What's different between IdM (Identity Manager) bundled with RHEL and Directory Server?

There's a monster piece of software now called IdM - or IPA - that does identity management. It's part of RHEL and there are docs describing what it does and how to install and set it up.

Great.

But there's also a separate subscription product called Directory Server. What's different? Directory Server costs a bunch of money every year, so it must offer a bunch more than IPA. So what does one have that the other doesn't have?

And then I saw some stuff at the April 2014 Summit suggesting that IPA with RHEL7 offers a whole bunch more than IPA with RHEL6. Looking over the docs - there's a whole book about Windows integration with IPA/RHEL7, while Windows integration is just a section of the RHEL6 IPA Guide. Does anyone have any info?

thanks

• Greg