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IPv6 Enterprise Network Analysis - IP Layer 3 Focus

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 4852.
Authors David Green , Steve Klynsma , Yanick Pouffary , Jim Bound , Tim Chown
Last updated 2020-01-21 (Latest revision 2006-12-11)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Additional resources Mailing list discussion
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 4852 (Informational)
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Responsible AD David Kessens
Send notices to
IPv6 Operations WG                                         Jim Bound
Internet-Draft                                       Yanick Pouffary
Expires June 8, 2007                                 Hewlett-Packard
                                                       Steve Klynsma
                                                           Tim Chown
                                           University of Southampton
                                                          Dave Green
                                                 Command Information
                                                    December 8, 2007

        IPv6 Enterprise Network Analysis - IP Layer 3 Focus


Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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Copyright Notice

   Copyright (C) The Internet Society (2006).


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 This document analyzes the transition to IPv6 in enterprise
 networks focusing on IP Layer 3.  These networks are characterized
 as a network that has multiple internal links, one or more router
 connections, to one or more Providers, and is managed by a network
 operations entity.  The analysis will focus on a base set of
 transition notational networks and requirements expanded from a
 previous Enterprise Scenarios document. Discussion is provided on a
 focused set of transition analysis required for the enterprise to
 transition to IPv6, assuming a Dual-IP layer (IPv4 and IPv6)
 network and node environment, within the enterprise. Then a set of
 transition mechanisms are recommended for each notational network.

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Table of Contents:

1.  Introduction................................................4
2.  Terminology.................................................7
3.  Enterprise Matrix Analysis for Transition...................8
4.  Wide-Scale Dual-Stack Deployment Analysis..................12
4.1 Staged Dual-Stack Deployment...............................12
4.2 Routing Capability Analysis for Dual-IP Deployment.........13
4.2.1 IPv6 Routing Capability..................................13
4.2.2 IPv6 Routing Non-Capability..............................14 Tunnel IPv6 over the IPv4 infrastructure...............14 Deploy a parallel IPv6 infrastructure..................14
4.3 Remote IPv6 access to the enterprise.......................15
4.4 Other considerations.......................................15
5.  Sparse Dual-Stack Deployment Analysis......................16
5.1 Internal versus External Tunnel End Point..................16
5.2 Manual versus Autoconfigured...............................17
6.  IPv6 Dominant Network Deployment Analysis..................18
7.  General Issues from Analysis...............................20
7.1 Staged Plan for IPv6 Deployment............................20
7.2 Network Infrastructure Requirements........................20
7.3 Stage 1: Initial connectivity steps........................20
7.3.1 Obtaining external connectivity..........................20
7.3.2 Obtaining global IPv6 address space......................21
7.4 Stage 2: Deploying generic basic service components........21
7.4.1 Developing an IPv6 addressing plan.......................21
7.4.2 IPv6 DNS.................................................22
7.4.3 IPv6 Routing.............................................22
7.4.4 Configuration of Hosts...................................23
7.4.5 Security.................................................23
7.5 Stage 3: Widespread Dual-Stack deployment on-site..........24
8.  Applicable Transition Mechanisms...........................26
8.1 Recognizing Incompatible Network touchpoints...............26
8.2 Recognizing Application incompatibilities..................27
8.3 Using Multiple Mechanisms to Support IPv6 Transition.......28
9.  Security Considerations....................................29
10. IANA Considerations........................................29
11. References.................................................29
11.1 Normative References......................................29
11.2 Non-Normative References..................................31
Change Log.....................................................32
Author's Addresses.............................................35
Intellectual Property and Copyright Statements.................36
Appendix A - Crisis Management Network Scenarios...............37

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1.  Introduction

 This document analyzes the transition to IPv6 in enterprise
 networks focusing on IP Layer 3.  These networks are characterized
 as a network that has multiple internal links, one or more router
 connections, to one or more Providers, and is managed by a network
 operations entity.  The analysis will focus on a base set of
 transition notational networks and requirements expanded from a
 previous Enterprise Scenarios document. Discussion is provided on a
 focused set of transition analysis required for the enterprise to
 transition to IPv6, assuming a Dual-IP layer (IPv4 and IPv6)
 network and node environment, within the enterprise. Then a set of
 transition mechanisms are recommended for each notational network.

 The audience for this document is the enterprise network team
 considering deployment of IPv6.  The document will be useful for
 enterprise teams that will have to determine the IPv6 transition
 strategy for their enterprise.  It is expected those teams include
 members from management, network operations, and engineering. The
 analysis and notational networks presented provide an example set
 of cases the enterprise can use to build an IPv6 transition

 The enterprise analysis will begin by describing a matrix as a tool
 to be used to portray the different IPv4 and IPv6 possibilities for
 deployment.  The document will then provide analysis to support a
 wide Dual-IP layer deployment strategy across the enterprise, to
 provide the reader a view of how that can be planned and what are
 the options available. The document will then discuss the
 deployment of sparse IPv6 nodes within the enterprise and what
 requirements need to be considered and implemented, when the
 enterprise will remain with IPv4-only routing infrastructure for
 some time. The next discussion focuses on the use of IPv6 when it
 is determined to be dominant across or within parts of the
 enterprise network.

 The document then begins to discuss the general issues and
 applicability from the previous analysis. The document concludes
 providing a set of current transition mechanism recommendations for
 the notational network scenarios to support an enterprise planning
 to deploy IPv6.

 This document, as stated in the introduction, focuses only on the
 deployment cases where a Dual-IP Layer 3 is supported across the
 network and on the nodes in the enterprise.  Additional deployment
 transition analysis will be required from the effects of IPv6-only
 node or Provider deployments, and beyond the scope of this

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 document.  In addition this document does not attempt to define or
 discuss any use with network address translation [NATPT] or the use
 of Provider Independent address space.

 The following specific topics are currently out of scope for this

  - Multihoming
  - Application transition/porting (see [APPS]).
  - IPv6 VPN, firewall or intrusion detection deployment
  - IPv6 network management and QoS deployment
  - Detailed IT Department requirements
  - Deployment of novel IPv6 services, e.g. Mobile IPv6
  - Requirements or Transition at the Providers network
  - Transport protocol selection for applications with IPv6
  - Application layer and configuration issues.
  - IPv6 only future deployment scenarios.

 We are focusing in this document on IP Layer 3 deployment, in the
 same way as the other IPv6 deployment analysis works have done
 [UMAN] [ISPA] [3GPA].  This document covers deployment of IPv6 "on
 the wire", including address management and DNS services.

 We are also assuming that the enterprise deployment is being
 undertaken by the network administration team, i.e. this document
 is not discussing the case of an individual user gaining IPv6
 connectivity (to some external IPv6 provider) from within an
 enterprise network.  Much of the analysis is applicable to wireless
 networks, but there are additional considerations for wireless
 networks not contained within this document.

 In Section 2 we introduce the terminology used in this document. In
 Section 3 we introduce and define a tools matrix and define the IP
 layer 3 connectivity requirements. In Section 4 we discuss wide
 scale Dual-IP layer use within an enterprise. In section 5 we
 discuss sparse Dual-IP layer deployment within an enterprise. In
 section 6 we discuss IPv6-dominant network deployment within the
 enterprise. In section 7 we discuss general issues and
 applicability. In section 8 a set of transition mechanisms are
 recommended that can support the deployment of IPv6 with an

 This document then provides Appendix A for readers depicting a
 Crisis Management enterprise network to demonstrate an enterprise
 network example that requires all the properties as analyzed in
 Sections 3, 4, 5, 6, and 7.  In addition we recommend readers of
 this document also read another use case document to support an

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 IPv6 Transition for a Campus Network [CAMP].

 Readers should also be aware a parallel effort for an enterprise to
 transition to IPv6 is training, but out of scope for this document.

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2.  Terminology

 Enterprise Network - A network that has multiple internal links,
                      one or more router connections, to one or
                      more Providers and is actively managed by a
                      network operations entity.

 Provider           - An entity that provides services and
                      connectivity to the Internet or
                      other private external networks for the
                      enterprise network.

 IPv6-capable       - A node or network capable of supporting both
                      IPv6 and IPv4.

 IPv4-only          - A node or network capable of supporting only

 IPv6-only          - A node or network capable of supporting only
                      IPv6.  This does not imply an IPv6 only
                      stack, in this document.

 Dual-IP            - References a network or node that supports
                      both IPv4 and IPv6.

 IP-capability      - The ability to support IPv6 only, IPv4 only,
                      or Dual IP Layer

 IPv6-dominant      - A network running IPv6 routing and control plane
                      services that provides transport for both IPv4 and
                      IPv6 protocol services

 Transition         - The network strategy the enterprise uses to
 Implementation       transition to IPv6.

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3.  Enterprise Matrix Analysis for Transition

 In order to identify the best suited transition mechanisms for an
 enterprise, it is recommended that the enterprise have an in-depth
 up-to-date understanding of its current IT environment. This
 understanding will help choose the best suited transition
 mechanisms. It is important to note that one size does not fit all.
 While selecting a mechanism it is suggested to select mechanisms
 which reduce the impact on the existing environment. When selecting
 a transition mechanism one must consider the functionality
 required, its scalability characteristic, and the security
 implications of each mechanism.

 To provide context for an analysis of the transitioning enterprise
 at layer 3 we have provided a matrix which describes various
 scenarios which might be encountered during an IPv6 transition.
 The notional enterprise network is comprised of hosts attached to
 an enterprise-owned intranet(s) at two different global locations
 separated by the Internet.  The enterprise owns, operates and
 maintains its own intranetworks, but relies on an external provider
 organization that offers Internet Service. Both local and
 destination intranetworks are operated by different organizations
 within the same enterprise and consequently could have different
 IP-capability, than other intranetworks, at certain times in the
 transition period.

 Addressing every possible combination of network IP-capability in
 this notional enterprise network is impractical, therefore trivial
 (i.e. pure IPv4, pure IPv6, and ubiquitous Dual-IP) are not
 considered. In addition, the authors could not conceive of any
 scenarios involving IPv6-only ISPs or IPv6-only nodes in the near
 term and consequently have not addressed scenarios with IPv6-only
 ISPs or IPv6-only nodes. We assume all nodes that host IPv6
 applications are Dual IP. The matrix does not assume or suggest
 that network address translation is used.  The authors recommend
 that network address translation not be used in these notional

 Future enterprise transitions that support IPv6-only nodes and
 IPv6-only ISPs will require separate analysis, that is beyond the
 scope of this document.

 Table 1 scenarios below is a matrix of ten possible Transition
 Implementations that, being encountered in an enterprise, may
 require analysis and the selection of an IPv6 transition mechanism
 for that notional network.  Each possible implementation is
 represented by the rows of the matrix.  The matrix describes a set

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 of notional networks as follows:

     - The first column represents the protocol used by the
       application and below, the IP-capability of the node
       originating the IP packets.
       (Application/Host 1 OS).

     - The second column represents the IP-capability of the
       host network wherein the node originated the packet.
       (Host 1 Network)

     - The third column represents the IP-capability of the
       service provider network.
       (Service Provider)

     - The fourth column represents the IP-capability of the
       destination network wherein the originating IP packets
       are received.
       (Host 2 Network)

     - The fifth column represents the protocol used by the
       application and, below, the IP-capability of the
       destination node receiving the originating IP packets.
       (Application/Host 2 OS).

 As an example, notional network 1 is an IPv6 application residing
 on a Dual-IP layer host trying to establish a communications
 exchange with a destination IPv6 application. To complete the
 information exchange the packets must first traverse the host's
 originating IPv4 network (intranet), then the service provider's,
 and destination hosts Dual-IP network.

 Obviously Table 1 does not describe every possible scenario.
 Trivial notional networks (such as pure IPv4, pure IPv6, and
 ubiquitous Dual-IP) are not addressed. However, the authors feel
 these ten represent the vast majority of transitional situations
 likely to be encountered in today's enterprise. Therefore, we will
 use these ten to address the analysis for enterprise deployment.

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   Table 1 - Enterprise Scenario Deployment Matrix

      |Application |Host 1 |Service |Host 2 |Application |
      |----------- |Network|Provider|Network|----------  |
      | Host 1 OS  |       |        |       | Host 2 OS  |
      |    IPv6    |       |Dual IP |       |    IPv6    |
    A |    ----    | IPv4  |  or    |Dual IP|    ----    |
      |    Dual IP |       | IPv4   |       |    Dual IP |
      |    IPv6    |       |        |       |    IPv6    |
    B |    ----    | IPv6  | IPv4   | IPv4  |    ----    |
      |    Dual IP |       |        |       |    Dual IP |
      |    IPv4    |       |        |       |    IPv4    |
    C |    ----    | IPv4  |Dual IP | IPv6  |    ----    |
      |    Dual IP |       |        |       |    Dual IP |
      |    IPv4    |Dual IP|        |       |    IPv4    |
    D |    ----    |  or   | IPv4   | IPv6  |    ----    |
      |    Dual IP | IPv6  |        |       |    Dual IP |
      |    IPv6    |Dual IP|        |Dual IP|    IPv4    |
    E |    ----    |  or   |Dual IP |  or   |    ----    |
      |    Dual IP | IPv6  |        | IPv6  |    Dual IP |
      |    IPv6    |       |        |       |    IPv4    |
    F |    ----    | IPv6  | IPv4   | IPv4  |    ----    |
      |    Dual IP |       |        |       |    Dual IP |
      |    IPv4    |       |        |       |    IPv6    |
    G |    ----    | IPv6  | Dual IP| IPv6  |    ----    |
      |    Dual IP |       |        |       |    Dual IP |
      |    IPv4    |       |        |       |    IPv6    |
    H |    ----    | IPv6  |Dual IP | IPv4  |    ----    |
      |    IPv4    |       |        |       |    Dual IP |
      |    IPv4    |       |        |       |    IPv6    |
    I |    ----    | IPv6  |  IPv4  | IPv6  |    ----    |
      |    IPv4    |       |        |       |    Dual IP |
      |    IPv6    |       |        |       |    IPv4    |
    J |    ----    | IPv4  |  IPv4  | IPv6  |    ----    |
      |    Dual IP |       |        |       |    Dual IP |

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 The reader should note that scenarios A-C in Table 1 are variations
 of compatible hosts communicating across largely (but not entirely)
 homogenous networks. In each of the first three scenarios, the
 packet must traverse at least one incompatible network component.
 For example, scenario B represents an enterprise which wishes to
 use IPv6 applications, but has yet to transition its internal
 networks and its Service Provider also lags, offering only a v4
 IP-service.  Conversely, Scenario C represents an enterprise which
 has completed transition to IPv6 in its core networks (as has its
 Service Provider), but continues to require a legacy IPv4-based

 Scenario D represents the unusual situation where the enterprise
 has transitioned its core intranetworks to IPv6, but (like scenario
 B) it's ISP provider has yet to transition.  In addition, this
 Enterprise continues to retain critical legacy IPv4-based
 applications which must communicate over this heterogeneous network

 Scenarios E-J represent transitional situations wherein the
 Enterprise has both IPv4 and IPv6 based instantiations of the same
 application that must continue to interoperate.  In addition, these
 scenarios show that the Enterprise has not completed transition to
 IPv6 in all its organic and/or Service Provider networks.  Instead,
 it maintains a variety of heterogeneous network segments between
 the communicating applications.  Scenarios E and J represent
 distinctly different extremes on either end of the spectrum.  In
 scenario E, the enterprise has largely transitioned to IPv6 in both
 its applications and networks. However, scenario E shows that a few
 legacy IPv4-based applications may still be found in the
 enterprise.  On the other hand, scenario J shows an Enterprise that
 has begun its transition in a very disjointed manner and, in which
 IPv6-based applications and network segments are relatively rare.

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4.  Wide-Scale Dual-Stack Deployment Analysis

 In this section we address Scenario 1 as described in Section 3.1
 of [BSCN].  The scenario, assumptions and requirements are driven
 from the [BSCN] text.  This analysis further corresponds to
 Scenario A in Section 3 above (although Scenario A shows a
 transitional situation wherein the enterprise has one network
 segment still lagging on transition to Dual-IP).

 Within these IPv6 deployment scenarios the enterprise network
 administrator would introduce IPv6 by enabling IPv6 on the wire
 (i.e. within the network infrastructure) in a structured fashion
 with the existing IPv4 infrastructure. In such scenarios, a number
 of the existing IPv4 routers (and thus subnets) will be made dual-
 IP, such that communications can run over either protocol.

 Nodes on the dual-IP links may themselves be IPv4-only or IPv6-
 capable.  The driver for deploying IPv6 on the wire may not be for
 immediate wide-scale usage of IPv6, but rather to prepare an
 existing IPv4 infrastructure to support IPv6-capable nodes.  Thus,
 while IPv6 is not used, dual-IP nodes exist, and the enterprise can
 be transitioned to IPv6 on demand.

 Analyzing this scenario against existing transition mechanisms for
 their applicability, suggests a staged approach for IPv6 deployment
 in the enterprise.

4.1 Staged Dual-Stack Deployment

 Under these scenarios (as well as most others), the site
 administrator should formulate a staged plan for the introduction
 of a dual-IP IPv6 network.  We suggest that the generic plan of
 Section 7 of this document provides a good basis for such a plan.

 In an enterprise network, the administrator will generally seek to
 deploy IPv6 in a structured, controlled manner, such that IPv6 can
 be enabled on specific links at various stages of deployment. There
 may be a requirement that some links remain IPv4 only, or some that
 specifically should not have IPv6 connectivity (e.g. Scenario A of
 Table 1).  There may also be a requirement that aggregatable global
 IPv6 addresses, assigned by the enterprise's upstream provider from
 the address space allocated to them by the Regional Internet
 Registries (RIRs), be assigned.

 In this document we do not discuss the deployment of Unique Local

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 IPv6 Unicast Addresses [ULA] because the address type and scope
 selected is orthogonal to the layer 3 analysis of this document.

 A typical deployment would initially involve the establishment of a
 single "testbed" Dual-IP subnet at the enterprise site prior to
 wider deployment.  Such a testbed not only allows the IPv6
 capability of specific platforms and applications to be evaluated
 and verified, but also permits the steps in Sections 7.3 and 7.4 of
 this document to be undertaken without (potential) adverse impact
 on the production elements of the enterprise.

 Section 7.5 describes the stages for the widespread deployment in
 the enterprise, which could be undertaken after the basic building
 blocks for IPv6 deployment are in place.

4.2 Routing Capability Analysis for Dual-IP Deployment

 A critical part of Dual-IP deployment is the selection of the
 IPv6-capable routing infrastructure to be implemented. The path
 taken will depend on whether the enterprise has existing Layer 2/3
 switch/router equipment that has an IPv6 (routing) capability, or
 that can be upgraded to have such capability.

 In Section 4, we are not considering sparse IPv6 deployment; the
 goal of Dual-IP deployment is widespread use in the enterprise.

4.2.1 IPv6 Routing Capability

 Where IPv6 routing capability exists within the infrastructure, the
 network administrator can enable IPv6 on the same physical hardware
 as the existing IPv4 service. This is the end goal of any
 enterprise to support Dual-IP deployment, when the capability,
 performance, and robustness of the Dual-IP operational deployment
 has been verified.

 Ideally, the IPv6 capability will span the entire enterprise,
 allowing deployment on any link or subnet.  If not, techniques from
 Section 4.4 below may be required.

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4.2.2 IPv6 Routing Non-Capability

 If the enterprise cannot provide IPv6 routing initially there are
 alternative methods for transition.  In this case the enterprise
 administrator faces two basic choices, either to tunnel IPv6 over
 some or all of the existing IPv4 infrastructure, or to deploy a
 parallel IPv6 routing infrastructure providing IPv6 connectivity
 into existing IPv4 subnets.

 It may thus be the case that a nodes IPv4 and IPv6 default routes
 to reach other links (subnets) are through different routing
 platforms. Tunnel IPv6 over the IPv4 infrastructure

 Consider the situation where there exists IPv6 edge routers which
 are IPv6-capable, while others,and perhaps the enterprise backbone
 itself, are not IPv6-capable (Scenario B of Table 1).  Tunneling,
 as described in [BCNF] would be established between the Dual-IP
 capable routers on the enterprise, thus "bypassing" existing non
 IPv6-capable routers and platforms.

 In the widespread dual-IP scenario, a more structured, manageable
 method is required, where the administrator has control of the
 deployment per-link and (ideally) long-term, aggregatable global
 IPv6 addressing is obtained, planned and used from the outset. Deploy a parallel IPv6 infrastructure

 Alternatively,the administrator may deploy a new, separate IPv6-
 capable router (or set of routers).  It is quite possible that such
 a parallel infrastructure would be IPv6-dominant.

 Such an approach would likely require additional hardware, but it
 has the advantage that the existing IPv4 routing platforms are not
 disturbed by the introduction of IPv6.

 To distribute IPv6 to existing IPv4 enterprise subnets, either
 dedicated physical infrastructure can be employed or, if available,
 IEEE 802.1q VLANs could be used, as described in [VLAN].  The
 latter has the significant advantage of not requiring any
 additional physical cabling/wiring and also offers all the

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 advantages of VLANs for the new dual-IP environment.  Many router
 platforms can tag multiple VLAN IDs on a single physical interface
 based on the subnet/link the packet is destined for; thus multiple
 IPv6 links can be collapsed for delivery on a single (or small
 number of) physical IPv6 router interfaces in the early stages of

 The parallel infrastructure should only be seen as an interim step
 towards full Dual-IP deployment on a unified infrastructure.  The
 parallel infrastructure however allows all other aspects of the
 IPv6 enterprise services to be deployed, including IPv6 addressing,
 thus making the enterprise ready for that unifying step at a later

4.3 Remote IPv6 access to the enterprise

 When the enterprise's users are off-site, and using an ISP that
 does not support any native IPv6 service or IPv6 transition aids,
 the enterprise may consider deploying it's own remote IPv6 access
 support. Such remote support might for example be offered by
 deployment of an IPv6 Tunnel Broker [TBRK].

4.4 Other considerations

 There are some issues associated with turning IPv6 on by default,
 including application connection delays, poor connectivity, and
 network insecurity, as discussed in [V6DEF]. The issues can be
 worked around or mitigated by following the advice in [V6DEF]

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5.  Sparse Dual-Stack Deployment Analysis

 This section covers the Scenario 2 as described in Section 3.1 of
 [BSCN]. This scenario assumes the requirements defined within the
 [BSCN] text.

 IPv6 deployment within the enterprise network, with an existing
 IPv4 infrastructure, could be motivated by mission critical or
 business applications or services that require IPv6. In this case
 the prerequisite is that only the nodes using those IPv6
 applications need to be upgraded to be IPv6-capable. The routing
 infrastructure will not be upgraded to support IPv6, nor does the
 enterprise wish to deploy a parallel IPv6 routing infrastructure at
 this point, since this is an option in section 4.

 There is a need for end-to-end communication with IPv6, but the
 infrastructure only supports IPv4 routing. Thus, the only viable
 method for end-to-end communication with IPv6 is to tunnel the
 traffic over the existing IPv4 infrastructure, within this analysis
 documents boundaries defined.

 The network team needs to decide which are the most efficient the
 available transition tunneling mechanisms to deploy, so they can be
 used without disrupting the existing IPv4 infrastructure.  Several
 conditions require analysis, as introduced in the following sub

5.1 Internal versus External Tunnel End Point

 Let's assume the upstream provider has deployed some IPv6 services,
 either native IPv6 in its backbone or in the access network, or
 some combination of both (Scenario B of Table 1). In this case, the
 provider will likely also deploy one or more transition mechanisms
 to support their IPv6 subscribers. Obviously, the enterprise could
 decide to take advantage of those transition services offered from
 the Provider. However, this will usually mean that individual nodes
 in the network will require their own IPv6-in-IPv4 tunnel. The end
 result is somewhat inefficient IPv6 intranetworks communication,
 because all IPv6 traffic must be forwarded by the Enterprise's IPv4
 infrastructure to the Tunnel End-Point offered by the Provider.
 Nevertheless, this may be acceptable paticularly if the IPv6
 applications do not require intranetworks communication at all. For
 example when an application's server is located outside of the
 enterprise network, or on other intranetworks of the same

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 Alternatively, the enterprise could decide to deploy its own
 transition mechanism node, possibly collocating it adjacent to the
 border router that connects to the upstream Provider. In this case,
 intranetnetworks communication using this tunnel end point is also

5.2 Manual versus Autoconfigured

 If the number of nodes to be using IPv6 is low, the first option is
 to use statically configured tunnels.  However, automatically
 configured tunnels may be preferable, especially if the number is

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6.  IPv6 Dominant Network Deployment Analysis

 In this section we are covering Scenario 3 as described in Section
 3.1 of [BSCN]. The scenario, assumptions and requirements are
 driven from the [BSCN] text.  Within this document, this situation
 is captured in Scenario C of Table 1.

 Some enterprise networks may wish to employ an IPv6-dominant
 network deployment strategy. What this means essentially is that
 the network or specific sites within the enterprise network will
 transition to IPv6 using only IPv6 routing to transfer both IPv4
 and IPv6 packets over the network, even though the network may be
 Dual-IP capable.  IPv4 routing would not be turned on within an
 IPv6-dominant network, except if required to support edge IPv4

 Under this scenario, communications between IPv6 nodes will use
 IPv6. When IPv6-capable nodes in the IPv6-dominant network need to
 communicate with IPv4 nodes, the IPv6 nodes will use their Dual-IP
 implementation to tunnel IPv4 packets in IPv6 [V6TUN]. An edge
 router within the IPv6-dominant network will decapsulate the IPv4
 packet and route to the path of the IPv4 node on the network.  This
 permits Dual-IP layer nodes to communicate with legacy IPv4 nodes
 within an IPv6-dominant network.

 From Table 1 scenarios E and F depict additional cases where an
 IPv6- dominant deployment strategy could be in place.  In scenario
 E the entire network could be IPv6-dominant, but the Host OS 2
 system is running an IPv4 application.  In scenario F the Host OS 1
 system network could be IPv6-dominant, but the rest of the networks
 are all IPv4.

 In each case, communicating with an IPv4 end host or over an IPv4
 network requires a transition point exist within the network to
 support that operation. Furthermore, the node in the IPv6-dominant
 network must acquire an IPv4 address (to interoperate with the IPv4
 end host), and locate a tunnel endpoint on their network which
 permits the IPv4 packet to be tunneled to the next hop IPv6 router
 and eventually to a destination Dual IP router.

 While retaining interoperability with IPv4 is a noble goal for
 Enterprise architects, it is an unfortunate fact that maintaining
 IPv4 services in an IPv6-dominant network slows and may even impede
 your ability to reap the maximum benefits of IPv6.

 The decision whether or not to use an IPv6-dominant network
 deployment strategy is completely driven by the Enterprise's

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 business and operational objectives and guided by the Enterprise's
 transition plan.

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7.  General Issues from Analysis

 In this section we describe generic enterprise IPv6 deployment
 issues, applicable to the analysis sections 4-6 in this document.

7.1 Staged Plan for IPv6 Deployment
 The enterprise network administrator will need to follow a staged
 plan for IPv6 deployment.  What this means is that a strategic
 identification of the enterprise network must be performed for all
 points and components of the transition.

7.2 Network Infrastructure Requirements

 The considerations for the enterprise components are detailed in
 Section 3.2 of [BSCN].  We do not go into detail of all aspects of
 such components in this document.  In this document we focus on
 Layer 3 issues.

7.3 Stage 1: Initial connectivity steps

 The first steps for IPv6 deployment do not involve technical
 aspects per se; the enterprise needs to select an external IPv6
 provider, and obtain globally routable IPv6 address space from that

7.3.1 Obtaining external connectivity

 The enterprise service provider would typically be a
 topographically close IPv6 provider that is able to provide an IPv6
 upstream link.  It would be expected that the enterprise would use
 either native IPv6 upstream connectivity or, in its absence, a
 manually configured tunnel [BCNF] to the upstream provider.

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7.3.2 Obtaining global IPv6 address space

 The enterprise will obtain global IPv6 address space from its
 selected upstream provider, as provider assigned (PA) address

 The enterprise should receive at least a /48 allocation from its
 provider, as described in [ALLOC].

 Should an enterprise change their provider, a procedure for
 enterprise renumbering between providers is described in [RENUM].

7.4 Stage 2: Deploying generic basic service components

 Most of these are discussed in Section 4 of [BSCN]. Here we comment
 on those aspects that we believe are in scope for this analysis
 document.   Thus we have not included network management,
 multihoming, multicast or application transition analysis here, but
 these aspects should be addressed in Stage 2.

7.4.1 Developing an IPv6 addressing plan

 A site will need to formulate an IPv6 addressing plan, utilizing
 the globally aggregatable public IPv6 prefix allocated to it by its
 upstream connectivity provider.

 In a Dual-IP deployment, the site will need to decide whether it
 wishes to deploy IPv6 links to be congruent with existing IPv4
 subnets. In this case, nodes will fall into the same links or
 subnets for both protocols. Such a scheme could be followed, with
 IPv6 prefix allocations being made such that room for topological
 growth is provisioned (reducing the potential requirement for
 future renumbering due to restructuring).

 A beneficial property of IPv6 is that an administrator will not
 need to invest as much effort in address conservation.  With IPv4,
 a site will likely allocate IPv4 subnets to be as small as possible
 for the number of hosts currently in the subnet (e.g. a /26 for 50
 nodes), because IPv4 address conservation is required. This creates
 problems when the number of nodes on a subnet grows, larger IPv4
 prefixes are then required, and potentially time-consuming and
 disruptive renumbering events will follow.

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 With IPv6, a link can in effect have any number of nodes, allowing
 link growth without the need to adjust prefix allocations with the
 associated renumbering requirement.   The size of the initial site
 allocation (currently recommended to be a /48) also is likely to
 allow room for site growth without a need to return to the
 connectivity provider to obtain more, potentially non-sequential,
 address space (as is the case for IPv4 today, with the associated
 paperwork and probable delays).

 At the time of writing, best practice in IPv6 site address planning
 is restricted due to limited wide-scale deployments. Administrators
 should allocate /64 size prefixes for subnets, and do so in a way
 that has scope for growth within a site.  The site should utilize a
 plan that reserves space for topological growth in the site, given
 that its initial IPv6 prefix allocation (currently recommended to
 be a /48) is likely to include such room for growth. Also see IPv6
 unicast address assignments document in process [UNAD].

7.4.2 IPv6 DNS

 The enterprise site should deploy a DNS service that is capable of
 both serving IPv6 DNS records using the AAAA format [DNSV6R] and of
 communicating over IPv6 transport.

 Specific IPv6 DNS issues are reported in [DNSOP6].

7.4.3 IPv6 Routing

 The enterprise network will need to support methods for internal
 and external routing.

 For a single-homed single-site network, a static route to a single
 upstream provider may be sufficient, although the site may choose
 to use an exterior routing protocol, especially where it has
 multiple upstream providers.

 For internal routing, an appropriate interior routing protocol may
 be deployed.  IPv6 routing protocols that can be used are as
 follows: BGP4+ [BGP4], IS-IS [ISIS], OSPFv3 [OSPF] and RIPng

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7.4.4 Configuration of Hosts

 An enterprise network will have a number of tools available for
 IPv4 address and other configuration information delegation and
 management, including manual configuration, NIS [NIS] or DHCP

 In an IPv6 enterprise, Stateless Address Autoconfiguration [CONF]
 may be used to configure a host with a global IPv6 address, a
 default router, and an on-link prefix information.

 Where support for secure autoconfiguration is required, SEND [SEND]
 can be used.  Readers should see the applicability statements to
 IPsec [IPSEC] within the SEND document.

 A stateless configured node wishing to gain other configuration
 information (e.g. DNS, NTP servers) will likely need a Stateful
 DHCPv6 [DHCPv6] service available.

 For nodes configuring using DHCPv6, where DHCPv6 servers are
 offlink, a DHCPv6 Relay Agent function will be required. Where
 DHCPv4 and DHCPv6 service are deployed together, dual-stack
 considerations need to be made, as discussed within current work on
 DHCP dual stack issues [DHDS].

 Hosts may also generate or request IPv6 Privacy Addresses [PRIVv6];
 there is support for DHCPv6 to assign privacy addresses to nodes in
 managed environments.

7.4.5 Security

 When deploying IPv6 within a Dual-IP network, a site will need to
 implement its site security policy for IPv6-capable nodes as it
 does for IPv4-capable nodes.   For example, a border firewall
 should be capable of filtering and controlling IPv6 traffic by
 enforcing the same policy as it already does for IPv4.

 However, a site will also need to review its security policy in
 light of IPv6 specific functionality that will be deployed in the
 site, e.g.  Mobile IPv6, stateless autoconfiguration (and SEND),
 IPv6 Privacy Extensions, end-to-end IPsec, and, not least, the use
 of globally aggregatable public address space where for IPv4
 private addressing and NAT may have been used.

 An overview of how Network Architecture Protection (NAP) using IPv6

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 can provide the same or more benefits without the need for NAT can
 be found in [NAP].   This describes how the perceived security with
 IPv4 NAT can be achieved and surpassed with IPv6, i.e. how IPv6
 technology can be used to provide the market-perceived benefits of
 IPv4 NAT.

 Where deployed, intrusion detection systems will need to be
 enhanced to both check IPv6 transport for known application layer
 attack patterns and also to check for new potential IPv6 threats,
 e.g. excessive hop-by-hop headers, or errant IPv6 header options.

 The deployment of specific transition mechanisms may also introduce
 threats, e.g. carrying IPv6 data tunnelled in IPv4.   The site
 security policy should embrace the transition mechanisms that are

 An overview of IPv6 security issues can be found in [V6SEC].  This
 includes discussion of issues specific to the IPv6 protocol, to
 transition mechanisms, and to IPv6 deployment itself.

 In addition an enterprise should review all current Host Based
 security requirements for their networks and verify support for

7.5 Stage 3: Widespread Dual-Stack deployment on-site

 With the basic building blocks of external connectivity, interior
 IPv6 routing, an IPv6 DNS service and address allocation management
 in place, the IPv6 capability can be rolled out to the wider
 enterprise. This involves putting IPv6 on the wire in the desired
 links, and enabling applications and other services to begin using
 an IPv6 transport.

 In the Dual-IP deployment case, this means enabling IPv6 on
 existing IPv4 subnets.   As described in Section 7.4.4 above, it is
 likely that IPv6 links will be congruent with IPv4 subnets, because
 IPv4 subnets tend to be created for geographic, policy or
 administrative reasons that would be IP version-independent.

 While the use of IPv6 by some applications can be administratively
 controlled (e.g. in the case of open source software by compiling
 the application without IPv6 support enabled), the use of IPv6
 transport, and preference over IPv4 transport, will vary per
 application based on the developer/author's implementation.

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 A Dual-IP deployment will often be made by sites wishing to support
 use of IPv6 within a site, even if IPv6 transport is not preferred
 by all applications.   Putting support for IPv6 in all site
 infrastructure (DNS, email transport, etc) allows IPv6 usage to be
 phased in over time.   As nodes become IPv6 capable, and
 applications and services IPv6 enabled, the IPv6 capable
 infrastructure can be leveraged.   For most networks, Dual-IP will
 be at the very least a medium-term transition towards an IPv6-
 dominant future.  However, the introduction of IPv6 support, with
 the potential benefits of globally aggregatable public address
 usage (with [NAP]), and other new IPv6 capabilities, can bring more
 immediate benefits for the site.

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8.  Applicable Transition Mechanisms

 This section will provide general guidance for the use of specific
 transition mechanisms which in turn can be used by the enterprise
 to support the enterprise matrix notional networks (rows) in
 Section 3, and within the context of the analysis discussed in
 Sections 4, 5, and 6.

 Table 1 provides a number of common scenarios that an enterprise
 architect might encounter as they consider how and where they
 should consider deploying transition mechanisms to support the
 network transition to IPv6.  Selecting the most appropriate
 mechanism for each scenario is more of an art than a science and
 consequently making recommendations against each of the ten
 scenarios would be simply fodder for sharpshooters touting their
 favored product.  However we can provide some high-level guidance
 that should benefit the architect's decision making process.

8.1 Recognizing Incompatible Network touchpoints

 Mapping your specific situation into one of the ten scenarios of
 Table 1 is far less important than recognizing the critical
 touchpoints within the enterprise networks where incompatible
 networks interface. Unless a transition mechanism is being offered
 by the enterprise as a service, it is at these touchpoints that a
 mechanism must be considered.

 A quick review of Table 1 reveals that the ten scenarios can be
 boiled down to variations of four major themes.  The simplest, but
 also most favored (due to its flexibility), is wide spread Dual IP
 with compatible hosts at either end.  This situation is illustrated
 in Scenario A and transition mechanism considerations have already
 been described in some detail in Section 4.

 In the second common theme (depicted in Scenarios B-D of Table 1),
 the enterprise is comprised of compatible hosts, with one or more
 incompatible network touchpoints in between.  As described in
 Section, tunneling can be used to "bypass" the incompatible
 network segments.  One tunneling option, Manual Configured Tunnels
 [BCNF] could be used by the enterprise, but as the name implies,
 this mechanism provides no automated tunnel configuration.

 6TO4 [6TO4] can be used to support enterprises that do not have an
 assigned IPv6 prefix address.

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 Identifying the responsible device to perform the tunneling is
 driven by the position of the incompatible touchpoint.  If a local
 network is incompatible then host tunneling is appropriate.  If the
 backbone (provider) network is incompatible then gateway-to-gateway
 tunneling might be a better choice.  By working to ensure tunnel
 endpoints are always configured at dual-IP devices, end-to-end
 communication or services (IPv4 or IPv6) can be preserved.

 Readers should review the current work regarding tunnels within the
 IETF Softwire working group and problem statement [SOFTW].

 Having IPv6 applications on a Dual-IP host on a v4-only network
 requires some form of tunneling. Where configured tunnels are not
 sufficient a more automatic solution may be appropriate. Available
 solutions include ISATAP [ISTP] or Teredo [TRDO] to tunnel to a v6
 end service. ISATAP [ISTP] can be used to provide end node IPv6
 connectivity from nodes on an isolated IPv4 network, through the
 use of automatic tunneling of IPv6 in IPv4. Teredo [TRDO] can be
 used when the enterprise network is behind a NAT.

 Enterprise architects should consider providing a Tunnel Broker
 [TBRK] [TSPB] as a cost effective service to local users or
 applications. Tunnel Brokers can be used to provide tunnel setup
 for an enterprise using manual configured tunnels and 6TO4 [6TO4].
 Tunnel Brokers can automate the use of tunnels across an enterprise
 deploying IPv6.

 Later in the transition process, after the enterprise has
 transitioned to a predominately IPv6 infrastructure, the architect
 will need to determine a network transition strategy to tunnel IPv4
 within IPv6 [V6TUN] across IPv6-dominant links, or the enterprise
 Intranet.  Or in the case of early deployment of IPv6-dominant
 networks the architect will need to address this from the beginning
 of the required transition planning.

8.2 Recognizing Application incompatibilities

 Having recognized incompatible network touchpoints, it is also
 incumbent on the architect to identify application
 incompatibilities.  During the transition period, particularly for
 large enterprises, it is to be expected that applications hosted at
 one location may lead (or lag) the IPv6-compability of its peer (or
 server) at some other location.

 This leads us to the third theme represented by Scenario E and G,

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 i.e. incompatible applications communicating across a homogenous
 network.  Translation is an obvious solution, but not recommended
 except for legacy devices at the network edge which cannot or never
 will be upgraded to IPv6.  A more scaleable solution would be to
 use an Application Layer Gateways (ALG) between the incompatible

8.3 Using Multiple Mechanisms to Support IPv6 Transition

 Inevitably, during the course of transitioning a large enterprise
 to IPv6, the architect will be faced with both incompatible hosts
 and simultaneously (at different parts of the enterprise)
 incompatible networks.  These highly complex situations represent
 the fourth common theme in Table 1 and are specifically depicted by
 Scenarios F, H, I and J.  Maintaining IP interoperability in these
 situations requires additional planning and may require multiple or
 even nested use of diverse transition mechanisms.  For example, an
 ALG co-located with the application server may be required to
 service both IPv4 and IPv6 data streams that are simultaneously
 tunneled through incompatible network segment(s).

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9.  Security Considerations

 Security considerations for IPv6 deployment in a Dual-IP
 environment are discussed above in section 7.4.5, where external
 references to overview documents [V6SEC] [NAP] are also included.

10. IANA Considerations

 This document has no actions for IANA.

11. References

11.1 Normative References

 [CONF]   Thomson, S., Narten, T., "IPv6 Stateless
          Autoconfiguration" RFC 2462 December 1998.

 [DHCPv6] Droms, R., Bound, J., Volz, B., Lemon, T.,
          et al. "Dynamic Host Configuration Protocol
          for IPv6 (DHCPv6)" RFC 3315 July 2003.

 [6TO4]  Carpenter, B., Moore, K., "Connection of IPv6
         Domains via IPv4 Clouds" RFC 3056 February 2001.

 [BSCN]  Bound, J., (Ed) et al. "IPv6 Enterprise Network
         Scenarios" RFC 4057 June 2005.

 [TRDO]  Huitema, C., "Teredo: Tunneling IPv6 over UDP
         through NATs" RFC 4380.

 [ISTP]  Templin, F., et al "Intra-Site Automatic Tunnel
         Addressing Protocol (ISATAP)".
         RFC 4214 October 2005.

 [V6TUN] Conta, A., Deering, S., "Generic Packet Tunneling
         in IPv6" RFC 2473 December 1998.

 [TBRK]  Durand, A., et al "IPv6 Tunnel Broker"
         RFC 3053 January 2001.

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 [ALLOC] IAB, IESG, "IAB/IESG Recommendations on IPv6
         Address Allocations to Sites"
         RFC 3177 September 2001.

 [NATPT] Tsirtsis, G., Srisuresh, P., "Network Address
         `Translation - Protocol Translation (NAT-PT)"
         RFC 2766 February 2000

 [UMAN]  Huitema, C.,. et al "Evaluation of IPv6
         Transition Mechanisms for Unmanaged Networks".
         RFC 3904 September 2004.

 [ISPA]  Lind, M., et al "Scenarios and Analysis for
         Introducing IPv6 into ISP Networks".
         RFC 4029 March 2005.

 [3GPA]  Wiljakka, J., "Analysis on IPv6 Transition in
         3GPP Networks" RFC 4215 October 2005.

 [OSPF]  Coltun, R., Ferguson, D., Moy, J. "OSPF for
         IPv6" RFC2740 December 1999.

 [BGP4]  Bates, T., Rekhter, Y. et. al. "Multiprotocol
         Extensions for BGP-4", RFC2858 June 2000.

 [ISIS]  Oran, D. EDITOR, "OSI IS-IS Intra-domain
         Routing Protocol", RFC1142 February 1990.

 [RIPng] Malkin, G., Minnear, R. "RIPng for IPv6"
         RFC2080 January 1997

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

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

 [BCNF]  Nordmark, E., Gilligan, R., "Basic Transition
         Mechanisms for IPv6 Hosts and Routers"
         RFC 4213 October 2005

 [ULA]   Hinden, B., Haberman, B., "Unique Local IPv6
         Addresses". RFC 4193 October 2005.

 [DNSOP6] Durand, A., Ihren, J. and P. Savola,

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          "Operational Considerations and Issues with
          IPv6 DNS". RFC 4472 April 2006.

 [DNSV6R] Thomson, S., Huitema, C., et al "DNS
          Extensions to Support IP Version 6".
          RFC 3596 October 2003.

 [NIS]    Kalusivalingam. V, "Network Information
          Service (NIS) Configuration Options for D
          HCPv6. RFC 3898 October 2004.

 [DHCPv4] Droms, R., "Dynamic Host Configuration
          Protocol" RFC 2131 March 1997.

 [IPSEC]  Eastlake. D., "Cryptographic Algorithm
          Implementation Requirements for Encapsulating
          Security Payload (ESP) and Authentication
          Header (AH)". RFC 4305 December 2005.

 [SEND]   Arkko, J. et al. "Secure Neighbor Discovery
          (SEND)". RFC 3971 March 2005.

 [PRIVv6] Narten, T., Draves, R., "Privacy Extensions
          for Stateless Address Autoconfiguration in
          IPv6. RFC 3041 January 2001.

11.2 Non-Normative References

 [TSPB]  Blanchet, M., Parent, F. "IPv6 Tunnel Broker
         with the Tunnel Setup Protocol".
         Work in Progress.

 [V6SEC] Davies, E. et al "IPv6 Transition/Co-existence
         Security Considerations". Work in Progress.

 [NAP]   Van de Velde, G. et al "IPv6 Network
         Architecture Protection". Work in Progress.

 [CAMP]  Chown, T., "IPv6 Campus Transition Scenario
         Description and Analysis". Work in Progress.

 [DHDS]  Chown, T., "DHCP: IPv4 and IPv6 Dual-Stack

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         Issues", Work in Progress.

 [UNAD]  Van de Velde, G., Popoviciu, C., Chown, T.,
         "IPv6 Unicast Address Assignment".
         Work in Progress.

 [VLAN]  Chown, T. "Use of VLANs for IPv4-IPv6
         Coexistence in Enterprise Networks".
         Work in Progress.

 [V6DEF] Roy, S., Durand, A., Paugh, J., "IPv6 Neighbor
         Discovery On-Link Assumption Considered
         Harmful". Work in Progress.

 [SOFTW] Dawkins, S. (Ed) "Softwire Problem Statement"
         Work in Progress

Change Log

June 2006 - Oct 2006
ID 06-07
   - Add IP Layer 3 Focus to the title
   - Remove IPsec use SEND for Autoconfiguration
   - Remove all mentions of DSTM
   - Add Softwire Tunnel Reference
   - Add Host Based Security check to security section

May 2006 - June 2006
ID 05 - 06
   - Fix ID Nits for IESG

February - May 2006
ID 04 to 05
   - Edits: Intro, Sections 4 and 7, References
   - Update definition IPv6-Dominant
   - Add Campus Deployment Reference
   - Fix ID-Nits

July 2005 - February 2006
ID 03 to 04

   - Edits to document (minor).

   - Removed any reference to DSTM as IETF supported mechanism.

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   - Remove 8.4 Transition Mechanisms Recommendations.

   - Updated references move to RFC.

   - Added Normative references.

June 2005 - to July 2005
ID 02 to 03

  - Fixed more IETF id-nits.

  - Added Section 8.4 Transition Mechanism Summary

March 2005 to June 2005
ID 01 to 02

  - Fixed IETF id-nits.

  - Updated Section 3 Table 1 and added discussion of intent and
    scenario analysis per WG input.

  - Completed sections 6, 7, and 8.

  - Completed required Security Section.

  - Fixed normative vs. non-normative references.

  - Changed abstract and context of document to only deal with dual
    IP layer networks and nodes.

  - Removed Table of Content Campus VLAN appendix place holder.

November 2004 to March 2005
ID 00 to 01

  - Changed introduction, Section 1-3 to reflect authors and IETF WG
    discussions to attempt consensus on these initial sections.

  - Added explanation of why Appendix A is in the document to

  - Expanded what topics are out of scope for this document.

  - Updated terminology section.

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  - Updated section 3 matrix and description to simplify and focus
    on dual IP layer.

  - Edited base text of Sections 4-7 but all three require extensive
    additional test for descriptions.

  - Edited section 8 and removed table and will reference table in
    section 3. This section still needs to be written.


 The Author's would like to acknowledge contributions from the
 following: IETF v6ops Working Group members, Fred Baker, Pekka
 Savola, and Jordi Palet

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Author's Addresses

 Jim Bound
 110 Spitbrook Road
 Nashua, NH 03062
 Phone: 603.465.3130

 Yanick Pouffary
 HP Competency Center
 950, Route des Colles, BP027,
 06901 Sophia Antipolis CEDEX
 Phone: + 33492956285

 Tim Chown
 School of Electronics and Computer Science
 University of Southampton
 Southampton SO17 1BJ
 United Kingdom

 David Green
 Command Information
 13655 Dulles Technology Drive
 Suite 500
 Herndon, VA 20171
 Phone: 703.561.5937

 Steve Klynsma
 The MITRE Corporation
 7515 Colshire Drive
 McLean, VA 22102-5708

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Intellectual Property and Copyright Statements

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at

Disclaimer of Validity

   This document and the information contained herein are provided on an

Copyright Statement

   Copyright (C) The Internet Society (2006).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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Appendix A - Crisis Management Network Scenarios


 This appendix first describes different scenarios for the
 introduction of IPv6 into a crisis management network for emergency
 services, defense, or security forces that are currently running
 IPv4 service. Then, the scenarios for introducing IPv6 are analyzed
 and the relevance of already defined transition mechanisms are
 evaluated. Known challenges are also identified.

 When a crisis management enterprise deploys IPv6, its goal is to
 provide IPv6 connectivity on it's institutional fixed networks and
 on the mobile wireless services that are deployed to a crisis area.
 The new IPv6 service must be added to an already existing IPv4
 service, the introduction of IPv6 must not interrupt this IPv4
 service, and the IPv6 services must be interoperable with existing
 IPv4 services.

 Crisis management enterprises accessing IPv4 service across mobile
 ground networks, airborne networks, and satellites will find
 different ways to add IPv6 to this service based on their network
 architecture, funding, and institutional goals. This document
 discusses a small set of scenarios representing the architectures
 for IPv6 expected to be dominant in crisis management networks
 during the next decade. It evaluates the relevance of the existing
 transition mechanisms in the context of these deployment scenarios,
 and points out the lack of essential functionality in these methods
 to the ISP's operation of an IPv6 service.

 The document is focused on services that include both IPv6 and IPv4
 and does cover issues surrounding accessing IPv4 services across
 IPv6-only networks. It is outside the scope of this document to
 describe detailed implementation plans for IPv6 in defense networks

 Scenarios for IPv6 Deployment in Crisis Management Networks:

 Scenario 1:  Limited IPv6 Deployment Network.....................

 Sparse IPv6 dual-stack deployment in an existing IPv4 network
 infrastructure. Enterprise with an existing IPv4 network wants to
 deploy a set of particular IPv6 "applications" and have some
 ability to interoperate with other institutions that are using IPv6
 services. The IPv6 deployment is limited to the minimum required to
 operate this set of applications.

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 Assumptions:  IPv6 software/hardware components for the application
 are available, and platforms for the application are IPv6 capable.

 Requirements: Do not disrupt IPv4 infrastructure.

 Scenario 2:    Dual Stack Network

 Wide-scale/total dual-stack deployment of IPv4 and IPv6 capable
 hosts and network infrastructure. Enterprise with an existing IPv4
 network wants to deploy IPv6 in conjunction with their IPv4 network
 in order to take advantage of emerging IPv6 network-centric
 capabilities and to be interoperable with other agencies,
 international partners, and commercial enterprises that are
 deploying an IPv6 architecture.

 Assumptions:  The IPv4 network infrastructure used has an
 equivalent capability in IPv6.

 Requirements: Do not disrupt existing IPv4 network infrastructure
 with IPv6. IPv6 should be equivalent or "better" than the network
 infrastructure in IPv4. It may not be feasible to deploy IPv6 on
 all parts of the network immediately. Dual stacked defense
 enterprise network must be interoperable with both IPv4 and IPv6
 networks and applications.

 Scenario 3: IPv6 Dominant Network

 Enterprise has some limited IPv4-capable/only nodes/applications
 needing to communicate over the IPv6 infrastructure. Crisis
 management enterprise re-structuring an existing network, decides
 to pursue aggressive IPv6 transition as an enabler for network-
 centric services and wants to run some native IPv6-only networks to
 eliminate cost/complexity of supporting a dual stack. Some legacy
 IPv4 capable nodes/applications within the enterprise will have
 slow technical refresh/replacement path and will need to
 communicate over the IPv6 dominant infrastructure for years until
 they are replaced. The IPv6 dominant enterprise network will need
 to be interoperable with it's own legacy networks, commercial
 networks, and the legacy networks of similar organizations that
 will remain IPv4 dominant during a long transition period. Reserve
 units, contractors, other agencies, and international partners may
 need IPv4 service across this enterprise's IPv6 dominant backbone.

 Assumptions: Required IPv6 network infrastructure is available, or
 available over some defined timeline, supporting the aggressive
 transition plan.

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 Requirements: Reduce operation and maintenance requirements and
 increase net-centricity through aggressive IPv6 transition.
 Interoperation and coexistence with legacy IPv4 networks and
 applications is required. Legacy IPv4 nodes/applications/networks
 will need to be able to operate across the IPv6 backbone and need
 to be able to interoperate with the IPv6-dominant network's

 Description of a Generic Crisis Management Network

 A generic network topology for a crisis management reflects the
 various ways a crisis management network can connect customers
 through their network infrastructure. Because the institution's
 existing wired and fixed site wireless infrastructure can be
 destroyed or unavailable in a crisis, the crisis management network
 must be able to deploy it's own mobile wireless network or connect
 through external wired and wireless networks provided by ISPs or
 partner organizations.  This infrastructure lets us divide the
 basic areas for IPv4/IPv6 interoperability into three main areas:
 the customer applications, the local network, and the network

 The basic components in a crisis management network are depicted in
 Figure 1.

       ------------    ----------       ---- Wired Connection
      | Network and|  |          |      .... Wireless Connection
      |  Service   |--| Backbone |
      | Operation  |  |          |
       ------------    ----------
                        /  |          ---------------------
                       /   :        _|Connection to        |
                      /    :         |Commercial Internet  |
                     /     :          ---------------------
                                       Network Backbone
     -------------- /------|-------------|--------------------
       ----------  /  ----------     ----------
      | Home     |/  | Wireless |   External  |.............
      | Base     |   | Mobile   |    |Untrusted |+---------  :
      | Network  |   | Network  |    |Network   |          | :
       ----------     ----------      ----------           | :
           | :            :                                | :
                                       Local Network
                                       Custome Applications

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           | :            :                                | :
        +--------+    +--------+      +--------+           | :
        |        |    |        |      |        |           | :
        |Customer|    |Customer|      |Customer|+----------- :
        |        |    |        |      |        |..............
        +--------+    +--------+      +--------+

 Figure 1: Crisis Management Network Topology.

 Stages of IPv6 Deployment:

 The stages are derived from the generic description of scenarios
 for crisis management networks in Section 2. Combinations of
 different building blocks that constitute an crisis network
 environment lead to a number of scenarios from which the network
 engineers can choose. The scenarios most relevant to this document
 are those that maximize the network's ability to offer IPv6 to its
 customers in the most efficient and feasible way. The assumption in
 the first three stages the goal is to offer both IPv4 and IPv6 to
 the customer, and that in the distant future all IPv4 services will
 be eventually switched to IPv6. This document will cover
 engineering the first four stages.

    The four most probable stages are:

          o Stage 1      Limited Launch
          o Stage 2      Dual Stack Dominance
          o Stage 3      IPv6 Dominance
          o Stage 4      IPv6 Transition Complete

 Generally, a crisis management network is able to entirely upgrade
 a current IPv4 network to provide IPv6 services via a dual-stack
 network in Stage 2 and then slowly progress to stages 3 and 4 as
 indicted in Figure 2. During stage 2, When most applications are
 IPv6 dominant, operational and maintenance costs can be reduced on
 some networks by moving to stage 3 and running backbone networks
 entirely on IPv6 while adding IPv4 backwards compatibility via v4
 in v6 tunneling or translation mechanisms to the existing
 configuration from stage 2. When designing a new network, if a new
 IPv6-only service is required, it can be implemented at a lower
 cost jumping directly to stage 3/4 if there are only limited/no
 legacy concerns.

 Stage 1 Scenario: Limited Launch

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 The first stage begins with an IPv4-only network and IPv4
 customers. This is the most common case today and the natural
 starting point for the introduction of IPv6.  During this stage the
 enterprise begins to connect individual IPv6 applications run on
 dual stacked hosts through host based tunneling using Tunnel
 Broker, ISATAP, Teredo. Some early adopter networks are created for
 pilot studies and networked together through configured tunnels and

 The immediate first step consists of obtaining a prefix allocation
 typically a /32) from the appropriate RIR (e.g. AfriNIC, APNIC,
 ARIN, LACNIC, RIPE) according to allocation procedures.

 The crisis management enterprise will also need to establish IPv6
 connectivity between its home base networks and mobile wireless
 networks over it's backbone and negotiate IPv6 service with its
 service providers and with peer organizations; it is of utmost
 importance to require IPv6 capability or an upgrade plan when
 negotiating purchases of network applications and infrastructure.
 In the short term, network connections, especially legacy wireless
 networks, that cannot provide IPv6 services can provide IPv6
 services through the use of tunnels. However, the longer-term goal
 must be requiring and obtaining IPv6 native connectivity from the
 transit networks, because otherwise the quality of IPv6
 connectivity will likely be poor and the transition to stage 2 will
 be delayed.

 Stage 2 Scenario: Dual Stack Dominance

 Stage 2 occurs when most applications, local networks, and network
 backbones become dual-stacked so that native IPv6 connections are
 enabled. At this point there is a mix of IPv4 and IPv6 applications
 and services in use across the enterprise. The enterprise may be
 made IPv6-capable through either software upgrades, hardware
 upgrades, or a combination of both. Generally IPv6 is added during
 normal technical refresh as the enterprise buys new equipment that
 is IPv6 ready.

 Specialty legacy applications and wireless/satellite networks may
 be especially slow to transition to IPv6 capability due to upgrade
 costs so plans must be made for backwards compatibility for these
 systems. Since some new IPv6 services cannot be provided through
 IPv4, and some legacy network connections may not yet be upgraded,
 tunneling mechanisms have to be provided on the backbone to provide
 IPv6 connectivity through to customer IPv6 applications still
 relying on legacy IPv4-only networks. The tunnels may provide
 host-based tunneling for individual customers or site-to-site

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 tunnels to connect small IPv6 domains through IPv4 only networks.
 If any new applications are IPv6-only rather than dual-stacked, and
 need to interact with IPv4-only legacy applications, translators
 will be used as a transition mechanism of last resort during this

 Stage 3 Scenario: IPv6 Dominance

 Applications are deployed specifically to use IPv6 as benefit, thus
 network backbone and nodes use IPv6 and not IPv4, except where IPv4
 is legacy.

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