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CHAPTER 2 : BASIC CONCEPTS OF NETWORKS 7/26/200 09 Idawaty Ahmad : Semesterr 1 : 2009/2010

Five concepts provide the basis for the relationship between the communicating devices :

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1) 2) 3) 4) 5)

Line configuration Topology Transmission mode Categories of networks Internetworks

2.1 LINE CONFIGURATION 

Line configuration - the way two or more communication devices attach to a link link - the physical communication pathway that transfers data from one device to another.

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There are two possible line configuration:

1. point to point  

provides a dedicated link between two devices entire capacity of channel is only for transmission those two devices

2. multipoint  also known multidrop  more than two devices share a single link  capacity of the channel is shared: spatially shared, timeshared

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Point-to-Point Line Configuration

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STRAIGHT/CROSSOVER CABLE 7/26/2009

Crossover cable

( Network cable : PC to hub,switch etc)

( PC to PC)

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Straight / Patch cable

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Multipoint Line Configuration 7/26/2009 Idawaty Ahmad : Semester 1 : 2009/2010

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2.2 TOPOLOGY

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Term topology – the way a network is laid out, either physically or logically Two/more devices connect to a link; two/more links form a topology. Network topology – the geometric representation of the relationship of all links and linking devices to each other. The five basic topologies:  Mesh  Star  Tree  Bus B  Ring Two relationships are possible:  

Peer-to-peer, the devices share the link equally Primary-secondary, one device controls traffic and the other must transmit through it.

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2.2 TOPOLOGY

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Nodes in ring and mesh topology - peer-to-peer relationship. Star and tree - primary-secondary primary secondary relationship. relationship Bus topology is equally convenient for both. Mesh  Every device has a dedicated point-to-point link to every other device  Dedicated -> means the link carries traffic only between the two devices it connects.  Fully connected mesh – has n(n-1)/2 physical channels to link n devices, devices every device has n-1 I/O ports  Advantages: 

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1. Use dedicate links – each connection, own data – eliminates the traffic problem 2. Robust – doesn't affect the entire connection 3. Privacy/security – physical boundaries prevent other users 4. fault identification is easy – route to another

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2.2 TOPOLOGY

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Mesh Topology

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2.2 TOPOLOGY 7/26/2009

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Mesh  Disadvantages:

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 Implemented as a backbone of a hybrid network Star  Each device has a dedicated point-to-point link only to a central controller (hub)  Controller acts as an exchange – receive and relays the data  Advantages:

1. Less expensive than mesh – need 1 link/cable and 1 I/O port --?  2. Robustness – if one link fails, other links remain active 



Disadvantages: 

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1 Amount 1. A t off cable bl and d number b off I/O portt required i d expensive.  2. Installation and reconfiguration – difficult 

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1.more cabling required compared to tree, ring, bus topologies.

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HUB 7/26/2009

Uplink port on hub

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2.2 TOPOLOGY

 

generally same as a star topology Addition of secondary hubs  

allow more devices to be attached allows the network to isolate and prioritize communication

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Tree  Star variation  Nodes N d are linked li k d to t central t l hub h b that th t controls t l the th traffic to the network, h/ever not every device plugs directly into the central hub  It has secondary hub which connected to the central hub  Central hub also called active hub which contains a repeater  Secondary hubs may be active or passive hubs.  Passive hub – provides a simple physical connection between the attached devices  Advantages & Disadvantages:

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Tree Topology

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TREE TOPOLOGY EXAMPLE

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2.2 TOPOLOGY

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Easy for installation

Disadvantages:  

Difficult to reconfiguration and fault isolation Signal reflection at the taps can cause degradation in quality

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Bus  multipoint  One O l long cable bl acts t as a backbone b kb t link to li k allll the th devices in the network  Nodes are connected to the bus cable by drop lines and taps.  Drop line – connection running between the device and the main cable  Advantages:

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Bus Topology

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2.2 TOPOLOGY

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Ring  Each device has a dedicated point-to-point p p line configuration with adjacent node.  Signal passed along the ring in one direction  Each devices incorporates a repeater  Advantage :Relatively easy to install and reconfigure  Disadvantage: unidirectional traffic  Dual ring

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2.2 TOPOLOGY 7/26/2009

Hybrid Topologies  Often Oft a network t k combines bi severall topologies t l i as subnetworks linked together in a larger topology  Several topology can be connected to each other via a central controller in a star topology 

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2.3 TRANSMISSION MODE

Simplex Half-duplex  Full-duplex  

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Simplex The communication is unidirectional. Only one of two stations on a link can transmit; the other can only receive  E.g: E g: keyboards and traditional monitor 

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Half-duplex

Each station can both transmit and receive, but not at the same time.  When one device is sending, the other can only receive, and vice versa  The entire capacity of a channel is taken over at the time  E.g: walkie-talkie 

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Term transmission mode – the direction of signal flow between two linked devices. There are three types:

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2.3 TRANSMISSION MODE full-duplex 

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Both stations can transmit and receive simultaneously. Like two way street, traffic flowing in both directions at the same time. Sharing the capacity of the link. E.g: telephone line, videoconferencing

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SIMPLEX

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(Only 1 communication at a single time can be transmitted)

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HALF-DUPLEX

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Half Duplex

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FULL-DUPLEX

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2.4 CATEGORIES OF NETWORKS

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Privately owned Link the devices in a single office, building, or campus Limited to a few kilometer Resource sharing between PC/workstation Other factor: transmission media and topology Most common topologies: bus, ring, star Data rate/speed up to 100Mbps

MAN   

Designed to extend over an entire city Ex: cable TV network, LAN to LAN resource sharing Operates as private company or public company maxis

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Is based on size, ownership, the distance it covers and physical architecture.  LAN 

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2.4 CATEGORIES OF NETWORKS WAN 

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Provides long distance transmission of data, voice, i image, video id conference f over large l geographic hi areas May utilize as public, leased or private communication equipment. Enterprise network – refer to WAN that wholly owned and used by a single company.

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CATEGORIES OF NETWORKS

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CATEGORIES OF NETWORKS: LAN

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CATEGORIES OF NETWORKS:LAN

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CATEGORIES OF NETWORKS:MAN

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CATEGORIES OF NETWORKS:WAN 7/26/2009 Idawaty Ahmad : Semester 1 : 2009/2010

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WAN CONNECTION (THRU TRACERT WWW.FU.IS.SAGA-U.AC.JP) FSKTM, UPM 7/26/2009

IDEC, UPM

TELEGLOBE

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JARING MIMOS (MALAYSIA)

(LOS ANGELES, USA) KYOTO, JAPAN KYUSHU, JAPAN 36

SAGA, JAPAN

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2.5 : INTERNETWORKS

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Internetwork/internet – two or more networks are connected Internetworking devices – routers, gateways internet – a generic term used to mean an interconnection of networks Internet I t t – a specific ifi worldwide ld id network t k

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QUESTIONS…

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What are the advantages of a multipoint connection over point-topoint to point connection? Categorize the five basic topologies in terms of line configuration For n devices in a network, what is the number of cable links required for a mesh, ring, bus and star topology?

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