H.323 Global Dialling Scheme (GDS)

The Global Dialling Scheme has been adopted by a number of European Countries for H.323 interzone dialling - including Ireland, The Netherlands, Germany, Switzerland and the UK. More countries are currently being added to the system.

The scheme defines 00 as an international dialling prefix and the use of the well-known ITU-T country telephone codes. Zone prefixes and extension numbers are defined by the national managing agent - usually the National  Research Network (NRN) in that country.

E.g. To dial a conference hosted in the UK, dial 0044 01002 468 where:

  • 00 is the international dialling prefix
  • 44 is the code for the UK
  • 01002 is the zone in which the MCU hosting the test conference is registered
  • 468 is the conference number

It is also possible to dial existing ViDeNet numbers through systems connected to the dial plan. Dial the ViDeNet dial number as if you were connected directly to a ViDe zone. ViDe numbers usually begin with a single 0. All other numbers begin with 00.

Note: Within your country system it may be necessary to dial an additional prefix or 'Exit Zone' prefix. This is similar to dialling 9 for an outside line from an internal telephone system. Contact your national gatekeeper manager for more information.

The Global Dialling Scheme uses a hierarchy of gatekeepers (see below) to route call set-up information nationally and internationally. National gatekeepers have knowledge of all zones within a country, World gatekeepers have knowledge of all National gatekeepers.

Where a country does not have a National Gatekeeper and an institution within that country would like to join the system, it will be possible for another National Gatekeeper to act as a 'Virtual Gatekeeper' until that country has its own Gatekeeper in place. This means that the institution can have a number within its own country code from the beginning.

Gatekeeper Hierarchy