2. Welcome to CMPE003 Personal Computer Concepts: Hardware and Software Winter 2003 UC Santa Cruz Instructor: Guy Cox

3. January 23, 20032 Class Information Midterm #2  Monday – February 24, 2002.  ID required.  Covers Chapters 5, 7, 9, 10 and 12. Book reading plus lectures.  Multiple choice Requires Scantron #F-1712-ERI-L (pink) ~50 questions  No make-ups after the fact

4. January 23, 20033 Assignments Assignment #5 – Due February 28, 2003 Programming  Edit a Java Script program file If you want more information about javascript,  visit http://www.htmlgoodies.com.http://www.htmlgoodies.com http://www.soe.ucsc.edu/classes/cmpe003/Winter03/hw5_javascript.h tml

5. Networking: Computer Connections Chapter 7 Part A

6. January 23, 20035 Objectives Describe the basic components of a network Explain the methods of data transmission, including types of signals, modulation, and choices among transmission modes Differentiate among the various kinds of communications links and appreciate the need for protocols Describe various network configurations List the components, types, and protocols of a local area network Appreciate the complexity of networking Describe some examples of networking

7. January 23, 20036 Data Communications Send and receive information over communications lines

8. January 23, 20037 Centralized Data Processing All processing, hardware, software in one central location Inefficient Inconvenient

9. January 23, 20038 Distributed Data Processing Computers at a distance from central computer Can do some processing on their own Can access the central computer

10. January 23, 20039 Networking Uses communication equipment to connect two or more computers and their resources  Can be PC based Allows connected users to share data and resources LAN – Local Area Network  shares among users in close proximity WAN – Wide Area Network  shares among users who are geographically distant

11. January 23, 200310 Basic Components Sending device Communications link Receiving device

12. January 23, 200311 Network Design Transmission speed (ie, data rate) Medium (wired, wireless….) Topology – Physical layout of components Protocol – Rules governing communication Distance  LAN  MAN  WAN Technology  Peer-to-peer  File server  Client/server

13. January 23, 200312 Data Transmission Digital lines  Sends data as distinct pulses  Need digital line Analog lines  Sends a continuous electrical signal in the form of a wave  Conversion from digital to analog needed  Telephone lines, coaxial cables, microwave circuits

14. January 23, 200313 An electrical signal reflects from the end of a metal wire the same way that light reflects from a mirror. Signals:  Lose strength as they pass across the wire.  Emit electromagnetic radiation that interferes with nearby wires. Signals on Wires

15. January 23, 200314 Modulation Amplitude Modulation Frequency Modulation Phase Modulation Modulation means imposing information on an electrical signal (called the carrier)

16. January 23, 200315 Analog Transmission Alter the carrier wave Amplitude Modulation (AM)–  height of the wave is increased to represent 1 Frequency Modulation (FM)–  number of times wave repeats during a specific time interval can be increased to represent a 1

17. January 23, 200316 Dialup Modem MODEM -- Mo(dulator)/Dem(odulator) Modulate  Convert from digital to analog Demodulate  Convert from analog to digital Speeds up to 56,000 bps (56K)

18. January 23, 200317 Modem Transmission process Modulation – Computer digital signals converted to analog Sent over analog phone line Demodulation – Analog signal converted back to digital

19. January 23, 200318 Modems Modems …  Allows two-way communication Designed to either use two different signals or Agree to take turns sending data  In either case, data appears to flow simultaneously in both directions.  Dial-up modems Can dial the phone line and set up call Talk only to other modems  Newer modems can talk to older slower modems

20. January 23, 200319 Types of Modems Direct-connect  External  Internal PCMCIA  Personal Computer Memory Card International Association  Notebook and laptop computers

21. January 23, 200320 (A)DSL (Asymmetric) Digital Subscriber Line Uses conventional telephone lines Uses multiple frequencies to simulate many modems transmitting at once No industry standard  Equipment  Speed Phone line shared between computer and voice

22. January 23, 200321 Cable Modem Coaxial cables Does not interfere with cable TV reception Up to 10 million bits per second (mbps) Always on Shared capacity with neighbors Security problem  Sniffing the the wire is easy…

23. January 23, 200322 Cellular Modems Uses cellular telephone system Slow speed (9600 bps)

24. January 23, 200323 ISDN: Integrated Services Digital Network Digital transmission Speeds of 128 kbps Connect and talk at same time Need  Adapter  Upgraded phone service Initial costs high Ongoing monthly fees may be high Not available in all areas Old technology -- almost dead…  OBE – like DSL

25. January 23, 200324 Transmission: Asynchronous and Synchronous Sending and receiving devices must work together to communicate

26. January 23, 200325 Asynchronous Transmission Start/stop transmission  Start signal  Group – generally one character  Stop signal Low-speed communications

27. January 23, 200326 Synchronous Transmission Blocks of data transmitted at a time  Send bit pattern  Align internal clock of sending / receiving devices  Send data  Send error-check bits More complex More expensive Faster transmission

28. January 23, 200327 Transmission Types Identifies direction of data flow Simplex  One direction  Television broadcasting  Arrival/departure screens at airport Half-duplex  Either direction, but one way at a time CB radio Message sent, confirmation received Full-duplex  Both directions at once  Telephone conversation

29. January 23, 200328 Communications Media Physical means of transmission Bandwidth  Range of frequencies that the medium can carry  Measure of capacity

30. January 23, 200329 Network Cable Twisted pair Coaxial cable Fiber optic cable Wireless  Uses infrared or low-power radio wave transmissions  No cables  Easy to set up and reconfigure  Slower transmission rates  Small distance between nodes

31. January 23, 200330 Twisted Pair: Wire Pair Inexpensive Susceptible to electrical interference (noise) Telephone systems Physical characteristics  Requires two conductors  Twisted around each other to reduce electrical interference  Plastic sheath Shielded twisted pair  Metallic protective sheath  Reduces noise  Increases speed

32. January 23, 200331 Coaxial Cable Higher bandwidth Less susceptible to noise Used in cable systems Physical characteristics  Center conductor wire  Surrounded by a layer of insulation  Surrounded by a braided outer conductor  Encased in a protective sheath

33. January 23, 200332 Fiber Optics Transmits using light Higher bandwidth Less expensive Immune to electrical noise More secure – easy to notice an attempt to intercept signal Physical characterizes  Glass or plastic fibers  Very thin (thinner than human hair)  Material is light

34. January 23, 200333 Microwave Transmission Line-of-site High speed Cost effective Easy to implement Weather can cause interference Physical characteristics  Data signals sent through atmosphere  Signals cannot bend of follow curvature of earth  Relay stations required

35. January 23, 200334 Satellite Transmission Microwave transmission with a satellite acting as a relay Long distance  Incurs longer delay -- ~2.5 secs rtt Components  Earth stations – send and receive signals  Transponder – satellite Receives signal from earth station (uplink) Amplifies signal Changes the frequency Retransmits the data to a receiving earth station (downlink)

36. January 23, 200335 Satellite Transmission

37. January 23, 200336 Mixed & Matched…. Example – East and West coast: Request made  Twisted pair in the phone lines on the East Coast  Microwave and satellite transmission across the country  Twisted pair in the phone lines on the West coast Data transferred  Twisted pair in the phone lines on the West Coast  Microwave and satellite transmission across the country  Twisted pair in the phone lines on the East coast

38. January 23, 200337