slide 1 what is a computer network? a computer network is a linked set of computer systems capable...
TRANSCRIPT
Slide 1
What is a Computer Network?
• A computer network is a linked set of computer systems capable of sharing computer power and resources such as printers, large disk drives, CD-ROM and other databases.
• There are two types of network: Local Area Network (LAN) Wide Area Network (WAN)
Slide 2
Local Area Networks
• A local area network is a computer network across one building or site.
Fileserver
Printer
Work Station
Network Cable
Slide 3
Peer to Peer Network
• This describes a very simple network structure where shared resources such as printers are available but where there are very few other facilities.
• All computers on the network have similar specification and status.
Slide 4
Client-Server Network
• This method of network organisation requires one or more servers to which a number of clients may obtain services.
• The servers act as central resource managers for the network.
• A star topology is often used for this form of network.
Slide 5
Network Hardware
• Network hardware will include: stations servers
• file, print, web passive components
• cables, connections, etc active components
• repeaters, hubs, switches
Slide 6
Network Stations
• The network station (often called the client) will normally comprise: PC Network interface card (NIC).
• The NIC allows the computer to communicate with the network
Network Operating Systems• eg. Windows 95/98, Windows NT,
Appleshare, etc
Slide 7
Network Servers
• A network server is a computer which acts as a central storage point for files and applications.
• Servers also act as a connection point to shared peripherals such as printers.
Slide 8
Active Components
• Active components are required for all but the simplest of networks.
• These include: repeaters hubs switches
Slide 9
Repeaters
• Due to loss of signal strength it is often necessary to use a repeater to boost the signal.
• A repeater is a hardware device to link together two cable segments.
• The repeater amplifies the signal it receives before passing it on.
Slide 10
Hubs
• A hub is a device which allows the interconnection of a group of users. A hub will forward any packet of data it receives over one port from one station to all of the remaining ports.
• Hubs are used in the star topology.
Slide 11
Switches
• A switch is “smarter” than a hub and offers more bandwidth. A switch forwards data packets only to the appropriate port for the intended recipient.The switch establishes a temporary connection between the source and the destination.
Slide 12
Routers
• A router receives packets of data transmitted over a network, and using their IP address, forwards them to the correct destinations over the most efficient available path.
Slide 13
Network Topologies
• The network topology is the theoretical arrangement of components on a network.
• There are four network topologies which you need to be aware of: bus star Ring mesh
Slide 15
Star Topology
• In the star topology all stations are connected to a central node, called a hub.
Slide 16
Ring Topology
• Each device is connected to a ring around which signals are sent. The devices are connected to the ring via spurs, or the connection may pass through the interface card
Slide 18
Protocols
• A protocol is a standard set of rules used to ensure the proper transfer of data between devices.
• In network design it is vital that a recognised protocol is used.
Slide 19
TCP/IP
• TCP/IP is a protocol which allows computer on different networks to communicate.
• TCP/IP is a pair of protocols TCP - transmission control protocol IP Internet Protocol
Slide 20
IP Addressing
• Every computer station on the internetwork must have an IP address.
• This IP address must be unique but is not encoded in the network interface. It is set by software in the computer.
Slide 21
Internetwork Hardware
• Connecting LANs together will require extra hardware: bridges routers gateways
Slide 22
Bridges
• A bridge acts as a link between LANs.
• This will allow two LANs to appear to users as though they are a single LAN.
Slide 23
Routers
• A router is a device which receives data packets and sends them on via an appropriate route.
• It will have a number of network interface ports to allow connection to different segments to which data packets may be directed.
Slide 24
Gateways
• A gateway is a link between two dissimilar networks..
• The communications between the networks are usually via public telecommunications networks.
• A gateway will normally be used to connect a LAN to the Internet.
Slide 25
Implications of Networks
• Computer networks have developed as a result of a perceived need and as a result of economic and technical factors.
• Computer networks have social, legal and ethical implications
Slide 26
Economic Factors
• The cost of communication technology equipment costs are continually reducing and
improving features mean that more is available for the same money.
• Access to expensive equipment printers and mass storage are expensive so it makes
sense to share them.
• Geographic spread of organsiations video-conferencing and email, etc allow
organisations to cope with geographic isolation.
Slide 27
Technical Factors
• Adoption of Internet technology TCP/IP
• Adoption of International Standards ISO OSI
• Development of Communication Technology fast modems, ISDN, etc
Slide 28
Social Implications
• Individuals may become withdrawn from society
• Personal privacy may be compromised as a result of monitoring network use
• People may not have to move from rural communities to find
• Home working may allow strengthening of family life (?)
Slide 29
Ethical Implications
• Bogus doctors could easily offer medical advice over the Internet.
• Availability of unacceptable and inappropriate material within education
• Antisocial, criminal, racist or other prejudiced material may be distributed freely.