Wireline Incremental IPv6
draft-ietf-v6ops-wireline-incremental-ipv6-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (v6ops WG) | |
|---|---|---|---|
| Authors | Victor Kuarsingh , Lee Howard | ||
| Last updated | 2012-02-01 (Latest revision 2011-11-27) | ||
| Replaces | draft-kuarsingh-wireline-incremental-ipv6 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
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| Stream | WG state | WG Document | |
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| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-v6ops-wireline-incremental-ipv6-01
v6ops V. Kuarsingh, Ed.
Internet-Draft Rogers Communications
Intended status: Informational L. Howard
Expires: August 5, 2012 Time Warner Cable
February 2, 2012
Wireline Incremental IPv6
draft-ietf-v6ops-wireline-incremental-ipv6-01
Abstract
Operators worldwide are in various stages of preparing for, or
deploying IPv6 into their networks. The operators often face
difficult challenges related to both 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 depleting supply of IPv4
addresses. The IPv6 transition will take most networks from an IPv4-
only environment to an IPv6 focused environment with long period of
dual stack operation varying by operator. This document helps
provide a framework for Wireline providers who are faced with the
challenges of introducing IPv6 along meeting the legacy needs of IPv4
connectivity utilizing well defined and commercially available IPv6
transition technologies.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 5, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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.
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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 . . . . . . . . . . . . . . . . 5
3.2. IPv4 Resource Challenges . . . . . . . . . . . . . . . . . 6
3.3. IPv6 Introduction and Operational Maturity . . . . . . . . 6
3.4. Service Management . . . . . . . . . . . . . . . . . . . . 7
3.5. Sub-Optimal Operation of Transition Technologies . . . . . 8
3.6. Future IPv6 Network . . . . . . . . . . . . . . . . . . . 8
4. IPv6 Transition Technology Analysis . . . . . . . . . . . . . 9
4.1. Automatic Tunnelling using 6to4 and Teredo . . . . . . . . 9
4.2. Carrier Grade NAT (NAT444) . . . . . . . . . . . . . . . . 9
4.3. 6RD . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Native Dual Stack . . . . . . . . . . . . . . . . . . . . 10
4.5. DS-Lite . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.6. NAT64 . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5. IPv6 Transition Phases . . . . . . . . . . . . . . . . . . . . 12
5.1. Phase 0 - Foundation . . . . . . . . . . . . . . . . . . . 12
5.1.1. Phase 0 - Foundation: Training . . . . . . . . . . . . 12
5.1.2. Phase 0 - Foundation: Routing . . . . . . . . . . . . 13
5.1.3. Phase 0 - Foundation: Network Policy and Security . . 13
5.1.4. Phase 0 - Foundation: Transition Architecture . . . . 13
5.1.5. Phase 0- Foundation: Tools and Management . . . . . . 14
5.2. Phase 1 - Tunnelled IPv6 . . . . . . . . . . . . . . . . . 14
5.2.1. 6RD Deployment Considerations . . . . . . . . . . . . 15
5.3. Phase 2: Native Dual Stack . . . . . . . . . . . . . . . . 17
5.3.1. Native Dual Stack Deployment Considerations . . . . . 18
5.4. Intermediate Phase for CGN . . . . . . . . . . . . . . . . 18
5.4.1. CGN Deployment Considerations . . . . . . . . . . . . 20
5.5. Phase 3 - IPv6-Only . . . . . . . . . . . . . . . . . . . 21
5.5.1. DS-Lite Deployment Considerations . . . . . . . . . . 22
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.1. Normative References . . . . . . . . . . . . . . . . . . . 23
9.2. Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
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1. Introduction
This draft sets out to help Wireline operators in planning their IPv6
deployments while ensuring continued support for IPv6-incapable
consumer devices and applications. We will identify which
technologies can be used incrementally to transition from IPv4-only
to an IPv6 anchored environment with support for dual stack
operation. The end state goal for most operators will be IPv6-only,
but the path to this final state will heavily depend 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 for all
operators, options listed herein provide a baseline which can be
included in many plans.
This draft is intended for Wireline environments which includes
Cable, DSL and/or Fibre as the access method to the end consumer.
This draft also attempts to follow the methodologies set out in
[I-D.ietf-v6ops-v4v6tran-framework] to identify how transition
technologies can be used individually and in combination. This
document also attempts to follow the principles laid out in [RFC6180]
which provides guidance on using IPv6 transition mechanisms. This
document will focus on technologies which enable and mature IPv6
within the operator's network, but will also include a cursory view
of IPv4 connectivity continuance. The focal transition technologies
include 6RD [RFC5969], DS-Lite [RFC6333] and Dual Stack operation
with a view into NAT44/Carrier Grade NAT (NAT44 without tunnelling as
distinct from DS-Lite). Focus on these technologies include their
inclusion in many off-the-shelf CPEs and availability in commercially
available network vendor equipment.
2. Operator Assumptions
For the purposes of this document, the authors assume:
- The operator is considering deploying IPv6 or is in progress in
deploying IPv6
- The operator has a legacy IPv4 customer base which will continue
to exist for a period of time
- The operator will want to minimize the level of disruption to
the existing and new customers by minimizing number of
technologies and functions that are needed to mediate any given
set of customer flows (overall preference for Native IP flows)
- The operator is able to run Dual Stack on their own core network
and is alble to transition their own services to support IPv6
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Based on these assumptions, an operator will want to utilize
technologies which minimize the need to tunnel, translate or mediate
flows to help simplify traffic flow and lower cost impacts of
transition technologies. Technology selections should be made to
interact with the non-dominant flows and allow Native IP 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 system scaling needed by the relevant
transition technology systems.
3. Reasons and Considerations for a Phased Approach
When faced with the challenges described in the Introduction,
operators may need to consider a phased approach when adding IPv6 to
an existing IPv4 service. A phased approach allows the operator to
add in IPv6 while not ignoring legacy IPv4 connection requirements.
Some of the main challenges which the operator will face include:
- IPv4 exhaustion may occur long before all traffic is able to
delivered over IPv6, necessitating IPv4 address sharing
- IPv6 will pose operational challenges since some of the software
is unvetted in large production environments and organizations are
not acclimatized to support IPv6 as a service
Many access network devices or customer controlled CPEs may not
support native IPv6 operation for a period of time
- Connectivity modes will move from IPv4-only to Dual Stack in the
home, changing functional behaviours in the consumer network
increasing support requirements for the operator
These challenges will occur over a period of time which means the
operator's plans need to address the ever changing requirements of
the network and customer demand. The following few sections
highlight some of the key reasons why a phased approach to IPv6
transition may be warranted and desired.
Although phases will be presented in this document, not all operators
may need to enable each desecrate phase. It is possible that
characteristics in individual networks may allow certain operators to
skip various phases.
3.1. Relevance of IPv6 and IPv4
The delivery of IPv6 connectivity should be the primary goal for
operators. Even though the operator may be focused on IPv6 delivery,
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they should be aware that both IPv4 and IPv6 will play a role in the
Internet experience during transition. Many customers use older
operating systems and hardware which support IPv4-only operation.
Internet customers don't buy IPv4 or IPv6 connections, they buy
Internet connections, which demands the need to support both IPv4 and
IPv6 for as long at the customer's home network demands such support.
The Internet is made of of many interconnecting systems, networks,
hardware, software and content sources - all of which will move to
IPv6 at different rates. The Operator's mandate during this time of
transition will be to support connectivity to both IPv6 and IPv4
through various technological means. The operator may be able to
leverage one or the other protocol to help bridge connectivity, but
the home network will 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 addressees for additional endpoints means that
growth in demand of IPv4 connections in some networks will be based
on 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 endpoints. IPv4 address constraints will
likely affect many if not most operators at some point increasing the
benefits of IPv6. IPv4 exhaustion is a consideration for
technologies which rely on IPv4 to supply IPv6 services, such as 6RD.
Also, if native Dual Stack is considered by the operator, challenges
on the IPv4 path is also of concern.
Some operators may be able to reclaim some IPv4 addresses through
efficiency in the network and the replacement of globally-unique IPv4
assignments with private addresses [RFC1918]. These measures are
tactical and do are not long term strategic options. The lack of new
IPv4 addresses 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 the operationalization of IPv6.
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 specific to IPv6 will
be needed.
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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. DS-Lite is one such
technology which requires IPv6 to support IPv4.
Further, some of these transition technologies are new and require
refinement within running code. Deployment experience may be needed
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,
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, understand its relevance to the IP Service
offering, how it operates and how to troubleshoot it - the deployment
is maturing. This fact should not incline an operator to delay their
IPv6 deployment, but should drive them to deploy IPv6 sooner to gain
the much needed experience before IPv6 is the only 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 which has has 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 of their network the work outward towards
the customer edge.
3.4. Service Management
Services are managed within most networks and are often based on the
gleaning and monitoring of IPv4 addresses. Operators will need to
address such management tools, troubleshooting methods and storage
facilities (such as databases) to deal with not just a new address
type containing 128-bits, but often both IPv4 and IPv6 at the same
time. Examination of address type, and recording delegated prefixes
along with single addresses, will likely require additional
development.
With any Dual Stack service - whether Native, 6RD based, DS-Lite
based or otherwise - two address families may need to be managed
simultaneously to help provide for the full Internet experience.
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This would indicate that IPv6 management is not just an 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 un-
monitored and impairments undetected.
These issues may be of consideration when selecting technologies
which require IPv6 as the base protocol to delivery IPv4.
Instability on the IPv6 service in such case would impact IPv4
services.
3.5. Sub-Optimal Operation of Transition Technologies
When contrasting native Dual Stack versus other transition
technologies it should be noted that 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 removing many network efficiencies built for native
IP flows. Tunnelling and translation devices may not be located on
the most optimal path in line with natural traffic flow and may
increase latency. These paths may also add additional points of
failure.
To minimize risk, an operator should use transition technologies for
the lesser-used address family if possible. During earlier phases of
transition, IPv4 traffic volumes may still be dominant, so tunnelling
of IPv6 traffic is reasonable. Over time, as IPv6 traffic volumes
will increase, native delivery of IPv6 traffic becomes advantageous.
When IPv4 connectivity demands diminish, translation and tunnelling
of IPv4 over IPv6 may be acceptable and more optimal.
When IPv6 tunnelling is used, an operator may not want to enable IPv6
for their services, especially high traffic services. Likewise, if
CGN is deployed, the operator may wish to promote native IPv6 access.
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. 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 required. The operators should plan for this
state and not make IPv6 inherently dependant on IPv4 as this would
unnecessarily constrain an operator.
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4. IPv6 Transition Technology Analysis
Operators should understand the main transition technologies for IPv6
deployment and IPv4 runout. This draft 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 or
infrastructure support.
The technologies in focus for this document are targeted on those
commercially available and in deployment.
4.1. Automatic Tunnelling using 6to4 and Teredo
Even when operators may not be actively deploying IPv6, automatic
mechanisms exist on customer 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 provides
guidelines on how to improve it's 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
[I-D.jjmb-v6ops-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 address are used for NAT444/CGN 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 is likely
to occur if any space other than [RFC1918] is used, including Shared
CGN Space [I-D.weil-shared-transition-space-request] or space
registered to another organization (squat space). The operator can
use 6to4-PMT [I-D.kuarsingh-v6ops-6to4-provider-managed-tunnel] or
attempt to block 6to4 operation entirely by blocking the ancycast
ranges associated with [RFC3068].
4.2. Carrier Grade NAT (NAT444)
Carrier Grade NAT (GGN), specifically as deployed in a NAT444
scenario [I-D.ietf-behave-lsn-requirements], may prove beneficial for
those operators who offer Dual Stack services to customer 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], but will often be necessary for a time.
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In a network where IPv4 address availability is low, CGN based on
NAT444 may provide continued access to IPv4 endpoints. Other
technologies (4rd, IVI) may also be used in place of the NAT444 model
with CGN. Some of the advantages of using CGN using NAT444 include
the similarities in provisioning and activation of IPv4 hosts and are
part of current network and operational procedures for managing such
hosts or CPEs (i.e. DHCPv6, DNSv4, TFTP, TR-069 etc).
4.3. 6RD
6RD [RFC5969] does provide a quick and effective way to deliver IPv6
services to customer endpoints when native IPv6 addressing on the
access network is not yet possible. 6RD provides tunnelled
connectivity for IPv6 over the existing IPv4 path. As the access
edge is upgraded and customer premise equipment is replaced, 6RD can
be superseded by native IPv6 access. 6RD can be delivered along side
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 while IPv6
traffic volumes are low. During this period, the operator can gain
experience with IPv6 on the core and improve their peering framework
to match those of the IPv4 service. 6RD scales easily by adding
relays. As IPv6 traffic volume grows, the operator can gradually
replace 6RD with native IPv6.
6RD client support is required, but most currently deployed CPEs do
not have 6RD client functionality built into them and may not be
upgradable. 6RD deployments would most likely require the replacement
of the home CPE. An advantage of 6RD in the early stages of
transition is that the WAN side interface does not need to implement
IPv6 to function correctly which may make it easier to deploy to
field hardware which is restricted in memory footprint, processing
power and storage space. 6RD will also require parameter
configuration which can be powered by the operator through DHCPv4,
manually provisioned on the CPE or automatically 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 which is
already used in many existing IPv6 deployments. Native Dual Stack
does however require that Native IPv6 be delivered to the customer
premise. This technology option is desirable in many cases and can
be used immediately if the access network and customer premise
equipment supports native IPv6.
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An operator who runs out of IPv4 addresses to assign to customers
will not be able to provide traditional native Dual Stack. In cases
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 network to support IPv6. Other systems like DHCP, DNS, and
diagnostic/management facilities need to be upgraded to support IPv6.
The upgrade of such systems may often be non-trivial.
4.5. DS-Lite
Dual-Stack Lite (DS-Lite, [RFC6333]) is based on an native IPv6
service delivery model where IPv4 services are supported. DS-Lite
provides tunnelled connectivity for IPv4 over the IPv6 path between
the customer's network device and a provider managed gateway (AFTR).
DS-Lite can only be used where there is native IPv6 connectivity
between the AFTR and the customer premise endpoint. This may mean
that the technology's use may not be viable during early transition
if the core or access network lacks IPv6 support. Early transition
stages may also occur when a significant about of content and
services are delivered over the legacy IPv4 path. Operators may be
sensitive to this and may not want the newer IPv6 path to be the only
bridge to IPv4 at that time. The provider may also want to make sure
that most of their internal services and a significant about of
external content is 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 run out. There are some functional considerations to
consider event with DS-Lite such as those described in
[draft-donley-nat444-impacts].
Similar to 6RD, DS-Lite requires client support on the CPE to
function. Client functionality is likely to be more prevalent in the
future as IPv6 capable (WAN side) CPEs begin to penetrate the market.
This includes both retail and operator provided gateways.
4.6. NAT64
NAT64 [RFC6146] provides the ability to connect IPv6-only connected
clients and hosts to IPv4 servers without any tunnelling. NAT64
requires that the host and home network supports IPv6-only modes of
operation. All IPv6-capable equipment scenarios are not considered
typical in most traditional Wireline hosted customer networks, are
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are not likely to be so in the near future.
Viability of NAT64 will increase in Wireline networks as consumer
equipment is replaced by IPv6 capable versions.
5. IPv6 Transition Phases
The Phases described in this document are not provided as a rigid set
of steps, but are considered a guideline which should be analyzed by
an operator planning their IPv6 transition. Operators may choose to
skip steps based on technological capabilities within their specific
networks.
The phases are based on an 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 volume
will correspondingly decrease, until IPv6 is the predominant address
family used. For each phase, the predominant address family should
be native, while mediation (tunnelling or translation) may be
acceptable for address family which generates the lower amount of
volume on the network.
Additional guidance and information on utilizing IPv6 transition
mechanisms can be found in [RFC6180]. Also, guidance on incremental
CGN for IPv6 transition can also 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 - 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 they train the various parts of their 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 staff who support the network and other systems
need to be trained closer to the deployment timeframes, so they
immediately use their new-found knowledge before forgetting.
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Customer support staff would require much more basic but large scale
training since many organizations have massive call centres to
support the customer base.
5.1.2. 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 number of ways
including the number of addresses which are made available, careful
attention to a scalable and manageable architecture needs to be made.
Also, given that home network environments will no longer receive a
token single address as is common in IPv4, operators will need to
understand the impacts of delegating a large sum of addresses
(prefixes) to consumer endpoints. Delegating prefixes can be of
specific importance in access network environments where downstream
customers 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).
5.1.3. 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 they are of consideration and should be
addressed when delivering IPv6 services. Other IETF documents
([RFC4942], [RFC6092], [RFC6169], for instance) are excellent
resources.
5.1.4. Phase 0 - Foundation: Transition Architecture
The operator should plan out their transition architecture in advance
(with room for flexibility) to help optimize how they will build out
and scale their networks. If the operator should want to use
multiple technologies like CGN/NAT444, DS-Lite and 6RD, they may want
to plan out where network resident equipment may be located and
potentially choose locations which can be used for all three
functional roles (i.e. placement of NAT44 translator, AFTR and 6RD
relays). This would allow for the least disruption as the operator
evolves the transition environment to meet the needs of the customer
base. This approach may also prove beneficial if traffic patterns
change rapidly in the future and the operator may need to evolve
their transition infrastructure faster than originally anticipated.
Operators should inform their vendors of what technologies they plan
to support over the course of the transition to make sure the
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equipment is suited to support those modes of operation. This is
important for both network gear and customer premise equipment.
The operator should also plan their overall strategy to meet the
target needs of an IPv6-only deployment. Over time, IPv4 maintenance
will become cumbersome so support and an operator may want to remove
it from the access connectivity portion of their network. Planning
for this eventual stage, no matter how far off this may be, will help
the operator embrace this end state when needed.
5.1.5. Phase 0- Foundation: Tools and Management
The operator should thoroughly analyze all provisioning and
operations 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 (PD) and the ability to detect either or both
address families when determining if a customer has full Internet
service.
If an operator stores usage information, this would need to be
aggregated to include both the IPv4 and IPv6 traffic flows. Also,
tools that verify connectivity may need to query the IPv4 and IPv6
addresses.
5.2. Phase 1 - Tunnelled IPv6
Tunnelled access to IPv6 offers a viable early stage transition
option to operators. Many network operators can deploy native IPv6
from access edge to peering edge fairly quickly but may not be able
to offer IPv6 natively to the customer edge device. During this
period of time, tunnelled access to IPv6 is a viable alternative to
native IPv6. It is also possible that operators my be rolling out
IPv6 natively to the customer edge but the time involved may be long
due to logistics and other factors. Even while slowly rolling out
native IPv6, operators can deploy relays for automatic tunnelling
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 behaviours from 6RD [RFC3484].
Additional guidelines on deploying and supporting 6to4 can be found
in [RFC6343].
The operator can deploy 6RD relays easily and scale them as needed to
meet the early customer needs of IPv6. Since 6RD requires the
upgrade or replacement of CPE gateways, the operator may want ensure
that the gateways support not just 6RD but native Dual Stack and
other tunnelling technologies if possible such as DS-Lite. 6RD
clients are becoming available in some retail channel products and
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within the 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.
+--------+ -----
| | / \
Encap IPv6 Flow | 6RD | | IPv6 |
- - -> | BR | <- > | Net |
+---------+ / | | \ /
| | / +--------+ -----
| 6RD + <----- -----
| | / \
| Client | IPv4 Flow | IPv4 |
| + < - - - - - - - - - - - - - - -> | Net |
| | \ /
+---------+ -----
Figure 1: 6RD Basic Model
6RD used as an initial phase technology also provides the added
benefit of a deterministic IPv6 prefix which is 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
customer host/CPE. So a simple tool and/or method can be built to
help the operational staff in an organization know that the IPv6
prefix is for 6RD based on knowledge of the IPv4 address.
An operator may choose to not offer internal services over IPv6 if
tunnelled access to IPv6 is used since some services generate a large
amount of traffic. This mode of operation should avoid the need to
greatly increase the scale of the 6RD Relay environment.
5.2.1. 6RD Deployment Considerations
Deploying 6RD can greatly speed up an operator's ability to support
IPv6 to the customer network. Consider by whom the system would be
deployed, provisioned, scaled and managed.
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 here is that it may be difficult manage
the traffic volume among additional relays, since all 6RD traffic
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will find the nearest (in terms of IGP cost) relay. Use of specific
addresses can help provide more control but has the disadvantage of
being more complex to provision as CPEs will contain different
information. An alternative approach is to use a hybrid model using
multiple anycast service IPs for clusters of 6RD relays should the
operator anticipate massive scaling of the environment. This way,
the operator has multiple vectors by which to scale the service.
+--------+
| |
IPv4 Addr.X | 6RD |
- - - > | BR |
+-----------+ / | |
| Client A | <- - - +--------+
+-----------+
Separate IPv4 Service Addresses
+-----------+
| Client B | < - - +--------+
+-----------+ \ | |
- - - > | 6RD |
IPv4 Addr.Y | BR |
| |
+--------+
Figure 2: 6RD Multiple IPv4 Service Address Model
+--------+
| |
IPv4 Addr.X | 6RD |
- - - > | BR |
+-----------+ / | |
| Client A |- - - - +--------+
+-----------+
Common (Anycast) IPv4 Service Addresses
+-----------+
| Client B | - - - +--------+
+-----------+ \ | |
- - - > | 6RD |
IPv4 Addr.X | BR |
| |
+--------+
Figure 3: 6RD Anycast IPv4 Service Address Model
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Provisioning of the endpoints is affected by the deployment model
chosen (i.e. anycast vs. specific service IPs). Using multiple IPs
may require more planning and management as customer 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 customer 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 counted on the operator edge, but if it requires source/
destination flow details, data must be collected after the 6RD relay
(IPv6 side of connection).
+---------+ IPv4 Encapsulation +------------+
| +- - - - - - - - - - - + |
| 6RD +----------------------+ 6RD +---------
| | IPv6 Packet | Relay | IPv6 Packet
| Client +----------------------+ +---------
| +- - - - - - - - - - - + | ^
+---------+ ^ +------------+ |
| |
| |
IPv4 IP (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 "Tunnelled IPv6" or as an initial
step, the operator may deploy native IPv6 to the customer premise.
This phase would then allow for both IPv6 and IPv4 to be natively
accessed by the customer home gateway/CPE. The native Dual Stack
phase can be rolled out across the network while the tunnelled IPv6
service remains running, if used. As areas begin to support native
IPv6, customer home equipment can be set to use it in place of
technologies like 6RD. Hosts using 6to4 and/or Teredo will
automatically prefer [RFC3484] the IPv6 address delivered via native
IPv6 (assumed to be a Delegated Prefix as per [RFC3769]).
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.
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5.3.1. Native Dual Stack Deployment Considerations
Native Dual Stack is a a very desirable option for the IPv6
transition. The operator must enable IPv6 on the network core and
peering before they attempt to turn on native IPv6 services.
Additionally, provisioning and support systems such as DHCPv6, DNS
and other functions which support the customer's IPv6 Internet
connection need to be in place.
The operator must treat IPv6 connectivity as seriously as IPv4. Poor
IPv6 service may be worse than not offering an IPv6 service at all,
since users may disable IPv6, which will be difficult for the
operator to reverse. 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
IA_PDs), but installation and propagation of routing information for
the prefix, especially during access layer instability, is often
poorly understood. The Operator should develop processes for
renumbering customers who they move to new Access nodes.
Operators need to keep track of both the dynamically assigned IPv4
and IPv6 addresses. Any additional dynamic elements, such as auto-
generated DNS names, need to be considered and planned for.
5.4. Intermediate Phase for CGN
At some point during the first two phases, acquiring more IPv4
addresses may become challenging or impossible, therefore CGN/NAT444
may be required on the IPv4 path. The operator may have a preference
to move directly to a more efficient way of IPv4 address shared such
as DS-LIte, but conditions may dictate that CGN/NAT444 is the only
workable option. CGN is less optimal and should be used cautiously
in a 6RD deployment (if used with 6RD to a given endpoint) since all
traffic must transverse some type of operator service node (relay and
translator).
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+--------+ -----
| | / \
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 a IPv6+CGN/NAT444 model the
native IPv6 path is available for higher quality connectivity helping
host operation over the network while the CGN path may offer a less
then optimal performance.
+--------+ -----
| | / \
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 CGN Address Space [I-D.weil-shared-
transition-space-request]. It is also possible that operators may
use part of their own RIR assigned address space for CGN zone
addressing if RFC918 addresses pose technical challenges in their
network. It is not recommended that operators use squat space as it
may pose additional challenges with filtering and policy control.
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5.4.1. CGN Deployment Considerations
CGN is often considered undesirable by operators but required in many
cases. An operator who needs to deploy CGN services should consider
it's impacts to 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 also be needed at low scale
at first and grown to meet future demands based on traffic and
connection dynamics of the customer, 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 costs of
the system and only spend money on equipment with the actual growth
of traffic (demand on CGN system). The operator will need a
deployment model and architecture which allows 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
[draft-sivakumar-behave-nat-logging]. This logging may require
significant investment in external systems which ingest, aggregate
and report on such information
[draft-donley-behave-deterministic-cgn].
Since CGN has impacts on some applications
[draft-donley-nat444-impacts], operators may deploy CGN only for
those customers who do not use affected applications. Affected
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customers could be selected by observing usage, or by offering CGN
and Native IPv4 for different prices.
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 customer endpoints. During this final
phase, IPv4 connectivity may or may not need to be supported
depending on the conditions of the network and customer demand. If
legacy IPv4 connectivity is still demanded, DS-Lite may be used to
tunnel the traffic. If IPv4 connectivity is not required, but access
to legacy IPv4 content is only required, NAT64 can be used as well or
as a follow-up to DS-Lite.
DS-Lite allows continued access for the IPv4 customer base using
address sharing for IPv4 Internet connectivity, but with only a
single layer of translation, compared to CGN/NAT444. This mode of
operation also removes the need to directly address customer
endpoints with an IPv4 address 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 reclaim IPv4 addresses for redeployment or general
simplification of the routing domain. 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 was forced to enable CGN for a NAT444 deployment,
they may be able to co-locate the AFTR and CGN functions within the
network to simplify capacity management and the engineering of flows.
DS-Lite however requires configuration of the CPE and the
implementation of the AFTR.
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5.5.1. DS-Lite Deployment Considerations
The same deployment considerations associated with Native IPv6
deployments apply to DS-LIte. IPv4 will now be dependent on IPv6
service quality, so the IPv6 network and service must be running well
to ensure a quality experience for the end customer. Tools and
processes will be needed to manage the encapsulated IPv4 service. If
flow analysis is required for IPv4 traffic, this should be enabled at
a point beyond the AFTR (after de-capsulation).
+---------+ IPv4 Encapsulation +------------+
| + - - - - - - - - - - -+ |
| AFTR +----------------------+ AFTR +---------
| | IPv4 Packet | | IPv4 Packet
| Client +----------------------+ +---------
| + - - - - - - - - - - -+ | ^
+---------+ ^ +------------+ |
| |
| |
IPv6 IP (Tools/Mgmt) IPv4 Packet Flow Analysis
Figure 9: DS-Lite Tools and Flow Analysis
DS-Lite also requires client support. 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.
6. IANA Considerations
No IANA considerations are defined at this time.
7. Security Considerations
No Additional Security Considerations are made in this document.
8. Acknowledgements
Special thanks to Wes George and John Brzozowski for their extensive
review and comments.
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Thanks to the following people for their textual contributions and/or
guidance on IPv6 deployment considerations: Jason Weil, Nik Lavorato,
John Cianfarani, Chris Donley, and Tina TSOU.
9. References
9.1. Normative References
[RFC6180] Arkko, J. and F. Baker, "Guidelines for Using IPv6
Transition Mechanisms during IPv6 Deployment", RFC 6180,
May 2011.
9.2. Informative References
[I-D.donley-nat444-impacts]
Donley, C., Howard, L., Kuarsingh, V., Berg, J., and U.
Colorado, "Assessing the Impact of Carrier-Grade NAT on
Network Applications", draft-donley-nat444-impacts-03
(work in progress), November 2011.
[I-D.ietf-behave-lsn-requirements]
Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common requirements for Carrier Grade NATs
(CGNs)", draft-ietf-behave-lsn-requirements-05 (work in
progress), November 2011.
[I-D.ietf-v6ops-v4v6tran-framework]
Carpenter, B., Jiang, S., and V. Kuarsingh, "Framework for
IP Version Transition Scenarios",
draft-ietf-v6ops-v4v6tran-framework-02 (work in progress),
July 2011.
[I-D.jjmb-v6ops-comcast-ipv6-experiences]
Brzozowski, J. and C. Griffiths, "Comcast IPv6 Trial/
Deployment Experiences",
draft-jjmb-v6ops-comcast-ipv6-experiences-02 (work in
progress), October 2011.
[I-D.kuarsingh-v6ops-6to4-provider-managed-tunnel]
Kuarsingh, V., Lee, Y., and O. Vautrin, "6to4 Provider
Managed Tunnels",
draft-kuarsingh-v6ops-6to4-provider-managed-tunnel-04
(work in progress), September 2011.
[I-D.weil-shared-transition-space-request]
Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
M. Azinger, "IANA Reserved IPv4 Prefix for Shared Address
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Space", draft-weil-shared-transition-space-request-14
(work in progress), January 2012.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[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.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC3769] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix
Delegation", RFC 3769, June 2004.
[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.
[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.
[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.
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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.
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
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