International gateway exchange
# International gateway exchange

In telephony, an international gateway exchange is a telephone switch that forms the gateway between a national telephone network and one or more other international gateway exchanges, thus providing cross-border connectivity.

## Requirements

Whereas international gateway exchanges are commonly implemented using hardware that could also serve to build a Class 4 (national transit) switch, some of the differences between an international gateway exchange and a Class 4 switch include:

* International variants of signalling protocols, such as International ISUP and #5, in addition to the relevant national signalling protocols.
* Support for echo cancellers.
* Support for DCME
* Support for international accounting and settlement agreements.
* Support for A-law/mu-law transcoding
* High capacity (some of the largest telephone exchanges in the world are international gateway exchanges).
* Support for the numbering plans of each of the countries that may be dialed.
* Advanced traffic routing capabilities, in order to take advantage of the best available tariffs for each destination.
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