1. Basic Concepts Behind the Internet

2. Before the Internet… Computer components are connected to each other internally via wires Wires also connected some external components, like tape drives and terminals Terminals could be connected to a specific remote computer via a phone line (a phone call to the specific computer). 1965: first experimental connection of 2 computers over a phone line

3. Beginning of the Internet 1966 – 1969: various researchers develop ideas for how networked computers could communicate with each other. (ARPANET) 1969: DARPA (Defense Advanced Research Projects Agency) funds the connection of mainframe computers at UCLA and Stanford Research Institute (SRI), followed by UC Santa Barbara and Univ. of Utah. 4 nodes by end of 1969; 14 by end of 1970; 19 by end of 1971 (1972: First networked email application) 1975: ARPANET has 60+ nodes, daily traffic exceeds 3 million packets

4. From ARPANET to Internet mid-70’s-80’s: other networks Ethernet (for Local Area Networks) BITNET, JANET, CSNET, NSFNet, USENET development of TCP/IP to connect networks mid-80’s: Internet interoperability of various networks TCP/IP becomes de facto standard protocol 1985: 2000 hosts on the internet

5. What does it consist of? Local computers, connected to… Higher-speed regional connections (e.g., ISP), connected to… Very high-speed backbone between major connection points Information is broken down into packets and routed via TCP/IP protocol Analogy: send a very long letter to a friend by putting each page in a separate envelope (packets); the protocol specifies what should go on the envelope (e.g., sender’s name & address, receiver’s name & address, page x of XX, etc)

6. Growth of the Internet 1969: 2, then 3, then 4 nodes 1975: 60+ nodes 1985: 2000 hosts 1987: nearly 30,000 hosts 1989: 80,000 (Jan) -> 130,000 (July) -> 160,000 (Nov) 1990: ARPANET shuts down; over 300,000 hosts 1991: 100+ countries; 600,000 hosts; nearly 5000 separate networks 1992: WWW and growth explodes (doubling in 3 months, not a year)

7. Internet Speeds 1969: 50 Kbps (ARPANET) 1984: 56 Kbps (CSNet) (personal modems in the 1980’s and 1990’s: 300 bps, 1200 bps, 9600 bps) 1985-88: 1.544 Mbps (T1, NSFNet backbone) 1992: 44.736Mbps (T3, NSFNet backbone) 1994: 145Mbps (ATM, NSFNet backbone) Current fiber: 100 Gbps; research 10 Tbps

8. The “net” vs. the “web” Internet: loose collection of computers & networks that communicate via TCP/IP Web: files (usually hypertext) across the internet + web browsers that know how to display them + server programs that, given a page address (URL), know how to find that page http: HyperText Transfer Protocol (a TCP protocol) html: HyperText Markup Language

9. Sources Leiner, Cerf, et al, “Brief History of the Internet”, Internet Society, www.internetsociety.org/internet/what- internet/history-internet/brief-history-internet. www.internetsociety.org/internet/what- internet/history-internet/brief-history-internet Computer History Museum, “Internet History”, www.computerhistory.org/internet_history/. www.computerhistory.org/internet_history/ Eha, Brian Patrick, “An Accelerated History of Internet Speed (Infographic)”, Entrepreneur, www.entrepreneur.com/article/228489. www.entrepreneur.com/article/228489 Internet speed info: misc. web sites