Title . - Fast Path Ethernet Switching : On - demand Efficient Transparent Bridges for

Ethernet bridging in campus networks offers advantages like zero configuration, no need of IP addresses administration in subnets, high performance and low costs. But Ethernet bridging does not scale. Current proposals under standardization, like Shortest Path Bridges and Routing Bridges use a link-state routing protocol to compute shortest paths. As a simpler alternative, we propose an evolution of the transparent bridges learning mechanism, that provides loop-free, full infrastructure utilization for campus and datacenter networks. Fast Path Ethernet Switches double use the standard ARP Request and Reply packets to set up fast on-demand paths between hosts when needed. This architecture uses standard Ethernet frame format, is fully transparent to hosts and compatible with 802.1D bridges in core-island mode. A proof of concept has been implemented in Linux. Preliminary simulations in metropolitan and campus newtork topologies show clearly superior to spanning tree and even shortest path routers, at a fraction of the complexity.