User`s guide

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Glossary
proxy server - proxy server
DNS: See DNS
FTP: Abbreviation of File Transfer Protocol, the protocol used on the
Internet for sending files.
HTTP: Short for HyperText Transfer Protocol, the underlying protocol
used by the World Wide Web. HTTP defines how messages are
formatted and transmitted, and what actions Web servers and browsers
should take in response to various commands.
ICMP: Short for Internet Control Message Protocol, an extension to the
Internet Protocol (IP) defined by RFC 792. ICMP supports packets
containing error, control, and informational messages. The ping
command, for example, uses ICMP to test an Internet connection.
RPC: Abbreviation of remote procedure call, a type of protocol that allows
a program on one computer to execute a program on a server computer.
Using RPC, a system developer need not develop specific procedures
for the server. The client program sends a message to the server with
appropriate arguments and the server returns a message containing the
results of the program executed.
P proxy server
A server that sits between a client application, such as a web browser,
and a real server. It intercepts all requests to the real server to see if it
can fulfill the requests itself. If not, it forwards the request to the real
server. Proxy servers have two main purposes:
Improve Performance: Proxy servers can dramatically improve
performance for groups of users, since a proxy server saves the results
of all requests for a certain amount of time. Consider the case where both
user X and user Y access the Web through a proxy server. First user X
requests a certain Web page, which we will call Page 1. Sometime later,
user Y requests the same page.
Instead of forwarding the request to the Web server where Page 1
resides, which can be a time-consuming operation, the proxy server
returns the Page 1 it already fetched for user X. Since the proxy server is
often on the same network as the user, this is a much faster operation.
Real proxy servers support hundreds or thousands of users.
Filter Requests: Proxy servers can also be used to filter requests. For
example, a company might use a proxy server to prevent its employees
from accessing a specific set of Web sites.