Pilgrimage feasts and Jerusalem, His resting place forever

Three of the seven commanded feasts, are pilgrimage festivals. That means that the celebrant is to go up to Jerusalem for the feast. These three festivals are: the Feast of Unleavened bread, Shavuot and Sukkot. Are we required to follow this commandment to go up to Jerusalem? Is it only for the inhabitants of the land Israel? Maybe it was solely commanded while the Tabernacle or the Temple was still in use? We all want to do what is right. We will endeavor in this study to answer these questions.