3.13 Localized Call Egress

This topic describes localization at call egress.

The figure shows how localized call egress at gateways is implemented.

The only requirement is to change the calling-party and called-party numbers from the +E.164 format to the format that the PSTN provider expects.

This requirement can be best achieved by using outbound-call, called-party, and calling-party transformationCSSs.

In the example, the called-party transformation patterns that are applicable to the San Jose gateway (based on the partition and called-party transformation CSS) are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+.! DDI PreDot, Prefix 011
\+.1XXXXXXXXXX DDI PreDot
\+1408.XXXXXXX DDI PreDot
Note

In this example, the San Jose gateway does not support number types, but it requires the use of national and international access codes. Therefore, 011 must be prefixed on international calls. For national calls, the plus (+) sign and country code (1) must be replaced by the national access code. Even though the country code and the national access code are identical, only by coincidence, the transformation can be simplified by removing only the + sign.

The called-party transformation patterns that are applicable to a gateway in Hamburg, Germany (based on the partition and called-party transformation CSS), are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+.! DDI PreDot, type international
\+49.! DDI PreDot, type national
\+4940.! DDI PreDot, type subscriber
Note

In this example, the Hamburg gateway uses number types instead of international (00) or national (0) access codes (in contrast to the San Jose gateway, which does not use number types).

In the example, the calling-party transformation patterns that are applicable to the San Jose gateway (based on the partition and calling-party transformation CSS) are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+.! DDI PreDot, type international
\+1.XXXXXXXXXX DDI PreDot, type national
\+1408.XXXXXXX DDI PreDot, type subscriber
Note

In this example, number types are used at the San Jose gateway for the calling-party number. If no number types were used, typically 7-digit numbers (local source of the call), 10-digit numbers (national source of the call), or more than 10 digits (international source of the call) are used. In some areas, 10-digit local dialing is used instead of 7-digit local dialing.

Having nonlocal calling-party numbers implies the use of features such as TEHO, PSTN backup over the IP WAN, or mobility features with local PSTN breakout. Nonlocal calling-party numbers are not permitted in some countries and by some PSTN providers. Some providers verify that the calling-party number on PSTN calls that they receive matches the locally configured PSTN number. If a different PSTN number is set for the caller ID, the call is either rejected or the calling-party number is removed or replaced by the locally assigned PSTN number.

The calling-party transformation patterns that are applicable to a gateway in Hamburg, Germany (based on the partition and calling-party transformation CSS) are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+.! DDI PreDot, type international
\+49.! DDI PreDot, type national
\+4940.! DDI PreDot, type subscriber

Localized Call Egress at Phones

The figure illustrates how you can implement localized call egress at phones.

The only requirement is to change the calling number from the +E.164 format to the preferred format of the end user.

This task can be best achieved by using the calling-party transformation CSS for the remote number.

In the example, the calling-party transformation patterns that are applicable to a phone that is located in San Jose (based on the partitions and calling-party transformation CSS) are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+1.XXXXXXXXXX DDI PreDot
Note

In this example, international calls are shown in globalized format (+E.164 format) because there is no \+! calling-party transformation pattern. National and local calls are shown with 10-digit caller IDs.

In the United States, it is common to use 10-digit caller IDs for local and national callers.

In the example, the calling-party transformation patterns that are applicable to a phone located in Hamburg, Germany (based on the partitions and calling-party transformation CSS), are configured as shown in the following table:

Transformation Pattern Performed Transformation
\+49.! DDI PreDot, Prefix 0
\+4940.! DDI PreDot
Note

Because there is no calling-party transformation pattern \+!, international calls are preserved in the normalized format (+E.164 format). Other than in the San Jose example, phones that are located in Hamburg use the national access code prefix (“0,” which is equivalent to the long-distance “1” in theNANP). The reason is that in Germany, variable-length PSTN numbering plans are used and therefore national and local numbers cannot be distinguished based on their length (like the United States with 7-digit and 10-digit numbers). When prefixing the national access code “0” to national callers, an end user can identify national calls by the leading “0.”

When users call back PSTN callers, the globalized number is used for the outgoing call. Therefore, there is no need to edit the localized number from a call list and to add PSTN access codes or national or international access codes.