RFC 1982 (rfc1982) - Page 1 of 7

Serial Number Arithmetic

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Network Working Group                                             R. Elz
Request for Comments: 1982                       University of Melbourne
Updates: 1034, 1035                                              R. Bush
Category: Standards Track                                    RGnet, Inc.
                                                             August 1996


                        Serial Number Arithmetic

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 memo defines serial number arithmetic, as used in the Domain
   Name System.  The DNS has long relied upon serial number arithmetic,
   a concept which has never really been defined, certainly not in an
   IETF document, though which has been widely understood.  This memo
   supplies the missing definition.  It is intended to update RFC 1034
   and RFC 1035.

1. Introduction

   The serial number field of the SOA resource record is defined in
   RFC 1035 as

   SERIAL   The unsigned 32 bit version number of the original copy of
            the zone.  Zone transfers preserve this value.  This value
            wraps and should be compared using sequence space
            arithmetic.

   RFC 1034 uses the same terminology when defining secondary server zone
   consistency procedures.

   Unfortunately the term "sequence space arithmetic" is not defined in
   either RFC 1034 or RFC 1035, nor do any of their references provide
   further information.

   This phrase seems to have been intending to specify arithmetic as
   used in TCP sequence numbers [RFC 793], and defined in [IEN-74].

   Unfortunately, the arithmetic defined in [IEN-74] is not adequate for
   the purposes of the DNS, as no general comparison operator is



Elz & Bush                  Standards Track
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