Welcome to CMPE003 Personal Computers: Hardware and Software Dr. Chane Fullmer Fall 2002 UC Santa Cruz

October 21, 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 –

October 21, Class Information Midterm results: Average… = ~70% (Strong ‘C’) Low – 18 High – 46 Will be handed back after lecture today

Networking: Computer Connections Chapter 7 Part B

October 21, 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

October 21, Network Topology Physical layout Star Ring Bus Node – any device connected to the network Server Computer Printer Other peripheral

October 21, Star Central hub All messages routed through hub Hub prevents collisions Node failure – no effect on overall network Hub failure – network fails

October 21, 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

October 21, Bus Single pathway All nodes attached to single line Collisions result in re-send Node failure – no effect on overall network

October 21, 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…

October 21, 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 – , 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 …

October 21, 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

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.

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.

October 21, Introduction to Networks Connecting Computers A minimum network – two nodes Computer AComputer B

October 21, Introduction to Networks Connecting Computers Adding a new computer to the network… Computer AComputer B Computer C

October 21, 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

October 21, Introduction to Networks Connecting Computers Example: Thin Net (Ethernet) Computer A Computer CComputer B LAN Hub Terminator

October 21, Introduction to Networks Connecting Computers Example: 10BaseT (Ethernet) Computer AComputer B Computer C LAN Hub

October 21, 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

October 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..

October 21, 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…

October 21, 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

October 21, 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

October 21, 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

October 21, 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

October 21, 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

October 21, How Does a Network Work Wide Area Backbone LAN Net  A Happy Router

October 21, 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

October 21, 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

October 21, 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

October 21, WAN Technology WAN G1 G2 G3

October 21, WANs Today Link computers in geographically distant locations

October 21, 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)

October 21, High Capacity Digital Lines T1 (DS1) 1.54 Mbps 24 simultaneous voice connections T3 (DS3) 28 T1 lines 43 Mbps Expensive High-volume traffic

October 21, 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

October 21, 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

October 21, Digital Signaling (DS) Hierarchy:

October 21, 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

October 21, 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)

October 21, 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

October 21, 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

October 21, Using the Network Communications Software Applications

October 21, File Transfer Software FTP,SFTP,SCP: Download Receive a file from another computer Upload Send a file to another computer

October 21, Terminal Emulation Software TELNET, SSH: PC imitates a terminal for communication to remote system Micro-to-mainframe link

October 21, 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

October 21, Organization of Resources Client/Server and File Server

October 21, Organization of Resources File Server Server transmits file to client Client does own processing

October 21, 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, Benefits Reduces volume of data traffic Allows faster response for each client Nodes can be less expensive computers

October 21, 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

October 21, Office Automation Communication Applications Facsimile (Fax) Groupware Teleconferencing Video conferencing ATM Electronic fund transfers Telecommuting Online services The Internet Electronic data interchange (EDI)

October 21,