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Versions: 00 01 02 03 04                                                
Internet Engineering Task Force                                 M. Smith
Internet-Draft                                                      IMOT
Updates: 4291,5156,6303                                 January 14, 2013
(if approved)
Intended status: Standards Track
Expires: July 18, 2013


                   A Larger Loopback Prefix for IPv6
            draft-smith-v6ops-larger-ipv6-loopback-prefix-02

Abstract

   During the development and testing of a network application, it can
   be useful to run multiple instances of the application using the same
   transport layer protocol port on the same development host, while
   also having network access to the application instances limited to
   the local host.  Under IPv4, this has been possible by using
   different loopback addresses within 127/8.  It is not possible under
   IPv6, as the loopback prefix of ::1/128 only provides a single
   loopback address.  This memo proposes a new larger loopback prefix
   that will provide many loopback IPv6 addresses.

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 July 18, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   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
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Larger Loopback Prefix Requirements  . . . . . . . . . . . . .  4
   3.  Proposed Larger Loopback Prefix  . . . . . . . . . . . . . . .  4
   4.  Address Assignment and Configuration . . . . . . . . . . . . .  5
   5.  Larger Loopback Prefix Processing Rules  . . . . . . . . . . .  6
     5.1.  Host Rules . . . . . . . . . . . . . . . . . . . . . . . .  6
       5.1.1.  Packets Originated with Larger Loopback Source
               and/or Destination Addresses . . . . . . . . . . . . .  6
       5.1.2.  Packets Received Externally With Larger Loopback
               Source and/or Destination Addresses  . . . . . . . . .  6
     5.2.  Router Rules . . . . . . . . . . . . . . . . . . . . . . .  7
       5.2.1.  Packets Originated with Larger Loopback Source
               and/or Destination Addresses . . . . . . . . . . . . .  7
       5.2.2.  Packets Received Externally With Larger Loopback
               Source and/or Destination Addresses  . . . . . . . . .  7
   6.  DNS Considerations . . . . . . . . . . . . . . . . . . . . . .  7
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   10. Change Log [RFC Editor please remove]  . . . . . . . . . . . .  9
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     11.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     11.2. Informative References . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
















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1.  Introduction

   During the development and testing of a network application, it can
   be useful to run multiple instances of the application on the same
   development host.  It may also be useful or important for network
   access to these application instances to be limited to the
   development host itself.

   Networked applications that use fixed and usually well known
   transport layer protocol ports will typically accept incoming traffic
   on that port for any address assigned to the host.  This will prevent
   multiple instances of the application running on the same port.  This
   port reuse limitation can be overcome by having each application
   instance bind to different individual addresses available on the
   host.

   Under IPv4, the 127/8 loopback prefix [RFC1122] provides many
   addresses that can be used to run multiple instances of an
   application on the same port, while also limiting access to the local
   host.

   Under IPv6, the ::1/128 loopback prefix [RFC4291] only provides a
   single address.  Multiple application instances using the the same
   port, bound to different loopback addresses, is not possible.

   The IPv4-Mapped IPv6 Address form of 127/8, ::ffff:127.0.0.0/104
   [RFC4291], could be used to provide more host local loopback
   addresses.  However these addresses do not have native IPv6 address
   properties.  For example, they cannot accomodate 64 bit Interface
   Identifiers.

   A Unique Local IPv6 Unicast Address (ULA) prefix [RFC4193] could be
   used to increase the number of addresses available on the local host.
   However this prefix would need to be manually generated and
   configured at least once by a system administrator or operator.
   Without additonal configuration, traffic towards addresses not
   assigned to the local host would not be prevented from leaving the
   host, and access may not be limited to the local host.  A ULA prefix
   would not be well known, and would not be convenient to remember and
   type without violating the randomness requirements of the Global ID
   component of a ULA prefix.

   This memo proposes a new larger IPv6 loopback prefix that provides
   more loopback addresses, has properties of native IPv6 addresses, and
   is easy to remember and type.  This prefix will also suit other uses
   of multiple loopback addresses that may emerge.

   This memo, if published, updates [RFC4291], [RFC5156] and [RFC6303].



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1.1.  Requirements Language

   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 [RFC2119].


2.  Larger Loopback Prefix Requirements

   A new larger loopback prefix should attempt to satisfy all of the
   following requirements:

   o  be a well known prefix,

   o  be within an existing special purpose prefix, such as ::/8 (the
      parent prefix of ::/128 and ::1/128),

   o  be easy for a human to remember,

   o  be easy for a human to type,

   o  should cover the existing loopback prefix,

   o  should support 64 bit Interface Identifiers,

   o  should provide a large number of /64 subnets.


3.  Proposed Larger Loopback Prefix

   Ideally, the prefix length of ::1/128 could be shortened, resulting
   in a larger loopback prefix.  However, if the existing loopback
   prefix length was shortened enough to satisfy all of the larger
   loopback prefix requirements, it would then cover the IPv4 Mapped
   IPv6 Address prefix, ::ffff:0.0.0.0/96, and prevent its use described
   in [RFC4038].

   Giving up the requirement of covering the existing loopback prefix,
   the proposed larger loopback prefix is:

      0001:0000:0000:0000:0000:0000:0000:0000/32

   or concisely,

      1::/32

   This prefix satisfies all remaining larger loopback prefix
   requirements.



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   Allocating a /32 prefix for the loopback function may seem excessive,
   as a /48 prefix would adequately meet the larger loopback prefix
   requirements.  However, within the parent ::/8 special purpose
   prefix, there are approximately 16 million /32 prefixes, so a single
   /32 for the larger loopback prefix is easily afforded.  A /32 larger
   loopback prefix will satisfy all current and likely future uses of
   the loopback function.


4.  Address Assignment and Configuration

   Consistent with the IPv6 addressing model [RFC4291], all addresses
   within the larger loopback prefix are to be logically assigned to one
   or more of the node's interfaces.  Typically, the addresses will be
   logically assigned to a single virtual "loopback" interface, which
   returns or loops outgoing packets back to the originating node.

   It is also common to configure a well known loopback address on the
   loopback interface during system initialisation.  For IPv4, this
   address is 127.0.0.1/8, while in IPv6, it is ::1/128.  For the new
   larger loopback prefix, the address automatically configured on the
   loopback interface should be:

      1::1/64

   A /64 prefix length has been chosen over /32 to provide a 64 bit
   Interface Identifier for the loopback interface.  This is different
   from the use of the IPv4 loopback prefix length of /8 when
   configuring the IPv4 127.0.0.1 loopback address.

   Some implementations may support more than one loopback interface.
   These subsequent loopback interfaces, when initialised, should be
   assigned a locally unique larger loopback prefix /64 subnet, with all
   addresses within the /64 being logically assigned to the interface.
   Additionally, the ":1" address for the subnet should be configured on
   the loopback interface.

   /64 subnet identifier uniqueness could be achieved by using the
   loopback interface instance number as the subnet identifier (with the
   first instance numbered 0, to suit the use of 1::1/64 on the first
   loopback interface).  For example, the second loopback interface
   could be assigned 1:0:0:1::/64, while the forth loopback interface
   could be assigned 1:0:0:3::/64.  Alternatively, the interfaces'
   ifIndex [RFC1213] could be used to determine these subsequent
   interfaces' loopback /64 subnet identifier.  Other schemes which
   ensure subnet identifier uniqueness would be acceptable.

   It should be possible for an operator to remove these automatically



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   configured loopback addresses.  It should also be possible for an
   operator to configure further loopback addresses from within the
   assigned /64, or addresses from a different /64 from within the
   larger loopback prefix.

   The larger loopback prefix addresses that are outside of the
   subsequent loopback interface assigned /64s would continue to be
   logically assigned to the first or oldest loopback interface.


5.  Larger Loopback Prefix Processing Rules

5.1.  Host Rules

5.1.1.  Packets Originated with Larger Loopback Source and/or
        Destination Addresses

   Packets originated with larger loopback source and/or destination
   addresses MUST be returned to the origin host for standard processing
   by the local IPv6 protocol implementation.  They MUST NOT be sent
   over any external links attached to the host.

   If the implementation supports multiple loopback interfaces, the
   egress loopback interface SHOULD be the interface assigned the
   matching destination loopback address.  The ingress loopback
   interface MUST be the interface assigned the matching destination
   loopback address.  This will facilitate loopback interface specific
   handling of the looped traffic, such as traffic filtering or traffic
   conditioning, which may be useful during network application
   development.  Note that standard IPv6 longest match packet forwarding
   will facilitate this multiple loopback interface processing.

   All addresses within the larger loopback prefix MUST be considered
   assigned to one or more of the host's interfaces.

5.1.2.  Packets Received Externally With Larger Loopback Source and/or
        Destination Addresses

   Packets with larger loopback source and/or destination addresses
   received over any of the external links attached to the host MUST be
   dropped.  ICMPv6 error messages, such as Destination Unreachable
   messages, MUST NOT be generated for these dropped packets.

   For these dropped packets, it may be useful to generate an
   appropriate system log message, indicating a packet with an invalid
   source or destination address (a "martian") was received over an
   external interface.  By default, these messages should be suppressed.
   If they are enabled, they should be appropriately rate limited to



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   prevent a system log denial-of-service attack.

5.2.  Router Rules

   IPv4 loopback packet processing rules for routers, specified in
   [RFC1812], by default prohibited forwarding of packets with 127/8
   destinations, other than those originated locally and returned back
   to the router itself.  A software switch could be provided to disable
   this prohibition.  This special case of allowing forwarding of
   packets towards 127/8 destinations has been taken advantage of by
   [RFC4379].  An equivalent function for IPv6 is provided by using the
   IPv4-Mapped IPv6 prefix of ::ffff:127.0.0.0/104.

   The existing ::1/128 packet processing rules for routers is the same
   as for IPv6 hosts [RFC4291].

   For the new larger loopback prefix, the IPv6 router processing rules
   are changed to match those of IPv4.

5.2.1.  Packets Originated with Larger Loopback Source and/or
        Destination Addresses

   By default, a router MUST follow the host processing rules, described
   previously, for packets originated with larger loopback source and/or
   destination addresses.

   A software switch may be provided to permit packets with larger
   loopback source and/or destination addresses to be sent via an
   external interface.  If provided, this software switch MUST default
   to off.

5.2.2.  Packets Received Externally With Larger Loopback Source and/or
        Destination Addresses

   By default, a router MUST follow the host processing rules, described
   previously, for packets received externally with larger loopback
   source and/or destination addresses.

   A software switch may be provided to permit received packets with
   larger loopback source and/or destination addresses to be forwarded
   via an external interface.  This software switch MUST default to off.


6.  DNS Considerations

   The DNS zone for 1::/32, 0.0.0.0.1.0.0.0.IP6.ARPA, SHOULD be served
   locally.  [RFC6303] provides further discussion regarding local
   serving of DNS zones for non-global IP address space.



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7.  Acknowledgements

   Nick Hilliard provided valuable review, comments and advice on this
   memo.

   Review and comments where provided by Bill Atwood, Brian Carpenter,
   Roland Chan, Chris Chaundy, Chris Donovan, Matts Kallioniemi, Erik
   Kline and Tina Tsou.

   This memo was prepared using the xml2rfc tool.


8.  IANA Considerations

   IANA is requested to allocate 1::/48 from within ::/8 of the Internet
   Protocol Version 6 Address Space, for use as a larger loopback prefix
   for IPv6, as described in this memo, and record to it in the
   [IANA-IPV6REG].


9.  Security Considerations

   During deployment of a new larger loopback prefix, there will be a
   transition period where some hosts and routers have implemented the
   larger loopback processing rules defined in this memo while others
   haven't.  These legacy hosts and routers will forward larger loopback
   traffic using conventional unicast processing.  For traffic towards
   non-local larger loopback addresses, traffic will most likely leave
   the legacy originating host via it's default route, and may be
   forwarded by legacy routers using their default route.  This may
   disclose sensitive information, violating security policy.

   Packet filters, matching traffic with larger loopback source and/or
   destination addresses, should be used to prevent unintended
   forwarding of loopback traffic.  They should be deployed at the
   following locations:

   o  on the legacy hosts themselves,

   o  on legacy routers interconnecting two different networks,

   o  on appropriate security domain boundary legacy routers within the
      local network, if not all legacy routers within the local network.

   Routes for the new larger loopback prefix should not be announced or
   accepted if received.





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10.  Change Log [RFC Editor please remove]

   draft-smith-larger-ipv6-loopback-prefix-00, initial version,
   2012-07-24

   draft-smith-larger-ipv6-loopback-prefix-01, much less verbose
   version, 2012-08-17

   draft-smith-larger-ipv6-loopback-prefix-02, clarifications,
   2013-01-07

   o  clarification that the larger loopback prefix should fall within
      ::/8, the parent prefix of ::/128 and ::1/128

   o  Change from 1::/48 to 1::/32

   o  text about logically assigning addresses to interface(s), as per
      IPv6 addressing model

   o  automatic loopback address configuration to multiple loopback
      interfaces

   o  local serving of 0.0.0.1.0.0.0.IP6.ARPA zone in DNS


11.  References

11.1.  Normative References

   [IANA-IPV6REG]
              Internet Assigned Numbers Authority, "IPv6 Special Purpose
              Address Registry", 2013, <http://www.iana.org/assignments/
              iana-ipv6-special-registry>.

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

   [RFC1213]  McCloghrie, K. and M. Rose, "Management Information Base
              for Network Management of TCP/IP-based internets:MIB-II",
              STD 17, RFC 1213, March 1991.

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

11.2.  Informative References

   [RFC1812]  Baker, F., "Requirements for IP Version 4 Routers",
              RFC 1812, June 1995.



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   [RFC4038]  Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.
              Castro, "Application Aspects of IPv6 Transition",
              RFC 4038, March 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4379]  Kompella, K. and G. Swallow, "Detecting Multi-Protocol
              Label Switched (MPLS) Data Plane Failures", RFC 4379,
              February 2006.

   [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
              April 2008.

   [RFC6303]  Andrews, M., "Locally Served DNS Zones", BCP 163,
              RFC 6303, July 2011.


Author's Address

   Mark Smith
   In My Own Time
   PO BOX 521
   HEIDELBERG, VIC  3084
   AU

   Email: markzzzsmith@yahoo.com.au





















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