Internet Overview 1Internet Technology. What is the Internet? An internet is a set of computer...
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Transcript of Internet Overview 1Internet Technology. What is the Internet? An internet is a set of computer...
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Internet Overview
1Internet Technology
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Internet Technology
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.
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Internet Technology
What is the Internet?
widit.knu.ac.kr155.230.194.245
www.whitehouse.gov96.16.242.135
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google.com74.125.224.72
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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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Internet Technology
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
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Networking Basics:Circuit and Packet Switching
Internet Technology
Packet Switched Communication
Circuit Switched Communication
Dedicated Line
Sender Receiver
Data broken up into packets
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Internet Technology
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 source/destination IP address
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Internet Technology
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
IP Packet LAN8
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Internet Technology
Networking Basics: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
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Internet Technology
How does the Internet work? Communication on the Internet
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)
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Internet Technology
Internet Addressing
IP address ► a 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 Technology
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
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Internet Technology
Internet Addressing: DNS is Hierarchical
.edu
unc.eduncsu.edu duke.edu
med.unc.educs.unc.edu ils.unc.edu
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Internet Technology
Internet Addressing Hostname vs. IP Address
SpecificityMost Least
Top Level Domain
Specificity
Assigned locallyIANA assigned155.230.194.245
widit.knu.ac.kr
Least Most
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Internet Technology
Internet Addressing:Anatomy of a URL
URL stands for Universal Resource Locator► sometimes seen as Uniform Resource Locator
http:// knu.ac.kr /~kiyang/teaching/IT/s13/schedule.htm
Protocol Domain Item requested
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., http://widit.knu.ac.kr:8800/
widit.
Hostname
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Internet Technology
ClientInitiates a Connection
Server Waits & Responds to Incoming Connections
Client Application Server Applicationprogram running on
client machine(e.g., Internet Explorer)
Application Protocol(HTTP)
Client-Server Model
155.230.194.233 155.230.194.245
program running on server machine
(e.g., Apache Web Server)
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Internet Technology
Client-Server Model: Overview Servers
► Can be 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 given 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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Web Authoring
18Internet Technology
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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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Internet Technology 20
An Opte Project visualization of routing paths through a portion of the Internet