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RFC 3572 - Internet Protocol Version 6 over MAPOS (Multiple Acce


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Network Working Group                                           T. Ogura
Request for Comments: 3572                                   M. Maruyama
Category: Informational                      NTT Network Innovation Labs
                                                              T. Yoshida
                                                      Werk Mikro Systems
                                                               July 2003

                Internet Protocol Version 6 over MAPOS
               (Multiple Access Protocol Over SONET/SDH)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

IESG Note

   This memo documents a way of carrying IPv6 packets over MAPOS
   networks.  This document is NOT the product of an IETF working group
   nor is it a standards track document.  It has not necessarily
   benefited from the widespread and in-depth community review that
   standards track documents receive.

Abstract

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

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Frame Format for Encapsulating IPv6 Datagrams. . . . . . . . .  3
       2.1.  Frame Format . . . . . . . . . . . . . . . . . . . . . .  3
       2.2.  Maximum Transmission Unit (MTU). . . . . . . . . . . . .  3
       2.3.  Destination Address Mapping. . . . . . . . . . . . . . .  4
             2.3.1.  Unicast. . . . . . . . . . . . . . . . . . . . .  4
            2.3.2.  Multicast . . . . . . . . . . . . . . . . . . . .  4
   3.  Interface Identifier . . . . . . . . . . . . . . . . . . . . .  6
   4.  Duplicate Address Detection. . . . . . . . . . . . . . . . . .  8
   5.  Source/Target Link-layer Address Option. . . . . . . . . . . .  9
   6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 10
       6.1.  Issues concerning Link-layer Addresses . . . . . . . . . 10
             6.1.1.  Protection against fraudulent reception
                     of traffic . . . . . . . . . . . . . . . . . . . 10
             6.1.2.  Protection against improper traffic. . . . . . . 11
       6.2.  Uniqueness of Interface Identifiers. . . . . . . . . . . 11
   7.  References. . . .  . . . . . . . . . . . . . . . . . . . . . . 12
   8.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
   9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14

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 (High
   Level Data Link Control) 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 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 HDLC
   address.  In MAPOS 16, the address field is extended to 16 bits, and
   the control field of 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 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 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.

   +----------+----------+----------+----------+
   |          |          | 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 [1][2].  The default
   maximum transmission unit (MTU) is 65,280 octets.

   However, the MTU 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 HDLC
   address that has been assigned via NSP (Node Switch Protocol) [6] to
   the MAPOS interface, which has the IPv6 unicast destination address.

   In order to determine the destination HDLC address that corresponds
   to an IPv6 unicast 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.

   MAPOS version 1:

   The address field of the MAPOS version 1 frame header contains an 8-
   bit-wide destination HDLC 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 a 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 frame header
   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 frame header contains the 16-bit-
   wide destination HDLC address [2].  The LSB of the first octet must
   always be 0 to indicate the continuation of this field, and the LSB
   of the second octet must always be 1 to indicate the end of this
   field.  The MSB of the first octet is used to indicate whether the
   frame is a unicast or a multicast frame.

   In the case of an IPv6 multicast, the MSB of the first octet is 1 to
   indicate that the frame is multicast.  As described above, the LSB of
   the first octet is 0 and the LSB of the second octet is 1.  The other
   13 bits of the address field must contain the lowest-order 13 bits of
   the IPv6 multicast address.  Figure 3 shows the address field of the
   MAPOS 16 frame header 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 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 interface identifiers from HDLC addresses of MAPOS
   interfaces is undesirable for the following reasons.

   1. When a node is connected to a frame switch, an HDLC address is
      assigned to the interface of the node from the frame switch via
      NSP [6].  (In the remainder of this document, the term "MAPOS
      address" is used to refer to the address.)  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 environment
      separated by IP routers.  Therefore, the uniqueness of a MAPOS
      address is guaranteed only within a MAPOS multi-switch
      environment.

      Furthermore, if an 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
      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 built-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 an 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 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:

   MSB                                                               LSB
   |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.

   MSB                                                               LSB
   |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 octets, 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:

   MSB                                              LSB
   |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.

   MSB                                                               LSB
   |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 a MAPOS interface.  The assignment is not completed
   until the adjacent frame switch, or adjacent node in the case of a
   point-to-point connection between two nodes, has delivered the MAPOS
   address to the interface via NSP [6].  Until then, no data
   transmission can be performed on the interface.  Thus, a node must

   conduct duplicate address detection [11] on all unicast addresses of
   MAPOS interfaces 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 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).

   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

   In MAPOS, a link-layer address (MAPOS address) is assigned to a
   network interface by a frame switch via NSP; unlike other link-layer
   protocols such as Ethernet that use a built-in address on a network
   interface.  Security considerations derived from this are described
   in 6.1 and 6.2.  Because there is no link-layer security in MAPOS,
   the same security considerations as those of other link-layer
   protocols would be applied to other points.

6.1.  Issues concerning Link-layer Addresses

6.1.1.  Protection against fraudulent reception of traffic

   In MAPOS, a MAPOS address is assigned by a frame switch, and it
   consists of the switch number and the port number of the switch to
   which the network interface is connected.  (In the case of a point-
   to-point connection between two nodes, a fixed address is assigned to
   their network interfaces.)  This brings the following advantages.

   1. The value of the MAPOS address of a MAPOS network interface
      indicates the location of the interface in the MAPOS network.  In
      other words, the value itself of the destination address of a
      MAPOS frame defines the actual location of the network interface
      to which the frame should be finally delivered.  Therefore, as
      long as MAPOS addresses of network interfaces of nodes that have

      been connected to the network through proper administrative
      process are held and frames are delivered only to those addresses,
      other nodes cannot receive frames unless their network interfaces
      are connected to the same ports of frame switches as those to
      which network interfaces of properly administered nodes are
      connected. This makes fraudulent reception of traffic difficult.

   2. In the case where MAPOS addresses are not administered as
      mentioned above, it is possible that a malicious node could hijack
      traffic by spoofing its IPv6 address in a response to an IPv6
      Neighbor Discovery.  Even in this case, the node must advertise
      the true MAPOS address of its network interface in the response so
      that it can receive successive frames.  This makes it easy to
      pinpoint the location of the host.

6.1.2.  Protection against improper traffic

   A MAPOS frame does not have a field for including its sender's
   address.  Therefore, in the case where a node sends one-way improper
   traffic maliciously or accidentally, there is no way to obtain the
   sender's MAPOS address from the traffic and this leads to difficulty
   in identifying the node (because source IP addresses might be
   forged).

   An effective way to alleviate the difficulty is to moderate the size
   of MAPOS multi-switch environment [6].  A common approach is to
   separate it using IP routers.  This makes it easy to identify the
   node sending improper traffic within the multi-switch environment.
   To secure the environment against improper traffic from outside it,
   boundary IP routers need to block it using packet filtering based on
   IP layer information.

6.2.  Uniqueness of Interface Identifiers

   Global uniqueness of a MAPOS address is not guaranteed, and a MAPOS
   address is not a built-in address but can be changed without
   performing a system re-start if an implementation ensures that the
   link between the network 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
   network interfaces other than MAPOS that have IEEE global identifier
   based addresses has great importance in creating interface
   identifiers.  However, it may be common for there to be no such
   interfaces on a node, so 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.

   [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., Ed., "PPP in HDLC-like Framing", STD 51, 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, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

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

   [9]  Haskin, D. 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

   EMail: ogura@core.ecl.net

   Mitsuru Maruyama
   NTT Network Innovation Laboratories
   3-9-11, Midori-cho
   Musashino-shi
   Tokyo 180-8585, Japan

   EMail: mitsuru@core.ecl.net

   Toshiaki Yoshida
   Werk Mikro Systems
   250-1, Mikajiri
   Kumagaya
   Saitama 360-0843, Japan

   EMail: yoshida@peta.arch.ecl.net

9.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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   The limited permissions granted above are perpetual and will not be
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   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

 

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