Difference between bytes, rbytes and bytes.src metakey

[VishamRawat]

I see bytes.src metakey is said to capture Bytes Sent.

rbytes metakey is said to capture Bytes Received, and yet it is always empty.

I do also see bytes metakey, the value of which is always greater than bytes.src, but this key is not indexed. What exactly is bytes capturing?

[WilliamMotley1]

bytes is the total number of bytes sent and received, inclusive of packet and frame headers and footers.

No packet content currently registers rbytes nor bytes.src.