This multiple-valued attribute contains a list of service principal names (SPN) to show the equivalence of SPN types. The SPN is the name a client uses to uniquely identify an instance of a service. If you install multiple instances of a service on computers throughout a forest, each instance must have its own SPN. A given service instance can have multiple SPNs if there are multiple names that clients might use for authentication. For example, "ldap/..." SPNs could be mapped so that they are equivalent to "host/..." SPNs.
This value is set during the product installation. It can be modified by the system administrator at a later time.