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Network Working Group O. Troan, Ed.
Internet-Draft cisco
Intended status: Standards Track October 24, 2011
Expires: April 26, 2012
Mapping of Address and Port (MAP)
draft-mdt-softwire-mapping-address-and-port-00
Abstract
This document describes a generic mechanism for mapping between an
IPv4 prefix, address or parts thereof, and transport layer ports and
an IPv6 prefix or address.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Mapping Rules . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Port mapping algorithm . . . . . . . . . . . . . . . . . . 6
4.2. Basic mapping rule - IPv4 address and port assignment . . 7
4.3. Forwarding mapping rule - from address and port to
IPv6 address . . . . . . . . . . . . . . . . . . . . . . . 8
4.4. Default mapping rule - from address and port to BR . . . . 8
5. Use of the IPv6 Interface identifier . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Requirements . . . . . . . . . . . . . . . . . . . . 13
Appendix B. Deployment considerations . . . . . . . . . . . . . . 15
B.1. Flexible Assigment of Port Range . . . . . . . . . . . . . 15
B.2. Traffic Classification . . . . . . . . . . . . . . . . . . 15
B.3. Prefix Delegation Deployment . . . . . . . . . . . . . . . 15
B.4. Coexisting Deployment . . . . . . . . . . . . . . . . . . 15
B.5. Friendly to Network Provisioning . . . . . . . . . . . . . 16
B.6. Enable privacy addresses . . . . . . . . . . . . . . . . . 16
B.7. Facilitating 4v6 Service . . . . . . . . . . . . . . . . . 16
B.8. Independency with IPv6 Routing Planning . . . . . . . . . 16
B.9. Optimized Routing Path . . . . . . . . . . . . . . . . . . 17
Appendix C. Guidelines for Operators . . . . . . . . . . . . . . 17
C.1. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 17
C.2. Understanding address formats: their difference and
relevance . . . . . . . . . . . . . . . . . . . . . . . . 17
C.3. A generic logic of working with MAP . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
The mechanism of mapping IPv4 addresses in IPv6 address has been
described in numerous mechanisms dating back to [RFC1933] from 1996.
The Automatic tunneling mechanism described in RFC1933, assigned a
globally unique IPv6 address to a host by combining the hosts IPv4
address with a well known IPv6 prefix. Given an IPv6 packet with an
destination address with an embedded IPv4 address, a node could
automatically tunnel this packet by extracting the IPv4 tunnel end-
point address from the IPv6 destination address.
There are numerous variations of this idea, described in 6over4
[RFC2529], ISATAP [RFC5214] and 6rd [RFC5969]. The differences are
the use of well known IPv6 prefixes, or Service Provider assigned
IPv6 prefixes, and the exact position of the IPv4 bits embedded in
the IPv6 address. Teredo [RFC4380] added a twist to this to achieve
NAT traversal by also encoding transport layer ports into the IPv6
address. 6rd to achieve more efficient encoding, allowed for only an
IPv4 address suffix to be embedded, with the IPv4 prefix being
deducted from other provisioning mechanisms.
NAT-PT [RFC2766](deprecated) combined with a DNS ALG used address
mapping to put NAT state, namely the IPv6 to IPv4 binding encoded in
an IPv6 address. This characteristic has been inherited by NAT64
[RFC6146] and DNS64 [RFC6147] which rely on an address format defined
in [RFC6052]. [RFC6052] specifies the algorithmic translation of an
IPv6 address to IPv4 address suffix to be embedded, with the deducted
from other provisioning mechanisms. DNS ALG used address IPv4
binding encoded in it a corresponding IPv4 address, and vice versa.
In particular, [RFC6052] specifies the address format to build IPv4-
converted and IPv4-translatable IPv6 addresses. RFC6052 discusses
the transport of the port range information in an IPv4-embedded IPv6
address but the conclusion was the following (excerpt from
[RFC6052]):
"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, could be defined later, using
bits currently reserved as null in the suffix."
The commonalities of all these mechanisms are:
o Provisions an IPv6 address for a host or an IPv6 prefix for a site
o Algorithmic or implicit address resolution for tunneling or
encapsulation. Given an IPv6 destination address, an IPv4 tunnel
endpoint address can be calculated. Likewise for translation, an
IPv4 address can be calculated from an IPv6 destination address
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and vice versa.
o Embedding of an IPv4 address or part thereof and optionally
transport layer ports into an IPv6 address.
In the later phases of IPv4 to IPv6 migration, IPv6 only networks
will be common, while there will still be a need for residual IPv4
deployment. This document describes a more generic mapping of IPv4
to IPv6 that can be used both for encapsulation (IPv4 over IPv6) and
for translation between the two protocols.
Just as the IPv6 over IPv4 mechanisms refereed to above, the residual
IPv4 over IPv6 mechanisms must be capable of:
o Provisioning an IPv4 prefix, an IPv4 address or a shared IPv4
address.
o Algorithmically map between an IPv4 prefix, IPv4 address or a
shared IPv4 address and an IPv6 address.
This document describes delivery of IPv4 unicast service across an
IPv6 infrastructure. IPv4 multicast is not considered further in
this document.
The unified mapping scheme described here supports translation mode,
encapsulation mode, in both mesh and hub and spoke topologies.
Other work that has motivated the work on a unified mapping mechanism
for translation and encapsulation are:
[I-D.sun-softwire-stateless-4over6]
[I-D.murakami-softwire-4v6-translation]
[I-D.despres-softwire-4rd-addmapping]
[I-D.chen-softwire-4v6-add-format] [I-D.bcx-address-fmt-extension]
[I-D.mrugalski-dhc-dhcpv6-4rd]
[I-D.boucadair-dhcpv6-shared-address-option]
[I-D.despres-softwire-sam] [I-D.chen-softwire-4v6-pd]
[I-D.boucadair-softwire-stateless-requirements]
[I-D.dec-stateless-4v6] [I-D.boucadair-behave-ipv6-portrange]
[I-D.bsd-softwire-stateless-port-index-analysis]
[I-D.despres-softwire-stateless-analysis-tool]
[I-D.mrugalski-dhc-dhcpv6-4rd] [I-D.xli-behave-divi-pd]
[I-D.murakami-softwire-4rd] [I-D.mrugalski-dhc-dhcpv6-4rd].
In particular the architecture of shared IPv4 address by distributing
the port space is described in [RFC6346]. The corresponding stateful
solution DS-lite is described in [RFC6333]
Requirements and deployment considerations are documented in appendix
A to C. These are kept in the document for informational purposes for
now, but are in no way to be considered normative.
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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 RFC 2119 [RFC2119].
3. Terminology
MAP domain: A set of MAP CEs and BRs connected to the same
virtual link. A service provider may deploy a
single MAP domain, or may utilize multiple MAP
domains.
MAP Rule A set of parameters describing the mapping
between an IPv4 prefix, IPv4 address or shared
IPv4 address and an IPv6 prefix or address.
Each MAP node in the domain has the same set of
rules.
MAP Border Relay (BR): A MAP enabled router managed by the service
provider at the edge of a MAP domain. A Border
Relay router has at least an IPv6-enabled
interface and an IPv4 interface connected to
the native IPv4 network. A MAP BR may also be
referred to simply as a "BR" within the context
of MAP.
MAP Customer Edge (CE): A device functioning as a Customer Edge
router in a MAP deployment. In a residential
broadband deployment, this type of device is
sometimes referred to as a "Residential
Gateway" (RG) or "Customer Premises Equipment"
(CPE). A typical MAP CE adopting MAP rules
will serve a residential site with one WAN side
interface, one or more LAN side interfaces. A
MAP CE may also be referred to simply as a "CE"
within the context of MAP.
Shared IPv4 address: An IPv4 address that is shared among multiple
CEs. Each node has a separate part of the
transport layer port space; denoted as a port
set. Only ports that belong to the assigned
range can be used for communication.
End user IPv6 prefix: The IPv6 prefix assigned to an End user CE by
other means than MAP itself.
MAP IPv6 address: The IPv6 address used to reach the MAP function
of a CE from other CE's and from BR's.
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Port-set ID (PSID): Algorithmically identifies a set of ports
exclusively assigned to the CE.
Rule IPv6 prefix: An IPv6 prefix assigned by a Service Provider
for a mapping rule.
Rule IPv4 prefix: An IPv4 prefix assigned by a Service Provider
for a mapping rule.
IPv4 Embedded Address (EA) bits: The IPv4 EA-bits in the IPv6
address identify an IPv4 prefix/address (or
part thereof) or a shared IPv4 address (or part
thereof and a port set identifier.
4. Mapping Rules
A MAP node is provisioned with one or more mapping rules.
Mapping Rules consists of the following items:
o Rule IPv6 prefix
o Rule IPv4 prefix
o Port set parameters
Mapping rules are used somewhat differently depending on its
function. Every MAP node must be provisioned with a Basic mapping
rule. This is used by the node to map from an end-user IPv6 prefix
to an IPv4 prefix, address or shared IPv4 address. This same basic
rule can also be used for forwarding (either encapsulation or
translation), where an IPv4 destination address and optionally a
destination port is mapped into an IPv6 address or prefix.
Additional mapping rules can be specified to allow for e.g. multiple
different IPv4 subnets to exist within the domain. Additional
mapping rules are recognized by having a Rule IPv6 prefix different
from the base End user IPv6 prefix.
Traffic outside of the domain (IPv4 address not matching (using
longest matching prefix) any Rule IPv4 prefix in the Rules database)
will be forward using the Default Rule. The Default Rule maps
outside destinations to the BR's IPv6 address or prefix.
4.1. Port mapping algorithm
Note that various algorithms have been proposed to encode the port
set. The effort to reach consensus on a port indexing algorithm
meeting the requirements listed in the Requirements section is
ongoing.
The simplest port mapping algorithm one could imagine would be a
simple CIDR style prefix. E.g. define a /6 worth of port space (out
of the total 16 bits), giving the user 1024 ports. The issue with
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that scheme is that it does not exclude the well known ports
(0-1023). In a deployment where IPv6 address planning is independent
of IPv4 address planning, that would result in some users being
assigned that port space. To avoid that, Remi Despres invented a
clever algorithm shown below. This algorithm uses an "infix" instead
of a "prefix. By requiring that the 'Y' field (the first 6 bits) are
larger then 0, results in all well known ports being excluded, while
still sharing the ports fairly among all users.
| Port range (16 bits) |
+-------------------------+
| YYYY YY | P S I D | XX |
+-------------------------+
| Y > 0 |
Figure 1
4.2. Basic mapping rule - IPv4 address and port assignment
| n bits | o bits | m bits | 128-n-o-m bits |
+--------------------+---------+-----------+------------+----------+
| Domain IPv6 prefix | EA bits | subnet ID | interface ID |
+--------------------+---------+-----------+-----------------------+
|<---IPv6 delegated prefix --->|
Figure 2
The first half of the EA bits contain the IPv4 address, prefix or
IPv4 suffix. The second half of the EA bits, in the case of a shared
IPv4 address contains the PSID.
| r bits | p bits | | q bits |
+-------------+---------------------+ +------------+
| IPv4 prefix | IPv4 Address suffix | |Port Set ID |
+-------------+---------------------+ +------------+
Figure 3
To create a complete IPv4 address, the IPv4 address suffix from the
EA bits, are concatenated with a provisioned IPv4 prefix.
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The PSID bits are not a prefix, but an infix. And is used to create
a port range.
| Port range (16 bits) |
+-------------------------+
| YYYY YY | P S I D | XX |
+-------------------------+
| Y > 0 |
Figure 4
4.3. Forwarding mapping rule - from address and port to IPv6 address
| 32 bits | | 16 bits |
+--------------------------+ +-------------------+
| IPv4 destination address | | IPv4 dest port |
+--------------------------+ +-------------------+
| p bits | | q bits |
+------------------+ +------------+
| IPv4 addr suffix | |Port Set ID |
+------------------+ +------------+
| n bits | o bits | m bits | 128-n-o-m bits |
+--------------------+---------+-----------+------------+----------+
| Domain IPv6 prefix | EA bits | subnet ID | interface ID |
+--------------------+---------+-----------+-----------------------+
|<---IPv6 delegated prefix --->|
Figure 5
4.4. Default mapping rule - from address and port to BR
TBD
5. Use of the IPv6 Interface identifier
In an encapsulation solution, an IPv4 address and port is mapped to
an IPv6 address. This is the address of the tunnel end point of the
receiving MAP CE. For traffic outside the MAP domain, the IPv6
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tunnel end point address is the IPv6 address of the BR. As long as
the interface-id is well known or provisioned and the same for all
MAP nodes, it can be any interface identifier. E.g. ::1.
When translating the destination IPv4 address is translated into a
corresponding IPv6 address. In the case of traffic outside of the
MAP domain, it is translated to the BR's IPv6 prefix. For the BR to
be able to reverse the translation, the full destination IPv4 address
must be encoded in the IPv6 address. There are multiple proposals
for how to encode the IPv4 address, and if also the destinatino port
or PSID should also be included. A couple of the proposals are shown
in the figure below.
Note: The encoding of the full IPv4 address into the interface
identifier, both for the source and destination IPv6 addresses have
been shown to be useful for troubleshooting. The format finally
agreed upon here, will apply for both encapsulation and translation.
Simple format similar to ISATAP:
| 32 bits | 32 bits |
+------------------+------------------+
| 02-00-5E-FE | IPv4 address |
+------------------+------------------+
Figure 6
Parsable format including address length and PSID:
<-8-><-------- L>=32 -------><48-L><8->
+---+----------------+------+-----+---+
| u | IPv4 address | PSID | 0 | L |
+---+----------------+------+-----+---+
Figure 7
6. IANA Considerations
This specification does not require any IANA actions.
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7. Security Considerations
There are no new security considerations pertaining to this document.
8. Contributors
The members of the MAP design team are:
Mohamed Boucadair, Gang Chen, Wojciech Dec, Congxiao Bao, Xiaohong
Deng, Jouni Korhonen, Xing Li, Maoke, Satoru Matsushima, Tomasz
Mrugalski, Jacni Qin, Qiong Sun, Tina Tsou, Dan Wing, Leaf Yeh and
Jan Zorz
9. Acknowledgements
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the
IPv4 Address Shortage", RFC 6346, August 2011.
10.2. Informative References
[I-D.bcx-address-fmt-extension]
Bao, C. and X. Li, "Extended IPv6 Addressing for Encoding
Port Range", draft-bcx-address-fmt-extension-02 (work in
progress), October 2011.
[I-D.boucadair-behave-ipv6-portrange]
Boucadair, M., Levis, P., Grimault, J., Villefranque, A.,
Kassi-Lahlou, M., Bajko, G., Lee, Y., Melia, T., and O.
Vautrin, "Flexible IPv6 Migration Scenarios in the Context
of IPv4 Address Shortage",
draft-boucadair-behave-ipv6-portrange-04 (work in
progress), October 2009.
[I-D.boucadair-dhcpv6-shared-address-option]
Boucadair, M., Levis, P., Grimault, J., Savolainen, T.,
and G. Bajko, "Dynamic Host Configuration Protocol
(DHCPv6) Options for Shared IP Addresses Solutions",
draft-boucadair-dhcpv6-shared-address-option-01 (work in
progress), December 2009.
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[I-D.boucadair-softwire-stateless-requirements]
Boucadair, M., Bao, C., Skoberne, N., and X. Li,
"Requirements for Extending IPv6 Addressing with Port
Sets", draft-boucadair-softwire-stateless-requirements-00
(work in progress), September 2011.
[I-D.bsd-softwire-stateless-port-index-analysis]
Boucadair, M., Skoberne, N., and W. Dec, "Analysis of Port
Indexing Algorithms",
draft-bsd-softwire-stateless-port-index-analysis-00 (work
in progress), September 2011.
[I-D.chen-softwire-4v6-add-format]
Chen, G. and Z. Cao, "Design Principles of a Unified
Address Format for 4v6",
draft-chen-softwire-4v6-add-format-00 (work in progress),
October 2011.
[I-D.chen-softwire-4v6-pd]
Chen, G., Sun, T., and H. Deng, "Prefix Delegation in
4V6", draft-chen-softwire-4v6-pd-00 (work in progress),
August 2011.
[I-D.dec-stateless-4v6]
Dec, W., Asati, R., Bao, C., Deng, H., and M. Boucadair,
"Stateless 4Via6 Address Sharing",
draft-dec-stateless-4v6-04 (work in progress),
October 2011.
[I-D.despres-softwire-4rd-addmapping]
Despres, R., Qin, J., Perreault, S., and X. Deng,
"Stateless Address Mapping for IPv4 Residual Deployment
(4rd)", draft-despres-softwire-4rd-addmapping-01 (work in
progress), September 2011.
[I-D.despres-softwire-sam]
Despres, R., "Stateless Address Mapping (SAM) - a
Simplified Mesh-Softwire Model",
draft-despres-softwire-sam-01 (work in progress),
July 2010.
[I-D.despres-softwire-stateless-analysis-tool]
Despres, R., "Analysis of Stateless Solutions for IPv4
Service across IPv6 Networks - A synthetic Analysis Tool",
draft-despres-softwire-stateless-analysis-tool-00 (work in
progress), September 2011.
[I-D.mrugalski-dhc-dhcpv6-4rd]
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Mrugalski, T., "DHCPv6 Options for IPv4 Residual
Deployment (4rd)", draft-mrugalski-dhc-dhcpv6-4rd-00 (work
in progress), July 2011.
[I-D.murakami-softwire-4rd]
Murakami, T., Troan, O., and S. Matsushima, "IPv4 Residual
Deployment on IPv6 infrastructure - protocol
specification", draft-murakami-softwire-4rd-01 (work in
progress), September 2011.
[I-D.murakami-softwire-4v6-translation]
Murakami, T., Chen, G., Deng, H., Dec, W., and S.
Matsushima, "4via6 Stateless Translation",
draft-murakami-softwire-4v6-translation-00 (work in
progress), July 2011.
[I-D.sun-softwire-stateless-4over6]
Sun, Q., Xie, C., Cui, Y., Wu, J., Wu, P., Zhou, C., and
Y. Lee, "Stateless 4over6 in access network",
draft-sun-softwire-stateless-4over6-00 (work in progress),
September 2011.
[I-D.xli-behave-divi]
Bao, C., Li, X., Zhai, Y., and W. Shang, "dIVI: Dual-
Stateless IPv4/IPv6 Translation", draft-xli-behave-divi-03
(work in progress), July 2011.
[I-D.xli-behave-divi-pd]
Li, X., Bao, C., Dec, W., Asati, R., Xie, C., and Q. Sun,
"dIVI-pd: Dual-Stateless IPv4/IPv6 Translation with Prefix
Delegation", draft-xli-behave-divi-pd-01 (work in
progress), September 2011.
[RFC1933] Gilligan, R. and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 1933, April 1996.
[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766,
February 2000.
[RFC3194] Durand, A. and C. Huitema, "The H-Density Ratio for
Address Assignment Efficiency An Update on the H ratio",
RFC 3194, November 2001.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
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Network Address Translations (NATs)", RFC 4380,
February 2006.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[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.
[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,
April 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
Appendix A. Requirements
This list of requirements for a stateless mapping of address and
ports solution may not be complete. The requirements are listed in
no particular order, and they may be conflicting.
R-1: To allow for a single user delegated IPv6 prefix to be used
for native IPv6 service and for MAP, the representation of an
IPv4 prefix, address or shared IPv4 address and PSID must be
efficient. As an example it must be possible to represent a
shared IPv4 address and PSID in 24 bits or less. (Given a
typical prefix assignment of /56 to the end-user and a MAP
IPv6 prefix of /32.)
R-2: The IPv6 address format and mapping must be flexible, and
support any placement of the embedded bits from IPv4 prefix/
address and port set in the IPv6 address.
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R-3: Algorithm complexity. The mapping from an IPv4 address and
port to an IPv6 address is done in the forwarding plane on MAP
nodes. It is important that the algorithm is bounded and as
efficient as possible.
R-4: MAP must allow service providers to define their own address
sharing ratio. MAP MUST NOT in particular restrict by design
the possible address sharing ratio; ideally 1:1 and 1:65536
should be supported. The mapping must at least support a
sharing ratio of 64, 1024 ports per end-user.
R-5: The mapping may support deployments using differentiated port-
ranges. That is, end-users are assigned different sized port-
ranges and direct communication between MAP CEs are permitted.
R-6: The mapping should support differentiated port ranges within a
single shared IPv4 address. (i.e., be able to assign port
ranges of different sizes to customers without requiring any
per customer state to be instantiated in network elements
involved in data transfer).
R-7: The MAP solution should support excluding the well known ports
0-1023.
R-8: It MUST be possible to assign well known ports to a CE.
R-9: There must not be any dependency between IPv6 addressing and
IPv4 addressing. With the exception where full IPv4 addresses
or prefixes are encoded. Then IPv6 prefix assignment must be
done so that martian IPv4 addresses are not assigned.
R-10: The mapping must not require IPv4 routing to be imported in
IPv6 routing.
R-11: The mapping should support legacy RTP/RTCP compatibility.
(Allocating two consecutive ports).
R-12: The mapping may be UPnP 1.0 friendly. A UPnP client will keep
asking for the next port (as in current port + 1) a scattered
port allocation will be more UPnP friendly.
R-13: For out of domain traffic the mapping must support embedding a
full IPv4 address in the IPv6 interface identifier. This is
required in the translation case. It also simplifies pretty
printing and other operational tools.
R-14: For Service Providers requiring to apply specific policies on
per Address-Family (e.g., IPv4, IPv6), some provisioning tools
(e.g., DHCPv6 option) may be required to derive in a
deterministic way the IPv6 address to be used for the IPv4
traffic based on the IPv6 prefix delegated to the home
network.
R-15: It should/must/may be possible to use the same IPv6 prefix
(/64) for native IPv6 traffic and MAPed traffic.
R-16: When only one single IPv6 prefix is assigned for both native
IPv6 communications and the transport of IPv4 packets, the
IPv4-translatable IPv6 prefix MUST have a length less than
/64. When distinct prefixes are used, this requirement is
relaxed.
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R-17: The same mapping must support both translation and
encapsulation solutions.
Appendix B. Deployment considerations
Regarding MAP solutions, the community has granted to investigate
encap/decap and translation for different deployment cases. A new
designed solutions should not impact customary behavior on existing
network nodes. below has listed some deployment considerations.
B.1. Flexible Assigment of Port Range
Different classes of customers would require port sets of different
sizes. In the context of shared IPv4 addresses, some customers would
be satisfied with an shared IPv4 addresses, while others may need to
be assigned with a single IPv4 address or delegated with IPv4
prefixes shorter than 32 bits due to increasing traffic demands. MAP
would allow such flexibilities to allocate different port- set sizes
for satisfy different demands.
B.2. Traffic Classification
Usually, ISPs adopt traffic classification to ensure service quality
for different classes of customers. This feature is also helpful for
customer behavior monitoring and security protection. for example,
DIA (Dedicated Internet Access) has been provided by operators for
corporations to cater for their Internet communications needs.
Service is made by means of the edge router features and key systems,
like ACL(Access List Control) to classify different traffic. Five
tuples would be identified from IP header and UDP/TCP header.
Currently, it is very well supported in IPv4. Vendors are delivering
or committed to support that feature for IPv6. In order to
facilitating IPv6 deployment, 4v6 solution would support this feature
on IPv6 plane.
B.3. Prefix Delegation Deployment
Prefix delegation is an important feature both for broadband and
mobile network. In mobile network, prefix delegation is introduced
in 3GPP network in Release 10. The deployment of PD would be
supported in 4v6 case. Variable length of IPv6 prefix is assigned to
CPE for deriving IPv4 information.
B.4. Coexisting Deployment
4v6 solutions(i.e. encapsulation and translation) would not only
coexist with each other, but also can harmonize with other deployment
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cases. Here lists some coexisting cases. (Note: more coexisting
cases are expected to be investigated in future.)
o Case 1: Coexisting between 4v6 encapsulation and 4v6 translation
o Case 2: Coexisting between 4v6 translation and NAT64 (Single
Translation)
o Case 3: Coexisting between 4v6 solutions and SLAAC
B.5. Friendly to Network Provisioning
Network management plane normally has an ability to to identify
different users and the compatible with the address assignment
techniques in the domain. 4v6 would conform to current practices on
management plane. In 3GPP network, for example, only the IPv6 prefix
is assigned to the devices, used to identify different users. And
management plane for one family address is better than two, namely
the operating platform does not need to manage both IPv4 and IPv6.
Since only IPv6 prefix is assigned, 4v6 on the management plane is
naturally conducted only via IPv6.
B.6. Enable privacy addresses
User privacy should be taken into account when 4v6 solution is
deployed. Some security concern associated with non-changing IPv6
interface identifiers has been expressed in RFC4941[RFC4941].
Ability to change the interface identifier over time makes it more
difficult for eavesdroppers and other information collectors to
identify when different addresses used in different sessions actually
correspond to the same node.
B.7. Facilitating 4v6 Service
Some ISPs may need to offer services in a 4v6 domain with a shared
address, e.g. 4v6 node hosts FTP server. The service provisioning
may require well-know port range(i.e. port range belong to 0-1023).
MAP would provide operators with possibilities to generate a port
range including the 0-1023. Afterwards, operators could decide to
assign it to any requesting user.
B.8. Independency with IPv6 Routing Planning
The IPv6 routing is easier to plan if it's not impacted by the
encoded IPv4 or port ID information. MAP would prohibit IPv4 routing
imported in IPv6.
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B.9. Optimized Routing Path
MAP could achieve optimized routing path both for hub case and mesh
case. Traffic in hub and spoke case could follow asymmetric routing,
in which incoming routes would not be binded to a given border point
but others geographically closed to traffic initiators. In mesh
cases, traffic between CPEs could directly communicate without going
through remote border point.
Appendix C. Guidelines for Operators
C.1. Terms
4pfx the index for an IPv4 prefix.
ug-octet the octet consisting of 64-71 bits in the IPv6
address, containing the bits u and g defined by
EUI-64 standard.
Common prefix an aggregate decided by a domain for the MAP
deployment. It is a subset of the operator's
aggregates by its RIR or provider.
IPv4 suffix the part of IPv4 address bits used for
identifying CEs.
Host suffix the IPv6 suffix assigning to an end system.
NOTE: it doesn't mean this should be really
configured on a certain interface of a host.
MAP format the address mapping format defined by this
document.
RFC6052 format the address mapping format defined by [RFC6052]
and its succeeding extensions (or updates) for
port-space sharing
C.2. Understanding address formats: their difference and relevance
It is important for an operator to understand what the MAP is
designed for and where it could be applied.
MAP introduces an address format of embedding IPv4 information to
IPv6 address. On the other hand, we also have [RFC6052] defines an
address format with the similar property. With extending port-set
id, it can also support address sharing among different CEs
[I-D.xli-behave-divi]. What are their differences and relations?
We present a common abstract format for them both, as is depicted in
Fig.A-1. For the easy expression, we exclude the ug-octet, which is
not concerned in this appendix.
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|<----- 120 bits (IPv6 address excluding ug-octet) --------->|
+-------------+------+-------------+------+-----------//-----+
|Common Prefix| 4pfx | IPv4 suffix | PSID | Host Suffix |
+-------------+------+-------------+------+-----------//-----+
Figure C-1. Abstract view of MAP and RFC6052 formats
Figure 8
Only two parts in Fig.A-1 are different for MAP and RFC6052 formats.
We compare them in Fig.A-2 and following paragraphs.
+----------------+--------------+------------+
| | MAP | RFC6052 |
+----------------+--------------+------------+
| from IPv4 | coding with | same, w/o |
| prefix to 4pfx | compression | change |
+----------------+--------------+------------+
| Host | full v4.addr | padding to |
| Suffix | or 4rd IID | zero |
+----------------+--------------+------------+
Figure A-2. Difference between MAP and RFC6052 formats
Figure 9
This comparison clarifies that the major role of full IPv4 address
embedded in the RFC6052 format is replaced by the MAP's coded IPv4
prefix index and the uncoded IPv4 suffix. The following Fig.A-3
illustrates this relationship.
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(delegated prefix in RFC6052 format, w/o rule)
+-------------+-------------+-------------+------+
|Common Prefix| full IPv4 address (32bit) | PSID |
+-------------+-------------+-------------+------+
: : : :
+-------------+-------------+
32 bits: | 4pfx | IPv4 suffix | :
+-------------+-------------+ +
: . . .
: . . .
: . . .
+-----+-------------+ +
m bits: |4pfx | IPv4 suffix | : (w/ rules)
+-----+-------------+
: : : :
+-------------+-----+-------------+------+
| Rule IPv6 Prefix | CE index |
+-------------+-----+-------------+------+
(delegated prefix in MAP format)
Fig.A-3. Relevance between MAP and RFC6052 formats
Figure 10
Why is it needed to code the IPv4 prefix?
Precisely speaking, it is not "to compress the IPv4 prefix" but "to
establish correspondence between IPv6 delegated prefixes and the
residual IPv4 prefixes."
MAP is designed for IPv4 residual deployment, which refers to
efficiently applying residual (not-yet-assigned) IPv4 addresses in
response to IPv4 communication demands of the IPv6 network in
deployment. Therefore, the delegated CE prefixes are determined
prior to finding proper IPv4 address blocks in hand to be mapped to
the CE index and the IPv4 prefix index as well as the Rule IPv6
prefix, respectively.
Because the IPv6 delegation planning is independent of the IPv4
addressing, the /64 prefix is a canonical configuration for all IPv6
local network. It is highly impossible to directly match some IPv4
prefixes to the already-determined IPv6 prefixes, and therefore the
prefixes have to be coded and typically it is a compression.
If we have a short-enough Common Prefix, it is also possible to
deploy a direct matching where 4pfx is equal to IPv4 prefix. Only in
this case, the MAP format is as same as the RFC6052 format and the
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rule set could be simplified to a unique rule for 0.0.0.0/0.
Why does MAP copy IPv4 address in the suffix?
The full IPv4 address copied in the suffix plays auxiliary roles.
Although the compression makes full IPv4 address not directly appear
in the IPv6 address, the delegated prefix is sufficient to extract
the corresponding IPv4 address for the CE. However, this relies on
the distribution of rules. Embedding the full IPv4 address again in
the suffix helps simple processing at IPv6-to-IPv4 translator when
utilizing MAP for double translation. It also helps in setting
filters at middle boxes, with exposing the IPv4 full addresses
dispatched to the CEs.
Although MAP is designed for the residual deployment, it is also
suitable for the objective of providing stateless encapsulation or
double translation for the ever deployed IPv4 networks whose provider
backbone has upgraded to IPv6. However, unlike the residual
deployment, the latter case needs to introduce IPv4 routing entropy
into the IPv6 routing infrastructure.
C.3. A generic logic of working with MAP
This section illustrate how we can use MAP in the operation of
residual deployment. It starts from IPv6 address planning.
(A) IPv6 considerations (A1) Determine the maximum number N of CEs to
be supported, and, for generality, suppose N = 2^n. (A2) Choose the
length x of IPv6 prefixes to be assigned to ordinary customers (e.g.,
x = 60). (A3) Multiply N by a margin coefficient K, a power of two
(K = 2 ^ k), to take into account that: - Some privileged customers
may be assigned IPv6 prefixes of length x', shorter than x, to have
larger addressing spaces than ordinary customers, both in IPv6 and
IPv4. - Due to the hierarchy of routable prefixes, many theoretically
delegatable prefixes may not be actually delegatable (ref: host
density ratio of [RFC3194]). (B) IPv4 considerations (B1) List all
(non overlapping, not yet assigned to any in-running networks) IPv4
prefixes Hi that are available for IPv4 residual deployment. (B2)
Take enough of them, among the shortest ones, to get a total space
whose size M is a power of two (M = 2 ^ m), and includes a good
proportion of the available IPv4 space. If the M < N, addresses
should be shared by N CEs and thus each is shared by N/M = 2^(n - m)
CEs with PSID length of (n - m). (B3) For each IPv4 prefix Hi of
length hi, choose a "rule index", i.e., the 4pfx in Fig.C-1 and
Fig.C-3, say Ri of length ri = m - (32 - hi). All these indexes must
be non overlapping prefixes (e.g. 0, 10, 110, 111 for one /10, one
/11, and two /12). (C) After (A) and (B), deriving the rule(s) (C1)
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Derive the length c of the "Common prefix" C that will appear at the
beginning of all delegated prefixes (c = x - (n + k)). (C2) Take any
prefix for this C of length c that starts with a RIR-allocated IPv6
prefix. (C3) For each IPv4 prefix Hi, make a rule, in which the key
is Hi, and the value is the Common prefix C followed by the Rule
index Ri. Then this i-th rule's Rule IPv6 Prefix will have the
length of (c + ri).
If different sharing ratio is expected, we may partition all CEs into
subsets and do (A) and (B) for each subset, determining the PSID
length for them separately.
NOTE: Applying MAP for the operation other than residual deployment
(e.g., the IPv6 mapping for already-deployed old IPv4 CEs and
subnets) can reference the above text but please pay attention to the
differences in prerequisites and demands. The condition for the
deployment feasibility is possibly different.
Author's Address
Ole Troan (editor)
cisco
Oslo
Norway
Email: ot@cisco.com
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