Computers Knowledge is gaining importance in the Bank Exams of IBPS or SBI and the Computer Network is one of the key components. It’s very essential to know the basics of Computer Networks so that candidates can answer correctly in exams.
Also learn about the History of Computers, Computer Hardware, and Operating Systems.
Table of Contents
What is a Computer Network?
A Computer Network is a set of computers that are connected together so that they can share information or data. Computer networks can be classified on many criteria.
For example, the transmission medium is used to carry signals, bandwidth, and communications protocols to organize network traffic, network size, the topology, traffic control mechanism, and organizational intent. The best-known computer network is the Internet.
The following are the types of computer networks where few are basic and widely used networks such as LAN, PAN, and WAN.
Local Area Network – LAN
Local Area Network or LAN – A local area network that connects computers and devices in a limited geographical area such as a home, school, office building, etc.
Computer Network Topology
Below are a few common Local Area Network Topology:
- Bus Topology
- Ring Topology
- Star Topology
- Tree Topology
- Hybrid Topology
Bus Topology – In bus topology there is the main cable to which all other devices are connected through drop lines. This dropline is connected to
the main cable via tap. It transmits the data from one end to another end in a single direction. There is no bi-directional feature in bus topology.
Ring Topology – In a ring topology, it forms a ring connecting a device with its two neighboring devices. It comprises of 4 stations connected with each forming a ring.
Star Topology – In star topology all devices are connected to a single hub through cable. This hub is the central hub and other are nodes are connected to this node. This topology doesn’t allow direct communication between devices, a device must have to communicate through the hub.
Tree Topology – This topology is the variation of star topology. It’s a hierarchical flow of data.
Hybrid Topology – A combination of two or more topologies is known as hybrid topology. For example, a combination of star and tree topology
can be called a hybrid topology.
Personal Area Network – PAN
Personal Area Network or PAN – A personal area network is a computer network used for communicating among computers and different
devices close to one person. This network may be wired or wireless. Examples of such devices are personal computers, printers, fax machines, scanners, etc.
Wide Area Network – WAN
Wide Area Network or WAN – A wide area network is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental area. This network uses a communication channel that combines many types of media such as cables, telephone lines, etc.
WAN technologies mainly function at 3 layers of OSI model mainly :
- Physical layer
- Datalink layer
- Network layer
Physical layer – The physical layer is the lowest and the first layer in the OSI reference model. This layer consists of electronic circuit transmission technologies of a network. This layer translates logical communications requests from the data link layer into hardware-specific operations.
Datalink layer – This is the 7th layer of the OSI reference model. This layer transfers data between the adjacent network in WAN or between nodes on the same LAN.
This layer is concerned with the local delivery of frames between nodes on the same level of the network. Examples of data link protocols are Ethernet for LAN, PPP (Point-to-Point Protocol, HDLC, and ADCCP connections.
Network Layer – In the seven layers of the OSI reference model of the computer network, this layer is at the third level. It is responsible for packet forwarding including routing.
This layer provides the means of transferring variable-length network packets from a source to a destination through one or more networks.
Computers are identified through IP addresses over the network.
What is IP Address?
IP Address or Internet Protocol Address – An Internet Protocol Address is made up of numbers or characters. All devices connected to an internet connection have a unique IP address. Example of an IP address is: 506.457.14.510
A version of IP Address
There are two versions of IP
- IPv4
- IPv6
IPv4
IPv4 – IPv4 is the older and the most common version used. IPv4 is a 32-bit number. Which might be a concern for the increasing use of the internet. 172.16.252.1
IPv6
IPv6 – Due to an increase in the use of the internet nowadays a new version IPv6 was introduced using 128-bits, which was standardized in 1998.
Classes in IPv4
Below are the Classes in IPv4:
Class A – In class A first 8 bits or the first dotted decimal, is the network part of the address with the remaining part of the address being the host part. There are 128 possible Class A networks.
Class B – In Class B, the first 16 bits are the network part of the address.
All Class B networks have their first bit set to 1 and the second bit set to 0. There is a 16,3484 possible class B network.
Class C – In Class C, the first two bits are set to 1, and the third bit is set to 0.
Which makes the first 24 bits of the address the network address and rest as the host address. There are over 2 million possible class c networks.
Class D – This class is used for multicasting applications. Like previous classes, class D is not used for normal networking operations.
It has the first 3 bits set to ‘1’ and their fourth bit set to ‘0’. Class D addresses are 32-bit network addresses.
Class E – In class E first 4 network address bits are set to 1. this class is reserved, its usage is never defined, hence most network implementations discard these addresses as illegal or undefined.
Port Numbers
A port number is a 16-bit unsigned integer, which has a range from 0 to 65535. The process of sending and receiving data over the internet works on the binding.
This binding enables the Transfer Protocol and IP address to be combined together. A transfer protocol in a standard agreement between the sender and listener to connect via agreed port number only.
Below is the list of Protocols along with there port numbers:
| S.No. | Port Number | Protocol |
| 1 | 07 | Internet Control Message Protocol (ICMP) |
| 2 | 20 | File Transfer Protocol (FTP) Data Transfer |
| 3 | 21 | File Transfer Protocol (FTP) Command Control |
| 4 | 22 | Secure Shell (SSH) Secure Login |
| 5 | 23 | Telnet remote login service, unencrypted text messages |
| 6 | 25 | Simple Mail Transfer Protocol (SMTP), e-mail routing |
| 7 | 38 | Route Access Protocol |
| 8 | 39 | Resource Location Protocol |
| 9 | 53 | Domain Name System (DNS) |
| 10 | 67, 68 | Dynamic Host Configuration Protocol (DHCP) |
| 11 | 80 | Hypertext Transfer Protocol (HTTP) used in the World Wide Web |
| 12 | 110 | Post Office Protocol (POP3) |
| 13 | 119 | Network News Transfer Protocol (NNTP) |
| 14 | 123 | Network Time Protocol (NTP) |
| 15 | 143 | Internet Message Access Protocol (IMAP) |
| 16 | 161 | Simple Network Management Protocol (SNMP) |
| 17 | 194 | Internet Relay Chat (IRC) |
| 18 | 443 | HTTP Secure (HTTPS) HTTP over TLS/SSL |
Characteristics of Computer Network
Characteristics of a Computer network are as below
- It shares resources from one computer to another.
- It also creates files and stores them in the computer and access those files from other computer connected over a network.
- Can connect any printer, fax machine to one of the computers in network and let other system within network to access such machines.
Computer Network Hardware
Below are the hardware devices required to set up the computer network.
- Routers
- Network Cables
- Distributors
- Internal Network Cards
- External Network Cards