Chapter 4

Learning Objectives

• What are Networks and why one needs them for business applications?

• What is the different kind of data communications channels that exists and are there any defined standards for these channels?

• How many types of networks exist and what are the different topologies that these networks may follow?

• What are the different components of networks and how one can select a network?

• What are the roles, Internet, Intranet and Extranet play for success of the business?

Networks• A Network is interconnection of resources that

organization owns. • A Network is a technology solution that helps

organization to interconnect its hardware, software, databases and various media to achieve interconnectivity between its employees and stakeholders.

• Data communication or data conferencing allows two or more users to share the common data resource either on the common computer server or their networked computers.

Types of Networks

• Local Area Network (LAN)– A local area network (LAN) interconnects two or more

computers or devices within a relatively small, well-defined area, such as a room, building, or cluster of buildings using physical wires, infrared links or wireless systems.

• Wide Area Network (WAN)– A wide area network (WAN) interconnects two or

more computers that are geographically dispersed. • Virtual Private Network (VPN)

Network Topologies

• Topology is the process and method of connecting different nodes in a network. A network can be arranged as per one of the four different topologies:– Star Topology– Ring Topology– Bus Topology– Tree Topology– Mesh Topology

Network Components• There are two basic components to the backbone

of a network: the network connectivity (cable or wireless) and the hardware devices that connect networks to the network backbone. – Twisted Pairs Cables– Coaxial Cables– Fiber Optical Cables– Microwave Transmission– Satellite Transmission– Infrared– Bluetooth

Cellular Technology• Cellular networks are divided up into cells, each cell being serviced by one

or more radio transceivers (transmitter/receiver). Communication in a cellular network is full duplex, where communication is attained by sending and receiving messages on two different frequencies - frequency division duplexing (FDD). – First Generation (1G): First generation services were analogue services for cell

phones. – Second Generation (2G): 2G services were digital. The transition to 2G

provided the ability to store, copy, encrypt and compress data, and allowed data transmission without loss and with error-correction. There are two kinds of 2G services

• Global System for Mobility (GSM)• Code Division Multiple Access (CDMA)

– 2.5 / 3G: The introduction of packet switching for data rather than circuit switching.

– "True" 3G: Third Generation networks offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. Services include wide-area wireless voice telephony, video calls, and broadband wireless data, all in a mobile environment.

Network Components• Ethernet• Hubs - Hubs are very simple devices that pass all traffic in both

directions between the LAN sections they link. • Bridges - Bridges connect two LAN segments that use the same data

link and network segments. • Switches - Switches are similar to bridges but connect more that

two LAN segments. • Routers - Routers connect two or more LANs that use the same or

different data link protocols but employ the same network protocol.

• Brouters - Brouters are devices that combine the functions of both bridges and routers; they bridge same data link layer LANs and route different data link layer LANs.

• Gateways - Gateways connect two or more LANs that use the same or different data link and network protocols.

Communication• Data Communication: Data communication is the process

of sending data electronically from one point to another. • Telecommunication, or teleprocessing, is the processing of

using communication facilities, such as the telephone system, microwave relays, and satellite to send data between computers.

• Analog Data Transmissions: Analog data transmission is the transmission of data in a continuous waveform.

• Digital Data Transmission: Digital data transmission is the transmission of data using distinct on and off electrical states.

• Modem is a modulation-demodulation device which converts the digital signal to analog and vice-versa.

Communication Channels• A communication channel is the medium, or pathway, along

which data are transmitted between devices. Communication channels fall into two basic types: wire cable and wireless.

• Two methods that are used to regulate the flow of data from communication channels into a computer are multiplexing and concentration.

• Multiplexing: Multiplexing is the process of combining the transmissions from several devices into a single data stream that can be sent over a single high-seed communication channel.

• Concentration: Concentration is the process of connecting and serving the networked devices; a concentrator, often a computer, provides the concentration.

Data Transmission• Baud Rate: It is the rate at which data are transferred.

Baud is often equated with bits per second (bps).• Two factors that determine the rate at which data can

be transmitted are the bandwidth of the communication channel and the method of data transmission – asynchronous or synchronous.– Bandwidth of a communication channel determines the

rate, or speed, at which data can be transmitted over that channel.

– Asynchronous transmission of data is a method that sends one character at a time.

– In Synchronous transmission, blocks of characters are transmitted in timed sequences.

Seven-layered OSI model for network

communications

Application layer

Physical layer

Application layer

Physical layer

Networklayer

Transportlayer

Sessionlayer

Presentation layer

Data-linklayer

Presentation layer

Sessionlayer

Transportlayer

Networklayer

Data-linklayer

Physical layer

Data-linklayer

Networklayer

Host Node Intermediate Nodes User Node

Comparative Charts between OSI and TCP/IP Model

Network Architectures

• Broadly there are two types of network architecture that are being implemented by most of the organizations.

• Centralized• Distributed

• Client-Server

Network Technologies for Business

• Internet– Public Network

• Intranet– Private Network using Internet technologies

• Extranet– Private-Private Network using Internet

Technologies

Summary• A computer network is created when several computers and other devices, such as printers and secondary

storage devices, are linked together by data communication channels. Each computer or device in a network is organized as per the topology. Network topologies include a star network, ring network, tree, mesh and bus network.

• A wide-area network (WAN) consists of two or more computers that are geographically dispersed but are linked by communication facilities provided by third-party telecommunication service provider, such as the telephone system or microwave relays.

• A local-area network (LAN) consists of two or more computers directly lined within a small, well-defined area, such as a room, building, or cluster of buildings.

• There are three basic components to a backbone network; the network cable, wireless and the hardware devices that connect other network to the backbone. The cable is essentially the same as the one used in LANs, except that it is usually higher quality to provide higher data rates. The hardware devices include hubs, bridges, switches, routers, brouters, and gateways.

• Data communication is the process of sending data electronically from one point to another. Using communication facilities such as the telephone system and microwave relays to send data between computers is a type of data communication often referred to as telecommunications.

• The transmission of data takes one of the two forms: analog or digital. • Modulation is the process of converting a digital signal into an analog signal. Demodulation is the process of

converting an analog signal into a digital signal. A modem (modulator-demodulator) is the device that converts the signals.

• A communication channel is the pathway along which data arc transmitted between devices. The three basic types of communication channels are wire cable microwave, and fiber optics.

Summary• Multiplexing is the process of combining the transmissions of several computers or other devices so

that the transmissions can share the same communication channel. Concentration allows a communication chan11el to be connected to and serve more devices than the capacity of that channel normally allows.

• The baud rate of a communication channel is the number of times per second that the transmitted signal changes (modulates or demodulates). The bandwidth, or band, of a communication channel determines the speed at which that channel can transmit data.

• Asynchronous transmission transmits data one character at a time. Synchronous transmission transmits data as a block of characters in timed sequences. Protocol is the set of rules and procedures defining the technical details of data transfer between two devices. Data transfer can occur in three modes: simplex, half-duplex and full-duplex.

• Distributed data processing (DDP) is the concept of dispersing into the areas where the computers, devices, software, and data are connected through communication channels.

• In C/S architecture, Client is any PC or end-user computer, which is connected using networking technologies to a Server, which manages the network and also the part of data processing, depending on how the C/S architecture is configured. C/S architecture can be two-tier, three-tier or n-tier depending on the size and spread of the organization.

• Internet, Intranet and Extranet are three technological innovations that most of the organization in the world stared using. Internet is a universal network that allows anyone to everyone a free and easy access. It is a public network. Intranet is a private internet meant for defined users of an organization. Extranet is a extended intranet that allows sharing of data across business partners. Both intranet and extranet uses internet technologies, which means they are created using TCP/IP.