PCE southbound behavior

The following describes VSR-NRC PCE redundancy rules:

• steady state behavior

  1. The PCC establishes a PCEP session to each of the primary active VSR-NRC and secondary standby VSR-NRC. The secondary standby VSR-NRC is either in the primary site with single site redundancy or at the secondary site with dual site redundancy, however, the secondary standby VSR-NRC sets PCEP sessions with the PCCs in the overload state. The VSR-NRC enters this PCEP overload state when its upstream cproto session to the NSP cluster is down, or is being instructed by the NRC-P to enter the standby state as described in VSR-NRC 1+1 redundancy.

  2. The VSR-NRC acting as a PCE signals the overload state to the PCCs in a PCEP notification message. While in the overload state, the VSR-NRC PCE accepts reports (PCRpt) without delegation but rejects requests (PCReq) and reject reports (PCRpt) with delegation. The VSR-NRC PCE also does not originate initiate messages (PCInitiate) and update messages (PCUpd).

  3. The secondary standby VSR-NRC maintains its BGP and IGP peerings with the network and updates its TE database as a result of any network topology changes.

• primary active NSP cluster failure

  When the NSP cluster at the primary active site is down (two out of three servers must be inactive, shut down, or failed), the heartbeat mechanism between the primary active and secondary standby NSP clusters fails. This initiates the NSP cluster activity at the secondary standby site.

  The following are the procedures on the VSR-NRC:

  1. The primary VSR-NRC detects cproto global channel failure and puts all its PCEP sessions to the PCCs into the overload state.

  2. The NRC-P in the NSP cluster at the secondary site follows the procedures in VSR-NRC 1+1 redundancy to transition the secondary VSR-NRC into active state.

  3. The VSR-NRC at the primary site must also return the delegation of all LSPs back to the PCCs by sending an empty LSP Update Request that has the Delegate flag set to 0 in accordance with RFC 8231. To accommodate third party PCE implementations which may not return delegations, each PCC concurrently revokes the delegation of its LSPs from the primary VSR-NRC PCE. This allows the PCCs to delegate all eligible LSPs, including PCE-initiated LSPs, to the PCE function in the VSR-NRC at the secondary site. If the entire primary active site fails, the PCE side procedure in this step does not apply.

• VSR-NRC complex failure at the primary site (NSP server is still up)

  A VSR-NRC complex failure at the primary active NSP triggers the failover to backup VSR-NRC procedures in VSR-NRC 1+1 redundancy.