Computer Notes For BS Chapter 7 Data Communication & Networking

Computer Notes For BS Chapter 7 Data Communication & Networking

Computer Notes For BS Chapter 7 Data Communication & Networking. Data communication refers to the transfer of digital data between two or more computers, and a computer network or data network is a telecommunications network that allows computers to exchange data. Physical connections between networked computing devices are established using either cable media or wireless media. The most popular computer network is the Internet.

Computer Notes For BS Chapter 7 Data Communication & Networking
Computer Notes For BS Chapter 7 Data Communication & Networking

BS Computer Notes Chapter 7 Data Communication & Networking

word image 274 Computer Network

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.


A computer Network is a system in which a number of independent computers are linked together to share data and peripherals, such as files and printers.

All major businesses and governmental and educational institutions make use of computer networks to such an extent that it is now difficult to imagine a world without them. Three very common types of networks include.

word image 275 Local Area Network (LAN)

A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Simply the computers connected in the 100m distance are called Local Area Network (LAN).

Computers connected to a network are broadly categorized as servers or workstations. Servers are generally not used by humans directly, but rather run continuously to provide “services” to the other computers (and their human users) on the network. Services provided can include printing and fax, software hosting, file storage and sharing, messaging, data storage and retrieval, complete access control (security) for the network’s resources, and many others.

word image 276 Metropolitan Area Network (MAN)

A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches, and hubs are connected to create a Metropolitan Area Network.

word image 277 Wide Area Network (WAN)

Wide Area Networks (WANs) connect networks in larger geographic areas, such as Florida, the United States, or the world.

Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of global network. Computer networks exist on various scales, from links between two computers in one room to connect computers in a building or campus to national and global networks. Various media are used to carry the communications signals: copper wire, fiber optic cables, and wireless or radio transmissions etc. Similarly, the network connecting an organization’s computers might be owned and managed by the organization itself (typically in small-scale networks linking machines in a room or building) or capacity can be rented from a firm providing telecommunications services (typically in wider area networks).

word image 278 Communication media

Communication media are the links that provide paths for communicating devices. It is an important part of communication model. Transmission medium should provide communication with good quality. Communication media can be classified into two main types.

  • Guided media
  • Unguided media

word image 279 Guided media

Guided media are the physical links in which signals are confined (limited) along a narrow path.

These are also called bounded media. Three common types of bounded media (types of cable):

  • Twisted pair cable
  • Coaxial cable
  • Fiber optic cable

word image 280 Twisted pair cable

Twisted pair cable is formed of two insulated copper wires twisted together. The wires are twisted with each other to minimize interference from other twisted pair cable. Wire pairs have fewer bandwidths then coaxial cable or optical fiber cable. Two main types of twisted pair cable unshielded twisted pair (UTP) cable and shielded twisted pair (STP) cable.

Computer Notes For BS Chapter 7 Data Communication & Networking
Computer Notes For BS Chapter 7 Data Communication & Networking

word image 282 Coaxial cable

Coaxial cable has a central core conductor of solid or standard wire (usually copper) enclosed in an insulating sheath which is in turn encased in an outer conductor of foil braid or a combination of a two. The outer metallic wrapping is a second conductor to complete the circuit and shielded against noise. This outer conductor is also enclosed in an insulating sheath and the whole cable is protected by a plastic cover. Because coaxial cable have very little distortion and are less prone to interference they have low error rates. Although coaxial cables are difficult in installation, it is highly resistant to signal interference. In addition it contains support greater cable lengths between network devices than twisted pair cable.

word image 283 Fiber optic cable

Fiber optic cable consists of a very narrow strand or fiber of glass called the core. The core is surrounded by a concentric layer of glass called cladding. The cladding is covered by a protective coating of plastic jacket. It transmits signals in the form of light rather than electronic signals. This eliminates the problem of electrical interference.

The fiber optic cable is becoming more popular. Nowadays telephone internet and television companies are replacing their existing cables with fiber optic cables. Fiber optic cable has bandwidth more than 2 Gaps (gaga bytes per second).

word image 285 Unguided media

Unguided media also called wireless media transports signal without using any physical conductor between the two devices communicating. Signals are normally broadcast through the air and thus are available to any who has the device capable of receiving them.

The commonly used wireless transmission media are:

  • Radio weave
  • Micro weave
  • Infrared weave

word image 286 Radio weaves

Radio weave distributes radio signals through the air cover long distance such as between cities, regions and countries, and short distance such as within an office or home. Radio weave are normally multi-dimensional. It has frequency between 10 KHz to 1 GHz.

word image 287 Micro weaves

Micro weave is a wireless transmission technology that travels at high frequency than radio weaves and provide throughput as a wireless network media. It has frequency between 1 KHz to 300 GHz.

word image 288 Infrared weave

Infrared is a short distance wireless transmission medium that sends signals using infrared light weave. Infrared frequencies are just below visible light. This technology is similar to the use of remote control for the use of TV.

word image 289

Components of a Data Communication

Data communication is a process of transferring data electronically from one place to another. Data can be transferred by using a different medium. The basic components of data communications are as follows:

  1. Sender
  2. Encoder
  3. Medium/ communication channel
  4. Decoder
  5. Receiver
Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 20: Diagrammatic Representation of Computer Network/Data Communication

word image 291 Sender

Sender is a device that sends a message. The message can consist of text, numbers, pictures etc. it is also called source or transmitter. Normally, the computer is used as the sender in information communication systems.

word image 292 Encoder

The encoder is a device that converts digital signals in a form that can pass through a transmission medium.

word image 293 Medium / Communication Channel

Medium is the physical path that connects sender and receiver. It is used to transmit data. The medium can be a copper wire, a fiber optic cable, microwaves etc. it is also called communication channel.

word image 294 Decoder

The decoder is a device that converts the encoded signals into digital form. The receiver can understand the digital form of message. Sender and receiver cannot communicate successfully without encoder and decoder.

word image 295 Receiver

Receiver is a device that receives the message. It is also called sink. The receiver can be a computer, printer or another computer-related device. The receiver must be capable of accepting the message.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 21: Components of Data Communication

word image 297

Modes of Data Communication or Modes of Network

Transmission mode means transferring of data between two devices. It is also known as the communication mode. Buses and networks are designed to allow communication to occur between individual devices that are interconnected. There are three types of transmission mode:- 1. Simplex Mode

  1. Half-Duplex Mode
  2. Full-Duplex Mode
Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 22: Transmission Modes

word image 299 Simplex Mode

In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit, the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one direction.

Example: Keyboard and traditional monitors. The keyboard can only introduce input; the monitor can only give the output, Radio, and Television (TV) etc.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 23: Simplex Mode of Communication

word image 301 Half-Duplex Mode

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is used in cases where there is no need for communication in both directions at the same time. The entire capacity of the channel can be utilized for each direction.

Example: Walkie-talkie in which message is sent one at a time and messages are sent in both the directions.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 24: Half-Duplex Mode of Communication

word image 303

Full-Duplex Mode of Communication

In full-duplex mode, both stations can transmit and receive simultaneously. In the full duplex mode, signals going in one direction share the capacity of the link with signals going in other direction, this sharing can occur in two ways:

  1. Either the link must contain two physically separate transmission paths, one for sending and other for receiving.
  2. Or the capacity is divided between signals traveling in both directions.

Full-duplex mode is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions.

Example: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 25: Full-Duplex Mode of Communication

word image 305 Synchronous Mode of Communication

In synchronous transmission large volumes of information can be transmitted at a time. In this type of transmission, data is transmitted block by block or word by word simultaneously. Each block may contain several byte of data

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 26: Synchronous Mode of Communication

These clocks must be synchronized at the beginning of the session so that the timing of the transmission—not the use of start and stop bits, as in asynchronous communication—defines where data begins and ends.

word image 307 Asynchronous Communication

In a synchronous transmission data is transmitted. 1byte at a time. This type of transmission is most commonly used by microcomputer. The data is transmitted character by character.

Asynchronous communication sends small blocks of data with many control bits for error correction, synchronous techniques use large blocks of data with control bits only at the start and end of the transmission.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 27: Asynchronous Mode of Communication

word image 309 Parallel Communication

In data transmission, parallel communication is a method of conveying multiple binary digits (bits) simultaneously.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 28: Parallel Mode of Communication

word image 311 Serial Communication

With serial communication, which conveys only a single bit at a time?

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 29: Parallel Mode of Communication

word image 313

Network Topology

Think of a topology as a network’s virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network.

For example, the computers on a home network may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there.

Network topologies are categorized into the following basic types:

  1. Bus
  2. Ring
  3. Star
  4. Mesh

More complex networks can be built as hybrids of two or more of the above basic topologies.

word image 314 Bus Topology

Bus networks use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium those devices attach or tap into with an interface connector.

A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 30: Bus Topology

word image 316 Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 31: Ring Topology

All messages travel through a ring in the same direction (either “clockwise” or “counter clockwise”).

A failure in any cable or device breaks the loop and can take down the entire network.

word image 318 Star Topology

Many home networks use the star topology. A star network features a central connection point called a “hub node” that may be a network hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 32: Star Topology

word image 320 Mesh Topology

Mesh topology introduces the concept of routes

Computer Notes For BS Chapter 7 Data Communication & Networking

Figure 33: Mesh Topology

Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. Some WANs, most notably the Internet, employ mesh routing.

word image 323 Internet

The Internet, sometimes called simply “the Net,” is a worldwide system of computer networks – a network of networks in which users at any one computer can, if they have permission, get information from any other computer

Today, the Internet is a public, cooperative and self-sustaining facility accessible to hundreds of millions of people worldwide. Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks.

word image 324 Collaborative Computing:

Collaborative computing is a diverse collection of information technologies designed to support work between individuals. Organizations implementing collaborative computing technologies do so as a way to improve workforce productivity and creativity by enabling individual workers to more readily access each other and the information they need when they need it. OR

Interactive multimedia conferencing application software, that enables multiple parties to collaborate on textual and graphical documents. Through special software, each party to the call can contribute to such documents, working together with the other parties.

word image 325 What is Social Networking?

A network of social interactions and personal relationships?


A dedicated website or application software that enables the user to communicate with each other, by posting information, comments, messages, and images etc.

A social network is a website that brings people together to talk, share ideas and interests, or make new friends. This type of collaboration and sharing is known as social media. Unlike traditional media that is typically created by no more than ten people, social media sites contain content created by hundreds or even millions of different people.

Below is a small list of some of the biggest social networks used nowadays?

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