Physical Transmission Options

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Physical Transmission Options

• Chapter 3

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Learning Objectives

• Describe the functions of the principal
  networking standards organizations
• Describe the various kinds of network media,
  including coaxial, twisted-pair, and fiber-optic
  media, and identify which to use in a given
  network configuration
• Describe the basics of wireless communications

continued
3
Learning Objectives

• Discuss 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
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ANSI

• Established in 1918
• Standards for wide range of products
• Computer industry standards
• Screen-display attributes
• Digital telecommunications
• Fiber-optic cable transmissions

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IEEE

• International organization of scientists,
  engineers, technicians, and educators
• Develops networking standards for network cabling
  and data transmissions
• 802 standards

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ITU

• Sets telecommunications standards for modem and
  WAN communications
• International organization

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ISO

• Establishes communications and networking
  standards
• Known for its contributions to network protocol
  standards
• International organization

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ISOC and IETF

• ISOC
• Sponsors conferences and publications and
  oversees Internet standards
• Nonprofit international organization
• Supporter of Internet Corporation for Assigned
  Names and Numbers (ICANN)
• IETF
• Arm of ISOC that works on Internet-related
  technical issues such as routing

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EIA and TIA

• EIA
• Network cabling standards and electrical
  interface standards
• TIA
• Standards body within EIA that develops
  telecommunications and cabling standards
• Structured wiring, horizontal cabling, backbone
  cabling
• Wiring closet configurations

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Physical Transmission Options for LANs and WANs

• Media types
• Interface types
• WAN carrier types

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Communications Media Types

• Coaxial cable
• Based on copper wire construction
• Twisted-pair cable
• Based on copper wire construction
• Fiber-optic cable
• Glass (usually), or plastic
• Wireless technologies
• Radio or microwaves

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Factors to Consider When Choosing a Medium

• Data transfer speed
• Use in specific network topologies
• Distance requirements
• Cable and cable component costs
• Additional network equipment that might be
  required
• Flexibility and ease of installation
• Immunity to interference from outside sources
• Upgrade options

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Coaxial Cable

• Copper core surrounded by insulation
• Insulation surrounded by another conducting
  material, which is covered by an outer insulating
  material
• Types
• Thick 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 Cable

• Attaches to a bayonet nut connector (BNC)

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Thin Coax Cable Properties
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Twisted-Pair Cable

• Flexible cable that contains pairs of insulated
  copper wires that are twisted together for
  reduction of EMI and RFI and covered with an
  outer insulating jacket
• Typically used on LANs to bring network to
  desktop
• Connects to network devices with RJ-45 plug-in
  connectors

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Twisted-Pair Cable
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Types of Twisted-Pair Cable

• Shielded 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) cable
• No shielding material between pairs of insulated
  wires twisted together and cables 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 Cable

• Glass 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 Cable

• Advantages
• Able to sustain transmissions over long distances
  due to high bandwidth and low attenuation
• No EMI or RFI problems
• Difficult to place unauthorized taps
• Disadvantages
• Very fragile
• Relatively expensive
• Requires specialized training to install

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Fiber-Optic Cable Modes

• Single-mode
• Multimode
• Step 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 Ethernet

• Ethernet communications at speeds up to 100 Mbps
  as defined under the
• 802.3u standard
• More commonly used
• Based on CSMA/CD
• 802.12 standard
• Uses 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 Ethernet

• Provides even faster network communications
• Particularly important for backbone architectures

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Gigabit Ethernet Specifications
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10 Gigabit Ethernet

• Positioned 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 Communications

• Transmit 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 available
• Radio waves and infrared signals (short-distance)
• Microwave and satellite (long-distance)

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Data Interface Types

• Data is transported on networks in packets or
  cells
• Each type of transport requires specialized
  interfaces for physical network connections

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Packet Transmission

• Used at lower bandwidth installations
• Most commonly used to carry data on LANs
• Requires transceivers, appropriate cable
  interfaces, and network drivers
• Timing information for multiple packet transfers
• Packets 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 Format

• Format determined by protocol used on network

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Cell Transmission

• Used for very high-bandwidth implementations
• Enables high-speed communications between LANs
  and on WANs
• Requires transceivers, appropriate cable
  interfaces, and network drivers
• Cells contain fixed amount of data formatted to
  be transmitted at high speeds
• Primarily used in Asynchronous Transfer Mode (ATM)

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Generic Cell Format
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WAN Carrier Types

• Point-to-point
• T-carrier
• SONET (synchronous optical network)
• ISDN (Integrated Services Digital Network)

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Point-to-Point

• Two stations communicate through public dial-up
  or leased lines

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T-Carrier

• Normally 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-Carrier

• DS-x
• Relates to OSI Physical layer, which influences
  electrical transmission
• T-x
• Relates 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 Connections

• Digital 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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SONET

• Uses 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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ISDN

• WAN technology for delivering voice, data, and
  video services over telephone lines, using a
  combination of channels
• Physical line is a POTS or T-1 (twisted-pair or
  fiber-optic), with ISDN equipment at the telco
  and customer
• Methods of placing digital signals on network
• Time-compression multiplexing (TCM)
• Echo cancellation

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Chapter Summary

• Standards organizations that influence network
  transmission techniques and media
• Communications cabling media
• High-speed technologies
• Fast Ethernet
• Gigabit Ethernet
• 10 Gigabit Ethernet

continued
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Chapter Summary

• How data is transported by using packets and cell
  formats
• Specialized carrier methods
• Point-to-point
• T-carrier
• SONET
• ISDN
• Wireless transmission