Logical Addressing

Logical Addressing

Position of network layer

The network layer is responsible for the delivery of individual packets from the source to the destination host



Network Layer: Logical Addressing

19.1 IPv4 Addresses
19.2 IPv6 Addresses

IPv4 Addresses

An IP address is a 32-bits long
The IP addresses are unique and universal
The address space of IPv4 is 232 or 4,294,967,296
Binary notation: 01110101 10010101 00011101 00000010
Dotted-decimal notation: 117.149.29.2

Example

Change the following IP addresses from binary notation to dotted-decimal notation.
a. 10000001 00001011 00001011 11101111
b. 11111001 10011011 11111011 00001111

We replace each group of 8 bits with its equivalent decimal number and add dots for separation:
a. 129.11.11.239
b. 249.155.251.15

Classful addressing

In classful addressing, the address space is divided into five classes: A, B, C, D, E
A new architecture, called classless addressing was introduced in the mid-1990s

Classful Addressing: Example

Find the class of each address.
a. 00000001 00001011 00001011 11101111
b. 11000001 10000011 00011011 11111111
c. 14.23.120.8
d. 252.5.15.111


Classful Addressing: Example Solution

Solution
a. The first bit is 0. This is a class A address.
b. The first 2 bits are 1; the third bit is 0. This is a class C address.
c. The first byte is 14; the class is A.
d. The first byte is 252; the class is E.