How to configure pppoe-server (rp-pppoe) on NetBSD 3.0?

I want my NetBSD play as a pppoe server, and WindowsXP as a pppoe
client.

/etc/ppp/pppoe-server-options:
require-pap
lcp-echo-interval 10
lcp-echo-failure 2

and run below command under shell:
# pppoe-server -I fxp0 -L 192.168.70.1 -R 192.168.70.100 -N 10

When a Windows XP try to client connect it, /var/log/messages says:

May 30 19:07:04 serv01 pppoe-server[16051]: Session 4 created for client
00:40:c
a:82:8b:96 (192.168.70.103) on fxp0 using Service-Name ''
May 30 19:07:04 serv01 pppd[16051]: pppd 2.4.3 started by root, uid 0
May 30 19:07:04 serv01 pppd[16051]: Using interface ppp0
May 30 19:07:04 serv01 pppd[16051]: Connect: ppp0 <--> /dev/ttyp0
May 30 19:07:04 serv01 pppoe[16275]: Interface=fxp0
HWaddr=00:90:27:22:80:06 Device=/dev/bpf0 Buffer size=32768
May 30 19:07:06 serv01 pppoe[16275]: read (asyncReadFromPPP): Session 4:
Invalid argument
May 30 19:07:06 serv01 pppd[16051]: Modem hangup
May 30 19:07:06 serv01 pppd[16051]: Connection terminated.
May 30 19:07:06 serv01 pppd[16051]: Exit.

What's wrong? What "Invalid argument" means?

BTW, the same configuration work well on Linux 2.6.11

Thanks.