In addition to the grouping and window mechanisms, you can configure replication compression on Solaris and Linux platforms. Replication compression streamlines replication flow, which substantially reduces the incidence of bottlenecks in replication over a WAN. Compression of replicated data can increase replication performance in specific cases, such as networks with sufficient CPU but low bandwidth, or when there are bulk changes to be replicated. You can also benefit from replication compression when initializing a remote replica with large entries. Do not set this parameter in a LAN (local area network) where there is wide network bandwidth, because the compression and decompression computations will slow down replication.
The replication mechanism uses the Zlib compression library. Empirically test and select the compression level that gives you best results in your WAN environment for your expected replication usage.
For more information on configuring replication compression, see Configuring Replication Compression in Sun Java System Directory Server Enterprise Edition 6.3 Administration Guide.