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Chapter 1 Introduction 1. 1 Network and the Internet 1. 1. 1 Traditional Needs of Networking 1. 1. 2 The needs of Home Networks 1. 1. 3 Networking and Economics 1. 2 Network Hardware Components 1. 2. 1 Servers 1. 2. 2 Workstations 1. 2. 3 Connecting Devices 1. 2. 4 Networking Medium
Chapter 1 Introduction 1. 1 Network and the Internet (1/4) z A network is a set of nodes connected together by a shared medium. y. A node can be a computer or a connecting device. x. It is any device with an IP address. x. A computer on a network is also called a host. y. The medium may be a cable or radio wave z The most elementary network yconnects two computers together using a cross-over cable. z The Internet is a large collection of networks.
Chapter 1 Introduction 1. 1 Network and the Internet (2/4)
Chapter 1 Introduction 1. 1 Network and the Internet (3/4) z The Internet and a home network: ythey use the same protocol xto connect and send information. z Technologies to connect a network to the Internet: ydial-up access y. DSL ycable modems ywireless technologies etc.
Chapter 1 Introduction 1. 1 Network and the Internet (4/4)
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking z Networking is yto connect computers together for the purpose of xcommunication, and xsharing of resources. y. The resources on a network refer to xdata xhardware xsoftware, and xservices (e. g. Internet access).
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking z A. Sharing of Data z B. Sharing of Hardware z C. Sharing of Software z D. Communication z E. Internet Sharing
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking A. Sharing of Data z On a network, folders and files in a computer can be shared out y to allow authorised users to access from other computers. z A file server has y a larger storage capacity, and y allows access to files by different users. z Advantages: y Better Version Control x. User can always access the most updated version of data which may be modified by different users. x. Without a network, the same file may be stored in several computers -- it is difficult to tell which one is the most updated. y Data treated with more intensive care xmore frequent backup, xautomatic file duplication using another hard disk.
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking B. Sharing of Hardware
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking B. Sharing of Hardware z Hardware can be shared out so that it can be accessed by other computers on the network. ye. g. a printer, CD-ROM drive or fax modem, z Advantage: ysaves the cost in purchasing many hardware yno need to use a particular computer for printing
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking C. Sharing of Software z Some software to work in a networked environment ye. g. the network version of a DBMS x. The DBMS is installed in a computer called database server z Some software vendors provide site licensed software ythe software may be installed xin all the computers in a site, or xsome computers, xdepending on the agreement. y. Site license is less expensive than purchasing individual copies for computers xif there are large number of computers in a site
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking D. Communications z On a network, users may communicate with others ye-mails ynotice boards ychat rooms ynewsgroups yvideoconferencing etc. x. Each user is identified by the user name. z If the network is connected to the Internet, communication means yreaching people in another part of the world.
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking E. Internet Sharing
Chapter 1 Introduction 1. 1. 1 Traditional Needs of Networking E. Internet Sharing z Internet sharing means ysimultaneous use of one Internet connection by more than one computer within an organisation. y. Most ISPs assign one global IP address per subscriber x. A router with NAT function allows computers to use the same global IP address z Business plans of an ISP yallow Internet sharing y. Target customers xoffices, and xschools.
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks z A home network is ysimilar to the network of a business, but ycomprises smaller amount of nodes and yless sophisticated software and connecting devices. z Why setting up a home network? y. A. Internet sharing y. B. setting up a smart home y. C. setting up a home entertainment system.
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks A. Internet Sharing z (As of May 2005, more than 60% of the families in HKSAR have access to the Internet) z Very often, Internet sharing happens in these families. z ISP’s Plans for home customers are ylower in price than those business plans ymost ISPs do not agree with Internet sharing by home customers. x. However, with the growing reality of Internet sharing, many ISPs begin to adjust their policies xcheck your subscriber agreement to see your ISP's policy.
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks B. Smart Home
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks B. Smart Home z Smart home y Also called Home automation system y combining technologies in networking and controlling home appliances xto enable people to manage their homes from a computer, even remotely z Some of the tasks: y 1. Automatic light control y 2. Control home appliances remotely y 3. Control access to a home y 4. Monitor home remotely y 5. Enhance home security y 6. Others xalert you changes in environment such as temperature, brightness and moisture
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks C. Home Entertainment System
Chapter 1 Introduction 1. 1. 2 The Needs of Home Networks C. Home Entertainment System z Home Entertainment System y. Combines x. DVD player, TV tuners of PC x. Traditional audio-visual equipment • such as TV and Hi-Fi system x. Network technology y. Allows xaudio and video signals, movies and music xto be played from a computer and xdistributed over the network. y. Example is x. Windows® XP Media Center Edition (MCE)
Chapter 1 Introduction 1. 1. 3 Networking and Economics z An entire industry has emerged that y develops networking technologies and y provides networking services. z A new platform for people to conduct business y e-commerce z Telecommuting y employees are working at home, rather than in the office y kept together by x the company network and x other telecommunication channels. y flexible workplace and time y less traffic congestion y more quality family time y increased productivity y less company overhead
Chapter 1 Introduction 1. 2 Network Hardware Components z On a network, hardware include z 1. 2. 1 servers z 1. 2. 2 workstations z 1. 2. 3 connecting devices z 1. 2. 4 networking medium.
Chapter 1 Introduction 1. 2. 1 Servers z A server is a computer that yperforms tasks for other computers ymanages the network xenforcing security xsharing of files xsharing of hardware y. A dedicated server is expensive, because xperformance features, and xfault-tolerant features • reliable, and • robust
Chapter 1 Introduction 1. 2. 1 Servers A. Performance Features z 1. Multiple Processors y. Servers can run using one or more processors. y. Requirement: xthe architecture of the motherboard and xthe Operating System (OS). y. Note: x 2 processors may not double (2 x) the overall performance because • not all instructions can take the advantage of multiple processors.
Chapter 1 Introduction 1. 2. 1 Servers A. Performance Features
Chapter 1 Introduction 1. 2. 1 Servers A. Performance Features z 2. Larger and more reliable RAM y If RAM is not enough , xswapping is needed and xthe performance suffers y Buffering requires memory x. Buffering: look ahead and retrieve data from disks to improve the performance. y ECC RAM x. Error Correcting Code RAM xable to • detect errors in two bits, and • correct error in one bit xbetter than parity check: • detect error in one bit
Chapter 1 Introduction 1. 2. 1 Servers A. Performance Features z 3. Bus capabilities y. Bus: the path between xthe processor, RAM and peripheral devices. y. In a server, large volume of data is moving over the bus. y. Peripheral Component Interconnect (PCI) bus x 32 -bit (33 MHz) xused by traditional PC xmay form a bottleneck in a server with several Network Interface Cards y. Wider and faster buses are needed x. For example, 64 -bit PCI-X bus (133 MHz).
Chapter 1 Introduction 1. 2. 1 Servers A. Performance Features z 4. Disk Interface y IDE (Integrated Drive Electronics) xless expensive xmeets the needs in ordinary PCs y SCSI (Small Computer Systems Interface) xhandle simultaneous access to more than one hard disk xmore common in servers
Chapter 1 Introduction 1. 2. 1 Servers B. Fault-tolerant Features z Fault-tolerant means that yeven a part fails, the whole system can still operate z Fault-tolerant yguarantees the uptime of a network, and yprovides continued data availability. z Fault-tolerant requires yredundant components xtake over when there is a failure. y“hot swap” components xcan be replaced without turning off the computer
Chapter 1 Introduction 1. 2. 1 Servers B. Fault-tolerant Features z 1. RAID System (Redundant Array of Inexpensive Disks) ya set of hard disks that appear to as a logical disk yfor xfault tolerant and/or ximproving performance. y. Some standards x. RAID-0, 1, 2, 3, 4, 5 x. RAID-10 = RAID-1+ RAID-0 y. A. How is speed improved? xdisk heads can work independently y. B. How is data loss prevented in case of disk failure? xredundancy
Chapter 1 Introduction 1. 2. 1 Servers B. Fault-tolerant Features
Chapter 1 Introduction 1. 2. 1 Servers B. Fault-tolerant Features z 2. UPS (Uninterruptible Power Supply) y connected between x the mains power supply, and x the computer. y includes x a battery, and x charging circuit y Advantages: x Data availability • the server is still accessible when power fails x Preventing data loss • alerts user to save data in files x Avoiding hardware damage • power fluctuation can reduce lifeexpectancy of electrical devices
Chapter 1 Introduction 1. 2. 1 Servers B. Fault-tolerant Features z 3. Backup Server ytakes over services when needed by xinstalled with the services in duplicate xholding an updated copy of the important information • e. g. the user account database yneeds not be exactly the same as the working server y. Examples “backup domain controllers” BDC
Chapter 1 Introduction 1. 2. 2 Workstations z A workstation is a computer that yallows users to make access to the resources on the network yalso called clients on a client/server network ymay be connected to network using xcables, or xradio waves ycan be converted from a standalone PC xby installing • Network Interface Card (NIC), and • networking software.
Chapter 1 Introduction 1. 2. 2 Workstations A. Network Interface Card (NIC) (1/4) z Network Interface Card (NIC) y Also called network adapter y is required in all computers xincluding servers and workstations y consists of circuitry that prepares/receives data y several types: x. Ethernet NIC • 10 Base-2, 10 Base-T, 100 Base-T and 1000 Base-T, 10 Base-F, 10 GBase-LR etc. • different data transmission rates and for different cables x. Token Ring NIC xwireless NIC
Chapter 1 Introduction 1. 2. 2 Workstations A. Network Interface Card (NIC) (2/4)
Chapter 1 Introduction 1. 2. 2 Workstations A. Network Interface Card (NIC) (3/4) z MAC address (Medium Access Control) yunique identifier of NIC ysix-byte (48 -bit) code yburnt permanently xin the ROM of the NIC C: >IPCONFIG /ALL. . . Description. . . . : VIA Rhine II Fast Ethernet Adapter Physical Address. . . : 00 -30 -18 -52 -68 -2 E. .
Chapter 1 Introduction 1. 2. 2 Workstations A. Network Interface Card (NIC) (4/4) y. The first 3 bytes identify the manufacturer xe. g. 00 -11 -11(16) represents Intel® Corporation.
Chapter 1 Introduction 1. 2. 2 Workstations B. Networking Software (1/4)
Chapter 1 Introduction 1. 2. 2 Workstations B. Networking Software (2/4) z Operating systems (OS) forms the major difference between xa workstation, and a server z Servers are installed with y. Network Operating System (NOS) xmanages the network, and xentertains requests from clients z Workstations are installed with y. Desktop OS + networking software for xcommunicating with other computers, and xsending and receiving data over the network ydrivers for the NIC, and programs for protocols
Chapter 1 Introduction 1. 2. 2 Workstations B. Networking Software (3/4) z Workstations may use OS from different vendors y e. g. a Windows 2003 network allows Macintosh PC as well as Windows PC to connect z The networking software for workstations y may be available from the NOS of the server y or from the desktop OS itself Type of Operating compute System r Server Network Operating System Client Desktop OS with networking software
Chapter 1 Introduction 1. 2. 2 Workstations B. Networking Software (4/4)
Chapter 1 Introduction 1. 2. 3 Connecting Devices z A connecting device ymoves data from one network cable to another ydirects traffic xwithin a network, or xacross multiple networks. yinclude xrepeaters xhubs xbridges xswitches, and xrouters.
Chapter 1 Introduction 1. 2. 3 Connecting Devices A. Repeater z Attenuation y signal travelling along a cable would become weaker and weaker z Effective transmission length y guarantees signal transmission over the given distance x beyond which the signals may become too weak to be detected. y e. g. 100 m for Cat-5 UTP z A repeater y amplifies signals y are electrically powered y does not understand the signals y cannot help direct traffic y cannot join dissimilar networks x e. g. Ethernet network and Token Ring network are dissimilar
Chapter 1 Introduction 1. 2. 3 Connecting Devices B. Hubs z A hub y also called cable concentrator y common connection for cables x. Each cable connects • the NIC of a computer to a port of the hub y consist of multiple ports y can be used as a repeater z Broadcasting y A hub broadcasts xbecause it echoes incoming signals to all ports y A hub-based network would easily get overloaded
Chapter 1 Introduction 1. 2. 3 Connecting Devices C. Bridge z A bridge yis not dumb because yit can confine the traffic within each segment xby examining the data xagainst a forwarding table that • records the MAC addresses of all nodes xand forward data to the correct segment ycan divide a larger network into smaller segments xto improve efficiency yconnects two dissimilar networks xe. g. Token Ring and Ethernet
Chapter 1 Introduction 1. 2. 3 Connecting Devices C. Bridge
Chapter 1 Introduction 1. 2. 3 Connecting Devices D. Switches z A switch y is a cable concentrator xjoins the network cables together y does not echo signals to all other ports, because it xexamines data against • a table of the MAC address of each port xforwards data to the correct port • similar to a bridge. y produces less “collisions” y allows several pairs of nodes to transmit at the same time y allows full-duplex z Conclusion: y switch-based networks are faster than hubbased
Chapter 1 Introduction 1. 2. 3 Connecting Devices E. Routers z A router y connects two or more networks together y routes data between networks y keeps a routing table y is able to determine the best path for signals x. Note: a router port is either connected to • a network, or • another router. y is a vital equipment for a LAN to connect to the Internet xcalled • SOHO router, broadband router or residential gateway
Chapter 1 Introduction 1. 2. 4 Networking Medium z Networking media are classified into ytangible xexists in the form of a physical cable, • e. g. coaxial cable, twisted pair and fiber optic yintangible xuses in wireless technology • e. g. radio waves z Note: y Data is always transmitted in the form of physical signals x known as carrier. x e. g. electronic or optical signals in cables; x radio waves in wireless technology
Chapter 1 Introduction 1. 2. 4 Networking Medium A. Coaxial Cable (1/2) z A coaxial cable y consists of xa central copper wire (core) xan insulating layer xa wire mesh • used as shielding xan outer plastic jacket y needs a BNC connector y has effective transmission length up to 500 m y is mainly used in bus network xe. g. old Ethernet networks (10 Base 2 and 10 Base-5) y is used in cable TV network xfor broadband Internet accesses.
Chapter 1 Introduction 1. 2. 4 Networking Medium A. Coaxial Cable (1/2) z Shielding yis done by wire mesh ystops xexternal electromagnetic interference (EMI) • due to other electric currents xthe cable from interfering neighbouring cables • to eliminate cross-talk z Advantages of shielding: yincrease effective transmission length yincrease rate of transmission
Chapter 1 Introduction 1. 2. 4 Networking Medium B. Twisted Pair Cable z A twisted pair cable yconsists of copper wires twisted in pairs z Why use twists? y. To cancel the magnetic fields due to xboth wires y. Result: xcables do not produce EMI xeliminate cross-talk
Chapter 1 Introduction 1. 2. 4 Networking Medium B. Twisted Pair Cable z 1. UTP (Unshielded Twisted Pair) Cables y can be placed side by side without affecting each other y But, susceptible to external EMI xbecause unshielded y are lower price than STP. y several grades : Cat-3, Cat-5, Cat-7 etc. x. Cat-5 • the most popular • maximum effective transmission length: 100 m • consists of 4 pairs of wires • used in – Ethernet, ATM and Token Ring networks. • speed: 100 Mbps, 1 Gbps (1000 Mbps)
Chapter 1 Introduction 1. 2. 4 Networking Medium B. Twisted Pair Cable z 2. STP (Shielded Twisted Pair) cables yare able to xresist external EMI xeliminate cross-talk between two cables yare xmore expensive, but xhigher speed xlonger effective transmission length yare best used in “noisy” environment xe. g. near a transformer station.
Chapter 1 Introduction 1. 2. 4 Networking Medium C. Powerline z Powerline communication (PLC) y uses powerline as networking medium y has two types xindoor, and xoutdoor. z Indoor PLC y for setting up local area network z Outdoor PLC y Broadband over Power Lines (BPL) y Advantage: xinfrastructure is already available y Major problem: xinterfere with radio transmission, because power cable is • unshielded and • untwisted
Chapter 1 Introduction 1. 2. 4 Networking Medium D. Fiber-optic Cable z Fiber-optic cables y use glass to carry light signals xinstead of electrical signals y are used as network backbone xto provide high speed connection xup to 10 Gbps y cannot be intercepted easily because xthey do not emit electromagnetic waves (radio waves) x. So, very secure y have little attenuation xcan span miles of distance xoften used across floors in a building or between buildings. y are expensive xcostly to install and maintain.
Chapter 1 Introduction 1. 2. 4 Networking Medium E. Radio waves z Radio waves y are used in wireless technology y require x wireless NIC in computers, and x an access point • for common connection y Advantages: x inexpensive x flexible x easy to install y Disadvantages: x slow in transmission x radio signals can be intercepted easily.