RFC 1995 (rfc1995) - Page 1 of 8

Incremental Zone Transfer in DNS

Network Working Group                                            M. Ohta
Request for Comments: 1995                 Tokyo Institute of Technology
Updates: 1035                                                August 1996
Category: Standards Track


                    Incremental Zone Transfer in DNS

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.

Abstract

   This document proposes extensions to the DNS protocols to provide an
   incremental zone transfer (IXFR) mechanism.

1. Introduction

   For rapid propagation of changes to a DNS database [STD13], it is
   necessary to reduce latency by actively notifying servers of the
   change.  This is accomplished by the NOTIFY extension of the DNS
   [NOTIFY].

   The current full zone transfer mechanism (AXFR) is not an efficient
   means to propagate changes to a small part of a zone, as it transfers
   the entire zone file.

   Incremental transfer (IXFR) as proposed is a more efficient
   mechanism, as it transfers only the changed portion(s) of a zone.

   In this document, a secondary name server which requests IXFR is
   called an IXFR client and a primary or secondary name server which
   responds to the request is called an IXFR server.

2. Brief Description of the Protocol

   If an IXFR client, which likely has an older version of a zone,
   thinks it needs new information about the zone (typically through SOA
   refresh timeout or the NOTIFY mechanism), it sends an IXFR message
   containing the SOA serial number of its, presumably outdated, copy of
   the zone.





Ohta                        Standards Track