Softwire Working Group Y. Cui
Internet-Draft Tsinghua University
Intended status: Standards Track Q. Sun
Expires: August 29, 2013 China Telecom
M. Boucadair
France Telecom
T. Tsou
Huawei Technologies
Y. Lee
Comcast
I. Farrer
Deutsche Telekom AG
February 25, 2013
Lightweight 4over6: An Extension to the DS-Lite Architecture
draft-cui-softwire-b4-translated-ds-lite-11
Abstract
DS-Lite [RFC6333] describes an architecture for transporting IPv4
packets over an IPv6 network. This document specifies an extension
to DS-Lite called Lightweight 4over6 which moves the Network Address
Translation function from the DS-Lite AFTR to the B4, removing the
requirement for a Carrier Grade NAT function in the AFTR. This
reduces the amount of centralized state that must be held to a per-
subscriber level. In order to delegate the NAPT function and make
IPv4 Address sharing possible, port-restricted IPv4 addresses are
allocated to the B4s.
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
working documents as Internet-Drafts. The list of current Internet-
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 19, 2013.
Copyright Notice
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Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Lightweight 4over6 Architecture . . . . . . . . . . . . . . . 5
5. Lightweight B4 Behavior . . . . . . . . . . . . . . . . . . . 7
5.1. Lightweight B4 Provisioning . . . . . . . . . . . . . . . 7
5.2. Lightweight B4 Data Plane Behavior . . . . . . . . . . . . 8
6. Lightweight AFTR Behavior . . . . . . . . . . . . . . . . . . 9
6.1. Binding Table Maintenance . . . . . . . . . . . . . . . . 9
6.2. lwAFTR Data Plane Behavior . . . . . . . . . . . . . . . . 10
7. Provisioning of IPv4 address and Port Set . . . . . . . . . . 11
8. ICMP Processing . . . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. Author List . . . . . . . . . . . . . . . . . . . . . . . . . 13
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 16
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
13.1. Normative References . . . . . . . . . . . . . . . . . . . 16
13.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
Dual-Stack Lite (DS-Lite, [RFC6333]) defines a model for providing
IPv4 access over an IPv6 network using two well-known technologies:
IP in IP [RFC2473] and Network Address Translation (NAT). The DS-
Lite architecture defines two major functional elements as follows:
Basic Bridging BroadBand element: A B4 element is a function
implemented on a dual-stack capable
node, either a directly connected
device or a CPE, that creates a
tunnel to an AFTR.
Address Family Transition Router: An AFTR element is the combination
of an IPv4-in-IPv6 tunnel endpoint
and an IPv4-IPv4 NAT implemented on
the same node.
As the AFTR performs the centralized NAT44 function, it dynamically
assigns public IPv4 addresses and ports to requesting host's traffic
(as described in [RFC3022]). To achieve this, the AFTR must
dynamically maintain per-flow state in the form of active NAPT
sessions. For service providers with a large number of B4 clients,
the size and associated costs for scaling the AFTR can quickly become
prohibitive. It can also place a large NAPT logging overhead upon
the service provider in countries where legal requirements mandate
this.
This document describes a mechanism called Lightweight 4 over 6
(lw4o6), which provides a solution for these problems. By relocating
the NAPT functionality from the centralized AFTR to the distributed
B4s, a number of benefits can be realised:
o NAPT44 functionality is already widely supported and used in
today's CPE devices. Lw4o6 uses this to provide private<->public
NAPT44, meaning that the service provider does not need a
centralized NAT44 function.
o The amount of state that must be maintained centrally in the AFTR
can be reduced from per-flow to per-subscriber. This reduces the
amount of resources (memory and processing power) necessary in the
AFTR.
o The reduction of maintained state results in a greatly reduced
logging overhead on the service provider.
Operator's IPv6 and IPv4 addressing architectures remain independent
of each other. Therefore, flexible IPv4/IPv6 addressing schemes can
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be deployed.
Lightweight 4over6 provides a solution for a hub-and-spoke softwire
architecture only. It does not offer direct, meshed IPv4
connectivity between subscribers without packets traversing the AFTR.
If this type of meshed interconnectivity is required,
[I-D.ietf-softwire-map] provides a suitable solution.
The tunneling mechanism remains the same for DS-Lite and Lightweight
4over6. This document describes the changes to DS-Lite that are
necessary to implement Lightweight 4over6. These changes mainly
concern the configuration parameters and provisioning method
necessary for the functional elements.
Lightweight 4over6 features keeping per-subscriber state in the
service provider's network. It is categorized as Binding approach in
[I-D.bfmk-softwire-unified-cpe] which defines a unified IPv4-in-IPv6
Softwire CPE.
This document is an extended case, which covers address sharing for
[I-D.ietf-softwire-public-4over6]. It is also a variant of A+P
called Binding Table Mode (see Section 4.4 of [RFC6346]).
This document focuses on architectural considerations and
particularly on the expected behavior of the involved functional
elements and their interfaces. Deployment-specific issues are
discussed in a companion document. As such, discussions about
redundancy and provisioning policy are out of scope.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Terminology
The document defines the following terms:
Lightweight 4over6 (lw4o6): Lightweight 4over6 is an IPv4-over-IPv6
hub and spoke mechanism, which extends
DS-Lite by moving the IPv4 translation
(NAPT44) function from the AFTR to the
B4.
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Lightweight B4 (lwB4): A B4 element (Basic Bridging BroadBand
element [RFC6333]), which supports
Lightweight 4over6 extensions. An lwB4
is a function implemented on a dual-
stack capable node, (either a directly
connected device or a CPE), that
supports port-restricted IPv4 address
allocation, implements NAPT44
functionality and creates a tunnel to
an lwAFTR
Lightweight AFTR (lwAFTR): An AFTR element (Address Family
Transition Router element [RFC6333]),
which supports Lightweight 4over6
extension. An lwAFTR is an IPv4-in-
IPv6 tunnel endpoint which maintains
per-subscriber address binding only and
does not perform a NAPT44 function.
Restricted Port-Set: A non-overlapping range of allowed
external ports allocated to the lwB4 to
use for NAPT44. Source ports of IPv4
packets sent by the B4 must belong to
the assigned port-set. The port set is
used for all port aware IP protocols
(TCP, UDP, SCTP etc.)
Port-restricted IPv4 Address: A public IPv4 address with a restricted
port-set. In Lightweight 4over6,
multiple B4s may share the same IPv4
address, however, their port-sets must
be non-overlapping.
Throughout the remainder of this document, the terms B4/AFTR should
be understood to refer specifically to a DS-Lite implementation. The
terms lwB4/lwAFTR refer to a Lightweight 4over6 implementation.
4. Lightweight 4over6 Architecture
The Lightweight 4over6 architecture is functionally similar to DS-
Lite. lwB4s and an lwAFTR are connected through an IPv6-enabled
network. Both approaches use an IPv4-in-IPv6 encapsulation scheme to
deliver IPv4 connectivity services. The following figure shows the
data plane with main functional change between DS-Lite and lw4o6:
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+--------+ +---------+ IPv4-in-IPv6 +------+ +-------------+
|IPv4 LAN|---|lwB4/NAPT|===================|lwAFTR|------|IPv4 Internet|
+--------+ +---------+ +------+ +-------------+
^ |
+--------------------------+
NAPT function relocated
to lwB4 in lw4o6
Figure 1 Lightweight 4over6 Data Plane Overview
There are three main components in the Lightweight 4over6
architecture:
o The lwB4, which performs the NAPT function and encapsulation/
de-capsulation IPv4/IPv6.
o The lwAFTR, which performs the encapsulation/de-capsulation IPv4/
IPv6.
o The provisioning system, which tells the lwB4 which IPv4 address
and port set to use.
The lwB4 differs from a regular B4 in that it now performs the NAPT
functionality. This means that it needs to be provisioned with the
public IPv4 address and port set it is allowed to use. This
information is provided though a provisioning mechanism such as DHCP,
PCP or TR-69.
The lwAFTR needs to know the binding between the IPv6 address of each
subscriber and the IPv4 address and port set allocated to that
subscriber. This information is used to perform ingress filtering
upstream and encapsulation downstream. Note that this is per-
subscriber state as opposed to per-flow state in the regular AFTR
case.
The consequence of this architecture is that the information
maintained by the provisioning mechanism and the one maintained by
the lwAFTR MUST be synchronized (See figure 2). The details of this
synchronization depend on the exact provisioning mechanism and will
be discussed in a companion draft.
The solution specified in this document allows to assign either a
full IPv4 address or shared IPv4 address to requesting CPEs.
[I-D.ietf-softwire-public-4over6] provides a mechanism supporting to
assign a full IPv4 address only, which could be referred to in this
case.
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+------------+
/-------|Provisioning|<-------\
| +------------+ |
| |
V V
+--------+ +---------+ IPv4/IPv6 +------+ +-------------+
|IPv4 LAN|---|lwB4/NAPT|===================|lwAFTR|------|IPv4 Internet|
+--------+ +---------+ +------+ +-------------+
Figure 2 Lightweight 4over6 Provisioning Synchronization
5. Lightweight B4 Behavior
5.1. Lightweight B4 Provisioning
With DS-Lite, the B4 element only needs to be configured with a
single DS-Lite specific parameter so that it can set up the softwire
(the IPv6 address of the AFTR). Its IPv4 address can be taken from
the well-known range 192.0.0.0/29.
In lw4o6, due to the distributed nature of the NAPT function, a
number of lw4o6 specific configuration parameters must be provisioned
to the lwB4. These are:
o IPv6 Address for the lwAFTR
o IPv4 External (Public) Address for NAPT44
o Restricted port-set to use for NAPT44
An IPv6 address from an assigned prefix is also required for the lwB4
to use as the encapsulation source address for the softwire.
Normally, this is the lwB4's globally unique WAN interface address
which can be obtained via an IPv6 address allocation procedure such
as SLAAC, DHCPv6 or manual configuration.
In the event that the lwB4's encapsulation source address is changed
for any reason (such as the DHCPv6 lease expiring), the lwB4's
dynamic provisioning process must be re-initiated.
For learning the IPv6 address of the lwAFTR, the lwB4 SHOULD
implement the method described in section 5.4 of [RFC6333] and
implement the DHCPv6 option defined in [RFC6334]. Other methods of
learning this address are also possible.
An lwB4 MUST support dynamic port-restricted IPv4 address
provisioning. The potential port set algorithms are described in
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[I-D.sun-dhc-port-set-option], and Section 5.1 of
[I-D.ietf-softwire-map]. Several different mechanisms can be used
for provisioning the lwB4 with its port-restricted IPv4 address such
as: DHCPv4, DHCPv6, PCP and PPP. Some alternatives are mentioned in
Section 7 of this document.
In this document, lwB4 can be a binding mode CPE. Its provisioning
method is RECOMMENDED to follow that is specified in section 3.3 of
[I-D.bfmk-softwire-unified-cpe], which will evolve to reflect the
consensus from DHC Working Group.
In the event that the lwB4 receives and ICMPv6 error message (type 1,
code 5) originating from the lwAFTR, the lwB4 SHOULD interpret this
to mean that no matching entry in the lwAFTR's binding table has been
found. The lwB4 MAY then re-initiate the dynamic port-restricted
provisioning process. The lwB4's re-initiation policy SHOULD be
configurable.
The DNS considerations described in Section 5.5 and Section 6.4 of
[RFC6333] SHOULD be followed.
5.2. Lightweight B4 Data Plane Behavior
Several sections of [RFC6333] provide background information on the
B4's data plane functionality and MUST be implemented by the lwB4 as
they are common to both solutions. The relevant sections are:
5.2. Encapsulation Covering encapsulation and de-
capsulation of tunneled traffic
5.3. Fragmentation and Reassembly Covering MTU and fragmentation
considerations (referencing
[RFC2473])
7.1. Tunneling Covering tunneling and traffic
class mapping between IPv4 and IPv6
(referencing [RFC2473] and
[RFC4213])
The lwB4 element performs IPv4 address translation (NAPT44) as well
as encapsulation and de-capsulation. It runs standard NAPT44
[RFC3022] using the allocated port-restricted address as its external
IPv4 address and port numbers.
The lwB4 should behave as is depicted in (2.2) of section 3.2 of
[I-D.bfmk-softwire-unified-cpe] when it starts up. The working flow
of the lwB4 is illustrated with figure 3.
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+-------------+
| lwB4 |
+--------+ IPv4 |------+------| IPv4-in-IPv6 +----------+
|IPv4 LAN|------->| |Encap.|-------------->|Configured|
| |<-------| NAPT | or |<--------------| lwAFTR |
+--------+ | |Decap.| +----------+
+------+------+
Figure 3 Working Flow of the lwB4
Internally connected hosts source IPv4 packets with an [RFC1918]
address. When the lwB4 receives such an IPv4 packet, it performs a
NAPT44 function on the source address and port by using the public
IPv4 address and a port number from the allocated port-set. Then, it
encapsulates the packet with an IPv6 header. The destination IPv6
address is the lwAFTR's IPv6 address and the source IPv6 address is
the lwB4's IPv6 tunnel endpoint address. Finally, the lwB4 forwards
the encapsulated packet to the configured lwAFTR.
When the lwB4 receives an IPv4-in-IPv6 packet from the lwAFTR, it de-
capsulates the IPv4 packet from the IPv6 packet. Then, it performs
NAPT44 translation on the destination address and port, based on the
available information in its local NAPT44 table.
The lwB4 is responsible for performing ALG functions (e.g., SIP,
FTP), and other NAPT traversal mechanisms (e.g., UPnP, NAPT-PMP,
manual binding configuration, PCP) for the internal hosts. This
requirement is typical for NAPT44 gateways available today.
It is possible that a lwB4 is co-located in a host. In this case,
the functions of NAPT44 and encapsulation/de-capsulation are
implemented inside the host.
6. Lightweight AFTR Behavior
6.1. Binding Table Maintenance
The lwAFTR maintains an address binding table containing the binding
between the lwB4's IPv6 address, the allocated IPv4 address and
restricted port-set. Unlike the DS-Lite extended binding table
defined in section 6.6 of [RFC6333] which is a 5-tuple NAT table,
each entry in the Lightweight 4over6 binding table contains the
following 3-tuples:
o IPv6 Address for a single lwB4
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o Public IPv4 Address
o Restricted port-set
The entry has two functions: the IPv6 encapsulation of inbound IPv4
packets destined to the lwB4 and the validation of outbound IPv4-in-
IPv6 packets received from the lwB4 for de-capsulation.
The lwAFTR does not perform NAPT and so does not need session
entries.
The lwAFTR MUST synchronize the binding information with the port-
restricted address provisioning process. If the lwAFTR does not
participate in the port-restricted address provisioning process, the
binding MUST be synchronized through other methods (e.g. out-of-band
static update).
If the lwAFTR participates in the port-restricted provisioning
process, then its binding table MUST be created as part of this
process.
For all provisioning processes, the lifetime of binding table entries
MUST be synchronized with the lifetime of address allocations.
6.2. lwAFTR Data Plane Behavior
Several sections of [RFC6333] provide background information on the
AFTR's data plane functionality and MUST be implemented by the lwAFTR
as they are common to both solutions. The relevant sections are:
6.2. Encapsulation Covering encapsulation and de-
capsulation of tunneled traffic
6.3. Fragmentation and Reassembly Fragmentation and re-assembly
considerations (referencing
[RFC2473])
7.1. Tunneling Covering tunneling and traffic
class mapping between IPv4 and IPv6
(referencing [RFC2473] and
[RFC4213])
When the lwAFTR receives an IPv4-in-IPv6 packet from an lwB4, it de-
capsulates the IPv6 header and verifies the source addresses and port
in the binding table. If both the source IPv4 and IPv6 addresses
match a single entry in the binding table and the source port in the
allowed port-set for that entry, the lwAFTR forwards the packet to
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the IPv4 destination.
If no match is found (e.g., no matching IPv4 address entry, port out
of range, etc.), the lwAFTR MUST discard or implement a policy (such
as redirection) on the packet. An ICMPv6 type 1, code 5 (source
address failed ingress/egress policy) error message MAY be sent back
to the equesting lwB4. The ICMP policy SHOULD be configurable.
When the lwAFTR receives an inbound IPv4 packet, it uses the IPv4
destination address and port to lookup the destination lwB4's IPv6
address in its binding table. If a match is found, the lwAFTR
encapsulates the IPv4 packet. The source is the lwAFTR's IPv6
address and the destination is the lwB4's IPv6 address from the
matched entry. Then, the lwAFTR forwards the packet to the lwB4
natively over the IPv6 network.
If no match is found, the lwAFTR MUST discard the packet. An ICMPv4
type 3, code 1 (Destination unreachable, host unreachable) error
message MAY be sent back. The ICMP policy SHOULD be configurable.
The lwAFTR MUST support hairpinning of traffic between two lwB4s, by
performing de-capsulation and re-encapsulation of packets. The
hairpinning policy MUST be configurable.
7. Provisioning of IPv4 address and Port Set
There are several dynamically provisioning protocols for IPv4 address
and port set. These protocols MAY be implemented. Some possible
alternatives include:
o DHCP: Extending DHCP protocol MAY be used for the provisioning
[I-D.ietf-dhc-dhcpv4-over-ipv6] [I-D.ietf-softwire-map-dhcp].
o PCP[I-D.ietf-pcp-base]: a lwB4 MAY use [I-D.tsou-pcp-natcoord] to
retrieve a restricted IPv4 address and a set of ports.
In a Lightweight 4over6 domain, the same provisioning mechanism MUST
be enabled in the lwB4s, the AFTRs and the provisioning server.
DHCP-based provisioning mechanism (DHCPv4/DHCPv6) is RECOMMENDED in
this document. The provisioning mechanism for port-restricted IPv4
address will evolve according to the consensus from DHC Working
Group.
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8. ICMP Processing
ICMP does not work in an address sharing environment without special
handling [RFC6269]. Due to the port-set style address sharing,
Lightweight 4over6 requires specific ICMP message handling not
required by DS-Lite.
The following behavior SHOULD be implemented by the lwAFTR to provide
ICMP error handling and basic remote IPv4 service diagnostics for a
port restricted CPE: for inbound ICMP messages, the lwAFTR MAY behave
in two modes:
Either:
1. Check the ICMP Type field.
2. If the ICMP type is set to 0 or 8 (echo reply or request), then
the lwAFTR MUST take the value of the ICMP identifier field as
the source port, and use this value to lookup the binding table
for an encapsulation destination. If a match is found, the
lwAFTR forwards the ICMP packet to the IPv6 address stored in the
entry; otherwise it MUST discard the packet.
3. If the ICMP type field is set to any other value, then the lwAFTR
MUST use the method described in REQ-3 of [RFC5508] to locate the
source port within the transport layer header in ICMP packet's
data field. The destination IPv4 address and source port
extracted from the ICMP packet are then used to make a lookup in
the binding table. If a match is found, it MUST forward the ICMP
reply packet to the IPv6 address stored in the entry; otherwise
it MUST discard the packet.
Or:
o Discard all inbound ICMP messages.
The ICMP policy SHOULD be configurable.
The lwB4 SHOULD implement the requirements defined in [RFC5508] for
ICMP forwarding. For ICMP echo request packets originating from the
private IPv4 network, the lwB4 SHOULD implement the method described
in [RFC6346] and use an available port from its port-set as the ICMP
Identifier.
For both the lwAFTR and the lwB4, ICMPv6 MUST be handled as described
in [RFC2473].
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9. Security Considerations
As the port space for a subscriber shrinks due to address sharing,
the randomness for the port numbers of the subscriber is decreased
significantly. This means it is much easier for an attacker to guess
the port number used, which could result in attacks ranging from
throughput reduction to broken connections or data corruption.
The port-set for a subscriber can be a set of contiguous ports or
non-contiguous ports. Contiguous port-sets do not reduce this
threat. However, with non-contiguous port-set (which may be
generated in a pseudo-random way [RFC6431]), the randomness of the
port number is improved, provided that the attacker is outside the
Lightweight 4over6 domain and hence does not know the port-set
generation algorithm.
More considerations about IP address sharing are discussed in Section
13 of [RFC6269], which is applicable to this solution.
10. IANA Considerations
This document does not include an IANA request.
11. Author List
The following are extended authors who contributed to the effort:
Jianping Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-62785983
Email: jianping@cernet.edu.cn
Peng Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-62785822
Email: pengwu.thu@gmail.com
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Qi Sun
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-62785822
Email: sunqi@csnet1.cs.tsinghua.edu.cn
Chongfeng Xie
China Telecom
Room 708, No.118, Xizhimennei Street
Beijing 100035
P.R.China
Phone: +86-10-58552116
Email: xiechf@ctbri.com.cn
Xiaohong Deng
France Telecom
Email: xiaohong.deng@orange.com
Cathy Zhou
Huawei Technologies
Section B, Huawei Industrial Base, Bantian Longgang
Shenzhen 518129
P.R.China
Email: cathyzhou@huawei.com
Alain Durand
Juniper Networks
1194 North Mathilda Avenue
Sunnyvale, CA 94089-1206
USA
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Email: adurand@juniper.net
Reinaldo Penno
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: repenno@cisco.com
Alex Clauberg
Deutsche Telekom AG
GTN-FM4
Landgrabenweg 151
Bonn, CA 53227
Germany
Email: axel.clauberg@telekom.de
Lionel Hoffmann
Bouygues Telecom
TECHNOPOLE
13/15 Avenue du Marechal Juin
Meudon 92360
France
Email: lhoffman@bouyguestelecom.fr
Maoke Chen
FreeBit Co., Ltd.
13F E-space Tower, Maruyama-cho 3-6
Shibuya-ku, Tokyo 150-0044
Japan
Email: fibrib@gmail.com
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12. Acknowledgement
The authors would like to thank Ole Troan, Ralph Droms and Suresh
Krishnan for their comments and feedback.
This document is a merge of three documents:
[I-D.cui-softwire-b4-translated-ds-lite], [I-D.zhou-softwire-b4-nat]
and [I-D.penno-softwire-sdnat].
13. References
13.1. Normative References
[I-D.bfmk-softwire-unified-cpe]
Boucadair, M. and I. Farrer, "Unified IPv4-in-IPv6
Softwire CPE", draft-bfmk-softwire-unified-cpe-02 (work in
progress), January 2013.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
January 2001.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC5508] Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT
Behavioral Requirements for ICMP", BCP 148, RFC 5508,
April 2009.
[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-
Cui, et al. Expires August 19, 2013 [Page 16]
Internet-Draft B4-translated DS-Lite February 2013
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, August 2011.
[RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the
IPv4 Address Shortage", RFC 6346, August 2011.
[RFC6431] Boucadair, M., Levis, P., Bajko, G., Savolainen, T., and
T. Tsou, "Huawei Port Range Configuration Options for PPP
IP Control Protocol (IPCP)", RFC 6431, November 2011.
13.2. Informative References
[I-D.cui-softwire-b4-translated-ds-lite]
Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the DS-Lite
Architecture", draft-cui-softwire-b4-translated-ds-lite-10
(work in progress), February 2013.
[I-D.ietf-dhc-dhcpv4-over-ipv6]
Cui, Y., Wu, P., Wu, J., and T. Lemon, "DHCPv4 over IPv6
Transport", draft-ietf-dhc-dhcpv4-over-ipv6-05 (work in
progress), September 2012.
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)",
draft-ietf-pcp-base-29 (work in progress), November 2012.
[I-D.ietf-softwire-map]
Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S., and
T. Murakami, "Mapping of Address and Port with
Encapsulation (MAP)", draft-ietf-softwire-map-04 (work in
progress), February 2013.
[I-D.ietf-softwire-map-dhcp]
Mrugalski, T., Troan, O., Dec, W., Bao, C.,
leaf.yeh.sdo@gmail.com, l., and X. Deng, "DHCPv6 Options
for Mapping of Address and Port",
draft-ietf-softwire-map-dhcp-03 (work in progress),
February 2013.
[I-D.ietf-softwire-public-4over6]
Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public
IPv4 over IPv6 Access Network",
Cui, et al. Expires August 19, 2013 [Page 17]
Internet-Draft B4-translated DS-Lite February 2013
draft-ietf-softwire-public-4over6-04 (work in progress),
October 2012.
[I-D.penno-softwire-sdnat]
Penno, R., Durand, A., Hoffmann, L., and A. Clauberg,
"Stateless DS-Lite", draft-penno-softwire-sdnat-02 (work
in progress), March 2012.
[I-D.sun-dhc-port-set-option]
Sun, Q., Lee, Y., Sun, Q., Bajko, G., and M. Boucadair,
"Dynamic Host Configuration Protocol (DHCP) Option for
Port Set Assignment", draft-sun-dhc-port-set-option-00
(work in progress), October 2012.
[I-D.tsou-pcp-natcoord]
Sun, Q., Boucadair, M., Deng, X., Zhou, C., Tsou, T., and
S. Perreault, "Using PCP To Coordinate Between the CGN and
Home Gateway", draft-tsou-pcp-natcoord-09 (work in
progress), November 2012.
[I-D.zhou-softwire-b4-nat]
Zhou, C., Boucadair, M., and X. Deng, "NAT offload
extension to Dual-Stack lite",
draft-zhou-softwire-b4-nat-04 (work in progress),
October 2011.
Authors' Addresses
Yong Cui
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-62603059
Email: yong@csnet1.cs.tsinghua.edu.cn
Qiong Sun
China Telecom
Room 708, No.118, Xizhimennei Street
Beijing 100035
P.R.China
Phone: +86-10-58552936
Email: sunqiong@ctbri.com.cn
Cui, et al. Expires August 19, 2013 [Page 18]
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Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Tina Tsou
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1-408-330-4424
Email: tena@huawei.com
Yiu L. Lee
Comcast
One Comcast Center
Philadelphia, PA 19103
USA
Email: yiu_lee@cable.comcast.com
Ian Farrer
Deutsche Telekom AG
GTN-FM4,Landgrabenweg 151
Bonn, NRW 53227
Germany
Email: ian.farrer@telekom.de
Cui, et al. Expires August 19, 2013 [Page 19]
