Computer Network Tutorial

Introduction of Computer Network Types of Computer Network Network Topology Computer Networking Architecture Transmission Modes (Data Flow) Basic Networking Devices Integrate Services Digital Network (ISDN)


OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography


Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network

Address Mapping

Address Mapping: Internet is made of a combination of physical networks connected together by internetworking devices such as routers. A logical address is an internetwork address. A physical address is a local address. It is usually implemented in hardware (but not always), so it is called a physical address. The physical address and the logical address are two different identifiers. This address information can be achieved through static and dynamic mapping.

Static mapping: In static mapping, it creates a table that contains a logical address with a physical address.

Dynamic mapping: When a machine knows one of two addresses (logical or physical) through dynamic mapping, it may use this protocol to find the other one address. There are designed two protocols for done dynamic mapping.

  • Address Resolution Protocol (ARP)
  • Reverse Address Resolution Protocol (RARP)

Address Resolution Protocol (ARP)

It is a dynamic mapping protocol that is used to find out the physical address associated with the logical address and then sent it to the data link layer. The working of ARP is shown below in the figure.

Address Mapping
  • Firstly, the client broadcasts the ARP request packet to all the hosts in the network.
  • In this ARP request packet, stores the logical address and physical address of the client and the IP address of the receiver.
  • Each host receives this ARP request packet, but only the one who is the authorized host completes the ARP service.
  • Finally, the authorized host sends the ARP response packet to the client in which its physical address is stored.

Note: ARP request is broadcast, and ARP response is unicast.

ARP Packet Format

Address Mapping

Reverse Address Resolution Protocol (RARP)

It is a dynamic mapping protocol that is the opposite of ARP. It is used to find out the logical address of the machine associated with the physical address. The working of RARP is shown below in the figure.

Address Mapping
  • Firstly, the client broadcasts the RARP request packet to all the hosts in the network.
  • The physical address of the client is stored in this RARP request packet.
  • Each host receives this RARP request packet, but only the one who is the authorized host completes the RARP service. This authorized host is called the RARP server.
  • RARP server sends the RARP response packet to the client in which its logical address is stored.

RARP is not used nowadays, it was replaced by BOOTP (Bootstrap protocol), and now BOOTP has been replaced by DHCP (dynamic host configuration protocol).


BOOTP stands for Bootstrap Protocol. It is a computer networking protocol that is used to assign IP addresses to network devices in a network. In other words, it is an internet protocol that is used by the client to obtain the IP address from the server. It was defined in RFC 951 and 1084. It was designed to replace RARP (resource address resolution protocol).

Address Mapping

Working of BOOTP

When the Bootstrap protocol started by the client, it does not have an IP address. Therefore, it broadcasts a message in the network, and Its MAC address is inside this message. This message is called "BOOTP request," and takes this request by the BOOTP server. The server then provides the following information in reply to the client.

  • It provides the IP address, subnet mask, and gateway address of the client.
  • It also provides the IP address and hostname of the server.

When the client receives the BOOTP server information, it configures and initializes the TCP/IP protocol stack and then connects to the server that has the boot image. The client loads this boot image and starts the operating system.


DHCP stands for Dynamic Host Configuration Protocol. It is designed to provide the static and dynamic address allocation that can be done manual or automatic. It was designed to replace the BOOTP (Bootstrap Protocol).


ICMP stands for Internet Control Message Protocol. It is designed to overcome the following two problems in the IP protocol.

  • No error reporting and correcting mechanism
  • Lacks a mechanism for queries

ICMP messages are not sent directly to the intended data-link layer. Instead, messages are first explained within the IP datagram before moving to the lower layer.

Type of Message

The messages of ICMP are divided into two categories: error-reporting messages and query messages.

Error-Reporting Messages: Error-reporting messages report problems that can occur while transmitting an IP packet with a router or host (destination).

Type of Error-Reporting Messages

Address Mapping

Query Messages: It helps to important or specific information from a route or network manager.

General Message Format  

Address Mapping


IGMP stands for Internet Group Management Protocol. This protocol is used for multicast, which is connected to the one-to-many communication channel. The best example of this protocol is online gaming and video streaming. Types of IGMP message is shown below.

Address Mapping


IGMP Message Format

Address Mapping