How many network surveillance cameras can one switch drive?

For example, is your switch 100M or 1Gb?

What is the POE power of the whole machine and the POE power of the port?

What is the brand of the switch?

Some cheap and no-name switches have false performance standards, which directly affects your project.

How many network surveillance cameras can one switch drive?

How many 2 million network cameras can be connected to a Gigabit switch?

With 24 network heads, can I use a 24-port 100M switch?

1. Choose according to the code stream and quantity of the camera

Camera stream: Before choosing a switch, you must first find out how much bandwidth each image occupies.

Number of cameras: Find out the bandwidth capacity of the switch. Commonly used switches include 100M switches and Gigabit switches.

Their actual bandwidth is generally only 60~70% of the theoretical value, so the available bandwidth of their ports is roughly 60Mbps or 600Mbps.

For example: Look at a single code stream based on the brand of network camera you are using, and then estimate how many cameras a switch can connect.

1) 1.3 million: The code stream of a single 960p camera is usually 4M. If you use a 100M switch, you can connect 15 units (15×4=60M); if you use a Gigabit switch, you can connect 150 units (150×4=600M).

2) 2 million: The code stream of a single 1080P camera is usually 8M. If you use a 100M switch, you can connect 7 units (7×8=56M); if you use a Gigabit switch, you can connect 75 units (75×8=600M).

These are explained to you using the mainstream H.264 camera as an example. H.265 can be halved.

In terms of network topology, a local area network is usually a two- to three-layer structure. The end where the camera is connected is the access layer. Generally, a 100M switch is enough, unless you connect many cameras to one switch.

The aggregation layer and core layer are calculated based on how many channels of images the switch aggregates.

The calculation method is as follows:

If you connect a 960P network camera, generally within 15 channels of images, use a 100M switch;

If there are more than 15 channels, use a Gigabit switch. If you connect a 1080P network camera, generally use a 100M switch if there are less than 8 channels of images, and use a Gigabit switch if there are more than 8 channels.

2. Switch selection requirements

1) Selection of access layer switches

  Camera bit stream: 4Mbps, 20 cameras is 20*4=80Mbps.

In other words, the access layer switch upload port must meet the transmission rate requirement of 80Mbps/s. Considering the actual transmission rate of the switch (usually 50% of the nominal value, 100M is about 50 M), so the access layer The switch should be a switch with a 1000M upload port.

Switch backplane bandwidth: If you choose a 24-port switch with two 1000M ports, a total of 26 ports, the switch backplane bandwidth requirement at the access layer is: (24*100M*2+1000*2*2)/1000 =8.8Gbps backplane bandwidth.

Packet forwarding rate: The packet forwarding rate of a 1000M port is 1.488Mpps/s, then the switching rate of the access layer switch is: (24*100M/1000M+2)*1.488=6.55Mpps.

Based on the above conditions, it can be concluded that when 20 720P cameras are connected to a switch, the switch must have at least one 1000M upload port and more than 20 100M access ports to meet the demand.

2) Selection of aggregation layer switches

If there are a total of 5 switches connected, each switch has 20 cameras, and the code stream is 4M, then the traffic of the aggregation layer is: 4Mbps*20*5=400Mbps, then the upload port of the aggregation layer must be above 1000M.

If 5 IPCs are connected to a switch, an 8-port switch is generally required. Does this 8-port switch meet the requirements? You can look at the following three aspects:

Backplane bandwidth: number of ports * port speed * 2 = backplane bandwidth, that is, 8 * 100 * 2 = 1.6Gbps.

Packet switching rate: number of ports * port speed / 1000 * 1.488Mpps = packet switching rate, that is, 8 * 100 / 1000 * 1.488 = 1.20Mpps. The packet switching rate of some switches is sometimes calculated to be unable to meet this requirement, so it is a non-line-speed switch. When performing large-capacity throughput, it is easy to cause delays.

Cascade port bandwidth: IPC code stream * number = minimum bandwidth of the upload port, that is, 4.*5 = 20Mbps. Normally, when the IPC bandwidth exceeds 45Mbps, it is recommended to use a 1000M cascade port.

3. How to choose your switch

for example:

There is a campus network with more than 500 high-definition cameras and a code stream of 3 to 4 megabytes. The network structure is divided into access layer-aggregation layer-core layer. Stored in aggregation layers, each aggregation layer corresponds to 170 cameras.

Problems faced: How to choose products, the difference between Fast and Gigabit, what are the reasons that affect the transmission of images in the network, and what factors are related to switches...

2 times the sum of all port capacity * port number should be less than the nominal backplane bandwidth, which can achieve full-duplex non-blocking wire-speed switching, proving that the switch has the conditions to maximize data switching performance.

For example: a switch that can provide up to 48 Gigabit ports should have a fully configured capacity of 48 × 1G × 2 = 96Gbps to ensure that it can provide non-blocking wire-speed packet switching when all ports are in full duplex. .

1) Packet forwarding rate

Fully configured packet forwarding rate (Mbps) = number of fully configured GE ports × 1.488Mpps + number of fully configured 100M ports × 0.1488Mpps. The theoretical throughput of one Gigabit port when the packet length is 64 bytes is 1.488Mpps.

For example: If a switch can provide up to 24 Gigabit ports, but the declared packet forwarding rate is less than 35.71 Mpps (24 x 1.488Mpps = 35.71), then there is reason to believe that the switch adopts a blocking structural design.

Generally, a suitable switch is a switch that meets both the backplane bandwidth and packet forwarding rate.

In addition to retaining the ability to upgrade and expand, switches with relatively large backplanes and relatively small throughput have problems with software efficiency/dedicated chip circuit design; switches with relatively small backplanes and relatively large throughput have relatively high overall performance.

The camera code stream affects the definition, usually the code stream setting of the video transmission (including the codec capabilities of the encoding sending and receiving equipment, etc.). This is the performance of the front-end camera and has nothing to do with the network.

Usually users think that the clarity is not high and think that it is caused by the network. This is actually a misunderstanding.

Based on the above case, calculate:

Code stream: 4Mbps

Access: 24*4=96Mbps<1000Mbps<4435.2Mbps

Aggregation: 170*4=680Mbps<1000Mbps<4435.2Mbps

2) Access switch

The main consideration is the link bandwidth between access and aggregation, that is, the uplink link capacity of the switch needs to be greater than the number of cameras that can be accommodated at the same time * the bit rate.

In this way, there is no problem with real-time video recording, but if a user sees the video in real time, the bandwidth needs to be considered. The bandwidth occupied by each user viewing a video is 4M. If each camera connected to the switch If one person is watching, the bandwidth of the number of cameras*bit rate*(1+N) is required, that is, 24*4*(1+1)=128M.

3) Aggregation switch

The aggregation layer needs to process the 3-4M code streams of 170 cameras at the same time (170* 4M=680M), which means that the aggregation layer switches need to support simultaneous forwarding of more than 680M switching capacity.

Generally, storage is connected to the aggregation, so video recording is forwarded at line speed.

However, the bandwidth for real-time monitoring must be taken into account. Each connection occupies 4M, and a 1000M link can support 250 cameras being debugged and called.

Each access switch is connected to 24 cameras, 250/24, which means that the network can withstand the pressure of 10 users viewing each camera in real time at the same time.

4) Core switch

Core switches need to consider switching capacity and link bandwidth to aggregation. Because storage is placed at the aggregation layer, core switches do not have the pressure of video recording. That is, they only need to consider how many people watch how many videos at the same time.

Assume that in this case, there are 10 people monitoring at the same time, and each person watches 16 channels of video, that is, the switching capacity needs to be greater than 10*16*4=640M.

5) Key points in switch selection

When selecting switches for video surveillance in a LAN, it is usually enough to consider switching capacity when selecting access and aggregation layer switches, because users usually connect and obtain video through core switches.

In addition, since the main pressure is on the aggregation layer switch, because it must not only monitor the storage traffic, but also bear the pressure of real-time viewing and call monitoring, it is very important to choose an appropriate aggregation switch.