MIB: IF-MIB
An estimate of the interface's current bandwidth in units of 1,000,000 bits per second.
If this object reports a value of `n`, then the speed of the interface is somewhere in the range of `n-500,000` to `n+499,999`.
For interfaces which do not vary in bandwidth or for those where no accurate estimation can be made, this object should contain the nominal bandwidth.
For a sub-layer which has no concept of bandwidth, this object should be zero.