MPLS FRR Protection Overview

Multiprotocol Label Switching (MPLS) fast reroute (FRR) refers to local protection methods such as one-to-one and many-to-one (facility) backup. In the general networking community, the term FRR has become a shorthand way of describing the entire spectrum of MPLS traffic protection mechanisms. This should not be confused with the JUNOS software fast reroute feature. In this book, the acronym FRR is used to describe general MPLS traffic protection, while the distinct JUNOS software feature is described as fast reroute.

In the JUNOS software, general MPLS traffic protection for Resource Reservation Protocol (RSVP)-signaled label-switched path (LSP) failures is provided by several complementary mechanisms. These protection mechanisms include local protection (fast reroute, link protection, and node-link protection), and path protection (primary and secondary paths). Local protection in conjunction with path protection can provide minimum packet loss for an LSP, and control the way the LSP is rerouted after a failure.

Traditionally, both types of protection rely on fast detection of connectivity failure at the physical level. However, for transmission media without fast physical level detection, the JUNOS software supports the configuration of bidirectional forwarding detection (BFD) and MPLS ping for fast-failure detection. It is beyond the scope of this document to cover BFD or MPLS ping. For more information on BFD and MPLS ping, see the JUNOS MPLS Applications Configuration Guide.

The terms node and router are used interchangeably throughout this book.