1 / 60

NT1210 Introduction to Networking

NT1210 Introduction to Networking. Unit 4: Chapter 4, Transmitting Bits. 1. Objectives. Differentiate among major types of LAN and WAN technologies and specifications and determine how each is used in a data network. Explain basic security requirements for networks. 

ringo
Download Presentation

NT1210 Introduction to Networking

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NT1210 Introduction to Networking Unit 4: Chapter 4, Transmitting Bits 1

  2. Objectives • Differentiate among major types of LAN and WAN technologies and specifications and determine how each is used in a data network. • Explain basic security requirements for networks.  • Install a network (wired or wireless), applying all necessary configurations to enable desired connectivity and controls. •  Explain the fundamentals of electrical circuits. • Identify different types of physical cabling. 2

  3. Objectives • Identify wireless network communication needs. • Distinguish among the different needs for wired and wireless networks. • Classify Layer 2 networking components used in a typical LAN. • Compare and contrast advantages and disadvantages of network media. • Use basic troubleshooting techniques to ensure network connectivity at Layers 1 and 2. 3

  4. Transmitting Bits: Communication Analogy • When two friends talk, one talks while other listens and understands (we hope!). • Speaker makes sounds that travel through air to listener’s ears. • Sounds have no meaning unless each person’s brain works to interpret those sounds. • In networks, nodes send data to each other over link: Sending node acts like person talking; receiving node acts like person listening. 4

  5. Transmitting Bits: Communication Analogy General idea of how a TCP/IP network forwards IP packets from one host to another: Nodes (routers in this example) each make a choice of where to send the packet next so the data arrives at the correct destination. Always keep the big goal of the network in mind: Delivering data from the source to the destination. Sending Data Through a Network of Nodes and Links Figure 4-1 5

  6. Sending Bits with Electricity and Copper Wires: Electrical Circuits • Electrical circuit must exist as complete loop of material (medium) over which electricity can flow. • Material used to create circuit can’t be just any material; must be good electrical conductor (e.g., copper wire). Simple Direct Current Circuit Using a Battery Figure 4-2 6

  7. Sending Bits with Electricity and Copper Wires: Electrical Circuits • Direct Current (DC) electrical circuits • Electricalcurrent: Amount of electricity that flows past single point on circuit (amount of electron flow in circuit). • Current always flows away from negative (-) lead in circuit and towards positive (+) lead. Powering a Light Bulb with a DC Circuit Figure 4-3 7

  8. Sending Bits with Electricity and Copper Wires: Frequency, Amplitude, Phase • DC circuit (on left) and AC circuit (on right) both use 1 volt. • DC shows constant +1 volt signal. • AC circuit slowly rises to +1 volt, falls to 0 then falls to -1 volt (1 volt, but in opposite direction), repeating over time. • Resulting AC wave: Sinewave Graphs of 1 Volt (Y-Axis) over time: DC (Left) vs AC (Right) Figure 4-4 8

  9. Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase • To send data, networking Physical layer standards can change amplitude, frequency, phase, period of AC electrical signal. Graphs of AC Circuit: Amplitude, Period, Frequency Figure 4-5 9

  10. Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase • Most commonly used in networking encoding schemes. • One signal used by encoding scheme means binary 0, other means binary 1. Encoding Options: Frequency, Amplitude, and Phase Shifts Figure 4-6 10

  11. Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase, Period Common Features Used by Encoding Schemes Table 4-1 11

  12. Sending Bits with Electricity and Copper Wires: Network Cabling • Before a node can send data, it needs to create a circuit between itself and the destination node. • Copper cable has outer plastic cover (jacket) that holds wires (conductors). • Sending/receiving nodes use a pair of wires connected at their ends to create circuit. Photo of Wires Inside a Networking Cable Figure 4-7 12

  13. Sending Bits with Electricity and Copper Wires: Network Cabling Example • Cable has 4 pairs of wires: 2 used, 2 unused. • Hardware of each node must agree which wires to use and which to ignore. • For wires chosen to use, nodes loop ends together to create a circuit. Physical Components to Create an Electrical Circuit Between Two Nodes Figure 4-8 13

  14. Sending Bits with Electricity and Copper Wires: Network Cabling • Loop (circuit) can’t create circuit by itself: something has to create electrical current. • Transmitting node creates electrical signal, changing signal over time to encode different bit values. • Transmitter: Part of node that sends data. • Receiver: Part that listens for signal of incoming bits. Transmitter Generating a Current to Send; Receiver Sensing Current to Receive Figure 4-9 14

  15. Sending Bits with Electricity and Copper Wires: Circuit Bit Rates • Bit rate (link speed): Defines number of bits sent over link per second (bps). • Impacts how nodes send data over circuit. • Example of how bit rate and encoding scheme work together: Bit rate = 10 bps; encoding scheme states that binary 1 should be +2 volts and binary 0 as +1 volts. Example where Encoder Changes Signal Every Bit Time Figure 4-10 15

  16. Sending Bits with Electricity and Copper Wires: Encoding Scheme • Works like language: Defines electrical equivalent of 1’s and 0’s. • Different frequencies represent binary 1’s and 0’s. • Example sending 1010: Lower frequency represents binary 1, higher frequency represents binary 0. Frequency Shift Keying: Low Frequency = 1, High Frequency = 0 Figure 4-11 16

  17. Sending Bits with Electricity and Copper Wires: Manchester Encoding Scheme • Used on some early Ethernet networks. • Does not choose one electrical signal at beginning of bit time, instead changes signal in middle of bit time. • Follows this logic: • To encode 0: Start high, and transition low in the middle of bit time. • To encode 1: Start low, and transition high in the middle of bit time. Manchester Encoding: 0 = High-to-Low, 1 = Low-to-High Figure 4-12 17

  18. Sending Bits with Electricity and Copper Wires: Using Multiple Circuits • Simplex transmissions are one way: If encoding scheme works in only one direction (on single circuit): • Devices must take turns using that circuit or … • Devices must use different circuits for each direction. • Half-duplex transmissions take turns: Node1 sends while Node2 listens; when Node1 finishes, Node2 sends while Node1 listens. • Full duplex transmissions can send/receive simultaneously: Both endpoints can send at same time because they use multiple wire pairs. Full Duplex Using Two Pair, One for Each Direction Figure 4-13 18

  19. Sending Bits with Electricity and Copper Wires: Using Multiple Circuits Full Duplex Using Two Pair, One for Each Direction Figure 4-13 19

  20. Sending Bits with Electricity and Copper Wires: Problems with Electricity • Noise: Electro-Magnetic Interference (EMI) • Cables help prevent effects of EMI in many ways, including shielding. • Twisting of wire pairs creates “cancellation” effect to help stop EMI effect. • Attenuation: Signals fade away over distance to point where devices can’t interpret individual bits • Ethernet standards limit copper links to 100 meters. • Very important when designing network. 20

  21. Sending Bits with Electricity and Copper Wires: Unshielded Twisted Pair (UTP) • 10Base-T, 100Base-T & 1000Base-T uses Unshielded Twisted Pair (UTP). • Cable contains twisted pairs of wires and no added shielding materials. • Twisting reduces EMI effects between pairs in same jacket and in nearby cables. • Lack of shielding makes cables less expensive, lighter, easier to install. • Supports full-duplex. Note: Twisted pair cables with shielding are called Shielded Twisted Pair (STP). 21

  22. Sending Bits with Electricity and Copper Wires: LAN Standards Progression • Ethernet has long history (developed in 1970s and is still used today). • IEEE standardized Ethernet in 802.3 standard in early 1980s. • Has added many more Ethernet standards since then. • Each standard took years to grow in marketplace and eventually drive prices down. Timeline of the Introduction of Ethernet Standards Figure 4-14 22

  23. Sending Bits with Electricity and Copper Wires: RJ-45 Connectors, Ports • Ethernet standards allow use of RJ-45 connectors on twisted pair cable and matching RJ-45 ports (sockets) on NICs, switch ports, and other devices. • Again, RJ-45 connectors and ports accommodate 8 wires (pins) in single row. Example RJ-45 Connectors and Sockets Figure 4-15 23

  24. Sending Bits with Electricity and Copper Wires: Cable Pinouts • Pinouts: How each wire in cable should be connected to each pin in connector according to Ethernet standards. • Wires must be in correct order so correct wires in twisted pair send to correct direction. Wires, Connector Pin numbers, and Socket Pin Numbers Figure 4-16 24

  25. Sending Bits with Electricity and Copper Wires: Cable Pinouts Straight-through: Each wire connects to the same pin number on both ends of the cable. Conceptual Drawing of Straight-Through Cable Figure 4-17 25

  26. Sending Bits with Electricity and Copper Wires: Cable Pinout Standards • Ethernet uses TIA (Telecommunications Industry Association) standards to define specific wires to use for pinouts. • UTP cables have four pairs of wires, each using a different color: green, blue, orange, brown. • Each pair has 1 wire with solid color and other one with white stripe. TIA Cable Pinouts – T568A On Each End Creates a Straight-Through Cable Figure 4-18 26

  27. Sending Bits with Electricity and Copper Wires: Cable Pinout Standards—568A/568B NOTE: 568B switches green and orange wires. TIA Cable Pinouts – T568A On Each End Creates a Straight-Through Cable Figure 4-18 27

  28. Sending Bits with Electricity and Copper Wires: Cable Pinout Standards • UTP cable with four pairs (8 wires) can support four circuits. • 10Base-T and 100Base-T only use two pairs. NOTE: 1000BaseT uses all 4 wire pairs. • Ethernet uses following rules for creating circuits: • One pair at pins 1 and 2 • One pair at pins 3 and 6 PC NIC Transmitting on Pair at 1,2, Receiving on Pair 3,6 Figure 4-19 28

  29. Break Take 15 29

  30. Sending Bits with Light and Fiber Optic Cables • Fiber optics transmission like turning light switch on and off: ON = 1, OFF = 0. • Endpoints agree to use same speed and same basic encoding scheme. Encoding Bits Using Light On/Off Figure 4-20 30

  31. Sending Bits with Light and Fiber Optic Cables • Fiber cables contain several parts that wrap around glass or plastic fiber core. • Core is about as thin as human hair. • Fiber breaks easily without some type of support. • Core and cladding have direct effect on how light travels down cable. • Optical transmitter (laser or LED) shines light into core to transmit data. Components of a Fiber Optic Cable Figure 4-21 31

  32. Sending Bits with Light and Fiber Optic Cables • Cladding surrounds core for entire length of cable. • Reflects light back into core • Light waves reflect off cladding back into core until light waves reach other end of cable • Fiber optic cables work well to send light in one direction at time, but not two. • Cable acts like dark tunnel so nodes can easily see light coming through cable. • If both ends try to shine light and look for light at same time, couldn’t tell whether light is coming from local or remote node. Cladding Reflecting the Light Back into the Fiber Optic Cable’s Core Figure 4-22 32

  33. Sending Bits with Light and Fiber Optic Cables • Instead of using one fiber cable for half-duplex communication, most fiber links use pair of cables so can use full-duplex. • Each fiber NIC, port, interface, etc., has interface with two sockets: One for send cable, one for receive cable. • Each node’s transmit socket must connect to same cable as other node’s receive socket. NOTE: In addition to sending data using light over cables, fiber technology also includes free space optics (e.g., TV remote) which sends light through air; requires line-of-sight. Two Fiber Optic Cables, with Connectors Figure 4-23 33

  34. Sending Bits with Light and Fiber Optic Cables: Transmitters • Key technical difference between LEDs and lasers: LEDs shine light in multiple directions; lasers shine in one direction. • Fiber cables come in two major categories: Multimode (MM), singlemode (SM). • Multimode have larger cores and work best with LED transmitters. • Single mode have smaller diameter cores and work best with laser transmitters. LEDs with Multiple Modes (Angles), and Lasers, with a Single Mode (Angle) Figure 4-24 34

  35. Sending Bits with Light and Fiber Optic Cables: Ethernet LANs • Fiber cables do not create EMI. • Fiber links more secure. • Example: Typical campus LAN has employees in two buildings in office park that sit 150 meters apart, which exceeds Ethernet standards for copper cabling. However, multimode links can run past 200 meters. Typical Use of Fiber Optics in a LAN: Links Between Neighboring Buildings Figure 4-25 35

  36. Sending Bits with Light and Fiber Optic Cables: WAN Links Telcos and ISPs that support WAN services use fiber optics because they service businesses that sit far apart. To do this, Telco/ISP must have a link from the customer to the Telco central office (CO) or ISP Point of Presence (POP). Two Perspectives on a Leased Line Figure 4-26 36

  37. Sending Bits with Light and Fiber Optic Cables: WAN Links • Example: Fiber that connects equipment in CO to other Telco sites (called core sites). • COs sit at edge sites of Telco network and have links to core sites. • Physical locations include office buildings with server rooms. • In this figure, all links use fiber except links from CO to customer routerwhich use copper. Fiber Links Used to Help Create a Telco Network Figure 4-27 37

  38. Sending Bits with Light and Fiber Optic Cables: WAN Links • Synchronous Optical Network (SONET): One of longer-established standards for WAN links. • SONET defines series of Physical layer standards for data transmission over optical links. • Uses hierarchy of speeds that are multiples of base speed (51.84 Mbps) plus some overhead. SONET Optical Carrier (OC) Names and (Rounded) Line Speeds Table 4-2 38

  39. Sending Bits with Radio Waves and No Cables: Radio Basics • Radio stations broadcast signals so anyone near enough to station’s large antenna (radio tower) can hear broadcast. • Radio tower sends electricity through antenna to create radio waves. • More electrical power creates stronger radio waves that can travel longer distances. • Radio tower sends signals upward because radio waves bounce off ionosphere (one of layers of Earth’s atmosphere). • Bouncing radio waves off ionosphere lets radio waves reach wider area. A Radio Station Broadcasting a Radio Signal to a Car Radio Figure 4-28 39

  40. Sending Bits with Radio Waves and No Cables: Radio Basics A Radio Station Broadcasting a Radio Signal to a Car Radio Figure 4-28 40

  41. Sending Bits with Radio Waves and No Cables: Radio Basics • Electromagneticradiation (ER): Described using electromagneticspectrum conceptual model • These types of energy travel as waves, so have specific wavelength. • Spectrum categorizes energy based on wavelength. • Radio waves make up one category in EM spectrum. • Other parts include visiblelight, X-rays, microwaves. • Radio waves work well for networking because can be changed (modulated) over time to send data. A Radio Station Broadcasting a Radio Signal to a Car Radio Figure 4-28 41

  42. Sending Bits with Radio Waves and No Cables: Radio Basics • Three facts summarize key points about why radio can be used to wirelessly send data. • Radio waves have energy level that moves up and down over time, so when graphed, waves look like sine wave. • Radio waves can be changed and sensed by networking devices, including changes to frequency, amplitude, phase, period, wavelength. • EM energy does not need physical medium to move. A Radio Station Broadcasting a Radio Signal to a Car Radio Figure 4-28 42

  43. Sending Bits with Radio Waves and No Cables: WANs—Mobile Phones & Voice • Mobile network provider creates its own network. • But most phone users want to communicate with more phones than just those on same mobile company’s network, as well as landline phones. • Enter the Public Switched Telephone Network (PSTN) Major Components in the Mobile Phone Network Model Figure 4-29 43

  44. Sending Bits with Radio Waves and No Cables: WANs—Mobile Phones & Voice • Most mobile phones act as digital phones. • Send and receive digits (bits) that represent voice traffic. • To transmit bits, phones use wireless radio technology. • Phone sends bits encoded as radio waves to nearby radio antenna on tower owned by mobile phone company. Connecting a Mobile Phone Call through a Radio Tower to the Telco Network Figure 4-30 44

  45. Sending Bits with Radio Waves and No Cables: WANs—Mobile Phones & Voice Steps to place call on mobile phone: • Person speaks creating sound waves (as usual). • Phone converts sound waves into bits (as with all digital phones). • Phone sends (encodes) bits as radio waves through air towards cell tower. • Radio equipment at tower receives (decodes) radio waves back into original bits. • Rest of trip uses various technology (details not included here). 45

  46. Sending Bits with Radio Waves and No Cables: WANs—Mobile Phones & Data • Radio link on phone supports data service just as it does for voice. • When sending or receiving data, phone passes bits using radio waves between itself and radio tower. • Phone encapsulates data. • To support data applications, mobile network connects to Internet and any other networks that support data apps requested by user. • Mobile network forwards data to correct destination in Internet, not through PSTN. Smart Phone: Using Radio to Forward Bits to the Tower, and then to the Internet Figure 4-31 46

  47. Sending Bits with Radio Waves and No Cables: WANs—Mobile Phones & Data Steps in accessing Internet via mobile phone: • Person types URL or taps hyperlink. • Phone encapsulates HTTP request into IP packet, then Data Link layer frame. • Phone sends (encodes) frame’s bits as radio waves towards cell tower. • Radio equipment at tower receives (decodes) radio waves back into original bits. • Equipment near cell tower forwards bits into Internet as for any IP packet. 47

  48. Sending Bits with Radio Waves and No Cables: WANs—Other Mobile Devices • Laptops, tablets can connect to same network as mobile phone. • Laptops typically need wireless NIC that supplies radio to connect to network radio towers. • Also need contract with mobile provider for connectivity to wireless network. Using the Wireless WAN (Mobile Network) from Computers Instead of Phones Figure 4-32 48

  49. Sending Bits with Radio Waves and No Cables: WAN Standards Mobile Wireless Standards and Terms Table 4-3 49

  50. Sending Bits with Radio Waves and No Cables: WLANs—Devices & Topology • Wireless LAN devices need WLAN Network Interface Card (NIC). • Gives PC ability to connect WLAN • Uses radio antenna that allows NIC to send and receive data • Most WLANs use Access Points (AP) which are small devices that acts like small radio tower. • All wireless user devices communicate through AP. A Small Wireless LAN with One Access Point (AP) Figure 4-33 50

More Related