Network Working Group J. Bound
Request for Comments: 4852 Y. Pouffary
Category: Informational Hewlett-Packard
S. Klynsma
MITRE
T. Chown
University of Southampton
D. Green
Command Information
April 2007
IPv6 Enterprise Network Analysis - IP Layer 3 Focus
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document analyzes the transition to IPv6 in enterprise networks
focusing on IP Layer 3. These networks are characterized as having
multiple internal links and one or more router connections to one or
more Providers, and as being managed by a network operations entity.
The analysis focuses on a base set of transition notational networks
and requirements expanded from a previous document on enterprise
scenarios. 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.
Bound, et al. Informational [Page 1]RFC 4852 IPv6 Enterprise Network Analysis April 2007
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................5
3. Enterprise Matrix Analysis for Transition .......................5
4. Wide-Scale Dual-Stack Deployment Analysis ......................10
4.1. Staged Dual-Stack Deployment ..............................10
4.2. Routing Capability Analysis for Dual-IP Deployment ........11
4.2.1. IPv6 Routing Capability ............................11
4.2.2. IPv6 Routing Non-Capability ........................11
4.2.2.1. Tunnel IPv6 over the IPv4 infrastructure ..12
4.2.2.2. Deploy a Parallel IPv6 Infrastructure .....12
4.3. Remote IPv6 Access to the Enterprise ......................12
4.4. Other Considerations ......................................13
5. Sparse Dual-Stack Deployment Analysis ..........................13
5.1. Internal versus External Tunnel Endpoint ..................13
5.2. Manual versus Autoconfigured ..............................14
6. IPv6-Dominant Network Deployment Analysis ......................14
7. General Issues from Analysis ...................................15
7.1. Staged Plan for IPv6 Deployment ...........................15
7.2. Network Infrastructure Requirements .......................15
7.3. Stage 1: Initial Connectivity Steps .......................15
7.3.1. Obtaining External Connectivity ....................16
7.3.2. Obtaining Global IPv6 Address Space ................16
7.4. Stage 2: Deploying Generic Basic Service Components .......16
7.4.1. Developing an IPv6 Addressing Plan .................16
7.4.2. IPv6 DNS ...........................................17
7.4.3. IPv6 Routing .......................................17
7.4.4. Configuration of Hosts .............................18
7.4.5. Security ...........................................18
7.5. Stage 3: Widespread Dual-Stack Deployment On-Site .........19
8. Applicable Transition Mechanisms ...............................20
8.1. Recognizing Incompatible Network Touchpoints ..............20
8.2. Recognizing Application Incompatibilities .................21
8.3. Using Multiple Mechanisms to Support IPv6 Transition ......22
9. Security Considerations ........................................22
10. References ....................................................22
10.1. Normative References .....................................22
10.2. Informative References ...................................24
11. Acknowledgments ...............................................25
Appendix A. Crisis Management Network Scenarios ...................26
A.1. Introduction ..............................................26
A.2. Scenarios for IPv6 Deployment in Crisis Management
Networks ..................................................26
A.3. Description of a Generic Crisis Management Network ........28
A.4. Stages of IPv6 Deployment .................................29
Bound, et al. Informational [Page 2]RFC 4852 IPv6 Enterprise Network Analysis April 2007
1. Introduction
This document analyzes the transition to IPv6 in enterprise networks
focusing on IP Layer 3. These networks are characterized as having
multiple internal links, and one or more router connections to one or
more Providers, and as being managed by a network operations entity.
The analysis focuses on a base set of transition notational networks
and requirements expanded from a previous document on enterprise
scenarios. 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 have to determine the IPv6 transition strategy
for their enterprise. It is expected that 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 strategy.
The enterprise analysis begins 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
enterprise-wide Dual-IP layer deployment strategy, to provide the
reader with a view of how that can be planned and what options are
available. The document then discusses the deployment of sparse IPv6
nodes within the enterprise and the requirements that need to be
considered and implemented when the enterprise remains with an 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 discusses the general issues and applicability from
the previous analysis. The document concludes by providing a set of
current transition mechanism recommendations for the notational
network scenarios to support an enterprise that is planning to deploy
IPv6.
As stated, this document 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 an IPv6-only node or Provider
deployments, and is beyond the scope of this document. In addition,
this document does not attempt to define or discuss any use with
network address translation [NATPT] or Provider Independent address
space.
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The following specific topics are currently out of scope for this
document:
- 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.
This document focuses 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
does not discuss 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 that can
support the deployment of IPv6 with an enterprise are recommended.
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 that readers of this
document also read another use-case document to support an IPv6
Transition for a Campus Network [CAMP].
Readers should also be aware that a parallel effort for an enterprise
to transition to IPv6 is training, but out of scope for this
document.
Bound, et al. Informational [Page 4]RFC 4852 IPv6 Enterprise Network Analysis April 2007
2. Terminology
Enterprise Network - A network that has multiple internal links, and
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
IPv4.
IPv6-only - A node or network capable of supporting only
IPv6. This does not imply an IPv6 only stack in
this document.
Dual-IP - 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.
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. Selection of
mechanisms that reduce the impact on the existing environment is
suggested. 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 that describes various scenarios
Bound, et al. Informational [Page 5]RFC 4852 IPv6 Enterprise Network Analysis April 2007
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
notional networks (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 cases.
Future enterprise transitions that support IPv6-only nodes and IPv6-
only ISPs will require separate analysis, which is beyond the scope
of this document.
Table 1 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 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)
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- 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
host's 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 scenarios 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 |
======================================================
Bound, et al. Informational [Page 8]RFC 4852 IPv6 Enterprise Network Analysis April 2007
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 that wishes to use
IPv6 applications, but has yet to transition its internal networks;
its Service Provider also lags, offering only a v4 IP-service.
Conversely, Scenario C represents an enterprise that has completed
transition to IPv6 in its core networks (as has its Service
Provider), but continues to require a legacy IPv4-based application.
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 that must communicate over this heterogeneous network
environment.
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 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
IPv6 Unicast Addresses [ULA] because the address type and scope
selected is orthogonal to the Layer 3 analysis of this document.
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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. Enabling both 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 may be required.
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 node's IPv4 and IPv6 default routes to
reach other links (subnets) are through different routing platforms.
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4.2.2.1. Tunnel IPv6 over the IPv4 infrastructure
Consider the situation where there exists IPv6 edge routers that 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.
4.2.2.2. 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 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 interface(s) in the early stages of deployment.
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 date.
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].
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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].
5. Sparse Dual-Stack Deployment Analysis
This section covers 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 as defined in this
analysis document.
The network team needs to decide which of the available transition
tunneling mechanisms are the most efficient to deploy, so they can be
used without disrupting the existing IPv4 infrastructure. Several
conditions require analysis, as introduced in the following sub-
sections.
5.1. Internal versus External Tunnel Endpoint
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 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 Endpoint offered by the Provider.
Nevertheless, this may be acceptable, particularly if the IPv6
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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 enterprise.
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 endpoint is also
possible.
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
higher.
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 networks.
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.
Scenarios E and F from Table 1 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.
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In each case, communicating with an IPv4 end host or over an IPv4
network requires that 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 business
and operational objectives and guided by the enterprise's transition
plan.
7. General Issues from Analysis
In this section, we describe generic enterprise IPv6 deployment
issues, applicable to the analysis in Sections 4-6 of 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 on 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 provider.
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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.
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 space.
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;
however, 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
Bound, et al. Informational [Page 16]
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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.
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 Assignment" [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
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 [RIPng].
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7.4.4. Configuration of Hosts
An enterprise network will have a number of tools available for the
delegation and management of IPv4 addresses and other configuration
information. These include manual configuration, NIS [NIS], and DHCP
[DHCPv4].
In an IPv6 enterprise, Stateless Address Autoconfiguration [CONF] may
be used to configure a host with a global IPv6 address, a default
router, and 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, and end-to-end IPsec. In addition, a site will
need to review 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
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
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technology can be used to provide the market-perceived benefits of
IPv4 NAT.
Where deployed, intrusion detection systems will need to be enhanced
to check IPv6 transport both for known application layer attack
patterns and 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 tunneled in IPv4. The site
security policy should embrace the transition mechanisms that are
deployed.
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 IPv6.
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.
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
Bound, et al. Informational [Page 19]
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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.
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 widespread 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
4.2.2.1, tunneling can be used to "bypass" the incompatible network
segments. One tunneling option, manually configured tunnels [BCNF]
could be used by the enterprise, but as the name implies, this
mechanism provides no automated tunnel configuration.
Bound, et al. Informational [Page 20]
RFC 4852 IPv6 Enterprise Network Analysis April 2007
"Connection of IPv6 Domains via IPv4 Clouds" [6TO4] can be used to
support enterprises that do not have an assigned IPv6 prefix address.
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 the Intra-Site Automatic Tunnel Addressing Protocol
(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 manually 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 an application hosted at one location may lead
(or lag) the IPv6-compatibility of its peer (or server) at some other
location.
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This leads us to the third theme (represented by Scenarios E and G):
incompatible applications communicating across a homogenous network.
Translation is an obvious solution, but not recommended except for
legacy devices that are at the network edge and cannot or never will
be upgraded to IPv6. A more scalable solution would be to use an
Application Layer Gateway (ALG) between the incompatible hosts.
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 (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 collocated with
the application server may be required to service both IPv4 and IPv6
data streams that are simultaneously tunneled through incompatible
network segment(s).
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. References
10.1. Normative References
[CONF] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[DHCPv6] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[6TO4] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via
IPv4 Clouds", RFC 3056, February 2001.
[BSCN] Bound, J., Ed., "IPv6 Enterprise Network Scenarios", RFC
4057, June 2005.
[TRDO] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380, February
2006.
Bound, et al. Informational [Page 22]RFC 4852 IPv6 Enterprise Network Analysis April 2007
[ISTP] Templin, F., Gleeson, T., Talwar, M., and D. Thaler,
"Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)",
RFC 4214, October 2005.
[V6TUN] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998.
[TBRK] Durand, A., Fasano, P., Guardini, I., and D. Lento, "IPv6
Tunnel Broker", RFC 3053, January 2001.
[ALLOC] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address
Allocations to Sites", RFC 3177, September 2001.
[NATPT] Tsirtsis, G. and P. Srisuresh, "Network Address Translation
- Protocol Translation (NAT-PT)", RFC 2766, February 2000.
[UMAN] Huitema, C., Austein, R., Satapati, S., and R. van der Pol,
"Evaluation of IPv6 Transition Mechanisms for Unmanaged
Networks", RFC 3904, September 2004.
[ISPA] Lind, M., Ksinant, V., Park, S., Baudot, A., and P. Savola,
"Scenarios and Analysis for Introducing IPv6 into ISP
Networks", RFC 4029, March 2005.
[3GPA] Wiljakka, J., Ed., "Analysis on IPv6 Transition in Third
Generation Partnership Project (3GPP) Networks", RFC 4215,
October 2005.
[OSPF] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC
2740, December 1999.
[BGP4] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
[ISIS] Oran, D., Ed., "OSI IS-IS Intra-domain Routing Protocol",
RFC 1142, February 1990.
[RIPng] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
January 1997.
[APPS] Shin, M-K., Ed., Hong, Y-G., Hagino, J., Savola, P., and E.
Castro, "Application Aspects of IPv6 Transition", RFC 4038,
March 2005.
[RENUM] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
September 2005.
Bound, et al. Informational [Page 23]RFC 4852 IPv6 Enterprise Network Analysis April 2007
[BCNF] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[ULA] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[DNSOP6] Durand, A., Ihren, J., and P. Savola, "Operational
Considerations and Issues with IPv6 DNS", RFC 4472, April
2006.
[DNSV6R] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS
Extensions to Support IP Version 6", RFC 3596, October 2003.
[NIS] Kalusivalingam, V., "Network Information Service (NIS)
Configuration Options for Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)", RFC 3898, October 2004.
[DHCPv4] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[IPSEC] Eastlake 3rd, D., "Cryptographic Algorithm Implementation
Requirements for Encapsulating Security Payload (ESP) and
Authentication Header (AH)", RFC 4305, December 2005.
[SEND] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.
[PRIVv6] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
10.2. Informative References
[TSPB] Blanchet, M., and F. Parent, "IPv6 Tunnel Broker with the
Tunnel Setup Protocol (TSP", Work in Progress, August 2005.
[V6SEC] Davies, E., Krishnan, S., and P. Savola, "IPv6
Transition/Co-existence Security Considerations", Work in
Progress, October 2006.
[NAP] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and E.
Klein, "Local Network Protection for IPv6", Work in
Progress, January 2007.
[CAMP] Chown, T., "IPv6 Campus Transition Scenario Description and
Analysis", Work in Progress, March 2007.
Bound, et al. Informational [Page 24]RFC 4852 IPv6 Enterprise Network Analysis April 2007
[DHDS] Chown, T., Venaas, S., and C. Strauf, "Dynamic Host
Configuration Protocol (DHCP): IPv4 and IPv6 Dual-Stack
Issues", RFC 4477, May 2006.
[UNAD] Van de Velde, G., Popoviciu, C., and T. Chown, "IPv6 Unicast
Address Assignment", Work in Progress, March 2007.
[VLAN] Chown, T., "Use of VLANs for IPv4-IPv6 Coexistence in
Enterprise Networks", RFC 4554, June 2006.
[V6DEF] Roy, S., Durand, A., and J. Paugh, "IPv6 Neighbor Discovery
On-Link Assumption Considered Harmful", Work in Progress,
January 2006.
[SOFTW] Dawkins, S., Ed., "Softwire Problem Statement", Work in
Progress, March 2007.
11. Acknowledgments
The authors would like to acknowledge contributions from the
following: IETF v6ops Working Group members, Fred Baker, Pekka
Savola, and Jordi Palet
Bound, et al. Informational [Page 25]RFC 4852 IPv6 Enterprise Network Analysis April 2007
Appendix A. Crisis Management Network Scenarios
A.1. Introduction
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 its 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. This document evaluates the relevance of the existing
transition mechanisms in the context of these deployment scenarios,
and points out the lack of essential functionality within these
methods for a provider to support IPv6 services for these scenarios.
The document focuses 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.
A.2. 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.
Assumptions: IPv6 software/hardware components for the application
are available, and platforms for the application are IPv6 capable.
Bound, et al. Informational [Page 26]
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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 paths 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
its 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.
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
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be able to interoperate with the IPv6-dominant network's
nodes/applications.
A.3. Description of a Generic Crisis Management Network
A generic network topology for 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 its
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 backbone.
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
-----:------------:-----------------------------------
Customer Applications
| : : | :
+--------+ +--------+ +--------+ | :
| | | | | | | :
|Customer| |Customer| |Customer|+----------- :
| | | | | |..............
+--------+ +--------+ +--------+
Figure 1: Crisis Management Network Topology.
Bound, et al. Informational [Page 28]RFC 4852 IPv6 Enterprise Network Analysis April 2007
A.4. 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 a 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. In the first three stages, the goal is
to offer both IPv4 and IPv6 to the customer, and it is assumed 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
indicated 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 by jumping
directly to Stage 3/4 if there are only limited or no legacy
concerns.
Stage 1: Limited Launch
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, or Teredo.
Some early adopter networks are created for pilot studies and
networked together through configured tunnels and 6to4.
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.
Bound, et al. Informational [Page 29]RFC 4852 IPv6 Enterprise Network Analysis April 2007
The crisis management enterprise will also need to establish IPv6
connectivity between its home base networks and mobile wireless
networks over its backbone. It will need to 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. Otherwise, the quality of IPv6 connectivity will likely be
poor and the transition to Stage 2 will be delayed.
Stage 2: 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 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.
Stage 3: 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.
Bound, et al. Informational [Page 30]
RFC 4852 IPv6 Enterprise Network Analysis April 2007
Authors' Addresses
Jim Bound
HP
110 Spitbrook Road
Nashua, NH 03062
USA
Phone: 603.465.3130
EMail: jim.bound@hp.com
Yanick Pouffary
HP Competency Center
950, Route des Colles, BP027,
06901 Sophia Antipolis CEDEX
FRANCE
Phone: + 33492956285
EMail: Yanick.pouffary@hp.com
Tim Chown
School of Electronics and Computer Science
University of Southampton
Southampton SO17 1BJ
United Kingdom
EMail: tjc@ecs.soton.ac.uk
David Green
Command Information
13655 Dulles Technology Drive
Suite 500
Herndon, VA 20171
USA
Phone: 703.561.5937
EMail: green@commandinformation.com
Steve Klynsma
The MITRE Corporation
7515 Colshire Drive
McLean, VA 22102-5708
USA
Phone: 703-883-6469
EMail: sklynsma@mitre.org
Bound, et al. Informational [Page 31]
RFC 4852 IPv6 Enterprise Network Analysis April 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
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.
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Bound, et al. Informational [Page 32]
