Solved Outbound Rules for Least Cost Routing

[GiannisA]

Hello all,

I am implementing Least Cost Routing (LCR) between our mpls connected offices and i am facing the below issue.

I have Site A in USA with number +1 703 123 4567 and Site B also in USA with number +1 562 765 4321

The calls between the 2 offices can be done with 3 different ways

First: Call with +1 or 001 and the number
Second: Call with just 1 and the number
Third: Just call the number without country code

I have created an outbound rule that when someone calls from A --> B using +1 , strips 7 digits and calls (for our example) 654321 number using the SIP trunk that i have for the internal calls.
This dummy number is an outbound rule on Site B which it is using as a Route a loopback trunk.
This loopback trunk has been configured to call main line when we are during office hours.

With the way i have implemented it, if someone calls using just 1 or without country code, LCR will not work and it will the SIP trunk from the provider and the call will be charged.

I could implement 3 different outbound rules for each office, but i have many offices in USA and this will end to have many outbound rules to do actually the same thing.

Is there any to combine the 3 different ways of calling into one rule ?

Thank you

 

[ChrisC_3CX]

Just so that we first get a better understanding of you current configuration, how did you connect the two 3CX PBXs? Are you using a generic SIP Trunk or bridge, etc?

You mention having a SIP Trunk for internal calls, is that the one? By internal calls do you mean from one PBX to the other? If yes, why are you then using an outbound rule and loopback trunk instead of just routing the call to its destination directly?

 

[GiannisA]

The 2 PBXs are connected through a bridge.
Yes, when i say internal calls i mean to call from one PBX to the other.

I am using the loopback because in the outbound rules of my PBXs, there is a generic outbound rule that matches the non-internal calls and it's using a SIP trunk by the provider

The problem that i want to solve with LCR is that there are users that instead to call the extension of another user in the other office, they call the main number of the office, which is reachable from the outside(public) network.
That means, we will be charged for that call.

 

[leejor]

If you are using a Loopback trunk, then I assume you are using two concurrent calls, out, and back in, before the call routes to the destination?. If so, then that is not a very efficient way of emplementing, if there is any volume of calling.

I think that one issue,that you've created for yourself, is that you do not seem to have standardised the dialling of outbound numbers, and allow users to dial them in several ways. While this makes it "easier" for the originator, it is going to make it more complicated for you, and require more outbound rules, to compensate.

 

[GiannisA]

Yes, that's correct, we are using 2 concurrent calls to achieve LCR.
We have specific rulea to call to each office(e.g. when you call a 4 digit starting with 10 then use this route, etc..) but the outbound rule for the calls outside of the company it's indeed very generic in order to match every possible number in every country.

Is there any more sufficient way to achieve LCR with the current setup or generally a better approach for LCR ?

 

[ChrisC_3CX]

I have to agree with @leejor on this one and say that, ideally, users should not be attempting to reach the other PBX using the DID in the first place, and using a loopback SIP Trunk should be avoided.

If you are set on using this setup though, in theory, you should be able to replace the 3 Outbound rules with one by having 1 Outbound rule match all cases like +198765432,00198765432,19876543, and so on. Then have that same Outbound rule on the second PBX to catch the call and route it back. You will of course need one outbound rule on each side for every DID.

 

[GiannisA]

Yes, i agree that ideally the users shouldn't call the main number but they do it. That's why i am trying to overcome this problem with LCR.
Could you please let explain me why the loopback SIP trunk should be avoided ?

 

[ChrisC_3CX]

Well first of all, as @leejor already mentioned, it will consume two sim calls when in use, second, troubleshooting an issue involving a Loopback SIP Trunk will most definitely render the whole endeavor problematic as such call routing is non-conventional and hence harder to trace.

You might want to consider using an Outbound Rule to block all calls to the said DIDs and therefore force users to use the internal extensions for the other PBX. Just a thought.

 

[GiannisA]

Thank you @ChrisC_3CX and @leejor for your suggestions!