With the use of high-definition camera, how to choose the right, to meet the monitoring of the overall network architecture performance of the switch has become a very important role in the early development of the HD monitoring system, project quotation. A suitable exchange, not only can play the function of monitoring network should be able to effectively reduce the waste of resources. The following small share a bowl of dry cargo and everybody, let you get every minute of network video monitoring switch.
First, "3" - three layer network architecture
In terms of network topology, a medium and large high-definition network video surveillance system needs to adopt three layer network architecture: access layer, convergence layer, core layer, each layer network architecture performance and the different access bandwidth, the switch is not the same.
1, access layer:
Can choose 8 or 16 ordinary Ethernet switch, that access switch quantity control in Taiwan 6-10 camera.
We used the actual bandwidth switch is the theoretical value of 50%-70%, so a fast and practical bandwidth in 50M-70M. 4M*12=48M, therefore suggest a fast access to the 720P network access switch maximum 12 cameras. At the same time, considering the current network monitoring using dynamic encoding mode, the camera may exceed 4M stream peak bandwidth, considering the bandwidth redundancy design, so a fast access switch control in 8 less than the best, more than 8 Taiwan recommended Gigabit port.
2, convergence layer:
The performance is higher than the access switch requirements, can choose to take the two layer switch with a thousand. The switch port is connected with the grounding switch Baizhao Gigabit port, and the monitoring center core switch connect aggregation switch camera number should be controlled at around 30.
720P network camera 4M stream computing, 720P network has 6 cameras in front of each switch in access layer, the aggregation switch under 5 access layer switch. The aggregation layer switch under the total bandwidth of 4M*6*5=120M, so the aggregation switch and the core switch port Gigabit port should cascade.
3, core layer:
The core switch is the core of digital monitoring system, the uplink aggregation switch, video surveillance platform, storage server, digital matrix and other equipment, it is recommended to select a three Gigabit core layer switches, the number of cameras more than 150 Taiwan consider three layer Gigabit core switch.
Two, "2" - two important parameters
1, the back board bandwidth
The bandwidth of the back board is the maximum amount of data that can be between the switch interface processor or the interface card and the data bus. The back band width is the symbol of the data exchanging ability, and the unit is Gbps. The higher the bandwidth of a switch, the more powerful it is to process the data.
The method of calculating the bandwidth of the back board: the port number x port speed x 2 = the back - back bandwidth.
HUAWEI S1724G, for example, the switch has 24 Gigabit ports. =24 x 1000 x 2 / 1000 48Gbps.
The back - back bandwidth is nominal, and the switching device is a linear, or no block, on the back - back - bandwidth.
2, forwarding performance (the port packet forwarding rate and)
Packet forwarding rate, also known as port throughput, refers to the router in a port to carry out the packet forwarding capability, the unit is usually used to measure the PPS (packet per second). Generally speaking, the low end of the router packet forwarding rate is only a few K to tens of Kpps, and the high-end router is able to reach tens of Mpps (millions of packets per second) or even hundreds of Mpps.
Packet forwarding rate calculation method: full configuration Gigabit port number * 1.488Mpps + full configuration fast port number * 0.1488Mpps = packet forwarding rate (1 Gigabit ports in the packet length is 64 bytes for the theoretical throughput of 1 Mbps in port 1.488Mpps, packet length is 64 bytes of the theoretical throughput for 0.1488Mpps).
HUAWEI S2700-26TP-SI as an example, the switch has 24 megabytes, two Gigabit uplink ports.
Packet forwarding rate =2 x 1.488Mpps + 24 x 0.1488Mpps = 6.5472Mpps.
The forwarding rate of the whole machine is nominal packet forwarding rate, so the switching equipment is on the whole forwarding, which is linear, also called no blocking.
Three, the selection of attention:
1, in order to manage the convenience, optional WEB switch; 2, due to the video traffic is large, optional wire speed switch; 3, video data has the characteristics of sudden switch, the switch is better; 4, switch traffic control functions; 5, the convergence of switches and core switches are recommended to select well-known enterprise products.
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