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. 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 February 27, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the Chen, et al. Expires February 27, 2012 [Page 1] Internet-Draft Prefix Delegation in 4V6 August 2011 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 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. 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 Chen, et al. Expires February 27, 2012 [Page 2] Internet-Draft Prefix Delegation in 4V6 August 2011 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. Chen, et al. Expires February 27, 2012 [Page 3] Internet-Draft Prefix Delegation in 4V6 August 2011 +-------------+ |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 Chen, et al. Expires February 27, 2012 [Page 4] Internet-Draft Prefix Delegation in 4V6 August 2011 [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. Chen, et al. Expires February 27, 2012 [Page 5] Internet-Draft Prefix Delegation in 4V6 August 2011 +------------+-------------------------+---------------+ | 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 Chen, et al. Expires February 27, 2012 [Page 6] Internet-Draft Prefix Delegation in 4V6 August 2011 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. Chen, et al. Expires February 27, 2012 [Page 7] Internet-Draft Prefix Delegation in 4V6 August 2011 [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 Chen, et al. Expires February 27, 2012 [Page 8]