Chapter 4. Designing the Directory Tree42• The attribute selected for naming should be unlikely to change.• The name must be unique across the directory.A unique name ensures that a DN can refer to at most one entry in the directory.When creating entries, define the RDN within the entry. By defining at least the RDN within the entry,the entry can be located more easily. This is because searches are not performed against the actualDN but rather the attribute values stored in the entry itself.Attribute names have a meaning, so try to use the attribute name that matches the type of entryit represents. For example, do not use l to represent an organization, or c to represent anorganizational unit.• Section 4.2.3.1, “Naming Person Entries”• Section 4.2.3.2, “Naming Group Entries”• Section 4.2.3.3, “Naming Organization Entries”• Section 4.2.3.4, “Naming Other Kinds of Entries”4.2.3.1. Naming Person EntriesThe person entry's name, the DN, must be unique. Traditionally, distinguished names use thecommonName, or cn, attribute to name their person entries. That is, an entry for a person named BabsJensen might have the distinguished name of cn=Babs Jensen, dc=example,dc=com.While using the common name makes it easier to associated the person with the entry, it might not beunique enough to exclude people with identical names. This quickly leads to a problem known as DNname collisions, multiple entries with the same distinguished name.Avoid common name collisions by adding a unique identifier to the common name, such as cn=BabsJensen+employeeNumber=23,dc=example,dc=com.However, this can lead to awkward common names for large directories and can be difficult tomaintain.A better method is to identify the person entries with some attribute other than cn. Consider using oneof the following attributes:• uidUse the uid attribute to specify some unique value of the person. Possibilities include a user loginID or an employee number. A subscriber in a hosting environment should be identified by the uidattribute.• mailUse the mail attribute to contain the value for the person's email address. This option can lead toawkward DNs that include duplicate attribute values (for example: mail=bjensen@example.com,dc=example, dc=com), so use this option only if there is not some other unique value to use withthe uid attribute. For example, use the mail attribute instead of the uid attribute if the enterprisedoes not assign employee numbers or user IDs for temporary or contract employees.• employeeNumber
