Discover why configuring Media Bypass is critical for deploying a Survivable Branch Appliance (SBA) with Microsoft Teams Direct Routing to ensure PSTN continuity during outages.
Table of Contents
Question
You have a Microsoft Teams Phone deployment that uses Direct Routing.
You have a branch office that contains a Session Border Controller (SBC) named SBC1. SBC1 provides PSTN connectivity.
You plan to deploy a Survivable Branch Appliance (SBA) to the branch office.
You need to configure SBC1 to support the deployment.
What should you do?
Select only one answer.
A. Assign a public IP address to SBC1.
B. Configure Local Media Optimization.
C. Configure Location-Based Routing (LBR).
D. Configure Media Bypass for SBC1.
Answer
To deploy a Survivable Branch Appliance (SBA) in a Microsoft Teams Direct Routing environment, Media Bypass must be configured on SBC1 (Option D).
D. Configure Media Bypass for SBC1.
Explanation
For an SBA to function correctly, you must have Media Bypass configured on the SBC.
Why Media Bypass is Required
Media Bypass ensures direct media flow between Teams clients and the SBC, bypassing Microsoft’s cloud media processors. This is critical for SBA functionality because:
- Survivability During Internet Outages: If the branch loses connectivity to Microsoft 365, the SBA allows Teams clients to route PSTN calls directly through SBC1.
- Prerequisite for SBA: Microsoft mandates Media Bypass for SBA deployments to ensure media traffic stays local during outages.
- ICE Protocol Support: Media Bypass leverages Interactive Connectivity Establishment (ICE) on Teams clients and ICE Lite on the SBC, enabling direct media negotiation.
Analysis of Other Options
- A. Public IP Address: While SBCs often use public IPs for external connectivity, this is not a strict SBA requirement. Media Bypass can use internal or external IPs based on network topology.
- B. Local Media Optimization (LMO): LMO optimizes media paths but does not guarantee survivability. SBA specifically requires Media Bypass to function.
- C. Location-Based Routing (LBR): LBR enforces geographic call routing policies but does not address outage resiliency.
Configuration Steps
Enable Media Bypass via PowerShell:
Set-CsOnlinePSTNGateway -Identity sbc1.contoso.com -MediaBypass $true
Ensure SBC firmware supports ICE Lite and bypass.
Verify firewall rules allow direct media flow between Teams clients and SBC1.
Failure to enable Media Bypass would force media through Microsoft’s cloud, rendering the SBA ineffective during outages. Summary: Media Bypass (Option D) is the only configuration that ensures SBC1 supports SBA by enabling direct media paths critical for PSTN survivability.
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