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Asterisk catch e164 patterns

Catching e164 patterns with Asterisk

In the realm of telephony, ensuring seamless call routing and processing hinges on the ability to accurately identify and handle phone numbers in a standardized format. Enter e164, a widely adopted standard that provides a consistent structure for international telephone numbers. This blog post delves into the intricacies of working with e164 patterns within the context of Asterisk, a powerful open-source communication platform.

What is e164?

E164 format is a standard for the international telephone numbering plan that ensures each number is unique. It follows a specific structure, starting with a "+" sign, followed by the country code, and finally the local telephone number. For instance, the e164 format for a French number could be +33123456789.

Why do e164 is not matched by "_X."?

Let's consider a scenario where we aim to match an incoming call from a French number using Asterisk. Initially, we might attempt to use the pattern "_X." within our dialplan, assuming it would match any sequence of digits. However, we encounter an issue: the "+" sign, being a non-digit character, is not matched by the "_X." pattern.

Let's illustrate this with a code snippet: 


exten => +33234567890,1,NoOp(Before Goto SDA de test, with ${EXTEN})
exten => +33234567890,2,Goto(sda_de_test,${EXTEN},1)

Then, lower in the file: 


[sda_de_test]
exten => _X.,1,NoOp(Entering SDA de test)
 same => 2,Dial(PJSIP/0123456789@trunkoftelco1)
 same => n,Hangup()

In this example, the incoming call with the e164 number "+33234567890" would not be matched by the "_X." pattern in the "sda_de_test" context.

To rectify this, we need to explicitly include the "+" sign in our pattern. Modifying the pattern to "_+X." would successfully match the e164 number.

However, a more robust approach involves incorporating the entire e164 pattern directly into the extension. This eliminates the need for separate patterns and simplifies the dialplan. 


[sda_de_test]
exten => +33234567890,1,NoOp(Entering SDA de test)
 same => 2,Dial(PJSIP/0123456789@trunkoftelco1)
 same => n,Hangup()

By specifying the complete e164 number in the extension, we ensure accurate matching and streamline call handling within our Asterisk dialplan.

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