Course Overview

Internet Technology 1

Course Objectives

Develop an understanding of how web pages work.

Become familiar with SSH, SFTP, HTML, CSS/JavaScript.

Gain hands-on experience in web authoring.

Construct a website

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Course Requirements Grading

Homework Assignments (40%)

Midterm Project (20%)

Final Projects (40%)

Participation (Extra Credit)

Prerequisites Basic computer skills (e.g., know how to use PC and Web browser)

Technical background is not required.

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Course Policy

Students are encouraged to work together in all aspects of the course (e.g., homework and group projects).

This class advocates an open book policy of allowing students to consult textbooks, Internet resources, and classmates when working on assignments to facilitate learning and promote collaboration.

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Course Resources Homepage

http://widit.knu.ac.kr/~kiyang/teaching/IT/

Required Readings Lecture material and online contents

Supplemental Readings Creating Web Pages for Dummies (9th Edition, 2008)

by Bud E Smith, November The Wiley Publishing

The Internet for Dummies (13th Edition, November 2011) by John R. Levine, Margaret Levine YoungThe Wiley Publishing

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Internet Overview

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• Introduction to Internet Technology

• Overview of Web Authoring

What is the Internet?

An internet is a set of computer networks that are connected to each other (e.g. intranet).

The Internet is a world-wide set of networksthat interoperate using TCP/IP protocols.

Think of “communication software” or “standards” when you see “protocol”

more on TCP/IP and other protocols later…

A global channel for digital communication and data exchange.

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What is the Internet?

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widit.knu.ac.kr155.230.194.245

www.whitehouse.gov104.118.93.61

google.com74.125.232.230

How does the Internet work?

Postal Analogy Common language

e.g., Korean, English

A letter

An envelope

stamped & addressed

Physical delivery

via the postal stream

Internet Application protocols

HTTP, SMTP, SSH, SFTP

Digitized data

Communication protocols

TCP/IP

Connection to the Internet

NIC, wire/wireless, routers

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How does the Internet work?Key Components

Need homogeneous communications between heterogeneous hardware and software.

Communication Protocols

Transmission Control Protocol / Internet Protocol

Addressing System

Domain Name System (Service)

Networking Structure

Four Layer Model

Need efficient method of data exchange for a distributed and decentralized system

Application Structure

Client Server Architecture/Model

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Networking Basics:Circuit and Packet Switching

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Packet Switched Communication- Data is broken up into packets

Circuit Switched Communication- Dedicated line

Sender Receiver

A B C A B C

A

B

C

Hello

Who’s calling?

Networking Structure:Four Layer Model

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• Applications Interface

• e.g., HTTP, SMTP, SSHApplications

• Reliable Delivery

• i.e., TCPTransport

• Source to Destination

• i.e., IPNetwork

• Hosts, routers, wires, etc.Physical

Communication ProtocolsTransport & Network Layers

TCP (Transmission Control Protocol) Responsible for ensuring reliable & accurate delivery of data

e.g., error-checking, end-to-end acknowledgement, etc.

Breaks up a file to transmit into a set of TCP “segments”. TCP header contains sequence #, ACK, checksum

IP (Internet Protocol) Method for Routing Data

Defines how packets reach specified destination

Best-effort delivery (i.e. connectionless, unreliable)

data corruption, lost packets can occur

Encapsulates a TCP segment in an IP packet IP header contains the source/destination IP address

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Ensure that the sender and receiver are speaking the same language, and that the letter can be interpreted

HTTP, FTP, SMTP , Telnet/SSH

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HyperText Transfer

Protocol

File Transfer

Protocol

Simple Mail

Transfer ProtocolTelnet Protocol

Transmission Control Protocol

Internet Protocol

IP Packet

Communication ProtocolsApplications Layer

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Data

Packet Packet Packet

Application(e.g. Chrome)

Network Interface(i.e. TCP/IP)

Data

Packet Packet Packet

Application(e.g. Web server)

Network Interface(i.e. TCP/IP)

Physical (wire, router, hosts)

Communication on the Internet

Internet Addressing

IP address An unique number assigned to a host Assigned by IANA e.g. 155.230.194.245

Hostname

A human-readable name assigned to a host

Named by organizations e.g. widit.knu.ac.kr

Domain name

A name assigned to an entity.

e.g. knu.ac.kr

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Internet Addressing:Domain Name System (DNS)

Hostname to IP Address mapping system DNS servers store the name-address pair.

Applications use resolvers to query DNS servers.

Main Characteristics

Hierarchical Sub-domains on the left (e.g. lis.knu.ac.kr)

DistributedAuthoritative name servers for each domain & sub-domainsWhen a DNS server is missing an entry, next server is checkedA client (resolver) must know at least 1 DNS server

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Internet Addressing: DNS is Hierarchical

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.edu

unc.eduncsu.edu duke.edu

med.unc.educs.unc.edu ils.unc.edu

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Internet Addressing:Hostname vs. IP Address

SpecificityMost Least

Top Level Domain

Specificity

Assigned locallyIANA assigned155.230.194.245

widit.knu.ac.kr

Least Most

URL stands for Universal Resource Locator a.k.a. Uniform Resource Locator

Certain protocols assume certain ports (e.g., http → port 80)

When non-standard port is use, it can be specified in the URL http://widit.knu.ac.kr:8800/

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http:// knu.ac.kr/~kiyang/teaching/IT/w16/schedule.htm

Protocol Domain Item requested

Fully qualified resource name

widit.

Hostname

Internet Addressing:Anatomy of a URL

Client-Server Model

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ClientInitiates a Connection

ServerWaits & Responds to

Incoming Connections

Client Application Server Applicationprogram running on the client machine

(e.g., Internet Explorer)

Application Protocol(e.g., HTTP)

155.230.194.233 155.230.194.245

program running on the server machine

(e.g., Apache Web Server)

Client-Server Model: Overview

Servers Can refer to hardware (computers) or software (programs)

One computer can run many server applications. e.g., http (web), ftp, email, telnet, etc.

Server Address = IP address + port number

Each server application listens on a different port e.g., http → 80, SMTP → 25, telnet → 23, ssh → 22, ftp → 21

Clients There can be many clients for a server application

People interface with them directly

HTTP Clients: Internet Explorer, Firefox, Chrome

Email Clients: Outlook, Pine, Lotus Notes

Telnet/SSH Clients: Putty, SSH Secure Shell

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http server

SMTP server

SSH server

http client

http client

http client

SMTPclient

SMTPclient

SSHclient

Web Authoring

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Publishing HTML

Content Creation Mode #1 Create HTML pages on the local PC using Notepad, Dreamweaver, etc.

Upload the files to the server to be displayed on the Web

Content Creation Mode #2 Create HTML pages directly on the server using pico, vi, etc.

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Edit

Edit

Publish

Publish

Display

Display

upload

Q&A

What is the Internet?

How does it work?

Describe

Domain Name System

Client-Server Model

4-Layer Model

TCP/IP

How can you publish content on the Web?

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An Opte Project visualization of routing paths through a portion of the Internet

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