How to choose the right switch in wireless monitoring system

In the wireless monitoring system, except for the camera and the transmission equipment, the switch occupies a very crucial role. Many friends have no concept of this piece, or do not realize the importance of the switch, hastily used low-performance equipment, resulting in the entire system often problems or even the system can not run.

So, in a wireless monitoring system, how should the switch be chosen? We will proceed from the following aspects.

First, the important parameters of the switch

Backplane bandwidth

The backplane bandwidth is the maximum amount of data that can be handled between the switch interface processor or interface card and the data bus. The backplane bandwidth marks the switch's total data exchange capacity in Gbps, also called switching bandwidth. The higher the backplane bandwidth of a switch, the stronger the ability to process data.

Backplane bandwidth calculation method: port number * port speed * 2 = backplane bandwidth, backplane bandwidth ≤ nominal backplane bandwidth, then the switching device is line rate on the backplane bandwidth, also known as non-blocking.

Forwarding performance (sum of packet forwarding rates of ports)

Packet forwarding rate, also known as port throughput, refers to the packet forwarding capability of a router on a port. Units usually use pps (packet per second) to measure. In general, the low-end router packet forwarding rate is only a few K to several tens of Kpps, while high-end routers can reach several tens of Mpps (million packets per second) and even hundreds of Mpps.

The calculation method of packet forwarding rate: full configuration Gigabit ports × 1.488Mpps + full configuration 100Mbit ports × 0.1488Mpps = packet forwarding rate, complete machine forwarding rate ≤ nominal packet forwarding rate, then the switching equipment is in the whole forwarding Line speed, also known as non-blocking.

Second, switch selection suggestions

For a large and medium-sized network monitoring system, its switch configuration is generally composed of three parts: access layer, convergence layer, and core layer.

Access layer:

You can select 8- or 16-channel Fast Ethernet switches. It is recommended that you control the number of cameras on the access switch at 6-10.

The actual bandwidth of our commonly used switches is 50%-70% of the theoretical value, so the actual bandwidth of a 100Mbit is 50M-70M. 4M*12=48M, so it is recommended that a 100M access switch should have access to a maximum of 12 720P network cameras. At the same time consider that the current network monitoring using dynamic encoding, the camera code stream peak value may exceed 4M bandwidth, while taking into account the bandwidth of redundant design, so a 100M access switch to control the best within 8 units, more than 8 units recommended Gigabit mouth.

Convergence layer:

The performance is higher than that of the access switch. You can select a Layer 2 switch with 1000 uplinks. The 100M Ethernet port of the switch is connected to the switch. The number of cameras connected to the gigabit port and the core switch of the monitoring center should be controlled at about 30 sets.

With the 720P network camera 4M bitstream calculation, each access layer switch on the front end has six 720P network cameras. The aggregation switch is connected with five access layer switches. The total bandwidth under the aggregation layer switch is 4M*6*5=120M. Therefore, the gigabit interface should be selected for the cascade port of the aggregation switch and the core switch.

Core layer:

The core switch is the core of the entire digital surveillance system, the next aggregation switch, uplink video surveillance platform, storage server, digital matrix and other equipment, it is recommended to select three full-gigabit core switches, the number of cameras exceeds 150 sets Consider three-tier 10G core switches .

Third, when selecting the type of attention:

1, for management convenience, optional WEB managed switches;

2, due to the larger video traffic, optional line speed switch;

3, video data has a sudden nature, the greater the better the buffer cache;

4, the flow control function of the switch;

5. It is recommended that aggregation switches and core switches select well-known enterprise products.

If you are unsure about the process of purchasing, you can consult the relevant manufacturers. But one thing is not to blindly choose only cheap equipment from the price. Consider the overall effect. The switch suggests that it is better to purchase.