Hello Rahul NIrmalkar,
The I/O rate is counter which counts the number of packet averaged out over a period of one load interval. For example if the interface has received x no of bits in a load inteval of y ( in secs) then the input rate would be x/y bits per sec. As simple as this.
However these counters are almost never accurate and should be not be relied upon for accounting purpose, as we do not want to interrupt the cpu to count the packet when the priority is to forward them as quickly as possible. If you need to count the actual data rate on a link then an inline sniffer should be your option.
Reference: https://community.cisco.com/t5/switching/how-is-input-rate-calculated/td-p/1625353
Best regards
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