Chapter2(BasicConcepts)

8/3/2019 Chapter2(BasicConcepts)

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Basic ConceptsBasic Concepts


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Basic ConceptsBasic Concepts

t Five general concepts provide the basis for the relationship

between the communicating devices.

Line configuration

Topology

Transmission mode

Categories of Networks

Internetworks


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2.1 Line configuration2.1 Line configuration

~ refers to the way two or more communication devices attach

to a link

~ defines the attachment of communication devices to a link

Line configuration

Line configuration

Multipiont

MultipiontPoint-to-point

Point-to-point


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Line configuration (contd)Line configuration (contd)

tPoint-to-point

~ provides a dedicated link between two devices.

tMultipoint (multidrop)

~ is configuration in which more than two specific devices

share a single link


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t Point-to-point

Link


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t Point-to-point

Link


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t Point-to-point


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t Multipoint

Link


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TopologyTopology

~ refers to the way a network is laid out, either physically

or logically

~ defines the physical or logical arrangement of link in a

network

tA consideration when choosing a topology is therelative status of the devices to be linked.

peer-to-peer : the devices share the link equally(ring, mesh)

primary-secondary : one device controls traffic and the others

must transmit through it (star, tree)


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Categories of topologyCategories of topology

TopologyTopology

MeshMesh

StarStar

TreeTree

BusBus

RingRing


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MeshMesh

tEvery device has a dedicated point-to-point link to

every other device.

tA fully connected mesh network therefore has n(n-1)/2

physical channels to link n devices.


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contdcontd

tMesh topology


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Mesh (contd)Mesh (contd)

tAdvantages

The use of dedicated links guarantees that each

connection can carry its data load.

Mesh topology is robust.

Privacy and security.

Point-to-point links make fault identification and fault

isolation easy.


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contdcontd

tDisadvantages

~ are related to the amount of cabling and the number of I/O

ports

because every device must be connected to every other

device, installation and reconfiguration are difficult

the sheer bulk of the wiring can be greater than theavailable space(in walls, ceiling, or floors) can

accommodate

the hardware required to connect each link (I/O port and

cable) can be prohibitively expensive


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StarStar

tEach device has a dedicated point-to-point link only to

a central controller, usually called a hub


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Star (contd)Star (contd)

tStar topology


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Star (contd)Star (contd)

tAdvantage

Each device needs only one link and one I/O port to

connect it to any number of others (easy to install

and reconfigure)

Robustness

q if one link fails, only that link is affected


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TreeTree

t is a variation of a star

active hub(central hub)

~ contains a repeater, which is a hardware device that

generates the received bit patterns before sending them

out

passive hub

~ provides a simple physical connection between the

attached devices


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Tree (contd)Tree (contd)

tTree topology

Hub Hub

Hub


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Tree (contd)Tree (contd)

tAdvantage & Disadvantage

are generally the same as those of a star


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BusBus

t is multipoint. One long cable acts as a backbone to link all

the devices in the network

tNodes are connected to the bus cable by drop lines and

taps

drop line

~ is a connection running between the device and the main cable

tap

~ is a connector either splices into the main cable or punctures the

sheathing of a cable to create a contact with the metallic core


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Bus (contd)Bus (contd)

tBus topology


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Bus (contd)Bus (contd)

t AdvantagesAdvantages

~ include ease of installation

t DisadvantagesDisadvantages

~ include difficult reconfiguration and fault isolation


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RingRing

tEach device has a dedicated point-to-point line

configuration only with the two devices on either side of it

tAdvantageAdvantage

~ is relatively easy to install and reconfigure

~ fault isolation is simplified

tDisadvantageDisadvantage

unidirectional traffic

q break in the ring can disable the entire network

--> needs dual ring

Ri ( td)Ri ( td)


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Ring (contd)Ring (contd)

tRing topology

H b id t lH b id t l


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Hybrid topologyHybrid topology

2 3 T i i d2 3 T i i d


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2.3 Transmission mode2.3 Transmission mode

~ is used to define the direction of signal flow between two link

devices

t Simplex

is unidirectional, as on a one-way street (keyboard, monitor)

t Half-Duplex

each station can both transmit and receive, but not at the same

time

t Full-Duplex

both stations can transmit and receive simultaneously

T i i M d ( td)Transmission Mode (contd)


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Transmission Mode (contd)Transmission Mode (contd)

Transmission modesTransmission modes

Half-duplexHalf-duplexSimplexSimplex Full-duplexFull-duplex



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tSimplex

MainframeMonitor

Direction of data



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Transmission Mode (contd)Transmission Mode (cont d)

tHalf-Duplex

Workstation Workstation

Direction of data at time 1

Direction of data at time 2



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Transmission Mode (cont d)Transmission Mode (cont d)

tFull-Duplex

Workstation Workstation

Direction of data at all the time

2 4 Categories of Networks2 4 Categories of Networks


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2.4 Categories of Networks2.4 Categories of Networks

t three primary categories

LAN

MAN

WAN

tsize, ownership, distance it cover, physical architecture

Categories of Networks (contd)Categories of Networks (contd)


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Categories of Networks (cont d)Categories of Networks (cont d)

Metropolitan area network

(MAN)

Metropolitan area network

(MAN)Local area networks

(LAN)

Local area networks

(LAN)Wide area network

(WAN)

Wide area network

(WAN)

NetworkNetwork



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tLAN(Local Area Networks)

~ is usually privately owned and links the devices in asingle office, building or campus



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tSingle building LAN



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tMultiple building LAN

Backbone



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tMAN(Metropolitan Area Networks)

~ is designed to extend over an entire city



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tMAN

Public city network



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Categories of Networks (cont d)g ( )

tWAN(Wide Area networks)

~ provides long-distance transmission of data, voice,image, and video information over large

geographical areas that may comprise a country, a

continent, or even the whole world



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g ( )g ( )

tWAN

2.5 Internetworks2.5 Internetworks


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~ is an interconnection of networks by the use of

internetworking device(router and gateway)

t cf.

internet: an interconnection of networks

Internet: a specific worldwide network

Internetworks (contd)Internetworks (contd)


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( )( )

t Internetwork (internet)

Chapter2(BasicConcepts)

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