One document matched: draft-jiang-incremental-cgn-00.txt
Network Working Group S. Jiang
Internet Draft D. Guo
Intended status: Informational Huawei Technologies Co., Ltd
Expires: August 29, 2009 B. Carpenter
University of Auckland
March 1, 2009
An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition
draft-jiang-incremental-cgn-00.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on August 29, 2009.
Copyright Notice
Copyright (c) 2009 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Jiang, et al. Expires August 29, 2009 [Page 1]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
Abstract
Global IPv6 deployment was slower than originally expected in the
last ten years. As IPv4 address exhaustion gets closer, the IPv4/IPv6
transition issues become more critical and complicated. Host-based
transition mechanisms are not able to meet the requirements while
most end users are not sufficiently expert to configure or maintain
these transition mechanisms. Carrier Grade NAT with integrated
transition mechanisms can simplify the operation of end users during
the IPv4/IPv6 migration or coexistence period. This document proposes
an incremental Carrier-Grade NAT (CGN) solution for IPv6 transition.
It can provide IPv6 access services for IPv6-enabled end hosts and
IPv4 access services for IPv4 end hosts while remaining most of
legacy IPv4 ISP networks unchanged. It is suitable for the initial
stage of IPv4/IPv6 migration. Unlike CGN alone, it also supports and
encourages transition towards dual-stack or IPv6-only ISP networks.
Table of Contents
1. Introduction................................................3
2. Terminology.................................................4
3. An Incremental CGN Solution..................................4
3.1. Incremental CGN Solution Overview.......................4
3.2. Behaviour of Dual-stack Home Gateway....................5
3.3. Behaviour of Dual-stack Carrier-Grade NAT...............5
3.4. Impact for end hosts and remaining networks.............6
4. Migration towards IPv6 Core Network..........................6
5. Security Considerations......................................6
6. IANA Considerations.........................................7
7. References..................................................7
7.1. Normative References....................................7
7.2. Informative References..................................7
Author's Addresses.............................................9
Jiang, et al. Expires August 29, 2009 [Page 2]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
1. Introduction
Up to now, global IPv6 deployment does not happen as was expected 10
years ago. The progress was much slower than originally expected.
Network providers were hesitant to take the first move while IPv4 was
and is still working well. However, IPv4 address exhaustion is now
confirmed to happen soon. The dynamically-updated IPv4 Address Report
[IPUSAGE] has analyzed this issue. It predicts early 2011 for IANA
unallocated address pool exhaustion and middle 2012 for RIR
unallocated address pool exhaustion. Based on this fact, the Internet
industry appears to have reached consensus that global IPv6
deployment is inevitable and has to be done quite quickly.
IPv4/IPv6 transition issues therefore become more critical and
complicated for the soon-coming global IPv6 deployment. Host-based
transition mechanisms alone are not able to meet the requirements.
They are too complicated for most end users who do not have enough
technical knowledge to configure or maintain these transition
mechanisms. New transition mechanisms with simple user-side operation
are needed.
Carried Grade NAT (CGN) alone creates operational problems, but does
nothing to help IPv4/IPv6 transition. In fact it allows ISPs to delay
the transition, and therefore causes double transition costs (once to
add CGN, and again to support IPv6).
Carrier-Grade NAT that integrates multiple transition mechanisms can
simplify the operation of end user services during the IPv4/IPv6
migration or coexistence period. CGNs are deployed on the network
side and managed/maintained by professionals. On the user side, new
CPE devices may be needed too. They may be provided by network
providers, depending on the specific business model. Dual-stack lite
[DSLite] is a CGN-based solution that supports transition, but it
requires the ISP to upgrade its network to IPv6 immediately. Many
ISPs hesitate to do this as the first step.
This document proposes an incremental CGN solution for IPv6
transition. The solution is similar to DSLite, but the other way
around. Technically, it mainly combines v4-v4 NAT with v6-over-v4
tunnelling functions along with some minor adjustment. It can provide
IPv6 access services for IPv6-enabled end hosts and IPv4 access
services for IPv4 end hosts, while leaving most of legacy IPv4 ISP
networks unchanged. The deployment of this solution does not affect
legacy IPv4 hosts with global IPv4 addresses at all. It is suitable
for the initial stage of IPv4/IPv6 migration. It also supports
transition towards dual-stack or IPv6-only ISP networks.
Jiang, et al. Expires August 29, 2009 [Page 3]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
2. Terminology
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. An Incremental CGN Solution
Most ISP networks are still IPv4. Network providers are starting to
provide IPv6 access services for end users. However, at the initial
stage of IPv4/IPv6 migration, IPv4 connectivity and traffic would be
the majority for ISP networks. ISPs would like to minimize the
changes on their IPv4 networks. Switching the whole ISP network into
IPv6-only would be considered as a radical strategy. Switching the
whole ISP network to dual stack is less radical, but introduces
operational costs and complications.
3.1. Incremental CGN Solution Overview
The incremental CGN solution we propose is illustrated as the
following figure.
+-------------+
|IPv6 Internet|
+-------------+
|
+-----+ +--+ +-------+ +-----+ +--------+
|v4/v6|----|DS|----| IPv4 |----| CGN |---------| IPv4 |
|Host | |HG| |Network| | | | |Internet|
+-----+ +--+ +-------+ +-----+ | +--------+
_ _ _ _ _ _ _ _ _ _ _ +---------------------+
()_6_o_4_ _t_u_n_n_e_l_() | Existing IPv4 hosts |
+---------------------+
Figure 1: Phase 1 of incremental CGN solution with IPv4 ISP network
DS HG = Dual-Stack Home Gateway.
The above figure shows only Phase 1, in which the ISP has not
significantly changed its IPv4 network. This solution enables IPv4
hosts to access the IPv4 Internet and IPv6 hosts to access the IPv6
Internet. A dual stack host can be treated as an IPv4 host when it
uses IPv4 access service and as an IPv6 host when it uses IPv6 access
service. In order to enable IPv4 hosts to access IPv6 Internet and
IPv6 hosts to access IPv4 Internet, NAT-PT [RFC2766, RFC4966] (or its
replacement) can be integrated with CGN. The integration of NAT-PT is
out of scope for this document
Jiang, et al. Expires August 29, 2009 [Page 4]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
Two new types of devices need to be deployed in this solution: a
dual-stack home gateway, which may follow the requirements of [6CPE],
and dual-stack Carrier-Grade NAT. The dual-stack home gateway
integrates IPv4 forwarding and v6-over-v4 tunnelling functions. It
may integrate v4-v4 NAT function, too. The dual-stack CGN integrates
v6-over-v4 tunnelling and carrier-grade v4-v4 NAT functions. Modified
6RD [6RD] technology may be used to support v6-over-v4 tunnelling.
Other tunnelling mechanisms such as ISATAP [RFC5214] could also be
considered, but 6RD appears to fit well and allows re-use of existing
support for 6to4 [RFC3056].
3.2. Behaviour of Dual-stack Home Gateway
When a dual-stack home gateway receives a data packet from an end
host, it firstly checks whether the packet is IPv4 or IPv6. For IPv4
data, the HG can directly forward it if there is no v4-v4 NAT running
on the HG. Or the HG translates packet source address from a HG-scope
private IPv4 address into a CGN-scope private IPv4 address. The HG
should record the v4-v4 address mapping information for inbound
packets, just like normal NAT does.
For IPv6 data, the HG needs to encapsulate the data into an IPv4
tunnel, which sets the dual-stack CGN as another end. Then the HG
sends the new IPv4 packet towards CGN.
The HG should record the mapping information between the tunnel and
the source IPv6 address for inbound packets if HG uplinks to more
than one CGN. Detailed considerations for the use of multiple CGNs by
one HG are for further study.
3.3. Behaviour of Dual-stack Carrier-Grade NAT
When a dual-stack CGN receives a data packet from a dual-stack home
gateway, it firstly checks whether the packet is a normal IPv4 packet
or a v6-over-v4 tunnel packet. For a normal IPv4 packet, the CGN
translates packet source address from a CGN-scope private IPv4
address into a public IPv4 address, and then send it to IPv4 Internet.
The CGN should record the v4-v4 address mapping information for
inbound packets, just like normal NAT does. For a v6-over-v4 tunnel
packet, the CGN needs to decapsulate it into the original IPv6 packet
and then send it to IPv6 Internet. The CGN should record the mapping
information between the tunnel and the source IPv6 address for
inbound packets.
Depending on the deployed location of the CGN, it may use v6-over-v4
tunnels to connect to the IPv6 Internet.
Jiang, et al. Expires August 29, 2009 [Page 5]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
3.4. Impact for end hosts and remaining networks
This solution does not affect the remaining networks at all. Legacy
IPv4 ISP networks and their IPv4 devices remain in use. The existing
IPv4 hosts, shown as the right box in Figure 1, either having global
IPv4 addresses or behind v4-v4 NAT can connect to IPv4 Internet as it
is now.
3.5. Discussion
It should be noted that for IPv4 traffic, this solution inherits all
the problems of CGN (e.g., scaling, and the difficulty of supporting
well-known ports for inbound traffic). Application layer problems
created by double NAT are for further study.
However, for IPv6 traffic, a user behind the DS HG will see normal
IPv6 service. It is strongly recommended that all IPv6 tunnels
support a large MTU, at least 1500 bytes, to avoid fragmentation
problems. This, and the absence of NAT problems for IPv6, will create
an incentive for users and application service providers to prefer
IPv6.
4. Migration towards IPv6 Core Network
When the core network starts transition to IPv6, this solution can
easily be transited into Phase 2, in which the ISP network is either
dual-stack or IPv6-only. For dual-stack ISP networks, dual-stack home
gateways can simply switch off the v6-over-v4 function and forward
both IPv6 and IPv4 traffic directly; dual-stack CGN should only keep
v4-v4 NAT function. For IPv6-only ISP networks, the dual-stack lite
solution, which also has dual-stack home gateway and CGN devices, can
be adopted for Phase 2. The best business model for this solution is
that CPE has integrated the functions for both Phase 1 and 2, and can
automatically detect the change. Then when ISPs decide to switch from
Phase 1 to Phase 2, it may be that only a configuration change or a
minor software update is needed on the CGNs. The DS HG will then
switch automatically to basic dual stack or DSLite mode. The only
impact on the home user will be to receive a different IPv6 prefix.
Note that if the 6RD mechanism is used in Phase 1, the user will most
likely have a /64 prefix during Phase 1, but could get a shorter
prefix such as /56 in Phase 2. This would be an improved service
offering available as a result of the Phase 1 to Phase 2 transition.
5. Security Considerations
Security issues associated with NAT have been documented in [RFC2663]
and [RFC2993].
Jiang, et al. Expires August 29, 2009 [Page 6]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
Further security analysis will be needed to understand double NAT
security issues and tunnel security issues. However, since the tunnel
exists entirely in a single ISP network, between the CPE and the CGN,
the threat model is relatively simple. [RFC4891] describes how to
protect tunnels using IPSec, but it is not clear whether this would
be an important requirement.
The dual-stack home gateway will need to provide basic security for
IPv6 [6CPESec]. Other aspects are described in [RFC4864].
6. IANA Considerations
This draft does not request any IANA action.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations", RFC 2663,
August 1999.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address Translation
- Protocol Translation (NAT-PT)", RFC 2766, February 2000.
[RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993,
November 2000.
[RFC3056] B. Carpenter, K. Moore, "Connection of IPv6 Domains via
IPv4 Clouds", RFC3056, February 2001.
[RFC4864] G. Van de Velde, T. Hain, R. Droms, B. Carpenter, E. Klein,
"Local Network Protection for IPv6", RFC4864, May 2007.
[RFC4891] R. Graveman, "Using IPsec to Secure IPv6-in-IPv4 Tunnels",
RFC4891, May 2007.
[RFC4966] Aoun, C. and E. Davies, "Reasons to Move the Network
Address Translator - Protocol Translator (NAT-PT) to
Historic Status", RFC 4966, July 2007.
Jiang, et al. Expires August 29, 2009 [Page 7]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
[RFC5214] F. Templin, T. Gleeson, and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[DSLite] A. Durand, R. Droms, B. Haberman, J. Woodyatt, "Dual-stack
lite broadband deployments post IPv4 exhaustion", draft-
durand-softwire-dual-stack-lite-01, work in progress.
[IPUSAGE] Huston, G., IPv4 Address Report, March 2009,
http://www.potaroo.net/tools/ipv4/index.html.
[6RD] R. Despres, "IPv6 Rapid Deployment on IPv4 infrastructures
(6rd)", draft-despres-6rd-02, work in progress.
[6CPE] H. Singh, "IPv6 CPE Router Recommendations", draft-wbeebee-
ipv6-cpe-router-03, work in progress.
[6CPESec] J. Woodyatt, "Recommended Simple Security Capabilities in
Customer Premises Equipment for Providing Residential IPv6
Internet Service", draft-ietf-v6ops-cpe-simple-security-03,
work in progress.
Jiang, et al. Expires August 29, 2009 [Page 8]
Internet-Draft draft-jiang-incremental-cgn-00.txt March 2009
Author's Addresses
Sheng Jiang
Huawei Technologies Co., Ltd
KuiKe Building, No.9 Xinxi Rd.,
Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085
P.R. China
Phone: 86-10-82836774
Email: shengjiang@huawei.com
Dayong Guo
Huawei Technologies Co., Ltd
KuiKe Building, No.9 Xinxi Rd.,
Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085
P.R. China
Phone: 86-10-82836284
Email: guoseu@huawei.com
Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland, 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Jiang, et al. Expires August 29, 2009 [Page 9] | PAFTECH AB 2003-2026 | 2026-04-23 05:38:40 |