Guide to Networking Essentials Fifth Edition Chapter 3

Guide to Networking Essentials Fifth Edition Chapter 3 Networking Media

Objectives • Identify general cabling characteristics applied to physical media • Describe the primary cable types used in networking • Identify the components in a structured cabling installation • Describe wireless transmission techniques used in LANs and WANs Guide to Networking Essentials, Fifth Edition 2

Network Cabling: Tangible Physical Media • The interface between a computer and the medium to which it attaches defines the translation from a computer’s native digital information into the form needed to send outgoing messages – Because all media must support the basic tasks of sending and receiving signals, you can view all networking media as doing the same thing; only the methods vary – You need to know the physical characteristics and limitations of each kind of network media so that you can make the best use of each type • Each has a unique design and usage, with associated cost, performance, and installation criteria Guide to Networking Essentials, Fifth Edition 3

General Cable Characteristics • The following characteristics apply network cabling: – – – – – Bandwidth rating Maximum segment length Maximum number of segments per internetwork Maximum number of devices per segment Interference susceptibility Connection hardware Cable grade Material costs Installation costs Guide to Networking Essentials, Fifth Edition 4

Baseband Broadband Transmission • Baseband transmission uses a digital encoding scheme at a single fixed frequency, where signals take the form of discrete pulses of electricity or light – Repeaters can be used to deal with “attenuation” • Broadband transmission systems use analog techniques to encode binary 1 s and 0 s across a continuous range of values – Multiple analog transmission channels can operate on a single broadband cable – Amplifiers can be used to deal with attenuation – Two primary approaches: mid-split and dual-cable Guide to Networking Essentials, Fifth Edition 5

The Importance of Bandwidth • The trend in networking is to offer more complex, comprehensive, and powerful services – These require much higher bandwidth • Users demand access to these applications and have increased their use of existing networked applications, consuming still more bandwidth • Technologists find ways to stretch bandwidth limits of existing technologies so that older, difficult-toreplace networking components can remain, yet support higher bandwidth than originally rated Guide to Networking Essentials, Fifth Edition 6

Primary Cable Types • All forms of cabling are similar, in that they provide a medium across which network information can travel in the form of a physical signal, whether electrical or light pulses • The primary cable types are: – Coaxial cable – Twisted-pair – Fiber-optic cable Guide to Networking Essentials, Fifth Edition 7

Coaxial Cable • Was the predominant form of network cabling • Shielding: protective layer(s) wrapped around cable to protect it from external interference • Less susceptible to interference and attenuation than twisted-pair, but more susceptible than fiber-optic Guide to Networking Essentials, Fifth Edition 8

Coaxial Cable (continued) Guide to Networking Essentials, Fifth Edition 9

The Use of Coaxial Cable for Ethernet • Ethernet’s beginnings are in coaxial cable – First, it was run on a very thick, rigid cable, usually yellow, referred to as thicknet (10 Base 5) – Later, a more manageable coaxial cable called thinnet (10 Base 2) was used • 10 Base 5 is an IEEE designation – 10 Mbps – Baseband – Maximum segment length is 500 meters Guide to Networking Essentials, Fifth Edition 10

Coaxial Cable in Cable Modem Applications • Coaxial cable in LANs has become obsolete • delivers cable television (CATV) to millions of homes nationwide is also being used for Internet access Guide to Networking Essentials, Fifth Edition 11

Coaxial Cable in Cable Modem Applications (continued) Guide to Networking Essentials, Fifth Edition 12

Other Coaxial Cable Types • Other applications for coax include ARCnet and computer terminal attachments to mainframes and minicomputers – Attached resource computing network (ARCnet) is an older networking technology developed at Data. Point Corporation in the late 1970 s • Supports a bandwidth of only 2. 5 Mbps • Implementations that use fiber-optic and twisted-pair cable are available but usually limited to specialized applications that require properties unique to ARCnet (e. g. , deterministic communication and low overhead) Guide to Networking Essentials, Fifth Edition 13

Twisted-Pair Cable Guide to Networking Essentials, Fifth Edition 14

Unshielded Twisted Pair (UTP) • 10 Base. T – Maximum length is 100 meters • UTP is now the most popular form of LAN cabling • The UTP cable used for networking usually includes one or more pairs of insulated wires • UTP specifications govern the number of twists per foot (or per meter), depending on the cable’s intended use • UTP is used for telephony, but requirements for networking uses differ from the telephony ones Guide to Networking Essentials, Fifth Edition 15

UTP Cabling Categories • UTP cabling is rated according to a number of categories devised by the TIA and EIA; since 1991, ANSI has also endorsed these standards – ANSI/TIA/EIA 568 Commercial Building Wiring Standard for commercial environments includes: • • Category 1 (voicegrade) Category 2: up to 4 Mbps Category 3: up to 10 Mbps (16 MHz) Category 4 (datagrade): up to 16 Mbps (20 MHz) Category 5: up to 100 Mbps (100 MHz) Category 5 e: up to 1000 Mbps (100 MHz) Category 6: up to 1000 Mbps (200 MHz) Guide to Networking Essentials, Fifth Edition 16

Shielded Twisted Pair (STP) • Shielding reduces crosstalk and limits external interference – Usually, wiring includes a wire braid inside cladding or sheath, and a foil wrap around each wire pair • Enables support of higher bandwidth over longer distances than UTP – No set of standards for STP corresponds to the ANSI/TIA/EIA 568 Standard, yet it’s not unusual to find STP cables rated according to those standards – Uses two pairs of 150 ohm wire (defined by the IBM cabling system), and was not designed to be used in Ethernet applications, but it can be adapted to Guide to Networking Essentials, Fifth Edition 17

Twisted-Pair Cable (continued) Guide to Networking Essentials, Fifth Edition 18

Twisted-Pair Cable (continued) • Typically, twisted-pair systems include the following elements, often in a wiring center: – – Distribution racks and modular shelving Modular patch panels Wall plates Jack couplers Guide to Networking Essentials, Fifth Edition 19

Twisted-Pair Cable (continued) Guide to Networking Essentials, Fifth Edition 20

Twisted-Pair Cable (continued) Guide to Networking Essentials, Fifth Edition 21

Fiber-Optic Cable Guide to Networking Essentials, Fifth Edition 22

Fiber-Optic Cable (continued) Guide to Networking Essentials, Fifth Edition 23

Fiber-Optic Cable (continued) • Installation of fiber-optic networks is more difficult and time-consuming than copper media installation • Connectors and test equipment are considerably more expensive than their copper counterparts • Two types – Single-mode: costs more and generally works with laser-based emitters, but spans the longest distances – Multimode: costs less and works with light emitting diodes (LEDs), but spans shorter distances Guide to Networking Essentials, Fifth Edition 24

Cable Selection Criteria • Criteria to be considered for a network installation – – – – Bandwidth Budget Capacity Environmental considerations Placement Span Local requirement Existing cable plant Guide to Networking Essentials, Fifth Edition 25

Cable Selection Criteria (continued) Guide to Networking Essentials, Fifth Edition 26

Wireless Networking: Intangible Media • Wireless technologies continue to play an increasing role in all kinds of networks • Since 1990, the number of wireless options has increased, and the cost continues to decrease • Wireless networks can now be found in most towns and cities in the form of hot spots, and more home users have turned to wireless networks • Wireless networks are often used with wired networks to interconnect geographically dispersed LANs or groups of mobile users with stationary servers and resources on a wired LAN – Microsoft calls networks that include both wired and wireless components hybrid networks Guide to Networking Essentials, Fifth Edition 27

The Wireless World • Wireless networking can offer the following: – Create temporary connections to existing wired networks – Establish backup or contingency connectivity for existing wired networks – Extend a network’s span beyond the reach of wirebased or fiber-optic cabling, especially in older buildings where rewiring might be too expensive – Enable users to roam with their machines within certain limits (called “mobile networking”) Guide to Networking Essentials, Fifth Edition 28

The Wireless World (continued) • Common wireless applications include: – Ready access to data for mobile professionals – Delivery of network access into isolated facilities or disaster-stricken areas – Access in environments where layout and settings change constantly – Improved customer services in busy areas, such as check-in or reception centers – Network connectivity in structures where in-wall wiring would be impossible to install or too expensive – Home networks where the installation of cables is inconvenient Guide to Networking Essentials, Fifth Edition 29

The Wireless World (continued) Guide to Networking Essentials, Fifth Edition 30

Types of Wireless Networks • Three main categories – Local Area Networks (LANs) – Extended LANs – Mobile computing • An easy way to differentiate among these uses is to distinguish in-house from carrier-based facilities – Mobile computing typically involves a third party that supplies transmission and reception devices to link the mobile part of a network with the wired part • Most often, the company providing these services is a communications carrier (such as MCI or AT&T) Guide to Networking Essentials, Fifth Edition 31

Wireless LAN Components • NIC attaches to an antenna and an emitter • At some point on a cabled network, a transmitter/receiver device, called a transceiver or an access point, must be installed to translate between the wired and wireless networks • An access point device includes an antenna and a transmitter to send and receive wireless traffic, but also connects to the wired side of the network • Some wireless LANs use small transceivers, which can be wall mounted or freestanding, to attach computers or devices to a wired network Guide to Networking Essentials, Fifth Edition 32

Wireless LAN Transmission • Wireless LANs send/receive signals broadcast through the atmosphere – Waves in the electromagnetic spectrum – Frequency of the wave forms is measured in Hz • Affects the amount and speed of data transmission – Lower-frequency transmissions can carry less data more slowly over longer distances • Commonly used frequencies for wireless data communications – Radio— 10 KHz (kilohertz) to 1 GHz (gigahertz) – Microwave— 1 GHz to 500 GHz – Infrared— 500 GHz to 1 THz (terahertz) Guide to Networking Essentials, Fifth Edition 33

Wireless LAN Transmission (continued) • Higher-frequency technologies often use tight-beam broadcasts and require a clear line of sight between sender and receiver • Wireless LANs make use of four primary technologies for transmitting and receiving data – – Infrared Laser Narrowband (single-frequency) radio Spread-spectrum radio Guide to Networking Essentials, Fifth Edition 34

Infrared LAN Technologies • Infrared light beams send signals between pairs of devices • High bandwidth (10 to 100 Mbps) • Three main kinds of infrared LANs – Line of sight networks – Reflective wireless networks – Broadband optical telepoint networks • Infrared transmissions are being used increasingly for virtual docking • Ir. DA: Infrared Device Association Guide to Networking Essentials, Fifth Edition 35

Laser-Based LAN Technologies • Laser-based transmissions also require a clear line of sight between sender and receiver • Any solid object or person blocking a beam blocks data transmissions • To protect people from injury and avoid excess radiation, laser-based LAN devices are subject to many of the same limitations as infrared, but aren’t as susceptible to interference from visible light sources Guide to Networking Essentials, Fifth Edition 36

Narrowband Radio LAN Technologies Guide to Networking Essentials, Fifth Edition 37

Narrowband Radio LAN Technologies (continued) Guide to Networking Essentials, Fifth Edition 38

Spread-Spectrum LAN Technologies Guide to Networking Essentials, Fifth Edition 39

802. 11 Wireless Networking • The 1997 802. 11 standard is also referred to as Wireless Fidelity (Wi-Fi) – Current standards include 802. 11 b and 802. 11 g running at a 2. 4 GHz frequency (11 Mbps and 54 Mbps, respectively), and 802. 11 a, which specifies a bandwidth of 54 Mbps at a 5 GHz frequency – 802. 11 wireless is an extension to Ethernet using airwaves as the medium; most 802. 11 networks incorporate wired Ethernet segments – Networks can extend to several hundred feet – Many businesses are setting up Wi-Fi hot spots, which are localized wireless access areas Guide to Networking Essentials, Fifth Edition 40

Wireless Extended LAN Technologies Guide to Networking Essentials, Fifth Edition 41

Wireless MAN: The 802. 16 Standard • One of the latest wireless standards, 802. 16 Worldwide Interoperability for Microwave Access (Wi. Max), comes in two flavors: 802. 162004 (previously named 802. 16 a), or fixed Wi. Max, and 802. 16 e, or mobile Wi. Max – Promise wireless broadband to outlying and rural areas, where last-mile wired connections are too expensive or impractical because of rough terrain – Delivers up to 70 Mbps of bandwidth at distances up to 30 miles – Operates in a wide frequency range (2 to 66 GHz) Guide to Networking Essentials, Fifth Edition 42

Fixed Wi. Max: 802. 16 -2004 • Besides providing wireless network service to outlying areas, fixed Wi. Max is being used to deliver wireless Internet access to entire metropolitan areas rather than the limited-area hot spots available with 802. 11 • Fixed Wi. Max can blanket an area up to a mile in radius, compared to just a few hundred feet for 802. 11 • Los Angeles has begun implementing fixed Wi. Max in an area of downtown that encompasses a 10 mile radius Guide to Networking Essentials, Fifth Edition 43

Mobile Wi. Max: 802. 16 e • Promises to bring broadband Internet roaming to the public • Promises to allow users to roam from area to area without losing the connection, which offers mobility much like cell phone users enjoy • The mobile Wi. Max standard is not yet finalized – Expected to be approved in late 2005 or early 2006 • Fixed Wi. Max is expected to be the dominant technology for the next several years, but mobile Wi. Max will win out in the end Guide to Networking Essentials, Fifth Edition 44

Microwave Networking Technologies Guide to Networking Essentials, Fifth Edition 45

Microwave Networking Technologies (continued) Guide to Networking Essentials, Fifth Edition 46

Summary • Working with network media requires attention to requirements, budget, distance, bandwidth, and environmental factors • Cabled networks typically use one of two transmission schemes: broadband or baseband • For wired networks, the primary choices are twistedpair and fiber-optic cables – Twisted-pair cable can be unshielded or shielded – Fiber-optic cable: highest bandwidth, best security and resistance to interference, but the most expensive • Structured cabling facilitates troubleshooting, modifying, and expanding a network cable plant Guide to Networking Essentials, Fifth Edition 47

Summary (continued) • Wireless networking is gaining popularity – A typical wireless network acts like a wired network, except that wires aren’t needed to carry the signals – Wireless networks use a variety of electromagnetic frequency ranges (narrowband, spread-spectrum radio, microwave, infrared, and laser transmission) – 802. 11 family promises to make wireless networking commonplace in homes and corporate environments – 802. 16 provides up to 70 Mbps of bandwidth over long distances (30 miles) and can be used to create MANs – Mobile computing involves using broadcast frequencies and communications carriers to transmit and receive signals with cellular or satellite communications techniques Guide to Networking Essentials, Fifth Edition 48