Distributed, Multivendor Directories
Standard protocols go a long way to promote interoperability. While the schema for representing an LDAP referral can vary from vendor to vendor, the method of returning referral information to clients is defined as part of the core LDAPv3 protocol. This means that LDAP servers from various vendors can be linked into a single, logical, distributed directory.
But why go through all the trouble of building a multivendor directory? Why not settle on a single LDAP vendor, who has no doubt made it easy to build distributed directories by developing schemas to represent referrals and solving other problems that aren’t addressed by the standards? And, as I’ve said elsewhere, we shouldn’t use technologies just because they’re there; if LDAP doesn’t make life easier for us as administrators, and for the users of our systems, there’s little point going through the effort of setting up an LDAP directory at all, let alone a distributed, multivendor directory.
However, sooner or later a single-vendor directory will force you to make decisions that you’re uncomfortable with. Let’s assume that you’re adding a new application server, such as a calendaring system, at your site. This server is backed by an LDAP directory and requires certain protocol extensions from the directory. Naturally, the vendor has tested the application server with a particular LDAP server in mind—perhaps the vendor even sells an LDAP product (which, of course, is guaranteed to work with ...