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Bus topology

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

the networks total bus capacities.

In this configuration adding more computers will

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

on the network independently this is referred to as

PEER-TO-PEER networking


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How a Bus Peer to Peer

Network Works

All computers on a network have a distinct

address just like your house does

a message would be send from onecomputer with the address of another

computer attached to the message

The message is broadcasted to all thecomputers on the network until the

addressed PC accepts the message


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How it worked

The type of wires used for Bus Networks in the80s were called Thicknet and Thinnet

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

Thinnet cables were connected to the PCs NICand a Transceiver. The Transceiver was tappedinto the Thicknet cable

To stop the message from bouncing back and

forward down the wire (known as signal bounce)both ends of the network are terminated with 50resistors


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Problems

One of the main problems with this type of

network is that it is not very fault tolerant, a

break or defect in the bus would affect the

whole network


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Ring Topology

In Ring topology each node is connected to the

two nearest nodes so the entire network forms a

circle

Data only travels in one direction on a Ringnetwork


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How this Topology works

a node has information to send to anothercomputer on the network so it sends theinformation out on the network to the PC it isconnected to, if the information is for this PC (the

recipients NIC address is attached to themessage, which is like putting an address on anenvelope) then the PC accepts the data

otherwise it passes the information on to the next

PC by repeating the data back out on the line This method of repeating the data helps keep the

integrity of the data readable by other computers


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How it Works

As it is better to have computers take turnsusing the connecting Data cable, Ringtopologies incorporated a system called

Token passing In this topology, to transmit on the wire your

computer must have control of the token or

wait for the token to be free Larger Token Ring networks use multiple

tokens


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Problems and Solutions

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

To make sure all the information is sent the receiving PCsends the token back to the sending PC after it has

received all the data If the sending PC is finished sending it passes the token to

the next PC

This type of network was also widely used in the 1980s

This type of network used Thinnet cable joining nodes.

In the mid 1980s Thinnet cable was replaced byCategory 3 Ethernet cable capable of handling up to10Mbps


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Star topology

In a Star topology every node is connected

through a central device such as a Hub,

Switch or Router Compared to a Ring or Bus topology a Star

topology requires that more thought be put

into its setup

HUB


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The Good and Bad of a

Star Network

The upside of a star network is that if any

one cable fails then only the node

connected on that cable would be affected

Another positive point to this type of network

is that it is very simple to join two star

networks together by connecting their

central devices to each other


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The Good and Bad of a

Star Network

As each computer is connected to a central

device (Hub) the location of the Hub must

be made as central as possible, so as to

reduce cable lengths

The drawback to this type of topology is if a

central device was to fail then all computers

connected to that device would not be able

to see the network


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What is a Hub?

A hub is usually a small rectangular box,

often made of plastic, which receives its

power from an ordinary wall outlet

A hub joins multiple computers (or other

network devices) together to form a single

network segment

On this network segment, all computers can

communicate directly with each other
http://compnetworking.about.com/library/glossary/bldef-segment.htmhttp://compnetworking.about.com/library/glossary/bldef-segment.htm


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What is a Hub?

Ethernet hubs are by far the most common

type, but hubs for other types of networks

such as USB also exist

A hub includes a series ofports that each

accepts a network cable

Small hubs can network four computers

together

They contain four or sometimes five ports
http://compnetworking.about.com/library/glossary/bldef-ethernet.htmhttp://compnetworking.about.com/library/glossary/bldef-usb.htmhttp://compnetworking.about.com/library/glossary/bldef-port.htmhttp://compnetworking.about.com/library/glossary/bldef-port.htmhttp://compnetworking.about.com/library/glossary/bldef-usb.htmhttp://compnetworking.about.com/library/glossary/bldef-ethernet.htm


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What is a Hub?

Many times the fifth port is reserved for

"uplink" which is the connecting of one hub

to another hub or similar device (joining two

segments together).

Larger hubs contain eight, 12, 16, and even

24 ports


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Key Features of Hubs

Hubs classify as Layer 1 devices in the OSI model

OSI stands for :

The Open Systems Interconnection Basic Reference

Model

At the physical layer, hubs can support little in the

way of sophisticated networking

Hubs do not read any of the data passing throughthem and are not aware of their source or

destination
http://compnetworking.about.com/library/glossary/bldef-osi.htmhttp://compnetworking.about.com/library/glossary/bldef-osi.htmhttp://compnetworking.about.com/library/glossary/bldef-osi.htmhttp://compnetworking.about.com/library/glossary/bldef-osi.htm


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Key Features of Hubs

Essentially, a hub simply receives incoming

packets, possibly amplifies the electrical

signal, and broadcasts these packets out to

all devices on the network - including the

one that originally sent the packet!

a packet is a formatted block of data carried

by a computernetwork
http://compnetworking.about.com/library/glossary/bldef-packet.htmhttp://compnetworking.about.com/library/glossary/bldef-packet.htm


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Different Types of Hubs

Technically speaking, three different types

of hubs exist

PassiveActive

Intelligent


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Passive hubs

Passive hubs do not amplify the electricalsignal of incoming packets before

broadcasting them out to the network

Active hubs

amplify the electrical signal of incomingpackets back to their original level before

broadcasting them back out on the network


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Intelligent hubs

add extra features to an active hub that areof particular importance to businesses

An intelligent hub is typically stackable (built

in such a way that multiple units can beplaced one on top of the other to conserve

space).


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Intelligent hubs

It also typically includes remote

management capabilities via SNMP and

virtual LAN (VLAN) support (You can

configure or check it from a computer that is

connected to it).

SNMP-Simple Network Management

Protocol
http://compnetworking.about.com/cs/snmp/index.htmhttp://compnetworking.about.com/cs/virtuallans/index.htmhttp://compnetworking.about.com/cs/virtuallans/index.htmhttp://compnetworking.about.com/cs/snmp/index.htm


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What is a Network Switch?

A network switch is a small hardware

device that joins multiple computers

together within one local area network (LAN)

Technically, network switches operate at

layer two (Data Link Layer) of the OSI model
http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://compnetworking.about.com/cs/designosimodel/g/bldef_osi.htmhttp://compnetworking.about.com/cs/designosimodel/g/bldef_osi.htmhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm


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Network Switch

Network switches appear nearly identical tonetwork hubs, but a switch generallycontains more "intelligence" (and a slightly

higher price tag) than a hub Unlike hubs, network switches are capable

of inspecting data packets as they are

received, determining the source anddestination device of that packet, andforwarding it appropriately
http://compnetworking.about.com/cs/internetworking/g/bldef_hub.htmhttp://compnetworking.about.com/library/glossary/bldef-packet.htmhttp://compnetworking.about.com/library/glossary/bldef-packet.htmhttp://compnetworking.about.com/cs/internetworking/g/bldef_hub.htm


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Network Switch

By delivering each message only to the

connected device it was intended for, a

network switch conserves network

bandwidth and offers generally better

performance than a hub
http://compnetworking.about.com/library/glossary/bldef-bandwidth.htmhttp://compnetworking.about.com/library/glossary/bldef-bandwidth.htmhttp://compnetworking.about.com/library/glossary/bldef-bandwidth.htmhttp://compnetworking.about.com/library/glossary/bldef-bandwidth.htm


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What is a Router?

Routers are physical devices that joinmultiple wired or wireless networks together

Technically, a wired or wireless router is a

Layer 3 gateway, meaning that thewired/wireless router connects networkstogether

A Gateway is a device that acts like asecurity guard and only allows data in or outif it has the right network headers
http://compnetworking.about.com/library/glossary/bldef-gateway.htmhttp://compnetworking.about.com/library/glossary/bldef-gateway.htmhttp://compnetworking.about.com/library/glossary/bldef-gateway.htmhttp://compnetworking.about.com/library/glossary/bldef-gateway.htm


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Routers

Home networkers often use an Internet Protocol

(IP) wired or wireless router

IP is the most common OSI network layer protocol

Protocols are the rules governing the transfer of

data information, it can also be compared to how

humans use languages (to get your point across

you must talk in the same language as the personyou are speaking to).


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Routers

An IP router such as a DSL or cable modem

are broadband routers and joins the home's

local area network (LAN) to the wide-area

network (WAN) of the Internet

A Broadband Router is a device that allows

multiple PCs to access the Internet using

only one address.
http://compnetworking.about.com/cs/dslcablerouters/g/bldef_bbrouter.htmhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://compnetworking.about.com/cs/dslcablerouters/g/bldef_bbrouter.htm

Documents

01 Network Topologies