RFC 2644 (rfc2644) - Page 1 of 4

Changing the Default for Directed Broadcasts in Routers

Network Working Group                                           D. Senie
Request for Comments: 2644                        Amaranth Networks Inc.
Updates: 1812                                                August 1999
BCP: 34
Category: Best Current Practice


        Changing the Default for Directed Broadcasts in Routers

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

1. Introduction

   Router Requirements [1] specifies that routers must receive and
   forward directed broadcasts. It also specifies that routers MUST have
   an option to disable this feature, and that this option MUST default
   to permit the receiving and forwarding of directed broadcasts.  While
   directed broadcasts have uses, their use on the Internet backbone
   appears to be comprised entirely of malicious attacks on other
   networks.

   Changing the required default for routers would help ensure new
   routers connected to the Internet do not add to the problems already
   present.

   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 RFC 2119.

2. Discussion

   Damaging denial of service attacks led to the writing of [2] on
   Ingress Filtering. Many network providers and corporate networks have
   endorsed the use of these methods to ensure their networks are not
   the source of such attacks.

   A recent trend in Smurf Attacks [3] is to target networks which
   permit directed broadcasts from outside their networks. By permitting
   directed broadcasts, these systems become "Smurf Amplifiers."




Senie                    Best Current Practice