Introduction to Computer Network

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Introduction toComputer Network
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Course Outline

• Introduction
• Protocol Concept OSI 7 Layers
• Data Link Layer
• Frame Control bit-oriented, character-oriented
• Error Control checksum, Hamming code, CRC
• Flow Control stop wait, go-back-n, selective
  repeat
• Medium Access Control Slotted-Aloha, CSMA-CD,
• Token Passing CSMA-CA
• LAN Ethernet, Token-Ring, Token-Bus, Wireless
  LAN
• Network Layer
• Routing
• Algorithms
• Protocol
• Congestion
• Transport Layer

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Reference books

• Computer Networks,
• by Andrew Tanenbaum
• Data Communication, Computer Network and Open
  System
• by Fred Halsall

4
Grading

• What you get into your brain is more importance
  than what you get into your transcript

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What Are the Goals Of This Course?

• Understand how Internet works
• Its philosophy
• Its protocols and mechanisms
• Have fun!

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Introduction

• Administrative trivias
• What is a network protocol?

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Questions?
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Outline

• Administrative trivias
• What is a network protocol?
• A brief introduction to the Internet past and
  present
• Summary

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What is a Network Protocol?

• A network protocol defines the format and the
  order of messages exchanged between two or more
  communicating entities, as well as the actions
  taken on the transmission and/or receipt of a
  message or other event.

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Format
IP Packet
TCP segment
Ethernet Frame
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netstat --tcp -a
CLOSED
LISTEN
SYN RCVD
ESTABLSIHED
ESTABLSIHED
ESTABLSIHED
FINWAIT 1
FIN
CLOSEWAIT
LASTACK
FINWAIT 2
TIMEWAIT
ACK
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An Example Simple Mail Transfer Protocol (SMTP)

• Messages from a client to a mail server
• HELO
• MAIL FROM ltaddressgt
• RCPT TO ltaddressgt
• DATAltThis is the text end with a line with a
  single .gt
• QUIT
• Messages from a mail server to a client
• status code
• The first digit of the response broadly indicates
  the success, failure, or progress of the previous
  command.
• 1xx - Informative message
• 2xx - Command ok
• 3xx - Command ok so far, send the rest of it.
• 4xx - Command was correct, but couldn't be
  performed for some reason.
• 5xx - Command unimplemented, or incorrect, or a
  serious program error occurred.
• content

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Internet Standardization Process

• All standards of the Internet are published as
  RFC (Request for Comments)
• but not all RFCs are Internet Standards !
• available http//www.ietf.org
• A typical (but not the only) way of
  standardization
• Internet draft
• RFC
• Proposed standard
• Draft standard (requires 2 working
  implementations)
• Internet standard (declared by Internet
  Architecture Board)
• David Clark, 1992
• We reject kings, presidents, and voting. We
  believe in rough consensus and running code.

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Outline

• Administrative trivias
• What is a network protocol?
• A brief introduction to the Internet
• past
• present
• Summary

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A Brief History of the Internet

• 1957
• USSR launches Sputnik, US formed Advanced
  Research Projects Agency (ARPA) as a response
• 1968
• Bolt Beranek and Newman, Inc. (BBN) was awarded
  Packet Switch contract to build Interface Message
  Processors (IMPs) for ARPANET

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A Brief History of the Internet

• 1969
• ARPANET commissioned 4 nodes, 50kbps

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Initial Expansion of the ARPANET
Dec. 1969
March 1971
July 1970
Apr. 1972
Sep. 1972
rfc 527 ARPAWOCKY rfc 602 The Stockings Were
Hung by the Chimney with Care
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Multiple Networks

• 1974 Initial design of TCP to connect multiple
  networks
• 1981 BITNET (Because Its Time NETwork) between
  CUNY and Yale
• 1986 NSF builds NSFNET as backbone, links 6
  supercomputer centers, 56 kbps this allows an
  explosion of connections, especially from
  universities
• 1987 10,000 hosts
• 1988 NSFNET backbone upgrades to 1.5Mbps
• 1989 100,000 hosts rfc 1121 Act One
  The Poem WELCOME by Leonard
  Kleinrock We've gathered here for two days to
  examine and debate And reflect on data
  networks and as well to celebrate. To
  recognize the leaders and recount the path we
  took. We'll begin with how it happened for
  it's time to take a look. Yes, the history is
  legend and the pioneers are here. Listen to
  the story - it's our job to make it clear.
  We'll tell you where we are now and where we'll
  likely go. So welcome to ACT ONE, folks.
• Sit back - enjoy the show!!

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Web and Commercialization of the Internet

• 1990 ARPANET ceases to exist
• 1991 NSF lifts restrictions on the commercial
  use of the Net Berners-Lee of European
  Organization for Nuclear Research (CERN) released
  World Wide Web
• 1992 1 million hosts (RFC 1300 Remembrances of
  Things Past)
• 1994 NSF reverts back to research network
  (vBNS) the backbone of the Internet consists of
  multiple private backbones
• Today backbones run at 10Gbps, 100s millions
  computers in 150 countries
• For a link of interesting RFCs, please see
  http//zoo.cs.yale.edu/classes/cs433/readings/int
  erestingrfcs.html
• For more on Internet history, please see
  http//www.zakon.org/robert/internet/timeline/

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Growth of the Internet in Terms of Number of
Hosts

• Number of Hosts on the Internet
• Aug. 1981 213
• Oct. 1984 1,024
• Dec. 1987 28,174
• Oct. 1990 313,000
• Jul. 1993 1,776,000
• Jul. 1996 19,540,000
• Jul. 2000 93,047,000
• Jul. 2002 162,128,493

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Outline

• Administrative trivias
• What is a network protocol?
• A brief introduction to the Internet
• past
• present
• Summary

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Internet Physical Infrastructure
Local/Regional ISP
BackboneNational ISP
Local/RegionalISP

• Residential Access
• Modem
• DSL
• Cable modem

• Access to ISP, Backbone transmission
• T1/T3, OC-3, OC-12
• ATM, SONET, WDM

• Internet Service Providers
• Local/Regional/National
• They exchange packets at Point of Presence (POP)

• Campus network access
• Ethernet
• FDDI
• Wireless

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Local Access ADSL

• Asymmetrical Digital Subscriber Loop (ADSL)
• Telephone companys solution to last mile
  problem

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Local Access Cable Modems

• Fiber node 500 - 1K homes
• Distribution hub 20K - 40 K homes
• Regional headend 200 K - 400 K homes

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Access of the Internet from Yale through Internet2

• cicada.cs.yale.edu /usr/sbin/traceroute
  www.cs.utexas.edu
• 1 zoo-gatew.cs.yale.edu (128.36.232.1) 0.693
  ms 0.606 ms 0.658 ms
• 2 bifrost.net.yale.edu (130.132.1.100) 0.681
  ms 0.528 ms 0.448 ms
• 3 ATM10-540-OC3-GIGAPOPNE.NOX.ORG (192.5.89.69)
  4.906 ms 5.041 ms 5.205 ms
• 4 192.5.89.10 (192.5.89.10) 15.545 ms 10.098
  ms 10.660 ms
• 5 washng-nycmng.abilene.ucaid.edu (198.32.8.85)
  29.270 ms 14.716 ms 14.880 ms
• 6 wash-washng.abilene.ucaid.edu (198.32.11.127)
  14.414 ms 14.696 ms 14.565 ms
• 7 atla-wash.abilene.ucaid.edu (198.32.8.65)
  29.915 ms 29.789 ms 29.394 ms
• 8 hstn-atla.abilene.ucaid.edu (198.32.8.33)
  48.445 ms 48.588 ms 48.549 ms
• 9 hstnng-hstn.abilene.ucaid.edu (198.32.11.112)
  48.645 ms 48.879 ms 48.755 ms
• 10 ser3-a0-0-1.gw.utexas.edu (128.83.37.21)
  52.776 ms 52.458 ms 52.693 ms
• 11 ser10-msfc1-v728.gw.utexas.edu (128.83.10.25)
  52.956 ms 52.836 ms 52.591 ms
• 12 ser11-msfc-v708.gw.utexas.edu (128.83.10.14)
  52.623 ms 52.696 ms 52.578 ms
• 13 128.83.37.18 (128.83.37.18) 53.044 ms
  53.371 ms 53.341 ms
• 14 net2.cs.utexas.edu (128.83.120.155) 53.236
  ms 52.865 ms 52.645 ms

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Access of the Internet from Yale through Qwest

• cicada.cs.yale.edu /usr/sbin/traceroute
  www.amazon.com
• 1 zoo-gatew.cs.yale.edu (128.36.232.1) 0.676
  ms 2.278 ms 2.558 ms
• 2 bifrost.net.yale.edu (130.132.1.100) 1.506
  ms 0.559 ms 0.496 ms
• 3 bos-edge-02.inet.qwest.net (63.145.0.13)
  5.035 ms 5.400 ms 5.335 ms
• 4 bos-core-02.inet.qwest.net (205.171.28.29)
  4.938 ms 5.016 ms 4.632 ms
• 5 jfk-core-01.inet.qwest.net (205.171.8.19)
  10.240 ms 10.106 ms 10.096 ms
• 6 jfk-core-03.inet.qwest.net (205.171.230.6)
  10.923 ms 10.305 ms 10.387 ms
• 7 jfk-brdr-02.inet.qwest.net (205.171.230.25)
  9.980 ms 10.160 ms 9.887 ms
• 8 qwest-gw.n54ny.ip.att.net (192.205.32.169)
  10.459 ms 10.259 ms 10.426 ms
• 9 tbr1-p014001.n54ny.ip.att.net (12.123.3.1)
  10.468 ms 10.437 ms 10.938 ms
• 10 tbr1-p013801.cgcil.ip.att.net (12.122.10.50)
  31.165 ms 30.894 ms 30.656 ms
• 11 tbr2-p012501.cgcil.ip.att.net (12.122.9.134)
  30.871 ms 30.683 ms 30.974 ms
• 12 gbr4-p20.st6wa.ip.att.net (12.122.10.62)
  84.733 ms 84.385 ms 84.279 ms
• 13 gbr2-p100.st6wa.ip.att.net (12.122.5.170)
  84.311 ms 84.334 ms 84.415 ms
• 14 gar1-p370.st6wa.ip.att.net (12.123.44.62)
  84.214 ms 84.176 ms 84.582 ms
• 15 12.127.79.30 (12.127.79.30) 98.027 ms
  98.378 ms 98.244 ms
• 16 177-173.amazon.com (207.171.177.173) 98.390
  ms 98.099 ms 98.202 ms

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From http//stat.qwest.net/index_flash.html
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ATT Global Backbone IP Network
From http//www.business.att.com
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From ATT web site.
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Summary

• Course administrative trivias
• A protocol defines the format and the order of
  messages exchanged between two or more
  communicating entities, as well as the actions
  taken on the transmission and/or receipt of a
  message or other event.
• The past
• The Internet started as ARPANET in late 1960s
• The initial link bandwidth was 50 kbps
• The number of hosts at the end of 1969 was 4
• Current
• The number of hosts connected to the Internet
  grows at an exponential speed
• The backbone speed of the current Internet is
  about 10 Gbps
• The number of hosts attached to the Internet in
  July 2002 was about 162 millions

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Summary Internet structure network of networks

• roughly hierarchical
• national/international backbone providers (NBPs)
• e.g. BBN/GTE, Sprint, ATT, IBM, UUNet
• interconnect (peer) with each other privately, or
  at public Network Access Point (NAPs)
• regional ISPs
• connect into NBPs
• local ISPs
• connect into regional ISPs

regional ISP
NBP B
NBP A
regional ISP
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Observing the Internet (1)

• Read the manual of ping and traceroute, and try
  them on unix.kmitl.ac.th machine
• /bin/ping ltmachine_namegt
• ping www.yahoo.com
• /usr/sbin/traceroute ltmachine_namegt
• Look at the web sites of the routers you see
  through traceroute