Accounting-On and Accounting-Off being sent on a per-BSS basis not per-NAS

[Nick Lowe]

The Accounting-On is useful today on receipt after an unexpected
reboot where Stops and an Accounting-Off will not have been received
to mop up all stale sessions that pertain to the NAS without having to
resort to timeouts. I certainly do not feel that it should be removed
from hostapd therefore.

The salient consideration and concern here should be that, today,
Accounting-On and Accounting-Off are handled by all the RADIUS servers
that use them as applying to the whole NAS.
It is for this reason that what hostapd does today ought to change.

There is no definition of what does or should constitute a session
identifying attribute for Accounting-On and Accounting-Off. The RADIUS
accounting RFC doesn't go here and doesn't touch on this critical
point. The original intention of the accounting RFC, clarified with
its author Carl Rigney, was that it would apply to the whole NAS.
Thus, if somebody attempts to scope/limit by adding extra attributes,
it is incompatible behaviour with nasty unexpected side effects when
these are handled as applying to the whole NAS.

I don't think that Accounting-On and Accounting-Off needs to be
deprecated. It can happily work in conjunction with a proposed
Subsystem-on/Subsystem-off. There is no mutual exclusivity.

Nick