Networks & telecommunicationsLEARNING GOALSStand-alone computers v. Network?Why Networking ?Computer NetworkComputer Network (cont.)Network scopeTransmission MediaTransmission Media (Continued)Wireless transmission mediaWireless Media issuesComputing EquipmentSmall Network illustratedHub operationSwitch operationNetwork SoftwareProtocolsNetwork TopologiesBus Network TopologyStar Network TopologyRing TopologyNetwork Architectures/ModelsClient-server modelSlide 24Slide 25Peer-to-Peer modelSummary QuestionsSummary Questions (cont.)Slide 29ProblemTelecommunicationsVoice vs. Data CommunicationCircuit Switching and Reserved CapacityPros and cons of Reserved CapacityPacket-Switching Data NetworksSlide 36Networks & telecommunicationsOctober 9, 2014LEARNING GOALS•Identify the major hardware components in networks.•Identify and explain the various types of computer networks.•Identify the various types of transmission media•Describe the role of software used in networks.•Discuss telecommunications’ principles.2Stand-alone computers v. Network?– – – – – – – – – – 3Why Networking ?• Resource sharing–Sharing hardware (printers, processors, etc.)–Sharing software (programs, data files)• High reliability–Can set automatic backup of programs and data at different locations–Fault tolerance (if one server is down, others can provide service. If a disk fails, data available through mirror or RAID-3 disks)• Possible cost savings• Communication tool–Internal email service–Remote Access service4Computer Network•An interconnection of computers and computing equipment using either wires or wireless transmission media over small or large geographical distances.“Connect to GHI”ABCDEFGHIJKLMNOOnce connected to the network, the computer (or another device) becomes a network node5Computer Network (cont.)•Based on the definition from the previous slide, what hardware elements are needed to implement a computer network?6Network scope•Local area network (LAN): computer network where the nodes are all in close proximity spanning a room, building, or campus•Metropolitan area network (MAN): network that serves an area of 3 to 30 miles - approximately the area of a typical city.•Wide area network (WAN): a large network that encompasses parts of states, multiple states, countries, and the world7Transmission Media•Physical media–Transmission media used to physically connect nodes to the network–Transmits electrical or optical signals–Could be copper wire or fiber optic cablePhysicalWireless8Transmission Media (Continued)•Twisted PairCategory Use Signal Data rate Distance ProblemCategory 1 Telephone Analog/Digital <100Kbps 3-4 miles Security, noiseCategory 2 T1, ISDN Digital <2 Mbps 3-4 miles Security, noiseCategory 3 LANs Digital 10 Mbps 100 m Security, noiseCategory 4 LANs Digital 20 Mbps 100 m Security, noiseCategory 5 LANs Digital 100 Mhz 100 m Security, noiseCategory 6 LANs Digital 250 Mhz 100 m Security, noiseCategory 7 LANs Digital 600 Mhz 100 m Security, noise•Fiber optic–Thin glass fibers surrounded by coating–Uses laser or light for data transmission–Very fast (10+ Gbps, 100 miles without any repeater)–Very secureSourcePhoto diode(LED or LD)DestinationPhoto receptor(LED or LD)Fiber optic cable910Wireless transmission media•Infrared light–Has many of the same characteristics as visible light–Travels in straight lines–Cannot penetrate solid objects•Radio waves–Travel in straight lines–Can penetrate through nonmetallic objects–Can travel long distances11Wireless Media issues•Use electromagnetic waves or electromagnetic radiation for data transmission•Propagation through space, and indirectly, through solid objects•Many problems:LaptopComm. TowerShadowZoneRadio waves tend to bounce off objects. Receiver can receive 2 or more signals.Thick objects can block the direct path. So, Receiver will be in a Shadow zone where it cannot well receive.Insecure: Easier to “intercept” messagesElectromagneticInterference (EMI) from Other stations,Microwave ovens, etcMultipathInterference+ Much more attenuation: Inverse Square lawComputing Equipment•Network interface card (NIC): Device that–provides a computer with unique address–Converts data into signal for transmission•Hub / Switch: Central collection point for transmission media that interconnect computers•Modem–Converts digital data into analog signal and back again•Router –special hardware that determines optimal routing path for data packets –Usually used to connect a LAN to a WAN•Bridge–Forwards messages between LANs12Small Network illustratedHub or SwitchMediaWide Area Network131.Station A transmitsto the Hub2.Hub broadcaststo all stationsStation C must wait,or its signal willcollide with Station A'ssignalStationAStationBStationCStationAStationBStationCHub operationHubs split available bandwidth among computers, i.e. with a 100 Mbps hub, the network speed will be 100 Mbps / n (where n is the number of computers)Active hubs include repeater capabilities for regenerating signals.Passive hubs don't regenerate signals. Limited to a 30meter distance apart from computers.(Except sending station)Switch operationStationCStationDSwitchStationBStation ATransmitsto Station CSwitch SendsSignal out aSingle Port162345StationAStation BTransmitsSimultaneouslyto Station DSwitches send out a single port: destination port.Most switches can efficiently handle simultaneous transmissionsSwitches provide a full bandwidth to all connected computers.Switching tableMAC Address PortA1-44-D55-1F-AA-4C 1 (Station A)B2-CD-13-5B-E4-65 2 (Station B)C3-2D-55-3B-A9-4F 5 (Station C) ; ;Network Software•Network operating system–Used on servers–Used for managing network resources–Examples: Novell NetWare, Windows Server 2008•Workstation operating system–Used on client PCs–Used to manage local resources & access network resources•Network monitoring software–Packet sniffers – allow seeing data as it moves over network–Keystroke monitors – allow seeing what users are typing16Protocols•An agreed upon set of rules that govern communication in a network•All computers on a network must use same protocol for effective communication•Example of protocols: •Ethernet (for communication in a LAN)•Token Ring (for communication in a LAN)•TCP/IP suite (for communication in a LAN and the Internet)Computer 1Rules for Task 1Rules for Task 2Rules