In some cases, a DSA may not be able to provide service to a DUA because the required information is held elsewhere in the network. A DSA can simply choose to inform the DUA or the calling DSA where the information can be found. This is called referral and can occur because of the user's preference or the DSA's circumstances.
Referrals are possible because the distinguished name provided by the DUA identifies where in the DIT the requested entry is located. DSAs use their knowledge of the DIT to inform the DUA of the DSA that holds the requested information.
The following figure shows an example of a referral. DSA1 passes a referral to DSA2 back to the DUA. The DUA then makes a request to DSA2.
An Example of a Referral
