What is a IP Addressing
Understanding IP Addressing:
Everything You Ever Wanted To Know
Background
The Internet continues to grow at a phenomenal rate. This is reflected in the
tremendous popularity of the World Wide Web (WWW), the opportu-nities that
businesses see in reaching customers from virtual storefronts, and the emergence of new ways of doing business. It is clear that expanding business and public awareness will continue to increase demand for access to resources on the Internet.
Internet Scaling Problems
Over the past few years, the Internet has experienced two major scaling issues as it
has struggled to provide continuous and uninterrupted growth:
The eventual exhaustion of IP version 4 (IPv4) address space
The need to route traffic between the ever increasing number of net-works that comprise the Internet
The first problem is concerned with the eventual depletion of the IP address space. IPv4 defines a 32-bit address which means that there are only 232 (4,294,967,296) IPv4 addresses available. As the Internet con-tinues to grow, this finite number of IP addresses will eventually be exhausted.
The address shortage problem is aggravated by the fact that portions of the IP address space have not been efficiently allocated. Also, the tradi-tional model of
classful addressing does not allow the address space to be used to its maximum
potential. The Address Lifetime Expectancy (ALE) Working Group of the Internet Engineering Task Force (IETF) has expressed concerns that if the current address allocation policies are not modified, the Internet will experience a near to medium term exhaus-tion of its unallocated address pool. If the Internet’s address supply problem is not solved, new users may be unable to connect to the global Internet.
More than half of all possible IPv4 addresses have been assigned to ISPs,
corporations, and government agencies, but only an estimated 69 million addresses are actually in use.
About IP Addressing
IP Address is short for Internet Protocol Address.
It is a unique address assigned to each computing device in an IP network.
ISP assigns IP Address to all the devices present on its network.
Computing devices use IP Address to identify and communicate with other devices in the IP network.
Types Of IP Address-
IP Addresses may be of the following two types
Static IP Address
Static IP Address is an IP Address that once assigned to a network element always remains the same.
They are configured manually.
Some ISPs do not provide static IP addresses.
Static IP Addresses are more costly than dynamic IP Addresses
Dynamic IP Address
Dynamic IP Address is a temporarily assigned IP Address to a network element.
It can be assigned to a different device if it is not in use.
DHCP or PPPoE assigns dynamic IP addresses.
IP Address Format-
IP Address is a 32 bit binary address written as 4 numbers separated by dots.
The 4 numbers are called as octets where each octet has 8 bits.
The octets are divided into 2 components- Net ID and Host ID.
Format of an IP Address
Network ID represents the IP Address of the network and is used to identify the network.
Host ID represents the IP Address of the host and is used to identify the host within the network.
IP Address Example-
Example of an IP Address is-
00000001.10100000.00001010.11110000
(Binary Representation)
OR
1.160.10.240
(Decimal Representation)
There are two systems in which IP Addresses are classified
Classful Addressing
In Classful Addressing System, IP Addresses are organized into following 5 Classes-
1. Class A- If the 32 bit binary address starts with a bit 0, then IP Address belongs to class A.
In class A IP Address,
The first 8 bits are used for the Network ID.
The remaining 24 bits are used for the Host ID.
Total Number Of IP Addresses-
Total number of IP Addresses available in class A
= Numbers possible due to remaining available 31 bits = 231
Total Number Of Networks-
Total number of networks available in class A
= Numbers possible due to remaining available 7 bits in the Net ID – 2= 2^7– 2 = 126
Total Number Of Hosts-
Total number of hosts that can be configured in class A
= Numbers possible due to available 24 bits in the Host ID – 2 = 2^24– 2
(The reason for subtracting 2 is explained later.)
Range Of 1st Octet- We have-
Minimum value of 1st octet = 00000000 = 0
Maximum value of 1st octet = 01111111 = 127
From here,
Range of 1st octet = [0, 127]
But 2 networks are reserved and unused.
So, Range of 1st octet = [1, 126]
Use- Class A is used by organizations requiring very large size networks like
NASA, Pentagon etc.
2. Class B- If the 32 bit binary address starts with bits 10, then IP Address belongs to class B.
In class B IP Address,
The first 16 bits are used for the Network ID.
The remaining 16 bits are used for the Host ID.
Class B IP Address
Total Number Of IP Addresses-
Total number of IP Addresses available in class B
= Numbers possible due to remaining available 30 bits = 230
Total Number Of Networks-
Total number of networks available in class B
= Numbers possible due to remaining available 14 bits in the Net ID = 214
Total Number Of Hosts-
Total number of hosts that can be configured in class B
= Numbers possible due to available 16 bits in the Host ID – 2 = 216
– 2
Range Of 1st Octet- We have-
Minimum value of 1st octet = 10000000 = 128
Maximum value of 1st octet = 10111111 = 191
So, Range of 1st octet = [128, 191]
Use- Class B is used by organizations requiring medium size networks like
IRCTC, banks etc.
3. Class C- If the 32 bit binary address starts with bits 110, then IP Address
belongs to class C. In class C IP Address,
The first 24 bits are used for the Network ID. The remaining 8 bits are used for the Host ID.
Class C IP Address
Total Number Of IP Addresses-
Total number of IP Addresses available in class C
= Numbers possible due to remaining available 29 bits= 229
Total Number Of Networks-
Total number of networks available in class C
= Numbers possible due to remaining available 21 bits in the Net ID = 221
Total Number Of Hosts-
Total number of hosts that can be configured in class C
= Numbers possible due to available 8 bits in the Host ID – 2 = 28
– 2
Range Of 1st Octet-We have-
Minimum value of 1st octet = 11000000 = 192
Maximum value of 1st octet = 110111111 = 223
So, Range of 1st octet = [192, 223]
Use-Class C is used by organizations requiring small to medium size networks.
For example- engineering colleges, small universities, small offices etc.