Global Dial Plan - Using Gatekeeper

Unanswered Question
Jul 14th, 2010
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Hi,


Im hoping someone can help me out here.


We have been taksed with defining a global dial plan as a suggestion in our company. The problem is we have no authority to enforce it and we are using different systems throughout the globe. Everything we suggest causes problems for someone, the best we could come up with was 8 digit global id consisting of C(1 digit continent or cluster)SSS(3 digit site id)XXXX(4 digit user extension).This seemed to work for most but some systems aparently didnt allow overlaps as it clashed with an internal number range and some just didnt like it because it was very different to a dial plan they have within their country.


In any case, we were always going to need a gatekeeper and a directory gatekeeper to manage this so i thought how about we define a global dial plan but allow each site to send whatever digits they like to the gatekeeper then we translate them into the global dial plan, route it and send only the required digits.


Ive used gatekeeper in a simple fashion in the LAB but even designing this is proving difficult. My thoughts were (for now);


2 x Zones - EUZone and USZone


In the EUZone for now there needs to be 2 x CUCM in UK, 2 x CCME in UK, 1 x CUCM in Germany


In the USZone for now there will be 1 x Avaya in Mexico and 1 x Avaya in US


The config i have is;


gatekeeper
zone local EUZone ***.com 10.48.90.29
zone prefix EUZone 3.......
gw-type-prefix 1#* default-technology
no shutdown


The CUCM in the lab in UK (e.g 30205000) can dial the other CUCM Live in UK (30102085) by its 8 digit id i can see the gatekeeper handle the call. When calling from the CUCM Live in UK to the CUCM Lab the gatekeeper handles the call but it is sending it back to the CUCM Live so it loops out and the CUCM Live says 'call cannot be completed'


I appreciate this is a massive essay and would love it to get some other opinions.


Best wishes


Jon

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rodmont74 Fri, 07/16/2010 - 10:37
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Hi Jon, my company is set across globe and we have been recently lots of migration from TDM (to which is refered as legacy internally) to IP Telephony or IPT. Americas region is Cisco bound except for Canada which had recently migrated to Nortel last year. Europe and Asia are mixed Cisco and Alcatel deployments depending on the country.

There was two iniciatives in paralel because there was no global coordination at the time they began. Americas use a cluster for routing calls between a number of clusters in US and some countries in South America use this routing cluster to resolve numbers to US. Same path back from US to South America clusters do work. The routing cluster knows destinations and a call placed with full international dialing code followed by E.164 number is routed by IP and if there is no bandwidth, it fails back to PSTN (next route group in the route list). There is even an HTTP app for phones for a Global Directory where people can find numbers across the world and dial directly from it. One con is that for each dialing partition there can be several outbound and globally routes. In US there are more than a 100 destinations, but hopefully, you can set a route using .XXXXXXXXXX as NAMP has no variable lenght, routing cluster checks for known destinations and forward call to destination cluster, or fails the call from which a local route group reach local PSTN gateway with minimal impact in WAN and call setup time.


Another solution that started in Europe and probably because of non Cisco IPT deployment is by using gatekeepers with prefixes and zones for countries or continents. Calls places to **44..... reach UK destinations, **33.... reach France, it all depends on extension lenght used in each country and consider there is no overlap between them. Unfortunatelly this is not always true. Brazil has 10 offices with 4 or 5 digits lenghts as they are slowing progressing into 5 digits lenght plus IPT migration (some locations use a legacy PBX behind a gateway) and there are some overlapping. Testing solution was to include a location/area code after country code and set individual Gatekeeper controlled trunks and zones. So dialing from UK to Rio de Janeiro would be like **5521.... but dialing to Brasilia 5561..... as there is 4 and 5 digits lenght for those locations. While it simplifies routing from partitions as you only need a **.! route for each one of them, gatekeeper zoning and ICTs are needed to be considered and end users need to know of when dialing an area code or not for a country. Also, there is no easy way to fail a connection to PSTN as the clusters don't know prefixes before extensions. It's assumed bandwidth is plenty for the calls, which is not always possible (considering cost of bandwidth x amount of toll traffic avoided).


A third possibility I saw in some companies, are using a global dialing plan that do not map to DID. So suppose a New York office DID is +1 212 555 1000 to 9999, office uses 5 digits globaly but extensions are 31000 to 39999 instead of 51000 to 59999. People would need to know just internal extensions to use internally but require to know complete external numbers when calling from outside the company. I suppose a gatekeeper could be loaded with zones pointing to clusters and IP PBX across the global with not too much difficult. Some of the challenges go to end user getting to know around telephony system.


Usually the easier you do for them, more difficult to keep but I'd be glad to hear new ideas in the forum.


Good luck with your design.

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