Improving Server-To-Server Connection - Novell EDIRECTORY 8.8 SP5 - ADMINISTRATION Administration Manual

To locate a server that holds the data needed to fulfill the client request, Server A must either get the
data from Server B or Server C. To do this, Server A must send the request to either Server B or C.
Server A happens to choose Server B; the process of choosing server is unpredictable. Server B is
available on the network and accepts the request, but is unable to complete the request quickly,
resulting in Server A waiting for Server B even though Server C could also provide the required
data. Until Server B either fulfills the request or is no longer available on the network, the request
from Server A must wait.
The following sections provide information about how you can improve the performance of
eDirectory servers:
Section 19.1.1, "Improving Server-to-Server Connection," on page 516
Section 19.1.2, "Advantages of Referral Costing," on page 518
Section 19.1.3, "Deploying ARC," on page 519
Section 19.1.4, "Enabling Advanced Referral Costing," on page 520
Section 19.1.5, "Tuning Advanced Referral Costing," on page 520
Section 19.1.6, "Monitoring Advanced Referral Costing," on page 521

19.1.1 Improving Server-to-Server Connection

Advanced Referral Costing (ARC) is an improved costing algorithm that is disabled by default. It is
available in eDirectory 8.7.3.9 and eDirectory 8.8.2. The main purpose of ARC is to prevent server
outages. Some of the benefits of ARC can include:
Improved server performance and fault tolerance
Better server-to-server communications
Load distribution
Remote server health monitoring
Simplified isolation and identification of communication problems
Who Should Use ARC?
Servers that don't hold a local copy of an object or service need to walk the tree for information
benefit from ARC, because they frequently communicate with the other servers. ARC is very
effective in an LDAP environment, especially during prefer chaining.
For example, a server is sometimes overwhelmed by other servers that always make requests to that
server, as illustrated in
516 Novell eDirectory 8.8 Administration Guide
Figure 19-2.