Higher ComputingHigher Computing

NetworkingNetworking

Networking – Networking – Local Area NetworksLocal Area Networks

Networking – Networking – Local Area Local Area NetworksNetworks

► Cover a small area such as a room or one building. Cover a small area such as a room or one building. ► A Network Interface Card (NIC) lets the computer A Network Interface Card (NIC) lets the computer

communicate with the network.communicate with the network.► Each NIC has a Each NIC has a Media Access ControlMedia Access Control address (48 address (48

bit). A unique number that identifies each bit). A unique number that identifies each computer on the network.computer on the network.

► Wireless NICs (WNIC) are used on a wireless LAN.Wireless NICs (WNIC) are used on a wireless LAN.

LAN – Transmission MediaLAN – Transmission Media

► Have very high Have very high bandwidthbandwidth i.e. 100 – i.e. 100 – 1000 Mbps.1000 Mbps.

► They frequently use They frequently use (CAT5) copper cable.(CAT5) copper cable.

► For very high For very high bandwidth, fibre optic bandwidth, fibre optic cables can be used.cables can be used.

► Wireless transmission Wireless transmission media such as media such as WiFiWiFi are are becoming more becoming more common.common.

LANsLANs

AdvantagesAdvantages

► Access to sharedAccess to shared hardwarehardware such as printers. such as printers.

► Access to shared Access to shared softwaresoftware such as applications such as applications packages or anti virus.packages or anti virus.

► Provide Provide communicationscommunications facilities for network users facilities for network users such as internet and such as internet and email.email.

DisadvantagesDisadvantages

► Network cards and Network cards and cabling, cabling, costscosts can be can be high.high.

► A A faultfault with a server with a server can effect all can effect all workstations. workstations.

► Security procedures Security procedures are neededare needed to restrict to restrict access to user's files access to user's files and to prevent the and to prevent the introduction of viruses.introduction of viruses.

LAN - BusLAN - Bus

► All computers All computers communicate using a communicate using a shared shared communications communications channelchannel called the called the bus.bus.

► Data from different Data from different computers can collide.computers can collide.

► In order to share this one In order to share this one cable, CSMA/CD is used.cable, CSMA/CD is used.

► Relatively cheap and Relatively cheap and easy to install.easy to install.

► Too many computers = Too many computers = increased collisions = increased collisions = reduced performance.reduced performance.

LAN - StarLAN - Star

► Each computer has its own Each computer has its own communications channel.communications channel.

► All data passes through a All data passes through a central computer, either a central computer, either a HUBHUB or a or a SWITCH.SWITCH.

► A break in a communication A break in a communication channel only affects one channel only affects one computer.computer.

► If the central computer fails, If the central computer fails, the whole network will not the whole network will not work – no communication.work – no communication.

► Uses CSMA/CD with a HUB.Uses CSMA/CD with a HUB.

LAN - RingLAN - Ring

► Like a BUS network, this Like a BUS network, this has a shared has a shared communications channel communications channel but it forms a ring.but it forms a ring.

► If the communications If the communications channel fails, the whole channel fails, the whole network fails.network fails.

► Uses a system called Uses a system called token passing so many token passing so many computers can share the computers can share the one cable.one cable.

► can be expensive to set can be expensive to set up. up.

LAN - MeshLAN - Mesh

► Multiple connections Multiple connections between each between each computer.computer.

► Offers protection Offers protection against against communications communications channel failure.channel failure.

► Avoids bottlenecks as Avoids bottlenecks as there are several there are several paths.paths.

► Expensive to set up.Expensive to set up.

Networking - HUBNetworking - HUB

► Used to connect nodes Used to connect nodes on a network.on a network.

► Data entering one port Data entering one port is sent out all of the is sent out all of the other ports.other ports.

► All nodes on a network All nodes on a network ‘hear’ a message even ‘hear’ a message even if its’ not for them.if its’ not for them.

► Can be used to connect Can be used to connect LAN segments together LAN segments together to form a larger LAN.to form a larger LAN.

Networking - SwitchNetworking - Switch

► Unlike a HUB, this makes Unlike a HUB, this makes ‘point to point’ ‘point to point’ connections.connections.

► A message received in A message received in one port is only sent back one port is only sent back out the port the intended out the port the intended target node is on.target node is on.

► No data collisions.No data collisions.► Each node receives the Each node receives the

full bandwidth available full bandwidth available on the network.on the network.

► More than one node can More than one node can ‘speak’ at once.‘speak’ at once.

Network - RouterNetwork - Router

► Links 2 or more Links 2 or more networks i.e. home or networks i.e. home or business networks to business networks to the Internet.the Internet.

► It looks at the It looks at the destination address destination address of data passing of data passing through it and through it and decided on the most decided on the most efficient route.efficient route.

► Directs traffic across Directs traffic across the Internet.the Internet.

Networking – Networking – Wide Area Wide Area

NetworksNetworks Many large organisations, including Many large organisations, including governments and international governments and international companies, have widely scattered companies, have widely scattered offices, possibly with each having its offices, possibly with each having its own LAN. A WAN is used to link all of own LAN. A WAN is used to link all of these dispersed networks.these dispersed networks.

WANsWANs

►WANs are WANs are geographically geographically widespread, the widespread, the can cover a city, can cover a city, country or stretch country or stretch around the world.around the world.

WANsWANs

► A WAN uses A WAN uses telecommunication telecommunication systems owned by systems owned by other companies and other companies and covering large covering large distancesdistances

► WANs still use copper WANs still use copper and fibre cables but and fibre cables but also use satellite and also use satellite and microwave wireless microwave wireless communication.communication.

WANsWANs

►WANs are mainly used for file transfer, WANs are mainly used for file transfer, email, shared access to multi user email, shared access to multi user databases and video conferencing.databases and video conferencing.

►Not peripheral sharing.Not peripheral sharing.►Bandwidth depends on the Bandwidth depends on the

telecommunications link.telecommunications link.

IntranetIntranet

► For internal For internal company use only.company use only.

► Looks like a private Looks like a private version of the version of the Internet.Internet.

►Mainly used to Mainly used to share company share company information via web information via web pages and group pages and group work.work.

InternetworkInternetwork

► A collection of two A collection of two or more LANs.or more LANs.

► Connected via Connected via routers so all users routers so all users and devices can and devices can communicate.communicate.

► The Internet is the The Internet is the largest example.largest example.

Internet ConnectionInternet Connection

►Dial – upDial – up► Cable ModemCable Modem

► ISDNISDN► ADSLADSL► Leased LineLeased Line

► 56 Kbps56 Kbps►Max of 36 Mbps but Max of 36 Mbps but

shared between shared between usersusers

► 1.5 Mbps1.5 Mbps► 2 – 100 Mbps2 – 100 Mbps► 1.5 – 274 Mbps1.5 – 274 Mbps

T1 – T4 linesT1 – T4 lines

Widespread use of Networks Widespread use of Networks – Technical Reasons– Technical Reasons

►Processors – Becoming faster with Processors – Becoming faster with more than one processor per chip.more than one processor per chip.

►Memory – More memory means the Memory – More memory means the development of more complex development of more complex network operating systems.network operating systems.

►Data transfer rates – increasing.Data transfer rates – increasing.► Improving network related software – Improving network related software –

browsers and operating systems.browsers and operating systems.