Softwires Working Group M. Boucadair, Ed.
Internet-Draft France Telecom
Intended status: Informational S. Matsushima
Expires: March 3, 2013 Softbank Telecom
Y. Lee
Comcast
O. Bonness
Deutsche Telekom
I. Borges
Portugal Telecom
G. Chen
China Mobile
August 30, 2012
Motivations for Carrier-side Stateless IPv4 over IPv6 Migration
Solutions
draft-ietf-softwire-stateless-4v6-motivation-04
Abstract
IPv4 service continuity is one of the most pressing problems that
must be resolved by Service Providers during the IPv6 transition
period - especially after the exhaustion of the public IPv4 address
space. Current standardization effort that addresses IPv4 service
continuity focuses on stateful mechanisms. This document elaborates
on the motivations for the need to undertake a companion effort to
specify stateless IPv4 over IPv6 approaches.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 3, 2013.
Copyright Notice
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Why Stateless IPv4 over IPv6 Solutions are Needed? . . . . . . 4
3.1. Network Architecture Simplification . . . . . . . . . . . 5
3.1.1. Network Dimensioning . . . . . . . . . . . . . . . . . 5
3.1.2. No Intra-domain Constraint . . . . . . . . . . . . . . 5
3.1.3. Logging - No Need for Dynamic Binding Notifications . 6
3.1.4. No Additional Protocol for Port Control is Required . 6
3.2. Operational Tasks and Network Maintenance Efficiency . . . 6
3.2.1. Preserve Current Practices . . . . . . . . . . . . . . 6
3.2.2. Planned Maintenance Operations . . . . . . . . . . . . 7
3.2.3. Reliability and Robustness . . . . . . . . . . . . . . 7
3.2.4. Support of Multi-Vendor Redundancy . . . . . . . . . . 7
3.2.5. Simplification of Qualification Procedures . . . . . . 7
3.3. Facilitating Service Evolution . . . . . . . . . . . . . . 8
3.3.1. Implicit Host Identification . . . . . . . . . . . . . 8
3.3.2. No Organizational Impact . . . . . . . . . . . . . . . 9
3.4. Cost Minimization Opportunities . . . . . . . . . . . . . 9
4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Dependency Between IPv4 and IPv6 Address Assignments . . . 10
4.2. IPv4 Port Utilisation Efficiency . . . . . . . . . . . . . 11
4.3. IPv4 Port Randomization . . . . . . . . . . . . . . . . . 11
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
10. Informative References . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
When the global IPv4 address space is exhausted, Service Providers
will be left with an address pool that cannot be increased anymore.
Many services and network scenarios will be impacted by the lack of
IPv4 public addresses. Providing access to the (still limited) IPv6
Internet only won't be sufficient to address the needs of customers,
as most of them will continue to access legacy IPv4-only services.
Service Providers must guarantee their customers that they can still
access IPv4 contents although they will not be provisioned with a
global IPv4 address anymore. Means to share IPv4 public addresses
are unavoidable [RFC6269].
Identifying the most appropriate solution(s) to the IPv4 address
exhaustion as well as IPv4 service continuity problems and deploying
them in a real network with real customers is a very challenging and
complex process for all Service Providers. There is nothing like a
"One size fits all" solution or one target architecture that would
work for all situations. Each Service Provider has to take into
account its own context (e.g., service infrastructures), policies and
marketing strategy (a document that informs Service Providers about
the impact of the IPv4 address shortage, and provides some
recommendations and guidelines, is available at [EURESCOM]).
Current standardization effort that is meant to address this IPv4
service continuity issue focuses mainly on stateful mechanisms that
sharing of global IPv4 addresses between Customers is based upon the
deployment of NAT (Network Address Translation) capabilities in the
network. Because of some caveats of such stateful approaches the
Service Provider community feels that a companion effort is required
to specify stateless IPv4 over IPv6 approaches. Note that the
stateless solution elaborated in this document focuses on the
carrier-side stateless IPv4 over IPv6 solution. In the context of
address sharing, states should be maintained in other equipments,
e.g. customer premises equipment or host.
This document provides elaboration on the need for carrier-side
stateless IPv4 over IPv6 solution.
More discussions about stateless vs. stateful can be found at
[RFC6144].
2. Terminology
This document makes use of the following terms:
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State: as used in [RFC1958].
Session state: refers to an information state as defined in Section
2.3 of [RFC2663]. In particular, it refers to the state
maintained by the NAT so that datagrams pertaining to a session
are routed to the right node. Note, TCP/UDP sessions are
uniquely identified by the tuple of (source IP address, source
TCP/UDP port, target IP address, target TCP/UDP port) while ICMP
query sessions are identified by the tuple of (source IP
address, ICMP query ID, target IP address).
User-session state: refers to session state belonging to a given
user.
Stateful 4/6 solution (or stateful solution in short): denotes a
solution where the network maintains user-session states relying
on the activation of a NAT function in the Service Providers'
network [I-D.ietf-behave-lsn-requirements]. The NAT function is
responsible for sharing the same IPv4 address among several
subscribers and to maintain user-session state.
Stateless 4/6 solution (or stateless solution in short): denotes a
solution which does not require any per-user state (see Section
2.3 of [RFC1958]) to be maintained by any IP address sharing
function in the Service Provider's network. This category of
solutions assumes a dependency between an IPv6 prefix and IPv4
address. In an IPv4 address sharing context, dedicated
functions are required to be enabled in the CPE router to
restrict the source IPv4 port numbers. Within this document,
"port set" and "port range" terms are used interchangeably.
3. Why Stateless IPv4 over IPv6 Solutions are Needed?
Below is provided a list of motivations which justify the need for a
stateless solution (in no particular order):
(1) Minimizes impact on OSS and logging systems. Ideally, it does
not require OSS & logging systems that wouldn't be there in a
pure IPv6 network.
(2) Does not require maintaining per-subscriber configuration on
active data plane network elements.
(3) Scales in terms of IP forwarding capacity, rather than amount
of dynamic state, or new session creation rate.
(4) Supports a single architecture that allows 1:1 or N:1 (port
range) NAT44 usage without additional extensions.
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(5) Preserves current engineering practices (e.g., anycast-based
load-balancing).
(6) Relies on IPv6 and supports transition to an IPv6-only network.
(7) Supports asymmetric routing to/from the IPv4 Internet.
(8) Maximizes the ease of deployment and redundancy of nodes.
(9) Readily supports a multi-vendor environment (including
redundancy).
(10) Allows direct user-user traffic flows (i.e., allows for no-
tromboning)
(11) Retains today's user experience (NAT on CPE) and supports
today's operational model.
(12) Does not require deployment of (additional) dynamic signaling
protocols to the end-user CPE beyond those already used.
(13) Minimizes required non-regression testing effort.
(14) Does not require organizational changes.
(15) Assumes a clear separation between the service and the network
layer and therefore there is no interference between delivered
services and underlying network transfer capabilities.
This section elaborates further on the aforementioned motivations.
3.1. Network Architecture Simplification
The activation of the stateless function in the Service Provider's
network does not introduce any major constraint on the network
architecture and its engineering. The following sub-sections
elaborate on these aspects.
3.1.1. Network Dimensioning
Because no per-user state [RFC1958] is required, a stateless solution
does not need to take into account the maximum number of simultaneous
user-sessions and the maximum number of new user-sessions per second
to dimension its networking equipment. Like current network
dimensioning practices, only considerations related to the customers
number, traffic trends and the bandwidth usage need be taken into
account.
3.1.2. No Intra-domain Constraint
Stateless IPv4/IPv6 interconnection functions can be ideally located
at the boundaries of an Autonomous System (e.g., ASBRs that peer with
external IPv4 domains); in such case intra-domain paths are not
altered: there is no need to force IP packets to cross a given node
for instance; intra-domain routing processes are not tweaked to
direct the traffic to dedicated nodes. Stateless solutions optimize
CPE-to-CPE communication in that packets don't go through the
interconnection function.
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3.1.3. Logging - No Need for Dynamic Binding Notifications
Network abuse reporting requires traceability [RFC6269]. To provide
such traceability, prior to IPv4 address sharing, logging the IPv4
address assigned to a user was sufficient and generates relatively
small logs. The advent of stateful IPv4 address allows dynamic port
assignment, which then requires port assignment logging. This
logging of port assignments can be considerable.
In contrast, static port assignments do not require such considerable
logging. The volume of the logging file may not be seen as an
important criterion for privileging a stateless approach because
stateful approaches can also be configured (or designed) to assign
port ranges and therefore lead to acceptable log volumes.
If a dynamic port assignment mode is used, dedicated interfaces and
protocols must be supported to forward binding data records towards
dedicated platforms. The activation of these dynamic notifications
may impact the performance of the dedicated device. For stateless
solutions, there is no need for dynamic procedures (e.g., using
SYSLOG) to notify a mediation platform about assigned bindings.
Some Service Providers have a requirement to use only existing
logging systems and to avoid introducing new ones (mainly because of
CAPEX considerations). This requirement is easily met with stateless
solutions.
3.1.4. No Additional Protocol for Port Control is Required
Stateless solutions do not require activating a new dynamic signaling
protocol in the end-user CPE in addition to those already used. In
particular, existing protocols (e.g., UPnP IGD:2 [UPnP-IGD]) can be
used to control the NAT mappings in the CPE.
3.2. Operational Tasks and Network Maintenance Efficiency
3.2.1. Preserve Current Practices
Service Providers require as much as possible to preserve the same
operations as for current IP networking environments.
If stateless solutions are deployed, common practices are preserved.
In particular, the maintenance and operation of the network do not
require any additional constraints such as: path optimization
practices, enforcing traffic engineering policies, issues related to
traffic oscillation between stateful devices, load-balancing the
traffic or load sharing the traffic among egress/ingress points can
be used, etc. Particularly,
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o anycast-based schemes can be used for load-balancing and
redundancy purposes.
o asymmetric routing to/from the IPv4 Internet is natively supported
and no path-pinning mechanisms have to be additionally
implemented.
3.2.2. Planned Maintenance Operations
Since no state is maintained by stateless IPv4/IPv6 interconnection
nodes, no additional constraint needs to be taken into account when
upgrading these nodes (e.g., adding a new service card, upgrading
hardware, periodic reboot of the devices, etc.). In particular,
current practices that are enforced to (gracefully) reboot or to
shutdown routers can be maintained.
3.2.3. Reliability and Robustness
Compared to current practices (i.e., without a CGN in place), no
additional capabilities are required to ensure reliability and
robustness in the context of stateless solutions. Since no state is
maintained in the Service Provider's network, state synchronization
procedures are not required.
High availability (including failure recovery) is ensured owing to
best current practices in the field.
3.2.4. Support of Multi-Vendor Redundancy
Deploying stateful techniques, especially when used in the Service
Providers networks, constrains severely deploying multi-vendor
redundancy since very often proprietary vendor-specific protocols are
used to synchronize state. This is not an issue for the stateless
case. Concretely, the activation of the stateless IPv4/IPv6
interconnection function does not prevent nor complicate deploying
devices from different vendors.
This criterion is very important for Service Providers having a
sourcing policy to avoid mono-vendor deployments and to operate
highly-available networks composed on multi-vendors equipment.
3.2.5. Simplification of Qualification Procedures
The introduction of new functions and nodes into operational networks
follows strict procedures elaborated by Service Providers. These
procedures include in-lab testing and field trials. Because of their
nature, stateless implementations optimize testing time and
procedures:
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o The specification of test suites to be conducted should be
shorter;
o The required testing resources (in terms of manpower) are likely
to be less solicited that they are for stateful approaches.
One of the privileged approaches to integrate stateless IPv4/IPv6
interconnection function consists in embedding stateless capabilities
in existing operational nodes (e.g., IP router). In this case, any
software or hardware update would require to execute non-regression
testing activities. In the context of the stateless solutions, the
non-regression testing load due to an update of the stateless code is
expected to be minimal.
For the stateless case, testing effort and non-regression testing are
to be taken into account for the CPE side. This effort is likely to
be lightweight compared to the testing effort, including the non-
regression testing, of a stateful function which is co-located with
other routing functions for instance.
3.3. Facilitating Service Evolution
3.3.1. Implicit Host Identification
Service Providers do not offer only IP connectivity services but also
added value services (a.k.a., internal services). Upgrading these
services to be IPv6-enabled is not sufficient because of legacy
devices. In some deployments, the delivery of these added-value
services relies on implicit identification mechanism based on the
source IPv4 address. Due to address sharing, implicit identification
will fail [RFC6269]; replacing implicit identification with explicit
authentication will be seen as a non acceptable service regression by
the end users (less Quality of Experience (QoE)).
When a stateless solution is deployed, implicit identification for
internal services is likely to be easier to implement: the implicit
identification should be updated to take into account the port range
and the IPv4 address. Techniques as those analyzed in
[I-D.ietf-intarea-nat-reveal-analysis] are not required for the
delivery of these internal services if a stateless solution is
deployed.
Note stateful approaches configured to assign port ranges allow also
to support implicit host identification.
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3.3.2. No Organizational Impact
Stateless solutions adopt a clear separation between the IP/transport
layers and the service layers; no service interference is to be
observed when a stateless solution is deployed. This clear
separation:
Facilitates service evolution: Since the payload of IPv4 packets is
not altered in the path, services can evolve without requiring any
specific function (e.g., Application Level Gateway (ALG)) in the
Service Provider's network;
Limits vendor dependency: The upgrade of value-added services does
not involve any particular action from vendors that provide
devices embedding the stateless IPv4/IPv6 interconnection
function.
No service-related skills are required for network operators who
manage devices that embed the IPv4/IPv6 interconnection function: IP
teams can be in charge of these devices; there is a priori no need
to create a dedicated team to manage and to operate devices
embedding the stateless IPv4/IPv6 interconnection function. The
introduction of stateless capabilities in the network are unlikely
to degrade management costs.
3.4. Cost Minimization Opportunities
To make decision for which solution is to be adopted, Service
Providers usually undertake comparative studies about viable
technical solutions. It is not only about technical aspects but also
economical optimization (both CAPEX and OPEX considerations). From a
Service Provider perspective, stateless solutions are more attractive
because they do less impact the current network operations and
maintenance model that is widely based on stateless approaches.
Table 1 shows the general correspondence between technical benefits
and potential economic reduction opportunities.
While not all Service Providers environments are the same, a detailed
case study from one Service Provider
[I-D.matsushima-v6ops-transition-experience] reports that stateless
transition solutions can be considerably less expensive than stateful
transition solutions.
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+---------------+--------------------------------------+------------+
| Section | Technical and Operation Benefit | Cost Area |
+---------------+--------------------------------------+------------+
| Section 3.1.1 | Network dimensioning | Network |
+---------------+--------------------------------------+------------+
| Section 3.1.2 | No Intra-domain constraint | Network |
+---------------+--------------------------------------+------------+
| Section 3.1.3 | Logging | Network & |
| | | Ops |
+---------------+--------------------------------------+------------+
| Section 3.1.4 | No additional control protocol | Network |
+---------------+--------------------------------------+------------+
| Section 3.2.1 | Preserve current practices | Ops |
+---------------+--------------------------------------+------------+
| Section 3.2.2 | Planned maintenance | Ops |
+---------------+--------------------------------------+------------+
| Section 3.2.3 | Reliability and robustness | Network & |
| | | Ops |
+---------------+--------------------------------------+------------+
| Section 3.2.4 | Multi-Vendor Redundancy | Network |
+---------------+--------------------------------------+------------+
| Section 3.2.5 | Simple qualification | Ops |
+---------------+--------------------------------------+------------+
| Section 3.3.1 | Implicit Host Identification for | Ops |
| | internal services | |
+---------------+--------------------------------------+------------+
| Section 3.3.2 | Organizational Impact | Ops |
+---------------+--------------------------------------+------------+
Table 1: Cost minimization considerations
4. Discussion
Issues common to all address sharing solutions are documented in
[RFC6269]. The following sub-sections enumerate some open questions
for a CPE-based stateless solution. There are no universal answers
to these open questions since each Service Provider has its own
constraints (e.g., available address pool, address sharing ratio,
etc.).
4.1. Dependency Between IPv4 and IPv6 Address Assignments
Complete stateless mapping implies that the IPv4 address and the
significant bits that are used to encode the set of assigned ports
can be retrieved from the IPv6 prefix assigned to the CPE. This
requirement can be addressed by either using the IPv6 prefix also
used to forward IPv6 traffic natively, or allocating two prefixes to
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the CPE (one that will be used to forward IPv6 traffic natively, and
the other one to forward IPv4 traffic).
o Providing two IPv6 prefixes avoids the complexity that may be
related to the adaptation of the IPv6 addressing scheme to the
IPv4 addressing scheme. The drawback is the need to allocate two
prefixes instead of one to each CPE and to announce them
accordingly, possibly at the cost of jeopardizing the routing and
forwarding efficiencies.
o The use of a single prefix to cover both the forwarding of IPv6
and IPv4-in-IPv6 traffic avoids the need to maintain a double
information (e.g., for customer identification and management
purposes and for forwarding table maintenance purposes). This
scheme somewhat links strongly the IPv4 addressing scheme to the
allocated IPv6 prefixes. For Service Providers requiring to apply
specific policies on per Address-Family (e.g., IPv4, IPv6), some
provisioning tools (e.g., DHCPv6 option) may be required to derive
in a deterministic way the IPv6 address to be used for the IPv4
traffic based on the IPv6 prefix delegated to the home network.
4.2. IPv4 Port Utilisation Efficiency
CGN-based solutions, because they can dynamically assign ports,
provide better IPv4 address sharing ratio than stateless solutions
(i.e., can share the same IP address among a larger number of
customers). For Service Providers who desire an aggressive IPv4
address sharing, a CGN-based solution is more suitable than the
stateless. However
1: When port overloading is used, some applications are likely to be
broken.
2: in case a CGN pre-allocates port ranges, e.g.- to alleviate
traceability complexity (see Section 3.1.3), it also reduces its
port utilization efficiency.
4.3. IPv4 Port Randomization
Preserving port randomization [RFC6056] may be more or less difficult
depending on the address sharing ratio (i.e., the size of the port
space assigned to a CPE). The CPE can only randomize the ports
inside a fixed port range.
More discussion to improve the robustness of TCP against Blind In-
Window Attacks can be found at [RFC5961]. Other means than the
(IPv4) source port randomization to provide protection against
attacks should be used (e.g., use [I-D.vixie-dnsext-dns0x20] to
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protect against DNS attacks, [RFC5961] to improve the robustness of
TCP against Blind In-Window Attacks, use IPv6).
5. Conclusion
As discussed in Section 3, stateless solutions provide several
interesting features. Trade-off between the positive vs. negative
aspects of stateless solutions is left to Service Providers. Each
Service Provider will have to select the appropriate solution
(stateless, stateful or even both) meeting its requirements.
This document recommends to undertake as soon as possible the
appropriate standardization effort to specify a stateless IPv4 over
IPv6 solution.
6. IANA Considerations
No action is required from IANA.
7. Security Considerations
Except for the less efficient port randomization of and routing loops
[RFC6324], stateless 4/6 solutions are expected to introduce no more
security vulnerabilities than stateful ones. Because of their
stateless nature, they may in addition reduce denial of service
opportunities.
8. Contributors
The following individuals have contributed to this document:
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Christian Jacquenet
France Telecom
Email: christian.jacquenet@orange.com
Pierre Levis
France Telecom
Email: pierre.levis@orange.com
Masato Yamanishi
SoftBank BB
Email: myamanis@bb.softbank.co.jp
Yuji Yamazaki
Softbank Mobile
Email: yuyamaza@bb.softbank.co.jp
Hui Deng
China Mobile
Email: denghui02@gmail.com
9. Acknowledgments
Many thanks to the following individuals who provided valuable
comments:
+---------------+---------------+---------------+---------------+
| X. Deng | W. Dec | D. Wing | A. Baudot |
| E. Burgey | L. Cittadini | R. Despres | J. Zorz |
| M. Townsley | L. Meillarec | R. Maglione | J. Queiroz |
| C. Xie | X. Li | O. Troan | J. Qin |
| B. Sarikaya | N. Skoberne | J. Arkko | D. Lui |
+---------------+---------------+---------------+---------------+
Special thanks to W. Dec who provided a summary of the motivation
items.
10. Informative References
[EURESCOM]
Levis, P., Borges, I., Bonness, O. and L. Dillon L., "IPv4
address exhaustion: Issues and Solutions for Service
Providers", March 2010, <http://archive.eurescom.eu/~pub/
deliverables/documents/P1900-series/P1952/D2bis/
P1952-D2bis.pdf>.
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[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-09 (work in
progress), August 2012.
[I-D.ietf-intarea-nat-reveal-analysis]
Boucadair, M., Touch, J., Levis, P., and R. Penno,
"Analysis of Solution Candidates to Reveal a Host
Identifier (HOST_ID) in Shared Address Deployments",
draft-ietf-intarea-nat-reveal-analysis-04 (work in
progress), August 2012.
[I-D.matsushima-v6ops-transition-experience]
Matsushima, S., Yamazaki, Y., Sun, C., Yamanishi, M., and
J. Jiao, "Use case and consideration experiences of IPv4
to IPv6 transition",
draft-matsushima-v6ops-transition-experience-02 (work in
progress), March 2011.
[I-D.vixie-dnsext-dns0x20]
Vixie, P. and D. Dagon, "Use of Bit 0x20 in DNS Labels to
Improve Transaction Identity",
draft-vixie-dnsext-dns0x20-00 (work in progress),
March 2008.
[RFC1958] Carpenter, B., "Architectural Principles of the Internet",
RFC 1958, June 1996.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC5961] Ramaiah, A., Stewart, R., and M. Dalal, "Improving TCP's
Robustness to Blind In-Window Attacks", RFC 5961,
August 2010.
[RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport-
Protocol Port Randomization", BCP 156, RFC 6056,
January 2011.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
Roberts, "Issues with IP Address Sharing", RFC 6269,
June 2011.
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[RFC6324] Nakibly, G. and F. Templin, "Routing Loop Attack Using
IPv6 Automatic Tunnels: Problem Statement and Proposed
Mitigations", RFC 6324, August 2011.
[UPnP-IGD]
UPnP Forum, "Universal Plug and Play (UPnP) Internet
Gateway Device (IGD) V 2.0", December 2010,
<http://upnp.org/specs/gw/igd2/>.
Authors' Addresses
Mohamed Boucadair (editor)
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange.com
Satoru Matsushima
Softbank Telecom
Tokyo
Japan
Email: satoru.matsushima@tm.softbank.co.jp
Yiu Lee
Comcast
US
Email: Yiu_Lee@Cable.Comcast.com
Olaf Bonness
Deutsche Telekom
Germany
Email: Olaf.Bonness@telekom.de
Isabel Borges
Portugal Telecom
Portugal
Email: Isabel@ptinovacao.pt
Boucadair, et al. Expires March 3, 2013 [Page 15]
Internet-Draft Solution Motivations August 2012
Gang Chen
China Mobile
53A,Xibianmennei Ave.
Beijing, Xuanwu District 100053
China
Email: chengang@chinamobile.com
Boucadair, et al. Expires March 3, 2013 [Page 16]
