TIPS Poly ATA 402 - RTP

[networkguy]

Hi All,

hoping you can help me with an issue. I'm looking for some expert advice!
I've got a Poly ATA 402, configured with two active SIP registrations - one to Microsoft Teams public SIP gateway, the other to an on-prem SIP server for an analogue intercom.

The problem - when I dial our tenant number, the call is initiated and passes through to the ATA 402, with the RTP stream unencrypted. This call is then direct to the microsoft teams SIP service (sp3 > sp1) , and when attempting to bridge, Microsoft provides a SIP BYE with response "Reason: SIP ;cause=488 ;text="488 Not Acceptable Here".
From the syslog capture, I can see microsoft is denying the connection due to my Poly bridging through the AVP/RTP/non-encrypt stream.

My question:
Is it possible to re-encrypt the RTP stream from the on-prem SIP server, prior to sending the SIP in vite to teams telephony?
I've set the teams SIP service to Force SRTP, but that doesn't seem to work.

Please let me know if i've left out anything important. Network engineering is my forte, this is a new foray into telephony for me..

Thanks!!

 

[chris_c_]

You should read the tutorial on how to do the reverse, how to use iPBX (FreePBX) as a Direct Routing (to provide inbound and outbound calling) for Microsoft Teams Phone System. The same but in reverse of that, what you're dong, is using a SIP phone - or in this case, your ATA - as an extension on Microsoft Teams. Set your ATA so that SIP always TLS 1.2 or higher with ciphers:

• LS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
• TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
• TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
• TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,

SRTP must use ciphers such as these:

• AES_CM_128_HMAC_SHA1_80
• AES_CM_128_HMAC_SHA1_32

EDIT: Go to MS Teams Admin Center, Teams Devices, SIP devices

Sign in to your account

admin.teams.microsoft.com

Tap on "Actions", "Provision Devices".
It will bring you to this page:

Sign in to your account

admin.teams.microsoft.com

Tap on Add MAC Address Manually.
Enter the MAC Address for your Poly 402 SIP ATA device.
Continue the process and follow the prompts.