Lecture: Protocols in Detail

1. Lecture: Protocols in Detail

2. PROTOCOLS file: local file access telnet: login remotely ftp: transfer files http: access web pages mailto: (send email)

3. telnet: the client-server model Client (you) vs Server (_____________)

4. What happens when you say telnet grove.ufl.edu Telnet looks up grove’s internet address You and grove are now considered NVTs (network virtual terminals)

5. Terminal Emulation Needed because you and the server may have different ____________ A safe choice when you’re asked: VT-100 (vt=virtual terminal)

6. While you’re dialed upYou and grove have virtual “Keyboards” to send data from one nvt to the other AND “ Printers” to receive incoming info and display it on the screen

7. Transmitting Text Your typed text accumulates in a buffer until it’s signaled to be transmitted (enter or line break) It goes to the host with telnet commands as to how the other nvt should handle it. There may be an apparent delay due to packet-switching.

8. ftp (file transfer protocol) A permanent procedure that: uploads (from your local drive to a remote computer) downloads (from __________to ____________)

9. ftp Continued ftp programs use either: 1. words (____ and ____) or 2. click and drag (example: _______)

10. Two Types of Links Used by ftp 1. command link passes instructions ex: changing directories 2. data link sends files closes automatically when finished

11. Two transmission formats 1. ASCII sends text files but alters commands like CR 2. Binary sends files unaltered

12. HTTP (hypertext transfer protocol) Transports text (HTML) documents

13. An Example http uses www.cise.ufl.edu/class/cgs3066sp07/syllabus.html To send the text file “syllabus” to the cache memory of my browser

14. What’s “cache”? stores most often-used things (commands or files) so they’re accessible quickly

15. Two Types of Cache - Browser Cache (this is what html is using) - Processor Cache

16. Browser Cache • keeps pages, graphics, sounds, and URLs of online places you’ve visited recently • stored on your hard drive -- for instance C:\program files\netscape\users\lola\cache

17. For Privacy, empty cache periodically sequence using IE: View (version 4.0) or Tools (version 5.0) Internet Options. General Temporary Internet Files Delete Files. History Clear History. OK

18. Sequence Using Netscape Edit (on the tool bar) Preferences. Advanced expand by clicking + Cache Clear Memory Cache Clear Disk Cache. OK

19. Processor Cache stores most often used commands so that the processor doesn't have to wait for the (slower) hard drive to get them

20. More about Processor Cache - aka high-speed Static RAM (SRAM) operates between CPU and main memory 2 levels L1 built into the processor chip itself –very small L2 chip(s) external to the processor

21. Web Pages An html file is not the same as a web page! It becomes a web page only when it’s ________________________________ ____ (like IE or Netscape).

22. Public Directories • For your web page to be accessed by anyone else, it must be on a web server • and in a public folder within the your root directory

23. How Public Directories Work the server gets an http request it looks for whatever the webmaster decided the public directory should be called example: public_html

24. Index Files -A non-specific request to public_html activates the file named (usually) “index” - So most main web pages are called index.html - the index convention applies to subdirectories too

25. More about Index Files If there is no index file in your public_html _______________________________________________

26. A Final Word on http • Clicking a link is the same as typing its _______ in the window above • You don’t have to click on a link to see the url– you can just __________________________