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Versions: (draft-boucadair-pcp-nat64-prefix64-option) 00 01 02 03 04 05 06 RFC 7225

PCP Working Group                                           M. Boucadair
Internet-Draft                                            France Telecom
Intended status: Standards Track                       February 12, 2013
Expires: August 16, 2013


                    Learn NAT64 PREFIX64s using PCP
                    draft-ietf-pcp-nat64-prefix64-00

Abstract

   This document defines a new PCP extension to learn the IPv6
   prefix(es) used by a PCP-controlled NAT64 device to build IPv4-
   embedded IPv6 addresses.  This extension is needed for successful
   communications when IPv4 addresses are used in referrals.

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
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   This Internet-Draft will expire on August 16, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Issues  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . 3
       3.2.1.  AAAA Synthesis by Stub-resolver . . . . . . . . . . . . 3
       3.2.2.  Applications Referrals  . . . . . . . . . . . . . . . . 4
     3.3.  Illustration Example  . . . . . . . . . . . . . . . . . . . 4
   4.  PREFIX64 Option . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.2.  Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Flow Example  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 9
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9






























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1.  Introduction

   This document defines a new PCP extension [I-D.ietf-pcp-base] to
   inform PCP Clients about the Pref64::/n [RFC6052] used by a PCP-
   controlled NAT64 device [RFC6146].

   This extension is required to help establishing communications
   between IPv6-only hosts and remote IPv4-only hosts.


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.  Problem Statement

3.1.  Issues

   This document proposes a deterministic solution to solve the
   following issues:
   o  Learn the Pref64::/n used by an upstream NAT64 function.  This is
      needed to help:
      *  distinguishing between IPv4-converted IPv6 addresses and native
         IPv6 addresses.
      *  implementing IPv6 address synthesis for applications not
         relying on DNS.
   o  Avoid stale Pref64::/n.
   o  Discover multiple Pref64::/n when multiple prefixes in a network.
   o  Use DNSSEC in the presence of NAT64.

   Section 3.2 lists some applications which encounter the issues listed
   above.

3.2.  Use Cases

3.2.1.  AAAA Synthesis by Stub-resolver

   The extension defined in this document can be used for hosts with
   DNS64 capability [RFC6147], added to the host's stub-resolver.

   The stub resolver on the host will try to obtain (native) AAAA
   records and if it they are not found, the DNS64 function on the host
   will query for A records and then synthesizes AAAA records.  Using
   the PREFIX64 PCP extension, the host's stub-resolver can learn the
   prefix used for IPv6/IPv4 translator and synthesize AAAA records



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   accordingly.

   Learning the Pref64::/n used to construct IPv4-converted IPv6
   addresses [RFC6052] allows to make use of DNSSEC.

3.2.2.  Applications Referrals

   This PCP extension can be used by applications making use of address
   referrals.

   As Peer-to-Peer (P2P) communications for real-time communication is
   becoming popular with RTCWEB (e.g., P2P for Media, data channels for
   file transfer etc), this extension can be used to help for NAT64
   traversal.  SIP [RFC3261] is only one example among those protocols.

3.3.  Illustration Example

   An illustration example is shown in Figure 1.  In this example, NAT64
   is co-located with a PCP server while IPv6-only SIP UA interacts with
   a PCP Client.

   In Figure 1, the PCP Client issues a PCP MAP request with
   PORT_RESERVATION_OPTION to reserve a pair of ports preserving parity
   and contiguity [I-D.boucadair-pcp-rtp-rtcp].  A pair of ports and an
   external IPv4 address are then returned by the PCP server to the
   requesting PCP Client.  This information is used by the IPv6-only SIP
   UA to build its SDP offer which contains exclusively IPv4 addresses
   (especially in the "c=" line, the port indicated for media port is
   the external port assigned by the PCP server).  The INVITE request
   including the SDP offer is then forwarded by the NAT64 to the Proxy
   Server which will relay it to the called party (i.e., IPv4-only SIP
   UA) (Steps (1) to (3)).  IPv4-only SIP UA accepts the offer and sends
   back its SDP answer in a "200 OK" message which is relayed by the SIP
   Proxy Server and NAT64 until being delivered to IPv6-only SIP UA
   (Steps (4) to (6)).

   At the end of this process, IPv4-only SIP UA can send media streams
   to the IPv4 address/port as indicated in the SDP offer while IPv6-
   only SIP UA can not send media streams as only IPv4 addresses are
   present in the SDP answer.











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   +---------+              +-----+       +------------+     +---------+
   |IPv6-only|              |NAT64|       |  IPv4 SIP  |     |IPv4-only|
   | SIP UA  |              |     |       |Proxy Server|     | SIP UA  |
   +---------+              +-----+       +------------+     +---------+
       | (a) PCP MAP REQUEST   |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       |======================>|                |                 |
       | (b) PCP MAP RESPONSE  |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       |<======================|                |                 |
       |                       |                |                 |
       |  (1) SIP INVITE       | (2) SIP INVITE |  (3) SIP INVITE |
       |======================>|===============>|================>|
       |   (6) SIP 200 OK      | (5) SIP 200 OK |  (4) SIP 200 OK |
       |<======================|<===============|<================|
       |                       |                |                 |


                                 Figure 1


4.  PREFIX64 Option

4.1.  Format

   The format of PREFIX64 PCP Option is depicted in Figure 2.

        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 Code  |  Reserved     |   Option Length               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Prefix64 (Variable)                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: Prefix64 PCP Option

   The description of the fields is as follows:

   o  Option Code: To be assigned by IANA.
   o  Option Length: Indicates in octets the length of the Pref64::/n.
      Allowed values are 4, 5, 6, 7, 8, or 12 [RFC6052].
   o  Prefix64: This field identifies the IPv6 unicast prefix to be used
      for constructing an IPv4-embedded IPv6 address from an IPv4
      address.  The address synthesize MUST follow the guidelines
      documented in [RFC6052].





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         Option Name: PREFIX64
         Number: To be assigned by IANA.
         Purpose: Learn the prefix used by the NAT64 to build
          IPv4-embedded IPv6 addresses. This is be used by a host
          for local address synthesis (e.g., when IPv4 address is
          present in referrals).
         Valid for Opcodes: MAP
         Length: Variable
         May appear in: request, response.
         Maximum occurrences: 1

4.2.  Behaviour

   A PCP Client MAY include a PREFIX64 PCP Option in a MAP request to
   learn the IPv6 prefix used by an upstream PCP-controlled NAT64
   device.  When enclosed in a MAP request, PREFIX64 MUST be set to
   ::/96.  PREFIX64 PCP Option can be inserted in a MAP request used to
   learn the external IP address as detailed in Section 11.6 of
   [I-D.ietf-pcp-base].

   A PCP Server controlling a NAT64 SHOULD be configured to return to
   requesting PCP Clients the value of the Pref64::/n used to build
   IPv4-embedded IPv6 addresses.  When enabled, PREFIX64 PCP Option
   conveys the value of Pref64::/n.

   A PCP Server controlling a NAT64 MAY be configured to inject a
   PREFIX64 PCP Option in all MAP responses even if the option is not
   listed in the associated request.

   Upon receipt of the PREFIX64 PCP Option, the host embedding the PCP
   Client uses Pref64::/n for local address synthesize [RFC6052].  How
   the content of PREFIX64 PCP Option is passed to the OS is
   implementation-specific.

   A PCP Client SHOULD associate each received Pref64::/n with the PCP
   Server from which the Pref64::/n information was retrieved.


5.  Flow Example

   Figure 3 shows an example of the use of the option defined in
   Section 4.









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   +---------+              +-----+       +------------+     +---------+
   |IPv6-only|              |NAT64|       |  IPv4 SIP  |     |IPv4-only|
   | SIP UA  |              |     |       |Proxy Server|     | SIP UA  |
   +---------+              +-----+       +------------+     +---------+
       | (a) PCP MAP REQUEST   |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       |     PREFIX64_OPTION   |                |                 |
       |======================>|                |                 |
       | (b) PCP MAP RESPONSE  |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       |     PREFIX64_OPTION   |                |                 |
       |<======================|                |                 |
       |  (1) SIP INVITE       | (2) SIP INVITE |  (3) SIP INVITE |
       |======================>|===============>|================>|
       |   (6) SIP 200 OK      | (5) SIP 200 OK |  (4) SIP 200 OK |
       |<======================|<===============|<================|
       |     (7) SIP ACK       |  (8) SIP ACK   |    (9) SIP ACK  |
       |======================>|===============>|================>|
       |                       |                |                 |
       |<======IPv6 RTP=======>|<============IPv4 RTP============>|
       |<===== IPv6 RTCP======>|<============IPv4 RTCP===========>|
       |                       |                                  |


          Figure 3: Example of IPv6 to IPv4 SIP initiated Session

   In Steps (a) and (b), the IPv6-only SIP UA retrieves a pair of ports
   to be used for RTP/RTCP, the external IPv4 address and the Pref64::/n
   to be used to build IPv4-embedded IPv6 addresses.  The retrieved IPv4
   address and port numbers are used to build the SDP offer in Step (1)
   while Pref64::/n is used to construct a corresponding IPv6 address of
   the IPv4 address enclosed in the SDP answer made by the IPv4-only SIP
   UA (Step 6).  RTP/RTCP flows are exchanged between an IPv6-only SIP
   UA and an IPv4-only UA without requiring any ALG at the NAT64 and no
   particular function to be supported by the IPv4-only SIP Proxy Server
   to help establishing the session (e.g., Hosted NAT traversal).

   When the session is initiated from IPv4 SIP UA (see Figure 4): Steps
   (a) and (b), the IPv6-only SIP UA retrieves a pair of ports to be
   used for RTP/RTCP, the external IPv4 address and the Pref64::/n to be
   used to build IPv4-embedded IPv6 addresses.  These two steps can be
   delayed until receiving the INVITE message (Step 3).

   The retrieved IPv4 address and port numbers are used to build the SDP
   answer in Step (4) while Pref64::/n is used to construct a
   corresponding IPv6 address of the IPv4 address enclosed in the SDP
   offer made by the IPv4-only SIP UA (Step 3).  RTP/RTCP flows are
   exchanged between an IPv6-only SIP UA and an IPv4-only UA without



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   requiring any ALG at the NAT64 and no particular function to be
   supported by the IPv4-only SIP Proxy Server to help establishing the
   session (e.g., Hosted NAT traversal).


   +---------+              +-----+       +------------+     +---------+
   |IPv6-only|              |NAT64|       |  IPv4 SIP  |     |IPv4-only|
   | SIP UA  |              |     |       |Proxy Server|     | SIP UA  |
   +---------+              +-----+       +------------+     +---------+
       | (a) PCP MAP REQUEST   |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       |     PREFIX64_OPTION   |                |                 |
       |======================>|                |                 |
       | (b) PCP MAP RESPONSE  |                |                 |
       |PORT_RESERVATION_OPTION|                |                 |
       | PREFIX64_OPTION =     |                |                 |
       |     2001:db8:122::/48 |                |                 |
       |<======================|                |                 |
       |  (3) SIP INVITE       | (2) SIP INVITE |  (1) SIP INVITE |
       |<======================|<===============|<================|
       |   (4) SIP 200 OK      | (5) SIP 200 OK |  (6) SIP 200 OK |
       |======================>|===============>|================>|
       |     (9) SIP ACK       |  (8) SIP ACK   |    (7) SIP ACK  |
       |<======================|<===============|<================|
       |                       |                |                 |
       |<======IPv6 RTP=======>|<============IPv4 RTP============>|
       |<===== IPv6 RTCP======>|<============IPv4 RTCP===========>|
       |                       |                                  |


          Figure 4: Example of IPv4 to IPv6 SIP initiated Session


6.  IANA Considerations

   This document requests a new PCP option:
      PREFIX64


7.  Security Considerations

   This document does not introduce any security issue in addition to
   what is taken into account in [I-D.ietf-pcp-base].


8.  Acknowledgements

   Many thanks to S. Perreault , R. Tirumaleswar, T. Tsou, D. Wing, J.



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   Zhao and R. Penno for the comments and suggestions.


9.  References

9.1.  Normative References

   [I-D.ietf-pcp-base]
              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)",
              draft-ietf-pcp-base-29 (work in progress), November 2012.

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

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

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

   [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.

9.2.  Informative References

   [I-D.boucadair-pcp-rtp-rtcp]
              Boucadair, M. and S. Sivakumar, "Reserving N and N+1 Ports
              with PCP", draft-boucadair-pcp-rtp-rtcp-05 (work in
              progress), October 2012.












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Author's Address

   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Email: mohamed.boucadair@orange.com











































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