Configuring PCE+ to Calculate Paths for MPLS TE Tunnels

The PCE function is used to calculate a path over which an MPLS TE tunnel is established, which more efficiently uses network resources than constrained shortest path first (CSPF).

Usage Scenario

Ingress nodes run the CSPF algorithm and use information stored in the traffic engineering database (TEDB) to calculate paths for MPLS TE tunnels. On an MPLS TE network, multiple tunnels originate from different ingress nodes and are established over paths that the ingress nodes independently calculate. As a result, network-wide resources cannot be efficiently used.

The PCE+ solution can help resolve the preceding issue. PCE+ devices are classified as servers and clients. A server calculates paths and stores network-wide path information. A client initiates a request to calculate a path and functions as the ingress. After the client sends a request to the server, the server calculates a path based on the network resources, which achieves optimal network resource usage.

The NetEngine 8000 F can function as a PCE client.

Different from CSPF configured on the ingress, the PCE algorithm allows a PCE server to configure and manage network-wide TE information, including node, link, and tunnel attributes. Some steps in the following procedures are mandatory when CSPF is used, while are optional when PCE is used.

Pre-configuration Tasks

Before configuring PCE+ to calculate paths for MPLS TE tunnels, complete the following tasks:

Configure IS-IS to implement network layer connectivity.
Enable MPLS TE and RSVP-TE.
Enable IS-IS TE.
(Optional) Configure TE attributes for links.
Configure a tunnel interface.

If a PCE server is used to configure and manage network-wide TE information and the PCE server and client have the same parameters, the configurations on the PCE server take precedence. For example, the bandwidth is set to 1000 kbit/s on a tunnel interface of a PCE client, and the bandwidth is set to 2000 kbit/s for the same tunnel on a PCE server. Only the bandwidth configured on the PCE server is used to calculate a path. If a tunnel attribute is configured on a PCE client, not on a PCE server, the attribute can take effect on the tunnel.

To improve the reliability of a TE tunnel established using PCE+, configure CR-LSP hot standby on the tunnel interface on which the TE tunnel is established.

Configuring the Ingress as a PCE Client: A PCE client can be configured on the ingress so that the ingress establishes a PCEP session with a PCE server and sends a request to the server over the session to calculate a path.

Specifying a Candidate Server for a PCE Client: Candidate servers can be specified for a PCE client to provide redundancy, which improves network reliability.

(Optional) Configuring PCEP Session Authentication: PCEP session authentication can be configured to improve network security and defend against attacks.

(Optional) Configuring Timers for a PCE Client: The Keepalive timer, Hold timer, and LSP Delegate-hold timer can be set for a PCE client.

(Optional) Configuring Whitelist Session-CAR for PCEP: You can configure whitelist session-CAR for PCEP to isolate bandwidth resources by session for PCEP packets. This configuration prevents bandwidth preemption among PCEP sessions in the case of a traffic burst.

(Optional) Configuring a PCE Client to Delegate TE LSPs to All PCE Servers: A PCE client can be configured to delegate TE LPSs to all PCE servers. This configuration prevents a PCE server path calculation failure if forwarders select a master PCE server different from that configured on a controller.

(Optional) Enabling a PCE Client to Support the IETF-Compliant Association Object Format: A PCE client can be enabled to support the association object in the IETF-compliant format to a PCE server.

(Optional) Enabling PCE Sessions to Support IETF-defined AO and PPAG TLV Encoding Formats: To facilitate interoperability tests, enable PCE sessions on Huawei devices so that they support IETF-defined Association Object (AO) and Path Protection Association Group (PPAG) TLV encoding formats.

Verifying the PCE Configuration: After configuring the PCE function to calculate paths for MPLS TE tunnels, you can view PCEP session information and PCEP statistics.