RHEL Linux 3 - AS vs ES

[Yard, John]

Forgive the elementary nature of this question.

I am adding 2 Sun Directory Server 5.2 systems 
on RHEL Linus 3 :

Linux version 2.4.21-27.0.2.ELsmp (bhcompile at tweety.build.redhat.com)
(gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-47)) #1 SMP Wed Jan 12
23:35:44 EST 2005.

The Sun documentation says I should be at Red Hat Advanced Server 3 or 4
for the new Directory Server level.

I am confused as to how Red Hat Linux 3.2.3 is considered AS or not....

What is considered AS ( Advanced Server ) or not....

JYard
UCLA