Presentation on theme: "INTRODUCTION TO COMPUTER NETWORKS"— Presentation transcript:
1 INTRODUCTION TO COMPUTER NETWORKS Chapter 2INTRODUCTION TO COMPUTER NETWORKS
2 Learning outcomes The difference between networks and internets The difference between logical and physical addressesWhat is a protocol in the context of computer networkingHow protocols are used on remote computers to communicate easilyExplain the concept of layeringOSI ,TCP/IP andhybrid models
3 Reading Joe Casad, Teach Yourself TCP/IP, Chs 1-2 William Buchana, Mastering the Internet, Ch. 3Neil Briscoe, Understanding the 7-layer OSI model, July 2000.Julian Moss, Understanding TCP/IP (first part September 1997)
4 What is a network? A network consists of two or more computers connected by network media.i.e cables, telephone lines, radio wavesshare the same resources such as database, printerExchange filesExchange electronic message between each others
10 Local Area NetworkA LAN is a network that is used for communicating among computer devices, usually within an office building or homeLAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple usersIs limited in size, typically spanning a few hundred meters, and no more than a mileIs very fast, with speeds from 10 Mbps to 10 GbpsRequires very little wiring, typically a single cable connecting to each deviceHas lower cost compared to MAN’s or WAN’s
13 Metropolitan-Area Networks (MAN) MAN is designed extended over an entire city.May be wholly owned and operated by a private company, or it may be a service provided by a public company, such as a local telephone company.
14 Wide-Area Networks (WAN) Provides long-distance transmission of data, voice, image, and video information over large geographic areas
15 WAN (Continued)WANs connect larger areas, such as whole states, or even the world.Transoceanic cables and satellites are used to connect WANs
16 TopologyThe physical topology of a network refers to the configuration of cables, computers and other peripherals.The main types of network topologies are:Linear BusStarRingTree or Hybrid
17 Linear Bus topologyA linear bus topology consists of a main run of cable with a terminator at each end. All servers workstations and peripherals are connected to the linear cable
18 Star topologyA star network is designed with each node (file server, workstation, peripheral) connected directly to a central network hub or server
19 Ring topologyA ring network is one where all workstations and other devices are connected in a continuous loop. There is no central server
20 Tree or hybrid topology A tree or hybrid topology combines characteristics of linear bus and star and/or ring topologies.It consists of groups of star-configured workstations connected to a linear bus backbone cable
22 Network Operating Software Network operating systems co-ordinate the activities of multiple computers across a networkThe two major types of network OS are:Peer-to-peerClient/server
23 Peer to peer network OSIn peer to peer network OS, there is no file server or central management source; all computers are considered equalPeer to peer networks are design primarily for small to medium LANSAppleShare and Windows for Workgroups are examples of programs that can function as peer to peer
24 Client/Server network OS Client/server network OS centralise functions and applications in one or more dedicated file servers.The file server provides access to resources and provides securityNovel Netware and Windows NT Server are examples of client/server network operating systems
25 Network Hardware and Physical Media Network hardware includes:ComputersPeripheralsInterface cards andOther equipment needed to perform data processing and communications within the network
26 File serversA very fast computer with a large amount of RAM and storage space along with a fast network interface cardThe network operating system software resides on this computer
27 WorkstationsAll computers connected to the file server on a network are called workstations
28 Network interface cards The network interface card (NIC) provides the physical connection between the network and the computer workstation.Most NICs are internal with the card fitting into an expansion slot in the computer.Three common network interface connections are Ethernet cards, Local Talk connectors and Token Ring cards
29 Ethernet cardsThe most common Network Interface Cards are Ethernet cardsThey contain connections for either coaxial or twisted pair cables, or bothCo-axial cableTwisted pair cable
30 Concentrators / HubsA concentrator is a device that provides a central connection point for cables from workstations, servers and peripheralsHubs are multi-slot concentrators
31 Switcheshubs provide an easy way to scale up and shorten the distance that the packets must travel to get from one node to anotherthey do not break up the actual network into discrete segments. That is where switches come in.
32 Switches (continued) A vital difference between a hub and a switch is all the nodes connected to a hub share the bandwidth among themselves.while a device connected to a switch port has the full bandwidth all to itself.Think of a switch as a ‘clever’ hub
33 RepeatersA signal loses strength as it passes along a cable, so it is often necessary to boost the signal with a device called a repeaterA repeater might be a separate device, or might be part of a concentrator
34 BridgesA bridge is a device that allows you to segment a large network into two smaller, more efficient networks
35 An example of a network with a bridge RouterHubBridgeSegmentNodeHubInternet
36 Routers A router translates information from one network to another The router directs traffic to prevent “head-on” collisionsIf you have a LAN that you want to connect to the Internet, you will need a router to serve as the translator between information on your LAN and the Internet
38 Physical MediaPhysical media provide the connections between network devices that make networking possibleThere are four main types of physical media in widespread use today:Coaxial CableTwisted PairFiber Optic CableWireless Media
39 Ethernet Physical Media :- Maximum Segment Length LAN Technologies 10 Base Thick Co-axial Cable with Bus Topology10 Base Thin Co-axial Cable with Bus Topology10 BaseT UTP Cat 3/5 with Tree Topology10 BaseFL Multimode/Singlemode Fiber with TreeTopologyMaximum Segment Length10 Base m with at most 4 repeaters (Use Bridge to extend the network)10 Base m with at most 4 repeaters (Use Bridge to extend the network)10 BaseT m with at most 4 hubs (Use Switch to extend the network)
40 Thick Coaxial Cable Used in the first Ethernet networks Type RG-11 / 10Base5Usually orange/blackThickness of a small garden hoseVery expensive and heavy cableTwo strands along the axisConductor down the centerInsulator surrounds conductorShielded mesh serves as outsideThick Ethernet cable:is a specially manufactured cable to be used only in certain Ethernet environmentsprovides many layers of shielding.
41 Thin Coaxial Cable Alternative to Thick Ethernet Cable Type RG-58 / 10Base2 / “Cheapnet”Usually blackThickness of a pencilMore flexible than thick EthernetReduced the cost of the cablingFlexibleThin Ethernet cable:was designed in 1984 as an alternative to thick Ethernet cable.provides a simplification of the Ethernet cabling scheme.uses a commonly manufactured cable type.reduces installation time from about 5 minutes to around 1minute.eliminated or moved certain thick coaxial components whichintroduced new connectors
42 Coaxial cable connectors The most common type of connector used with coaxial cables is the BNC connector
43 Twisted Pair Cable Phone Systems Twisted Pair Cable consists of two copper wires, usually twisted around each other to cancel out any noise in the circuitTwo main type of Twisted Pair CablingShielded Twisted Pair (STP)Unshielded Twisted Pair (UTP)
44 Shielded Twisted Pair (STP) STP is the original media used for token ring networksSTP can be used for high-speed networks, such as FDDI or ATM, where shielding is important.RJ-45
45 Unshielded Twisted Pair (UTP) UTP has four pairs of wires inside the jacketEach pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs
46 UTP (Continued) Most commonly used twisted pair cable Uses common telephone wireUTP was standardized by the IEEE committee in October of 1990UTP for LANs is now classified as:Category 3 - used for LANs up to 10 MbpsCategory 4 - used for LANs up to 16 MbpsCategory 5 - used for LANs up to 100 MbpsUnshielded Twisted Pair (UTP) cable:provides an alternative, easy to use, less expensive cable type for Ethernet networks..implements the star topology on Ethernet which allows for better network managementintroduced a new component called the concentrator which allows for network cabling to be collapsed into one entity.
47 Fiber Optic CableFiber optic cabling consists of a center glass core surrounded by several layers of protective materialsIt transmits light rather than electronic signalsIt is the standard for connecting networks between buildings, due to its immunity to the effects of moisture and light
48 Fiber Optic (continued) Fiber optic cable has the ability to transmit signals over much longer distances than coaxial or twisted pairIt can also carry information at vastly greater speedsFiber optic cable is more difficult to install than other cabling
49 Wireless LANSWireless networks use high frequency radio signals to communicate between the workstations and the fileserver or hubs.Disadvantages of wireless networks are:they are expensive (relatively),provide poor security,are susceptible to interference andare slower than cabled networks
50 Introduction network Protocol A protocol is a set of rules that governs the communications between computers on a networkThese rules include guidelines that regulate:the method of access,types of cabling andspeed of size data transferPROTOCOL =SET OF RULES ABOUT COMMUNICATIONS BETWEEN NETWORKS!
51 The most common protocols are: EthernetLocal TalkToken RingFDDIATMProtocol = a formal description of a set of rules and conventions that govern how devices on a network exchange informationDid you ever wonder what HTTP in web addresses was about? It stands for HyperText Transfer Protocol
52 Ethernet Most widely used Uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection
53 A bit like waiting for some one to get What does that mean?Each computer in the network ‘listens’ to the cable before sending anything through the network. If the network is clear, the computer will transmit.If another computer is already transmitting on the cable, the computer will wait and try again when the line is clearA bit like waiting for some one to getoff the telephone
54 CSMA/CD =Carrier Sense Multiple Access /Collision Detection Ethernet (continued)A collision happens if two computers attempt to transmit at the same time.Each computer then backs off and waits a random amount of time before attempting to retransmit.It is normal to have collisions using this method,but the delays caused by collisions and transmissions is small, and does not effect speed of transmission on the networkCSMA/CD =Carrier Sense Multiple Access /Collision Detection
55 Ethernet (continued)Ethernet protocol allows for data to be transmitted over twisted pair, coaxial or fiber optic cable at a speed of 10 Mbps(more on that later)
56 Fast EthernetTo allow for faster transmission, the Ethernet protocol has developed a new standard that supports 100 MbpsFast Ethernet requires the use of more expensive equipment and network cards
57 One gigabit per second = one thousand megabits per second Gigabit EthernetThe Ethernet protocol has also developed a new standard that allows transmission of 1 Gbps (gigabit per second)One gigabit per second = one thousand megabits per second
58 Local TalkLocal Talk is a network protocol that was developed by Apple for Macintosh computersLocal Talk uses the CSMA/CACarrier Sense Multiple Access with Collision AvoidanceIt works in a similar way to CSMA/CDIt is a lot slower than Ethernet (only 230 Kbps)
59 Token Ring Token ring protocol involves ‘token-passing’. It is not as popular as Ethernet protocolA single electronic ‘token’ moves around the ring from one computer to the next. If a computer wishes to transit and receives an empty token, it attaches data to the token which then proceeds around the ring until it comes to the computer the data is meant for.
60 FDDI Stands for Fiber Distributed Data Interface Is used mainly to connect two or more LANs, often over large distancesCan operate over fiber optic cable at 100 Mbps
61 ATM- Asynchronous Transfer Mode Transmit data at a speed of 155 Mbps and higherWorks by transmitting all data in small packets of fixed size (other protocols transfer variable size packets)Like FDDI , is most often used to connect two or more LANs
62 Where does TCP/IP fit into all this? TCP/IP is the protocol that is used for the transmission of information over the InternetIP (Internet Protocol) - the main delivery system for information over the InternetTCP (Transport Control Protocol) - used to break apart and rebuild information that travels over the InternetIn Chapter 3 We will look into this protocol in details.