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detektor security academy
Temperature
Figure 3
shows the environmental
testing standard of a switch with
PoE/PD load to simulate a full
workload. Passing conditions
should ensure the switch can oper-
ate continuously under low and
high temperatures without any
data transmission errors.
Reviewing product specifica-
tions is only a basic step of the PoE
switch decision making process.
Making the right decision requires
a comprehensive testing report to
ensure that the network product
is designed with high quality engi-
neering. Only then will you be able
to count on them for the success of
your surveillance system.
After PoE comes PoL
Generally speaking, Power over
Ethernet technology is a useful tool
for solving power source issues,
however there are also limitations
relating to the applied media and
distance. An alternative to compen-
sate the PoE technology limitations
is PoL (Power over Link) technol-
ogy. PoL supports power over one
twisted copper pair and coaxial
cables, and the distance can be over
1 kilometre. This new technology
makes projects more flexible and
efficient. It is also easy to use, and
this technology should also be in-
cluded when evaluating TCO (total
cost of ownership) benefits.
* You can read more general advice on
getting the correct switch for your surveil-
lance needs in the Detektor Security
Adacemy article "Infrastructure for
efficient IP surveillance" which can be
found on the website www.securityworld-
hotel.com under the section "Security
Academy".
** You can read more on PoE in the
Detektor Security Academy article
"Effective IP surveillance with Power
over Ethernet" which also can be found
on www.security worldhotel.com. n
play. No sophisticated engineering
effort is needed, however these
switches might be bigger, more
expensive and best used in a con-
trolled climate.
Total power budget
this often
cheaper PoE switch operates as a
"total power budget", but users
need to consider a number of
points when selecting this type
of system. For instance, features
like pan-tilt-zoom, cooling fans,
heaters or infrared illuminators
may require extra power. If the
total power consumption is over
the total power budget of the PoE
switch, it may cause the entire sys-
tem to malfunction. Users should
accurately measure the total power
of all devices to effectively avoid
errors from occurring in the field.
Poe testing
When an IP surveillance system
is planned, users may perform a
simple test, under room tem-
perature, by connecting the
IP cameras to all PoE ports on
the switch. Users should let the
system run for a few days to see if
it is operating at a stable rate. If it
is, users are highly recommended
to test the system again under a
full workload and various operat-
ing temperatures. Occasionally,
instability will occur under long
periods with a high workload or
in rapidly fluctuating tempera-
tures. A good PoE switch should
be able to withstand functional
and environmental challenges.
PSE Conformance Testing can
be performed in quality assurance
labs. A test suite can analyse hun-
dreds of test parameters depending
upon the capabilities of the PSE.
These parameters are measured
in several distinct tests that cover
most of the PSE PICS (conform-
ance check list items) in the IEEE
802.3at/af specifi cations.
tural malfunction when there is
a sudden change in the network
environment.
Poe capabilities**
PoE (Power over Ethernet) is
a convenient and cost-efficient
power solution for IP surveillance
systems. Power over Ethernet
technology describes a system to
pass electrical power over Ethernet
cabling, along with data. This
means that a network device can
be powered and operated using
the same cable as for network
connection, eliminating the need
for power outlets close to an IP
camera, for example.
Two types
Most PoE switches come in two
types off-the-shelf: "guarantee per
port" operation and "total power
budget" operation both useful in
their own way.
Guarantee per port
this type
of PoE switch provides a lot more
flexibility to users when planning
and expanding their IP surveil-
lance system. PoE switches that act
as power source equipment (PSE)
should successfully feed sufficient
power to connected powered
devices (PD) after retrieving the
power consumption information
of each IP camera and comparing
the data to the total number of
connected IP cameras. When each
port is guaranteed a full power
design in compliance with either
IEEE802.3af or IEEE802.3at,
the switch is effectively plug-and-
in the following graphs should
match. As the ports were paired
for testing, actual throughput
should be 3000 Mbps x 2 = 6000
Mbps (6 Gbps).
The specifications for the
switch used here was 10-port
10/100 BASE (8 x PoE) with a
2-port Gigabit Ethernet Switch
(10 x 100 Mbps + 2 x 1000
Mbps) = 3000 Mbps. Under
full duplex mode, the operating
bandwidth should be 3000 Mbps
x 2 = 6000 Mbps. Our calcula-
tions were consistent with the
actual test results, so this switch
supports full wired-speed. While
it is not that easy to obtain the
necessary testing equipment to
carry out the experiment when we
put these devices into service, we
can still ask the vendor to provide
test reports shown as figure 2 that
back up their claims.
Needs adjustments
One can´t expect to operate
equipment at their full capacity
over an extended period of time.
Not only is this poor infrastruc-
ture planning, it also places sig-
nificant stress on the equipment
and indirectly impacts network
stability. In actual applications,
once the equipment performance
has been fully understood, ap-
propriate performance adjust-
ments must continuously be
made. These adjustments should
include network device manage-
ment and data traffic planning.
The equipment must also have
spare capacity to avoid struc-
Choosing the best network switch for IP surveillance
focusonbackbonefullwiredspeed,PoEcapabilityandtesting
About the sponsor
EtherWAN Systems, founded in 1996 with the US headquarters in California
and the Pacific Rim headquarters in Taiwan, has become a leader in Ethernet
connectivity for applications in various markets including IP surveillance,
intelligent transportation systems (ITS), electric utility, oil and mining, factory
automation, etc. EtherWAN specialises in designing and manufacturing fibre
optic Ethernet products and Ethernet equipment made especially for harsh en-
vironments. Technical engineers are available for network topology consultancy.
For more information about EtherWAN's solutions, visit: www.etherwan.com
Contact info: info@etherwan.com.tw
Figure 3.
Environmental testing standard of switch with PoE/PD load to stimulate
a full workload.
Sponsored by
SECURITY ACADEMY
Network switches for
IP surveillance