I’m currently building an application that is intended to run on an embedded system hooked up to a cellular data card. I’ve been made aware of some low-data plans from several carriers, and our application only generates about 5 bytes/second, lending itself to such plans.
However, I can’t seem to figure out if the TCP/IP header overhead (about 40 bytes, give or take) is included in the calculation for data usage. Since I need real-time data, I’ve disabled Nagle’s algorithm. This means for each 5 byte burst I send out, I’m sending out a new header. If TCP/IP headers are factored into the data usage pricing, it will dwarf the amount of data I’m sending.
I can’t answer definitively, but I would assume they must. Otherwise this could be exploited by adding extra data to the headers. With TCP you send a 40 byte packet and then you receive a 40 byte acknowledgement packet. You could try using UDP instead of TCP so that you don’t have to waste data with the acknowledgement packets.