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IPV4 Addressing in Computer Network

Computer Network | IPV4 Addressing: In this tutorial, we will learn about the IPV4 addressing, its Header, and types. By Mahima Rao Last updated : May 04, 2023

What is IPV4 Addressing?

Internet protocol version 4 in any network, is a standard protocol for assigning a logical address (IP address) to hosts. You are currently using the same protocol. This protocol is capable of providing a unique address to the devices available in this world, but will not be available after a few years. Therefore its advanced version IPV6 has been introduced, which you can read in the tutorial of IPV6.

The IP address in IPV4 is 32 bits. It is represented in 4 blocks of 8 bits. The lower IPV4 address is represented in both binary and decimal form.

 Binary:    11000000.10101000.00001010.00000001

These blocks represent networks and hosts. The starting block represents the network and represents the subsequent hosts that how many blocks will represent the network and how many hosts will represent these are defined by classes of IP address. If you want to know more about the format and classes of the IPV4 address, you can read it in the Addressing tutorial.

IPv4 Header Format

Internet Protocol (IP) works on layer 3 (Network Layer). They break the segments (when using TCP as protocol) or datagram (when using UDP as protocol) sent through layer layer 4 (Transport Layer) in packets. After breaking in packets, IP header is attached with these packets. This provides the necessary information receiver side related to the header packet. This information is represented by different fields in the IP header.

The lower IP header is represented by a diagram. After this all the fields have been explained in detail:

IPv4 Header Format Diagram


IPv4 Header Structure and Fields

The IPv4 header contains 14 fields. They are: Version Number, Header Length, Types of Service, Total Length, Identification, Flags, Fragment Offset, Time to Live, Protocol, Header Checksum, Source IP Address, Destination IP Address, Options, and Data. All these fields are explained below:

1. Version Number

The version number of Internet Protocol is used to define the version number field. Here the IPV4 header is being spoken, so the version will also be 4th.

2. Header Length

The length of the IP header is defined by this field. The length of the IPV4 header is represented by 32 bit words (with options). If no option is defined in the header then this filed has value of 5 set.

3. Types of Service

This field defines the way by which the router should queue the packets when the packets are waiting to be forwarded. If the priority of a packet is high then this field's value is 1. This packet has 0 value for regular packets.

4. Total Length

This field shows the total length of the IP data-gram. Define the header length defines the length of the field header and defines the total length of data-gram, including field data and header. This is a 16 bit field.

5. Identification

This field is the identification of a segment. This is a 16 bit number, which together with the source address uniquely identifies a segment.

6. Flags

This field shows whether the router can fragment any segment. This field has 3 bits. The first bit is reserved. If the second bit is set in this field then it means do not fragment and if the field is set to a third bit then it means the segment is fragmented.

7. Fragment Offset

If the packet is fragmented, then this field shows the starting 8 packs of the original packet. This field is of 13 bits.

8. Time to Live

This field sets a limit. Let the value of this field be 15. If the packet does not reach the destination even after passing from 15 routers, then that packet is discarded. This is an important field from the perspective of authenthenticity. The size of this field is 8 bits.

9. Protocol

This field contains the name of the protocol that passed the packet network layer because for de-multiplexing on the receiver side, it should know which protocol to pass the data.

10. Header Checksum

This field is used to check errors. When the packet is sent from source then this field has a value that is calculated by the algorithm through the header. When this packet reaches the receiver side, then the value is calculated by the same algorithm back to the head if the value matches the source side then it is believed that the packet error is free. This field is of 8 bits.

11. Source IP Address

This represents the IP address of the field source. The size of this field is 32 bits.

12. Destination IP Address

The destination address is represented by this field. The size of this field is 32 bits.

13. Options

This field represents some options that some packets can use. Although this field is not used, whenever it is used, the header length exceeds 32 bits.

14. Data

This field contains the main data that is passed by the transport layer protocols to the IP.

IPV4 Address Types

Whenever IPV4 packets are sent or received, they are sent / received by one of the three types given address. Let's us learn about them in detail.

1. Unicast

A unicast address represents a specific host. This type of address represents the specific destination host in the IPV4 packet. This type of address is used for one-to-one communication. For example a host of LAN A will send a packet to a host of LAN B, then it will be called unicast addressing.

2. Multicast

Multicast addresses are used to send a packet to more than one host. These are used for one-to-many communication. For example, a host can send a packet to an IP address group in another network. These packets are only received by those hosts that are in the multicast group.

3. Broadcast

Broadcast addresses are used by IPV4 to spread the packet of a single host across the network. This is a one-to-all communication. For example, a host can send a packet to the other available hosts in the LAN.

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