They are invisible to current IP routers, and like conventional routers, RBridges terminate the broadcast, unknown-unicast and multicast traffic of DIX Ethernet and the frames of IEEE 802.2 LLC including the bridge protocol data units of the Spanning Tree Protocol.
TRILL was designed as a successor to the Spanning Tree Protocol, both having been created by the same person, Radia Perlman.
The catalyst for TRILL was an event at Beth Israel Deaconess Medical Center which began on 13 November 2002.
[3][4] The concept of Rbridges[5] [sic] was first proposed to the Institute of Electrical and Electronics Engineers in 2004,[6] who in 2005[7] rejected what came to be known as TRILL, and in 2006 through 2012[8] devised an incompatible variation known as Shortest Path Bridging.
This gives RBridges enough information to compute pair-wise optimal paths for unicast, and calculate distribution trees for delivery of frames either to destinations whose location is unknown or to multicast or broadcast groups.
IS-IS was chosen because: To mitigate temporary loop issues, RBridges forward based on a header with a hop count.
[17] During its development, the IEEE 802.1aq standard (Shortest Path Bridging – SPB) was considered the major competitor of TRILL.
As one 2011 book noted, "the evaluation of relative merits and difference of the two standards proposals is currently a hotly debated topic in the networking industry.