2.3.5 SQL Server Resolution Protocol
The SQL Server Resolution Protocol (SSRP) [MC-SQLR] is a simple application-level protocol for the transfer of requests and responses between clients and database server discovery services. To determine the communication endpoint information of a particular database instance, the client sends a single request to a specific machine and waits for a single response. To enumerate database instances in the network and obtain the endpoint information of each instance, the client broadcasts or multicasts a request to the network and waits for responses from different discovery services on the network.
SSRP is always implemented over the User Datagram Protocol (UDP) [RFC768] because it depends on the latter protocol to communicate with the database server or to broadcast/multicast its requests to the network. The types of addresses used might differ based on the underlying IP protocol version ([MC-SQLR] section 2.1). For details, see Internet Protocol version 4 (IPv4) [RFC791] and Internet Protocol version 6 (IPv6) [RFC2460].
The SQL Server Resolution Protocol is appropriate for retrieving database endpoint information or for database instance enumeration in scenarios where network or local connectivity is available.