Skip to content
geeksforgeeks
  • Courses
    • DSA to Development
    • Get IBM Certification
    • Newly Launched!
      • Master Django Framework
      • Become AWS Certified
    • For Working Professionals
      • Interview 101: DSA & System Design
      • Data Science Training Program
      • JAVA Backend Development (Live)
      • DevOps Engineering (LIVE)
      • Data Structures & Algorithms in Python
    • For Students
      • Placement Preparation Course
      • Data Science (Live)
      • Data Structure & Algorithm-Self Paced (C++/JAVA)
      • Master Competitive Programming (Live)
      • Full Stack Development with React & Node JS (Live)
    • Full Stack Development
    • Data Science Program
    • All Courses
  • Tutorials
    • Data Structures & Algorithms
    • ML & Data Science
    • Interview Corner
    • Programming Languages
    • Web Development
    • CS Subjects
    • DevOps And Linux
    • School Learning
  • Practice
    • Build your AI Agent
    • GfG 160
    • Problem of the Day
    • Practice Coding Problems
    • GfG SDE Sheet
  • Contests
    • Accenture Hackathon (Ending Soon!)
    • GfG Weekly [Rated Contest]
    • Job-A-Thon Hiring Challenge
    • All Contests and Events
  • Aptitude
  • Engineering Mathematics
  • Discrete Mathematics
  • Operating System
  • DBMS
  • Computer Networks
  • Digital Logic and Design
  • C Programming
  • Data Structures
  • Algorithms
  • Theory of Computation
  • Compiler Design
  • Computer Org and Architecture
Open In App
Next Article:
Difference between Unicast, Broadcast and Multicast in Computer Network
Next article icon

IPv4 Datagram Header

Last Updated : 04 Feb, 2025
Comments
Improve
Suggest changes
Like Article
Like
Report

IP stands for Internet Protocol and v4 stands for Version Four (IPv4). IPv4 was the primary version brought into action for production within the ARPANET in 1983. IP version four addresses are 32-bit integers which will be expressed in decimal notation. In this article, we will discuss about IPv4 datagram header.

IPv4 is a connectionless protocol used for packet-switched networks. Internet Protocol Version 4 (IPv4) is the fourth revision of the Internet Protocol and a widely used protocol in data communication over different kinds of networks. IPv4 is a connectionless protocol used in packet-switched layer networks, such as Ethernet. It provides a logical connection between network devices by providing identification for each device. There are many ways to configure IPv4 with all kinds of devices – including manual and automatic configurations – depending on the network type. IPv4 uses 32-bit addresses for Ethernet communication in five classes: A, B, C, D and E. Classes A, B, and C have a different bit length for addressing the network host. Class D addresses are reserved for multicasting, while class E addresses are reserved for military purposes. IPv4 uses 32-bit (4-byte) addressing, which gives 232 addresses. IPv4 addresses are written in the dot-decimal notation, which comprises four octets of the address expressed individually in decimal and separated by periods, for instance, 192.168.1.5. 

Characteristics of IPv4

  • IPv4 could be a 32-Bit IP Address.
  • IPv4 could be a numeric address, and its bits are separated by a dot.
  • The number of header fields is twelve and the length of the header field is twenty.
  • It has Unicast, broadcast, and multicast style of addresses.
  • IPv4 supports VLSM (Virtual Length Subnet Mask).
  • IPv4 uses the Post Address Resolution Protocol to map to the MAC address.
  • RIP may be a routing protocol supported by the routed daemon.
  • Networks ought to be designed either manually or with DHCP.
  • Packet fragmentation permits from routers and causing host.

IPv4 Datagram Header

  • VERSION: Version of the IP protocol (4 bits), which is 4 for IPv4 
  • HLEN: IP header length (4 bits), which is the number of 32 bit words in the header. The minimum value for this field is 5 and the maximum is 15. 
  • Type of service: Low Delay, High Throughput, Reliability (8 bits) 
  • Total Length: Length of header + Data (16 bits), which has a minimum value 20 bytes and the maximum is 65,535 bytes. 
  • Identification: Unique Packet Id for identifying the group of fragments of a single IP datagram (16 bits) 
  • Flags: 3 flags of 1 bit each : reserved bit (must be zero), do not fragment flag, more fragments flag (same order) 
  • Fragment Offset: Represents the number of Data Bytes ahead of the particular fragment in the particular Datagram. Specified in terms of number of 8 bytes, which has the maximum value of 65,528 bytes. 
  • Time to live: Datagram’s lifetime (8 bits), It prevents the datagram to loop through the network by restricting the number of Hops taken by a Packet before delivering to the Destination.
  • Protocol: Name of the protocol to which the data is to be passed (8 bits) 
  • Header Checksum: 16 bits header checksum for checking errors in the datagram header 
  • Source IP address: 32 bits IP address of the sender 
  • Destination IP address: 32 bits IP address of the receiver 
  • Option: Optional information such as source route, record route. Used by the Network administrator to check whether a path is working or not.
IPv4-Datagram-Header

IPv4 Datagram Header

Due to the presence of options, the size of the datagram header can be of variable length (20 bytes to 60 bytes). 


Next Article
Difference between Unicast, Broadcast and Multicast in Computer Network
author
kartik
Improve
Article Tags :
  • Computer Networks
  • Network Layer

Similar Reads

  • CCNA Tutorial for Beginners
    This CCNA Tutorial is well-suited for the beginner as well as professionals, and It will cover all the basic to advanced concepts of CCNA like Components of Computer Networking, Transport Layer, Network Layer, CCNA training, Cisco Networking, Network Design, Routing and Switching, etc. which are req
    8 min read

    • Basics of Computer Networking

    • Network and Communication
      Networks and communication involve connecting different systems and devices to share data and information. This setup includes hardware like computers, routers, switches, and modems, as well as software protocols that manage how data flows between these devices. Protocols such as TCP/IP and HTTP are
      8 min read
    • LAN Full Form - Local area network
      A Local area network (LAN) is a network that is used to link devices in a single office, building, or campus of up to a short distance. LAN is restricted in size. In LAN networks internet speed is from 10 Mbps to 100 Mbps (But now much higher speeds can be achieved). The most common topologies used
      10 min read
    • What is OSI Model? - Layers of OSI Model
      The OSI (Open Systems Interconnection) Model is a set of rules that explains how different computer systems communicate over a network. OSI Model was developed by the International Organization for Standardization (ISO). The OSI Model consists of 7 layers and each layer has specific functions and re
      14 min read
    • TCP/IP Model
      The TCP/IP model (Transmission Control Protocol/Internet Protocol) is a four-layer networking framework that enables reliable communication between devices over interconnected networks. It provides a standardized set of protocols for transmitting data across interconnected networks, ensuring efficie
      7 min read
    • How Data Encapsulation and De-encapsulation Works?
      Data encapsulation and de-encapsulation are fundamental concepts in computer networking and communication protocols. These processes are essential for transferring data across networks efficiently and securely. What is Data Encapsulation?Encapsulation is the process of adding additional information
      4 min read

    Components of Computer Networking

    • NIC Full Form - Network Interface Card
      NIC stands for Network Interface Card. NIC is additionally called Ethernet or physical or network card. NIC is one of the major and imperative components of associating a gadget with the network. Each gadget that must be associated with a network must have a network interface card. Even the switches
      4 min read
    • What is a Network Switch and How Does it Work?
      The Switch is a network device that is used to segment the networks into different subnetworks called subnets or LAN segments. It is responsible for filtering and forwarding the packets between LAN segments based on MAC address.  Switches have many ports, and when data arrives at any port, the desti
      9 min read
    • What is Network Hub and How it Works?
      Hub in networking plays a vital role in data transmission and broadcasting. A hub is a hardware device used at the physical layer to connect multiple devices in the network. Hubs are widely used to connect LANs. A hub has multiple ports. Unlike a switch, a hub cannot filter the data, i.e. it cannot
      6 min read
    • Introduction of a Router
      Network devices are physical devices that allow hardware on a computer network to communicate and interact with one another. For example Repeater, Hub, Bridge, Switch, Routers, Gateway, Router, and NIC, etc. What is a Router?A Router is a networking device that forwards data packets between computer
      12 min read
    • Types of Ethernet Cable
      An ethernet cable allows the user to connect their devices such as computers, mobile phones, routers, etc, to a Local Area Network (LAN) that will allow a user to have internet access, and able to communicate with each other through a wired connection. It also carries broadband signals between devic
      5 min read

    Transport Layer

    • Transport Layer responsibilities
      The transport Layer is the second layer in the TCP/IP model and the fourth layer in the OSI model. It is an end-to-end layer used to deliver messages to a host. It is termed an end-to-end layer because it provides a point-to-point connection rather than hop-to-hop, between the source host and destin
      5 min read
    • Introduction of Ports in Computers
      A port is basically a physical docking point which is basically used to connect the external devices to the computer, or we can say that A port act as an interface between the computer and the external devices, e.g., we can connect hard drives, printers to the computer with the help of ports. Featur
      3 min read
    • What is TCP (Transmission Control Protocol)?
      Transmission Control Protocol (TCP) is a connection-oriented protocol for communications that helps in the exchange of messages between different devices over a network. It is one of the main protocols of the TCP/IP suite. In OSI model, it operates at the transport layer(Layer 4). It lies between th
      5 min read
    • TCP 3-Way Handshake Process
      The TCP 3-Way Handshake is a fundamental process that establishes a reliable connection between two devices over a TCP/IP network. It involves three steps: SYN (Synchronize), SYN-ACK (Synchronize-Acknowledge), and ACK (Acknowledge). During the handshake, the client and server exchange initial sequen
      6 min read
    • User Datagram Protocol (UDP)
      User Datagram Protocol (UDP) is a Transport Layer protocol. UDP is a part of the Internet Protocol suite, referred to as UDP/IP suite. Unlike TCP, it is an unreliable and connectionless protocol. So, there is no need to establish a connection before data transfer. The UDP helps to establish low-late
      10 min read

    Network Layer

    • IPv4 Datagram Header
      IP stands for Internet Protocol and v4 stands for Version Four (IPv4). IPv4 was the primary version brought into action for production within the ARPANET in 1983. IP version four addresses are 32-bit integers which will be expressed in decimal notation. In this article, we will discuss about IPv4 da
      4 min read
    • Difference between Unicast, Broadcast and Multicast in Computer Network
      The cast term here signifies some data(stream of packets) is being transmitted to the recipient(s) from the client(s) side over the communication channel that helps them to communicate. Let's see some of the "cast" concepts that are prevailing in the computer networks field. What is Unicast?This typ
      5 min read
    • Structure and Types of IP Address
      IP addresses are an important part of the Internet. It can be represented as Internet Protocol address. A unique address that identifies the device over the network. They are made up of a series of numbers or alphanumeric characters that help us to identify devices on a network. Almost every device
      8 min read

    IPv4 Addressing

    • What is IPv4?
      IP stands for Internet Protocol version v4 stands for Version Four (IPv4), is the most widely used system for identifying devices on a network. It uses a set of four numbers, separated by periods (like 192.168.0.1), to give each device a unique address. This address helps data find its way from one
      5 min read
    • Role of Subnet Mask
      A subnet mask is a 32-bit number that separates an IP address into two parts: the network ID and the host ID. It tells devices which portion of the address belongs to the network and which identifies individual devices. By doing this it helps to determine which devices belong to the same local netwo
      5 min read
    • Introduction of Classful IP Addressing
      An IP address is an address that has information about how to reach a specific host, especially outside the LAN. An IP address is a 32-bit unique address having an address space of 232. Classful IP addressing is a way of organizing and managing IP addresses, which are used to identify devices on a n
      11 min read

    Subnetting

    • Introduction To Subnetting
      Subnetting is the process of dividing a large network into smaller networks called "subnets." Subnets provide each group of devices with their own space to communicate, which ultimately helps the network to work easily. This also boosts security and makes it easier to manage the network, as each sub
      9 min read
    • Classless Inter Domain Routing (CIDR)
      Classless Inter-Domain Routing (CIDR) is a method of IP address allocation and IP routing that allows for more efficient use of IP addresses. CIDR is based on the idea that IP addresses can be allocated and routed based on their network prefix rather than their class, which was the traditional way o
      6 min read
    • Introduction of Variable Length Subnet Mask (VLSM)
      Variable Length Subnet Mask (VLSM) is a technique used in IP network design to create subnets with different subnet masks. VLSM allows network administrators to allocate IP addresses more efficiently and effectively, by using smaller subnet masks for subnets with fewer hosts and larger subnet masks
      6 min read
    • Private IP Addresses in Networking
      Private IP addresses play an important role in computer networking, permitting organizations to build internal networks that communicate securely without conflicting with public addresses. In this article, we will see private IP addresses in networking. What is a Private IP Address?Private IP Addres
      8 min read

    Data Link Layer

    • What is Ethernet?
      A LAN is a data communication network connecting various terminals or computers within a building or limited geographical area. The connection between the devices could be wired or wireless. Ethernet, Token rings, and Wireless LAN using IEEE 802.11 are examples of standard LAN technologies.In this a
      9 min read
    • What is MAC Address?
      To communicate or transfer data from one computer to another, we need an address. In computer networks, various types of addresses are introduced; each works at a different layer. A MAC address, which stands for Media Access Control Address, is a physical address that works at the Data Link Layer. I
      13 min read
    • What is an IP Address?
      Imagine every device on the internet as a house. For you to send a letter to a friend living in one of these houses, you need their home address. In the digital world, this home address is what we call an IP (Internet Protocol) Address. It's a unique string of numbers separated by periods (IPv4) or
      14 min read

    Physical Layer

    • Ethernet Frame Format
      The basic frame format which is required for all MAC implementation is defined in IEEE 802.3 standard. Though several optional formats are being used to extend the protocol's basic capability. Ethernet frame starts with the Preamble and SFD, both work at the physical layer. The ethernet header conta
      8 min read
    • What is Power Over Ethernet (POE)?
      Power Over Ethernet (POE) is a technique used for building wired Ethernet local area networks (LANs) which use Ethernet data cables instead of normal electrical power cords and wiring to carry the electrical current required to operate each device. The transfer of power through network cabling is po
      8 min read

    Cisco Networking Devices

    • Network Devices (Hub, Repeater, Bridge, Switch, Router, Gateways and Brouter)
      Network devices are physical devices that allow hardware on a computer network to communicate and interact with each other. Network devices like hubs, repeaters, bridges, switches, routers, gateways, and brouter help manage and direct data flow in a network. They ensure efficient communication betwe
      9 min read
    • Collision Detection in CSMA/CD
      CSMA/CD (Carrier Sense Multiple Access/ Collision Detection) is a media access control method that was widely used in Early Ethernet technology/LANs when there used to be shared Bus Topology and each node ( Computers) was connected by Coaxial Cables. Nowadays Ethernet is Full Duplex and Topology is
      7 min read
    • Collision Domain and Broadcast Domain in Computer Network
      Prerequisite - Network Devices, Transmission Modes The most common network devices used are routers and switches. But we still hear people talking about hubs, repeaters, and bridges. Do you ever wonder why these former devices are preferred over the latter ones? One reason could be: 'because they ar
      5 min read
    • Difference between layer-2 and layer-3 switches
      A switch is a device that sends a data packet to a local network. What is the advantage of a hub? A hub floods the network with the packet and only the destination system receives that packet while others just drop due to which the traffic increases a lot. To solve this problem switch came into the
      5 min read
geeksforgeeks-footer-logo
Corporate & Communications Address:
A-143, 7th Floor, Sovereign Corporate Tower, Sector- 136, Noida, Uttar Pradesh (201305)
Registered Address:
K 061, Tower K, Gulshan Vivante Apartment, Sector 137, Noida, Gautam Buddh Nagar, Uttar Pradesh, 201305
GFG App on Play Store GFG App on App Store
Advertise with us
  • Company
  • About Us
  • Legal
  • Privacy Policy
  • In Media
  • Contact Us
  • Advertise with us
  • GFG Corporate Solution
  • Placement Training Program
  • Languages
  • Python
  • Java
  • C++
  • PHP
  • GoLang
  • SQL
  • R Language
  • Android Tutorial
  • Tutorials Archive
  • DSA
  • Data Structures
  • Algorithms
  • DSA for Beginners
  • Basic DSA Problems
  • DSA Roadmap
  • Top 100 DSA Interview Problems
  • DSA Roadmap by Sandeep Jain
  • All Cheat Sheets
  • Data Science & ML
  • Data Science With Python
  • Data Science For Beginner
  • Machine Learning
  • ML Maths
  • Data Visualisation
  • Pandas
  • NumPy
  • NLP
  • Deep Learning
  • Web Technologies
  • HTML
  • CSS
  • JavaScript
  • TypeScript
  • ReactJS
  • NextJS
  • Bootstrap
  • Web Design
  • Python Tutorial
  • Python Programming Examples
  • Python Projects
  • Python Tkinter
  • Python Web Scraping
  • OpenCV Tutorial
  • Python Interview Question
  • Django
  • Computer Science
  • Operating Systems
  • Computer Network
  • Database Management System
  • Software Engineering
  • Digital Logic Design
  • Engineering Maths
  • Software Development
  • Software Testing
  • DevOps
  • Git
  • Linux
  • AWS
  • Docker
  • Kubernetes
  • Azure
  • GCP
  • DevOps Roadmap
  • System Design
  • High Level Design
  • Low Level Design
  • UML Diagrams
  • Interview Guide
  • Design Patterns
  • OOAD
  • System Design Bootcamp
  • Interview Questions
  • Inteview Preparation
  • Competitive Programming
  • Top DS or Algo for CP
  • Company-Wise Recruitment Process
  • Company-Wise Preparation
  • Aptitude Preparation
  • Puzzles
  • School Subjects
  • Mathematics
  • Physics
  • Chemistry
  • Biology
  • Social Science
  • English Grammar
  • Commerce
  • World GK
  • GeeksforGeeks Videos
  • DSA
  • Python
  • Java
  • C++
  • Web Development
  • Data Science
  • CS Subjects
@GeeksforGeeks, Sanchhaya Education Private Limited, All rights reserved
We use cookies to ensure you have the best browsing experience on our website. By using our site, you acknowledge that you have read and understood our Cookie Policy & Privacy Policy
Lightbox
Improvement
Suggest Changes
Help us improve. Share your suggestions to enhance the article. Contribute your expertise and make a difference in the GeeksforGeeks portal.
geeksforgeeks-suggest-icon
Create Improvement
Enhance the article with your expertise. Contribute to the GeeksforGeeks community and help create better learning resources for all.
geeksforgeeks-improvement-icon
Suggest Changes
min 4 words, max Words Limit:1000

Thank You!

Your suggestions are valuable to us.

What kind of Experience do you want to share?

Interview Experiences
Admission Experiences
Career Journeys
Work Experiences
Campus Experiences
Competitive Exam Experiences