Bidirectional Mpls Te Tunnel; Cr-Lsp Backup; Frr - HPE 5820X Series Configuration Manual

The configuration of IGP shortcut and forwarding adjacency is broken down into tunnel configuration
and IGP configuration. When making tunnel configuration on a TE tunnel interface, consider the
following:
•
The tunnel destination address must be in the same area where the tunnel interface is located.
•
The tunnel destination address must be reachable through intra-area routing.

Bidirectional MPLS TE tunnel

MPLS Transport Profile uses bidirectional MPLS TE tunnels to implement 1:1 and 1+1 protection
switching and support in-band detection tools and signaling protocols such as OAM and PSC.
A bidirectional MPLS TE tunnel contains two CR-LSPs in opposite directions. It can be established in
co-routed mode or associated mode:
•
Co-routed mode uses the extended RSVP-TE protocol to establish a bidirectional MPLS TE
tunnel. RSVP-TE uses a Path message to advertise labels assigned by the upstream LSR to
the downstream LSR and a Resv message to advertise labels assigned by the downstream
LSR to the upstream LSR. The path message establishes a CR-LSP in one direction. The Resv
message establishes a CR-LSP in the other direction. The CR-LSPs of a bidirectional MPLS TE
tunnel use the same path.
•
In associated mode, you establish a bidirectional MPLS TE tunnel by binding two unidirectional
CR-LSPs in opposite directions. The two CR-LSPs can be established in different modes and
use different paths. For example, one CR-LSP is established statically and the other CR-LSP is
established dynamically by RSVP-TE.

CR-LSP backup

CR-LSP backup provides end-to-end path protection for the entire LSP without time limitation. This is
different from FRR, which provides quick but temporary per-link or per-node protection on an LSP.
In the same TE tunnel, the LSP used to back up a primary LSP is called a secondary LSP. When the
ingress of a TE tunnel detects that the primary LSP is unavailable, it switches traffic to the secondary
LSP and after the primary LSP becomes available, switches traffic back. This is how LSP path
protection is achieved.
The following approaches are available for CR-LSP backup:
•
Hot backup where a secondary CR-LSP is created immediately after a primary CR-LSP is
created. MPLS TE switches traffic to the secondary CR-LSP after the primary CR-LSP fails.
•
Standard backup where a secondary CR-LSP is created to take over after the primary CR-LSP
fails.

FRR

FRR provides a quick per-link or per-node protection on an LSP.
In this approach, once a link or node fails on a path, FRR comes up to reroute the path to a new link
or node to bypass the failed link or node. This can happen in as fast as 50 milliseconds, thereby
minimizing data loss.
Once a link or node on an LSP configured with FRR fails, traffic is switched to the protection link and
the ingress node of the LSP starts attempting to set up a new LSP.
The following are basic concepts of FRR:
•
Protected LSP—A primary LSP to be protected.
•
Bypass LSP—An LSP used to protect primary LSPs.
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