Thanks for your work!

Heads up, the netdev collector for Darwin is gathering data from ifi_ibytes and ifi_obytes, and those are 32-bit integers, so they're wrapping around after 4 GB of traffic. Graphing node_network_receive_bytes and node_network_transmit_bytes results in a sawtooth pattern, and this introduces noise to irate for those metrics.

There are other resources available - netstat -I en0 -b can report larger numbers. I looked around the netstat code a little but didn't find an obvious fix for the node collector.

Thanks again, and sorry I can't offer a PR for this!