In an embodiment, a server computer comprises service processing logic that implements a Multi Step Retry Reinitialization Protocol Flow, and a protocol-aware rate limiting unit configured to cause one or more processors to perform receiving a message from a client; determining whether the received client message is a start type of message that requests starting the Flow; in response to determining that the received client message is a start type of message, determining whether to provide the received client message to the service processing logic using a discriminating rate limiting process. As a result, service unavailability may be prevented by rate limiting start types of messages, thereby allowing services to finish processing in-process protocol flows, when large numbers of clients concurrently attempt to obtain the services.