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:
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 |
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
Each of such a unique address is mapped to an (also unique) IP address. The corresponding IP address for the above name would
be
This mapping mechanism is called the
THE NEXT GENERATIONdomain name system.
How this mapping is done can be found in the DNS section.
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
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
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. I 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
IPv6 or
IPng. More Information can be found at the following
addresses: