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 Network Topology Physical layout  Star  Ring  Bus Node – any device connected to the network  Server  Computer  Printer  Other peripheral

8. January 23, 20037 Star Central hub All messages routed through hub Hub prevents collisions Node failure – no effect on overall network Hub failure – network fails

9. January 23, 20038 Ring Travel around circular connection in one direction Node looks at data as it passes  Addressed to me?  Pass it on if not my address No danger from collisions Node failure – network fails

10. January 23, 20039 Bus Single pathway All nodes attached to single line Collisions result in re-send Node failure – no effect on overall network

11. January 23, 200310 Introduction to Networks The Local Area Network (LAN)  Early data transfers were accomplished by physically “moving the data” around Magnetic tapes, disk packs  “Never underestimate the bandwidth of a station wagon loaded full of mag tapes headed for LA” --- anonymous  Interconnecting computers was becoming necessary to facilitate the information flow…

12. January 23, 200311 Introduction to Networks Interconnecting the computers  Circuit boards Specific to hardware platform  IBM, DEC, CDC, NCR….  Today it is better standardized – ISA, PCI, PCMCIA Specific to physical medium and protocol  Wire -- Ethernet, X.25…  Wireless – 802.11, HIPERLAN…  Physical layers are standardized  A Sun running Ethernet can talk to an IBM running Ethernet or a Windows PC running Ethernet or anything running Ethernet …

13. January 23, 200312 Circuit Boards Plug Into A Computer Computers are built such that they contain a set of sockets.  Using wires to connect sockets together  Using wires to carry power and data  Plugging circuit boards into sockets to control external devices

14. January 23, 200313 Illustration of the components visible in a computer when the cover has been removed. A circuit board can plug into each socket; wires connect the sockets to other components.

15. January 23, 200314 NIC (Network Interface Card) A computer needs network interface hardware and a cable that connects to the LAN. A computer uses the network interface card (NIC) to send and receive data.

16. January 23, 200315 Introduction to Networks Connecting Computers  A minimum network – two nodes Computer AComputer B

17. January 23, 200316 Introduction to Networks Connecting Computers  Adding a new computer to the network… Computer AComputer B Computer C

18. January 23, 200317 Early Systems Advantage of early LANs were speed. Disadvantages of early LANs were inconvenience and cost. Requiring effort to:  Add a new computer  Connect incompatible hardware

19. January 23, 200318 Introduction to Networks Connecting Computers  Example: Thin Net (Ethernet) Computer A Computer CComputer B LAN Hub Terminator

20. January 23, 200319 Introduction to Networks Connecting Computers  Example: 10BaseT (Ethernet) Computer AComputer B Computer C LAN Hub

21. January 23, 200320 Introduction to Networks LANs A computer communication technology is classified as a Local Area Network (LAN) if it provides a way to interconnect multiple computers across short distances.  Modern day LANs are inexpensive, reliable and convenient to install and manage

22. January 23, 200321 Introduction to Networks LAN technology is standardized  The LAN is isolated from the computers that use it (via the circuit cards – aka network interface card (NIC) ) LAN parameters are independent of user machines – speed, distance, etc..

23. January 23, 200322 Introduction to Networks LANs have changed the economies of computing  LANs allow the sharing of resources Use of inexpensive computers to access expensive resources Printers, disks…  Remote printing is common LANs came along just in time..  Internet design assumed many LANs would be interconnected via the Internet…

24. January 23, 200323 Connecting LANs Bridge – connects networks with similar protocols Router – directs traffic via best path  Routers are the Building Blocks of the Internet IP switches  Replacing routers  Less expensive  Faster Gateway  Connects LANs with dissimilar protocols  Performs protocol conversion

25. January 23, 200324 How Does a Network Work? Various network technologies are incompatible…  Many tradeoffs – cost, speed, extensibility, etc.. It is impractical, or infeasible, to require all computers to use the same network technology  Needs of Engineering vs. Administration

26. January 23, 200325 How Does A Network Work A computer can have multiple NICs  Each NIC can connect to a separate network Network A Network A Network B Network B

27. January 23, 200326 How Does a Network Work What is a router?  A dedicated computer  Special software Restarts automatically on power up  Goal is to forward packets from one network to another – quickly, efficiently and correctly Process is called routing Computers are called routers

28. January 23, 200327 How Does a Network Work Routers – Building blocks of the Internet The Internet is not a conventional network. It consists of thousands of computer networks interconnected by dedicated special purpose computers called routers  Routers can interconnect LANs and WANs

29. January 23, 200328 How Does a Network Work Wide Area Backbone LAN Net  A Happy Router

30. January 23, 200329 How Does the Network Work? Interconnecting networks was a revolutionary idea….  Simply connect to your closest neighbor and you are in!  Issues now arise Privacy Politics Borders

31. January 23, 200330 Wide Area Networks… Wide Area Networks (WAN)  First WANs used dialup technology to form a set of long-haul transmission lines  Today leased lines are used – always on..  Uses a dedicated machine at each local site to unify the transmission lines into a coordinated system

32. January 23, 200331 WANs  A WAN differs from a disjoint set of transmission lines because of the inclusion of a special computer (Gateway) at each site that connects to the transmission lines and keeps communication independent of the computers that use the WAN

33. January 23, 200332 WAN Technology WAN G1 G2 G3

34. January 23, 200333 WANs Today Link computers in geographically distant locations

35. January 23, 200334 Communication Services Common carriers licensed by FCC (Federal Communications Commission) Switched / dial-up service  Temporary connection between 2 points  Ex: plain old telephone service (POTS) Dedicated service  Permanent connection between 2 or more locations  Ex: Build own circuits, Lease circuits (leased lines)

36. January 23, 200335 High Capacity Digital Lines T1 (DS1)  1.54 Mbps  24 simultaneous voice connections T3 (DS3)  28 T1 lines  43 Mbps Expensive High-volume traffic

37. January 23, 200336 Multiplexer Combines data streams from slow-speed devices into single higher speed data stream Transmits over high-speed circuit (ex DS1) Multiplexer on receiving end needed to restore to component data streams

38. January 23, 200337 Time Division Multiplexing Carry many voice conversations (or data streams) on one link Example: 24-to-1 multiplexer  Samples 24 voice links 24 times as fast as the input rate  24 samples constitute a frame  Multiplexed links can be multiplexed further

39. January 23, 200338 Digital Signaling (DS) Hierarchy:

40. January 23, 200339 Protocols – Rules to live by… Set of rules governing the exchange of data Assists with coordination of communications  Was message received properly ? TCP/IP  Transmission Control Protocol / Internet Protocol  Internet standard  All computers in world speak same language

41. January 23, 200340 Beginnings of The Internet Xerox gave universities a prototype of a new LAN technology from their Palo Alto Research Center (Xerox PARC).  Beginning of Ethernet  Developing the idea of inexpensive and widely available LANs (The Internet early design was based on the concept of interconnecting many LANS)

42. January 23, 200341 Ethernet Dominant protocol Bus or star topology Uses CSMA/CD CSMA/CD Carrier sense multiple access with collision detection  Tries to avoid 2 or more computers communicating at the same time  Computer listens and transmits when cable is not in use  Collision results in waiting a random period and transmitting again  Performance degrades with multiple collisions

43. January 23, 200342 Token Ring Ring topology No danger from collisions Token passing  Token has an address  Node looks at token as it passes Addressed to me? Retrieve data Pass it on if not my address  Send Empty token? Attach message Pass it on if not empty

44. January 23, 200343 Using the Network Communications Software Applications

45. January 23, 200344 File Transfer Software FTP,SFTP,SCP: Download Receive a file from another computer Upload Send a file to another computer

46. January 23, 200345 Terminal Emulation Software TELNET, SSH: PC imitates a terminal for communication to remote system Micro-to-mainframe link

47. January 23, 200346 Organization of Resources Client/Server and File Server Clients Other computers on network Thin client – no processing Server Controls the network Hard disk holding shared files

48. January 23, 200347 Organization of Resources Client/Server and File Server

49. January 23, 200348 Organization of Resources File Server Server transmits file to client Client does own processing

50. January 23, 200349 Organization of Resources Client/Server How it works  Client sends request for service to server  Server fulfills request and send results to client  Client and server may share processing  Ex: Web browsing, EMAIL Benefits  Reduces volume of data traffic  Allows faster response for each client  Nodes can be less expensive computers

51. January 23, 200350 Organization of Resources Peer-to-Peer All computers have equal status Share data and devices as needed Common with up to 12 computers Disadvantage – slow transmission

52. January 23, 200351 Office Automation Communication Applications E-mail Facsimile (Fax) Groupware Teleconferencing Video conferencing ATM Electronic fund transfers Telecommuting Online services The Internet Electronic data interchange (EDI)

53. January 23, 200352