IP and its properties address space subnetting with real time example

by Jesmin Akther | May 25, 2021 | Computer Network

What is IP and its properties

“IP” stands for Internet Protocol where data is sent by which the method or protocol from one computer to another.  Actually, each computer on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. An IP address is a unique global address for a network interface.

IP is an real life example of the postal system. It allows you to address a package and drop it in the system, but there’s no direct link between you and the recipient. TCP/IP, in contrast, creates a connection between two hosts, so that they can send messages back and forth for a period of time.

TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

Two (2) IP addressing standards are in use today. The IPv4 standard is most familiar to people and supported everywhere on the Internet, but the newer IPv6 standard is gradually replacing it.

• IPv4 addresses consist of four (4) bytes (32 bits)
• IPv6 addresses are sixteen (16) bytes (128 bits) long.

IP Address space

An IPv4 address is a 32-bit or  4 byte address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet.

An IPv4 address consists of four numbers, with a single dot (.) separating each number or set of digits.

Each of the four numbers can range from 0 to 255.

An address space is the total number of addresses used by the protocol. If a protocol uses N bits to define an address, the address space is  2^N  because each bit can have two different values (0 or 1) and N bits can have 2^N  values.

IPv4 uses 32-bit addresses, which means that the address space is 2³²  or 4,294,967,296 (more than 4 billion).

• There are two prevalent notations to show an IPv4 address:

(1) Binary notation and

(2) Dotted decimal notation.

Binary Notation:

01110101   10010101   00011101   00000010

Dotted-Decimal Notation:   117.  149.  29.  2

Classful Addressing

IPv4 addressing, at its inception, used the concept of classes. This architecture is called classful addressing. In classful addressing, the address space is divided into five classes: A, B, C, D, and E.

Exercise

193. 193.14.56.22

The first byte is 193 (between 192 and 223); the class is C.

14. 14.23.120.8

The first byte is 14 (between 0 and 127); the class is A.

In classful addressing, an IP address of class A, B and C is divided into two parts : Netid and Hostid.

The netid and hostid are of varying lengths that is varies on depending on the class of the address.

Netid(n): The part of an IP address that identifies the network.

Hostid(32-n): The part of an IP address that identifies a host in a network.

Class A address

• If the first decimal number in IP address is 0 to 127, then it is a class A address.
• Class A IP addresses use the 1^st 8 bits (1^st Octet) to designate the Network address.
• The 1^st bit which is always a 0, is used to indicate the address as a Class A address & the remaining 7 bits are used to designate the Network.
• The other 3 octets contain the Host address.
• There are 128 (2⁷) Class A Network Addresses, but because addresses with all zeros aren’t used & address 127 is a special purpose address, 126 Class A Networks are available.
• formula to compute the number of hosts available in any of the class addresses, where “ⁿ” represents the number of bits in the host portion:
• (2ⁿ – 2) = Number of available hosts
• For a Class A network, there are:
• 2²⁴ – 2 or 16,777,214 hosts.
• Half of all IP addresses are Class A addresses.
• You can use the same formula to determine the number of Networks in an address class.
• , a Class A address uses 7 bits to designate the network, so (2⁷ – 2) = 126 or there can be 126 Class A Networks.

Class B IP Addresses

• If the first decimal number in IP address is 128 to 191, then it is a class B address.
• Class B addresses use the 1^st 16 bits (two octets) for the Network address.
• The last 2 octets are used for the Host address.
• The 1^st 2 bit, which are always 10, designate the address as a Class B address & 14 bits are used to designate the Network. This leaves 16 bits (two octets) to designate the Hosts.
• So how many Class B Networks can there be?

Using our formula, (2¹⁴ – 2), there can be 16,382 Class B Networks & each Network can have (2¹⁶ – 2) Hosts, or 65,534 Hosts

Class C IP address

• If the first three bits of the address are 1 1 0, it is a class C network address.
• The first three (3) bits are class identifiers.
• The next 21 bits are for the network address.
• The last eight (8) bits  identify the host.
• There are millions of class C network numbers.
• However, each class C network can have 254 hosts.

Mask

the form /n where n can be 8, 16, or 24 in classful addressing. This notation is also called slash notation or Classless Interdomain Routing (CIDR) notation.

• the length of the netid and hostid (in bits) is predetermined in classful addressing, we can also use a mask.
• Default Mask:

The next article give example of subnetting, Now do practice with blog Subnetting with real time example