Networks What is a network A

Networks

What is a network ? A group of computers and associated devices connected by communications facilities (both hardware and software) to share information and peripheral devices, such as printers and modems.

LAN? WAN? PAN? MAN?

LAN or WAN ? LAN Local area network WAN Wide area network PAN Personal area network MAN Metropolitan area network

Network protocol A protocol is a set of rules that governs the communication Between computers on a network Network protocols include: • Ethernet (most widely used) • Localtalk • Token ring

Ethernet n Each computer listens along the cable to see if it is clear before they transmit data through the network, if the network is clear the node (usually a computer) will transmit or wait for the line to be clear. n If 2 nodes (computers) attempt to transmit at the same time a collision will occur, each computer will then back off, wait and retransmit

Network Topologies - Bus Server PC PC PC

Bus topology Advantages Disadvantages Easy to connect pc or peripheral n Requires less cabling than other topologies n n Entire network breaks down if there is a break in the main cable n Difficult to identify where the problem is coming from if network crashes n Cannot be used as a stand alone solution in large buildings

Network Topologies - Ring PC PC PC Server PC

Ring topology Advantages Disadvantages All nodes have equal access n Growth in the system has minimal effect on performance n Because data travels in one direction high data transmission speeds are enabled n n Often the most expensive topology n Failure of one computer may affect others

Network Topologies - Star PC Hub or Switch PC PC Server PC

Star topology Advantages Disadvantages Easy to install and wire n No disruption to the network when connecting or removing devices n Easy to detect faults and remove parts n n Requires more cable than a bus n If the hub fails the nodes attached are disabled n More expensive than a bus

Network Topologies - Wireless PC PC Wireless Hub or Switch Server PC

Wireless topology Advantages Disadvantages No cables n Can use remote access points (hotspots) n Can convert wired networks to become wireless relatively inexpensively n n Data transfer speeds can be slower than cable networks n Signal strength can sometimes be weak depending on location

Network Topologies - Hybrid PC Wireless Hub or Switch Server PC PC

Network Topologies - Hybrid PC Wireless Hub or Switch Server PC Classroom / Office

Hybrid topology Advantages Disadvantages One company can combine benefits of several different types of topology n Workgroup efficiency can be customised n n Devices on one topology can’t be placed onto another topology without some hardware changes

Network Interface Cards Allows a computer to be connected to a network. Must be the right type for the network (e. g. Ethernet, Token Ring). RJ 45 Connector

Network Cabling • Depends on the network type, speed of operation and distance covered. Common types are: Twisted pair wire (Ethernet) Fibre Optic (FDDI)

Bluetooth PAN – Personal area network • Named (bizarrely) after a 10 th century Danish king • Replacing infrared as the instant transfer mode of choice with a better range and no line of sight restrictions • Allows up to 8 devices to connect as a mini network (short range of 30 ft) • Devices include – Mobile phones, printers, PDA’s, GPS, digital cameras, keyboards and mice

Centrino technology Intel has branded a combination of technologies used in laptops under one name Pentium M (mobile) chip Wireless network connection capability 855 chipset (including graphics chip) Only Centrino if all 3 components included

Cable vs wireless Cabled network Pro’s • Inexpensive • Capabilty included on most pc’s Wireless networks Pro’s • No cabling • Can use wireless access points anywhere (Hotspots) Cons • Requires cabling • Additional hardware required for bigger networks such as hubs and switches Cons • Data speeds slower than Cabled networks • Wireless capability only available on newer pc’s Range • 91 m (300 ft) per segment Range • 30 m (100 ft)

Sharing Information Once PCs are networked, users may share each other files, printers and Internet connection. PC Hub or Switch PC Printer PC Internet

Network Operating System For much greater control over the sharing, access and security of files on a network. Familiar systems are: MS Windows 2000 Professional. Novelle Netware.

Internet The interconnection of a number of networks across the globe. Connected by a backbone of telephone lines, high speed ISP cable, satellite, undersea cable and wireless links. The different parts of the Internet (or any large WAN) are connected together using a number of devices including: Bridges, Routers, Repeaters and Switches.

Connecting to the Internet There are two types of Internet connection: Analogue – via a modem (typically 56 k. Bps) Broadband – via a broadband modem (typically 256 kbps, 512 kbps, 1 Mbps or 2 Mbps)

Installing Broadband • You need to be in an area of broadband coverage (i. e you need an Asynchronous Digital Subscriber Network – ADSN – and BT need to reconfigure you to it). • You need to sign up with a company to give you broadband (e. g. BT, Telewest). • You need a Broadband modem.

Typical Broadband Configuration Modem could be wireless

Internet website suffixes. com or. co Commercial site, generally going to shed a Positive light on its product as always money behind it . edu or. ac Academic or educational institutions . org Traditionally non-profit organisations, such as the Red cross, though sometimes there may be commercial Interests if the site is being sponsored . gov Government sites . net Network, any kind of site can have this suffix as it Acts as a catch all for any sites not fitting into the other catorgories

Example country domain suffixes. uk United Kingdom. au Australia. in India. br Brazil. it Italy. ca Canada. mx Mexico. fr France. tw Taiwan. il Israel

Exercise / Activity This week – Exercise 1 (network questions). Next week - Construct a small network.