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The Global Dialing Scheme Explained

Egon Verhayen

The Global Dialling Scheme (GDS) is a new numbering plan for the global
video and voice over IP network test bed, developed by ViDeNet. It
resembles the international telephone system numbering plan, with some
exceptions. With the GDS, you can number each participating
videoconferencing endpoint, MCU conference and gateway. GDS provides
easy, uniform dialling throughout the world.

Each basic number consists of four parts

  1. The International Access Code (IAC) (also called the world gatekeeper prefix) This is defined as 00
  2. A Country Code (CC) This follows the ITU international access code system. For instance, the country code for the Netherlands is 31. See the following PDF document for country codes:
  3. An Organisational Prefix (OP) Many national research organisations follow the telephone number system in their country and use their area code and organisational telephone exchange prefix. For instance, SURFnet's OP is 302305. However, there are other possibilities. Some organisations use their administration number or make one up. National research organisations or videoconferencing service providers could instead supply you with an OP, as was the case with the old ViDeNet system. In any case, your OP MUST be unique within a country. If you don't know your OP, please contact your videoconferencing service provider, your national gatekeeper, or the NASM working group (see below).
  4. An Endpoint Number (EN) Your EN can be any number and is decided by each organisation. However, we recommend that it be no longer than seven digits. Each endpoint number MUST be unique within the organisation. Both 305 and 1234567 are fine examples as long as they are unique.

The whole numeric number therefore looks like: <IAC><CC><OP><EN>


The Megaconference informal test MCU: 00(IAC) 1(CC) 189(OP) 7201234(EN)
Typed into your videoconferencing endpoint, the number would simply look
like: 0011897201234

The GDS also defines an alphanumeric dialplan (not used during the
Megaconference game). This part is equal to the alphanumeric dialplan of
the old ViDeNet and should be in the form:
< station ID>@<fully qualified domain name of the institution>

An example is:

More information on the GDS and the Numerical Addressing Space Management (NASM) working group overseeing its development can be found at: and