Basic ConceptsBasic Concepts

Basic ConceptsBasic Concepts

Line ConfigurationLine Configuration TopologyTopology Transmission ModeTransmission Mode Categories of NetworksCategories of Networks InternetworksInternetworks

Line ConfigurationLine Configuration

The way two or more communication The way two or more communication devices attach to the devices attach to the linklink

The The linklink = physical pathway that = physical pathway that transfers data from one device to transfers data from one device to anotheranother

Point-to-PointPoint-to-Point MultipointMultipoint

Point-to-PointPoint-to-Point

workstation

workstation workstation

workstation

workstation

server

link

link

link

MultipointMultipoint

link

server

workstation

workstation

Capacity of the channel is shared

spatially shared line several devices can use the link simultaneously

time-shared line users must take turn

Basic ConceptsBasic Concepts

Line ConfigurationLine Configuration TopologyTopology Transmission ModeTransmission Mode Categories of NetworksCategories of Networks InternetworksInternetworks

TopologyTopology

Topology = the way a network is laid Topology = the way a network is laid outout PhysicallyPhysically LogicallyLogically

MeshMesh StarStar TreeTree BusBus RingRing

Relationship StatusRelationship Status

Peer-to-peerPeer-to-peer The devices share the link equallyThe devices share the link equally

Primary-secondaryPrimary-secondary One device control traffic and the other One device control traffic and the other

must transmit through itmust transmit through it Ring and mesh topology Ring and mesh topology peer-to- peer-to-

peer transmissionpeer transmission Star and tree topology Star and tree topology primary- primary-

secondarysecondary Bus Bus both both

Mesh Mesh

Advantages:

no shared link, each communication carries its own data load

robust – if one link is unusable, there are still other links to use

privacy and security

fault identification and fault isolation -- easy

MeshMesh

DisadvantagesDisadvantages Requires many cables, ports, hardwareRequires many cables, ports, hardware N devices requireN devices require

N(N-1)/2 physical channelsN(N-1)/2 physical channels N-1 I/O ports for each deviceN-1 I/O ports for each device

Star Star

hub

Central control

Each device needs only one link, one I/O port

Easy to install, reconfigure

Less cables

Fault detection /isolation easy

robust

Tree Tree

hub

Central control

hubhubhub

hub

(Active hub)

BusBus

Tap Tap Tap

Cable end

Cable end

Tap

Drop line

Drop line

backbone

BusBus

Advantages

easy to install

less cables

Disadvantages

fault isolation is difficult

difficult to add new devices

Basic ConceptsBasic Concepts

Line ConfigurationLine Configuration TopologyTopology Transmission ModeTransmission Mode Categories of NetworksCategories of Networks InternetworksInternetworks

Transmission ModeTransmission Mode

Defines the direction of signal flow Defines the direction of signal flow between two linked devicesbetween two linked devices

Three typesThree types SimplexSimplex Half-duplexHalf-duplex Full-duplexFull-duplex

Transmission ModeTransmission Mode SimplexSimplex

Unidirectional, like a one way streetUnidirectional, like a one way street Only one device can transmit, the other Only one device can transmit, the other

only receives only receives

monitorserver

Direction of data

Transmission ModeTransmission Mode

Half-duplexHalf-duplex Each station can both transmit and receive but Each station can both transmit and receive but

not at the same timenot at the same time When one device is sending, the other can When one device is sending, the other can

only receiveonly receive E.g. Walkie-talkie E.g. Walkie-talkie

Direction of data at time 2

Direction of data at time 1

Transmission ModeTransmission Mode

Full-duplexFull-duplex Both stations can transmit and receive Both stations can transmit and receive

simultaneouslysimultaneously E.g. telephone networkE.g. telephone network

Direction of data at the time

Basic ConceptsBasic Concepts

Line ConfigurationLine Configuration TopologyTopology Transmission ModeTransmission Mode Categories of NetworksCategories of Networks InternetworksInternetworks

Categories of NetworksCategories of Networks

LAN (Local Area Network)LAN (Local Area Network) MAN (Metropolitan Area Network)MAN (Metropolitan Area Network) WAN (Wide Area Network)WAN (Wide Area Network)

InternetworksInternetworks

Two or more networks are connectedTwo or more networks are connected