Effective Shortest Path Routing for Gigabit Ethernet

Ethernet´s native routing algorithm, the spanning tree protocol, causes a major performance bottleneck when network connectivity increases. Since the spanning tree protocol avoids deadlocks and infinitely looping packets by turning any topology into a tree, it leaves a large portion of links unused and thus wastes bandwidth. In this paper we address this weakness by proposing a new routing algorithm that avoids disabling links and prohibiting turns, and that guarantees shortest path routing. Through the use of layered routing we show how to improve performance with respect to both the spanning tree protocol and a more recent proposal called tree-based turn-prohibition. The concept of layered routing is used to group virtual channels into network layers, and assign a limited set of source/destination address pairs to each layer. Extensive simulations show that we are able to increase throughput by a factor of more than 3.5 compared to the spanning tree protocol and a factor of 1.8 compared to tree-based turn-prohibition. Our concept relies on features introduced in IEEE standards 802.1Q, 802.1D and 802.3x, as well as changes currently discussed in IEEE task forces.