NSX introduced a new licensing model in May 2016.

If you have an active support contract, when you upgrade from NSX 6.2.2 or earlier to NSX 6.2.3 or later, your existing license is converted to a NSX Enterprise license, and you will be entitled to the same functionality in the Enterprise offering.

For information about the NSX licencing editions and associated features, see https://kb.vmware.com/kb/2145269.