Te Graceful Shutdown; Soft Pre-Emption Of Diff-Serv Rsvp Lsp - Alcatel-Lucent 7450 Manual

The operator enables the use by CSPF of the user SRLG database by entering the user-srlg-db
enable command in the config>router>mpls context. When the MPLS module makes a request to
CSPF for the computation of an SRLG secondary path, CSPF will query the local SRLG and
computes a path after pruning links which are members of the SRLG IDs of the associated primary
path. Similarly, when MPLS makes a request to CSPF for a FRR bypass or detour path to associate
with the primary path, CSPF queries the user SRLG database and computes a path after pruning
links which are members of the SRLG IDs of the PLR outgoing interface.
The operator can disable the use of the user SRLG database by entering the user-srlg-db disable in
command in the config>router>mpls context. CSPF will then resumes queries into the TE
database for SRLG membership information. However, the user SRLG database is maintained
The operator can delete the entire SRLG database by entering the no srlg-database command in
the config>router>mpls context. In this case, CSPF will assume all interfaces have no SRLG
membership association if the user has not disabled the use of this database.

TE Graceful Shutdown

Graceful shutdown provides a method to bulk re-route transit LSPs away from the node during
software upgrade of a node. A solution is described in RFC 5817, Graceful Shutdown in MPLS
and Generalized MPLS Traffic Engineering Networks. This is achieved in this RFC by using a
PathErr message with a specific error code Local Maintenance on TE link required flag. When a
LER gets this message, it performs a make-before-break on the LSP path to move the LSP away
from the links/nodes which IP addresses were indicated in the PathErr message.
Graceful shutdown can flag the affected link/node resources in the TE database so other routers
will signal LSPs using the affected resources only as a last resort. This is achieved by flooding an
IGP TE LSA/LSP containing link TLV for the links under graceful shutdown with the traffic
engineering metric set to 0xffffffff and 0 as unreserved bandwidth.

Soft Pre-emption of Diff-Serv RSVP LSP

A Diff-Serv LSP can pre-empt another LSP of the same or of a different CT if its setup priority is
strictly higher (numerically lower) than the holding priority of that other LSP.
7450 ESS MPLS Guide
MPLS and RSVP
Page 141