[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 RFC 6179

Internet Research Task Force                             F. Templin, Ed.
(IRTF)                                      Boeing Research & Technology
Internet-Draft                                              July 8, 2010
Intended status: Informational
Expires: January 9, 2011


              The Internet Routing Overlay Network (IRON)
                       draft-templin-iron-08.txt

Abstract

   Since the Internet must continue to support escalating growth due to
   increasing demand, it is clear that current routing architectures and
   operational practices must be updated.  This document proposes an
   Internet Routing Overlay Network for supporting sustainable growth
   through Provider Independent addressing while requiring no changes to
   end systems and no changes to the existing routing system.  This
   document is a product of the IRTF Routing Research Group (RRG).

Status of this Memo

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

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

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

   This Internet-Draft will expire on January 9, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Templin                  Expires January 9, 2011                [Page 1]


Internet-Draft                    IRON                         July 2010


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Internet Routing Overlay Network (IRON)  . . . . . . . . .  5
     3.1.  IR(CP) - IRON Customer Premises Router . . . . . . . . . .  7
     3.2.  IR(BR) - IRON Border Router  . . . . . . . . . . . . . . .  7
     3.3.  IR(GW) - IRON Gateway  . . . . . . . . . . . . . . . . . .  8
   4.  IRON Organizational Principles . . . . . . . . . . . . . . . .  9
   5.  IRON Initialization  . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  IR(GW) Initialization  . . . . . . . . . . . . . . . . . . 11
     5.2.  IR(BR) Initialization  . . . . . . . . . . . . . . . . . . 11
     5.3.  IR(CP) Initialization  . . . . . . . . . . . . . . . . . . 11
   6.  IRON Operation . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  IR(CP) Operation . . . . . . . . . . . . . . . . . . . . . 12
     6.2.  IR(BR) Operation . . . . . . . . . . . . . . . . . . . . . 14
     6.3.  IR(GW) Operation . . . . . . . . . . . . . . . . . . . . . 14
     6.4.  IRON Reference Operating Scenarios . . . . . . . . . . . . 15
       6.4.1.  Both Hosts Within EP-Addressed EUNs  . . . . . . . . . 15
       6.4.2.  Mixed IRON and Non-IRON Hosts  . . . . . . . . . . . . 21
     6.5.  Mobility, Multihoming and Traffic Engineering
           Considerations . . . . . . . . . . . . . . . . . . . . . . 24
       6.5.1.  Mobility Management  . . . . . . . . . . . . . . . . . 24
       6.5.2.  Multihoming  . . . . . . . . . . . . . . . . . . . . . 25
       6.5.3.  Inbound Traffic Engineering  . . . . . . . . . . . . . 25
       6.5.4.  Outbound Traffic Engineering . . . . . . . . . . . . . 25
     6.6.  Renumbering Considerations . . . . . . . . . . . . . . . . 25
     6.7.  NAT Traversal Considerations . . . . . . . . . . . . . . . 25
   7.  Additional Considerations  . . . . . . . . . . . . . . . . . . 26
   8.  Related Initiatives  . . . . . . . . . . . . . . . . . . . . . 26
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 27
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 27
     12.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Appendix A.  IRON VPs Over Non-Native Internetworks  . . . . . . . 29
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 31








Templin                  Expires January 9, 2011                [Page 2]


Internet-Draft                    IRON                         July 2010


1.  Introduction

   Growth in the number of entries carried in the Internet routing
   system has led to concerns for unsustainable routing scaling
   [I-D.narten-radir-problem-statement].  Operational practices such as
   increased use of multihoming with IPv4 Provider-Independent (PI)
   addressing are resulting in more and more fine-grained prefixes
   injected into the routing system from more and more end user
   networks.  Furthermore, the forthcoming depletion of the public IPv4
   address space has raised concerns for both increased deaggregation
   (leading to yet further routing table entries) and an impending
   address space run-out scenario.  At the same time, the IPv6 routing
   system is beginning to see growth in IPv6 Provider-Aggregated (PA)
   prefixes [BGPMON] which must be managed in order to avoid the same
   routing scaling issues the IPv4 Internet now faces.  Since the
   Internet must continue to scale to accommodate increasing demand, it
   is clear that new routing methodologies and operational practices are
   needed.

   Several related works have investigated routing scaling issues and
   proposed solutions.  Virtual Aggregation (VA) [I-D.ietf-grow-va] and
   Aggregation in Increasing Scopes (AIS) [I-D.zhang-evolution] are
   global routing proposals that introduce routing overlays with Virtual
   Prefixes (VPs) to reduce the number of entries required in each
   router's Forwarding Information Base (FIB) and Routing Information
   Base (RIB).  Routing and Addressing in Networks with Global
   Enterprise Recursion (RANGER) [RFC5720] examines recursive
   arrangements of enterprise networks that can apply to a very broad
   set of use case scenarios [I-D.russert-rangers].  In particular,
   RANGER supports encapsulation and secure redirection by treating each
   layer in the recursive hierarchy as a virtual non-broadcast, multiple
   access (NBMA) "link".  RANGER is an architectural framework that
   includes Virtual Enterprise Traversal (VET) [I-D.templin-intarea-vet]
   and the Subnetwork Adaptation and Encapsulation Layer (SEAL)
   (including the SEAL Control Message Protocol (SCMP))
   [I-D.templin-intarea-seal] as its functional building blocks.

   This document proposes an Internet Routing Overlay Network (IRON)
   with goals of supporting sustainable growth while requiring no
   changes to the existing routing system.  IRON borrows concepts from
   VA, AIS and RANGER, and further borrows concepts from the Internet
   Vastly Improved Plumbing (Ivip) [I-D.whittle-ivip-arch] architecture
   proposal along with its associated Translating Tunnel Router (TTR)
   mobility extensions [TTRMOB].  Indeed, the TTR model to a great
   degree inspired the IRON mobility architecture design discussed in
   this document.  The Network Address Translator (NAT) traversal
   techniques adapted for IRON were inspired by the Simple Address
   Mapping for Premises Legacy Equipment (SAMPLE) proposal



Templin                  Expires January 9, 2011                [Page 3]


Internet-Draft                    IRON                         July 2010


   [I-D.carpenter-softwire-sample].

   IRON specifically seeks to provide scalable PI addressing without
   changing the current BGP [RFC4271] routing system.  IRON observes the
   Internet Protocol standards [RFC0791][RFC2460].  Other network layer
   protocols that can be encapsulated within IP packets (e.g., OSI/CLNP
   [RFC1070], etc.) are also within scope.

   The IRON is a global overlay network routing system comprising
   Virtual Prefix Companies (VPCs) that own and manage Virtual Prefixes
   (VPs) from which End User Network (EUN) PI prefixes (EPs) are
   delegated to customer sites.  The IRON is motivated by a growing
   customer demand for multihoming, mobility management and traffic
   engineering while using stable PI addressing to avoid network
   renumbering [RFC4192][RFC5887].  The IRON uses the existing IPv4 and
   IPv6 global Internet routing systems as virtual links for tunneling
   inner network protocol packets within outer IPv4 or IPv6 headers
   (see: Section 3).  The IRON requires deployment of a small number of
   new routers that can often be simple commodity hardware platforms.
   No modifications to hosts, and no modifications to most routers are
   required.

   Note: This document is offered in compliance with Internet Research
   Task Force (IRTF) document stream procedures [RFC5743]; it is not an
   IETF product and is not a standard.  The views in this document were
   considered controversial by the IRTF Routing Research Group (RRG) but
   the RG reached a consensus that the document should still be
   published.  The document will undergo a period of review within the
   RRG and through selected expert reviewers prior to publication.  The
   following sections discuss details of the IRON architecture.


2.  Terminology

   This document makes use of the following terms:

   End User Network (EUN)
      an edge network that connects an organization's devices (e.g.,
      computers, routers, printers, etc.) to the Internet and possibly
      also the IRON.

   Internet Service Provider (ISP)
      a service provider which physically connects customer EUNs to the
      Internet.







Templin                  Expires January 9, 2011                [Page 4]


Internet-Draft                    IRON                         July 2010


   Provider Aggregated (PA) prefix
      a network layer address prefix delegated to an EUN by a service
      provider.

   Provider Independent (PI) prefix
      a network layer address prefix delegated to an EUN by a third
      party independently of the EUN's ISP arrangements.

   Virtual Prefix (VP)
      a highly-aggregated PI prefix block (e.g., an IPv4 /16, an IPv6
      /20, etc.) that is owned and managed by a Virtual Prefix Company
      (VPC).

   Virtual Prefix Company (VPC)
      a company that owns and manages a set of VPs from which it
      delegates End User Network PI Prefixes (EPs) to EUNs

   Master Virtual Prefix database (MVPd)
      a distributed database that maintains VP-to-locator mappings for
      all VPs in the IRON.

   End User Network PI prefix (EP)
      a more-specific PI prefix derived from a VP (e.g., an IPv4 /28, an
      IPv6 /56, etc.) and delegated to an EUN by a VPC.

   EP Address (EPA)
      a network layer address taken from an EP address range and
      assigned to the interface of an end system in an EUN.

   locator
      an IP address taken from a non-EP address range and assigned to
      the interface of a router or end system within a public or private
      network.  Locators taken from public IP address spaces are
      routable within the global Internet while locators taken from
      private IP address spaces are routable only within the network
      where the private IP addressing plan is deployed.

   Internet Routing Overlay Network (IRON)
      an overlay network configured over the global Internet.  The IRON
      supports routing through encapsulation of inner packets with EPA
      addresses within outer headers that use locator addresses.


3.  The Internet Routing Overlay Network (IRON)

   The Internet Routing Overlay Network (IRON) consists of IRON Routers
   (IRs) that use Virtual Enterprise Traversal (VET) and the Subnetwork
   Encapsulation and Adaptation Layer (SEAL) to encapsulate inner



Templin                  Expires January 9, 2011                [Page 5]


Internet-Draft                    IRON                         July 2010


   network layer packets within outer IP and SEAL headers (see:
   Figure 1) for transmission over the global Internet.  Each such IR
   connects to the IRON via a VET tunnel virtual interface used for
   automatic tunneling.

                                         +-------------------------+
                                         |   Outer IP Header with  |
                                         ~     locator addresses   ~
                                         |     (IPv4 or IPv6)      |
                                         +-------------------------+
                                         |       SEAL Header       |
       +-------------------------+       +-------------------------+
       |   Inner Packet Header   |  -->  |   Inner Packet Header   |
       ~    with EP addresses    ~  -->  ~    with EP addresses    ~
       | (IPv4, IPv6, OSI, etc.) |  -->  | (IPv4, IPv6, OSI, etc.) |
       +-------------------------+       +-------------------------+
       |                         |  -->  |                         |
       ~    Inner Packet Body    ~  -->  ~    Inner Packet Body    ~
       |                         |  -->  |                         |
       +-------------------------+       +-------------------------+

          Inner packet before                Outer packet after
          before encapsulation               after encapsulation

     Figure 1: Encapsulation of Inner Packets Within Outer IP Headers

   The IRON is manifested through a business model in which Virtual
   Prefix Companies (VPCs) own and manage a set of IRs that are
   distributed throughout the Internet and serve highly-aggregated
   Virtual Prefixes (VPs).  VPCs delegate sub-prefixes from their VPs
   which they lease to customers as End User Network PI prefixes (EPs).
   The customers in turn assign the EPs to their customer premises IRs
   which connect their End User Networks (EUNs) to the IRON.  VPCs may
   have no affiliation with the ISP networks from which customers obtain
   their basic connectivity.  Therefore, VPCs can open for business and
   begin serving their customers immediately without the need to
   coordinate their activities with ISPs or with other VPCs.

   The IRON requires no changes to end systems and no changes to most
   routers in the Internet.  Instead, the IRON comprises IRs that are
   deployed either as new platforms or as modifications to existing
   platforms.  IRs may be deployed incrementally without disturbing the
   existing Internet routing system, and act as waypoints (or "cairns")
   for navigating the IRON.  The functional roles of IRs are described
   in the following sections.






Templin                  Expires January 9, 2011                [Page 6]


Internet-Draft                    IRON                         July 2010


3.1.  IR(CP) - IRON Customer Premises Router

   An "IR(CP)" is a Customer Premises router (or host with embedded
   gateway function) that logically connects the customer's EUNs and
   their associated EPs to the IRON via tunnels.  IR(CP)s obtain EPs
   from VPCs and use them to number subnets and interfaces within their
   EUNs.  An IR(CP) can be deployed on the same physical platform that
   also connects the customer's EUNs to its ISPs, but it may also be a
   separate router or even a singleton end system located within the
   EUN.  (This model applies even if the EUN connects to the ISP via a
   Network Address Translator (NAT) - see Section 6.7).  An IR(CP)
   connects its EUNs to the IRON via tunnels as shown in Figure 2:
                           .-.
                        ,-(  _)-.
        +--------+   .-(_    (_  )-.
        | IR(CP) |--(_     ISP      )
        +---+----+     `-(______)-'
            |   <= T         \     .-.
           .-.       u        \ ,-(  _)-.
        ,-(  _)-.       n     .-(_    (-  )-.
     .-(_    (_  )-.      n  (_   Internet   )
    (_     EUN      )       e   `-(______)-
       `-(______)-'           l          ___
            |                   s =>    (:::)-.
       +----+---+                   .-(::::::::)
       |  Host  |                .-(::::::::::::)-.
       +--------+               (:::: The IRON ::::)
                                 `-(::::::::::::)-'
                                    `-(::::::)-'

                Figure 2: IR(EP) Connecting EUN to the IRON

3.2.  IR(BR) - IRON Border Router

   An "IR(BR)" is a Border Router that is managed by a VPC and that
   provides forwarding and mapping services for the EPs owned by their
   customer IR(CP)s.  In typical deployments, a VPC will deploy many
   IR(BR)s in a globally-distributed fashion (e.g., see Figure 3) so
   that IR(CP) clients can discover those that are nearby.  IR(BR)s
   often will require only a single physical network interface, and can
   be deployed on a variety of hardware platforms ranging from
   traditional high-end routers to commodity general-purpose processors.









Templin                  Expires January 9, 2011                [Page 7]


Internet-Draft                    IRON                         July 2010


             +--------+    +--------+
             | IR(BR) |    | IR(BR) |
             | Boston |    | Tokyo  |
             +--------+    +--------+
     +--------+
     | IR(BR) |       ___
     | Seattle|      (:::)-.       +--------+
     +--------+  .-(::::::::)      | IR(BR) |
              .-(::::::::::::)-.   | Paris  |
             (:::: The IRON ::::)  +--------+
              `-(::::::::::::)-'
   +--------+    `-(::::::)-'        +--------+
   | IR(BR) |                        | IR(BR) |
   | Moscow |     +--------+         | Sydney |
   +--------+     | IR(BR) |         +--------+
                  | Cairo  |
                  +--------+

               Figure 3: IR(VP) Global Distribution Example

3.3.  IR(GW) - IRON Gateway

   An "IR(GW)" is a core router that is managed by a VPC and that acts
   as a gateway between the IRON and the native public Internet.  Each
   VPC configures one or more IR(GW)s which advertise the company's VPs
   into the IPv4 and/or IPv6 global Internet BGP routing systems.  An
   IR(GW) may be configured on the same physical platform as an IR(BR),
   or as a separate standalone platform.  The IR(GW) role is depicted in
   Figure 4:






















Templin                  Expires January 9, 2011                [Page 8]


Internet-Draft                    IRON                         July 2010


                   ,-(  _)-.
                .-(_    (_  )-.
               (_   Internet   )
                  `-(______)-'
                        |
                   +----+---+
                   | IR(GW) |
                   +----+---+
                       _|_
                      (:::)-.
                  .-(::::::::)
   +--------+  .-(::::::::::::)-.  +--------+
   | IR(BR) | (:::: The IRON ::::) | IR(BR) |
   +--------+  `-(::::::::::::)-'  +--------+
                  `-(::::::)-'

                   +--------+
                   | IR(BR) |
                   +--------+

            Figure 4: IR(GW) Connecting VPC to Native Internet


4.  IRON Organizational Principles

   The IRON consists of the union of all VPC overlay networks worldwide.
   Each such overlay network represents a distinct "patch" on the
   Internet "quilt", where the patches are stitched together by tunnels
   over the links, routers, bridges, etc that connect the public
   Internet.  When a new VPC overlay network is deployed, it becomes yet
   another patch on the quilt.  The IRON is therefore a composite
   overlay network consisting of multiple individual patches, where each
   patch can be discussed independently of all others.

   Each VPC in the IRON maintains a set of IR(GW)s that connect its
   overlay network directly to the public IPv4 and/or IPv6 Internets.
   In particular, if the VPC serves IPv4 VPs the IR(GW)s must configure
   locator addresses on the public IPv4 Internet, and if the VPC serves
   IPv6 VPs the IR(GW)s must configure locator addresses on the public
   IPv6 Internet.  Each IR(GW) advertises the VPC's IPv4 VPs into the
   IPv4 BGP routing system and advertises the VPC's IPv6 VPs into the
   IPv6 BGP routing system.  IR(GW)s will therefore receive packets with
   EPA destination addresses sent by end systems in the Internet then
   (re)encapsulate and forward them to the correct EPA-addressed end
   systems connected to the VPC overlay network.

   Each VPC also manages a set of IR(BR)s that connect its overlay
   network directly to the public IPv4 and/or IPv6 Internets the same as



Templin                  Expires January 9, 2011                [Page 9]


Internet-Draft                    IRON                         July 2010


   for IR(GW)s, except that IR(BR)s need not be BGP routers and can
   often be simple commodity hardware platforms.  As such, the IR(BR)
   and IR(GW) functions can be deployed together on the same physical
   platform but they will more commonly be deployed on separate
   platforms to achieve economies of scale.  Each IR(BR) maintains a
   working set of IR(CP)s for which it caches EP-to-IR(CP) mappings in
   its Forwarding Information Base (FIB).  Each IR(BR) also in turn
   propagates the list of EPs in its working set to each of the VPC's
   IR(GW)s via a dynamic routing protocol.  Each IR(BR) will therefore
   commonly maintain only partial topology information representing the
   EPs in its working set, while each IR(GW) will maintain a full EP-to-
   IR(BR) mapping table that represents reachability information for all
   EPs in the VPC overlay network.

   Customers establish IR(CPs) to connect their EUNs to the VPC overlay
   network.  Unlike IR(GW)s and IR(BR)s, IR(CP)s may use private
   addresses behind one or several layers of NATs.  The IR(CP) initially
   discovers a list of nearby IR(BR)s through an exchange with its VPC.
   It then forms tunnels with one or more of the IR(BR)s through initial
   exchanges followed by periodic keepalives, and adds each IR(BR) to
   its default routers list.  When the IR(CP) configures a locator
   address behind a NAT (or, when the IR(CP) does not configure a
   locator of the same protocol version of its EPs), it uses
   encapsulation to forward all packets from its EUNs via one of the
   IR(BR)s in its default router list.  The IR(BR)s in turn will forward
   the packets further toward their final destination.  When the IR(CP)
   configures a locator on the public Internet with the same protocol
   version of its EPs, however, it can forward packets with EPA
   destination addresses directly to the IR(BR)s of its correspondents
   via encapsulation without involving one of the IR(BR)s in its default
   router list.  (The IR(CP) must instead forward packets with non-EPA
   destination addresses to an IR(BR) in its default router list via
   encapsulation to avoid ISP ingress filtering.)

   The IRON can also be used to support VPs of network layer protocols
   that cannot be routed natively in the underlying Internetwork (e.g.,
   OSI/CLNP within the public Internet, IPv6 within in IPv4-only private
   Internetworks, IPv4 within IPv6-only private Internetworks, etc.).
   In that case, however, the native routing capabilities of the
   Internetwork cannot be leveraged such that a more rigid structure
   that depends on a globally-distributed mapping database is required.
   Further details for support of IRON VPs over non-native Internetworks
   are discussed in Appendix A.


5.  IRON Initialization

   IRON initialization entails the startup actions of IRs within the VPC



Templin                  Expires January 9, 2011               [Page 10]


Internet-Draft                    IRON                         July 2010


   overlay network and customer EUNs.  The following sections discuss
   these startups procedures.

5.1.  IR(GW) Initialization

   Before its first operational use, each IR(GW) in the VPC company's
   overlay network is pre-provisioned with the list of VPs that it will
   serve as well as the locators for all IR(BR)s that also serve the
   VPs.  The IR(GW) is also provisioned with BGP peerings the same as
   for any BGP router.

   Upon startup, the IR(GW) engages in BGP routing exchanges with its
   peers in the IPv4 and/or IPv6 Internets the same as for any BGP
   router.  It then connects to all of the IR(BR)s that service its VPs
   for the purpose of discovering EP->IR(BR) mappings.  After the IR(GW)
   has thus fully populated its EP->IR(BR) mapping information database,
   it is said to be "synchronized" wrt its VPs.  The IR(GW) then
   advertises its synchronized VPs into the IPv4 and/or IPv6 Internet
   BGP routing systems and engages in ordinary packet forwarding
   operations.

5.2.  IR(BR) Initialization

   Before its first operational use, each IR(BR) in the VPC company's
   overlay network is pre-provisioned with the list of VPs that it will
   serve as well as the locators for all IR(GW)s that also serve the
   VPs.  In order to support route optimization, the IR(BR) must also be
   pre-provisioned with the list of all VPs in the IRON (i.e., and not
   just the VPs of this VPC) so that it can discern EPA and non-EPA
   addresses.

   Upon startup, the IR(BR) connects to all of the IR(GW)s that service
   its VPs for the purpose of reporting its EP->IR(BR) mappings.  The
   IR(BR) then actively listens for IR(CP) customers which will create a
   two-way tunnel while registering its EP prefixes.  When a new IR(CP)
   registers its EP prefixes, the IR(BR) informs all IR(GW)s of the new
   EP additions; when an existing IR(CP) unregisters its EP prefixes,
   the IR(BR) informs all IR(GW)s of the deletions.

5.3.  IR(CP) Initialization

   Before its first operational use, each IR(CP) must obtain one or more
   EPs from a VPC along with a certificate and a public/private key pair
   from the VPC that it can later use to prove ownership of its EPs.
   This implies that each VPC must run its own key infrastructure to be
   used only for the purpose of verifying a customer's claimed right to
   use an EP.  Hence, the VPC need not coordinate its key infrastructure
   with any other organizations.  In order to support route



Templin                  Expires January 9, 2011               [Page 11]


Internet-Draft                    IRON                         July 2010


   optimization, the IR(CP) must also be pre-provisioned with the list
   of all VPs in the IRON (i.e., and not just the VPs of this VPC) so
   that it can discern EPA and non-EPA addresses.

   Upon startup, the IR(CP) contacts its VPC (e.g., via a simple client/
   server exchange) to discover a list of locators of the company's
   nearby IR(BRs).  (This list is analogous to the ISATAP Potential
   Router List (PRL) [RFC5214].)  The IR(CP) then selects a subset of
   IR(BR)s from this list and tests them through a qualification
   procedure.  The IR(CP) then registers its EP prefixes with one or
   more qualified IR(BR)s and adds them to a default router list.


6.  IRON Operation

   Following this IRON initialization, IRs engage in the steady-state
   process of receiving and forwarding packets.  All IRs forward
   encapsulated packets over the IRON using the mechanisms of VET
   [I-D.templin-intarea-vet] and SEAL [I-D.templin-intarea-seal], while
   IR(GW)s and IR(BR)s additionally forward packets to and from the
   native IPv6 and IPv4 Internets.  IRs also use the SEAL Control
   Message Protocol (SCMP) to coordinate with other IRs, including the
   process of sending and receiving redirect messages for route
   optimization.  Each IR operates as specified in the following sub-
   sections.

6.1.  IR(CP) Operation

   During its initialization phase, the IR(CP) qualifies candidate
   IR(BR)s by sending SEAL Control Message Protocol (SCMP) Router
   Solicitation (SRS) test messages to elicit SCMP Router Advertisement
   (SRA) messages.  The IR(BR) will include the header of the soliciting
   SRS message in its SRA message so that the IR(CP) can determine the
   number of hops along the forward path.  The IR(BR) also includes a
   metric in its SRA messages indicating its current load average so
   that the IR(CP) can avoid selecting IR(BR)s that are overloaded.  The
   IR(CP) can also measure the round trip time between sending the SRS
   and receiving the SRA as an indication of round-trip delay.  Finally,
   the IR(CP) examines the SRA messages to determine whether there is a
   NAT on the path to its candidate IR(BR)s via each of its ISP
   connections.  The IR(CP) determines whether there is a NAT on the
   path by examining the address and UDP port number in the header of
   the soliciting SRS message that the IR(BR) will reflect in its SRA
   messages.  If the locator and port number reflected in the SRA
   messages does not match the locator and port number the IR(CP) uses
   for tunneling, then the IR(CP) can know that it is behind a NAT.

   After the IR(CP) determines one or more preferred IR(BR)s, it



Templin                  Expires January 9, 2011               [Page 12]


Internet-Draft                    IRON                         July 2010


   registers its EP-to-locator bindings with the IR(BR)s by sending SRS
   messages with signed certificates and prefix information to prove
   ownership of its EPs.  The SRS message will elicit an SRA message
   from the IR(BR) that includes a non-zero default router lifetime and
   that signifies the establishment of a two-way tunnel.  (A zero
   default router lifetime on the other hand signifies that the IR(BR)
   is currently unable to establish a two-way tunnel, e.g., due to heavy
   load.)  The IR(CP) should send separate beacons to each IR(BR) via
   each of its ISP connections in order to establish multiple two-way
   tunnels for multihoming purposes.

   After the initial EP-to-locator registrations, the IR(CP) sends
   periodic SRS beacons to its IR(BR)s to keep its two-way tunnels
   alive.  These beacons need not include signed certificates since
   prefix proof of ownership was already established in the initial
   exchange and the SEAL ID in the SEAL header can be used to confirm
   that the beacon was sent by the correct tunnel far end.  If the
   IR(CP) ceases to receive SRA messages from an IR(BR) via a specific
   ISP connection, it marks the IR(BR) as unreachable for that locator.
   If the IR(CP) ceases to receive SRA messages from multiple IR(BR)s
   via a specific ISP connection, it marks the ISP connection as failed/
   failing.  The IR(CP) also uses the same SRS/SRA beaconing procedure
   to inform its IR(BR)s of a change in locator, e.g., due to changing
   to a new ISP connection during a mobility event.

   When an end system in an EUN has a packet to send, the packet is
   forwarded through the EUN via normal routing until it reaches the
   IR(CP), which then encapsulates the packet and forwards it either to
   one of its serving IR(BR)s or directly into the public Internet.  In
   particular, if the IR(CP) is located behind a NAT, if the IR(CP) does
   not configure a locator of the same protocol version as the packet's
   destination, or if the destination address is a non-EPA address, the
   IR(CP) encapsulates the packet in an outer header with its locator as
   the source address and the locator of one of its serving IR(BR)s as
   the destination address then forwards the encapsulated packet to the
   IR(BR).  Otherwise, the IR(CP) encapsulates the packet in an outer
   header with its locator as the source address and the destination
   address of the inner packet copied into the destination address of
   the outer packet, then forwards the packet into the public Internet
   via a default or more-specific route.  This arrangement will ensure
   that the encapsulated packet is forwarded toward the final
   destination while bypassing the IR(CP)'s default routers in order to
   reduce path stretch.

   The IR(CP) uses the mechanisms specified in VET and SEAL to
   encapsulate each forwarded packet.  The IR(CP) further uses the SCMP
   protocol to coordinate with other IRs, including accepting redirect
   messages that indicate a better next hop.  When the IR(CP) receives



Templin                  Expires January 9, 2011               [Page 13]


Internet-Draft                    IRON                         July 2010


   an SCMP redirect, it checks the identification field of the
   encapsulated message to verify that the redirect corresponds to a
   packet that it had previously sent and accepts the redirect if there
   is a match.  Thereafter, subsequent packets forwarded by the source
   IR(CP) will follow a route-optimized path.

6.2.  IR(BR) Operation

   After an IR(BR) is initialized, it responds to SRSs from IR(CP)s by
   sending SRAs as described in Section 6.1.  When the IR(BR) receives
   an SRS with signed certificates and prefix information, it
   authenticates the message.  If authentication fails, the IR(BR)
   discards the message.  Otherwise, it creates tunnel state for this
   new IR(CP), records the EPs in its FIB, and records the locator
   address from the SCMP message as the link-layer address of the next
   hop.  The IR(BR) next sends an SRA message back to the IR(CP) to
   complete the tunnel establishment.

   When the IR(BR) receives an encapsulated packet from one of its
   IR(CP) tunnel endpoints, it decapsulates the packet and examines the
   inner destination address.  If the inner destination address is an
   EPA, the IR(BR) re-encapsulates the packet, sets the outer source
   address of the packet to one of its own locator address, sets the
   outer destination address of the packet to the inner destination
   address then forwards the encapsulated packet into the native
   Internet via a default or more-specific route.  If the inner
   destination address is not an EPA, however, the IR(EP) does not re-
   encapsulate the packet but simply forwards it unencapsulated into the
   native Internet.

   When the IR(BR) receives an encapsulated packet from the Internet, if
   the inner destination address matches an EP in its FIB the IR(BR) 'A'
   re-encapsulates the packet using VET/SEAL and forwards it to the
   next-hop IR(CP) 'B' which in turn decapsulates the packet and
   forwards it to the correct end system in the EUN.  If 'B' has left
   notice with 'A' that it has moved to a new IR(BR) 'C', however, 'A'
   will instead forward the re-encapsulated packet to 'C' and also send
   an SCMP redirect message back to the source of the packet.  In this
   way, IR(CP)s can change between IR(BR)s (e.g., due to mobility
   events) without exposing EPA packets to loss.

6.3.  IR(GW) Operation

   After an IR(GW) has synchronized its VPs (see: Section 5.1) it
   advertises the full set of the company's VP's into the IPv4 and/or
   IPv6 Internet BGP routing systems.  The VPs will be seen as ordinary
   routing information in the BGP, and any packets originating from the
   IPv4 or IPv6 Internet destined to an EPA covered by one of the VPs



Templin                  Expires January 9, 2011               [Page 14]


Internet-Draft                    IRON                         July 2010


   will be forwarded into the VPC's overlay network by an IR(GW).

   When an IR(GW) receives a packet from the Internet destined to an EPA
   covered by one of its VPs, it looks in its FIB for a matching EP to
   discover the locator of a next-hop IR(BR), then examines the packet
   format.  If the packet is not a SEAL-encapsulated packet, the IR(GW)
   simply encapsulates the packet with its own locator as the outer
   source address and the locator of the IR(BR) as the outer destination
   address and forwards the packet to the IR(BR).

   If the packet is a SEAL-encapsulated packet, however, the IR(GW)
   sends an SCMP redirect message back to the source of the packet with
   the locator of the IR(BR) as the redirected target.  It then rewrites
   the outer source address of the packet to one of its own locators,
   rewrites the outer destination address of the packet to the locator
   of the IR(BR) and forwards the (re)encapsulated packet to the IR(BR).
   In this way, the IR(GW) "bends" the initial encapsulated packets of a
   flow in flight to deflect them toward a correct IR(BR), while
   subsequent packets in the flow will be sent directly to the IR(BR)
   after the source receives a redirect.

6.4.  IRON Reference Operating Scenarios

   The IRON is used to support communications when one or both hosts are
   located within EP-addressed EUNs regardless of whether the EPs are
   provisioned by the same VPC or by different VPCs .  When both hosts
   are within IRON EUNs, route optimizations that eliminate the IR(GW)
   from the path are possible.  When only one host is within an IRON
   EUN, however, the IR(GW) cannot be eliminated from the path.

   The following sections discuss the two scenarios.  Note that it is
   sufficient to discuss the scenarios in a unidirectional fashion,
   i.e., by tracing packet flows only in the forward direction from the
   source host to destination host.  The reverse direction can be
   considered separately, and incurs the same considerations as for the
   forward direction.

6.4.1.  Both Hosts Within EP-Addressed EUNs

   When both hosts are within EP-addressed EUNs, the initial packets of
   the flow may need to involve an IR(GW) of the destination host but
   route optimization can eliminate the IR(GW) from the path for
   subsequent packets.  The two sub-scenarios that exist occur based on
   whether or not the IR(CP) of the source host is behind a NAT (and/or
   configures a locator of the same version as the packet).  The sub-
   cases are discussed in the following sections.





Templin                  Expires January 9, 2011               [Page 15]


Internet-Draft                    IRON                         July 2010


6.4.1.1.  IR(CP) of Source Host Not Behind a NAT

   Figure 5 shows the flow of initial packets from host A to host B
   within two EP-addressed EUNs when the IR(CP) of the source host A
   configures a locator of the same protocol version as the inner packet
   and that is routable on the public Internet:
                 ________________________________________
              .-(                 .-.                    )-.
           .-(                 ,-(  _)-.                    )-.
        .-( +=================+       _ +========+             )-.
      .(   //              (_|| Internet|| _)   ||                ).
    .(    //                 ||-(______)||      vv                  ).
  .(     //                  ||         ||    +------------+          ).
  (     //                   vv         ||    | IR(BR(B))) |====+      )
  (    //                    +------------+   +------------+    \\     )
  (   //  .-.                | IR(GW(B))) |                  .-. \\    )
  (  //,-(  _)-.             +------------+               ,-(  _)-\\   )
  ( .||_    (_  )-.           /                        .-(_    (_  ||. )
  ( _||  ISP A    .)        /  (redirect)             (__   ISP B  ||_))
  (  ||-(______)-'        /                              `-(______)||  )
  (  ||    |            /                                     |    vv  )
   ( +-----+-----+  <=/                                 +-----+-----+ )
     | IR(CP(A)) |                                      | IR(CP(B)) |
     +-----+-----+              The IRON                +-----+-----+
           |    (   (Overlaid on the native Internet)     )   |
          .-.     .-(                                .-)     .-.
       ,-(  _)-.      .-(________________________)-.      ,-(  _)-.
    .-(_    (_  )-.                                    .-(_    (_  )-.
   (_  IRON EUN A  )                                  (_  IRON EUN B  )
      `-(______)-'                                       `-(______)-'
           |                                                  |
       +---+----+                                         +---+----+
       | Host A |                                         | Host B |
       +--------+                                         +--------+

             Figure 5: IR(CP) of Source Host Not Behind a NAT

   In this scenario, host A sends its unencapsulated packets with
   destination address B on its network interface connected to EUN A.
   Routing with EUN A will direct the packets to IR(CP(A)) which then
   uses VET and SEAL to encapsulate them in outer headers with its
   locator address as the outer source address and B as the outer
   destination address (i.e., the inner and outer destination address
   will be the same).  Since IR(CP(A)) configures a locator on the
   public Internet, it simply releases the encapsulated packets into the
   native Internet via the ISP connection that provided its locator.
   The ISP will pass the packets without filtering since the (outer)
   source address is topologically correct.  Once the packets have been



Templin                  Expires January 9, 2011               [Page 16]


Internet-Draft                    IRON                         July 2010


   released into the Internet, routing will direct them to the nearest
   IR(GW) that advertises reachability to a VP that covers destination
   address B (namely, IR(GW(B))).

   IR(GW(B)) will receive the encapsulated packets from IR(CP(A)) then
   check its FIB to discover an entry that covers destination address B
   with IR(BR(B)) as the next hop.  IR(GW(B)) will then issue SCMP
   redirect messages to inform IR(CP(A)) that IR(BR(B)) is a better next
   hop (*).  IR(GW(B) then rewrites the outer source address of the
   encapsulated packets to its own locator address and rewrites the
   destination address of the encapsulated packets to the locator
   address of IR(BR(B)).  IR(BR(B) then releases these (re)encapsulated
   packets into the native Internet, where routing will direct them to
   IR(BR(B)).

   IR(BR(B)) will receive the encapsulated packets from IR(GW(B)) then
   check its FIB to discover an entry that covers destination address B
   with IR(CP(B)) as the next hop.  IR(BR(B)) then rewrites the outer
   source address of the packets to its own locator address and rewrites
   the outer destination address to the locator address of IR(CP(B)).
   (If IR(CP(B)) is located behind a NAT, then IR(BR(B)) also rewrites
   the UDP destination port number in the encapsulating header in order
   to support NAT traversal.)  IR(BR(B)) then releases these
   (re)encapsulated packets into the native Internet, where routing will
   direct them to IR(CP(B)).  IR(CP(B)) will in turn decapsulate the
   packets and forward the inner packets to host B via EUN B.

   (*) Note that after the initial flow of packets, IR(CP(A)) will have
   received one or more SCMP redirect messages from IR(GW(B)) informing
   it of IR(BR(B)) as a better next hop.  Thereafter, IR(CP(A)) will
   forward its encapsulated packets directly to the locator address of
   IR(BR(B)) without involving IR(GW(B)) as shown in Figure 6:



















Templin                  Expires January 9, 2011               [Page 17]


Internet-Draft                    IRON                         July 2010


                 ________________________________________
              .-(                 .-.                    )-.
           .-(                 ,-(  _)-.                    )-.
        .-( +=============> .-(_    (_  )-.======+             )-.
      .(   //              (__ Internet   _)    ||                ).
    .(    //                  `-(______)-'      vv                  ).
  .(     //                                   +------------+          ).
  (     //                                    | IR(BR(B))) |====+      )
  (    //                                     +------------+    \\     )
  (   //  .-.                                                .-. \\    )
  (  //,-(  _)-.                                          ,-(  _)-\\   )
  ( .||_    (_  )-.                                    .-(_    (_  ||. )
  ( _||  ISP A    .)                                  (__   ISP B  ||_))
  (  ||-(______)-'                                       `-(______)||  )
  (  ||    |                                                  |    vv  )
   ( +-----+-----+              The IRON                +-----+-----+ )
     | IR(CP(A)) |  (Overlaid on the native Internet)   | IR(CP(B)) |
     +-----+-----+                                      +-----+-----+
           |    (                                         )   |
          .-.     .-(                                .-)     .-.
       ,-(  _)-.      .-(________________________)-.      ,-(  _)-.
    .-(_    (_  )-.                                    .-(_    (_  )-.
   (_  IRON EUN A  )                                  (_  IRON EUN B  )
      `-(______)-'                                       `-(______)-'
           |                                                  |
       +---+----+                                         +---+----+
       | Host A |                                         | Host B |
       +--------+                                         +--------+

               Figure 6: Non-NATted Scenario After Redirects

6.4.1.2.  IR(CP) of Source Host Behind a NAT

   Figure 7 shows the flow of initial packets from host A to host B
   within two EP-addressed EUNs when the IR(CP) of the source host A is
   located behind a NAT, i.e., when it configures a locator that is not
   routable on the public Internet.  In that case, IR(CP) is obliged to
   forward its packets through one of its serving IR(BR)s since it
   cannot use its locator as a source address for forwarding packets
   directly to the native Internet.  Note that this scenario also
   applies to the case when the IR(CP) of source host A cannot configure
   a locator of the same protocol version as the inner network layer
   protocol.  For example, if the IR(CP) configures only an IPv4
   locator, but EUN A uses IPv6 natively, IR(CP) is obliged to forward
   its packets through a serving IR(BR) as though it were behind a NAT.






Templin                  Expires January 9, 2011               [Page 18]


Internet-Draft                    IRON                         July 2010


                 ________________________________________
              .-(                 .-.                    )-.
           .-(                 ,-(  _)-.                    )-.
        .-(          +========+(_    (_  +=====+               )-.
      .(             ||    (_|| Internet ||_) ||                  ).
    .(               ||      ||-(______)-||   vv                    ).
  .(        +--------++--+   ||          ||   +------------+          ).
  (     +==>| IR(BR(A))) |   vv          ||   | IR(BR(B))) |====+      )
  (    //   +------------+   +--++----++--+   +------------+    \\     )
  (   //  .-.                | IR(GW(B))) |                  .-. \\    )
  (  //,-(  _)-.             +------------+               ,-(  _)-\\   )
  ( .||_    (_  )-.           /                        .-(_    (_  ||. )
  ( _||  ISP A    .)        /  (redirect)             (__   ISP B  ||_))
  (  ||-(______)-'        /                              `-(______)||  )
  (  || <<NAT>>         /                                  <<NAT>> vv  )
   ( +-----+-----+  <=/                                 +-----+-----+ )
     | IR(CP(A)) |                                      | IR(CP(B)) |
     +-----+-----+              The IRON                +-----+-----+
           |    (   (Overlaid on the native Internet)     )   |
          .-.     .-(                                .-)     .-.
       ,-(  _)-.      .-(________________________)-.      ,-(  _)-.
    .-(_    (_  )-.                                    .-(_    (_  )-.
   (_  IRON EUN A  )                                  (_  IRON EUN B  )
      `-(______)-'                                       `-(______)-'
           |                                                  |
       +---+----+                                         +---+----+
       | Host A |                                         | Host B |
       +--------+                                         +--------+

               Figure 7: IR(CP) of Source Host Behind a NAT

   In this scenario, host A sends its unencapsulated packets with
   destination address B on its network interface connected to EUN A.
   Routing with EUN A will direct the packets to IR(CP(A)) which then
   uses VET and SEAL to encapsulate them in outer headers with its
   locator address as the outer source address and the locator address
   of a serving IR(BR) (i.e., IR(BR(A)) as the outer destination
   address.  The encapsulated packet will pass through a NAT, which will
   rewrite the packet's outer source address and source port according
   to the NAT state.  The NAT will then release the translated packets
   into the ISP connection that provided its locator (where the packets
   may undergo multiple additional layers of NAT before being released
   into the public Internet).  The ISP will pass the packets without
   filtering since the (outer) source address is topologically correct.
   Once the packets have been released into the native Internet, routing
   will direct them to IR(BR(A)).

   IR(BR(A)) receives the encapsulated packets from IR(CP(A)) then



Templin                  Expires January 9, 2011               [Page 19]


Internet-Draft                    IRON                         July 2010


   rewrites the outer source address to its own locator address and
   rewrites the outer destination address to B (i.e., the inner and
   outer destination address will be the same).  IR(BR(A)) then releases
   the (re)encapsulated packets into the native Internet, where routing
   will direct them to IR(GW(B)).

   IR(GW(B)) will receive the encapsulated packets from IR(BR(A)) then
   check its FIB to discover an entry that covers destination address B
   with IR(BR(B)) as the next hop.  IR(GW(B)) will then issue SCMP
   redirect messages to inform IR(BR(A)) that IR(BR(B)) is a better next
   hop (*).  IR(GW(B)) then rewrites the outer source address of the
   encapsulated packets to its own locator address and rewrites the
   outer destination address to the locator address of IR(BR(B)).
   IR(BR(B) then releases these (re)encapsulated packets into the native
   Internet, where routing will direct them to IR(BR(B)).

   IR(BR(B)) will receive the encapsulated packets from IR(GW(B)) then
   check its FIB to discover an entry that covers destination address B
   with IR(CP(B)) as the next hop.  IR(BR(B)) then rewrites the outer
   source address of the packets to its own locator address and rewrites
   the outer destination address to the locator address of IR(CP(B)).
   (If IR(CP(B)) is located behind a NAT, then IR(BR(B)) also rewrites
   the UDP destination port number in the encapsulating header in order
   to support NAT traversal.)  IR(BR(B)) then releases these
   (re)encapsulated packets into the native Internet, where routing will
   direct them to IR(CP(B)).  IR(CP(B)) will in turn decapsulate the
   packets and forward the inner packets to host B via EUN B.

   (*) Note that after the initial flow of packets, IR(BR(A)) will have
   received one or more SCMP redirect messages from IR(GW(B)) informing
   it of IR(BR(B)) as a better next hop.  Thereafter, IR(BR(A)) will
   forward its encapsulated packets directly to the locator address of
   IR(BR(B)) without involving IR(GW(B)) as shown in Figure 8:


















Templin                  Expires January 9, 2011               [Page 20]


Internet-Draft                    IRON                         July 2010


                 ________________________________________
              .-(                 .-.                    )-.
           .-(                 ,-(  _)-.                    )-.
        .-(          +====> .-(_    (_  )-.======+             )-.
      .(             ||    (__ Internet   _)    ||                ).
    .(               ||       `-(______)-'      vv                  ).
  .(        +--------++--+                    +------------+          ).
  (     +==>| IR(BR(A))) |                    | IR(BR(B))) |====+      )
  (    //   +------------+                    +------------+    \\     )
  (   //  .-.                                                .-. \\    )
  (  //,-(  _)-.                                          ,-(  _)-\\   )
  ( .||_    (_  )-.                                    .-(_    (_  ||. )
  ( _||  ISP A    .)                                  (__   ISP B  ||_))
  (  ||-(______)-'                                       `-(______)||  )
  (  || <<NAT>>                                            <<NAT>> vv  )
   ( +-----+-----+              The IRON                +-----+-----+ )
     | IR(CP(A)) |  (Overlaid on the native Internet)   | IR(CP(B)) |
     +-----+-----+                                      +-----+-----+
           |    (                                         )   |
          .-.     .-(                                .-)     .-.
       ,-(  _)-.      .-(________________________)-.      ,-(  _)-.
    .-(_    (_  )-.                                    .-(_    (_  )-.
   (_  IRON EUN A  )                                  (_  IRON EUN B  )
      `-(______)-'                                       `-(______)-'
           |                                                  |
       +---+----+                                         +---+----+
       | Host A |                                         | Host B |
       +--------+                                         +--------+

                 Figure 8: NATted Scenario After Redirects

6.4.2.  Mixed IRON and Non-IRON Hosts

   When one host is within an IRON EUN and the other is in a non-IRON
   EUN (i.e., one that connects to the native Internet instead of the
   IRON), the IR elements involved depend on the packet flow directions.
   Note that the same scenario holds if there is a NAT between the IRON
   EUN and the native Internet, since communications must always involve
   one of the IRON EUN's serving IR(BR)s.  The cases are described in
   the following sections:

6.4.2.1.  From IRON Host A to Non-IRON Host B

   Figure 9 depicts the IRON reference operating scenario for packets
   flowing from Host A in an IRON EUN to Host B in a non-IRON EUN:






Templin                  Expires January 9, 2011               [Page 21]


Internet-Draft                    IRON                         July 2010


                  _________________________________________
               .-(         )-.                             )-.
            .-(      +-------)----+                           )-.
         .-(         |            |                             )-.
       .(    +======>+  IR(BR(A)) +---------------+                ).
     .(    //        |            |                \                ).
   .(     //         +--------)---+                 \                 ).
   (     //                   )                      \                 )
   (    //      The IRON      )                       \                )
   (   //  .-.                )                        \     .-.       )
   (  //,-(  _)-.             )                         \ ,-(  _)-.    )
   ( .||_    (_  )-.          ) The Native Internet    .-|_    (_  )-. )
   ( _||  ISP A     )         )                       (_ |  ISP B     ))
   (  ||-(______)-'           )                          |-(______)-'  )
   (  ||    |             )-.                            v    |        )
    ( +-----+ ----+    )-.                               +-----+-----+ )
      | IR(CP(A)) |)-.                                   |  Router B |
      +-----+-----+                                      +-----+-----+
            |  (                                            )  |
           .-.   .-(____________________________________)-.   .-.
        ,-(  _)-.                                          ,-(  _)-.
     .-(_    (_  )-.                                    .-(_    (_  )-.
    (_  IRON EUN A  )                                  (_ non-IRON EUN )
       `-(______)-'                                       `-(___B___)-'
            |                                                  |
        +---+----+                                         +---+----+
        | Host A |                                         | Host B |
        +--------+                                         +--------+

               Figure 9: From IRON Host A to Non-IRON Host B

   In this scenario, host A sends its unencapsulated packets with
   destination address B on its network interface connected to IRON EUN
   A. Routing with EUN A will direct the packets to IR(CP(A)) which then
   uses VET and SEAL to encapsulate them in outer headers with its
   locator address as the outer source address and the locator address
   of a serving IR(BR) (i.e., IR(BR(A)) as the outer destination
   address.  The ISP will pass the packets without filtering since the
   (outer) source address is topologically correct.  Once the packets
   have been released into the native Internet, routing will direct them
   to IR(BR(A)).

   IR(BR(A)) receives the encapsulated packets from IR(CP(A)) then
   simply decapsulates them and releases the unencapsulated packets into
   the native Internet.  Once the packets are released into the native
   Internet, routing will direct them to the final destination B.





Templin                  Expires January 9, 2011               [Page 22]


Internet-Draft                    IRON                         July 2010


6.4.2.2.  From Non-IRON Host B to IRON Host A

   Figure 9 depicts the IRON reference operating scenario for packets
   flowing from Host B in an Non-IRON EUN to Host A in an IRON EUN:

                  _______________________________________
               .-(         )-.                             )-.
            .-(      +-------)----+                           )-.
         .-(         |            |                             )-.
       .(    +=======+  IR(GW(A)) +<--------------+                ).
     .(    //        |            |                \                ).
   .(     vv         +--------)---+                 \                 ).
   (    +-----------+         )                      \                 )
   (    | IR(BR(A)) |         )                       \                )
   (    +-----------+         )                        \     .-.       )
   (  //,-(  _)-.     IRON    )                         \ ,-(  _)-.    )
   ( .||_    (_  )-.          ) The Native Internet    .-|_    (_  )-. )
   ( _||  ISP A     )         )                       (_ |  ISP B     ))
   (  ||-(______)-'           )                          |-(______)-'  )
   (  vv    |             )-.                            |    |        )
    ( +-----+ ----+    )-.                               +-----+-----+ )
      | IR(CP(A)) |)-.                                   |  Router B |
      +-----+-----+                                      +-----+-----+
            |  (                                            )  |
           .-.   .-(____________________________________)-.   .-.
        ,-(  _)-.                                          ,-(  _)-.
     .-(_    (_  )-.                                    .-(_    (_  )-.
    (_  IRON EUN A  )                                  (_ non-IRON EUN )
       `-(______)-'                                       `-(___B___)-'
            |                                                  |
        +---+----+                                         +---+----+
        | Host A |                                         | Host B |
        +--------+                                         +--------+

              Figure 10: From Non-IRON Host B to IRON Host A

   In this scenario, host B sends its unencapsulated packets with
   destination address A on its network interface connected to IRON EUN
   B. Routing will direct the packets to IR(GW(A)) which then uses VET
   and SEAL to encapsulate them in outer headers with its locator
   address as the outer source address and the locator address of a
   serving IR(BR) (i.e., IR(BR(A)) as the outer destination address.
   IR(GW(A)) will then release the encapsulated packets into the native
   Internet, where routing will direct them to IR(BR(A)).

   IR(BR(A)) will receive the encapsulated packets from IR(GW(A)) then
   check its FIB to discover an entry that covers destination address A
   with IR(CP(A)) as the next hop.  IR(BR(A)) then rewrites the outer



Templin                  Expires January 9, 2011               [Page 23]


Internet-Draft                    IRON                         July 2010


   source address of the packets to its own locator address and rewrites
   the outer destination address to the locator address of IR(CP(A)).
   (If IR(CP(A)) is located behind a NAT, then IR(BR(A)) also rewrites
   the UDP destination port number in the encapsulating header in order
   to support NAT traversal.)  IR(BR(A)) then releases these
   (re)encapsulated packets into the native Internet, where routing will
   direct them to IR(CP(A)).  IR(CP(A)) will in turn decapsulate the
   packets and forward the inner packets to host A via EUN A.

   Note that this scenario always involves an IR(GW(A)) owned by the VPC
   that provides service to IRON EUN A. This scenario therefore imparts
   a cost that would need to be borne by either the VPC or its
   customers.

6.5.  Mobility, Multihoming and Traffic Engineering Considerations

   While IR(BR)s and IR(GW)s can be considered as fixed infrastructure,
   IR(CP)s may need to move between different network points of
   attachment, connect to multiple ISPs, or explicitly manage their
   traffic flows.  The following sections discuss mobility, multi-homing
   and traffic engineering considerations for IR(CP)s.

6.5.1.  Mobility Management

   When an IR(CP) changes its network point of attachment (e.g., due to
   a mobility event), it configures a new locator.  It then asks its VPC
   (e.g., via a short transaction protocol) for a new list of nearby
   IR(BR)s.  If the IR(CP)'s current list of serving IR(BR)s are also
   included in the new list received from the VPC, this serves as
   indication that the IR(CP) has not moved far enough to warrant
   changing to a new set of serving IR(BR)s.  Otherwise, the IR(CP) may
   wish to move to a new set of serving IR(BR)s in order to maintain
   optimal routing.

   To move to a new set of IR(BR)s, the IR(CP) first engages in the EP
   registration process with the new set of IR(BR)s and maintains the
   registrations through periodic SRS/SRA exchanges the same as
   described in Section 6.1.  The IR(CP) then informs its former set of
   IR(BR)s that it has moved by providing them with the locator
   addresses of the new IR(BR)s.  The IR(CP) then discontinues the SRS/
   SRA beaconing process with the former IR(BR)s, which will garbage-
   collect the stale FIB entries when their lifetime expires.  This will
   allow the former IR(BR)s to redirect existing correspondents to the
   new set of IR(BR)s so that no packets are lost.







Templin                  Expires January 9, 2011               [Page 24]


Internet-Draft                    IRON                         July 2010


6.5.2.  Multihoming

   An IR(CP) may register with multiple IR(BR)s via multiple locators.
   It can assign metrics with its registrations to inform its IR(BR)s of
   preferred locators, and can select outgoing IR(BR)s and locators
   according to its local preferences.  Multihoming is therefore
   naturally supported.

6.5.3.  Inbound Traffic Engineering

   An IR(CP) can dynamically adjust the priorities of its prefix
   registrations with its serving IR(BR)s in order to influence inbound
   flows of traffic.  It can also change between serving IR(BR)s when
   multiple IR(BR)s are available, but should strive for stability in
   its IR(BR) selection in order to limit routing churn.

6.5.4.  Outbound Traffic Engineering

   An IR(CP) can register with multiple IR(BR)s via multiple locators.
   It can therefore select outgoing IR(BR)/locator pairs, e.g., based on
   current QoS considerations.

6.6.  Renumbering Considerations

   As better link layer technologies and service plans emerge, customers
   will be motivated to select their service providers through healthy
   competition between ISPs.  If a customer's EUN addresses are tied to
   a specific ISP, however, the customer may be forced to undergo a
   painstaking EUN renumbering process if it wishes to changes to a
   different ISP [RFC4192][RFC5887].

   When a customer obtains EP prefixes from a VPC, it can change between
   ISPs seamlessly and without need to renumber.  If the VPC itself
   applies unreasonable costing structures for use of the EPs, however,
   the customer may be compelled to seek a different VPC and would again
   be required to confront a renumbering scenario.  The IRON approach to
   renumbering avoidance therefore depends on VPCs conducting ethical
   business practices with reasonable rates.

6.7.  NAT Traversal Considerations

   The Internet today consists of a global public IPv4 routing and
   addressing system with non-IRON EUNs that use either public or
   private IPv4 addressing.  The latter class of EUNs connect to the
   public IPv4 Internet via Network Address Translators (NATs).  When an
   IR(CP) is located behind a NAT, its selects IR(BR)s using the same
   procedures as for IR(CP)s with public addresses, i.e., it will send
   SRS messages to IR(BR)s in order to get SRA messages in return.  The



Templin                  Expires January 9, 2011               [Page 25]


Internet-Draft                    IRON                         July 2010


   only requirement is that the IR(CP) must configure its SEAL
   encapsulation to use a transport protocol that supports NAT
   traversal, namely UDP.

   Since the IR(BR) maintains state about its IR(CP) customers, it can
   discover locator information for each IR(CP) by examining the UDP
   port number and IPv4 address in the outer headers of SRS messages.
   When there is a NAT in the path, the UDP port number and IPv4 address
   in the SRS message will correspond to state in the NAT box and might
   not correspond to the actual values assigned to the IR(CP).  The
   IR(BR) can then encapsulate packets destined to hosts serviced by the
   IR(CP) within outer headers that use this IPv4 address and UDP port
   number.  The NAT box will receive the packets, translate the values
   in the outer headers to match those assigned to the IR(CP), then
   forward the packets to the IR(CP).


7.  Additional Considerations

   Considerations for the scalability of Internet Routing due to
   multihoming, traffic engineering and provider-independent addressing
   are discussed in [I-D.narten-radir-problem-statement].  Route
   optimization considerations for mobile networks are found in
   [RFC5522].


8.  Related Initiatives

   IRON builds upon the concepts RANGER architecture [RFC5720], and
   therefore inherits the same set of related initiatives.

   Virtual Aggregation (VA) [I-D.ietf-grow-va] and Aggregation in
   Increasing Scopes (AIS) [I-D.zhang-evolution] provide the basis for
   the Virtual Prefix concepts.

   Internet vastly improved plumbing (Ivip) [I-D.whittle-ivip-arch] has
   contributed valuable insights, including the use of real-time
   mapping.  The use of IR(BR)s as mobility anchor points is directly
   influenced by Ivip's associated TTR mobility extensions [TTRMOB].

   Numerous publications have proposed NAT traversal techniques.  The
   NAT traversal techniques adapted for IRON were inspired by the Simple
   Address Mapping for Premises Legacy Equipment (SAMPLE) proposal
   [I-D.carpenter-softwire-sample].







Templin                  Expires January 9, 2011               [Page 26]


Internet-Draft                    IRON                         July 2010


9.  IANA Considerations

   There are no IANA considerations for this document.


10.  Security Considerations

   Security considerations that apply to tunneling in general are
   discussed in [I-D.ietf-v6ops-tunnel-security-concerns].  Additional
   considerations that apply also to IRON are discussed in RANGER
   [RFC5720], VET [I-D.templin-intarea-vet] and SEAL
   [I-D.templin-intarea-seal].

   IR(CP)s require a means for securely registering their EP-to-locator
   bindings with their VPC.  Each VPC provides its customer IR(CP)s with
   a secure means for registering and re-registering their mappings.


11.  Acknowledgements

   This ideas behind this work have benefited greatly from discussions
   with colleagues; some of which appear on the RRG and other IRTF/IETF
   mailing lists.  Mohamed Boucadair, Wesley Eddy and Robin Whittle
   provided review input.


12.  References

12.1.  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.

12.2.  Informative References

   [BGPMON]   net, B., "BGPmon.net - Monitoring Your Prefixes,
              http://bgpmon.net/stat.php", June 2010.

   [I-D.carpenter-softwire-sample]
              Carpenter, B. and S. Jiang, "Legacy NAT Traversal for
              IPv6: Simple Address Mapping for Premises Legacy Equipment
              (SAMPLE)", draft-carpenter-softwire-sample-00 (work in
              progress), June 2010.

   [I-D.ietf-grow-va]



Templin                  Expires January 9, 2011               [Page 27]


Internet-Draft                    IRON                         July 2010


              Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and
              L. Zhang, "FIB Suppression with Virtual Aggregation",
              draft-ietf-grow-va-02 (work in progress), March 2010.

   [I-D.ietf-v6ops-tunnel-security-concerns]
              Hoagland, J., Krishnan, S., and D. Thaler, "Security
              Concerns With IP Tunneling",
              draft-ietf-v6ops-tunnel-security-concerns-02 (work in
              progress), March 2010.

   [I-D.narten-radir-problem-statement]
              Narten, T., "On the Scalability of Internet Routing",
              draft-narten-radir-problem-statement-05 (work in
              progress), February 2010.

   [I-D.russert-rangers]
              Russert, S., Fleischman, E., and F. Templin, "Operational
              Scenarios for IRON and RANGER", draft-russert-rangers-03
              (work in progress), June 2010.

   [I-D.templin-intarea-seal]
              Templin, F., "The Subnetwork Encapsulation and Adaptation
              Layer (SEAL)", draft-templin-intarea-seal-15 (work in
              progress), June 2010.

   [I-D.templin-intarea-vet]
              Templin, F., "Virtual Enterprise Traversal (VET)",
              draft-templin-intarea-vet-15 (work in progress),
              June 2010.

   [I-D.whittle-ivip-arch]
              Whittle, R., "Ivip (Internet Vastly Improved Plumbing)
              Architecture", draft-whittle-ivip-arch-04 (work in
              progress), March 2010.

   [I-D.zhang-evolution]
              Zhang, B. and L. Zhang, "Evolution Towards Global Routing
              Scalability", draft-zhang-evolution-02 (work in progress),
              October 2009.

   [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.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC4192]  Baker, F., Lear, E., and R. Droms, "Procedures for



Templin                  Expires January 9, 2011               [Page 28]


Internet-Draft                    IRON                         July 2010


              Renumbering an IPv6 Network without a Flag Day", RFC 4192,
              September 2005.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

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

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

   [RFC5522]  Eddy, W., Ivancic, W., and T. Davis, "Network Mobility
              Route Optimization Requirements for Operational Use in
              Aeronautics and Space Exploration Mobile Networks",
              RFC 5522, October 2009.

   [RFC5720]  Templin, F., "Routing and Addressing in Networks with
              Global Enterprise Recursion (RANGER)", RFC 5720,
              February 2010.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
              Reserved for Documentation", RFC 5737, January 2010.

   [RFC5743]  Falk, A., "Definition of an Internet Research Task Force
              (IRTF) Document Stream", RFC 5743, December 2009.

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

   [TTRMOB]   Whittle, R. and S. Russert, "TTR Mobility Extensions for
              Core-Edge Separation Solutions to the Internet's Routing
              Scaling Problem,
              http://www.firstpr.com.au/ip/ivip/TTR-Mobility.pdf",
              August 2008.


Appendix A.  IRON VPs Over Non-Native Internetworks

   The IRON architecture leverages the native Internet routing system by
   providing generally shortest-path routing when EPAs are taken from
   VPs that are routable.  When the VPs are not routable within the
   native underlying Internetwork, however (e.g., when OSI/NSAP
   [RFC4548] VPs are used within a private IPv4 Internetwork) packets
   with EPA addresses covered by the VPs must be carried solely via
   tunnels within the IRON.  In such an environment, the IR(GW) role is



Templin                  Expires January 9, 2011               [Page 29]


Internet-Draft                    IRON                         July 2010


   deprecated since there is no native underlying Internetwork to
   support VP routing.  This restricted model therefore entails only
   IR(CP)s and IR(BR)s.

   When IRON VPs are carried over a non-native Internetwork, a global
   mapping database is required to allow IR(BR)s to map VPs to locators
   which are assigned to the interfaces of other IR(BR)s.  Each such
   non-routable VP in the IRON must therefore be represented in a
   globally distributed Master VP database (MVPd).  The MVPd is
   maintained by a globally-managed assigned numbers authority in the
   same manner as the Internet Assigned Numbers Authority (IANA)
   currently maintains the master list of all top-level IPv4 and IPv6
   delegations.  The database can be replicated across multiple servers
   for load balancing much in the same way that FTP mirror sites are
   used to manage software distributions.

   Each VP in the MVPd is encoded as the tuple: "{address family,
   prefix, prefix-length, FQDN}", where:

   o  "address family" is one of IPv4, IPv6, OSI/CLNP, etc.

   o  "prefix" is the VP, e.g. - 2001:DB8::/32 (IPv6) [RFC3849],
      192.2/16 (IPv4) [RFC5737], etc.

   o  "prefix-length" is the length (in bits) of the associated VP

   o  FQDN is a DNS Fully-Qualified Domain Name

   For each VP entry in the MVPd, the VPC maintains a FQDN in the DNS to
   map the VP to a list of IR(BR)s that serve it.  Other IR(BR)s
   discover the mappings by resolving the FQDN into a list of resource
   records.  Each resource record corresponds to an individual IR(BR),
   and encodes the tuple : "{address family, locator, WGS 84
   coordinates}" where "address family" is the address family of the
   locator, "locator" is the routing locator assigned to an IR(BR)
   interface, and "WGS 84 coordinates" identify the physical location of
   the IR(BR).

   Upon startup, each IR(BR) managed by the VPC discovers the full set
   of VPs for the IRON by reading the MVPd.  Each IR(BR) reads the MVPd
   from a nearby server upon startup time, and periodically checks the
   server for deltas since the database was last read.  Upon reading the
   MVPd, each IR(BR) resolves the FQDN corresponding to each VP into a
   list of locators.  Each locator is an address that is routable within
   the underlying Internetwork and assigned to an interface of an IR(BR)
   that serves the VP.

   For each VP, each IR(BR) sorts the list of locators to determine a



Templin                  Expires January 9, 2011               [Page 30]


Internet-Draft                    IRON                         July 2010


   priority ranking (e.g., based on distance from the locator) and
   inserts each "VP->locator" mapping into its FIB in order of priority.
   The FIB entries must be configured such that packets with destination
   addresses covered by the VP are forwarded to the corresponding
   locator using encapsulation of the inner network layer packet in an
   outer header of a network layer protocol that is routable within the
   Internetwork.  This is accomplished by configuring the routing table
   entry to use the locator addresses as the L2 address corresponding to
   an imaginary L3 next-hop address.

   Note that the VP and locator may be of different address families;
   hence, possible encapsulations include IPv6-in-IPv4, IPv4-in-IPv6,
   IPv6-in-IPv6, IPv4-in-IPv4, OSI/CLNP-in-IPv6, OSI/CLNP-in-IPv4, etc.
   After each IR(BR) reads in the list of VPs and sorts the information
   accordingly, it is said to be "synchronized with the IRON".  Each
   IR(BR) next installs all EPs derived from its VPs into its FIB based
   on the mapping information received from the IR(CP)s each of its EUN
   customers.


Author's Address

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

   Email: fltemplin@acm.org






















Templin                  Expires January 9, 2011               [Page 31]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/