1.4 Relationship to Other Protocols

The DRS Protocol Extensions for SMTP are a means of encapsulating serialized DRS RPC messages and transporting them inside an SMTP mail message.

The following figure illustrates the relationship between the DRS Protocol Extensions for SMTP and other protocols.

Relationship between DRS Protocol Extensions for SMTP and other protocols

Figure 4: Relationship between DRS Protocol Extensions for SMTP and other protocols

The Directory System Agent (DSA) implements the functionality of a DC and is specified in [MS-ADTS]. The Directory Replication Service (DRS) Remote Protocol (as specified in [MS-DRSR]) controls how an NC is replicated between DCs. DRS transports its messages between DCs by using the DRS Protocol Extensions for SMTP specified in this document or by using another transport, such as RPC (as specified in [MS-RPCE]).

In carrying out the processing steps specified in section 3, the DRS Protocol Extensions for SMTP use the following additional protocols. Messages sent by DRS are serialized and deserialized by using the RPC serialization encode and decode process using type serialization, as specified [MS-RPCE] section 2.2.6. The DRS compression algorithm (as specified in [MS-DRSR] section 4.1.10.5.20) is used to compress the payload. The compressed result is optionally encrypted using RC4 (as specified in [RC4]); it is always encapsulated in a cryptographically signed request structure, as specified in [MS-WCCE] and [PKCS1]. The hash algorithm that is used for the signature is specified in [RFC1321]. MIME encoding (as specified in [RFC2045], [RFC2046], and [RFC2047]) is used to represent binary information in a format suitable for inclusion in an SMTP message. The MIME encoded message is sent as the body of an SMTP message, as specified in [RFC2822]. An SMTP Mail Transfer Agent (MTA) (as specified in [RFC2821]) is used to transport SMTP messages to the remote DC.