--On Tuesday, 08 October, 2002 12:25 -0700 Dave Crocker <dhc2@dcrocker.net> wrote: > At 11:38 PM 10/7/2002 +0700, Robert Elz wrote: >> Attempting to give these things absolute numbers, other than >> for ease of reference in some particular context is lunacy. > > Not that I disagree with your primary point, it is worth > noting that there is some basis for hovering about 7, for an > *overall* model. > > It's that memory limit thing (7, plus or minus 2.) The plus > or minus is statistical, so if you want to make sure that > people really have no trouble grokking the total set, 5 is a > better choice. I would suggest that this particular situation has almost nothing to do with the Miller result. In particular, that hypothesis derives from work with short-term memory and the number of things one can keep track of at a time. The purpose of layering is, to some extent, similar to that of modularization of other types, i.e., to reduce the number of things you need to think of at a time. And, from that standpoint, kre's observation to the effect that "the one you are looking at, one up, and one down" is what is relevant is exactly the right short-term memory analysis. And that number is lots smaller than seven. Or even five. But this is getting very far afield from anything relevant to the IETF or network modelling. john