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Building a Network: Topology and Protocols Chapter 4

Chapter 4. Understand network connectivity. Peer-to-Peer network & Client-Server network Understand network topology Star, Bus & Ring topology

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Building a Network: Topology and Protocols

Chapter 4

Prepared by Saher H. Mohammed 2

Understand network connectivity.

Peer-to-Peer network & Client-Server network

Understand network topology

Star, Bus & Ring topology

Understand congestion control techniques

Network equipment

Chapter Objective

Prepared by Saher H. Mohammed 3

The arrangement of nodes (hosts, machines, computers,

printers, etc.) is called topology.

The way the networks are arranged, constructed is called

topology.

Network Connectivity Basics

Node 1 Node 2 •This is called a n = 2 network•If both the nodes are computers, then it is called a point-to-point network

Prepared by Saher H. Mohammed 4

Network consist of two or more nodes, connected by one or

more channels.

When many computers and peripherals are connected to a

common communication channel, it is called a multi-point

network or multi-node network.

Network Connectivity Basics

Node 1 Node 4Node 2 Node 3

Printer

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Any devices such as a hard disk or printer that are accessed

and used by all the nodes on the network are called shared

resources.

Two kinds of relationship exist between the connected nodes

Peer-to-Peer network.

Cooperative processing.

Distributed processing.

Client – Server network.

Relationship between Nodes

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In a Peer-to-Peer network, all the computers in the network are of

same standing (level) and neither is a master or a slave (Server-

Client).

A way to enhance the use of resources is cooperative processing,

the sharing of processing tasks between two or more processors,

either within or between computers.

Distributed processing is the dispersion of the data processing

among computers in multiple sites.

Peer-to-Peer network

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In Client - Server relationship, the nodes are not equal. One

node is the Server (master) and the rest of the nodes are

Clients (slave).

All the clients request service from the server, such as file

space, common printer, and shared processing.

Client – Server Architecture

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Client – Server Architecture

Hub

Client

Client

Client

Client

Client

Server

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In the client – server architecture, if the clients have no

storage nor the processing capabilities, then the clients are

called dumb terminal.

Example old mainframes systems.

In current client – server architecture, most of the clients have

processing capabilities.

Client – Server Architecture

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The client – server architecture is the basis for the current

day Local Area Networks and Wide Area Network.

In client – server architecture, the client can be of two types

Thin Client – they have very limited processing and storage

capabilities.

Example – Smart phones.

Fat Client – they have large storage and processing capabilities.

Example – Desktop and Laptops.

Client – Server Architecture

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Client – Server Architecture

Hub

Client - Laptop

Client – Smart phone

Client - IPad

Client - Desktop

Client - Laptop

Server

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Advantages

Resource sharing.

Share processing.

Easy maintenance.

Client – Server Architecture

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Network Operation systems

Example Microsoft Windows 2003/2008 Server OS.

A networking device

Hub, Switch, Router.

Network Interface Card (NIC)

Media (Wire)

Components of a Network

CATegory Definition

Means Usage

3 10BaseT

10 Mbps on baseline Ethernet

5 100BaseT

100 Mbps on baseline Fast Ethernet

6 1000BaseT

1000 Mbps on baseline

Giga Ethernet

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Geographical arrangement of a network’s components is also

called a topology.

Topology can be of two types

Physical Topology – how the wiring is laid out.

Electrical Topology – how the nodes use the path.

Toplology

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The most common type of the network topology.

All the cables from the end nodes (clients and server) are

connected to a central point – Hub or a Switch.

Star Topology

Client - PC

Client - Laptop

Client - Scanner

Client - Printer

Client - PC

Active Node

Client

Client

Server Client

Client Hub

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In the star topology, the end nodes acquire the attention of

the central node before communication can take place, this

process is called polling.

One disadvantage of star topology is congestion.

If the central active node is busy, then the network becomes

congested.

Star Topology

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In a bus topology, all the nodes are connected to a single,

central wire called as bus.

One major drawback of a bus topology is the single point of

failure.

If the central wire fails, then the entire network breaks down.

Bus Topology

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Bus Topology

Client

Server

Client

Client

Client

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In the ring topology, each node is connected to the one

above node and the one below node.

All the messages pass around the ring and each transmitted

node will see part of the message.

In order to transmit, a node must possess a token.

At any time, only one node can have a token.

Ring Topology

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Ring Topology

Client

ClientServer

Client

Client

Client

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Collision occurs when two or more nodes transmit at the

same time.

Collision can make all the communication in the network to

stop.

There are two methods of collision control

Collision Avoidance.

Collision Detection.

Collision Control

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In a star topology, all the end nodes are connected to a

central node. So, before communicating, the end nodes must

get the attention of the central node – polling.

Central node will poll/ query all the end nodes to check if some end

node is ready to transmit or the central node is ready to receive any

message from the end nodes.

The end nodes will poll/ query the central node to signal that they are

ready to transmit, and will wait till the central node is ready.

Collision Avoidance – Star Topology

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Only one node in the ring topology will have the token, only

that node will have the permission to send the messages.

Once the node is finished with sending the message, it will

release the token for the other nodes to use.

In the ring topology, messages are passed from one node to

the next until the messages reaches the destination.

Collision Avoidance – Ring Topology

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Collision detection – react to the collisions, instead of

avoiding it.

The bus topology uses carrier sense multiple access/

collision detection (CSMA/ CD).

Carrier sense is the primary way of gaining the access to the

central wire/ bus.

Collision Detection – Bus Topology

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The node willing to transmit will sense the carrier (central

wire). If there are no signals on the carrier, the node will

broadcast the message.

All the nodes in the network will get the message, but only

the correct recipient will be able to access the message.

Collision Detection – Bus Topology

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To build a network, certain networking devices are used

Repeater.

Hub.

Switch.

Router.

Gateway.

Bridge.

Network Equipments

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A repeater is a simple hardware device that receives a weak

signal and regenerates it.

Since the repeater creates a new signal, the distortion or

attenuation is removed and the signal is made stronger.

Repeaters are used at Layer 1( Physical) of the OSI Model.

Repeaters are generally used to extend the coverage of a

network by extending the length of the segment.

Repeater

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Repeater

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A hub is a hardware device that physically connects multiple

cables, providing a common connection point.

Hubs are passive devices. They will forward a message to all

the nodes connected via the ports.

Hubs will divide the bandwidth among all the nodes.

Hubs are used at Layer 1( Physical) of the OSI Model.

Hub

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Hub

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A switch is a special type of hub.

A switch is an active device.

Switch operates at the second layer (DLL) of OSI model.

A switch will forward the packets only the correct destination.

A switch will not divide the bandwidth, thus the transmission

speed is higher.

Switch

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Switch

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A bridge is software or a hardware device that connects two

LAN’s or two segments of the same LAN.

Bridge is a layer 2 (DLL) device.

Two LAN’s or the two segments of the same LAN must use

the same data link protocol.

Example (Ethernet, Token, Ring)

Bridges

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Transparent Bridge: Connects two LAN’s that use the same

data link protocol.

Ethernet network– Ethernet network.

Token ring network – Token ring network.

Translating Bridge: Connects two LAN’s that use different data

link protocol.

Ethernet network– Token ring network.

Token ring network – Ethernet network.

Bridges Types

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Bridges

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Routers are hardware devices used to forward the data

packets between different networks.

Routers intelligent devices, they have routing protocols and

store the path information in the routing tables.

Routers operate at the third layer (Network) of OSI model.

Router

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Routers can be static or dynamic.

Static – the routing table cannot be changes.

Dynamic – the routing table can change depending on the situation to

find the next best route.

Routers

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Router

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A gateway is a node on a network that serves as an entrance

to another network.

Gateway is a device that uses software to connect networks

with different architecture by performing protocol conversion

at the application level.

Gateway operates at all the 7 layers of the OSI Model.

Gateways

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Gateways

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Network Device OSI Layer

Repeater Layer 1 – Physical Layer

Hub Layer 1 – Physical Layer

Switch Layer 2 – Data Link Layer

Bridge Layer 2 – Data Link Layer

Router Layer 3 – Network Layer

Gateway All 7 Layers

OSI Levels of Network Devices

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Gateways

Routers

Switches

Comparison

Going up from switches – Routers – Gateways, the capabilities, complexities and the cost increases.

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A Complete Network