Data Communication and Networking

_According to syllabus, students must be able to:

1. Describe the communication system with its basic elements and model

2. Describe the data communication with its elements and mode.

3. Define and apply LAN and WAN

4. Describe transmission medium and use it.

5. Define terminologies for transmission impairments.

6. Introduce network architecture.

7. Define basic terms and tools used in computer network.

8. Define network tools, devices and topologies and use them.

9. State the concept of OSI Reference Model and Internet Protocol Addressing.

Concept of Communication System

Communication refers to the sending, receiving and processing of information by electronic media. Communication started with wire telegraphy in 1840s.

Computer Network

A computer network is defined as two or more computing devices linked together to communicate, sharing information and other hardware resources. Similarly, the concept of connected computers sharing resources is called networking.

Advantages of using Computer Network

1. Resource sharing: It is easy to share information and other hardware resources using the computer network. Most institutions cannot afford enough laser printer, fax machines, MODEMs, scanners and CD-ROM players for each computer because these all are shared by all users in a node (node is a network in which different computers are connected).
2. Centralized control and management: The networks provide centralized control and management. The entire computers in the network are normally connected to a server, which defines the policy and security measures for the resources used by the network members.
3. Speedy and cost-effective communication: Since the entire computer is connected, the message can send from one computer to another within few seconds.
4. Backup and recovery: The network is used to recover data and system in case of system crash using backup or through the server.
5. Flexible access: The network allows people to easily access their files from any computer throughout the network.
6. Workgroup computing: Workgroup software allows many users to work on a document or project concurrently.

Disadvantages of using Computer Network

1. Expensive: Extra devices like NIC, Hub, cables are required to connect computers which makes the cost more expensive.
2. Security problem: Data shared in this system is public. So, there is lack of security and also there is a chance of computer crimes.
3. Needs special technical knowledge: Skilled manpower is required to establish, maintain and operate a networking system.
4. Network failure: Failure of the network may hamper the day to day operation of the organization.
5. Complex: The network itself is difficult to establish, manage and operate.

Basic Elements of Communication System

The communication system is a system which describes the information exchange between two points. The process of transmission and reception of information is called communication.

The elements of communication system are as follows:

1. Transmitter of information: The transmitters function is to process the message signal into a form suitable for transmission over the communication channel. It is the sender which sends data to the receiver.
2. Channel or medium of communication: Its function is to provide a pathway between the transmitters output and the receivers input. It transmits data from the sender to the receiver.
3. Receiver of information: The job of the receiver is to process the received signal to recover the appropriate message signal. It receives data sent by the sender.

Elements of Data Communication/Transmission

1. Information or input signal: The information can be in the form of sound signals like speech or music or it can be in the form of pictures.
2. Input transducer: Information is not transmitted in the form of sound, picture or data signals. Instead of that it has to be converted into a suitable electrical signal.
3. Transmitter: Transmitter is a device which converts the information into suitable electrical signal. The transmitter consists of the electronics circuits such as amplifier, mixer, oscillator, and power amplifier.
4. Communication channel or medium: It is the medium used for the transmission of electronic signals from one place to another. It can be wires, cables, optical fibres or free space.
5. Noise: It is the extra unwanted electrical signal which combines with the transmitted signal when it is travelling towards receiver. Due to this, the quality of the transmitted information will degrade.
6. Receiver: The received signal is amplified and demodulated and converted in a suitable form. The receiver consists of electronic circuits like a mixer, oscillator, detector and amplifier.
7. Output transducer: In this, the electrical signal is again converted in original form. The example of output transducer are loud speakers, picture tubes etc.

Communication Mode

The direction of data flow in the communication is known as communication mode.

There are three types of modes:

1. Simplex: In this mode, transmission is possible in only one direction similar to a one-way street. It can be either only receive or send data.
2. Half-duplex: In this mode, transmission is possible in both directions, but not simultaneously i.e one direction at a time. for eg: walkie-talkie, wireless microphone, cc camera etc.
3. Full-Duplex: In this mode, transmission is possible in both directions simultaneously, similar to two-way street. for eg: mobile phones/telephone communication.

Types of Computer Network

Based on geographical area coverage; the computer network is classified into three basic types:

1.LAN (Local Area Network)

LAN is the interconnection of computers in a limited geographical area like in a single room, rooms within a building, or buildings on one site. It is smaller, simpler and cheaper than other network. The LAN can operate at a speed of several 100 Mbps. It is useful for sharing resources like files, software programs, printers, plotters, disk droves, games or other applications services.

Advantages of LAN

1. Data transmission speed is faster than MAN and WAN.
2. It has higher security to resources of the network.
3. It is cheaper to establish.
4. It is easier to establish, manage and operate.

Disadvantages of LAN

1. It is limited only to a small area.
2. It connects small number of computers.
3. Lack of backup provision compares to MAN and WAN.

2. MAN (Metropolitan Area Network)

MAN is extended up to a city or a large geographical area than the LAN. It is used to connect multiple systems or networks within a single city. It can use either wired or wireless transmission media.

Advantages of MAN

1. It is spread to a larger area than LAN.
2. It comparatively connects many numbers of computer than the LAN.
3. It can connect dissimilar systems and networks.
4. Public libraries and government agencies typically use a MAN.

Disadvantages of MAN

1. It uses comparatively expensive devices than used in the LAN.
2. Transmission speed is usually slower compared to the LAN.
3. It is complex to establish, manage and provide security.
4. It is expensive to run than LAN.

3. WAN (Wide Area Network)

WAN is used to interconnect computers spread to a larger geographical area like in separate cities or countries. It is also known as Long Haul Networks (LHNs). Communication is usually done through satellite, microwave systems or optical fibers. The transmission speed is usually slower and maintaining security is comparatively complex.

Advantages of WAN

1. It is spread to a large area than LAN and MAN.
2. It connects comparatively larger number of computers than LAN and MAN.
3. It also connects dissimilar systems and networks.

Disadvantages of WAN

1. It uses comparatively expensive devices than used in LAN and MAN.
2. Transmission speed is usually slower compare to LAN and MAN.
3. It is complex to establish, manage and provide security.
4. High qualified technical personnel and government agencies are worked together to establish this type o network. Thus, invest money and effort is very top.

Differences between LAN and MAN

S.N	LAN	WAN
1.	LAN is limited only to a small geographical area.	WAN is expanded to a large geographical area.
2.	Smaller number of computers can be connected.	Larger number of computers can be connected.
3.	Data transmission speed is faster.	Data transmission is slower.
4.	Devices used in LAN are Hub, Switch, NIC etc	Devices used in WAN are Router, Gateway etc.
5.	Cost of data transmission is cheaper.	Cost of data transmission is expensive.
6.	There is very low error rate in LAN.	There is comparatively high error rate in WAN.

Transmission Media

Transmission media refers to the wires, cables and other means through which data travels from its source to its destination. Transmission media are often called communication media.

The basic requirements for the working of a communication system are:

A sender which creates the message to be transmitted.

A medium which carries the message from sender to receiver.

A receiver which receives the message.

Transmission media can be categorized as guided media and unguided media.

Guided media contains wires or cable such as:

• Twisted pair cable
• Coaxial cable
• Fiber optics cable

Unguided media includes:

• Microwave system
• Satellite communication
• Infrared technology

Twisted pair cable

Twisted pair cable is a pair of copper wires. Copper wires are the most common wires used for transmitting signal because of good performance at low costs. A twisted pair consists of two conductors (normally copper), each with its own plastic insulation twisted together to form a single media. Out of these two wires, only one carries actual signal and another is used for ground reference. To identify every cable, these cables are colour coated. The twists between the wires are helpful in reducing noise (electro-magnetic interference) and cross talk. This type of cable is used in telephone lines to provide voice and data channels.

Types of twisted pair cable:

1. Unshielded Twisted Pair (UTP)

2. Shielded Twisted Pair (STP)

Differences between UTP and STP

S.N	UTP	STP
1.	It is the most common twisted pair.	It is rarely used.
2.	It does not contain an extra covering.	It contains an extra metal foil outside plastic cover of each pair.
3.	It cannot carry data signals for longer distances compared to STP.	It can carry data signals for longer distances.
4.	It is cheaper.	It is expensive.

Advantages and Disadvantages of Twisted Pair Cable

Advantages

1. It is light and thin, so it is more flexible to fit on a LAN.
2. It is cheaper than other cables.
3. It can transmit data at a higher bandwidth for short distance.

Disadvantages

1. It cannot be used for long distance transmission.
2. It is slower for data transmission than other cables.
3. It can be affected by electrical and magnetic field.

Coaxial Cable (COAX)

Coaxial cables are copper cables with better shielding than twisted pair cables, so that transmitted signals may travel longer distances at higher speeds. The shield minimizes electrical and radio frequency interference. Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet.

Coaxial cable has two wires of copper. The inner copper wire in center is made of solid conductor, It is enclosed in an insulating sheath. The outer copper wire is wrapped around, and is used to protect from external noise (electromagnetic interference). This all is covered by plastic cover used to protect the inner layers from physical damage such as fire ore water.

Types of Coaxial Cable:

1. Thin coax (thinnet): It has speed of 10mbps upto 200m.

2. Thick coax (thicknet): It has speed of 10mbps upto 500m.

Advantages of Coaxial Cable

1. It provides faster data transmission than the twisted pair cable.
2. It can transmit data over medium-range distances.
3. It is easier to install, modify and manage the network.

Disadvantages of Coaxial Cable

1. It is expensive to install.
2. It is not appropriate for long distance transmission.
3. It is rarely used at present for a computer network.

Fiber Optics Cable

A fiber-optic cable is made of glass or plastic and transmits signals in the form of light. Fiber optic cables are not affected by electromagnetic interference, so noise and distortion is very less. Fiber optic cables carry communication signals using pulses of light generated by small lasers or light-emitting diodes (LEDs).

The cable consists of one or more strands of glass, each only slightly thicker than a human hair. The center of each strand is called the core, which provides the pathway for light to travel. The core is surrounded by a layer of glass called cladding that reflects light inward to avoid loss of signal and allow the light to pass through bends in the cable. No light escapes the glass core because of this reflective cladding.

Advantages

1. It provides the fastest data transmission than other transmission media.
2. It can be used for both short to long distance transmission.
3. It provides error-free and highly secured transmission.
4. It can transmit multiple data at the same time due to the use of multiple fibers in a cable.

Disadvantages

1. It is highly expensive and difficult to install.
2. It is not appropriate for short-distance transmission due to its thickness and difficult to bend.
3. Skilled technical manpower is required to install and are rare.
4. It is not preferred to use hillside area; like up and down-field connection among stations.

Microwave System

Microwaves are a type of radio waves with high frequencies. It can be classified as a subclass of radio waves. The frequency of microwaves lies in the 300 MHz to 300GHz. Microwaves are unidirectional, in which the sending and receiving antennas need to be aligned. Microwaves are widely used for point-to-point communications because their small wavelength, which means that the signal is focused into a narrow beam. Additionally, each antenna must be within line of sight of the next antenna. Microwaves have high frequencies and do not penetrate wall like obstacles. It is used for satellite communication, navigation, radar, remote sensing and other short distance communication systems.

Satellite Communication

Satellite communication is the most common worldwide communication system at present. It uses a satellite as a repeater. The satellite is the repeater that orbits in space. Satellite communication systems have receivers and transmitters located in ground stations. In this communication, microwave signal is transmitted from a transmitter on earth to the satellite in space. The satellite amplifies the weak signal and transmits it back to the receiver. To make communication possible in the even longer distance, multiple satellites are used.

Infrared wave

Infrared signals have frequencies between 300 GHz to 400 THz. They are used for short-range communication. Infrared waves are used for very short distance communication like TV remote, wireless speakers, automatic doors, hand held devices etc. Infrared waves having high frequencies prevents interference between one system to another. Infrared signals have high frequencies and cannot penetrate walls. Due to its short-range communication system, the use of an infrared communication system in one room will not be affected by the use of another system in the next room. This is why using an infrared TV remote control in our home will not interfere with the use of our neighbours infrared TV remote control.

Terminology for transmission impairments

In the data communication system, analog and digital signals go through the transmission media.

The error that occur during data communication from one point to another are called transmission impairment.

When a signal is transmitted over a communication medium, it may have different types of impairments.

Impairment occur due to imperfect characteristics of communication medium.

Some of the transmission impairments terminologies are:

1. Jitter:

Jitter states that small irregular delays during data transfers i.e. the delay between when a signal is transmitted and when it is received.

2. Attenuation:

Attenuation is the loss or reduction in the strength of a transmission signal in networking cables or connections.

Attenuation is the fall of signal strength with the distance as signal travels through the communication media. If the attenuation too much, the receiver may not be able to detect the signal at all.

3. Distortion:

The change in the form or shape of the original signal or waveform is known as distortion.

Distortion refers to change in shape or frequency of digital signal when it is transmitted over a communication line.

4. Noise:

The random or unwanted signal that mixes up with the original signal is called noise. There are several types of noise such as industrial noise, induced noise, crosstalk noise, thermal noise and impulse noise which may corrupt the signal.

5. Echo:

Echo is a reflection of sound that arrives at the listener with a delay after the direct sound.

6. Singing:

Singing may be regarded as echo that is completely out of control. This can occur at the frequency at which the circuit is resonant.

7. Crosstalk:

Crosstalk is unwanted signals in a communication channel caused by the transference of energy from another circuit.

8. Bandwidth:

The maximum amount of data transfer rate of a network or Internet connection in a given amount of time is known as bandwidth.

9. Number of receivers:

When the number of receivers increases the transmission distance and/or data rate are limited.

Basic Concept of Networks Architecture

Network Architecture is the design of computers, media and other devices in a network and how the communicate.

The network architecture explains how the computer in a network interacts with each other and the network devices.

Based on network architecture, the computer network can be classified into:

Peer-to-Peer architecture

Client/Server architecture

Peer-to-Peer Architecture

In a peer-to-peer architecture, all computers have equal authority to access data and therefore are known as  peers. Each computer functions as both a client and a server. There is no dedicated server. 

A peer-to-peer network is also called workgroup.

Workgroup refers to the small group of individual computers, who work together.

Advantages

1. It is simple and easier to set up.
2. The overall cost of implementing and managing the network is cheaper.
3. If a computer fails to operate, it will not affect others.
4. Users cab manage their own system, so dedicated system administrator is not required.

Disadvantages

1. Administration of the network is difficult without a dedicated server.
2. Data security is poor in this architecture.
3. Data recovery and backup process are difficult.
4. It is not appropriate for a large organization having a large number of computers.

Client-Server Architecture

The client-server architecture contains at least one dedicated server and client computers. The server always provides services to clients, and a client always receives services from the server. The server provides services like data, webpage, email, SMS, file , print, etc.

Advantages

1. Centralized administration is possible through the network.
2. High security cab be provided by using the appropriate server.
3. It is appropriate for a large organization having a large number of computers.
4. Data recovery and backup process the easier.

Disadvantages

1. It is expensive due to the use of dedicated servers.
2. It is complex to establish and manage.
3. Experienced administrators are required to implement and manage the network.
4. If the server fails, it will affect the network.

Differences between Peer-to-Peer Network and Client-Server Network

S.N	Peer-to-Peer Network	Client-Server Network
1.	It is simple connection of similar type computers called peers.	This type of network contains two types of computer called a client and server.
2.	It is appropriate for small organization with limited number of computers.	It is appropriate for large organization with large number of computers.
3.	It is easier and cheaper to establish and manage.	It is complex and expensive to establish and manage.
4.	Difficult to manage high security without dedicated server.	Higher security can be maintained through server.
5.	Highly skilled manpower is not required to operate.	Skilled manpower is required to operate.

Some basic terms and tools used in Computer Network

1. IP Address

Internet Protocol (IP) is a unique identifying number assigned to each computing device connected to a network that uses the Internet protocol for communication. A typical IP address looks like this: 216.27.61.137

IP address in binary looks like; 11011000.00011011.00111101.10001001

The four numbers in an IP address are called octets.

2. MAC Address

Media Access Control (MAC) address is a unique number associated with a network adapter (NIC). It is also known as physical or hardware address. MAC address is a 12-digit hexadecimal number. for eg: 0:A0:C9:14;C8:29

3. Internet

The Internet is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide.

The internet is an interconnected network of thousands of networks and millions of computers linking business, education institutions, government agencies, and individuals together.

4. Intranet

Intranet is inter connected network in a company or an organization.

An intranet is a LAN or WAN that uses TCP/IP protocol but, belongs exclusively to a corporation, school, or organization. The intranet is accessible only to the organization workers.

Differences between Internet and Intranet

S.N	Internet	Intranet
1.	A global system of interconnected computer networks that uses the internet protocol (TCP/IP) to link devices worldwide.	A private network that contained within an enterprise.
2.	It is a public network.	It is a private network.
3.	Anyone can access the information.	Only the users of organization have access.
4.	It is less secure.	It is more secure.
5.	It has large number of users.	It has limited number of users.
6.	It has more traffic because it is worldwide network.	It has low traffic because it is a private network.

5. Extranet

An extranet is a private intranet that can be accessed by outside users over the Internet using the dedicated and secure channel.

Network Tool

1. Packet tracer

2. Remote login

Network Connecting Devices

1. NIC (Network Interface Card)

NIC is a device that connects the computer and network cable. It prepare data from the computer for the network cable. It send/receive the data to another computer. It also control the flow of data between the computer and the cabling system.

2. MODEM (Modulator and Demodulator)

MODEM is a device which translate data from binary codes to analog data that can be transmitted over the telephone network and translates analog data into binary codes. Modulation is the process of converting data from binary to analog and demodulation is the reverse process.

3. Hub

Hub is a connectivity device with multiple ports for connecting computers in a star topology. It accepts data, amplifies them, and then broadcasts. Due to broadcasting, data traffic is increased. It is used to connect computers in a LAN.

4. Switch

A switch connect devices in a network to each other. It is also known as intelligent hub. When the switch receives a data packet, it creates a direct connection between sender and receiver and forwards the data packet to the destination computer only.

5. Bridge

The bridge is used to connect two different network segment. It is the connecting device between hubs. It passes data packets between multiple network segments that use same communication protocol.

6. Router

The router is used to connect two or more different networks having different network addresses. Its main job is to find out the best route that can be used for transmission. 

7. Brouter (Bridge Router)

A brouter is a bridge and a router combined in a single product. It can connect two networks using the same protocol (as bridge) as well as different networks (as router). It is a hybrid of a bridge and a router.

8. Repeater

The repeater is a device that amplifies a signal being transmitted on the network. It is used to increase the length of the transmission media, in which data can be transmitted. It receives signals, amplifies them and retransmits towards the receiver.

9. Gateway

Gateway enables communication between networks using different network architectures. It acts as a translator between networks using incompatible transport protocols, such as between TCP/IN and SNA or between SNA and X.25.

10. Bluetooth

Bluetooth is a wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks (PNAs) with high level of security.

11. Wi-Fi

The devices such as laptop, mobile devices can easily connect to the network or internet when within a range of a wireless network connected to the Internet using Wireless-Fidelity (Wi-Fi). Wi-Fi allows communications directly from one computer to another without the involvement of an access point.

12. Workstation

Workstation refers to any computer connected to a local-area network. Workstations are typically linked together to form a local-area network, although they can also be used as stand-alone systems.

Network Topologies

1. Bus Topology

2. Star Topology

3. Ring Topology

4. Tree Topology

5. Mesh Topology

6. Hybrid Topology

Bus Topology

A bus topology connects each computer to a segment called trunk (bus). Coaxial cables are mostly used. It consists of the main cable with terminators at both ends.

Advantages

1. It is easier to implement and extend.
2. It is well suited for the temporary network.
3. It is typically the cheapest topology to implement.
4. Failure of one computer does not affect other.

Disadvantages

1. It is difficult to troubleshoot.
2. It has limited cable length and number of nodes.
3. A cable break can disable the entire network.
4. Data traffic is high, which increases data collision rate and data error rate.

Star Topology

The star topology is the most common network topology found in most offices and home networks. In a star topology, each computer or node is connected to the central device such as a hub. Data on the star network passes through the hub before reaching its destination.

Advantages

1. Easier to add or remove computers.
2. Easier to monitor and troubleshoot.
3. Failure of one computer does not affect the entire network.
4. The centralized control system can be established.

Disadvantages

1. Failure of hub affects all nodes.
2. It is more expensive than bus topology because of the cost of the hub.'
3. Data traffic, data collision rate, and data error rate will be high.
4. Each computer requires dedicated cable so; more cable is required and proper cable naming is required to identify each computer cable.

Ring Topology

In the ring topology, each station is attached to nearby computers on a point-to-point basis so that the entire system is in the form of a ring. The entire computers are connected in a closed loop. Data are transmitted in only one direction.

Advantages

1. The growth of system has minimal impact on performance.
2. Terminators are not necessary as in bus topology.
3. Data traffic is reduced as data flows in only one direction.
4. Each computer has equal priority to communicate on the network.

Disadvantages

1. More expensive than bus topology because of the cost of the MAU.
2. Difficult on set up than bus and star topology.
3. Failure of a computer affects the entire network.
4. Less flexible, difficulty in adding and removing the computers from the ring.

Basic Concept of OSI Reference Model

OSI stands for Open System Interconnection model, it has been developed by Standard Organization ISO (International Organization for Standerization) in 1984.

It is a 7 layer architecture where each layer having specific functionality.

All these 7 layer work collaboratively to transmit the data from one network to another network across the globe.

Seven layers of the OSI Model

1. Application layer

2. Presentation layer

3. Session layer

4. Transport layer

5. Network layer

6. Data link layer

7. Physical layer

Explanation will come soon