The effect of a link or bridge failure ranges from a minor inconvenience to a crisis that results in the loss of substantial amounts of productivity. Many users want to build redundancy into their bridged networks to prevent a single point of failure.
The Spanning Tree Protocol is the standard, universally accepted method of building redundancy into a bridged Ethernet LAN. It enables the bridges in a LAN to activate backup links when connectivity fails.
A second mechanism called link aggregation enables a set of links connecting two systems to behave like a single link. If one link fails, its traffic is diverted onto the remaining live links.
The subsections that follow present brief introductions to these technologies. ...