Links? WHAT links? Gimme a break!
Oh, all right - you've twisted my arm.
I came up with a few relevant links that I came across as I have been learning about LDAP, notably OpenLDAP, a schema description, and a document up on tldp.org relating to LDAP. If you want more of the nitty-gritty about how the internal format is defined under Linux, then take a look at LDAP-Implementation-HOWTO as well. Various RFCs cover it too.