Network Working Group                                       D. Farinacci
Intended status: Experimental                                C. Cantrell
Expires: September 8, 2019                                         Nexus
                                                           March 7, 2019

               A Decent LISP Mapping System (LISP-Decent)


   This draft describes how the LISP mapping system designed to be
   distributed for scale can also be decentralized for management and

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on September 8, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Push-Based Mapping System . . . . . . . . . . . . . . . . . .   5
     4.1.  Components of a Pushed-Based LISP-Decent xTR  . . . . . .   5
     4.2.  No LISP Protocol Changes  . . . . . . . . . . . . . . . .   6
     4.3.  Configuration and Authentication  . . . . . . . . . . . .   7
     4.4.  Core Seed-Group . . . . . . . . . . . . . . . . . . . . .   7
   5.  Pull-Based Mapping System . . . . . . . . . . . . . . . . . .   9
     5.1.  Components of a Pulled-Based LISP-Decent xTR  . . . . . .   9
     5.2.  Deployment Example  . . . . . . . . . . . . . . . . . . .  10
     5.3.  Management Considerations . . . . . . . . . . . . . . . .  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  13
   Appendix B.  Document Change Log  . . . . . . . . . . . . . . . .  14
     B.1.  Changes to draft-farinacci-lisp-decent-03 . . . . . . . .  14
     B.2.  Changes to draft-farinacci-lisp-decent-02 . . . . . . . .  14
     B.3.  Changes to draft-farinacci-lisp-decent-01 . . . . . . . .  14
     B.4.  Changes to draft-farinacci-lisp-decent-00 . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The LISP architecture and protocols [RFC6830] introduces two new
   numbering spaces, Endpoint Identifiers (EIDs) and Routing Locators
   (RLOCs) which is intended to provide overlay network functionality.
   To map from EID to a set or RLOCs, a control-plane mapping system are
   used [RFC6836] [RFC8111].  These mapping systems are distributed in
   nature in their deployment for scalability but are centrally managed
   by a third- party entity, namely a Mapping System Provider (MSP).
   The entities that use the mapping system, such as data-plane xTRs,
   depend on and trust the MSP.  They do not participate in the mapping
   system other than to register and retrieve information to/from the
   mapping system [RFC6833].

   This document introduces a Decentralized Mapping System (DMS) so the
   xTRs can participate in the mapping system as well as use it.  They
   can trust each other rather than rely on third-party infrastructure.
   The xTRs act as Map-Servers to maintain distributed state for scale
   and reducing attack surface.

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2.  Definition of Terms

   Mapping System Provider (MSP):  is an infrastructure service that
      deploys LISP Map-Resolvers and Map-Servers [RFC6833] and possibly
      ALT-nodes [RFC6836] or DDT-nodes [RFC8111].  The MSP can be
      managed by a separate organization other than the one that manages
      xTRs.  This model provides a business separation between who
      manages and is responsible for the control-plane versus who
      manages the data-plane overlay service.

   Decentralized Mapping System (DMS):  is a mapping system entity that
      is not third-party to the xTR nodes that use it.  The xTRs
      themselves are part of the mapping system.  The state of the
      mapping system is fully distributed, decentralized, and the trust
      relies on the xTRs that use and participate in their own mapping

   Pull-Based Mapping System:  the mapping system is pull-based meaning
      that xTRs will lookup and register mappings by algorithmic
      transformation to locate which Map-Resolvers and Map-Servers are
      used.  It is required that the lookup and registration uses a
      consistent algorithmic transformation function.  Map-Registers are
      pushed to specific Map-Servers.  Map-Requests are external lookups
      to Map-Resolvers on xTRs that do not participate in the mapping
      system and internal lookups when they do.

   Modulus Value:  this value is used in the Pull-Based Mapping System.
      It defines the number of map-server sets used for the mapping
      system.  The modulus value is used to produce a Name Index used
      for a DNS lookup.

   Name Index:  this index value <index> is used in the Pull-Based
      Mapping System.  For a mapping system that is configured with a
      map-server set of DNS names in the form of <name>, the
      name index is prepended to <name> to form the lookup name
      <index>.<name>  If the Modulus Value is 8, then the
      name indexes are 0 through 7.

   Hash Mask:  The Hash Mask is used in the Pull-Based Mapping System.
      It is a mask value with 1 bits left justified.  The mask is used
      to select what high-order bits of an EID-prefix is used in the
      hash function.

   Push-Based Mapping System:  the mapping system is push-based meaning
      that xTRs will push registrations via IP multicast to a group of
      Map-Servers and do local lookups acting as their own Map-

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   Replication List Entry (RLE):  is an RLOC-record format that contains
      a list of RLOCs that an ITR replicates multicast packets on a
      multicast overlay.  The RLE format is specified in [RFC8060].
      RLEs are used with the Pushed-Based mapping system.

   Group Address EID:  is an EID-record format that contains IPv4
      (, G) or IPv6 (0::/0, G) state.  This state is encoded as
      a Multicast Info Type LCAF specified in [RFC8060].  Members of a
      seed-group send Map-Registers for (, G) or (0::/0, G)
      with an RLOC-record that RLE encodes its RLOC address.  Details
      are specified in [RFC8378].

   Seed-Group:  is a set of Map-Servers joined to a multicast group for
      the Push-Based Mapping system or are mapped by DNS names in a
      Pull-Based Mapping System.  A core seed-group is used to bootstrap
      a set of LISP-Decent xTRs so they can learn about each other and
      use each other's mapping system service.  A seed-group can be
      pull-based to bootstrap a push-based mapping system.  That is, a
      set of DNS mapped map-servers can be used to join the mapping
      system's IP multicast group.

3.  Overview

   The clients of the Decentralized Mapping System (DMS) are also the
   providers of mapping state.  Clients are typically ETRs that Map-
   Register EID-to-RLOC mapping state to the mapping database system.
   ITRs are clients in that they send Map-Requests to the mapping
   database system to obtain EID-to-RLOC mappings that are cached for
   data-plane use.  When xTRs participate in a DMS, they are also acting
   as Map-Resolvers and Map-Servers using the protocol machinery defined
   in LISP control-plane specifications [RFC6833], [I-D.ietf-lisp-sec],
   and [I-D.ietf-lisp-ecdsa-auth].  The xTRs are not required to run the
   database mapping transport system protocols specified in [RFC6836] or

   This document will describe two decentralized and distributed mapping
   system mechanisms.  A Push-Based Mapping System uses IP multicast so
   xTRs can find each other by locally joining an IP multicast group.  A
   Pull-Based Mapping System uses DNS with an algorithmic transformation
   function so xTRs can find each other.

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4.  Push-Based Mapping System

   The xTRs are organized in a mapping-system group.  The group is
   identified by an IPv4 or IPv6 multicast group address or using a
   pull-based approach in described in Section 5.  When using multicast,
   the xTRs join the same multicast group and receive LISP control-plane
   messages addressed to the group.  Messages sent to the multicast
   group are distributed when the underlay network supports IP multicast
   [RFC6831] or is achieved with the overlay multicast mechanism
   described in [RFC8378].  When overlay multicast is used and LISP Map-
   Register messages are sent to the group, they are LISP data
   encapsulated with a instance-ID set to 0xffffff in the LISP header.
   The inner header of the encapsulated packet has the destination
   address set to the multicast group address and the outer header that
   is prepended has the destination address set to the RLOC of mapping
   system member.  The members of the mapping system group are kept in
   the LISP data-plane map-cache so packets for the group can be
   replicated to each member RLOC.

   All xTRs in a mapping system group will store the same registered
   mappings and maintain the state as Map-Servers normally do.  The
   members are not only receivers of the multicast group but also send
   packets to the group.

4.1.  Components of a Pushed-Based LISP-Decent xTR

   When an xTR is configured to be a LISP-Decent xTR (or PxTR
   [RFC6832]), it runs the ITR, ETR, Map-Resolver, and Map-Server LISP
   network functions.

   The following diagram shows 3 LISP-Decent xTRs joined to mapping
   system group  When the ETR function of xTR1 originates a
   Map-Register, it is sent to all xTRs (including itself) synchronizing
   all 3 Map-Servers in xTR1, xTR2, and xTR3.  The ITR function can
   populate its map-cache by sending a Map-Request locally to its Map-
   Resolver so it can replicate packets to each RLOC for EID

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 Map-Request    +--------------------+
(always local)  |  +-----+  +-----+  |
   +---------------| ITR |  | ETR |-------------+
   |            |  +-----+  +-----+  |          |
   |            |                    |          |    Map-Register to EID
   |            |      +-------+     |          | encapsulated to
   +------------------>| MR/MS |<---------------+  RLOCs xTR1, xTR2, and xTR3
                |      +-------+     |          |
                +--------------------+          |
                           |                                 |
                           |                                 |
                +----------v---------+            +----------v---------+
                |     +--------+     |            |     +--------+     |
                |     |  MR/MS |     |            |     |  MR/MS |     |
                |     +--------+     |            |     +--------+     |
                |  +-----+  +-----+  |            |  +-----+  +-----+  |
                |  | ITR |  | ETR |  |            |  | ITR |  | ETR |  |
                |  +-----+  +-----+  |            |  +-----+  +-----+  |
                +--------------------+            +--------------------+
                         xTR2                              xTR3

   Note if any external xTR would like to use a Map-Resolver from the
   mapping system group, it only needs to have one of the LISP-Decent
   Map-Resolvers configured.  By doing a looking to this Map-Resolver
   for EID 224.1.1,1, the external xTR could get the complete list of
   members for the mapping system group.

   For future study, an external xTR could multicast the Map-Request to and either one of the LISP-Decent Map-Resolvers would
   return a Map-Reply or the external xTR is prepared to receive
   multiple Map-Replies.

4.2.  No LISP Protocol Changes

   There are no LISP protocol changes required to support the push-based
   LISP-Decent set of procedures.  However, an implementation that sends
   Map-Register messages to a multicast group versus a specific Map-
   Server unicast address must change to call the data-plane component
   so the ITR functionality in the node can encapsulate the Map-Register
   as a unicast packet to each member of the mapping system group.

   An ITR SHOULD lookup its mapping system group address periodically to
   determine if the membership has changed.  The ITR can also use the

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   pubsub capability documented in [I-D.ietf-lisp-pubsub] to be notified
   when a new member joins or leaves the multicast group.

4.3.  Configuration and Authentication

   When xTRs are joined to a multicast group, they must have their site
   registration configuration consistent.  Any policy or authentication
   key material must be configured correctly and consistently among all
   members.  When [I-D.ietf-lisp-ecdsa-auth] is used to sign Map-
   Register messages, public-keys can be registered to the mapping
   system group using the site authentication key mentioned above or
   using a different authentication key from the one used for
   registering EID records.

4.4.  Core Seed-Group

   A core seed-group can be discovered using a multicast group in a
   push-based system or a Map-Server set of DNS names in a pull-based
   system (see Section 5 for details).

   When using multicast for the mapping system group, a core seed-group
   multicast group address can be preconfigured to bootstrap the
   decentralized mapping system.  The group address (or DNS name that
   maps to a group address) can be explicitly configured in a few xTRs
   to start building up the registrations.  Then as other xTRs come
   online, they can add themselves to the core seed-group by joining the
   seed-group multicast group.

   Alternatively or additionally, new xTRs can join a new mapping system
   multicast group to form another layer of a decentralized mapping
   system.  The group address and members of this new layer seed-group
   would be registered to the core seed-group address and stored in the
   core seed-group mapping system.  Note each mapping system layer could
   have a specific function or a specific circle of trust.

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   This multi-layer mapping system can be illustrated:

              __________               ---------
             /   core   \  / layer-1 \
            | seed-group | --------> |     I     |
            | |           |    / \    |
             \__________/            |   J---K   |
                  |                   \_________/
             / layer-2 \
            |     X     |
            |    / \    |
            |   Y---Z   |

   Configured in xTRs A, B, and C (they make up the core seed-group): -> RLE: A, B, C

   core seed-group DMS, mapping state in A, B, and C: -> RLE: I, J, K -> RLE: X, Y, Z

   layer-1 seed-group DMS (inter-continental), mapping state in I, J, K:
      EID1 -> RLOCs: i(1), j(2)
      EIDn -> RLOCs: i(n), j(n)

   layer-2 seed-group DMS (intra-continental), mapping sate in X, Y, Z::
      EIDa -> RLOCs: x(1), y(2)
      EIDz -> RLOCs: x(n), y(n)

   The core seed-group multicast address is configured in xTRs
   A, B and C so when each of them send Map-Register messages, they
   would all be able to maintain synchronized mapping state.  Any EID
   can be registered to this DMS but in this example, seed-group
   multicast group EIDs are being registered only to find other mapping
   system groups.

   For example, lets say that xTR I boots up and it wants to find its
   other peers in its mapping system group  Group address is configured so xTR I knows what group to join for its
   mapping system group.  But xTR I needs a mapping system to register
   to, so the core seed-group is used and available to receive Map-

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   Registers.  The other xTRs J and K in the mapping system group do the
   same so when any of I, J or K needs to register EIDs, they can now
   send their Map-Register messages to group  Examples of
   EIDs being register are EID1 through EIDn shown above.

   When Map-Registers are sent to group, they are encapsulated
   by the LISP data-plane by looking up EID in the core seed-
   group mapping system.  For the map-cache entry to be populated for, the data-plane must send a Map-Request so the RLOCs I, J,
   and K are cached for replication.  To use the core seed-group mapping
   system, the data-plane must know of at least one of the RLOCs A, B,
   and/or C.

5.  Pull-Based Mapping System

5.1.  Components of a Pulled-Based LISP-Decent xTR

   When an xTR is configured to be a LISP-Decent xTR (or PxTR
   [RFC6832]), it runs the ITR, ETR, Map-Resolver, and Map-Server LISP
   network functions.

   Unlike the Push-Based Mapping System, the xTRs do not need to be
   organized by joining a multicast group.  In a Pull-Based Mappig
   System, a hash function over an EID is used to identify which xTR is
   used as the Map-Resolver and Map-Server.  The Domain Name System
   (DNS) [RFC1034] [RFC1035] is used as a resource discovery mechanism.

   The RLOC addresses of the xTRs will be A and AAAA records for DNS
   names that map algorithmically from the hash of the EID.  A SHA-256
   hash function [RFC6234] over the following ASCII formatted EID string
   is used:


   Where <iid> is the instance-ID and <eid> is the EID of any EID-type
   defined in [RFC8060].  And then the Modulus Value <mv> is used to
   produce the Name Index <index> used to build the DNS lookup name:

       eid = "[<iid>]<eid>/<ml>"
       index = hash.sha_256(eid) MOD mv

   The Hash Mask is used to select what bits are used in the SHA-256
   hash function.  This is required to support longest match lookups in
   the mapping system.  The same map-server set needs to be selected
   when looking up a more-specific EID found in the Map-Request message
   with one that could match a less-specific EID-prefix registered and
   found in the Map-Register message.  For example, if an EID-prefix

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   [0] is registered to the mapping system and EID
   [0] is looked up to match the registered prefix, a Hash
   Mask of 8 bytes can be used to AND both the /32 or /24 entries to
   produce the same hash string bits of "[0]240.0".

   For (*,G) and (S,G) multicast entries in the mapping system, the hash
   strings are:

       sg-eid = "[<iid>]<group>/<gml>-<source>/<sml>"
       index = hash.sha_256(sg-eid) MOD mv

       starg-eid = "[<iid>]<group>/<gml>-"
       index = hash.sha_256(starg-eid) MOD mv

   The Hash Mask MUST include the string "[<iid>]<group>" and not string
   <source>.  So when looking up [0](, that will match
   a (*,, the hash string produced with a Hash Mask of 12
   bytes is "[0]".

   When the <index> is computed from a unicast or multicast EID, the DNS
   lookup name becomes:


   When an xTR does a DNS lookup on the lookup name, it will send Map-
   Register messages to all A and AAAA records for EID registrations.
   For Map-Request messages, xTRs MAY round robin EID lookup requests
   among the A and AAAA records.

5.2.  Deployment Example

   Here is an example deployment of a pull-based model.  Let's say 4
   map-server sets are provisioned for the mapping system.  Therefore 4
   distinct DNS names are allocated and a Modulus Value 4 is used.  Each
   DNS name is allocated Name Index 0 through 3:

   The A records for each name can be assigned as:

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           A <rloc1-att>
           A <rloc2-verizon>
           A <rloc1-bt>
           A <rloc2-dt>
           A <rloc1-cn>
           A <rloc2-kr>
           A <rloc1-au>
           A <rloc2-nz>

   When an xTR wants to register "[1000]fd::2222", it hashes the EID
   string to produce, for example, hash value 0x66.  Using the modulus
   value 4 (0x67 & 0x3) produces index 0x3, so the DNS name is used and a Map-Regiter is sent to <rloc1-au>
   and <rloc2-nz>.

   Note that the pull-based method can be used for a core seed-group for
   bootstraping a push-based mapping system where multicast groups are

5.3.  Management Considerations

   There are no LISP protocol changes required to support the pull-based
   LISP-Decent set of procedures.  However, an implementation SHOULD do
   periodic DNS lookups to determine if A records have changed for a DNS

   When xTRs derive Map-Resolver and Map-Server names from the DNS, they
   need to use the same Modulus Value otherwise some xTRs will lookup
   EIDs to the wrong place they were registered.

   The Modulus Value can be configured or pushed to the LISP-Decent
   xTRs.  A future version of this document will describe a push
   mechanism so all xTRs use a consistent modulus value.

6.  Security Considerations

   Refer to the Security Considerations section of
   [I-D.ietf-lisp-rfc6833bis] for a complete list of security mechanisms
   as well as pointers to threat analysis drafts.

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7.  IANA Considerations

   At this time there are no specific requests for IANA.

8.  References

8.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <>.

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013,

   [RFC6831]  Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
              Locator/ID Separation Protocol (LISP) for Multicast
              Environments", RFC 6831, DOI 10.17487/RFC6831, January
              2013, <>.

   [RFC6832]  Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
              "Interworking between Locator/ID Separation Protocol
              (LISP) and Non-LISP Sites", RFC 6832,
              DOI 10.17487/RFC6832, January 2013,

   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation
              Protocol (LISP) Map-Server Interface", RFC 6833,
              DOI 10.17487/RFC6833, January 2013,

   [RFC6836]  Fuller, V., Farinacci, D., Meyer, D., and D. Lewis,
              "Locator/ID Separation Protocol Alternative Logical
              Topology (LISP+ALT)", RFC 6836, DOI 10.17487/RFC6836,
              January 2013, <>.

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   [RFC8060]  Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060,
              February 2017, <>.

   [RFC8111]  Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A.
              Smirnov, "Locator/ID Separation Protocol Delegated
              Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111,
              May 2017, <>.

   [RFC8378]  Moreno, V. and D. Farinacci, "Signal-Free Locator/ID
              Separation Protocol (LISP) Multicast", RFC 8378,
              DOI 10.17487/RFC8378, May 2018,

8.2.  Informative References

              Farinacci, D. and E. Nordmark, "LISP Control-Plane ECDSA
              Authentication and Authorization", draft-ietf-lisp-ecdsa-
              auth-00 (work in progress), September 2018.

              Rodriguez-Natal, A., Ermagan, V., Leong, J., Maino, F.,
              Cabellos-Aparicio, A., Barkai, S., Farinacci, D.,
              Boucadair, M., Jacquenet, C., and S. Secci, "Publish/
              Subscribe Functionality for LISP", draft-ietf-lisp-
              pubsub-02 (work in progress), November 2018.

              Fuller, V., Farinacci, D., and A. Cabellos-Aparicio,
              "Locator/ID Separation Protocol (LISP) Control-Plane",
              draft-ietf-lisp-rfc6833bis-24 (work in progress), February

              Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D.
              Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-17
              (work in progress), November 2018.

Appendix A.  Acknowledgments

   The authors would like to thank the LISP WG for their review and
   acceptance of this draft.

   The authors would also like to give a special thanks to Roman
   Shaposhnik for several discussions that occured before the first
   draft was published.

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Appendix B.  Document Change Log

   [RFC Editor: Please delete this section on publication as RFC.]

B.1.  Changes to draft-farinacci-lisp-decent-03

   o  Posted March 2019.

   o  Introduce the Hash Mask which is used to grab common bits from a
      registered prefix and a lookup prefix.

   o  Spec how multicast lookups are done in the pull-based mapping

   o  Indicate the hash string includes the unicast EID mask-length and
      multicast group and source mask-lengths.

B.2.  Changes to draft-farinacci-lisp-decent-02

   o  Posted November 2018.

   o  Changed references from peer-group to seed-group to make the
      algorithms in this document more like how blockchain networks
      initialize the peer-to-peer network.

   o  Added pull mechanism to compliment the push mechanism.  The pull
      mechanism could be used as a seed-group to bootstrap the push

B.3.  Changes to draft-farinacci-lisp-decent-01

   o  Posted July 2018.

   o  Document timer and reference update.

B.4.  Changes to draft-farinacci-lisp-decent-00

   o  Initial draft posted January 2018.

Authors' Addresses

   Dino Farinacci
   San Jose, CA


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   Colin Cantrell
   Tempe, AZ


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