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IT263-502 (Winter 2012)

Applied Networks and Security

Week 1-AOrientation/Introduction

Prof. Andrew S. Wang

DePaul University

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Announcements

1. Sign in

2. Fill out the 1st Class Survey

3. Received my emails?

4. Syllabus on COL?

5. Week 1-A slides on COL?

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Agenda

1. Course Orientation

2. OSI 7-layer Network Model

3. Demo of 4 OSI Layers Operations4. TCP/IP 4-layer Network Model

5. Student Intro.

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1. Course Orientation

Syllabus on COL:

https://col.cdm.depaul.edu

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2. OSI 7-Layer Network Model

OSI = Open Systems Interconnection To truly understand and learn computer network

operations data networking:

an open, generic network model

capturing most networking functionalities

used as a foundation for developing networking

systems/products

teaching/education/training tool

1984, OSI model published by ISO (International

Organization for Standardization)

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3. Demo of 4 OSI Layers Operations

Web Browser (1):

Users perspective

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Bob: Enter www.cnn.comLarry = CNN news

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3. Demo of 4 OSI Layers Operations

Web Browser (2): HTTPs perspective

HTTP = HyperText Transfer Protocol

one Application Layer protocol (Layer 7)

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Bob: Sends an HTTP (Layer-7) message to LarryLarry: Responds by sending two things (1) OK (2) home.htm

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3. Demo of 4 OSI Layers Operations

Web Browser (4): IPs perspective (Layer 3)IP = Internet Protocol one Network Layer protocol

R1, R2, R3 = Routers (devices connecting Local Area Networks)

Destination IP address = 1.1.1.1 Source IP address = 2.2.2.2

Encapsulation: Top-down direction

PDU = Protocol Data Unit

Current-layer PDU = current-layer data + current-layer header

= upper-layer PDU + current-layer header 10

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3. Demo of 4 OSI Layers Operations

Web Browser (5): PPPs perspective (Layer 2)PPP = Point-to-Point Protocol one Data-Link Layer protocol for WAN (Wide-

Area Network)

Ethernet (the)Data-Link Layer protocol for LAN (Local Area Network)

R2 changes Ethernet layer 2 header to PPP layer 2 header.

R1 changes PPP layer 2 header to Ethernet layer 2 header.

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3. Demo of 4 OSI Layers Operations

Summary:

HTTP = a Layer 7 protocol

TCP = a Layer 4 protocol

IP = a Layer 3 protocol

PPP = a Layer 2 protocol

Ethernet = a Layer 2 protocol

Encapsulation = going from Layer 7 to Layer 1 (downward)

(the sender)

Decapsulation = going from Layer 1 to Layer 7 (upward)(the receiver)

In addition: Same-layer interaction on (one, two) computer(s)?

Adajcent-layer interaction on (one, two) computer(s)?

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4. TCP/IP 4-layer Model

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TCP/IP existed way before OSI 7-layer model.

TCP/IP is an actual model, OSI 7-layer is theoretical. TCP/IP model is also referred to as the DoD model.

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5. Student Intro Career interest?

Bears, Bulls, Whitesox, Cubs, Blackhawks, Fire

(or: None of the above)

Travel experience (the most beautiful place)

Student clubs (poker club?) ROTC

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Time for a checkpoint:

Are you ready?

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Checkpoint 1

________ True or False.

The OSI 7-layer model is the most cost-effectivenetwork model that has ever been implemented so

far.

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Checkpoint 2

HTTP is a protocol for which OSI layer? __________

a) Application layer

b) Presentation layer

c) Session layerd) Transport layer

e) Network layer

f) Datalink layer

g) Physical layer

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Checkpoint 3

PPP is a protocol for which OSI layer? __________

a) Application layer

b) Presentation layer

c) Session layerd) Transport layer

e) Network layer

f) Datalink layer

g) Physical layer

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Checkpoint 4

The most important reason for your PC to connect to anetwork is: __________

a) To connect to Internet

b) To do multitaskingc) To save cost

d) To be more efficient

e) To share resources with other PCs or servers on

the same network or on a different networkf) To be able to send email to and receive email

from other PCs on the same network

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Checkpoint 5

The name of the network device that connects two(local area) networks is called _______ ?

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Checkpoint 6

What are the pros and cons for a wireless network interms of convenience, speed, cost, security?

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