IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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S 5.2 Selection of an appropriate network
topography
Initiation responsibility: Head of IT Section
Implementation responsibility: Network planner; Head of Site/Bldg
Technical Service
The topography of a network is the purely physical structure of the network as
it is visible with cables. In contrast to this, the topology of a network is the
logical structure as it appears to network components. The topography and
topology of a network are therefore not necessarily identical. By nature,
topography mostly relates to the spatial environment of the building. These are
amongst others:
- locations of the network subscribers
- available space for cable routes and cables (S 1.21 Sufficient dimensioning
of lines)
- required cable types (S 1.20 Selection of cable types suited in terms of their
physical/mechanical properties)
- specifications regarding cable protection (S 1.22 Physical protection of
lines and distributors)
The advantages and disadvantages of various possible topographies are
discussed in the following. Other conceivable topographies which are not
mentioned in this chapter can be considered as special cases of the structures
described here.
In general, a distinction can be made between two basic types of
configuration, star and bus, which can also be extended to form the tree and
ring configurations respectively. These four types are described briefly in the
following:
Star
All subscribers in a star network are linked with a central node via a dedicated
line. The cabling of the frequently-used Token-Ring architecture
topographically results in a star configuration, but functions topologically as a
ring.
Advantages:
- Impairment of a line will only affect the operations of the system
connected to it.
- Changes in the allocation of network subscribers to connection points at
the central node and separation of individual subscribers can be performed
centrally.
- A topographical star configuration can serve as a basis for forming any
conceivable topology.
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IT-Baseline Protection Manual: Oktober 2000