Prefix Unreachable Announcement
China Telecom
Huawei Technologies
ZTE Corporation
New H3C Technologies
This document describes a mechanism that can trigger the switchover of the services which rely on the reachability of the peer endpoints, for example the BGP or the tunnel services. It is mainly used in the scenarios that the summary prefixes are advertised at the border routers whereas the services endpoints are located in different IGP areas or levels, whose reachabilities are covered by the summary prefixes. It introduces a new signaling mechanism using a negative prefix announcement called Prefix Unreachable Announcement Mechanism(PUAM), utilized to detect a link or node down event and signal the overlay services that the communication endpoint is unreachabe to force the overlay service headend switchover immediately.