internet overview · 2016. 3. 9. · what is the internet? an internet is a set of computer...
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Internet Overview • Introduction to Internet Technology • Overview of Web Authoring
Internet Technology 1
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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 2
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What is the Internet?
Internet Technology 3
widit.knu.ac.kr 155.230.194.245
www.whitehouse.gov 104.118.93.61
google.com 74.125.232.230
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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 4
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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
Internet Technology
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Networking Basics: Circuit and Packet Switching
Internet Technology 6
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?
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Networking Structure: Four Layer Model
Internet Technology 7
• 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
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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
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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
Internet Technology 9
HyperText Transfer Protocol
File Transfer Protocol
Simple Mail Transfer Protocol
Telnet Protocol
Transmission Control Protocol
Internet Protocol
IP Packet
Communication Protocols Applications Layer
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Internet Technology 10
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
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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
Internet Technology
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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)
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
Internet Technology 12
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Internet Addressing: DNS is Hierarchical
Internet Technology 13
.edu
unc.edu ncsu.edu duke.edu
med.unc.edu cs.unc.edu ils.unc.edu
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Internet Technology 14
Internet Addressing: Hostname vs. IP Address
Specificity Most Least
Top Level Domain
Specificity
Assigned locally IANA assigned 155.230.194.245
widit.knu.ac.kr
Least Most
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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/
Internet Technology 15
http:// knu.ac.kr /~kiyang/teaching/IT/s16/schedule.htm
Protocol Domain Item requested
Fully qualified resource name
widit.
Hostname
Internet Addressing: Anatomy of a URL
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Client-Server Model
Internet Technology 16
Client Initiates a Connection
Server Waits & Responds to Incoming Connections
Client Application Server Application program 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)
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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
Internet Technology
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http server
SMTP server
SSH server
http client
http client
http client
SMTP client
SMTP client
SSH client
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Web Authoring
Internet Technology 18
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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.
Internet Tecnology 19
Edit
Edit
Publish
Publish
Display Display
upload
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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 20
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Internet Technology 21
An Opte Project visualization of routing paths through a portion of the Internet
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Internet Technology 22