# Technical Details

### Concepts

This section contains some key concepts and terminology used throughout this documentation.

### Endpoint <a href="#endpoint" id="endpoint"></a>

You can send your `INVITE` requests to 9bits IP address once the trunk is in an active state.

### Authentication

Authentication is by IP address only and only the registered IP address(s) are allowed for signaling and RTP flow.

### Recipient

Recipient numbers must be in E.164 format.

### Codecs

The following codecs are supported:

* PCMA (G711a)
* PCMA (G711u)
* G722

### ACL

An Access Control List (ACL) is a set of IP ranges which are allowed to interact with a SIP system, which could be either a 9bits or customer SIP system.


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