Novell EDIRECTORY 8.8 SP3, Administration Manual, Page: 323 / 634

Understanding LDAP Services for Novell eDirectory 323
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Description: An LDAP Server object
13.1.3 Referrals
Referral— A message that the LDAP server sends to the LDAP client telling the client that this
server can't provide complete results and that more data might be on another LDAP server.
The referral contains all the information needed to progress the operation.
Scenario: An LDAP client issues a request to an LDAP server but the server can't find the target
entry of the operation locally. Using the knowledge references that it has about partitions and other
servers, the LDAP server identifies another server that knows more about the entry. The LDAP
server sends that information to the client.
The client establishes a new LDAP connection with the identified server and retries the operation.
Referrals have the following advantages:
Š
The LDAP client keeps control of the operation.
Because the client always knows what is happening, it can make better decisions and provide
feedback to the user. Also, the client can opt not to follow through on a referral, or prompt a
user before following it.
Š Referrals often use network resources more efficiently than chaining.
In chaining, a requested search operation with many entries could be transmitted across the
network twice. The first transmission would come from the server holding the data to the server
doing the chaining. The second transmission would come to the client from the server doing the
chaining.
With a referral, the client gets the data directly from the server that held the data, in one
transmission.
Š
When a client knows where an entry is stored, the client can go directly to the server that has
the data.
Chaining hides details from the client. Not knowing where data came from previously, the
client most likely won't go directly to the server holding the data.
Referrals have the following disadvantages:
Š
The client must be able to recognize referrals and know how to follow them.
Š LDAPv2 clients don't recognize referrals, or they use an obsolete, non-standard method for
recognizing them.
Š
Every eDirectory partition must be serviced by an LDAP server.
Otherwise, referrals won’t be sent for data in that partition.
Superior Referral— A referral to a server that holds data higher in the tree than the server being
communicated with. See Section 14.8, “Configuring for Superior Referrals,” on page 378 .