Chapter 3

Data Transmission and Networking Media

Network+ Guide to Networks, 4e*ObjectivesExplain basic data transmission concepts, including full duplexing, attenuation, and noiseDescribe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic mediaCompare the benefits and limitations of different networking mediaIdentify the best practices for cabling buildings and work areasSpecify the characteristics of popular wireless transmission methods, including 802.11, infrared, and Bluetooth

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Physical characteristic cableCoaxial Cable(Shielded Twisted Pair) STP Cable.(Unshielded Twisted Pair) UTP Cable.Fiber Optic

Network+ Guide to Networks, 4e*Coaxial CableHigh resistance to noise; expensiveImpedance: resistance that contributes to controlling signal (expressed in ohms)Thickwire Ethernet (Thicknet): original Ethernet medium10BASE-5 EthernetThin Ethernet (Thinnet): more flexible and easier to handle and install than Thicknet10BASE-2 Ethernet

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Coaxial Cable

Network+ Guide to Networks, 4e*Twisted-Pair CableColor-coded pairs of insulated copper wires twisted togetherTwist ratio: twists per meter or footHigher twist ratio reduces crosstalk and increases attenuationTIA/EIA 568 standard divides twisted-pair wiring into several categoriesLevel 1 or CAT 3, 4, 5, 5e, 6, 6e, 7Most common form of cabling found on LANs today

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Network+ Guide to Networks, 4e*STP (Shielded Twisted-Pair)Figure 3-18: STP cable

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Network+ Guide to Networks, 4e*UTP (Unshielded Twisted-Pair)Less expensive, less resistant to noise than STPCategories:CAT 3 (Category 3): up to 10 Mbps of dataCAT 4 (Category 4): 16 Mbps throughputCAT 5 (Category 5): up to 1000 Mbps throughputCAT 5e (Enhanced Category 5): higher twist ratioCAT 6 (Category 6): six times the throughput of CAT 5CAT 6e (Enhanced Category 6): reduced attenuation and crosstalkCAT 7 (Category 7): signal rates up to 1 GHz

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UTPJacketTwisted pair

Network+ Guide to Networks, 4e*Comparing STP and UTPThroughput: STP and UTP can both transmit data at 10, 100, and 1000 Mbps Depending on grade of cabling and transmission method usedCost: STP usually more expensive than UTPConnector: Both use RJ-45 and RJ-11Noise Immunity: STP more noise-resistantSize and scalability: Max segment length for both is 100 m on 10BASE-T and 100BASE-T networksMaximum of 1024 nodes

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Network+ Guide to Networks, 4e*10BASE-TFault tolerance: capacity for component or system to continue functioning despite damage or partial malfunction5-4-3 rule of networking: between two communicating nodes, network cannot contain more than five network segments connected by four repeating devices, and no more than three of the segments may be populated

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Network+ Guide to Networks, 4e*100BASE-T (Fast Ethernet)Figure 3-23: A 100BASE-T network

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Network+ Guide to Networks, 4e*Fiber-Optic CableContains glass or plastic fibers at core surrounded by layer of glass or plastic claddingReflects light back to coreFigure 3-24: A fiber-optic cable

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Network+ Guide to Networks, 4e*SMF (Single-mode Fiber)Narrow core through which laser-generated light travels over one path, reflecting very littleAccommodates high bandwidths and long distancesExpensive

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Network+ Guide to Networks, 4e*MMF (Multimode Fiber)Benefits over copper cabling:Nearly unlimited throughputVery high resistance to noiseExcellent securityAbility to carry signals for much longer distances before requiring repeaters than copper cableIndustry standard for high-speed networking

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Network+ Guide to Networks, 4e*MMF (continued)Throughput: transmission rates exceed 10 Gigabits per secondCost: most expensive transmission mediumConnector: 10 different types of connectorsTypically use ST or SC connectorsNoise immunity: unaffected by EMISize and scalability: segment lengths vary from 150 to 40,000 metersOptical loss: degradation of light signal after it travels a certain distance away from its source

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Network+ Guide to Networks, 4e*Summary of Physical Layer StandardsTable 3-2: Physical layer networking standards

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Network+ Guide to Networks, 4e*Summary of Physical Layer Standards (continued)Table 3-2 (continued): Physical layer networking standards

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Network+ Guide to Networks, 4e*ThroughputProbably most significant factor in choosing transmission methodLimited by signaling and multiplexing techniques used in given transmission methodTransmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connectionsNoise and devices connected to transmission medium can limit throughput

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Network+ Guide to Networks, 4e*Noise ImmunitySome types of media are more susceptible to noise than othersFiber-optic cable least susceptibleInstall cabling away from powerful electromagnetic forcesMay need to use metal conduit to contain and protect cablingPossible to use antinoise algorithms

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Network+ Guide to Networks, 4e*Size and Scalability Three specifications determine size and scalability of networking media: Maximum nodes per segmentDepends on attenuation and latencyMaximum segment lengthDepends on attenuation, latency, and segment typePopulated segment contains end nodesMaximum network lengthSum of networks segment lengths

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Network+ Guide to Networks, 4e*CostMany variables can influence final cost of implementing specific type of media:Cost of installationCost of new infrastructure versus reusing existing infrastructureCost of maintenance and supportCost of a lower transmission rate affecting productivityCost of obsolescence

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Network+ Guide to Networks, 4e*Wireless TransmissionNetworks that transmit signals through the atmosphere via infrared or RF waves are known as wireless networks or wireless LANs (WLANs)

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Network+ Guide to Networks, 4e*The Wireless SpectrumFigure 3-37: The wireless spectrum

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Network+ Guide to Networks, 4e*Characteristics of Wireless TransmissionFigure 3-38: Wireless transmission and reception

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Network+ Guide to Networks, 4e*AntennasRadiation pattern describes relative strength over three-dimensional area of all electromagnetic energy the antenna sends or receivesDirectional antenna issues wireless signals along a single directionOmnidirectional antenna issues and receives wireless signals with equal strength and clarity in all directionsRange: geographical area an antenna or wireless system can reach

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Network+ Guide to Networks, 4e*Signal PropagationFigure 3-39: Multipath signal propagation

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Network+ Guide to Networks, 4e*Signal DegradationFading: change in signal strength resulting from electromagnetic energy being scattered, reflected, or diffracted after being issued by transmitterWireless signals experience attenuationMay be amplified and repeatedInterference is significant problem for wireless communications Atmosphere saturated with electromagnetic waves

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Network+ Guide to Networks, 4e*Narrowband, Broadband, and Spread Spectrum SignalsNarrowband: transmitter concentrates signal energy at single frequency or in very small range of frequenciesBroadband: uses relatively wide band of wireless spectrumOffers higher throughputsSpread spectrum: use of multiple frequencies to transmit a signalFrequency hopping spread spectrum (FHSS)Direct sequence spread spectrum (DSSS)

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Network+ Guide to Networks, 4e*Fixed versus MobileFixed wireless system: locations of transmitter and receiver do not movePoint-to-point linkEfficient use of signal energyMobile wireless system: receiver can be located anywhere within transmitters rangeMore flexible

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Network+ Guide to Networks, 4e*Infrared TransmissionTransmitted by frequencies in the 300-GHz to 300,000-GHz rangeMost often used for communications between devices in same roomRelies on the devices being close to each otherMay require line-of-sight pathThroughput rivals fiber-optics

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Network+ Guide to Networks, 4e*Wireless LAN (WLAN) ArchitectureFigure 3-40: An ad-hoc WLAN

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Network+ Guide to Networks, 4e*Wireless LAN Architecture (continued)Figure 3-41: An infrastructure WLAN

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Network+ Guide to Networks, 4e*Wireless LAN Architecture (continued)Figure 3-42: Wireless LAN interconnection

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Network+ Guide to Networks, 4e*Connectors and Media ConvertersConnectors: pieces of hardware connecting wire to network deviceEvery networking medium requires specific kind of connectorMedia converter: hardware enabling networks or segments running on different media to interconnect and exchange signalsType of transceiverDevice that transmits and receives signals

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Network+ Guide to Networks, 4e*Cable Design and ManagementCable plant: hardware making up enterprise-wide cabling systemStructured cabling: TIA/EIAs 568 Commercial Building Wiring StandardEntrance facilities point where buildings internal cabling plant beginsDemarcation point: division between service carriers network and internal networkBackbone wiring: interconnection between telecommunications closets, equipment rooms, and entrance facilities

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Network+ Guide to Networks, 4e*Cable Design and Management (continued)Structured cabling (continued):Equipment room: location of significant networking hardware, such as servers and mainframe hostsTelecommunications closet: contains connectivity for groups of workstations in area, plus cross connections to equipment roomsHorizontal wiring: wiring connecting workstations to closest telecommunications closetWork area: encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet

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Network+ Guide to Networks, 4e*Installing CableMany network problems can be traced to poor cable installation techniquesTwo methods of inserting UTP twisted pairs into RJ-45 plugs: TIA/EIA 568A and TIA/EIA 568BStraight-through cable allows signals to pass straight through between terminationsCrossover cable: termination locations of transmit and receive wires on one end of cable reversed

Network+ Guide to Networks, 4e

ISP (Internet Service Provider)An Internet service provider (ISP), also sometimes referred to as an Internet access provider (IAP), is acompany that offers its customers access to theInternet. The ISP connects to its customers using adata transmission technology appropriate fordelivering Internet Protocol Paradigm, such as dial-up, DSL, cable modem, wireless or dedicatedhigh-speed interconnects

Relationship between ISP and internetISP Internet Service Provider (telephone, cable or wireless) creates the medium/link under whichhomeowners, businesses or almost any entity canconnect the world wide web (Internet), by configuringcomputing equipment that can send and receivedifferent types of queries (send) and data/web pages(receive).

Options of ConnectionISPs employ a range of technologies to enableconsumers to connect to their network. For users andsmall businesses, the most popular options includedial-up, DSL (typically Asymmetric Digital SubscriberLine, ADSL), broadband wireless, cable modem, fiberto the premises (FTTH), and Integrated Services Digital Network (ISDN) (typically basic rate interface).

Options of ConnectionFor customers with more demanding requirements,such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and synchronous optical networking (SONET) are morelikely to be used.

ISP level of serviceMulti-Service Providers like AOL or MSN premium - services that provide you not only with connectivity, but with their own software and premium content. In the past they've provided dialup, and now also often partner with some of the companies below to provide broadband connectivity as well.Telephone Companies like Qwest, Verizon, BellSouth and the like. Since these folks provide you the phone line into your home, they've been quick to offer ISP services in support of their DSL offering that uses those phone lines.Cable, Satellite and Cellular Companies like Comcast, HughesNet, Verizon Wireless and many others. These companies all provide the physical connectivity over cable, satellite or your cellular phone. In these cases they also act as your ISP for this connection.National ISPs like Earthlink or PeoplePC. Once again, these folks offer dialup, and conveniently nationwide, but can also provide you with the ISP services for your DSL broadband as well.Regional ISPs exist in many communities, and are often a great value. They operate in many ways like the larger national ISPs, but within a more limited region

Every computer that is connected to the Internet is part of a network, even the one in your home. For example, you may use a modem and dial a local number to connect to an Internet Service Provider (ISP). At work, you may be part of a local area network (LAN), but you most likely still connect to the Internet using an ISP that your company has contracted with. When you connect to your ISP, you become part of their network. The ISP may then connect to a larger network and become part of their network. The Internet is simply a network of networks.Most large communications companies have their own dedicated backbones connecting various regions. In each region, the company has a Point of Presence (POP). The POP is a place for local users to access the company's network, often through a local phone number or dedicated line. The amazing thing here is that there is no overall controlling network. Instead, there are several high-level networks connecting to each other through Network Access Points or NAPs.

Importance of Internet Protocol(IP)The Internet shares its name with the Internet Protocol as both are based on the interconnection of individual networks. IP has the responsibility of addressing packets to be transmitted across a network or across the Internet. This means that every location on the Internet is identified by an IP address. Private networks use the same format of addressing. It is the IP address that gives the Internet Protocol its importance

Importance of Internet Protocol(IP)The importance of IP addresses is illustrated by the problems envisaged by the number of available addresses running out. A project to create a new standard for IP addresses is called IP version 6. The difficulty of changing the system is that it will create a large amount of disruption to the world's communication system

Before being sent on the Internet, messages are divided into packets. When a packet is sent across the Internet, the ISP determines whether the packet is destined for a local service located on the ISP network, or a remote service located on a different network

ISP handles packet

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