IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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a partial extent - in a star-shaped wiring of the terminal devices; for this
reason, hubs and concentrators are also termed star couplers.
As already mentioned in the case of repeaters, the smallest form of a
concentrator or a hub is a multi-port repeater. In contrast, modular hubs allow
the integration of various coupling elements (e.g. repeaters, bridges, routers)
which, in turn, can operate on several layers. This concentration of network
coupling components at a single point gives rise to advantages which facilitate
the administration of the network, although a failure of such a central hub
would affect the entire network. Appropriate precautionary measures, e.g.
redundant arrangement of the network components, should be taken for such a
contingency (refer to S 6.53 Redundant arrangement of network components).
Gateway
A gateway links two networks on the application layer (layer 7) of the OSI
model. For this reason, a gateway not only converts network protocols, but
also transports data on the application layer and, if necessary, modifies this
data and evaluates it from the perspective of security. One typical application
of a gateway is communications between systems in a TCP/IP network and a
SNA host. In this case, the gateway consists of a combination of hardware and
software. However, there are also gateways based purely on software. These
include, for example, mail gateways which can recognise and convert different
mail formats.
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IT-Baseline Protection Manual: Oktober 2000