This document provides troubleshooting tips for configuring and using the Ribbon SBC Edge to configure Local Media Optimization for Microsoft Teams Direct Routing. Local Media Optimization allows the Microsoft Teams Direct Routing media flow to always use the shortest path to improve the SBC Edge's media quality and bandwidth usage. 

488 Issue - Mismatch with Inbound Invite Header

Many LMO deployments encountering the 488 issue (particularly at the beginning of deployment), which is due the SBC host and domain name configuration mismatching against the X-MS-MediaPath header of inbound INVITE or 200 OK w SDP from Teams PSTN Hub. This “X-MS-MediaPath” header is posted by TEAMS in LMO deployment only.

Under the Microsoft Teams LMO setting, Teams sends the SBC the below sample inbound INVITE with extra LMO headers. The FQDN (aepsite35.sonusms01.com) configured in the X-MS-MediaPath header matches the SBC's node level host and domain settings. 

Verify Header

Verify in the header that the configuration is set correctly:

INVITE sip:+10355559005@aepsite35.sonusms01.com:5061;user=phone;transport=tls SIP/2.0^M

FROM: Ribbon User 21<sip:+10001001021@sip.pstnhub.microsoft.com:5061;user=phone>;tag=1ce6d6008ddc436fb728a0159615354e^M

TO: <sip:+10355559005@aepsite35.sonusms01.com:5061;user=phone>^M

CSEQ: 1 INVITE^M

CALL-ID: d777eecdc1965be8b14e3b77f6034a37^M

MAX-FORWARDS: 70^M

VIA: SIP/2.0/TLS 52.114.148.0:5061;branch=z9hG4bKbfcf5f82^M

RECORD-ROUTE: <sip:sip-du-a-us.pstnhub.microsoft.com:5061;transport=tls;lr>^M

CONTACT: <sip:api-du-c-asea.pstnhub.microsoft.com:443;x-i=ada01998-ef59-4e7f-8f4c-2214fe4d1606;x-c=d777eecdc1965be8b14e3b77f6034a37/d/8/dc39ee2b0e104511a58fc952e873812e>^M

CONTENT-LENGTH: 2439^M

USER-AGENT: Microsoft.PSTNHub.SIPProxy v.2021.2.16.6 i.USWE2.3^M

CONTENT-TYPE: application/sdp^M

ALLOW: INVITE,ACK,OPTIONS,CANCEL,BYE,NOTIFY^M

X-MS-UserLocation: external^M

X-MS-MediaPath: aepsite35.sonusms01.com^M
 

Verify Host Information

The instructions below detail how to confirm/configure the Host Name and Domain Name configuration in the SBC Edge.

  1. Access the WebUI
  2. In the WebUI, click the Settings tab.

  3. In the left navigation page, go to System > Node-Level Settings.

  4. Enter the Host Name (DNS host name for the system, e.g., aepsite35).
  5. Enter the Domain Name (DNS domain name for the system, e,g, sonusms01.com)

Verify Host Information