Windows 2000 used three transports for replication of Active Directory ( AD ).
High speed synchronous RPC over IP.
Active Directory always uses high speed RPC over IP for intrasite replication. Required. Not configurable. The replicated data is not compressed.
Point-to-Point low speed synchronous RPC over IP.
Active Directory always uses low speed RPC over IP to replicate between domain controllers in the same domain but in separate sites. Required. Not configurable.
Low speed, asynchronous SMTP.
SMTP is limited to replication of schema and global catalog. Low speed RPC over IP can also be used for this replication type.
Replicated data transmitted between sites is compressed to reduce the transport load on low capacity links. In synchronous replication, the destination domain controller sends the requested replication data and waits for the source domain controller to reply that replication is successful before it honors requests for updates from other source domain controllers. In asynchronous replication, the destination domain controller sends the requested replication data, and does not wait for a successful replication message from the source domain controller before initiating replication with another site.