1. Introduction to Internet Technology Overview of Web Authoring
Internet Overview
Introduction to Internet Technology
Overview of Web Authoring
Internet Technology

2. 4/18/2018
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

3. What is the Internet? google.com widit.knu.ac.kr www.whitehouse.gov
4/18/2018
What is the Internet?
google.com
widit.knu.ac.kr
Internet Technology

4. 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
Internet Technology

5. How does the Internet work? Key Components
4/18/2018
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
Layered structure makes it easier for hetero to homo
Maximize trade-offs between speed and distance.
Internet Technology

6. Networking Basics: Circuit and Packet Switching
Circuit Switched Communication
- Dedicated line
Hello
Who’s calling?
Packet Switched Communication
- Data is broken up into packets
Receiver
Sender A B C A B C A B C
Internet Technology

7. Networking Structure: Four Layer Model
4/18/2018
Networking Structure: Four Layer Model
Applications Interface
e.g., HTTP, SMTP, SSH
Applications
Reliable Delivery
i.e., TCP
Transport
Source to Destination
i.e., IP
Network
Hosts, routers, wires, etc.
Physical
Internet Technology 7

8. Communication Protocols Transport & Network Layers
4/18/2018
Communication Protocols Transport & 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
Internet Technology

9. LAN Communication Protocols Applications Layer
4/18/2018
Communication Protocols Applications Layer
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

10. Communication on the Internet
4/18/2018
Communication on the Internet
Application
(e.g. Chrome)
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

11. Internet Addressing IP address Hostname Domain name
4/18/2018
Internet Addressing
IP address
An unique number assigned to a host
Assigned by IANA
e.g
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
Internet Technology

12. Internet Addressing: Domain Name System (DNS)
4/18/2018
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)
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

13. Internet Addressing: DNS is Hierarchical
4/18/2018
Internet Addressing: DNS is Hierarchical
.edu
ncsu.edu
unc.edu
duke.edu
cs.unc.edu
med.unc.edu
ils.unc.edu
Internet Technology

14. Internet Addressing: Hostname vs. IP Address Most Least Least Most
4/18/2018
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

15. Fully qualified resource name
4/18/2018
Internet Addressing:
Anatomy of a URL
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
Protocol
Hostname
Domain
Item requested
widit.
knu.ac.kr
/~kiyang/teaching/IT/s16/schedule.htm
Fully qualified resource name
Internet Technology

16. Client-Server Model Client Server
4/18/2018
Client-Server Model
Client
Initiates a Connection
Server
Waits & Responds to Incoming Connections
Application Protocol
(e.g., HTTP)
Client Application
Server Application
program running on
the client machine
(e.g., Internet Explorer)
program running on
the server machine
(e.g., Apache Web Server)
Internet Technology

17. Client-Server Model: Overview
4/18/2018
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, , 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
Clients: Outlook, Pine, Lotus Notes
Telnet/SSH Clients: Putty, SSH Secure Shell
http server
SMTP server
SSH server
http client
SMTP client
http client
http client
SMTP client
SSH client
Internet Technology

18. Web Authoring
Internet Technology

19. Publishing HTML Content Creation Mode #1 Content Creation Mode #2 Edit
4/18/2018
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.
Edit
Edit
Publish
Display
Display
upload
Publish
Internet Tecnology

20. 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?
Internet Technology

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

22. Internet Technology