RFC 2671 (rfc2671) - Page 1 of 7
Extension Mechanisms for DNS (EDNS0)
Alternative Format: Original Text Document
Network Working Group P. Vixie
Request for Comments: 2671 ISC
Category: Standards Track August 1999
Extension Mechanisms for DNS (EDNS0)
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
The Domain Name System's wire protocol includes a number of fixed
fields whose range has been or soon will be exhausted and does not
allow clients to advertise their capabilities to servers. This
document describes backward compatible mechanisms for allowing the
protocol to grow.
1 - Rationale and Scope
1.1. DNS (see [RFC 1035]) specifies a Message Format and within such
messages there are standard formats for encoding options, errors,
and name compression. The maximum allowable size of a DNS Message
is fixed. Many of DNS's protocol limits are too small for uses
which are or which are desired to become common. There is no way
for implementations to advertise their capabilities.
1.2. Existing clients will not know how to interpret the protocol
extensions detailed here. In practice, these clients will be
upgraded when they have need of a new feature, and only new
features will make use of the extensions. We must however take
account of client behaviour in the face of extra fields, and design
a fallback scheme for interoperability with these clients.
Vixie Standards Track