When setting acceptable service levels, you must first understand the infrastructure that supports the messaging system. Service levels in a company that has an ATM network everywhere will exceed those of companies that have many dial-up links.
The following is a typical service level statement: "Messages sent from one Microsoft Exchange Server user to another Microsoft Exchange Server user within our company's network will be delivered in x minutes or less."
Service level statements are important primarily for setting expectations in other areas of a company outside messaging operations. If a user sends a message, then that user should wait the x minutes stated in the service level for the message to be delivered to its destination prior to assuming there is a problem in the messaging system.
It is good practice to be conservative in stating service levels for messaging in a large organization. Allow your department at least to react to a problem in the system within the stated service level times. For example, assume your company's network consists of very high bandwidth links that are rarely utilized above 35 percent. In this environment, Microsoft Exchange Server systems can be designed and implemented to deliver messages almost instantaneously anywhere. Even with this type of performance, you should not issue a service level statement that states, "…messages will be delivered in under 30 seconds." This timeframe does not allow you time to identify and react, in any way, to a problem. A better service level statement would be, "…messages will be delivered in 10 minutes or less." Messaging, for all its importance in today's organizations, rarely needs to be faster than that. Also, this amount of time allows your monitoring and systems staff to become aware of a problem and begin reacting to that problem. Don't set your service level time lower than the time it takes to see that there is a problem, notify someone, and let someone begin to resolve the problem.