>>	it seems that there's some issue in ath0 interface.
>>
>>	laptop
>>	  |ath0
>>	  |
>>	  |11a/b/g
>>	  |
>>	melco basestation (a/b/g)
>>	  |
>>	==+== 100bt ethernet
>>	  |sip2
>>	IPv6 router (*)
>>	  |
>>	  |IPv6 tunnel (MTU=1280)
>>	  |
>>	IPv6 router
>>	  |
>>	(((IPv6 cloud)))
>>	  |
>>	cvs.kame.net
>>
>>	if I try to copy large file from laptop to cvs.kame.net (or
>>	cvs.netbsd.org) over IPv6, file transfer will stuck after PMTUD.
>>	packet sized 1280 byte will not reach laptop from the 1st hop router
>>	(*).  i have never experienced such symptom when i was using wi0 on
>>	laptop.  i will test again with wi0 (since switching to net80211
>>	layer change might be the cause).

	"will not reach laptop from the 1st hop router" is confirmed by
	running tcpdump on ath0/laptop and sip2/1st hop router.
	packets appear on tcpdump ath0/laptop, but not on sip2/1st hop router.

itojun