Networking Technical Interview Questions

What is a network?

A computer network is a set of computers connected together. In order to be considered a network, at least two or more computers must be connected together, and they must be sharing resources. A computer network is also commonly referred to as a data network.

The network may be connected via cables, telephone lines, radio waves, satellites, or infrared light beams. Its primary function is to facilitate the transfer of data, including transmitting, receiving and exchanging data, voice and video traffic.

The two most common types of networks are Local Area Network (LAN) and Wide Area Network (WAN).

What does Computer Networking entail?

In the simplest words, computer networking entails working on a computer network. A network is a connection between two or more computer systems that share resources. Even though technically, any work done on a computer network counts as computer networking, realistically its various subjects and fields.

Officially, Computer Networking is described as an engineering discipline that aims to study and understand how the communication process works in a computer networks. Computer Networking also aims to push these communications to improve systems and to enhance what computer networks are capable of.

It can also be said that ‘computer networking depends on the theoretical application and practical implementation of fields like computer engineering, computer sciences, information technology and telecommunication.’

Define LAN, MAN and WAN

LAN, MAN and WAN are three different types of networks that can be used to connect computer systems.

LAN - Local Area Network

In a local area network, the computer and network devices that are connected together are usually located in a small local area, typically within an office or a single building. The speed on these networks is usually higher, hence providing faster and more efficient networking.  

MAN - Metropolitan Area Network

In a metropolitan area network, the network is usually more spread out than a LAN. Here it could be a larger local area, like an office complex, or a few buildings, or even a city block. The speeds are usually slower than LANs as there is more ground to be covered, however the actual speed depends on various factors.

WAN - Wide Area Network

Unlike the other two, a wide area network is not restricted to a geographical location. The location was be as wide or as located as the network specifications require. A WAN can connect various different LANs in its network. Additionally, it can be private or a publicly accessible network. Comparatively, WAN is very high speed but expensive. The internet is an example of a WAN.

What is TELNET?

Telnet is a user command that allows one to access a computer remotely. It is also a TCP/IP protocol, which means that it can be used over the internet (WAN), while also being able to be used over a local network (LAN).

Telnet is a helpful tool as it can allow an administrator or an authorized user to access someone else's computer remotely. This allows them to access the information, make changes, or even troubleshoot conveniently.

Another benefit of Telnet is that over the internet, it can be used via HTTP and FTP protocols to request specific files from remote computers, but without actually having to log on as a user of that computer.

What is switching?

In networking and IT, switching refers to the practice of directing a signal towards a particular hardware. Switching is the mechanism though which information travels between different computer networks and network segments. Basically, every time one accesses the internet or a computer network outside the immediate location, the signal and the information is sent through a maze of transmission media and connection devices. This process is called as switching.

What is a Link?

In computer networking, a link, also known as a hyperlink, is a reference. Specifically it references data or information that is stored elsewhere. When the link is click or utilized, it routes the user to that data, regardless of where it is stored.

A link is quick helpful, as it can be used to directly reference or lead to data that is stored elsewhere. This data no longer needs to be tracked manually. Due to this, the link is also often called a hot link.

What is the OSI reference model?

OSI stands for Open Systems Interconnection. It is a type of conceptual model that is intended to characterize the communication functions of a telecommunication or computing system. Basically, it breaks down the communication functions of a system into layers. The system defines seven layers, each one corresponding to one segment of system communications.

The primary purpose of the OSI reference model is to allow vendors and developers to define how their products and software programs will interoperate, i.e. work with each other.

However, in reality the OSI model is rarely fully implemented as few network products or standard tools define their communication functions in strict layers as per the OSI model.

What are the layers of the OSI reference model?

OSI stands for Open Systems Interconnection. It is a reference model for how applications can communicate over a network. It describes the communication functions of a system; so that a product or software program can define how it will interoperate will other products and software programs.

The OSI reference model breaks down the functions into seven layers, which are as follows:

Layer 1: Physical Layer – Transmission and reception of raw bit streams over a physical medium

Layer 2: Data Link Layer – Reliable transmission of data frames between two nodes that are connected by a physical layer

Layer 3: Network Layer – Structuring and managing a multi-node network, including addressing, routing and traffic control

Layer 4: Transport Layer – Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing

Layer 5: Session Layer – Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes

Layer 6: Presentation Layer – Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption

Layer 7: Application Layer – High-level APIs, including resource sharing, remote file access

What is backbone network?

A backbone network is a part of computer network. Its primary purpose is to connect various pieces of network together, thus providing a way for these different segments to communicate and transfer information. A backbone network is what allows for the exchange of information between different LANs or subnetworks.

It can be said that a backbone is a type of transmission line that carries data gathered from the smaller lines that connect to it.

Typically, a backbone network’s capacity is greater than the networks connected to it, which can include various different networks in the same building, in different buildings in a campus environment, or over wide areas. 

One example of a backbone network is the Internet backbone, which allows information to be shared over the internet.

Types of backbone network :

Serial Backbone: Serial backbone is formed when two or more devices are connected in a daisy chain (serial connection). The number of devices that can be connected in this is limited and hence it is not very scalable.

Distributed Backbone: In a distributed backbone network, the number of devices are connected to single or multiple connectivity devices. The connectivity devices can be switches, hubs or routers. Since more devices can be added to this, distributed backbone networks are easily scalable, so they are often preferred by large networks.

Collapsed Backbone: In collapsed backbone network, a single router or switch is connected to multiple local networks. The benefit of such a network is that everything can be managed from a single location. But it is also highly risky, as, if the central device fails, the whole network will crash.

Parallel Backbone: It is similar to collapsed backbone. This also has a central device, but it will have a duplicate connection when there is more than one router or switch. By having duplicate connections it ensures the network availability at any time and ensures that the network is running at high speed. The drawback of this network is that it is costly to implement since a duplicate connection is required.

What is a node?

A node is a point in a network. It is at this node where lines and pathways intersect and/or branch out from. It can be said that a node is somewhat like a junction, where traffic intersects, mergers and separates again.

Officially speaking, a node is either a redistribution point or a communication endpoint. Basically, this means that information either travels through here or ends up here.

In a communication network, where all the devices are accessible, these devices are all considered to be nodes. It is at these devices, where the information is merged, accessed and transferred from. Basically, nodes act as major centers through which Internet traffic is typically routed.

What are routers?

A router is a type of device which allows connection and/or access to the network. They are the ones that allow various devices to connect to the network, primarily the Internet.

Officially, a router is a device that determines the best way for a packet to be forwarded to its destination. In some cases, software on a computer can also act as a router. A router acts as a dispatcher as it decides which way to send each information packet.

The router can be located at any gateway, i.e. where one network meets another. This includes each point-of-presence on the internet. A router is also often included as part of a network switch.

What are Unicasting, Anycasting, Multicasting and Broadcasting?

Unicasting, Anycasting, Multicasting and Broadcasting are all different ways of sending data and information.

Unicasting: In unicasting, a piece of information is sent from one device to exactly one other receiver. There is only sender and one receiver.

Multicasting: In multicasting, a piece of information is sent from one device to one or more devices. The information is not received by all, but by selected devices in the network. The selected devices can be any number of devices.

Broadcasting: In broadcasting, a piece of information is sent from one device to all other devices. There is just one sender but the information is received by all others in the network.

Anycasting: In anycasting, a piece of information is sent from one device to the nearest receiver device. There is just one sender and one receiver device.

What is Stop-and-Wait Protocol?

Stop and wait protocol is used to send information between connected devices. The sender transmits one packet and waits for an acknowledgment (ACK) from the receiver before transmitting the next packet. When the ACK is received, the sender acknowledges that the packet is sent successfully and then transmits the next packet.

The sender keeps record of each packet it sends. To avoid confusion which can be caused by delayed or duplicated ACKs, in the stop and wait protocol the sender sends each packets with unique sequence numbers and verifies that number when it receives each ACK.

If the ACK is not received after a certain period of time for the previous sent packet, the sender times out and retransmits that packet again.

What is Piggybacking?

In piggybacking technique, when the receiver receives the data frame (message), it waits and doesn't send the acknowledgment (ACK) immediately. The receiver waits until it has a message to send and attaches the ACK to this message. This helps it to make better use of bandwidth. 

But a major disadvantage is that if the receiver waits too long for transmitting the acknowledgement, retransmission of frame would take place. To avoid the delay, the waiting period is fixed. If the delay is long, the receiver sends a separate ACK frame.

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