For Windows S.O
1. Win+R(shortcut for 'run'), type services.msc, Enter
2. You could find an entry like 'MySQL56', right click on it, select properties
3. You could see sth like "D:/Program Files/MySQL/MySQL Server 5.6/bin\mysqld" --defaults-file="D:\ProgramData\MySQL\MySQL Server 5.6\my.ini" MySQL56
4. change this max_allowed_packet=4M
5. Restart the MySQL service

I got this answer from http://bugs.mysql.com/bug.php?id=68516