The internet speed and facilities are fantastic at ISI Kolkata. This should be the least of your concerns. You will have also have access to a computer lab with high-speed Wi-Fi.
There used to be a gym, but it is not available anymore. A new canteen has taken over the floor where the gym used to be.
They have a well-kept large field that is primarily used for football and also hosts the annual Sports Meet. Volleyball, table tennis, and other sports are played within the hostel.