Mark Smith writes: > Firewalls could be considered to be performing QA for defined > protocol fields. I agree that reserved fields shouldn't be "QA"'ed for > their default values.
Except that a change from default values can be an excellent indicator that you are dealing with a software version different from what you expected (and possibly incompatible). > I can't remember exactly where I saw the > definition, I've understood reserved fields to mean "could change in > the future, don't rely on this default value". That's what reserved means, but very often "reserved" is accompanied by "must be zero."
