1. Introduction

1. Introduction

Segment Routing (SR) can be applied to the IPv6 data plane using a new type of routing header called the Segment Routing Header (SRH). This document describes the SRH and how it is used by nodes that are SR capable.

"Segment Routing Architecture" [RFC8402] describes Segment Routing and its instantiation in two data planes: MPLS and IPv6.

The encoding of IPv6 segments in the SRH is defined in this document.

1.1. Terminology

This document uses the terms Segment Routing (SR), SR domain, SR over IPv6 (SRv6), Segment Identifier (SID), SRv6 SID, Active Segment, and SR Policy as defined in [RFC8402].

1.2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.