Introduction Lecture 1 cs193i – Internet Technologies Summer 2004 Stanford University

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

The Ever-changing Internet Different colors based on IP address

What is the Internet? WWW WWW Video conferencing Video conferencing ftp ftp telnet telnet Instant messaging Instant messaging …

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

“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

Where Did It Come From? It was invented by Al Gore. JUST KIDDING! 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 Four host computers (UCLA, SRI, UCSB, University of Utah) Get more info at:

ARPANET,

History of the Internet RFCs begun by S. Crocker ( 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) 1980s – Hardware Explosion (LANs, PCs, and workstations) 1983 – Ethernet by Metcalfe 1983 – Ethernet by Metcalfe DNS – Distributed and scalable mechanism for resolving host names into IP addresses DNS – Distributed and scalable mechanism for resolving host names into IP addresses UC Berkeley implements TCP/IP into Unix BSD UC Berkeley implements TCP/IP into Unix BSD 1985 – Internet used by researchers and developers 1985 – Internet used by researchers and developers

History of the Internet Tim Berners-Lee at CERN in 1989 Tim Berners-Lee at CERN in 1989 Proposal for WWW in 1990 Proposal for WWW in 1990 First web page on November 13, 1990 First web page on November 13, 1990 Hypertext - Text that contains links to other text. Ted Nelson’s Xanadu Vannevar Bush’s Memex ( W3C Get more info at:

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

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

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

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

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

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

Administrative Details Contacting staff Contacting staff Newsgroup Newsgroup su.class.cs193i su.class.cs193i Grading/testing on Leland systems Grading/testing on Leland systems Honor Code Honor Code

Five Minute Break

Communicating Via the Internet

Bits and Bytes Computer Data is stored in Binary Binary Digits (bits) Base 2 representation Every 8 bits == 1 Byte (2 bytes (once known as octet)) Hexadecimal == Base 16 representation 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

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)

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

Any-to-Any Communication n 2 Network Effect (Metcalfe’s Law) n 2 Network Effect (Metcalfe’s Law) Total utility of system proportional to n 2 Total utility of system proportional to n 2 Think about Orkut, MSN Messenger Think about Orkut, MSN Messenger

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

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

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

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

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

Ethernet

Ethernet Variations

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

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

Next Time Network Layer Network Layer IP IP End-to-End or Transport Layer End-to-End or Transport Layer TCP TCP