LISP EID Block
draft-ietf-lisp-eid-block-06

Network Working Group                                         L. Iannone
Internet-Draft                                         Telecom ParisTech
Intended status: Informational                                  D. Lewis
Expires: April 21, 2014                              Cisco Systems, Inc.
                                                                D. Meyer
                                                                 Brocade
                                                               V. Fuller
                                                        October 18, 2013

                             LISP EID Block
                    draft-ietf-lisp-eid-block-06.txt

Abstract

   This is a direction to IANA to allocate a /16 IPv6 prefix for use
   with the Locator/ID Separation Protocol (LISP).  The prefix will be
   used for local intra-domain routing and global endpoint
   identification, by sites deploying LISP as EID (Endpoint IDentifier)
   addressing space.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 21, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Definition of Terms  . . . . . . . . . . . . . . . . . . . . .  3
   3.  Rationale and Intent . . . . . . . . . . . . . . . . . . . . .  3
   4.  Expected use . . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Block Dimension  . . . . . . . . . . . . . . . . . . . . . . .  5
   6.  3+3 Allocation Plan  . . . . . . . . . . . . . . . . . . . . .  6
   7.  Routing Considerations . . . . . . . . . . . . . . . . . . . .  7
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     11.1.  Normative References  . . . . . . . . . . . . . . . . . . 10
     11.2.  Informative References  . . . . . . . . . . . . . . . . . 11
   Appendix A.  LISP Terminology  . . . . . . . . . . . . . . . . . . 11
   Appendix B.  Document Change Log . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16

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1.  Introduction

   This document directs the IANA to allocate a /16 IPv6 prefix for use
   with the Locator/ID Separation Protocol (LISP - [RFC6830]), LISP Map
   Server ([RFC6833]), LISP Alternative Topology (LISP+ALT - [RFC6836])
   (or other) mapping system, and LISP Interworking ([RFC6832]).

   This block will be used as global Endpoint IDentifier (EID) space
   (Section 2).

2.  Definition of Terms

   The present document does not introduce any new term with respect to
   the set of LISP Specifications ( [RFC6830], [RFC6831], [RFC6832],
   [RFC6833], [RFC6834], [RFC6835], [RFC6836], [RFC6837]).  To help the
   reading of the present document the terminology introduced by LISP is
   summarized in Appendix A.

3.  Rationale and Intent

   Discussion within the LISP Working Group led to identify several
   scenarios in which the existence of a LISP specific address block
   brings technical benefits.  Hereafter the most relevant scenarios are
   described:

   Early LISP destination detection:  With the current specifications,
         there is no direct way to detect whether or not a certain
         destination is in a LISP domain or not without performing a
         LISP mapping lookup.  For instance, if an ITR is sending to all
         types of destinations (i.e., non-LISP destinations, LISP
         destinations not in the IPv6 EID Block, and LISP destinations
         in the IPv6 EID Block) the only way to understand whether or
         not to encapsulate the traffic is to perform a cache lookup
         and, in case of a LISP Cache miss, send a Map-Request to the
         mapping system.  In the meanwhile, packets may be dropped.

   Avoid penalize non-LISP traffic:  In certain circumstances it might
         be desirable to configure a router using LISP features to
         natively forward all packets that have not a destination
         address in the block, hence, no lookup whatsoever is performed
         and packets destined to non-LISP sites are not penalized in any
         manner.

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   Avoid excessive stretch:  In some deployment scenarios and in order
         to avoid packet drops, in case of LISP Cache miss packets are
         forwarded toward a PETR while a mapping lookup is performed
         over the LISP mapping system.  Once a mapping is obtained
         packets are not forwarded anymore toward the PETR, they are
         LISP encapsulated and forwarded according to the LISP
         specifications.  The existence of a LISP specific EID block
         would allow to avoid scenarios with excessive overhead, where
         the destination is a LISP EID and where (while the mapping is
         looked up) packets are forwarded over paths like
         Source->ITR->PETR->PITR->ETR->Destination, which may show an
         excessive stretch factor and degraded performance.

   Traffic Engineering:  In some deployment scenarios it might be
         desirable to apply different traffic engineering policies for
         LISP and non-LISP traffic.  A LISP specific EID block would
         allow improved traffic engineering capabilities with respect to
         LISP vs. non-LISP traffic.  In particular, LISP traffic might
         be identified without having to use DPI techniques in order to
         parse the encapsulated packet, performing instead a simple
         inspection of the outer header is sufficient.

   Transition Mechanism:  The existence of an LISP specific EID Block
         may prove useful in transition scenarios.  A non-LISP domain
         would ask an allocation in the LISP EID Block and use it to
         deploy LISP in its network.  Such allocation will not be
         announced in the BGP routing infrastructure (cf., Section 4).
         This approach will avoid non-LISP domains to fragment their
         already allocated non-LISP addressing space, which may lead to
         BGP routing table inflation since it may (rightfully) be
         announced in the BGP routing infrastructure.

   Limit the impact on BGP routing infrastructure:  As described in the
         previous scenario, LISP adopters will avoid fragmenting their
         addressing space, which would negatively impact the BGP routing
         infrastructure.  Adopters will use addressing space from the
         EID block which might be announced in large aggregates and in a
         tightly controlled manner only by proxy xTRs.

   Is worth to mention that new use cases can arise in the future, due
   to new and unforeseen scenarios.

   Furthermore, this will give a tighter control, especially filtering,
   over the traffic in the initial experimental phase, while
   facilitating its large-scale deployment.

   [RFC3692] considers assigning experimental and testing numbers
   useful, and the request of a reserved IPv6 EID prefix is a perfect

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   match of such practice.  The present document follows the guidelines
   provided in [RFC3692], with one exception.  [RFC3692] suggests the
   use of values similar to those called "Private Use" in [RFC2434],
   which by definition are not unique.  One of the purposes of the
   present request to IANA is to guarantee uniqueness to the EID block.
   The lack thereof would result in a lack of real utility of a reserved
   IPv6 EID prefix.

4.  Expected use

   Sites planning to deploy LISP may request a prefix in the IPv6 EID
   Block.  Such prefix will be used for routing and endpoint
   identification inside the site requesting it.  Mappings related to
   such prefix, or part of it, will be made available through the
   mapping system in use and registered to one or more Map Server(s).

   To guarantee reachability from the Legacy Internet the prefix may be
   announced in the BGP routing infrastructure by one or more PITR(s) as
   part of larger aggregates (ideally just the entire LISP EID block).
   Indeed, the use of PxTRs allow EID prefix aggregation; the deployment
   model for this element is described in [RFC6832] and
   [I-D.ietf-lisp-deployment].

   As the LISP adoption progress, the EID prefix space will potentially
   help in reducing the impact on the BGP routing infrastructure with
   respect to the case of the same number of adopters using global
   unicast space allocated by RIRs ([MobiArch2007]).  From a short-term
   perspective, the EID space offers potentially large aggregation
   capabilities since it is announced by PxTRs possibly concentrating
   several contiguous prefixes.  Such trend should continue with even
   lower impact from a long-term perspective, since more aggressive
   aggregation can be used, potentially leading at using few PxTRs
   announcing the whole EID space ([FIABook2010]).

   The EID Block will be used only at configuration level, it is
   recommended not to hard-code in any way the IPv6 EID Block in the
   router hardware.  This allows avoiding locking out sites that may
   want to switch to LISP while keeping their own IPv6 prefix, which is
   not in the IPv6 EID Block.

   The prefix must not be used as normal prefix and announced in the BGP
   routing infrastructure.

5.  Block Dimension

   The working group reached consensus on an initial allocation of a /16

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   prefix out of a /12 block which is asked to remain reserved for
   future use as EID space.  The reason of such consensus is manifold:

   o  The working group agreed that /16 prefix is sufficiently large to
      cover initial allocation and requests for prefixes in the EID
      space in the next few years for very large-scale experimentation
      and deployment.

   o  As a comparison, it is worth mentioning that the current LISP Beta
      Network ([BETA]) is using a /32 prefix, with more than 250 sites
      using a /48 sub prefix.  Hence, a /16 prefix looks as sufficiently
      large to allow the current deployment to scale up and be open for
      interoperation with independent deployments using EIDs space in
      the new /16 prefix.

   o  A /16 prefix is sufficiently large to only allow deployment of
      independent (commercial) LISP enabled networks by third parties,
      but may as well boost LISP experimentation and deployment.

   o  The /16 size and alignment allows the use to current policies to
      allocate and distribute prefixes out of this space, without the
      need to introduce any new specific address management policy.

   o  The proposed alignment provides as well a natural support for DNS.
      In particular, reverse DNS for IPv6 in the special ip6.arpa domain
      is represented as sequence of nibbles.  A different alignment
      would force to a binary representation.

   o  The use of a /16 prefix is in line with previous similar prefix
      allocation for tunnelling protocols ([RFC3056]).

6.  3+3 Allocation Plan

   This document requests IANA to initially assign a /16 prefix out of
   the IPv6 addressing space for use as EID in LISP (Locator/ID
   Separation Protocol).

   It is suggested to IANA to temporarily avoid allocating any other
   address block the same /12 prefix the EID /16 prefix belongs to.
   This is to accommodate future requests of EID space without
   fragmenting the EID addressing space.  This will also help from an
   operational point of view, since it will be sufficient to change the
   subnet mask length in existing deployments.  If in the future there
   will be need for a larger EID Block the address space adjacent the
   EID Block could be allocate by IANA according to the current
   policies.

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   IANA should assign the requested address space by beginning 2014 for
   a duration of 3 (three) initial years (through December 2017), with
   an option to extend this period by 3 (three) more years (until
   December 2020).  By the end of the first period, the IETF will
   provide a decision on whether to transform the prefix in a permanent
   assignment or to put it back in the free pool.

   In the first case, i.e., if the IETF decides to transform the block
   in a permanent allocation, the EID block allocation period will be
   extended for three years (until December 2020) so to give time to the
   IETF to define the final size of the EID block, the transition phase,
   and the allocation and management policies.

   In the latter case, i.e., if the IETF decides to stop the EID block
   experimental use, by December 2017 all temporary prefix allocations
   in such address range must expire and be released, so that by January
   2018 the entire /12 is returned to the free pool.

   The allocation and management of the Global EID Space for the initial
   3 years period (and the optional 3 more years) is detailed in
   [I-D.iannone-lisp-eid-block-mgmnt].

7.  Routing Considerations

   In order to provide connectivity between the Legacy Internet and LISP
   sites, PITRs announcing large aggregates (ideally one single large
   aggregate) of the IPv6 EID Block could be deployed.  By doing so,
   PITRs will attract traffic destined to LISP sites in order to
   encapsulate and forward it toward the specific destination LISP site.
   Routers in the Legacy Internet must treat announcements of prefixes
   from the IPv6 EID Block as normal announcements, applying best
   current practice for traffic engineering and security.

   Even in a LISP site, not all routers need to run LISP elements.  In
   particular, routers that are not at the border of the local domain,
   used only for intra-domain routing, do not need to provide any
   specific LISP functionality but must be able to route traffic using
   addresses in the IPv6 EID Block.

   For the above-mentioned reasons, routers that do not run any LISP
   element, must not include any special handling code or hardware for
   addresses in the IPv6 EID Block.  In particular, it is recommended
   that the default router configuration does not handle such addresses
   in any special way.  Doing differently could prevent communication
   between the Legacy Internet and LISP sites or even break local intra-
   domain connectivity.

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8.  Security Considerations

   This document does not introduce new security threats in the LISP
   architecture nor in the Legacy Internet architecture.

9.  IANA Considerations

   This document instructs the IANA to assign a /16 IPv6 prefix for use
   as the global LISP EID space using a hierarchical allocation as
   outlined in [RFC5226] and summarized in Table 1.

               +----------------------+--------------------+
               | Attribute            | Value              |
               +----------------------+--------------------+
               | Address Block        | XXX0::/16 [1]      |
               | Name                 | EID Space for LISP |
               | RFC                  | [This Document]    |
               | Allocation Date      | September 2013     |
               | Termination Date     | September 2023     |
               | Source               | True [2]           |
               | Destination          | True               |
               | Forwardable          | True               |
               | Global               | True               |
               | Reserved-by-protocol | True [3]           |
               +----------------------+--------------------+

   [1] XXX value to be provided by IANA before published as RFC. [2] Can
   be used as a multicast source as well. [3] To be used as EID space by
                      LISP [RFC6830] enabled routers.

                         Table 1: Global EID Space

   During the discussion related to this document, the LISP Working
   Group agreed in suggesting to IANA to reserve adjacent addressing
   space, more specifically the /12 covering the assigned /16 prefix,
   for future use as EID space if needs come.  Table 2 summarizes the
   request.  Following the policies outlined in [RFC5226], such space
   will be assigned only upon IETF Review.

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              +----------------------+----------------------+
              | Attribute            | Value                |
              +----------------------+----------------------+
              | Address Block        | XXX0::/12 [1]        |
              | Name                 | ) EID Space for LISP |
              | RFC                  | [This Document]      |
              | Allocation Date      | September 2013       |
              | Termination Date     | September 2023       |
              | Source               | False                |
              | Destination          | False                |
              | Forwardable          | False                |
              | Global               | False                |
              | Reserved-by-protocol | True [2]             |
              +----------------------+----------------------+

   [1] XXX value to be provided by IANA before published as RFC. [2] To
          be used as EID space by LISP [RFC6830] enabled routers.

           Table 2: Reserved for Future Use as Global EID Space

   This document does not specify any specific value for the requested
   address block but suggests that should come from the 2000::/3 Global
   Unicast Space.  Furthermore, it is suggested to assign the /16 prefix
   from the first /16 block out of the reserved /12 prefix.  IANA is not
   requested to issue a AS0 ROA, since the Global EID Space will be used
   for routing purposes.

   The reserved address space is requested for a period of time of three
   initial years starting in beginning 2014 (until December 2017), with
   an option to extend it by three years (until December 2020) up on
   decision of the IETF.  Following the policies outlined in [RFC5226],
   upon IETF Review, by December 2017 decision should be made on whether
   to keep the assignment making the reserved prefix assignment
   permanent (this includes final decision on the size of the prefix).
   If the IETF review outcome will be that is not worth to have a
   reserved prefix as global EID space, the whole /12 (and all sub-block
   assigned out of it) will be taken out from the IPv6 Special Purpose
   Address Registry and put back in the free pool managed by IANA by end
   of January 2018.

   Allocation and management of the Global EID Space is detailed in a
   different document.  Nevertheless, all prefix allocations out of this
   space must be temporary and no allocation must go beyond December
   2017 unless the IETF Review decides that the Global EID Space is
   permanently assigned.

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10.  Acknowledgments

   Special thanks to Roque Gagliano for his suggestions and pointers.
   Thanks to David Conrad, Scott Bradner, John Curran, Paul Wilson,
   Geoff Huston, Wes George, Arturo Servin, Sander Steffann, Brian
   Carpenter, Roger Jorgensen, Terry Manderson, Brian Haberman, Adrian
   Farrel, Job Snijders, Marla Azinger, Chris Morrow, and Peter
   Schoenmaker, for their insightful comments.  Thanks as well to all
   participants to the fruitful discussions on the IETF mailing list.

11.  References

11.1.  Normative References

   [I-D.iannone-lisp-eid-block-mgmnt]
              Iannone, L., Jorgensen, R., and D. Conrad, "LISP EID Block
              Management Guidelines",
              draft-iannone-lisp-eid-block-mgmnt-03 (work in progress),
              October 2013.

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

   [RFC3692]  Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful", BCP 82, RFC 3692, January 2004.

   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, August 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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

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

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

   [RFC6834]  Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID
              Separation Protocol (LISP) Map-Versioning", RFC 6834,
              January 2013.

   [RFC6835]  Farinacci, D. and D. Meyer, "The Locator/ID Separation
              Protocol Internet Groper (LIG)", RFC 6835, January 2013.

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

   [RFC6837]  Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to
              Routing Locator (RLOC) Database", RFC 6837, January 2013.

11.2.  Informative References

   [BETA]     LISP Beta Network, "http://www.lisp4.net".

   [FIABook2010]
              L. Iannone, T. Leva, "Modeling the economics of Loc/ID
              Separation for the Future Internet.", Towards the Future
              Internet - Emerging Trends from the European Research,
              Pages 11-20, ISBN: 9781607505389, IOS Press , May 2010.

   [I-D.ietf-lisp-deployment]
              Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo-
              Pascual, J., and D. Lewis, "LISP Network Element
              Deployment Considerations", draft-ietf-lisp-deployment-10
              (work in progress), August 2013.

   [MobiArch2007]
              B. Quoitin, L. Iannone, C. de Launois, O. Bonaventure,
              "Evaluating the Benefits of the Locator/Identifier
              Separation", The 2nd ACM-SIGCOMM International Workshop on
              Mobility in the Evolving Internet Architecture
              (MobiArch'07) , August 2007.

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

Appendix A.  LISP Terminology

   LISP operates on two name spaces and introduces several new network

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   elements.  To facilitate the reading, this section provides high-
   level definitions of the LISP name spaces and network elements and,
   as such, it must not be considered as an authoritative source.  The
   reference to the authoritative document for each term is included in
   every term description.

   Legacy Internet:  The portion of the Internet that does not run LISP
      and does not participate in LISP+ALT or any other mapping system.

   LISP site:  A LISP site is a set of routers in an edge network that
      are under a single technical administration.  LISP routers that
      reside in the edge network are the demarcation points to separate
      the edge network from the core network.  See [RFC6830] for more
      details.

    Endpoint ID (EID):  An EID is a 32-bit (for IPv4) or 128-bit (for
      IPv6) value used in the source and destination address fields of
      the first (most inner) LISP header of a packet.  A packet that is
      emitted by a system contains EIDs in its headers and LISP headers
      are prepended only when the packet reaches an Ingress Tunnel
      Router (ITR) on the data path to the destination EID.  The source
      EID is obtained via existing mechanisms used to set a host's
      "local" IP address.  An EID is allocated to a host from an EID-
      prefix block associated with the site where the host is located.
      See [RFC6830] for more details.

   EID-prefix:  A power-of-two block of EIDs that are allocated to a
      site by an address allocation authority.  See [RFC6830] for more
      details.

   EID-Prefix Aggregate:  A set of EID-prefixes said to be aggregatable
      in the [RFC4632] sense.  That is, an EID-Prefix aggregate is
      defined to be a single contiguous power-of-two EID-prefix block.
      A prefix and a length characterize such a block.  See [RFC6830]
      for more details.

   Routing LOCator (RLOC):  A RLOC is an IPv4 or IPv6 address of an
      egress tunnel router (ETR).  A RLOC is the output of an EID-to-
      RLOC mapping lookup.  An EID maps to one or more RLOCs.
      Typically, RLOCs are numbered from topologically aggregatable
      blocks that are assigned to a site at each point to which it
      attaches to the global Internet; where the topology is defined by
      the connectivity of provider networks, RLOCs can be thought of as
      Provider Aggregatable (PA) addresses.  See [RFC6830] for more
      details.

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    EID-to-RLOC Mapping:  A binding between an EID-Prefix and the RLOC-
      set that can be used to reach the EID-Prefix.  The general term
      "mapping" always refers to an EID-to-RLOC mapping.  See [RFC6830]
      for more details.

   Ingress Tunnel Router (ITR):  An Ingress Tunnel Router (ITR) is a
      router that accepts receives IP packets from site end-systems on
      one side and sends LISP-encapsulated IP packets toward the
      Internet on the other side.  The router treats the "inner" IP
      destination address as an EID and performs an EID-to-RLOC mapping
      lookup.  The router then prepends an "outer" IP header with one of
      its globally routable RLOCs in the source address field and the
      result of the mapping lookup in the destination address field.
      See [RFC6830] for more details.

   Egress Tunnel Router (ETR):  An Egress Tunnel Router (ETR) receives
      LISP-encapsulated IP packets from the Internet on one side and
      sends decapsulated IP packets to site end-systems on the other
      side.  An ETR router accepts an IP packet where the destination
      address in the "outer" IP header is one of its own RLOCs.  The
      router strips the "outer" header and forwards the packet based on
      the next IP header found.  See [RFC6830] for more details.

   Proxy ITR (PITR):  A Proxy-ITR (PITR) acts like an ITR but does so on
      behalf of non-LISP sites which send packets to destinations at
      LISP sites.  See [RFC6832] for more details.

   Proxy ETR (PETR):  A Proxy-ETR (PETR) acts like an ETR but does so on
      behalf of LISP sites which send packets to destinations at non-
      LISP sites.  See [RFC6832] for more details.

   Map Server (MS):  A network infrastructure component that learns EID-
      to-RLOC mapping entries from an authoritative source (typically an
      ETR).  A Map Server publishes these mappings in the distributed
      mapping system.  See [RFC6833] for more details.

   Map Resolver (MR):  A network infrastructure component that accepts
      LISP Encapsulated Map-Requests, typically from an ITR, quickly
      determines whether or not the destination IP address is part of
      the EID namespace; if it is not, a Negative Map-Reply is
      immediately returned.  Otherwise, the Map Resolver finds the
      appropriate EID-to-RLOC mapping by consulting the distributed
      mapping database system.  See [RFC6833] for more details.

   The LISP Alternative Logical Topology (ALT):  The virtual overlay
      network made up of tunnels between LISP+ALT Routers.  The Border
      Gateway Protocol (BGP) runs between ALT Routers and is used to
      carry reachability information for EID-prefixes.  The ALT provides

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      a way to forward Map-Requests toward the ETR that "owns" an EID-
      prefix.  See [RFC6836] for more details.

   ALT Router:  The device on which runs the ALT.  The ALT is a static
      network built using tunnels between ALT Routers.  These routers
      are deployed in a roughly-hierarchical mesh in which routers at
      each level in the topology are responsible for aggregating EID-
      Prefixes learned from those logically "below" them and advertising
      summary prefixes to those logically "above" them.  Prefix learning
      and propagation between ALT Routers is done using BGP.  When an
      ALT Router receives an ALT Datagram, it looks up the destination
      EID in its forwarding table (composed of EID-Prefix routes it
      learned from neighboring ALT Routers) and forwards it to the
      logical next-hop on the overlay network.  The primary function of
      LISP+ALT routers is to provide a lightweight forwarding
      infrastructure for LISP control-plane messages (Map-Request and
      Map-Reply), and to transport data packets when the packet has the
      same destination address in both the inner (encapsulating)
      destination and outer destination addresses ((i.e., a Data Probe
      packet).  See [RFC6836] for more details.

Appendix B.  Document Change Log

   Version 06 Posted October 2013.

   o  Clarified the rationale and intent of the EID block request with
      respect to [RFC3692], as suggested by S. Bradner and J. Curran.

   o  Extended Section 3 by adding the transion scenario (as suggested
      by J. Curran) and the TE scenario.  The other scenarios have been
      also edited.

   o  Section 6 has been re-written to introduce the 3+3 allocation plan
      as suggested by B. Haberman and discussed during 86th IETF.

   o  Section 9 has also been updated to the 3+3 years allocation plan.

   o  Moved Section 10 at the end of the document.

   o  Changed the original Definition of terms to an appendix.

   Version 05 Posted September 2013.

   o  No changes.

   Version 04 Posted February 2013.

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   o  Added Table 1 and Table 2 as requested by IANA.

   o  Transformed the prefix request in a temporary request as suggested
      by various comments during IETF Last Call.

   o  Added discussion about short/long term impact on BGP in Section 4
      as requested by B. Carpenter.

   Version 03 Posted November 2012.

   o  General review of Section 5 as requested by T. Manderson and B.
      Haberman.

   o  Dropped RFC 2119 Notation, as requested by A. Farrel and B.
      Haberman.

   o  Changed "IETF Consensus" to "IETF Review" as pointed out by Roque
      Gagliano.

   o  Changed every occurrence of "Map-Server" and "Map-Resolver" with
      "Map Server" and "Map Resolver" to make the document consistent
      with [RFC6833].  Thanks to Job Snijders for pointing out the
      issue.

   Version 02 Posted April 2012.

   o  Fixed typos, nits, references.

   o  Deleted reference to IANA allocation policies.

   Version 01 Posted October 2011.

   o  Added Section 5.

   Version 00 Posted July 2011.

   o  Updated section "IANA Considerations"

   o  Added section "Rationale and Intent" explaining why the EID block
      allocation is useful.

   o  Added section "Expected Use" explaining how sites can request and
      use a prefix in the IPv6 EID Block.

   o  Added section "Action Plan" suggesting IANA to avoid allocating
      address space adjacent the allocated EID block in order to
      accommodate future EID space requests.

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   o  Added section "Routing Consideration" describing how routers not
      running LISP deal with the requested address block.

   o  Added the present section to keep track of changes.

   o  Rename of draft-meyer-lisp-eid-block-02.txt.

Authors' Addresses

   Luigi Iannone
   Telecom ParisTech

   Email: luigi.iannone@telecom-paristech.fr

   Darrel Lewis
   Cisco Systems, Inc.

   Email: darlewis@cisco.com

   David Meyer
   Brocade

   Email: dmm@1-4-5.net

   Vince Fuller

   Email: vaf@vaf.net

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