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What is the Purpose of the IPv4 Header?


Have you ever wondered, how your computer communicates with other computers across the globe? Thanks to the “Internet Protocol (IP)”. The Internet relies heavily on a system of rules and protocols in order to make smooth data flow. These protocols are responsible for everything including the streaming of shows or even if you send a mail.

The IP protocol mainly defines how data is packaged, addressed, and routed across the network. There are two versions of IP i.e., IPv4 and IPv6. In this blog, we will look into the IPv4 header, and its components and most importantly you will learn about its core purpose.

Before getting into the purpose of the IPv4 header, let’s first understand what the IPv4 header is.

What is IPv4 Header?

The IPv4 header is a small yet crucial part of every IP packet. It is an invisible roadmap that guides data packets on their journey through the Internet. One can think of it as the label on a package that contains all the information about the contents and destination of the packet.

The IPv4 header is crucial as it tells the network about three major tasks. These are:

  • How to handle the packet
  • Where to send it
  • What kind of information does it contain?

Let’s discuss the IPv4 header format for a better understanding.

IPv4 Header Format

The header part in the IPv4 is 20 bytes long, divided into various fields, each serving a specific function. Let’s discuss each field in detail.

  • Version: It identifies the IP version. For example, here in IPv4, the version is 4.
  • Header Length: It gives information about the size of the header in 32-bit words.
  • Type of Service: Its main purpose is to prioritize traffic. It is important to note that, in modern networks, it is not always used.
  • Total Length: It simply indicates the total length of the packet which includes both headers as well as data.
  • Identification: It is mainly used to identify a particular packet in a large data stream. It can be useful for fragmented packets.
  • Flags: It is used for fragmentation as well as reassembly of large packets.
  • Fragment Offset: It tells the position of the fragment within a large packet.
  • Time to Live: TTL indicates the maximum number of hops the packet can take before it is discarded. This will simply prevent the packet from the endless loop within the network.
  • Protocol: It helps in choosing the best-suited protocol in order to carry the data.
  • Header Checksum: This field is used to ensure that the header hasn't been corrupted during transmission.
  • Source/Destination Address: It gives information regarding the IP address of the device that is sending the packet and the IP address of the device that is receiving the packet.

Now that we have a basic understanding of both IPv4 header as well as IPv4 header format. It is time to discuss the purpose of the IPv4 header.

Purpose of the IPv4 Header

It is IPv4 that ensures that every single packet reaches its destination by means of performing various sets of roles. Let us discuss its core purpose in detail.

Packet Addressing

One of its primary purposes is packet addressing. We are already aware of the fact that each device on a network is assigned a unique IP address. This unique IP address is mainly for identifying the source as well as the destination of data packets. The IPv4 Header contains both the source as well as destination IP address.

Packet Identification and Fragmentation

Its second purpose is first to identify the packet and then assist in managing the fragmentation process i.e., splitting large data packets into smaller ones for easy transmission.

Packet Routing

Another crucial purpose of the IPv4 header is packet addressing. As we already know the header contains both the source and destination IP addresses. Now these IP addresses are usually the one that guides the packet through the complex web of routers and networks.

Error Detection and Correction

Another purpose of the IPv4 Header is error detection and correction. For error detection, IPv4 Header makes use of its checksum field which is mainly for verifying the integrity of the header. The process is simple, whenever a device receives a packet, it first calculates the checksum and then compares it with the one in the header. If the two values match, the packet is valid else it is discarded.

For the correction part, the Header of IPv4 makes use of identification and fragment offset field.

Protocol Identification

It is known that without a protocol, the data packet doesn’t have any idea of which route is ideal in order to reach the destination. The header of IPv4 makes use of the protocol field to carry out this important purpose.


The IPv4 header is small yet it plays a crucial role in carrying out the smooth operation of the Internet. In this blog, we have explained what an IPv4 header is as well as the IPv4 header format. We also discussed some of its core purposes which lead to a better world of connectivity all over the world. So always remember, the next time you send an email or download a file, the IPv4 Header is silently working to connect you to the vast world of information.

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