1. (Representation of …) URLs, IP addresses in the computer era 114 – Lecture 8

2. Path: Hierarchical “tree” structures A logical way of organizing our stuff

3. U-R-L  Uniform Resource Locator  T. B-L wanted URI: Universal Resource Identifier  It tells you where something is located, i.e., the name of the server that has it  It also tells you how you could get it Server and domainAccess method Static URL DocumentPath http://www.wellesley.edu/Resources/about/index.html gov - Government agencies edu - Educational institutions org - Organizations (nonprofit) mil - Military com - commercial business net - Network organizations ca – Canada kz–…

4. 2/11/2009Harvard Bits4

5. URL invoking a web program Server and domainAccess method Dynamic URL ParameterWeb program http://www.db-url.com/website-monitor.html?gclid=CLfYzO_bq5QodzReMiw Server and domainAccess method Dynamic fake URL Web program and parameter http://wiki.answers.com/Q/What_does_URL_mean

6. 6 Clients and Servers Client Computers Web Server www.wellesley.edu Web Server cs.wellesley.edu e-mail Server firstclass.wellesley.edu downloadupload THE INTERNET

7. You have been enumerated Every server is enumerated in an IP address IPv4: 32 bits written as 4 decimal numerals up to 256, e.g. 149.130.12.213 (Wellesley College)149.130.12.213Wellesley College – How many addresses can it represent? – IPv6: 128 bits written as 8 blocks of 4 hex digits each, e.g. AF43:23BC:CAA1:0045:A5B2:90AC:FFEE:8080 – How many addresses are in IPv6? Client translates URLs to IP addresses, e.g. cs.wellesley.edu  149.130.136.19149.130.136.19 – Uses authoritative sites for address translation a.k.a: “Domain Name Server” (DNS)DNS

8. What is your IP address? IP: Internet Protocol

9. What is the Internet? “Ten movies streaming across that, that Internet, and what happens to your own personal Internet? I just the other day got...an Internet was sent by my staff at 10 o'clock in the morning on Friday. I got it yesterday [Tuesday]. Why? Because it got tangled up with all these things going on the Internet commercially. [...] They want to deliver vast amounts of information over the Internet. And again, the Internet is not something that you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled and if they are filled, when you put your message in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material.”Ten movies streaming across that, that Internet, and what happens to your own personal Internet? I just the other day got...an Internet was sent by my staff at 10 o'clock in the morning on Friday. I got it yesterday [Tuesday]. Why? Because it got tangled up with all these things going on the Internet commercially.They want to deliver vast amounts of information over the Internet. And again, the Internet is not something that you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled and if they are filled, when you put your message in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material Senator Ted Stevens, Chair, Comm. on Commerce, Science and Transportation (charged with regulating the internet)