Glossary •
231
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Proxy gateway
A proxy gateway (or proxy
server,
too) allows systems which do not have
direct access to the
Internet
, indirect access to the network. These can be
systems which are excluded from direct access by a
firewall
for security
reasons.
A proxy can filter out individual data packets between the Internet and a
local network to increase security. Proxies are also used to limit access to
particular servers.
In addition, proxy gateways can also have a cache function, in which case
they check whether the respective
URL
address is already available locally
and return it immediately, if necessary. This saves time and costs when there
are multiple accesses. If the URL is not in the cache, the proxy forwards the
request
as normal.
The user should not notice the proxy
gateway
apart from the single
configuration in the
web browser
. Most web browsers can be configured so
that they use different or no proxy gateways per access method (
FTP
,
HTTP
).
R
Repeater
Repeaters are physical amplifiers without their own processing function.
They refresh data without detecting damaged data and forward all signals.
Repeaters are used for longer transmission distances or when the maximum
number of nodes of 64 devices per
twisted pair
segment is exceeded. A
request from a client to server is a provision to act on a serivce or funtion
call.
Request
A service request from a client which requests the provision of a service
from a server.
Response
The server’s reply to a client’s request.
RFC specifications
Specifications, suggestions, ideas and guidelines regarding the
Internet
are
published in the form of RFCs (Request For Comments).
RJ45 connector
Also referred to as a Western connector. This connector allows the
connection of two network controllers via
twisted pair
cables.
