CSE 245: Computer Networks and Data Communication
http://www.cse.uconn.edu/~jcui/courses/cse245/
Jun-Hong Cui
08/26/2003
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Outline
Course information What is a network protocol? A brief introduction to the Internet: past
and present Summary
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Course Information
Personnel instructor
• Jun-Hong Cui, [email protected], ITEB 267• office hours
– TuTh 03:30pm-4:30pm or by appointments
– Feel free to stop by if you see my door open: ITEB 267
– e-mail is the best way to communicate with me
grader• TBA
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Course Information Textbook
Computer Networking: A Top-Down Approach Featuring the Internet,
2/e by Kurose and Ross Reference books
Computer Networks, 4/e by Andrew Tanenbaum Unix Network Programming by W. Richard StevensAnd more (see handout)
Resource Home page
• http://www.cse.uconn.edu/~jcui/courses/cse245/
Mailing list• TBA
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What Are the Goals Of This Course?
Understand how Internet works Its philosophy Its protocols and mechanisms
Learn network programming
Have fun!
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What Will We Cover?
Introduction (3 lectures) Internet architecture and design philosophy
Applications (4 lectures) HTTP, Email, DNS
transport services (4 lectures) reliability; congestion control; transport protocols:
TCP/UDP
network services (5 lectures) routing; network protocols: IP/IPv6
link and physical layers (4 lectures) multiple access; Ethernet, FDDI, hubs and bridges
multimedia networking & security (if time permits) audio/video applications; network support
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What Do You Need To Do?
Your prerequisites algorithms: e.g. shortest path algorithms programming: C/C++, or Java basic concepts of operating systems
Your workload reading assignment for every lecture homework assignments
• 4 written assignments• 2 programming projects
one mid-term exam, and one final exam
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Grading
More important is what you learn than the grades
Homework 20% (5% each)
Projects 30% (15% each)
Mid-term exam
20%
Final exam 30%
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Class Survey
Please take the class surveyhelp me to determine your background
help me to determine the depth and topics
any suggestions on the tentative schedule
http://www.cse.uconn.edu/~jcui/courses/cse245/schedule.html
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Outline
Course information 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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An Example: Simple Mail Transfer Protocol (SMTP)
Messages from a client to a mail server
HELO MAIL FROM: <address> RCPT TO: <address> DATA
<This is the text end with a line with a single .>
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
user mailbox
outgoing message queue
mailserver
useragent
useragent
useragent
mailserver
useragentuser
agent
mailserver
useragent
SMTP
SMTP
SMTP
POP3,IMAPSMTP
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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)
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Outline
Course information 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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Multiple Networks
1974: Initial design of TCP to connect multiple networks
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
WELCOME by Leonard Kleinrock …
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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 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
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Growth of the Internet in Terms of Number of Hosts
Number of Hosts on the Internet:
Aug. 1981 213Oct. 1984 1,024Dec. 1987 28,174 Oct. 1990 313,000 Jul. 1993 1,776,000Jul. 1996 19,540,000Jul. 2000 93,047,000Jul. 2002 162,128,493 1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
1981 1984 1987 1990 19931996 1999 2002
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Outline
Course information What is a network protocol? A brief introduction to the Internet
past present
Summary
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Backbone:National ISP
Local/RegionalISP
Local/RegionalISP
Internet Physical Infrastructure
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 Line (ADSL) Telephone company’s 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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Summary
Course information 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,
AT&T, 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
NBP A
NBP B
NAP NAP
regional ISP
regional ISP
localISP
localISP
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