Transmission Basics and Networking Media

1. Transmission Basics and Networking Media

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. 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. 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. Transmission Basics Example of an analog signal

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. Transmission Basics • Phase • Refers to progress of a wave over time in relationship to a fixed point Phase differences

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. Transmission Basics Example of a digital signal

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. 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. Simplex, half-duplex, and full-duplex communication Transmission Direction

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. 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. 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. 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. 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. 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. 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. Coaxial Cable • Consists of central copper core surrounded by an insulator, braiding, and outer cover called a sheath Coaxial cable

21. Coaxial Cable Some types of coaxial cable

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 Twisted-pair cable

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

24. Unshielded Twisted-Pair • Consists of one or more insulated wire pairs encased in a plastic sheath • Does not contain additional shielding UTP cable

25. 10BaseT • Popular Ethernet networking standard that replaced 10Base2 and 10Base5 technologies A 10BaseT Ethernet network

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. 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. 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. Fiber-Optic Cable • Contains one or several glass fibers at its core • Surrounding the fibers is a layer of glass called cladding

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. 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. 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. Fiber-Optic Cable • Two popular connectors used with fiber-optic cable: • ST connectors • SC connectors

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. Physical Layer Networking Standards

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. 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. Choosing the Right Transmission Media • Corners and small spaces • Distance • Security • Existing infrastructure • Growth