Configuring PCE-initiated LSPs

About this task

Perform the following steps to configure and program a PCE-initiated SR-TE LSP.

Procedure

  1. Enable the pce-initiated-lsp sr-te command using the CLI or using the OSS.
    Optionally, configure a limit to the number of PCE-initiated LSPs that the PCE can instantiate on a node using the max-srte-pce-init-lsps command in the CLI or using the OSS.
  2. Configure at least one LSP template of type using the pce-init-p2p-srte command to select the value of the LSP parameters that remain under the control of the PCC.
    At a minimum, a default template should be configured (type pce-init-p2p-srte default). In addition, LSP templates with a defined template ID can be configured. The template ID can be included in the path profile of the PCInitiate message to indicate which non-default template to use for a particular LSP. If the PCInitiate message does not include the PCE path profile, MPLS uses the default PCE-initiated LSP template. Table: LSP template parameters lists the applicable LSP template parameters. These are grouped into:

    • parameters that are controlled by the PCE and that the PCC cannot change (invalid, implicit, and signaled in PCEP)

    • parameters that are controlled by the PCC and are used for signaling the LSP in the control plane

    • parameters that are controlled by the PCC and are related to the usability of the LSP by MPLS and other applications such as routing protocols, services, and OAM

    The user can configure these parameters in the template.

    Table: LSP template parameters
    Controlled by PCE Controlled by PCC
    Invalid Implicit Signaled in PCEP LSP signaling options LSP usability options

    auto-bandwidth

    pce-report

    bandwidth

    —

    —

    retry-limit

    —

    exclude

    —

    bgp-shortcut

    retry-timer

    pce-control

    from

    —

    bgp-transport-tunnel

    shutdown

    pce-report

    hop-limit

    default-path (mandatory, must be empty)

    —

    least-fill

    path-computation-method pce

    include

    —

    —

    metric-type

    —

    —

    —

    entropy-label

    —

    —

    —

    —

    override-tunnel-elc

    —

    —

    setup-priority

    —

    igp-shortcut

    —

    —

    hold-priority

    —

    —

    —

    —

    —

    —

    load-balancing-weight

    —

    —

    —

    —

    max-sr-labels

    —

    —

    —

    —

    additional-frr-labels

    —

    —

    —

    —

    metric

    —

    —

    —

    —

    vprn-auto-bind

    —

    —

    —

    —

    admin-tag

    All PCE-initiated LSPs that use a particular LSP template are deleted if the user deletes the template. The default template can be created or deleted if the pce-initiated-lsp>sr-te context does not exist. However, the pce-init-p2p-sr-te default lsp-template cannot be deleted if the pce-initiated-lsp>sr-te context exists and is not shutdown. This context must be shutdown to delete the pce-init-p2p-sr-te default LSP template, which brings down all PCE-initiated LSPs. The pce-initiated-lsp>sr-te context cannot be administratively enabled if the pce-init-p2p-sr-te default lsp-template is not configured.

    A shutdown of an LSP template does not bring down any already established LSPs. Parameters can only be changed when in the shutdown state and the changes do not take effect until a no shutdown is performed. This means that PCE updates use older parameters if the template is still shut down.

    MPLS copies the lsp-template parameters into the lsp-entry when a PCE initiated LSP is created. MPLS handles lsp-updates based on the last copied parameters.

    After the lsp-template parameter changes, when the lsp-template is no shutdown.

    • MPLS copies the related TTM parameters (listed below) into the LSP entry, and updates TTM

    • If there is a change in max-sr-labels, MPLS reevaluates the related LSPs, and brings paths down if applicable (for example, if current hopCount is greater than the applicable max-sr-labels value).

      The TTM LSP-related parameters include:

      • Metric

      • VprnAutoBind

      • LoadBalWeight

      • MaxSrLabels

      • AdditionalFrrLabels

      • MetricOffset

      • IgpShortCut

      • IgpShortcutLfaOnly

      • IgpShortcutLfaProtect

      • LspBgpShortCut

      • LspBgpTransTunnel

    A PCE-initiated LSP update request is accepted regardless of the LSP template administrative state, as follows:

    • If the LSP template is administratively up, the system copies the LSP template parameters to the LSP/path.

    • If the LSP template is administratively down, the system uses the previously copied LSP template parameters and responds to the update with an LSP operUp report.

  3. Set the redelegation and state timers on the PCC (known as the Redelegation Timeout Interval and StateTimeout Interval respectively in RFC 8231).
    The redelegation and state timers are started when the PCEP session goes down or the PCE signals overload. The redelegation timer applies to both PCC-initiated and PCE-initiated LSPs, while the state timer applies only to PCE-initiated LSPs. The redelegation and state timers are configured in the CLI or through management, as follows:

    config>router>pcep>pcc>

    [no] redelegation-timer seconds

    [no] state-timer seconds [action {remove | none}]

    If the delegated PCE-initiated LSPs cannot be redelegated by the time these timers expire, a configurable action is performed by the PCC. The supported actions are remove or none, with a default of remove.

  4. After configuration, the PCE can then initiate and remove LSPs on the PCC.
    These procedures are described in LSP instantiation using PCEP, LSP deletion using PCEP, and Dynamic state handling for PCE initiated LSPs.
Parent topic: LSP initiation