This document provides an introduction to IP addressing, including: - A brief history of IP development and the OSI and TCP/IP models. - An overview of IP address classes (A, B, C, D, E), how they are determined, and their characteristics like address ranges and network/host portions. - Explanations of limitations of classful addressing, subnetting, and how classless or CIDR addressing helps address those limitations by allowing flexible prefix lengths. - An example is given of how CIDR allows efficient allocation of addresses to networks of different sizes.

1. Introduction to IP(Internet Protocol)
Addressing
PREPARED BY
SHETH KUSHAL (130510111011)

2. Index
History
Introduction
OSI Model V/S TCP/IP Model
IP addressing Basic class ful addressing
Various Classes of IP Address
Explanation of all classes
Limitation of Classful IP Addressing
Subnetting
Classless IP addressing (CIDR)
Brief Example of Classless IP Addressing

3. History
Computer network is getting connected in Late 60’s.
In 1978 ISO (International Standard Organization) proposed a new model for
networking for easy access and understanding. Which is of 7 layers and known as
OSI (Open System Interface) model.
As the updatation in OSI model TCP/IP (Transmission Control Protocol/ Internet
Protocol) is developed and merged in 1st January 1983 with APRANET (The
Advanced Research Projects Agency Network).
The TCP/IP model have 4 layers which strictly follow the 7 layers of OSI model.

4. Introduction
The IP (Internet Protocol) is basically a unique address of any device by which the
device can communicate with other devices or communicate world wide in terms of
Internet.
There are two basic Types of IP address.
◦ IPv4 (IP version 4) (Earlier technology still used by 70% devices)
◦ IPv6 (IP version 6) (Newer version as the addresses range is about to complete of IPv4)
IPv4 (The address is divided into four parts each having 8 bits and separated by dotted
decimal point and usually written in decimal for easy understanding)
*We are learning only about IPv4 addressing here.

5. OSI model V/S TCP/IP model
OSI Model TCP/IP Model
1. Application Layer 1. Application Layer
2. Presentation Layer Telnet FTP DNS
3.Session Layer
4. Transportation Layer 2. Transport Layer
TCP UDP
5. Network Layer 3. Internet Layer
IP
6. Data link Layer 4. Host to Host network
7. Physical Layer LAN X.25

6. IP addressing Basic class ful
addressing
An IP address basically a 32-bit address that uniquely universally defines
connection of host or a router to the Internet. IP address is unique.
Address space of IPv4 is 232.
Introduced by IANA (Internet Assigned Numbers Authority).
32 bit is divided into 4 equal parts of 8-8 bits separated by dotted decimal notation.
It is in the range of minimum 0.0.0.0 to 255.255.255.255.
Each 8 bit group is known by OCTET.

7. Various IP classes
IP has five different classes differentiated by characteristics.
◦ Class-A ranges from 0 to 127
◦ Class-B ranges from 128 to 191
◦ Class-C ranges from 192 to 223
◦ Class-D ranges from 224 to 239
◦ Class-E ranges from 240 to 255
First Octet is defines the class of particular IP e.g. - 128.11.3.31 is follow in class –B
127.0.0.0 to 127.255.255.255 is a range of look back IP.

8. IP Classes (Contd.)
Official Method to find the class of particular IP.
Check the first octet, Convert it to Binary, then
If, 1st bit is 0 then it comes to class A, If 1st bit is 1 and 2nd bit is 0 then it comes to class B, If 1st
two bit is 1 and 3rd bit is 0 then it comes to class C. If 1st three bits are 1and 4th bit is 0 then it
comes to class D and if all 4 bits are 1 then it comes to class E.
Class C network id host11 0
Network Prefix
24 bits
Host Number
8 bits
bit # 0 1 23 242 313
Class B 1 network id host
bit # 0 1 15 162
Network Prefix
16 bits
Host Number
16 bits
0
31
Class A 0
Network Prefix
8 bits
bit # 0 1 7 8
Host Number
24 bits
31
Class D multicast group id11 1
bit # 0 1 2 313
0
4
Class E (reserved for future use)11 1
bit # 0 1 2 313
1
4
0
5

9. Classes of IP addresses
Class-A
This IP ranges from 0 to 126 Decimal value in first octet. And 1st octet defines network part
and remaining three octet defines the Host part. It patterns like this NHHH (N-Network; H-
Host).
First 8bits defines network and remaining 24 bits defines host parts.
It has a highest nos. of address 231.which is about 16,277,216.
It is denoted by IP/8.
Private Network IP ranges from 10.0.0.0 to 10.255.255.255. in general formation of 10.0.0.0/8

10. Class B
This IP ranges from 128 to 191 Decimal value in first octet. And 1st two bit defines network
part and remaining two octet defines the Host part. It patterns like this NNHH (N-Network;
H-Host).
First 16 bits defines network and remaining 16 bits defines host parts.
It has a highest nos. of address 230.which is about 65,536.
It is denoted by IP/16.
Private Network IP ranges from 172.16.0.0 to 172.31.255.255. in general formation of
172.16.0.0/12

11. Class C
This IP ranges from 192 to 223 Decimal value in first octet. And 1st three bit defines network
part and remaining one octet defines the Host part. It patterns like this NNNH (N-Network;
H-Host).
First 24 bits defines network and remaining 8 bits defines host parts.
It has a highest nos. of address 229.which is about 256.
It is denoted by IP/24.
Private Network IP ranges from 192.168.0.0 to 192.168.255.255. in general formation of
192.168.0.0/16.

12. Class-D
This IP ranges from 224 to 239 Decimal value in first octet.
It is not usually use in general applications.
It is use in Special purpose applications known as Multicast.

13. Class-E
This IP ranges from 240 to 255 Decimal value in first octet.
It is not usually use in general applications.
It is reserved range of IP by R & D (Research and Development) department.
Usually, Class-A to C is supported by PC and Class-D and E is not supported.

14. Limitations of Classful IP Addressing
• Running out of address space soon
232 = 4,294,967,296 addresses
• Class boundaries did not foster
efficient allocation of address space
Lack of address class to support medium size company
Class B: 65534 hosts/network, too big!
-- Class C: 254 hosts/network, too small!
-- Use multiple class C addresses,
increase routing table!

15. Subnetting
Subnetting is the process to divide a Big network in some smaller networks for ease of access.
Ex.
University Network
Engineering
School
Medical
School
Library
Add another level of hierarchy to the IP addressing structure this is also called Subnetting.

16. Basic Idea of Subnetting
Split the host number portion of an IP address into a subnet number and a (smaller) host
number.
Result is a 3-layer hierarchy
Then:
◦ Subnets can be freely assigned within the organization
◦ Internally, subnets are treated as separate networks
◦ Subnet structure is not visible outside the organization
network prefix
host number
host number
network prefix
subnet number

17. Advantages of subnetting
With subnetting, IP addresses use a 3-layer hierarchy:
◦ Network
◦ Subnet
◦ Host
Improves efficiency of IP addresses by not consuming an entire address space for each
physical network.
Reduces router complexity. Since external routers do not know about subnetting, the
complexity of routing tables at external routers is reduced.
Note: Length of the subnet mask need not be identical at all sub networks.

18. Classless IP Addressing
The Process of give the classless IP is also called “CIDR ”
It is announced in 1996, allows an ISP to assign as few or as many IP addresses as requested.
Two terms often used in classless addressing
◦ Prefix – another name for the common part of the address range (netid)
◦ Prefix length – the length of the prefix
In classless addressing, the last address in the block does not necessarily end in 255.
In CIDR (Classless Inter Domain Routing) notation, the block granted is defined by the first
address and the prefix length.
When an organization is granted a block of addresses, it can create subnets to meet its needs.
The prefix length increases to define the subnet prefix length.
In fixed-length subnetting, the number of subnets is a power of 2.

19. Subnet Mask Table
The addresses in color are the default masks for classes A, B, and C.
Thus, classful addressing is a special case of classless addressing.

20. How classless IP Addressing helps??
Consider a network that contains 9 hosts
Only 4 bits of host suffix are needed to represent all possible host values.
However, a class C address has names for 256 hosts.
Classless addressing solves this problem by allowing an ISP to assign a prefix that is 28 bits
long and the suffix then is 4 bits long.
With 4 bits for the suffix, there are 16-2 = 14 host numbers

21. CIDR Block Example
If an ISP has two computers each with only 12 computers each, the ISP can use CIDR to
partition a class B IP address into three parts: two for each of the customers and the
remainder available for future use.
One customer can be assigned: 128.211.0.16/28
The other customer can be assigned: 128.211.0.32/28