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Versions: (draft-despres-sam-scenarios) 00 01 02 03

Internet Engineering Task Force                               R. Despres
Internet-Draft                                        September 29, 2008
Intended status: Standards Track
Expires: April 2, 2009


   Stateless Address Mapping with A+P Extended IPv4 addressing (SAM)
                          draft-despres-sam-00

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on April 2, 2009.

Abstract

   Stateless Local Address Mapping (SAM) is a generic tool for global-
   address packets to traverse transit domains where routing is
   performed in different address spaces.  To share IPv4 global
   addresses among several CPEs and/or hosts, port prefixes can be used
   as extensions of IPv4 global addresses.  In this space (IPv4E), a
   node having an n-bits IPv4E prefix with n>32 may only use or delegate
   ports having its port prefix of length /32-n.  Static Address Mappers
   can be placed in CPEs, in hosts, and/or in ISP Internet gateways.
   Applications include various IPv6 in IPv4 and IPv4E in IPv6
   encapsulations.





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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  SAM operation  . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Detailed processing rules  . . . . . . . . . . . . . . . . . .  7
   4.  Parameter values for ISATAP - 6to4 - 6rd . . . . . . . . . . . 12
   5.  Security considerations  . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  Informative References . . . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 15







































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1.  Introduction

   This document introduces Stateless Local Address Mapping (SAM), a
   generic tool for global-address packets to traverse transit domains
   where routings are in different address spaces.

   To statically share IPv4 global addresses among several CPEs and/or
   hosts, port prefixes are used as extensions of IPv4 global addresses.
   In this space (IPv4E), a node having an n-bits IPv4E prefix with n >
   32 may only use, or delegate, ports that start with its port prefix
   (the n - 32 low order bits of the IPv4E prefix).

   Mechanisms that have already been deployed for IPv6 packets to
   traverse IPv4 domains, in particular ISATAP, 6to4, and 6rd, are
   applications of SAM with specific parameter values.

   Section 2 describes the general architecture of SAM configurations,
   with all their possible parameters.  It also describes stateless
   mapping rules by which source and destination addresses of
   encapsulating packets are derived from those of packets to be
   tunneled.

   In Section 3, detailed packet processing, including anti-spoofing
   checks, is presented in pseudo-code.  Until some running code is
   written and tested, these algorithms are not claimed to be error
   proof.  They should therefore be considered as provisional.

   Section 4 indicates how ISATAP [RFC4214], 6to4 [RFC3056] and 6rd [I-D
   a]can be seen as specific applications of the general SAM model, with
   ad hoc parameter values.

   A companion document, [I-D b], presents several configurations where
   SAM is used to provide global IPv4 connectivity to customer sites
   that have only shared global IPv4 addresses in a more scalable way
   than with NATs in ISP infrastructures, and with possible end-to-end
   network transparency to IPv4 packets in favorable configurations.


2.  SAM operation

   As shown on Figure 1, SAM concerns packets that traverse a "transit
   domain" situated between a "core domain" and a number of "branch
   domains".

   Stateless Address Mappers (SAMs) are placed at borders between these
   domains.  Being stateless, they can be duplicated any number of times
   for load sharing.  Routes toward them are for this based on prefixes
   or on anycast addresses.



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   SAMs that are between branch domains and the transit domain are the
   "branch SAMs".  They can receive all their parameters in DHCP
   (possibly DHCPv6).  Those that are placed between the transit domain
   and the core domain are the "core SAMs".  Their parameter settings
   would typically be less automatic.

   The global Internet, in IPv4 and/or in IPv6, is accessible via the
   core domain, in which the address space is global.

   Global packets that are exchanged between hosts of the branch domain
   ("branch hosts"), and hosts accessible via the core domain ("core
   hosts") are encapsulated to traverse the transit domain.

   In each address family v (IPv4E or IPv6) in which a branch host X has
   an address, this address is structured as follows: Xv = Tv.Ivi.Sv,
   where Tv is the global prefix of the transit domain, Ivi is an infix
   that identifies the branch domain in the transit domain, and Sv is a
   suffix that identifies X in the branch domain.  The infix is the same
   for both address families.

   In an encapsulating packet of address family v that conveys a packet
   of family w toward or from branch host X, the address TXv that is
   derived from Xw, that of X, is structured as follows: TXv =
   Hv.Ivi.Sw.0/n, where Hv is a header that, in the transit domain, is
   at the beginning of all prefixes of branch domains, and where n is 32
   for IPv4 encapsulating packets and 128 for IPv6 encapsulating packets
   [Figure 2].  Thus, although IPv4E addresses have 32 + 16 = 48 bits,
   packets can traverse the transit domain without routers having to
   route on more than 32 bits.  (If k bits are necessary to identify
   branch domains, H4 should be taken equal to 32 - k.)

   The address that, in encapsulating packets, corresponds to that of a
   core host Y is the anycast address Cv of core SAM gateways of the
   transit domain.

   To be complete, the SAM model doesn't deal only with the transparent
   traversal of transit domains by global packets.  It deals also with
   packets of branch host that have private IPv4 addresses and must be
   encapsulated in IPv6 to reach a NAT at the transit domain - core
   domain border (a Carrier grade NAT or CGN).  The CGN can be IPv4 only
   as far as packet content is concerned, but they have to exercise
   their stateful address mapping with "composite" addresses at their
   transit side.  The composite address of a host X that has XS as its
   private address is a combination of this address and of the
   encapsulating address derived from it.  In the encapsulating packet
   of a CGN traversing packet, the core side address is the unicast IPv6
   address N6 of the CGN in the transit domain.




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                   BRANCH SAMs               CORE SAMs
               possible parameters:     possible parameters:
                 idem core SAM             T4, H4, C4
                + I4i, I6i, N4, N6         T6, H6, C6
                          |                     |
                          |                     V
                          |                     .----------------
                          V                     |  CORE domain
                          .---------------------|
                          |    TRANSIT domain   |
          ----------------|                     |
          BRANCH domain i |              C4 ---> <--- T4
                          |              C6 ---> <--- T6
                          |                     |
            0.0.0.0/0 ---> <--- B4i=H4.Ii       |
                0::/0 ---> <--- B6i=H6.Ii       |
                          |                     |
     <--- BRANCH host X   |                     |  CORE host Y --->
                          |  TRANSIT addresses  |
          addresses in    |   in encapsulating  |     addresses in
      encapsulated packets|        packets      | encapsulated packets
        <== [Xv, Yv] ==>  o  <== [TXv, Cv] ==>  o <== [Xv, Yv] ==>
        <== [Xv, X'v] ==> o  <== [TXv, TX'v] =. |
                          |                   | |
                          |                <==' |
                          |                     |
        <== [X4B, Y4] ==> o  <== [TX6, N6] ==>  |
                          |                     |
          ----------------|           N6 ---> [CGN] <--- T4b
                          |                     |
                          |                     |
                          '---------------------'
                                                |
                                                '----------------
          v    : address family 4 or 6 (for IPv4 or IPv6)
          Hv   : Header of all addresses in the transit domain
          Bvi  : prefix of Branch domain i in in the transit domain
                 (Bvi = Hvi.Ii)
          Ivi  : Infix of branch domain i (Ivi = Bvi - Hv)
          Cv   : anycast address of core domain gateways
          Nv   : unicast address of a CGN at the core domain border
          Tv   : prefix of the transit domain in the core domain
          TXv  : Transit address of branch host X

       ARCHITECTURE AND POSSIBLE PARAMETERS OF STATIC ADDRESS MAPPINGS

                                 Figure 1




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                         glob. v4 add.    port
                       <------32------><---16-->
                      +-----.---------+-.------.
                      |  T4 |     Ii    |  S4  |
                      +-----'---------+-'------'
                      <--g--><----i-----><--s-->
                      Branch host IPv4E address (X4)


     <-------------------------------128----------------------------->
     +-----------------.-----------.---------------------------------+
     |       T6        |     Ii    |               S6                |
     +-----------------'-----------'---------------------------------+
     <-------g---------><----i-----><---------------s---------------->
                       Branch host IPv6 address (X6)


                          <------32------>
                          +---.-----------+
                          |H4 |     Ii    |
                          +---'-----------+
                          <-h-><----i----->
             IPv4 TRANSIT address (TX4) for a Branch host


     <-------------------------------128----------------------------->
     +-------------.-----------.-------------------------------------+
     |      H6     |     Ii    |                  0                  |
     +-------------'-----------'-------------------------------------+
     <-----h-------><----i-----><--s-->
              IPv6 TRANSIT address (TX6) for a Branch host
                  the global address of which is IPv4


      <-------------------------------128----------------------------->
     +-------------.-----------.------.------------------------------+
     |      H6     |     Ii    |   Sv |             0                |
     +-------------'-----------'------'------------------------------+
     <-----h-------><----i-----><--s-->
              IPv6 TRANSIT address (TX6) for a Branch host
                  the global address of which is IPv6


             GLOBAL TO TRANSIT ADDRESS MAPPINGs FOR BRANCH HOST

                                 Figure 2





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3.  Detailed processing rules

   Processing rules that result from the above description are detailed
   in Figure 6 to Figure 8.  They include anti-spoofing tests whereby
   consistency between addresses of encapsulating packets and
   encapsulated packets are systematically verified.

   In the pseudo-code, A and B are prefixes with B contained at the
   beginning of A, A - B stands for what follows B in A. In other words,
   with he dot as concatenation operator, A = B.(A - B).  The pseudo-
   code notation is otherwise expected to be self explanatory.



           CASE X4 = G4..
           DO    CASE  Y4 NOT= G4..
                 DO    CASE  C4 NOT= nil
                       DO    TY4 <- C4
                             TX4 <- H4.(X4E-G4).0/32
                             Encapsulate 4/4
                       CASE  C4 = nil & C6 NOT= nil
                       DO    TY6 <- C6
                             TX6 <- H6.(X4E-G4).0/128
                             Encapsulate 4/6
                       CASE  C4=nil & C6=nil & N4 NOT= nil
                       DO    TY4 <- N4
                             TX4 <- H4.(X4E-G4).0/32
                             Encapsulate 4/4
                       CASE  C4=nil & C6=nil & N4=nil
                             & N6 NOT= nil
                       DO    TY6 <- N6
                             TX6 <- H6.(X4E-G4).0/128
                             Encapsulate 6/4
                 CASE  Y4 = G4..
                 DO    CASE  H4 NOT= nil
                       DO    TY4 <- H4.(Y4E-G4).0/32
                             TX4 <- H4.(S4E-G4).0/32
                             Encapsulate 4/4
                       CASE  H4 = nil & H6 NOT= nil
                       DO    TY6 <- Y6.(Y4E-G4).0/128
                             TX6 <- H6.(X4E-G4).0/128
                             Encapsulate 4/6
           CASE  X4 NOT= G4..
           DO    Discard packet

             BRANCH-SAM PROCESSING OF AN IPV4E CORE-BOUND PACKET

                                 Figure 3



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            CASE X6 = G6..
                  CASE  Y6 NOT= G6::
                  DO    CASE  H4 NOT= nil
                        DO    TY4 <- C4
                              TX4 <- H4.(X6-G6).0/32
                              Encapsulate 6/4
                        CASE  H4 = nil & H6 NOT= nil
                        DO    TY6 <- C6
                              TX6 <- H6.(X6-G6).0/128
                              Encapsulate 6/6
                        CASE  C4=nil & C6=nil & N4 NOT= nil
                        DO    TY4 <- N4
                              TX4 <- H4.(X6-G6).0/32
                              Encapsulate 4/4
                        CASE  C4=nil & C6=nil & N4=nil
                              & N6 NOT= nil
                        DO    TY6 <- N6
                              TX6 <- H6.(X6-G6).0/128
                              Encapsulate 6/4
                  CASE  Y6 = G6..
                  DO    CASE  H4 NOT= nil
                        DO    TY4 <- H4.(Y6-G6).0/32
                              TX4 <- H4.(X6-G6).0/32
                              Encapsulate 6/4
                        CASE  H4 = nil & H6 NOT= nil
                        DO    TY6 <- Y6.(Y6-G6).0/128
                              TX6 <- H6.(X6-G6).0/128
                              Encapsulate 6/6
            CASE  X6 NOT= G6..
            DO    Discard packet

              BRANCH-SAM PROCESSING OF AN IPV6 CORE-BOUND PACKET

                                 Figure 4

















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           CASE Encapsulating packet is v4
                 CASE  Encapsulated packet is v4
                 DO    Decapsulate 4/4, getting X4 and Y4
                       IF    X4=G4.. & TX4 =  H4.(X4-G4).0/32
                             & [TY4=C4 OR TY4=N4
                                OR (Y4 = G4.. & TY4=H4.(Y4-G4)..]
                       DO    Forward decapsulated packet
                       ELSE  Discard packet
                 CASE  Encapsulated packet is v6
                 DO    Decapsulate 6/4, getting X4 and Y4
                       IF    X6=G6.. & TX4 =  H4.(X6-G6).0/32
                             & [TY4=C4 OR TY4=N4
                                OR (Y6 = G6.. & TY4=H4.(Y6-G6)..]
                       DO    Forward decapsulated packet
                       ELSE  Discard packet
           CASE Encapsulating packet is v6
                 CASE  Encapsulated packet is v4
                 DO    Decapsulate 4/6, getting X4 and Y4
                       IF    X4=G4.. & TX6 =  H6.(X4-G4).0/128
                             & [TY6=C6 OR TY6=N6
                                OR (Y4 = G4.. & TY6=H6.(Y4-G4)..]
                       DO    Forward decapsulated packet
                       ELSE  Discard packet
                 CASE  Encapsulated packet is v6
                 DO    Decapsulate 6/6, getting X6 and Y6
                       IF    X6=G6.. & TX6 =  H6.(X6-G6).0/128
                             & [TY6=C6 OR TY6=N6
                                OR (Y6 = G6.. & TY6=H6.(Y6-G6)..]
                       DO    Forward decapsulated packet
                       ELSE  Discard packet

             BRANCH-SAM PROCESSING OF A BRANCH-BOUND PACKET

                                 Figure 5

















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            CASE  Encapsulating packet is v4
                  CASE  Encapsulated packet is v4
                  DO    Decapsulate 4/4, getting X4 and Y4
                        IF    X4 = G4.. & TX4 = H4.(X4-G4).0/32
                              & Y4 NOT= G4..
                        DO    Forward decapsulated packet
                        ELSE  Discard packet
                  CASE  Encapsulated packet is v6
                  DO    Decapsulate 6/4, getting X6 and Y6
                        IF    X6 = G6.. & TX4 = H4.(X6-G6).0/32
                              & Y4 NOT= G4..
                        DO    Forward decapsulated packet
                        ELSE  Discard packet
            CASE Encapsulating packet is v6
                  CASE  Encapsulated packet is v4
                  DO    Decapsulate 4/6, getting X4 and Y4
                        IF    X4 = G4.. & TX6 = H6.(X4-G4).0/128
                              & Y4 NOT= G4..
                        DO    Forward decapsulated packet
                        ELSE  Discard packet
                  CASE  Encapsulated packet is v6
                  DO    Decapsulate 6/6, getting X6 and Y6
                        IF    X6 = G6.. & TX6 = H6.(X6-G6).0/128
                              & [ Y6 NOT = G6..
                        DO    Forward decapsulated packet
                        ELSE  Discard packet

                CORE-SAM PROCESSING OF CORE-BOUND PACKET

                                 Figure 6





















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           CASE  Y4 NOT= G4..
           DO    CASE  C4 NOT= nil
                 DO    TY4 <- C4
                       TX4 <- H4.(X4E-G4).0/32
                       Encapsulate 4/4
                 CASE  C4 = nil & C6 NOT= nil
                 DO    TY6 <- C6
                       TX6 <- H6.(X4E-G4).0/128
                       Encapsulate 4/6
           CASE  Y4 = G4..
           DO    Discard packet

              CORE-SAM PROCESSING OF AN IPV4 BRANCH-BOUND PACKET

                                 Figure 7



           CASE  Y6 NOT= G6..
           DO    CASE  C4 NOT= nil
                 DO    TY4 <- C4
                       TX4 <- H4.(X6-G6).0/32
                       Encapsulate 6/4
                 CASE  C4 = nil & C6 NOT= nil
                 DO    TY6 <- C6
                       TX6 <- H6.(X6-G6).0/128
                       Encapsulate 6/6
           CASE  Y4 = G4..
           DO    Discard packet

              CORE-SAM PROCESSING OF AN IPV6 BRANCH-BOUND PACKET

                                 Figure 8


















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4.  Parameter values for ISATAP - 6to4 - 6rd

   ISATAP [RFC4214], 6to4 [RFC3056], and 6rd [I-D a], are techniques
   that provide IPv6 connectivity via various IPv4 domains.  They can be
   implemented as specific applications of the SAM architecture with the
   ad hoc parameter values shown in the following table.





   +----------------+---------------+---------------+-----------------+
   |                |     ISATAP    |     6to4      |      6rd        |
   +----------------+---------------+---------------+-----------------+
   | Branch domains |   DS hosts    |customer sites | customer sites  |
   +----------------+---------------+---------------+-----------------+
   | Transit domain |customer site  | global IPv4   |   ISP IPv4      |
   |                |               |   Internet *  | infrastructure  |
   +----------------+---------------+---------------+-----------------+
   |  Core domain   |   ISP IPv6    | global IPv6   |  global IPv6    |
   |                |infrastructure |   Internet    |    Internet     |
   +----------------+---------------+---------------+-----------------+
   |       T6       |Site v6 prefix |   2002::/16   | ISP v6 prefix **|
   +----------------+---------------+---------------+-----------------+
   |       H4       |  0.0.0.0/0    |  0.0.0.0/0    |   0.0.0.0/0     |
   +----------------+---------------+---------------+-----------------+
   |       C4       | CPE local Add.|  192.88.99.1  |  192.88.99.2 ***|
   +----------------+---------------+---------------+-----------------+
   |    Ii length   |      32       |      32       |       32        |
   +----------------+---------------+---------------+-----------------+

   *   For full connectivity between 6to4 sites, the 2002 prefix must be
       routed from the global IPv6 Internet to the global IPv4 Internet
   **  A /28 prefix in the Iliad-Free deployment (initially a /32)
   *** Value used in the Iliad-Free deployment. Any anycast address
       that is local to the ISP infrastructure can do.

          SAM PARAMETERS OF EXISTING ENCAPSULATIONS OF IPv6 IN IPv4

                                 Figure 9


5.  Security considerations

   With anti-spoofing checks in processing rules of Section 3, no
   security risk inherent to SAM has been identified.





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6.  IANA Considerations

   To automate parameter settings of branch SAMs, DHCP and DHCPv6 option
   codes will have to be assigned.


7.  Acknowledgements

   So far, the SAM design has essentially been worked out by the author,
   with various intermediate stages like the so called Address Borrowing
   Protocol and the Global Address Protocol, without any sponsoring or
   company contract, and without seeking intellectual property
   protection.  He therefore wishes to expresses its first
   acknowledgment to his wife: she accepted that traveling and other
   expenses be supported by the uni-personal enterprise of the author,
   the money of which cannot be distinguished from family money.

   One important and recent progress of the approach has been the
   recognition that, with the flexibility of DHCP, no new protocol would
   be necessary to automate SAM parameter settings.  Acknowledgment is
   due to Gabor Bajko and Teemu Savolainen for pointing it out at IETF
   72.


8.  Informative References

   [I-D a]    "IPv6 Rapid Deployment on IPv4 infrastructures (6rd) -
              Work in progress", September 2008.

   [I-D b]    "IPv4-IPv6 Coexistence Scenarios based on Stateless
              Address mapping - Work in progress", September 2008.

   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, February 2001.

   [RFC4214]  Templin, F., Gleeson, T., Talwar, M., and D. Thaler,
              "Intra-Site Automatic Tunnel Addressing Protocol
              (ISATAP)", RFC 4214, October 2005.













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Author's Address

   Remi Despres
   3 rue du President Wilson
   Levallois,
   France

   Email: remi.despres@free.fr











































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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
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