NETWORK TOPOLOGIESNETWORK TOPOLOGIES

There are three basic There are three basic configurations used to connect configurations used to connect

computers they are the computers they are the Bus Bus Ring Ring Star Star

Bus topologyBus topology

This type of network was widely used in the 1980’s This type of network was widely used in the 1980’s In this configuration every computer (node) shares In this configuration every computer (node) shares

the networks total bus capacities. the networks total bus capacities. In this configuration adding more computers will In this configuration adding more computers will

reduce the access speed on the network. reduce the access speed on the network. Each computer communicates to other computers Each computer communicates to other computers

on the network independently this is referred to as on the network independently this is referred to as PEER-TO-PEER networking PEER-TO-PEER networking

How a Bus Peer to Peer How a Bus Peer to Peer Network WorksNetwork Works

All computers on a network have a distinct All computers on a network have a distinct address just like your house doesaddress just like your house does

a message would be send from one a message would be send from one computer with the address of another computer with the address of another computer attached to the messagecomputer attached to the message

The message is broadcasted to all the The message is broadcasted to all the computers on the network until the computers on the network until the addressed PC accepts the message addressed PC accepts the message

How it workedHow it worked

The type of wires used for Bus Networks in the The type of wires used for Bus Networks in the 80’s were called Thicknet and Thinnet80’s were called Thicknet and Thinnet

A Thicknet cable (very large about 1 inch in A Thicknet cable (very large about 1 inch in diameter usually yellow was hung around a room)diameter usually yellow was hung around a room)

Thinnet cables were connected to the PC’s NIC Thinnet cables were connected to the PC’s NIC and a Transceiver. The Transceiver was tapped and a Transceiver. The Transceiver was tapped into the Thicknet cable into the Thicknet cable

To stop the message from bouncing back and To stop the message from bouncing back and forward down the wire (known as signal bounce) forward down the wire (known as signal bounce) both ends of the network are terminated with 50Ω both ends of the network are terminated with 50Ω resistors resistors

ProblemsProblems

One of the main problems with this type of One of the main problems with this type of network is that it is not very fault tolerant, a network is that it is not very fault tolerant, a break or defect in the bus would affect the break or defect in the bus would affect the whole network whole network

Ring TopologyRing Topology

In Ring topology each node is connected to the In Ring topology each node is connected to the two nearest nodes so the entire network forms a two nearest nodes so the entire network forms a circle circle

Data only travels in one direction on a Ring Data only travels in one direction on a Ring network network

How this Topology worksHow this Topology works

a node has information to send to another a node has information to send to another computer on the network so it sends the computer on the network so it sends the information out on the network to the PC it is information out on the network to the PC it is connected to, if the information is for this PC (the connected to, if the information is for this PC (the recipients NIC address is attached to the recipients NIC address is attached to the message, which is like putting an address on an message, which is like putting an address on an envelope) then the PC accepts the data envelope) then the PC accepts the data

otherwise it passes the information on to the next otherwise it passes the information on to the next PC by repeating the data back out on the line PC by repeating the data back out on the line

This method of repeating the data helps keep the This method of repeating the data helps keep the integrity of the data readable by other computers integrity of the data readable by other computers

How it WorksHow it Works

As it is better to have computers take turns As it is better to have computers take turns using the connecting Data cable, Ring using the connecting Data cable, Ring topologies incorporated a system called topologies incorporated a system called Token passing Token passing

In this topology, to transmit on the wire your In this topology, to transmit on the wire your computer must have control of the token or computer must have control of the token or wait for the token to be free wait for the token to be free

Larger Token Ring networks use multiple Larger Token Ring networks use multiple tokens tokens

Problems and SolutionsProblems and Solutions

The drawback to this type of topology is that a single The drawback to this type of topology is that a single malfunctioning workstation can disable the whole network malfunctioning workstation can disable the whole network

To make sure all the information is sent the receiving PC To make sure all the information is sent the receiving PC sends the token back to the sending PC after it has sends the token back to the sending PC after it has received all the datareceived all the data

If the sending PC is finished sending it passes the token to If the sending PC is finished sending it passes the token to the next PCthe next PC

This type of network was also widely used in the 1980’s This type of network was also widely used in the 1980’s This type of network used Thinnet cable joining nodes.This type of network used Thinnet cable joining nodes. In the mid 1980’s Thinnet cable was replaced by In the mid 1980’s Thinnet cable was replaced by

Category 3 Ethernet cable capable of handling up to Category 3 Ethernet cable capable of handling up to 10Mbps10Mbps

Star topologyStar topology

In a Star topology every node is connected In a Star topology every node is connected through a central device such as a Hub, through a central device such as a Hub, Switch or Router Switch or Router

Compared to a Ring or Bus topology a Star Compared to a Ring or Bus topology a Star topology requires that more thought be put topology requires that more thought be put into its setup into its setup

HUB

The Good and Bad of a The Good and Bad of a Star NetworkStar Network

The upside of a star network is that if any The upside of a star network is that if any one cable fails then only the node one cable fails then only the node connected on that cable would be affected connected on that cable would be affected

Another positive point to this type of network Another positive point to this type of network is that it is very simple to join two star is that it is very simple to join two star networks together by connecting their networks together by connecting their central devices to each other central devices to each other

The Good and Bad of a The Good and Bad of a Star NetworkStar Network

As each computer is connected to a central As each computer is connected to a central device (Hub) the location of the Hub must device (Hub) the location of the Hub must be made as central as possible, so as to be made as central as possible, so as to reduce cable lengthsreduce cable lengths

The drawback to this type of topology is if a The drawback to this type of topology is if a central device was to fail then all computers central device was to fail then all computers connected to that device would not be able connected to that device would not be able to see the network to see the network

What is a Hub?What is a Hub?

A hub is usually a small rectangular box, A hub is usually a small rectangular box, often made of plastic, which receives its often made of plastic, which receives its power from an ordinary wall outlet power from an ordinary wall outlet

A hub joins multiple computers (or other A hub joins multiple computers (or other network devices) together to form a single network devices) together to form a single network network segmentsegment

On this network segment, all computers can On this network segment, all computers can communicate directly with each other communicate directly with each other

What is a Hub?What is a Hub?

EthernetEthernet hubs are by far the most common hubs are by far the most common type, but hubs for other types of networks type, but hubs for other types of networks such as such as USBUSB also exist also exist

A hub includes a series of A hub includes a series of portsports that each that each accepts a network cable accepts a network cable

Small hubs can network four computers Small hubs can network four computers together together

They contain four or sometimes five ports They contain four or sometimes five ports

What is a Hub?What is a Hub?

Many times the fifth port is reserved for Many times the fifth port is reserved for "uplink" which is the connecting of one hub "uplink" which is the connecting of one hub to another hub or similar device (joining two to another hub or similar device (joining two segments together). segments together).

Larger hubs contain eight, 12, 16, and even Larger hubs contain eight, 12, 16, and even 24 ports 24 ports

Key Features of HubsKey Features of Hubs

Hubs classify as Layer 1 devices in the Hubs classify as Layer 1 devices in the OSI modelOSI model OSI stands for :OSI stands for :

The Open Systems Interconnection Basic Reference The Open Systems Interconnection Basic Reference Model Model

At the physical layer, hubs can support little in the At the physical layer, hubs can support little in the way of sophisticated networking way of sophisticated networking

Hubs do not read any of the data passing through Hubs do not read any of the data passing through them and are not aware of their source or them and are not aware of their source or destination destination

Key Features of HubsKey Features of Hubs

Essentially, a hub simply receives incoming Essentially, a hub simply receives incoming packetspackets, possibly amplifies the electrical , possibly amplifies the electrical signal, and broadcasts these packets out to signal, and broadcasts these packets out to all devices on the network - including the all devices on the network - including the one that originally sent the packet! one that originally sent the packet!

a a packetpacket is a formatted block of data carried is a formatted block of data carried by a computer by a computer networknetwork

Different Types of HubsDifferent Types of Hubs

Technically speaking, three different types Technically speaking, three different types of hubs exist of hubs exist

PassivePassive

ActiveActive

IntelligentIntelligent

Passive hubsPassive hubs Passive hubsPassive hubs do not amplify the electrical do not amplify the electrical

signal of incoming packets before signal of incoming packets before broadcasting them out to the networkbroadcasting them out to the network

Active hubsActive hubs

amplify the electrical signal of incoming amplify the electrical signal of incoming packets back to their original level before packets back to their original level before broadcasting them back out on the network broadcasting them back out on the network

Intelligent hubsIntelligent hubs

add extra features to an active hub that are add extra features to an active hub that are of particular importance to businessesof particular importance to businesses

An intelligent hub is typically stackable (built An intelligent hub is typically stackable (built in such a way that multiple units can be in such a way that multiple units can be placed one on top of the other to conserve placed one on top of the other to conserve space). space).

Intelligent hubsIntelligent hubs

It also typically includes remote It also typically includes remote management capabilities via management capabilities via SNMPSNMP and and virtual LAN (VLAN)virtual LAN (VLAN) support (You can support (You can configure or check it from a computer that is configure or check it from a computer that is connected to it). connected to it).

SNMP-SNMP-Simple Network Management Simple Network Management ProtocolProtocol

What is a Network Switch?What is a Network Switch?

A A network switchnetwork switch is a small hardware is a small hardware device that joins multiple computers device that joins multiple computers together within one together within one local area network (LAN)local area network (LAN)

Technically, network switches operate at Technically, network switches operate at layer two (Data Link Layer) of the layer two (Data Link Layer) of the OSI modelOSI model

Network SwitchNetwork Switch

Network switches appear nearly identical to Network switches appear nearly identical to network hubsnetwork hubs, but a switch generally , but a switch generally contains more "intelligence" (and a slightly contains more "intelligence" (and a slightly higher price tag) than a hub higher price tag) than a hub

Unlike hubs, network switches are capable Unlike hubs, network switches are capable of inspecting data of inspecting data packetspackets as they are as they are received, determining the source and received, determining the source and destination device of that packet, and destination device of that packet, and forwarding it appropriately forwarding it appropriately

Network SwitchNetwork Switch

By delivering each message only to the By delivering each message only to the connected device it was intended for, a connected device it was intended for, a network switch conserves network switch conserves network bandwidthnetwork bandwidth and offers generally and offers generally better performance than a hub better performance than a hub

What is a Router?What is a Router?

RoutersRouters are physical devices that join are physical devices that join multiple wired or wireless networks togethermultiple wired or wireless networks together

Technically, a wired or wireless router is a Technically, a wired or wireless router is a Layer 3 Layer 3 gatewaygateway, meaning that the , meaning that the wired/wireless router connects networks wired/wireless router connects networks together together

A Gateway is a device that acts like a A Gateway is a device that acts like a security guard and only allows data in or out security guard and only allows data in or out if it has the right network if it has the right network headersheaders

RoutersRouters

Home “networkers” often use an Internet Protocol Home “networkers” often use an Internet Protocol (IP) wired or wireless router (IP) wired or wireless router

IP is the most common OSI network layer protocol IP is the most common OSI network layer protocol Protocols are the rules governing the transfer of Protocols are the rules governing the transfer of

data information, it can also be compared to how data information, it can also be compared to how humans use languages (to get your point across humans use languages (to get your point across you must talk in the same language as the person you must talk in the same language as the person you are speaking to).you are speaking to).

RoutersRouters

An IP router such as a DSL or cable modem An IP router such as a DSL or cable modem are are broadband routersbroadband routers and joins the home's and joins the home's local area network (LAN)local area network (LAN) to the to the wide-area network (WAN)wide-area network (WAN) of the Internet of the Internet

A Broadband Router is a device that allows A Broadband Router is a device that allows multiple PC’s to access the Internet using multiple PC’s to access the Internet using only one address.only one address.