NWA-PCUG Newsletter Article
Number Please
by John R. Clark - July 97
(click to email author)

Remember the phrase "number please"? It may have disappeared from our spoken vocabulary due to the introduction of automatic switching equipment for the phone companies. However, numbers are still there in the biggest switching game in the world: namely, the Internet.

Surfers on the big-wire like to use names like "www.foo.bar.com" to make a contact, but in reality that alphabetic type name is converted to a unique number and a contact is made. Each Internet Service Provider (ISP) has an IPv4 number assigned to it of the form xxx.xxx.xxx.xxx where each of the xxx values range from zero to 255. This format allows for 4,294,967,296 possible values, but due to some design on the original allocation of these numbers, problems are coming up.

(Format of a typical address)

Domain Name
          |       |     |_ Top Level describes the organization
          |       |_ 2nd Level {Name Registered by InterNIC}
          |_ 3rd Level {The Host and/or Sub-System Name}

Most e-mail addresses do not reference the host -- only the 1st and 2nd level {e.g. bshook1019@aol.com or ghh1@juno.com but some do rcmahq@nwark.com}

There are 5 classes of domain numbers used on the Internet. The best explanation of the 5 classes of IPv4 numbers can be located at "http://www.3com.com/nsc/501302.html"

Each domain is mapped to 4 numbers in the range 0 .. 255 xxx.yyy.zzz.www People familiar with base 2 recognize a domain is represented by 4 bytes and it is the first few bits of the first byte that indicates the class.

Class A 0...x xx xx xx a /8  system with 126  possible domains
        1    to 126.xxx.xxx.xxx
Class B 10..x xx xx xx  a /16  system with 16385  possible domains
        128  to 191.255.xxx.xxx
Class C 110.x xx xx xx  a /24  system with 2099152 possible domains
        192  to 223.255.255.xxx
Class D 111.x xx xx xx    used for multicasting
        224  to
Class E 1111x xx xx xx    used experimentally
        240  to

The main problem is the owner of a class A domain can setup 16.77 million subsystems while the owner of a class C domain can only set up 255 systems.

To locate the numbers assigned to most addresses in the USA try "http://rs.internic.net/cgi-bin/whois"

In the last month this writer has been searching various sites to determine the format of these numbers, and who has the authority to determine which ISP gets which numbers and makes sure that no two ISPs get the same number. After several hours of mouse clicking and squinting at the CRT some interesting data has been obtained.

World wide it appears that Internet Assigned Numbers Authority {IANA} "http://www.isi.edu/div7/iana/" is the controlling authority for the distribution of numbers to the various regional controlling agencies. Currently there are three of these regional agencies in operation.

  The Americas and So Africa -- InterNIC "http://www.internic.net/"
  For Europe and No Africa   -- RIPE     "http://www.ripe.net/"
  Asia Pacific area          -- APNIC    "http://www.apnic.net/"

A breakdown of the various top/high level Domains can be found at "http://www.apnic.net/domain_reg.html". There you can find about the two letter domains like .uk or .us, etc.

In each of these web sites you will find a lot of information, perhaps a lot more than you want to know about the internet. However, it is more interesting that mowing the yard in these afternoons. If you want to check some of the sites by number, try and learn a bit about Intel.

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