1. Course Overview
Internet Technology

2. 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
Internet Technology

3. Course Requirements Grading Prerequisites 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.
Internet Technology

4. Course Policy
Students are encouraged to work together in all aspects of the course (e.g., homework and group projects) except for the final exam. 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.
Internet Technology

5. Course Resources Homepage Required Readings Supplemental Readings
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 Young The Wiley Publishing
Internet Technology

6. Internet Overview
Internet Technology

7. 6/12/2018
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 networks that 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.
Internet Technology

8. What is the Internet? An internet
6/12/2018
What is the Internet? An internet
Local Area Network
“kiyang.kmu.ac.kr” “
Internet Technology

9. How does the Internet work? What happens between Point A and Point B?
6/12/2018
How does the Internet work? What happens between Point A and Point B?
Point A
Point B
Internet Technology

10. 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
HTML, SMTP, SSH, SFTP
Digitized data
Communication protocols
TCP/IP
Connection to the Internet
NIC, wire/wireless, routers
Internet Technology

11. Networking Basics: Main considerations for the Internet
6/12/2018
Networking Basics: Main considerations for the Internet
Need homogeneous communications between heterogeneous hardware and software.
Communication Protocols
Transmission Control Protocol / Internet Protocol
Addressing System
Domain Name System (Service)
Layered Networking Structure
Need efficient method of data exchange for a distributed and decentralized system
Client-Server model
Layered structure makes it easier for hetero to homo
Maximize trade-offs between speed and distance.
Internet Technology

12. Networking Basics: Circuit and Packet Switching
Circuit Switched Communication
Dedicated Line
Packet Switched Communication
Receiver
Sender
Data broken up into packets
Internet Technology

13. Communication Protocol
6/12/2018
Communication Protocol
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 destination IP address
Internet Technology

14. Internet Protocols Application Layer Protocols
6/12/2018
Internet Protocols Application Layer Protocols
Application layer protocols
ensure that the sender and receiver are speaking the same language, and that the letter can be interpreted
HTTP, FTP, SMTP , Telnet, SSH
HyperText Transfer Protocol
File Transfer Protocol
Simple Mail Transfer Protocol
Telnet Protocol
Transmission Control Protocol
Internet Protocol
LAN
IP Packet
Internet Technology

15. Networking Basics: Four Layer Model
6/12/2018
Networking Basics: Four Layer Model
Applications
Applications Interface
e.g., HTTP, SMTP, SSH
Transport
Reliable Delivery
i.e., TCP
Network
Source to Destination
i.e., IP
Physical
Hosts, routers, wires, etc.
Internet Technology 15

16. How does the Internet work? Communication on the Internet
6/12/2018
How does the Internet work? Communication on the Internet
Application
(e.g. Firefox)
Application
(e.g. Web server)
Data
Data
Network Interface
(i.e. TCP/IP)
Network Interface
(i.e. TCP/IP)
Is TCP/IP driver right for NI?
You can see there are layers of things going on and several pieces that all work together.
We will talk about later why data gets chopped up.
Packet
Packet
Packet
Packet
Packet
Packet
Physical (wire, router, hosts)
Internet Technology

17. Internet Addressing IP address Hostname Domain name
6/12/2018
Internet Addressing
IP address
a unique number assigned to a host
assigned by IANA
e.g
Hostname
a unique 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
Internet Technology

18. Internet Addressing: Domain Name System (DNS)
6/12/2018
Internet Addressing: Domain Name System (DNS)
Hostname to IP Address mapping system
DNS servers store the name/address pair.
Applications use resolvers query DNS servers.
Main Characteristics
Hierarchical
Sub-domains on the left (e.g. lis.knu.ac.kr)
Distributed
Authoritative name servers for each domain & sub-domains
When a DNS server is missing an entry, next server is checked
A client (resolver) must know at least 1 DNS server
The domain name system (DNS) is the way that Internet domain names are located and translated into IP (Internet Protocol) addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.
Because maintaining a central list of domain name/IP address correspondences would be impractical, the lists of domain names and IP addresses are distributed throughout the Internet in a hierarchy of authority. There is probably a DNS server within close geographic proximity to your access provider that maps the domain names in your Internet requests or forwards them to other servers in the Internet.
Originally included com, gov, edu, org, net
Also country codes (doled out by IANA)
Ca canada
Au australia
Ch switzerland
New domain names governance in place
Internet Technology

19. Internet Addressing: DNS is Hierarchical
6/12/2018
Internet Addressing: DNS is Hierarchical
.edu
ncsu.edu
unc.edu
duke.edu
cs.unc.edu
med.unc.edu
ils.unc.edu
Internet Technology

20. Internet Addressing Hostname vs. IP Address Most Least Least Most
6/12/2018
Internet Addressing
Hostname vs. IP Address
widit.knu.ac.kr
Top Level Domain
Specificity
Most
Least
IANA assigned
Assigned locally
Specificity
Least
Most
Internet Technology

21. Internet Addressing: Anatomy of a URL
6/12/2018
Internet Addressing: Anatomy of a URL
URL stands for Universal Resource Locator
sometimes seen as Uniform Resource Locator
Protocol
Hostname
Domain
Item requested
widit.
knu.ac.kr
/~kiyang/teaching/IT/s13/schedule.htm
Fully qualified resource name
Certain protocols assume certain ports (e.g., http → port 80)
When non-standard port is use, it can be specified in the URL
- e.g.,
Internet Technology

22. Client-Server Model Client Server
6/12/2018
Client-Server Model
Client
Initiates a Connection
Server
Waits & Responds to Incoming Connections
Application Protocol
(HTTP)
Client Application
Server Application
program running on
client machine
(e.g., Internet Explorer)
program running on
server machine
(e.g., Apache Web Server)
Internet Technology

23. Client-Server Model: Overview
6/12/2018
Client-Server Model: Overview
Servers
Can be hardware (computers) or software (programs)
One computer can run many server applications.
e.g., http (web), ftp, , 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 given application
People interface with them directly
HTTP Clients: Internet Explorer, Firefox, Chrome
Clients: Outlook, Pine, Lotus Notes
Telnet/SSH Clients: Putty, SSH Secure Shell
Internet Technology