NetworksNetworksNetwork ComponentsNetwork Components

Learning ObjectivesLearning Objectives

Describe different media for transmitting data and their carrying capabilities. Explain the different purposes of network components.

Transmission Media Transmission Media (cables)(cables)

Presented in order of performancePresented in order of performance(increasing expense, (increasing expense, speed of communication, level of traffic that can be speed of communication, level of traffic that can be

managedmanaged, difficulty and usable length of installation and decreasing , difficulty and usable length of installation and decreasing susceptibility to interference)susceptibility to interference)

http://members.tripod.com/barhoush_2/cabling.htmhttp://fcit.usf.edu/network/chap4/chap4.htmhttp://www.ecst.csuchico.edu/~sim/547/Old547/notes/NOTE4.htm

UTP UTP && Shielded TP Shielded TP

UUnshielded nshielded TTwisted wisted PPair (air (UTPUTP) ) Two conductors, enclosed in a Two conductors, enclosed in a

plastic sheath, twisted together. plastic sheath, twisted together.

Shielded Shielded TTwisted wisted PPairair Has a grounded screen around the Has a grounded screen around the

conductors to shield the cable from conductors to shield the cable from extraneous electromagnetic extraneous electromagnetic radiation. radiation.

Used in pre-existing telephone networks.Used in pre-existing telephone networks.Changing current denotes different signals.Changing current denotes different signals.

Coaxial cableCoaxial cable

Baseband coaxial:Baseband coaxial: Single copper braid shield.Single copper braid shield.

Broadband coaxial:Broadband coaxial: Two shieldsTwo shields

1 - aluminium & 1 - copper.1 - aluminium & 1 - copper.

Central conductorPlastic insulators

Copper screen conductor

A central conductor enclosed in a plastic sheath A central conductor enclosed in a plastic sheath surrounded by a copper sheath which is surrounded by a copper sheath which is surrounded by a plastic coating.surrounded by a plastic coating.

Used in pre-existing telephone networks.Used in pre-existing telephone networks.Changing current denotes different signals.Changing current denotes different signals.

Optical FiberOptical Fiber- Used as backbones (- Used as backbones (fast route)fast route) for LANs for LANs

or in WANsor in WANs

Contains many optical fibers:Contains many optical fibers: Glass or plastic fibers designed Glass or plastic fibers designed

to guide light along them.to guide light along them. Signals transmitted as light Signals transmitted as light

pulses so travel at the speed of pulses so travel at the speed of light with the highest bandwidth light with the highest bandwidth currently possible.currently possible.

Separate fibres can be used for Separate fibres can be used for separate signals. separate signals.

NNetwork etwork IInterface nterface CCards (ards (NICNIC))

Provides the hardware Provides the hardware interface interface (circuit board)(circuit board) to to connect a computer to a connect a computer to a network. network. Some NIC cards work Some NIC cards work with wired connections with wired connections while others are wireless.while others are wireless.

http://en.wikipedia.org/wiki/Network_interface_controller

Wireless Communication

Radio signals: Satellite communications.

Microwave signals: Communication must be a straight line from

sender to receiver.

Wireless communication allows for mobile communication.

Network ComponentsNetwork Components

RepeaterRepeaterHas only 2 ports and amplifies the signals between two Has only 2 ports and amplifies the signals between two networks or segments of a bus network that are too far networks or segments of a bus network that are too far apart.apart.Is not intelligent and simply amplifies all signals whether Is not intelligent and simply amplifies all signals whether they are intended for the other segment or not.they are intended for the other segment or not.Operate at the physical layer of OSI.Operate at the physical layer of OSI.

Repeater

Segment

HubsHubs

Hub

HubsHubs

All signals received by a hub are All signals received by a hub are retransmitted down every other cable retransmitted down every other cable connected to it enabling a physical star connected to it enabling a physical star network network (but still theoretically a bus network as (but still theoretically a bus network as collisions are possible)collisions are possible).. Multi-port repeaters.Multi-port repeaters.

Operate at the physical layer of OSI.Operate at the physical layer of OSI.

BridgesBridgesLinks only Links only 22 LANs (which may or may not be LANs (which may or may not be similar)similar) by controlling access from one part by controlling access from one part of the network to the other.of the network to the other. Could be thought of as an intelligent repeater.Could be thought of as an intelligent repeater.

Bridge

Segment

BridgesBridgesHas the ability to learn the layouts of the Has the ability to learn the layouts of the networks.networks. Initially, all data the bridge receives is buffered and Initially, all data the bridge receives is buffered and

passed to both segments. passed to both segments. The bridge stores a table containing the addresses of The bridge stores a table containing the addresses of

sending nodes and the segment from which the data sending nodes and the segment from which the data was sent. was sent.

Eventually, when all nodes have sent data, the bridge Eventually, when all nodes have sent data, the bridge will know on which segment each node is.will know on which segment each node is.

Now it can use the address information in each Now it can use the address information in each packet to route data efficiently packet to route data efficiently (either directing it back to (either directing it back to the segment it came from or on to the other segment)the segment it came from or on to the other segment)..

Is software based as it uses software to make its Is software based as it uses software to make its decisions.decisions.Operate at the data layer of OSI.Operate at the data layer of OSI.

Bridge AlgorithmBridge Algorithm

1.1. Data arrives at the bridge and is Data arrives at the bridge and is buffered.buffered.

2.2. Bridge checks destination address.Bridge checks destination address.3.3. If destination is on same segment as If destination is on same segment as

sender thensender then discard the datadiscard the data

4.4. ElseElse pass data to other segment.pass data to other segment.

Backbone

ServerStations

Switch

ServerStations

Switch

ServerStations

Switch

ServerStations

Switch

SwitchSwitchAn ‘intelligent’ hub which looks at the destination An ‘intelligent’ hub which looks at the destination address of each packet it receives and delivers each address of each packet it receives and delivers each packet to the correct destination packet to the correct destination (i.e. connects nodes in a (i.e. connects nodes in a circuit switching network)circuit switching network)..

Like a bridge but can link many LANs. Like a bridge but can link many LANs.

It allows many terminals all to use the same It allows many terminals all to use the same communications line (backbone – communications line (backbone – fast medium e.g. optical fast medium e.g. optical fibre)fibre) between network segments at different times. between network segments at different times.

If all stations want to access the main network, the switch has If all stations want to access the main network, the switch has no affect on the speed of this link and it may be necessary to no affect on the speed of this link and it may be necessary to upgrade the link to the main network.upgrade the link to the main network.

Operate at the data layer of OSI.Operate at the data layer of OSI.

SwitchSwitch

Only stores physical addresses and can Only stores physical addresses and can only deal with simple networks where only deal with simple networks where there is only one possible path for any there is only one possible path for any given packet.given packet.

If this is not the case ‘routers’ must be used If this is not the case ‘routers’ must be used (next).(next).

Is hardware based as uses chips to Is hardware based as uses chips to make its decisions.make its decisions.

RoutersRouters

LAN Router Public network

Router LAN

RoutersRouters

Connect different types of network Connect different types of network together.together. Stores logical IP addresses and can deal with Stores logical IP addresses and can deal with

complex networks where there is more than complex networks where there is more than one possible path to a destination by one possible path to a destination by calculating the optimum route at the time.calculating the optimum route at the time.

i.e. Directs packets across a packet switched i.e. Directs packets across a packet switched network.network.

Is software based as it uses its own operating Is software based as it uses its own operating system to make its decisions.system to make its decisions.

RoutersRouters

Directs messages down different routes Directs messages down different routes according to their desired destinations.according to their desired destinations. Use Use network addressesnetwork addresses and and addresses of other addresses of other

routersrouters to create a route between two networks so to create a route between two networks so must keep tables of addresses. must keep tables of addresses.

These tables are copied between routers using These tables are copied between routers using routing information protocol (RIP). routing information protocol (RIP).

Often used to connects LANs & WANs e.g. connect a Often used to connects LANs & WANs e.g. connect a LAN to the internet using one IP address.LAN to the internet using one IP address.

Operates at all layers up to the transport layer of OSI.Operates at all layers up to the transport layer of OSI.

Routing AlgorithmRouting Algorithm

1.1. Router receives a network level packet.Router receives a network level packet.2.2. Network destination address is checked.Network destination address is checked.3.3. Packet is sent to the appropriate Packet is sent to the appropriate

network.network.

GatewayGatewayA gateway is a network point/router that acts as an A gateway is a network point/router that acts as an entrance to another network.entrance to another network.On the Internet, a node/router or stopping point can be On the Internet, a node/router or stopping point can be either a gateway node or a host (end-point) node/router. either a gateway node or a host (end-point) node/router. Both the computers of Internet users and the computers Both the computers of Internet users and the computers that serve pages to users are host nodes. that serve pages to users are host nodes. The computers that control traffic within your company's The computers that control traffic within your company's network or at your local Internet service provider (ISP) are network or at your local Internet service provider (ISP) are gateway nodes/routers.gateway nodes/routers.In the network for an enterprise, a computer server acting In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server as a gateway node is often also acting as a proxy server and a firewall server.and a firewall server.

http://en.wikipedia.org/wiki/Default_gatewayhttp://en.wikipedia.org/wiki/Default_gateway

ModemsModems

Necessary if communication link is Necessary if communication link is analogue analogue e.g. To transmit and receive data on the e.g. To transmit and receive data on the

internet.internet.

Hardware which converts digital signals to Hardware which converts digital signals to analogue for transmission and vice versa analogue for transmission and vice versa for receiving.for receiving.

Firewall

Software (and possibly hardware) to control unauthorised outside access to a private network.

PlenaryPlenary

Explain the part played in network Explain the part played in network systems by:systems by:

SwitchesSwitches RoutersRouters BridgesBridges ModemsModems

PlenaryPlenary

SwitchesSwitches A device that allows many terminals all to use the A device that allows many terminals all to use the

same communications line at different times.same communications line at different times.

RoutersRouters Connects different types of network together.Connects different types of network together. Software at a node (on the network).Software at a node (on the network). Which directs messages down different routes.Which directs messages down different routes. According to their desired destination.According to their desired destination.

PlenaryPlenary

BridgesBridges Links two LANs (which may or may not be similar).Links two LANs (which may or may not be similar). Uses address information in packets.Uses address information in packets. Has the ability to learn the layouts of the networks.Has the ability to learn the layouts of the networks. Can control access from one part of the network to Can control access from one part of the network to

the other.the other.

ModemsModems Necessary if communication link is analogue.Necessary if communication link is analogue. Converts digital signals to analogue for Converts digital signals to analogue for

transmission.transmission.