# Pre-planning & Prerequisites

### Overview

Direct Routing lets Microsoft Teams send/receive PSTN calls through your SIP trunk (Cebod Telecom) by connecting a certified SBC (Session Border Controller) to Microsoft Teams. In this setup:

* Outbound calls from Teams go to the SBC → Cebod SIP trunk → PSTN.
* Inbound calls from PSTN arrive at Cebod → SIP trunk → SBC → Teams user.

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1. **Microsoft Licensing:**
   * Each Teams user who will make/receive PSTN calls requires a Phone System license (*Microsoft Teams Essentials with Phone*). Ensure numbers are assigned or available.
   * You will need Resource account licenses (*Microsoft Teams Phone Resource Account*) to set up features like Call Centre/Queue, Ring Group, Auto-attendant/IVR, etc.
2. **Phone numbers (DIDs) from Cebod Telecom:**
   * Decide which numbers from your Cebod Telecom account will be assigned to Teams.