SR-MPLS

This document describes a mechanism used to collect Segment Routing (SR) Policy information that is locally available in a node and advertise it into BGP - Link State (BGP-LS) updates. Such information can be used by external components for path computation, reoptimization, service placement, network visualization, etc.

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.

This document expands the applicability of Virtual Private Wire Service (VPWS) bit-stream payloads beyond Time Division Multiplexing (TDM) signals and provides pseudowire transport with complete signal transparency over Packet Switched Networks (PSNs).

This document specifies the application of the MPLS loss and delay measurement techniques (originally defined in RFCs 6374, 7876, and 9341) within Segment Routing (SR) networks that utilize the MPLS data plane, also referred to as Segment Routing over MPLS (SR-MPLS). SR enables the forwarding of packets through an ordered list of instructions, known as segments, which are imposed at the ingress node. This document defines the procedures and extensions necessary to perform accurate measurement of packet loss and delay in SR-MPLS environments, ensuring that network operators can effectively measure and maintain the quality of service across their SR-based MPLS networks. This includes coverage of links and end-to-end SR-MPLS paths, as well as SR Policies.

Segment Routing (SR) allows a node to steer a packet flow along any path. Intermediate per-path states are eliminated thanks to source routing. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. Packet flows are steered into an SR Policy on a node where it is instantiated called a headend node. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy.

This document updates RFC 8402 as it details the concepts of SR Policy and steering into an SR Policy.

Segment Routing (SR) leverages the source-routing paradigm. A node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. In the MPLS data plane, the SR header is instantiated through a label stack. This document specifies the forwarding behavior to allow instantiating SR over the MPLS data plane (SR-MPLS).

A Segment Routing (SR) node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. A segment can represent any instruction, topological or service based. SR allows enforcing a flow through any topological path while maintaining per-flow state only at the ingress node to the SR domain.

The Segment Routing architecture can be directly applied to the MPLS data plane with no change in the forwarding plane. This document describes how Segment Routing MPLS operates in a network where LDP is deployed and in the case where SR-capable and non-SR-capable nodes coexist.

MPLS Segment Routing (SR-MPLS) is a method of source routing a packet through an MPLS data plane by imposing a stack of MPLS labels on the packet to specify the path together with any packet-specific instructions to be executed on it. SR-MPLS can be leveraged to realize a source-routing mechanism across MPLS, IPv4, and IPv6 data planes by using an MPLS label stack as a source-routing instruction set while making no changes to SR-MPLS specifications and interworking with SR-MPLS implementations.

This document describes how SR-MPLS-capable routers and IP-only routers can seamlessly coexist and interoperate through the use of SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-over-UDP as defined in RFC 7510.