CSE 245: Computer Networks and
Data Communications
http://vista.uconn.edu
Jun-Hong Cui
08/29/2006
Outline
 Course information
 What is a network protocol?
 A brief introduction to the Internet: past
and present
 Summary
2
Course Information
 Personnel
 Instructor
• Jun-Hong Cui, jcui@cse.uconn.edu, ITEB 267
• Office hours
– Tu/Th 10:30am-11:30am or by appointments
– Feel free to stop by if you see my door open
– e-mail is the best way to communicate with me

Teaching assistant
• James Zheng Peng, zheng.peng@uconn.edu
• Office hours
– Time: TBA
– Location: ITEB 230
3
Course Information
 Textbook
 Computer Networking: A Top-Down Approach
Featuring the Internet,
3/e by Kurose and Ross
-Buy through Co-Op or On-line
-Make good use of On-line materials
 Reference books
 Computer Networks,
4/e by Andrew Tanenbaum
 Unix Network Programming
by W. Richard Stevens
And more (see handout)
 Resource
 On-line resources (using NetID)
• http://vista.uconn.edu

Class discussion forum
• Check WebCT (class discussions)
4
What Are the Goals of This Course?
 Understand how Internet works
 Its philosophy
 Its protocols and mechanisms
 Learn network programming
 And have fun!
5
What Will We Cover?
 Introduction (3 lectures)
 Internet architecture and design philosophy
 Applications (5 lectures)
 HTTP, Email, DNS + socket programming (+ C programming)
 transport services (5 lectures)
 reliability; congestion control; transport protocols:
TCP/UDP
 network services (5 lectures)
 routing; network protocols: IP/IPv6
 link and physical layers (5 lectures)
 multiple access; ARP; Ethernet, hubs and bridges
 wireless & mobile networks, multimedia networking
network security (if time permits)
6
What Do You Need To Do?
 Your prerequisites
 basic concepts of operating systems
 programming: C/C++ (tested by proj0)
 Unix/Linux system experience
 probabilities, and basic algorithms
 Your workload
 textbook reading for every lecture (*****)
 assignments
• 5 homework assignments
• 3 programming projects

two mid-term exams, and one final exam
7
What Do You Need To Do?
 Homework: Do on your own
 Programming projects:
 Proj. 0--- C/C++ Programming (not graded)
 Proj. 1--- HTTP Client (group work)
 Proj. 2--- HTTP Server (group work)
 Proj. 3--- Routing Simulation
 Can do advanced part for extra credits
 Proj. 1 and Proj. 2 can be done in a small group (up to 2
people), and others are individual work
 Late policy:
 20% deduction (1 day), 40% (2 days), 80% (3 days), …
8
Grading
Homework
15% (3% each)
Projects
30% (10% each)
Mid-term exam 1
10%
Mid-term exam 2
20%
Final exam
25%
 More important is what you learn than the grades
9
Academic Policy
 Homework and projects should be done on
your own unless specified as group work
 In any homework or project, copying from
other students (or groups) or solution books
are prohibited. Refer to handout for details.
 We follow the University Policy on Academic
Integrity!!!
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Class Attendance and Computers
 Attendance in class …
 Is Responsibility of each Student
 Absence may Result in Missing Hint/Clarification/Error on
Homework or Projects
 May Announce Change in Due Date or Exam Date
 I Might NOT Make ALL information to WebCT
 Computers for projects …
 Use Unix/Linux machines in ECS (TA grading)
 Unix/Linux labs in ITEB and Engineering II
 Apply for an ECS Unix/Linux account on-line
 Use SSH to remotely login those Unix/Linux boxes
 Test on these machines before you hand in your projects
 More info: http://www.engr.uconn.edu/ecs/linux/
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Class Survey
 Please take the class survey

help me to determine your background

help me to determine depth and topics

any suggestions on topics and schedule
 Hand in at the end of the class
12
Questions?
Outline
 Course information
 What is a network protocol?
 A brief introduction to the Internet: past
and present
 Summary
14
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.
15
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
outgoing
message queue
user mailbox
mail
server
user
agent
SMTP
SMTP
mail
server
user
agent
SMTP
POP3,
IMAP
SMTP
user
agent
mail
server
user
agent
user
agent
user
agent
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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)
17
Outline
 Course information
 What is a network protocol?
 A brief introduction to the Internet
 past
 present
 Summary
18
A Brief History of the Internet
 1961


Kleinrock - queueing theory shows effectiveness of packetswitching (telephone network: circuit switching)
1968

Bolt Beranek and Newman, Inc. (BBN) was awarded Packet Switch
contract to build Interface Message Processors (IMPs) for
ARPANET
19
A Brief History of the Internet
 1969

ARPANET commissioned: 4 nodes, 50kbps
20
Initial Expansion of the ARPANET
Dec. 1969
July 1970
Apr. 1972
March 1971
Sep. 1972
21
Multiple Networks
 1974: Initial design of TCP to connect multiple




networks
1986: NSF builds NSFNET as backbone, links 6
supercomputing 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 1,000,000,000
Internet:
100,000,000
Aug. 1981
213
10,000,000
Oct. 1984
1,024
1,000,000
Dec. 1987
28,174
100,000
10,000
Oct. 1990
313,000
1,000
Jul. 1993
1,776,000
100
Jul. 1996 19,540,000
10
Jul. 2000 93,047,000
1
Jul. 2002 162,128,493
1981 1984 1987 1990 1993 1996 1999 2002
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Outline
 Course information
 What is a network protocol?
 A brief introduction to the Internet
 past
 present
 Summary
25
Internet Physical Infrastructure
Local/Regional
ISP
 Residential
Access



Modem
DSL
Cable modem
 Campus
network access



Ethernet
FDDI
Wireless
 Access to ISP,
Backbone
transmission


Local/Regional
ISP
Backbone:
National ISP
 Internet Service
T1/T3, OC-3, OC-12
ATM, SONET, WDM
Providers


Local/Regional/
National
They exchange
packets at Point of
Presence (POP)
26
ATT Global Backbone IP Network
From http://www.business.att.com
27
From AT&T web site.
28
Summary
 Course information
 Concept of network protocol
 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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Hands-on Exercises
 Read the manual of ping and traceroute (or
tracert), and try them on an ECS machine
1.
2.
% /bin/ping <machine_name>
% /usr/sbin/traceroute <machine_name>
 Look at the web sites of the routers you see




through traceroute
Have fun …
Check WebCT Vista for Proj. 0
Buy your textbook on-line (cheaper & faster)
Dot not forget to find your group members!
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