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Welcome to CMPE003 Personal Computers: Hardware and Software Dr. Chane Fullmer Dr. Chane Fullmer Fall 2002 Fall 2002 UC Santa Cruz UC Santa Cruz
Welcome to CMPE003 Personal Computers: Hardware and Software
Dr. Chane FullmerDr. Chane Fullmer
Fall 2002Fall 2002
UC Santa CruzUC Santa Cruz
October 21, 2002 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
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Class Information
Midterm results: Average….. 34.6 = ~70% (Strong ‘C’)
Low – 18 High – 46
Will be handed back after lecture today
Networking: Computer Connections
Chapter 7
Part B
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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
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Network Topology
Physical layout Star Ring Bus
Node – any device connected to the network Server Computer Printer Other peripheral
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Star
Central hub All messages routed through hub Hub prevents collisions Node failure – no effect on overall network Hub failure – network fails
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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
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Bus
Single pathway All nodes attached to single line Collisions result in re-send Node failure – no effect on overall network
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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…
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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 …
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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.
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Introduction to Networks
Connecting Computers A minimum network – two nodes
Computer A Computer B
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Introduction to Networks
Connecting Computers Adding a new computer to the network…
Computer A Computer B
Computer C
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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
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Introduction to Networks
Connecting Computers Example: Thin Net (Ethernet)
Computer A Computer CComputer B
LAN Hub
Terminator
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Introduction to Networks
Connecting Computers Example: 10BaseT (Ethernet)
Computer A Computer B
Computer C
LAN Hub
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Introduction to Networks
LANsA 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
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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..
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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…
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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
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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
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How Does A Network Work
A computer can have multiple NICs Each NIC can connect to a separate network
NetworkA
NetworkA
NetworkB
NetworkB
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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
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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
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How Does a Network Work
Wide Area Backbone
LAN
LANLAN
LAN LAN
LAN
LAN
Net
Net
Net
A Happy Router
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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
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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
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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
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WAN Technology
WAN
G1
G2
G2 G3
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WANs Today
Link computers in geographically distant locations
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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)
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High Capacity Digital Lines
T1 (DS1) 1.54 Mbps 24 simultaneous voice connections
T3 (DS3) 28 T1 lines 43 Mbps
Expensive High-volume traffic
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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
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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
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Digital Signaling (DS) Hierarchy:
DS # Voice Circuits BandwidthDS0 1 64 kbpsDS1 24 1.544 MbpsDS2 96 6.312 MbpsDS3 672 44.736 Mbps
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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
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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)
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Ethernet
Dominant protocol
Bus or star topology
Uses CSMA/CD
CSMA/CDCarrier 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
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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
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Using the Network
Communications Software Applications
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File Transfer Software
FTP,SFTP,SCP:Download
Receive a file from another computer
UploadSend a file to another computer
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Terminal Emulation Software
TELNET, SSH:PC imitates a terminal for
communication to remote system
Micro-to-mainframe link
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Organization of ResourcesClient/Server and File Server
Clients
Other computers on network
Thin client – no processing
Server
Controls the networkHard disk holding shared
files
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Organization of Resources Client/Server and File Server
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Organization of ResourcesFile Server
Server transmits file to client
Client does own processing
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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
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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
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Office AutomationCommunication Applications
E-mail Facsimile (Fax) Groupware Teleconferencing Video conferencing ATM
Electronic fund transfers
Telecommuting Online services The Internet Electronic data
interchange (EDI)
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