A problem with stacking many layers for some set of features is that most layers add their own header to each message, hence overhead can be considerable. For normal data communication it is important to make the header overhead as small as possible. The FAST layer uses the same protocol as the NAK (FIFO) layer during normal operation, but the message path bypasses most layers. When a view change starts, or a message is lost, the FAST layer switches back to the original message path and retransmits unstable messages. When the abnormal condition disappears, it switches back to the accelerated path. The FAST layer provides only FIFO communication currently, so that the CAUSAL and TOTAL layers need be run over the FAST layer if such ordering is required. In addition, it is important to run the flow control layer over the FAST layer if traffic is high, since high rates of loss cause frequent switching between the FAST path and the normal one, and consequent high overhead. We are considering ways of modifying this to automatically use the flow control layer if the rate of message loss exceeds some threshold.