Adressing on the Internet

Unlike commercial computer networks, where the information is accessible from special clients having several menus, you have to know where the desired information is located when using the Internet. Each computer which is connected to the internet - no matter if permanent or temporarily - is assigned a unique address. This unique address is called an IP-Address Such an IP address is made up of four numbers, ranging from 0 to 255 (8 bytes), separated by a point. So the entire IP address consists of 32 bytes (8 x 4 bytes). An example of such an IP address would be: 140.78.34.45 To simplify administration of addresses, netclasses have been introduced. There currently are five classes (A thru E) defined. The Addresses from 1.0.0.0 to 126.255.255.255 are using the first number for the network number. The other three numbers are available for the host number. Such a network is defined as a class A network. Normally class A networks are used for general purposes like the ARPAnet itself. Large organizations normally are assigned a class B network. A class B network uses the first two numbers for the network number. Valid network numbers are 128.0.0.0 thru 191.255.255.255. Addresses beginning with 127 are reserved for special use. A class B network can serve up to 65536 computers. The smallest, a class C network, uses the first three numbers for the network number, ranging from 192.0.0.0 to 223.255.255.255. A class C network can serve up to 255 computers (hosts). Addresses above 223 are reserved for future use as a class E network, but are currently not defined. To illustrate this, have a look at the following graphic: IMAGE: Illustration of netclasses in an IP-address The first bits are used for determination of the netclass. A class A network is determined by a zero in the first bit. A class B network by a one and a zero and a class C network by a one, one and zero. The following table gives an overview of currently defined netclasses. Have a look at the image below, which shows how the addresses are organized. Netclass Valid Numbers Max. # computers Max. # networks C 192.0.0.0 to 223.255.255.255 255 16 777 216 B 128.0.0.0 to 191.255.255.255 65 536 65 536 A 1.0.0.0 to 126.255.255.255 16 777 216 256 TABLE: Currently used netclasses, valid addresses, max. networks and number of addressable computers. If haven't made any calculation mistakes, this results in a total of 857 3157 376 addressable computers on the internet. Don't be mislead by this number. If the number of Internet users keeps growing in the current way, then in a few years there won't be sufficient addresses left. If a company now requests a new IP address, then the company is not assigned a single IP number, but instead they are assigned a netclass due to their requirements. This assignment is handled by Network Information Centers. Normally each country has such a NIC, which is usually hosted by a university or a large ISP. To make life easier for the Internet user - such an IP address is hard to remember - computers have been assigned a unique name. An example for such a name would be www.yahoo.com Each of such a unique address is mapped to an (also unique) IP address. The corresponding IP address for the above name would be: 205.216.146.70 This mapping mechanism is called the domain name system. How this mapping is done can be found in the DNS section. Top IPv6 - the next generation Due to the rapid growth of the Internet, there won't be sufficient IP addresses to address all computers in a few years time. To prevent this, the IETF and other organizations and companies are working on a new standard for tcp/ip. Apart from the technical improvements made, there will also be a new way to address computers on the Internet. The new address format will possibly look something like 1080:0:0:0:800:417A Instead of 4 numbers between 0 and 255 there will be eight hexadecimal numbers, separated by a ":". The result is, that there are 2128 possible Internet addresses. That are around 300000000000000000000000000000000000 (should be 38 zeros) possible addresses. We do not know how to pronounce this number, but there are quite a few number of possible addresses. Some people have calculated, that using the new scheme, there can be around 1500 addresses per square meter (m2) on earth. There also has been put a lot of effort to stay compatible with the current addressing scheme. So an old style address would look like ::134.245.74.43 But, there is no need to panic. Until the new scheme will be officially introduced, there are still some years to go (about 10). The new protocol will be called IPv6 or IPng. More Information can be found at the following addresses: IPv6 specification Implementing the IPv6 in the Marine Corps Tactical Data Network

Top