I have noticed similar behavior, and have gone so far as to set up local firewall rules to block all traffic outside of those sent directly to hologram.io. But, I suspect that the PPP overhead is being counted against usage even when no traffic is being generated, and possibly even network announcements leading to data “usage” as long as the modem is powered on even if it isn’t connected.
I really would like someone with Hologram to comment and give a detailed breakdown about what counts as traffic and what doesn’t. It would be nice to know how much data is consumed during the session setup, and then how much data is used per minute/hour/day to maintain the connection so that we can figure out if it makes more sense to open up the session and leave it running sending small amounts of data frequently (because the session maintenance cost is low but the setup cost is high), or maybe we would be better off queue up larger payloads and then opening a session just long enough to send them and disconnect (because the setup cost is low, but the maintenance is relatively high).
And if someone really wanted to have an honest discussion about why $.40-.60/MB is seen as reasonable for hobbyist/developers in an era where we typically pay $.01/MB or less for consumer data. I mean I understand that it makes sense for businesses that monetize their traffic, but for hobbyist is is kind of a smack to the face. I assume that Hologram is acting as a VAR, aggregating user traffic in order to buy data in bulk from the major carriers, so I would expect them to get a wholesale prices much closer to the consumer rate, and if that is the case is a $.49-.59/MB markup really justified by the small amount of traffic devs and hobbyist typically generate. If someone was just willing to give us a real idea about how all of this works then maybe these CompuServe era data rates wouldn’t seems so crazy.
Now, if you could get us down in the $.01-.10/MB rate the cell and ppp overhead creep wouldn’t be such an issue, but since the system isn’t transparent, and the logs don’t separate out overhead, it is kind of frustrating when you run a short test sending a few dozen < 100B messages over one or two days only to find you are somehow getting close to exceeding your 1M/month allotment. And trying to be frugal means shutting down your modem for the rest of the month in order to avoid unexpected overages and waiting for your counter to reset.