Network Classes. Difference between IPv4 and IPv6 Addressing?

Network Classes:

IP Addresses are classified into 5 classes. Each class consists of a different set of network and host IDs and also contains a subnet mask to determine the exact IP Address from the local area network.

These classes are defined in the table below:

Classes	Range	Default Subnet Mask	Max. Range of Network ID	Max. Range of Host ID
A	1.0.0.0 to 126.255.255.255	255.0.0.0	2⁸	2²⁴
B	128.0.0.0 to 191.255.255.255	255.255.0.0	2¹⁶	2¹⁶
C	192.0.0.0 to 223.255.255.255	255.255.255.0	2²⁴	2⁸
D	224.0.0.0 to 239.255.255.255	Reserved for Multicasting	Reserved for Multicasting	Reserved for Multicasting
E	240.0.0.0 to 254.255.255.255	Reserved for Future used	Reserved for Future used	Reserved for Future used

Class A Type:

When an IP Address first eight bits from the left side lies in the range 0-127, it is in a class A type network. This class has more numbers of host id (2²⁴) than network id (2⁸).

Class B Type:

In class B type, 16 bits from the left are used for determining network id, and the remaining 16 bits are to determine the host id. This class has 2¹⁶ network id and 2¹⁶ host id.

Class C Type:

In class C type, 24 bits from the left are used for determining network id (2²⁴) and remaining 8 bits are used for determining host id (2⁸).

What is Subnetting? Why we use Subnetting?

Subnetting is the process of dividing the host id bits into two or more networks. It is an efficient way of utilizing the IP Address. Let understand by taking an example, let the XYZ college having an IP Address (192.168.12.12) has 5 departments and each department has 100 computers. To provide internet to each computer, the college has to take or more specifically registered 500 IP Addresses. This is practically not possible for the internet service provider to allocate so many IP Addresses to only one college. So, to solve this problem, subnetting is used. Using only one IP Address, we can provide services to many computers at a time. Subnetting is done using a subnet mask which is fixed for each class.

Difference between IPv4 and IPv6 Addressing?

IPv4 and IPv6 are the IP Addresses used to identify the machine or devices connected to a network. IPv4 is a 32-bit address length in decimal number whereas IPv6 is a 128-bits address length in a hexadecimal number. The similarities and difference between IPv4 and IPv6 address are given in the figure below:

S. No.	IPv4	IPv6
1	It has 32-bit address length.	It has a 128-bit address length.
2	In IPv4, Encryption and Authentication are not provided.	In IPv6, Encryption and Authentication are provided.
3	It has a header length of 20-60 bytes.	It has a header length of 40 bytes.
4	It uses Address Resolution Protocol (ARP) to map to MAC address.	It uses Neighbor Discovery Protocol (NDP) to map to MAC Address.
5	Checksum field is available.	Checksum field is not available.
6	Internet Protocol Security (IPsec) concerns are optional.	IPsec concern is mandatory.
7	The IPv4 Address is represented in the format: 192.168.12.12	The IPv6 Address is represented as in the format: 0:0:0:0:0:ffff:c0a8:c0c

The IPv4 and IPv6 header format is shown below:

Figure 1: IPv4 and IPv6 Header format.

Version: It specifies the type of version IPv4 and IPv6 i.e., 4 bit or 6 bits respectively.

Source Address: It contains the sender address of the sender.

Destination Address: It contains the destination address of the receiver.

HLEN: It specifies the IP header length.

Type of service: The services such as low delay, high throughput, and reliability are provided.

Identification: It is used to identify the unique packet id from a group of fragments of a single IP datagram.

Flag: It is used to check whether a fragment is required or not.

Fragment Offset: It determines the number of data bytes ahead of the particular fragment in the particular datagram.

Time to live: It prevents the datagram from the infinite loop by restricting the number of Hops taken to the destination address. At every loop, it decrements its counter until zero is reached. When zero is reached, it informs the source about the packets not delivered or the address not found.

Checksum: It is used to find error bits in the datagram header.

Option: Optional information such as source route, record route is used by the network administrator for future use.

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