Microsoft have recently announced MC299922, aka “Direct Routing will stop processing SIP requests which have ‘Replaces’ headers”. The timescale is fairly aggressive as from the 3rd January 2022, Microsoft will start updating their platform to reject SIP requests that have ‘Replaces’ headers. Works are expected to be completed by mid-January 2022, and this is going to impact all tenants with Direct Routing provisioned, regardless of any Education/Government tenant status.
If you have an Audiocodes SBC, the way to confirm if this will impact you is nice and easy! Simply log into the SBC’s web portal, navigate to Setup> Signaling & Media > Coders & Profiles > IP Profiles.
Select your IP profile configured for Microsoft Teams, then under the “SBC Forward and Transfer” section, there’s a parameter called “Remote Replaces Mode“. By default this will be “Standard”, change this to “Handle Locally” and you should be all good! Now would be a good time to review your configuration against Audiocodes’ recommendations for Microsoft Teams.
Audiocodes provide documentation for configuration recommendations, navigate to their technical documents section and search for “LTRT-13331” (Enterprise Model) or “LTRT-13330” (Hosting Model) for further information.