[usr1106]

Does APN type go out over the network?

I thought that's an Android internal thing to decide which of several APNs to use.

Also the first 2 references that Google returns say dun is obsolete and not in use with today's devices. I believe that belongs to the ATD *99# era

(Havent't worked in the field for 10+ years, could be wrong.)

[bonzini]

No it doesn't go out, but the APN itself does go out on the network and can be used to apply different billing to tethered vs mobile browser data usage. https://news.ycombinator.com/item?id=25244052 for more info.