Networks 1 Introduction to Networks Dr John Cowell phones off (please) 1

Overview Introduction to networks what is a network, why? basic types of networks Geographical descriptions LAN, MAN, WAN Intranets, extranets and the Internet definitions 2

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What is a Network? A network is a communication system a collection of resources hardware & software objects people Varying types of network computer telephones Any two or more interconnected computer systems can be described as a network 4

Why use a Network? Improve communications team working Share resources hardware software data Central services Efficiency 5

Types of Networks There are several different types of networks Depends on connectivity geographic area covered topology/protocol Connectivity peer to peer client / server distributed system three tier architecture 6

Peer to Peer Simplest is peer-to-peer, connected via serial/parallel ports RS 232 null modem cable 7

Windows Peer-to-Peer Windows allows creation of larger peer-to-peer networks, using network protocols resources, e.g. printers, modems, attached to one PC, but can be shared by other users Use Control Panel/Networks to configure 8

Client / Server As number of users / workstations increases, it is more efficient to create a client / server network Multiple workstations connected to one or more network servers file server print server communications server fax server 9

Client / Server Communication Clients and servers can also be viewed as being software applications Interact by using one of several methods message passing remote procedure calls Synchronicity is important i.e. server cannot process until client has sent request client passes values to server, then waits server processes values, returns results asynchronous relationship Servers may have higher network priority access to otherwise restricted system resources 10

Servers 1 File server shared data can be stored and managed centrally access can be controlled/logged Print server multiple printers can be connected to server server organises print queues Network printers direct connection to network 11

Servers 2 Communications server acts as interface between network and ‘outside world’ other networks the Internet Fax server faxes are a different technology to , etc server handles user requests to send faxes 12

Distributed Systems Physically separate computers in a network operate together as a single logical unit Beowulf clusters Appears to a user to be a single computer physically separated an operating system that supports distributed systems is required, e.g. UNIX advantages include reduction in costs and delays in transmitting and processing data reduced load on the ‘host’ processor better local control and service 13

Three Tier Architecture Client / server model has some problems not scaleable business rules not deployed centrally consumes too many resources on client machine inefficient One proposed solution is to partition applications into logical parts each part can have multiple units 14

Three Tier Model The three parts are 15 user services front end application data services database engine business logic Controls interaction between a Database and a user interface

Three Tier Benefits Four major benefits (are claimed) reuse components are shared between applications time in design and implementation not wasted maintenance as business changes, modifications in applications and business rules are easier to implement performance optimised as individual components can be upgraded manageability complex application is broken down into smaller components easier to work with 16

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Geographical Network Areas Networks can be split into three types by geographical coverage Local Area Network LAN Metropolitan Area Network MAN Wide Area Network WAN 18

Local Area Network - LAN Single campus Can be multiple networks interconnected No special telecommunications hardware is necessary, as cables/signals never leave the company’s premises Fast data transfer rates reliability of transmission not always top priority damaged data can be re-transmitted easily Video-conferencing is feasible 19

Metropolitan Area Network - MAN Multiple campuses e.g. within a city small geographical area Australians use MANs to interconnect South Eastern cities Slower data transfer rates? need reliability of WANs with speed of LANs 20

Wide Area Network - WAN The rest of the planet Slower data transfer rates (end to end) reliability is a high priority retransmission of missing data is a large overhead extensive use of external telecommunication systems backbone transfer rate is now faster than LANs! The Internet International telecommunications Satellite systems e.g. Global Positioning System - GPS 21

Janet backbone All UK academic institutions access the internet via the Janet network.ac.uk domain Funded by Joint Information Systems Committee (JISC) In October 2006 SuperJANET5 was launched after £29 million of investment. It provides a 10Gbit/s backbone, with an upgrade path to 40GBit/s over the next few years. Most organisations connected by twenty WANs 22 Map from

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Intranets Private network contained within an enterprise May be a combined topology network leased lines for a WAN gateways to external internet Uses Internet protocols TCP/IP HTTP, FTP, DNS, etc Typically, an intranet is contained within security firewalls it can be thought of as a private internet 24

Intranet Features Uses private network features Personal Information Manager using Lotus Notes, Microsoft Outlook Uses Internet features web-page browsing standard browsers Uses dedicated (not shared lines) 25

Extranets Uses Internet protocols and the PSTN (public switched telephone network) securely shares enterprises’ information or operations part of company’s intranet extended to external users Security achieved with firewalls digital certificates issued by an agency, establishes credentials on-line Used by Tele-workers at home, consultants, partners, customers other companies suppliers, vendors, etc. 26

Extranet Usage Exchange large volumes of data Electronic Data Interchange (EDI) Collaborate with other companies or customers Jointly develop and use training programs Provide or access services provided by one company to a group of other companies online banking application managed by one company on behalf of affiliated banks Share news of common interest 27

The Internet International computer network connecting government agencies, universities, research institutions, businesses, and individuals Started as a US Defence Department network to distribute US military computing capability resist (nuclear) attacks / natural disasters Evolved into a network used by academics, scientists, governments and, now, everybody! the US government ceased to administer it in 1992 became civilian 28

Summary Introduction to networks what is a network, why? basic types of networks Geographical descriptions LAN, MAN, WAN Intranets, extranets and the Internet definitions 29