UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
The disadvantage to a star topography is that if one of the links is disabled or severed
then communication is lost to that node. The unconnected node may still well operate
through distributed intelligence, but will be unable to receive updates from the rest of the
system. For example, if a new credential holder were added to the access list this
information could be downloaded to a remote site or panel from a central location. With
a severed link, these updates are not available unless the information were uploaded at
the local site/panel. Conversely, if a credential holder were deleted from the access
database, a "severed" site/panel would continue to allow access until communications
were re-established or a local upload made. Figure 6-1 shows a star topography for
both an inter-site architecture and an intra-site architecture.
6-4.2.2 Ring. The ring topography communicates through a loop. This topography is
slightly more robust than a star topography that in the event of failed link,
communications can sill be maintained through the "backside" direction on the loop.
Communications may be a slower in this backup mode of operation, but would be
sustainable. Figure 6-2 shows a ring topography for both the inter-site and intra-site
scenario.
6-4.2.3 Fully Meshed. The most robust topography is a fully meshed topography
depicted in Figure 6-3. This topography has backup means of communication, such that
if any one link is disabled or severed, communications have an alternate path to
communicate directly between nodes. This is the preferred ESS network topography.
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