Modern networks of workstations connected by Gigabit networks have the ability to run high-performance computing applications at a reasonable performance, but at a significantly lower cost. The performance of these applications is usually dominated by their efficiency of the underlying communication mechanisms. However, efficient communication requires that not only messages themselves are sent fast, but also notification about message arrival should be fast as well. For example, a message that has arrived at its destination is worthless until the recipient is alerted to the message arrival.