Global Dialing Scheme
From Wikipedia, the free encyclopedia
The Global Dialing Scheme (GDS) is numbering plan for H.323 networks. Based on the numerology provided by the United Nations International Telecommunications Union, GDS numerology resembles the international telephone system numbering plan, with some exceptions.
The Global Dialing Scheme uses a hierarchy of gatekeepers 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.
Each basic number consists of four parts: <IAC><CC><OP><EN>. [1]
[edit] GDS in North America
The North American root gatekeepers serve the United States and its territories, Canada, Bermuda, and many Caribbean nations, including Anguilla, Antigua & Barbuda, Bahamas, Barbados, British Virgin Islands, Cayman Islands, Dominica, Dominican Republic, Grenada, Jamaica, Montserrat, St. Kitts and Nevis, St. Lucia, St. Vincent and the Grenadines, Trinidad and Tobago, and Turks & Caicos. Their purpose is to resolve h.323 numbers at the '001' prefix level under the Global Dialing Scheme (GDS) plan.
Terminology in this document follows the <IAC><CC><OP><EN> format of general GDS documentation.The ‘001’ above refers to the IAC of 00 and the CC of 1 for North America.
This North American node of the Global Dialing Scheme utilizes an enhanced version of the North American Numbering Plan (NAMP) to distribute addresses. The address space is divided into two parts: North American E.164 Space and North American Super Space. North American E.164 Space correlates to existing telephone number assignments and is well-suited for IP telephony applications. North American Super Space utilizes unused NAMP address space starting with 0 or 1 to create an address space that is separate from existing telephone numbering addresses. This North American Super Space is well suited to video over IP or other all-IP applications that desire to be distinct from telephony applications and NAMP regulations.
GDS users in North America may request addresses in either or both spaces, if needed.
North American E.164 Space
Addresses allocated from this range will be based upon the ITU-T e.164 telephone number assigned to the current subscriber of a range of telephone numbers, rather than to the service provider carrying those numbers. For example, if a university held +1.919.226.6100 through +1.919.226.6199, then that university would be eligible for the GDS prefix 00191922661. That university could assign the remaining two digits to endpoints 00-99. Aside from maintaining direct inward dial (DID) capability for endpoints, there is no reason to limit endpoint numbering to two digits. For example, the university might use five digit endpoint numbers for a total address space of 001919226610000 through 001919226619999, yielding 10,000 usable addresses. Organizations that do not have a DID range may use this extension technique to map their entire address space onto a single 10-digit telephone number. Implementors of voice over IP applications may wish to adhere more strictly to the NAMP numbering convention.
North America Super Space
The organizational prefixes <OP> of addresses in North American Super Space (NASS) start with a 0 or 1 immediately following the country code (1). These digits are not assigned under the NAMP, being used rather for special indications as described in 1947 by AT&T and Bell Laboratories.
NASS addresses are of the form:
001PX9<EN>
Where P is a 0 or 1. X is a variable length string of digits consisting of any digit between 0 and 8. 9 is used as a delimiter. <EN> is a variable length user-defined number consisting of any digits 0-9. Thus, NASS addresses are variable in length.
Some examples of fully qualified GDS NASS addresses; all address below contain the GDS IAC (00) and CC (1) with endpoint numbers indicated as <EN>:
0010 Reserved
00119<EN> (OP = 19)
001109<EN> (OP = 109)
001119<EN> (OP = 119)
001129<EN> (OP = 129)
001139<EN> (OP = 139)
001189<EN> (OP = 189)
00110123456789<EN> (OP = 10123456789)
