Novell EDIRECTORY 8.8 - GUIDE, Manual

Page: 356 / 574

Configuring LDAP Services for Novell eDirectory 357
no
vd
ocx (
E
NU)
01
F
ebr
ua
ry
200
6
Prefer Chaining
The Prefer Chaining option indicates that search operations will not normally return referrals.
Instead, the LDAP server progresses the search operation across all eDirectory DSAs required to
complete it.
The exception is a search operation that is accompanied by the persistent search control. In this case,
because the Novell implementation of persistent search does not support chaining, referrals are sent
if the scope of the search operation is not all held locally.
The LDAP server receives a search operation. If the entry in the tree is not stored locally, the server
automatically chains to other servers. After the entry has been located, the LDAP server acts as
proxy for the LDAP client. Using the same identify that the LDAP client is bound with, the LDAP
server authenticates to the remote server and continues the search operation there.
The LDAP server that received the original search request sends the LDAP client all search entries
and the search result. Because the LDAP server fully takes care of the request, the LDAP client is
unaware that other servers were involved.
Through chaining on eDirectory, an LDAP server that doesn't have much data can appear to hold the
data of the entire tree.
Prefer Chaining is important concerning partitions.
Scenario: Finding Information in another Partition— At the Digital Airlines Company, Luc
selects the Prefer Chaining option for LDAP server DAir43. DAir43 is in Partition A. Partition B is
a subpartition of A and contains LDAP server DAir44.
An LDAP client requests a search. DAir43 searches locally for the entry but only finds part of the
data. DAir43 automatically chains to DigitalAir44, which has the needed entry. DAir44 sends the
data to DAir43, and DAir43 sends the entry to the LDAP client.
The Prefer Chaining option causes the LDAP server to chain to other servers for search requests
(when needed) unless the operation is a Persistent Search. For information on Persistent Search, see
Section 13.10, “Persistent Search: Configuring for eDirectory Events,” on page 367 .
Prefer Referrals
The Prefer Referrals options indicates that search operations will return referrals to other eDirectory
servers in the eDirectory tree when needed. Referrals are sent only if the local server can ensure that
the server holding the data is operational and that the LDAP service is running. Otherwise, the
operation is chained to the other server, or the operation fails if the other server in inoperable.
You have two partitions and are doing a subtree search. You get down to a point where the search
entries are no longer held on the local server. Therefore, the search must go to another server. If the
server that holds the replica of that data (that partition) is also running
nldap.nlm
, the LDAP
server builds an LDAP referral and sends it back to the LDAP client.
If the server holding the replica isn't running
nldap.nlm
, LDAP server chains the request to the
other server, thereby completing the search.
When
nldap.nlm
starts up, the LDAP server communicates to eDirectory that the LDAP server is
a referral point. If a client has received referrals but the referrals stop, the LDAP server is not
running.