| Rfc | 6782 |
|---|
| Title | Wireline Incremental IPv6 |
|---|
| Author | V. Kuarsingh, Ed., L. Howard |
|---|
| Date | November
2012 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | INFORMATIONAL |
|---|
|
Internet Engineering Task Force (IETF) V. Kuarsingh, Ed.
Request for Comments: 6782 Rogers Communications
Category: Informational L. Howard
ISSN: 2070-1721 Time Warner Cable
November 2012
Wireline Incremental IPv6
Abstract
Operators worldwide are in various stages of preparing for or
deploying IPv6 in their networks. These operators often face
difficult challenges related to IPv6 introduction, along with those
related to IPv4 run-out. Operators will need to meet the
simultaneous needs of IPv6 connectivity and continue support for IPv4
connectivity for legacy devices with a stagnant supply of IPv4
addresses. The IPv6 transition will take most networks from an IPv4-
only environment to an IPv6-dominant environment with long transition
periods varying by operator. This document helps provide a framework
for wireline providers who are faced with the challenges of
introducing IPv6 along with meeting the legacy needs of IPv4
connectivity, utilizing well-defined and commercially available IPv6
transition technologies.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6782.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................4
2. Operator Assumptions ............................................4
3. Reasons and Considerations for a Phased Approach ................5
3.1. Relevance of IPv6 and IPv4 .................................6
3.2. IPv4 Resource Challenges ...................................6
3.3. IPv6 Introduction and Operational Maturity .................7
3.4. Service Management .........................................8
3.5. Suboptimal Operation of Transition Technologies ............8
3.6. Future IPv6 Network ........................................9
4. IPv6 Transition Technology Analysis .............................9
4.1. Automatic Tunneling Using 6to4 and Teredo .................10
4.2. Carrier-Grade NAT (NAT444) ................................10
4.3. 6rd .......................................................11
4.4. Native Dual Stack .........................................11
4.5. DS-Lite ...................................................12
4.6. NAT64 .....................................................12
5. IPv6 Transition Phases .........................................13
5.1. Phase 0 - Foundation ......................................13
5.1.1. Phase 0 - Foundation: Training .....................13
5.1.2. Phase 0 - Foundation: System Capabilities ..........14
5.1.3. Phase 0 - Foundation: Routing ......................14
5.1.4. Phase 0 - Foundation: Network Policy and Security ..15
5.1.5. Phase 0 - Foundation: Transition Architecture ......15
5.1.6. Phase 0 - Foundation: Tools and Management .........16
5.2. Phase 1 - Tunneled IPv6 ...................................16
5.2.1. 6rd Deployment Considerations ......................17
5.3. Phase 2 - Native Dual Stack ...............................19
5.3.1. Native Dual Stack Deployment Considerations ........20
5.4. Intermediate Phase for CGN ................................20
5.4.1. CGN Deployment Considerations ......................22
5.5. Phase 3 - IPv6-Only .......................................23
5.5.1. DS-Lite ............................................23
5.5.2. DS-Lite Deployment Considerations ..................24
5.5.3. NAT64 Deployment Considerations ....................25
6. Security Considerations ........................................26
7. Acknowledgements ...............................................26
8. References .....................................................26
8.1. Normative References ......................................26
8.2. Informative References ....................................26
1. Introduction
This document sets out to help wireline operators in planning their
IPv6 deployments while ensuring continued support for IPv6-incapable
consumer devices and applications. This document identifies which
technologies can be used incrementally to transition from IPv4-only
to an IPv6-dominant environment with support for Dual Stack
operation. The end state or goal for most operators will be
IPv6-only, but the path to this final state will depend heavily on
the amount of legacy equipment resident in end networks and
management of long-tail IPv4-only content. Although no single plan
will work for all operators, options listed herein provide a baseline
that can be included in many plans.
This document is intended for wireline environments that include
cable, DSL, and/or fiber as the access method to the end consumer.
This document attempts to follow the principles laid out in
[RFC6180], which provides guidance on using IPv6 transition
mechanisms. This document will focus on technologies that enable and
mature IPv6 within the operator's network, but it will also include a
cursory view of IPv4 connectivity continuance. This document will
focus on transition technologies that are readily available in
off-the-shelf Customer Premises Equipment (CPE) devices and
commercially available network equipment.
2. Operator Assumptions
For the purposes of this document, the authors assume the following:
- The operator is considering deploying IPv6 or is in the process of
deploying IPv6.
- The operator has a legacy IPv4 subscriber base that will continue
to exist for a period of time.
- The operator will want to minimize the level of disruption to the
existing and new subscribers.
- The operator may also want to minimize the number of technologies
and functions that are needed to mediate any given set of
subscribers' flows (overall preference for native IP flows).
- The operator is able to run Dual Stack in its own core network and
is able to transition its own services to support IPv6.
Based on these assumptions, an operator will want to utilize
technologies that minimize the need to tunnel, translate, or mediate
flows to help optimize traffic flow and lower the cost impacts of
transition technologies. Transition technology selections should be
made to mediate the non-dominant IP family flows and allow native
routing (IPv4 and/or IPv6) to forward the dominant traffic whenever
possible. This allows the operator to minimize the cost of IPv6
transition technologies by minimizing the transition technology
deployment size.
An operator may also choose to prefer more IPv6-focused models where
the use of transition technologies is based on an effort to enable
IPv6 at the base layer as soon as possible. Some operators may want
to promote IPv6 early on in the deployment and have IPv6 traffic
perform optimally from the outset. This desire would need to be
weighed against the cost and support impacts of such a choice and the
quality of experience offered to subscribers.
3. Reasons and Considerations for a Phased Approach
When faced with the challenges described in the introduction,
operators may want to consider a phased approach when adding IPv6 to
an existing subscriber base. A phased approach allows the operator
to add in IPv6 while not ignoring legacy IPv4 connection
requirements. Some of the main challenges the operator will face
include the following:
- IPv4 exhaustion may occur long before all traffic is able to be
delivered over IPv6, necessitating IPv4 address sharing.
- IPv6 will pose operational challenges, since some of the software
is quite new and has had short run time in large production
environments and organizations are also not acclimatized to
supporting IPv6 as a service.
- Connectivity modes will move from IPv4-only to Dual Stack in the
home, changing functional behaviors in the consumer network and
increasing support requirements for the operator.
- Although IPv6 support on CPEs is a newer phenomenon, there is a
strong push by operators and the industry as a whole to enable
IPv6 on devices. As demand grows, IPv6 enablement will no longer
be optional but will be necessary on CPEs. Documents like
[RFC6540] provide useful tools in the short term to help vendors
and implementors understand what "IPv6 support" means.
These challenges will occur over a period of time, which means that
the operator's plans need to address the ever-changing requirements
of the network and subscriber demand. Although phases will be
presented in this document, not all operators may need to enable each
discrete phase. It is possible that characteristics in individual
networks may allow certain operators to skip or jump to various
phases.
3.1. Relevance of IPv6 and IPv4
The delivery of high-quality unencumbered Internet service should be
the primary goal for operators. With the imminent exhaustion of
IPv4, IPv6 will offer the highest quality of experience in the long
term. Even though the operator may be focused on IPv6 delivery, it
should be aware that both IPv4 and IPv6 will play a role in the
Internet experience during transition. The Internet is made of many
interconnecting systems, networks, hardware, software, and content
sources -- all of which will support IPv6 at different rates.
Many subscribers use older operating systems and hardware that
support IPv4-only operation. Internet subscribers don't buy IPv4 or
IPv6 connections; they buy Internet connections, which demand the
need to support both IPv4 and IPv6 for as long as the subscriber's
home network demands such support. The operator may be able to
leverage one or the other protocol to help bridge connectivity on the
operator's network, but the home network will likely demand both IPv4
and IPv6 for some time.
3.2. IPv4 Resource Challenges
Since connectivity to IPv4-only endpoints and/or content will remain
common, IPv4 resource challenges are of key concern to operators.
The lack of new IPv4 addresses for additional devices means that
meeting the growth in demand of IPv4 connections in some networks
will require address sharing.
Networks are growing at different rates, including those in emerging
markets and established networks based on the proliferation of
Internet-based services and devices. IPv4 address constraints will
likely affect many, if not most, operators at some point, increasing
the benefits of IPv6. IPv4 address exhaustion is a consideration
when selecting technologies that rely on IPv4 to supply IPv6
services, such as 6rd (IPv6 Rapid Deployment on IPv4 Infrastructures)
[RFC5969]. Additionally, if native Dual Stack is considered by the
operator, challenges related to IPv4 address exhaustion remain a
concern.
Some operators may be able to reclaim small amounts of IPv4 addresses
through addressing efficiencies in the network, although this will
have few lasting benefits to the network and will not meet longer-
term connectivity needs. Secondary markets for IPv4 addresses have
also begun to arise, but it's not well understood how this will
complement overall demand for Internet growth. Address transfers
will also be subject to market prices and transfer rules governed by
the Regional Registries.
The lack of new global IPv4 address allocations will therefore force
operators to support some form of IPv4 address sharing and may impact
technological options for transition once the operator runs out of
new IPv4 addresses for assignment.
3.3. IPv6 Introduction and Operational Maturity
The introduction of IPv6 will require new operational practices. The
IPv4 environment we have today was built over many years and matured
by experience. Although many of these experiences are transferable
from IPv4 to IPv6, new experience and practices specific to IPv6 will
be needed.
Engineering and operational staff will need to develop experience
with IPv6. Inexperience may lead to early IPv6 deployment
instability, and operators should consider this when selecting
technologies for initial transition. Operators may not want to
subject their mature IPv4 service to a "new IPv6" path initially
while it may be going through growing pains. Dual Stack Lite
(DS-Lite) [RFC6333] and NAT64 [RFC6146] are both technologies that
require IPv6 to support connectivity to IPv4 endpoints or content
over an IPv6-only access network.
Further, some of these transition technologies are new and require
refinement within running code. Deployment experience is required to
expose bugs and stabilize software in production environments. Many
supporting systems are also under development and have newly
developed IPv6 functionality, including vendor implementations of
DHCPv6, management tools, monitoring systems, diagnostic systems, and
logging, along with other elements.
Although the base technological capabilities exist to enable and run
IPv6 in most environments, organizational experience is low. Until
such time as each key technical member of an operator's organization
can identify IPv6 and can understand its relevance to the IP service
offering, how it operates, and how to troubleshoot it, the deployment
needs to mature and may be subject to events that impact subscribers.
This fact should not incline operators to delay their IPv6 deployment
but should drive them to deploy IPv6 sooner, to gain much-needed
experience before IPv6 is the only viable way to connect new hosts to
the network.
It should also be noted that although many transition technologies
may be new, and some code related to access environments may be new,
there is a large segment of the networking fabric that has had IPv6
available for a long period of time and has had extended exposure in
production. Operators may use this to their advantage by first
enabling IPv6 in the core network and then working outward towards
the subscriber edge.
3.4. Service Management
Services are managed within most networks and are often based on the
gleaning and monitoring of IPv4 addresses assigned to endpoints.
Operators will need to address such management tools, troubleshooting
methods, and storage facilities (such as databases) to deal with not
only new address types containing 128-bit IPv6 addresses [RFC2460]
but often both IPv4 and IPv6 at the same time. Examination of
address types, and recording delegated prefixes along with single
address assignments, will likely require additional development.
With any Dual Stack service -- whether native, 6rd-based, DS-Lite,
NAT64, or some other service -- two address families may need to be
managed simultaneously to help provide the full Internet experience.
This would indicate that IPv6 management is not just a simple add-in
but needs to be well integrated into the service management
infrastructure. In the early transition phases, it's quite likely
that many systems will be missed, and that IPv6 services will go
unmonitored and impairments will go undetected.
These issues may be worthy of consideration when selecting
technologies that require IPv6 as the base protocol to deliver IPv4
connectivity. Instability of the IPv6 service in such a case would
impact IPv4 services.
3.5. Suboptimal Operation of Transition Technologies
Native delivery of IPv4 and IPv6 provides a solid foundation for
delivery of Internet services to subscribers, since native IP paths
are well understood and networks are often optimized to send such
traffic efficiently. Transition technologies, however, may alter the
normal path of traffic or reduce the path MTU, removing many network
efficiencies built for native IP flows. Tunneling and translation
devices may not be located on the most optimal path in line with the
natural traffic flow (based on route computation) and therefore may
increase latency. These paths may also introduce additional points
of failure.
Generally, the operator will want to deliver native IPv6 as soon as
possible and utilize transition technologies only when required.
Transition technologies may be used to provide continued access to
IPv4 via tunneling and/or translation or may be used to deliver IPv6
connectivity. The delivery of Internet or internal services should
be considered by the operator, since supplying connections using a
transition technology will reduce overall performance for the
subscriber.
When choosing between various transition technologies, operators
should consider the benefits and drawbacks of each option. Some
technologies, like Carrier-Grade NAT (CGN)/NAT444, utilize many
existing addressing and management practices. Other options, such as
DS-Lite and NAT64, remove the IPv4 addressing requirement to the
subscriber premises device but require IPv6 to be operational and
well supported.
3.6. Future IPv6 Network
An operator should also be aware that longer-term plans may include
IPv6-only operation in all or much of the network. The IPv6-only
operation may be complemented by technologies such as NAT64 for long-
tail IPv4 content reach. This longer-term view may be distant to
some but should be considered when planning out networks, addressing,
and services. The needs and costs of maintaining two IP stacks will
eventually become burdensome, and simplification will be desirable.
Operators should plan for this state and not make IPv6 inherently
dependent on IPv4, as this would unnecessarily constrain the network.
Other design considerations and guidelines for running an IPv6
network should also be considered by the operator. Guidance on
designing an IPv6 network can be found in [IPv6-DESIGN] and
[IPv6-ICP-ASP-GUIDANCE].
4. IPv6 Transition Technology Analysis
Operators should understand the main transition technologies for IPv6
deployment and IPv4 run-out. This document provides a brief
description of some of the mainstream and commercially available
options. This analysis is focused on the applicability of
technologies to deliver residential services and less focused on
commercial access, wireless, or infrastructure support.
This document focuses on those technologies that are commercially
available and in deployment.
4.1. Automatic Tunneling Using 6to4 and Teredo
Even when operators may not be actively deploying IPv6, automatic
mechanisms exist on subscriber operating systems and CPE hardware.
Such technologies include 6to4 [RFC3056], which is most commonly used
with anycast relays [RFC3068]. Teredo [RFC4380] is also used widely
by many Internet hosts.
Documents such as [RFC6343] have been written to help operators
understand observed problems with 6to4 deployments and provide
guidelines on how to improve their performance. An operator may want
to provide local relays for 6to4 and/or Teredo to help improve the
protocol's performance for ambient traffic utilizing these IPv6
connectivity methods. Experiences such as those described in
[COMCAST-IPv6-EXPERIENCES] show that local relays have proved
beneficial to 6to4 protocol performance.
Operators should also be aware of breakage cases for 6to4 if
non-[RFC1918] addresses are used within CGN/NAT444 zones. Many
off-the-shelf CPEs and operating systems may turn on 6to4 without a
valid return path to the originating (local) host. This particular
use case can occur if any space other than [RFC1918] is used,
including Shared Address Space [RFC6598] or space registered to
another organization (squat space). The operator can use 6to4
Provider Managed Tunnels (6to4-PMT) [RFC6732] or attempt to block
6to4 operation entirely by blocking the anycast ranges associated
with [RFC3068].
4.2. Carrier-Grade NAT (NAT444)
Carrier-Grade NAT (CGN), specifically as deployed in a NAT444
scenario [CGN-REQS], may prove beneficial for those operators who
offer Dual Stack services to subscriber endpoints once they exhaust
their pools of IPv4 addresses. CGNs, and address sharing overall,
are known to cause certain challenges for the IPv4 service [RFC6269]
[NAT444-IMPACTS] but may be necessary, depending on how an operator
has chosen to deal with IPv6 transition and legacy IPv4 connectivity
requirements.
In a network where IPv4 address availability is low, CGN/NAT444 may
provide continued access to IPv4 endpoints. Some of the advantages
of using CGN/NAT444 include similarities in provisioning and
activation models. IPv4 hosts in a CGN/NAT444 deployment will
likely inherit the same addressing and management procedures as
legacy IPv4 globally addressed hosts (i.e., DHCPv4, DNS (v4), TFTP,
TR-069, etc.).
4.3. 6rd
6rd [RFC5969] provides a way of offering IPv6 connectivity to
subscriber endpoints when native IPv6 addressing on the access
network is not yet possible. 6rd provides tunneled connectivity for
IPv6 over the existing IPv4 path. As the access edge is upgraded and
subscriber premises equipment is replaced, 6rd can be replaced by
native IPv6 connectivity. 6rd can be delivered on top of a CGN/
NAT444 deployment, but this would cause all traffic to be subject to
some type of transition technology.
6rd may also be advantageous during the early transition period while
IPv6 traffic volumes are low. During this period, the operator can
gain experience with IPv6 in the core network and improve the
operator's peering framework to match those of the IPv4 service. 6rd
scales by adding relays to the operator's network. Another advantage
of 6rd is that the operator does not need a DHCPv6 address assignment
infrastructure and does not need to support IPv6 routing to the CPE
to support a delegated prefix (as it's derived from the IPv4 address
and other configuration parameters).
Client support is required for 6rd operation and may not be available
on deployed hardware. 6rd deployments may require the subscriber or
operator to replace the CPE. 6rd will also require parameter
configuration that can be powered by the operator through DHCPv4,
manually provisioned on the CPE, or automatically provisioned through
some other means. Manual provisioning would likely limit deployment
scale.
4.4. Native Dual Stack
Native Dual Stack is often referred to as the "gold standard" of IPv6
and IPv4 delivery. It is a method of service delivery that is
already used in many existing IPv6 deployments. Native Dual Stack
does, however, require that native IPv6 be delivered through the
access network to the subscriber premises. This technology option is
desirable in many cases and can be used immediately if the access
network and subscriber premises equipment support native IPv6.
An operator who runs out of IPv4 addresses to assign to subscribers
will not be able to provide traditional native Dual Stack
connectivity for new subscribers. In Dual Stack deployments where
sufficient IPv4 addresses are not available, CGN/NAT444 can be used
on the IPv4 path.
Delivering native Dual Stack would require the operator's core and
access networks to support IPv6. Other systems, like DHCP, DNS, and
diagnostic/management facilities, need to be upgraded to support IPv6
as well. The upgrade of such systems may often be non-trivial and
costly.
4.5. DS-Lite
DS-Lite [RFC6333] is based on a native IPv6 connection model where
IPv4 services are supported. DS-Lite provides tunneled connectivity
for IPv4 over the IPv6 path between the subscriber's network device
and a provider-managed gateway (Address Family Transition Router
(AFTR)).
DS-Lite can only be used where there is a native IPv6 connection
between the AFTR and the CPE. This may mean that the technology's
use may not be viable during early transition if the core or access
network lacks IPv6 support. During the early transition period, a
significant amount of content and services may by IPv4-only.
Operators may be sensitive to this and may not want the newer IPv6
path to be the only bridge to IPv4 at that time, given the potential
impact. The operator may also want to make sure that most of its
internal services and a significant amount of external content are
available over IPv6 before deploying DS-Lite. The availability of
services on IPv6 would help lower the demand on the AFTRs.
By sharing IPv4 addresses among multiple endpoints, like CGN/NAT444,
DS-Lite can facilitate continued support of legacy IPv4 services even
after IPv4 address run-out. There are some functional considerations
to take into account with DS-Lite, such as those described in
[NAT444-IMPACTS] and in [DSLITE-DEPLOYMENT].
DS-Lite requires client support on the CPE to function. The ability
to utilize DS-Lite will be dependent on the operator providing
DS-Lite-capable CPEs or retail availability of the supported client
for subscriber-acquired endpoints.
4.6. NAT64
NAT64 [RFC6146] provides the ability to connect IPv6-only connected
clients and hosts to IPv4 servers without any tunneling. NAT64
requires that the host and home network support IPv6-only modes of
operation. Home networks do not commonly contain equipment that is
100% IPv6-capable. It is also not anticipated that common home
networks will be ready for IPv6-only operation for a number of years.
However, IPv6-only networking can be deployed by early adopters or
highly controlled networks [RFC6586].
Viability of NAT64 will increase in wireline networks as consumer
equipment is replaced by IPv6-capable versions. There are incentives
for operators to move to IPv6-only operation, when feasible; these
include the simplicity of a single-stack access network.
5. IPv6 Transition Phases
The phases described in this document are not provided as a rigid set
of steps but are considered a guideline that should be analyzed by
operators planning their IPv6 transition. Operators may choose to
skip steps based on technological capabilities within their specific
networks (residential/corporate, fixed/mobile), their business
development perspectives (which may affect the pace of migration
towards full IPv6), or a combination thereof.
The phases are based on the expectation that IPv6 traffic volume may
initially be low, and operator staff will gain experience with IPv6
over time. As traffic volumes of IPv6 increase, IPv4 traffic volumes
will decline (in percentage relative to IPv6), until IPv6 is the
dominant address family used. Operators may want to keep the traffic
flow for the dominant traffic class (IPv4 vs. IPv6) native to help
manage costs related to transition technologies. The cost of using
multiple technologies in succession to optimize each stage of the
transition should also be compared against the cost of changing and
upgrading subscriber connections.
Additional guidance and information on utilizing IPv6 transition
mechanisms can be found in [RFC6180]. Also, guidance on incremental
CGN for IPv6 transition can be found in [RFC6264].
5.1. Phase 0 - Foundation
5.1.1. Phase 0 - Foundation: Training
Training is one of the most important steps in preparing an
organization to support IPv6. Most people have little experience
with IPv6, and many do not even have a solid grounding in IPv4. The
implementation of IPv6 will likely produce many challenges due to
immature code on hardware, and the evolution of many applications and
systems to support IPv6. To properly deal with these impending or
current challenges, organizations must train their staff on IPv6.
Training should also be provided within reasonable timelines from the
actual IPv6 deployment. This means the operator needs to plan in
advance as it trains the various parts of its organization. New
technology and engineering staff often receive little training
because of their depth of knowledge but must at least be provided
opportunities to read documentation, architectural white papers, and
RFCs. Operations personnel who support the network and other systems
need to be trained closer to the deployment timeframes so that they
immediately use their newfound knowledge before forgetting.
Subscriber support staff would require much more basic but large-
scale training, since many organizations have massive call centers to
support the subscriber base. Tailored training will also be required
for marketing and sales staff to help them understand IPv6 and build
it into the product development and sales process.
5.1.2. Phase 0 - Foundation: System Capabilities
An important component with any IPv6 network architecture and
implementation is the assessment of the hardware and operating
capabilities of the deployed equipment (and software). The
assessment needs to be conducted irrespective of how the operator
plans to transition its network. The capabilities of the install
base will, however, impact what technologies and modes of operation
may be supported and therefore what technologies can be considered
for the transition. If some systems do not meet the needs of the
operator's IPv6 deployment and/or transition plan, the operator may
need to plan for replacement and/or upgrade of those systems.
5.1.3. Phase 0 - Foundation: Routing
The network infrastructure will need to be in place to support IPv6.
This includes the routed infrastructure, along with addressing
principles, routing principles, peering policy, and related network
functions. Since IPv6 is quite different from IPv4 in several ways,
including the number of addresses that are made available, careful
attention to a scalable and manageable architecture is needed. One
such change is the notion of a delegated prefix, which deviates from
the common single-address phenomenon in IPv4-only deployments.
Deploying prefixes per CPE can load the routing tables and require a
routing protocol or route gleaning to manage connectivity to the
subscriber's network. Delegating prefixes can be of specific
importance in access network environments where downstream
subscribers often move between access nodes, raising the concern of
frequent renumbering and/or managing movement of routed prefixes
within the network (common in cable-based networks).
5.1.4. Phase 0 - Foundation: Network Policy and Security
Many, but not all, security policies will map easily from IPv4 to
IPv6. Some new policies may be required for issues specific to IPv6
operation. This document does not highlight these specific issues
but raises the awareness that they are to be taken into consideration
and should be addressed when delivering IPv6 services. Other IETF
documents, such as [RFC4942], [RFC6092], and [RFC6169], are excellent
resources.
5.1.5. Phase 0 - Foundation: Transition Architecture
Operators should plan out their transition architecture in advance
(with room for flexibility) to help optimize how they will build out
and scale their networks. Should operators consider multiple
technologies, like CGN/NAT444, DS-Lite, NAT64, and 6rd, they may want
to plan out where network resident equipment may be located and
potentially choose locations that can be used for all functional
roles (i.e., placement of a NAT44 translator, AFTR, NAT64 gateway,
and 6rd relays). Although these functions are not inherently
connected, additional management, diagnostic, and monitoring
functions can be deployed alongside the transition hardware without
the need to distribute these functions to an excessive or divergent
number of locations.
This approach may also prove beneficial if traffic patterns change
rapidly in the future, as operators may need to evolve their
transition infrastructure faster than originally anticipated. One
such example may be the movement from a CGN/NAT44 model (Dual Stack)
to DS-Lite. Since both traffic sets require a translation function
(NAT44), synchronized pool management, routing, and management system
positioning can allow rapid movement (the technological means to
re-provision the subscriber notwithstanding).
Operators should inform their vendors of what technologies they plan
to support over the course of the transition to make sure the
equipment is suited to support those modes of operation. This is
important for both network gear and subscriber premises equipment.
Operators should also plan their overall strategy to meet the target
needs of an IPv6-only deployment. As traffic moves to IPv6, the
benefits of only a single stack on the access network may eventually
justify the removal of IPv4 for simplicity. Planning for this
eventual model, no matter how far off this may be, will help
operators embrace this end state when needed.
5.1.6. Phase 0 - Foundation: Tools and Management
The operator should thoroughly analyze all provisioning and
management systems to develop requirements for each phase. This will
include concepts related to the 128-bit IPv6 address, the notation of
an assigned IPv6 prefix (Prefix Delegation), and the ability to
detect either or both address families when determining if a
subscriber has full Internet service.
If an operator stores usage information, this would need to be
aggregated to include both IPv4 and IPv6 information as both address
families are assigned to the same subscriber. Tools that verify
connectivity may need to query the IPv4 and IPv6 addresses.
5.2. Phase 1 - Tunneled IPv6
Tunneled access to IPv6 can be regarded as an early-stage transition
option by operators. Many network operators can deploy native IPv6
from the access edge to the peering edge fairly quickly but may not
be able to offer IPv6 natively to the subscriber edge device. During
this period of time, tunneled access to IPv6 is a viable alternative
to native IPv6. It is also possible that operators may be rolling
out IPv6 natively to the subscriber edge, but the time involved may
be long, due to logistics and other factors. Even while carefully
rolling out native IPv6, operators can deploy relays for automatic
tunneling technologies like 6to4 and Teredo. Where native IPv6 to
the access edge is a longer-term project, operators can consider 6rd
[RFC5969] as an option to offer in-home IPv6 access. Note that 6to4
and Teredo have different address selection [RFC6724] behaviors than
6rd. Additional guidelines on deploying and supporting 6to4 can be
found in [RFC6343].
The operator can deploy 6rd relays into the network and scale them as
needed to meet the early subscriber needs of IPv6. Since 6rd
requires the upgrade or replacement of CPE devices, the operator may
want to ensure that the CPE devices support not just 6rd but native
Dual Stack and other tunneling technologies, such as DS-Lite, if
possible [IPv6-CE-RTR-REQS]. 6rd clients are becoming available in
some retail channel products and within the original equipment
manufacturer (OEM) market. Retail availability of 6rd is important,
since not all operators control or have influence over what equipment
is deployed in the consumer home network. The operator can support
6rd access with unmanaged devices using DHCPv4 Option 212
(OPTION_6RD) [RFC5969].
+--------+ -----
| | / \
Encap IPv6 Flow | 6rd | | IPv6 |
- - -> | Relay | <- > | Net |
+---------+ / | | \ /
| | / +--------+ -----
| 6rd + <----- -----
| | / \
| Client | IPv4 Flow | IPv4 |
| + < - - - - - - - - - - - - - - -> | Net |
| | \ /
+---------+ -----
Figure 1: 6rd Basic Model
6rd used as an initial transition technology also provides the added
benefit of a deterministic IPv6 prefix based on the IPv4 assigned
address. Many operational tools are available or have been built to
identify what IPv4 (often dynamic) address was assigned to a
subscriber CPE. So, a simple tool and/or method can be built to help
identify the IPv6 prefix using the knowledge of the assigned IPv4
address.
An operator may choose to not offer internal services over IPv6 if
tunneled access to IPv6 is used, since some services generate a large
amount of traffic. Such traffic may include video content, like
IPTV. By limiting how much traffic is delivered over the 6rd
connection (if possible), the operator can avoid costly and complex
scaling of the relay infrastructure.
5.2.1. 6rd Deployment Considerations
Deploying 6rd can greatly speed up an operator's ability to support
IPv6 to the subscriber network if native IPv6 connectivity cannot be
supplied. The speed at which 6rd can be deployed is highlighted in
[RFC5569].
The first core consideration is deployment models. 6rd requires the
CPE (6rd client) to send traffic to a 6rd relay. These relays can
share a common anycast address or can use unique addresses. Using an
anycast model, the operator can deploy all the 6rd relays using the
same IPv4 interior service address. As the load increases on the
deployed relays, the operator can deploy more relays into the
network. The one drawback is that it may be difficult to manage the
traffic volume among additional relays, since all 6rd traffic will
find the nearest (in terms of IGP cost) relay. The use of multiple
relay addresses can help provide more control but has the
disadvantage of being more complex to provision. Subsets of CPEs
across the network will require and contain different relay
information. An alternative approach is to use a hybrid model using
multiple anycast service IP addresses for clusters of 6rd relays,
should the operator anticipate massive scaling of the environment.
Thus, the operator has multiple vectors by which to scale the
service.
+--------+
| |
IPv4 Addr.X | 6rd |
- - - > | Relay |
+-----------+ / | |
| Client A | <- - - +--------+
+-----------+
Separate IPv4 Service Addresses
+-----------+
| Client B | < - - +--------+
+-----------+ \ | |
- - - > | 6rd |
IPv4 Addr.Y | Relay |
| |
+--------+
Figure 2: 6rd Multiple IPv4 Service Address Model
+--------+
| |
IPv4 Addr.X | 6rd |
- - - > | Relay |
+-----------+ / | |
| Client A |- - - - +--------+
+-----------+
Common (Anycast) IPv4 Service Addresses
+-----------+
| Client B | - - - +--------+
+-----------+ \ | |
- - - > | 6rd |
IPv4 Addr.X | Relay |
| |
+--------+
Figure 3: 6rd Anycast IPv4 Service Address Model
Provisioning of the 6rd endpoints is affected by the deployment model
chosen (i.e., anycast vs. specific service IP addresses). Using
multiple IP addresses may require more planning and management, as
subscriber equipment will have different sets of data to be
provisioned into the devices. The operator may use DHCPv4, manual
provisioning, or other mechanisms to provide parameters to subscriber
equipment.
If the operator manages the CPE, support personnel will need tools
able to report the status of the 6rd tunnel. Usage information can
be collected on the operator edge, but if source/destination flow
details are required, data must be collected after the 6rd relay (the
IPv6 side of the connection).
6rd [RFC5969], like any tunneling option, is subject to a reduced
MTU, so operators need to plan to manage this type of environment.
+---------+ IPv4 Encapsulation +------------+
| +- - - - - - - - - - - + |
| 6rd +----------------------+ 6rd +------------
| | IPv6 Packet | Relay | IPv6 Packet
| Client +----------------------+ +------------
| +- - - - - - - - - - - + | ^
+---------+ ^ +------------+ |
| |
| |
IPv4 (Tools/Mgmt) IPv6 Flow Analysis
Figure 4: 6rd Tools and Flow Management
5.3. Phase 2 - Native Dual Stack
Either as a follow-up phase to "tunneled IPv6" or as an initial step,
the operator may deploy native IPv6 down to the CPEs. This phase
would then allow both IPv6 and IPv4 to be natively accessed by the
subscriber home network without translation or tunneling. The native
Dual Stack phase can be rolled out across the network while the
tunneled IPv6 service remains operational, if used. As areas begin
to support native IPv6, subscriber home equipment will generally
prefer using the IPv6 addresses derived from the delegated IPv6
prefix versus tunneling options as defined in [RFC6724], such as 6to4
and Teredo. Specific care is needed when moving to native Dual Stack
from 6rd, as documented in [6rd-SUNSETTING].
Native Dual Stack is the best option at this point in the transition
and should be sought as soon as possible. During this phase, the
operator can confidently move both internal and external services to
IPv6. Since there are no translation devices needed for this mode of
operation, it transports both protocols (IPv6 and IPv4) efficiently
within the network.
5.3.1. Native Dual Stack Deployment Considerations
Native Dual Stack is a very desirable option for the IPv6 transition,
if feasible. The operator must enable IPv6 on the network core and
peering edge before attempting to turn on native IPv6 services.
Additionally, provisioning and support systems such as DHCPv6, DNS,
and other functions that support the subscriber's IPv6 Internet
connection need to be in place.
The operator must treat IPv6 connectivity with the same operational
importance as IPv4. A poor IPv6 service may be worse than not
offering an IPv6 service at all, as it will negatively impact the
subscriber's Internet experience. This may cause users or support
personnel to disable IPv6, limiting the subscriber from the benefits
of IPv6 connectivity as network performance improves. New code and
IPv6 functionality may cause instability at first. The operator will
need to monitor, troubleshoot, and resolve issues promptly.
Prefix assignment and routing are new for common residential
services. Prefix assignment is straightforward (DHCPv6 using
Identity Associations for Prefix Delegation (IA_PDs)), but
installation and propagation of routing information for the prefix,
especially during access layer instability, are often poorly
understood. The operator should develop processes for renumbering
subscribers who move to new access nodes.
Operators need to keep track of the dynamically assigned IPv4 address
along with the IPv6 address and prefix. Any additional dynamic
elements, such as auto-generated host names, need to be considered
and planned for.
5.4. Intermediate Phase for CGN
Acquiring more IPv4 addresses is already challenging, if not
impossible; therefore, address sharing may be required on the IPv4
path of a Dual Stack deployment. The operator may have a preference
to move directly to a transition technology such as DS-Lite [RFC6333]
or may use Dual Stack with CGN/NAT444 to facilitate IPv4 connections.
CGN/NAT444 requires IPv4 addressing between the subscriber premises
equipment and the operator's translator; this may be facilitated by
shared addresses [RFC6598], private addresses [RFC1918], or another
address space. CGN/NAT444 is only recommended to be used alongside
IPv6 in a Dual Stack deployment and not on its own. Figure 5
provides a comparative view of a traditional IPv4 path versus one
that uses CGN/NAT444.
+--------+ -----
| | / \
IPv4 Flow | CGN | | |
- - -> + + < -> | |
+---------+ / | | | |
| CPE | <- - - / +--------+ | IPv4 |
|---------+ | Net |
| |
+---------+ IPv4 Flow | |
| CPE | <- - - - - - - - - - - - - - - > | |
|---------+ \ /
-----
Figure 5: Overlay CGN Deployment
In the case of native Dual Stack, CGN/NAT444 can be used to assist in
extending connectivity for the IPv4 path while the IPv6 path remains
native. For endpoints operating in an IPv6+CGN/NAT444 model, the
native IPv6 path is available for higher-quality connectivity,
helping host operation over the network. At the same time, the CGN
path may offer less than optimal performance. These points are also
true for DS-Lite.
+--------+ -----
| | / \
IPv4 Flow | CGN | | IPv4 |
- - -> + + < -> | Net |
+---------+ / | | \ /
| | <- - - / +--------+ -------
| Dual |
| Stack | -----
| CPE | IPv6 Flow / IPv6 \
| | <- - - - - - - - - - - - - - - > | Net |
|---------+ \ /
-----
Figure 6: Dual Stack with CGN
CGN/NAT444 deployments may make use of a number of address options,
which include [RFC1918] or Shared Address Space [RFC6598]. It is
also possible that operators may use part of their own Regional
Internet Registry (RIR) assigned address space for CGN zone
addressing if [RFC1918] addresses pose technical challenges in their
networks. It is not recommended that operators use 'squat space', as
it may pose additional challenges with filtering and policy control
[RFC6598].
5.4.1. CGN Deployment Considerations
CGN is often considered undesirable by operators but is required in
many cases. An operator who needs to deploy CGN capabilities should
consider the impacts of the function on the network. CGN is often
deployed in addition to running IPv4 services and should not
negatively impact the already working native IPv4 service. CGNs will
be needed on a small scale at first and will grow to meet the demands
based on traffic and connection dynamics of the subscriber, content,
and network peers.
The operator may want to deploy CGNs more centrally at first and then
scale the system as needed. This approach can help conserve the
costs of the system, limiting the deployed base and scaling it based
on actual traffic demand. The operator should use a deployment model
and architecture that allow the system to scale as needed.
+--------+ -----
| | / \
| CGN | | |
- - -> + + < -> | |
+---------+ / | | | |
| CPE | <- - - / +--------+ | IPv4 |
| | ^ | |
|---------+ | | Net |
+--------+ Centralized | |
+---------+ | | CGN | |
| | | CGN | | |
| CPE | <- > + + <- - - - - - - > | |
|---------+ | | \ /
+--------+ -----
^
|
Distributed CGN
Figure 7: CGN Deployment: Centralized vs. Distributed
The operator may be required to log translation information
[CGN-REQS]. This logging may require significant investment in
external systems that ingest, aggregate, and report such information
[DETERMINISTIC-CGN].
Since CGN has noticeable impacts on certain applications
[NAT444-IMPACTS], operators may deploy CGN only for those subscribers
who may be less affected by CGN (if possible).
5.5. Phase 3 - IPv6-Only
Once native IPv6 is widely deployed in the network and well supported
by tools, staff, and processes, an operator may consider supporting
only IPv6 to all or some subscriber endpoints. During this final
phase, IPv4 connectivity may or may not need to be supported,
depending on the conditions of the network, subscriber demand, and
legacy device requirements. If legacy IPv4 connectivity is still
demanded (e.g., for older nodes), DS-Lite [RFC6333] may be used to
tunnel the traffic. If IPv4 connectivity is not required but access
to legacy IPv4 content is, then NAT64 [RFC6144] [RFC6146] can be
used.
5.5.1. DS-Lite
DS-Lite allows continued access for the IPv4 subscriber base using
address sharing for IPv4 Internet connectivity but with only a single
layer of translation, as compared to CGN/NAT444. This mode of
operation also removes the need to directly supply subscriber
endpoints with an IPv4 address, potentially simplifying the
connectivity to the customer (single address family) and supporting
IPv6-only addressing to the CPE.
The operator can also move Dual Stack endpoints to DS-Lite
retroactively to help optimize the IPv4 address-sharing deployment by
removing the IPv4 address assignment and routing component. To
minimize traffic needing translation, the operator should have
already moved most content to IPv6 before the IPv6-only phase is
implemented.
+--------+ -----
| | / \
Encap IPv4 Flow | AFTR | | IPv4 |
-------+ +---+ Net |
+---------+ / | | \ /
| | / +--------+ -----
| DS-Lite +------- -----
| | / \
| Client | IPv6 Flow | IPv6 |
| +-------------------------------| Net |
| | \ /
+---------+ -----
Figure 8: DS-Lite Basic Model
If the operator had previously decided to enable a CGN/NAT444
deployment, it may be able to co-locate the AFTR and CGN/NAT444
processing functions within a common network location to simplify
capacity management and the engineering of flows. This case may be
evident in a later transition stage, when an operator chooses to
optimize its network and IPv6-only operation is feasible.
5.5.2. DS-Lite Deployment Considerations
The same deployment considerations associated with native IPv6
deployments apply to DS-Lite and NAT64. IPv4 will now be dependent
on IPv6 service quality, so the IPv6 network and services must be
running well to ensure a quality experience for the end subscriber.
Tools and processes will be needed to manage the encapsulated IPv4
service. If flow analysis is required for IPv4 traffic, this may be
enabled at a point beyond the AFTR (after decapsulation) or where
DS-Lite-aware equipment is used to process traffic midstream.
+---------+ IPv6 Encapsulation +------------+
| + - - - - - - - - - - -+ |
| AFTR +----------------------+ AFTR +------------
| | IPv4 Packet | | IPv4 Packet
| Client +----------------------+ +------------
| + - - - - - - - - - - -+ | ^
+---------+ ^ ^ +------------+ |
| | |
| | |
IPv6 (Tools/Mgmt) | IPv4 Packet Flow Analysis
|
Midstream IPv4 Packet Flow Analysis (Encapsulation Aware)
Figure 9: DS-Lite Tools and Flow Analysis
DS-Lite [RFC6333] also requires client support on the subscriber
premises device. The operator must clearly articulate to vendors
which technologies will be used at which points, how they interact
with each other at the CPE, and how they will be provisioned. As an
example, an operator may use 6rd in the outset of the transition,
then move to native Dual Stack followed by DS-Lite.
DS-Lite [RFC6333], like any tunneling option, is subject to a reduced
MTU, so operators need to plan to manage this type of environment.
Additional considerations for DS-Lite deployments can be found in
[DSLITE-DEPLOYMENT].
5.5.3. NAT64 Deployment Considerations
The deployment of NAT64 assumes that the network assigns an IPv6
address to a network endpoint that is translated to an IPv4 address
to provide connectivity to IPv4 Internet services and content.
Experiments such as the one described in [RFC6586] highlight issues
related to IPv6-only deployments due to legacy IPv4 APIs and IPv4
literals. Many of these issues will be resolved by the eventual
removal of this undesirable legacy behavior. Operational deployment
models, considerations, and experiences related to NAT64 have been
documented in [NAT64-EXPERIENCE].
+--------+ -----
| | / \
IPv6 Flow | NAT64 | | IPv4 |
-------+ DNS64 +---+ Net |
+---------+ / | | \ /
| | / +--------+ -----
| IPv6 +------- -----
| | / \
| Only | IPv6 Flow | IPv6 |
| +-------------------------------| Net |
| | \ /
+---------+ -----
Figure 10: NAT64/DNS64 Basic Model
To navigate some of the limitations of NAT64 when dealing with legacy
IPv4 applications, the operator may choose to implement 464XLAT
[464XLAT] if possible. As support for IPv6 on subscriber equipment
and content increases, the efficiency of NAT64 increases by reducing
the need to translate traffic. NAT64 deployments would see an
overall decline in translator usage as more traffic is promoted to
IPv6-to-IPv6 native communication. NAT64 may play an important part
in an operator's late-stage transition, as it removes the need to
support IPv4 on the access network and provides a solid go-forward
networking model.
It should be noted, as with any technology that utilizes address
sharing, that the IPv4 public pool sizes (IPv4 transport addresses
per [RFC6146]) can pose limits to IPv4 server connectivity for the
subscriber base. Operators should be aware that some IPv4 growth in
the near term is possible, so IPv4 translation pools need to be
monitored.
6. Security Considerations
Operators should review the documentation related to the technologies
selected for IPv6 transition. In those reviews, operators should
understand what security considerations are applicable to the chosen
technologies. As an example, [RFC6169] should be reviewed to
understand security considerations related to tunneling technologies.
7. Acknowledgements
Special thanks to Wes George, Chris Donley, Christian Jacquenet, and
John Brzozowski for their extensive review and comments.
Thanks to the following people for their textual contributions,
guidance, and comments: Jason Weil, Gang Chen, Nik Lavorato, John
Cianfarani, Chris Donley, Tina TSOU, Fred Baker, and Randy Bush.
8. References
8.1. Normative References
[RFC6180] Arkko, J. and F. Baker, "Guidelines for Using IPv6
Transition Mechanisms during IPv6 Deployment", RFC 6180,
May 2011.
8.2. Informative References
[464XLAT] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation", Work
in Progress, September 2012.
[6rd-SUNSETTING]
Townsley, W. and A. Cassen, "6rd Sunsetting", Work
in Progress, November 2011.
[CGN-REQS]
Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common requirements for Carrier Grade
NATs (CGNs)", Work in Progress, August 2012.
[COMCAST-IPv6-EXPERIENCES]
Brzozowski, J. and C. Griffiths, "Comcast IPv6 Trial/
Deployment Experiences", Work in Progress, October 2011.
[DETERMINISTIC-CGN]
Donley, C., Grundemann, C., Sarawat, V., and K.
Sundaresan, "Deterministic Address Mapping to Reduce
Logging in Carrier Grade NAT Deployments", Work
in Progress, July 2012.
[DSLITE-DEPLOYMENT]
Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M.
Boucadair, "Deployment Considerations for Dual-Stack
Lite", Work in Progress, August 2012.
[IPv6-CE-RTR-REQS]
Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
Requirements for IPv6 Customer Edge Routers", Work
in Progress, October 2012.
[IPv6-DESIGN]
Matthews, P., "Design Guidelines for IPv6 Networks", Work
in Progress, October 2012.
[IPv6-ICP-ASP-GUIDANCE]
Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet
Content and Application Service Providers", Work
in Progress, September 2012.
[NAT444-IMPACTS]
Donley, C., Ed., Howard, L., Kuarsingh, V., Berg, J., and
J. Doshi, "Assessing the Impact of Carrier-Grade NAT on
Network Applications", Work in Progress, October 2012.
[NAT64-EXPERIENCE]
Chen, G., Cao, Z., Byrne, C., Xie, C., and D. Binet,
"NAT64 Operational Experiences", Work in Progress,
August 2012.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
RFC 3068, June 2001.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
February 2006.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
Co-existence Security Considerations", RFC 4942,
September 2007.
[RFC5569] Despres, R., "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd)", RFC 5569, January 2010.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in
Customer Premises Equipment (CPE) for Providing
Residential IPv6 Internet Service", RFC 6092,
January 2011.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6169] Krishnan, S., Thaler, D., and J. Hoagland, "Security
Concerns with IP Tunneling", RFC 6169, April 2011.
[RFC6264] Jiang, S., Guo, D., and B. Carpenter, "An Incremental
Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264,
June 2011.
[RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
Roberts, "Issues with IP Address Sharing", RFC 6269,
June 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6343] Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
RFC 6343, August 2011.
[RFC6540] George, W., Donley, C., Liljenstolpe, C., and L. Howard,
"IPv6 Support Required for All IP-Capable Nodes", BCP 177,
RFC 6540, April 2012.
[RFC6586] Arkko, J. and A. Keranen, "Experiences from an IPv6-Only
Network", RFC 6586, April 2012.
[RFC6598] Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address
Space", BCP 153, RFC 6598, April 2012.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
[RFC6732] Kuarsingh, V., Lee, Y., and O. Vautrin, "6to4 Provider
Managed Tunnels", RFC 6732, September 2012.
Authors' Addresses
Victor Kuarsingh (editor)
Rogers Communications
8200 Dixie Road
Brampton, Ontario L6T 0C1
Canada
EMail: victor.kuarsingh@gmail.com
URI: http://www.rogers.com
Lee Howard
Time Warner Cable
13820 Sunrise Valley Drive
Herndon, VA 20171
US
EMail: lee.howard@twcable.com
URI: http://www.timewarnercable.com