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Introduction Lecture 1

Introduction Lecture 1. cs193i – Internet Technologies Summer 2004 Stanford University. Outline. What is the Internet? Where did it come from? What are we going to discuss in cs193i? Break Networking basics Physical Infrastructure. The Ever-changing Internet.

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Introduction Lecture 1

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  1. IntroductionLecture 1 cs193i – Internet Technologies Summer 2004 Stanford University

  2. Outline • What is the Internet? • Where did it come from? • What are we going to discuss in cs193i? • Break • Networking basics • Physical Infrastructure

  3. The Ever-changing Internet Different colors based on IP address http://research.lumeta.com/ches/map

  4. What is the Internet? • WWW • Video conferencing • ftp • telnet • Email • Instant messaging • …

  5. What is the Internet? • WWW • Video conferencing • ftp • telnet • Email • Instant messaging • … A communication infrastructure Usefulness is in exchanging information

  6. “On-line interactive communities... will be communities not of common location, but of common interest.... the total number of users...will be large enough to support extensive general purpose [computers]. All of these will be interconnected by telecommunications channels... [to] constitute a labile network of networks--ever changing in both content and configuration.” J. C. R. Licklider

  7. Where Did It Come From? • It was invented by Al Gore. JUST KIDDING! • Early 1960’s - DARPA (ARPA in 1960’s) project headed by Licklider • Late 1960’s - ARPANET & research on packet switching by Roberts • First node installed by BBN at UCLA in September 1969 • 1969 - Four host computers (UCLA, SRI, UCSB, University of Utah) Get more info at: http://www.isoc.org/internet/history/ http://www.packet.cc/internet.html

  8. ARPANET, 1980 http://mappa.mundi.net/maps/maps_001/

  9. History of the Internet • 1969 - RFCs begun by S. Crocker (http://rfc.sunsite.dk/) • 1972 - Email by Ray Tomlinson & Larry Roberts • 1970’s - TCP by Vint Cerf & Bob Kahn • Evolved into TCP/IP, and UDP • 1980s – Hardware Explosion (LANs, PCs, and workstations) • 1983 – Ethernet by Metcalfe • DNS – Distributed and scalable mechanism for resolving host names into IP addresses • UC Berkeley implements TCP/IP into Unix BSD • 1985 – Internet used by researchers and developers

  10. History of the Internet • Tim Berners-Lee at CERN in 1989 • Proposal for WWW in 1990 • First web page on November 13, 1990 • Hypertext - Text that contains links to other text. • Ted Nelson’s Xanadu • Vannevar Bush’s Memex (http://www.theatlantic.com/unbound/flashbks/computer/bushf.htm) • W3C Get more info at: http://www.isoc.org/internet/history/

  11. What will cs193i cover? • Basic Networking Issues • Network Interoperability and Standards • TCP/IP • Sockets and Client/Server Structures • Services • Applications • HTML, HTTP, CGI, Servlets • Security and Privacy • Advanced Topics

  12. Kelly A. Shaw Instructor Professor at Univ. of Richmond in Fall PhD Candidate w/ Distinction in Teaching BS from Duke University Gates 255 Office hours: MW 2-4pm Silas Boyd-Wickizer Teaching Assistant Office hours: TTh 4-6pm Sweet hall Course Staff

  13. Meeting Times • Lecture • MW 4:15-6:05 McCullough 115 • Broadcast Live on E3 • Stanford Online • Two review sessions - TBA • Perl • Java

  14. Reading Materials • No required textbook • Recommended: • Core Web Programming by Marty Hall and Larry Brown. • Handouts • On-line only

  15. Course Details • Grading • 50% Homework (4 assignments) • 5% Labs (4 labs) • 10% Midterm • 30% Final • 5% Class participation (if not SCPD) • May work in groups of 1 or 2 students • C/NC students

  16. Homework Assignments • HW #1 • POP email client • Server/Client pair with authentication • HW #2 • Simple Web Client • Simple Web Server • HW #3 • CGI Programming (e.g. for maintaining Netflix Movie Queue) • HW #4 • Java / JSP / Servlets and Javascript • Amazon.edu Bookstore

  17. Administrative Details • Contacting staff • cs193i-sum0304-staff@lists.stanford.edu • Newsgroup • su.class.cs193i • Grading/testing on Leland systems • Honor Code

  18. Five Minute Break

  19. Communicating Via the Internet

  20. Bits and Bytes • Computer Data is stored in Binary • Binary Digits (bits) Base 2 representation 1011100001101010 • Every 8 bits == 1 Byte 10111000 01101010 (2 bytes (once known as octet)) • Hexadecimal == Base 16 representation 1011 1000 0110 1010 B 8 6 A • Decimal == Base 10 (we have 10 fingers) 0...9, A = 10, B= 11, C = 12, D = 13, E = 14, F = 15

  21. Bits and Bytes • Kilobyte (2^10=1024 Bytes, 10^3=1000 Bytes in networking) • Megabyte (2^20 Bytes, 10^6 in Networking) • Gigabyte (2^30 Bytes, 10^9 in Networking) • Terabyte (2^40, 10^12) • Petabyte (2^50, 10^15)

  22. link bandwidth latency Performance: Latency and Bandwidth • Latency • How long minimum communication takes in seconds (s) • Round trip vs. single trip • More difficult to overcome than bandwidth • Bandwidth • Number of bits per time unit usually seconds (bps)

  23. Any-to-Any Communication • n2 Network Effect (Metcalfe’s Law) • Total utility of system proportional to n2 • Think about Orkut, MSN Messenger

  24. Babel • Internet consists of many different types of networks • Ethernet • Token ring • Different types of operating systems and other software • How do they work together? • Standards

  25. 01010 01010 0 1 0 1 0 01010 01010 a b Divide Work into Layers • make network simple and reliable • connect segments, address (locating points on graph) and route (navigating graph) • physically encode bits on “wire”

  26. Sending Data Along Wires • Connection-oriented • Circuit switched • Persistent connection set up between sender and receiver • Example: telephone system • Connectionless • Packet switched • Data partitioned into packets and sent individually from sender to receiver • Reassembled at receiver

  27. Circuit switched Advantages Only route once Latency and bandwidth constant Disadvantages Idle resources unavailable for other connections Large setup time Single point of failure Distributed state Packet switched Advantages Efficient use of wires Small startup overhead Disadvantages Route each packet Per packet overhead Bursty Comparison of Switching Technologies

  28. Ethernet • Bob Metcalfe at Xerox PARC • Used for local area networks (LANs) • Physically near one another • 200 computers within 100 meters • Broadcast medium • Single wire connects all computers • Each computer has unique 48-bit MAC address • All computers constantly listen • “Carrier Sense, Multiple Access with Collision Detect” • Sender waits until wire unused before sending • If hears collision, stops, waits random time, retransmits

  29. Ethernet

  30. Ethernet Variations

  31. Ethernet Properties • Shared • Distributed (not Centralized) • Insecure • Unpredictable Latency & Bandwidth • But it works! • Under light load (<30%), appears to be point-to-point

  32. Alternative to Ethernet:Token Ring • Alternative introduced by IBM (1980s) • “Passing the Conch Shell”

  33. Next Time • Network Layer • IP • End-to-End or Transport Layer • TCP

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