FTP

Question 1

FTP

Answer 1

• File Transfer Protocol- FTP
• Use FTP to download or upload files
• Works on client/server model
• Run FTP client software on your computer to connect to an FTP server on the Internet. On FTP server, a program called FTP daemon allows you to download and upload files
• To logon to FTP site and download files, must type in an account number and password before the daemon will allow you to enter
• Compress files to speed up file transfers and save space on FTP server

Question 2

How does an FTP session work?

Answer 2

1. To begin FTP session, run the FTP client software and contact FTP server from which you want to download files. You can get FTP client software on the Internet. FTP programs also are included on Windows based computers, but typically offer less functionality than these FT clients
2. FTP daemon runs on the FTP server and handles all FTP transactions. Daemon asks for account number and password- anonymous FTP allows anyone log on to them to download files and software.
3. When you log on to FTP server, a connection called command link is opened up between your comp and the server. Your comp uses this link for sending commands to the server, and the server uses this link for sending messages and info back to your computer
4. When you want to change directions on the FTP server, your client software sends an instruction to the FTP daemon using the command link. Daemon changes directories and then sends back a listing of files on that directory via the command link. When you want to download a file, the request is issued over the command link.
5. When you issue a command to download a file, you open second connection called the data connection (also called the data link). This connection can be opened up in ASCII mode or binary mode. ASCII mode is used for sending text files and alters things such as line feed and carriage return; binary mode is used for sending binary files and lets files through untouched.
6. File is downloaded from the server to your computer via the data connection. After the file is downloaded, the data link closes automatically
7. When file is downloaded and data link closes, command link stays open. You can then change directories or download more files. After you’re done, log off and the command link closes. You’re no longer connected to the FTP server.

Question 3

command link

Answer 3

When you log on to FTP server, a connection called command link is opened up between your comp and the server. Your comp uses this link for sending commands to the server, and the server uses this link for sending messages and info back to your computer

Question 4

ASCII vs. Binary Mode

Answer 4

ASCII mode is used for sending text files and alters things such as line feed and carriage return; binary mode is used for sending binary files and lets files through untouched.

Question 5

How does file compression work?

Answer 5

1. Compression programs use algorithms- complex mathematical formulas- to shrink files. The algorithm examines the file to be compressed and looks for repeating patterns of data
   
   2. When the algorithm finds patterns of data that repeat, it replaces the patterns with smaller tokens. In a file that has many repeating patterns, many tokens are used to replace data so the compressed file is much smaller than the original file
   3. A header can be added to the file as it is compressed, contains info about the file such as filename, size, and compression method used
   4. File extensions tell you whether and how a file is compressed
   5. Some compression software can also archive files by combining several compressed files
   6. When you want to use a compressed file you find on the Internet, transfer it over the Internet to your computer
   7. Decompression software looks into the file’s header and examines tokens in the file. Decompression software uses an algorithm to reconstruct the original file, which you can then use on your computer