> I’m pretty sure it has something to do with how/where I’m fixing the
> contact.  Any suggestions?
>
> Also how do I get one of those nice sip traffic flows given everything is
> on TLS?  I’m grabbing stuff out of the debug log and it’s not pretty.
>
>
> For future reference this is a great resource on MSTeams expected SIP
> traffic
> https://docs.microsoft.com/en-us/microsoftteams/direct-routing-protocols-sip
>
> For all incoming calls to the Microsoft SIP proxy, the Contact header must
> have the paired SBC FQDN in the URI hostname as follows:
> Syntax: Contact: <sip:phone or sip address at FQDN of the SBC;transport=tls>
>
> If more than one value in the Contact header presented in a SIP message is
> sent by the SBC, only the FQDN portion of the first value of the Contact
> header is used.
>
> Use of an IP address is not supported in either Record-Route or Contact.
> The only supported option is an FQDN, which must match either the Common
> Name or Subject Alternative Name of the SBC certificate (wildcard values in
> the certificate are supported).
> • If an IP address is presented in Record-route or Contact, the
> certificate check fails and the call fails.
> • If the FQDN does not match the value of the Common or Subject
> Alternative Name in the presented certificate, the call fails.
>
> But there is nothing in the instructions in the
> https://blog.opensips.org/2019/09/16/opensips-as-ms-teams-sbc/ that
> specifies fixing the contact in anything other than OPTIONS
>
>
>
>
>
> *James Hogbin*
> *Director*
> [image: IP Sentinel Logo] <http://ip-sentinel.com>
> t. +44 (0)20 3011 4150 <+442030114150>
> m. +44 7786910895
> w. https://www.ip-sentinel.com
>
> On 8 May 2020, at 09:12, John Quick <john.quick at smartvox.co.uk> wrote:
>
> James,
>
> Just to add to Alexey's last comment, if your SBC *is* changing the
> transport from UDP to TLS, then you must ensure the correct socket is used
> on the SBC when it is sending requests to the Teams Proxy:
> force_send_socket(tls:137.117.136.143:5091);
>
> You may also find it helpful to add " AS sbc.ip-sentinel.com:5091" on the
> end of your tls listen statement
>
> John Quick
> Smartvox Limited
> Web: www.smartvox.co.uk
>
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