Internet DRAFT - draft-bcx-behave-address-fmt-extension
draft-bcx-behave-address-fmt-extension
behave C. Bao
Internet-Draft X. Li
Intended status: Standards Track CERNET Center/Tsinghua
Expires: April 20, 2018 University
October 17, 2017
Extended IPv6 Addressing for Encoding Port Range
draft-bcx-behave-address-fmt-extension-11
Abstract
This document discusses an extension of the algorithmic translation
between IPv4 and IPv4-translatable IPv6 addresses. The extended
address format contains transport-layer port set identification
(PSID) which allows several IPv6 nodes to share a single IPv4 address
with each node managing a different range of ports. This address
format extension can be used for IPv4/IPv6 translation, as well as
IPv4 over IPv6 tunneling.
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 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
(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
Bao & Li Expires April 20, 2018 [Page 1]
Internet-Draft Extended IPv6 Addressing October 2017
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.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Applicability Scope . . . . . . . . . . . . . . . . . . . 3
1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
2. Port Mapping Algorithm . . . . . . . . . . . . . . . . . . . . 4
2.1. Mathematical representation of the Algorithm . . . . . . . 4
2.2. Bit Representation of the Algorithm . . . . . . . . . . . 5
2.3. Example of the Algorithm . . . . . . . . . . . . . . . . . 5
2.3.1. PSID with fixed prefix length . . . . . . . . . . . . 5
2.3.2. PSID with variable prefix length . . . . . . . . . . . 6
2.4. Features of the Algorithm . . . . . . . . . . . . . . . . 6
3. Extended IPv4-translatable IPv6 Address . . . . . . . . . . . 6
3.1. Address Format . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Considerations of Using a Shorter Prefix length . . . . . 8
3.3. Mapping Extended IPv4-translatable IPv6 Address to
RFC1918 Space . . . . . . . . . . . . . . . . . . . . . . 9
4. DHCP Options Extensions . . . . . . . . . . . . . . . . . . . 9
5. Comparisons with MAP . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Bao & Li Expires April 20, 2018 [Page 2]
Internet-Draft Extended IPv6 Addressing October 2017
1. Introduction
This document discusses an extension of the address format defined in
[RFC6052]. In Section 2.2, the IPv4-embedded IPv6 address format is
defined which composed of a variable length prefix, the embedded IPv4
address, and a variable length suffix, as presented in the following
diagram, in which PL designates the prefix length:
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PL| 0-------------32--40--48--56--64--72--80--88--96--104-112-120-|
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|32| prefix |v4(32) | u | suffix |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|40| prefix |v4(24) | u |(8)| suffix |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|48| prefix |v4(16) | u | (16) | suffix |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|56| prefix |(8)| u | v4(24) | suffix |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|64| prefix | u | v4(32) | suffix |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|96| prefix | v4(32) |
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 1: Address Format
In [RFC6052] Section 3.5, it states:
"There have been proposals to complement stateless translation
with a port-range feature. Instead of mapping an IPv4 address to
exactly one IPv6 prefix, the options would allow several IPv6
nodes to share an IPv4 address, with each node managing a
different range of ports. If a port range extension is needed, it
could be defined later, using bits currently reserved as null in
the suffix."
This document defines such a suffix encoding scheme and the
corresponding port mapping algorithm.
1.1. Applicability Scope
The address format extension presented in this document is used for
IPv4/IPv6 stateless translation and dual IPv4/IPv6 stateless
translation without prefix delegation [I-D.xli-behave-divi]. The
address format used for dual IPv4/IPv6 stateless translation and
encapsulation with prefix delegation should refer to [RFC7599]
[RFC7597].
Bao & Li Expires April 20, 2018 [Page 3]
Internet-Draft Extended IPv6 Addressing October 2017
1.2. 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].
2. Port Mapping Algorithm
2.1. Mathematical representation of the Algorithm
There exist many port mapping algorithms and each one may have
advantages and disadvantages, as well as has its best application
scenario. Since different PSID MUST have non-overlapped port range,
the two extreme cases are: (1) the port number is not continue for
each PSID, but uniformly distributed cross the whole port range
(0-65535); (2) the port number is continue in a single range for each
PSID. The port mapping algorithm proposed here is called generalized
modulus algorithm and it is flexible, meets these two cases and
simple.
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.
Bao & Li Expires April 20, 2018 [Page 4]
Internet-Draft Extended IPv6 Addressing October 2017
2.2. Bit Representation of the Algorithm
Given sharing ratio (R=2^k), the maximum number of continue ports
(M=2^m), for any PSID (K) available ports (P) can be represented as:
0 8 15
+---------------+----------+------+-------------------+
| P |
----------------+-----------------+-------------------+
| A (j) | PSID (K) | M (i) |
+---------------+----------+------+-------------------+
|<----a bits--->|<-----k bits---->|<------m bits----->|
|<---c bits--->|<-----(k+m-c) bits--->|
Figure 2: Bit representation
Where j and i are the same indexes defined in the port mapping
algorithm.
For any port number, the PSID can be obtained by bit mask operation
and therefore the generalized modulus algorithm does not introduce
the computational complexity.
Note that in above figure there is a PSID prefix length (c). Based
on this definition, PSID is also in CIDR style and more ports can be
assigned to a single CE when PSID prefix length (c < k).
When m=0, the generalized modulus algorithm becomes modulus
operation. When a=0, the generalized modulus algorithm becomes
division operation.
2.3. Example of the Algorithm
2.3.1. PSID with fixed prefix length
For example, for R=128 (k=7), M=4 (m=2)
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 3: Example 1
Bao & Li Expires April 20, 2018 [Page 5]
Internet-Draft Extended IPv6 Addressing October 2017
2.3.2. PSID with variable prefix length
For example, different PSIDs have different prefix length (c)
Host | PSID prefix | Number of ports
-------------------------------------------------------
Host0 | 000/2 | 2x8192
Host1 | 010/3 | 1x8192
Host2 | 011/3 | 1x8192
Host3 | 100/1 | 4x8192
-------------------------------------------------------
Figure 4: Example 2
2.4. Features of the Algorithm
The generalized modulus operation has the following features:
1. There is no waste of the port number, except the well-known
ports.
2. The algorithm is flexible, the control parameters are sharing
ratio (R), the continue port range (M) and PSID prefix length
(c).
3. It does not introduce algorithm complexity.
4. It allows service providers to define their own address sharing
ratio, the theoretical value is from 1:1 to 1:65536 and a more
practical value is from 1:1 to 1:4096.
5. It supports deployments using differentiated port ranges.
6. It supports differentiated port ranges within a single shared
IPv4 address.
7. It support excluding the well known ports 0-1023.
8. It supports assigning well known ports to a CE.
9. It supports legacy RTP/RTCP compatibility.
3. Extended IPv4-translatable IPv6 Address
Bao & Li Expires April 20, 2018 [Page 6]
Internet-Draft Extended IPv6 Addressing October 2017
3.1. Address Format
Based on the port mapping algorithm, the extended address format is
shown in the following figure.
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|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 5: Address Format
Where PL designates the prefix length.
The PSID is placed right after the IPv4 address, since the
combination of the IPv4 address and the PSID represents the more
specifics in CIDR style which is sharing an IPv4 address with others.
The PSID prefix length (Q=c) 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.
Bao & Li Expires April 20, 2018 [Page 7]
Internet-Draft Extended IPv6 Addressing October 2017
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 6: Port range
Since newly defined IPv6 addresses with suffix are more specifics
compared with the original address format defined in [RFC6052], the
routing considerations in that document are also applied here.
Furthermore, the port range is embedded in the extended IPv4-
translatable IPv6 addresses and bound to the PSID therefore the
packets containing extended IPv4-translatable IPv6 addresses as the
destination can be routed to different IPv6 nodes.
3.2. Considerations of Using a Shorter Prefix length
Since IPv4 address plus variable length PSID represents the more
specifics, the prefix length (PL) defined in [RFC6052] can be
shorter. In these cases, the interface identifier (IID: second 64
bits) will not contains PSID and therefore can be used for regular
prefix delegation, as shown in the following figure.
+--+---+---+----+----+-------+----+----+----+---+---+---+------+
|PL| 0-----24---28---32------56---60---64---72------96-----120-|
+--+---+---+----+----+-------+----+----+----+---+---+---+------+
|24| prefix| v4(32) | PSID | u | | Q |
+--+---+---+----+----+-------+----+----+----+---+---+---+------+
|28| prefix | v4(32) |PSID| u | | Q |
+--+---+---+----+----+-------+----+----+----+---+---+---+------+
|32| prefix | v4(32) | u | | Q |
+--+---+---+----+----+-------+----+----+----+---+---+---+------+
Figure 7: Shorter PL
Note that PL can take any value. For example,
Bao & Li Expires April 20, 2018 [Page 8]
Internet-Draft Extended IPv6 Addressing October 2017
o PL=24: Q=8, R=256
o PL=25: Q=7, R=128
o PL=26: Q=6, R=64
o PL=27: Q=5, R=32
o PL=28: Q=4, R=16
o PL=29: Q=3, R=8
o PL=30: Q=2, R=4
o PL=31: Q=1, R=2
o PL=32: Q=0, R=1
However, there will be a waste of the IPv6 address space in order to
represent the IPv4-converted addresses.
3.3. Mapping Extended IPv4-translatable IPv6 Address to RFC1918 Space
Based on the algorithm defined in this document, a public IPv4
address and PSID can be mapped to extended IPv4-translatable IPv6
address and vise versa.
On the other hand, it is also possible to map the extended IPv4-
translatable IPv6 address to [RFC1918] address space. In this case,
one public IPv4 address can be mapped to several RFC1918 addresses
and used by IPv4 or dual stack hosts.
For public IPv4 address a.b.c.d,
o If R <= 256, the corresponding RFC1918 address is 10.c.d.PSID
(PSID has 8 bits)
o Otherwise, the corresponding RFC1918 address is 10.d.[PSID] (PSID
has 16 bits)
4. DHCP Options Extensions
Based on the address format and the port mapping algorithm defined in
this document, the IPv6 host needs to get the corresponding
parameters via DHCPv6 [RFC3315][RFC3633] or others signaling scheme.
These parameters are:
1. The IPv6 prefix
2. The IPv6 prefix length
3. The IPv4 prefix
4. The IPv4 prefix length
Bao & Li Expires April 20, 2018 [Page 9]
Internet-Draft Extended IPv6 Addressing October 2017
5. The sharing ratio (R)
6. The maximum number of continue ports (M)
7. The PSID (K)
8. The PSID length (c)
5. Comparisons with MAP
There are common parts and differences between this document and the
address format defined in [RFC7597] [RFC7599].
1. The address format extension defined in this document is used for
single and dual stateless translation without prefix delegation,
while MAP is used for encapsulation and dual stateless
translation with prefix delegation.
2. The address format extension defined in this document uses same
IPv6 prefix for the source address from a CE to any destination
(IPv4-translatable address) and the destination address from a CE
to the outside IPv4 Internet (IPv4-converted address), while MAP
uses different IPv6 prefixes, due to the requirements of prefix
delegation.
3. The address format extension defined in this document uses same
IPv6 prefix for all CEs, so there is no need to define prefix
encoding scheme (e.g. CE index, or EA-bits), while MAP defines
the prefix encoding scheme, due to the requirements of prefix
delegation.
4. Due to the nature of using same IPv6 prefix for both IPv4-
translatable address and IPv4-converted address, there is no
referral problem and mesh scenarios can be supported without
additional mapping rules, while MAP does require additional
mapping rule for supporting mesh scenario.
5. The address format extension defined in this document and MAP
share the same suffix coding scheme (IPv4 address + PSID).
6. The AFT and MAP share the same port mapping algorithm
(generalized modulus algorithm).
Bao & Li Expires April 20, 2018 [Page 10]
Internet-Draft Extended IPv6 Addressing October 2017
6. IANA Considerations
This memo adds no new IANA considerations.
7. Security Considerations
There is no special security consideration.
8. Acknowledgements
Thanks to Wojciech Dec, Remi Despres, Ole Troan, Rajiv Asati,
Chongfeng Xie, Qiong Sun, Fred Baker, Wing Dan, M. Boucadair and all
the friends for the fruitful discussions during the unification of
the port mapping algorithm of
[I-D.mdt-softwire-mapping-address-and-port]. Also thanks to Wentao
Shang, Guoliang Han, Yu Zhai, Haotao Zhang and Weicai Wang for their
contributions.
9. References
9.1. Normative References
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<https://www.rfc-editor.org/info/rfc1918>.
[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>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315,
July 2003, <https://www.rfc-editor.org/info/rfc3315>.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
DOI 10.17487/RFC3633, December 2003,
<https://www.rfc-editor.org/info/rfc3633>.
[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,
Bao & Li Expires April 20, 2018 [Page 11]
Internet-Draft Extended IPv6 Addressing October 2017
<https://www.rfc-editor.org/info/rfc6052>.
9.2. Informative References
[I-D.mdt-softwire-mapping-address-and-port]
Bao, C., Troan, O., Matsushima, S., Murakami, T., and X.
Li, "Mapping of Address and Port (MAP)",
draft-mdt-softwire-mapping-address-and-port-03 (work in
progress), January 2012.
[I-D.xli-behave-divi]
Bao, C., Li, X., Zhai, Y., and W. Shang, "dIVI: Dual-
Stateless IPv4/IPv6 Translation", draft-xli-behave-divi-07
(work in progress), January 2017.
[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>.
[RFC6346] Bush, R., Ed., "The Address plus Port (A+P) Approach to
the IPv4 Address Shortage", RFC 6346, DOI 10.17487/
RFC6346, August 2011,
<https://www.rfc-editor.org/info/rfc6346>.
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597, DOI 10.17487/
RFC7597, July 2015,
<https://www.rfc-editor.org/info/rfc7597>.
[RFC7599] Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
and T. Murakami, "Mapping of Address and Port using
Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599,
July 2015, <https://www.rfc-editor.org/info/rfc7599>.
Authors' Addresses
Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing, 100084
China
Phone: +86 10-62785983
Email: congxiao@cernet.edu.cn
Bao & Li Expires April 20, 2018 [Page 12]
Internet-Draft Extended IPv6 Addressing October 2017
Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing, 100084
China
Phone: +86 10-62785983
Email: xing@cernet.edu.cn
Bao & Li Expires April 20, 2018 [Page 13]
