This article originally appeared in the August 2022 issue of Security Business Magazine. When sharing, don’t forget to mention Security Business Magazine on LinkedIn and @SecBusinessMag on Twitter.
We often judge the performance of a product by its specifications. Although it is valid, it neglects the role of the network that connects these devices. Regardless of a camera’s or server’s performance, its specifications are meaningless if its signal quality or even the signal itself cannot travel reliably from point A to point B. The role of the network is the most important part of performance and reliability.
Analog security systems were simple – just plug in the cable and go; in fact, even the most complex video components simply required connecting two ends of a coaxial cable.
IP/PoE security systems are much more complex, and added to this complexity is the assumption that “standard” networking products – those designed for data files – will work for security video applications. . Based on this concept, each network should be designed according to its own application requirements. There is no single solution.
When approaching network design for security applications, start with the simple concept that security networks have unique requirements that are not met by standard network equipment.
For security systems, the most challenging networks involve PoE-powered cameras, so we’ll focus on cameras, but the same requirements can be applied to any type of device.
Security networks have two components: bandwidth and PoE. Both are moving targets. Since the introduction of PoE powered IP cameras, their demands for increased bandwidth and PoE have increased. Often these requirements have grown faster than the ability to develop standards to support them. All of this adds to the confusion and complexity of network design for security applications.
Making a purchasing decision solely based on the performance of an individual component without considering all network components and connected devices is a recipe for failure.
According to the networking standards established by the Institute of Electrical Engineers (IEEE), the cable must be CAT 5, (later CAT 5e, 6, 6a). The distance cannot exceed 328 feet (100 m). PoE transmission must also conform to this and adds very specific limited ranges of power and signal signatures for source and destination to recognize each other.
5 Steps to Designing Networks for Security Systems
Integrators should be aware of five key considerations for designing secure networks for security technology. It starts with the connected device itself and progresses to Power over Ethernet compatibility, cable choice, number of connected devices per location and finally collection devices. Here is an overview of each step:
Step 1: Connected Device Power
The pixel size of the camera can range from 2 MP to 33 MP. The ability to process camera resolutions must remain consistent across the network, even as the size of the resulting image packet changes, depending on activity and image composition. If a network lacks the capacity to handle packet size or bandwidth, the result is distortion and dropped frames.
Picture issues don’t mean much if you can’t power the cable. A camera specification indicates a specific amount of power. First, determine whether this specification indicates the source power required or the power required at the camera. Cameras will typically increase by approximately 20% when accessory functions such as day/night, LED lighting, and PTZ operation are enabled. If these functions cause the PoE source to exceed its ability to supply the necessary power, the source may stop supplying PoE, shutting down the camera.
This is often the case when a user discovers that some of their cameras have stopped working during the night when functions such as day/night and LEDs are most active.
Rule 1: If the datasheet lists PoE power both as a value and as a PoE class, always supply sufficient PoE power equal to the highest level of PoE class.
Step 2: PoE compatibility
Not only is the amount of PoE important, but also the type. PoE standards or lack of means that even if you have the right amount, it may not work with the connected device. PoE is defined in several ways. One of them is type. 802.3af, 802.3at are standards that also define PoE levels. Recently, a third 802.3b standard has been adapted as the standard increasing PoE levels to 90 watts. In need of increased power, camera makers didn’t wait for standard approvals. This has led to non-standard types such as PoE++ and UPoE. The most important are not compatible with 802.3ab. A device requiring 60W but based on UPoE will not work with a connected device requiring 802.3bt.
Second rule: the source must match the requirements of the device.
Step 3: Transmission and Cables
Start by knowing that IP/PoE transmission was only designed for CAT cable. Requirements such as resistance and capacitance are very specific for a PoE source to successfully power a connected device. Outside of a limited range, the connected device will either not power up or it will not be able to successfully handle the normal PoE surges that occur, causing the device to go offline.
There are various applications and installations that require exiting CAT cable at a distance limit of 328. These include CAT cable at distances greater than 328 feet and the use of coaxial cable and single pair . Regardless of cable type or cable distance, the two critical cable values of CAT cable resistance value of 22 ohms and for Coax between 19 to 33 ohms and cable capacitance of less than 10uf. All cable types will have different characteristics that affect performance.
An additional consideration is the amount of power a cable can handle. Referring to CAT 5 cable, which is 24 AWG, the maximum power is limited to 37 W in the 802.3af/at range. As PoE requirements increase to over 37W, more pairs are needed. CAT cable consists of 4 pairs, but coaxial and single cables are limited to a single pair, which limits their PoE capacity to a maximum of 37W.
Step 4: Bandwidth
The number of cameras routed to a single location will determine the total bandwidth required. Typically, this point is a network switch. Packet size should also be considered. Can the switch you selected handle jumbo frames at 100 Mbps? Can it transmit all connected cameras operating at the highest bandwidth? Without answers to these questions, the video frames (packets) can either be discarded by the switch or be transmitted with distortions.
Step 5: The endpoint
The endpoint has two considerations: First, how the switches are configured; then the server or NVR.
General switch configurations are either IDF to MDF where a switch in the field is directly connected to a main switch usually referred to as the main switch, or where multiple switches are connected in a daisy chain configuration. In either case, the ability to maintain bandwidth and packet handling is reduced. The highest bandwidth and transmission values should be maintained throughout the total path.
Finally, there is the server or NVR. Recording devices can have three individual paths: recording, viewing, and playback; or viewing and recording can be combined, with playback being separate. Can the recording/viewing device handle the bandwidth? Whatever the configuration, a terminal must be able to manage all the images transmitted to it.
Neil Heller is Vice President of Business Development at Vigitron, a provider of IP/PoE transmission and networking solutions. The company offers several educational resources on the unique requirements of network design for security applications. Email [email protected] for details, or request more information at www.securityinfowatch.com/10215546.