CSCD 218 DATA COMMUNICATIONS AND NETWORKING 1 LECTURE

CSCD 218 : DATA COMMUNICATIONS AND NETWORKING 1 LECTURE 2 INTRODUCTION AND BASIC CONCEPTS NETWORK TYPES, NETWORK COMPONENTS/DEVICES NETWORKING IMPORTANCE AND THE INTERNET LECTURER : FERDINAND KATSRIKU (Ph. D)

Computer Network – Some Terminologies Ø Computer Network : A collection of computing devices connected in order to communicate and share resources. ØConnections between computing devices can be physical using wires or cables or wireless using radio waves or infrared signals. Ø Host (Node): Any device on a network Ø Data Transfer Rate (Bandwidth): The speed with which data is moved from one place to another on a network. Internet Service Provider (ISP): A company that provides other companies or individuals with access to the Internet.

Some Terminologies (Cont. ) Protocol : A set of rules that defines how data is formatted and processed on a network; i. e. , rules that allow client/server interaction. File Server : A computer that stores and manages files for multiple users on a network. Web Server : A computer dedicated to responding to requests (from the browser client) for web pages. Internet Backbone : A set of high-speed networks that carry Internet traffic, provided by companies such as AT&T, Verizon, GTE, British Telecom, and IBM

Types of Networks Ø Several different types of computer networks. Ø Can be characterized by their size as well as their purpose. Ø Size can be expressed by the geographic area they occupy and the number of computers that are part of the network. Ø Networks can cover anything from a handful of devices within a single room to millions of devices spread across the entire globe.

Types of Networks The main types are : i)Local Area Network ii)Metropolitan Area Network iii)Wide Area Network iv)Personal Area Network v)Campus Area Network Some types of networks serve a very particular purpose. Such include : Storage Area Network, Enterprise Private Network and Virtual Private Network.

Local Area Network (LAN) Ø A network that connects a relatively small number of machines in a relatively close geographical area. Ø Traditionally were all cabled but now often use wireless technology. Ø Distances between buildings dictate the type of communication media used (fibre optic, radio links). Ø Wireless LAN uses radio waves, satellite, microwave to transmit signals between nodes. Ø A local area network may serve as few as two or three users or as many as thousands of users.

Local Area Network (LAN)

Local Area Network (LAN) Advantages : 1. 2. 3. Cost reductions through sharing of information and databases, resources and network services. Increased information exchange between different departments in an organization, or between individuals. The trend to automate communication and manufacturing process Disadvantages : 1. 2. 3. Special security measures are needed to stop users from using programs and data that they should not have access to. Networks are difficult to set up and need to be maintained by skilled technicians. If the file server develops a serious fault, all the users are affected, rather than just one user in the case of a stand-alone machine.

Metropolitan Area Network (MAN) Ø A Metropolitan Area Network (MAN) is a network that is utilized across multiple buildings Ø Commonly used in school campuses or large companies with multiple buildings Ø Is larger than a LAN, but smaller than a WAN Ø Is also used to mean the interconnection of several LANs by bridging them together. This sort of network is also referred to as a campus network

Metropolitan Area Network (MAN)

Metropolitan Area Network (MAN) Advantages : v It provides a good back bone for a large network and provides greater access to WANs. v The dual bus used in MAN helps the transmission of data in both direction simultaneously. v A Man usually encompasses several blocks of a city or an entire city. Disadvantages : v More cable required for a MAN connection from one place to another. v It is difficult to make the system secure from hackers and industrial espionage (spying) graphical regions.

Wide Area Network (WAN) Ø The WAN is a communications network that makes use of existing technology to connect local computer networks into a larger working network that may cover both national and international locations. Ø WAN provides long distance transmission of data, voice, image and video information over large geographical areas that may comprise a country, a continent. Ø Range: Beyond 100 km. Eg: The internet

Wide Area Network (WAN)

Wide Area Network (WAN)

Wide Area Network (WAN)

Wide Area Network (WAN) Advantages : 1. Covers a large geographical area so long distance businesses can connect on the one network. 2. Shares software and resources with connecting workstations. 3. Messages can be sent very quickly to anyone else on the network. These messages can have pictures, sounds, or data included with them (called attachments). 4. Expensive things (such as printers or phone lines to the internet) can be shared by all the computers on the network without having to buy a different peripheral for each computer. 5. Everyone on the network can use the same data. This avoids problems where some users may have older information than others. Disadvantages : 1. Need a good firewall to restrict outsiders from entering and disrupting the network 2. Setting up a network can be an expensive, slow and complicated. The bigger the network the more expensive it is. 3. Once set up, maintaining a network is a full-time job which requires network supervisors and technicians to be employed. 4. Security is a real issue when many different people have the ability to use information from other computers. Protection against hackers and viruses adds more complexity and expense.

Personal Area Network (PAN) Ø A computer network organized around an individual person within a single building. This could be inside a small office or residence. Ø A typical PAN would include one or more computers, telephones , peripheral devices , video game consoles and other personal entertainment devices. Ø If multiple individuals use the same network within a residence, the network is sometimes referred to as home area network, or HAN.

TYPES OF NETWORK - BY ARCHITECTURE Architecture : design of a computer network; way in which they are connected. Client / Server – one machine (the server) serves out data or files to a number of other machines (clients) Peer to Peer – all devices are at the same level, no server. Internet Peer to Peer – allows users to connect to someone else’s computer over the internet.

TYPES OF NETWORK - BY ARCHITECTURE Client/Server : • One computer program (the ‘client’) asks another computer program (the ‘server’) to provide a service, such as looking up and providing data, delivering email, sending web pages, bank balances etc. • The server is a larger, faster more expensive computer that is designed to handle a number of tasks at once. All server software is multi-tasking; (able to process instructions from more than 1 program at the same time). • Some different types of servers: • file servers, store files for use on client computers • application servers, store applications to enable clients access

Client/Server : types of servers Print servers, accepts print jobs over the network faster than a printer; workstation gets on with other tasks whilst printing is done Database server; hold d/bases and allows them to be used by many users Web servers, connected to internet and serve webpages to viewers Domain name servers, (DNS’s); translate domain names into IP addresses; browsers request the DNS to provide the IP address so that it can locate website or mail server. Dynamic host configuration protocol server, (DHCP), hand out the node number to each device

Peer-to-Peer networks Ø Each computer on network shares its hardware and software with all other computers on the network. Ø No server, so costs are low and installation is simple Ø All computers and users have equal authority and rights Ø Little protection of one workstation against another Ø Used at home or in small organisations with trusted users Ø Allows sharing of files, internet connection, printer

Intranets Ø An internal secured environment that has a similar look and feel of the internet, but operates as a LAN (ie: within one organisation). Benefits include: • access to info is controlled • improves communication within an organisation • reduces costs as requires less paper documents • documents are easier to find access • less document maintenance is required.

NETWORK COMPONENTS / DEVICES Several components make up a network. Such components include : • hosts (PCs, laptops, handhelds) • bridges • routers & switches (IP router, Ethernet switch) • links (wired, wireless) • gateways • repeaters • hubs

Hubs Ø A hub interconnects two or more workstations into a local area network. Ø When a workstation transmits to a hub, the hub immediately resends the data frame to all connecting links. Ø A hub is the central meeting point where cables join to carry information to other resources through a network. Ø Hubs have a simple design and they rarely wear out.

Hubs

Hubs

Hubs – How hubs work

Switches Ø Switches, like hubs, provide a centralized connection. Ø Rather than forwarding data to all the connected ports, a switch forwards data only to the port on which the destination system is connected. Ø It looks at the Media Access Control (MAC) addresses of the devices connected to it to determine the correct port. Ø Switches learn certain information about the data packets that they receive from computers on the network. Ø They use this to build forwarding tables to determine the destination of data being sent by one computer to another on the network. Ø They help segment a network and reduce network traffic congestion by limiting each port to its own collision domain

Switches

Switches – How switches work

Bridges Ø Bridges operate at the data link layer of the OSI model. Ø The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network. Ø When a bridge sees a frame on the network, it looks at the destination MAC address and compares it to the forwarding table to determine whether to filter, flood, or copy the frame onto another segment. Ø The basic function of a bridge is to join two or more separate networks that use the same networking language, called protocol.

Bridges

Routers Ø Routers operate at the Network layer of the OSI model. Ø They are slower than bridges and switches but make "smart" decisions on how to route packets received on one port to a network on another port. Ø Routers are capable of segmenting the network. Ø Routers are network devices that literally route data around the network. Ø They depend on IP addresses to determine the destination of packets than MAC addresses of various connected stations. Ø Connects 2 or more networks and uses network layer addresses (like IP address) to make data forwarding decisions.

Routers

Repeaters Ø A repeater receives the signal, regenerates it, and passes it on. Ø Repeaters are used mainly at the edges of networks to extend the wire so more workstations can be added. Ø Repeaters clean, amplify, and resend signals that are weakened by long cable length. Ø Built-in to hubs or switches. Ø Allows extension of a network beyond physical length limitations

Repeaters

Gateways Ø Connects 2 or more networks that can be of different types and provides protocol conversion so that end devices with dissimilar protocol architectures can interoperate.

Gateways 137. 22. 144. 6 Netware Gateway TCP/IP 145. 65. 23. 102

Advantages of Computer Networks Ø File sharing Ø Resource sharing Ø Communication and collaboration Ø Remote access Ø Data protection

THE INTERNET

THE INTERNET

SHORT VIDEO ON INTERNET HISTORY