Welcome to CMPE003 Personal Computers: Hardware and Software

1. Welcome toCMPE003Personal Computers: Hardware and Software Dr. Chane Fullmer Fall 2002 UC Santa Cruz

2. Assignments • Homework #4 – Due October 25 (That’s this coming Friday  ) • Design your own resume • Must use a Word Processor (ie, M$ Word) • Notepad will not suffice. • Details and sample resume – see class page – http://www.soe.ucsc.edu/classes/cmpe003/Fall02/hw4_resume.html

3. Class Information • Midterm results: • Average….. 34.6 = ~70% (Strong ‘C’) • Low – 18 • High – 46 • Will be handed back after lecture today

4. Networking: Computer Connections Chapter 7 Part B

5. 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

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

7. Star • Central hub • All messages routed through hub • Hub prevents collisions • Node failure – no effect on overall network • Hub failure – network fails

8. 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

9. Bus • Single pathway • All nodes attached to single line • Collisions result in re-send • Node failure – no effect on overall network

10. 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…

11. 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 …

12. 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

13. Illustrations 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.

14. 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.

15. Introduction to Networks • Connecting Computers • A minimum network – two nodes Computer A Computer B

16. Introduction to Networks • Connecting Computers • Adding a new computer to the network… Computer C Computer A Computer B

17. 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

18. Introduction to Networks • Connecting Computers • Example: Thin Net (Ethernet) Computer B Computer C Computer A Terminator LAN Hub

19. Introduction to Networks • Connecting Computers • Example: 10BaseT (Ethernet) Computer C LAN Hub Computer A Computer B

20. 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

21. 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..

22. 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…

23. 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

24. 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

25. How Does A Network Work • A computer can have multiple NICs • Each NIC can connect to a separate network Network A Network B

26. 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

27. 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 calledrouters • Routers can interconnect LANs and WANs

28. How Does a Network Work Net LAN LAN Net LAN LAN Wide Area Backbone LAN LAN LAN Net  A Happy Router

29. 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

30. 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

31. 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

32. WAN Technology WAN G2 G1 G3 G2

33. WANs Today Link computers in geographically distant locations

34. 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)

35. High Capacity Digital Lines • T1 (DS1) • 1.54 Mbps • 24 simultaneous voice connections • T3 (DS3) • 28 T1 lines • 43 Mbps • Expensive • High-volume traffic

36. 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

37. 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

38. Digital Signaling (DS) Hierarchy:

39. 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

40. 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)

41. 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 Ethernet

42. 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

43. Using the Network • Communications • Software Applications

44. File Transfer Software FTP,SFTP,SCP: Download Receive a file from another computer Upload Send a file to another computer

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

46. Organization of ResourcesClient/Server and File Server Server Controls the network Hard disk holding shared files Clients Other computers on network Thin client – no processing

47. Organization of ResourcesClient/Server and File Server

48. Organization of ResourcesFile Server Server transmits file to client Client does own processing

49. Organization of ResourcesClient/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

50. Organization of ResourcesPeer-to-Peer • All computers have equal status • Share data and devices as needed • Common with up to 12 computers • Disadvantage – slow transmission