1. Introduction

1. Introduction

Segment Routing [RFC8402] leverages the source routing paradigm. An ingress node steers a packet through an ordered list of instructions, called "segments". Each one of these instructions represents a function to be called at a specific location in the network. A function is locally defined on the node where it is executed and may range from simply moving forward in the segment list to any complex user-defined behavior. Network Programming combines Segment Routing functions, both simple and complex, to achieve a networking objective that goes beyond mere packet routing.

This document defines the SRv6 Network Programming concept and specifies the main Segment Routing behaviors to enable the creation of interoperable overlays with underlay optimization.

[SRV6-NET-PGM-ILLUST] illustrates the concepts defined in this document.

Familiarity with the Segment Routing Header [RFC8754] is expected.