Source: ZYXEL

With the increasing availability of high quality, low-cost IP cameras and Power Over Ethernet (POE) enabled Switches, video surveillance based on traditional analogue closed circuit television (CCTV) is now rapidly giving way to digitized, IP-network-based systems known collectively as IP surveillance.

The advantages of IP surveillance over analogue CCTV include:

• Economies of scale from sharing a common network infrastructure with IT systems
• Greater all-round ease of use that comes from a digital, software-based system:
  • View from anywhere
  • Distribute recordings automatically to any location
  • Easier, more secure storage and back-up
  • Easier and faster digital search and retrieval
• Increased image quality with no degradation over time
• The ability to record and play simultaneously
• Integration with email and other IT systems for automatic alerts

The key components of any IP surveillance system are:

• IP camera, preferably capable of accepting Power over Ethernet (POE)
• Managed Switch with POE as well as advanced security and resilience capabilities
• Server-based video management software
• Storage that is accessible via the IP network

Why POE?
There are three main reasons why POE should be considered a mandatory requirement for professional IP surveillance:

• Simplicity and cost of installation
  Selecting a POE-enabled IP camera greatly simplifies (and reduces the cost of) installation, since each camera now only requires one cable (typically cat5e or cat6) and can therefore be located up to 100m from any other equipment or power source. This is especially useful for outdoor surveillance, where optimal camera placements are seldom close to power sockets.
• Ease of Management and operating cost
  The more advanced, managed, POE switches allow the operating power to each camera to be remotely controlled from any point on the IP network. This means that the administrator can easily reboot any frozen, non-responding IP camera without having to send a technician out to the camera’s location. This process can even be automated to occur at preset times of the day and week, simplifying the day-to-day management of the system and thus reducing operating expenses.
• Resilience to power failure
  Since power to all cameras is derived from a single source (the switch), a central UPS (Uninterruptible Power Supply) attached to that switch can be used to ensure continued surveillance in the event of a power cut.

In determining the best POE switch for your IP surveillance goals, the most important considerations are the following:

• POE specifications and management:
  • Total power budget
    – The greater the total wattage that can be supplied by each switch, the greater the number of cameras and other POE devices that can be connected. This can lead to fewer switches needing to be deployed thereby significantly reducing the overall cost.
  • Power management per port
    Some POE ports can automatically detect the class of device attached and allocate the maximum stated power requirement for that device.
    Other switches have an additional capability to measure the actual power draw for each device (which will also depend on the length of cable for example).
  • POE Scheduling
    – Some switches offer the ability to automatically control the supply of power to each port on a timed basis. This can be useful for routine rebooting of the cameras or to limit surveillance to certain times of the day and week – for example you may wish to preserve the privacy of your employees during office hours and provide surveillance only at night.
• Spanning Tree Support
  To ensure that critical parts of the IP surveillance network can still be reached in the event of a link failure, it is important to create some link redundancy. The only way to do this within an Ethernet network is to use switches supporting of one or more variants of the Spanning Tree Protocol (STP), RSTP, or MSTP.
• Optical Fibre and Fibre Aggregation
  Where there is a requirement to ensure high quality video transmission between multiple sites, especially where distances exceed the 100m limitation of twisted pair copper cabling, optical fibre will need to be deployed and so the switch will need to support the chosen format. For extra capacity and resilience, the ability to aggregate two or more of these optical links is also advantageous.
• Remote Monitoring (RMON) Support
  For additional security and resilience, switches with RMON functionality can continuously monitor key network traffic parameters and generate alarms and alerts when certain predefined conditions or thresholds are met or exceeded. This can provide an early warning system, alerting the surveillance operator to any unusual or potentially problematic scenarios before they become too serious.
• Video transmission control
  A number of technologies can be combined to provide more efficient control of video transmission and avoid unwanted packet flooding. These include:
  • Multicast
  • Secure Virtual Private Network (VPN) tunnelling
  • IGMP Snooping 
• VLAN support
  The security derived from IP surveillance can be undermined if measures are not taken to secure the data flowing between cameras, management software and storage. One way to do this is to assign all IP surveillance traffic to its own VLAN. Not only will this increase security by isolating this traffic from the rest of the network, but it also allows Quality of Service (QOS) to be applied through traffic prioritization, ensuring at all times that sufficient bandwidth is reserved for high quality video transmission. Beyond choosing a managed switch capable of creating VLANs, it is worth looking closely at the ease of setup. Some switches for example, can be configured to automatically assign new IP cameras to the correct VLAN based on the vendor-specific portion of their MAC addresses, greatly simplifying the installation process.
• QOS – Quality of Service
  Since IP surveillance traffic will typically share the network with other IT applications, and given that video requires both relatively high bandwidth and low latency, the quality of video playback can be degraded by high levels of non-video traffic on the network. To avoid this, it is usual to assign IP surveillance traffic to its own VLAN and then prioritizes this using one or more QOS techniques.
• MAC freeze
  For additional security of IP camera ports, particularly those connected to outside cameras, some switches offer a function known as MAC freeze which, when enabled, prevents any device other than the previously installed IP camera from establishing a valid connection to that port.