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Independent Submission                                   S. Russert, Ed.
Request for Comments: 6139                                  Unaffiliated
Category: Informational                               E. Fleischman, Ed.
ISSN: 2070-1721                                          F. Templin, Ed.
                                            Boeing Research & Technology
                                                           February 2011

                Routing and Addressing in Networks with
             Global Enterprise Recursion (RANGER) Scenarios


   "Routing and Addressing in Networks with Global Enterprise Recursion
   (RANGER)" (RFC 5720) provides an architectural framework for scalable
   routing and addressing.  It provides an incrementally deployable
   approach for scalability, provider independence, mobility,
   multihoming, traffic engineering, and security.  This document
   describes a series of use cases in order to showcase the
   architectural capabilities.  It further shows how the RANGER
   architecture restores the network-within-network principles
   originally intended for the sustained growth of the Internet.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any
   other RFC stream.  The RFC Editor has chosen to publish this
   document at its discretion and makes no statement about its value
   for implementation or deployment.  Documents approved for
   publication by the RFC Editor are not 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

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RFC 6139                         RANGERS                   February 2011

Copyright Notice

   Copyright (c) 2011 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.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Approach ........................................................7
   4. Scenarios ......................................................11
      4.1. Global Concerns ...........................................11
           4.1.1. Scaling the Global Inter-Domain Routing Core .......11
           4.1.2. Supporting Large Corporate Enterprise Networks .....13
      4.2. Autonomous System Concerns ................................16
      4.3. Small Enterprise Concerns .................................16
      4.4. IPv4/IPv6 Transition and Coexistence ......................18
      4.5. Mobility and MANET ........................................21
           4.5.1. Global Mobility Management .........................21
           4.5.2. First-Responder Mobile Ad Hoc Networks (MANETs) ....23
           4.5.3. Tactical Military MANETs ...........................24
      4.6. Provider Concerns .........................................27
           4.6.1. ISP Networks .......................................27
           4.6.2. Cellular Operator Networks .........................28
           4.6.3. Aeronautical Telecommunications Network (ATN) ......28
           4.6.4. Unmanaged Networks .................................31
   5. Mapping and Encapsulation Concerns .............................32
   6. Problem Statement and Call for Solutions .......................32
   7. Summary ........................................................33
   8. Security Considerations ........................................33
   9. Acknowledgements ...............................................34
   10. References ....................................................34
      10.1. Normative References .....................................34
      10.2. Informative References ...................................34

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1.  Introduction

   The Internet is continually required to support more users, more
   internetwork connections, and increasing complexity due to diverse
   policy requirements.  This growth and change strains the
   infrastructure and demands new solutions.  Some of the complementary
   approaches to transform Internet technology are being pursued
   concurrently within the IETF: translation (including Network Address
   Translation (NAT)), tunneling (map and encapsulate), and native IPv6
   [RFC2460] deployment.  Routing and Addressing in Networks with Global
   Enterprise Recursion (RANGER) [RFC5720] describes the architectural
   elements of a "map and encapsulate" approach that also facilitates
   the other two approaches.  This document discusses RANGER operational

   RANGER provides an architectural framework for scalable routing and
   addressing.  It provides for scalability, provider independence,
   mobility, multihoming, and security for the next-generation Internet.
   The RANGER architectural principles are not new.  They can be traced
   to the deliberations of the ROAD group [RFC1380], and also to still
   earlier works including NIMROD [RFC1753] and the Catenet model for
   internetworking [CATENET] [IEN48] [RFC2775].  [RFC1955] captures the
   high-level architectural aspects of the ROAD group deliberations in a
   "New Scheme for Internet Routing and Addressing (ENCAPS) for IPNG".

   The Internet has grown tremendously since these architectural
   principles were first developed, and that evolution increases the
   need for these capabilities.  The Internet has become a critical
   resource for business, for government, and for individual users
   throughout the developed world.  RANGER carries forward these
   historic architectural principles, creating a ubiquitous enterprise
   network structure that can represent collections of network elements
   ranging from the granularity of a singleton router all the way up to
   an entire Internet.  This enterprise network structure uses border
   routers that configure tunnel endpoints to connect potentially
   recursively nested networks.  Each enterprise network may use
   completely independent internal Routing Locator (RLOC) address
   spaces, supporting a virtual overlay network connecting edge networks
   and devices that are addressed with globally unique Endpoint
   Interface iDentifiers (EIDs).  The RANGER virtual overlay can
   transcend traditional administrative and organizational boundaries.
   In its purest form, this overlay network could therefore span the
   entire Internet and restore the end-to-end transparency envisioned in

   The RANGER architecture drew early observations from the Intra-Site
   Automatic Tunnel Addressing Protocol (ISATAP) [RFC5214] [RFC5579] but
   now uses Virtual Enterprise Traversal (VET) [RFC5558], the Subnetwork

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   Encapsulation and Adaptation Layer (SEAL) [RFC5320], and other
   mechanisms including IPsec [RFC4301] as its functional building
   blocks.  This document describes use cases and shows how the RANGER
   mechanisms apply.  Complementary mechanisms (e.g., DNS, DHCP, NAT,
   etc.) are included to show how the various pieces can work together.
   It expands on the concepts introduced in "IPv6 Enterprise Network
   Scenarios" [RFC4057] and "IPv6 Enterprise Network Analysis - IP Layer
   3 Focus" [RFC4852], and shows how the enterprise network model
   generalizes to a broad range of scenarios.  These use cases are
   included to provide examples, invite criticism and comment, and
   explore the potential for creating the next-generation Internet using
   the RANGER architecture.  Familiarity with RANGER, VET, SEAL, and
   ISATAP are assumed.

2.  Terminology

   Internet Topology Hierarchy
      The Internet Protocol (IP) natively supports a topology hierarchy
      comprised of increasing aggregations of networked elements.
      Network interfaces of devices are grouped into subnetworks, and
      subnetworks are grouped into larger aggregations.  Subnetworks can
      be optionally grouped into areas and the areas grouped into an
      autonomous system (AS).  Alternatively, subnetworks can be
      directly grouped into an AS.  The foundation of the IP Topology
      Hierarchy is the AS, which determines the administrative
      boundaries of a network deployment including its routing,
      addressing, quality of service, security, and management.
      Intra-domain routing occurs within an autonomous system, and
      inter-domain routing links autonomous systems into a "network of
      networks" (Internet).

   Routing Locator (RLOC)
      an address assigned to an interface in an enterprise-interior
      routing region.  Note that RLOC space is local to each enterprise

      The IPv4 public address space currently in use today can be
      considered as the RLOC space for the global Internet as a giant
      "enterprise network".

   Endpoint Interface iDentifier (EID)
      an address assigned to an edge network interface of an end system.
      Note that EID space is global in scope, and must be separate and
      distinct from any RLOC space.

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      an enterprise-interior routing region that provides a subnetwork
      for cooperative peering between the border routers of diverse
      organizations that may have competing interests.  An example of a
      commons is the Default-Free Zone (DFZ) of the global Internet.
      The enterprise-interior routing region within the commons uses an
      addressing plan taken from RLOC space.

   enterprise network
      the same as defined in [RFC4852], where the enterprise network
      deploys a unified RLOC space addressing plan within the commons,
      but may also contain partitions with disjoint RLOC spaces and/or
      organizational groupings that can be considered as enterprises
      unto themselves.  An enterprise network therefore need not be "one
      big happy family", but instead provides a commons for the
      cooperative interconnection of diverse organizations that may have
      competing interests (e.g., such as the case within the global
      Internet Default-Free Zone).

      Historically, enterprise networks are associated with large
      corporations or academic campuses.  However, in RANGER an
      enterprise network may exist at any IP Topology Hierarchy level.
      The RANGER architectural principles apply to any networked entity
      that has some degree of cooperative active management.  This
      definition therefore extends to home networks, small office
      networks, a wide variety of Mobile Ad hoc Networks (MANETs), and
      even to the global Internet itself.

      a logical and/or physical grouping of interfaces within an
      enterprise network commons, where the topology of the site is a
      proper subset of the topology of the enterprise network.  A site
      may contain many interior sites, which may themselves contain many
      interior sites in a recursive fashion.

      Throughout the remainder of this document, the term "enterprise"
      refers to either enterprise or site; i.e., the RANGER principles
      apply equally to enterprises and sites of any size or shape.  At
      the lowest level of recursive decomposition, a singleton
      Enterprise Border Router can be considered as an enterprise unto

   Enterprise Border Router (EBR)
      a node at the edge of an enterprise network that is also
      configured as a tunnel endpoint in an overlay network.  EBRs
      connect their directly attached networks to the overlay network,
      and connect to other networks via IP-in-IP tunneling across the
      commons to other EBRs.  This definition is intended as an

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      architectural equivalent of the functional term "EBR" defined in
      [RFC5558], and is synonymous with the term "xTR" used in other
      contexts (e.g., [LISP]).

   Enterprise Border Gateway (EBG)
      an EBR that also connects the enterprise network to provider
      networks and/or to the global Internet.  EBGs are typically
      configured as default routers in the overlay, and provide
      forwarding services for accessing IP networks not reachable via an
      EBR within the commons.  This definition is intended as an
      architectural equivalent of the functional term "EBG" defined in
      [RFC5558], and is synonymous with the term "default mapper" used
      in other contexts (e.g., [APT]).

   overlay network
      a virtual network manifested by routing and addressing over
      virtual links formed through automatic tunneling.  An overlay
      network may span many underlying enterprise networks.

      "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels"
      [RFC2529]; functional specifications and operational practices for
      automatic tunneling of unicast/multicast IPv6 packets over
      multicast-capable IPv4 enterprise networks.

      Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) [RFC5214]
      [RFC5579]; functional specifications and operational practices for
      automatic tunneling over unicast-only enterprise networks.

      Virtual Enterprise Traversal (VET) [RFC5558]; functional
      specifications and operational practices that provide a functional
      superset of 6over4 and ISATAP.  In addition to both unicast and
      multicast tunneling, VET also supports address/prefix
      autoconfiguration as well as additional encapsulations such as
      IPsec, SEAL, UDP, etc.

      Subnetwork Encapsulation and Adaptation Layer (SEAL) [RFC5320]; a
      functional specification for robust packet identification and link
      MTU adaptation over tunnels.  SEAL supports effective ingress
      filtering and adapts to subnetworks configured over links with
      diverse characteristics.

      Within the RANGER architectural context, the SEAL "subnetwork" and
      RANGER "enterprise" should be considered as identical

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   Provider-Independent (PI) prefix
      an EID prefix (e.g., 2001:DB8::/48, 192.0.2/24, etc.) that is
      routable within a limited scope and may also appear in enterprise
      network mapping tables.  PI prefixes that can appear in mapping
      tables are typically delegated to a BR by a registry, but are not
      aggregated by a provider network.

   Provider-Aggregated (PA) prefix
      an EID prefix that is either derived from a PI prefix or delegated
      directly to a provider network by a registry.  Although not widely
      discussed, it bears specific mention that a prefix taken from a
      delegating router's PI space becomes a PA prefix from the
      perspective of the requesting router.

   Customer Premises Equipment (CPE) Router
      a residential or small office router that provides IPv4 and/or
      IPv6 support.  The user or the service provider may manage the

   Carrier-Grade NAT (CGN)
      a special (usually high capacity) IPv4-to-IPv4 NAT deployed within
      the service provider network that serves multiple subnets.

3.  Approach

   The RANGER [RFC5720] architecture seeks to fulfill the objectives set
   forth in [RFC1955]:

   o  No Changes to Hosts

   o  No Changes to Most Routers

   o  No New Routing Protocols

   o  No New Internet Protocols

   o  No Translation of Addresses in Packets

   o  Reduce the Routing Table Size in All Routers

   o  Use the Current Internet Address Structure

   The RANGER enterprise network is a cooperative networked collective
   sharing a common (business, social, political, etc.) goal.  An
   enterprise network can be simple or complex in composition and can
   operate at any IP Topology Hierarchy level.  Although RANGER focuses
   on encapsulation, it is also compatible with both native and
   translated routing and addressing.

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   RANGER enables a protocol and/or addressing system to be connected in
   a virtual overlay across an untrusted transit network, or "commons".
   While it does not show all possible uses, Figure 1 illustrates that
   RANGER supports the creation of a distributed network across an
   intervening commons, which could implement a dissimilar IP version,
   routing protocol, or addressing system.

              .--------------.     .--------------.     .-------------.
             /                \_ _/                \_ _/               \
             \ Enterprise A   /   \    Commons     /   \  Enterprise B /
              \_ _ _ _ _ _ _ /     \_ _ _ _ _ _ _ /     \_ _ _ _ _ _ _/

  Network    /        IPvx              IPvy               IPvz
  Protocol   \        IPv6              IPv4               IPv6

  IP Security        secured          unsecured          secured

  Mgmt Domain      Entity A              ISP              Entity B

             | Public Addresses   Private Addresses   Public Addresses
  Addressing |Private Addresses    Public Addresses   Private Addresses
             |   PA Addresses        PI Addresses         PA Addresses
              \   PI Addresses       PA Addresses         PI Addresses

          Figure 1.  RANGER Links Distributed Enterprise Networks

   The RANGER concepts can be applied recursively.  They can be
   implemented at any level within the IP Topology Hierarchy to create
   an enterprise-within-enterprise organizational structure extending
   traditional AS, area, or subnetwork boundaries.  This structure uses
   border routers that configure tunnel endpoints to enable
   communications between potentially recursively nested enterprise
   networks in a virtual overlay network that transcends traditional
   administrative and organizational boundaries.  In its purest form,
   this overlay network could therefore span the entire Internet and
   restore end-to-end transparency [RFC2775].

   The RANGER architecture applies the best current practice insights
   from previous encapsulation systems as they are currently articulated
   within the Virtual Enterprise Traversal [RFC5558], and Subnetwork
   Encapsulation and Adaptation Layer [RFC5320] functional
   specifications.  The result is an architecture and protocol system
   that can be used to create arbitrarily complex, scalable IP
   deployments that support both unicast and multicast routing and
   addressing systems.

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   RANGER supports scalable routing through a recursively nested
   enterprise-within-enterprise network capability.  The fundamental
   building block is the Enterprise Border Router (EBR) (see Figure 2).
   The EBR is the limiting factor for RANGER recursion, and in certain
   contexts a singleton EBR can be viewed as an enterprise network unto
   itself.  Traditional network infrastructures can be extended to
   support complex structures solely with the addition of EBRs with no
   other modification to any networked entity.

   An EBR can be a commercial off-the-shelf router, a tactical military
   radio, an aircraft mobile router, etc., but it can also be an end
   system (e.g., a laptop computer, a soldiers' handheld device, etc.)
   with an embedded gateway function [RFC1122].

                         Provider-Edge Interfaces
                                  x   x        x
                                  |   |        |
             +--------------------+---+--------+----------+    E
             |                    |   |        |          |    n
             |    I               |   |  ....  |          |    t
             |    n           +---+---+--------+---+      |    e
             |    t           |   +--------+      /|      |    r
             |    e  I   x----+   |  Host  |   I /*+------+--< p  I
             |    r  n        |   |Function|   n|**|      |    r  n
             |    n  t        |   +--------+   t|**|      |    i  t
             |    a  e   x----+              V e|**+------+--< s  e
             |    l  r      . |              E r|**|  .   |    e  r
             |       f      . |              T f|**|  .   |       f
             |    V  a      . |   +--------+   a|**|  .   |    I  a
             |    i  c      . |   | Router |   c|**|  .   |    n  c
             |    r  e   x----+   |Function|   e \*+------+--< t  e
             |    t  s        |   +--------+      \|      |    e  s
             |    u           +---+---+--------+---+      |    r
             |    a               |   |  ....  |          |    i
             |    l               |   |        |          |    o
             +--------------------+---+--------+----------+    r
                                  |   |        |
                                  x   x        x
                        Enterprise-Edge Interfaces

                 Figure 2.  Enterprise Border Router (EBR)

   EBRs connect networks and end systems to one or more enterprise
   networks via a repertoire of interface types.  Enterprise-interior
   interfaces attach to a commons.  Provider-edge interfaces support

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   traditional routing relationships up the IP Topology Hierarchy, and
   enterprise-edge interfaces support traditional relationships down the
   IP Topology Hierarchy.  Internal virtual interfaces are typically
   loopback interfaces or VMware-like host-in-host interfaces.

   VET interfaces support RANGER recursion and IP-in-IP encapsulation.
   VET interfaces are configured over provider-edge, enterprise-
   interior, or enterprise-edge interfaces to allow recursion
   horizontally or vertically within the IP Topology Hierarchy.  A VET
   interface may be configured over several underlying interfaces that
   all connect to the same enterprise network.  This creates a link-
   layer multiplexing capability that can provide several advantages
   (see [RFC1122], Section 3.3.4).  One important advantage is
   continuous operation across failovers between multiple links attached
   to the same enterprise network, without any need for readdressing.

   Figure 3 shows two enterprise networks (each with their own internal
   addressing and routing systems) that communicate over a virtual
   overlay network across a commons.  The virtual overlay is manifested
   by tunneling, which links enterprise networks separated by
   geographical remoteness, protocol incompatibility, or both.  An
   ingress EBR (iEBR) within the left enterprise network seeks to
   forward encapsulated packets across the commons to the egress EBR
   (eEBR) within the right enterprise network.

   The figure shows that the eEBR assigns a Routing Locator (RLOC)
   address on its interface to the commons' interior IP routing and
   address space, while the destination host assigns an Endpoint
   Interface iDentifier (EID) on its enterprise-edge interface.  The
   iEBR uses a mapping system to discover the RLOC of an eEBR on the
   path to the destination EID address.  A distinct mapping system is
   maintained within each recursively nested enterprise network instance
   operating at a specific level of the IP Topology Hierarchy.  RANGER
   uses the mapping system to join peer enterprise networks via a
   virtual overlay across a commons.

               Mapping System                   RLOC       EID
               . (BGP, DNS, etc.)                 .         .
         .---.------.          .----------.       .  .------.---.
        /  .         \        /            \      . /       .    \
       /  (O)      iEBR------/--------------\------eEBR     *     \
       \              /      \   Commons    /       \             /
        \_ _ _ _ _ _ /        \_ _ _ _ _ _ /         \_ _ _ _ _ _/

     Enterprise Network A                        Enterprise Network B

                        Figure 3.  The RANGER Model

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   EBRs must configure both RLOC and EID addresses and/or prefixes.
   Autoconfiguration is coordinated with Enterprise Border Gateways
   (EBGs) that connect to the next-higher layer in the recursive
   hierarchy, as specified in VET.  Standard mechanisms including DHCP
   [RFC2131] [RFC3315] and Stateless Address Autoconfiguration (SLAAC)
   [RFC4862] are used for this purpose.

   Similarly, EBRs require a means to discover other EBRs and EBGs that
   can be used as enterprise network exit points.  VET specifies
   mechanisms for border router discovery using the global DNS and/or
   enterprise-local name services such as Link-Local Multicast Name
   Resolution (LLMNR) [RFC4795].

   The mapping system is a distributed database that is synchronized
   among a limited set of mapping agents.  Database synchronization can
   be achieved by many different protocol alternatives.  The most
   commonly used alternatives are either the Border Gateway Protocol
   (BGP) [RFC4271] or the Domain Name System (DNS) [RFC1035].  Mapping-
   system databases can be populated by many different mechanisms
   including administrative configuration and automated prefix

   EBRs forward initial packets for which they have no mapping to an
   EBG.  The EBG in turn forwards the packet toward the final
   destination and returns a redirect to inform the EBR of a better next
   hop if necessary.  The EBR then receives a mapping reply that it can
   use to populate its Forwarding Information Base (FIB).  It then
   encapsulates each forwarded packet in an outer IP header for
   transmission across the commons to the remote RLOC address of an
   eEBR.  The eEBR in turn decapsulates the packets and forwards them to
   the destination EID address.  The Routing Information Base (RIB)
   within the commons only needs to maintain state regarding RLOCs and
   not EIDs.  The synchronized EID-to-RLOC mapping state is not subject
   to oscillations due to link state changes within the commons.  RANGER
   supports scalable addressing by selecting a suitably large EID
   addressing range that is distinct from any enterprise-interior RLOC
   addressing ranges.

4.  Scenarios

4.1.  Global Concerns

4.1.1.  Scaling the Global Inter-Domain Routing Core

   Growth in the Internet has created challenges in routing and
   addressing that have been recognized for many years
   [RADIR-PROB-STATE].  IPv4 [RFC0791] address space is limited, and
   Regional Internet Registry (RIR) allocation is passing the "very

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   painful" Host Density (HD) ratio threshold of 86% (that is, 192M
   allocated addresses) [RFC3194].  As a result, exhaustion of the IPv4
   address pool is predicted within the next two years [IPv4POOL],
   [HUSTON-END].  IPv6 promises to resolve the address shortage with a
   much larger address space, but transition is costly and could
   exacerbate BGP problems described below.  Richer interconnection,
   increased multihoming (especially with provider-independent (PI)
   addresses), and a desire to support traffic engineering via finer
   control of routing has led to super-linear growth of BGP routing
   tables in the Default-Free Zone, or "DFZ", of the Internet.  This
   growth is placing increasing pressures on router capacities and
   technology costs that are unsustainable for the longer term within
   the current Internet routing framework.

   RANGER allows the coordinated reuse of addresses from enterprise to
   enterprise by making RLOC address spaces independent of one another.
   Figure 4 shows how the RANGER architecture allows the use of separate
   address spaces for RLOC and EID addressing in the Internet.  This
   yields more endpoint address space, especially with the use of IPv6,
   and also reduces the load on BGP in the Internet routing core.  Note
   that Figure 4 could represent variants of RFC 4057 scenarios 1 and 2.

      EID                          RLOC                       EID
       PA                         Spaces                       PI
   Allocation                                             Registration
                    .-------------------------------.          ^
                   /           Internet Commons      \         |
                   |  .---------------------------.   |        |
  2001:DB8::/40    | /         Enterprise A        \  | 2001:DB8:10::/56
        |          |/              10.1/16          \ |        ^
        |          ||  .-------------------------.   ||        |
        V          || /         Enterprise A.1    \  ||        |
  2001:DB8::/48    || |            10.1/16        |  || 2001:DB8:11::/56
                   ||  \_________________________/  / |
                   | \                             /  |
                   |   ---------------------------    |
                   |                                  |
                   |  .---------------------------.   |
                   | /         Enterprise B        \  |
 2001:DB8:100::/40 | |            10.1/16           | | 2001:DB8:12::/56
                   |  \____________________________/  |
                    \                                 /

              Figure 4.  Enterprise Networks and the Internet

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   RLOC address spaces are entirely independent of one another, as they
   are used only within an enterprise network (recall that an enterprise
   network can exist at any level of the IP Topology Hierarchy).  Such
   an arrangement allows each RLOC space to maintain an independent
   routing system and thereby avoid the inherent scaling issues if a
   single monolithic routing system were used for all.

   EID address space can be provider-aggregated (PA) or PI, and taken
   from either IPv4 or IPv6.  EID addresses (barring the use of Network
   Address Translation (NAT)) are globally unique, even when routable
   only within a more limited scope (e.g., in their own edge networks).

   The IRTF routing research group is investigating a Preliminary
   Recommendation for a routing architecture [RFC6115] that provides a
   taxonomy for routing scaling solutions for the global Internet
   inter-domain routing core.  RANGER presents a core/edge separation
   architecture within this taxonomy that uniquely shows applicability
   from the core all the way out to edge networks via its recursive
   enterprise-within-enterprise framework.  RANGER is further compatible
   with a number of schemes intending to address routing scaling issues,
   including "APT: A Practical Transit Mapping Service" [APT], "FIB
   Suppression with Virtual Aggregation" [GROW-VA], "Locator/ID
   Separation Protocol (LISP)" [LISP], and others.

4.1.2.  Supporting Large Corporate Enterprise Networks

   Each enterprise network operator must be able to manage its internal
   networks and use the Internet infrastructure to achieve its
   performance and reliability goals.  Enterprise networks that are
   multihomed or have mobile components frequently require provider-
   independent addressing and the ability to coordinate with multiple
   providers without renumbering "flag days" [RFC4192] [RFC5887].
   RANGER provides a way to coordinate addressing plans and
   inter-enterprise routing, with full support for scalability, provider
   independence, mobility, multihoming, and security.

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RFC 6139                         RANGERS                   February 2011

                      _.---''                         -.
                 ,--''           ,---.                 `---.
              ,-'              X5     X6            .---..  `-.
            ,\'  ,.X1-..       /         \        ,'       `.  `.
          ,\'  ,'       `.    .'  E2     '.     X8    Em     \   `.
         /   /           \   |   ,--.    |     / _,.._        \    \
        /   /   E1        \  | Y3    `.  |    | /     Y7      |     \
       ;   |    ___        | |  ` W  Y4  |... | `Y6  ,'       |      :
       |   | ,-'   `.     X2 |   `--'    |    |   `''         |      |
       :   | |  V  Y2      | \    _      /    |               |      ;
        \  | `-Y1,,'       |  \ .' Y5   /      \    ,-Y8'`-  /      /
         \  \             /    \ \_'   /       X9   `.    ,'/      /
          `. \          X3      `.__,,'          `._  Y9'','     ,'
            ` `._     _,'      ___.......X7_        `---'      ,'
              `  `---'      ,-'             `-.              -'
                 `---.      `.    E3     Z   _'        _.--'
                      `-----. \---.......---'   _.---''

       <------------------- Global IPv4 Internet ------------------>

        Figure 5.  Enterprise Networks within the Internet Commons

   Figure 5 depicts enterprise networks E1 through Em connected to the
   global IPv4 Internet via Enterprise Border Routers (EBRs) X1 through
   X9.  These same border nodes also act as Enterprise Border Gateways
   (EBGs) that provide default routing services for nodes within their
   respective enterprise networks.  The global Internet forms a commons
   across which the various enterprise networks connect as cooperating
   yet potentially competing entities.  Within each enterprise network
   there may be arbitrarily many hosts, routers, and networks (not shown
   in the diagram) that use addresses taken from that enterprise
   network's RLOC space and over which both encapsulated IP packets with
   (global-scoped) EID addresses and unencapsulated IP packets with
   (enterprise-local) RLOC addresses can be forwarded.

   Each enterprise network may encompass lower-tier networks; for
   instance, the singleton EBR "W" in network E2 resides in a lower-tier
   network (say E2.1), and (along with any of its attached devices) may
   be considered as an enterprise unto itself.  W sees Y3 and Y4 as
   EBGs, which in turn see X5 and X6 as EBGs that connect to a common
   provider network (in this case, the Internet).  Each enterprise
   network has one or more Endpoint Interface iDentifier (EID) address
   prefixes used for addressing nodes on edge networks.  RANGER's map-
   and-encaps approach separates the mapping of EIDs to Routing Locators
   (RLOCs) from the Routing Information Base (RIB) in the Internet
   commons that are assigned to EBR router interfaces.  Not only does

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RFC 6139                         RANGERS                   February 2011

   BGP in the Internet commons only need to maintain state regarding
   RLOCs in the Internet commons, it has fewer unique routes to maintain
   because only routes to EBRs are needed; traffic engineering can
   therefore be accommodated via the mapping database.

   In Figure 5, enterprise network E2 represents a corporation that has
   multiple locations and connections to multiple ISPs.  The corporation
   has recently merged with another corporation so that its internal
   network has two disjoint RLOC address spaces, but neither of the
   formerly separate entities can bear the burden of address
   renumbering.  Enterprise network E2 can use a suitably large IPv4
   and/or IPv6 EID addressing range (that is distinct from any
   enterprise-interior RLOC addressing range) to support end systems on
   enterprise-edge networks with no disruption to preexisting address

   As EBRs are deployed to connect enterprise networks together,
   ordinary routers within the enterprise network continue to function
   as normal and deliver both ordinary and encapsulated packets across
   the existing Internet infrastructure and the network's own RLOC
   commons.  Legacy IPv4 services that bind to RLOC addresses continue
   to be supported even as EID-based services are rolled out.  Where a
   legacy IP client and server are within the same RLOC address space,
   they simply communicate by using RLOC-based routing across the
   enterprise network commons.  If the client and server are not within
   the same RLOC address space, they communicate through some form of
   network address and/or protocol translation (see [RFC5720],
   Section 3.3.4 for details).  EBRs from the various enterprise
   networks publish their EID prefixes to an enterprise-specific mapping
   system, so that other EBRs from the various enterprise networks can
   consult the mapping system to receive the RLOC address of one or more
   EBRs that serve the EID prefix.

   As an example, when an end system connected to W in E2.1 has a packet
   to send to node Z in enterprise network E3, W sends the packet to EBR
   Y4, which encapsulates the packet in an outer IP packet with its own
   source address and the RLOC address of the next-hop EBR as the
   destination -- in this case, X6.  X6 decapsulates the packet and
   looks up the destination EID prefix, obtaining the RLOC of X7 as
   next-hop.  X6 then encapsulates the IPv6 packet in a packet with RLOC
   address X6 as the source and X7 as the destination.  X7 decapsulates
   the packet on receipt and forwards it via its enterprise-edge
   interface to node Z.

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RFC 6139                         RANGERS                   February 2011

   This example uses one thread out of many that are possible using
   RANGER; see [RFC5720] and [RFC5558] for other options and details.
   Many enterprise networks that use proxies and firewalls at their
   border routers today will wish to maintain that control over their
   enterprise borders, and the use of RANGER does not preclude such
   configurations (for example, see Section 4.3).

4.2.  Autonomous System Concerns

   An enterprise network such as E2 in Figure 5 above can represent an
   AS within the IP Topology Hierarchy.  A possible configuration for
   enterprise network E2 is for each of its enterprise components to
   also be recursive ASs linked together using the RANGER constructs.
   Such a configuration is increasingly commonplace today for the
   networks of very large corporations (e.g., Boeing's corporate
   enterprise network).  These networks support an internal instance of
   the BGP linking many corporate-internal ASs and independent from the
   BGP instance that maintains the RIB within the global Internet
   Default-Free Zone (DFZ).  Such configurations are often motivated by
   scaling or administrative requirements.

   Such a corporate entity is internally an Internet unto itself, albeit
   with separate default routes leading to the true global Internet.
   The enterprise network E2 therefore appears to the rest of the
   Internet as if it were a traditional IP Topology Hierarchy AS.  Since
   RANGER supports recursion, each AS within such a network may itself
   use BGP internally in place of an IGP, and can therefore also
   internally be composed of a locally internal Internet in a recursive
   fashion.  This enterprise-within-enterprise framework can recursively
   be extended as broadly and as deeply as required in order to achieve
   the specific requirements of the deployment (e.g., scaling, unique
   administration, and/or functional compartmentalization).

4.3.  Small Enterprise Concerns

   Global enterprise networks operating at the autonomous system level
   of the IP Topology Hierarchy include multiple geographical regions,
   multiple ISPs, and complex internal structures that naturally benefit
   from the application of RANGER techniques.  However, all other
   enterprise network instances (both large and small) can also be
   served by RANGER.  For example, Small and Home Office (SOHO) networks
   may comprise only a few computers on a single network segment or may
   extend to larger configurations with security islands, internal
   routers and switches, etc.

   An important concern of the small enterprise network is the ability
   to grow the network, change ISPs, or expand to more locations without
   readdressing the existing network.  Consider a small company that has

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RFC 6139                         RANGERS                   February 2011

   a single location in California.  The ISP connection is via a router
   that acts as a Network Address Translator and firewall for the
   company.  Addresses of the few computers ("Wksta") are taken from the
   [RFC1918] private address space.

                      -------|-----            Wksta        Wksta
                      |  Firewall  |_____________|____________|
                      |    NAT     |

                      Figure 6.  Simple SOHO Network

   This configuration has been adequate for the few employees performing
   software development work, since there is no need to expose services
   within the site to the outside world.  But now a web presence is
   required as product introduction approaches.  The network manager
   deploys an EBR either as a co-resident function on the existing NAT/
   firewall platform (as depicted in Figure 7) or on a separate

   The EBR has a provider-edge interface connected to the ISP; the
   preexisting workstations; the preexisting enterprise-edge interfaces
   connecting the workstations; and enterprise-edge interfaces
   connecting several network segments connected by routers that host
   web servers, workstations, and other enterprise network services.  A
   VET interface is configured over the new service network to allow the
   servers to be addressed from the public Internet.

                |           <|--
                |     VET2 < |
                |           <|---
                |            |
                |            |      Server     Server
                |      VET1 <|--------|-----------|-------
                |            |
                | +--------+ |           Wksta        Wksta
                | |Firewall| |_____________|____________|
                | |   NAT  | |
                | +--------+ |

                Figure 7.  RANGER Serving the Small Company

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RFC 6139                         RANGERS                   February 2011

   In this new configuration, the EBR maintains the services within a
   "demilitarized zone (DMZ)" that is accessible from the public
   Internet without exposing other corporate assets that are still
   protected by the preexisting firewall/NAT functions.

   Shortly afterward, an infusion of venture capital allows acceleration
   of the product development and marketing work by adding programmers
   in Tokyo and sales offices in New York and London.  These new
   branches connect via Virtual Private Network (VPN) links across the
   Internet, and a new VET interface (VET2) is configured over these
   links to form a new sub-enterprise:

                 |           <|------------London
                 |     VET2 < |
                 |           <|--------------------New York
                 |            |
                 |            |      Server     Server
                 |     VET1  <|--------|-----------|-------
                 |            |
                 | +--------+ |          Wksta        Wksta
                 | |Firewall| |_____________|____________|
                 | |   NAT  | |
                 | +--------+ |

                 Figure 8.  RANGER for Multiple Locations

4.4.  IPv4/IPv6 Transition and Coexistence

   End systems and networks need to accommodate long-term support for
   both IPv4 and IPv6.  Requirements for transition include support for
   IPv4 applications running over IPv4 protocol stacks, IPv4
   applications over IPv6 stacks, IPv4 applications over dual stacks,
   and IPv6 or IPv4/IPv6-capable applications over both IPv6 and dual
   stacks.  Both encapsulation and translation will likely be needed to
   allow applications, enterprises, and providers to incorporate IPv6,
   including all intermediate states, without global coordination or a
   "flag day".

   The RANGER architecture facilitates the addition of IPv6 addressing
   to existing IPv4 end systems and routers (i.e., via dual stack) as
   well as the addition of IPv6 networks to the existing set of IPv4
   networks.  RANGER (with VET and SEAL) makes it possible to carry
   packets originated in one protocol across a network infrastructure
   supporting another protocol or routing system.  Figure 1 shows how

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RFC 6139                         RANGERS                   February 2011

   RANGER supports various combinations of edge (EID) and core (RLOC
   commons) technologies, going beyond IP version differences to include
   mixed security, management, and addressing as well.

   The RANGER architecture supports end-to-end communications across
   arbitrarily long paths of concatenated enterprise networks connected
   by EBRs.  When IPv6 is used as Endpoint Interface iDentifier (EID)
   space, each EBR can provision a globally unique set of IPv6 EID
   prefixes without scaling limitations, due to the expanded IPv6
   address space.  For example, Figure 9 shows a pair of end systems,
   "H" and "J", separated by an intervening set of enterprise networks
   spanned by VET interfaces labeled "vet1" through "vet4", where the
   path between "H" and "J" traverses the EBR path "V->Y1->X2->X7->Z":

                                                            | IPv6 |
       " " " " " " " "" " " " " " " " " " " " " " " "       |  S1  |
     "                                               "      +--+---+
   "     . . . . . . .       . . . .      . . . .     "        |
   "   .               .    .       .    .       .    "        |
   "   .  +----+   v   +----+   v   +----+       +----+  +-----+-------+
   "   .  | V  +=  e  =+ Y1 +=  e  =+ X2 +=     =+ R2 +==+   Internet  |
   "   .  +-+--+   t   +----+   t   +----+       +----+  +-----+-------+
   "   .    |      1   .    .   2   .    .       .    "        |
   "    .   H         .     .       .    .   v   .    "        |
   "      . . . . . .        . . . .     .   e   .    "     +--+---+
   "                                     .   t   .    "     | IPv4 |
   "                  . . . . . . ,      .   3   .    "     |Server|
   "                .  +----+   v   +----+       .    "     |  S2  |
   "                .  | Z  +=  e  =+ X7 +=      .    "     +------+
   "                .  +-+--+   t   +----+       .    "
   "                .    |      4   .    .       .    "
   "                .    J         .      . . . .     "
    "                 . . . . . . .                   "
      "                                              "
        " " " " " " " " " " " " " " "" " " " " " " "

               Figure 9.  EBR Waypoint Navigation Using IPv6

   When each EBR in the path is assigned a unique set of IPv6 EID
   prefixes (and registers these prefixes in the appropriate routing/
   mapping tables), IPv6 can be used for navigation purposes with each
   EBR in the path seen as a waypoint for navigation.  This is true even
   if IPv4 is used as the enterprise-local Routing Locator (RLOC)
   address space and there were many IPv4 hops on the path between each
   pair of neighboring EBRs.

Russert, et al.               Informational                    [Page 19]

RFC 6139                         RANGERS                   February 2011

   RANGER further provides a compatible framework for incorporating
   supporting mechanisms including protocol translation, application-
   layer aspects of IPv4/IPv6 transition discussed in [RFC4038], and DNS
   issues for IPv6 from [RFC4472].  For instances where IPv4
   applications remain in use, RANGER expects that IPv4<->IPv6
   translation will be supported via network-based [BEHAVE-v6v4] and/or
   end system stack-based (e.g., [RFC2767]) protocol translation
   systems.  Figure 10 shows the NAT - Protocol Translation
   (NAT-PT)-equivalent translation in the VET router, and Figure 11
   shows the "Bump-In-the-Stack" (BIS)-equivalent translation in end
   systems ([RFC2767]).  These examples address scenarios not mentioned
   in RFC 4852.

              IPv4 App A                               IPv4 App B
            _____________                            _____________
           |_TCP or UDP__|                          |_TCP or UDP__|
           |____IPv4_____|                          |____IPv4_____|
            ______|______                           _______|_____
           /             \                         /             \
           |  IPv4-Only   |                        |  IPv4-Only   |
           |   Site 1     |                        |   Site 2     |
           \_____________/                         \_____________/
            ______|______                            ______|_______
           |____IPv4_____|       _____________      |____IPv4_____|
           |NAT-PT-equiv_|      /             \     |NAT-PT-equiv_|
           |_TCP or UDP__|      |   Internet   |    |_TCP or UDP__|
           |____IPv6_____|      |   (RANGER)   |    |____IPv6_____|
           |__VET/SEAL___|      \_____________/     |__VET/SEAL___|
                  \_______________/         \___________/

                    Figure 10.  Translation in Routers

   In Figure 10, an IPv4 application on end system A operates normally,
   and the end system sends IPv4 packets on the IPv4-only site network.
   The IPv4 packets are received by an Enterprise Border Router (EBR)
   that translates them into IPv6 packets by a NAT-PT-equivalent
   process.  The EBR then encapsulates the packets into IPv4 and sends
   them across the RANGER-enabled Internet to Site 2 where they are
   received and decapsulated by an EBR for Site 2.  The EBR uses NAT-PT-
   equivalent translation to translate the resulting IPv6 packet back to
   an IPv4 packet that is delivered across the Site 2 IPv4-only network
   to an IPv4 application on end system B.

Russert, et al.               Informational                    [Page 20]

RFC 6139                         RANGERS                   February 2011

           IPv4 App A                               IPv4 App B
         _____________        _____________       _____________
        |_TCP or UDP__|      /             \     |_TCP or UDP__|
        |____BIS______|      |   Internet   |    |____BIS______|
        |____IPv6_____|      |   (RANGER)   |    |____IPv6_____|
        |__VET/SEAL___|      \_____________/     |__VET/SEAL___|
               \_______________/         \___________/

        Figure 11.  BIS-Style Translation in Dual-Stack End Systems

   Figure 11 shows the simplified approach using a BIS translation
   process within dual-stack end systems ([RFC2767]).  In this case, the
   IPv4 application on dual-stack end system A forms an IPv4 payload,
   which is then transformed into an IPv6 packet within the end system
   protocol stack itself.  The IPv6 packet can then be encapsulated and
   sent across the Internet to be decapsulated and sent to the dual-
   stack end system hosting IPv4 application B.  The BIS-equivalent
   process on end system B reverses the translation, yielding an IPv4
   packet for consumption by the IPv4-only application.

   Other issues besides IP protocol translation may arise during
   IPv4-IPv6 transition; [RFC4038] points out issues including
   IPv4/IPv6-capable applications running on IPv4-only protocol stacks,
   DNS responses that include addresses of both IP versions, and the
   difficulty of supporting multiple application versions.  It also
   advises that applications be converted to dual support as a preferred
   solution.  These issues are outside the scope of this document.

4.5.  Mobility and MANET

4.5.1.  Global Mobility Management

   Ubiquitous wireless access enables connection to network
   infrastructure nearly anywhere.  Vehicles and even persons can host
   networks that move around with them.  For example, commercial
   aircraft networks include requirements for nomadic networks, local
   mobility, and global mobility where the connection point between
   airplane and ground station can move from one continent to another.
   Mobile networks need to be able to use provider-independent (PI) as
   well as provider-aggregated (PA) address prefixes.  Some applications
   such as voice require rapid or seamless connection handoffs -- also
   known as session survivability.  Internet routing should not be
   unduly disrupted by mobility, so movement of mobile nodes or edge
   networks should not cause large ripples of routing protocol traffic,
   especially in the DFZ.

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RFC 6139                         RANGERS                   February 2011

   When a RANGER enterprise network is overlaid on the Internet, mobile
   nodes or mobile routers (that connect arbitrarily complex edge
   networks or enterprise networks) can move between different points of
   attachment while remaining reachable and without creating excessive
   routing churn.  In a commercial airline scenario, an aircraft with a
   mobile router would move between ground station points of attachment
   (that may be on different continents) without the readdressing of its
   onboard networks.  Figure 12 shows an aircraft transiting between
   four different access points: two that are part of Air Communications
   Service Provider (ACSP) 1, one in ACSP2, and the last directly to the
   Air Navigation Service Provider (ANSP).  ACSP1 and ACSP2 in this
   example might be on different continents, so a traditional Mobile IP
   Home Agent scheme [RFC3775] [RFC5944] would result in very
   inefficient paths for one ACSP or the other.  The aero enterprise
   network is an overlay that spans both continents and allows efficient
   paths by providing multiple entry and exit points (only one, R2, is

  Aircraft - - - - - - ,.- - - - - -.- - ->
        .             ,  .           .                        +------+
         .           ,    .           .                       | IPv6 |
          .         ,      .           .                      |Server|
         " ." " " ", "" " " ." " "  " " .? " " " " "          |  S1  |
       "    .     ,          .           .            "       +--+---+
     "       .   ,            .           .            "         |
     "     . ...            . . .         . . +----+    "        |
     "   .       .        .      .      .    =+ X3 +    "        |
     "   .   v  +--- +   . v      .     .  v  +----+    ?        |
     "   .   e =+ Y1 +   . e      .     .  e  .       +----+  +--------+
     "   .   t  +----+   . t    +----+  .  t  .      =+-R2-+==+Internet|
     "   .   1   .       . 2   =+ X2 +  .  3  .       +----+  +--------+
     "    .     .         .     +----+   .   .          "        |
     "      . .             . . .         . .           "     +------+
      "    <ACSP1>       <ACSP2>        <ANSP>          "     | IPv4 |
        "                                              "      |Server|
          "                - - vet4 - -               "       |  S2  |
            " " " " " " " " " " " " " "" " " " " " "          |  S2  |
                 <-- Aero Enterprise Network -->              +------+

                 Figure 12.  Commercial Airplane Mobility

   When the plane moves between ground stations that are located within
   the ACSP1 enterprise network, no routing or mapping changes need be
   made outside ACSP1.  Moreover, if link-layer multiplexing (as
   mentioned in Section 3 above) is used, then the VET interface network
   layer is unaware of the movement.  When the point of access moves to
   ACSP2, no changes are made outside the aero enterprise network.  When
   the aircraft moves between ground stations of the same parent

Russert, et al.               Informational                    [Page 22]

RFC 6139                         RANGERS                   February 2011

   enterprise network (as indicated by the two different links from the
   aircraft to ACSP1 in Figure 12), the aircraft announces its PI
   prefixes at its new point of attachment and withdraws them from the
   old.  The worldwide Internet sees no change, and mapping-system churn
   is confined to ACSP1, since the prefixes need not be announced or
   withdrawn within the parent aero enterprise network; i.e., the churn
   is isolated to lower tiers of the recursive hierarchy.  This can be
   contrasted with the deprecated mobility solution previously fielded
   by Connexion, which propagated disruptive BGP changes into the
   Internet routing system to support mobile onboard networks.

4.5.2.  First-Responder Mobile Ad Hoc Networks (MANETs)

   Many emerging network scenarios require autoconfiguration of Mobile
   Ad hoc Networks (MANETs).  Where first responders need networking for
   communications and coordination between teams, RANGER allows each
   team or agency to quickly stand up a network and then use the
   autoconfiguration described in [RFC5558] to coordinate address/prefix
   autoconfiguration and discover border routers needed for teams and
   agencies to interconnect.

   For example, Figure 13 shows how police units arriving on a scene
   with no network infrastructure can create a wireless network using
   vehicle-mounted 802.11 hotspots with one or more cellular, 802.16, or
   satellite links in order to reach the Internet.  In this example, the
   California Highway Patrol sets up an incident management center with
   a satellite link to the Internet and vet1 serving network L1.  The
   Los Angeles County Sheriff team sets up network L1.1 at their field
   headquarters, and the Altadena police force creates the L1.2 network
   with their mobile units.  R2 is the router that serves as an EBG for
   border routers X3 and X4, which connect networks L1.2 and L1.1,
   respectively.  X3 serves vet3, and X4 serves vet2.

   In like manner, the Angeles National Forest creates enterprise
   network F1, with the San Gabriel Ranger District setting up
   enterprise network F1.1 and the Fire Response Team Enterprise Network
   F1.2.  R1 and R2 discover one another and become peer EBRs across the
   Internet by means of manual configuration.  In network L1, individual
   PI address prefixes are announced from L1.2 and L1.1 to L1, and R2
   advertises them to the satellite ISP.  R1 receives a PA prefix from
   its WiMAX provider and delegates parts of the prefix to X1 and X2.
   R2 also runs an IGP with R1, advertising the PI prefixes to R1 and
   learning the PA prefixes there.

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RFC 6139                         RANGERS                   February 2011

                                                            | IPv6 |
       " " " " " " " "" " " " " " " " " " " " " " " "       |  S1  |
     "      Law Enforcement Enterprise Network       "      +--+---+
    "    2001:DB8:10::/56 (PI)  ---------------->     "        |
   "      . . . . . . . +--- +            . . . .     "        |
   "    .              =+ X3 +===========.       .    "  +-----+-------+
   "   .  +----+   v    +--- +           .   v   +----+  |             +
   "   .  | V  +=  e    .      . .       .   e  =+ R2 +==+             |
   "   .  +-+--+   t    .    .      +----+   t   +----+  |             |
   "   .    |      3   .    . vet2  + X4 +=  1   .    "  |             |
   "    .   H1        .     .       +----+       .    "  |             |
   "      . . . . . .        . . . .      . . . .     "  |             |
    "       <L1.2>           <L1.1>        <L1>       "  |             |
      "      10/8             10/8         10/8      "   |             |
        " " " " " " " " " " " " " " "" " " " " " " "     |   Internet  |
                                                         |             |
       " " " " " " " "" " " " " " " " " " " " " " " "    |             |
     "     USDA Forest Service Enterprise Network    "   |             |
    "         <----------------- 2001:DB8::/40 (PA)  "   |             |
   "      . . . . . . . +--- +            . . . .     "  |             |
   "    .              =+ X1 +===========.       .    "  |             |
   "   .  +----+   v    +--- +           .   v   +----+  |             |
   "   .  | J  +=  e    .      . .       .   e  =+ R1 +==+             |
   "   .  +-+--+   t    .    .      +----+   t   +----+  |             |
   "   .    |      6   .    . vet5  + X2 +=  4   .    "  +-----+-------+
   "    .   H2        .     .       +----+       .    "        |
   "      . . . . . .        . . . .      . . . .     "     +--+---+
    "       <F1.2>           <F1.1>        <F1>       "     | IPv4 |
      "      10/8             10/8         10/8      "      |Server|
        " " " " " " " " " " " " " " "" " " " " " " "        |  S2  |

                     Figure 13.  First-Responder MANET

4.5.3.  Tactical Military MANETs

   Military networks reflect well-defined policy requirements that
   differ in many ways from civilian networks.  The military's
   information security requirements result in information being labeled
   into specific classifications.  The Bell-LaPadula model
   [BELL-LaPADULA] provides a mechanism to extend information security
   policy into networked environments.  This extension creates
   communications security (COMSEC), whose routing and addressing
   elements are cleanly supported by RANGER concepts.

Russert, et al.               Informational                    [Page 24]

RFC 6139                         RANGERS                   February 2011

   Figure 3 shows that RANGER supports creation of a VET interface
   between the enterprise-interior (network) interface of two Enterprise
   Border Routers (EBR) located within separate enterprise networks, A
   and B.  When this concept is applied to enterprise networks operating
   above the subnetwork level of the IP Topology Hierarchy, then this
   VET interface uses IP-in-IP encapsulation.  This corresponds with a
   popular COMSEC approach (IPsec -- [RFC4301]).  When this same RANGER
   concept is applied to enterprise networks operating at the subnetwork
   level of the IP Topology Hierarchy, then this corresponds to an older
   form of COMSEC (Link Layer Encryption).  When the same RANGER concept
   is applied to enterprise networks being singleton EBR nodes (i.e.,
   the interface level of the IP Topology Hierarchy), then this
   corresponds to a third military COMSEC alternative (Link Encryption).

   The previous paragraph shows the flexibility of the RANGER
   architecture to describe COMSEC approaches in terms of IP Topology
   Hierarchy structured relationships.  The power of the RANGER
   architecture becomes apparent when one recognizes that each of the
   entities in Figure 3 may themselves be simple or complex network
   structures operating at any specific level of the IP Topology
   Hierarchy.  (Complex structures refer to architectures that have been
   extended by RANGER recursion.)  For example, the commons in the
   figure may itself be an interface, a subnetwork, an autonomous
   system, or an Internet.  Enterprise networks A and B can be a single
   end system, a subnetwork, an autonomous system, or an Internet.

   Tactical military MANETs differ from traditional networks in many
   ways, the most obvious being the high mobility of tactical
   deployments and self-forming-network attributes of MANETs themselves.
   Because each networked tactical entity supports a radio/router, the
   numbers of routers within military MANETs can be orders of magnitude
   more numerous (denser) than traditional civilian networks.  This
   means that even small deployments have comparatively large router
   populations when compared to non-MANET deployments.  Larger router
   populations directly create greater sensitivity to protocol
   scalability issues.  Router scalability issues are further
   exacerbated because IP protocols react unfavorably to signal
   intermittence, which effectively dampens and constrains router
   scaling even when mitigation techniques are employed.  Signal
   intermittence itself is a characteristic of mobility and the radio
   signal propagation attributes of local deployment environments (e.g.,
   such issues as terrain, foliage, buildings, weather, distance, etc.).
   War fighting also encourages war fighters to locate into more
   defensible terrain features, many of which naturally reduce radio
   signal propagation, further increasing the probability of signal

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RFC 6139                         RANGERS                   February 2011

   RANGER recursion enables MANETs that naturally encourage route
   aggregation and scaling through simple "plug and play" hierarchical
   arrangements that parallel organizational structures and do not
   entail complex manual configurations.  For example, a MANET
   autonomous system may benefit from RANGER recursion by being
   physically comprised of enterprise networks that are autonomous
   systems themselves.  This relationship can be recursively extended
   vertically as deep as required in order to create route aggregation
   between entities having common mission assignments at differing
   levels of abstraction.  Since MANET routing is an active research
   topic, it is helpful to realize that these structures may or may not
   use routing protocols similar to their civilian IP Topology Hierarchy
   peers.  For example, because of the behavior of BGP within highly
   mobile environments, the Exterior Gateway Protocol (EGP) used to link
   ASs may or may not be BGP and, if it is BGP, it may have unusual
   timer settings.  However, whatever IGP and EGP is used, RANGER
   constructs can increase route aggregation between entities sharing
   common mission assignments to enable route scaling.

   Tactical military MANETs often have requirements to communicate with
   stationary infrastructures.  By localizing mobility into an
   enterprise network, the specific mobility-friendly protocols can then
   be localized and their aggregation results presented to the
   stationary network using a protocol supported by the stable network.
   This also reduces the impact of mobility upon routing and addressing
   systems as reported to the stationary infrastructure.  Mobility-
   induced route fluctuations (e.g., routing flaps) can still occur, but
   their impact can be dampened if RANGER constructs are used to
   localize them in lower tiers of the IP Topology Hierarchy.  For
   example, enterprise network A in Figure 3 can be a military MANET,
   and enterprise network B may be a stationary military entity.  Recall
   that enterprise networks A and B interface at a specific IP Topology
   Hierarchy level, but they may be physically extended by RANGER
   mechanisms.  For example, enterprise network A can be a MANET
   enterprise that is physically a network-of-networks Internet that
   interfaces to enterprise network B as if it were an autonomous
   system.  This gives enterprise network B a more stable and aggregated
   view of the enterprise network A Internet than would be the case if
   it were directly aware of A's various sub-enterprise components.

   Another key distinctive feature of tactical military networks is
   that, because radio networks operate at a different classification
   level than the data they convey, tactical military networks have
   several orders of magnitude more COMSEC devices than do equivalently
   sized stationary military deployments (i.e., the number of COMSEC
   devices is a function of the number of mobile war-fighting entities).
   This can create significant scalability issues within the overlay
   COMSEC network relationships themselves.  COMSEC scaling problems are

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RFC 6139                         RANGERS                   February 2011

   manifested in several dimensions.  It is important to recognize,
   however, that just as RANGER recursion was used vertically to create
   IP Topology enterprise-within-enterprise structures in order to
   improve routing aggregation and scaling, so RANGER recursion allows
   for authorization of route-optimized transactions between peer
   enterprises (within the same IP Topology Hierarchy level) to improve
   COMSEC aggregation and scaling of the network overlay system.  The
   RANGER use of VET also combines with the Subnetwork Encapsulation and
   Adaptation Layer (SEAL) to provide robust packet identification and
   maximum transmission unit (MTU) link adaptation services over
   tunnels.  These capabilities protect against both source address
   spoofing and black holes caused by MTU limitations.

4.6.  Provider Concerns

   Network providers must have a way to support the protocol transitions
   and network types mentioned above and still remain reliable and
   financially sound.  The RANGER architecture provides ways to support
   general Internet Service Providers (ISPs), cellular operator
   networks, and specialized networks such as the Aeronautical
   Telecommunications Network (ATN).

4.6.1.  ISP Networks

   Internet service provider networks provide a commons for the
   connection of Customer Premises Equipment (CPE) routers [CPE-RTRS]
   that connect arbitrarily complex customer networks.  This is true
   whether the ISP permits direct customer-to-customer communications,
   or whether all communications are forwarded through ISP provider-edge

   The ISP commons must potentially support hundreds of thousands of CPE
   routers (or more); hence the ISP may be obliged to assign private
   IPv4 address allocations (i.e., instead of public) as RLOCs for CPE
   routers.  This gives rise to a "nested NATs" scenario, which can
   increase the overall brittleness brought on by NAT traversal.

   To address this brittleness, the ISP can deploy "Carrier-Grade NATs"
   (CGNs) [INCR-CGN] that provide a second level of RLOC address
   translation on the path from the CPE to the Internet.  When the CGNs
   are also configured as EBGs, CPE routers can discover them as default
   routers for reaching EID-based services using the EBG discovery
   mechanisms specified in VET.

   "Scenarios and Analysis for Introducing IPv6 into ISP Networks"
   [RFC4029] discusses both ISP backbone network and customer connection
   transition considerations; however, this document considers router-
   to-router tunneling use cases.  Therefore the ISATAP mechanism (which

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   only supports host-to-router or host-to-host tunneling) is not
   mentioned as a candidate technology.  Early point solutions (e.g.,
   the Tunnel Setup Protocol (TSP) [RFC5572], the Simple IPv6-in-IPv4
   Tunnel Establishment Procedure (STEP) [STEP], etc.) were recommended.
   This document suggests that RANGER, VET, and SEAL would also be
   suitable solutions in these networks.

4.6.2.  Cellular Operator Networks

   [RFC4215] provides a (dated) "Analysis on IPv6 Transition in Third
   Generation Partnership Project (3GPP) Networks".  It envisions an
   extended period of support for both IPv4 and IPv6 protocols in the
   operator network.  User Equipment (UE) uses the Packet Data Protocol
   (PDP) context to establish tunnels through the operator network to a
   Gateway General Packet Radio Service (GPRS) Support Node (GGSN).
   RANGER could be used in 3GPP transition; when the UE uses IPv6, and
   the PDP context is established across an IPv4 provider network, the
   UE can configure itself as an EBR and contact the GGSN (as a RANGER
   EBG) through VET tunneling.

   Other [RFC4215] scenarios examine IPv4-only UEs, IPv6-only UEs, and
   various combinations of IPv4 and IPv6 within the operator network.
   Also to be considered are scenarios in which the UE is configured as
   a router or bridge that connects an end system such as a laptop
   computer.  In that case, the UE could be the first-hop router/bridge
   into the cellular provider network, and the laptop computer could be
   configured as an EBR in the RANGER model.  Again, the GGSN or a
   device reachable through the GGSN could serve as a RANGER EBG.

4.6.3.  Aeronautical Telecommunications Network (ATN)

   The Aeronautical Telecommunications Network (ATN) is currently based
   on the OSI and IPv4 protocols and is deployed only in limited areas.
   The future ATN under consideration within the civil aviation industry
   will be IPv6-based.  The IP variant of ATN is expected to take the
   form of a worldwide enterprise network that internally comprises an
   aeronautical-only Internet that has additional external interfaces to
   the global Internet.  Within the ATN, there may be many Air
   Communications Service Provider (ACSP) and Air Navigation Service
   Provider (ANSP) networks that are internally organized either as
   autonomous systems or internets within the ATN, i.e., as depicted in
   Figure 5.  Each of these entities may themselves be further
   internally subdivided into lower-tier enterprise networks organized
   as regional, organizational, or functional compartments.  It is
   important to note that while ACSPs and ANSPs within the ATN will
   share a common objective of safety-of-flight for civil aviation
   services, enterprise networks may have competing business, social, or
   political interests that require that components be distinct ASs.

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   The RANGER principles therefore support collaborative objectives
   while allowing very diverse local policy distinctions.  In this
   manner, entities that do not trust each other can create
   collaborative infrastructures to achieve common goals.

   Operational associations like this will characterize many future
   deployments, including the US Department of Defense's Global
   Information Grid (GIG).  In particular, although the routing and
   addressing arrangements of all enterprise networks require a mutual
   level of cooperative active management at a certain level, scaling
   issues, security policy differences, free market forces,
   organizational differences, political distinctions, or other factors
   may create internal competition among entities that otherwise share
   common goals.  This will require different enterprise networks within
   that association to be separated into distinct ASs that are linked
   within their own functional Internet relationship.

   The ATN illustrates transition from OSI protocols to IPv6.  It must
   support mobility (see Section 4.5.1), and it serves many government
   and private entities that cooperate to provide safe and efficient air
   travel while often competing with one another.  One possible way to
   meet these needs with RANGER is to create an overlay using IP-in-IP
   tunneling across the Internet, as illustrated in Figure 14.  The aero
   overlay forms an enterprise network, so that inner packets from ACSP
   and ANSP edge networks that travel between VET interfaces on EBRs see
   their passage across the Internet as only one hop.

              /                                              \
             (                  IPv4 Internet                 )
                    |         /       |       \       |
                    |        /        |        \      |
              /                                              \
             (                  Aero Overlay                  )
               .  .         .          .            .   .
              .   .           .       .             .    .
       _...-------.._       _...-------.._      _...-------.._
      /              \     /              \    /              \
     (      ACSP1     )   (      ANSP      )  (     ACSP2      )
      -...________...-     -...________...-    -...________...-

                     Figure 14.  Aeronautical Overlay

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   Each Aeronautical Communications Service Provider (ACSP), and
   Aeronautical Navigation Service Provider (ANSP) constitute an
   enterprise network recursively nested below the aero overlay.
   Relationships between the various enterprise networks can vary from
   slight to tight integration.  In the example, the ACSP and ANSP might
   choose to exchange full routing information for their edge networks
   using a coordinated global-scope RLOC address space across which ACSP
   and ANSP EBRs can route traffic without further mapping lookups or
   re-encapsulation at intermediate EBRs.  Other enterprise networks
   that have the aero network as a common parent may not have any
   knowledge of each other's interior routing but will merely forward
   packets on a default route up to the aero overlay.

   The ATN is currently an OSI network but is projected to transition to
   IPv6 over time.  RANGER can bridge OSI networks together across the
   IPv4 (or IPv6) Internet, or bridge IPv4 or IPv6 networks across an
   OSI network.  A pair of EBRs that have IP interfaces on a common
   enterprise network (whether it is the Internet, the aero network, or
   another parent or child enterprise network) can support
   communications between their attached OSI edge networks by looking up
   ISO network service access point (NSAP) addresses [IS8348] instead of
   IP addresses for RLOC mappings.  OSI ConnectionLess Network Protocol
   (CLNP) [IS8473] packets can therefore be encapsulated within IPv4 (or
   IPv6) headers for transmission across an Internet Protocol enterprise
   network.  Some OSI networks may transition to IPv6 addressing
   [RFC4548] while applications are adapted by using RFC 2126 [RFC2126]
   to carry OSI upper layers over TCP/IP, with the resulting IP packets
   carried across and between RANGER enterprises in the normal way.
   Another approach is to use subnetwork convergence to tunnel OSI
   network protocol data units over Internet Protocol networks

   Figure 15 depicts an ACSP and ANSP connected via an IPv4 aero
   overlay.  Host H represents a system onboard an aircraft that has a
   wireless link to the ACSP, connected via an enterprise-edge network
   interface on EBR F within the ACSP enterprise network.  H resides on
   an IPv6 edge network, and its EID is taken from the ACSP IPv6 prefix.
   H needs to send a query to server S in the ANSP enterprise network.
   H starts by sending a DNS query to the server at G, and in return it
   receives the EID of server S.  H then creates an IPv6 packet with
   source EID(H) and destination EID(S) and forwards it to its default
   router, F.  F consults G for a mapping from EID(S) to the appropriate
   RLOC.  In this case, EBR F encapsulates the IPv6 packet in an IPv6
   outer packet and forwards the packet to its default EBG, A.  A
   decapsulates the packet and looks up the destination EID(S) by
   querying the DNS server at EBR B.  B returns a mapping with the RLOC
   of EBR E.  A encapsulates the IPv6 inner packet in an IPv4 outer
   packet with source RLOC(A) and destination RLOC(E).  The packet is

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   forwarded via EBRs C and D in the aero overlay until it reaches E,
   where it is decapsulated.  E consults its cache of EID/RLOC mappings
   and finds that the EBR for S is N.  E encapsulates the packet in an
   IPv6 packet with source RLOC(E) and destination RLOC(N).  When the
   packet reaches N, it is decapsulated, and the inner IPv6 packet is
   forwarded on the edge network to the server, S.

            /           (B)                   (D)          \
           (                  Aero Overlay (IPv4)           )
                 .                  .            .
               (A)                (C)            .
               .                  .              .
      _...------------------------.._           (E)
     /                               \           .
    /      (F)                        \          .
   (     [H]       ACSP (IPv6)         )         .
    \                      (G)        /          .
     \...__________________________...           .
                                     /                               \
                                    /     (M)                (N)      \
                                   (               ANSP (IPv6)         )
                                    \                          [S]    /

          Figure 15.  Packet Forwarding for Aeronautical Networks

4.6.4.  Unmanaged Networks

   "Evaluation of IPv6 Transition Mechanisms for Unmanaged Networks"
   [RFC3904] considers four cases for support of IPv6-enabled routers
   and end systems connected to an ISP network via a gateway:

   a. a gateway that does not provide IPv6 at all;

   b. a dual-stack gateway connected to a dual-stack ISP;

   c. a dual-stack gateway connected to an IPv4-only ISP; and

   d. a gateway connected to an IPv6-only ISP.

   Case a is typified by the widespread practice of customer networks
   using IPv4-only NAT boxes to connect to their service providers.
   RANGER does not address this scenario directly; however, the Teredo
   mechanism [RFC4380] can provide a sufficient solution in many cases.

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   Case d is a scenario that has not yet seen widespread adoption.  In
   this scenario, the customer network could be configured as IPv6 only,
   and the deployment could be considered as an IPv6-only extension to a
   RANGER enterprise-edge network.  End systems in this scenario would
   still require support for legacy IPv4-only applications, and if the
   customer network contained IPv4-only routers and end systems the
   RANGER encapsulation mechanisms would still apply.

   Cases b and c correspond to the scenario of the customer gateway to
   the ISP becoming an IPv6 router.  In that case, the gateway could
   become a RANGER EBR, and the scenario becomes the same as the SOHO
   network use cases discussed in Section 4.3.  In particular, when
   traditional home network IPv4 NAT boxes are updated to also support
   IPv6 routing, the NAT box becomes a RANGER EBR.

5.  Mapping and Encapsulation Concerns

   Mapping and encapsulation concerns related to RANGER have been
   discussed in Section 3.7 of [RFC5720].  These include effects of
   mapping systems to application traffic, the need to secure the
   mapping system, MTU effects, and the ability of legacy Internet
   networks to connect to those employing RANGER.

6.  Problem Statement and Call for Solutions

   The scenarios discussed in this document have not closely examined
   future growth of the native IPv6 and IPv4 Internets independently of
   any growth in RANGER overlay networking.  For example, it is likely
   that current-day major Internet services that support millions of
   customers simultaneously (e.g., Google, Yahoo, eBay, Amazon, etc.)
   will continue to be served best by native Internet routing and
   addressing rather than by overlay network arrangements that require
   dynamic mapping state coordination.  At the same time, however, more
   and more small end user networks will wish to use provider-
   independent addressing for multihoming via multiple ISPs as well as
   support traffic engineering and mobility management.

   These requirements call for an overlay network solution that is
   compatible with both RANGER and the IPv6 and IPv4 native Internet
   routing system without adversely affecting Internet routing scaling.
   The solution must avoid the mapping and encapsulation concerns
   discussed in Section 3.7 of [RFC5720]; for example, it must provide
   generally shortest path routing without imparting unacceptable delays
   for initial packets.  The solution must further provide mobility
   management capabilities for mobile end user networks that can take

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   advantage of route optimization while requiring no modifications to
   end systems.  Finally, the solution must be based on a business model
   that allows end user networks to obtain Internet access services from
   multiple ISPs simultaneously with support for traffic engineering and
   fault tolerance.

7.  Summary

   The Internet today can be considered as a giant enterprise network,
   with nodes in the Internet addressed from the public IPv4 address
   space as RLOCs.  Due to the 32-bit addressing limitations of IPv4,
   however, continued expansion has occurred through the widespread
   deployment of IPv4 Network Address Translators (NATs) while IPv6 has
   yet to see wide adoption.

   In many senses, however, this has resulted in a degenerate
   manifestation of the network-of-networks model originally envisaged,
   e.g., in the Catenet model.  Indeed, these NATed domains have the
   external appearance of being a simple host within the global Internet
   RLOC space even though they may be proxying for arbitrarily large
   networks of end systems.  The end result is a loss of transparency in
   the end-to-end model; it is no longer true that any node in the
   Internet can directly address any other node.

   RANGER enables a true network-within-network (or enterprise-within-
   enterprise) framework.  This is true even across a wide array of
   deployment scenarios as documented here, and even for networks-
   within-networks that may be recursively nested to an arbitrary depth.
   RANGER therefore brings a unifying architecture applied consistently
   across all layers of recursion, rather than a mixed bag of point
   solutions that may or may not be mutually compatible.  When coupled
   with an overlay network solution that supports coexistence with the
   IPv6 and IPv4 native Internet routing systems, a unified future
   Internet architecture is possible.

8.  Security Considerations

   Security considerations are addressed in [RFC5720], [RFC5558], and
   [RFC5320].  While the RANGER architecture does not in itself address
   security considerations, it proposes an architectural framework for
   functional specifications that do.  Security concerns with tunneling,
   along with recommendations that are compatible with the RANGER
   architecture, are found in [TUNNEL-SEC].  Security considerations for
   specific use cases are discussed there.

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9.  Acknowledgements

   This work was inspired by the original architectural principles of
   the Internet supplemented with "lessons learned" by many peers from
   actual Internet deployments and experience developing encapsulation
   protocols.  The editors acknowledge that they are furthering work
   initiated by many.

10.  References

10.1.  Normative References

   [RFC0791]   Postel, J., "Internet Protocol", STD 5, RFC 791,
               September 1981.

   [RFC2460]   Deering, S. and R. Hinden, "Internet Protocol, Version 6
               (IPv6) Specification", RFC 2460, December 1998.

   [RFC5720]   Templin, F., "Routing and Addressing in Networks with
               Global Enterprise Recursion (RANGER)", RFC 5720, February

10.2.  Informative References

   [APT]       Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and
               L. Zhang, "APT: A Practical Transit Mapping Service",
               Work in Progress, November 2007.

               Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
               IPv4/IPv6 Translation", Work in Progress, August 2010.

               Bell, D. and L. LaPadula, "Secure Computer Systems:
               Mathematical Foundations and Model", October 1974.

   [CATENET]   Pouzin, L., "A Proposal for Interconnecting Packet
               Switching Networks", May 1974.

   [CPE-RTRS]  Singh, H., Beebee, W., Donley, C., Stark, B., and O.
               Troan, Ed., "Basic Requirements for IPv6 Customer Edge
               Routers", Work in Progress, December 2010.

   [GROW-VA]   Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R.,
               and L. Zhang, "FIB Suppression with Virtual Aggregation",
               Work in Progress, August 2010.

Russert, et al.               Informational                    [Page 34]

RFC 6139                         RANGERS                   February 2011

               Huston, G., "The End of the (IPv4) World is Nigher!",
               July 2007.

   [IEN48]     Cerf, V., "The Catenet Model for Internetworking", July

   [INCR-CGN]  Jiang, S., Guo, D., and B. Carpenter, "An Incremental
               Carrier-Grade NAT (CGN) for IPv6 Transition", Work in
               Progress, March 2009.

   [IPv4POOL]  Hain, T., "The IPv4 Address Pool Projection", April 2009.

   [IS8348]    International Organization for Standardization,
               International Electrotechnical Commission, "Open Systems
               Interconnection -- Network service definition", 2002.

   [IS8473]    International Organization for Standardization,
               International Electrotechnical Commission, "Protocol for
               providing the connectionless-mode network service:
               Protocol specification", 1998.

   [LISP]      Farinacci, D., Fuller, V., Meyer, D., and D. Lewis,
               "Locator/ID Separation Protocol (LISP)", Work in
               Progress, March 2009.

               Narten, T., "On the Scalability of Internet Routing",
               Work in Progress, February 2010.

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

   [RFC1070]   Hagens, R., Hall, N., and M. Rose, "Use of the Internet
               as a subnetwork for experimentation with the OSI network
               layer", RFC 1070, February 1989.

   [RFC1122]   Braden, R., Ed., "Requirements for Internet Hosts -
               Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1380]   Gross, P. and P. Almquist, "IESG Deliberations on Routing
               and Addressing", RFC 1380, November 1992.

   [RFC1753]   Chiappa, N., "IPng Technical Requirements Of the Nimrod
               Routing and Addressing Architecture", RFC 1753, December

Russert, et al.               Informational                    [Page 35]

RFC 6139                         RANGERS                   February 2011

   [RFC1918]   Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
               and E. Lear, "Address Allocation for Private Internets",
               BCP 5, RFC 1918, February 1996.

   [RFC1955]   Hinden, R., "New Scheme for Internet Routing and
               Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.

   [RFC2126]   Pouffary, Y. and A. Young, "ISO Transport Service on top
               of TCP (ITOT)", RFC 2126, March 1997.

   [RFC2131]   Droms, R., "Dynamic Host Configuration Protocol",
               RFC 2131, March 1997.

   [RFC2529]   Carpenter, B. and C. Jung, "Transmission of IPv6 over
               IPv4 Domains without Explicit Tunnels", RFC 2529, March

   [RFC2767]   Tsuchiya, K., Higuchi, H., and Y. Atarashi, "Dual Stack
               Hosts using the "Bump-In-the-Stack" Technique (BIS)",
               RFC 2767, February 2000.

   [RFC2775]   Carpenter, B., "Internet Transparency", RFC 2775,
               February 2000.

   [RFC3194]   Durand, A. and C. Huitema, "The H-Density Ratio for
               Address Assignment Efficiency An Update on the H ratio",
               RFC 3194, November 2001.

   [RFC3315]   Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
               C., and M. Carney, "Dynamic Host Configuration Protocol
               for IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3775]   Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
               in IPv6", RFC 3775, June 2004.

   [RFC3904]   Huitema, C., Austein, R., Satapati, S., and R. van der
               Pol, "Evaluation of IPv6 Transition Mechanisms for
               Unmanaged Networks", RFC 3904, September 2004.

   [RFC4029]   Lind, M., Ksinant, V., Park, S., Baudot, A., and P.
               Savola, "Scenarios and Analysis for Introducing IPv6 into
               ISP Networks", RFC 4029, March 2005.

   [RFC4038]   Shin, M-K., Ed., Hong, Y-G., Hagino, J., Savola, P., and
               E.  Castro, "Application Aspects of IPv6 Transition",
               RFC 4038, March 2005.

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RFC 6139                         RANGERS                   February 2011

   [RFC4057]   Bound, J., Ed., "IPv6 Enterprise Network Scenarios",
               RFC 4057, June 2005.

   [RFC4192]   Baker, F., Lear, E., and R. Droms, "Procedures for
               Renumbering an IPv6 Network without a Flag Day",
               RFC 4192, September 2005.

   [RFC4215]   Wiljakka, J., Ed., "Analysis on IPv6 Transition in Third
               Generation Partnership Project (3GPP) Networks",
               RFC 4215, October 2005.

   [RFC4271]   Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
               Border Gateway Protocol 4 (BGP-4)", RFC 4271, January

   [RFC4301]   Kent, S. and K. Seo, "Security Architecture for the
               Internet Protocol", RFC 4301, December 2005.

   [RFC4380]   Huitema, C., "Teredo: Tunneling IPv6 over UDP through
               Network Address Translations (NATs)", RFC 4380, February

   [RFC4472]   Durand, A., Ihren, J., and P. Savola, "Operational
               Considerations and Issues with IPv6 DNS", RFC 4472, April

   [RFC4548]   Gray, E., Rutemiller, J., and G. Swallow, "Internet Code
               Point (ICP) Assignments for NSAP Addresses", RFC 4548,
               May 2006.

   [RFC4795]   Aboba, B., Thaler, D., and L. Esibov, "Link-local
               Multicast Name Resolution (LLMNR)", RFC 4795, January

   [RFC4852]   Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D.
               Green, "IPv6 Enterprise Network Analysis - IP Layer 3
               Focus", RFC 4852, April 2007.

   [RFC4862]   Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
               Address Autoconfiguration", RFC 4862, September 2007.

   [RFC5214]   Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
               Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
               March 2008.

   [RFC5320]   Templin, F., Ed., "The Subnetwork Encapsulation and
               Adaptation Layer (SEAL)", RFC 5320, February 2010.

Russert, et al.               Informational                    [Page 37]

RFC 6139                         RANGERS                   February 2011

   [RFC5558]   Templin, F., Ed., "Virtual Enterprise Traversal (VET)",
               RFC 5558, February 2010.

   [RFC5572]   Blanchet, M. and F. Parent, "IPv6 Tunnel Broker with the
               Tunnel Setup Protocol (TSP)", RFC 5572, February 2010.

   [RFC5579]   Templin, F., Ed., "Transmission of IPv4 Packets over
               Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
               Interfaces", RFC 5579, February 2010.

   [RFC5887]   Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering
               Still Needs Work", RFC 5887, May 2010.

   [RFC5944]   Perkins, C., Ed., "IP Mobility Support for IPv4,
               Revised", RFC 5944, November 2010.

   [RFC6115]   Li, T., Ed., "Recommendation for a Routing Architecture",
               RFC 6115, February 2011.

   [STEP]      Savola, P., "Simple IPv6-in-IPv4 Tunnel Establishment
               Procedure (STEP)", Work in Progress, January 2004.

               Krishnan, S., Thaler, D., and J. Hoagland, "Security
               Concerns With IP Tunneling", Work in Progress, October

Russert, et al.               Informational                    [Page 38]

RFC 6139                         RANGERS                   February 2011

Authors' Addresses

   Steven W. Russert (editor)
   1078 Ridge Crest Dr.
   Wenatchee, WA  98801

   EMail: russerts@hotmail.com

   Eric W. Fleischman (editor)
   Boeing Research & Technology
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124

   EMail: eric.fleischman@boeing.com

   Fred L. Templin (editor)
   Boeing Research & Technology
   P.O. Box 3707 MC 7L-49
   Seattle, WA  98124

   EMail: fltemplin@acm.org

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