There are three main network topologies used to connect computers: bus, ring, and star. A bus topology has all computers connected to a single cable in a line. A ring topology connects each computer to the two nearest nodes in a circular configuration. A star topology connects each computer to a central device like a hub or switch. Hubs and switches are used to connect computers in a star topology network and operate at the physical and data link layers, while routers connect multiple networks and operate at the network layer.

1. NETWORK TOPOLOGIESNETWORK TOPOLOGIES
There are three basicThere are three basic
configurations used to connectconfigurations used to connect
computers they are thecomputers they are the
BusBus
RingRing
StarStar

2. Bus topologyBus topology
 This type of network was widely used in the 1980’sThis type of network was widely used in the 1980’s
 In this configuration every computer (node) sharesIn this configuration every computer (node) shares
the networks total bus capacities.the networks total bus capacities.
 In this configuration adding more computers willIn 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 computersEach computer communicates to other computers
on the network independently this is referred to ason the network independently this is referred to as
PEER-TO-PEER networkingPEER-TO-PEER networking

3. How a Bus Peer to PeerHow a Bus Peer to Peer
Network WorksNetwork Works
 All computers on a network have a distinctAll computers on a network have a distinct
address just like your house doesaddress just like your house does
 a message would be send from onea message would be send from one
computer with the address of anothercomputer with the address of another
computer attached to the messagecomputer attached to the message
 The message is broadcasted to all theThe message is broadcasted to all the
computers on the network until thecomputers on the network until the
addressed PC accepts the messageaddressed PC accepts the message

4. How it workedHow it worked
 The type of wires used for Bus Networks in theThe 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 inA 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 NICThinnet cables were connected to the PC’s NIC
and a Transceiver. The Transceiver was tappedand a Transceiver. The Transceiver was tapped
into the Thicknet cableinto the Thicknet cable
 To stop the message from bouncing back andTo 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 50Ωboth ends of the network are terminated with 50Ω
resistorsresistors

5. ProblemsProblems
 One of the main problems with this type ofOne of the main problems with this type of
network is that it is not very fault tolerant, anetwork is that it is not very fault tolerant, a
break or defect in the bus would affect thebreak or defect in the bus would affect the
whole networkwhole network

6. Ring TopologyRing Topology
 In Ring topology each node is connected to theIn Ring topology each node is connected to the
two nearest nodes so the entire network forms atwo nearest nodes so the entire network forms a
circlecircle
 Data only travels in one direction on a RingData only travels in one direction on a Ring
networknetwork

7. How this Topology worksHow this Topology works
 a node has information to send to anothera node has information to send to another
computer on the network so it sends thecomputer on the network so it sends the
information out on the network to the PC it isinformation out on the network to the PC it is
connected to, if the information is for this PC (theconnected to, if the information is for this PC (the
recipients NIC address is attached to therecipients NIC address is attached to the
message, which is like putting an address on anmessage, which is like putting an address on an
envelope) then the PC accepts the dataenvelope) then the PC accepts the data
 otherwise it passes the information on to the nextotherwise it passes the information on to the next
PC by repeating the data back out on the linePC by repeating the data back out on the line
 This method of repeating the data helps keep theThis method of repeating the data helps keep the
integrity of the data readable by other computersintegrity of the data readable by other computers

8. How it WorksHow it Works
 As it is better to have computers take turnsAs it is better to have computers take turns
using the connecting Data cable, Ringusing the connecting Data cable, Ring
topologies incorporated a system calledtopologies incorporated a system called
Token passingToken passing
 In this topology, to transmit on the wire yourIn this topology, to transmit on the wire your
computer must have control of the token orcomputer must have control of the token or
wait for the token to be freewait for the token to be free
 Larger Token Ring networks use multipleLarger Token Ring networks use multiple
tokenstokens

9. Problems and SolutionsProblems and Solutions
 The drawback to this type of topology is that a singleThe drawback to this type of topology is that a single
malfunctioning workstation can disable the whole networkmalfunctioning workstation can disable the whole network
 To make sure all the information is sent the receiving PCTo make sure all the information is sent the receiving PC
sends the token back to the sending PC after it hassends 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 toIf 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’sThis 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 byIn the mid 1980’s Thinnet cable was replaced by
Category 3 Ethernet cable capable of handling up toCategory 3 Ethernet cable capable of handling up to
10Mbps10Mbps

10. Star topologyStar topology
 In a Star topology every node is connectedIn 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 RouterSwitch or Router
 Compared to a Ring or Bus topology a StarCompared to a Ring or Bus topology a Star
topology requires that more thought be puttopology requires that more thought be put
into its setupinto its setup
HUB

11. The Good and Bad of aThe Good and Bad of a
Star NetworkStar Network
 The upside of a star network is that if anyThe upside of a star network is that if any
one cable fails then only the nodeone cable fails then only the node
connected on that cable would be affectedconnected on that cable would be affected
 Another positive point to this type of networkAnother positive point to this type of network
is that it is very simple to join two staris that it is very simple to join two star
networks together by connecting theirnetworks together by connecting their
central devices to each othercentral devices to each other

12. The Good and Bad of aThe Good and Bad of a
Star NetworkStar Network
 As each computer is connected to a centralAs each computer is connected to a central
device (Hub) the location of the Hub mustdevice (Hub) the location of the Hub must
be made as central as possible, so as tobe made as central as possible, so as to
reduce cable lengthsreduce cable lengths
 The drawback to this type of topology is if aThe drawback to this type of topology is if a
central device was to fail then all computerscentral device was to fail then all computers
connected to that device would not be ableconnected to that device would not be able
to see the networkto see the network

13. 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 itsoften made of plastic, which receives its
power from an ordinary wall outletpower from an ordinary wall outlet
 A hub joins multiple computers (or otherA hub joins multiple computers (or other
network devices) together to form a singlenetwork devices) together to form a single
networknetwork segmentsegment
 On this network segment, all computers canOn this network segment, all computers can
communicate directly with each othercommunicate directly with each other

14. What is a Hub?What is a Hub?
 EthernetEthernet hubs are by far the most commonhubs are by far the most common
type, but hubs for other types of networkstype, but hubs for other types of networks
such assuch as USBUSB also existalso exist
 A hub includes a series ofA hub includes a series of portsports that eachthat each
accepts a network cableaccepts a network cable
 Small hubs can network four computersSmall hubs can network four computers
togethertogether
 They contain four or sometimes five portsThey contain four or sometimes five ports

15. What is a Hub?What is a Hub?
 Many times the fifth port is reserved forMany 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 twoto another hub or similar device (joining two
segments together).segments together).
 Larger hubs contain eight, 12, 16, and evenLarger hubs contain eight, 12, 16, and even
24 ports24 ports

16. Key Features of HubsKey Features of Hubs
 Hubs classify as Layer 1 devices in theHubs classify as Layer 1 devices in the OSI modelOSI model
 OSI stands for :OSI stands for :
TheThe Open Systems InterconnectionOpen Systems Interconnection Basic ReferenceBasic Reference
ModelModel
 At the physical layer, hubs can support little in theAt the physical layer, hubs can support little in the
way of sophisticated networkingway of sophisticated networking
 Hubs do not read any of the data passing throughHubs do not read any of the data passing through
them and are not aware of their source orthem and are not aware of their source or
destinationdestination

17. Key Features of HubsKey Features of Hubs
 Essentially, a hub simply receives incomingEssentially, a hub simply receives incoming
packetspackets, possibly amplifies the electrical, possibly amplifies the electrical
signal, and broadcasts these packets out tosignal, and broadcasts these packets out to
all devices on the network - including theall devices on the network - including the
one that originally sent the packet!one that originally sent the packet!
 aa packetpacket is a formatted block of data carriedis a formatted block of data carried
by a computerby a computer networknetwork

18. Different Types of HubsDifferent Types of Hubs
 Technically speaking, three different typesTechnically speaking, three different types
of hubs existof hubs exist
PassivePassive
ActiveActive
IntelligentIntelligent

19. Passive hubsPassive hubs
 Passive hubsPassive hubs do not amplify the electricaldo not amplify the electrical
signal of incoming packets beforesignal of incoming packets before
broadcasting them out to the networkbroadcasting them out to the network
Active hubsActive hubs
 amplify the electrical signal of incomingamplify the electrical signal of incoming
packets back to their original level beforepackets back to their original level before
broadcasting them back out on the networkbroadcasting them back out on the network

20. Intelligent hubsIntelligent hubs
 add extra features to an active hub that areadd extra features to an active hub that are
of particular importance to businessesof particular importance to businesses
 An intelligent hub is typically stackable (builtAn intelligent hub is typically stackable (built
in such a way that multiple units can bein such a way that multiple units can be
placed one on top of the other to conserveplaced one on top of the other to conserve
space).space).

21. Intelligent hubsIntelligent hubs
 It also typically includes remoteIt also typically includes remote
management capabilities viamanagement capabilities via SNMPSNMP andand
virtual LAN (VLAN)virtual LAN (VLAN) support (You cansupport (You can
configure or check it from a computer that isconfigure or check it from a computer that is
connected to it).connected to it).
 SNMP-SNMP-Simple Network ManagementSimple Network Management
ProtocolProtocol

22. What is a Network Switch?What is a Network Switch?
 AA network switchnetwork switch is a small hardwareis a small hardware
device that joins multiple computersdevice that joins multiple computers
together within onetogether within one
local area network (LAN)local area network (LAN)
 Technically, network switches operate atTechnically, network switches operate at
layer two (Data Link Layer) of thelayer two (Data Link Layer) of the
OSI modelOSI model

23. Network SwitchNetwork Switch
 Network switches appear nearly identical toNetwork switches appear nearly identical to
network hubsnetwork hubs, but a switch generally, but a switch generally
contains more "intelligence" (and a slightlycontains more "intelligence" (and a slightly
higher price tag) than a hubhigher price tag) than a hub
 Unlike hubs, network switches are capableUnlike hubs, network switches are capable
of inspecting dataof inspecting data packetspackets as they areas they are
received, determining the source andreceived, determining the source and
destination device of that packet, anddestination device of that packet, and
forwarding it appropriatelyforwarding it appropriately

24. Network SwitchNetwork Switch
 By delivering each message only to theBy delivering each message only to the
connected device it was intended for, aconnected device it was intended for, a
network switch conservesnetwork switch conserves
network bandwidthnetwork bandwidth and offers generallyand offers generally
better performance than a hubbetter performance than a hub

25. What is a Router?What is a Router?
 RoutersRouters are physical devices that joinare physical devices that join
multiple wired or wireless networks togethermultiple wired or wireless networks together
 Technically, a wired or wireless router is aTechnically, a wired or wireless router is a
Layer 3Layer 3 gatewaygateway, meaning that the, meaning that the
wired/wireless router connects networkswired/wireless router connects networks
togethertogether
 A Gateway is a device that acts like aA Gateway is a device that acts like a
security guard and only allows data in or outsecurity guard and only allows data in or out
if it has the right networkif it has the right network headersheaders

26. RoutersRouters
 Home “networkers” often use an Internet ProtocolHome “networkers” often use an Internet Protocol
(IP) wired or wireless router(IP) wired or wireless router
 IP is the most common OSI network layer protocolIP is the most common OSI network layer protocol
 Protocols are the rules governing the transfer ofProtocols are the rules governing the transfer of
data information, it can also be compared to howdata information, it can also be compared to how
humans use languages (to get your point acrosshumans use languages (to get your point across
you must talk in the same language as the personyou must talk in the same language as the person
you are speaking to).you are speaking to).

27. RoutersRouters
 An IP router such as a DSL or cable modemAn IP router such as a DSL or cable modem
areare broadband routersbroadband routers and joins the home'sand joins the home's
local area network (LAN)local area network (LAN) to theto the
wide-area network (WAN)wide-area network (WAN) of the Internetof the Internet
 A Broadband Router is a device that allowsA Broadband Router is a device that allows
multiple PC’s to access the Internet usingmultiple PC’s to access the Internet using
only one address.only one address.