Alcatel-Lucent 7450 Manual page 264

MPLS Commands
operational metric as returned by MPLS and capped to maximum link metric allowed in that IGP.
Both the main SPF and the LFA SPFs will use the local IGP database to resolve the routes.
The no form of this command disables the use of a specific RSVP LSP by IS-IS and OSPF routing
protocols as a shortcut or a forwarding adjacency for resolving IGP routes.
Default igp-shortcut. All RSVP LSPs originating on this node are eligible by default as long as the
destination address of the LSP corresponds to a router-id of a remote node.
Parameters
lfa-protect — An LSP is included in both the main SPF and the LFA SPF.
lfa-only — An LSP is included in the LFA SPF only.
relative-metric [offset] — The shortest IGP cost between the endpoints of the LSP plus the
least-fill
Syntax [no] least-fill
Context config>router>mpls>lsp
Description This command enables the use of the least-fill path selection method for the computation of the path
of this LSP.
When MPLS requests the computation of a path for this LSP, CSPF will find all equal cost shortest
paths which satisfy the constraints of this path. Then, CSPF identifies the single link in each of these
paths which has the least available bandwidth as a percentage of its maximum reservable bandwidth.
It then selects the path which has the largest value of this percentage least available bandwidth figure.
CSPF identifies the least available bandwidth link in each equal cost path after it has accounted for
the bandwidth of the new requested path of this LSP.
CSPF applies the least-fill path selection method to all requests for a path, primary and secondary, of
an LSP for which this option is enabled. The bandwidth of the path can be any value, including zero.
CSPF applies the least-fill criterion separately to each pre-emption priority in the base TE. A higher
setup priority path can pre-empt lower holding priority paths.
CSPF also applies the least-fill criterion separately to each Diff-Serv TE class if Diff-Serv TE is
enabled on this node. A higher setup priority path can pre-empt lower holding priority paths within a
Class Type.
MPLS will re-signal and move the LSP to the new path in the following cases:
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configured offset, instead of the LSP operational metric returned by MPLS, is used when
calculating the cost of prefix resolved to this LSP. The offset parameter is an integer and is
optional. An offset value of zero is used when the relative-metric option is enabled without
specifying the offset parameter value.
Values
[-10, +10]
• Initial LSP path signaling.
• Re-try of an LSP path after failure.
• Make-before-break (MBB) due to pending soft pre-emption of the LSP path.
• MBB due to LSP path configuration change, i.e., a user change to bandwidth parameter of pri-
mary or secondary path, or a user enabling of fast-reroute option for the LSP.
7450 ESS MPLS Guide