1. Lecture: Protocols in Detail

2. PROTOCOLS file: local file access telnet: login remotely
ftp: transfer files
http: access web pages
mailto: (send )
You create your web page as a local file then upload it, often using ftp

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 up You 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 To send the text file “syllabus” to
To send the text file “syllabus” to
the cache memory of my browser
NOTE TO SELF—what are the two slashes for?

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 __________________________