Relationship Between The Number of Switch Ports And The Number Of Cameras  
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Relationship Between The Number of Switch Ports And The Number Of Cameras (Part 1)

Time:2021-03-16 Source:UTEPO


You may have following doubts:

How many cameras can be driven by one switch?

How many 2MP cameras can be connected to a gigabit switch in general?

Is it ok to connect 24 cameras to a 24-port 100 megabit switch?


In this post, we would get to understand the relationship between the number of switch ports and the number of cameras.

switch


SELECT THE SWITCH ACCORDING TO THE DATA RATE AND NUMBER OF CAMERA

Date rate

Before the selection, you need to figure out how much bandwidth each image would take up.


The number of cameras

It is important to find out the bandwidth of the switch. In general, the common switches are 100-gigabit switches and gigabit switches. Their actual bandwidth is generally only 60 to 70% of the theoretical value, so the available bandwidth of their ports is roughly 60Mbps or 600Mbps.

8 ports poe switch


Example

You can estimate how many cameras could be connected to a switch after checking the data rate of a camera according to its brand.The data rate of a 1.3MP(960P) camera usually is about 4M. You can connect 15 cameras (15*4M=60M) with a 100 megabit switch or 150 cameras (150*4M=600M) with a gigabit switch.

The data rate of a 2MP(1080P) camera usually is about 8M. You can connect 7 cameras (7*8M=56M) with a 100 megabit switch or 75 cameras (75*8M=600M) with a gigabit switch.


The above calculation bases on the mainstream H.264 camera, and if the camera is H.265, the value is half on above.


In terms of network topology, a LAN is usually a two layer or three layer structure. The access layer is for the camera, usually a 100 megabit switch is enough, unless you have many cameras on this switch.

The aggregation layer and core layer should be calculated according to how many images are aggregated by the switch. Calculation method is as follows.


You can connect the 960P network camera (within 15 images) with a 100 megabit switch or 960P network camera (more than 15 images) with a gigabit switch.

You can connect the 1080P network camera (within 8 images) with a 100 megabit switch or 1080P network camera (more than 8 images) with a gigabit switch.


SWITCH SELECTION REQUIREMENTS

1. Access layer switch selection

Data rate. If the data rate of a camera is 4Mbps, 80Mbps for 20 cameras (20*4Mbps=80Mbps).


Therefore, the Uplink port of the access layer must meet the transmission rate requirement of 80Mbps/s. Considering the actual transmission rate of the switch usually is 50% of the nominal value, such as the rate of 100M switch is only about 50M, you should select the access layer switch with 1000M Uplink port.


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


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

UTEPO, access switch

According to the above conditions: when there are 20 720P cameras access to a switch, the switch must have at least one 1000M Uplink port, 20 or more 100M access ports to meet the demand.


To be continued...

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