Network Working Group M. Boucadair, Ed. Internet-Draft C. Jacquenet Intended status: Standards Track JL. Grimault Expires: August 28, 2010 M. Kassi-Lahlou P. Levis France Telecom D. Cheng, Ed. Huawei Technologies Co., Ltd. Y. Lee, Ed. Comcast February 24, 2010 Deploying Dual-Stack Lite (DS-Lite) in IPv6 Network draft-boucadair-dslite-interco-v4v6-03 Abstract This document describes a proposal to enhance dual-stack lite solution with an additional feature to ease interconnection between IPv4 and IPv6 realms. When deployed, no 'dual-stack'-enabled network is required for the delivery of both IPv4 and IPv6 connectivity services to customers. IPv6 transfer capabilities are used for the transfer of IPv4-addressed packets in a completely stateless scheme between the interconnection nodes and the dual-stack lite AFTR node(s). The proposed dual-stack lite extension is meant to encourage (if not accelerate) IPv6 deployment in networks. 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 to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." Boucadair, et al. Expires August 28, 2010 [Page 1] Internet-Draft Extended DS-lite February 2010 The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 28, 2010. Copyright Notice Copyright (c) 2010 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 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 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. Boucadair, et al. Expires August 28, 2010 [Page 2] Internet-Draft Extended DS-lite February 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. DS-Lite AFTR . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Provisioning . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 9 5. IPv6-IPv4 Interconnection Function (ICXF) . . . . . . . . . . 11 5.1. Provisioning . . . . . . . . . . . . . . . . . . . . . . . 11 5.2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Routing Architecture and Considerations . . . . . . . . . . . 12 6.1. Forwarding Packets from ICXF Router to AFTR . . . . . . . 12 6.1.1. Static Routing . . . . . . . . . . . . . . . . . . . . 13 6.1.2. Dynamic Routing . . . . . . . . . . . . . . . . . . . 13 6.2. Forwarding Packets from AFTR to ICXF Router . . . . . . . 13 6.2.1. Static Routing . . . . . . . . . . . . . . . . . . . . 13 6.2.2. Dynamic Routing . . . . . . . . . . . . . . . . . . . 13 7. Multicast Considerations . . . . . . . . . . . . . . . . . . . 15 8. Fragmentation . . . . . . . . . . . . . . . . . . . . . . . . 16 9. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. Security Considerations . . . . . . . . . . . . . . . . . . . 17 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 13.1. Normative References . . . . . . . . . . . . . . . . . . . 17 13.2. Informative References . . . . . . . . . . . . . . . . . . 17 Appendix A. What's New Compared To RFC5565 . . . . . . . . . . . 18 Appendix B. Changes Since 02 . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Boucadair, et al. Expires August 28, 2010 [Page 3] Internet-Draft Extended DS-lite February 2010 1. Introduction Dual-stack lite (a.k.a., DS-Lite) [I-D.ietf-softwire-dual-stack-lite], as one IPv6 migration technique, directly connects users to IPv6 networks but at the same time provides IPv4 services by tunneling IPv4 packets over an IPv6 network. AFTR element, as defined in the DS-Lite architecture, is the combination of an IPv4-in-IPv6 tunnel end-point and an IPv4-IPv4 NAT implemented in the same node. In addition, the specification assumes that an AFTR is directly connected to the IPv4 network. In some deployments, for example, where the service provider wants to deploy AFTR in to the IPv6 core network. AFTR nodes may not be directly connected to the IPv4 network. In this scenario, IPv4 packets after NAT44 function applied on an AFTR node need to be transported over the IPv6 core network to the IPv4 network, and vice versa. This document proposes a framework for this scenario as an extension to the DS-Lite specification. In this specification, we define a new stateless IPv6-IPv4 interconnection function (referred to as IPv6-IPv4 ICXF), in a border node located at the boundaries between the IPv6 and IPv4 networks. The ICXF encapsulates IPv4 packets into IPv6 ones and vice versa. The ICXF may be hosted in an ASBR (Autonomous System Border Router) or a dedicated node located at the interconnection between IPv6 and IPv4 domains. A router that hosts the ICXF is referred to as an ICXF router. A customer's outbound IPv4 packet is de-capsulated from IPv4-in-IPv6 tunnel and then normal NAT44 function is applied on an AFTR. Since an AFTR does not directly connect to the IPv4 network, AFTR will encapsulate the IPv4 packet in an IPv4-in-IPv6 packet, with an IPv4- Embedded IPv6 destination address [I-D.ietf-behave-address-format], and forward it to an ICXF router located in the same IPv6 network but with direct connection to the IPv4 network (Note that the traffic is received by an ICXF only if the destination IPv4 address is not managed by other AFTR nodes in the same IPv6 domain, otherwise encapsulated traffic will be handled by an AFTR node). When the ICXF router receives the IPv4-Embedded IPv6 packet, it will de-capsulate the packet and forward the IPv4 packet based on the IPv4 destination address as usual. For an inbound IPv4 packet, the ICXF router will encapsulate the IPv4 packet into IPv6 packet with the IPv4-Embedded IPv6 address and forward it to the appropriate DS-Lite AFTR node, which de-capsulates Boucadair, et al. Expires August 28, 2010 [Page 4] Internet-Draft Extended DS-lite February 2010 the IPv4 packet and then follows the normal procedure defined by DS- Lite architecture as if the IPv4 packet is received from a directly connected IPv4 network. Figure 1 provides an overview of the global architecture. Customers are connected to the service domain via a CPE device. Several DS- Lite AFTR nodes are deployed to manage the traffic sent and received by the end-user terminal devices. The service domain is IPv6 only and interconnection with adjacent IPv4 realms is implemented using IPv6-IPv4 ICXF. The distributed deployment mode of AFTR nodes is motivated by several reasons such as optimizing intra-domain paths, avoiding single point of failure, minimizing the impact on geo- localization services, minimizing the amount of customers to be impacted by an AFTR node failure, etc. AFTR deployment model varies from service provider to service provider and it is out of scope of this specification. Note in this architecture, the DS-Lite B4 element (located in a CPE) and AFTR still behave exactly as defined in [I-D.ietf-softwire-dual-stack-lite], but with additional functions added to the AFTR when it does not directly connect to the IPv4 network. A new ICXF function is introduced to perform stateless IPv6- IPv4 interconnection. This specification defines new requirements on addressing scheme and routing. More details are provided in the following sections. Boucadair, et al. Expires August 28, 2010 [Page 5] Internet-Draft Extended DS-lite February 2010 +--------------------------------+ | Service Domain | +----------- +----+ | +---------+ | IPv4 |CPE1|---------| |IPv6-IPv4|----| Domain A +----+ | | ICXF | | | +---------+ +----------- | +-------+ | | |DS-Lite| | +----------- +----+ | |AFTR A | +---------+ | IPv4 |CPE2|---------| +-------+ |IPv6-IPv4|----| Domain B +----+ | | ICXF | | | +---------+ +----------- | +-------+ | | | |DS-Lite| | | +----------- +----+ | |AFTR B | | | | IPv4 |CPEi|---------| +-------+ | +-------| Domain C +----+ | | | | | +----------- +--------------------------------+ |<---IPv6----------->|<-----IPv6------------->|<---IPv4---- Figure 1: Global Architecture 2. Terminology This memo defines the following terms: o IPv6-IPv4 Interconnection Function (IPv6-IPv4 ICXF): refers to the function that de-capsulates (resp., encapsulates) the IPv6 (resp., IPv4) packet from DS-Lite AFTR node(s) and forwards the IPv4 (resp., IPv6) packets to the IPv4 (resp., IPv6) networks. o ICXF router: refers to the border router implemented with IPv6- IPv4 ICXF. o DS-Lite AFTR node: refers to the AFTR node whose behavior is specified in [I-D.ietf-softwire-dual-stack-lite]. This node embeds a Carrier Grade-NAT (CGN) function. In addition, this specification assumes that the DS-Lite AFTR node is only connected to an IPv6 network. In this specification, the AFTR will encapsulate the IPv4 packet in an IPv6 packet (IPv4-in-IPv6) after the NAT44 function. The encapsulated IPv6 packet will be forwarded to the ICXF router. This IPv4-inIPv6 encapsulation is stateless. Boucadair, et al. Expires August 28, 2010 [Page 6] Internet-Draft Extended DS-lite February 2010 o Access segment: This segment encompasses both the IP access to the customers and to the service provider's network. o Interconnection segment: Includes all nodes and resources which are deployed at the border of a given AS (Autonomous System) a la BGP. o Core segment: Denotes a set of IP networking capabilities and resources which are located between the interconnection and the access segments. o IP connectivity information: A set of information (e.g., IP address, default gateway, etc.) required to access IP transfer delivery service. o Pref6: An IPv6 prefix assigned by LIR. This prefix is configured on both ICXF and AFTR. o FROM-AFTR Address: An IPv4-Embedded IPv6 address that combines an IPv6 prefix Pref6 and the destination IPv4 address as defined in [I-D.ietf-behave-address-format]. o TO-AFTR Address: An IPv4-Embedded IPv6 address [I-D.ietf-behave-address-format] that combines an IPv6 prefix Pref6 and a destination IPv4 address which configured in an AFTR NAT pool. 3. Addressing When a DS-Lite AFTR does not directly connect to the IPv4 network, IPv4 packets sent to and received from the IPv4 network by the AFTR, must be encapsulated in IPv6 packets. For outbound IPv4 packets, the AFTR performs encapsulation and the ICXF router performs de-capsulation (if the traffic is destined to destination which is not managed by an AFTR router attached to the same IPv6 network), and for inbound IPv4 packets, the ICXF router performs IPv4-in-IPv6 encapsulation and an AFTR performs de- capsulation. When an AFTR forwards an IPv6 packet with an IPv4 payload to an ICXF router, the source IPv6 address is one of the AFTR's IPv6 address, which is normally a global IPv6 address configured on an interface of the node (e.g., an address of a loopback interface), and the destination IPv6 address is the FROM-AFTR Address. When an ICXF router receives an IPv4 packet, it encapsulate the IPv4 Boucadair, et al. Expires August 28, 2010 [Page 7] Internet-Draft Extended DS-lite February 2010 packet with an IPv6 header where the source IPv6 address is the ICXF router's global IPv6 address and the destination IPv6 address is the TO-AFTR address. The TO-AFTER address is constructed by combining the Pref6 and the destination IPv4 address in the IPv4 packet. The destination IPv4 address is one of the addresses configured in the AFTR NAT pool. In both cases, the Pref6 is an IPv6 prefix assigned by the service provider, and is used to construct an IPv4-Embedded IPv6 address, as described in [I-D.ietf-behave-address-format]. Figure 2 gives an example of the address format. In this example, Pref6 is 2a01:c::/20 and the IPv4_Addr is 193.51.145.206. Then, the corresponding IPv6 prefix is: 2a01:cc13: 391c:e0::/56. 2a01:c::11000001001100111001000111001110 = 2a01:cc13:391c:e0::/56 |Pref6 | <--------193.51.145.206--------> Figure 2: Example for an IPv4-Embedded IPv6 Prefix In the example, we use a /20 prefix for Pref6. However, an operator can decide to use a longer prefix. More examples about IPv4-Embedded IPv6 addresses can found at [I-D.ietf-behave-address-format]. 4. DS-Lite AFTR The AFTR function is defined in [I-D.ietf-softwire-dual-stack-lite]. To support the extension as defined in this document, additional provisioning and functions are required as described in the following sub-sections. 4.1. Provisioning The provisioning of an AFTR is according to that described in [I-D.ietf-softwire-dual-stack-lite], including a set of global IPv4 addresses that are used for its NAT44 operations. In addition, an IPv6 prefix (i.e., Pref6) is configured in the AFTR. The Pref6 is used to construct FROM-AFTR addresses. These IPv6 addresses are used as destination addresses of IPv4-in-IPv6 packets. In practice, , the set of global IPv4 addresses is aggregatable, leading to a set of aggregated IPv4-Embedded IPv6 prefixes, for the sake of routing scalability, as described in Section 6. Boucadair, et al. Expires August 28, 2010 [Page 8] Internet-Draft Extended DS-lite February 2010 4.2. Procedure Figure 3 shows the input and output of a DS-Lite AFTR node. +-------------------+ ----IPv6---\ | |----IPv6---\ ----IPv4---\\| |----IPv4---\\ -----------//| |-----------// -----------/ | |-----------/ Customer | DS-Lite | Core Node Interface /----IPv6---| AFTR | /----IPv6--- //---IPv4----| |//---IPv4---- \\-----------| |\\----------- \-----------| | \----------- +-------------------+ Figure 3: Modified DS-Lite AFTR Two main (logical) interfaces may be distinguished in a DS-Lite AFTR node as follows: a. Interface with the customer device, i.e.- DS-Lite interface per [I-D.ietf-softwire-dual-stack-lite]. b. Interface with core nodes. Note that the DS-Lite AFTR does not directly connect to an IPv4 domain. The processing of the IPv4 traffic received from a customer device is as follows. Processing Ingress Traffic from Customer Interface 1. De-capsulate the IPv6 header from the IPv4-in-IPv6 packets (sent by the customer device) 2. 2. NAT the IPv4 packet and create an entry in the NAT binding table 3. Encapsulate the NAT-ed IPv4 packets in IPv6 with a destination IPv6 address built according to the addressing scheme described in Section 3. Encapsulated packet is forwarded based on the FROM-AFTR IPv6 address by standard routing. Depending on the target IPv4 address, the destination can be Boucadair, et al. Expires August 28, 2010 [Page 9] Internet-Draft Extended DS-lite February 2010 an AFTR node inside the service provider's domain if the IPv4 address is one of the addresses owned by another AFTR (See Figure 4). Or, the destination can be an ICXF router if the IPv4 address is external. Processing Ingress Traffic from Core Interface 1. De-capsulate the IPv6 header and extract the IPv4 packet. 2. Process the embedded IPv4 packet according to [I-D.ietf-softwire-dual-stack-lite]. 3. Forward the resulting IPv6 packet to the corresponding B4. +------+ +---------+ +---------+ +------+ | |--IPv6---\ | |------IPv6-----\ | |---IPv6--\ | | | |--IPv4---\\| |-----IPv4------\\| |---IPv4--\\| | | |---------//| |---------------//| |---------//| | | |---------/ | |---------------/ | |---------/ | | | CPE 1| | DS-Lite | | DS-Lite | | CPE2 | | | /---IPv6--| AFTR A | /-----IPv6------| AFTR B | /---IPv6--| | | |//---IPv4--| |//----IPv4-------| |//--IPv4---| | | |\\---------| |\\---------------| |\\---------| | | | \---------| | \---------------| | \---------| | +------+ +---------+ +---------+ +------+ Note that hosts connected to each CPE are not represented in the figure. Figure 4: Flow Example involving two devices attached to distinct AFTRs Boucadair, et al. Expires August 28, 2010 [Page 10] Internet-Draft Extended DS-lite February 2010 The following figure illustrates an example of CPE connected to a DS- Lite AFTR node, which establishes a communication with a remote host (referred to as RH) which is on an IPv4 network. +------+ +---------+ +---------+ +------+ | |--IPv6---\ | |------IPv6-----\ | | | | | |--IPv4---\\| |-----IPv4------\\| |---IPv4--\| | | |---------//| |---------------//| |---------/| | | |---------/ | |---------------/ | | | | | CPE 1| | DS-Lite | |IPv6-IPv4| | RH | | | /---IPv6--| AFTR A | /-----IPv6------| ICXF | | | | |//---IPv4--| |//----IPv4-------| |/--IPv4---| | | |\\---------| |\\---------------| |\---------| | | | \---------| | \---------------| | | | +------+ +---------+ +---------+ +------+ Note that host connected to CPE1 are not represented in the figure. Figure 5: Flow Example involving only one device attached to a DS- lite enabled domain 5. IPv6-IPv4 Interconnection Function (ICXF) ICXF is a border element that encapsulate IPv4 packets from external IPv4 network to AFTR and de-capsulate IPv6 packets from AFTR to external IPv4 network The following sub-sections provide more information about the behavior of this function. 5.1. Provisioning An IPv6-IPv4 ICXF router is provisioned with an IPv6 prefix (i.e., Pref6). Pref6 is used to build TO-AFTR addresses as described in Section 3. The ICXF is connected to IPv4 network. It maintains IPv4 routing information of the IPv4 networks. The routing information can be provisioned statically or dynamically. 5.2. Procedure Figure 6 shows the input and output of an IPv6-IPv4 ICXF. Boucadair, et al. Expires August 28, 2010 [Page 11] Internet-Draft Extended DS-lite February 2010 +-------------------+ ----IPv6---\ | | ----IPv4---\\| |----IPv4---\ -----------//| |-----------/ -----------/ | | | IPv6-IPv4 | /----IPv6---| ICXF | //---IPv4----| |/---IPv4---- \\-----------| |\----------- \-----------| | +-------------------+ Figure 6: IPv6-IPv4 Interworking Function When the ICXF router receives an IPv4 packet from an external IPv4 domain, it encapsulates the IPv4 packet in IPv6 packet using the following information: o Source IPv6 address: One of its own IPv6 addresses. o Destination IPv6 address: TO-AFTR Address which is an IPv4- Embedded IPv6 address using the Pref6 and destination IPv4 address of the encapsulated IPv4 packet. As for the outbound IPv6 packets, an ICXF router performs de- capsulation and forwards the embedded IPv4 packets to the connected IPv4 networks according to IPv4 routing rule. 6. Routing Architecture and Considerations This section describes the routing consideration to support this specification, i.e.- how an IPv6 packet with an IPv4-Embedded IPv6 destination address is forwarded from a DS-Lite AFTR to an ICXF router, and vice versa, in the IPv6 network. 6.1. Forwarding Packets from ICXF Router to AFTR When an ICXF router forwards IPv4-in-IPv6 packets to a DS-Lite AFTR, the destination IPv6 address is an IPv4-Embedded IPv6 address, where the Pref6 is an IPv6 prefix assigned to the service provider and the IPv4 address is in the AFTR IPv4 NAT address pool. The ICXF must have the routing information of the IPv4-Embedded IPv6 addresses. The routing information can be configured statically or dynamically. Boucadair, et al. Expires August 28, 2010 [Page 12] Internet-Draft Extended DS-lite February 2010 6.1.1. Static Routing Each ICXF router is configured with static routes, and each static route points to an IPv4-Embedded IPv6 prefix. 6.1.2. Dynamic Routing Dynamic routing may be more desirable especially when there are multiple ICXF routers and AFTRs, where each ICXF router learns how to forward IPv4-in-IPv6 packets to corresponding AFTRs without provisioning static routes. To achieve dynamic routing, each DS-Lite AFTR (or the upstream router of the DS-Lite AFTR) advertises the set of IPv4-Embedded IPv6 addresses and/or prefixes it manages by IPv6 IGP (e.g., OSPFv3) in the IPv6 network. The ICXF router will learn the prefixes via IPv6 IGP and install the prefixes in the IPv6 routing table. Note that these prefixes MUST NOT be advertised outside the IPv6 domain, e.g.- to adjacent e-BGP peers. 6.2. Forwarding Packets from AFTR to ICXF Router When a DS-Lite AFTR forwards IPv4-in-IPv6 packets to an ICXF router, the destination IPv6 address is an IPv4-Embedded IPv6 address, where the Pref6 is an IPv6 prefix assigned to the service provider and the IPv4 address is reachable through one or more ICXF routers. The forwarding decision can be made based on static configuration or dynamic routing. 6.2.1. Static Routing The AFTR is configured with static routes, and each static route points to an IPv4-Embedded IPv6 prefix. Alternatively, the AFTR can contain a default route where the default is the ICXF. 6.2.2. Dynamic Routing Dynamic routing is more desirable for the deployments where there are multiple DS-Lite AFTRs and ICXF routers. This specification suggests four dynamic routing options as documented below: Option 1: AFTRs and ICXF routers are configured as a softwire mesh [RFC5565] and i-BGP is used to exchange IPv4 reachability information. AFTR and ICXF will peer with each other over i-BGP and exchange their IPv4 reachability. Each AFTR and ICXF will compute an IPv4 routing table based upon the BGP table. Boucadair, et al. Expires August 28, 2010 [Page 13] Internet-Draft Extended DS-lite February 2010 Given an IPv4 network managed by the AFTR or ICXF, the next-hop of this network is the IPv6 address of the AFTR or ICXF. This routing option offers an optimized forwarding for IPv4-in- IPv6 packets in the IPv6 network with the cost of running i-BGP on all DS-Lite AFTRs and ICXF routers, and storing BGP routers on all these nodes. Note when this option is used, the mechanism described in Section 6.1.2 must not be used in the same network. Option 2: ICXF router advertises its IPv4 reachability information in IGP. This routing option does not require AFTRs and ICXFs to be i-BGP peers, it also doesn't require AFTR to maintain an IPv4 routing table. For the AFTR IPv6 routing table, it contains all FROM_AFTR prefixes and the ICXF IPv4 reachability information in the form on IPv4-Embedded IPv6 prefixes (i.e., Pref6 + ICXF IPv4 routing information). Given that the ICXF advertises all its IPv4 network reachability in IPv6 network, the AFTR can choose the best path to forward the packet. However, this optimization has a drawback: ICXF routers are required to advertise its full IPv4 reachability to in IGP. As such, IPv6 routers will maintain the full IPv4 reachability in its IPv6 routing table. Option 3: With this option, each ICXF router advertises a Pref6 (Section 5.1) in the IPv6 IGP. An AFTR forwards an IPv4-in- IPv6 packet always to a nearest ICXF router, which, after the de-capsulation, will then forward the IPv4 packet according to its IPv4 routing table. Note in this case, the ICXF router, which is the nearest to the AFTR, may not have the best route (if there is a route at all) to the final destination in the IPv4 network, comparing to other ICXF routers that may be present, depending on the actual IPv4 network in question, which is beyond the scope of this document. This routing option does not create any overhead in the IPv6 network nor on DS-Lite AFTR, and the forwarding path for IPv4- in-IPv6 packets is also optimized, with the cost of possible sub-optimization when forwarding IPv4 packets after de- Boucadair, et al. Expires August 28, 2010 [Page 14] Internet-Draft Extended DS-lite February 2010 capsulation on ICXF routers. Option 4: Option 4 requires every router in the IPv6 network to learn the IPv4-Embedded IPv6 prefixes advertised by the AFTR and ICXF. These prefixes are only meaningful to the AFTR and ICXF, other IPv6 routers may not be interested in them. To address this issue, a separate topology ([I-D.boucadair-ospf-v4v6-ospfv3-mt] or [I-D.boucadair-isis-v4v6-mt]) that is dedicated to the reachability of IPv4-Embedded IPv6 prefixes can be used. This option requires the ICXF router and AFTR advertise the IPv4-Embedded IPv6 prefixes in the IPv4-Embedded IPv6 topology. This topology contains only the IPv4-Embedded IPv6 prefixes. Regular IPv6 routers will not participate this topology. With this option, each ICXF router advertises in the IPv6 network a set of IPv4-Embedded IPv6 addresses and/or prefixes, where each embedded IPv4 address or prefix represents an IPv6 destination or (sub)network that is reachable through the ICXF router, respectively. Also, the mechanism as described in Section 6.1.2 is used but with separate IGP topology or instance, i.e.- each DS-Lite AFTR advertises in the IPv6 network a set of IPv4-Embedded IPv6 addresses and/or prefixes, where each embedded IPv4 address or prefix represents a global IPv4 address or the aggregation of a set of IPv4 addresses, respectively. This option is very similar to Option 2. The major advantage for multi-topology is to create a separate an IPv4-Embedded IPv6 network that only AFTR and ICXF install the prefixes in the IPv6 routing table. However, ICXF still advertises its IPv4 reachability into IGP. Similar to Option 3, ICXF can advertise only the Pref6 in the IPv6 IGP. AFTR will install only a default to the closest ICXF. Since the closet ICXF may not contain the best path for the destination IPv4 address, sub-optimal routing is possible for the destination IPv4 network. 7. Multicast Considerations This document describes an IPv4-IPv6 inter-connection extension to DS-Lite [I-D.ietf-softwire-dual-stack-lite], which currently limits the scope to transporting unicast IPv4 traffic over IPv6 network only. Considerations on transporting multicast IPv4 traffic over Boucadair, et al. Expires August 28, 2010 [Page 15] Internet-Draft Extended DS-lite February 2010 IPv6 network is out of scope. 8. Fragmentation Tunneling IPv4 over IPv6 between AFTR and ICXF reduce the effective MTU size by the size of an IPv6 header. Since ICXF tunnel is stateless, the tunnel endpoint can't fragment and re-assumable the oversized IPv4 packet. A service provider may increase the MTU size by 40-bytes on the IPv6 network. If this is not possible, AFTR and ICXF may use IPv6 Path MTU discovery. ICXF nodes are stateless and do not need to implement any re-assembly function (for IPv4 fragments) which is performed by the AFTR as defined in the base DS-Lite architecture. This stateless characteristic of the ICXF is aligned with inter-domain route asymmetry behaviour, e.g.- even fragments of a specific inbound (towards AFTRs) traffic flow may be transmitted by different ICXF routers, the same AFTR would receive those fragments, since ICXF does not need any transport-related information (e.g., TCP/UDP port number) which may not be in a given fragment, but only the destination IPv4 address for its operation (i.e., build an IPv4- Embedded IPv6 address and encapsulate the received IPv4 datagram in an IPv6 one destined to that IPv4-Embedded IPv6 address. 9. Conclusions This document describes the mechanism to extend DS-Lite to operate an IPv6-only network while offering: o Global IPv6 <==> IPv6 communications. o Global IPv4 <==> IPv4 communications. o A remote IPv6 host would reach a host connected to the DS-Lite enabled domain using IPv6. o A remote IPv4 host would reach a host connected to the DS-Lite enabled domain using IPv4-in-IPv6. 10. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. Boucadair, et al. Expires August 28, 2010 [Page 16] Internet-Draft Extended DS-lite February 2010 11. Security Considerations Security considerations defined in [I-D.ietf-softwire-dual-stack-lite] should be taken into account. In addition, current interconnection practices for ingress traffic filtering should be enforced in the interconnection points (ICXF). 12. Acknowledgements The authors would like to thank Eric Burgey for his support and suggestions. 13. References 13.1. Normative References [I-D.ietf-softwire-dual-stack-lite] Durand, A., Droms, R., Haberman, B., Woodyatt, J., Lee, Y., and R. Bush, "Dual-stack lite broadband deployments post IPv4 exhaustion", draft-ietf-softwire-dual-stack-lite-03 (work in progress), February 2010. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. 13.2. Informative References [I-D.boucadair-isis-v4v6-mt] Boucadair, M., Jacquenet, C., Cheng, D., and Y. Lee, "Multi-Topology/Multi-Instance ISIS for IPv4-Embedded IPv6", draft-boucadair-isis-v4v6-mt-02 (work in progress), February 2010. [I-D.boucadair-ospf-v4v6-ospfv3-mt] Boucadair, M., Jacquenet, C., Cheng, D., and Y. Lee, "Multi-Topology/Multi-Instance OSPFv3 for IPv4-Embedded IPv6", draft-boucadair-ospf-v4v6-ospfv3-mt-02 (work in progress), February 2010. [I-D.ietf-behave-address-format] Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", Boucadair, et al. Expires August 28, 2010 [Page 17] Internet-Draft Extended DS-lite February 2010 draft-ietf-behave-address-format-04 (work in progress), January 2010. [RFC4277] McPherson, D. and K. Patel, "Experience with the BGP-4 Protocol", RFC 4277, January 2006. [RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh Framework", RFC 5565, June 2009. Appendix A. What's New Compared To RFC5565 One of the two scenarios softwire mesh [RFC5565] covers is IPv4 tunneling through an IPv6-only backbone. Mesh defines an interconnection function at the backbone's edge routers called AFBR. All AFBRs exchange i-BGP routes. When an IPv4 datagram arrives at an AFBR, it uses a BGP-distributed route to retrieve the IPv6 destination address of the distant softwire endpoint. The AFBRs will form a mesh network tunneling the IPv4 datagrams over softwire. The AFBRs must maintain a stateful mapping table for encapsulation and de-capsulation purposes. This document covers a slightly different IPv4 over IPv6 scenario. This scenario is asymmetric. On one side of the IPv6 backbone, there are AFTRs, and on the other side of the IPv6 backbone there are IPv4 Internet access points. At each IPv4 Internet access point we define an interconnection function called ICXF. All ICXFs exchange i-BGP information. In some scenarios, AFTRs do not participate in the i-BGP exchanges (since IGP may be used, see Section 6 for more details). Unlike [RFC5565], the encapsulation at both sides is stateless: the IPv6 destination address of the distant softwire endpoint is automatically generated, based on the IPv4 destination address of the IPv4 datagram only, there is no need to refer to any route. The forwarding of the encapsulated datagrams is ensured by the installation of appropriate routes by i-BGP between ICXFs. Appendix B. Changes Since 02 The following changes have been made since the last version: 1. Add a new section to define addressing scheme; 2. Add a new section to list all routing options in the IPv6 network; Boucadair, et al. Expires August 28, 2010 [Page 18] Internet-Draft Extended DS-lite February 2010 3. Various editorial changes. Authors' Addresses Mohamed Boucadair (editor) France Telecom 3, Av Francois Chateaux Rennes 35000 France Email: mohamed.boucadair@orange-ftgroup.com Christian Jacquenet France Telecom Email: christian.jacquenet@orange-ftgroup.com Jean-Luc Grimault France Telecom France Email: jeanluc.grimault@orange-ftgroup.com Mohammed Kassi-Lahlou France Telecom Email: mohamed.kassilahlou@orange-ftgroup.com Pierre Levis France Telecom Email: pierre.levis@orange-ftgroup.com Dean Cheng (editor) Huawei Technologies Co., Ltd. Email: Chengd@huawei.com URI: http://www.huawei.com Boucadair, et al. Expires August 28, 2010 [Page 19] Internet-Draft Extended DS-lite February 2010 Yiu L. Lee (editor) Comcast Email: yiu_lee@cable.comcast.com URI: http://www.comcast.com Boucadair, et al. Expires August 28, 2010 [Page 20]