PoE switches, like what we often call ordinary switches, are all transmission devices. When we need PoE switches, we need to choose carefully. If we want to select PoE switches, we must first understand some important parameters and indicators.
1. backboard bandwidth
The backboard bandwidth of a switch is also called backplane capacity, which is the largest volume of data that can be huff and puff between the switch interface processor or the interface card and data bus. The bandwidth of the backplane indicates the total data exchange capability of the switch, the unit is Gbps, and the backboard bandwidth of the general switch ranges from several Gbps to hundreds of Gbps. The higher the backboard bandwidth of a switch, the stronger the ability to process data, but the higher the design cost will be.
Many people will confuse backplane bandwidth and switching capacity. In fact, switching capacity is generally smaller than backplane bandwidth, and some of the switching capacity is equal to backplane bandwidth. The switching capacity is the transmission capacity between the kernel CPU and the bus.
How to calculate: the sum of the maximum transmission speed of all ports is multiplied by 2.
Not to understand, for example, 4 PoE switches PS104, with 4 megabytes, and 1 megabytes (as shown below), and its backboard bandwidth is 100x5x2=1000Mbps=1Gbps. Is it very simple?
2. packet forwarding rate
The packet forwarding rate of the switch indicates the size of the packet forwarding capability. The unit is usually PPS (packet per second), and the packet forwarding rate of the general switch ranges from tens Kpps to hundreds of Mpps. Packet forwarding rate refers to the number of packets that can be forwarded by a switch per second (Mpps), that is, the number of packets that a switch can transmit at the same time. The packet forwarding rate reflects the switching capability of the switchboard in the form of data packets.
One of the important indicators that determines the packet forwarding rate is the backboard bandwidth of the switch. The higher the backboard bandwidth of a switch, the stronger the ability to process data, and the higher the packet forwarding rate.
Calculation method: x0.1488Mpps, Gigabit port x1.488Mpps, Gigabit port x14.88Mpps, and then add all the different ports.
Or take the above Fengrun PS104 PoE switch for example, there are 4 hundred megabytes, and 1 hundred megabytes, the packet forwarding rate is =5x0.1488Mbps=0.744Mpps.
3. port transmission rate
Port transmission speed refers to the data exchange speed of the switch port, also known as port bandwidth. At present, there are several kinds of 10Mbps, 100Mbps, 1000Mbps and so on. In addition, there are 10GMbps switches. Port transmission speed must match with the access network device to maximize the performance of the port. If 100Mbps's device is connected to 1000Mbps's switch port, it can only work in 100Mbps mode.
Remember, all PoE switches are now adaptive port rates, such as the port rate of 10/100/1000Mbps, indicating that the transmission rate can be 10 Mbps, 100 Mbps, and 1000 Mbps.
4. port number
The number of ports in the switch device is the most intuitive measure of the switch, usually for fixed port switches, the number of common standard fixed port switches is 8, 12, 16, 24, 48, and so on. In addition, some switches also provide special uplink ports, such as 24+2 switches, 24 ports for downlink, usually a hundred megabytes or gigabytes of the electric port; 2 ports are used for uplink, and the upper port is generally Gigabit net port, and the port has an electric port and a light mouth.
5. network management function
Network management refers to the centralized management of resources on the network through network administrators, including configuration management, performance and account management, problem management, operation management and change management. The management level supported by a device reflects the manageability and operability of the device.
If the request is not high, you can not choose the PoE switch with network management, non network management, and the price is cheaper.
Switch delay (Latency) refers to the time interval between receiving packets from the switch and copying packets from the destination port to the destination port. There are many factors that will affect the delay size, such as forwarding technology and so on. The switch using direct pass technology has a fixed delay. Because the direct switch can decide the forwarding direction only according to the destination address regardless of the overall size of the packet. Therefore, the delay is fixed, depending on the rate of interpretation of the destination address in the 6 bytes before the packet is interpreted.
A switch using storage and forward technology is related to the packet size because it has to receive a complete packet before it begins to forward the packet. When the packet size is large, the delay is large, and the packet is small, and the delay is small. In practical applications, the latency of perception also comes from the attrition time of platform access, transcoding, forwarding and other mechanisms.
Whether it's a choice or an Ethernet switch or a PoE switch that can be powered, it can be considered from the above aspects. In fact, in addition to the above parameters, brand and price are often one of the factors that must be considered, so choosing a switch is not a simple matter, but a series of comprehensive considerations.