Sometimes Internet in Vietnam is very slow by "AGG Cable is Cut" incident
Today i introduce to you how to change to Singapore DNS to make it speed up
DNS singapore : 165.21.83.88 / 165.21.100.88.
Do following steps
Step 1: Go to start --> type Network and Sharing Center
Choose your network item
Properties
Internet Protocol Version 4 ( TCP/IPv4), > Properties ,> Internet Protocol vertions 4.
Type in IP : 165.21.83.88 / 165.21.100.88.

Or try these DNS changer software:
DNS changer for Windows
For android search for DNS Changer
After do the above steps
Go to CMD, type
ipconfig /flushdns
DONE
When the internet come back to normal, just try to use these DNS:
1. Google DNS
8.8.8.8
8.8.4.4
2. Open DNS
208.67.222.222
208.67.220.220