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Physical Transmission Options

Chapter 3

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Learning ObjectivesDescribe the functions of the principal networking standards organizationsDescribe the various kinds of network media, including coaxial, twisted-pair, and fiber-optic media, and identify which to use in a given network configurationDescribe the basics of wireless communications

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Learning ObjectivesDiscuss high-speed technologies for twisted-pair and fiber-optic cable

Compare packet and cell implementations and the interfaces used by each

Explain WAN carrier types for point-to-point, T-carrier, SONET, ISDN, and wireless topologies

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Network Standards Organizations

Help ensure that equipment from different manufacturers can be integrated

Key role in growth of networks and network equipment

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Network Standards Organizations

ANSI American National Standards Institute

IEEE Institute of Electrical and Electronics Engineers

ITU International Telecommunications Union

ISO International Organization for Standardization

ISOC Internet Society

IETF Internet Society and the Internet Engineering Task Force

EIA/TIA Electronic Industries Alliance and the Telecommunications Industry Association

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ANSIEstablished in 1918

Standards for wide range of products

Computer industry standards:Screen-display attributes

Digital telecommunications

Fiber-optic cable transmissions

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IEEEInternational organization of scientists, engineers, technicians, and educators

Develops networking standards for network cabling and data transmissions

802 standards

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ITUSets telecommunications standards for modem and WAN communications

International organization

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ISOEstablishes communications and networking standards

Known for its contributions to network protocol standards

International organization

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ISOC and IETFISOC

Sponsors conferences and publications and oversees Internet standardsNonprofit international organizationSupporter of Internet Corporation for Assigned Names and Numbers (ICANN)

IETFArm of ISOC that works on Internet-related technical issues such as routing

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EIA and TIAEIA

Network cabling standards and electrical interface standards

TIAStandards body within EIA that develops telecommunications and cabling standards

Structured wiring, horizontal cabling, backbone cablingWiring closet configurations

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Physical Transmission Options for LANs and WANsMedia types

Interface types

WAN carrier types

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Communications Media TypesCoaxial cable

Based on copper wire construction

Twisted-pair cableBased on copper wire construction

Fiber-optic cableGlass (usually), or plastic

Wireless technologiesRadio or microwaves

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Factors to Consider When Choosing a Medium

Data transfer speedUse in specific network topologiesDistance requirementsCable and cable component costsAdditional network equipment that might be requiredFlexibility and ease of installationImmunity to interference from outside sourcesUpgrade options

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Coaxial CableCopper core surrounded by insulation

Insulation surrounded by another conducting material, which is covered by an outer insulating material

TypesThick coax cable (thickwire or thicknet)

Thin coax cable

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Thick Coax Cable

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Connecting to Thick Coax Cable

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Thick Coax Cable Properties

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Thin Coax CableAttaches to a bayonet nut connector (BNC)

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Thin Coax Cable Properties

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Twisted-Pair CableFlexible cable that contains pairs of insulated copper wires that are twisted together for reduction of EMI and RFI and covered with an outer insulating jacketTypically used on LANs to bring network to desktopConnects to network devices with RJ-45 plug-in connectors

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Twisted-Pair Cable

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Types of Twisted-Pair CableShielded twisted-pair (STP) cable

Pairs of insulated wires that are twisted together, surrounded by shielding material for added EMI and RFI protection, all inside a protective jacket

Unshielded twisted-pair (UTP) cableNo shielding material between pairs of insulated wires twisted together and cable’s outside jacket

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STP and UTP Cable

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Twisted-Pair Cable Standards

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Twisted-Pair Cable Types for Token Ring Applications

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Properties ofTwisted-Pair Cable

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Properties ofTwisted-Pair Cable

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Token Ring Design Specs

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Fiber-Optic CableGlass or plastic fiber core inside protective cladding material, covered by plastic PVC outer jacket

Usually uses infrared light for signal transmission

Used to connect networks on LANsand to connect LANs into WANs

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Fiber-Optic CableAdvantages

Able to sustain transmissions over long distances due to high bandwidth and low attenuation

No EMI or RFI problems

Difficult to place unauthorized taps

DisadvantagesVery fragile

Relatively expensive

Requires specialized training to install

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Fiber-Optic Cable ModesSingle-mode

MultimodeStep index

Graded index

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Properties of Single-Mode Fiber-Optic Cable

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Properties of Multimode Fiber-Optic Cable

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Hybrid Fiber/Coax(HFC) Cables

Single cable sheath containing a combination of fibers and copper cables in different combinations for different implementations

Full HFC system can deliver:Plain Old Telephone Service (POTS)

Up to 37 analog TV channels

Up to 188 digital TV channels

Up to 464 digital point channels

High-speed, two-way digital data link for PCs

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High-Speed Technologies for Twisted-Pair and Fiber-Optic Cable

Fast Ethernet

Gigabit Ethernet

10 Gigabit Ethernet

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Fast EthernetEthernet communications at speeds up to 100 Mbps as defined under the:

802.3u standardMore commonly used

Based on CSMA/CD

802.12 standardUses demand priority

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The IEEE 802.3u Standard

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The IEEE 802.12 Standard

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Gigabit EthernetProvides even faster network communications

Particularly important for backbone architectures

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Gigabit Ethernet Specifications

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10 Gigabit EthernetPositioned to become popular LAN and WAN alternative; promises very high-speed communications

Does not use CSMA/CD as the transmission method

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10 Gigabit Ethernet Specifications

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Wireless CommunicationsTransmit signal through air or atmosphere

Good alternative when cable is not physically or economically feasible

Can experience interference from other signals using same media

Types availableRadio waves and infrared signals (short-distance)

Microwave and satellite (long-distance)

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Data Interface TypesData is transported on networks in packets or cells

Each type of transport requires specialized interfaces for physical network connections

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Packet TransmissionUsed at lower bandwidth installationsMost commonly used to carry data on LANsRequires transceivers, appropriate cable interfaces, and network driversTiming information for multiple packet transfersPackets are physically transported on a network via network interface card (NIC)Packets contain variable amount of data in multiples of eight bits

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Generic Packet FormatFormat determined by protocol used on network

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Cell TransmissionUsed for very high-bandwidth implementationsEnables high-speed communications between LANs and on WANsRequires transceivers, appropriate cable interfaces, and network driversCells contain fixed amount of data formatted to be transmitted at high speedsPrimarily used in Asynchronous Transfer Mode (ATM)

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Generic Cell Format

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WAN Carrier TypesPoint-to-point

T-carrier

SONET (synchronous optical network)

ISDN (Integrated Services Digital Network)

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Point-to-PointTwo stations communicate through public dial-up or leased lines

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T-CarrierNormally available through telecommunications carriers

Typically come out of channel banks at telecommunications company

Five types of channel banks: D-1 through D-4 and Digital Carrier Trunk

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T-CarrierDS-x

Relates to OSI Physical layer, which influences electrical transmission

T-xRelates to Data Link layer, which addresses protocol and data-formatting issues

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T-Carrier Switching Techniques

Time division multiple access (TDMA)

Combination of TDMA and statistical multiple access

Fast packet technology

Multiplexer

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T-Carrier ConnectionsDigital access cross-connects (DACS)

DS-1 (T-1) connectivity

Combined DS-0 or fractional connectivity

Single DS-0 channels

Combination channel service unit (CSU) and data service unit (DSU)

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Connecting with a CSU/DSU

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SONETUses single-mode and multimode fiber-optic cable and communications based on T-3 services

Allows for high-speed data transmission, enabling delivery of voice, data, and video

Converts electrical-based STS-x signal to optical-based signal (optical carrier or OC)

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SONET STS-1 Frame

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SONET STS-x and OC-x Transmission Rates

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ISDNWAN technology for delivering voice, data, and video services over telephone lines, using a combination of channelsPhysical line is a POTS or T-1 (twisted-pair or fiber-optic), with ISDN equipment at the telco and customerMethods of placing digital signals on network

Time-compression multiplexing (TCM)Echo cancellation

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Chapter SummaryStandards organizations that influence network transmission techniques and media

Communications cabling media

High-speed technologiesFast Ethernet

Gigabit Ethernet

10 Gigabit Ethernet

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Chapter SummaryHow data is transported by using packets and cell formatsSpecialized carrier methods

Point-to-pointT-carrierSONETISDNWireless transmission