SIP Trunk Overview

A SIP trunk is a virtual phone line delivered by an Internet Telephony Service Provider (ITSP). Once a trunk is connected to Cloud Voice, your users place and answer calls over the internet rather than over traditional analog or digital lines.

Key terms

SIP: Session Initiation Protocol, a signaling protocol defined by the IETF. It operates at the application layer to set up, change, and tear down real-time sessions between one or more parties.

ITSP: Internet Telephony Service Provider, a company that sells VoIP (Voice over Internet Protocol) calling service. You may also see these providers called VoIP service providers.

Trunk types

Cloud Voice works with three kinds of SIP trunk.

SIP Register Trunk

A registration-based trunk that authenticates to the provider with a username and password.

Note

A register trunk needs at least one DID (Direct Inward Dialing) number, which is a phone number the provider routes straight to your system.

SIP Peer Trunk

An IP-based trunk that authenticates using the IP address and port of your PBX (Private Branch Exchange, your phone system) rather than a login. Cloud Voice offers three variants:

• Peer Trunk (DID Based): the provider routes incoming calls by DID number.
• Peer Trunk (Port Based): the provider routes incoming calls by the SIP registration port.
• Peer Trunk (Private Network): for setups where the provider and the PBX sit on the same private network.

Note

• DID-based peer trunks require at least one DID number.
• You can configure up to five port-based peer trunks.

SIP Account Trunk

Use this type to link Cloud Voice with another device. Here Cloud Voice takes the role of the VoIP account provider: it supplies an account that the other device registers against to establish the connection.

Ways to create a trunk

From a template. Cloud Voice includes ready-made configuration templates for many established ITSPs, letting you stand up a trunk with minimal setup. See Create a SIP Trunk from a Template.

Tip

If your provider has a template, use it. The template fills in most of the technical settings for you, so there is less to configure by hand and less chance of entering a value incorrectly.

As a general trunk. If your provider has not been validated against a template, build the trunk manually:

• Create a SIP Register Trunk
• Create a SIP Peer Trunk
• Create a SIP Account Trunk

Trunk status icons

Each trunk in Cloud Voice shows a status icon that reflects its current connection state.

Icon	Meaning
	Disabled.
	Unreachable, or registration failed. A failed registration can be caused by an authentication error, a mismatched transport type, or the request being rejected.
	Authentication failed.
	Registering.
	Registered.
	Unmonitored.
	Busy, every available channel is in use.