First, we need to understand the three-tier network structure. In terms of network topology, medium and large-scale HD network video monitoring system usually adopts three-tier network architecture, namely access layer, aggregation layer and core layer. Due to the different performance and access bandwidth of each layer of network architecture, they choose different switches. In the access layer, the switch in this layer is directly connected with the camera. Therefore, we usually choose 8 or 16 ordinary 100MB switches, and the number of cameras will be controlled at about 6-10 to ensure the stability of transmission. Since the actual bandwidth of our commonly used switches is generally only about 50% - 70% of the theoretical value, the actual bandwidth of 100m ports is about 50m-70m. Therefore, we all suggest that the 100m access switch can access up to 12 720p network cameras.

At the same time, we also consider that the current network monitoring adopts dynamic coding, and the peak value of camera code stream may exceed 4m bandwidth, so bandwidth redundancy design should be considered. Therefore, it is better to control 100 megabit access switches within 8, and Gigabit ports are recommended for more than 8. For the switch with higher performance than the access layer in the aggregation layer, the layer-2 switch with Gigabit upload port can be selected. The number of cameras on the switch connected between the Gigabit port of the switch and the core switch of the monitoring center shall be controlled at about 30. According to the 4m code stream calculation of 720p network camera, there are 6 720p network cameras on each access layer switch in the front end and 5 access layer switches in the lower end. The total bandwidth under the aggregation layer switch is 4m * 6 * 5 = 120m, so the cascade port between the aggregation switch and the core switch should be Gigabit. At the core layer, the core switch is the core of the whole digital monitoring system. The lower convergence switch, the upper video monitoring platform, the storage server, the digital matrix and other equipment layer 10 Gigabit core switches are connected.

Precautions for model selection:

1. In order to facilitate management, you can choose web management switch;

2. Due to the large video flow, line speed switch can be selected;

3. Video data has the characteristics of burst, and the larger the cache of the switch, the better;

4. Flow control function of the switch.