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Exploring Computer Science
(Part 3: The Internet)
Kansas 4-H Discovery Days 2015
J.C.R Licklider
"A network of such [computers], connected to one another by wide-band communication lines [which provided] the functions of present-day libraries together with anticipated advances in information storage and retrieval and [other] symbiotic functions."
J.C.R. Licklider - 1960
Man-Computer Symbiosis
Intergalactic Computer Network
- Global network of computers
- Instantly access data and programs from any other computers
October 29, 1969 - First Post!
Image Source: Wikipedia
Lots of Networks
- ARPANET
- NPL
- Merit
- CYCLADES
- X.25 & Public Networks
- UUCP - Usenet
Unification
Image Source: Wikipedia
Vinton Cerf Robert Kahn Pres. Bush
Transmission Control Protocol (TCP)
- Small networks could talk via a common standard (or protocol)
- No single point of failure in a system
- Computers could acknowledge successful transmission or request a retransmittal of missing data
- Data transmission was tolerant of errors and lost data
Applications
- POP/SMTP/IMAP - Email
- HTTP/FTP - World Wide Web
- DNS/DHCP - Network Setup
- SSH/RDP/Telnet - Connections
Domain Name System (DNS)
"Phonebook for the Internet"
- www.ksu.edu → 129.130.8.49
- www.google.com → 74.125.227.116
- www.ibm.com → 129.42.60.216
- www.yahoo.com → 98.138.253.109
Dynamic Host Configuration Protocol (DHCP)
Image Source: Tech Juice
HyperText Transfer Protocol (HTTP)
Image Source: Wikipedia
HTTP Status Codes
- 200 - OK
- 301 - Moved Permanently
- 403 - Forbidden
- 404 - Not Found
- 500 - Internal Server Error
- 503 - Service Unavailable
Packet Switching Activity
- Each server has a secret number
- Try to guess each server's secret number by playing the "Higher/Lower" game over HTTP
- Server with the most correct numbers when time runs out wins!
DHCP Request
DHCP Response
DNS Lookup
DNS Response
HTTP Request
HTTP Response
