CS4331/5331: Network Security
Instructor: Dr. Sunho Lim (Ph.D., Assistant Professor)
Lecture 00
sunho.lim@ttu.edu
CS4331/5331: Network Security, Summer I 2021
1
Administration
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Class Meetings:
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M/T/W/R/F, 12:00 PM – 1:50 PM (Synchronous Online)
 Recorded lectures will also be uploaded after the class
 Class attendance is highly required.
 A daily assignment (e.g., either review or quiz) will be assigned and it must be
completed before the due date, e.g., before the next class begins.
Instructor: Dr. Sunho Lim (Ph.D., Assistant Professor)

Office: 310 ENGCTR (Online)
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Tentative office hours: M/W, 2:00 PM – 3:00 PM, or by appointment (email or
Zoom meeting)
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E-mail: sunho.lim@ttu.edu

Class homepage,
 TTU Blackboard
 Check any update frequently
CS4331/5331: Network Security, Summer I 2021
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Administration (cont.)
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Class homepage, TTU Blackboard
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“Summer 2021 TTU - CS-4331-102 & CS-5331-102 & CS-5331-D02”
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Check any update frequently
Announcement

Post and email broadcasted from TTU Blackboard
Syllabus
Lecture Note
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Recorded lecture
Homework

Submit through TTU Blackboard
Quiz & Exam

Quiz/Review/Exam

Submit through TTU Blackboard
Zoom
CS4331/5331: Network Security, Summer I 2021
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Administration (cont.)
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Required Textbook:
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No required textbook but a couple of
reference books will be used
 Highly recommend: Computer
Networking – A Top-Down
Approach, by J. F. Kurose and K. W.
Ross, 7th Edition, Pearson

Important concepts/materials will be
included in the lecture notes from
various sources.
CS4331/5331: Network Security, Summer I 2021
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Administration (cont.)
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References:

Network Security Essentials – Applications and
Standards, 6th Edition, W. Stallings, Pearson

Cryptography and Network Security –
Principles and Practices, 4th Edition, W. Stallings,
Pearson
CS4331/5331: Network Security, Summer I 2021
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Administration (cont.)
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References: (cont.)
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Network Security – Private Communication in
a Public World, 2nd Edition, C. Kaufman, R.
Perlman, and M. Speciner, Person

Internet Security: A Hands-on Approach, 2nd
Edition, W. Du

Additional references or materials will be
included in the lecture note, or uploaded in the
Blackboard
CS4331/5331: Network Security, Summer I 2021
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Course Description
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

Description:
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This course will introduce the basic security risks, threats, countermeasures, and
applications in infrastructure-based networks. We will focus on the algorithms
and communication protocols embedded in the level of the link, network, transport,
and application layers.
Objectives:

The primary objective of this course is to introduce students the fundamental
principles of network security and its related techniques in infrastructure-based
networks.
Prerequisites:

Good background in computer science, good programming skill (e.g., Python or C),
or permission from the instructor
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Tentative Course Outline
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Introduction of Network Security
Basic Cryptography
Authentication and Integrity
Secure Email
Secure Socket Layer
IPsec
Intruder Detection
Firewalls
Wireless Security
CS4331/5331: Network Security, Summer I 2021
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Grading Policy
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No make-up exam/quiz!
Midterm Exam: 20%
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June 15th (Tuesday), 12:00 PM – 1:50 PM, online
Final Exam: 30%
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July 2nd (Friday), 11:00 AM – 1:30 PM, online
Quiz/Review: 20%
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Quiz/Review may not be announced in advance
Homework: 30%
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Late homework/quiz/review will NOT be accepted:
Grade
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A (90 – 100), B (80 - 89), C (70 - 79), D (60 - 69), and F (0 - 59)
CS4331/5331: Network Security, Summer I 2021
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In addition,
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Utilize office hours
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Instructor: M/W 2:00 PM - 3:00 PM, by appointment (Email or Zoom meeting)

TA: Mahfuzur Rahman <mahfrahm@ttu.edu>
When you send an email,

Please use the course number, e.g., CS4331/5331, in the title

Must use TTU email account
CS4331/5331: Network Security, Summer I 2021
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Basic Infrastructure-based Networks
Instructor: Dr. Sunho Lim (Ph.D., Assistant Professor)
Lecture 01
sunho.lim@ttu.edu
Adapted partially from Computer Networking – A Top-Down Approach, by J. F. Kurose and K. W. Ross,
7th Edition, Pearson
CS4331/5331: Network Security, Summer I 2021
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What’s the Internet:
“Nuts and Bolts” View
螺母和螺栓，指具体内容
PC

server
millions of connected computing
devices: hosts = end systems

running application programs
wireless
laptop
cellular
handheld  communication links
 fiber, copper, radio, satellite
access
 transmission rate =
points
bandwidth
wired
links

router
routers: forward packets (chunks of
data)
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Mobile network
Global ISP
Home network
Regional ISP
Institutional network
What’s the Internet:
“Nuts and Bolts” View (cont.)
Mobile network



protocols control sending, receiving of msgs

e.g., TCP, IP, HTTP, Ethernet, etc.
Internet: “network of networks”

loosely hierarchical

public Internet versus private intranet
Global ISP
Home network
Regional ISP
Internet standards

RFC: Request for comments

IETF: Internet Engineering Task Force
Institutional network
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What’s the Internet:
A Service View
Mobile network


communication infrastructure enables distributed
applications:
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Web, VoIP, email, games, e-commerce, file
sharing
communication services provided to apps:

reliable data delivery from source to
destination
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“best effort” (unreliable) data delivery
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Global ISP
Home network
Regional ISP
Institutional network
Protocol?
A network protocol defines the format, order of msgs
sent and received among network entities, and
actions taken on msg transmission, and/or
receipt of a msg or other event.
network protocols:

machines rather than humans

all communication activity in Internet
governed by protocols
human protocols:

“what’s the time?”

“I have a question”

introductions
… specific msgs sent
… specific actions taken when msgs
received, or other events
Hi
TCP connection
request
TCP connection
response
Hi
Get http://www.awl.com/kurose-ross
Got the
time?
2:00
<file>
time
CS4331/5331: Network Security, Summer I 2021
Q: a protocol for cutting a pizza equally?
15
Processor Vs. Process
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Multi-programming
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Single CPU with multiple programs?
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The OS creates a PROCESS for
each program

Control the switching of these
processes
What is a process?

The execution in program! ???

ACTIVITY!!
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Network Structure
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network edge:
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hosts: clients and servers
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servers often in data centers
access networks, physical media:

wired, wireless communication links
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connect an end system to the first
router
network core:

interconnected routers

network of networks
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Network Structure:
The Network Edge
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

end systems (hosts):

run application programs

e.g. Web, email

at “edge of network”
client/server model
 client host requests, receives service from
always-on server
 e.g. Web browser/server; email client/server
peer-peer model:
 minimal (or no) use of dedicated servers
 e.g. Skype, BitTorrent
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peer-peer
client/server
Access Networks and Physical Media
Q: How to connect end systems to edge router?
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physical medium
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residential access nets – e.g., coaxial cable
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institutional access networks (school,
company) – e.g., fiber optics
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mobile access networks – e.g., radio
channels
Keep in mind:

bandwidth (bits per second) of access
network?

shared or dedicated?
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Access Networks and Physical Media:
Sending Packets of Data
host sending function:

take application message
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break into smaller chunks, known as
packets, of length L bits

transmits packet into access network at
transmission rate R

link transmission rate, a.k.a., link
capacity, or link bandwidth
two packets,
L bits each
2 1
R: link transmission rate
host
packet
transmission
delay
=
time needed to
transmit L-bit
packet into link
=
L (bits)
R (bits/sec)
1-20
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Why Layering?
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dealing with complex systems
explicit structure allows identification, relationship of complex system’s pieces
modularization eases maintenance, updating of system
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change of implementation of layer’s service is transparent to the rest of system
layering – potential drawback?
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one layer may duplicate low-layer functionality

functionality at one layer may need information in another layer

violate the goal of separation of layers
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Layering of Airline Functionality
ticket (purchase)
ticket (complain)
baggage (check)
baggage (claim
gates (load)
gates (unload)
gate
runway (takeoff)
runway (land)
takeoff/landing
airplane routing
airplane routing
airplane routing
departure
airport
airplane routing
airplane routing
intermediate air-traffic
control centers
arrival
airport
Layers: each layer implements a service
 via its own internal-layer actions
 relying on services provided by layer below
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ticket
baggage
Internet Protocol Stack
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Application:
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supporting network applications
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FTP, SMTP, HTTP
Transport:
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process-process data transfer

TCP, UDP
Network:

routing of datagrams from source to destination

IP, routing protocols
Link:

data transfer between neighboring network elements

PPP, Ethernet
Physical:

bits “on the wire”
application
transport
network
link
physical
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source
message
segment
M
Ht
M
datagram Hn Ht
M
frame Hl Hn Ht
M
application
transport
network
link
physical
Encapsulation
link
physical
switch
destination
M
Ht
M
Hn Ht
M
Hl Hn Ht
M
application
transport
network
link
physical
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Hn Ht
M
Hl Hn Ht
M
network
link
physical
Hn Ht
M
router
Encapsulation
(cont.)
source
message
segment
datagram
frame
M
Ht
M
Hn Ht
M
Hl Hn Ht
M
application
transport
network
link
physical
link
physical
switch
M
Ht
M
Hn Ht
M
Hl Hn Ht
M
destination
Hn Ht
M
application
transport
network
link
physical
Hl Hn Ht
M
network
link
physical
Hn Ht
router
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Another Simple Reference Model

Application
Application
Transport
Transport
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
CS4331/5331: Network Security, Summer I 2021
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Network
Network
Data Link
Radio
M
Medium