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    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
       working documents as Internet-Drafts.  The list of current Internet-
       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
       time.  It is inappropriate to use Internet-Drafts as reference
       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
       Provisions Relating to IETF Documents
       (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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    1.  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.

    2.  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].

    3.  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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    4.  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.

    5.  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.

    6.  IANA Considerations

       This document makes no request of IANA.

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    7.  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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