On ordering requests to servers in a distributed system

A process offering a service in a distributed system receives request messages from client processes. For proper system behavior, it is often necessary for requests to be serviced in the same order that they are sent. Ensuring this order requires an elaborate scheme, unless certain restrictions are imposed on the distributed system.

We present some restrictions that ensure that requests are received at a server in the same order that they are sent. With these restrictions, each server can safely service requests in the order of arrival. The restrictions either apply to the message routing, or to the client/server communication. The restrictions on message routing are often satisfied by systems based on local networks, and the restrictions on client/server communication are satisfied by some existing message passing schemes.