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Networking Media (Tangible)Networking Media (Tangible)

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Define and understand technical terms related to cabling, including attenuation, crosstalk, shielding, and plenum

Identify three major types of both network cabling and wireless network technologies

Understand baseband and broadband transmission technologies and when to use each

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Learning Objectives

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Learning Objectives Decide what kinds of cabling and

connections are appropriate for particular network environments

Describe wireless transmission techniques used in LANs

Describe signaling technologies for mobile computing

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Network Cabling:Tangible Physical Media Provides a medium across which network

data can travel in the form of a physical signal, whether it is a type of electrical transmission or some sequence of light pulses

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Primary Cable Types Coaxial cable Twisted-pair (TP) cable

Unshielded (UTP) Shielded (STP)

Fiber-optic

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General Cable Characteristics

Bandwidth rating Number of bits that can be transferred per

second Maximum segment length

Signals weakens along with the distance they travel

Weakened signals should be restored Maximum number of segments per internetwork

Networks are subject to some kind of maximum tolerable delay, after which it’s assumed signals can no longer arrive

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General Cable Characteristics

Maximum number of devices per segment Each device insertion will typically cause

signal attenuation on a cable segment and this is called insertion loss

Interference susceptibility Each type of cable may be susceptible to other

signals that may be present in the environment, e.g., electromagnetic interference (EMI) or radio frequency interference (RFI)

We assume 4 levels of susceptibility, namely, none, low, moderate, and high

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General Cable Characteristics Connection hardware

Different cables are associated with different connectors

Cable grade The rate of a cable in transferring data Building and fire codes may require specific

cabling requirements such as the combustibility and toxicity of the sheath material of a cable, as well as the insulation that cover the cable

Plenum-rated cable is of low combustibility and it generates relatively nontoxic fumes when burned

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General Cable Characteristics Bend radius

Bending of cable of certain types is more prone to damage than others

Material costs Some cable is more expensive to build than

others Installation costs

Labor and auxiliary equipment can easily cost more than the cable when installing a network

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Primary Techniques for Sending Signals across a Cable Baseband transmission Broadband transmission

This has nothing to do with broadband and narrowband internet connections.

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Baseband Transmission Uses digital signals sent over a cable without

modulation Sends binary values (0s and 1s) as pulses of

different voltage levels (i.e., digital transmission)

Entire bandwidth of the cable is used to transmit a single data signal

Limits any single cable strand to half-duplex transmission

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Baseband Transmission Signal flow can be bi-directional Uses repeaters to restore the signal to its

original strength and quality before retransmitting it to another cable

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Broadband Transmission An analog transmission technique which may

use multiple communication channels simultaneously

Each data channel is represented by modulation on a particular frequency band, for which sending or receiving equipment must be tuned, like a TV set

Signal flow is one-way only; two channels are necessary for computers to send/receive data

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Broadband Transmission Primary approaches to supporting two-way

broadband communications Mid-split broadband Dual-cable broadband

Uses amplifiers to detect weak signals, strengthen those signals, and then rebroadcast them; noise may be amplified too

Offers higher bandwidths, but generally more expensive than baseband systems

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Coaxial Cable Uses a center

conductor – wrapped by an insulating layer, surrounded by a braided wire mesh and an outer jacket or sheath -- to carry high-bandwidth signals such as network traffic or broadcast television frequencies

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Coaxial Cable Uses shielding to increase the viability of the

signals that pass through a cable by absorbing stray electronic signals or fields

Less susceptible to interference and attenuation than twisted-pair cabling, but more so than fiber-optic

A connector must cap each end of the cable, and a terminator must screw into each end

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Types of Coaxial Cable for Ethernet Thin Ethernet (thinnet, thinwire, cheapernet,

10Base2) Thick Ethernet (thicknet, thickwire, 10Base5)

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Thinwire Ethernet Thin, flexible cable about 0.2” in diameter Easy to work with Relatively inexpensive to build or buy Well suited for small or constantly changing

networks Uses BNC T-connectors to attach directly to

networking devices and computers’ network adapter cards

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Thinwire Ethernet

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Radio Government (RG) Specifications Coaxial cable designation that reflects

coaxial cable’s original use as a conveyance for radio frequency data and signals

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Radio Government (RG) Specifications

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Thinwire Ethernet Cable

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Thickwire Ethernet Uses a rigid cable about 0.4” in diameter

(“frozen yellow garden hose”) Rarely used except as a backbone for a new

network installation (due to expense, large diameter, and lack of flexibility)

Uses a vampire tap to attach a device to the cable, which in turn attaches to a transceiver; transceiver attaches to a drop or transceiver cable that plugs into an attachment unit interface (AUI)

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Attaching to Thinwire Ethernet Cable

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Attaching to Thickwire Ethernet Cable

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Running Thickwire Cable

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Thickwire Ethernet Cable

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Coaxial Cable Characteristics Can handle moderate to serious bandwidth Supports intermediate to moderately long

cable runs Relatively affordable Resistant to interference; relatively safe from

electronic “eavesdropping”

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Twisted-pair Cable Consists of one or more pairs of insulated

strands of copper wire twisted around one another

Importance of twists Improve resistance to interference Limit the influence of crosstalk

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Types of TP Cable Unshielded twisted-pair (UTP)

Contains one or more pairs of insulated wires within an enclosing insulating sheath

Follows the ANSI/EIA/TIA 568 standard Prone to crosstalk

Shielded twisted-pair (STP) Encloses each pair of wires within a foil shield, as well

as within an enclosing insulating sheath Supports higher bandwidth over longer distances than

UTP Has no set of standards

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Types of TP Cable

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UTP cable (1/3) Most popular form of local area network cable UTP cables are classified to a number of categories

such that each of them is associated with a different specification which include its maximum data transmission speeds

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UTP cable (2/3) Category 6 UTP cable can support up to 1 gigabit per

second, with signaling rates up to 250 MHz; specification of category 7 UTP cable is being drafted

UTP is particularly prone to crosstalk and the shielding included with STP is designed specifically to alleviate the problem

Like STP, it employs RJ-45 telephone connectors to plug into computer network interfaces or other networked devices

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UTP cable (3/3) Keep cables run within 295 feet For more information and FAQs about UTP cable, see

http://www.lanshack.com/cat5e-tutorial.asp

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Twisted-pair Network Cabling Schemes Commonly employ RJ-45 telephone

connectors

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10BaseT’s Networking Characteristics

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Fiber-optic Cable Uses pulses of light sent along a light-

conducting fiber at the heart of the cable to transfer information

Sends data in one direction only; two cables are required to permit data exchange in both directions

Consists of a slender cylinder of glass fiber(s), called the core, surrounded by a concentric layer of cladding material and then by an outer sheath

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Fiber-optic Cable

Kevlar® is a kind of nylon that is used makes bullet-proof vest and puncture resistant bicycle tires.

(See http://www.psrc.usm.edu/macrog/fiberopt/of.htm for more information about what optic fibers are made of.)

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Primary Types of Fiber-optic Cables Single-mode cables

Include only one glass fiber at the core Cost more Work with laser-based emitters but span the

longest distances Multi-mode cables

Incorporate two or more glass fibers at the core

Cost less Work with light emitting diodes (LEDs) but

span shorter distances (< 2 km)

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Fiber-optic Cable Advantages Immune to interference Highly secure; eliminates possibility of

electronic eavesdropping Good medium for high-bandwidth, high-

speed, long-distance data transmissions

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Fiber-optic Cable Drawbacks High cost to install Difficult installation

Cable must be precisely polished on the cut ends Cables are sensitive to bending or shearing forces Sophisticated optical tests are needed to ensure

proper cable alignment to sensors and emitters Fiber-optic system's incompatibility with current

electronic hardware systems requires that communication hardware systems be somewhat retrofitted to the fiber-optic networks. Much of the speed that is gained through optical fiber transmission can be inhibited at the conversion points of a fiber-optic chain.

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Fiber-optic Cable Characteristics

Remark: The maximum bandwidth of an optical cable has been increased tremendously over years. Some can supportmore than 1 terabit per second.

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Fiber-optic Media Connectors Number of connector options for fiber-optic

media varies with the type of light-emitting source and light-detecting sensors being used ST (straight tip) SC (straight connection) MIC (medium interface connector) for FDDI SMA (subminiature type A)

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Reference Website for Fiber-optic Data Communications For more information about fiber-optic data

communications, visit http://www.lascomm.com/tutorial.htmSpecifically, read the section on wave division multiplexing.

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Cable Selection Criteria Bandwidth Budget Capacity (data, bandwidth) Environmental considerations Placement

Where will the cables run? Scope

Number of devices to be connected to the network

Span Distance that the network needs to span

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Comparison of General Cable Characteristics