Internet Hierarchy
U.S. Government Dept of Commerce
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ICANN
Internet Corporation of Assigned Names and Numbers - a non-profit corporation headquartered at the University of Southern California in Los Angeles U.S.A.
Functions as the IANA — Internet Assigned Numbers Authority — previously run by Jon Postel b.1943 d.1998
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Oversees the allocation of IP addresses 0.0.0.0 to 255.255.255.255
via five Regional Internet Registries.
Details of Asia Pacific registry follow.		Oversees a small root zone file of IP addresses for the registries of the *280 Top Level Domains .com, .uk, .au, .cn etc.
which it publishes on thirteen root name servers operated by twelve organizations.
Details of two of these TLD Name registries follow.
APNIC - Asia Pacific Network Information Centre based in Milton, Brisbane. Receives allocations in blocks of 16 million addresses which it reallocates in smaller blocks of, say, 64000 addresses to

ISP's - Internet Service Providers e.g. Telstra, Optus, AAPT, IINet, IPrimus, TPG, etc. The ISP's then allocate individual addresses, e.g. 202.139.83.152, to each computer, or computer network, as required.

Note that within the APNIC membership, there are also five National Internet Registries (NIRs), in Japan, China, Taiwan, Korea, and Indonesia.

1. AusRegistry, the official registry for the .au domain in Australia, publishes the file of IP addresses of all the open .au domains e.g. swcs.com.au which currently points to a name server on the WebMetrix network.

The WebMetrix name server then returns the IP address of the actual host computer for www.swcs.com.au

Your ISP caches (remembers) that domain name and IP address for, say, 48 hours, then deletes the record automatically. The cache reduces Internet traffic, and the automatic deletion enables a domain to change server hosts with only a 48 hour time delay for most ISP's to be updated.

Your PC saves a copy of the actual page in its cache, downloading a fresh copy normally only when the file size, or time of last update changes.

2. Verisign, the organization which actually maintains the root zone file and administers two root servers, is the official registry for the .com and .net domains, including google.com and microsoft.com

Google and other Search Engines store words and phrases, associating them with unique domain / page names.

They do this by simply following the hyperlinks within the web pages they know about, thus discovering new ones, and are thus building and refreshing the information in their databases continually.

Also, thus, when they display a search result, it may be a somewhat "stale" copy of the page. When you click on the link to download it, you then see the latest copy.

* Examples of Top Level Domain Registries: .com=80million (administered by Verisign), .cn=14million (China), .de=13million (Germany), .net=12million (also administered by Verisign), .org=7million, .uk=7million, .info=5million, .nl=3million (Netherlands), .eu=3million, .biz=2million with .au=1million
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