Anonymous FTP

FTP (File Transfer Protocol) is the primary method of transferring

files over the Internet. On many systems, it's also the name of the

program that implements the protocol. Given proper permission, it's

possible to copy a file from a computer in South Africa to one in Los

Angeles at very fast speeds (on the order of 5--10K per second).

This normally requires either a user id on both systems or a special

configuration set up by the system administrator(s).

There is a good way around this restriction---the anonymous FTP

service. It essentially will let anyone in the world have access to

a certain area of disk space in a non-threatening way. With this,

people can make files publicly available with little hassle. Some

systems have dedicated entire disks or even entire computers to

maintaining extensive archives of source code and information. They

include gatekeeper.dec.com (Digital), wuarchive.wustl.edu (Washington

University in Saint Louis), and archive.cis.ohio-state.edu (The Ohio

State University).

The process involves the "foreign" user (someone not on the system

itself) creating an FTP connection and logging into the system as the

user anonymous, with an arbitrary password:

Name (foo.site.com:you): anonymous

Password: jm@south.america.org

Custom and netiquette dictate that people respond to the

Password: query with an email address so that the sites can

track the level of FTP usage, if they desire. (Addresses for

information on email addresses).

The speed of the transfer depends on the speed of the underlying

link. A site that has a 9600bps SLIP connection will not get the same

throughput as a system with a 56k leased line (The Physical

Connection, for more on what kinds of connections can exist in a

network). Also, the traffic of all other users on that link will

affect performance. If there are thirty people all FTPing from one

site simultaneously, the load on the system (in addition to the

network connection) will degrade the overall throughput of the

transfer.

Zen and the Art of the Internet · 第 20 / 120 题