Network Topology

Overseeing a new installation of a video surveillance system recently gave me some useful insights into network hardware and layout. The system is relatively high-spec, using Arecont AV2100 and ACTi ACM-1231 megapixel network cameras, with a Mac Mini as the recording computer (running SecuritySpy of course!). If you are unfamiliar with Arecont, they produce simple box cameras with unparalleled visual quality. ACTi cameras were chosen for other areas because they offer additional features such as infrared night vision and audio.

A high-performance switch was required, and a Netgear FS116 was chosen:

This switch supplies power-over-ethernet (PoE) on 8 of the 16 ports, which is supported by both models of camera mentioned above, simplifying the wiring installation.

From my experience, it is not worth economising on such items of network hardware. Netgear is a company with a long history of making high-quality reliable products. You may be tempted by alternative cheaper products from little-known manufacturers but it is generally a false economy. The above switch costs around GBP £150, a small price to pay for such a critical component.

The first setup of the system was laid out as follows:

As you can see, the router connects the Mac Mini and the main switch – the router basically contains its own internal hub/switch that provides four ethernet ports. This setup was chosen because of the close proximity of the router and Mac Mini (therefore easier wiring), and also to implement as short a route as possible from the Mac Mini to the internet. As well as managing the video surveillance system, the Mac Mini is providing some important web server functionality to the internet, and the above layout means that a failure of the main switch would not cause an outage of these functions.

However, this setup was plagued with problems. There were frequent timeouts and disconnections in the communication between the Mac Mini and the cameras. Troubleshooting revealed that the problem was down to the router’s internal hub. As you can see from the above diagram, the traffic from the cameras has to pass through the router to get to the Mac Mini, and apparently the router’s hub wasn’t up to the task. This underlines the point made above about only using high-quality networking hardware – a point apparently ignored by router’s manufacturer. So, the topology was changed as follows:

Now, the Mac Mini connects directly to the main switch. The traffic from the cameras goes straight through the main switch to the Mac Mini, and the router doesn’t see any of this traffic. Since the change, performance has improved and reliability has been flawless.

The above switch works at “fast ethernet” speeds, up to 100Mbps. This works well for the system described above, which has only four cameras. With more cameras, this speed limitation may start to impact on performance (depending of course on the cameras’ resolutions and your desired frame rates). The solution is to to use a gigabit switch, which offers speeds 10 times that of fast ethernet. For this I would recommend the Netgear FS728:

As well as 24 fast ethernet ports (all of which provide PoE), this switch offers four gigabit ethernet ports, one of which you would use to connect the computer. This removes the speed limitation and will allow you to connect many more cameras without any problems of network bandwidth. In addition, this is a managed switch, so has a web interface that has some useful statistics as well as other features such as cable tests – very handy for troubleshooting network connections.

7 Comments

  1. I will use this system with other control4 equipments , should i use seperate switch for security cams or use all together in one switch? Thank you.

    Emre (from turkiye)

    Reply
    • In certain circumstances this could be a good idea – for example if you have many cameras and you need to maintain a high-bandwidth network for other applications. However for a small installation, especially if you have a fast (ideally a gigabit) ethernet switch, you would not normally see any significant benefit from separating the cameras to their own switch.

      Hope this helps!

      Reply
  2. I am installing a system with 3 Dahua IPC-HFW3200S cameras, at full frame rate and resolution. The switch will be mounted the attic. Can you recommend a gigabit PoE switch to use in this application? Thank you.

    Reply
    • Hi William, Netgear is a safe bet, they consistently produce high-quality products. The GS108PE switch should suit your needs: it’s an 8-port gigabit switch with four of the ports providing PoE. If you need more PoE ports, the GS110TP provides power on all its 8 ports.

      Reply
      • Would a Cisco Small Business 200 Series SLM2008PT-NA Smart 10/100/1000Mbps SG200-08P 8-Port Gigabit Ethernet PoE Switch work just the same? Thank you.

        Reply
        • That looks like it will do the job. I don’t have any personal experience with Cisco switches but they have a good reputation. And this particular switch seems to have decent reviews from what I can see.

          Reply
  3. My Router WRN2000, Switch GS105v4 , and Wifi Repeater wn2000rptv2 are Netgear.

    Cat6 RJ45 Modem Wan-to-Router-to-Switch as instructions indicate. Everything plugged into the Switch works, including the Q-See QCN 7001n.

    Unmanaged Switches may operate differently and not require the Switch inline before the Router? I use PoE injectors rather than a PoE switch, primarily because I had injectors, but secondarily because they’re simple to replace on a small system such as mine.

    Reply

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