Network Working Group C. Xie
Internet-Draft Q. Sun
Intended status: Standards Track Q. He
Expires: January 30, 2014 China Telecom
C. Zhou
Huawei Technologies
X. Li
C. Bao
CERNET Center/Tsinghua
University
July 29, 2013
The Approach for IPv4-only users to access IPv6-only Content
draft-sun-behave-v4tov6-01
Abstract
Current approaches can not solve the scenario that the users from
IPv4 Internet to access IPv6-only content. When IPv6 content are
becoming more and more popular, it is important to ensure that IPv6-
only content can be reachable from legacy IPv4-only clients via some
IPv4-only network. This document proposes two approaches for IPv4-
only users to access IPv6-only content. It is designed to cover the
Scenario 2 in [RFC6144].
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
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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 January 30, 2014.
Copyright Notice
Copyright (c) 2013 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
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(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. The NAT46 translator for IPv4 Internet to access IPv6
network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Approach 1: DNS-based solution . . . . . . . . . . . . . . . . 4
5. Approach 2: Redirect-based Solution . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
In [RFC6144], Scenario 2 is an important use case. Not only could
servers move directly to IPv6 without trudging through a difficult
transition period, but they could do so without risk of losing
connectivity with the IPv4-only Internet.
Existing solutions have not solved this scenario well. NAT-
PT[RFC2766]can be used in this scenario, but it requires a tightly
coupled DNS Application Level Gateway (ALG) in the translator, and
have been deprecated by the IETF [RFC4966]. The stateless
translation solution [RFC6219] can work too, but since each IPv6
server will consume one IPv4 public address, it is not suitable to
deploy in situation that operators are running out of IPv4 address.
[RFC6156] can be used for IPv4 client to communicate with IPv6
client. But this requires the IPv4 client and IPv6 client to
implement a TURN client. Therefore, it is not suitable for
C-S(Client-Server) and B-S (Browser-Server) mode.
[I-D.rfvlb-behave-v6-content-for-v4-clients] can work for IPv4-only
user to access IPv6 content. But since it uses private IPv4 address
to mapping the IPv6 server, it can only be used for IPv4 network to
reach IPv6 network.
This document is designed for IPv4 Internet to reach IPv6 network.
There are several requirements in this design:
1.Considering IPv4 address has been a scarce resource, the amount
of public IPv4 addresses consumed by the translator should be less
than that the number of IPv6 servers in the IPv6 network.
2. It should not require extra modifications on the server, e.g.
by using a dynamic port number, implementing TURN client, etc.
In this document, we propose two approaches for this scenario. These
two approaches can make use of existing DNS architecture. The
binding table in these two approaches are static. Therefore, there
will be no dynamic issue as in NAT-PT or DNS cache syncronization.
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].
Terminology defined in [RFC6144] is used extensively in this
document. Besides, this document uses the following terminologies:
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IPv6-converted addresses: IPv4 addresses used to represent IPv6 nodes
in an IPv4 Internet. They have an explicit mapping relationship to
IPv6 addresses.
NAT46: a stateful IPv4/IPv6 translation functionality. It is
consistent with IP/ICMP translation [RFC6145], and can also support
IPv6-converted address selection and binding table maintenance.
3. The NAT46 translator for IPv4 Internet to access IPv6 network
The NAT46 solution is used for IPv4 clients in IPv4 Internet to reach
IPv6 servers (depicted in Figure 1).
------- ------
// \\ Address Pool: // \\
/ \ {210.0.0.0/20, / \
23.0.0.1 | | 213.0.1.0/18...} | | 2001:c61::1
+---------+ | The IPv4 | +-----------------+ | The IPv6 | +--------+
| IPv4 | | Internet | | Translator | | Network | | IPv6 |
| Client |--+ +-| (NAT46) |----+ +--| Server |
+---------+ | | +-----------------+ | | +--------+
\ / Prefix:2001:c68::/96 \ /
\\ // \\ //
------- ------
Figure 1: Overall solution for IPv4 Internet to IPv6 network
In order to achieve the translation initiated from IPv4 side, two
addresses need to be determined by NAT46 translator. The first one
is the IPv6-converted address of the IPv6 server, which is is
selected from the IPv4 address pool configured in NAT46. The second
one is the IPv4-converted address for the IPv4 client, which can be
synthetized using the stateless approach defined in [RFC6052].
In our approach, the mapping relationship between IPv6-converted
address and the IPv6 address for the server is pre-determined in
advance. As a result, the A record in the DNS server for a
particular server is always the same for different IPv4 clients.
4. Approach 1: DNS-based solution
This approach is independent of translated protocol. For
applications without DNS process can not be solved by this approach.
In order to support IPv4 address sharing for multiple IPv6 servers,
one IPv4 address can be shared by multiple servers with different
service ports. If there are too many servers with the same service
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port, the second approach can be used as a complement.
The overall solution is depicted in Figure 3.
------- +---------------+ ------
// \\ | +-----------+ | // \\
/ \ | | DNS | | / \
+---------+ | The IPv4 | | +-----------+ | | The IPv6 | +--------+
| IPv4 | | Internet | | | | Network | | IPv6 |
| Client |--+ +-| +--------+ |--+ +--| Server |
+---------+ | | | | NAT46 | | | | +--------+
\ / | +--------+ | \ /
\\ // +---------------+ \\ //
------- ------
Figure 2: DNS-based approach
It consists of several functionalities:
1.NAT46: This functionality achieves the translation between IPv4
packet and IPv6 packet. It is consistent with [RFC6145]. Besides,
it maintained the binding table including the IPv6 server address,
IPv6-converted address for IPv6 server, and the service port
statically.
2.DNS: The DNS server is configured with the IPv6-converted address
as the A record for IPv6 server.
The workflow of this apporach is as follows:
+--------+ +--------+ +--------+ +--------+
| IPv4 | | DNS | | NAT46 | | IPv6 |
| Client | | | | | | Server |
+--------+ +--------+ +--------+ +--------+
| | | |
|DNS A record query| | |
| ipv6.example.com | | |
|----------------->| | |
| | | |
| return A record | | |
|<-----------------| | |
| IPv4 traffic | Lookup the |
|----------------------------------->| Binding Table |
| | IPv6 Traffic |
| |-------------->|
| IPv4 traffic(Returned) |<--------------|
|<-----------------------------------| |
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Figure 3: Workflow of DNS-based approach
1. An IPv4 client initiates a DNS query for A record (e.g.
ipv6.example.com).
2. DNS receives the query. As it is configured with the IPv6-
converted address in advance, the A record will be returned to the
IPv4 client.
3. IPv4 client sends IPv4 traffic with the returned IPv6-converted
address as the destination address.
4. When the IPv4 traffic arrives at the NAT46, NAT46 extracts the
destination address and destination port in the IPv4 traffic. It
will lookup the binding table maintained in NAT46 and NAT46
translates the IPv4 packet to IPv6 packet according to [RFC6145]. No
port translation will be performed here.
5. The return traffic is treated in the same way.
5. Approach 2: Redirect-based Solution
This approach is designed for HTTP application. It will have a high
address sharing ratio. In HTTP, since the traffic can be redirected
to a different service port, it is able to achieve address sharing
for IPv6 servers by using different ports (denoted as IPv6-converted
port). Therefore, one IPv4 address can support up to thousands of
IPv6 servers in theory.
The overall solution is depicted in Figure 4.
------- +--------------------+ ------
// \\ | +----------------+ | // \\
/ \ | |Redirect Server | | / \
+---------+ | The IPv4 | | +----------------+ | | The IPv6 | +--------+
| IPv4 | | Internet | | | | Network | | IPv6 |
| Client |--+ +-| +------------+ |--+ +--| Server |
+---------+ | | | | NAT46 | | | | +--------+
\ / | +------------+ | \ /
\\ // +--------------------+ \\ //
------- ------
Figure 4: Redirect-based Solution
It consists of several functionalities:
1. NAT46: This functionality is basically the same as the first
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approach, except for the binding table includes IPv6 server address,
IPv6 service port, IPv6-converted address and IPv6-converted port.
2. Redirect Server: A Redirect server is used to redirect traffic to
a different IPv6-converted address and IPv6-converted port. The
redirect server may either store the binding table, or query for the
redirected address and port from NAT46.
The workflow of this apporach is as follows:
+--------+ +--------+ +--------+ +--------+ +--------+
| IPv4 | | DNS | |Redirect| | NAT46 | | IPv6 |
| Client | | | | Server | | | | Server |
+--------+ +--------+ +--------+ +--------+ +--------+
| | | | |
| DNS A request | | | |
| ipv6.example.com | | | |
|----------------->| | | |
| A response with | | | |
| Redirect Ser Addr| | | |
|<-----------------| | | |
| HTTP GET request, with domain name | | |
| in HOST field | Request for | |
|----------------------------------->| IPv4 Dst Addr | Setup mapping |
| |-------------->| table |
|return 302 not found, carry IPv4 dst| | |
|addr in HTTP redirect packet | | |
|<-----------------------------------| | |
| IPv4 HTTP request with new v4 dst addr | |
|--------------------------------------------------->| Translate to IPv6 |
| |------------------>|
| |<------------------|
|<---------------------------------------------------| |
Figure 5: Workflow of Proxy-lite Approach
1. An IPv4 client initiates a DNS query for A record (e.g.
ipv6.example.com).
2. In DNS server, the address of the redirect server is configured
as the A record for ipv6.example.com and returns to the IPv4 client.
3. The IPv4 client sends HTTP GET request. The domain name (e.g.
ipv6.example.com) is carried in HOST field.
4. The redirect server interprets the domain name, and sends the
request to get IPv6-converted address to NAT46 (carrying the address
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of IPv4 client and the destination port). The specific protocol for
the request is now out of scope.
5. NAT46 selects IPv6-converted address and IPv6-converted port by
lookuping the binding table. It will also keep the destination port
in the binding table.
6. NAT46 returns the IPv6-converted address and IPv6-converted port
to redirect server and the redirect server in turn returns IPv6-
converted address in HTTP redirect packet with HTTP error "302 not
found".
7. IPv4 client replaces the destination IPv4 address with the
returned IPv6-converted address. The IPv4 traffic is routed to the
NAT46.
8. extracts the destination address and destination port in the IPv4
traffic. It will lookup the binding table maintained in NAT46 and
NAT46 translates the IPv4 packet to IPv6 packet according to
[RFC6145].
6. IANA Considerations
No requirement on IANA.
7. Acknowledgements
The authors would like to thank Dan Wing, Fred Baker for their review
and comments.
8. References
8.1. Normative References
[I-D.rfvlb-behave-v6-content-for-v4-clients]
Rajtar, B., Farrer, I., Ales, V., Li, X., and C. Bao,
"Framework for accessing IPv6 content for IPv4-only
clients", draft-rfvlb-behave-v6-content-for-v4-clients-01
(work in progress), July 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766,
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February 2000.
[RFC4966] Aoun, C. and E. Davies, "Reasons to Move the Network
Address Translator - Protocol Translator (NAT-PT) to
Historic Status", RFC 4966, July 2007.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6156] Camarillo, G., Novo, O., and S. Perreault, "Traversal
Using Relays around NAT (TURN) Extension for IPv6",
RFC 6156, April 2011.
[RFC6219] Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
China Education and Research Network (CERNET) IVI
Translation Design and Deployment for the IPv4/IPv6
Coexistence and Transition", RFC 6219, May 2011.
8.2. Informative References
Authors' Addresses
Chongfeng Xie
China Telecom
P.R.China
Phone: 86 10 58552116
Email: xiechf@ctbri.com.cn
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Qiong Sun
China Telecom
P.R.China
Phone: 86 10 58552936
Email: sunqiong@ctbri.com.cn
Qi He
China Telecom
P.R.China
Phone: 86 10 58552332
Email: heqi@ctbri.com.cn
Cathy Zhou
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Phone:
Email: cathy.zhou@huawei.com
Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building
Beijing 100084
P.R.China
Phone: +86 10 6278 5983
Email: xing@cernet.edu.cn
Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building
Beijing 100084
P.R.China
Phone: +86 10 6278 5983
Email: congxiao@cernet.edu.cn
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