Gamma
Gamma is one of the largest UK SIP trunk providers. Its trunks are usually registerless, authenticated on your public IP address, but Gamma IPDC can be provisioned either way.
Ask Gamma which authentication method they have provisioned for your account before you start. Both work, and configuring the wrong one is the most common reason a Gamma trunk does not come up.
Information to obtain from Gamma
- The SIP host or proxy for your service, and the port and transport
- Which authentication method your account uses: IP or registration
- Gamma’s signalling IP addresses, if the trunk is IP-authenticated
- The SIP username, password and realm, if the trunk registers
- Your inbound numbers, and an authorised outbound caller ID
Gamma will also need your SessionPBX region’s service address. Ask support for it.
Add the trunk
- Open the SessionPBX project and select Call Routing.
- On SIP trunks, select Add trunk.
- Name the trunk and choose Gamma as the Provider if listed, or Generic carrier (IP authentication).
- On Connection, enter the host, port and transport Gamma gave you.
- On Authentication, choose the method Gamma confirmed.
IP-authenticated
Choose By our IP address and list Gamma’s signalling ranges under Carrier IP addresses, one per line. These are Gamma’s addresses, not yours.
Registration
Choose Username and password, enter the credentials, and turn on Register to this carrier. See Registration-based Carriers for what happens next.
Numbers and caller ID
Enter your numbers on Inbound, in full international format. Set Caller ID on Outbound to a number Gamma has authorised for the account: Gamma rejects calls presenting a number that is not on your service.
If Gamma asks you to present the calling number in P-Asserted-Identity, set Assert caller ID in to that on the Outbound step.
Test
- Call one of your numbers from an outside phone and confirm the right extensions ring.
- Enable Outbound PSTN for one member, call a public number, and confirm two-way audio and the presented caller ID.