1. Introduction

1. Introduction

Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. The Protocol field in the IP header [RFC791] and MIME media types [RFC6838] are two examples of such coordinations.

The IETF selects an IANA Functions Operator (IFO) for protocol parameters defined by the IETF. In the contract between the IETF and the current IFO (ICANN), that entity is referred to as the IANA PROTOCOL PARAMETER SERVICES Operator, or IPPSO. For consistency with past practice, the IFO or IPPSO is referred to in this document as "IANA" [RFC2860].

In this document, we call the range of possible values for such a field a "namespace". The binding or association of a specific value with a particular purpose within a namespace is called an assignment (or, variously: an assigned number, assigned value, code point, protocol constant, or protocol parameter). The act of assignment is called a registration, and it takes place in the context of a registry. The terms "assignment" and "registration" are used interchangeably throughout this document.

To make assignments in a given namespace prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.

Typically, this information is recorded in a dedicated section of the specification with the title "IANA Considerations".