Transmission Basics and Networking Media

1. Transmission Basics and Networking Media

2. 7/2/2012 2 Objectives Explain data transmission concepts including full-duplexing, attenuation, and noise Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media Explain the benefits and limitations of different networking media Identify the best practices for cabling buildings and work areas Describe the methods of transmitting data through the atmosphere

3. 7/2/2012 3 Transmission Basics Transmission has two meanings: Refers to process of issuing data signals on a medium Refers to progress of data signals over a medium On a data network, information can be transmitted via one of two methods: Analog Digital

4. 7/2/2012 4 Transmission Basics Both analog and digital signals are generated by electrical current, pressure of which is measured in volts In analog signals, voltage varies continuously In digital signals, voltage turns off and on repeatedly

5. 7/2/2012 5 Transmission Basics

6. 7/2/2012 6 Transmission Basics Amplitude Measure of a signal�s strength Frequency Number of times a signal�s amplitude changes over a period of time Expressed in hertz (Hz) Wavelength Distances between corresponding points on a wave�s cycle

7. 7/2/2012 7 Transmission Basics Phase Refers to progress of a wave over time in relationship to a fixed point

8. 7/2/2012 8 Transmission Basics Binary system encodes using 1s and 0s Bits can only have a value of either 1 or 0 Eight bits together form a byte Noise or any interference that may degrade signals affects digital signals less than analog signals Channel: Distinct communication path between two or more nodes

9. 7/2/2012 9 Transmission Basics

10. 7/2/2012 10 Data Modulation Modem Name reflects function as modulator/demodulator Modulation Technique for formatting signals Frequency modulation (FM) Method of data modulation in which frequency of carrier signal is modified by application of a data signal Amplitude modulation (AM) Modulation technique in which amplitude of carrier signal is modified by application of a data signal

11. 7/2/2012 11 Transmission Direction Simplex Signals travel in only one direction Half-duplex Signals may travel in both directions over a medium but in only one direction at a time Full-duplex Signals are free to travel in both directions over a medium simultaneously Also referred to just as duplex

12. 7/2/2012 12 Transmission Direction

13. 7/2/2012 13 Transmission Direction Multiplexing Allows multiple signals to travel simultaneously over one medium To accommodate multiple signals, single medium is logically separated into subchannels For each type of multiplexing: Multiplexer (mux) is required at sending end of channel Demultiplexer (demux) separates the combined signals and regenerates them in original form

14. 7/2/2012 14 Relationships Between Nodes Point-to-point Transmission involving one transmitter and one receiver Broadcast Transmission involving one transmitter and multiple receivers Webcasting Broadcast transmission used over the Web

15. 7/2/2012 15 Throughput and Bandwidth Throughput is amount of data the medium can transmit during a given period of time Also called capacity Bandwidth measures difference between highest and lowest frequencies a media can transmit Range of frequencies is directly related to throughput

16. 7/2/2012 16 Baseband and Broadband Baseband Transmission form in which (typically) digital signals are sent through direct current (DC) pulses applied to the wire Broadband Transmission form in which signals are modulated as radiofrequency (RF) pulses that use different frequency ranges

17. 7/2/2012 17 Media Characteristics Throughput Perhaps most significant factor in choosing a transmission medium is throughput 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

18. 7/2/2012 18 Media Characteristics Size and scalability Specifications determining size and scalability: Maximum nodes per segment Maximum segment length Maximum network length Latency is the delay between the transmission of a signal and its receipt

19. 7/2/2012 19 Media Characteristics Connectors Connects wire to network device Noise immunity Thicker cables are generally less susceptible to noise Possible to use antinoise algorithms to protect data from being corrupted by noise Conduits can protect cabling from noise

20. 7/2/2012 20 Coaxial Cable Consists of central copper core surrounded by an insulator, braiding, and outer cover called a sheath

21. 7/2/2012 21 Coaxial Cable

22. 7/2/2012 22 Twisted-Pair (TP) Cable Color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating Twists in wire help reduce effects of crosstalk Number of twists per meter or foot known as twist ratio Alien Crosstalk When signals from adjacent cables interfere with another cable�s transmission

23. 7/2/2012 23 Shielded Twisted-Pair (STP) STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding made of metallic substance

24. 7/2/2012 24 Unshielded Twisted-Pair Consists of one or more insulated wire pairs encased in a plastic sheath Does not contain additional shielding

25. 7/2/2012 25 10BaseT Popular Ethernet networking standard that replaced 10Base2 and 10Base5 technologies

26. 7/2/2012 26 100BaseT Enables LANs to run at 100-Mbps data transfer rate Also known as Fast Ethernet Two 100BaseT specifications have competed for popularity as organizations move to 100-Mbps technology: 100BaseTX 100BaseT4

27. 7/2/2012 27 100BaseVG VG stands for voice grade Also called 100VG-AnyLAN Originally developed by Hewlett-Packard and AT&T Now governed by IEEE standard 802.12

28. 7/2/2012 28 Comparing STP and UTP Throughput Both can transmit up to 100 Mbps Cost Typically, STP is more expensive Connector Both use RJ-45 connectors and data jacks Noise immunity STP is more noise-resistant Size and scalability Maximum segment length for both is 100 meters

29. 7/2/2012 29 Fiber-Optic Cable Contains one or several glass fibers at its core Surrounding the fibers is a layer of glass called cladding

30. 7/2/2012 30 Fiber-Optic Cable Single-mode fiber Carries light pulses along single path Multimode fiber Many pulses of light generated by LED travel at different angles

31. 7/2/2012 31 Fiber-Optic Cable Throughput Reliable in transmitting up to 1 gigabit per second Cost Most expensive type of cable Connector You can use different types of connectors

32. 7/2/2012 32 Fiber-Optic Cable Noise immunity Unaffected Size and scalability Network segments made from fiber can span 100 meters Signals transmitted over fiber can experience optical loss

33. 7/2/2012 33 Fiber-Optic Cable Two popular connectors used with fiber-optic cable: ST connectors SC connectors

34. 7/2/2012 34 10BaseF and 100BaseFX 10BaseF Physical layer standard for networks specifying baseband transmission, multimode fiber cabling, and 10-Mbps throughput 100BaseFX Physical layer standard for networks specifying baseband transmission, multimode fiber cabling, and 100-Mbps throughput

35. 7/2/2012 35 Physical Layer Networking Standards

36. 7/2/2012 36 Atmospheric Transmission Media Infrared transmission Infrared networks use infrared light signals to transmit data through space Direct infrared transmission depends on transmitter and receiver remaining within line of sight In indirect infrared transmission, signals can bounce off of walls, ceilings, and any other objects in their path

37. 7/2/2012 37 Atmospheric Transmission Media RF transmission Radio frequency (RF) transmission relies on signals broadcast over specific frequencies Two most common RF technologies: Narrowband Spread spectrum

38. 7/2/2012 38 Choosing the Right Transmission Media Corners and small spaces Distance Security Existing infrastructure Growth