Just check with you your DNS server setting.
Is BTH using 10.0.16.31 Tokyo Hachioji DNS server?
If so, it will be too far from BTH to look up.
Please try test to use below DNS server at AT&T Asia DC instead of Japan DNS.
This will be faster than going to Japan.
• 10.243.4.5
• 10.243.4.6
It may improve your situation, especially after SAP go-live.