Chapter Four Networking Media

Chapter Objectives  Explain concepts related to data transmission and noise  Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media  Explain the benefits and limitations of different networking media

Chapter Objectives  Identify the best practices for cabling buildings and work areas  Describe the methods of transmitting data through the atmosphere  Identify the network media best suited to specific LAN environments

Data Transmission  Information can be transmitted via one of two methods –Analog –Digital  Amplitude –A measure of a signal’s strength

Analog Signal  Uses variable voltage to create continuous waves, resulting in an inexact transmission FIGURE 4-1 Example of an analog signal

Digital Signal  Digital pulses can have a value of 1 or 0 FIGURE 4-2 Example of a digital signal

Data Transmission  Binary system encodes using 1s and 0s  Bits can only have a value of either 1 or 0  Eight bits together form a byte

Data Transmission  Frequency –Number of times a signal’s amplitude changes over a period of time –Expressed in Hertz (Hz)  Noise –Interference from sources near network cabling

Data Transmission  Attenuate –Loss of signal strength as transmission travels away from source FIGURE 4-3 Analog signal distorted by noise and then amplified

Data Transmission  Regeneration –Process of retransmitting a digital signal  Repeater –Device used to regenerate a signal Figure 4-4 Digital signal distorted by noise and then repeated

Data Transmission  Modem –Name reflects function as mod ulator/ dem odulator –Modulates analog signals into digital sounds at the transmitting end for transmission over telephone lines –Demodulates digital signals into analog signals at the receiving end

Media Characteristics  Throughput and bandwidth  Cost  Size and scalability  Connectors  Noise immunity

Throughput and Bandwidth  Throughput is the amount of data the medium can transmit during a given period of time –Also called capacity  Bandwidth measures the difference between the highest and lowest frequencies a media can transmit –Range of frequencies is directly related to throughput

Throughput and Bandwidth FIGURE 4-5 A comparison of two digital frequencies

Cost  Cost of installation  Cost of new infrastructure versus reusing existing infrastructure  Cost of maintenance and support  Cost of a lower transmission rate affecting productivity  Cost of obsolescence

Size and Scalability  Specifications determining size and scalability –Maximum nodes per segment (dependent on attenuation ) –Maximum segment length –Maximum network length  Latency is the delay between the transmission of a signal and its receipt

Connectors and Noise Immunity  Connector –Connects wire to network device  Noise Immunity –Electromagnetic Interference (EMI) –Radio Frequency Interference (RFI) –Conduits can protect cabling

Network Cabling  Baseband and Broadband Transmission –In baseband transmission, digital signals are sent through direct current (DC) pulses applied to the wire –In broadband transmission, signals are modulated as radio frequency (RF) analog pulses that use different frequency ranges

Network Cabling  Coaxial Cable –Central copper core surrounded by an insulator –Braiding insulates coaxial cable –Sheath is the outer cover of a cable –Foundation for Ethernet network in the 1980s FIGURE 4-6 Coaxial cable

Network Cabling TABLE 4-1 Types of coaxial cable

Network Cabling  Thicknet (10Base5) –Thicknet Also called thickwire Ethernet Rigid coaxial cable used for original Ethernet networks –IEEE designates Thicknet as 10Base5 Ethernet

Network Cabling  Thicknet (10Base5) –Throughput –Cost –Connector –Noise immunity –Size and scalability FIGURE 4-7 Thicknet cable transceiver with detail of a vampire tap piercing the core

Network Cabling Thinnet (10Base2)  Also known as thin Ethernet, was most popular medium for Ethernet LANs in the 1980s –Throughput –Cost –Size and scalability –Connector –Noise Immunity FIGURE 4-8 Thinnet BNC connectors

Network Cabling  Signal Bounce –Caused by improper termination –Travels endlessly between two ends of network –Prevents new signals from getting through FIGURE 4-9 Typical coaxial network using a bus topology

Network Cabling  Twisted-Pair (TP) Cable –Similar to telephone wiring –Consists of color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating –Twists help reduce effects of crosstalk, interference caused by signals traveling on nearby wire pairs infringing on another pair’s signals –Alien Crosstalk occurs when signals from adjacent cables interfere with another cable’s transmission

Network Cabling  Twist Ratio –Number of twists per meter or foot in a twisted-pair cable FIGURE 4-10 Twisted-pair cable

Network Cabling  Shielded Twisted-Pair (STP) –Twisted wire pairs are individually insulated and surrounded by shielding FIGURE 4-11 STP cable

Network Cabling  Unshielded Twisted-Pair –Consists of one or more insulated wire pairs encased in a plastic sheath –Does not contain additional shielding FIGURE 4-12 UTP cable

Network Cabling  To manage network cabling, it’s necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5) Figure 4-13 CAT5 UTP cable

Network Cabling  STP and UTP –Throughput –Cost –Connector –Noise immunity –Size and scalability FIGURE 4-14 RJ-45 connector, used by both STP and UTP

Network Cabling  Fiber-Optic Cable –Contains one or several glass fibers at its core –Cladding is the glass shield around the core FIGURE 4-15 Fiber-optic cable

Network Cabling  Single-Mode Fiber –Carries single frequency of light to transmit data  Multimode Fiber –Carries many frequencies of light over a single or many fibers FIGURE 4-16 Single-mode and multimode fiber-optic cables

Network Cabling  Fiber-Optic Cable –Throughput –Cost –Connector –Noise immunity –Size and scalability FIGURE 4-17 SMA fiber connector