6 Networking: Concepts, Needs and Advantages
Lalitha Poluru
I. Objectives
The objectives of this module are to impart knowledge on the following aspects of networks:
• Aspects of communication technology
• Development of computer networks
• Basic components of computer communication networks
• Network Topologies
• Need for computer communication networks
• Services that are offered through computer communication networks
II. Learning Outcome
After studying this lesson, learners would attain knowledge about switching technologies including circuit switching, packet switching, cell switching and network media used for transmission. You will be introduced to the topologies used for interconnecting computers such as Bus, Ring, Star, Mesh, Hybrid topologies, etc. You will also be introduced to network devices such as Modems, Hub, Switches, Gateway and Routers.
III. Structure of Module
1. Introduction
2. Communication Networks
3. Computer Networks
4. Basic Components of Computer Networks
5. Network Topology
6. Need for Computer Networks
7. Advantages of Computer Networks
8. Summary
9. References
1. Introduction
Communication technology, with its ability to transmit data and information from one location to another, serve as a tool to exploit potentials and ability of computer to store and process vast amount of information. Initially computers were being used as ‘stand-alone’ systems to fulfill the organizational requirements. The concept of information sharing and services brought the computer networks into existence on which we are vastly dependent. ARPANET (Advanced Research Project Agency Network) was the first network that used technique of packet switching in 1970, which is used for transferring data between computer systems with an objective to facilitate networked computers to communicate seamlessly across multiple, geographically dispersed locations. Internet was in originating stage during 1973with the appearance of IP protocol(B.M.Leineret al.Brief History of the Internet – Internet Timeline / Internet Society,2012). The Transmission Control Protocol (TCP) and Internet Protocol (IP), called TCP / IP suite, is the backbone of Internet and other TCP /IP based networks.
2. Communication Networks
The communications networks can be grouped into the following three categories based on the technology and communication media used by them:
i. Public Switched Telephone Network: PSTN are managed by common carriers usually telephone companies / departments the world over. The PSTN generally provide two basic services, the normal dial-up connections to the subscribers and permanent leased connection between two subscriber’s points. The permanent leased connections provide single traceable line between two subscriber points. The leased lines are generally less prone to noise than dial-up lines.
ii. Public Data Network: Analogous to the public telephone network, many domestic common carriers provide data communications services via a specialized network called a Public Data Network (PDN). Most Internet Service Providers (ISPs) use combination of PDN and PSTN for providing Internet connectivity.
iii. Integrated Services Digital Networks (ISDN): An ISDN is a network that provides end-to-end digital connectivity to support a wide range of services, including voice and non-voice services.
3. Computer Networks
A computer communication network is an interconnection of a collection of several computers from which the user can select the service required and communicate with any computer as a local user. A computer communication networks can be viewed as a collection of nodes with computing resources and nodal-switching computers that facilitate communication through a set of transmission links. Developments in communication technology have made it possible to interconnect geographically dispersed computing resources of different kinds and makes. Users can access the network through PCs and terminals attached to a node and messages traverse these networks through the switching nodes. Since computer communicates using digitized signals instead of electric signals, it requires different transmission facilities than those used for transmitting analogue electrical signals. It is, however, a common practice to use conventional telecommunication links for data transmission by converting digital signals into analogue signals using a process called “Modulation” and the device that performs the conversion is called the MODEM (MOdulator – DEModulator). Currently, terrestrial, satellite-based data networks, Integrated Service Digital Network (ISDN) and wireless networks are available that can handle all kinds of communication requirements (i.e. voice, data, telemetry, facsimile and video) without discrimination. Computer networking can be defined as a group of interconnected systems sharing resources and interacting using a shared communication link.
The computer networks can be grouped into four categories based on geographical locations of its computer terminals, i.e.
i. Local Area Network (LAN): Interconnection of many computers within a given local area, more often premises of a single organization building. A very high speed of data transmission can be attained within a limited geographic area. LANs are typically configured in a star, bus or ring. Low speed LANs use telephone wires or copper cables, optical fibre cables are used to achieve high- speed transmission of data.
ii. Wide Area Network (WAN): WAN is used to interconnect a number of widely dispersed computers in various cities of a country or different countries. WANs use communication media maintained by telegraph or telephone companies. These networks usually have land telephone lines, underground coaxial cables, microwave communication and satellite communications.
iii. Metropolitan Area Network (MAN): MAN refers to inter- connection within geographical limits of a city or town.
iv. Gateways: Gateways consist of software and hardware that are required to interconnect networks amongst them. Gateways contend with any differences in packet sizes, protocols and addressing methods between the two networks it connect. Gateways are also used to connect LANs to WANs and WANs, in turn, can be linked through gateways to create national and international data communication networks.
Computer networks use physical channels through which information is transmitted between computers in a network. Media may be classified as bounded i.e., wires (twisted pair telephone wires or UTP CAT 5), cables (co-axial) and optical fibers; or unbounded i.e., radio waves or microwaves.
Data communication is an integral part of the modern information storage and retrieval systems in terms of their online access. Today, network technology works on client-server architecture with middleware used for connecting software components or applications on clients and servers. With developments in communication technology, institutions have options to set-up fiber optic-based gigabit LAN or wireless LAN. Depending on the geographical location, institutions have options to buy terrestrial or satellite-based Internet bandwidth its combinations from a number of Internet Service Providers (ISPs).
4. Basic Components of Computer Networks
The following are essential components for computer networking.
a. Network hardware
The basic component of computer network hardware is a computer. Computers on a network can be divided into two categories, server and clients or nodes. Server is the computer of higher power, and speed. It costs more. To this computer resources are attached. And the clients, also known as nodes access, are the resources which are attached to server. In peer to peer computer networks there are no servers.
b. Transmission media
Communication of data propagation and processing of signals is called transmission. Signals travel from transmitter to receiver via a path. This path is called medium. Medium can be guided or unguided.
Guided Media
In guided media, data is sent along a physical path i.e. cables. There are several types of cables used in network. The type of cable chosen for a network is related to the network’s topology, protocol and size. Different types of cables are: coaxial cables, twisted pair copper wire, and optical fiber cable.
• Coaxial cable looks like cable that brings the cable TV signal to television.
• Twisted pair copper wire cable looks like phone cable. Twisted pair cables come in two varieties, shielded and unshielded.
• Optical fiber cable
Unguided Media
Here no wire is installed. The data communication is predominantly sent by radio waves and microwaves.
Network Card
Most important part of connection is the network card. This is the middle part of connection. These cards are 8 bit cards, 16 bit cards and 32 bit cards. Each card has its own method of sending information (network protocol) through the cable. The most commonly used is Ethernet Protocol. A network card is called Interface card, network adapter, a NIC etc. It is a circuit board or chip which allows the computer to communicate to other computers on a network. Modem (MODulator / DEModulator) A modem converts digital signals (computer signals) from the computer into analogue signals for transmission and vice versa for reception over telephone line. There are four basic types of modems for a PC: External, USB, Internal and Built-in.External and USB are set on to desk outside the PC, while as Internal and Built-in are inside the PC. Present day modems have 56 kilobits per second speed. ISDN (Integrated Services Digital Network) circuits are digital. In this conversion from digital to analogue is not required.
• SwitchSwitches are basically bridges, but usually have multiple ports. Switches connect network segments, using a table of addresses to determine the segment on which a packet needs to be transmitted.
• HubsA hub is used to connect multiple computers and devices via a dedicated cable. It is cheap and connections are easy. It generally has 4, 8, 12, 24 ports.
• RouterThese are used to connect networks and to determine the optimal path along which the network traffic should be forwarded. They are occasionally called gateways. There are other network devices like repeaters, bridges, ports, etc.(Ganguly, n.d.).
c) Network Operating Software
Network operating software (NOS) is a collection of software and associated protocols that allow a set of autonomous computers, which are interconnected by a computer network, to be used together in a convenient and cost effective manner. It is similar to any other operating system like windows, DOS, etc. except it operates over more than one computer. It controls operation of the network system, including who uses it, when they can use it, what they have access to, and which network resources are available. At a basic level, the NOS allows network users to share files and peripherals such as disks and printers. They provide data integrity and security. The examples can be categories of NOS: The NetWare, LAN Manager, Solaris and Windows 2000 etc.
The main categories of network software are:
• Peer to peer software
In peer to peer networking operating software users can share resources and files located on their computers and can access shared resources on other computers. There is no central server. All computers in the network are equal. They have similar capabilities and resources. Centralized control is impossible in this kind of architecture. The user of each machine is also the machine’s administrator. Examples of Peer to peer network software is Windows 98 environment, workgroups are used for this type of organization.
• Client Server Based (Two Tier)
This software is in two parts. One part which includes functions and services resides in one or more exclusive (dedicated) computers. This part is called server. It provides security and access to resources. Another part called ‘client’ resides on other computers (nodes / client). They access resources on the server. The network operating system allows multiple users to simultaneously share the same resources irrespective of physical location. Examples of Server based networking software are: Novel Netware, Windows NT, UNIX, Window 2000 etc.
Client Server Based (Three Tier) where a client-software is split into two parts. Browser – (user-interface), (thin client) andLogic. Thus two tier client-server becomes three tier architecture. The logic which describes how to access and process data is moved to a new server. This new server is server for thin client. Nothing changes in the server side (Ganguly, n.d.).
5. Network Topology
The network topology defines the relative configuration of different pieces of network equipment like cables, computers, and other peripherals. There are number of network topologies and a network could be build using multiple topologies. Distinction is to be made between physical topology (with respect to lay out of the network) and logical topology (which defines information circulation at the lowest level) as it is very important to distinguish clearly between these two aspects (MCSE Networking Essentials, 2004). There are four main types of topology: Bus, Star, ring and tree
i. Linear Bus Topology
A linear bus topology consists of a main run of cable with a terminator at each end (See fig. 2). All nodes (file server, workstations, and peripherals) are connected to the linear cable.
Advantages
• Easy to connect a computer or peripheral to a linear bus.
• Requires less cable length than a star topology.
Disadvantages
• Entire network shuts down if there is a break in the main cable.
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
• Not meant to be used as a stand-alone solution in a large building (Florida Center for Instructional Technology. n.d.).
Fig.2: LinearBus Topology
ii. Star Topology
A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator (See fig. 3). Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fibre optic cable.
Advantages
• Easy to install and wire.
• No disruptions to the network when connecting or removing devices.
• Easy to detect faults and to remove parts.
Disadvantages
• Requires more cable length than a linear topology.
• If the hub, switch, or concentrator fails, nodes attached are disabled.
• More expensive than linear bus topologies because of the cost of the hubs, etc. (Florida Center for Instructional Technology. n.d.).\
iii. Ring Topology
In ring topology each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node – a ring (see Fig 4). Data travels from node to node, with each node along the way handling every packet. Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link. A node failure or cable break might isolate every node attached to the ring.
Advantages
• Performs better than a star topology under heavy network load.
• Can create much larger network using Token Ring.
• Does not require network server to manage the connectivity between the computers.
• Data is quickly transferred without a “bottle neck”. (very fast, all data traffic is in the same direction).
• The transmission of data is relatively simple as packets travel in one direction only.
Disadvantages
• One malfunctioning workstation or bad port in the MAU can create problems for the entire network.
• Data packets must pass through every computer between the senders and recipient therefore this makes it slower.
• Moves, adds and changes of devices can affect the network.
• Because all stations are wired together, to add a station you must shut down the network temporarily.
• Difficult to troubleshoot a ring network.
• In order for all computers to communicate with each other, all computers must be turned on (Network Troubleshooting and Resource Site for School IT Staff, n.d.).
iv. Tree or Expanded Star Topology
A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable (See fig. 5). Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.
Fig.5: Tree or Expanded Star Topology
Advantages
• Point-to-point wiring for individual segments.
• Supported by several hardware and software vendors.
Disadvantages
• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies (Florida Center for Instructional Technology. n.d.).
6. Need for Computer Networks
The transmission of data between computer networks is known as internetworking. Various networks within a country can be interconnected and country networks in turn can be connected to networks in other countries with interoperability. Interoperability is the ability of diverse computers from different vendors and with different operating systems to cooperate in solving computational problems. So that users use networks without knowing the details of hardware, software and communication methods involved in them. Internet is the best example that is now widely being used all over the world including India (Rajaram, 2001). The emergence of Internet, particularly the World Wide Web (WWW) as a new media of information delivery, coupled with availability of powerful hardware, software and networking technology facilitate fast and reliable information exchange between institutions as well as support resource sharing. In present days, almost all work areas are being provided with seamless access to computer networks.
7. Advantages of Computer Networks
Advantages of networks are manydue to which a lot of time and resources can be saved which is very cost benefit. The below mentioned are some of the uses of networks.
File Transferring and SharingResources: A file transfer program of Internet allows transferring large files containing programmes, data files, and devices such as printers, scanners, CD-ROM drives, hard drives and also various applications.
Speed: Sharing and transferring files within networks is very rapid. This saves time while maintaining the integrity of files.
User and Workgroup communication: Networks helps the users to communicate using e-mail, newsgroups, and video conferencing etc. Concurrently, it will also allow many users to work on a same project or document.
Increased Storage capacity: A standalone computer might fall short of storage capacity but when they are on a network they can share each other’s storage capacity. Further, the information can be stored on the servers which are located off-site thus protecting the data through regular back-ups.
Remote access: Users are allowed to access the files anddata even when they are not in the office. This access can even be given to mobile handheld devices. It saves the hassle of carrying a storage device every time data needs to be transported.
Centralized software management: It allows the users to share software within the network easily. Networkable versions of software are available at considerable cost as compared to individually licensed version of the same software. Therefore,large companies can reduce the cost of buying software by networking their computers.
8. Summary
Computer networks with the integration of Communication networks have brought revolutionary changes in information and resource sharing although the world. Computer networks have components namely nodes, transmission media, network operating system and protocols. They help in file sharing, hardware sharing, application sharing, network gaming, remote access, workgroup communication, increased storage capacity etc. Computer networks are mainly classified into LAN, MAN and WAN on the basis of geographical distances covered by them. The Internet is network of various countries networks. It has revolutionized the computer and communications world like nothing before. The invention of the telegraph, telephone, radio, and computer set the stage for this unprecedented integration of capabilities. The Internet is at once a world-wide broadcasting capability, a mechanism for information dissemination, and a medium for collaboration and interaction between individuals and their computers without barriers of geographic location. The Internet represents one of the most successful examples of the benefits of sustained investment and commitment to research and development of information infrastructure. Beginning with the early research in packet switching, the government, industry and academia have been partners in evolving and deploying this exciting new technology. Today, terms like “Yahoo” and “Google” are common part of our vocabulary. Library and Information Centers have widely adapted this technology for providing various online resources and web based information services.
9. References
1. Brief History of the Internet – Internet Timeline | Internet Society. (n.d.). Retrieved July 13, 2016, from http://www.internetsociety.org/internet/what-internet/history- internet/brief-history-internet
- Buzzle – Advantages and Disadvantages of Computer Networks. (n.d.). Retrived July 15, 2016, from www.buzzle.com/articles/advantages-and- disadvantags-of-computer-networks.html
- Florida Center for Instructional Technology. (n.d.). Topology. Retrieved July 14, 2016, from http://fcit.usf.edu/network/chap5/chap5.htm
- Ganguly, S. (n.d.). Retrieved July 14, 2016, from http://www.unesco.org/education/aladin/paldin/pdf/course02/unit_08.pdf
- Hunt, R and Shelley, J. (2002). Computers and Common Sense (4thed.). New Delhi: Prentice Hall of India Pvt Ltd.
- Internet History 1962 to 1992 | Internet History | Computer History Museum. (n.d.). Retrieved July 13, 2016, from http://www.computerhistory.org/internethistory/
- LANArchitectureDiag1.jpeg (610×479). (n.d.). Retrieved July 13, 2016, from http://www.excitingip.net/wp- content/uploads/2010/09/LANArchitectureDiag1.jpeg
- Network Troubleshooting and Resource Site for School IT Staff | Ring Topology. (n.d.). Retrieved July 15, 2016, from http://webpage.pace.edu/ms16182p/networking/ring.html
- Preparation for the MCSE exam 70-058: Networking Essentials. (2004). New Delhi: Firewall Media.
- Rajaram, V. (2001). Fundamentals of Computers (3rd ed.). New Delhi: Prentice Hall of India Pvt Ltd.
- TCP/IP Guide- Advantages, Benefits of Networking. (n.d.). Retrieved July 15, 2016, from http://www.tcpipguide.com/free/t_TheAdvantagesBenefitsofNetworking.htm
