http://www.rfc-editor.org/rfc/rfc5171.txt
RFC 5171: Cisco Systems UniDirectional Link Detection (UDLD) Protocol, M. Foschiano2008-04-01T23:00:00-00:00This document explains the protocol objectives and applications, illustrates the specific premises the protocol was based upon, and describes the protocol architecture and related deployment issues to serve as a possible base for future standardization. This memo provides information for the Internet community.