RFC 9494: Long-Lived Graceful Restart for BGP
Recent RFCs 2023-11-29
Summary:
This document introduces a BGP capability called the "Long-Lived
Graceful Restart Capability" (or "LLGR Capability"). The benefit of
this capability is that stale routes can be retained for a longer
time upon session failure than is provided for by BGP Graceful
Restart (as described in RFC 4724). A well-known BGP community called
"LLGR_STALE" is introduced for marking stale routes retained for a
longer time. A second well-known BGP community called "NO_LLGR" is
introduced for marking routes for which these procedures should not
be applied. We also specify that such long-lived stale routes be
treated as the least preferred and that their advertisements be
limited to BGP speakers that have advertised the capability. Use of
this extension is not advisable in all cases, and we provide
guidelines to help determine if it is.
This memo updates RFC 6368 by specifying that the LLGR_STALE
community must be propagated into, or out of, the path attributes
exchanged between the Provider Edge (PE) and Customer Edge (CE)
routers.