Introduction to networks

1. Click to add TextClick to add Text
CommunicationCommunication
and Networkand Network
ConceptsConcepts

2. NetworkNetwork
 Network, in computer science, a group of computers andNetwork, in computer science, a group of computers and
associated devices that are connected byassociated devices that are connected by
communications facilities.communications facilities.
 Network is an inter connected collection of autonomousNetwork is an inter connected collection of autonomous
computers.computers.
 When two or more computers are joined together so thatWhen two or more computers are joined together so that
they are capable of exchanging information , they form athey are capable of exchanging information , they form a
network.network.

3. Need for NetworkingNeed for Networking
 Resource sharingResource sharing - Through a network , data , s/w and- Through a network , data , s/w and
h/w resources can be shared irrespective of the physicalh/w resources can be shared irrespective of the physical
location of the resources and the user.location of the resources and the user.
 ReliabilityReliability – A file can have its copies on two or more– A file can have its copies on two or more
computers of the network.computers of the network.
 Reduced CostReduced Cost – Sharing resources reduces the cost– Sharing resources reduces the cost
 Fast CommunicationFast Communication – Information can be exchanged at a– Information can be exchanged at a
very fast speedvery fast speed

4. Evolution of NetworkEvolution of Network
 In 1969 , US deptt of Defence startedIn 1969 , US deptt of Defence started
ARPANET( Advance Research ProjectsARPANET( Advance Research Projects
Agency NETwork).Agency NETwork).
 Goal was to connect different universitiesGoal was to connect different universities
and US defence.and US defence.
 People exchanged info and played gamesPeople exchanged info and played games
 Expanded rapidlyExpanded rapidly

5. Evolution of NetworkEvolution of Network
 In mid 80’s National Science Foundation created a highIn mid 80’s National Science Foundation created a high
capacity network called NSFnet.capacity network called NSFnet.
 Allowed Academic use and private businessAllowed Academic use and private business
 Many private companies built their own networks whichMany private companies built their own networks which
were later interconnected along with ARPANET andwere later interconnected along with ARPANET and
NSFnet to form Internet.NSFnet to form Internet.
 Arpanet was shut down in 1990 .Arpanet was shut down in 1990 .
 Govt funding for NSFnet discontinued in 1995.Govt funding for NSFnet discontinued in 1995.
 But commercial services can into the scenario which areBut commercial services can into the scenario which are
still running the internet.still running the internet.

6. InternetInternet
Internet is worldwide network of computer networks.Internet is worldwide network of computer networks.
How does it work?
•Most computers are not connected
directly to the internet.
•They are connected to smaller
networks
•Which are connected through
gateways to the internet backbone

7. GatewayGateway
 Gateway is a deviceGateway is a device
that connectsthat connects
dissimilar networks.dissimilar networks.
 A backbone is aA backbone is a
centralcentral
interconnectinginterconnecting
structure thatstructure that
connects one or moreconnects one or more
networks just like thenetworks just like the
trunk of a tree.trunk of a tree.

8. How does internet work?How does internet work?
 At the source comp the message to be sent isAt the source comp the message to be sent is
broken down into small parts called packets.broken down into small parts called packets.
 Each packet is given a serial no e.g. 1,2,3Each packet is given a serial no e.g. 1,2,3
 All these packet are sent to the destinationAll these packet are sent to the destination
computercomputer
 The destination comp receives the packets inThe destination comp receives the packets in
random order( 10 may come before 1)random order( 10 may come before 1)
 The packets are reassembled in the order ofThe packets are reassembled in the order of
their no and message is restored.their no and message is restored.

9. How it functions smoothly?How it functions smoothly?
 Every computer connected to the internet uses same setEvery computer connected to the internet uses same set
of rules for communication.of rules for communication.
 Set of rules is called protocolSet of rules is called protocol
 Communication protocol used by internet is TCP/IPCommunication protocol used by internet is TCP/IP
 The TCP (Transmission control protocol) part isThe TCP (Transmission control protocol) part is
responsible for dividing the message into packets on theresponsible for dividing the message into packets on the
source comp and reassembling them at the destinationsource comp and reassembling them at the destination
comp.comp.
 The IP (Internet Protocol) is responsible for handling theThe IP (Internet Protocol) is responsible for handling the
address of the destination comp so that the packet isaddress of the destination comp so that the packet is
sent to its proper destination.sent to its proper destination.

10. Future of Internet- InterSpaceFuture of Internet- InterSpace
InterSpace is a client /server softwareInterSpace is a client /server software
program that allows multiple users toprogram that allows multiple users to
communicate online with real time audio ,communicate online with real time audio ,
video and text chat in dynamic 3Dvideo and text chat in dynamic 3D
environments.environments.

11. Few terms related to NetworkFew terms related to Network
 Workstation or NodesWorkstation or Nodes
refers to a computer that are attached to a networkrefers to a computer that are attached to a network
 ServerServer
The master comp is called server.The master comp is called server.
Facilitates the sharing of data, s/w and h/w concepts.Facilitates the sharing of data, s/w and h/w concepts.
Server

12. Few terms related to NetworkFew terms related to Network
Two types of serversTwo types of servers
Non Dedicated serverNon Dedicated server Dedicated serverDedicated server
Workstation doublesWorkstation doubles
up as a serverup as a server
Slower, requires more memorySlower, requires more memory
Used in small networks calledUsed in small networks called
Peer-to-peer networksPeer-to-peer networks
One computerOne computer
reserved forreserved for
server job.server job.
FasterFaster
The networks using such aThe networks using such a
server is called Master – slaveserver is called Master – slave
network.network.

13. Network Interface Unit (NIU)Network Interface Unit (NIU)
 It is a device attached to each workstation andIt is a device attached to each workstation and
server.server.
 Helps to make connections within the network.Helps to make connections within the network.
 Each NIU has a unique no identifying it calledEach NIU has a unique no identifying it called
node address.node address.
 NIU is also called terminal access point (TAP).NIU is also called terminal access point (TAP).
 Also called Network Interface Card (NIC)Also called Network Interface Card (NIC)
 Each NIC is given a unique physical addressEach NIC is given a unique physical address
called MAC address.called MAC address.

14. How data is transmitted across networks?How data is transmitted across networks?
Switching Techniques are used forSwitching Techniques are used for
transmitting data across networks.transmitting data across networks.
3 types of switching techniques are there.3 types of switching techniques are there.
 Circuit SwitchingCircuit Switching
 Message SwitchingMessage Switching
 Packet SwitchingPacket Switching

15. Circuit SwitchingCircuit Switching
 Physical connection between the two computers isPhysical connection between the two computers is
established and then data is transmitted from source toestablished and then data is transmitted from source to
destination computer.destination computer.
 When a computer places a telephone call , the switchingWhen a computer places a telephone call , the switching
equipment within the telephone system seeks out aequipment within the telephone system seeks out a
physical copper path from sender’s to receiver’sphysical copper path from sender’s to receiver’s
telephone.telephone.
 It sets up end-to-end connection between computersIt sets up end-to-end connection between computers
before any data can be sent.before any data can be sent.

16. Message SwitchingMessage Switching
 The source comp sends the data toThe source comp sends the data to
the switching office first which storesthe switching office first which stores
the data in its buffer.the data in its buffer.
 It then looks for a free link to anotherIt then looks for a free link to another
switching office and then sends theswitching office and then sends the
data to this office.data to this office.
 Process is continued till the data isProcess is continued till the data is
delivered to the destination computer.delivered to the destination computer.
 It is also known as store and forwardIt is also known as store and forward
technique.technique.

17. Packet SwitchingPacket Switching
 There is a tight upper limit on the block size. InThere is a tight upper limit on the block size. In
message switching there was no upper limit.message switching there was no upper limit.
 A fixed size of packet is specified.A fixed size of packet is specified.
 All the packets are stored inAll the packets are stored in main memorymain memory inin
switching office. In message switching packetsswitching office. In message switching packets
are stored onare stored on disk.disk.
 This increases the performance as access timeThis increases the performance as access time
is reduced.is reduced.

18. Network DeviceNetwork Device
ModemModem
 Modems are most frequently used toModems are most frequently used to
enable computers to communicate withenable computers to communicate with
each other across telephone lines.each other across telephone lines.
 Stands for Modulation – demodulation.Stands for Modulation – demodulation.
 Converts digital signal to analog signalConverts digital signal to analog signal
and vice versa.and vice versa.
 Two types- Internal and ExternalTwo types- Internal and External

19. RJ 45 ConnectorRJ 45 Connector
 Register Jack 45 is an 8 wire connectorRegister Jack 45 is an 8 wire connector
which is commonly used to connectwhich is commonly used to connect
computers on LAN.computers on LAN.
 Looks like RJ-11 telephone connectorLooks like RJ-11 telephone connector

20. Ethernet CardEthernet Card
 Ethernet,Ethernet, is a LAN architectureis a LAN architecture
developed by the Xerox corporationdeveloped by the Xerox corporation
in 1976, originally for linkingin 1976, originally for linking
minicomputers at the Palo Altominicomputers at the Palo Alto
Research Center.Research Center.
 Computers that uses EthernetComputers that uses Ethernet
architecture have to install ethernetarchitecture have to install ethernet
card .card .
 Now computers are coming fittedNow computers are coming fitted
with ethernet card.with ethernet card.

21. HubHub
•A common connection point for devices in a network.
• Hubs are commonly used to connect segments of a LAN.
•A hub contains multiple ports.
• A passive hub serves simply as a conduit for the data,
enabling it to go from one device (or segment) to another.
•Active hub electrically amplify the signal as it moves from one
connected device to another.
•Support 8, 12 or 24 RJ-45 ports
•Used in star or ring topology.

22. SwitchSwitch
 A switch (A switch (switchswitching hub) in the context of networking refers to a deviceing hub) in the context of networking refers to a device
which filters and forwards data packets across a network.which filters and forwards data packets across a network.
Unlike a standard hub which simply replicates what it receives on one portUnlike a standard hub which simply replicates what it receives on one port
onto all the other ports, a switching hub keeps a record of the MAConto all the other ports, a switching hub keeps a record of the MAC
addresses of the devices attached to it.addresses of the devices attached to it.
When the switch receives a data packet, it forwards the packet directly to theWhen the switch receives a data packet, it forwards the packet directly to the
recipient device by looking up the MAC address.recipient device by looking up the MAC address.
A network switch can utilise the full throughput potential of a networksA network switch can utilise the full throughput potential of a networks
connection for each device making it a natural choice over a standard hub.connection for each device making it a natural choice over a standard hub.
In other words, say for instance you had a network of 5 PCs and a server allIn other words, say for instance you had a network of 5 PCs and a server all
connected with 10Mbps UTP cable, with a hub the throughput (10Mbps)connected with 10Mbps UTP cable, with a hub the throughput (10Mbps)
would be shared between each device, with a switch each device could utilisewould be shared between each device, with a switch each device could utilise
the full 10Mbps connection.the full 10Mbps connection.

23. RepeaterRepeater
 AA repeaterrepeater is an electronic device that receives ais an electronic device that receives a
weak or low-level signal and retransmits it at aweak or low-level signal and retransmits it at a
higher level or higher power, so that the signal canhigher level or higher power, so that the signal can
cover longer distances without degradation.cover longer distances without degradation.

24. BridgeBridge – connects two LANS having the same– connects two LANS having the same
protocol – (e.g. Ethernet or Token ring)protocol – (e.g. Ethernet or Token ring)
LAN A
Bridge
LAN B
Data not
destined for
other network is
prevented from
passing over
the bridge.

25. BridgeBridge
 In telecommunication networks, a bridge is a product that connectsIn telecommunication networks, a bridge is a product that connects
a local area network (LAN) to another local area network that usesa local area network (LAN) to another local area network that uses
the same protocol (for example, Ethernet or Token Ring).the same protocol (for example, Ethernet or Token Ring).
 You can envision a bridge as being a device that decides whether aYou can envision a bridge as being a device that decides whether a
message from you to someone else is going to the local areamessage from you to someone else is going to the local area
network in your building or to someone on the local area network innetwork in your building or to someone on the local area network in
the building across the street.the building across the street.
 A bridge examines each message on a LAN, "passing" thoseA bridge examines each message on a LAN, "passing" those
known to be within the same LAN, and forwarding those known toknown to be within the same LAN, and forwarding those known to
be on the other interconnected LAN (or LANs).be on the other interconnected LAN (or LANs).

26. RouterRouter
 Router is a specialized network device used to interconnectRouter is a specialized network device used to interconnect
different types of computer network that uses different protocolsdifferent types of computer network that uses different protocols
e.g. Ethernet to a mainframe.e.g. Ethernet to a mainframe.

27. Uses of RouterUses of Router
A router can be used to connectA router can be used to connect
 a Local Area Network (LAN) to anothera Local Area Network (LAN) to another
LAN,LAN,
 a Wide Area Network (WAN) to anothera Wide Area Network (WAN) to another
WAN,WAN,
 a LAN to the Internet.a LAN to the Internet.

28. Working of RouterWorking of Router

Routers transmit data packetsRouters transmit data packets
through these networksthrough these networks
 determine the best path ofdetermine the best path of
transmission, based on a numbertransmission, based on a number
of factors, including traffic load,of factors, including traffic load,
line speed, and costsline speed, and costs..

29. GatewayGateway
 Gateway is a device thatGateway is a device that
connects dissimilar networks.connects dissimilar networks.
 Establishes intelligent connectionEstablishes intelligent connection
between a local network andbetween a local network and
external networks withexternal networks with
completely different structures.completely different structures.
 Gateway is the ISP that connectsGateway is the ISP that connects
the user to the internet.the user to the internet.

30. LAN design- General Network Design ProcessLAN design- General Network Design Process
Access needs and costs
Model Network workload
Select topologies and technologies to
satisfy needs
Simulate behavior under expected load
Perform sensitivity test
Rework design as needed

31. Thank youThank you