RFC 3385 (rfc3385) - Page 1 of 23

Internet Protocol Small Computer System Interface (iSCSI) Cyclic Redundancy Check (CRC)/Checksum Considerations

Network Working Group                                       D. Sheinwald
Request for Comments: 3385                                     J. Satran
Category: Informational                                              IBM
                                                               P. Thaler
                                                              V. Cavanna
                                                                 Agilent
                                                          September 2002


       Internet Protocol Small Computer System Interface (iSCSI)
         Cyclic Redundancy Check (CRC)/Checksum Considerations

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   In this memo, we attempt to give some estimates for the probability
   of undetected errors to facilitate the selection of an error
   detection code for the Internet Protocol Small Computer System
   Interface (iSCSI).

   We will also attempt to compare Cyclic Redundancy Checks (CRCs) with
   other checksum forms (e.g., Fletcher, Adler, weighted checksums), as
   permitted by available data.

1. Introduction

   Cyclic Redundancy Check (CRC) codes [Peterson] are shortened cyclic
   codes used for error detection.  A number of CRC codes have been
   adopted in standards: ATM, IEC, IEEE, CCITT, IBM-SDLC, and more
   [Baicheva].  The most important expectation from this kind of code is
   a very low probability for undetected errors.  The probability of
   undetected errors in such codes has been, and still is, subject to
   extensive studies that have included both analytical models and
   simulations.  Those codes have been used extensively in
   communications and magnetic recording as they demonstrate good "burst
   error" detection capabilities, but are also good at detecting several
   independent bit errors.  Hardware implementations are very simple and
   well known; their simplicity has made them popular with hardware




Sheinwald, et. al.           Informational