Tuesday, July 7, 2020

Commsverse 2020 - BRK197 - Demystifying Local Media Optimisation for Microsoft Teams voice

Presented by: John Stewart-Murray

Session summary:
Local media optimisation (LMO) delivers key benefits when using Microsoft Teams for enterprise voice communications. What are those benefits, how do you deploy it? Everything you need to know from an expert in the field.

My notes:

Local media optimisation (LMO) is a supplement to media bypass, it can be seen as Media Bypass on steroids.

Teams to Teams calling is using REST/HTTP for signaling, SBCs use SIP. The best media path is negotiated by ICE, sometimes a media relay must be used. With Media Bypass the client can send media straight to the SBC, SILK or OPUS (deprecated in Teams) codecs can be used. The Media Relay in Teams is "bypassed" (for media, not for signaling.)

With the ICE-Lite implementation used by Teams the SBC could only present the external IP address for Media Bypass scenarios. With LMO (Local media optimisation) the client can tell the SBC (via SIP headers) if it is external or internal to the corporate network. So LMO fixes the issue with media going out and back in of the network.

The client is internal - let's use the internal interface of the SBC.

LMO also enhances the use of centralised SBCs

Pre-requisites
Media Bypass must be enabled in Teams.
Network subnets and sites must be configured in Teams (as for Location Based Routing) New-CsTenantNetworkSubnet

What Codec is used?
Teams can use SILK, G.722, G.711 or G.729 (better quality from left to right) SILK is the preferred and is good for poor quality connections such as WiFi. The PSTN is always using G.711 - i.e. the SBC must transcode, and this is a CPU heavy operation. With LMO the SBC knows if a client is internal (use G.711) or external (use SILK) and transcoding can be avoided for internal calls and the performance (number of calls) of the SBC goes up.

The summary - why not use LMO if you can?

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