2.1 Background on SIP Trunks
The SIP Trunks are used for connecting PrivateServer to a local PBX or to a SIP Voice provider. The above statement implies that a Trunk can be used both for receiving and placing calls in a bidirectional way.
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| By Secure Call design the SIP Trunks are available only for the PrivateGSM Enterprise Edition. PrivateGSM Professional Edition can't place calls on a Trunk. |
The PrivateServer is designed to perform always as a client when configuring a SIP Trunk. This means that PrivateServer itself can not act as a Trunk Provider.
Even if each SIP Trunk can be used to both receive and place calls, PrivateServer has to be properly configured in order to act in a bidirectional way. By default the Inbound Trunks are configured for enabling the calls directed to external number through a different PBX. They can be later set up to let the PrivateServer receive incoming calls from a different PBX. This setup is made promoting one Inbound Trunk as an Outbound one.
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| Basically the Trunk setup has to be done for the outgoing calls first and after this function is enabled you can setup it for incoming calls as well. |
2.2 SIP Trunk's Families
From the PrivateServer version 2.5 you have two main SIP Trunk's Families:
- Secure Trunks
- Unsecure Trunks
The former ones entail both TLS and SRTP, while the latter none of them: they use just RTP over UDP (thus without TLS). Which one is to be used depends from many factors, major one is the kind of PBX on the trunk's end. For example Cisco Unity Call Manager and Avaya PBX are usually connected to PrivateServer via Secure Trunk, while SIP providers like Messagenet uses the Unsecure Trunk.
2.3 Authentication Models in SIP Ttrunks
Apart the Trunk's Families you should familiarise with the Authentication Model, that can be:
- Registered Trunks
- Unregistered Trunks
The Trunks using the Registered Authentication Model need an account on the other end. Then they use the account's credential to authenticate the Trunk when the PrivateServer is started and every communication that passes over that Trunk is considered authenticated, thus valid by default, and has the right to be processed and routed.
The Trunks with no registration, on the other hand, don't have needs for an account to be setup, instead they use the IP address to authorise every SIP communication directed to the PrivateServer. This model implies that any new SIP communication is authenticated against the sender's IP address (meaning the one belonging to the PBX connected to the PrivateServer).
The latter model is mostly used in production systems, eg with CUCM and Avaya. The former is mostly used with SIP Provider.
For each of the Families and the Authentication Models you are going to find a specific manual page describing the correct configuration and the possible parameters to be used.
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