What is the Global Dialing Scheme (GDS)?
All active elements of an H.323 videoconferencing network (endpoints, conferences, multipoint control units, and gateways) typically have a name ("H.323 name") and number ("E.164 number" or "H.323 extension") as well as an IP address. These H.323 elements can register with a service called an H.323 gatekeeper, which provides H.323 name and/or E.164 number resolution to a specific IP address. Like DNS servers, gatekeepers can be hierarchically interconnected to allow uniform dialing among systems registered to different gatekeepers. Indiana University participates in the Global Dialing Scheme (GDS), a voluntary numbering plan for the H.323-based global video and voice over IP network, developed by ViDeNet and now managed by the Internet2 Commons. GDS resembles the international telephone system numbering plan, with some exceptions.
Each GDS number consists of four parts:
International Access Code (IAC): Also called the
world gatekeeper prefix, this is defined as 00.
Country Code (CC): This follows the ITU
international access code system. For instance, the country code for
the United States is 1. Switzerland's code is 41.
Organizational Prefix (OP): Many national
research organizations are assigned a unique OP number by the
Internet2 Commons. For instance, IU currently has the organizational
- Endpoint Number (EN): An EN is a unique number that is assigned to a particular endpoint or conference within the organization. The EN can be of varying length, but must be unique. For instance, a conference on IU's video bridge that includes the "Copybird" uses the EN 22200.
The whole numeric code therefore follows this format:<IAC><CC><OP><EN>
For example, the code for the IU Copybird is:00(IAC) 1(CC) 1439(OP) 22200(EN)
Typed into your videoconferencing endpoint, the number would look like:001143922200
Note: At IU, if you are asked to dial an E.164 number
that begins with a double zero (
00), dial it. If the
remote system or conference is ready to receive calls, you will
For information on IU's H.323 numbering plan, see At IU, how do I configure my H.323 videoconferencing endpoint with a qualified GDS E.164 number? For more about the Global Dialing Scheme, see ViDeNet or the Internet2 Commons.
Last modified on May 16, 2013.