Internet DRAFT - draft-chen-softwire-4v6-pd
draft-chen-softwire-4v6-pd
Softwire WG G. Chen
Internet-Draft T. Sun
Intended status: Standards Track H. Deng
Expires: February 27, 2012 China Mobile
August 26, 2011
Prefix Delegation in 4V6
draft-chen-softwire-4v6-pd-00
Abstract
This draft presents the investigation of 4via6 in the scenario where
IPv6 prefix delegation is deployed. A practicable application
scenarios with IPv6 prefix delegation have been introduced in the
mobile network environments. The applicability of 4via6 mechnism has
been analyzed in term of mapping rules and 4via6 address structure.
Targeting to alignment with existing 4via6 mapping algorithm and
RFC6052 recommendation, an alternative 4via6 address structure have
been proposed to be capable of assigning flexible address/port set to
4via6 domains.
Requirements Language
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 27, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Applicability: Mapping Rules and Address Structure . . . . . . 4
4. Other Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Contributors and Acknowledgements . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
With the fast development of global Internet, the demands for IP
address are rapidly increasing currently. This year, IANA announced
that the global free pool of IPv4 depleted on 3 February. IPv6 is
the only real option on the table. Operators have to accelerate the
process of deploying IPv6 networks in order to address IP address
strains.
IPv6 deployment normally involves a step-wise approach where parts of
the network should properly updated gradually. As IPv6 deployment
progresses it may be simpler for operators to employ a single-version
network, since deploying both IPv4 and IPv6 in parallel would costs
more than IPv6-only network. Therefore switching to an IPv6-only
network will become more prevalent. Meanwhile, a significant part of
network will still stay in IPv4 for long time. There may not be
enough public or private IPv4 addresses to support end-to-end network
communication, without segmenting the network into small parts with
sharing one IPv4 address space. Operators have to choose a IPv6
transition technology to bridge these IPv4 islands through IPv6
network.
Currently, 4via6 stateless became a essential topic which motivates
IETF community taking efforts to advance the
work[I-D.operators-softwire-stateless-4v6-motivation].
Encapsulation/decapsulation solution[I-D.murakami-softwire-4rd] and
translation solution[I-D.murakami-softwire-4v6-translation] have been
proposed to fit into the solution set. The flexibilities of 4via6
mapping algorithm allow the variable length of IPv6 prefix assigned
to CE for deriving IPv4 information. This also could facilitate the
IPv6 prefix delegation implementation in the mobile environments.
The memo would discuss the applicability of 4via6 with pd mechanism.
Some observations for use scenarioes, mapping rules and 4via6
structure have been described in the following sections.
2. Scenario
This section describes the scenario of prefix delegation used in
mobile network. The architecture is depicted in Figure 1. Prefix
delegation is introduced in 3GPP network in Release 10. A UE (CPE)
obtains IPv6 prefix from the mobile network. It then initiates
DHCPv6 for prefix delegation.
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+-------------+
|Private IPv4 |
| Network | H1
+-------------+
|
|
O-------------------O
| UE (CPE) |
| +-------+-------+ | |------------| |------------|
| | NAT44 | 4via6 | | | | | |
| | | /64 | |==| E-UTRAN |----| EPC |
| +-------+-------+ | |------------| |------------|
| | | |
| | /56 | |
O---------+-------+-O
| |
| H3 | H2
+-------------+ +----------+
| /64 IPv6 | | /64 IPv6 |
|&Private IPv4| +----------+
| Network |
+-------------+
Figure 1: 4V6 UE perfoms as a CPE with prefix delegation
There are two phases for a 4V6 UE/CPE performs prefix delegation
function. For the first phase, the 4V6 UE/CPE attaches to the LTE
network. The network provides the UE with IPv6 only connection and
the UE obtains a /64 4V6 prefix. For the second phase, the 4V6 UE/
CPE initiate prefix delegation procedure. The network assign a
prefix shorter than 64 to the 4V6 UE/CPE. Figure 1 shows a case that
a /56 is assigned to UE/CEP during prefix delegation.
There may be three possible cases for a 4V6 UE performing as a CPE.
As shown in Figure 1 It privdes IPv4 only, IPv6 only or IPv6 and IPv4
connection to IP devices depicted as H1, H2 and H3. The 4V6 UE/CPE
may implement a internal NAT44 to provide IPv4 connectin for multiple
IP devices. The IP devices get /64 prefix from 4V6 UE/CPE through
RS/RA. Such a /64 prefix is generated from the prefix assigned by
the network through prefix delegation.
3. Applicability: Mapping Rules and Address Structure
In order to simplify PD implementation, 4via6 stateless should allow
a IPv6 prefix with variable length delegated to 4via6 CE for deriving
IPv4 address. 4via6 stateless mapping rules specified in
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[I-D.murakami-softwire-4rd] and [I-D.despres-softwire-4rd-addmapping]
have naturally supported that, in which a variable length field
inserting port index information has allowed encoded in the top 64
bits of IPv6 prefix. With different size of granted port space
assigned to customers, IPv6 prefix with shorter than 64bits length
could be produced. 4via6 CE could be delegated with the IPv6 prefix
for potential 4via6 stateless computations.
In some cases, operators may require an ability to assign address/
port sets of different sizes to different classes of customers
according dynamic traffic model. Current mapping rule could provide
such capacities by linking to different lengths of delegated IPv6
prefixes. The below has proposed alternative one, which could
compatible with the address structure defined in
[I-D.murakami-softwire-4rd], also could follow the recommendation in
[RFC6052].
|-------------64 bits --------------|-8-|prefix L| |
+--------------------- -------------+---+--------+----+
|IPv6 prefix |Add set|Port set|zero | u | v4 |zero|
+---------------------------- ------+---+--------+----+
Figure 2: 4via6-pd structure
Followings provide the desriptions for each field:
o IPv6 prefix
An IPv6 prefix assigned by an ISP to a 4via6 domain.
o Add set
The length of Add set is (32-IPv4 prefix length)long. The purpose of
the field is used to determine how many IPv4 address assigned to
customers connecting a given CE. It could be a IPv4 subnet or a
shared IPv4 address according to padding bits. Specifically, IPv4
subnet will be identified by the suffix of zero.
o Port set
Port set indicates the size of granted port space. The length is
determined by multiplexing ratio, which is shown in the table
[I-D.sun-intarea-4rd-applicability]. Also, the bits in the port set
field would serve for identifying a specific 4via6 CE.
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+------------+-------------------------+---------------+
| Port Set | User numbers that can | # of ports |
| length | share one v4 address | for each CE |
+------------+-------------------------+---------------+
| 1 | 1 - 2 | 30720 |
| 2 | 1 - 4 | 15360 |
| 3 | 1 - 8 | 7680 |
| 4 | 1 - 16 | 3840 |
| 5 | 1 - 32 | 1920 |
| 6 | 1 - 64 | 960 |
| 7 | 1 - 128 | 480 |
| 8 | 1 - 256 | 240 |
| 9 | 1 - 512 | 120 |
| 10 | 1 - 1024 | 60 |
| 11 | 1 - 2048 | 30 |
| 12 | 1 - 4096 | 15 |
| 13 | 1 - 8192 | 7 |
| 14 | 1 - 16384 | 3 |
| 15 | 1 - 32768 | 1 |
+------------+-------------------------+---------------+
Figure 3: 4via6-pd port set
o IPv4 Prefix
The preconfigured IPv4 prefix would be encoded in the last 64 bits,
which is following the recommendation in RFC6035.
o Delegated IPv6 Prefix
The delegated IPv6 prefix would be determined through the below
formula.
Delegated IPv6 prefix = IPv6 prefix + Add set + Port set
Therein, the field of (Add set+ Port set) is compatible with EA bits
in [I-D.murakami-softwire-4rd]. The additional gains here are to
provide the possibilities of assigning several shared IPv4 address in
a given CE domain.
4. Other Considerations
The total IPv6 address space available for the PDN connection (UE/CPE
4V6 prefix and the delegated IPv6 prefix) shall be possible to
aggregate into one IPv6 prefix that will represent all IPv6 addresses
that the UE may use. If the UE/CPE indicates that it supports prefix
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exclusion and the prefix to be delegated to the UE/CPE includes the
/64 prefix that was allocated as the 4V6 prefix, the network shall
utilise the prefix exclusion feature for DHCPv6 Prefix Delegation.
5. Contributors and Acknowledgements
This document would not have been possible without the significant
contribution provided by Cao Zhen.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
6.2. Informative References
[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-00 (work in
progress), August 2011.
[I-D.murakami-softwire-4rd]
Murakami, T. and O. Troan, "IPv4 Residual Deployment on
IPv6 infrastructure - protocol specification",
draft-murakami-softwire-4rd-00 (work in progress),
July 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.operators-softwire-stateless-4v6-motivation]
Boucadair, M., Matsushima, S., Lee, Y., Bonness, O.,
Borges, I., and G. Chen, "Motivations for Stateless IPv4
over IPv6 Migration Solutions",
draft-operators-softwire-stateless-4v6-motivation-02 (work
in progress), June 2011.
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[I-D.sun-intarea-4rd-applicability]
Sun, C., Matsushima, S., and J. Jiao, "4rd Applicability
Statement", draft-sun-intarea-4rd-applicability-01 (work
in progress), March 2011.
Authors' Addresses
Gang Chen
China Mobile
Unit2, 28 Xuanwumenxi Ave
Beijing, Xuanwu District 100053
China
Phone:
Email: chengang@chinamobile.com
Tao Sun
China Mobile
Unit2, 28 Xuanwumenxi Ave
Beijing, Xuanwu District 100053
China
Phone:
Email: suntao@chinamobile.com
Hui Deng
China Mobile
Unit2, 28 Xuanwumenxi Ave
Beijing, Xuanwu District 100053
China
Phone:
Email: denghui@chinamobile.com
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