Video Surveillance: Ask the IP Man

Sept. 9, 2014
System design expert answers your IP video installation questions

As a System Design/Support Engineer at ScanSource Security, I am often asked questions about IP video surveillance solutions by our reseller and dealer partners who are looking for ways to help their end-user customers implement or enhance a security solution. Here are two recent questions I received — one about remote recording; the other about Power over Ethernet:


Remote Recording

Dear IP Man: My end-user customer has asked me about recording IP camera streams remotely. The cameras will be at Location A, but they really want the actual recording to take place at Location B. Is this possible? If so, what do I need to know?

You are not the first dealer to ask about implementing remote IP camera surveillance. It can be done — the main factors you should consider for a remote recording scenario are: Bandwidth available between sites; video recording resolution; video compression/codec used; number of cameras; and camera frame rate.

Let’s say the end-user wants two IP cameras at site A and wants to record them at site B. Site A has a DSL connection with 1Mbps of upload speed (upload is the important number); the cameras are HD (1080p cameras); and they want to record at 4fps. Using a common bandwidth calculator, the estimated bandwidth is a little less than 2Mbps (results may vary slightly depending on the calculator); thus, you don’t have enough bandwidth.

You can either go back to the internet service provider for more bandwidth, or rethink the camera streaming requirements. Resolution, number of cameras, or frame rate are going to have to be reduced if you cannot get more bandwidth from the ISP. What if you go to just one camera? Or you decide to go with a lower resolution or frame rate? All these things can help to reduce the required bandwidth.

A small mom-and-pop shop may only have enough bandwidth for one low-resolution camera to record remotely. A large school district, on the other hand, may have gigabit fiber between sites and have all the bandwidth they could ever need. But you can see from this example that careful consideration should be made when going with a remote recording solution.


Power over Ethernet

Dear IP Man: I’m going to be upgrading a customer’s surveillance system from analog to IP video, and everything seems to run via Power over Ethernet (PoE). What do I need to know about PoE to get it right? What are my options for upgrading their network cost-efficiently while still having flexibility for future expansion?

There are two strategies for adding PoE to any network, and I’ll highlight the benefits of each; however, there are a few initial things you need to know about PoE in order to avoid technical issues both now and down the road.

PoE means that you are literally powering the end-device using the same CAT5 Ethernet cable that is transmitting data to and from the device. It is incredibly convenient to only need one cable when installing cameras; plus, it also enables you to install cameras in places that might not have been as easy before without ready access to a traditional power source.

PoE is also standards based (based on the ieee standard), which guarantees that two PoE devices — like a switch and a camera of the same standard — will work together. There are two standards, the 802.3af standard, which delivers power up to 15.4 watts, and the newer 802.3at standard (sometimes referred to as high PoE or PoE+), which delivers up to 30 watts (some manufacturers have actually used the new standard to deliver up to 60 watts).

PoE has a distance limitation of 100 meters, or 328 feet. This is the same as Ethernet; however, there are ways to overcome this distance, which we won’t get into right now. Not all cameras require the same level of power. PoE devices are rated based on their recommended wattage. Here is a PoE classification table from IEEE that might clear this up:

  • Class 0: Power range is .44 - 12.95 Watts — Classification unimplemented (The device doesn’t advertise itself as a specific classification, so typically the power source gives full power in this case.
  • Class 1: Power range is .44 - 3.84 Watts —
  • Class 2: Power range is 3.84 - 6.49 Watts —
  • Class 3: Power range is 6.49 - 12.95 Watts —
  • Class 4: Power range is 12.95 - 25.50 Watts —

This is how you determine a power budget — one of the most critical factors in implementing PoE solutions — and the only way to be sure that the power sourcing equipment is going to provide enough total wattage for the overall system. Make sure the power sourcing device works with this standard and check its recommended wattage; for example, I have seen outdoor PTZ cameras that require 60 watts.

At the heart of any PoE surveillance system is the power sourcing equipment: the network device that transmits the power to the device. You can either install a PoE-enabled switch (endspan) or a PoE midspan. Both accomplish the end goal, and each has unique strengths.

The advantage of a PoE-enabled switch is that power and data controls are integrated; thus requiring one CAT5 cable from the switch to each device. Additionally, many of the newest PoE network switches include smart capabilities that help regulate power flow to non-powered ports, reducing the customer’s overall energy use.

Midspans, on the other hand, can be added to an existing network infrastructure specifically to add PoE capabilities. Decoupling the power and data infrastructure does give you more granular control over the number of PoE ports available at any given time, allowing easier expansion for future devices. This is a great option if your customer(s) are not ready to upgrade their network switch, which can be a fairly expensive move depending on their bandwidth needs. If the customer only needs a few PoE ports to begin with, this is often the more cost-effective approach. With some midspans, there are web-based power management schemes to power up and down the ports as needed.

Often, the power budget for the system will help you navigate which strategy is best. If they have high-power PTZ cameras, thin clients or a WLAN network, midspans are the obvious choice, simply for the fact that they can provide a maximum amount of power.


The IP Man is Carl Smith, System Design/Support Engineer at ScanSource Security. To request more info about the distributor, please visit