Node-Link Protection
While link protection is useful for selecting an alternate path to the same router when a link fails, node-link protection establishes a bypass LSP through a different router altogether. For Case 1 in Figure 1, link protection allows an LSP to switch to link B and immediately bypass failed link A. However, if Router B fails, link B will fail and the link-protected LSP will be lost.
With node-link protection, the backup LSP can switch to link D instead and bypass the failed links and router. Another benefit of node-link protection shown in Case 2 is that a node-link-protected LSP can act like a link-protected LSP and switch to link B if link D is unavailable.
Junos OS signals bypass LSPs dynamically when a protected LSP transverses the protected link. The software determines if the protected LSP needs a node bypass or a link bypass and prepares the necessary bypass LSP automatically. The bypass LSP is torn down automatically when a protected LSP does not use the link.
Because the creation and removal of bypass LSPs is automatic, network resources can be used for other purposes when the bypass LSP is not needed. Likewise, network administrators do not need to configure bypass LSPs statically and can focus their maintenance efforts elsewhere.