CUCM Call Routing (part 3): Local and long-distance calls

The dial plan discussion continues…

• 911 Emergency Call Routing

• 9.911 Emergency Call Routing

• 9.[2-8]11 Three digit service codes

• 9.[2-9]XXXXXX Local 7-digit dialing

• 9.[2-9]XX[2-9]XXXXXX Local area code 10-digit dialing

• 9.1[2-9]XX[2-9]XXXXXX Long Distance 11-digit dialing

• 9.011! International dialing

• 9.011!# International dialing

• 9.0 PSTN operator

Local 10-digit dialing is the next route pattern to be discussed. 10-digit dialing has become the standard local dialing mechanisms in major cities where local service providers will no longer route 7-digit dialing. Every 7-digit phone call will require the end user to wait up to 15 seconds before the call is routed if both 7-digit and 10-digit dialing are configured in the dial plan as shown in the dial plan above. The T.302 timer must expire every time there is an overlapping dial plan entry. A 7-digit phone call to 9 738-3586 matches both the 9.[2-9]XXXXXX (7-digit) and

9.[2-9]XX[2-9]XXXXXX (10-digit) route patterns. This overlapping issue is easily avoided where 7-digit dialing options will not be routed by the PSTN service provider. If the provider is routing 7-digit phone numbers, measures can be taken to minimize the overlapping dial plan. Most providers will not route every 10-digit phone number, they will only route 10-digit numbers with an area code that matches area codes covered in the local geographic region. If a service provider in the New York area will allow call routing of the 914, 845, 212, 646, and 718 area codes, the 9.[2-9]XX[2-9]XXXXXX route pattern in the dial plan above will be replaced by the following 5 route patterns:

• 9.914[2-9]XXXXXX

• 9.845[2-9]XXXXXX

• 9.212[2-9]XXXXXX

• 9.646[2-9]XXXXXX

• 9.718[2-9]XXXXXX

This measure will minimize the overlap between the generic 9.[2-9]XXXXXX 7-digit numbering space and local 10-digit dialing.

The first 3 digits of the 10-digit route pattern is commonly referred to as the area code or the NPA (numbering plan area). The next 7-digits follows the same nomenclature as 7-digit dialing as covered in the last blog. Notice that the leading digit of the area code follows the same pattern as the leading digit in the three digit exchange (no zero or one) to minimize overlapping numbering spaces. Local area codes and local 3-digit exchange (NXX) numbers do not overlap. If a geographical region is running out of numbers and the provider must use local exchange numbers that overlap with the local area code, the provider will most probably stop routing 7-digit calls.

The next route pattern in our discussion is the 9.1[2-9]XX[2-9]XXXXXX 11-digit route pattern used for long distance dialing. The 11-digit long-distance dialing number does not overlap any of the other numbering spaces because the phone number begins with a 1 (after the 9 access codes is stripped out of the dialed pattern). The leading 1 indicates that the local exchange carrier (LEC) should switch the call to the long distance carrier for billing purposes. In many cases today, the LEC and long distance carrier are the same entity.

The generic 11-digit route pattern includes the continental United States, Canada, Puerto Rico, and many Caribbean islands. There are many 11-digit numbers that carry International tariffs. 1-900 and 1-976 pay services are also included in this generic range. Leaving these numbers in the dial plan could lead to a Resume Updating Event (RUE). The following ranges of phone numbers should be removed from most dial plans in the United States that do not have any business conducted in these areas:

• 9.1264xxxxxxx Anguilla

• 9.1268xxxxxxx Antigua/Barbuda

• 9.1242xxxxxxx Bahamas

• 9.1246xxxxxxx Barbados

• 9.1441xxxxxxx Bermuda

• 9.1284xxxxxxx British Virgin Islands

• 9.1345xxxxxxx Cayman Islands

• 9.1767xxxxxxx Dominica

• 9.1809xxxxxxx Dominican Republic

• 9.1473xxxxxxx Grenada

• 9.1876xxxxxxx Jamaica

• 9.1664xxxxxxx Montserrat

• 9.1787xxxxxxx Puerto Rico

• 9.1869xxxxxxx St. Kitts & Nevis

• 9.1758xxxxxxx St. Lucia

• 9.1784xxxxxxx St. Vincent and Grenadines

• 9.1900xxxxxxx Pay services

• 9.1976xxxxxxx Pay services

• 9.1868xxxxxxx Trinidad and Tobago

• 9.1649xxxxxxx Turks and Caicos

• 9.1340xxxxxxx United States Virgin Islands

What other phone numbers do you remove from your dial plan?

The next blog will explain different methods of removing these phone numbers from the dial plan and continue the dial plan conversation.

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