Setting Up Siblings

About Siblings.

Setting up Siblings in SAIL is very easy. Open the Trunks panel, select New Trunk and from the drop-down keys menu select SailToSail. This will bring up the Sibling definition panel. There are only three fields to fill out. Let's say, for example that we want to share extensions across two machines Sibling1 and Sibling2. Furthermore, only Sibling2 has access to external analogue lines. On the server-manager for Sibling1 we might enter the fields as you see in the screenshot. All we need is the hostname for Sibling2 and it's ip address. Press Save and we're done. We then do the same thing on Sibling2 server-manager but this time pointing the fields at SSibling1.

Finally, we need to add route information to the two siblings so that they know which traffic to transfer. Set up a route called INTRA and select Sibling1Sibling2? as the route. You may now code a dialplan like this

• • _XXXXXX _6XXX

This dialplan will direct all 6XXX series internal calls to Sibling2 (which owns those extensions) and also all 6 digit local calls to Sibling2 for despatch over it's analogue lines.

Privilege.

In order to understand privilege you need to understand the basic asymmetry of Asterisk. All (or at least most), asterisk implementations have two basic pathways through them. The unprivileged (or inbound) pathway which processes inbound calls and the privileged (or outbound) pathway which processes internal and outbound calls. We call the inside (outbound) pathways "privileged" because they usually have additional functionalities that inbound pathways do not.

In the case of siblings, we normally create them as privileged because we want, in the main, to allow internal calls between extensions on different machines, the ability to share conference rooms, outbound trunks and so forth. However there is one instance (trunk consolidation), where we want to route unprivileged calls. This happens when we wish to route an inbound trunk call to another instance of Asterisk for despatching. Unprivileged siblings are named differently and behave differently to their privileged counterparts. In order to distinguish them, unprivileged siblings carry the "»" or "~" symbol to signify their different status.

Unprivileged siblings do not appear in outbound route dropdowns but they do appear in inbound trunk route dropdowns (privileged siblings behave the opposite way). An inbound call arriving in to a switch can be passed on to a sibling across an unprivileged route and it will look to the receiving sibling as if it had arrived from outside of the system. The only other thing necessary at the receiving end is the requirement to provide a "hook" for the call to process through. We create a PTT-DiD trunk to server this purpose.

As an example, lets say that inbound calls to the number 01924918076 are to be processed by a sibling. In the inbound trunk corresponding to 01924918076 on the receiving switch (sibling1) we set the inbound route to point to the unprivileged sibling (sibling2).

Sibling2 will see the call arrive across the unprivileged link from Sibling1 with a DNID of 01924918076. So we can create a PTT-DiD entry in Sibling2 to receive the call and route it onwards.

The PTT-DiD can now terminate the call (or perhaps pass it on even further in the hierarchy) by handing it to an extension or group of extensions. Using privileged and unprivileged links it is possible to create a true "Telco" type hierarchy processing calls both up and down the network from arrival to termination.