VoIP Dial Plan

Voice over IP Dial Plans for both phone devices and PBXes.

Preface

This article discusses the essentials of a VoIP dial plan, detailed examples, and necessary guidelines pertaining to the order of dial plans.

Dial plans are one of the most confusing areas for beginner VoIP users and therefore should be planned carefully and thoroughly tested before putting them into a production environment. If a dial plan is not properly configured you make end up locking someone out from dialing a specific number.

Characters Used

Order Sequence is important

The sequence that you use for your dial plans is crucial. Each sequence must ensure that if one fails it would fail over to the next sequence until it finds the right dial plan to use. If there is no sequence to fail over to, then the numbers you dialed would not complete within the dialplan you used. Consequently, if you put a dial plan that would match everything in the front, it will never see the other dial plans behind it and therefore would either have a delay in dialing the number or fail to dial the number altogether. eg: xxxxxxx|xxx would allow a 7 digit number to dial but if you tried to dial a 3 digit number, it would fail cause it is expecting a 7 digit number instead. If you made your dial plan as xxx|xxxxxxx then it would work as it sees the 3 digits in the dial plan and allow it to dial.

Examples of Phone Based Dial Plans

Aastra

Default Dial Plan: X+#
The default dial plan will allow any number of digits or * symbol to be entered until the # or short intertimer expires. Since Aastra phones are meant to be managed by the PBX system this should be the default dial plan that you should be using within your aastra.cfg file for TFTP provisioning.
Any phone specific dial plan changes should be done via the .cfg file instead.

Linksys

Dial Plan Entry Functionality

* *xx Allow arbitrary 2 digit star code
* [3469] 11 Allow x11 sequences
* 0 Operator
* 00 Int’l Operator
* [2-9] xxxxxx US "local" number
* 1 [2-9] xx [2-9] xxxxxx US 1 + 10-digit long distance number
* xxxxxxxxxxxx. Everything else (Int’l long distance, FWD, ...)

If IP dialing is enabled, one can dial [user-id@] a.b.c.d [:port] , where ‘@’, ‘.’, and ‘:’ are dialed byentering “*”, user-id must be numeric (like a phone number) and a, b, c, d must be between 0 and255, and port must be larger than 255. If port is not given, 5060 is used. Port and User-Id areoptional.

Implicit sequences:The SPA implicitly appends the vertical code sequences entered in the Regional parameter settings to the end of the dial plan for both line 1 and line 2. Likewise, if Enable_IP_Dialing is enabled, then ip dialing is also accepted on the associated line.

Examples:
The following dial plan accepts only US-style 1 + area-code + local-number, with no restrictions on the area code and number.
( 1 xxx xxxxxxx )

The following also allows 7-digit US-style dialing, and automatically inserts a 1 + 212 (local area code) in the transmitted number.
( 1 xxx xxxxxxx | <:1212> xxxxxxx )

For an office environment, the following plan requires a user to dial 8 as a prefix for local calls and 9 as a prefix for long distance. In either case, an “outside line” tone is played after the initial 8 or 9, and neither prefix is transmitted when initiating the call.
( <9,:> 1 xxx xxxxxxx | <8,:1212> xxxxxxx )

The following allows only placing international calls (011 call), with an arbitrary number of digits past a required 5 digit minimum, and also allows calling an international call operator (00). In addition, it lengthens the default short interdigit timeout to 4 seconds.
S:4, ( 00 | 011 xxxxx x. )

The following allows only US-style 1 + area-code + local-number, but disallows area codes and local numbers starting with 0 or 1. It also allows 411, 911, and operator calls (0).
( 0 | [49] 11 | 1 [2-9] xx [2-9] xxxxxx )

The following allows US-style long distance, but blocks 9xx area codes.
( 1 [2-8] xx [2-9] xxxxxx )

The following allows arbitrary long distance dialing, but explicitly blocks the 947 area code.
( 1 947 xxxxxxx ! | 1 xxx xxxxxxx )

The following implements a Hot Line phone, which automatically calls 1 212 5551234.
( S0 <:12125551234> )

The following provides a Warm Line to a local office operator (1000) after 5 seconds, unless a 4 digit extension is dialed by the user.
( P5 <:1000> | xxxx )

Others

Add dial plans for other phone sets or expand the above features as well.

Examples of PBX Based Dial Plans

References