[cisco-voip] Local route group with CFA and other stuff

[Roger Wiklund]

In the old days of (IP)PBX and before LRG:

Phone A calls Phone B (onnet). Phone B has CFA to mobile phone. The
call to the mobile phone is sent via Phone B's gateway.

After LRG, same scenario, The call to the mobile phone is now sent via
Phone A's RG-gateway specified in the DP.

This of course poses a problem, especially if A and B are in different
countries. You cannot call a local mobile number in country B from
country A.

Solution: Globalize called number to E164 and then normalize on each
gateway. This is all fine and dandy, also simplifies TEHO, AAR etc
when the called number is already in the correct format in conjunction
with LRG.

Now to the problems.

CFA problem: I know there is a question of "who pays for the CFA". But
before LRG and all PBX configurations that I have encountered handles
this the "old" way. Phone B paying.

With the "old" solution, the call is at least a local call within the
country. With the new solution, the call is an international call if A
and B are in different countries. Also lets say that Phone A is not
even allowed to make an international call, then CFA won't work at
all.

Normalization problems:

If im in Sweden and call US I would dial: 001xxxxxxxxx
If I dial a number outside my area code I dial 018xxxxxxx for example
(018 being the area code)
If I dial a number in my area, I can skip the 0 and just dial the
local number 5 to 8 digits in length for Stockholm.

Now best practise is to send the numbers to the PSTN like this,
depending on where I call. It's easy to accomplish this with called
party transformation patterns to strip the E164 +46 +1 etc and prepend
00, or 0 etc.

Now this assumes that I have local gateways at each site. Because If I
have a gateway in Stockholm and one in London, I need to have
different transformation patterns to normalize.

Now what will happen if I have a central SIP trunk instead of local
gateways in each country. My SIP trunk provider only has one trunk,
and on that trunk there are "virtual" gateways if you will. I.E public
phone numbers for Sweden, UK, Germany etc. The SIP trunk provider
determines what location to use based on the calling number. So If i
place a call from Sweden to US for example, it will identify based on
the calling number that this call is from Sweden, and then it will
apply the Sweden dial plan and rates etc in the PSTN.

Now as I only have one SIP trunk, I can only apply one transformation
patterns. As far as I see it, there is no way to normalize the numbers
now.

So just because I use a central SIP trunk, I can no longer use LRG. So
I need to create route patterns over and over again for the same
country. It's like hey we have this cool new features, but you cannot
use them because you use a SIP trunk.

Have you encountered this problem or something similar? Any nice
workarounds or something like that that I have missed.

Thanks

/Roger