Mastering Active Directory

Inter-site transport protocols

There are two transport protocols, which can be used for replication via site links. Replication uses the Remote Procedure Call (RPC), and it can either be the IP or SMTP transport protocol. The default protocol used in site link is IP, and it performs synchronous replication between available domain controllers. The SMTP method can be used when the link between sites is not reliable. It will use mail messages to replicate Active Directory partition data including the schema changes between domain controllers. If it uses the SMTP method, it needs to have certification authority to encrypt the traffic.