FRR Terminology

Backup path

The LSP that is responsible for backing up a protected LSP. A backup path can be a backup tunnel (facility backup) or a detour LSP (one-to-one backup).

Backup tunnel

The LSP that is used to back up one of the many LSPs in FRR facility (many-to-one) backup

Bypass tunnel

An LSP that is used to protect a set of LSPs passing over a common facility in FRR facility backup. A bypass tunnel can be configured manually or dynamically (see Dynamic and Manual Bypass LSPs).

CSPF

Constraint-based shortest path first

Detour route

Any alternate route that protects the primary path, such as a secondary path, FRR bypass tunnel, or FRR detour LSP. The term ‟detour route” should not be confused with the term ‟detour LSP”. Detour route is a general term that refers to any alternate route, while detour LSP is a specific term that applies to one-to-one backup.

Detour LSP

The LSP that is used to reroute traffic around a failure in FRR one-to-one backup. The term ‟detour LSP” should not be confused with the term ‟detour route”. Detour route is a general term that refers to any alternate route, while detour LSP is a specific term that applies to one-to-one backup.

DMP

Detour merge point

In the case of one-to-one backup, this is an LSR where multiple detours converge. Only one detour is signaled beyond that LSR.

Disjoint

See SRLG disjoint

Facility backup

A local repair method in which a single bypass tunnel is used to protect one or more LSPs that traverse the PLR, the resource being protected, and the Merge Point (in that order). Facility backup is distinct from a one-to-one backup tunnel, which has one backup path per protected path.

MP

Merge point

The LSR where one or more backup tunnels rejoin the path of the protected LSP downstream of the potential failure. The same LSR may be both an MP and a PLR simultaneously.

NHOP bypass tunnel

Next-hop bypass tunnel

A backup tunnel that bypasses a single link of the protected LSP

NNHOP bypass tunnel

Next-next-hop bypass tunnel

A backup tunnel that bypasses a single node of the protected LSP

One-to-one backup

A local repair method in which a backup LSP is separately created for each protected LSP at a PLR

PLR

Point of local repair

The head-end router of a backup tunnel or a detour LSP, where the term local repair refers to techniques used to repair an LSP tunnel quickly when a node or link along an LSP path fails

Primary path

An LSP that uses the routers specified by the path defined by the primary path-name command

Protected LSP

An LSP is protected at a given hop if it has one or more associated backup tunnels originating at that hop

Reroutable LSP

Any LSP for which the head-end router requests local protection

Secondary path

An LSP that protects a primary path that uses LSP redundancy protection rather than FRR protection

SRLG disjoint

A path is considered to be SRLG disjoint from a given link or node if the path does not use any links or nodes that belong to the same SRLG as the given link or node