Network Working Group                                          L. Vegoda
Internet-Draft                                                     ICANN
Intended status: BCP                                    February 3, 2011
Expires: August 7, 2011


       Time to Remove Filters for Previously Unallocated IPv4 /8s
              draft-vegoda-no-more-unallocated-slash8s-00

Abstract

   It has been common for network administrators to filter IP traffic
   from unallocated IPv4 address space.  Now that there are no longer
   any unallocated IPv4 /8s, this practise is more complicated, fragile
   and expensive.  Network administrators are advised to remove filters
   based on the registration status of the address space.

   This document explains why any remaining filters for unallocated IPv4
   /8s should now be removed and documents those IPv4 unicast prefixes
   that should not be routed across the public Internet.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 6, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Traffic Filtering Options . . . . . . . . . . . . . . . . . . . 3
     3.1.  No Longer Filtering Based on Address Registration
           Status  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.2.  Continuing to Filter Traffic from Unallocated IPv4
           Space . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Prefixes That Should Not be Routed Across the Internet  . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 5






























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.  Introduction

   It has been common for network administrators to filter IP traffic
   from unallocated IPv4 address space.  Now that there are no longer
   any unallocated IPv4 /8s, this practise is more complicated, fragile
   and expensive.  Network administrators are advised to remove filters
   based on the registration status of the address space.

   This document explains why any remaining filters for unallocated IPv4
   /8s should now be removed and documents those IPv4 unicast prefixes
   that should not be routed across the public Internet.


.  Terminology

   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 BCP 14, RFC 2119
   [RFC2119].


.  Traffic Filtering Options

3.1.  No Longer Filtering Based on Address Registration Status

   Network administrators who implemented filters for unallocated IPv4
   /8s did so in the knowledge that those /8s were not a legitimate
   source of traffic on the Internet and that there was a small number
   of filters to implement.  Now that there are no longer any
   unallocated unicast IPv4 /8s, there will be legitimate Internet
   traffic from all unicast /8s that are not reserved for special
   purposes in an RFC.

   Removing filters based on the registration status of the IPv4 address
   is a simple approach that will avoid blocking legitimate Internet
   traffic.

3.2.  Continuing to Filter Traffic from Unallocated IPv4 Space

   Some network administrators might want to continue filtering
   unallocated IPv4 addresses managed by the Regional Internet
   Registries.  This requires significantly more granular filters and
   those filters need to be updated on a daily basis to avoid blocking
   legitimate traffic.







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.  Prefixes That Should Not be Routed Across the Internet

   Network operators who only wish to filter traffic originating from
   addresses that should never be routed across the Internet can deploy
   a set of filters designed to block traffic from address blocks
   reserved for special purposes.  These are:

      - 0.0.0.0/8 (Local identification) [RFC1122];

      - 10.0.0.0/8 (Private use) [RFC1918];

      - 127.0.0.0/8 (Loopback) [RFC1122];

      - 169.254.0.0/16 (Link local) [RFC3927];

      - 172.16.0.0/12 (Private use) [RFC1918];

      - 192.0.2.0/24 (TEST-NET-1) [RFC5737];

      - 192.168.0.0/16 (Private use) [RFC1918];

      - 198.18.0.0/15 (Benchmark testing) [RFC2544];

      - 198.51.100.0/24 (TEST-NET-2) [RFC5737];

      - 203.0.113.0/24 (TEST-NET-3) [RFC5737];

      - 224.0.0.0/4 (Multicast) [RFC5771]; and

      - 240.0.0.0/4 (Future use) [RFC1112].

   A full set of special use IPv4 addresses can be found in [RFC5735].
   It includes prefixes that are intended for Internet use.


.  Security Considerations

   The cessation of filters based on unallocated IPv4 /8 allocations is
   an evolutionary step towards reasonable security filters.  While
   these filters are no longer necessary, and in fact harmful, this does
   not obviate the need to continue other security solutions.  These
   other solutions are as necessary today as they ever were.


.  IANA Considerations

   This document makes no request of IANA.




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.  Normative References

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, August 1989.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544, March 1999.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              May 2005.

   [RFC5735]  Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
              BCP 153, RFC 5735, January 2010.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
              Reserved for Documentation", RFC 5737, January 2010.

   [RFC5771]  Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for
              IPv4 Multicast Address Assignments", BCP 51, RFC 5771,
              March 2010.


Appendix A.  Acknowledgments

   Thanks are owed to Kim Davies, Terry Manderson, Dave Piscitello and
   Joe Abley for helpful advice on how to focus this document.  Thanks
   also go to Andy Davidson, Philip Smith and Rob Thomas for early
   reviews and suggestions for improvements to the text.












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Author's Address

   Leo Vegoda
   Internet Corporation for Assigned Names and Numbers
   4676 Admiralty Way, Suite 330
   Marina del Rey, CA  90292
   United States of America

   Phone: +1-310-823-9358
   Email: leo.vegoda@icann.org
   URI:   http://www.iana.org/








































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