Hi @jpm ,
This is the beacon discovery stuff that lets Firestorm discover PBs and synchronize them (or between a PB in AP mode as well). It’s pretty small, but goes out once a second. These can’t be disabled currently. It is only broadcast locally, so its not going out to the internet or something or impacting your internet service / bandwidth.
This was recently asked about here too. Some more info on Wikipedia.
These are 12 bytes, 40 if you count UDP frame overhead. 36 days is a bit over 3 million seconds, and the math gets close to your 126MB figure. Put another way, it’s ~0.0003 Mbits/sec of bandwidth.