If you remember I've said that the trunks are the way a call gets out of the system. It's important to make this small distinction. Direct dialing is when you dial a extension in your system according to the dialplan. Indirect dialing assumes that you will leave the system via a trunk. But the trunk is just the way to exit not the logic behind it. The logic is made out of 2 parameters. One is the route patterns and the other is the ARS table (will discuss it in the next lesson).
So. Imagine your trunks as a highway with multiple lanes. Each lane (or lanes) are toll lanes so you have to pay to get to them. Some lanes require $10 to enter and some other lanes require $5 to enter. Each group of lanes that share the same cost are grouped together. In Avaya CM world, we can associate this group of lanes with what we call a route and the cost with FRL (or Facility Restriction Level).
So, what is a route ? A route is a group of one or more trunks that can be accessed only by stations that have a FRL greater of equal to the FRL of the route.
Remember when we setup the COR that we specified the FRL? The FRL determines the rights or permissions assigned of a user when it comes to determining if the user can access a route. We can say that when you assign a COR to a station you will give him a number of "tickets" that he can use when trying to access the routes patterns (just like the price for the highway). For the station to have access on a route (be allowed to make the call), the system will compare the number of "tickets" the user has with the number of tickets the route requires to be accessed. If the user has enough tickets then he will be allowed to make a call, otherwise he will not be allowed.
FRL can have values from 0 to 7 where 0 is the lowest permissions (most restrictive) and 7 is the highest (least restrictive). You don't configure it, you assign it!
Now, you can have multiple routes, each one on the same trunk but with different FRLs. Why ? Well, by default, you can make international calls and local calls on the same routes, don't you ? It would be difficult to ask from your telco 5 trunks and each one with different permissions on them. So, in order to distinguish between the calls, when you implement the system you will have to "create" virtual groups that will require different permissions. Each "group" will use the same route but will require a different "number" of tickets to be accessed.
Let's take this example:
You have to implement a system in North America. You know that local calls are free, then long distance calls are being payed and international calls are very expensive.
First thing you need to define your groups. In the case above we will have:
- local call only
- long distance calls
- international calls
You noticed that at this point i did not said what local calls means and what long distance calls means. We will define that later in the ARS table. At this point we're just slicing the trunk into "groups" that are separated by permissions (read different FRL's associated)
Each group will have a higher FRL. There is no rule in place other then less permission=higher FRL. Again, you can choose any numbers from 0 to 7 as you wish as long as you follow the rule. So any combination bellow is ok
- local call only, FRL 1
- long distance calls, FRL 2
- international calls, FRL 3
- local call only, FRL 3
- long distance calls, FRL 6
- international calls, FRL 7.
So, back to our implementation, you will need to add COR's. Let's assume that we will choose the second option (FRL 3,6 and 7). Each COR will have access to more routes. So we can have the following CORs
COR1 : FRL0
COR2: FRL 2
COR3: FRL 3
COR4: FRL 6
Any station that will have COR5 will be able to access any route (think VP's and senior management). On the other hand any station that will have a FRL of 0 cannot access any routes (think lobby phones). Stations assigned to COR3 could be your mailing room where a lot of people have access, while COR4 can be everybody else with the exception of the international sales team that will have assigned the COR5. Remember that the FRL works with greater or equal then so that means that COR4(FRL6) can access local calls (route FRL3<=cor FRL6) and long distance calls (route FRL6<= cor FRL6) but not international calls (route FRL7>cor FRL6).
Hope this explains the FRL. Next lesson, route-patterns.