RFC 3358 (rfc3358) - Page 1 of 4

Optional Checksums in Intermediate System to Intermediate System (ISIS)

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Network Working Group                                      T. Przygienda
Request for Comments: 3358                                         Xebeo
Category: Informational                                      August 2002


                         Optional Checksums in
           Intermediate System to Intermediate System (ISIS)

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

   This document describes an optional extension to the Intermediate
   System to Intermediate System (ISIS) protocol, used today by several
   Internet Service Proviers (ISPs) for routing within their clouds.
   ISIS is an interior gateway routing protocol developed originally by
   OSI and used with IP extensions as Interior Gateway Protocol (IGP).
   ISIS originally does not provide Complete Sequence Numbers Protocol
   Data (CSNP) and Partial Sequence Numbers Protocol Data Unit (PSNP)
   checksums, relying on the underlying layers to verify the integrity
   of information provided.  Experience with the protocol shows that
   this precondition does not always hold and scenarios can be imagined
   that impact protocol functionality.  This document introduces a new
   optional Type, Length and Value (TLV) providing checksums.

1.  Introduction

   ISIS [ISO90, Cal90a, Cal90b] CSNPs and PSNPs and IIHs can be
   corrupted in case of faulty implementations of L2 hardware or lack of
   checksuming on a specific network technology.  As a particularly ugly
   case, corruption of length and/or TLV length fields may lead to the
   generation of extensive numbers of "empty" LSPs in the receiving
   node.  Since we cannot rely on authentication as a checksum
   mechanism, this document proposes an optional TLV to add checksums to
   the elements.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [Bra97].




Przygienda                   Informational
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