Which of the following is true regarding the intersite transport protocols used for replication?

The statement regarding RPC over IP being a synchronous communication protocol that expects an immediate reply is accurate. In the context of intersite transport protocols used for replication, RPC (Remote Procedure Call) over IP operates by establishing a direct connection between servers. This connection allows for requests to be sent and expects an immediate response, which is crucial for maintaining consistent state and ensuring that replication occurs effectively.

This synchronous nature is particularly important for directory services that rely on immediate feedback to confirm actions such as updates or changes in directory partitions. Consequently, the use of RPC over IP can significantly impact the efficiency and reliability of replication in a network environment where timely communication is essential.

The other options which suggest behaviors of SMTP in relation to replication, such as replicating all directory partitions and being faster than RPC over IP, as well as the reliability of the network connection, do not hold true in the same context. SMTP (Simple Mail Transfer Protocol) is generally used for sending emails rather than for replication purposes. Additionally, it is not designed for synchronous communication like RPC over IP is. The assumptions in these statements may stem from a misunderstanding of how these different protocols function and their intended applications in network environments.