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Versions: 00                                                            
intarea Working Group                                             Y. Cui
Internet-Draft                                                     L. Li
Intended status: Standards Track                                  C. Liu
Expires: June 28, 2015                                             J. Wu
                                                     Tsinghua University
                                                                F. Baker
                                                           Cisco Systems
                                                       December 25, 2014


         DHCPv6 Options for Discovery of 464XLAT IPv6 Prefixes
                draft-cui-intarea-464xlat-prefix-dhcp-00

Abstract

   464XLAT provides limited IPv4 connectivity across an IPv6-only
   network using translation technology.  The customer-side translator
   (CLAT) performs stateless 1:1 mapping of an IPv4 destination address
   into a provider-side translator (PLAT) IPv6 prefix, which
   subsequently translates it back into IPv4.  Different PLATs will
   likely have different IPv6 prefixes, to attract traffic to the
   correct PLAT.  Thus, an automatic PLAT-side prefix discovery method
   is necessary for CLATs.

   This document defines a DHCPv6-based method to inform a CLAT of a
   PLAT's IPv6 prefix and the IPv4 prefixes it serves.

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 June 28, 2015.








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Copyright Notice

   Copyright (c) 2014 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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  New DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  PLAT Prefix List Option Format  . . . . . . . . . . . . .   3
     3.2.  PLAT Prefix Option Format . . . . . . . . . . . . . . . .   4
   4.  Client Behavior . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Message Flow Illustration . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   464XLAT [RFC6877] describes an IPv4-over-IPv6 solution as one
   technique for IPv4 service extension and encouragement of IPv6
   deployment.  The 464XLAT architecture uses IPv4/IPv6 translation,
   described in [RFC6144], and standardized in [RFC6052], [RFC6145], and
   [RFC6146].  It encourages the IPv6 transition by making IPv4 service
   reachable across IPv6-only networks and providing IPv6 and IPv4
   connectivity to single-stack IPv4 or IPv6 servers and peers.  In the
   464XLAT architecture, the CLAT must determine which of potentially
   several PLAT-side translation IPv6 prefix to use in order to send a
   packet to the PLAT with connectivity to its destination.

   [RFC7050] describes a mechanism to learn the PLAT-side IPv6 prefix
   for protocol translation by DNS64 [RFC6147].  Although it supports
   multiple PLAT-side prefix by responding with multiple AAAA records to
   a DNS64 query, it does not support mapping IPv4 prefixes to IPv6



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   prefix, which would be required, for example, if one PLAT has
   connectivity to the general Internet following a default route,
   another has connectivity to a BGP peer, and a third has connectivity
   to a network using private addressing [RFC1918].  Therefore, in the
   scenario with multiple PLATs, [RFC7050] does not directly support
   destination-based IPv4 routing among PLATs; instead, the DNS64
   database must contain equivalent information.  It also requires the
   additional deployment of DNS64 service in customer-side networks,
   which is not required in 464XLAT deployment.

   This document proposes a method for PLAT-side IPv6 prefix discovery
   based on DHCPv6, which is widely deployed and supported in customer
   networks.  It defines two new dhcpv6 options for use by a CLAT to
   discover the PLAT-side translation IPv6 prefix(es).  Also, the
   proposed mechanism can deal with the scenario with multiple
   independent DNS64 databases supporting separate PLATs.

2.  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 [RFC2119].

3.  New DHCPv6 Option

3.1.  PLAT Prefix List Option Format

   The PLAT Prefix List Option is a container for PLAT Prefix Option(s).
   A PLAT Prefix List Option MAY contain multiple PLAT Prefix Options.

   The format of the PLAT Prefix List Option is:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   OPTION_PLAT_PREFIX_LIST     |       option-length           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                           PLAT_PREFIX-options                 +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o  option-code: OPTION_PLAT_PREFIX_LIST (TBA1)

   o  option-length: length of PLAT_PREFIX-options, specified in octets.

   o  PLAT_PREFIX-options: one or more OPTION_PLAT_PREFIX options.




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3.2.  PLAT Prefix Option Format

   The PLAT Prefix Option is encapsulated in the PLAT Prefix List
   Option.  This option allows the mapping of destination IPv4 address
   ranges (contained in the IPv4 Prefix List) to a PLAT IPv6 prefix.  If
   there is more than one such prefix, each prefix comes in its own
   option, with its associated IPv4 prefix list.  In this way, the CLAT
   can select the PLAT with the corresponding destination IPv4 address.

   The format of the PLAT Prefix Option is:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   OPTION_PLAT_PREFIX         |         option-length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | platv6-prelen |                                               |
     +-+-+-+-+-+-+-+-+          platv6-prefix                        |
     |                       (variable length)                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                           (optional)                          .
     .              IPv4 Prefix List (variable length)               .
     .                       (see Figure 3)                          .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | IPv4-prelen   |   IPv4 Prefix (32 bits)                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    (cont.)    | IPv4-prelen   | IPv4 Prefix (32 bits)         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    IPv4 Prefix (cont)         |                ...            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            ...                                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o  option-code: OPTION_PLAT_PREFIX (TBA2)

   o  option-length: 1 + length of platv6-prefix + length of IPv4 Prefix
      List, specified in octets.

   o  platv6-prelen: length of platv6-prefix.

   o  platv6-prefix: The PLAT IPv6 prefix that the CLAT used for IPv6
      address synthesis.

   o  IPv4 Prefix List: This is an optional field.  The format of the



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      IPv4 Prefix List is shown in Figure 3.  It is a list of zero or
      more IPv4 Prefixes.  Each entry is formed by IPv4-prelen and IPv4
      Prefix.  The total length of the field is 5*number of IPv4
      prefixes.

   o  IPv4-prelen: the length of the IPv4 Prefix.

   o  IPv4 Prefix: the destination-based IPv4 Prefix.  The length is 4
      octets.

4.  Client Behavior

   The client requests the OPTION_PLAT_PREFIX_LIST option using the
   Option Request option (ORO) in every Solicit, Request, Renew, Rebind,
   and Information-request message.  If the DHCPv6 server includes the
   OPTION_PLAT_PREFIX_LIST option in its response, the CLAT may use the
   contained platv6-prefix to translate the destination IPv4 address
   into the destination IPv6 address.

   When receiving the OPTION_PLAT_PREFIX option with IPv4 Prefix List,
   the CLAT MUST record the received IPv6 prefix and the corresponding
   IPv4 prefixes in IPv4 Prefix List.  When receiving the
   OPTION_PLAT_PREFIX option without IPv4 Prefix List, the CLAT MUST
   treat the IPv6 prefix and the default IPv4 prefix 0.0.0.0/0 as one of
   the records.

   If the CLAT loses contact with the DHCPv6 server, the CLAT SHOULD
   clear the prefix(es) it learned from the DHCPv6 server.

   When translating the destination IPv4 address into the destination
   IPv6 address, CLAT MUST search an IPv4 routing database using the
   longest-match-first rule and select the IPv6 prefix offering that
   IPv4 prefix.

5.  Message Flow Illustration

   The figure below shows an example of message flow for a Client
   learning IPv6 prefixes using DHCPv6.

   In this example, two IPv6 prefixes are provided by the DHCPv6 server.
   The first IPv6 prefix is 2001:db8:122:300::/56, the corresponding
   IPv4 prefixes are 192.0.2.0/24 and 198.51.100.0/24.  The second IPv6
   prefix is 2001:db8:122::/48, the corresponding IPv4 prefix is
   192.0.2.128/25.

   When the CLAT receives the packet with destination IPv4 address
   192.0.2.1, according to the rule of longest prefix match, the PLAT
   with IPv6 prefix 2001:db8:122::/48 is chosen.  In the same way, the



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   PLAT with IPv6 prefix 2001:db8:122::/48 is chosen.

   +----------+                                     +-----------------+
   |   CLAT   |                                     |  DHCPv6 server  |
   +----------+                                     +-----------------+
        |            DHCPv6 query for IPv6 prefix            |
        |--------------------------------------------------->|
        |         ORO with OPTION_V6_PLATPREFIX_LIST         |
        |                                                    |
        |       DHCPv6 response with:                        |
        |         PLATPREFIX{                                |
        |           platv6-pre = 2001:db8:122:300::/56       |
        |           platv4-pre = 192.0.2.0/24                |
        |           platv4-pre = 198.51.100.0/24}            |
        |         PLATPREFIX{                                |
        |           platv6-pre = 2001:db8:122::/48           |
        |           platv4-pre = 192.0.2.128/25}             |
        |<---------------------------------------------------|
        |                                                    |
        |
        |                     +-----------------+   +-----------------+
        |                     |     PLAT 1      |   |     PLAT 2      |
        |                     +-----------------+   +-----------------+
        |                         platv6-pre =          platv6-pre =
        |                    2001:db8:122:300::/56   2001:db8:122::/48
        |                         platv4-pre =          platv4-pre =
        |                        192.0.2.0/24       192.0.2.128/25
        |                        198.51.100.0/24             |
        |                              |                     |
        |       Dest IPv4 addr:        |                     |
        |        192.0.2.1             |                     |
        |       Dest IPv6 addr:        |                     |
        |  2001:db8:122:300::c000:201  |                     |
        |----------------------------->|                     |
        |                              |                     |
        |                                                    |
        |     Dest IPv4 addr: 192.0.2.193                    |
        |     Dest IPv6 addr: 2001:db8:122::c000:2c1         |
        |--------------------------------------------------->|

6.  Security Considerations

   Considerations for security in this type of environment are primarily
   around the operation of the DHCPv6 protocol and the databases it
   uses.

   In the DHCPv6 server, should the database be compromised, it will
   deliver incorrect data to its CLAT clients.  In the CLAT, should its



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   database be compromised by attack or polluted by an incorrect DHCPv6
   server database, it will route data incorrectly.  In both cases, the
   security of the systems and their databases in an operational matter,
   not managed by protocol.

   However, the operation of the DHCPv6 protocol itself is also required
   to be correct - the server and its clients must recognize valid
   requests and reject invalid ones.  Therefore, DHCPv6 exchanges MUST
   be secured as described in [RFC3315].

7.  IANA Considerations

   We request that IANA allocate two DHCPv6 option codes for use by
   OPTION_V6_PLATPREFIX_LIST and OPTION_V6_PLATPREFIX from the "Option
   Codes" table

8.  References

8.1.  Normative References

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

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
              Combination of Stateful and Stateless Translation", RFC
              6877, April 2013.

8.2.  Informative References

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

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, April 2011.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.





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   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              April 2011.

   [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              the IPv6 Prefix Used for IPv6 Address Synthesis", RFC
              7050, November 2013.

Authors' Addresses

   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn


   Lishan Li
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-15201441862
   Email: lilishan9248@126.com


   Cong Liu
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5822
   Email: gnocuil@gmail.com











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   Jianping Wu
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5983
   Email: jianping@cernet.edu.cn


   Fred Baker
   Cisco Systems
   Santa Barbara, CA  93117
   United States

   Email: fred@cisco.com




































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