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Versions: (draft-jakab-lisp-deployment) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 7215

Network Working Group                                           L. Jakab
Internet-Draft                                             Cisco Systems
Intended status: Experimental                       A. Cabellos-Aparicio
Expires: June 12, 2014                                          F. Coras
                                                      J. Domingo-Pascual
                                                 Technical University of
                                                               Catalonia
                                                                D. Lewis
                                                           Cisco Systems
                                                        December 9, 2013


             LISP Network Element Deployment Considerations
                   draft-ietf-lisp-deployment-11.txt

Abstract

   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.  This memo
   represents one stable point in that evolution of understanding.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 12, 2014.

Copyright Notice

   Copyright (c) 2013 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



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   (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 . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Deployment Scenarios . . . . . . . . . . . . . . . . . . .  4
       2.1.1.  Customer Edge  . . . . . . . . . . . . . . . . . . . .  4
       2.1.2.  Provider Edge  . . . . . . . . . . . . . . . . . . . .  6
       2.1.3.  Tunnel Routers Behind NAT  . . . . . . . . . . . . . .  7
         2.1.3.1.  ITR  . . . . . . . . . . . . . . . . . . . . . . .  7
         2.1.3.2.  ETR  . . . . . . . . . . . . . . . . . . . . . . .  8
         2.1.3.3.  Additional Notes . . . . . . . . . . . . . . . . .  8
     2.2.  Functional Models with Tunnel Routers  . . . . . . . . . .  8
       2.2.1.  Split ITR/ETR  . . . . . . . . . . . . . . . . . . . .  8
       2.2.2.  Inter-Service Provider Traffic Engineering . . . . . . 10
     2.3.  Summary and Feature Matrix . . . . . . . . . . . . . . . . 12
   3.  Map Resolvers and Map Servers  . . . . . . . . . . . . . . . . 13
     3.1.  Map Servers  . . . . . . . . . . . . . . . . . . . . . . . 13
     3.2.  Map Resolvers  . . . . . . . . . . . . . . . . . . . . . . 15
   4.  Proxy Tunnel Routers . . . . . . . . . . . . . . . . . . . . . 16
     4.1.  P-ITR  . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     4.2.  P-ETR  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   5.  Migration to LISP  . . . . . . . . . . . . . . . . . . . . . . 18
     5.1.  LISP+BGP . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.2.  Mapping Service Provider (MSP) P-ITR Service . . . . . . . 19
     5.3.  Proxy-ITR Route Distribution (PITR-RD) . . . . . . . . . . 19
     5.4.  Migration Summary  . . . . . . . . . . . . . . . . . . . . 22
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 23
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 23
   Appendix A.  Step-by-Step Example BGP to LISP Migration
                Procedure . . . . . . . . . . . . . . . . . . . . . . 24
     A.1.  Customer Pre-Install and Pre-Turn-up Checklist . . . . . . 24
     A.2.  Customer Activating LISP Service . . . . . . . . . . . . . 26
     A.3.  Cut-Over Provider Preparation and Changes  . . . . . . . . 27
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27




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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, which new network elements are introduced, and 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 the 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:  Active or passive device that is connected to other
      active or passive devices for transporting packet switched data.

   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 which 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, discussing the impact of
   deployment scenarios on the protocol specification.  For definition
   of terms, please refer to the appropriate documents (as cited in the
   respective sections).

   This experimental document describing deployment 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



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   modifications and enhancements of the LISP protocol mechanisms.
   Additionally, at the time of this writing there is no standardized
   security to implement.  Beware that there are no counter measures for
   any of the threads identified in [I-D.ietf-lisp-threats].  See
   Section 15 [of RFC 6830] for specific, known issues that are in need
   of further work during development, implementation, and
   experimentation, and [I-D.ietf-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), performing one or both of two separate
   functions:

   1.  Encapsulating packets originating from an end host to be
       transported over intermediary (transit) networks towards the
       other end-point 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),
   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

   The first scenario we discuss is customer edge, when xTR
   functionality is placed on the router(s) that connect the LISP site
   to its upstream(s), but are 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.








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                                ISP1    ISP2
                                 |        |
                                 |        |
                               +----+  +----+
                            +--|xTR1|--|xTR2|--+
                            |  +----+  +----+  |
                            |                  |
                            |     LISP site    |
                            +------------------+

                    Figure 1: xTRs at the customer edge

   From the LISP site 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 (Loc-Status-Bits, defined in [RFC6830])
   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
   with many external connections, distributed in geographically diverse
   points of presence (PoPs), 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 scenario).

   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 is used).  Some transit
   networks are known to provide larger MTU than the typical value of
   1500 bytes of 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 on how to mitigate potential issues.  Still, even



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   with these mitigations, path MTU issues are still possible.

2.1.2.  Provider Edge

   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 it'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: xTR at the PE

   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, either to attract all the traffic or to 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.



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   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 Loc-Status-
   Bits (LSB) correctly on encapsulated packets.  Because of this, and
   due to the security concerns about LSB described in
   [I-D.ietf-lisp-threats] their use is discouraged (set the L-bit to
   0).  Mapping 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.

2.1.3.1.  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 most simple 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).





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   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.

2.1.3.2.  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
   equipment.

   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

2.1.3.3.  Additional Notes

   An implication of the issues described above is that LISP sites with
   xTRs can not be behind carrier based NATs, since two different sites
   would collide on the port forwarding.  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



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   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 destination EID, according to internal routing
   policy.

   In the following figure we can see an example.  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 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 uRPF filtering, this scenario may become
      impractical.  ITRs need to determine the exit ETR, for setting the



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      correct source RLOC in the encapsulation header.  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  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 cache hit ratio 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 ratio 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
      database.

   o  By placing the ITRs inside the site, they will still need global
      RLOCs, and this may add complexity to intra-site routing
      configuration, and further 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
   is either 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 applicable only to stub networks, however the
   LISP protocol can be also 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 and 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



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   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 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 the xTRs
   deployed at the participating ISPs must either 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 the solution scalable, 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.



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

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

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

   o  The ISP ITR must encapsulate packets and therefore must know the
      RLOC-to-RLOC binding.  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  The operational overhead of maintaining the shared mapping
      database.

2.3.  Summary and Feature Matrix

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

   For home users and small site who wish to multihome and have control
   over their ISP options, the "CE" scenario offers the most advantages:
   it's simple to deploy, in some cases it only requires a software
   upgrade of the CPE, getting mapping serice, and configuring the
   router.  It ratains 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 case of multihomed clients.  It is
   also unlikely that ISP wiching to offer LISP to their customers will
   choose the "CE" placement: they need to send a technician to each
   customer, and potentially a new CPE.  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, choice of PETR, and MS/MR.  It also lowers potential
   MTU issues, as dicussed above.  Network operators should also explore
   the "Inter-SP TE" (recursive) functional model for their TE needs.

   Large organizations can benefit the most from the "Split ITR/ETR"
   functional model, to optimize their traffic flow.




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   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
   include:

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

   No modifcations to existing int. network infrastruncture:  The
      scenario doesn't require the LISP site to modify internal network
      configurations.

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

   MTU/PMTUD issues minimized:  The scenario minimizes potential MTU and
      Path MTU Discovery 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
    Loc-Status-Bits sync             x     -      x         x        -
    MTU/PMTUD issues minimized       -     x      -         -        -



3.  Map Resolvers and Map Servers

   Map Resolvers and Map Servers 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 for, and then re-
   encapsulates and forwards it to a matching ETR.  Map Server
   functionality is described in detail in [RFC6833].



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   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., ALT
   [RFC6836], DDT [I-D.ietf-lisp-ddt]).  Participation in the mapping
   database, and the storing of EID-to-RLOC mapping data is 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 the scope of this document.

   The LISP DDT protocol is used by LISP Mapping Service providers 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 5 such instances, one of them being anycasted.
   The Root provides the list of server instances on their 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 by Regional Internet Registries 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 multi-homing 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 the 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 under the
   responsibility of a failed Map Server will be unable to look up any
   of their covering prefixes.  The only exception are the ITRs that



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   already contain the mappings in their local cache.  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 was
   inspired 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 the scope of 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 which 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
   [RFC6833].

   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, operation which 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 RLOCs [RFC4786] 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 know Map



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   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 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
   presence.


4.  Proxy Tunnel Routers

4.1.  P-ITR

   Proxy Ingress Tunnel Routers (P-ITRs) 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 simply by not
   encapsulating traffic.  See [RFC6832] for a detailed description of
   P-ITR functionality.

   The success of new protocols depends greatly on their ability to
   maintain backwards compatibility and inter-operate 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
   P-ITR 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 going
   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 P-ITR
   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



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   LISP-based ingress traffic engineering from all sites.  However, the
   placement of P-ITRs significantly influences performance and
   deployment incentives.  Section 5 is dedicated to the migration to a
   LISP-enabled Internet, and includes deployment scenarios for P-ITRs.

4.2.  P-ETR

   In contrast to P-ITRs, P-ETRs 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 their upstream 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 P-ITR, 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 P-ETR 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 P-ETR then
   decapsulates and forwards the packets.

   The second use case is IPv4-to-IPv6 transition.  Service providers
   using older access network hardware, which only supports IPv4 can
   still offer IPv6 to their clients, by providing a CPE device running
   LISP, and P-ETR(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
   P-ETR's IPv4 locator.  The P-ETR is in a native IPv6 network,
   decapsulating and forwarding packets.  For non-LISP destination, the
   packet travels natively from the P-ETR.  For LISP destinations with
   IPv6-only locators, the packet will go through a P-ITR, in order to
   reach its destination.

   For more details on P-ETRs see [RFC6832].

   P-ETRs can be deployed by ISPs wishing to offer value-added services



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   to their customers.  As is the case with P-ITRs, P-ETRs 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 few devices, farther away from the
   customers, minimizing cost instead.

   Since the deployment incentives for P-ITRs and P-ETRs are different,
   it is likely they will be deployed in separate devices, except for
   the CDN case, which may deploy both in a single device.

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


5.  Migration to LISP

   This section discusses a deployment architecture to support the
   migration to a LISP-enabled Internet.  The loosely defined terms of
   "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 go LISP with their PI prefix the least
   disruptive way is to upgrade their border routers to support LISP,
   register the prefix into the LISP mapping system, but 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.





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5.2.  Mapping Service Provider (MSP) P-ITR Service

   In addition to publishing their clients' registered prefixes in the
   mapping system, MSPs with enough transit capacity can offer them
   P-ITR service as a separate service.  This service is especially
   useful for new PI allocations, to sites without existing BGP
   infrastructure, that wish 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 adding path stretch.

   Routing all non-LISP ingress traffic through a third party which 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 their EIDs with BGP to
   the DFZ, this function can be outsourced to a third party, a P-ITR
   Service Provider (PSP).  This will result in a decrease of the
   operational complexity both at the site and at the MSP.

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

   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



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   EID Route Server, defined as a router that either propagates routes
   learned from other EID Route Servers, or it originates EID Routes.
   The EID-Routes that it originates are those that it is authoritative
   for.  It propagates these routes to Proxy-ITRs within the AS of the
   EID Route Server.  It is worth to note that a BGP capable router can
   be also considered as an EID Route Server.

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

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

            Figure 7: The P-ITR Route Distribution architecture

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

   o  Can accurately represent business relationships between P-ITR
      operators

   o  More mapping system agnostic

   o  Minor changes to P-ITR implementation, no changes to other
      components

   In the example in the figure 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, who may be a LIR.
   Existing PI allocations can be migrated as well.  The MSP ensures the



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   presence of the prefix in the mapping system, and runs an EID Route
   Server to distribute it to P-ITR service providers.  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 LISP site
   will be originated by the Route Server, and announced to the DFZ by
   the PSP's P-ITRs with AS path 64501 64500.  From that point on, the
   usual BGP dynamics apply.  This way, routes announced by P-ITR are
   still originated by the authoritative Route Server.  Note that the
   peering relationships between MSP/PSPs and those in the underlying
   forwarding plane may not be congruent, making the AS path to a P-ITR
   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, a careful placement of P-ITR
   could significantly reduce path-stretch between LISP and non-LISP
   sites.

   The architecture allows for flexible policies between MSP/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 to the common underlying forwarding plane.  For example,
   some MSP/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 the LISP site buys
   service from, and is also subject to agreement between the 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 does not come
   without a cost however: A PSP operator has to establish either
   transit or peering relationships to improve their connectivity.




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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.  The situation is similar with several other registration
   services.  A LISP mapping service provider (MSR) 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 P-ITR
   service providers (PSPs) will do it.  Clients not signing up become
   responsible for getting non-LISP traffic to their EIDs (using the
   LISP+BGP scenario).

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

   The following table presents the expected effects of the different
   transition scenarios during a certain phase on the DFZ routing table
   size:

    Phase            | LISP+BGP     | MSP P-ITR       | 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 co-exist with LISP+BGP during the
   migration, with the latter being more popular in the early transition
   phase.  As the transition progresses and the MSP P-ITR 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 route table size.  Other metrics may be
   impacted as well, but to the best of our knowlegde have not been
   measured as of yet.


6.  Security Considerations

   All security implications of LISP deployments are to be discussed in
   separate documents.  [I-D.ietf-lisp-threats] gives an overview of
   LISP threat models, while securing mapping lookups is discussed in
   [I-D.ietf-lisp-sec].





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7.  IANA Considerations

   This memo includes no request to IANA.


8.  Acknowledgements

   Many thanks to Margaret Wasserman for her contribution to the IETF76
   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.


9.  References

9.1.  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.

9.2.  Informative References

   [DDT-Root]
              "DDT Root", <http://ddt-root.org/>.

   [I-D.ietf-lisp-ddt]
              Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP
              Delegated Database Tree", draft-ietf-lisp-ddt-01 (work in
              progress), March 2013.

   [I-D.ietf-lisp-sec]
              Maino, F., Ermagan, V., Cabellos-Aparicio, A., Saucez, D.,
              and O. Bonaventure, "LISP-Security (LISP-SEC)",
              draft-ietf-lisp-sec-05 (work in progress), October 2013.

   [I-D.ietf-lisp-threats]
              Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats



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              Analysis", draft-ietf-lisp-threats-08 (work in progress),
              October 2013.

   [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.

   [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.

   [cache]    Jung, J., Sit, E., Balakrishnan, H., and R. Morris, "DNS
              performance and the effectiveness of caching", 2002.


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
   procedures.

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.





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   2.  Make sure customer router has LISP capabilities.

       *  Check OS version of the CE router.  If LISP is an add-on,
          check 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 customer upgrade (if necessary, software and/or hardware)
          to be LISP capable.

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

   4.  Verify MTU Handling

       *  Request increase in MTU to 1556 or more on service provider
          connections.  Prior to MTU change verify that 1500 byte packet
          from P-xTR to RLOC with do not fragment (DF-bit) bit set.

       *  Ensure they are not filtering ICMP unreachable or time-
          exceeded 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 for Path MTU Discovery to
       take place.

   5.  Validate member prefix allocation.

       This step is to check if the prefix used by the customer is a
       direct (Provider Independent), or if it is 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.





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

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

A.2.  Customer Activating LISP Service

   1.  Customer configures LISP on CE router(s) from service provider
       recommended configuration.

       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, the following:

       *  Ensure default route(s) to next-hop external neighbors are
          included and RLOCs are present in configuration.

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

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

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

       *  From CE router, use LIG to ensure 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 discover 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.








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A.3.  Cut-Over Provider Preparation and Changes

   1.  Verify site configuration and then active registration on Map
       Server(s)

       *  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 P-xTRs

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

       *  Modify ingress policers on core routers

       *  Ensure route announcement in looking glass servers, RouteViews

   4.  Perform traffic verification test

       *  Ensure 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
   USA

   Email: lojakab@cisco.com








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

   Email: acabello@ac.upc.edu


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

   Email: fcoras@ac.upc.edu


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

   Email: jordi.domingo@ac.upc.edu


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

   Email: darlewis@cisco.com

















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