INTERNET-DRAFT                                                   T.Ogura
Expires: October 2002                                         M.Maruyama
                                            NTT Network Innovation Labs.
                                                               T.Yoshida
                                                      Werk Mikro Systems
                                                              April 2002


                        IP Version 6 over MAPOS
                    <draft-ogura-ipv6-mapos-00.txt>


Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   Distribution of this memo is unlimited.  Please send comments to the
   authors <ogura@core.ecl.net> <mitsuru@core.ecl.net> and
   <yoshida@tera.core.ecl.net>.

Abstract

   Multiple Access Protocol over SONET/SDH (MAPOS) is a high-speed link-
   layer protocol that provides multiple access capability over
   SONET/SDH.

   This document specifies the frame format for encapsulating an IPv6
   datagram in a MAPOS frame. It also specifies the method of forming
   IPv6 interface identifiers, the method of detecting duplicate
   addresses, and the format of the Source/Target Link-layer Addresses
   option field used in IPv6 neighbor discovery messages.



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1. Introduction

   Multiple Access Protocol over SONET/SDH (MAPOS) [1][2] is a high-
   speed link-layer protocol that provides multiple access capability
   over SONET/SDH. Its frame format is based on the HDLC-like framing
   [3] for PPP.  A component called a "Frame Switch" [1] allows multiple
   nodes (hosts and routers) to be connected together in a star topology
   to form a LAN. Using long-haul SONET/SDH links, the nodes on such a
   "SONET-LAN" can span over a wide geographical area.

   This document specifies the frame format for encapsulating an
   Internet Protocol version 6 (IPv6) [4] datagram in a  MAPOS frame,
   the method of forming IPv6 interface identifiers, the method of
   detecting duplicate addresses, and the format of the Source/Target
   Link-layer Addresses option field used in neighbor discovery messages
   such as Router Solicitation, Router Advertisement, Neighbor
   Solicitation, Neighbor Advertisement, and Redirect messages.

   In the remainder of this document, the term "MAPOS" is used unless
   the distinction between MAPOS version 1 [1] and MAPOS 16 [2] is
   required.

2. Frame Format for Encapsulating IPv6 Datagrams

2.1 Frame Format

   MAPOS uses the same HDLC-like framing as PPP-over-SONET, described in
   [3]. The MAPOS frame begins and ends with a flag sequence 01111110
   (0x7E), and the MAPOS frame header contains address, control, and
   protocol fields. The address field contains a destination MAPOS
   address. In MAPOS 16, the address field is extended to 16 bits, and
   the control field in MAPOS version 1 is omitted. The frame check
   sequence (FCS) field is 16 bits long by default, but a 32-bit FCS may
   be used optionally.  Details of the MAPOS HDLC frame format are
   described in [1][2].

   An IPv6 datagram is encapsulated in the MAPOS frame. In the case of
   encapsulating an IPv6 datagram, the protocol field for it must
   contain the value 0x0057 (hexadecimal). The IPv6 datagram is stored
   in the information field which follows immediately after the protocol
   field. That is, this field contains the IPv6 header followed
   immediately by the payload. Figure 1 shows the frame format. The
   fields are transmitted from left to right.








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        +----------+----------+----------+----------+
        |          |          | Control/ | Protocol |
        |   Flag   | Address  | Address  |  16 bits |
        | 01111110 |  8 bits  |  8 bits  | (0x0057) |
        +----------+----------+----------+----------+
           +-------------+------------+----------+-----------
           |             |            |          | Inter-frame
           | IPv6 header |    FCS     |   Flag   | fill or next
           | and payload | 16/32 bits | 01111110 | address
           +-------------+------------+----------+------------

                         Figure 1.  Frame format.


2.2 Maximum Transmission Unit (MTU)

   The length of the information field of the MAPOS frame may vary, but
   shall not exceed 65,280 (64K - 256) octets; the maximum transmission
   unit (MTU) of MAPOS is 65,280 octets [1][2].

   This size may be reduced by a Router Advertisement [5] containing an
   MTU option that specifies a smaller MTU, or by manual configuration
   of each node. If a Router Advertisement received on a MAPOS interface
   has an MTU option specifying an MTU larger than 65,280, or larger
   than a manually configured value, that MTU option may be logged for
   the system management but must be otherwise ignored.

2.3 Destination Address Mapping

   This section specifies the method of mapping an IPv6 destination
   address to the address field in the MAPOS frame header.

2.3.1 Unicast

   In unicasting, the address field of a MAPOS frame contains the MAPOS
   address that has been assigned via NSP [6] to the destination MAPOS
   interface, which has the IPv6 unicast destination address.

   In order to determine the destination MAPOS address that corresponds
   to an IPv6 destination address, the sender uses Link-layer Address
   Resolution described in [5].

2.3.2 Multicast

   Address resolution is never performed on IPv6 multicast addresses. An
   IPv6 multicast destination address is mapped to the address field in
   the MAPOS frame header as described below for MAPOS version 1 and
   MAPOS 16.



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   MAPOS version 1:

    The address field of the MAPOS version 1 frame header contains an
    8-bit-wide destination MAPOS address [1]. The least significant bit
    (LSB) of the field must always be 1 to indicate the end of the
    field. The most significant bit (MSB) is used to indicate whether
    the frame is a unicast or multicast frame.

    In the case of an IPv6 multicast, the MSB of the address field is
    1 to indicate that the frame is multicast. As described above,
    the LSB of the address field is 1. The other six bits of the
    address field must contain the lowest-order six bits of the IPv6
    multicast address. Figure 2 shows the address field of the MAPOS
    version 1 in the case of an IPv6 multicast, where D(1) through
    D(6) represent the lowest-order six bits of the IPv6 multicast
    address. Exceptions arise when these six bits are either all zeros
    or all ones. In these cases, they should be altered to the bit
    sequence 111110. That is, the address field should be 0xFD
    (hexadecimal).


                           MSB             LSB
                           +-+-+-+-+-+-+-+-+
                           | |           | |
                           |1|D(6) - D(1)|1|
                           | |           | |
                           +-+-+-+-+-+-+-+-+
                            ^             ^
                            |             |
                            |             EA bit (always 1)
                            1 (multicast)

        Figure 2. Address mapping in multicasting (MAPOS version 1).


   MAPOS 16:

    The address field of the MAPOS 16 header contains the 16-bit-wide
    destination MAPOS address [2]. The LSB of the first byte must
    always be 0 to indicate the continuation of this field, and the
    LSB of the second byte must always be 1 to indicate the end of
    this field. The MSB of the first byte is used to indicate whether
    the frame is a unicast or multicast frame.

    In the case of an IP multicast, the MSB of the first byte is 1 to
    indicate that the frame is multicast. As described above, the LSB
    of the first byte is 0 and the LSB of the second byte is 1. The
    other 13 bits of the address field must contain the lowest-order



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    13 bits of the IPv6 multicast address. Figure 3 shows the address
    field of the MAPOS 16 in the case of an IPv6 multicast, where D(1)
    through D(13) represent the lowest-order 13 bits of the IPv6
    multicast address. Exceptions arise when these 13 bits are either
    all zeros or all ones. In these cases, the address field should be
    0xFEFD (hexadecimal).


                   MSB                           LSB
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   | |           | |             | |
                   |1|D(13)-D(8) |0|  D(7)-D(1)  |1|
                   | |           | |             | |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    ^             ^               ^
                    |             |               |
                    |             |               +-- EA bit (always 1)
                    |             +-- EA bit (always 0)
                    1 (multicast)

            Figure 3. Address mapping in multicasting (MAPOS 16).


3. Interface Identifier

   This section specifies the method of forming the interface identifier
   [7].

   A MAPOS node that has one or more MAPOS interfaces must create one or
   more EUI-64 [8] based interface identifiers. Here, it should be noted
   that deriving the interface identifier from the MAPOS address is
   undesirable for the following reasons.

   1. If a node is connected to a frame switch, a MAPOS address is
      assigned to the interface of the node from the frame switch via
      NSP [6]. The value of the MAPOS address assigned to the interface
      depends on the combination of the switch number of the frame
      switch and the port number of the frame switch to which the
      interface is connected. The switch number is required to be
      unique only within a MAPOS multi-switch environment [6]; that is,
      there can be frame switches that have the same switch number in
      different MAPOS multi-switch environments separated by IP
      routers. Therefore, the uniqueness of a MAPOS address is
      guaranteed only within a MAPOS multi-switch environment.

      Furthermore, if implementation ensures that the link between the
      interface of the node and the port of the frame switch is
      hot-swappable, the port number of the frame switch or the frame



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      switch connected to the interface of the node can be changed, so
      the MAPOS address assigned to the interface can also be changed
      without performing a system re-start of the node.

      In short, the global uniqueness of a MAPOS address is not
      guaranteed, and a MAPOS address is not a build-in address but
      can be changed without performing a system re-start. Thus, if an
      interface identifier were derived from a MAPOS address, it could
      also be changed without a system re-start. This would not follow
      the recommendation in [7].

   2. In the case of a point-to-point connection between two nodes,
      the same MAPOS address is assigned to each interface.
      Specifically, in the case of MAPOS version 1, the assigned address
      is 0x03 [6], and in the case of MAPOS 16, the assigned address is
      0x0003 [2]. It is not easy to achieve link-locality of the
      interface identifier in a strict manner using the same Link-layer
      address.

   For the above reasons, nodes with MAPOS interfaces must not derive
   their interface identifiers from their MAPOS addresses.

   The following are methods of forming a tentative interface
   identifier in the order of preference. These are almost the same as
   the methods described in [9] except that a MAPOS address must not be
   used as a source of uniqueness when an IEEE global identifier is
   unavailable.

   1) If an IEEE global identifier (EUI-48 or EUI-64) is available
      anywhere on the node, it should be used to construct the tentative
      interface identifier due to its uniqueness. When extracting an
      IEEE global identifier from another device on the node, care
      should be taken to ensure that the extracted identifier is
      presented in canonical ordering [10].

      The only transformation from an EUI-64 identifier is to invert the
      "u" bit (universal/local bit in IEEE EUI-64 terminology). For
      example, for a globally unique EUI-64 identifier as shown in
      Figure 4:












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   most-significant                                    least-significant
   bit                                                               bit
   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
   +----------------+----------------+----------------+----------------+

               Figure 4. Globally unique EUI-64 identifier.


      where "c" are the bits of the assigned company_id, "0" is the
      value of the universal/local bit to indicate global scope, "g"
      is the group/individual bit, and "e" are the bits of the extension
      identifier,

      the IPv6 interface identifier would be as shown in Figure 5. The
      only change is inverting the value of the universal/local bit.


   most-significant                                    least-significant
   bit                                                               bit
   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc1gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
   +----------------+----------------+----------------+----------------+

    Figure 5. IPv6 interface identifier derived from a globally unique
   EUI-64 identifier.


      In the case of an EUI-48 identifier, it is first converted to the
      EUI-64 format by inserting two bytes, with hexadecimal values of
      0xFF and 0xFE, in the middle of the 48-bit MAC (between the
      company_id and extension-identifier portions of the EUI-48 value).

      For example, for a globally unique 48 bit EUI-48 identifier as
      shown in Figure 6:












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           most-significant                   least-significant
           bit                                              bit
           |0              1|1              3|3              4|
           |0              5|6              1|2              7|
           +----------------+----------------+----------------+
           |cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|
           +----------------+----------------+----------------+

                   Figure 6. Globally unique EUI-48 identifier.


      where "c" are the bits of the assigned company_id, "0" is the
      value of the universal/local bit to indicate global scope, "g"
      is the group/individual bit, and "e" are the bits of the
      extension identifier,

      the IPv6 interface identifier would be as shown in Figure 7.


   most-significant                                    least-significant
   bit                                                               bit
   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc1gcccccccc|cccccccc11111111|11111110eeeeeeee|eeeeeeeeeeeeeeee|
   +----------------+----------------+----------------+----------------+

    Figure 7. IPv6 interface identifier derived from a globally unique
   EUI-48 identifier.


   2) If an IEEE global identifier is not available, a different
      source of uniqueness should be used. Suggested sources of
      uniqueness include machine serial numbers, etc. MAPOS addresses
      must not be used.

      In this case, the "u" bit of the interface identifier must be set
      to 0.

   3) If a good source of uniqueness cannot be found, it is
      recommended that a random number be generated.  In this case the
      "u" bit of the interface identifier must be set to 0.

4. Duplicate Address Detection

   Immediately after the system start-up, the MAPOS address has not
   yet been assigned to an interface. The assignment is not completed
   until the adjacent frame switch, or adjacent node in the case of a



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   point-to-point connection between two nodes, has delivered the MAPOS
   address to the interface via NSP protocol [6]. Until then, no data
   transmission can be performed on the interface. Thus, a MAPOS node
   must conduct duplicate address detection [11] on all unicast
   addresses after the MAPOS address assignment has been completed by
   NSP.

5. Source/Target Link-layer Address Option

   As specified in [5], the Source/Target Link-layer Address option is
   one of the options included in Neighbor Discovery messages. In [5],
   the length of the Source/Target Link-layer Address option field is
   specified to be expressed in units of 8 octets. However, in the case
   of MAPOS, the length of the address field is 2 octets (MAPOS 16) or
   1 octet (MAPOS version 1)[1][2]. Thus, if the exact form of the
   address field is embedded in the Link-layer Address field of the
   Source/Target Link-layer Address option field, the total length of
   the option field is 4 octets (MAPOS 16) or 3 octets (MAPOS version
   1), both of which are shorter than 8 octets.

   For the above reason, in the case of MAPOS, the Link-layer Address
   field of the Source/Target Link-layer Address option must be
   extended with zeros in order to extend the length of the option field
   to 8 octets, and the Length field must be set to 1 as shown below.

   MAPOS version 1:


     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |    Length     |             All 0             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     All 0     |    Address    |             All 0             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Fields:

       Type:                   1 for Source link-layer address.
                               2 for Target link-layer address.

       Length:                 1 (in units of 8 octets).

       Address:                MAPOS version 1 8-bit address.

      Figure 8. Format of the Source/Target Link-layer Address option
   field (MAPOS version 1).




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   MAPOS 16:


     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |    Length     |             All 0             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Link-layer Address        |             All 0             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Fields:

       Type:                   1 for Source link-layer address.
                               2 for Target link-layer address.

       Length:                 1 (in units of 8 octets).

       Link-layer Address:     MAPOS 16 16-bit address.

      Figure 9. Format of the Source/Target Link-layer Address option
   field (MAPOS 16).


6. Security Considerations

   Global uniqueness of a MAPOS address is not guaranteed, and a MAPOS
   address is not a build-in address but can be changed without
   performing a system re-start if implementation ensures that the
   link between the interface of the node and the port of the frame
   switch is hot-swappable. Thus, an interface identifier must not be
   derived from a MAPOS address in order to ensure that the interface
   identifier is not changed without a system re-start.

   As a consequence, in IP Version 6 over MAPOS, the existence of
   interfaces other than MAPOS that have IEEE global identifier based
   addresses has great importance in creating interface identifiers.
   However, it may be common that there are no such interfaces on a
   node and a different source of uniqueness must be used. Therefore,
   sufficient care should be taken to prevent duplication of interface
   identifiers. At present, there is no protection against duplication
   through accident or forgery.

7. References


   [1]  Murakami, K. and M. Maruyama, "MAPOS - Multiple Access
        protocol over SONET/SDH, Version 1", RFC-2171, June 1997.



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   [2]  Murakami, K. and M. Maruyama, "MAPOS 16 - Multiple Access
        Protocol over SONET/SDH with 16 Bit Addressing", RFC-2175,
        June 1997.

   [3]  Simpson, W., editor, "PPP in HDLC-like Framing," RFC-1662,
        July 1994.

   [4]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
        (IPv6) Specification", RFC-2460, December 1998.

   [5]  Narten, T., Nordmark, E. and W. Simpson, "Neighbor
        Discovery for IP Version 6 (IPv6)", RFC-2461, December 1998.

   [6]  Murakami, K. and M. Maruyama, "A MAPOS version 1 Extension -
        Node Switch Protocol", RFC-2173, June 1997.

   [7]  Hinden, R. and S. Deering, "IP Version 6 Addressing
        Architecture", RFC-2373, July 1998.

   [8]  IEEE, "Guidelines of 64-bit Global Identifier (EUI-64)
        Registration Authority",
        http://standards.ieee.org/db/oui/tutorials/EUI64.html, March
        1997.

   [9]  Dimitry, H. and E. Allen, "IP Version 6 over PPP", RFC-2472,
        December 1998.

   [10] Narten, T. and C. Burton, "A Caution On The Canonical Ordering
        Of Link-Layer Addresses", RFC-2469, December 1998.

   [11] Thompson, S. and T. Narten, "IPv6 Stateless Address
        Autoconfiguration", RFC-2462, December 1998.

8. Authors' Addresses

   Tsuyoshi Ogura
   NTT Network Innovation Laboratories
   3-9-11, Midori-cho
   Musashino-shi
   Tokyo 180-8585, Japan
   E-mail: ogura@core.ecl.net

   Mitsuru Maruyama
   NTT Network Innovation Laboratories
   3-9-11, Midori-cho
   Musashino-shi
   Tokyo 180-8585, Japan
   E-mail: mitsuru@core.ecl.net



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   Toshiaki Yoshida
   Werk Mikro Systems
   250-1, Mikajiri
   Kumagaya
   Saitama 360-0843, Japan
   E-mail: yoshida@tera.core.ecl.net

9. Full Copyright Statement

   "Copyright (C) The Internet Society (2001).  All Rights Reserved.

   This document and translations of it may be copied and furnished
   to others, and derivative works that comment on or otherwise
   explain it or assist in its implementation may be prepared, copied,
   published and distributed, in whole or in part, without
   restriction of any kind, provided that the above copyright notice
   and this paragraph are included on all such copies and derivative
   works.  However, this document itself may not be modified in any
   way, such as by removing the copyright notice or references to the
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   process must be followed, or as required to translate it into
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   The limited permissions granted above are perpetual and will not
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   This document and the information contained herein is provided on
   an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
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   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

















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