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Ask the Expert: Are IP-based systems really reliable?

Image New customers often ask if IP-based systems are reliable. That’s because video surveillance system downtime can jeopardize public safety and compromise the security of assets, operations and facilities. While infinite redundancy is theoretically achievable, you need to examine whether such a strategy would be cost effective and practical.  

June 20, 2008  By Bob Moore

No system – analogue or digital — has 100 per cent availability. For
example, analogue systems with VCR recording require that the tape be
changed every eight hours. During this swap out — albeit for a few
minutes — no video is recorded. Statistically, such a set-up delivers
an availability of around 99 per cent, which is considered very low in
the IT industry. Proprietary DVR-based systems also have comparably low
availability, often lower than the regular PC servers on which they are

Meanwhile, most networks deliver more than 99.99 per cent uptime, which
translates to less than one hour per year of downtime. Beyond that, you
can buy network cameras with memory card slots. So even if a network
fails temporarily, organizations with critical needs can maintain
backup video on these cards for 100 per cent reliability.

That said, network video systems require maintenance like other network
systems. Network cameras need patches and updates just like routers do
to improve system functionality and security. Video archives and video
management applications need updates the same as database servers and
financial record applications.

There are a number of best-practices options for maximizing availability of network camera systems:


: Hot swaps and redundant power supplies on switches and other
failover technologies are good options for the most critical components
of the WAN or LAN. Be sure to install cabling, especially in
multi-campus or exterior mounted nodes, with lightning protection and
with proper termination. The main drop, for example, requires both a
patch panel termination and a jack termination. For added protection,
never directly terminate the cable between the switch and network
camera. For easier maintenance, make sure service loops are at least
one foot at the network camera termination point.

Since the wide area network (WAN) supports mission-critical
surveillance, provide multiple alternate paths in the event of a single
path’s failure. Plan and test any network changes prior to
installation. Run patches and upgrades in the lab or on test equipment
to ensure stability before introducing them to the production
environment. Best practice is to always lag behind the latest service
revision releases to prevent new issues from arising. When performing
maintenance, do so in localized phases so as not to create problems
system-wide. With today’s robust technology, regular maintenance
requirements are minimal but they are still essential for the continued
health of the network.

Many video management applications have built-in failover
server capability for server clusters. If the primary server detects a
failure in one server, another identically configured server
automatically takes over all the recordings of the cameras originally
assigned to the failed server. It typically takes only seconds to
switch servers and requires no operator/administrator intervention.
This high level of failure protection is commonly used in mid-tier and
enterprise video surveillance installations.

For the highest level of protection, send video from the network
cameras to two different servers in separate locations simultaneously.
Alternatively, the backup can be sent at a pre-determined time using a
commonly supported archiving feature in the video management software.
If you use WAN links during operating hours, back up video after hours
to limit any disruption to other network applications using the WAN.
These offsite servers can, in turn, be equipped with RAID, work in
clusters or replicate data with servers even further away.

Additional safeguards include component redundancy such as dual network
interface cards and redundant hot swap power supplies. Network and
database monitoring tools running on a network management system ensure
data integrity and help maintain server health.

: Like the server component, system storage can benefit from a
redundant array of independent drives (RAID), allowing users to easily
replace drives in case of failure. Arranging standard, off-the-shelf
hard drives so that the operating system sees them as one large logical
hard disk increases storage throughput as well as reliability. There
are different levels of RAID — from minimal spares to a full “hot
swappable” mirrored solution where there is no disruption to the
operation of the system and no loss of data in the event of a hard disk

: Network cameras include a built-in watchdog that automatically
restarts them whenever service is interrupted. But the network camera
technology continues to evolve. When upgrading camera firmware, do the
upgrades one unit at a time to avoid creating major blind spots in the
surveillance network, which would occur if a large batch of cameras
were pulled offline at the same time. Schedule upgrades automatically
as a function of the video management software or use vendor-specific
tools that allow an administrator to
control batch upgrades.

Also remember to periodically check that cameras are not redirected,
pulled out of focus or covered by post-installation changes to the
environment. Many network cameras have the built-in intelligence to
automatically alert operators if they have been tampered with.

All electronics require power and sometimes that is the weakest
link in the chain. Providing hot swappable power supplies for the
servers and switches is one possibility, but if massive power outages
are a concern, consider deploying an Uninterruptible Power Supply (UPS)
system. Network video systems that use Power over Ethernet, however,
have the advantage that the complete surveillance system, including the
network cameras, will remain operational for some time in a power
outage.  Since most power failures are of short duration, this will go
a long way in ensuring uptime.

Each organization will make different technology choices based both on
the criticality of coverage and budget available. For example,
educational institutions may be able to schedule system maintenance in
late evenings with minor ramifications. Meanwhile, transportation or
medical-related organizations may have less leeway because of their
extended hours of operation. The bottom line is that using strategies
outlined in this column, organizations should be able to maintain
reliability that meets or exceeds their needs.

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