Decreasing WAN link traffic

If users are accessing the Directory tree through a WAN link, you can place a read-only replica of the necessary partition on a local server so they don't need to cross the WAN link.

Storing a read-only or writable replica on servers that are across a WAN link can be helpful because it cuts down on the traffic that has to cross the link when users try to access that partition's information. Nevertheless, there will be some increase in traffic due to the synchronization of replicas.

Note that read-only replicas do not support user login. Do not create a read-only replica of a partition that users must attach to before they authenticate to the network.

With a replica of a distant partition stored locally, users have immediate access to the objects they need. The only time Directory information crosses the link is when replicas are being updated.

However, remember that every server that carries a replica must receive all changes to any object within that partition. The more replicas of a given partition you have, the more time needed and the more WAN traffic that exists to fully synchronize the replicas.

Before you begin distributing replicas, think about how much data you want in a partition. Because replicas are stored on servers, unnecessary information in a replica is an inefficient use of disk space and network traffic.

If a partition becomes very large, and you only need to replicate a portion of it, you can use utilities to split the partition and replicate only the necessary portion.

The following figure shows one way to distribute replicas across the WAN on our example tree:

Replica Distribution across a WAN

This example reflects the following:

• Master replicas are stored at each local site. That is, a server at the New York site stores the master replica of the [Root] partition, a server at the Los Angeles site stores the master replica of the MFG partition, and so on.

• Servers at the Detroit location store replicas of the [Root] partition and the MFG partition so that information is locally accessible to users in the Engineering and Quality Assurance departments.

• A server at the Los Angeles office stores a replica of the Detroit partition so that developers in Los Angeles do not have to use a WAN link to access information from their counterparts in Detroit.

• A server in the New York office stores a replica of the Detroit partition to allow local access.

• Objects in the Detroit office often access objects in other parts of the Directory tree across the WAN. (This office operates as a self-contained business unit within the organization.)