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...
Internet Overview
1Internet Technology
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
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
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
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
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
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
Internet Technology 20
An Opte Project visualization of routing paths through a portion of the Internet