Compaq 222863-001 - TaskSmart W2200 Model 10 Administration Manual page 125

Glossary 11
Ping
A utility used to determine whether a network destination is online by sending
an echo request and waiting for a response.
Port
The point at which devices can be connected to computers or networks for
transmitting or receiving data.
Port Number
A 16-bit number local to the client that is used by TCP/IP. Port numbers are
used in conjunction with an IP address to identify a connection end-point. To
obtain TCP service, a connection must be explicitly established between a
port/IP address pair on the sending machine and a port/IP address pair on the
receiving machine.
Presentation Layer
See International Standards Organization Reference Model for Open Systems
Interconnection.
Proxy Server
In an enterprise that uses the Internet, a proxy server is a server that acts as an
intermediary between a workstation user and the Internet so that the enterprise
can ensure security, administrative control, and caching service. A proxy
server is associated with, or is part of, a gateway server that separates the
enterprise network from the outside network and a firewall server that protects
the enterprise network from outside intrusion.
A proxy server receives requests for Internet services (such as a webpage
request) from a user. If the request passes filtering requirements, the proxy
server, assuming it is also a cache server, looks in its local cache of previously
downloaded webpages. If it finds the page, it returns it to the user without
needing to forward the request to the Internet. If the page is not in the cache,
the proxy server, acting as a client on behalf of the user, uses one of its own IP
addresses to request the page from the server out on the Internet. When the
page is returned, the proxy server relates it to the original request and forwards
it on to the user.