“IP address” is short for “Internet Protocol address”. There are currently two different versions of IP addresses in use -IPv4 and IPv6. Our focus for this course is the IPv4 addresses. Every TCP/IP host that is connected to a network is identified by a logical IP address. The IP address is an OSI network layer address. It is independent of the Data-link layer address (MAC Address). IP addresses enable TCI/IP hosts to communicate with each other.
Example Google DNS Server IPv4 address
The IP address is a unique address that identifies the location of a TCP/IP host on the network. This is similar to the function of a full postal address. For example, the following postal address identifies the office of the United States president, the White House.
1600 Pennsylvania Avenue
NW Washington, D.C.
20500 United States
The above address uniquely identifies the White House from all other postal addresses in the world. If anyone in the world wants to send a letter to the White House they would use the above address and that letter will only go to the White House.
Similarly, IPv4 address 220.127.116.11 is a unique address that globally identifies the Google’s DNS server from all other TCP/IP hosts in the internet.
What do IPv4 addresses look like
Each IPv4 address is a string of 32 bits that are divided in to four sections called octets as shown below (1 Octet = 8 bits). This is what TCP/IP hosts understand. This representation of IP addresses using 0s and 1s, which TCP/IP hosts use is known as the binary notation.
11000000 10101000 00001010 00001010
Example Binary IPv4 address representation of decimal IPv4 address 192.168.10.10
However, the above binary notation is difficult for us humans to understand. Therefore, we use the following format shown below, which is much easier for us to understand. We call this the Dotted Decimal notation. Since each octet is separated by a dot hence the name dotted decimal notation is given.
Example dotted decimal IPv4 address
The notation w.x.y.z will be used when referring to the generalized IPv4 address in this course.