IETF RFC 5952 PDF

Introduction

A single IPv6 address can be text represented in many ways. Examples are shown below.

2001:db8:0:0:1:0:0:1

2001:0db8:0:0:1:0:0:1

2001:db8::1:0:0:1

2001:db8::0:1:0:0:1

2001:0db8::1:0:0:1

2001:db8:0:0:1::1

2001:db8:0000:0:1::1

2001:DB8:0:0:1::1

All of the above examples represent the same IPv6 address. This flexibility has caused many problems for operators, systems engineers, and customers. The problems are noted in Section 3. A canonical representation format to avoid problems is introduced in Section 4.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].