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COMPUTER NETWORKS MODULE I

BACHELOR OF COMMERCE FIFTH SEMESTER 

Introduction to Computer Network

A computer network is a group of devices connected with each other through a transmission medium such as wires, cables etc. These devices can be computers, printers, scanners, Fax machines etc.

The purpose of having computer network is to send and receive data stored in other devices over the network. These devices are often referred as nodes.

There are five basic components of a computer network
Introduction to Computer network
Message: It is the data or information which needs to be transferred from one device to another device over a computer network.

Sender: Sender is the device that has the data and needs to send the data to other device connected to the network.

Receiver: A receiver is the device which is expecting the data from other device on the network.
Transmission media: In order to transfer data from one device to another device we need a transmission media such as wires, cables, radio waves etc.

Protocol: A protocol is a set of rules that are agreed by both sender and receiver, without a protocol two devices can be connected to each other but they cannot communicate. In order to establish a reliable communication or data sharing between two different devices we need set of rules that are called protocol.

For example http and https are the two protocols used by web browsers to get and post the data to internet; similarly smtp protocol is used by email services connected to the internet.

Evolution of Networking

Computers became able to exchange data in automatic mode, which, essentially, is the basic mechanism of any computer network. Developers of the first networks implemented services for file exchange, database synchronization, e-mail and other network services.

ARPANET

ARPANET was established by the Advanced Research Projects Agency (ARPA) in 1969 for two main reasons:

• To allow the transfer of data between various institutes of research.

• To answer the call of the U.S. Department of Defence for a technology to provide messaging capabilities to the government in the event of nuclear war.

World Wide Web (WWW)

The World-Wide Web is a collection of documents and services. It is distributed across the Internet and linked together by hypertext links. The web is therefore a subset of the Internet.

World Wide Web was created by Timothy Berners Lee in 1989 at CERN in Geneva.

Web page is a document available on World Wide Web. A web page can contain information including text, graphics, audio, video and hyper links. These hyper links are the link to other web pages.

Web Browser is application software that allows us to view and explore information on the web.

Following are the most common web browser available today:

https://img.brainkart.com/imagebk37/Lmjfeuz.jpg

WWW Operation

WWW works on client- server approach. Following steps explains how the web works:

1. User enters the URL (say http://www. tngovernmentjobs.in/) of the web page in the address bar of web browser.

2. Then browser requests the Domain Name Server for the IP address corresponding to www.tngovernmentjobs.in.

3. After receiving IP address, browser sends the request to web page and web server using HTTP protocol.

4. Then web server receives request using HTTP protocol and checks for the requested web page. If found it returns it back to the web browser and close the HTTP connection.

5. Now the web browser receives the web page, it interprets and displays the contents of web page in web browser’s window.

https://img.brainkart.com/imagebk37/H7V0lRe.jpg

Web server is a computer where the web content is stored. Basically web server is used to host the web sites.

Internet

• Internet is a world-wide global system of interconnected computer networks.

• Internet uses the standard Internet Protocol (TCP/IP).

• Every computer in internet is identified by a unique IP address.

• IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer location.

• A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.

• Internet is accessible to every user all over the world.

Advantages

Ø    Internet allows us to communicate with the people sitting at remote locations. There are various apps available on the web that uses Internet as a medium for communication.

One can find various social networking sites such as:

*           Facebook

*           Twitter

*           Yahoo

*           Google+

*           Flickr

*           Orkut

Ø    One can surf for any kind of information over the internet with the help of a search engine.

Ø    Apart from communication and source of information, internet also serves a medium for entertainment.

Following are the various modes for entertainment over internet.

Online Television

Online Games

Songs

Videos

Social Networking Apps

Internet Services

Ø    Internet Banking

Ø    Online Educational Services

Ø    Online Shopping

Ø    Online Ticket Booking

Ø    Online Bill Payment

Ø    Data Sharing

Ø    E-mail

Internet provides concept of electronic commerce, that allows the business deals to be conducted on electronic systems

Data transmission

Data transmission is the process of sending digital or analog data over a communication medium to one or more computing, network, communication or electronic devices. It enables the transfer and communication of devices in a point-to-point, point-to-multipoint and multipoint-to-multipoint environment.

Data transmission is also known as digital transmission or digital communications.

Data transmission can be analog and digital but is mainly reserved for sending and receiving digital data. It works when a device or piece of equipment, such as a computer, intends to send a data object or file to one or multiple recipient devices, like a computer or server. The digital data originates from the source device in the form of discrete signals or digital bit streams. These data streams/signals are placed over a communication medium, such as physical copper wires, wireless carriers and optical fiber, for delivery to the destination/recipient device. Moreover, each outward signal can be baseband or passband.

In addition to external communication, data transmission also may be internally carried to a device.

For example, the random access memory (RAM) or hard disk that sends data to a processor is also a form of data transmission.

Difference between Analog Communication and Digital Communication

1. Analog Communication: 
In analog communication the data is transferred with the help of analog signal in between transmitter and receiver. Any type of data is transferred in analog signal. Any data is converted into electric form first and after that it is passed through communication channel. Analog communication uses a continuous signal which varies in amplitude, phase, or some other property with time in proportion to that of a variable. 

The below figure illustrates the Analog Communication System: 

https://media.geeksforgeeks.org/wp-content/uploads/20200824100253/analog.png

2. Digital Communication: 
In digital communication digital signal is used rather than analog signal for communication in between the source and destination. The digital signal consists of discrete values rather than continuous values. In digital communication physical transfer of data occurs in the form of digital bit stream i.e 0 or 1 over a point-to-point or point-to-multipoint transmission medium. In digital communication the digital transmission data can be broken into packets as discrete messages which is not allowed in analog communication. 

The below figure illustrates the Digital Communication System: 

https://media.geeksforgeeks.org/wp-content/uploads/20200824101738/digital.png

Difference between Analog Communication and Digital Communication: 

Sl No

         ANALOG COMMUNICATION

            DIGITAL COMMUNICATION

01.

In analog communication analog signal is used for information transmission.

In digital communication digital signal is used for information transmission.

02.

Analog communication uses analog signal whose amplitude varies continuously with time from 0 to 100.

Digital communication uses digital signal whose amplitude is of two levels either Low i.e., 0 or either High i.e., 1.

03.

It gets affected by noise highly during transmission through communication channel.

It gets affected by noise less during transmission through communication channel.

04.

In analog communication only limited number of channels can be broadcasted simultaneously.

It can broadcast large number of channels simultaneously.

05.

In analog communication error Probability is high.

In digital communication error Probability is low.

06.

In analog communication noise immunity is poor.

In digital communication noise immunity is good.

07.

In analog communication coding is not possible.

In digital communication coding is possible. Different coding techniques can be used to detect and correct errors.

08.

Separating out noise and signal in analog communication is not possible.

Separating out noise and signal in digital communication is possible.

09.

Analog communication system is having complex hardware and less flexible.

Digital communication system is having less complex hardware and more flexible.

10.

In analog communication for multiplexing 

Frequency Division Multiplexing (FDM) is used. 

In Digital communication for multiplexing 

Time Division Multiplexing (TDM) is used. 

 

11.

Analog communication system is low cost.

Digital communication system is high cost.

12.

It requires low bandwidth.

It requires high bandwidth.

13.

Power consumption is high.

Power consumption is low.

14.

It is less portable.

Portability is high.

15.

No privacy or privacy is low, so it is not highly secured.

Privacy is high, so it is highly secured.

16.

Not assures an accurate data transmission.

It assures a more accurate data transmission.

17.

Synchronization problem is hard.

Synchronization problem is easier.

The transmission media is nothing but the physical media over which communication takes place in computer networks.

Magnetic Media

One of the most convenient ways to transfer data from one computer to another, even before the birth of networking, was to save it on some storage media and transfer physical from one station to another. Though it may seem old-fashion way in today’s world of high speed internet, but when the size of data is huge, the magnetic media comes into play.

For example, a bank has to handle and transfer huge data of its customer, which stores a backup of it at some geographically far-away place for security reasons and to keep it from uncertain calamities. If the bank needs to store its huge backup data then its, transfer through internet is not feasible. The WAN links may not support such high speed. Even if they do; the cost too high to afford.

In these cases, data backup is stored onto magnetic tapes or magnetic discs, and then shifted physically at remote places.

Twisted Pair Cable

A twisted pair cable is made of two plastic insulated copper wires twisted together to form a single media. Out of these two wires, only one carries actual signal and another is used for ground reference. The twists between wires are helpful in reducing noise (electro-magnetic interference) and crosstalk.

https://www.tutorialspoint.com/data_communication_computer_network/images/twisted_pairs.jpg

There are two types of twisted pair cables:

Shielded Twisted Pair (STP) Cable

Unshielded Twisted Pair (UTP) Cable

STP cables comes with twisted wire pair covered in metal foil. This makes it more indifferent to noise and crosstalk.

UTP has seven categories, each suitable for specific use. In computer networks, Cat-5, Cat-5e, and Cat-6 cables are mostly used. UTP cables are connected by RJ45 connectors.

Coaxial Cable

Coaxial cable has two wires of copper. The core wire lies in the center and it is made of solid conductor. The core is enclosed in an insulating sheath. The second wire is wrapped around over the sheath and that too in turn encased by insulator sheath. This all is covered by plastic cover.

Coaxial Cable

Because of its structure, the coax cable is capable of carrying high frequency signals than that of twisted pair cable. The wrapped structure provides it a good shield against noise and cross talk. Coaxial cables provide high bandwidth rates of up to 450 mbps.

There are three categories of coaxial cables namely, RG-59 (Cable TV), RG-58 (Thin Ethernet), and RG-11 (Thick Ethernet). RG stands for Radio Government.

Cables are connected using BNC connector and BNC-T. BNC terminator is used to terminate the wire at the far ends.

Power Lines

Power Line communication (PLC) is Layer-1 (Physical Layer) technology which uses power cables to transmit data signals. In PLC, modulated data is sent over the cables. The receiver on the other end de-modulates and interprets the data.

Because power lines are widely deployed, PLC can make all powered devices controlled and monitored. PLC works in half-duplex.

There are two types of PLC:

Narrow band PLC

Broad band PLC

Narrow band PLC provides lower data rates up to 100s of kbps, as they work at lower frequencies (3-5000 kHz).They can be spread over several kilometers.

Broadband PLC provides higher data rates up to 100s of Mbps and works at higher frequencies (1.8 – 250 MHz).They cannot be as much extended as Narrowband PLC.

Fiber Optics

Fiber Optic works on the properties of light. When light ray hits at critical angle it tends to refracts at 90 degree. This property has been used in fiber optic. The core of fiber optic cable is made of high quality glass or plastic. From one end of it light is emitted, it travels through it and at the other end light detector detects light stream and converts it to electric data.

Fiber Optic provides the highest mode of speed. It comes in two modes, one is single mode fiber and second is multimode fiber. Single mode fiber can carry a single ray of light whereas multimode is capable of carrying multiple beams of light.

Fiber Optics

Fiber Optic also comes in unidirectional and bidirectional capabilities. To connect and access fiber optic special type of connectors are used. These can be Subscriber Channel (SC), Straight Tip (ST), or MT-RJ.

Classification of Networks (LAN, MAN, WAN)

Another important criterion for classifying networks is their scale (physical size). As shown in Figure there are:

1.               Personal Area Network (PAN)

2.               Local Area Network (LAN)

3.               Metropolitan Area Network (MAN)

4.               Wide Area Networks (WAN)

Personal Area Network (PAN): The interconnection of devices within the range of an individual person, typically within a range of 10 meters. For example, a wireless network connecting a computer with its keyboard, mouse or printer is a PAN. Also, a PDA that controls the user’s hearing aid or pacemaker fits in this category. Another example of PAN is a Bluetooth. Typically, this kind of network could also be interconnected without wires to the Internet or other networks.

Local Area Network (LAN): Privately-owned networks covering a small geographic area, like a home, office, building or group of buildings (e.g. campus). They are widely used to connect computers in company offices and factories to share resources (e.g., printers) and exchange information. LANs are restricted in size, which means that the worst-case transmission time is bounded and known in advance. Knowing this bound makes it possible to use certain kinds of designs that would not otherwise be possible. It also simplifies network management. Traditional LANs run at speeds of 10 Mbps to 100 Mbps, have low delay (microseconds or nanoseconds), and make very few errors. Newer LANs operate at up to 10 Gbps.

Early LAN (Local Area Network) networks were formed using coaxial cable, coax is an electric cable and it is used to carry radio signals. LAN (Local Area Network) setup is developed by connecting two or more than two computers with each other using a physical connection in order to share files and data overtime.

Metropolitan Area Network (MAN): Covers a larger geographical area than is a LAN, ranging from several blocks of buildings to entire cities. MANs can also depend on communications channels of moderate-to-high data rates. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. MANs might also be owned and operated as public utilities. They will often provide means for internetworking of LANs. Metropolitan Area Networks can span up to 50km, devices used are modem and wire/cable.

Most widely used technologies to develop a MAN (Metropolitan Area Network) network are FDDI (fiber distribution data interface), ATM (Asynchronous Transfer Mode) and SMDS (switched multi megabit data service).ATM (Asynchronous Transfer Mode) is the most frequently used of all. ATM (Asynchronous Transfer Mode) is a digital data transfer technology. It was developed in 1980 to improve the transportation of real time data over a single network. ATM (Asynchronous Transfer Mode) works just like cell relay system, where data is separated in the form of fixed equal sized packets and is transferred overtime. The purpose of ATM (Asynchronous Transfer Mode) was to access clear audio and video results during a video conferencing.

Wide Area Networks (WAN): Computer network that covers a large geographical area, often a country or continent. (Any network 1 whose communications links cross metropolitan, regional, national boundaries). Less formally, a network that uses routers and public communications links. Routers will be discussed later.

WAN (Wide Area Network) networks are established often by seeking help from telecomm departments who provide the] facility of leased lines. Router is connected to the LAN at one side and a hub is attached at the other end.

Routing and Switching

A business network enables everyone in your company to connect to each other, to customers, to business partners, to important applications and to the Internet. The beauty of a network is that information and applications can be shared and accessed easily by everyone on your team. Consider the following:

How do you connect to the Internet to watch important presentations?

Through your network.

Where is your company's software?

On the network.

How does an important presentation get shared by multiple members of your team?

Via the network.

What carries critical messages to your employees and partners?

Your network.

What Are Routing and Switching?

The way a network operates is to connect computers and peripherals using two pieces of equipment - switches and routers. These two let the devices connected to your network talk with each other as well as talk to other networks.

Though they look quite similar, routers and switches perform very different functions in a network:

Switches are used to connect multiple devices on the same network within a building or campus.

For example, a switch can connect your computers, printers and servers, creating a network of shared resources. The switch would serve as a controller, allowing the various devices to share information and talk to each other. Through information sharing and resource allocation, switches save you money and increase productivity.
There are two basic types of switches: managed and unmanaged.

An unmanaged switch works out of the box and does not allow you to make changes. Home-networking equipment often will have unmanaged switches.

A managed switch allows you access to program it. This provides greater flexibility because the switch can be monitored and adjusted locally or remotely to give you control on how traffic travels over the network and who has access to your network.

Routers are used to tie multiple networks together.

For example, you would use a router to connect your networked computers to the Internet and thereby share an Internet connection among many users. The router will act as a dispatcher, choosing the best route for your information to travel so that you receive it quickly.
Routers analyze the data being sent over a network, change how it is packaged and send it to another network or over a different type of network. They connect your business to the outside world, protect your information from security threats, and can even decide which computers get priority over others.
Depending on your business and your networking plans, you can choose routers that include different capabilities and functions

Firewall: specialized software that examines incoming data and protects your business network against attacks

Virtual Private Network (VPN): A way to allow remote employees to safely access your network remotely

IP Phone network : Combine your company's computer and telephone network, using voice and conferencing technology, to simplify and unify your communications

How Businesses Use Routing and Switching

Routers and switches are the building blocks for all business communications from data to voice and video to wireless access. They can improve a company's bottom line by enabling your company to increase productivity, cut business costs, and improve security and customer service.

Specifically, routers and switches support:

Ø    Sharing applications

Ø    Provide staff access to business applications

Ø    Improve employee productivity

Ø    Using routing and switching technologies allows your staff, even those located in different locations, to have equal access to all your business applications, information and tools. Keeping everyone connected to the same tools can increase employee productivity. Routing and switching also can provide access to advanced applications and enable services, such as IP voice, videoconferencing and wireless networks.

Ø    Speeding access to information

Ø    Manage information efficiently

Ø    Review what is happening across your business

Ø    Accurate, timely information is essential for making prudent business decisions. Routing and switching provides access to allow great visibility into real-time business information and provides a sound basis for effective decision-making.

Ø    Enhancing customer service

Ø    Provide ready access to customer information

Ø    Improve customer responsiveness

Ø    Today's customers expect rapid responses and personalized services whenever they're dealing with your business, either by phone, email or on a website. A responsive, reliable network is an absolute necessity to give your employees speedy access to customer information, and enable them to respond rapidly and intelligently to resolve customer requirements.

Ø    Reducing operating costs

Ø    Share office equipment for reduced costs

Ø    Provide high-speed Internet access

Ø    Routing and switching technologies can make a positive impact on your bottom line. You save expenses by sharing equipment, such as printers and servers, and services, such as Internet access. A reliable network also can grow with your business, keeping you from having to replace it as your needs grow.

Ø    Improving security

Ø    Reduce risk

Ø    Protect valuable business information
Because high-speed Internet connections are always on, you may be vulnerable to security threats. Viruses, spyware, Internet attacks, e-mail assaults, and other security concerns are real dangers. By installing a networked solution with switches and routers, you can protect valuable business data. For example, routers can protect your network with a built-in firewall and Intrusion Prevention System (IPS) - specialized software that examines incoming data and protects against attacks.

Ø    Enabling remote connections

Ø    Provide secure remote access for mobile workers

Ø    Get work done from anywhere

Ø    Globalization has changed the way we work. Virtual teams, mobile workers, and home-based telecommuters all need to share information at any time. Modern businesses need networks that can connect employees, suppliers, partners and customers regardless of location, whether they are across town or halfway around the globe. With remote connectivity through a VPN, employees can securely access company resources and tools and work more productively.

Getting Started with Routing and Switching

Once you understand the ways in which routing and switching technologies can help your business, the next step is to determine whether you have the right foundation for your company's needs.

The following is a list of considerations to get you started.

Ø    The quality of your existing equipment
Consumer grade or home networking products can't keep pace with the challenges posed by business growth. For example, these products may not be able to handle the traffic or allow you to add voice or video communications or wireless well and may require you to manage each device individually. Business grade routers and switches provide reliable communications to your company and provide economies via shared equipment.

Ø    Flexibility
Invest in a network that can grow over time so that you can add features and functionality when your company needs them. Additions might include new applications like video monitoring, IP telephony, integrated messaging and wireless.

Ø    Easy connectivity
Make sure your routing and switching gear is easy to install use, and manage For example, switches with in-line power allow you to place equipment, such as wireless access points and IP phones, anywhere there's a network wall jack. This saves you the trouble and expense of installing extra electrical outlets or wires to power the devices.

Ø    Reliability
Business crises come in all varieties - from power failures to hurricanes and everything in between. Your organization's ability to maintain normal operations during a crisis may rely on the health of your network. A network designed with reliability and redundancy will provide the reassurance you need that your business will continue.

What is multiplexing?

Multiplexing, or muxing, is a way of sending multiple signals or streams of information over a communications link at the same time in the form of a single, complex signal. When the signal reaches its destination, a process called demultiplexing, or demuxing, recovers the separate signals and outputs them to individual lines.

Multiplexing is a method used by networks to consolidate multiple signals -- digital or analog -- into a single composite signal that is transported over a common medium, such as a fiber optic cable or radio wave. When the composite signal reaches its destination, it is demultiplexed, and the individual signals are restored and made available for processing.

Networks use a variety of multiplexing techniques, but at a conceptual level, they all operate in a similar manner. The individual network signals are input into a multiplexer (mux) that combines them into a composite signal, which is then transmitted through a shared medium. When the composite signal reaches its destination, a demultiplexer (demux) splits the signal back into the original component signals and outputs them into separate lines for use by other operations

What Does Concentrator Mean?

A concentrator aggregates and forwards data packets within a system. A concentrator may also administrate various dial-up internet calls and function as a network router. In general, the term “concentrator” is used for either of these essential tasks.

Some IT professionals may use the term “network concentrator” to talk about a system that takes in buffered packets and puts them into a single queue. The concentrator may take packets from FIFO buffers and put them in a position for linear handling.

IT professionals may talk about a network concentrator as a “forwarder” or more generally point out this function within a network system that handles multiple streams or threads and combines them into a single point of service. Concentrators may also be part of troubleshooting efforts, where system administrators may check to see that the concentrator is taking in and outputting signals correctly.

Components of Computer Network

A computer network is a system of interconnected computing devices used to share information and communicate electronically among a wide variety of users. The devices may be connected with a wire or may use a wireless method for transmitting the information.

Every setup requires some hardware and software components for installing the networks. To run the network systematically, there are certain components with different features and abilities.

HARDWARE COMPONENTS

Hardware components are the ones that are visible and can be touched; these are the components that are connected to the network with or without a wire.

Some of the commonly used Hardware components are-

1. Network Interface Card

A network interface card is a must-install hardware component in all the devices as it enables the devices to be able to connect to the network. It is in the form of a circuit board with a unique MAC address installed in the computer. It performs the function of sending and receiving data and controlling the flow of data over the network. It is capable of transferring data at the speed of 10,100 to 1000 Mb/s. It is also called a LAN or Network Adapter.

2. Servers

Servers are supreme computers with high-level configurations responsible for holding shared files, programs, resources, and the network operating system. It is also called a Host Computer because they provide access to the network resources to all the connected users. Few examples are file servers, database servers, web servers.

3. Clients

Clients are computer device that connects to and uses the network and shared network resources. They are basically the users of the network. Many corporate organizations have client computers for their employees associated with a corporate server.

4. Peers

Peers refer to the same devices over the computer network that shares similar rights and functionality as another. Two PCs can be peers, but a PC and a Server are not because they don't share similar operations.

5. Transmission Media

These can be defined as the link used to transmit information among devices within the computer network. Transmission Media can be of two types- Guided Medium, which uses cables and wires to share data, for example, coaxial cable, power lines, or fibre optics. Secondly, a Non-Guided Medium (also known as the wireless medium) uses electromagnetic waves to transmit the data, such as radio transmission, infrared transmission, or light transmission.

6. Connecting Devices

Connecting devices act as the middleware between networks and computers, some of the commonly used connecting devices are-

Hubs- A hub is a central connection of all the devices in a network system. It also connects all the computer devices. It acts as a distribution point as it processes requests from the client computer and provides the required information from the target device to the client computer. Hubs nowadays are becoming obsolete because there are better technologies available in the form of Switches and Routers.

Switches-It acts as a controller which connects various devices like computers, printers, and other hardware devices together. It also enables the free flow of information, sharing of resources, and reducing the cost.

Routers- Routers are used to connect multiple devices with an internet connection. It is an inexpensive method as it enables sharing information and connecting multiple devices through one internet connection. 

SOFTWARE COMPONENTS

1. Network Operating System

Network Operating Systems are computer operating systems that facilitate the connection and communication of all the computing devices connected over a network. It enables file sharing, maintaining and creating a database, providing access to hardware such as printers, plotters, or fax machines. The benefit of a Network Operating System is that it facilitated stability, better security, and the capability of managing data, users, groups, and other network functionalities. Some common Network OS is Windows. Linus, Unix, etc.

2. Protocol Suite

A protocol is a set of defined rules guidelines to be followed by every other device connected to the network. Protocol suites are a group of related protocols designed for computer networks. Two Protocol Suites are- OSI Model (Open System Interconnections), which decides how the data must flow between multiple computers and TCP/IP (Transmission Protocol and Internet Protocol), which gives instructions on how to connect and share information over devices within a network.

Other network components

1. ARP

ARP or Address Resolution Protocol is a communication protocol used to find out the physical address (MAC address) associated with a given network. It is used during the data transmission because the IP address of the device alone isn't enough; the machine's physical address is required, which is discovered using ARP.

2. RARP

RARP or Reverse Address Resolution Protocol is used by the client, devices to get its Internet Protocol address over a computer network.

Computer Network Components

Computer network components are the major parts which are needed to install the software. Some important network components are NIC, switch, cable, hub, router, and modem. Depending on the type of network that we need to install, some network components can also be removed. For example, the wireless network does not require a cable.

Following are the major components required to install a network:

NIC

NIC stands for network interface card.

NIC is a hardware component used to connect a computer with another computer onto a network

It can support a transfer rate of 10,100 to 1000 Mb/s.

The MAC address or physical address is encoded on the network card chip which is assigned by the IEEE to identify a network card uniquely. The MAC address is stored in the PROM (Programmable read-only memory).

There are two types of NIC:

Computer Network Components

Wired NIC

Wireless NIC

Wired NIC: The Wired NIC is present inside the motherboard. Cables and connectors are used with wired NIC to transfer data.

Wireless NIC: The wireless NIC contains the antenna to obtain the connection over the wireless network.

For example, laptop computer contains the wireless NIC.

Hub

A Hub is a hardware device that divides the network connection among multiple devices. When computer requests for some information from a network, it first sends the request to the Hub through cable. Hub will broadcast this request to the entire network. All the devices will check whether the request belongs to them or not. If not, the request will be dropped.

The process used by the Hub consumes more bandwidth and limits the amount of communication. Nowadays, the use of hub is obsolete, and it is replaced by more advanced computer network components such as Switches, Routers.

Switch

A switch is a hardware device that connects multiple devices on a computer network. A Switch contains more advanced features than Hub. The Switch contains the updated table that decides where the data is transmitted or not. Switch delivers the message to the correct destination based on the physical address present in the incoming message. A Switch does not broadcast the message to the entire network like the Hub. It determines the device to whom the message is to be transmitted. Therefore, we can say that switch provides a direct connection between the source and destination. It increases the speed of the network.

Router

A router is a hardware device which is used to connect a LAN with an internet connection. It is used to receive, analyze and forward the incoming packets to another network.

A router works in a Layer 3 (Network layer) of the OSI Reference model.

A router forwards the packet based on the information available in the routing table.

It determines the best path from the available paths for the transmission of the packet.

Advantages of Router:

Security: The information which is transmitted to the network will traverse the entire cable, but the only specified device which has been addressed can read the data.

Reliability: If the server has stopped functioning, the network goes down, but no other networks are affected that are served by the router.

Performance: Router enhances the overall performance of the network. Suppose there are 24 workstations in a network generates a same amount of traffic. This increases the traffic load on the network. Router splits the single network into two networks of 12 workstations each, reduces the traffic load by half.

Modem

A modem is a hardware device that allows the computer to connect to the internet over the existing telephone line.

A modem is not integrated with the motherboard rather than it is installed on the PCI slot found on the motherboard.

It stands for Modulator/Demodulator. It converts the digital data into an analog signal over the telephone lines.

Based on the differences in speed and transmission rate, a modem can be classified in the following categories:

Ø    Standard PC modem or Dial-up modem

Ø    Cellular Modem

Ø    Cable modem

Ø    Cables and Connectors

Ø    Cable is a transmission media used for transmitting a signal.

There are three types of cables used in transmission:

Ø    Twisted pair cable

Ø    Coaxial cable

Ø    Fibre-optic cable

 

 

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