key length & fragmentation

[bmanning@karoshi.com]

	putzing about with keys of various lengths shows that 
	when keys are over a certain size, UDP fragmentation sets
	in,  In some cases, it is possible to actually get rollover
	to TCP (although this seems to be a corner case)

	now I've been told that UDP fragmentation can be a bad thing,
	leading to all sorts (well some kinds anyway) of odd 
	operational failures that are hard to debug.  UDP failure
	and rolling over to TCP is also considered a bad thing.

	so this question, "should key lengths be selected to 
	avoid fragmentation/TCP use?"

	if so, why?
	if not, why not?

--bill