Selection Guide for Industrial Switches at Each Layer of Monitoring Network

Industrial Switch is the core role of monitoring network transmission equipment. We all know that a complete monitoring network has three layers of architecture: core layer, aggregation layer and access layer. The core layer is the backbone network, and the convergence layer provides policy based connectivity to connect the preceding and the following. The access layer is mainly used to connect terminal equipment, just like the organizational structure of the company. The top management, middle management and grass-roots employees perform their respective duties to jointly ensure the normal operation of the company. What factors should be considered when selecting these industrial switches?

The number and rate of interfaces of industrial switches are the most important indicators for selecting and monitoring industrial switches. The number of interfaces of the industrial switch can be determined according to the number of access devices, and some interfaces will be reserved for subsequent expansion; In order to ensure non blocking, packet loss and real-time transmission of video traffic, it is necessary to select an industrial switch with appropriate port rate, mainly considering the following points:

The bandwidth used by the monitoring industrial switch is closely related to the code stream size of the IPC (IP Camera);

Peak bandwidth demand of IPC=code stream × 120%, which can ensure the stable use of IPC under peak bandwidth;

After adding IPC to NVR (Network Video Recorder), the main stream and sub stream of IPC will be taken at the same time;

It is recommended that the actual bandwidth of the industrial switch should not exceed 70% of the maximum port rate, that is, the 100M interface should not exceed 70M bandwidth, and the gigabit interface should not exceed 700M bandwidth. (Fast calculation formula: bandwidth value=(main stream+sub stream) * number of stream fetches * 1.2)

Camera code stream calculation method

When selecting the industrial switch, we should first know the number of cameras and the code stream of cameras. Now the mainstream camera coding technology mainly uses H 265 technology, the code stream of a single camera=main code stream+sub code stream. The sub code stream is generally used for network transmission, and the main code stream is used for high-definition preview and video recording of the camera.

Selection of access layer industrial switch

The access layer directly connects user computers and enables various network resources to access the network. It provides users with the ability to access the application system in the local network segment. Its main function is to solve the mutual access needs of adjacent users and provide sufficient bandwidth for these accesses. At the same time, in some large networks, the industrial switch at the access layer also has the functions of user management and user information collection, such as user authentication, user IP identification, and so on. The demand for the access layer switch is the largest. The switch connected at the terminal needs to meet the characteristics of multi port low-cost. Therefore, the cost performance factor is mainly considered, and the functional requirements are not very high.

After knowing the code stream of the camera, we can select the type of industrial switch. Generally, the actual theoretical bandwidth of an industrial switch is 50% - 70%, and the actual bandwidth of a 100M interface is 50M-70M. Here is a simple example. Based on the 4M code stream of 1080P network camera, how many 1080P network cameras can a 100M port access the industrial switch?

4M * 12=48M, it is recommended that a 100M access industrial switch can access up to 12 1080P network cameras. At the same time, considering that the current network monitoring adopts the dynamic coding mode, the peak value of the camera code stream may exceed the 4M bandwidth, and considering the bandwidth redundancy design, it is best to control a 100M access industrial switch within 8, and it is recommended to use gigabit ports if more than 8. In some UHD network monitoring systems, in order to ensure the high definition of video images and the high reliability of data transmission, the access layer can also directly choose the full gigabit industrial switch.

Selection of convergence layer industrial switch

From the name, the aggregation layer industrial switch is the aggregation part of multiple access layer industrial switches, which is used to transmit the information of the core layer industrial switch and the access layer industrial switch. The aggregation layer industrial switch can implement the strategy, and implement the routing, workgroup access, address filtering and other functions between VLANs according to the edited program.

Based on the 4M code stream of 1080P network camera, there are 6 1080P network cameras on each access layer industrial switch at the front end, and the convergence industrial switch is connected to 5 access layer industrial switches. The total bandwidth under the convergence layer industrial switch is 4M * 6 * 5=120M, so the cascade port between the convergence layer industrial switch and the core industrial switch should be gigabit port.

When selecting switches for video monitoring in the LAN, the main pressure is on the convergence layer switch. The convergence layer switch not only undertakes the traffic of monitoring storage, but also bears the pressure of real-time viewing and calling monitoring. Therefore, it is very important to choose the appropriate aggregation switch.

Selection of core layer industrial switch

The core switch is not a type of switch, but the switch placed in the core layer (network backbone) is called the core switch. The core layer industrial switch needs to meet more conditions. As the backbone transmission network, it needs high reliability, efficiency, manageability, low latency, etc. It is the core of the whole HD network monitoring system. When selecting the core industrial switch, it is necessary to consider the bandwidth capacity of the whole system and how to configure the core layer industrial switch improperly, which will inevitably lead to the inability of smooth display of video images.

The core layer industrial switch is the traffic forwarding center of the network video camera, which undertakes a large amount of data. Therefore, the monitoring center recommends selecting the full gigabit port core industrial switch. If there are many points, VLAN shall be divided, and layer 3 full gigabit core industrial switch shall also be selected. If the number of cameras exceeds 150 large monitoring systems, layer 3 10 gigabit core industrial switch shall be considered.