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, jcui@cse.uconn.edu, 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

Questions?

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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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1969 ARPANET commissioned: 4 nodes, 50kbps

A Brief History of the Internet

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Initial Expansion of the ARPANET

Dec. 1969 March 1971July 1970

Apr. 1972 Sep. 1972

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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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ATT Global Backbone IP Network

From http://www.business.att.com

27From AT&T web site.

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Network Access Point

Interconnect multiple ISP’s

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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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Hands-on Exercises

Read the manual of ping and traceroute, and try them on an ECS machine

1. % /bin/ping <machine_name>2. % /usr/sbin/traceroute <machine_name>

Look at the web sites of the routers you see through traceroute

Have fun …