Note that I'm not arguing that it *should* be the default, I'm just arguing that vendors have implemented it this way because that's the way they were told to in the RFC.

Umm.... this is only partially true. As of the writing of 1812 (and predecessors), vendors had implemented it one particular way and argued that the spec should reflect the implementations. Of course, at the time, the net was a kinder, gentler place, and the threats of smurfing were not well known. Live and learn. ;-) Tony