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INTERNET-DRAFT                                      D. Meyer
draft-ietf-grow-collection-communities-01.txt
Category                               Best Current Practice
Expires: June 2004                             December 2003


                  BGP Communities for Data Collection
            <draft-ietf-grow-collection-communities-01.txt>



Status of this Document

   This document is an Internet-Draft and is in full conformance with
   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
   other groups may also distribute working documents as Internet-
   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/ietf/1id-abstracts.txt

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

   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 RFC 2119 [RFC 2119].


   This document is a product of the GROW WG.  Comments should be
   addressed to the authors, or the mailing list at
   grow@lists.uoregon.edu.

Copyright Notice

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







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                                Abstract


   BGP communities (RFC 1997) are used by service providers for many
   purposes, including tagging of customer, peer, and geographically
   originated routes.  Such tagging is typically used to control the
   scope of redistribution of routes within a provider's network, and to
   its peers and customers. With the advent of large scale BGP data
   collection (and associated research), it has become clear that the
   information carried in such communities is essential for a deeper
   understanding of the global routing system. This document defines
   standard (outbound) communities and their encodings for export to BGP
   route collectors.






































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                           Table of Contents


   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2. Definitions. . . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.1. Peers and Peering . . . . . . . . . . . . . . . . . . . . .   5
    2.2. Customer Routes . . . . . . . . . . . . . . . . . . . . . .   5
    2.3. Peer Routes . . . . . . . . . . . . . . . . . . . . . . . .   5
    2.4. Internal Routes . . . . . . . . . . . . . . . . . . . . . .   5
    2.5. Internal More Specific Routes . . . . . . . . . . . . . . .   5
    2.6. Special Purpose Routes. . . . . . . . . . . . . . . . . . .   6
    2.7. Upstream Routes . . . . . . . . . . . . . . . . . . . . . .   6
    2.8. National Routes . . . . . . . . . . . . . . . . . . . . . .   6
    2.9. Regional Routes . . . . . . . . . . . . . . . . . . . . . .   6
   3. RFC 1997 Community Encoding and Values . . . . . . . . . . . .   7
    3.1. Community Values for BGP Data Collection. . . . . . . . . .   7
   4. Extended Communities . . . . . . . . . . . . . . . . . . . . .   9
    4.1. Four-octet AS specific extended communities . . . . . . . .  10
   5. Intellectual Property. . . . . . . . . . . . . . . . . . . . .  10
   6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .  11
   7. Security Considerations. . . . . . . . . . . . . . . . . . . .  12
    7.1. Total Path Attribute Length . . . . . . . . . . . . . . . .  12
   8. IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  12
   9. References . . . . . . . . . . . . . . . . . . . . . . . . . .  13
    9.1. Normative References. . . . . . . . . . . . . . . . . . . .  13
    9.2. Informative References. . . . . . . . . . . . . . . . . . .  13
   10. Author's Addresses. . . . . . . . . . . . . . . . . . . . . .  14
   11. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  14























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1.  Introduction


   BGP communities [RFC1997] are used by service providers for many
   purposes, including tagging of customer, peer, and geographically
   originated routes.  Such tagging is typically used to control the
   scope of redistribution of routes within a providers network, and to
   it's customers and peers. Communities are also used for a wide
   variety of other applications, such as allowing customers to set
   attributes such as LOCAL_PREF [RFC1771] by sending appropriate
   communities to their service provider. Other applications include
   signaling various types of VPNs (e.g., VPLS [VPLS]), and carrying
   link bandwidth for traffic engineering applications [EXTCOMM].

   With the advent of large scale BGP data collection [RIS,ROUTEVIEWS]
   (and associated research), it has become clear that the geographical
   and topological information, as well as the relationship the provider
   has to the source of a route (e.g., transit, peer, or customer),
   carried in such communities is essential for a deeper understanding
   of the global routing system. This document defines standard
   communities for export to BGP route collectors. These communities are
   not (necessarily) intended for internal use by service providers.
   Rather, they are meant to mirror the information that many service
   providers carry today, and to be a standardized representation of
   that information.

   The remainder of this document is organized as follows. Section 2
   provides both the definition of terms used as well as the semantics
   of the communities used for BGP data collection, and section 3
   defines the corresponding encodings for RFC 1997 [RFC1997]
   communities. Finally, section 4 defines the encodings for use with
   extended communities [EXTCOMM].



2.  Definitions


   In this section, we define the terms used and the categories of
   routes that may be tagged with communities. This tagging is often
   referred to coloring, and we refer to a route's "color" as its
   community value. The categories defined here are loosely modeled on
   those described in [WANG] and [HUSTON].








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2.1.  Peers and Peering


   Consider two network service providers, A and B. Service providers A
   and B are defined to be peers when (i). A and B exchange routes via
   BGP, and (ii). traffic exchange between A and B is settlement-free.
   This arrangement is also typically known as "peering". Peers
   typically exchange only their respective customer routes (see
   "Customer Routes" below), and hence exchange only their respective
   customer traffic. See [HUSTON] for a more in-depth discussion of the
   business models surrounding peers and peering.



2.2.  Customer Routes


   Customer routes are those routes which are heard from a customer via
   BGP and are propagated to peers and other customers. Note that a
   customer can be an enterprise or another network service provider.
   These routes are sometimes called client routes [HUSTON].



2.3.  Peer Routes


   Peer routes are those routes heard from peers via BGP, and not
   propagated to other peers. In particular, these routes are only
   propagated to the service provider's customers.



2.4.  Internal Routes


   Internal routes are those routes that a service provider originates
   and passes to its peers and customers. These routes are frequently
   taken out of the address space allocated to a provider.



2.5.  Internal More Specific Routes


   Internal more specific routes are those routes which are frequently
   used for circuit balancing purposes, IGP route reduction, and also
   may correspond to customer services which are not visible outside the



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   service provider's network. Internal more specific routes are not
   exported to any external peer.



2.6.  Special Purpose Routes


   Special purpose routes are those routes which do not fall into any of
   the other classes described here. In those cases in which such routes
   need to be distinguished, a service provider may color such routes
   with a unique value. Examples of special purpose routes include
   anycast routes, and routes for overlay networks.



2.7.  Upstream Routes


   Upstream routes are typically learned from upstream service provider
   as part of a transit service contract executed with the upstream
   provider.




2.8.  National Routes


   These are route sets that are sourced from and/or received within a
   particular country.



2.9.  Regional Routes


   Several global backbones implement regional policy based on their
   deployed footprint, and on strategic and business imperatives.
   Service providers often have settlement free interconnections with an
   AS in one region, and that same AS is a customer in another region.
   This mandates use of regional routing, including community attributes
   set by the network in question to allow easy discrimination among
   regional routes. For example, service providers may treat a route set
   received from another service provider in Europe differently than the
   same route set received in North America, as it is common practice to
   sell transit in one region while peering in the other.




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3.  RFC 1997 Community Encoding and Values


   In this section we provide standardized RFC 1997 [RFC1997] community
   values for the categories described above. RFC 1997 communities
   encoded as BGP Type Code 8, and are treated as 32 bit values ranging
   from 0x0000000 through 0xFFFFFFF. The values 0x0000000 through
   0x0000FFFF and 0xFFFF0000 through 0xFFFFFFFF are reserved.

   The best current practice among service providers is to use the high
   order two octets to represent the providers AS number, and the low
   order two octets to represent the classification of the route, as
   depicted below:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            <AS>               |         <Value>               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where <AS> 16 bit AS number, and <Value> is the encoding of the
   value. For example, the encoding 0x2A7C029A would represent the AS
   10876 with value 666.



3.1.  Community Values for BGP Data Collection


   In this section we define the RFC 1997 community encoding for the
   route types described above for use in BGP data collection. It is
   anticipated that a service provider's internal community values will
   be converted to these standard values for output to a route
   collector.

   This document follows the best current practice of using the basic
   format <AS>:<Value>. The values for the route categories are
   described in the following table:













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       Category                                 Value
     ===============================================================
     Reserved                                 <AS>:0000000000000000
     Customer Routes                          <AS>:0000000000000001
     Peer Routes                              <AS>:0000000000000010
     Internal Routes                          <AS>:0000000000000011
     Internal More Specific Routes            <AS>:0000000000000100
     Special Purpose Routes                   <AS>:0000000000000101
     Upstream Routes                          <AS>:0000000000000110
     Reserved                                 <AS>:0000000000000110-
                                              <AS>:0000111111111111
     National and Regional Routes             <AS>:0001000000000000-
                                              <AS>:1111111111111111
      Africa (AF)                              <AS>:0001<X><CC>
      Oceania (OC)                             <AS>:0010<X><CC>
      Asia (AS)                                <AS>:0011<X><CC>
      Antarctica (AQ)                          <AS>:0100<X><CC>
      Europe (EU)                              <AS>:0101<X><CC>
      Latin America/Caribbean islands (LAC)    <AS>:0110<X><CC>
      North America (NA)                       <AS>:0111<X><CC>
      Reserved                                 <AS>:1000000000000000-
                                               <AS>:1111111111111111

   In the above table,

    <AS> is the 16-bit AS
    <R>  is the 5-bit Region
    <X>  is 1-bit satellite link indication (1 if satellite link, 0 otherwise)
    <CC> is the 10-bit ISO-3166-2 country code

   that is:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            <AS>               |   <R>   |X|        <CC>       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For example, the encoding for a national route over a terrestrial
   link in AS 10876 from the Fiji Islands would be:

    <AS>  = 10876 = 0x2A7B
    <R>   = OC = 0010
    <X>   = 0x0
    <CC>  = Fiji Islands Country Code = 242 = 0011110010

   so that the low order 16 bits look like 001000011110010 = 0x10F2.



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      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           0x2A7C              |           0x10F2              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that a configuration language might have allow the specification
   of this community as 10876:4338 (0x1F2 == 4338 decimal).

   Finally, note that these categories are not intended to be mutually
   exclusive, and multiple communities can be attached where
   appropriate.



4.  Extended Communities


   In some cases, the encoding described in section 3.1 may clash with a
   service provider's existing community assignments.  Extended
   communities [EXTCOMM] provide a convenient mechanism that can be used
   to avoid such clashes.

   The Extended Communities Attribute is a transitive optional BGP
   attribute with the Type Code 16, and consists of a set of extended
   communities of the following format:

      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 high    |  Type low(*)  |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+          Value                |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For purposes of BGP data collection, we encode the communities
   described in section 3.1 using the two-octet AS specific extended
   community type, which has the following format:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      0x00     |   Sub-Type    |    Global Administrator       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Local Administrator                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   The two-octet AS specific extended community attribute encodes the
   service provider's two octet Autonomous System number assigned by
   IANA in the Global Administrator field, and the Local Administrator
   field may encode any information.

   This document assigns Sub-Type 0x05 for BGP data collection, and
   specifies that the <Value> field, as defined in section 3.1, is
   carried in the low order octets of the Local Administrator field. The
   two high order octets of the Local Administrator field are reserved,
   and are set to 0x00 when sending and ignored upon receipt.

   For example, the extended community encoding for 10876:4338
   (representing a terrestrial national route in AS 10876 from the Fiji
   Islands) would be:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      0x00     |      0x05     |           0x2A7C              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      0x00     |      0x00     |           0x10F2              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



4.1.  Four-octet AS specific extended communities


   The four-octet AS specific extended community is encoded as follows:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      0x02     |    0x05       |    Global Administrator       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Global Administrator (cont.)  |           0x10F2              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   In this case, the 4 octet Global Administrator sub-field contains a
   4-octets Autonomous System number assigned by the IANA.


5.  Intellectual Property


   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in



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   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11 [RFC2028].
   Copies of claims of rights made available for publication and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementors or users of this
   specification can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.



6.  Acknowledgments


   The community encoding described in this document germinated from an
   interesting suggestion from Akira Kato at WIDE. In particular, the
   idea would be to use the collection community values to select paths
   that would result in (hopefully) more efficient access to various
   services. For example, in the case of RFC 3258 [RFC3258] based DNS
   anycast service, BGP routers may see multiple paths to the same
   prefix, and others might be coming from the same origin with
   different paths, but others might be from different region/country
   (with the same origin AS).

   Joe Abley, Randy Bush, Sean Donelan, Xenofontas Dimitropoulos, Vijay
   Gill, John Heasley, Geoff Huston, Steve Huter, Olivier Marce, Ryan
   McDowell, Rob Rockell, Rob Thomas, and Patrick Verkaik all made many
   insightful comments on early versions of this draft. Henk Uijterwaal
   suggested the use of the ISO-3166-2 country codes.














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7.  Security Considerations


   While this document introduces no additional security considerations
   into the BGP protocol, the information contained in the communities
   defined in this document may in some cases reveal network structure
   that was not previously visible outside the provider's network. As a
   result, care should be taken when exporting such communities to route
   collectors. Finally, routes exported to a route collector SHOULD also
   be tagged with the NO_EXPORT community (0xFFFFFF01).



7.1.  Total Path Attribute Length


   The communities described in this document are intended for use on
   egress to a route collector. Hence an operator may choose to
   overwrite its internal communities with the values specified in this
   document when exporting routes to a route collector. However,
   operators should in general ensure that the behavior of their BGP
   implementation is well-defined when the addition of an attribute
   causes a PDU to exceed 4096 octets. For example, since it is common
   practice to use community attributes to implement policy (among other
   functionality such as allowing customers to set attributes such as
   LOCAL_PREF), the behavior of an implementation when the attribute
   space overflows is crucial. Among other behaviors, an implementation
   might usurp the intended attribute data or otherwise cause
   indeterminate failures. These behaviors can result in unanticipated
   community attribute sets, and hence result in unintended policy
   implications.



8.  IANA Considerations


   This document assigns a new Sub-Type for the AS specific extended
   community type. In particular, the IANA should assign Sub-type 0x05,
   using the "First Come First Served" policy defined in RFC 2434
   [RFC2434], for the Sub-Type defined in Section 4. This corresponds to
   a Type Field value of 0x0005.









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9.  References

9.1.  Normative References

   [EXTCOMM]       Sangali, S., D. Tappan and Y. Rekhter, "BGP
                   Extended Communities Attribute",
                   draft-ietf-idr-bgp-ext-communities-06.txt,
                   Work in Progress.

   [HOUSTON]       Huston, G., "Interconnection, Peering, and
                   Settlements",
                   http://www.isoc.org/inet99/proceedings/1e/1e_1.htm

   [ISO-3166-2]    http://www.iso.org/iso/en/prods-services/iso3166ma/index.html

   [RIS]           "Routing Information Service", http://www.ripe.net/ris

   [RIS-ISO-3166]  ftp://ftp.ripe.net/iso3166-countrycodes.txt

   [ROUTEVIEWS]    "The Routeviews Project", http://www.routeviews.org

   [RFC1771]       Rekhter, Y., and T. Li (Editors), "A Border
                   Gateway Protocol (BGP-4)",  RFC 1771, March,
                   1995.

   [RFC1997]       Chandra, R. and P. Traina, "BGP Communities
                   Attribute", RFC 1997, August, 1996.

   [VLPS]          Kompella, K., et. al., "Virtual Private LAN
                   Service", draft-ietf-l2vpn-vpls-bgp-00.txt,
                   Work in Progress.

   [WANG]          Wang, F. and L. Gao, "Inferring and Characterizing
                   Internet Routing Policies", ACM SIGCOMM Internet
                   Measurement Conference 2003.



9.2.  Informative References



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

   [RFC2026]       Bradner, S., "The Internet Standards Process --
                   Revision 3", RFC 2026/BCP 9, October, 1996.



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   [RFC2028]       Hovey, R. and S. Bradner, "The Organizations
                   Involved in the IETF Standards Process", RFC
                   2028/BCP 11, October, 1996.

   [RFC2434]       Narten, T., and H. Alvestrand, "Guidelines for
                   Writing an IANA Considerations Section in RFCs",
                   RFC 2434/BCP 26, October 1998.

   [RFC3258]       Hardie, T., "Distributing Authoritative Name
                   Servers via Shared Unicast Addresses", RFC 3258,
                   April, 2002.


10.  Author's Addresses


   D. Meyer

   Email: dmm@1-4-5.net


11.  Full Copyright Statement

   Copyright (C) The Internet Society (2003). 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 Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.



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