Network Components2

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CP2073 - NetworkingLecture 6


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CP2073 - Networking 2

IntroductionNetwork SegmentsNICs

RepeatersHubsBridgesSwitches

Routers and BroutersGateways


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Extending NetworksInternet

R o u t e r

S w i t c h

R e p e a t e r

R e p e a t e r

H u bH u b

F i l e S e r v e r

R e m o t e

O f f i c e


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CP2073 - Networking4

Network Segments No exact definition, usually an area of a LAN, the cable

connecting two devices

The area of the network bound by bridges or switches where

collisions are propagated, or the area bound by a router toprevent the propagation of broadcasts

The more devices which are added to the network the moretraffic solution use a device to filter the traffic

Such a device reduces congestion, and improves overall

performance Dividing a network in to segments allows the majority of

traffic to stay remain local


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CP2073 - Networking5

Switch

Hub

Hub

Hub

Segment 1

Segment 2

Segment 3


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BroadcastA broadcast is a signal sent by one device and read by all

other devices on the network

Can be used to send a message to all users, may be used bynetwork to find the identity of all the computers on thenetwork

Consumes bandwidth, problem quickly becomes evident asmore devices are added to the network

Broadcast Domain

defines the boundary of broadcasts,some devices stop a message passing through (edge ofdomain), others pass the message on (hubs)


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Collision DomainsCollisions occur when two or more devices transmit

at the same time.

This causes the electrical charge of the signal toincrease a collision

All devices in the same collision domain ceasetransmitting for a random amount of time to

ensure they do not all attempt to start transmittingat the same time again

Network, broadcast and collision domains are nolonger the same since the introduction of switches


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Network Interface Card (NIC) At source:Receives the data packet from the Network LayerAttaches its the MAC address to the data packetAttaches the MAC address of the destination device

to the data packetConverts data in to packets suitable for the particular

network (Ethernet, Token Ring, FDDI)Converts packets in to electrical, light or radio signalsProvides the physical connection to the media


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Network Interface Card (NIC) (2)

As a destination device

Provides the physical connection to the mediaTranslates the signal in to data

Reads the MAC address to see if it matchesits own address

If it does match, passes the data to theNetwork Layer


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Repeater Allows the connection of segments

Extends the network beyond the maximum length of a single

segment Functions at the Physical Layer of the OSI model

A multi-port repeater is known as a Hub

Connects segments of the same network, even if they usedifferent media

Has three basic functions Receives a signal which it cleans up

Re-times the signal to avoid collisions

Transmits the signal on to the next segment


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HubA central point of a star topology

Allows the multiple connection of devicesCan be more than a basic Hub providingadditional services (Managed Hubs,Switched Hubs, Intelligent Hubs)

In reality a Hub is a Repeater with multipleportsFunctions in a similar manner to a Repeater


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Hub (2)Works at the Physical Layer of the OSI

modelPasses data no matter which device it is

addressed to

This feature adds to congestionUse large Hubs (24 port), or stacking them

exacerbates this negative feature


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Hub FeaturesType of media connection needed

Number of portsSpeed

Managed or Unmanaged

Requirement for Uplink Port ? (allows two Hubs to

be connected using a patch cable crossovercable)

Token Ring Hubs are known as MAUs see lastweeks notes


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BridgeLike a Repeater or Hub it connects

segmentsWorks at Data Layer not PhysicalUses Mac address to make decisions

Acts as a filter, by determiningwhether or not to forward a packeton to another segment


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Bridge (2)Builds a Bridging Table, keeps track of devices on

each segmentFilters packets, does not forward them, by

examining their MAC address

It forwards packets whose destination address is

on a different segment from its ownIt divides a network in to multiple collision

domains so reducing the number of collisions


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Bridge (3) Uses the Spanning Tree Protocol (STP) to decide whether to pass

a packet on to a different network segment

A

B C

DE

F G

H

Bridge

Segment A Segment BA Transmits to

C, bridge will

not pass it to

Segment B

G Transmits to

B, bridge will

pass it to

Segment A


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Switch A multiport Bridge, functioning at the Data Link Layer

Each port of the bridge decides whether to forward datapackets to the attached network

Keeps track of the Mac addresses of all attached devices(just like a bridge)

Similarly priced to Hubs making them popular

Acts like a Hub, but filters like a Bridge Each port on a Switch is a collision domain


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BrouterFunctions both as Bridge and a Router hence

name

Can work on networks using different protocolsCan be programmed only to pass data packets

using a specific protocol forward to a segment inthis case it is functioning in a similar manner to a

BridgeIf a Brouter is set to route data packets to the

appropriate network with a routed protocol suchas IP, it is functioning as a Router


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Router Can connect different network segments, if they are in the

same building or even on the opposite side of the globe Work in LAN, MAN and WAN environments Allows access to resources by selecting the best path Can interconnect different networks Works at Network

Layer in an intelligent mannerEthernet with Token Ring Changes packet size and format to match the requirements

of the destination network


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Router (2)Two primary functions to determine the best path

and to share details of routes with other routers

Routing Table a database which keeps track of theroutes to networks and the associated costs

Static Routing routes are manually configured by anetwork administrator

Dynamic Routing adjust automatically to changes innetwork topology, and information it receives fromother routers

Routing Protocol uses a special algorithm to route

data across a network eg RIP


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GatewayAllows different networks to communicate byoffering a translation service from one protocolstack to another

They work at all levels of the OSI model due to

the type of translation service they are providingAddress Gateway connects networks using the

same protocol, but using different directory spacessuch as Message Handling Service

Protocol Gateway connects network using different

protocols. Translates source protocol so destinationcan understand itApplication Gateway translates between

applications such as from an Internet email serverto a messaging server


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Advantages and DisadvantagesRepeater

Advantages

Can connect different types of media,can extend a network in terms of distance, does notincrease network traffic

DisadvantagesExtends the collision domain, can

not filter data, can not connect different networkarchitectures, limited number only can be used innetwork


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Advantages and Disadvantages (2)

Hub

Advantages Cheap, can connect differentmedia types

Disadvantages Extends the collisiondomain, can not filter information, passespackets to all connected segments


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BridgeAdvantages Limits the collision domain, can extend

network distances, uses MAC address to filtertraffic, eases congestion, can connect differenttypes of media, some can connect differingarchitectures

Disadvantages Broadcast packets can not be

filtered, more expensive than a repeater, slowerthan a repeater due to additional processing ofpackets


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Switch

Advantages - Limits the collision domain, canprovide bridging, can be configured to limitbroadcast domain

Disadvantages More expensive than a hubor bridge, configuration of additionalfunctions can be very complex


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Router

Advantages Limits the collision domain, canfunction in LAN or WAN, connects differing mediaand architectures, can determine best path/route,can filter broadcasts

Disadvantages Expensive, must use routableprotocols, can be difficult to configure (staticrouting), slower than a bridge


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Summary Network Segments NICs

Repeaters Hubs Bridges Switches Routers and Brouters

Gateways Disadvantages/ Advantages

Questions ?

Documents

Network Components2