Introduction to Networking

Data Communications and NetworksMr. Greg VoglUganda Martyrs UniversityLecture 2, 19 March 2003

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Overview1. Definitions

1. LAN/WAN, Internet/Intranet, Client/Server/Peer

2. Local Area Networks1. Types, components, topologies, resources2. Benefits/costs, design questions

3. Wide Area NetworksA. Connecting networksB. Models, componentsC. Benefits/costs

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LAN vs. WAN Network

connection of computers so they can exchange data and share resources

LAN: Local Area Network link computers within a small geographic area,

such as a building or a group of buildings uses direct cables (or wireless signals)

WAN: Wide Area Network powerful computers linked across large

distances uses wires, cables, electromagnetic signals, etc.

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Internet vs. Intranet Internet

a global network of networks that connects millions of computers

Intranet a private version of the Internet,

using Web browsers and server on LANs

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Client-Server vs. Peer-to-Peer Server

computer that provides access to shared resources

e.g. printers and disks Client

computer accessing shared resources on servers Client-Server Network

one or more computers dedicated as servers many clients

Peer-to-Peer Network shares resources among a few “equal” computers

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Client-Server Networks Dedicated server computers provide resources Client computers access server’s resources Centralised administration and maintenance Requires highly trained network administrator Security is strong, user and group-based Performance depends on server capabilities Works well for large networks (>10 computers)

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Peer-to-Peer Networks Each computer acts as both client and server No server computer or network OS required Distributed administration and maintenance Users must act as administrators of their PCs Security is weak, resource-based Performance depends on peer workstations Best for small network of <10 advanced users

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LAN Hardware Components Computers: two or more, maybe a server Hub: at least one, with one port per computer NICs: Network Interface Cards/Adapters

One installed in each computer, connects to hub Cables: to connect computers

Unshielded twisted pair (UTP), co-axial, fibre optic Peripherals: to be shared on the network

Printers, scanners, disk drives, modems, etc.

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Network Operating Systems Peer-to-Peer

Windows 3.11/95/98/Me Windows NT/2000 Pro

Client-Server Windows NT/2000 Server Novell Netware UNIX/Linux

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Terminology Topology

physical layout of network connections Protocol

standard of how devices communicate Interface

connection to allow communication Bandwidth or Data Transfer Rate

data speed in bits per second

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Network Topologies: Star Each computer is attached to central

hub Easy to add/remove computers

connect cable to computer and to hub port

Bad cable only isolates one computer Hub is single point of failure Most popular for LANs

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Network Topologies: Bus Each computer attached to the

network cable Cheapest (no hub required) Difficult to add/remove computers Difficult to troubleshoot bad

connections Broken connection partitions network Sometimes used for small LANs

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Network Topologies: Ring Computers connected in a closed loop Token of data passed around in one

direction Often logical ring but physical star

Multi-station access unit (MSAU) hub Fibre distributed data interface (FDDI)

Used to connect high-speed networks

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Sharing Resources Resources that can be shared include:

hardware (disks, printers, scanners, fax...) software (programs) data (files, folders) servers: file, print, directory, mail, fax

Access to resources can be restricted: to certain users or groups (with NT Server) read-only password-protected

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Network Neighborhood Accessible through Desktop, My

Computer or Windows Explorer Shows computers in local area

network Computers are grouped into

workgroups or domains Each computer lists its shared

resources

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LAN Benefits Shared resources (hardware, software,

data) Economy of scale: low cost per user/computer

Communication and information exchange Email, Web browsing, conferencing, scheduling,

etc. Centralised, remote administration

Install, backup, monitor, cleanup, troubleshoot

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LAN Costs Network hardware Network OS Communications software Network design and development Administration and maintenance Training Security

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Client/Server Costs

Operations and support Application development Hardware, software Network installation, maintenance Education and trainingSource: Laudon & Laudon, Table 9.5

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Networking Problems

Connectivity problems Loss of management control Ogranizational changes required Hidden costs Network reliability and securitySource: Laudon & Laudon, Table 9.4

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Network Design Questions Who are your users? What are their individual and group goals? What are their computing/information

needs? What types of uses will the computers have? What software do they need to use? What hardware is needed to run the

software? What data traffic is the network likely to

have?

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Network Design Questions (cont’d) Is a dedicated server needed? What server specifications will be

needed? Is a network operating system needed? What backup media should be used? What shared resources should be

available? How should access to resources be

restricted? Other security problems/measures?

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Connecting Networks

Intranet Private version of Internet; protected by firewall

Extranet Intranet accessible to authorised outsiders

Virtual Private Network Secure Internet connection for data transmission

Internetworking Linking separate networks

Enterprise Network A network to link a company’s resources

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Connectivity Models

TCP/IP model Developed by US Defense Dept; used on Internet Five layers: physical, net, IP, TCP, application Every Internet site has an IP address

Open Systems Interconnect (OSI) model Developed by International Standards Org. for linking different types of computers, networks Seven layers, idealised, rarely implemented fully public, nonproprietary, portable

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WAN Hardware Components Gateway

Connects different types of networks by translating

Bridge Connects similar networks

Router Intelligently directs traffic to appropriate

networks Routes data packets through connected

LANs/WAN

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Communications Hardware Telephones, modems, PBX, voice mail,

Facsimile/Fax Information digitised, transmitted through phone

lines Cellular (mobile) phones, pagers

Wireless communication using radio waves Videoconferencing

Computers, video cameras, microphones, speakers Global Positioning System (GPS)

Satellites determine position of devices Used for tracking and navigation of vehicles, etc.

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Communications Software Personal Info. Management e.g. MS Outlook

Address book, notes, messages, task lists Scheduling (calendar, meetings, appointments, etc.)

Groupware e.g. Lotus Notes Scheduling, e-mail, conferencing, editing, databases

Project Management e.g. MS Project Planning, scheduling, analysing Tasks, events, resources, costs

Other e.g. dial-up networking, terminal emulators Connect to computers/networks, transfer files, run

programs

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Internet Components Network hardware and operating systems

to send/receive information over long distances Web pages

hypertext documents (linked together) multimedia (pictures, sounds, videos etc.)

Web server Computer that stores web documents

Web clients Browser software to retrieve and view web pages mail, newsgroups, chat, conferencing, file

transfer

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Internet Access Internet Service Provider (ISP)

Organisation with direct Internet connection Sells Internet connections to

businesses/individuals Providers of online services: AOL, MSN,

Prodigy Internet Café

Pays ISP to connect its LAN to Internet Allows individuals to use Internet for short

periods

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Internet Benefits to Organisations Connectivity and global reach Reduced communication costs Lower transaction costs Reduced agency costs Interactivity, flexibility, customization Accelerated distribution of knowledgeSource: Laudon & Laudon, Table 10.2

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Intranet Benefits

Easy to build and run; inexpensive Easy to update, expand or contract Easy to access by different

PCs/devices Easy to use (Web browser is familiar) Multimedia, interactive, responsive Reduced info. distribution costsSource: Laudon & Laudon, Table 10.6