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ISSA communications integrated with other subsystems should be selected to ensure that the SOC operator
is provided with a multimedia (voice, data, and video) presentation of alarm events.
Communications technologies should provide reliable and scalable support for the lifetime of the ISSA to
diagnose and resolve system problems that may arise. PACS communications systems can be network-
based (to operate over a LAN/WAN, MAN or private network) or less sophisticated (using communication
protocols that require point-to-point connections using twisted-pairs of cables).
Interfaces between system components should be fully compatible with – and supported by – the
communications architecture selected. Downstream compatibility between ISSA system components is
desirable to enhance the maximum lifetime of the investment.
System Design Considerations
A well designed network will be predictable and consistent in each of the following areas.
Performance: A well-designed network shows consistently high performance in application
response time, the variation in response time, and other performance parameters.
Resilience: The network should provide a resilient platform for the applications it supports. A
highly specified network might have to meet an availability target of 99.99 percent or higher for all
applications. Ideally, the failure of any one link or networking device should not result in the loss
of sessions or services. Switches and other network devices should have hot swappable blades and
power supplies. Automatic failover to an alternate path should occur within a time interval short
enough to minimize the effect on existing sessions. This interval can be defined as the span between
when a network topology change (such as the loss of a link) occurs and each device on the network
becoming aware of the change. Well-designed networks are characterized by consistently low
Redundancy: With communications systems beginning to bear responsibility for providing
communications connectivity for a variety of security and life safety systems, physical redundancy
in topology design is becoming paramount. Consideration should be given to not only duplicating
physical core connections, but doing so through completely separate routes to avoid single points
of catastrophic failure.
Scalability: A scalable network can support growth to a projected set of functions and/or capacity
over a stipulated time period without having to be radically redesigned and with minimum
obsolescence of core equipment. It can handle both the addition of users, network nodes or sites,
and the addition of new applications with increased bandwidth needs. Vendors should be required
to describe how the projected functions and/or capacity levels will be achieved and the resulting
impact on any proposed systems.
Affordability: The system should have life cycle costs compatible with the functional requirements,
operating and maintenance capabilities, and finances of the Owner.
Security: The system must protect both the operator and the system assets from physical and signal-
related intrusions and unauthorized attempts to exploit the network.
The network design should permit the addition of new nodes and users with the addition of a new section
or block to an existing structure that serves as the core or backbone of the network. It should also provide
for increased bandwidth demands to augment the LAN and WAN bandwidth as necessary without new
backbone cabling, such growth having been anticipated when the original cable plant was designed and
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