1 Planning for bandwidth: Effective bandwidth calculation is a crucial element of system installation and upgrading. At the design stage, make sure to consider each camera carefully. Will the camera produce MJPEG, MPEG4 or perhaps H.264 streams, or maybe even all three? Matching the camera resolution with the required level of detail will have an impact on bandwidth. Once this is established, think about the frame rate for each camera and work out the total bandwidth for the system – important if you are adding megapixel cameras to an existing system, which will have an impact on the total bandwidth. MJPEG compression is still widely used, but MPEG4 and H.264 are becoming popular, as they offer significant reductions in overall bandwidth – particularly for megapixel cameras. Exaggerate your calculations slightly to allow for bandwidth fluctuations. Leave approx 30 per cent head room (free bandwidth) in any system.
2 Planning for storage: There are a number of options, for instance, SCSI (Small Computer Systems Interface) units can be connected directly to the NVR servers in a distributed storage approach. This is arguably one of the most secure methods as long as the camera network remains operational. The ‘iSCSI’ approach allows SCSI commands to be encapsulated in TCP/IP to give servers and authorised users access to storage devices over common IP networks. This is, in essence, a ‘networkable’ version of SCSI. Another option is standard NAS (Network Attached Storage). In fact, iSCSI and NAS are very similar conceptually, but there are subtle differences between them operationally. Choosing between the two options will depend on how your system is configured. For block transfers of data (i.e. scheduled archive etc), iSCSI is likely the better option where the server will facilitate limited local storage. NAS is more efficient when writing files directly to the storage point.
3 Consider Data/Network Integrity: IP systems can offer a great deal of redundancy to guard against cable or hardware malfunction. This is an important detail, often overlooked in relatively basic systems. Redundancy needs to be designed into the system at conception, with consideration for system topology being key. A technique known as ‘spanning tree’ is often employed, where managed switches (typically layer 2) are used to make the system ‘topographically aware’. Systems can be configured in different ways, but should always offer several data paths from A to B, automatically re-routing the data via a new path if the existing path is lost.
4 Power over Ethernet: PoE is now used as standard in almost all IP CCTV systems. The convenience and simplicity of this approach is often accompanied by considerable cost savings. Another huge advantage of the POE approach is the ability to centralise the operation and power management of all mission critical network devices, including IP cameras. These will become inoperable unless they are protected by an uninterruptible power supply (UPS) with battery backup.
5 Head end recorder: It seems like a simplistic point, but always ensure that your client is happy with the look and feel of the NVR software being proposed. There is a plethora of options for security installers, and while the systems may appear to offer very similar functionality, they often handle data in very different ways. All manufacturers naturally claim to have produced the panacea of IP systems, but there is a fine balance to be struck between functionality and usability.