IP fast reroute

This document presents Topology Independent Loop-Free Alternate (TI-LFA) Fast Reroute (FRR), which is aimed at providing protection of node and Adjacency segments within the Segment Routing (SR) framework. This FRR behavior builds on proven IP FRR concepts being LFAs, Remote LFAs (RLFAs), and Directed Loop-Free Alternates (DLFAs). It extends these concepts to provide guaranteed coverage in any two-connected networks using a link-state IGP. An important aspect of TI-LFA is the FRR path selection approach establishing protection over the expected post-convergence paths from the Point of Local Repair (PLR), reducing the operational need to control the tie-breaks among various FRR options.

This document specifies the use of Topology Independent Loop-Free Alternate (TI-LFA) mechanisms with Multicast-only Fast Reroute (MoFRR) for Protocol Independent Multicast (PIM). The TI-LFA provides Fast Reroute (FRR) protection for unicast traffic in IP networks by precomputing backup paths that avoid potential failures. By integrating TI-LFA with MoFRR, this document extends the benefits of FRR mechanisms to multicast traffic, enabling enhanced resilience and minimized packet loss in multicast networks. The document outlines an optional approach to implement TI-LFA in conjunction with MoFRR for PIM, ensuring that multicast traffic is rapidly rerouted in the event of a failure.

The RSVP-TE Fast Reroute (FRR) extensions specified in RFC 4090 define two local repair techniques to reroute Label Switched Path (LSP) traffic over pre-established backup tunnels. Facility backup method allows one or more LSPs traversing a connected link or node to be protected using a bypass tunnel. The many-to-one nature of local repair technique is attractive from a scalability point of view. This document enumerates facility backup procedures in RFC 4090 that rely on refresh timeout, hence, making facility backup method refresh-interval dependent. The RSVP-TE extensions defined in this document will enhance the facility backup protection mechanism by making the corresponding procedures refresh-interval independent, and hence, compatible with the Refresh-Interval Independent RSVP (RI-RSVP) capability specified in RFC 8370. Hence, this document updates RFC 4090 in order to support the RI-RSVP capability specified in RFC 8370.

This document updates RFC 5440 to clarify usage of the Local Protection Desired bit signaled in the Path Computation Element Communication Protocol (PCEP). This document also introduces a new flag for signaling protection enforcement in PCEP.

This document updates RFC 4090 for the Resource Reservation Protocol (RSVP) Traffic Engineering (TE) procedures defined for facility backup protection. The updates include extensions that reduce the amount of signaling and processing that occurs during Fast Reroute (FRR); as a result, scalability when undergoing FRR convergence after a link or node failure is improved. These extensions allow the RSVP message exchange between the Point of Local Repair (PLR) and the Merge Point (MP) nodes to be independent of the number of protected Label Switched Paths (LSPs) traversing between them when facility bypass FRR protection is used. The signaling extensions are fully backwards compatible with nodes that do not support them.

This document specifies a fast reroute framework for protecting IP/MPLS services and MPLS transport tunnels against egress node and egress link failures. For each type of egress failure, it defines the roles of Point of Local Repair (PLR), protector, and backup egress router and the procedures of establishing a bypass tunnel from a PLR to a protector. It describes the behaviors of these routers in handling an egress failure, including local repair on the PLR and context-based forwarding on the protector. The framework can be used to develop egress protection mechanisms to reduce traffic loss before global repair reacts to an egress failure and control-plane protocols converge on the topology changes due to the egress failure.

Deployment experience gained from implementing algorithms to determine Loop-Free Alternates (LFAs) for multi-homed prefixes (MHPs) has revealed some avenues for potential improvement. This document provides explicit inequalities that can be used to evaluate neighbors as potential alternates for MHPs. It also provides detailed criteria for evaluating potential alternates for external prefixes advertised by OSPF ASBRs. This document updates Section 6 of RFC 5286 by expanding some of the routing aspects.

Resource Reservation Protocol (RSVP) association signaling can be used to bind two unidirectional Label Switched Paths (LSPs) into an associated bidirectional LSP. When an associated bidirectional LSP is co-routed, the reverse LSP follows the same path as its forward LSP. This document updates the fast reroute procedures defined in RFC 4090 to support both single-sided and double-sided provisioned associated bidirectional LSPs. This document also updates the procedure for associating two reverse LSPs defined in RFC 7551 to support co-routed bidirectional LSPs. The fast reroute procedures can ensure that, for the co-routed LSPs, traffic flows on co-routed paths in the forward and reverse directions after a failure event.

This document describes extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for locally protecting the ingress node of a Point-to-Point (P2P) or Point-to-Multipoint (P2MP) Traffic Engineered (TE) Label Switched Path (LSP). It extends the Fast Reroute (FRR) protection for transit nodes of an LSP to the ingress node of the LSP. The procedures described in this document are experimental.

This document describes extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for locally protecting the egress node(s) of a Point-to-Point (P2P) or Point-to-Multipoint (P2MP) Traffic Engineered (TE) Label Switched Path (LSP).

This document describes a mechanism for link-state routing protocols that prevents local transient forwarding loops in case of link failure. This mechanism proposes a two-step convergence by introducing a delay between the convergence of the node adjacent to the topology change and the network-wide convergence.

Because this mechanism delays the IGP convergence, it may only be used for planned maintenance or when Fast Reroute (FRR) protects the traffic during the time between the link failure and the IGP convergence.

The mechanism is limited to the link-down event in order to keep the mechanism simple.

Simulations using real network topologies have been performed and show that local loops are a significant portion (>50%) of the total forwarding loops.

This document specifies extensions to the Label Distribution Protocol (LDP) to support the creation of Label Switched Paths (LSPs) for Maximally Redundant Trees (MRTs). A prime use of MRTs is for unicast and multicast IP/LDP Fast Reroute, which we will refer to as "MRT-FRR".

The sole protocol extension to LDP is simply the ability to advertise an MRT Capability. This document describes that extension and the associated behavior expected for Label Switching Routers (LSRs) and Label Edge Routers (LERs) advertising the MRT Capability.

MRT-FRR uses LDP multi-topology extensions, so three multi-topology IDs have been allocated from the MPLS MT-ID space.

This document updates the Resource Reservation Protocol - Traffic Engineering (RSVP-TE) Fast Reroute (FRR) procedures defined in RFC 4090 to support Packet Switch Capable (PSC) Generalized Multiprotocol Label Switching (GMPLS) Label Switched Paths (LSPs). These updates allow the coordination of a bidirectional bypass tunnel assignment protecting a common facility in both forward and reverse directions of a co-routed bidirectional LSP. In addition, these updates enable the redirection of bidirectional traffic onto bypass tunnels that ensure the co-routing of data paths in the forward and reverse directions after FRR and avoid RSVP soft-state timeout in the control plane.

This document specifies a fast mechanism for protecting pseudowires (PWs) transported by IP/MPLS tunnels against egress endpoint failures, including egress attachment circuit (AC) failure, egress provider edge (PE) failure, multi-segment PW terminating PE failure, and multi-segment PW switching PE failure. Operating on the basis of multihomed customer edge (CE), redundant PWs, upstream label assignment, and context-specific label switching, the mechanism enables local repair to be performed by the router upstream adjacent to a failure. The router can restore a PW in the order of tens of milliseconds, by rerouting traffic around the failure to a protector through a pre-established bypass tunnel. Therefore, the mechanism can be used to reduce traffic loss before global repair reacts to the failure and the network converges on the topology changes due to the failure.

Loop-Free Alternates (LFAs), as defined in RFC 5286, constitute an IP Fast Reroute (IP FRR) mechanism enabling traffic protection for IP traffic (and, by extension, MPLS LDP traffic). Following early deployment experiences, this document provides operational feedback on LFAs, highlights some limitations, and proposes a set of refinements to address those limitations. It also proposes required management specifications.

This proposal is also applicable to remote-LFA solutions.

This document supports the solution put forth in "An Architecture for IP/LDP Fast Reroute Using Maximally Redundant Trees (MRT-FRR)" (RFC 7812) by defining the associated MRT Lowpoint algorithm that is used in the Default MRT Profile to compute both the necessary Maximally Redundant Trees with their associated next hops and the alternates to select for MRT-FRR.

This document defines the architecture for IP and LDP Fast Reroute using Maximally Redundant Trees (MRT-FRR). MRT-FRR is a technology that gives link-protection and node-protection with 100% coverage in any network topology that is still connected after the failure.

As IPTV deployments grow in number and size, service providers are looking for solutions that minimize the service disruption due to faults in the IP network carrying the packets for these services. This document describes a mechanism for minimizing packet loss in a network when node or link failures occur. Multicast-only Fast Reroute (MoFRR) works by making simple enhancements to multicast routing protocols such as Protocol Independent Multicast (PIM) and Multipoint LDP (mLDP).

This document describes an extension to the basic IP fast reroute mechanism, described in RFC 5286, that provides additional backup connectivity for point-to-point link failures when none can be provided by the basic mechanisms.

This document presents an illustrative framework for providing fast reroute in an IP or MPLS network through encapsulation and forwarding to "not-via" addresses. The general approach described here uses a single level of encapsulation and could be used to protect unicast, multicast, and LDP traffic against link, router, and shared risk group failure, regardless of network topology and metrics.

The mechanisms presented in this document are purely illustrative of the general approach and do not constitute a protocol specification. The document represents a snapshot of the work of the Routing Area Working Group at the time of publication and is published as a document of record. Further work is needed before implementation or deployment.

This document describes the methodology for benchmarking MPLS Fast Reroute (FRR) protection mechanisms for link and node protection. This document provides test methodologies and testbed setup for measuring failover times of Fast Reroute techniques while considering factors (such as underlying links) that might impact recovery times for real-time applications bound to MPLS Traffic Engineered (MPLS-TE) tunnels.

In this document, we analyze the applicability of the Loop-Free Alternate (LFA) method of providing IP fast reroute in both the core and access parts of Service Provider networks. We consider both the link and node failure cases, and provide guidance on the applicability of LFAs to different network topologies, with special emphasis on the access parts of the network. This document is not an Internet Standards Track specification; it is published for informational purposes.

This memo defines a portion of the Management Information Base for use with network management protocols in the Internet community. In particular, it describes managed objects used to support two fast reroute (FRR) methods for Multiprotocol Label Switching (MPLS)-based traffic engineering (TE). The two methods are the one-to-one backup method and the facility backup method. [STANDARDS-TRACK]

This document provides a framework for the development of IP fast- reroute mechanisms that provide protection against link or router failure by invoking locally determined repair paths. Unlike MPLS fast-reroute, the mechanisms are applicable to a network employing conventional IP routing and forwarding. This document is not an Internet Standards Track specification; it is published for informational purposes.

A micro-loop is a packet forwarding loop that may occur transiently among two or more routers in a hop-by-hop packet forwarding paradigm.

This framework provides a summary of the causes and consequences of micro-loops and enables the reader to form a judgement on whether micro-looping is an issue that needs to be addressed in specific networks. It also provides a survey of the currently proposed mechanisms that may be used to prevent or to suppress the formation of micro-loops when an IP or MPLS network undergoes topology change due to failure, repair, or management action. When sufficiently fast convergence is not available and the topology is susceptible to micro-loops, use of one or more of these mechanisms may be desirable. This document is not an Internet Standards Track specification; it is published for informational purposes.

This document describes the use of loop-free alternates to provide local protection for unicast traffic in pure IP and MPLS/LDP networks in the event of a single failure, whether link, node, or shared risk link group (SRLG). The goal of this technology is to reduce the packet loss that happens while routers converge after a topology change due to a failure. Rapid failure repair is achieved through use of precalculated backup next-hops that are loop-free and safe to use until the distributed network convergence process completes. This simple approach does not require any support from other routers. The extent to which this goal can be met by this specification is dependent on the topology of the network. [STANDARDS-TRACK]

This document defines RSVP-TE extensions to establish backup label-switched path (LSP) tunnels for local repair of LSP tunnels. These mechanisms enable the re-direction of traffic onto backup LSP tunnels in 10s of milliseconds, in the event of a failure.

Two methods are defined here. The one-to-one backup method creates detour LSPs for each protected LSP at each potential point of local repair. The facility backup method creates a bypass tunnel to protect a potential failure point; by taking advantage of MPLS label stacking, this bypass tunnel can protect a set of LSPs that have similar backup constraints. Both methods can be used to protect links and nodes during network failure. The described behavior and extensions to RSVP allow nodes to implement either method or both and to interoperate in a mixed network. [STANDARDS-TRACK]