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RFC 7215 - Locator/Identifier Separation Protocol (LISP) Network

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Internet Engineering Task Force (IETF)                          L. Jakab
Request for Comments: 7215                                 Cisco Systems
Category: Experimental                              A. Cabellos-Aparicio
ISSN: 2070-1721                                                 F. Coras
                                                      J. Domingo-Pascual
                                       Technical University of Catalonia
                                                                D. Lewis
                                                           Cisco Systems
                                                              April 2014

             Locator/Identifier Separation Protocol (LISP)
               Network Element Deployment Considerations


   This document is a snapshot of different Locator/Identifier
   Separation Protocol (LISP) deployment scenarios.  It discusses the
   placement of new network elements introduced by the protocol,
   representing the thinking of the LISP working group as of Summer
   2013.  LISP deployment scenarios may have evolved since then.  This
   memo represents one stable point in that evolution of understanding.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Tunnel Routers ..................................................5
      2.1. Deployment Scenarios .......................................5
           2.1.1. Customer Edge (CE) ..................................5
           2.1.2. Provider Edge (PE) ..................................6
           2.1.3. Tunnel Routers behind NAT ...........................8
         ITR ........................................8
         ETR ........................................9
         Additional Notes ...........................9
      2.2. Functional Models with Tunnel Routers ......................9
           2.2.1. Split ITR/ETR .......................................9
           2.2.2. Inter-Service-Provider Traffic Engineering .........11
      2.3. Summary and Feature Matrix ................................13
   3. Map-Servers and Map-Resolvers ..................................14
      3.1. Map-Servers ...............................................14
      3.2. Map-Resolvers .............................................16
   4. Proxy Tunnel Routers ...........................................17
      4.1. PITRs .....................................................17
      4.2. PETRs .....................................................18
   5. Migration to LISP ..............................................19
      5.1. LISP+BGP ..................................................19
      5.2. Mapping Service Provider (MSP) PITR Service ...............20
      5.3. Proxy-ITR Route Distribution (PITR-RD) ....................20
      5.4. Migration Summary .........................................23
   6. Security Considerations ........................................24
   7. Acknowledgements ...............................................24
   8. References .....................................................24
      8.1. Normative References ......................................24
      8.2. Informative References ....................................24
   Appendix A. Step-by-Step Example BGP-to-LISP Migration Procedure ..26
     A.1. Customer Pre-Install and Pre-Turn-Up Checklist .............26
     A.2. Customer Activating LISP Service ...........................28
     A.3. Cut-Over Provider Preparation and Changes ..................29

1.  Introduction

   The Locator/Identifier Separation Protocol (LISP) is designed to
   address the scaling issues of the global Internet routing system
   identified in [RFC4984] by separating the current addressing scheme
   into Endpoint IDentifiers (EIDs) and Routing LOCators (RLOCs).  The
   main protocol specification [RFC6830] describes how the separation is
   achieved and which new network elements are introduced, and it
   details the packet formats for the data and control planes.

   LISP assumes that such separation is between the edge and core and
   uses mapping and encapsulation for forwarding.  While the boundary
   between both is not strictly defined, one widely accepted definition
   places it at the border routers of stub autonomous systems, which may
   carry a partial or complete default-free zone (DFZ) routing table.
   The initial design of LISP took this location as a baseline for
   protocol development.  However, the applications of LISP go beyond
   just decreasing the size of the DFZ routing table and include
   improved multihoming and ingress traffic engineering (TE) support for
   edge networks, and even individual hosts.  Throughout this document,
   we will use the term "LISP site" to refer to these networks/hosts
   behind a LISP Tunnel Router.  We formally define the following
   two terms:

   Network element:  Facility or equipment used in the provision of a
      communications service over the Internet [TELCO96].

   LISP site:  A single host or a set of network elements in an edge
      network under the administrative control of a single organization,
      delimited from other networks by LISP Tunnel Router(s).

   Since LISP is a protocol that can be used for different purposes, it
   is important to identify possible deployment scenarios and the
   additional requirements they may impose on the protocol specification
   and other protocols.  Additionally, this document is intended as a
   guide for the operational community for LISP deployments in their
   networks.  It is expected to evolve as LISP deployment progresses,
   and the described scenarios are better understood or new scenarios
   are discovered.

   Each subsection considers an element type and discusses the impact of
   deployment scenarios on the protocol specification.  For definitions
   of terms, please refer to the appropriate documents (as cited in the
   respective sections).

   This experimental document describes deployment considerations.
   These considerations and the LISP specifications have areas that
   require additional experience and measurement.  LISP is not
   recommended for deployment beyond experimental situations.  Results
   of experimentation may lead to modifications and enhancements of LISP
   mechanisms.  Additionally, at the time of this writing there is no
   standardized security to implement.  Beware that there are no
   countermeasures for any of the threats identified in [LISP-THREATS].
   See Section 15 of [RFC6830] for specific known issues that are in
   need of further work during development, implementation, and
   experimentation, and see [LISP-THREATS] for recommendations to
   ameliorate the above-mentioned security threats.

2.  Tunnel Routers

   The device that is the gateway between the edge and the core is
   called a Tunnel Router (xTR); it performs one or both of two separate

   1.  Encapsulating packets originating from an end host to be
       transported over intermediary (transit) networks towards the
       other endpoint of the communication.

   2.  Decapsulating packets entering from intermediary (transit)
       networks, originated at a remote end host.

   The first function is performed by an Ingress Tunnel Router (ITR) and
   the second by an Egress Tunnel Router (ETR).

   Section 8 of the main LISP specification [RFC6830] has a short
   discussion of where Tunnel Routers can be deployed and some of the
   associated advantages and disadvantages.  This section adds more
   detail to the scenarios presented there and provides additional
   scenarios as well.  Furthermore, this section discusses functional
   models, that is, network functions that can be achieved by deploying
   Tunnel Routers in specific ways.

2.1.  Deployment Scenarios

2.1.1.  Customer Edge (CE)

   The first scenario we discuss is the customer edge, when xTR
   functionality is placed on the router(s) that connects the LISP site
   to its upstream(s) but is under its control.  As such, this is the
   most common expected scenario for xTRs, and this document considers
   it the reference location, comparing the other scenarios to this one.

                               ISP1    ISP2
                                |        |
                                |        |
                              +----+  +----+
                           |  +----+  +----+  |
                           |                  |
                           |     LISP site    |

                    Figure 1: xTRs at the Customer Edge

   From the LISP site's perspective, the main advantage of this type of
   deployment (compared to the one described in the next section) is
   having direct control over its ingress traffic engineering.  This
   makes it easy to set up and maintain active/active, active/backup, or
   more complex TE policies, adding ISPs and additional xTRs at will,
   without involving third parties.

   Being under the same administrative control, reachability information
   of all ETRs is easier to synchronize, because the necessary control
   traffic can be allowed between the locators of the ETRs.  A correct
   synchronous global view of the reachability status is thus available,
   and the Locator-Status-Bits can be set correctly in the LISP data
   header of outgoing packets.

   By placing the Tunnel Router at the edge of the site, existing
   internal network configuration does not need to be modified.
   Firewall rules, router configurations, and address assignments inside
   the LISP site remain unchanged.  This helps with incremental
   deployment and allows a quick upgrade path to LISP.  For larger sites
   distributed in geographically diverse points of presence (PoPs) and
   having many external connections and complex internal topology, it
   may, however, make more sense to both encapsulate and decapsulate as
   soon as possible, to benefit from the information in the IGP to
   choose the best path.  See Section 2.2.1 for a discussion of this

   Another thing to consider when placing Tunnel Routers is MTU issues.
   Encapsulation increases the amount of overhead associated with each
   packet.  This added overhead decreases the effective end-to-end path
   MTU (unless fragmentation and reassembly are used).  Some transit
   networks are known to provide larger MTU values than the typical
   value of 1500 bytes for popular access technologies used at end hosts
   (e.g., IEEE 802.3 and 802.11).  However, placing the LISP router
   connecting to such a network at the customer edge could possibly
   bring up MTU issues, depending on the link type to the provider as
   opposed to the following scenario.  See [RFC4459] for MTU
   considerations of tunneling protocols and how to mitigate potential
   issues.  Still, even with these mitigations, path MTU issues are
   still possible.

2.1.2.  Provider Edge (PE)

   The other location at the core-edge boundary for deploying LISP
   routers is at the Internet service provider edge.  The main incentive
   for this case is that the customer does not have to upgrade the CE
   router(s) or change the configuration of any equipment.
   Encapsulation/decapsulation happens in the provider's network, which
   may be able to serve several customers with a single device.  For

   large ISPs with many residential/business customers asking for LISP,
   this can lead to important savings, since there is no need to upgrade
   the software (or hardware, if that's the case) at each client's
   location.  Instead, they can upgrade the software (or hardware) on a
   few PE routers serving the customers.  This scenario is depicted in
   Figure 2.

                 +----------+        +------------------+
                 |   ISP1   |        |       ISP2       |
                 |          |        |                  |
                 |  +----+  |        |  +----+  +----+  |
                 +--|xTR1|--+        +--|xTR2|--|xTR3|--+
                    +----+              +----+  +----+
                       |                  |       |
                       |                  |       |
                       +--<[LISP site]>---+-------+

                    Figure 2: xTRs at the Provider Edge

   While this approach can make transition easy for customers and may be
   cheaper for providers, the LISP site loses one of the main benefits
   of LISP: ingress traffic engineering.  Since the provider controls
   the ETRs, additional complexity would be needed to allow customers to
   modify their mapping entries.

   The problem is aggravated when the LISP site is multihomed.  Consider
   the scenario in Figure 2: whenever a change to TE policies is
   required, the customer contacts both ISP1 and ISP2 to make the
   necessary changes on the routers (if they provide this possibility).
   It is, however, unlikely that both ISPs will apply changes
   simultaneously, which may lead to inconsistent state for the mappings
   of the LISP site.  Since the different upstream ISPs are usually
   competing business entities, the ETRs may even be configured to
   compete, to either attract all the traffic or get no traffic.  The
   former will happen if the customer pays per volume, the latter if the
   connectivity has a fixed price.  A solution could be to configure the
   Map-Server(s) to do proxy-replying and have the Mapping Service
   Provider (MSP) apply policies.

   Additionally, since xTR1, xTR2, and xTR3 are in different
   administrative domains, locator reachability information is unlikely
   to be exchanged among them, making it difficult to set the
   Locator-Status-Bits (LSBs) correctly on encapsulated packets.
   Because of this, and due to the security concerns about LSBs as
   described in [LISP-THREATS], their use is discouraged (set the L-bit
   to 0).  Map-Versioning is another alternative [RFC6834].

   Compared to the customer edge scenario, deploying LISP at the
   provider edge might have the advantage of diminishing potential MTU
   issues, because the Tunnel Router is closer to the core, where links
   typically have higher MTUs than edge network links.

2.1.3.  Tunnel Routers behind NAT

   "NAT" in this section refers to IPv4 network address and port
   translation.  ITR

           _.--.                                           _.--.
       ,-''     `--.              +-------+            ,-''     `--.
      '     EID     `   (Private) |  NAT  | (Public) ,'     RLOC    `.
     (                )---[ITR]---|       |---------(                 )
      .    space    ,'  (Address) |  Box  |(Address)  .    space    ,'
       `--.     _.-'              +-------+            `--.     _.-'
           `--''                                           `--''

                         Figure 3: ITR behind NAT

   Packets encapsulated by an ITR are just UDP packets from a NAT
   device's point of view, and they are handled like any UDP packet;
   there are no additional requirements for LISP data packets.

   Map-Requests sent by an ITR, which create the state in the NAT table,
   have a different 5-tuple in the IP header than the Map-Reply
   generated by the authoritative ETR.  Since the source address of this
   packet is different from the destination address of the request
   packet, no state will be matched in the NAT table and the packet will
   be dropped.  To avoid this, the NAT device has to do the following:

   o  Send all UDP packets with source port 4342, regardless of the
      destination port, to the RLOC of the ITR.  The simplest way to
      achieve this is configuring 1:1 NAT mode from the external RLOC of
      the NAT device to the ITR's RLOC (called "DMZ" mode in consumer
      broadband routers).

   o  Rewrite the ITR-AFI and "Originating ITR RLOC Address" fields in
      the payload.

   This setup supports only a single ITR behind the NAT device.  ETR

   An ETR placed behind NAT is reachable from the outside by the
   Internet-facing locator of the NAT device.  It needs to know this
   locator (and configure a loopback interface with it), so that it can
   use it in Map-Reply and Map-Register messages.  Thus, support for
   dynamic locators for the mapping database is needed in LISP

   Again, only one ETR behind the NAT device is supported.

           _.--.                                           _.--.
       ,-''     `--.              +-------+            ,-''     `--.
      '     EID     `   (Private) |  NAT  | (Public) ,'     RLOC    `.
     (                )---[ETR]---|       |---------(                 )
      .    space    ,'  (Address) |  Box  |(Address)  .    space    ,'
       `--.     _.-'              +-------+            `--.     _.-'
           `--''                                           `--''

                        Figure 4: ETR behind NAT  Additional Notes

   An implication of the issues described above is that LISP sites with
   xTRs cannot be behind carrier-based NATs, since two different sites
   would collide on the same forwarded UDP port.  An alternative to
   static hole-punching to explore is the use of the Port Control
   Protocol (PCP) [RFC6887].

   We only include this scenario due to completeness, to show that a
   LISP site can be deployed behind NAT should it become necessary.
   However, LISP deployments behind NAT should be avoided, if possible.

2.2.  Functional Models with Tunnel Routers

   This section describes how certain LISP deployments can provide
   network functions.

2.2.1.  Split ITR/ETR

   In a simple LISP deployment, xTRs are located at the border of the
   LISP site (see Section 2.1.1).  In this scenario, packets are routed
   inside the domain according to the EID.  However, more complex
   networks may want to route packets according to the destination RLOC.
   This would enable them to choose the best egress point.

   The LISP specification separates the ITR and ETR functionality and
   allows both entities to be deployed in separated network equipment.
   ITRs can be deployed closer to the host (i.e., access routers).  This
   way, packets are encapsulated as soon as possible, and egress point
   selection is driven by operational policy.  In turn, ETRs can be
   deployed at the border routers of the network, and packets are
   decapsulated as soon as possible.  Once decapsulated, packets are
   routed based on the destination EID according to internal routing

   We can see an example in Figure 5.  The Source (S) transmits packets
   using its EID, and in this particular case packets are encapsulated
   at ITR_1.  The encapsulated packets are routed inside the domain
   according to the destination RLOC and can egress the network through
   the best point (i.e., closer to the RLOC's Autonomous System (AS)).
   On the other hand, inbound packets are received by ETR_1, which
   decapsulates them.  Then, packets are routed towards S according to
   the EID, again following the best path.

      |                                       |
      |       +-------+                   +-------+         +-------+
      |       | ITR_1 |---------+         | ETR_1 |-RLOC_A--| ISP_A |
      |       +-------+         |         +-------+         +-------+
      |  +-+        |           |             |
      |  |S|        |    IGP    |             |
      |  +-+        |           |             |
      |       +-------+         |         +-------+         +-------+
      |       | ITR_2 |---------+         | ETR_2 |-RLOC_B--| ISP_B |
      |       +-------+                   +-------+         +-------+
      |                                       |

                     Figure 5: Split ITR/ETR Scenario

   This scenario has a set of implications:

   o  The site must carry more-specific routes in order to choose the
      best egress point, and typically BGP is used for this, increasing
      the complexity of the network.  However, this is usually already
      the case for LISP sites that would benefit from this scenario.

   o  If the site is multihomed to different ISPs and any of the
      upstream ISPs are doing unicast reverse path forwarding (uRPF)
      filtering, this scenario may become impractical.  To set the
      correct source RLOC in the encapsulation header, ITRs need to
      first determine which ETR will be used by the outgoing packet.
      This adds complexity and reliability concerns.

   o  In LISP, ITRs set the reachability bits when encapsulating data
      packets.  Hence, ITRs need a mechanism to be aware of the liveness
      of all ETRs serving their site.

   o  The MTU within the site network must be large enough to
      accommodate encapsulated packets.

   o  In this scenario, each ITR is serving fewer hosts than in the case
      when it is deployed at the border of the network.  It has been
      shown that the cache hit rate grows logarithmically with the
      amount of users [CACHE].  Taking this into account, when ITRs are
      deployed closer to the host the effectiveness of the mapping cache
      may be lower (i.e., the miss rate is higher).  Another consequence
      of this is that the site may transmit a higher amount of
      Map-Requests, increasing the load on the distributed mapping

   o  By placing the ITRs inside the site, they will still need global
      RLOCs.  This may add complexity to intra-site routing
      configurations and more intra-site issues when there is a change
      of providers.

2.2.2.  Inter-Service-Provider Traffic Engineering

   At the time of this writing, if two ISPs want to control their
   ingress TE policies for transit traffic between them, they need to
   rely on existing BGP mechanisms.  This typically means deaggregating
   prefixes to choose on which upstream link packets should enter.  This
   either is not feasible (if fine-grained per-customer control is
   required, the very-specific prefixes may not be propagated) or
   increases DFZ table size.

   Typically, LISP is seen as applicable only to stub networks; however,
   LISP can also be applied in a recursive manner, providing service
   provider ingress/egress TE capabilities without impacting the DFZ
   table size.

   In order to implement this functionality with LISP, consider the
   scenario depicted in Figure 6.  The two ISPs willing to achieve
   ingress/egress TE are labeled as ISP_A and ISP_B.  They are servicing
   Stub1 and Stub2, respectively.  Both are required to be LISP sites
   with their own xTRs.  In this scenario, we assume that Stub1 and
   Stub2 are communicating with each other; thus, ISP_A and ISP_B offer
   transit for such communications.  ISP_A has RLOC_A1 and RLOC_A2 as
   upstream IP addresses, while ISP_B has RLOC_B1 and RLOC_B2.  The
   shared goal among ISP_A and ISP_B is to control the transit traffic
   flow between RLOC_A1/A2 and RLOC_B1/B2.

    Stub1 ...   +-------+      ,-''     `--.      +-------+   ... Stub2
             \  |   R_A1|----,'             `. ---|R_B1   |  /
              --|       |   (     Transit     )   |       |--
     ...  .../  |   R_A2|-----.             ,' ---|R_B2   |  \... ...
                +-------+      `--.     _.-'      +-------+
     ...  ...     ISP_A            `--''            ISP_B     ... ...

               Figure 6: Inter-Service-Provider TE Scenario

   Both ISPs deploy xTRs on RLOC_A1/A2 and RLOC_B1/B2, respectively and
   reach a bilateral agreement to deploy their own private mapping
   system.  This mapping system contains bindings between the RLOCs of
   Stub1 and Stub2 (owned by ISP_A and ISP_B, respectively) and RLOC_A1/
   A2 and RLOC_B1/B2.  Such bindings are in fact the TE policies between
   both ISPs, and the convergence time is expected to be fast, since
   ISPs only have to update/query a mapping to/from the database.

   The packet flow is as follows.  First, a packet originated at Stub1
   towards Stub2 is LISP encapsulated by Stub1's xTR.  The xTR of ISP_A
   recursively encapsulates it, and according to the TE policies stored
   in the private mapping system the ISP_A xTR chooses RLOC_B1 or
   RLOC_B2 as the outer encapsulation destination.  Note that the packet
   transits between ISP_A and ISP_B double-encapsulated.  Upon reception
   at the xTR of ISP_B, the packet is decapsulated and sent towards
   Stub2, which performs the last decapsulation.

   This deployment scenario, which uses recursive LISP, includes three
   important caveats.  First, it is intended to be deployed between only
   two ISPs.  If more than two ISPs use this approach, then either the
   xTRs deployed at the participating ISPs must query multiple mapping
   systems, or the ISPs must agree on a common shared mapping system.
   Furthermore, keeping this deployment scenario restricted to only two
   ISPs maintains a scalable solution, given that only two entities need
   to agree on using recursive LISP and only one private mapping system
   is involved.

   Second, the scenario is only recommended for ISPs providing
   connectivity to LISP sites, such that source RLOCs of packets to be
   recursively encapsulated belong to said ISP.  Otherwise, the
   participating ISPs must register prefixes they do not own in the
   above-mentioned private mapping system.  This results in either
   requiring complex authentication mechanisms or enabling simple
   traffic redirection attacks.  Failure to follow these recommendations
   may lead to operational security issues when deploying this scenario.

   And third, recursive encapsulation models are typically complex to
   troubleshoot and debug.

   Besides these recommendations, the main disadvantages of this
   deployment case are:

   o  An extra LISP header is needed.  This increases the packet size
      and requires that the MTU between both ISPs accommodate double-
      encapsulated packets.

   o  The ISP ITR must encapsulate packets and therefore must know the
      RLOC-to-RLOC bindings.  These bindings are stored in a mapping
      database and may be cached in the ITR's mapping cache.  Cache
      misses lead to an additional lookup latency, unless a push-based
      mapping system is used for the private mapping system.

   o  Maintaining the shared mapping database involves operational

2.3.  Summary and Feature Matrix

   When looking at the deployment scenarios and functional models above,
   there are several things to consider when choosing an appropriate
   model, depending on the type of the organization doing the

   For home users and small sites that wish to multihome and have
   control over their ISP options, the "CE" scenario offers the most
   advantages: it's simple to deploy, and in some cases it only requires
   a software upgrade of the Customer Premises Equipment (CPE), getting
   mapping service, and configuring the router.  It retains control of
   TE and choosing upstreams by the user.  It doesn't provide too many
   advantages to ISPs, due to the lessened dependence on their services
   in cases of multihomed clients.  It is also unlikely that ISPs
   wishing to offer LISP to their customers will choose the "CE" model,
   as they would need to send a technician to each customer and,
   potentially, a new CPE device.  Even if they have remote control over
   the router and a software upgrade could add LISP support, the
   operation is too risky.

   For a network operator, a good option to deploy is the "PE" scenario,
   unless a hardware upgrade is required for its edge routers to support
   LISP (in which case upgrading CPEs may be simpler).  It retains
   control of TE as well as the choice of Proxy Egress Tunnel Router
   (PETR) and Map-Server/Map-Resolver.  It also lowers potential MTU
   issues, as discussed above.  Network operators should also explore
   the "inter-service-provider TE" (recursive) functional model for
   their TE needs.

   To optimize their traffic flow, large organizations can benefit the
   most from the "split ITR/ETR" functional model.

   The following table gives a quick overview of the features supported
   by each of the deployment scenarios discussed above (marked with an
   "x" in the appropriate column): "CE" for customer edge, "PE" for
   provider edge, "Split" for split ITR/ETR, and "Recursive" for
   inter-service-provider traffic engineering.  The discussed features

   Control of ingress TE:  This scenario allows the LISP site to easily
      control LISP ingress traffic engineering policies.

   No modifications to existing int. network infrastructure:  This
      scenario doesn't require the LISP site to modify internal network

   Locator-Status-Bits sync:  This scenario allows easy synchronization
      of the Locator Status Bits.

   MTU/PMTUD issues minimized:  The scenario minimizes potential MTU and
      Path MTU Discovery (PMTUD) issues.

   Feature                         CE    PE    Split   Recursive   NAT
   Control of ingress TE            x     -      x         x        x
   No modifications to existing
      int. network infrastructure   x     x      -         -        x
   Locator-Status-Bits sync         x     -      x         x        -
   MTU/PMTUD issues minimized       -     x      -         -        -

3.  Map-Servers and Map-Resolvers

   Map-Servers and Map-Resolvers make up the LISP mapping system and
   provide a means to find authoritative EID-to-RLOC mapping
   information, conforming to [RFC6833].  They are meant to be deployed
   in RLOC space, and their operation behind NAT is not supported.

3.1.  Map-Servers

   The Map-Server learns EID-to-RLOC mapping entries from an
   authoritative source and publishes them in the distributed mapping
   database.  These entries are learned through authenticated
   Map-Register messages sent by authoritative ETRs.  Also, upon
   reception of a Map-Request, the Map-Server verifies that the
   destination EID matches an EID-Prefix for which it is authoritative
   and then re-encapsulates and forwards it to a matching ETR.
   Map-Server functionality is described in detail in [RFC6833].

   The Map-Server is provided by a Mapping Service Provider (MSP).  The
   MSP participates in the global distributed mapping database
   infrastructure by setting up connections to other participants
   according to the specific mapping system that is employed (e.g.,
   Alternative Logical Topology (ALT) [RFC6836], Delegated Database Tree
   (DDT) [LISP-DDT]).  Participation in the mapping database and the
   storing of EID-to-RLOC mapping data are subject to the policies of
   the "root" operators, who should check ownership rights for the
   EID-Prefixes stored in the database by participants.  These policies
   are out of scope for this document.

   The LISP DDT protocol is used by LISP MSPs to provide reachability
   between those providers' Map-Resolvers and Map-Servers.  The DDT root
   is currently operated by a collection of organizations on an open
   basis.  See [DDT-ROOT] for more details.  Similarly to the DNS root,
   it has several different server instances using names of the letters
   of the Greek alphabet (alpha, delta, etc.), operated by independent
   organizations.  When this document was published, there were 6 such
   instances, with one of them being anycasted.  [DDT-ROOT] provides the
   list of server instances on its web site and configuration files for
   several Map-Server implementations.  The DDT root and LISP Mapping
   Providers both rely on and abide by existing allocation policies as
   defined by Regional Internet Registries (RIRs) to determine prefix
   ownership for use as EIDs.

   It is expected that the DDT root organizations will continue to
   evolve in response to experimentation with LISP deployments for
   Internet edge multihoming and VPN use cases.

   In all cases, the MSP configures its Map-Server(s) to publish the
   prefixes of its clients in the distributed mapping database and start
   encapsulating and forwarding Map-Requests to the ETRs of the AS.
   These ETRs register their prefix(es) with the Map-Server(s) through
   periodic authenticated Map-Register messages.  In this context, for
   some LISP sites, there is a need for mechanisms to:

   o  Automatically distribute EID-Prefix(es) shared keys between the
      ETRs and the EID-registrar Map-Server.

   o  Dynamically obtain the address of the Map-Server in the ETR of
      the AS.

   The Map-Server plays a key role in the reachability of the
   EID-Prefixes it is serving.  On one hand, it is publishing these
   prefixes into the distributed mapping database, and on the other
   hand, it is encapsulating and forwarding Map-Requests to the
   authoritative ETRs of these prefixes.  ITRs encapsulating towards
   EIDs for which a failed Map-Server is responsible will be unable to

   look up any of their covering prefixes.  The only exceptions are the
   ITRs that already contain the mappings in their local caches.  In
   this case, ITRs can reach ETRs until the entry expires (typically
   24 hours).  For this reason, redundant Map-Server deployments are
   desirable.  A set of Map-Servers providing high-availability service
   to the same set of prefixes is called a redundancy group.  ETRs are
   configured to send Map-Register messages to all Map-Servers in the
   redundancy group.  The configuration for fail-over (or
   load-balancing, if desired) among the members of the group depends on
   the technology behind the mapping system being deployed.  Since ALT
   is based on BGP and DDT takes its inspiration from the Domain Name
   System (DNS), deployments can leverage current industry best
   practices for redundancy in BGP and DNS.  These best practices are
   out of scope for this document.

   Additionally, if a Map-Server has no reachability for any ETR serving
   a given EID block, it should not originate that block into the
   mapping system.

3.2.  Map-Resolvers

   A Map-Resolver is a network infrastructure component that accepts
   LISP-encapsulated Map-Requests, typically from an ITR, and finds the
   appropriate EID-to-RLOC mapping by consulting the distributed mapping
   database.  Map-Resolver functionality is described in detail in

   Anyone with access to the distributed mapping database can set up a
   Map-Resolver and provide EID-to-RLOC mapping lookup service.
   Database access setup is mapping system specific.

   For performance reasons, it is recommended that LISP sites use
   Map-Resolvers that are topologically close to their ITRs.  ISPs
   supporting LISP will provide this service to their customers,
   possibly restricting access to their user base.  LISP sites not in
   this position can use open access Map-Resolvers, if available.
   However, regardless of the availability of open access resolvers, the
   MSP providing the Map-Server(s) for a LISP site should also make
   available Map-Resolver(s) for the use of that site.

   In medium- to large-size ASes, ITRs must be configured with the RLOC
   of a Map-Resolver; this type of operation can be done manually.
   However, in Small Office/Home Office (SOHO) scenarios, a mechanism
   for autoconfiguration should be provided.

   One solution to avoid manual configuration in LISP sites of any size
   is the use of anycast [RFC4786] RLOCs for Map-Resolvers, similar to
   the DNS root server infrastructure.  Since LISP uses UDP

   encapsulation, the use of anycast would not affect reliability.  LISP
   routers are then shipped with a preconfigured list of well-known
   Map-Resolver RLOCs, which can be edited by the network administrator,
   if needed.

   The use of anycast also helps improve mapping lookup performance.
   Large MSPs can increase the number and geographical diversity of
   their Map-Resolver infrastructure, using a single anycasted RLOC.
   Once LISP deployment is advanced enough, very large content providers
   may also be interested in running this kind of setup, to ensure
   minimal connection setup latency for those connecting to their
   network from LISP sites.

   While Map-Servers and Map-Resolvers implement different
   functionalities within the LISP mapping system, they can coexist on
   the same device.  For example, MSPs offering both services can deploy
   a single Map-Resolver/Map-Server in each PoP where they have a

4.  Proxy Tunnel Routers

4.1.  PITRs

   Proxy Ingress Tunnel Routers (PITRs) are part of the non-LISP/LISP
   transition mechanism, allowing non-LISP sites to reach LISP sites.
   They announce via BGP certain EID-Prefixes (aggregated, whenever
   possible) to attract traffic from non-LISP sites towards EIDs in the
   covered range.  They do the mapping system lookup and encapsulate
   received packets towards the appropriate ETR.  Note that for the
   reverse path, LISP sites can reach non-LISP sites by simply not
   encapsulating traffic.  See [RFC6832] for a detailed description of
   PITR functionality.

   The success of new protocols depends greatly on their ability to
   maintain backwards compatibility and interoperate with the
   protocol(s) they intend to enhance or replace, and on the incentives
   to deploy the necessary new software or equipment.  A LISP site needs
   an interworking mechanism to be reachable from non-LISP sites.  A
   PITR can fulfill this role, enabling early adopters to see the
   benefits of LISP, similar to tunnel brokers helping the transition
   from IPv4 to IPv6.  A site benefits from new LISP functionality
   (proportionally with existing global LISP deployment) when migrating
   to LISP, so it has the incentives to deploy the necessary Tunnel
   Routers.  In order to be reachable from non-LISP sites, it has two
   options: keep announcing its prefix(es) with BGP, or have a PITR
   announce prefix(es) covering them.

   If the goal of reducing the DFZ routing table size is to be reached,
   the second option is preferred.  Moreover, the second option allows
   LISP-based ingress traffic engineering from all sites.  However, the
   placement of PITRs significantly influences performance and
   deployment incentives.  Section 5 is dedicated to the migration to a
   LISP-enabled Internet and includes deployment scenarios for PITRs.

4.2.  PETRs

   In contrast to PITRs, PETRs are not required for the correct
   functioning of all LISP sites.  There are two cases where they can be
   of great help:

   o  LISP sites with unicast reverse path forwarding (uRPF)
      restrictions, and

   o  Communication between sites using different address family RLOCs.

   In the first case, uRPF filtering is applied at the LISP site's
   upstream provider's PE router.  When forwarding traffic to non-LISP
   sites, an ITR does not encapsulate packets, leaving the original IP
   headers intact.  As a result, packets will have EIDs in their source
   address.  Since we are discussing the transition period, we can
   assume that a prefix covering the EIDs belonging to the LISP site is
   advertised to the global routing tables by a PITR, and the PE router
   has a route towards it.  However, the next hop will not be on the
   interface towards the CE router, so non-encapsulated packets will
   fail uRPF checks.

   To avoid this filtering, the affected ITR encapsulates packets
   towards the locator of the PETR for non-LISP destinations.  Now the
   source address of the packets, as seen by the PE router, is the ITR's
   locator, which will not fail the uRPF check.  The PETR then
   decapsulates and forwards the packets.

   The second use case is IPv4-to-IPv6 transition.  Service providers
   using older access network hardware that only supports IPv4 can still
   offer IPv6 to their clients by providing a CPE device running LISP,
   and PETR(s) for accessing IPv6-only non-LISP sites and LISP sites,
   with IPv6-only locators.  Packets originating from the client LISP
   site for these destinations would be encapsulated towards the PETR's
   IPv4 locator.  The PETR is in a native IPv6 network, decapsulating
   and forwarding packets.  For non-LISP destinations, the packet
   travels natively from the PETR.  For LISP destinations with IPv6-only
   locators, the packet will go through a PITR in order to reach its

   For more details on PETRs, see [RFC6832].

   PETRs can be deployed by ISPs wishing to offer value-added services
   to their customers.  As is the case with PITRs, PETRs too may
   introduce path stretch (the ratio between the cost of the selected
   path and that of the optimal path).  Because of this, the ISP needs
   to consider the tradeoff of using several devices close to the
   customers to minimize it, or fewer devices farther away from the
   customers to minimize cost instead.

   Since the deployment incentives for PITRs and PETRs are different, it
   is likely that they will be deployed in separate devices, except for
   the Content Delivery Network (CDN) case, which may deploy both in a
   single device.

   In all cases, the existence of a PETR involves another step in the
   configuration of a LISP router.  CPE routers, which are typically
   configured by DHCP, stand to benefit most from PETRs.
   Autoconfiguration of the PETR locator could be achieved by a DHCP
   option or by adding a PETR field to either Map-Notify or Map-Reply

5.  Migration to LISP

   This section discusses a deployment architecture to support the
   migration to a LISP-enabled Internet.  The loosely defined terms
   "early transition phase", "late transition phase", and "LISP Internet
   phase" refer to time periods when LISP sites are a minority, a
   majority, or represent all edge networks, respectively.

5.1.  LISP+BGP

   For sites wishing to migrate to LISP with their Provider-Independent
   (PI) prefix, the least disruptive way is to upgrade their border
   routers to support LISP and register the prefix into the LISP mapping
   system, but to keep announcing it with BGP as well.  This way, LISP
   sites will reach them over LISP, while legacy sites will be
   unaffected by the change.  The main disadvantage of this approach is
   that no decrease in the DFZ routing table size is achieved.  Still,
   just increasing the number of LISP sites is an important gain, as an
   increasing LISP/non-LISP site ratio may decrease the need for
   BGP-based traffic engineering that leads to prefix deaggregation.
   That, in turn, may lead to a decrease in the DFZ size and churn in
   the late transition phase.

   This scenario is not limited to sites that already have their
   prefixes announced with BGP.  Newly allocated EID blocks could follow
   this strategy as well during the early LISP deployment phase,
   depending on the cost/benefit analysis of the individual networks.
   Since this leads to an increase in the DFZ size, the following
   architecture should be preferred for new allocations.

5.2.  Mapping Service Provider (MSP) PITR Service

   In addition to publishing their clients' registered prefixes in the
   mapping system, MSPs with enough transit capacity can offer PITR
   service to them as a separate service.  This service is especially
   useful for new PI allocations to sites without existing BGP
   infrastructure wishing to avoid BGP altogether.  The MSP announces
   the prefix into the DFZ, and the client benefits from ingress traffic
   engineering without prefix deaggregation.  The downside of this
   scenario is added path stretch.

   Routing all non-LISP ingress traffic through a third party that is
   not one of its ISPs is only feasible for sites with modest amounts of
   traffic (like those using the IPv6 tunnel broker services today),
   especially in the first stage of the transition to LISP, with a
   significant number of legacy sites.  This is because the handling of
   said traffic is likely to result in additional costs, which would be
   passed down to the client.  When the LISP/non-LISP site ratio becomes
   high enough, this approach can prove increasingly attractive.

   Compared to LISP+BGP, this approach avoids DFZ bloat caused by prefix
   deaggregation for traffic engineering purposes, resulting in slower
   routing table increase in the case of new allocations and potential
   decrease for existing ones.  Moreover, MSPs serving different clients
   with adjacent aggregatable prefixes may lead to additional decrease,
   but quantifying this decrease is subject to future research study.

5.3.  Proxy-ITR Route Distribution (PITR-RD)

   Instead of a LISP site or the MSP announcing its EIDs with BGP to the
   DFZ, this function can be outsourced to a third party, a PITR Service
   Provider (PSP).  This will result in a decrease in operational
   complexity at both the site and the MSP.

   The PSP manages a set of distributed PITR(s) that will advertise the
   corresponding EID-Prefixes through BGP to the DFZ.  These PITRs will
   then encapsulate the traffic they receive for those EIDs towards the
   RLOCs of the LISP site, ensuring their reachability from non-LISP

   While it is possible for a PSP to manually configure each client's
   EID-Routes to be announced, this approach offers little flexibility
   and is not scalable.  This section presents a scalable architecture
   that offers automatic distribution of EID-Routes to LISP sites and
   service providers.

   The architecture requires no modification to existing LISP network
   elements, but it introduces a new (conceptual) network element, the
   EID-Route Server, which is defined as a router that either propagates
   routes learned from other EID-Route Servers or originates EID-Routes.
   The EID-Routes that it originates are those for which it is
   authoritative.  It propagates these routes to Proxy-ITRs within the
   AS of the EID-Route Server.  It is worth noting that a BGP-capable
   router can also be considered an EID-Route Server.

   Further, an EID-Route is defined as a prefix originated via the Route
   Server of the MSP, which should be aggregated if the MSP has multiple
   customers inside a single large continuous prefix.  This prefix is
   propagated to other PITRs both within the MSP and to other PITR
   operators with which it peers.  EID-Route Servers are operated by
   either the LISP site, MSPs, or PSPs and may be collocated with a
   Map-Server or PITR, but they are functionally discrete entities.
   They distribute EID-Routes, using BGP, to other domains according to
   policies set by participants.

                              MSP (AS64500)
                              RS ---> PITR
                               |        /
                               |  _.--./
                              ,-''    /`--.
             LISP site   ---,' |     v     `.
                           (   |   DFZ       )----- Mapping system
         non-LISP site   ----. |    ^      ,'
                              `--. /   _.-'
                               |  `--''
                               v /
                             PSP (AS64501)

                      Figure 7: PITR-RD Architecture

   The architecture described above decouples EID origination from route
   propagation, with the following benefits:

   o  Can accurately represent business relationships between PITR

   o  Is more mapping system agnostic

   o  Makes minor changes to PITR implementation; no changes to other

   In the example in Figure 7, we have a MSP providing services to the
   LISP site.  The LISP site does not run BGP and gets an EID allocation
   directly from a RIR, or from the MSP, which may be a Local Internet
   Registry (LIR).  Existing PI allocations can be migrated as well.
   The MSP ensures the presence of the prefix in the mapping system and
   runs an EID-Route Server to distribute it to PSPs.  Since the LISP
   site does not run BGP, the prefix will be originated with the AS
   number of the MSP.

   In the simple case depicted in Figure 7, the EID-Route of a LISP site
   will be originated by the Route Server and announced to the DFZ by
   the PSP's PITRs with AS path 64501 64500.  From that point on, the
   usual BGP dynamics apply.  This way, routes announced by the PITR are
   still originated by the authoritative Route Server.  Note that the
   peering relationships between MSPs/PSPs and those in the underlying
   forwarding plane may not be congruent, making the AS path to a PITR
   shorter than it is in reality.

   The non-LISP site will select the best path towards the EID-Prefix
   according to its local BGP policies.  Since AS-path length is usually
   an important metric for selecting paths, careful placement of PITRs
   could significantly reduce path stretch between LISP and non-LISP

   The architecture allows for flexible policies between MSPs/PSPs.
   Consider the EID-Route Server networks as control plane overlays,
   facilitating the implementation of policies necessary to reflect the
   business relationships between participants.  The results are then
   injected into the common underlying forwarding plane.  For example,
   some MSPs/PSPs may agree to exchange EID-Prefixes and only announce
   them to each of their forwarding plane customers.  Global
   reachability of an EID-Prefix depends on the MSP from which the LISP
   site buys service and is also subject to agreement between the above-
   mentioned parties.

   In terms of impact on the DFZ, this architecture results in a slower
   routing table increase for new allocations, since traffic engineering
   will be done at the LISP level.  For existing allocations migrating
   to LISP, the DFZ may decrease, since MSPs may be able to aggregate
   the prefixes announced.

   Compared to LISP+BGP, this approach avoids DFZ bloat caused by prefix
   deaggregation for traffic engineering purposes, resulting in slower
   routing table increase in the case of new allocations and potential
   decrease for existing ones.  Moreover, MSPs serving different clients
   with adjacent aggregatable prefixes may lead to additional decrease,
   but quantifying this decrease is subject to future research study.

   The flexibility and scalability of this architecture do not come
   without a cost, however: A PSP operator has to establish either
   transit or peering relationships to improve its connectivity.

5.4.  Migration Summary

   Registering a domain name typically entails an annual fee that should
   cover the operating expenses for publishing the domain in the global
   DNS.  This situation is similar for several other registration
   services.  A LISP MSP client publishing an EID-Prefix in the LISP
   mapping system has the option of signing up for PITR services as
   well, for an extra fee.  These services may be offered by the MSP
   itself, but it is expected that specialized PSPs will do it.  Clients
   that do not sign up will be responsible for getting non-LISP traffic
   to their EIDs (using the LISP+BGP scenario).

   Additionally, Tier 1 ISPs have incentives to offer PITR services to
   non-subscribers in strategic places just to attract more traffic from
   competitors and thus more revenue.

   The following table presents the expected effects that the transition
   scenarios at various phases will have on the DFZ routing table size:

    Phase            | LISP+BGP     | MSP PITR        | PITR-RD
    Early transition | no change    | slower increase | slower increase
    Late transition  | may decrease | slower increase | slower increase
    LISP Internet    |             considerable decrease

   It is expected that PITR-RD will coexist with LISP+BGP during the
   migration, with the latter being more popular in the early transition
   phase.  As the transition progresses and the MSP PITR and PITR-RD
   ecosystem gets more ubiquitous, LISP+BGP should become less
   attractive, slowing down the increase of the number of routes in
   the DFZ.

   Note that throughout Section 5 we focused on the effects of LISP
   deployment on the DFZ routing table size.  Other metrics may be
   impacted as well but to the best of our knowledge have not been
   measured as yet.

6.  Security Considerations

   All security implications of LISP deployments are to be discussed in
   separate documents.  [LISP-THREATS] gives an overview of LISP threat
   models, including ETR operators attracting traffic by overclaiming an
   EID-Prefix (Section 4.4.3 of [LISP-THREATS]).  Securing mapping
   lookups is discussed in [LISP-SEC].

7.  Acknowledgements

   Many thanks to Margaret Wasserman for her contribution to the IETF 76
   presentation that kickstarted this work.  The authors would also like
   to thank Damien Saucez, Luigi Iannone, Joel Halpern, Vince Fuller,
   Dino Farinacci, Terry Manderson, Noel Chiappa, Hannu Flinck, Paul
   Vinciguerra, Fred Templin, Brian Haberman, and everyone else who
   provided input.

8.  References

8.1.  Normative References

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

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

8.2.  Informative References

   [CACHE]    Jung, J., Sit, E., Balakrishnan, H., and R. Morris, "DNS
              performance and the effectiveness of caching", IEEE/ACM
              Transactions on Networking (TON), Volume 10, Issue 5,
              pages 589-603, October 2002.

   [DDT-ROOT] "Introduction to LISP DDT: DDT Root", March 2014,

   [LISP-DDT] Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP
              Delegated Database Tree", Work in Progress, March 2013.

   [LISP-SEC] Maino, F., Ermagan, V., Cabellos-Aparicio, A., Saucez, D.,
              and O. Bonaventure, "LISP-Security (LISP-SEC)", Work in
              Progress, October 2013.

              Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats
              Analysis", Work in Progress, April 2014.

   [RFC4459]  Savola, P., "MTU and Fragmentation Issues with
              In-the-Network Tunneling", RFC 4459, April 2006.

   [RFC4786]  Abley, J. and K. Lindqvist, "Operation of Anycast
              Services", BCP 126, RFC 4786, December 2006.

   [RFC4984]  Meyer, D., Zhang, L., and K. Fall, "Report from the IAB
              Workshop on Routing and Addressing", RFC 4984,
              September 2007.

   [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.

   [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              April 2013.

   [TELCO96]  Federal Communications Commission, "Telecommunications Act
              of 1996", 1996, <http://transition.fcc.gov/telecom.html>.

Appendix A.  Step-by-Step Example BGP-to-LISP Migration Procedure

   To help the operational community deploy LISP, this informative
   section offers a step-by-step guide for migrating a BGP-based
   Internet presence to a LISP site.  It includes a pre-install/
   pre-turn-up checklist, and customer and provider activation

A.1.  Customer Pre-Install and Pre-Turn-Up Checklist

   1.  Determine how many current physical service provider connections
       the customer has, and their existing bandwidth and traffic
       engineering requirements.

       This information will determine the number of routing locators,
       and the priorities and weights that should be configured on
       the xTRs.

   2.  Make sure the customer router has LISP capabilities.

       *  Check the OS version of the CE router.  If LISP is an add-on,
          check to see if it is installed.

          This information can be used to determine if the platform is
          appropriate to support LISP, in order to determine if a
          software and/or hardware upgrade is required.

       *  Have the customer upgrade (if necessary, software and/or
          hardware) to be LISP capable.

   3.  Obtain the current running configuration of the CE router.  A
       suggested LISP router configuration example can be customized to
       the customer's existing environment.

   4.  Verify MTU handling.

       *  Request an increase in MTU to 1556 or more on service provider
          connections.  Prior to the MTU change, verify the transmission
          of a 1500-byte packet from the PxTR to the RLOC with the Don't
          Fragment (DF) bit set.

       *  Ensure that the customer is not filtering ICMP Unreachable or
          Time Exceeded messages on their firewall or router.

       LISP, like any tunneling protocol, will increase the size of
       packets when the LISP header is appended.  If increasing the MTU
       of the access links is not possible, care must be taken that ICMP
       is not being filtered in order to allow Path MTU Discovery to
       take place.

   5.  Validate member prefix allocation.

       This step checks to see whether the prefix used by the customer
       is a direct (Provider-Independent) prefix or a prefix assigned by
       a physical service provider (Provider Aggregatable).  If the
       prefixes are assigned by other service providers, then a Letter
       of Agreement is required to announce prefixes through the Proxy
       Service Provider.

   6.  Verify the member RLOCs and their reachability.

       This step ensures that the RLOCs configured on the CE router are
       in fact reachable and working.

   7.  Prepare for cut-over.

       *  If possible, have a host outside of all security and filtering
          policies connected to the console port of the edge router or

       *  Make sure the customer has access to the router in order to
          configure it.

A.2.  Customer Activating LISP Service

   1.  The customer configures LISP on CE router(s) according to the
       configuration recommended by the service provider.

       The LISP configuration consists of the EID-Prefix, the locators,
       and the weights and priorities of the mapping between the two
       values.  In addition, the xTR must be configured with
       Map-Resolver(s), Map-Server(s), and the shared key for
       registering to Map-Server(s).  If required, Proxy-ETR(s) may be
       configured as well.

       In addition to the LISP configuration:

       *  Ensure that the default routes(s) to next-hop external
          neighbors is included and RLOCs are present in the

       *  If two or more routers are used, ensure that all RLOCs are
          included in the LISP configuration on all routers.

       *  It will be necessary to redistribute the default route via IGP
          between the external routers.

   2.  When transition is ready, perform a soft shutdown on existing
       eBGP peer session(s).

       *  From the CE router, use the LISP Internet Groper (LIG)
          [RFC6835] to ensure that registration is successful.

       *  To verify LISP connectivity, find and ping LISP connected
          sites.  If possible, find ping destinations that are not
          covered by a prefix in the global BGP routing system, because
          PITRs may deliver the packets even if LISP connectivity is not
          working.  Traceroutes may help determine if this is the case.

       *  To verify connectivity to non-LISP sites, try accessing a
          landmark (e.g., a major Internet site) via a web browser.

A.3.  Cut-Over Provider Preparation and Changes

   1.  Verify site configuration, and then verify active registration on

       *  Authentication key.

       *  EID-Prefix.

   2.  Add EID space to map-cache on proxies.

   3.  Add networks to BGP advertisement on proxies.

       *  Modify route-maps/policies on PxTRs.

       *  Modify route policies on core routers (if non-connected

       *  Modify ingress policies on core routers.

       *  Ensure route announcement in looking glass servers,

   4.  Perform traffic verification test.

       *  Ensure that MTU handling is as expected (PMTUD working).

       *  Ensure Proxy-ITR map-cache population.

       *  Ensure access from traceroute/ping servers around Internet.

       *  Use a looking glass to check for external visibility of
          registration via several Map-Resolvers.

Authors' Addresses

   Lorand Jakab
   Cisco Systems
   170 Tasman Drive
   San Jose, CA  95134

   EMail: lojakab@cisco.com

   Albert Cabellos-Aparicio
   Technical University of Catalonia
   C/Jordi Girona, s/n
   BARCELONA  08034

   EMail: acabello@ac.upc.edu

   Florin Coras
   Technical University of Catalonia
   C/Jordi Girona, s/n
   BARCELONA  08034

   EMail: fcoras@ac.upc.edu

   Jordi Domingo-Pascual
   Technical University of Catalonia
   C/Jordi Girona, s/n
   BARCELONA  08034

   EMail: jordi.domingo@ac.upc.edu

   Darrel Lewis
   Cisco Systems
   170 Tasman Drive
   San Jose, CA  95134

   EMail: darlewis@cisco.com


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