In network engineering, systems quite often use RED (http://en.wikipedia.org/wiki/Random_early_detection http://en.wikipedia.org/wiki/Random_early_detection) -

In network engineering, systems quite often use RED (http://en.wikipedia.org/wiki/Random_early_detection http://en.wikipedia.org/wiki/Random_early_detection) - proactively drop a percentage of connections/packets/... when loads begins to climb, scaling from 0% (any easily handled load) to 100% (at capacity). In practice, this results in pretty robust systems. (But note that TCP et al. have mechanisms that help this, e.g. slowing down when packets are lost and retrying a connection with a backoff.)