  Modern Ethernet switches support many advanced features beyond route learning
and packet forwarding such as VLAN tagging, IGMP snooping, rate limiting, and
status monitoring, which can be controlled through a programmatic interface.
Traditionally, these features are mostly used to statically configure a
network. This paper proposes to apply them as dynamic control mechanisms to
maximize physical network link resources, to minimize failure recovery time, to
enforce QoS requirements, and to support link-layer multicast without
broadcasting. With these advanced programmable control mechanisms, standard
Ethernet switches can be used as effective building blocks for
metropolitan-area Ethernet networks (MEN), storage-area networks (SAN), and
computation cluster interconnects. We demonstrate the usefulness of this new
level of control over Ethernet switches with a MEN architecture that features
multi-fold throughput gains and sub-second failure recovery time.
