[development] How to do LDAP based SSO?

[antgiant]

We have several drupal installs that all use the same LDAP setup for
authentication.  We would like to setup Single Sign On for all of those
sites, but it is not feasible for us to use a shared database.
 Additionally, we are using LDAP groups to create the Drupal roles.  Any
advice on how to accomplish this?  Thanks in advance.