Home' RTCA Documents for Review : DO-230H FRAC Contents 188
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Fiber Channel, a high-speed dedicated file transfer protocol developed to be run over fiber optic
Redundant Array of Independent Disks (RAID), a set of protocols which configure multiple drives
to achieve various levels of security, redundancy, and fail-over.
Selecting network architectures and storage protocol are complex matters properly addressed by IT
professionals [Refer: Chapter 9: Communications for additional guidance). Requirements for video storage,
however, should be addressed by video surveillance managers and system designers before designing a
system and ordering equipment. What video information is to be collected, in what form (e.g., resolution,
frame rate, motion only events, etc.), for what period of time, and which stakeholders should have viewing
privileges are local issues, to be determined locally based on the assessment of stakeholder requirements
and cost-effective design analyses to develop the best solutions.
For example, not all stakeholders will require full frame resolution and full frame rate storage, or the storage
of video which does not contain motion or event information, or storage for more than a few weeks or even
days. A storage period of 30 days is often touted as a nominal baseline period, but this is not a regulatory
requirement; indeed, neither the TSA nor international bodies such as ICAO and the EU specify video
storage duration for airports.
Digital video storage exists in several forms, to be scaled according to the number of cameras (the trend is
to ever more cameras); the duration of storage and the frequency of recalling video streams; transmission
bandwidth requirements (of increasing concern because of the proliferation of MP cameras) and network
capacity; server computational capabilities (also of concern as the use of analytics increases); and local
access including displays in the Security Operations Center (SOC). For airport video surveillance systems
larger than about 500 cameras, scaling is an important issue to be addressed during system design.
Digital Video Recorder (DVR). The DVR basically functions as a multiplexer plus a computer disk(s) for
storage in place of tape, all housed in the same box together with ports for connectivity.
The DVR used to provide a convenient, if limited, replacement for the multiplexer + VCR combination
including non-linear access to recorded material usually selected by camera ID, time and date information.
Competent DVRs typically use UDP network ports so that the device can be provided with an IP address
and thereby become accessible over an Ethernet network. If the DVR fails, the stored imagery will probably
A Network Video Recorder (NVR) stores digital images directly from the IP network, and expands on the
capabilities of the DVR. The NVR input and output is IP data comprising compressed and encoded video.
NVRs can be located anywhere on a network – at the monitoring center, adjacent to camera clusters, on the
edge of a network, collected together in a hardened environment – and this affords the designer with
architectural flexibility and adds high availability options not available with DVRs.
In addition, NVRs record and replay simultaneously, and recordings on any one machine can be remotely
viewed by a number of authorized operators spread across the network simultaneously, all independently
and without affecting each other.
The system design should provide for convenient, multiple factor indexing of stored imagery so that
pertinent frames can be quickly accessed based on a number of factors including camera ID, date and time,
type of event trigger, etc. NVR location is transparent to operators, who can call up the recorded video
stream to be viewed if they have the necessary authorization.
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