>>>> [...]
>>> couterexample: if you put multiple interface into single ethernet
>>> broadcast domain, [...].  for ppp interface I feel it much easier to
>>> borrow interface ID from other interfaces (as there's no possibility
>>> of having two interface into the same ppp domain).
>>I don't see why not: two modems and two dialup sessions, for example,
>>for double the bandwidth....
>	if you are connected two the same RAS using two ppp sessions,
>	do these ppp interfaces (ppp0/1) share the same broadcast domain?
>	i believed not.
>	RAS box
>	 |ppp0|ppp1
>	my netbsd machine

	of did you mean situations with multilink PPP?  in that case
	i believed that there will be only a single ppp interface...
	(i have never used multilink PPP myself on netbsd)

itojun