Suggestions for control mechanism for reducing the number of priority changes in an adaptive loop
W. Yu, Jayanti C. Majithia · IEE Proceedings E Computers and Digital Techniques · 1980
A modified Pierce loop network has been described in an earlier paper, incorporating adaptive flow control. This involves a full duplex loop with two types of time slots, one for handling data packets and the other for the transmission of control packets. Each node adjusts its slot usage priority according to its current queue size. A loop supervisor maintains a record of node priorities, and assigns appropriate priority to slots. Since each priority change creates a control message, the number of control packets can become unnecessarily large and eventually cause congestion. In the paper, we describe the use of a statistical mechanism for reducing the number of unnecessary priority changes but with little adverse effect on data-traffic performance. The effectiveness of such a mechanism is evaluated in terms of its ability to prevent overreaction to random queue fluctuation while reacting correctly when a priority change is warranted.