- The packet forwarding rate (throughput) of the switch refers to the ability of the switch to forward packets, in PPS (packets per second), that is, how many packets per second the switch can forward.
- Switch interface rate: 100MBIT/S Ethernet interface, the students who have learned the computer know that every 8 bits make up a byte, so a gigabit interface is converted into a node =12.5mbyte/s, that is, the Ethernet interface can forward 12.5M bytes per second = 12500000byte.
- Because of the collision detection mechanism of Ethernet, there is a limit to the size of data frame when Ethernet transmits data frame, the data frame is 64byte, plus 8byte leading byte and 12byte inter-frame gap, the total is 84byte, that is, the data frame transmitted on Ethernet is minimum 84byte.
- In the case of a hundred Gigabit Ethernet port, a Gigabit Ethernet port forwards up to 12500000byte of data per second, assuming that all data frames transmitted in the worst case are the smallest 84byte (of course, if the larger data frames transferred are more advantageous to the switch forwarding, we assume an extreme, In the worst case), the data frame forwarded per second for this Gigabit Ethernet port is 12500000/84=148809pps (frames per second) =148.8kpps=0.1488mpps.
- So we can conclude that the packet forwarding rate of Gigabit Ethernet is 0.1488Mpps, then the packet forwarding rate of Gigabit Ethernet is 1.488Mpps, and the packet forwarding rate for 10G Ethernet is 14.88Mpps.
- For example, suppose there is a 24-port 10/100BASE-TX Ethernet switch, so the packet forwarding rate for this switch is 24*0.1488mpps=3.5712mpps, if plus 4 Gigabit Ethernet port 4*1.488mpps=5.952mpps. So the total is 3.5712mpps+5.952mpps=9.5232mpps. That is, a 24-port hundred + 4 Gigabit Ethernet switch, only the whole packet forwarding rate of 9.5232MPSS, to achieve wire-speed forwarding.
- The switching capacity (backplane bandwidth) of the switch refers to the maximum amount of data that can be throughput between the switch interface processor or interface card and the bus. The switching capacity indicates the total data exchange capability of the switch, in Gbps units.
- The switching capacity of the switch is calculated as: number of ports * corresponding Port rate * (full duplex). For example, a 24-port Gigabit switch switching capacity =24*100*2=4800mbit=4.8gbps
- Switch switching capacity and packet forwarding rate relationship: Packet forwarding rate *8* (64+8+12) =1344* packet forwarding rate.
- So the evaluation of a switch, not only the interface rate and the number of interfaces, but also from the packet forwarding rate and exchange capacity together to measure the performance of a switch.
- A 24-Port hundred Gigabit Switch, packet forwarding rate to reach 3.5712Mpps, exchange capacity to reach 4.8Gbps. If these two parameters do not reach this value, the performance of the switch is not standard.
(Transferred from Http://support.huawei.com/ecommunity/bbs/10169127.html)
Packet forwarding rate Exchange capacity detailed
