Network Working Group C. Bao
Internet-Draft X. Li
Intended status: Informational Y. Zhai
Expires: April 20, 2018 W. Shang
CERNET Center/Tsinghua
University
October 17, 2017
dIVI: Dual-Stateless IPv4/IPv6 Translation
draft-xli-behave-divi-08
Abstract
This document presents the concepts and the implementations of
address-sharing dual-stateless IPv4/IPv6 translation (dIVI).
The dIVI is an extension of 1:1 stateless IPv4/IPv6 translation with
features of IPv4 address sharing and dual translation. The major
benefits of those extensions are using public IPv4 addresses more
effectively and removing the requirements of DNS64 and ALG, without
loosing the stateless, end-to-end address transparency and
bidirectional-initiated communications.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 20, 2018.
Copyright Notice
Copyright (c) 2017 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Port Mapping Algorithm and Address Format Extension . . . . . 5
4.1. Port Mapping Algorithm . . . . . . . . . . . . . . . . . . 5
4.2. Address Format Extensions . . . . . . . . . . . . . . . . 6
4.3. Stateless Translation Algorithm with Address Sharing . . . 7
4.4. Partial-state Translation Algorithm with Address
Sharing . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Dual Stateless Translation . . . . . . . . . . . . . . . . . . 7
5.1. Header Translation and MTU Handling . . . . . . . . . . . 8
5.2. Port Mapping Algorithm in CPE . . . . . . . . . . . . . . 8
6. Implementation Considerations . . . . . . . . . . . . . . . . 8
6.1. Host implementation . . . . . . . . . . . . . . . . . . . 9
6.2. Port Mapping in the Core Translator . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Address Format and Workflow Examples . . . . . . . . 11
A.1. The address-sharing host on an IPv6 network initiates
communication . . . . . . . . . . . . . . . . . . . . . . 12
A.2. A host in the IPv4 Internet initiates communication . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
The experiences for the IPv6 deployment in the past 10 years strongly
indicate that for a successful transition, the communication between
IPv4 and IPv6 address families should be supported.
Recently, the stateless and stateful IPv4/IPv6 translation methods
are developed and became the IETF standards. The original stateless
IPv4/IPv6 translation (stateless 1:1 IVI) is scalable, maintains the
end-to-end address transparency and support both IPv6 initiated and
IPv4 initiated communications [RFC6052], [RFC6144], [RFC6145],
[RFC6147], [RFC6219]. But it can not use the IPv4 addresses
effectively. The stateful IPv4/IPv6 translation can share the IPv4
addresses among IPv6 hosts, but it only supports IPv6 initiated
communication [RFC6052], [RFC6144], [RFC6145], [RFC6146], [RFC6147].
In addition, both stateless and stateful IPv4/IPv6 translation
technologies require the application layer gateway (ALG) for the
applications which embed IP address literals.
In this document, we present concepts and the implementations of the
dual-stateless IPv4/IPv6 translation (dIVI). The dIVI can solve the
IPv4 address sharing and the ALG problems mentioned above, though
still keeps the stateless, end-to-end address transparency and
supporting of both IPv6 initiated and IPv4 initiated communications.
The dIVI is in the family of stateless IPv4/IPv6 translation, along
with IVI and dIVI-PD [I-D.xli-behave-divi-pd]. These techniques are
used for the following scenarios with second translation extension
defined in [RFC6144].
o Scenario 1: IPv4 hosts via an IPv6 network to the IPv4 Internet.
o Scenario 2: The IPv4 Internet via an IPv6 network to IPv4 hosts.
o Scenario 5: An IPv6 network via an IPv4 network to IPv4 hosts.
o Scenario 6: IPv4 hosts via an IPv4 network to an IPv6 network.
2. Applicability
The address sharing dual stateless IPv4/IPv6 translation (dIVI) is
shown in the following figure.
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----- ------
.-|CPE.0|---|Host.0|
/ ----- ------
------ ----- |
/ The \ ------ / An \ | ----- ------
| IPv4 |--| 1:N |---| IPv6 |------|CPE.1|---|Host.1|
\Internet/ | XLAT | \Network/ | ----- ------
------ ------ ----- |
|\ ----- ------
| -|CPE.2|---|Host.2|
| ----- ------
| ......
\ ----- ------
-|CPE.K|---|Host.K|
----- ------
......
Figure 1: dIVI
Where
o The 1:N XLAT (first translator) is the IPv4/IPv6 translator
perform stateless 1:N translation between the IPv4 Internet and an
IPv6 network.
o The CPE.0 to CPE.K (second translators) are 1:1 IPv6/IPv4
translators/IPv6 routers which also perform port mapping function
for Host.x when it is communicating with the IPv4 Internet with
IPv4 address sharing.
o The Host.1 to Host.N are the dual-stack hosts.
The IPv6 network routes the IPv6 more specific routes of the IPv4-
translatable addresses (longer than /64) defined in Section 5 of this
document to corresponding CPEs. In the case of prefix delegation
(shorter than /64), the dual stateless IPv4/IPv6 translation with
prefix delegation (dIVI-pd) defined in [I-D.xli-behave-divi-pd] can
be used.
3. Terminologies
This document uses the terminologies defined in [RFC6144].
The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].
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4. Port Mapping Algorithm and Address Format Extension
4.1. Port Mapping Algorithm
The dual stateless IPv4/IPv6 translation (dIVI) uses the port mapping
algorithm defined in [I-D.bcx-behave-address-fmt-extension].
For given sharing ratio (R) and the maximum number of continue ports
(M), the generalized modulus algorithm is defined as
1. The port number (P) of a given PSID (K) is composed of
P = R*M*j + M*K + i
Where
o PSID: K=0 to R-1
o Port range index: j = (1024/M)/R to ((65536/M)/R)-1, if the
well-known port numbers (0-1023) are excluded.
o Port continue index: i=0 to M-1
2. The PSID (K) of a given port number (P) is determined by
K = (floor(P/M)) % R
Where
o % is modular operator
o floor(arg) is a function returns the largest integer not
greater than arg
3. The well-known port number (0-1023) can be used, if additional
port mapping rule is defined.
For example, for R=128, M=4
Port range-1 | Port rang-2 | Port
-------------------------------------------------------------------
PSID=0 | 1024, 1025, 1026, 1027, | 1536, 1537, 1538, 1539, | 2048
PSID=1 | 1028, 1029, 1030, 1031, | 1540, 1541, 1542, 1543, | ....
PSID=2 | 1032, 1033, 1034, 1035, | 1544, 1545, 1546, 1547, | ....
PSID=3 | 1036, 1037, 1038, 1039, | 1548, 1549, 1550, 1551, | ....
...
PSID=127 | 1532, 1533, 1534, 1535, | 2044, 2045, 2046, 2047, | ....
Figure 2: Example
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4.2. Address Format Extensions
The dual stateless IPv4/IPv6 translation (dIVI) uses the address
format extension defined in [I-D.bcx-behave-address-fmt-extension].
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PL| 0-------------32--40--48--56--64--72--80--88--96--104-112-120-|
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|32| prefix |v4(32) | u | PSID | 0 | Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|40| prefix |v4(24) | u |(8)| PSID | 0 | Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|48| prefix |v4(16) | u | (16) | PSID | 0 | Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|56| prefix |(8)| u | v4(24) | PSID | 0 | Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|64| prefix | u | v4(32) |PSID |0| Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 3: Address Format
Where PL designates the prefix length.
The PSID prefix length (Q) is encoded in the last octet (bits 120-
127) to indicate the number of ports can be used. When Q=0, the
extended address format will become the address format defined in
[RFC6052]. The relations between Q, the sharing ratio (R), the
maximum continue port range (M) and the number of ports can be shown
in the following figure.
Q Ratio | Maximum M | # of Ports
------------------------------------------
0 1:1 65,536 65,536
1 1:2 32,786 32,786
2 1:4 16,384 16,384
3 1:8 8,192 8,192
4 1:16 4,096 4,096
5 1:32 2,048 2,048
6 1:64 1,024 1,024
7 1:128 512 512
8 1:256 256 256
9 1:512 128 128
10 1:1,024 64 64
11 1:2,048 32 32
12 1:4,096 16 16
------------------------------------------
Figure 4: Port Range
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4.3. Stateless Translation Algorithm with Address Sharing
For the stateless translation, the IPv6 nodes are required to follow
the port number range defined by the extended IPv4-translatable
address format when communicating with the IPv4 Internet. The port
number handling algorithm is:
o If the packets are from the IPv4 Internet to an IPv6 network, the
IPv4 source addresses are translated to the IPv4-converted
addresses and the source port numbers are unchanged before and
after translation; the IPv4 destination addresses are translated
to the extended IPv4-translatable addresses based on the
destination port number and the destination port numbers are
unchanged before and after translation. Note that this means that
only a specific IPv6 node can receive the packets for a specific
port number.
o If the packets are from an IPv6 network to the IPv4 Internet, the
IPv6 source addresses and the source port numbers are checked, if
the source port number matches the port number range defined by
the extended IPv4-translatable address format, the IPv6 source
addresses (which are the IPv4-translatable addresses) are
translated to the IPv4 addresses and the source port numbers are
unchanged before and after translation; the destination IPv6
addresses (which are the IPv4-converted addresses) are translated
to the IPv4 destination addresses and the destination port numbers
are unchanged before and after translation. However, if the
source port number does not match the port number range defined by
the extended IPv4-translatable address format, the packets will be
dropped.
4.4. Partial-state Translation Algorithm with Address Sharing
Stateless translation requires that IPv6 nodes generate source port
number in the range defined by the extended IPv4-translatable
address. If this condition does not hold, the partial-state
translation algorithm can be used, which can map the random source
port number to the extended IPv4-translatable address defined source
port number range. Due to the requirement of the states in the
translator for the port mapping (no states required for the address
mapping), it is named partial state. The technical details of the
port mapping state maintaining algorithm is an implementation issue
(see Section 6.2).
5. Dual Stateless Translation
In general dual stateful IPv4/IPv6 translations (IPv4-IPv6-IPv4) are
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considered harmful, since the two translators cannot synchronize the
parameter to translate the IPv4 address to its original format.
However, the dual stateless IPv4/IPv6 translation (IPv4-IPv6-IPv4)
can translate the IPv4 address to its original format based on
algorithm. There are several reasons for using dual stateless IPv4/
IPv6 translation.
o The second translator (CPE) performs the port-set mapping
algorithm discussed in Section 4.1, therefore, there is no need to
modify the host with IPv4 address sharing.
o ALG cannot be developed for some applications, or has not been
developed during the early transition stage.
o DNS64 is not allowed (due to DNSSec, etc.).
o All the IPv6 packet processing tools (routing, policy based
routing, packet filtering, traffic shaping based on layer 3 and
layer 4 can be used for dual stateless translation, while new
tools are required for encapsulation and tunneling.
5.1. Header Translation and MTU Handling
The general header and ICMP translation specifications are defined in
[RFC6145].
Special MTU and fragmentation actions must be taken in the case of
dual translation.
5.2. Port Mapping Algorithm in CPE
The port mapping algorithm is straightforward. The port mapping
device maintains a database of allowed port numbers defined by the
extended IPv4-translatable address format. If the packets from the
host contains the source port number which do not match the port
number range defined by the extended IPv4-translatable address
format, the CPE will map the source port number to an allowed one and
keep the record in the database for mapping back the returning
packets and all the packets in the same session.
The port number database can be refreshed via the corresponding
transport layer flags for TCP or via timeout for UDP sessions.
6. Implementation Considerations
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6.1. Host implementation
For the wireless mobile Internet environment, it is not difficult to
modify the operating system of the mobile device, therefore it
possible to integrate the port mapping algorithm and the second IPv4/
IPv6 translation function in the mobile device, which is an IPv6-only
host to the network and has a dual-stack socket API for the
applications running on this host.
6.2. Port Mapping in the Core Translator
The port mapping can be performed in the core translator, in this
case, there is no need to have the second translator (CPE.x) and no
need to modify the IPv6 host for the port restriction requirements.
7. Security Considerations
There are no security considerations in this document.
8. IANA Considerations
This memo adds no new IANA considerations.
Note to RFC Editor: This section will have served its purpose if it
correctly tells IANA that no new assignments or registries are
required, or if those assignments or registries are created during
the RFC publication process. From the author's perspective, it may
therefore be removed upon publication as an RFC at the RFC Editor's
discretion.
9. Acknowledgments
The authors would like to acknowledge the following contributors in
the different phases of the address-sharing IVI and dIVI development:
Maoke Chen, Hong Zhang, Weifeng Jiang, Yuncehng Zhu and Guoliang Han.
The authors would like to acknowledge the following contributors who
provided helpful inputs: Dan Wing, Fred Baker, Dave Thaler, Randy
Bush, Kevin Yin, Wojciech Dec and Rajiv Asati.
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, DOI 10.17487/RFC6144,
April 2011, <https://www.rfc-editor.org/info/rfc6144>.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, DOI 10.17487/RFC6145, April 2011,
<https://www.rfc-editor.org/info/rfc6145>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
DOI 10.17487/RFC6147, April 2011,
<https://www.rfc-editor.org/info/rfc6147>.
[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, DOI 10.17487/
RFC6219, May 2011,
<https://www.rfc-editor.org/info/rfc6219>.
10.2. Informative References
[I-D.bcx-behave-address-fmt-extension]
Bao, C. and X. Li, "Extended IPv6 Addressing for Encoding
Port Range", draft-bcx-behave-address-fmt-extension-10
(work in progress), January 2017.
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[I-D.xli-behave-divi-pd]
Sun, Q., Asati, R., Xie, C., Li, X., Dec, W., and C. Bao,
"dIVI-pd: Dual-Stateless IPv4/IPv6 Translation with Prefix
Delegation", draft-xli-behave-divi-pd-01 (work in
progress), September 2011.
Appendix A. Address Format and Workflow Examples
The prefix we selected is 2001:da8:a4a6::/48. The formats of the
IPv4-converted address and the IPv4-translatable address are:
IPv4-converted address
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PL| 0-------------32--40--48--56--64--72--80--88--92--104-112-120-|
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|48| prefix |v4(16) | u | (16) | 0 |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
IPv4-translatable address
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PL| 0-------------32--40--48--56--64--72--80--88--92--104-112-120-|
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|48| prefix |v4(16) | u | (16) |PSID| 0 | Q |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 5: Address format
The sharing ratio R=16, so the PSID has 4 bits (Q=4) and each PSID
can have (4096-1024/16)= 4032 concurrent port numbers to use. The
continue port range M=4, so each PSID will have 1008 available port
range.
The host in the IPv4 Internet is 202.112.35.254 and the corresponding
IPv4-converted address is 2001:da8:a4a6:ca70:23:fe00::
The shared IPv4 address is 202.38.117.1 with sharing ratio 16, the
corresponding IPv4-translatable addresses are
PSID=0 2001:da8:a4a6:ca26:75:100::4
PSID=1 2001:da8:a4a6:ca26:75:110::4
PSID=2 2001:da8:a4a6:ca26:75:120::4
PSID=3 2001:da8:a4a6:ca26:75:130::4
PSID=4 2001:da8:a4a6:ca26:75:140::4
PSID=5 2001:da8:a4a6:ca26:75:150::4
PSID=6 2001:da8:a4a6:ca26:75:160::4
PSID=7 2001:da8:a4a6:ca26:75:170::4
PSID=8 2001:da8:a4a6:ca26:75:180::4
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PSID=9 2001:da8:a4a6:ca26:75:190::4
PSID=10 2001:da8:a4a6:ca26:75:1a0::4
PSID=11 2001:da8:a4a6:ca26:75:1b0::4
PSID=12 2001:da8:a4a6:ca26:75:1c0::4
PSID=13 2001:da8:a4a6:ca26:75:1d0::4
PSID=14 2001:da8:a4a6:ca26:75:1e0::4
PSID=15 2001:da8:a4a6:ca26:75:1f0::4
A.1. The address-sharing host on an IPv6 network initiates
communication
An address-sharing Host.0 (202.38.117.1) in an IPv6 network behind
CPE initiates communication with Host 202.112.35.254:80 in the IPv4
Internet
On the Host.0
Src#p= 202.38.117.1#1881 (random port)
Dst#p= 202.112.35.254#80 (server port)
On an IPv6 network
Src#p= [2001:da8:a4a6:ca26:75:0100::4]#8192 (CPE mapped port)
Dst#p= [2001:da8:a4a6:ca70:23:fe00::]#80 (server port)
On the IPv4 Internet
Src#p= 202.38.117.1#8192 (CPE mapped port)
Dst#p= 202.112.35.254#80 (server port)
Figure 6: Workflow Example 1
The returning packets reverse the Src and Dst, the CPE maps the "CPE
mapped port (8192)" back to the original "random port (1881)".
A.2. A host in the IPv4 Internet initiates communication
A host 202.112.35.254 in the IPv4 Internet initiates communication to
the address-sharing Host.0 (202.38.117.1#4096)
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On the IPv4 Internet
Src#p= 202.112.35.254#36567 (random port)
Dst#p= 202.38.117.1#4096 (server port)
On an IPv6 network
Src#p= [2001:da8:a4a6:ca70:23:fe00::]#36567 (random port)
Dst#p= [2001:da8:a4a6:ca26:75:0100::4]#4096 (server port)
On the Host.0
Src#p= 202.112.35.254#36567 (random port)
Dst#p= 202.38.117.1#4096 (server port)
Figure 7: Workflow Example 2
The returning packets reverse the Src and Dst.
Authors' Addresses
Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: congxiao@cernet.edu.cn
Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: xing@cernet.edu.cn
Yu Zhai
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: jacky.zhai@gmail.com
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Wentao Shang
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: wentaoshang@gmail.com
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