Recently, I have always been asked by customers what the key parameters of switch products, such as wire speed forwarding, backplane bandwidth, etc., mean, I think that they are generally used for bidding, and they will not be too specific, while some manufacturers' equipment will be marked and some will not. But I think I've forgotten a little bit.,Review it again, and by the way, I also sent a content sharing and record~
Wire-speed forwarding
The switch has sufficient capacity to process the forwarding of the smallest packets at full speed, which means that the switching device can transmit the number of binary numbers per unit time (per second) of a single port, that is, how many zeros and 1s can be transmitted in 1 second, and the common ports are as follows:
- The 100 Gigabit network port is 100Mbps, that is, it can forward 10^8 binary numbers in 1 second;
- The Gigabit Ethernet port is 1000 Mbps, that is, 10^9 binary numbers are forwarded within 1 second.
Packet forwarding rate
- The metric is the number of packets sent per unit of time (1 second) that 64 bytes are sent (pps);
- There should be at least some frame gap between Ethernet frames in order to distinguish between two packets. Configure the frame gap between Ethernet frames to change the packet forwarding rate and adjust the packet forwarding capability on the device interface.
- Note: The default frame gap for Huawei switches is up to 12 bytes. If the frame gap of the interface is small, the receiver will not have enough time to receive the next data frame after receiving a data frame, resulting in packet loss due to the failure to process forwarded packets in a timely manner.
- The forwarding rates of different types of network port packets are as follows:
- 百兆网口：148.8Kpps，
- 1,000,000 Trillion Mouth: 1.488Mpps
- 万trillion网口:14.88Mpps
How do you calculate it? It's very simple, for example, how many 64Bytes of data packets can be forwarded by the Gigabit Ethernet port (1000Mbps) per second, and the 8bytes preamble and 12bytes frame gap must be added when calculating, that is to say, if a packet is not forwarded, 64 + 8 + 12 = 84 bytes must be transmitted. One bytes is 8 bits, and the conversion result is 84*8=672bits.
So the 1000Mbps line-rate port packet forwarding rate is as follows:
Similarly, packet forwarding rates for 100 megabits, 10 megabits, and other megabytes are calculated in the same way.
Backplane bandwidth
Some switch manufacturers also call it "switching capacity", which means a word. The unit is Gbps, which indicates the maximum amount of data that can be handled between the switch interface processor or interface card and the data bus. The higher the bandwidth of the backplane, the greater the ability to process data.
Calculation formula:
Total bandwidth = Number of ports × corresponding port rate×2 (full-duplex mode)
若总带宽 ≤ 标称背板带宽，那么在背板带宽符合线速。 以H3C S5130S-54S-HI-G为例：
48 Gigabit electrical ports + 6 10 Gigabit optical ports, the theoretical value of the switching capacity is calculated as follows:
(48×1G+6×10G)×2=216Gbps≤ 672Gbps
Therefore, its switching capacity conforms to the line speed (the nominal is not blind, the switch forwarding is not limited to the external interface, and the internal exchange also needs to be exchanged, so as long as the theoretical value is less than the nominal value, the interface forwarding can reach the line speed state).
throughput
It is also called the packet forwarding rate of the whole server, that is, the packet forwarding rate of all ports.
Packet forwarding rate = Number of Gigabit ports×1.488 Mpps + Number of 100 Gigabit ports×0.1488 Mpps + Number of other ports×
If the packet forwarding rate of the whole machine is ≤ the nominal Layer 2 packet forwarding rate, the switch can achieve the line speed when switching Layer 2. Take H3C S5130S-54S-HI-G as an example:
48 Gigabit electrical ports + 6 10 Gigabit optical ports, its nominal maximum packet forwarding rate is 207Mpps, and its throughput is the theoretical value:
48×1.488+6×14.88=160.7Mpps≤207Mpps
Therefore, the throughput is in line speed (the nominal is not blind, the switch forwarding is not limited to the external interface, and the internal exchange also needs to be exchanged, so as long as the theoretical value is less than the nominal value, the interface forwarding can reach the line speed state).
Address table depth
- The number of MAC address entries that can be recorded in the address table reflects the maximum number of MAC addresses that can be learned by the switch.
- The switch forwards data based on the MAC address, and if the address table is full, the switch adopts the policy of broadcasting to all ports.
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