Computer Networking -Most Asked Interview Topics

Arpit Singh
Sep 7, 2020 · 5 min read

In this article, I will mention all the important computer networking Interview topics and a brief description of each topic. For my interview preparation, I had focussed mainly on these topics. So, let’s crack the interview.

1. OSI Model (Open System InterConnection)

It is the layered framework for the design of the network System. It consists of 7 layers :


Application Layer serves as a window for application services

At Presentation Layer, data is manipulated on the basis of the required format

Session Layer is responsible for the establishment of connection, sessions, and authentication

Transport Layer involves end to end delivery of messages

Network Layer takes care of routing and Logical Addressing

Data Link Layer responsible for the error-free transmission of data packets i.e.Framing

Physical Layer is responsible for the actual physical connection between devices.

2. TCP/IP Model

TCP/IP model consists of 4 layers. It is developed before OSI model and is more reliable than the OSI model.

TCP/IP Layers

Application Layer controls user-interface specifications.

Host-to-Host Layer is responsible for end-to-end communication and error-free delivery of data.

Internet Layer involves logical transmission of data over the entire network.

Network Access layer involves hardware addressing and physical transmission of data.

3. ARQ (Automatic Repeat Request Technique)

It is the method of error Control i.e. whenever an error is detected in a signal, a request is made for the retransmission of that signal.

Flow Control: It is the procedures for restricting the amount of data that a transmitter can transmit before receiving any acknowledgment.

There are 3 types of ARQ Techniques:

  1. STOP and Wait ARQ: The sender sends one packet and then wait for ACK(acknowledgment). If the sender receives ACK, then the next packet will be sent, otherwise the previous packet will be retransmitted.
  2. GO Back-N ARQ: The sender sends N packets(N=window size) before any Ack. If acknowledgment for any packet is not received, then all the packets sent after this will be retransmitted.
  3. Selective Repeat ARQ: The sender sends N packets(N=window size) before any Ack. If Ack for any packet is not received, then only those packets will be retransmitted whose ACK is not received(A buffer is created at the receiver side for this purpose).

4. Most Asked Protocols

  1. Point to Point Protocol(PPP): It is a byte-oriented, data link layer protocol that establishes a direct connection between two routers without any host in-between.
  2. High-Level Data Link Control(HDLC): It is a bit-oriented, data link layer protocol used for both point-to-point and point-to-multipoint connection.
  3. Hypertext Transfer Protocol(HTTP): It is a request-response application-layer protocol used for communication between web browsers and web servers.
  4. Network Time Protocol(NTP): It is used to synchronize the clock of the computer system to one standard time source. It is useful for bank transactions.
  5. Address Resolution Protocol(ARP): It is used for discovering the link-layer address, such as a MAC address with the help of the IP address of the device in a network.
  6. Reverse Address Resolution Protocol(RARP): It is used by the client computer to request its IP address in a network with the help of the MAC address of the device.
  7. Internet Control Message Protocol(ICMP): It is a network layer protocol used by devices in a network to diagnose network communication issues. It sends control messages such as destination network unreachable, source route failed, and source quench.
  8. Domain Name System(DNS): It is a directory service that provides a mapping between the name of a host on the network and its numerical address i.e. IP address.
  9. File Transfer Protocol(FTP): It is a standard network protocol used for the transfer of computer files between a client and a server on a computer network.
  10. Simple Mail Transfer Protocol(SMTP): It is a push protocol and used to send the mail whereas Internet Message Access Protocol(IMAP) is used to retrieve those messages at the receiver side.
  11. Dynamic Host Configuration Protocol(DHCP): It is a network management protocol whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on the network.


HUB: It is a central device that splits the network connection into multiple devices. Whenever a request is made, the hub distributes this request to all the connected devices.

SWITCHES: It is similar to a hub that connects all the devices but it only sends the request to the device for which it belongs to.

ROUTERS: A router is a networking device that forwards data packets between computer networks. It inspects a given data packet’s destination IP address, calculates the best way for it to reach its destination, and then forwards it accordingly.


There are two types of Routing techniques:

i). Intradomain Routing (Within Autonomous System)

  1. Distance Vector Routing: In this, a router transmits its distance vector to each of its neighbors in a routing packet and each router recalculates its distance vector table. Routing Information Protocol (RIP) is used in DVR and Bellman-Ford algorithm is used for calculating the shortest path in a distance vector routing.
  2. Link State Routing: In this protocol, each node of the network maintains the entire topology of the network. Dijkstra Algorithm is used for calculating the shortest path in a network. Open Shortest Path First (OSPF) is an implementation of the Link State Routing Protocol.

ii). Interdomain Routing (Between two Autonomous System)

  1. Path Vector Routing: In this, the autonomous system boundary routers send path-vector messages to advertise the reachability of networks. Border Gateway Protocol(BGP) is an example of a path vector protocol.


  1. TCP is known as Transmission Control Protocol whereas UDP is called User-datagram Protocol.
  2. TCP is a connection-oriented protocol whereas UDP is a connectionless protocol.
  3. TCP is reliable as it provides the assurance for the delivery of data packets whereas UDP is unreliable.
  4. TCP is slower as it performs error checking and flow control whereas UDP is faster.
  5. TCP uses a three-way handshaking mechanism i.e. sender receives the ACK and then transmits data whereas UDP does not follow any such mechanism.
  6. TCP follows a flow-control mechanism whereas UDP follows no such mechanism.

8. Transmission Modes

There are three types of transmission mode:-

  1. Simplex Mode: Transmission in only one direction.
  2. Half-Duplex Mode: Transmission in both directions but one at a time.
  3. Full-Duplex Mode: Transmission in both directions simultaneously.

If you reached here, then I hope you liked my first medium article.

Is there anything I missed? I hope that the medium community shares their feedback and provide thoughts…


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