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Networking Networking Presentation Transcript

  • Networking FundamentalsStand-alone computers were insufficient ina business context Hard-drive capacities were insufficient Computers required a local printer Sharing documents via the sneakernet was cumbersome E-mail didnt existNetworks addressed these problems
  • Networking FundamentalsComputer networks allow computers tolink to each others resourcesNetworks can increase productivity as wellas decrease cash outlay for new hardwareand software
  • Networking FundamentalsNetworking today is a a relatively simpleplug-and-play processWireless network cards can automaticallydetect and join networksOf course, not all networks are that simple
  • Networking FundamentalsBackground information needed tounderstand how networks work LANs vs. WANs Primary network components Network operating systems (NOSs) Network resource access Network topologies Network architectures Transmitting data on a network
  • LANs vs. WANs Local area networks (LANs) connect computersin a single office Wide area networks (WANs) expand the LANs toinclude networks outside the local environment Think of a WAN as multiple, disbursed LANsconnected together LANs exist in many homes (wireless networks)and nearly all businesses
  • Local Area Networks (LANs)
  • Local Area Networks (LANs)
  • Local Area Networks (LANs)The earliest LANs could not cover largedistancesOnly a few software programs supportedthemThe first software programs wereconstrained by file lockingNowadays, multiple users can access aprogram at one time
  • Wide Area Networks (WANs)
  • Primary Network ComponentsThree types of components available on anetwork: Servers Clients or workstations Resources
  • Blurring the LinesLANs and WANs were often differentiatedby their connection speeds in the 1980sand 90s LANs connected computers with a 10Mbps connection or faster WANs often connected to each other by very expensive T1 connections (a maximum bandwidth of 1.544Mbps)
  • Blurring the LinesToday, connections of 1Gbps are fairly commonWAN, while still slower than LAN connectivity,can be several times faster than the T1Because of the speed increases, categorizingnetworks based on connection speed is outdatedToday, the most common way to classify anetwork is based on geographical distance
  • ServersCore component of the network Provide a link to the resources needed to perform tasks Direct client computers Centralize the control of resources and security Balance the load on computers Compartmentalize files
  • ServersPerform several different critical tasks File servers Print serversCan be multipurpose or single-purposeCan be dedicated or nondedicated
  • Dedicated ServersAssigned to provide specific applications orservices for the network and nothing elseRequires fewer resources from the computerthat is hosting itSavings in overhead may translate to a certainefficiencyA web server is an example of a dedicatedserver
  • Nondedicated ServersAssigned to provide one or more networkservices and local accessSlightly more flexible in its day-to-day use than adedicated serverOften serve as a front-end for the administratorCan act as a workstation as well as a serverCan function well in a peer-to-peer environment
  • Dedicated and NondedicatedMany networks use both dedicated andnondedicated serversOffers improved network performance andflexibility
  • WorkstationsThe computers on which the networkusers do their workConnected to a network that offersadditional resourcesCan range from diskless computersystems to desktop systemsAlso known as client computers
  • WorkstationsItems needed to make a workstation into anetwork client Network interface card (NIC) Special expansion card Cabling system Client software
  • WorkstationsTo users, being on a network changes afew things: They can store more information They can share and receive information from other users They can use programs that would be too large or complex for their computer They can use hardware not attached directly to their computer
  • Network ResourcesA resource is any item that can be used ona networkResources can include Printers and other peripherals Disk storage and file access Applications
  • Network ResourcesNetworks give users more storage spaceto store filesStoring files on a server allows theadministrator to back up user files
  • Network ResourcesFiles that all users need to access canalso be stored on a serverApplications (programs) no longer need tobe on every computer in the office
  • Being on a Network Brings ResponsibilitiesWhen you are on a network, you need totake responsibility for your actions You cannot randomly delete files or move documents from server to server You do not own your e-mail Printing does not mean that if you send something to print it will print immediately If your workstation has also been set up as a nondedicated server, you cannot turn it off
  • Network Operating Systems (NOSs)Networks use a NOS to control thecommunication with resources and theflow of data across the networkThe NOS runs on the serverWith todays NOSs, servers are able tomonitor memory, CPU time, disk space,and peripherals without a babysitter
  • Network Operating Systems (NOSs)LANs and WANs allow for a wide range ofcollaborationNOSs provide this functionality on anetwork
  • Network Resource AccessPeer-to-peer and client-serverQuestions to ask What is the size of the organization? How much security does the company require? What software or hardware does the resource require? How much administration does it need? How much will it cost? Will this resource meet the needs of the organization today and in the future? Will additional training be needed?
  • Peer-to-Peer Networks
  • Peer-to-Peer NetworksNo centralized administration or controlEvery station has unique control over theresources the computer ownsLack of centralized control can make it difficult toadminister the networkThe network isnt very secureMay not be easy to locate resourcesUsers need more training
  • Peer-to-Peer NetworksThe right choice for small companies thatdont expect future growthSetting up a peer-to-peer resource modelsimply because it is cheap and easy toinstall could be a costly mistake
  • Client-Server Resource Model
  • Client-Server Resource Model Server-based networks are also known asdomains The key characteristic of a domain is thatsecurity is centrally administered When you log in to the network, the login requestis passed to the server responsible for security In a peer-to-peer model, users need a useraccount set up on each machine In a domain, all user accounts are stored on theserver
  • Client-Server Resource ModelThe desired model for companies that arecontinually growing or that need to initiallysupport a large environmentServer-based networks offer flexibilityHardware costs may be more, but managingresources becomes less time consumingOnly a few administrators need to be trainedUsers are only responsible for their own workenvironment
  • Resource Access ModelAlways take the time to plan your networkbefore installing itYou dont want the type of network youchose to not meet the needs of thecompany
  • Network TopologiesA way of laying out the networkCan be physical or logicalFive primary topologies Bus (can be both logical and physical) Star (physical only) Ring (can be both logical and physical) Mesh (can be both logical and physical) Hybrid (usually physical)
  • Bus Topology
  • Bus TopologyEasy to installCheapest to installDifficult to add a workstationExpensive to maintain
  • Star Topology
  • Ring Topology
  • Mesh Topology
  • Mesh TopologyExpensive to install and maintainThe advantage you gain is high fault toleranceFound in WANs to connect multiple sites acrossWAN linksRouters are used to search multiple routesthrough the meshBecomes inefficient with five or more entities
  • Hybrid TopologyA mix of the other topologiesMost networks today are not only hybridbut heterogeneousMay be more expensive, but it exploits thebest features of all the other topologies
  • Network Topologies
  • Network ArchitecturesDefine the structure of the network,including hardware, software, and physicallayoutPerformance is usually discussed in termsof bandwidthMajor architectures used today areEthernet and Token Ring
  • Ethernet Original definition of the IEEE 802.3 modelincluded a bus topology using coaxial cable andbaseband signaling From this model came the first Ethernetarchitecture Has several specifications, each one specifyingthe speed, communication method, and cable Original Ethernet was given a designation of10Base5
  • Token RingExactly like the IEEE 802.5 specificationUses a physical star, logical ring topologyWorkstations are cabled to a centraldevice called a multistation access unit(MAU)Can use shielded or unshielded cable andcan transmit data at either 4Mbps or16Mbps
  • Transmitting Data on a NetworkTo facilitate communication across a network,computers use a common language called aprotocolProtocols are a language with rules that need tobe followed so that both computers understandthe right communication behaviorComputers need standards to follow to keeptheir communication OSI model IEEE 802 standards
  • OSI ModelThe International Organization forStandardization (ISO) introduced the OpenSystems Interconnection (OSI) modelThe ISO put together a seven-layer modelproviding a relationship between thestages of communicationAs transmission takes place data passesthrough the layers
  • OSI ModelThe OSI model layers from top to bottom 7. Application layer 6. Presentation layer 5. Session layer 4. Transport layer 3. Network layer 2. Data Link layer 1. Physical layer
  • OSI ModelApplication layer Allows access to network services The layer at which file and print services operatePresentation layer Determines the format of the data Performs protocol conversion and manages data compression, data translation, and encryption Character set information is determined at this level
  • OSI ModelSession layer Allows applications on different computers to establish, maintain, and end a session Enables network procedures, such as identifying passwords, logons, and network monitoringTransport layer Verifies that all packets were received by the destination host on a TCP/IP network Controls the data flow and troubleshoots any problems with transmitting or receiving datagrams Provides error checking and reliable, end-to-end communications
  • OSI ModelNetwork layer Responsible for logical addressing of messages At this layer, the data is organized into chunks called packets Manages traffic through packet switching, routing, and controlling congestion of dataData Link layer Arranges data into chunks called frames Describes the unique physical address (MAC address) Subdivided into two sections: Media Access Control (MAC) and Logical Link Control (LLC)
  • OSI ModelPhysical layer Describes how the data gets transmitted over a physical medium Defines how long each piece of data is and the translation of each into the electrical pulses that are sent over the wires Decides whether data travels unidirectionally or bidirectionally across the hardware Relates electrical, optical, mechanical, and functional interfaces to the cable
  • OSI Model
  • IEEE 802 StandardsDesigned primarily for enhancements tothe bottom three layers of the OSI modelBreaks the Data Link layer into twosublayers The LLC sublayer manages data link communications The MAC sublayer watches out for data collisions and assigns physical addresses
  • IEEE 802.3 CSMA/CD (Ethernet)Ethernet is the most well-known example of theIEEE 802.3 CSMA/CD standardThe original 802.3 CSMA/CD standard Defines a bus topology network that uses a 50 ohm coaxial baseband cable Carries transmissions at 10MbpsGroups data bits into frames and uses theCSMA/CD cable access methodCurrently, the 802.3 standard has beenamended to include speeds up to 10Gbps
  • IEEE 802.3 CSMA/CD (Ethernet)The CSMA/CD acronym illustrates how it works Carrier Sense (CS) means that computers on the network are listening to the wire at all times Multiple Access (MA) means that multiple computers have access to the line at the same time Collision Detection (CD) detects collisions and senders send againCSMA/CD technology is considered acontention-based access method
  • IEEE 802.3 CSMA/CD (Ethernet)The only major downside to 802.3 is thatwith large networks (more than 100computers on the same cable), the numberof collisions increases to the point wheremore collisions than transmissions aretaking place
  • IEEE 802.5 Token RingSpecifies a physical star, logical ringtopology that uses a token-passingtechnology to put the data on the cableIBM developed this technology for itsmainframe and minicomputer networks
  • IEEE 802.5 Token RingA chunk of data called a token circulates the ringA computer with data to transmit takes a freetoken off the ring, modifies it, places the token(along with the data) back on the ringThe token travels around the ringThe destination computer takes the token anddata off the wire and places the token back onthe wireWhen the original sender receives the tokenback, it modifies the token to make it free for useand sends the token back on the ring
  • IEEE 802.5 Token RingMain advantage of the token-passingaccess method is that it eliminatescollisionsWhole procedure takes place in a fewmillisecondsScales very well Not uncommon for Token Ring networks based on the IEEE 802.5 standard to reach hundreds of workstations on a single ring
  • Understanding Networking ProtocolsComputers use a protocol as a commonlanguage for communication A protocol is a set of rules that govern communications Protocols detail what "language" the computers are speaking when they talk over a network If two computers are going to communicate, they both must be using the same protocol
  • Understanding Networking ProtocolsThe A+ exam objectives list two commonprotocols: TCP/IP and NetBIOSOther common protocols IPX/SPX AppleTalk
  • TCP/IPMost popular network protocol in use todayNamed after two of its hardest-working protocols,Transmission Control Protocol (TCP) andInternet Protocol (IP), but contains dozens ofprotocolsProtocol of the InternetRobust and flexibleWorks on disparate operating systems such asUnix, Linux, and WindowsFlexibility comes from its modular nature
  • TCP/IP
  • TCP/IP
  • TCP/IP
  • IP AddressesEach device needs to have a unique IPaddressAny device with an IP address is referredto as a hostConfigure manually or automatically froma DHCP server
  • IP AddressesA 32-bit hierarchical address that identifies ahost on the networkTypically written in dotted-decimal notation, suchas 192.168.10.55 Each of the numbers represents eight bits (or one byte) of the address, also known as an octet The same address written in binary would be 11000000 10101000 00001010 00110111 Numbers will be between 0 and 255
  • IP AddressesAddresses are said to be hierarchicalNumbers at the beginning of the addressidentify groups of computers that belong tothe same network
  • Parts of the IP AddressEach IP address is made up of twocomponents: the network ID and the hostIDNetwork portion comes before the hostportionNetwork portion does not have to be aspecific fixed length
  • Parts of the IP AddressComputers differentiate where the networkaddress ends and the host address beginsthrough the subnet mask A value written just like an IP address and may look something like 255.255.255.0 Any bit that is set to a 1 in the subnet mask makes the corresponding bit in the IP address part of the network address The number 255 is the highest number you will ever see in IP addressing, and it means that all bits in the octet are set to 1
  • Parts of the IP AddressAn example The subnet mask of 255.255.255.0 indicates that the first three octets are the network portion of the address, and the last octet is the host portion In the IP address of 192.168.10.55, the network portion is 192.168.10 and the host portion is 55
  • IP Address ClassesClasses of networks are based on their size Class A - huge companies with thousands of computers Class C - companies with few computers Class B - medium-sized companies Class D and E - reservedThe class of address can be identified by the firstoctet of the IP address
  • Class ADesigned for very large networksDefault network portion for Class A networks isthe first 8 bitsOnly 126 Class A network addresses availableRemaining 24 bits of the address allow eachClass A network to hold as many as 16,777,214hostsAll possible Class A networks are in use; nomore are available
  • Class BDesigned for medium-sized networksDefault network portion for Class Bnetworks is the first 16 bitsAllows for 16,384 networks, each with asmany as 65,534 hosts attachedClass B networks are generally regardedas unavailable
  • Class CDesigned for smaller networksDefault network portion for Class C networks isthe first 24 bitsAllows for 2,097,152 networks, but each networkcan have a maximum of only 254 hostsMost companies have Class C networkaddressesClass C networks are still available
  • IP Address Classes
  • Common PortsEach protocol in the TCP/IP suite thatoperates at the Process/Application layeruses a port number to identify informationit sends or receivesThe port number, when combined with thehosts IP address, is called a socket
  • Common Ports65,536 ports numbered from 0 to 65535Ports 0 through 1023 are called the well-known ports1024 through 49151 are called theregistered portsAnything from 49152 to 65535 is free to beused by application vendors
  • Common Ports
  • DHCP and DNS Both are run off a server and provide keyservices to network clients A DHCP server can be configured toautomatically provide IP configurationinformation to clients IP address Subnet mask Default gateway (the "door" to the outside world) DNS server address
  • DHCP and DNSDNS resolves hostnames to IPaddressesAllows your computer to get theaddress of the website you want andtraverse the Internet to find it
  • DHCP and DNSDNS works the same way on an intranetInstead of helping you find google.com, itmay help you find Jennys print server orJoes file server
  • Other ProtocolsThere probably arent any reasons whyyou would want to use a different protocolOnly knock on TCP/IP is that it can bemore difficult to configure than otherprotocolsOnly other protocol called out on the A+Essentials exam objectives is NetBIOS
  • NetBEUI/NetBIOSNetBIOS is an acronym formed fromnetwork basic input/output systemIs a Session layer network protocolProvides an interface with a consistent setof commands for requesting lower-levelnetwork services to transmit informationfrom node to node
  • NetBEUI/NetBIOS NetBEUI is an acronym formed from NetBIOSExtended User Interface An implementation and extension of IBMsNetBIOS transport protocol from Microsoft Shipped with all versions of Microsofts operatingsystems and is generally considered to have alot of overhead Has no networking layer and therefore no routingcapability
  • NetBEUI/NetBIOSThese protocols make up a very fast protocolsuite that most people call NetBEUI/NetBIOSGood for small LANsAllows users to find and use the networkservices they need easilyBecause it contains no Network layer protocol, itcannot be routed and thus cannot be used on aWAN
  • IPX/SPXDefault communication protocol for versions ofthe Novell NetWare operating system beforeNetWare 5A communication protocol similar to TCP/IPUsed primarily in LANsTwo main protocols in IPX/SPX are IPX and SPX SPX provides similar functions to TCP IPX provides functions similar to the TCP/IP suite protocols IP and UDP
  • IPX/SPX
  • AppleTalkNot just a protocol - it is a proprietary networkarchitecture for Macintosh computersUses a Carrier Sense Multiple Access withCollision Avoidance (CSMA/CA) technology toput data on the cableUnlike Ethernet, which uses a CSMA/CD method(where the CD stands for Collision Detection), ituses smart interface cards to detect trafficbefore it tries to send dataA CSMA/CA card listens to the wire
  • AppleTalkBig selling point of AppleTalk Simple and cheap Came installed on Macintosh computers Assigned itself an addressProblems Slow Limited in capacity Had to license it from AppleToday, TCP/IP is the default networking protocolon Macs
  • Network Interface Cards (NICs)Physical interface between computer andcablingPrepares, sends, and controls flow of dataConsiderations when choosing a NIC Preparing data Sending and controlling data Configuration Drivers Compatibility Performance
  • Preparing DataIn the computer, data moves along busesin parallelThe NIC translates the data from thecomputer into signals that can flow easilyalong the cableIt translates digital signals into electricalsignals (and in the case of fiber-optic NICs,to optical signals)
  • Sending and Controlling DataFor two computers to send and receive data, thecards must agree on several things Maximum size of the data frames Amount of data sent before giving confirmation Time needed between transmissions Amount of time to wait before sending confirmation Amount of data a card can hold Speed at which data transmits
  • Sending and Controlling DataTo successfully send data on the network,all NICs need to use the same mediaaccess methodIf you try to use cards of different typesneither of them would be able tocommunicate with the other unless youhad a separate hardware device betweenthem that could translate
  • Sending and Controlling DataNICs can send data using either full-duplex orhalf-duplex mode Half-duplex means that between the sender and receiver, only one can transmit at any one time In full-duplex communication, a computer can send and receive data simultaneously Main advantage of full-duplex over half-duplex communication is performance NICs can operate twice as fast (200Mbps) in full- duplex mode as they do normally in half-duplex mode (100Mbps)
  • NIC ConfigurationThe NICs configuration may include Manufacturers hardware address IRQ address Base I/O port address Base memory addressEach card must have a unique MAC addressIf two cards on the same network have the sameMAC address, neither one will be able tocommunicateIEEE has established a standard for hardwareaddresses
  • NIC DriversFor the computer to use the NIC, it is veryimportant to install the proper devicedriversDrivers communicate directly with thenetwork redirector and adapterOperate in the Media Access Controlsublayer of the Data Link layer of the OSImodel
  • PC Bus TypeChoose NIC that fits the bus type of yourPCIf you have more than one type of bus inyour PC use a NIC that fits into the fastesttypeMore and more computers are usingnetwork cards that have either PC Card orUSB interfaces
  • Network Interface Card PerformanceMost important goal of the networkadapter card is to optimize networkperformance and minimize the amount oftime needed to transfer data packetsacross the networkEnsure you get the fastest card you canfor the type of network youre on
  • Cabling and ConnectorsCable properly moves the data to itsintended destinationFour main types of cabling methods Coaxial cable Twisted-pair cable Fiber-optic cable Wireless
  • Coaxial
  • CoaxialAvailable in various specifications that arerated according to the RG Type systemDistance and cost are considerationswhen selecting coax cable The thicker the copper, the farther a signal can travel -- and with that comes a higher cost and a less-flexible cable
  • Coaxial
  • Coax Connector Types
  • Coax Connector Types
  • Twisted Pair
  • Twisted PairCategory 1: voice-only transmissions, two twisted pairsCategory 2: 4Mbps, four twisted pairsCategory 3: 10Mbps, four twisted pairsCategory 4: 16Mbps, four twisted pairsCategory 5: 100Mbps, four twisted pairs of copper wireCategory 5e: up to 1Gbps, four twisted pairs of copperwire, but they are physically separated and contain moretwists per foot than Category 5Category 6: up to 1Gbps and beyond, four twisted pairsof copper wire, and they are oriented differently than inCategory 5 or 5e
  • Twisted-Pair Connector Types
  • Twisted-Pair Connector Types
  • Fiber-Optic
  • Fiber-OpticReferred to as either single-mode or multimodefiberMode refers to the bundles of light that enter thefiber-optic cableSingle-mode Uses only a single mode of light to propagateMultimode Allows multiple modes of light to propagate Light bounces off the cable walls as it travels through the cable, which causes the signal to weaken more quickly
  • Fiber-OpticMultimode Most often used as horizontal cable Permits multiple modes of light to propagate through the cable, which shortens cable distances and delivers a less available bandwidth Devices that use multimode fiber-optic cable typically use light-emitting diodes (LEDs) Higher bandwidth network devices such as Gigabit Ethernet are now using lasers with multimode fiber-optic cable ANSI/TIA/EIA-568-B recognizes two-fiber (duplex) 62.5/125 micron multimode fiber; ANSI/TIA/EIA-568-B also recognizes 50/125 micron multimode fiber-optic cable
  • Fiber-OpticSingle-mode Used as backbone cabling and in phone systems Light travels straight down the fiber and does not bounce off the cable walls Supports higher bandwidth and longer distances Devices that use single-mode typically use lasers to generate the light that travels through the cable ANSI/TIA/EIA-568-B recognizes 62.5/125 micron, 50/125 micron, 8.3/125 micron single-mode optical fiber cables Maximum backbone distance using single-modeis 3,000 meters; maximum backbone distanceusing multimode is 2,000 meters
  • Fiber-Optic Connector Types
  • Fiber-Optic Connector Types
  • Wireless Networks Offer the ability to extend a LAN without the useof traditional cabling methods Transmissions are made through the air byinfrared light, laser light, narrow-band radio,microwave, or spread-spectrum radio Most often in environments where standardcabling methods are not possible or wanted Not as fast or efficient as standard cablingmethods More susceptible to eavesdropping andinterference than standard cabling methods
  • Networking ComponentsConnectivity devices Allow communications to break the boundaries of local networks Let your computers talk to other computers in the next building, the next city, or the next country
  • Networking ComponentsThere are several categories of connectivitydevices Repeaters Hubs Switches Bridges RoutersMake it possible to lengthen networks to almostunlimited distances
  • RepeatersAllow a cabling system to extend beyond itsmaximum allowed length by amplifying thenetwork voltagesVery inexpensiveOperate at the Physical layer of the OSI modelOnly used to regenerate signals between similarnetwork segmentsMain disadvantage is that they just amplifysignals Not only network signals but any noise on the wire Used only as a temporary fix
  • HubsUsed to link several computers togetherMost often used on Ethernet networksJust multiport repeaters and work at Layer1 of the OSI model just as repeaters doRepeat any signal that comes in on oneport and copy it to the other ports (aprocess that is also called broadcasting)
  • HubsTwo types of hubs Passive Hubs  Connect all ports together electrically  Do not have their own power source Active hubs  Use electronics to amplify and clean up the signal before it is broadcast to the other ports  Includes a class called intelligent hubs, which can be remotely managed on the network
  • Switches Provide centralized connectivity just as hubs do(usually on twisted-pair Ethernet networks); oftenlook similar, so its easy to confuse them Switches examine the Layer 2 header of theincoming packet and forward it properly to theright port and only that port Greatly reduces overhead and thus performanceas there is essentially a virtual connectionbetween sender and receiver
  • Indicator LightsNearly every hub or switch has one or morestatus indicator lights If there is a connection to that port of the switch, a light will light up If traffic is crossing the port, the light may flash, or there may be a secondary light Many devices can also detect a problem in theconnection Bridges and routers will also have similar statuslights on them, as do network cards
  • BridgesOperate in the Data Link layer of the OSI modelJoin similar topologies and used to divide networksegmentsKeep traffic on one side from crossing to the otherOften used to increase performance on a high-trafficsegmentNot able to distinguish one protocol from another,because higher levels of the OSI model are not availableto themIf a bridge is aware of the destination MAC address, itcan forward packets; otherwise, it forwards the packets toall segments
  • BridgesMore intelligent than repeatersUnable to move data across multiplenetworks simultaneouslyMain disadvantage is that they forwardbroadcast packets Broadcasts are addressed to all computers, so the bridge just does its job and forwards the packets Cannot perform intelligent path selection
  • RoutersHighly intelligent devices that connect multiple networktypesRoute packets across multiple networksUse routing tables to store network addressesOperate at the Network layer of the OSI modelCan determine the best path for data to take to get to itsdestinationLike bridges, they can segment large networksSlower than bridges because they analyze every packetMore expensive
  • RoutersNormally used to connect one LAN toanotherTypically, when a WAN is set up, at leasttwo routers are usedWireless routers have become all the ragefor small and home networks Possess all of the functionality of routers historically associated with networking, but they are relatively inexpensive
  • Wired Networks A network where you are using a cable to pluginto a socket in the wall or a connectivity deviceon your table Historically, using wires was the only way toconnect several machines together Today, wired options are becoming few and farbetween Two broad categories of choices to get online Dial-up Broadband
  • Dial-upOne of the oldest ways of communicating withISPs and remote networksNot used much anymore due to limitations onmodem speed, which top out at 56KbpsCannot compare to speeds possible with DSLand cable modemsDial-up Internet connections dropped from 74percent in 2000 to 15 percent in 2008 Most of the people who still use dial-up do it because its cheaper than broadband or high-speed isnt available where they live
  • Dial-upBiggest advantage to dial-up is that itscheap and relatively easy to configureCompanies can grant users dial-up accessto their networksISPs and RAS servers would use the DataLink layer Point-to-Point Protocol (PPP) toestablish and maintain the connection
  • BroadbandA connection that is capable oftransmitting multiple pieces of datasimultaneously in order to achieve higherdata ratesThe opposite of broadband is basebandSeveral different types of broadbandInternet access are available, includingDSL, Cable, fiber-optic, and satellite
  • DSL
  • DSL There are several different forms of DSL,including High bit-rate DSL (HDSL) Symmetric DSL (SDSL) Very high bit-rate DSL (VDSL) Rate-adaptive DSL (RADSL) Asymmetric DSL (ADSL)The most popular in home use is ADSL Its asymmetrical because it supports faster download speeds than upload speeds
  • DSL
  • DSL First ADSL standard was approved in 1998 andoffered maximum download speeds of 8Mbpsand upload speeds of 1Mbps The newest standard supports speeds up to24Mbps download and 3.5Mbps upload Most ADSL communications are full-duplex One major advantage that ADSL providers toutis that with DSL you do not share bandwidth withother customers
  • Cable ModemProvides high-speed Internet access throughyour cable serviceYou plug your computer into the cable modemusing a standard Ethernet cableIn theory, cable Internet connections are fasterthan DSL connections Download speeds up to 30Mbps or 50Mbps and uploads of 5Mbps A caveat to these speeds is that they are not guaranteed and they can vary
  • Cable ModemSpeeds vary because you are sharingavailable bandwidth within your distributionnetworkSize of the network is usually between 100and 2,000 customersAccess can be slower during peak usagetimes
  • Cable ModemA simplified example Two users are sharing a connection that has a maximum capacity of 40Mbps Each person gets 20Mbps of bandwidth One user gets a boost that allows her to download 30Mbps The other user is left with 10Mbps of available bandwidth
  • Cable ModemIn practice, the speeds of a cable modem arepretty comparable to those of DSLBoth have pros and cons when it comes toreliability and speed of serviceA lot varies by service provider and isntnecessarily reflective of the technologyThe choice you make between DSL and cablemay depend on which company you get the bestpackage deal from
  • Fiber-Optic CableUsed mostly for high-speedtelecommunications and networkbackbonesMuch more expensive than copper toinstall and operateSome phone and media companies arenow offering fiber-optic Internetconnections for home subscribers
  • Fiber-Optic CableFiber-to-the-Home (FTTH) service As of the time of this writing, the fastest speeds offered are 50Mbps download and 20Mbps upload FTTH is capable of reaching speeds of 100Mbps, and 400Mbps implementations are being plannedFiber-to-the-Node (FTTN) Runs fiber to the phone or cable companys utility box near the street and then runs copper from there to your house Maximum speeds for this type of service are around 25Mbps
  • SatelliteTransmits signals through the air to you as opposed tousing a cableService provider beams a microwave signal from a dishon the ground to an orbiting satellite, which in turn sendsthe signal back down to your receiverReceivers are typically small satellite dishes but can alsobe portable satellite modems or portable satellite phonesCalled point-to-multipoint because one satellite canprovide a signal to a number of receiversUsed in a variety of applications fromtelecommunications to handheld GPSs to television andradio broadcasts
  • SatelliteConsiderations to keep in mind regardingsatellite Installation can be tricky Line of sight is required
  • SatelliteMore considerations Latency can be a problem Connections are pretty slow
  • Wireless NetworksAs a technician, you must make sure thattheir computers can connectFour methods of wireless communication 802.11x Bluetooth Cellular Infrared
  • 802.11xWLAN standards are created and managed bythe IEEEMost commonly used WLAN standards usedtoday are in the IEEE 802.11x familyIEEE 802.11 was ratified in 1997, and was thefirst standardized WLAN implementationOver twenty 802.11 standards defined, but youwill only see a few in common operation:802.11a, b, and gAmong all of the wireless technologies covered,802.11 is the one best suited for WLANs
  • 802.11x NetworksJust like an Ethernet network, only wirelessAt the center of the network is a connectivitydevice such as a hub or a router, and allcomputers connect to itIn order to connect to the wireless hub or router,the client needs to know the SSID of the deviceWireless access points eventually connect backto a wired connection with the rest of the network
  • 802.11x Technical Specifications802.11x networks use the CSMA/CAaccess method Similar to that of shared Ethernet Packet collisions are generally avoided If they do happen, the sender waits a random period of time (called a back-off time) before transmitting again
  • 802.11x Technical Specifications802.11 Defines WLANs transmitting at 1Mbps or 2Mbps bandwidths using the 2.4GHz frequency spectrum Uses FHSS or DSSS for data encoding802.11a Provides WLAN bandwidth of up to 54Mbps in the 5GHz frequency spectrum Uses OFDM, rather than FHSS or DSSS Never gained widespread popularity because 802.11b devices were significantly cheaper and its highly susceptible to external interference
  • 802.11x Technical Specifications802.11b Provides for bandwidths of up to 11Mbps in the 2.4GHz frequency spectrum Also called WiFi or 802.11 high rate Uses DSSS for data802.11g Provides for bandwidths of 54Mbps+ in the 2.4GHz frequency spectrum Uses OFDM encoding Is backward compatible with 802.11bSome devices marked as 802.11b/g that can run oneither network, and can be commingled on the samenetwork
  • 802.11x Technical SpecificationsInteroperability concerns Not capable of understanding OFDM transmissions To counteract this problem, uses an additional signaling mechanism RTS/CTS to provide backward compatibility  The client must first send an RTS signal to the access point  Once the access point sends a CTS back to the client, the client can transmit  Other clients interpret the CTS signal, they interpret it as a "do not send" message and wait for an all-clear to send
  • 802.11x Technical SpecificationsMore interoperability concerns When operating in mixed mode, 802.11g will use the less-efficient 802.11b back-off timing Slows down the throughput of the 802.11g access pointThe pros of 802.11g/b backwardcompatibility still far outweigh the cons
  • 802.11x Technical Specifications802.11n At the time of this writing, still in development Provides bandwidths from 54Mbps to 600Mbps, but more realistic to expect maximum throughput in the 300Mbps range Achieves faster throughput a couple of ways  MIMO  Channel bonding  SDM technologies
  • 802.11x Technical Specifications802.11n is backward compatible with802.11a/b/g802.11n hardware is on the market today,but as the standard is still not official thesedevices are called "pre-N" devices May have compatibility issues between different vendors pre-N products
  • 802.11x Technical Specifications
  • 802.11x Technical SpecificationsSignal modulation techniques used in the802.11 standards Direct-Sequence Spread Spectrum (DSSS) Frequency-Hopping Spread Spectrum (FHSS) Orthogonal Frequency Division Multiplexing (OFDM)
  • 802.11x Devices
  • 802.11x SecurityThe growth of wireless systems hascreated several opportunities for attackersUsing SSID configurations doesntnecessarily prevent wireless networks frombeing compromised
  • WEPA security standard for wireless devicesEncrypts data to provide data securityHas always been under scrutiny for notbeing as secure as initially intended
  • WEPVulnerable due to weaknesses in theencryption algorithmsThis makes WEP one of the morevulnerable protocols available for security
  • WPAAn improvement on WEP that wasdeveloped in 2003Implements some of the standards definedin the IEEE 802.11i specificationImprovement over WPA is WPA2, whichimplements the full 802.11i standard
  • MAC FilteringCan be used on a wireless network toprevent certain clients from accessing thenetwork You tell your wireless router to only allow access to certain MAC addresses Your router will allow you to deny service to a set list of MAC addresses (and allow all others) or allow service only to a set of MAC addresses (and deny all others)
  • BluetoothMakers of Bluetooth were trying to unitedisparate technology industriesFirst Bluetooth device arrived on the scene in2000By 2002, there were over 500 Bluetooth certifiedproductsAs of 2005 over 5 million Bluetooth chipsetsshipped each weekCurrent Bluetooth specification is Version 2.1+Enhanced Data Rate
  • Bluetooth Networks"Bluetooth wireless technology is a short-rangecommunications technology intended to replace thecables connecting portable and/or fixed devices whilemaintaining high levels of security."Operates at low power and low cost and can handlesimultaneous voice and data transmissionsOne of the unusual features of Bluetooth networks istheir temporary nature This dynamically created network is called a piconet A Bluetooth-enabled device can communicate with up to seven other devices in one piconet
  • Bluetooth NetworksWithin the piconet, one device is the master andthe other seven devices are slaves Communication can occur only between the master and a slave Role of master rotates quickly among the devices in a round-robin fashion All devices in a piconet can communicate with each other directly Current Bluetooth specifications allow for connecting two or more piconets together in a scatternet
  • Bluetooth Technical Specifications Version 1.2 Adopted in November 2003 Supports data transmissions of up to 1MbpsVersion 2.0+ Enhanced Data Rate (EDR) Adopted in November 2004 Supports data rates up to 3MbpsVersion 2.1+EDR Adopted in July 2007 Supports data rates up to 3MbpsAll standards transmit in the 2.4-2.485GHz range
  • Bluetooth Technical Specifications
  • Bluetooth DevicesThe first device was a wireless headset for a cellphoneBluetooth-enabled computer peripherals include Keyboards and mice Printers Digital cameras MP3 players PDAs and handheld computers Cars
  • Bluetooth Devices
  • Bluetooth Devices
  • InfraredLonger than light waves but shorter thanmicrowavesMost common use of infrared technologyis the television remote control"Walk-up" and "point-to-point" You need to be at very close range Designed for one-to-one communication Requires line of sight
  • Infrared
  • Infrared NetworksA point-to-point network between twodevicesNo master or slaveNo hub-type device requiredPoint one infrared-enabled device atanother and transmit
  • Infrared Technical SpecificationsCurrent IrDA specifications allow transmission ofdata up to 16Mbps and IrDA claims that100Mbps and 500Mbps standards are on thehorizonNo concerns of interference or signal conflictsAtmospheric conditions can play a role indisrupting infrared wavesSecurity is not an issue Data is directional, and you choose when and where to send it
  • Infrared DevicesMiceKeyboardsPrintersKeyboards for PDAsPDAsCell phonesRemote control
  • Cellular (Cellular WAN)Industry has revolutionized the way wecommunicatePrimarily been developing in the realm ofsmall handheld communications devices(phones and the BlackBerrys)Converging technologies -- cell phonesand computers
  • Cellular NetworksVery complex behind the scenesCell communications require the use of acentral access point, generally a cell tower,which is connected to a main hubVery large mesh networks with extensiverange
  • Cellular Technical SpecificationsTwo major cell standards in the United States:GSM and CDMA Not compatible with each otherGSM uses a variety of bands to transmit Most popular are 900MHz and 1800MHz 400, 450, and 850MHz are also usedGSM splits up its channels by time division, in aprocess called Time Division Multiple Access(TDMA)
  • Cellular Technical SpecificationsMaximum rate for GSM is about 270 kilobits persecond (Kbps)Maximum functional distance of GSM is about 22miles (35 kilometers)For security, GSM uses the A5/1 and A5/2stream ciphersNewer enhancement to GSM is called GeneralPacket Radio Service (GPRS) Designed to provide data transmissions over a GSM network at up to 171Kbps
  • Cellular Technical Specifications CDMA is considered a superior technology to GSM Doesnt break up its channels by time but rather by acode inserted into the communicated message Transmissions to occur at the same time withoutinterference Used in GPSs CDMA supports download rates of over 3Mbps, withupload speeds of nearly 2Mbps Works in ranges up to 100 kilometers Newer takeoffs of the CDMA technology include W-CDMA, CDMA2000, and EVDO
  • Cellular DevicesFurther developed in the phone industrythan the computer industryCell phones and BlackBerrys are the mostcommon cellular-equipped devicesCellular modems are widely available forlaptops, most of them with a PC Cardinterface
  • Virtual Private Networks (VPNs)Not necessarily wired or wirelessNot a LAN or a WAN but rather somethingin betweenMakes computers that are on oppositesides of a WAN link think they are on thesame safe and secure LAN with eachotherThe key word for VPNs really is security
  • Virtual Private Networks (VPNs)Device that provides VPN service is calleda VPN concentrator Create virtual private networks for users logging in using remote access or for a large site-to-site VPNVPNs provide higher data throughput andauthentication and encryption options