/etc/resolv.conf is required. You can copy it from Linux.
For example:
/etc/resolv.conf:
nameserver 202.103.88.3
nameserver 202.103.100.66
/etc/ppp/ppp.conf:
default:
set speed 115200
set device /dev/cuaa0
set ifaddr 10.0.0.1/0 10.0.0.2/0 255.255.255.0 0.0.0.0
add! default HISADDR
set timeout 0
enable dns
set log local phase
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \"\" AT OK-AT-OK ATE1Q0 OK \\
dATDT\\T TIMEOUT 40 CONNECT"
set login
set authname 163
set authkey 163
set phone 163