The base IETF TRILL protocol has a TRILL campus wide MTU feature,
specified in RFC 6325 and RFC 7177, that assures that link status
changes can be successfully flooded throughout the campus while being
able to take advantage of a campus wide capability to support jumbo
packets. This document specifies optional updates to that MTU feature
to take advantage, for appropriate link local packets, of link local
MTUs that exceed the TRILL campus MTU. In addition, it specifies an
efficient algorithm for local MTU testing. It updates RFC 7177.