Understand LSP Delegation and Undelegation
In Paragon Pathfinder, the Path Computation Element (PCE) computes paths in the network and applies computational constraints.
You can delegate the management of Path Computation Client-controlled LSPs (PCC-controlled LSPs) to the PCE either by using the Paragon Automation GUI (from the Configure LSP Delegation page [Network > Tunnels > Configure LSP Delegation]) or the Junos OS CLI. After delegation, such LSPs are managed by the PCE and are classified as PCC-delegated LSPs.
When LSPs are managed by the PCE, you can reprovision LSPs (directly from the GUI) for which provisioning has failed or for which the path isn’t the expected path. In addition, you can also enable optimization to re-establish an optimal set of paths for the network. Pathfinder does not support reprovisioning and optimization for PCC-controlled LSPs.
You can also delegate the LSPs back to the PCC (also known as undelegating the LSPs from the PCE), after which the LSPs are managed by the PCC and are re-classified as PCC-controlled LSPs. This is useful if Pathfinder is down or if the LSPs are not working as expected.
For the procedure to delegate and undelegate LSPs from the Paragon Automation GUI, see Add and Remove LSP Delegation.
Understand the Behavior of Delegated and Undelegated LSPs
In both standalone (where the Paragon Automation components run on a single primary node) and high availability (HA) cluster configurations (where the Paragon Automation components run on multiple primary nodes), whenever a Path Computation Element Protocol (PCEP) session on a PCC goes down, all the LSPs that originated from that PCC are removed from the Pathfinder database, except those LSPs with parameters configured from the GUI.
For PCC-controlled LSPs, all the configuration changes made to the LSP attributes from the router (that is, the PCC) are stored only in the router’s configuration file. When you delegate such LSPs to the PCE and change the LSP attributes from the GUI, the changes are stored only in the Pathfinder database. The PCE communicates the changes to the PCC by using PCEP.
You can still make changes to the LSP attributes from the router and these changes are stored in the router’s configuration file, but the changes do not take effect as long as the LSPs remain delegated to the PCE.
The configuration changes made from the PCC take effect automatically only after the LSPs are undelegated from the PCE, which means that the control of the LSPs is returned to the PCC. After undelegation, the PCE obtains the LSP state from the PCEP report messages. If you change the LSP attributes from the router and the PCE isn’t available at this time, the PCE obtains the latest LSP state after it becomes available. Therefore, if you delegate such LSPs to the PCE, the LSPs carry the latest state.
If you perform the Undelegate operation on a delegated LSP, the Path Computation Server (PCS) uses the bandwidth reported by the device for the planned bandwidth instead of the user input value.