Hello ,
Reliability is generally used to identify whether we successfully transmit or receive a packet and it is expressed as a fraction of 255.
It is calculated by summing all the packets received and transmitted and dividing that number into the sum of all input and ouput errors and expressing that as a fraction of 255.
It is then exponentially weighted over five minutes so that the most current reading has greater weight than the first reading.
Basic definition of reliability is errors/total frames. If your interface reads 255/255, then it means all is well.
Thanks,
Bhadri