Internet Engineering Task Force T. Murakami, Ed. Internet-Draft IP Infusion Intended status: Standards Track O. Troan Expires: July 30, 2012 cisco S. Matsushima SoftBank January 27, 2012 MAP Encapsulation (MAP-E) - specification draft-mdt-softwire-map-encapsulation-00 Abstract This document specifies the "Mapping of Address and Port" (MAP) encapsulation based solution (MAP-E) with an automatic tunneling mechanism for providing IPv4 connectivity service to end users over a service provider's IPv6 network. 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 July 30, 2012. Copyright Notice Copyright (c) 2012 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 Murakami, et al. Expires July 30, 2012 [Page 1] Internet-Draft MAP Encapsulation (MAP-E) January 2012 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. MAP-E Configuration . . . . . . . . . . . . . . . . . . . . . 5 5. MAP-E Node Behavior . . . . . . . . . . . . . . . . . . . . . 5 5.1. Provisioning of MAP-E BR . . . . . . . . . . . . . . . . . 5 5.2. Packet Forwarding Behavior on MAP-E BR . . . . . . . . . . 6 5.3. Provisioning of MAP-E CE . . . . . . . . . . . . . . . . . 7 5.4. Packet Forwarding Behavior on MAP-E CE . . . . . . . . . . 8 6. Deriving IPv6 address from IPv4 . . . . . . . . . . . . . . . 9 6.1. Deriving IPv6 address from IPv4 Address and Port Number at the BR . . . . . . . . . . . . . . . . . . . . . 9 6.2. Deriving IPv6 address from IPv4 Address and Port Number at the CE . . . . . . . . . . . . . . . . . . . . . 10 7. Encapsulation and Fragmentation Considerations . . . . . . . . 10 8. Packet Forwarding Considerations . . . . . . . . . . . . . . . 11 8.1. Mesh model . . . . . . . . . . . . . . . . . . . . . . . . 12 8.2. Hub & Spoke model . . . . . . . . . . . . . . . . . . . . 12 9. NAT Considerations . . . . . . . . . . . . . . . . . . . . . . 12 10. ICMP Considerations . . . . . . . . . . . . . . . . . . . . . 12 11. Security Considerations . . . . . . . . . . . . . . . . . . . 13 12. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 14 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 14.1. Normative References . . . . . . . . . . . . . . . . . . . 14 14.2. Informative References . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Murakami, et al. Expires July 30, 2012 [Page 2] Internet-Draft MAP Encapsulation (MAP-E) January 2012 1. Introduction MAP-E is a protocol mechanism of the &ldque;Mapping of Address and Port" (MAP) encapsulation based solution to deploy IPv4 to sites via a service provider's (SP's) IPv6 network with the automatic tunneling mechanism (IPv4-in-IPv6). Similar to Dual-Stack Lite [I-D.ietf-softwire-dual-stack-lite], MAP-E is designed to allow IPv4 traffic to be delivered over an IPv6 network without the direct provisioning of IPv4 addresses. Like 6rd [RFC5969], MAP-E is operated in a fully stateless manner within the SP network. MAP-E relies on IPv6 and is designed to deliver production-quality dual-stack service while allowing IPv4 to be phased out within the SP network. The phasing out of IPv4 within the SP network is independent of whether the end user disables IPv4 service or not. Further, &ldque;Greenfield&ldque; IPv6-only networks may use MAP-E in order to deliver IPv4 to sites via the IPv6 network in a way that does not require protocol translation between IPv4 and IPv6. MAP-E utilizes an algorithmic mapping, defined in MAP [I-D.mdt-softwire-mapping-address-and-port], between the IPv6 and IPv4 addresses that are assigned for use within the SP network. This mapping can provide automatic determination of IPv6 tunnel endpoints from IPv4 destination addresses, allowing the stateless operation of MAP-E. MAP-E views the IPv6 network as a link layer for IPv4 and supports an automatic tunneling abstraction similar to the Non- Broadcast Multiple Access (NBMA) [RFC2491] model. The MAP algorithmic mapping is also used to automatically provision IPv4 addresses and allocating a set of non-overlapping ports for each MAP-E CE. The "SP-facing" (i.e., "WAN") side of the MAP-E CE, operate as native IPv6 interface with no need for IPv4 operation or support. On the "end-user-facing" (i.e., "LAN") side of a CE, IPv6 and IPv4 might be implemented as for any native dual-stack service delivered by the SP. A MAP-E domain consists of MAP-E Customer Edge (CE) routers and one or more MAP-E Border Relays (BRs). IPv4 packets encapsulated by MAP-E follow the IPv6 routing topology within the SP network between CEs and among CEs and BRs. CE to CE traffic is direct, while BRs are traversed only for IPv4 packets that are destined to or are arriving from outside a given MAP-E domain. As MAP-E is stateless, BRs may be reached using anycast for failover and resiliency. MAP-E does not require any stateful NAPT [RFC3022] functions at the BRs or elsewhere within the SP network. Instead, MAP-E allows for sharing of IPv4 addresses among multiple sites by automatically allocating a set of non-overlapping ports for each CE as part of the Murakami, et al. Expires July 30, 2012 [Page 3] Internet-Draft MAP Encapsulation (MAP-E) January 2012 stateless mapping function. It is expected that the CE will, in turn, perform local IPv4 Network Address and Port Translation (NAPT) [RFC3022] functions for the site as is commonly performed today, except avoiding ports outside of the allocated port set. Although MAP-E is designed primarily to support IPv4 deployment to a customer site (such as a residential home network) by an SP, it can equally be applied to an individual host acting as a CE router. 2. 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]. 3. Terminology MAP-E: Mapping of Address and Port - Encapsulation mode. MAP-E utilizes a simple IPv4-in-IPv6 tunneling along with the MAP extensions for mapping between IPv4 and IPv6 defined in MAP [I-D.mdt-softwire-mapping-address-and-port] and this draft. MAP-E domain (Domain): A set of MAP-E CEs and BRs connected to the same virtual MAP-E link. A service provider may deploy MAP-E with a single MAP-E domain, or may utilize multiple MAP-E domains. Each domain requires a separate MAP-E rule set. MAP-E Border Relay (BR): A MAP-E enabled router managed by the service provider at the edge of a MAP-E domain. A Border Relay router has at least one of each of the following: an IPv6-enabled interface, a MAP-E virtual interface acting as an endpoint for the MAP-E IPv4 in IPv6 tunnel, and an IPv4 interface connected to the native IPv4 network. A MAP-E BR may also be referred to simply as a "BR" within the context of MAP-E. MAP-E Customer Edge (CE): A device functioning as a Customer Edge router in a MAP-E 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-E CE serving a residential site has one WAN side interface, Murakami, et al. Expires July 30, 2012 [Page 4] Internet-Draft MAP Encapsulation (MAP-E) January 2012 one or more LAN side interfaces, and a MAP-E virtual interface. A MAP-E CE may also be referred to simply as a "CE" within the context of MAP-E. Shared IPv4 address: An IPv4 address that is shared among multiple nodes. Each node has a separate part of the transport layer port space. MAP-E Rule: A MAP rule defining the mapping relationship for a given MAP-E domain between IPv4 and IPv6, defined in MAP [I-D.mdt-softwire-mapping-address-and-port] 4. MAP-E Configuration The IPv4 prefix, IPv4 address or shared IPv4 address for use at a customer site is automatically obtained based on BMR defined in MAP [I-D.mdt-softwire-mapping-address-and-port] from the IPv6 prefix delegated to the site. For a given MAP-E domain, the BR and CE MUST be configured with a set of mapping rules (BMR, FMR and DMR) defined in [I-D.mdt-softwire-mapping-address-and-port] . The configured values for these elements MUST be consistent for all CEs and BRs within a given MAP-E domain. The configuration elements in the set of mapping rules (BMR, FMR and DMR) may be provisioned via IPv6 DHCP defined in [I-D.mdt-softwire-map-dhcp-option] or manually. The only remaining provisioning information in order to enable MAP-E is an IPv6 prefix. This IPv6 prefix is configured as part of obtaining IPv6 Internet access (i.e., configured via SLAAC, DHCPv6, DHCPv6 PD, manual or otherwise). 5. MAP-E Node Behavior 5.1. Provisioning of MAP-E BR The MAP-E BR needs to be provisioned with information for the MAP-E domain or domains it is expected to handle, along with any necessary routing processes. For each MAP-E domain, the BR will have the following parameters: o The MAP Domain IPv4 and IPv6 prefix, and their lengths (Basic Murakami, et al. Expires July 30, 2012 [Page 5] Internet-Draft MAP Encapsulation (MAP-E) January 2012 Mapping Rule) o The MAP EA-bits (CE index), including IPv4 suffix, length and any port-range (including any excluded ports and the port number continuity parameter) o The BR prefix and its length (Default Mapping Rule) o The subnet ID A BR when configured for BMR, FMR and DMR, and performs the following functions: o Configures the IPv4/IPv6 stateless encapsulation parameters (BMR, FMR and DMR) Based on the above configuration, the IPv4-in-IPv6 encapsulation function can be performed by the BR. o Derive IPv4 address along with any applicable port-range from IPv4- translatable address (BMR) o Derive IPv4-translatable address from IPv4 address and port number (FMR) 5.2. Packet Forwarding Behavior on MAP-E BR (a) BR reception of an IPv4 packet Step 1 BR looks up an appropriate mapping rule (FMR) with a specific Domain IPv4 prefix which has the longest match with an IPv4 destination address in the received IPv4 packet. If the FMR is not found, the received packet should be discarded. If the length of Domain IPv4 prefix plus EA-bits associated with the FMR does not exceed 32 bits, BR proceeds to step 2. If the length exceeds 32 bits, BR checks that the received packet contains a complete IPv4 datagram. If the packet is fragmented, BR should reassemble the packet. Once BR can obtain the complete IPv4 datagram, BR proceeds to step 2 as though the datagram has been received in a single packet. Murakami, et al. Expires July 30, 2012 [Page 6] Internet-Draft MAP Encapsulation (MAP-E) January 2012 Step 2 BR generates a CE IPv6 address from the IPv4 destination address or the IPv4 destination address and the destination port based on the FMR found in step 1. If the CE IPv6 address can be successfully generated, BR encapsulates the IPv4 packet in IPv6 and forwards the IPv6 packet via the IPv6 interface. If the length of the IPv6 encapsulated packet exceeds the MTU of the IPv6 interface, the fragmentation should be done in IPv6. (b) BR reception of an IPv6 packet Step 1 If the received IPv6 packet is fragmented, the reassembly should be done in IPv6 at first. Once BR obtains a complete IPv6 packet, BR looks up an appropriate mapping rule (BMR) with a specific Domain IPv6 prefix which has the longest match with an IPv6 source address in the received IPv6 packet. If the BMR rule is not found, the received IPv6 packet should be discarded. BR derives a CE IPv6 address from the IPv4 source address or the IPv4 source address and the source port in the encapsulated IPv4 packet based on the BMR. If the CE IPv6 address is eqaul to the IPv6 source address in the received IPv6 packet, BR decapsulates the IPv4 packet and then forward it via the IPv4 interface. 5.3. Provisioning of MAP-E CE A MAP-E CE requires the following parameters for provisioning: o The MAP Domain IPv4 and IPv6 prefix, and their lengths (Basic Mapping Rule) o The MAP EA-bits (CE index), including IPv4 suffix, length and any port-range (including any excluded ports and the port number continuity parameter) o The BR prefix and its length (Default Mapping Rule) A MAP-E CE that receives a MAP DHCP option [I-D.mdt-softwire-map-dhcp-option] for BMR, FMR and DMR and performs the following (MAP initialization) functions: o Configures the NAT44 port-range mapping function parameters (BMR) Murakami, et al. Expires July 30, 2012 [Page 7] Internet-Draft MAP Encapsulation (MAP-E) January 2012 o Configures the IPv4/IPv6 stateless encapsulation parameters (BMR, FMR and DMR) Based on the above configuration, the IPv4/IPv6 encapsulation function can be performed in CE. o Derives IPv4 address along with any applicable port-range from IPv4-translatable address (BMR) o Derives IPv4-translatable address from IPv4 address (FMR) 5.4. Packet Forwarding Behavior on MAP-E CE (a) CE reception of an IPv4 packet Step 1 CE looks up an appropriate mapping rule (FMR) with a specific Doamin IPv4 prefix which has the longest match with an IPv4 destination address in the received IPv4 packet. If the FMR is found, the length of Domain IPv4 prefix plus EA-bits must be checked. If the length does not exceeds 32 bits, CE proceeds to step 2. If the length exceeds 32 bits, CE checks that the received IPv4 packet contains a complete IPv4 datagram. If the packet is fragmented, CE should reassemble the packet. Once CE can obtain the complete IPv4 datagram, CE proceeds to step 2 as though the datagram has been received in a single packet. If the FMR is not found, CE proceeds to step 2. Step 2 If the FMR is found in step 1, CE derives a IPv6 destination address from the IPv4 destination address or the IPv4 destination address and the destination port based on the FMR. If the IPv6 destination address can be derived successfully, CE encapsulates the IPv4 packet in IPv6 whose destination address is set to the derived IPv6 address. If the FMR is not found in step 1, CE uses the DMR and then CE encapsulates the IPv4 packet in IPv6 whose destination address is set to the BR IPv6 address. Then CE forwards the IPv6 packet via IPv6 interface. If the length of the IPv6 packet exceeds the MTU of the IPv6 interface, the fragmentation should be done in IPv6. Moreover, if using IPv4 shared address, a Datagram ID in the received IPv4 header must be over-written before encapsulating the IPv4 packet in IPv6. In case of shared IPv4 Murakami, et al. Expires July 30, 2012 [Page 8] Internet-Draft MAP Encapsulation (MAP-E) January 2012 address, the Datagram ID must be unique among CEs sharing the same IPv4 address. Hence, CE should assign the unique value and set this value to the datagram ID in IPv4 header. This value may be generated from the port-range assigned to the CE to keep the uniqueness among CEs sharing same IPv4 address. (b) CE reception of an IPv6 packet Step 1 If the received IPv6 packet is fragmented, the reassembly should be done in IPv6 at first. Once CE obtains a complete IPv6 packet, CE looks up an appropriate mapping rule (BMR) with a specific Domain IPv6 prefix which has the longest match with an IPv6 source address in the recieved IPv6 packet. If the BMR is found, the CE derives a CE IPv6 address from the IPv4 source address or the IPv4 source address and the source port based on the BMR and then checks that the IPv6 source address of the received IPv6 packet is matched to it. If the BMR is not found, CE checks that the IPv6 source address is matched to the BR IPv6 address. In case of success, the CE can decapsulate the IPv4 packet and forward it via the IPv4 interface. 6. Deriving IPv6 address from IPv4 6.1. Deriving IPv6 address from IPv4 Address and Port Number at the BR IPv6 Source Address and Source Port Number: At the BR, the IPv6 source address MUST be set to the BR IPv6 address as per DMR MAP [I-D.mdt-softwire-mapping-address-and-port]. The source Layer 4 port number MUST be unchanged. IPv6 Destination Address and Destination Port Number: At the BR, the IPv6 destination address (IPv4-translatable address) MUST be derived from the IPv4 destination address and the destination port number per FMR MAP [I-D.mdt-softwire-mapping-address-and-port]. The destination Layer 4 port number MUST be unchanged. Murakami, et al. Expires July 30, 2012 [Page 9] Internet-Draft MAP Encapsulation (MAP-E) January 2012 6.2. Deriving IPv6 address from IPv4 Address and Port Number at the CE IPv6 Source Address and Source Port Number: At the CE, the IPv6 source address (IPv4-translatable address) MUST be derived from the IPv4 source address as per BMR MAP [I-D.mdt-softwire-mapping-address-and-port]. The source port number MUST be unchanged. IPv6 Destination Address and Destination Port Number: At the CE, if Forwarding Mapping Rules (FMRs) are enabled, the IPv4 packet MUST be checked to see if the IPv4 destination address matches the FMR. If matching, the IPv6 destination address (IPv4-converted address) MUST be derived from the IPv4 destination address and the destination port number as per FMR. Otherwise, the IPv6 destination address MUST be set to the BR IPv6 address per DMR MAP [I-D.mdt-softwire-mapping-address-and-port]. The destination port number MUST be unchanged. 7. Encapsulation and Fragmentation Considerations Maximum transmission unit (MTU) and fragmentation issues for IPv4 in IPv6 tunneling are discussed in detail in Section 7.2 of [RFC2473]. MAP-E's scope is limited to a service provider network. IPv6 Path MTU discovery MAY be used to adjust the MTU of the tunnel as described in Section 7.2 of [RFC2473], or the MAP-E Tunnel MTU might be explicitly configured. The use of an anycast source address could lead to any ICMP error message generated on the path being sent to a different BR. Therefore, using dynamic tunnel MTU Section 7.2 of [RFC2473] is subject to IPv6 Path MTU blackholes. Multiple BRs using the same anycast source address could send fragmented packets to the same MAP-E CE at the same time. If the fragmented packets from different BRs happen to use the same fragment ID, incorrect reassembly might occur. For this reason, a BR using an anycast source address MUST NOT fragment the IPv6 encapsulated packet unless BR's having identical rules are required to use disjoint ranges of fragment ID. If the MTU is well-managed such that the IPv6 MTU on the CE WAN side interface is set so that no fragmentation occurs within the boundary of the SP, then the MAP-E Tunnel MTU should be set to the known IPv6 MTU minus the size of the encapsulating IPv6 header (40 bytes). For example, if the IPv6 MTU is known to be 1500 bytes, the MAP-E Tunnel Murakami, et al. Expires July 30, 2012 [Page 10] Internet-Draft MAP Encapsulation (MAP-E) January 2012 MTU might be set to 1460 bytes. Absent more specific information, the MAP-E Tunnel MTU SHOULD default to 1280 bytes. Alternatively, if BR's having identical rule are required to use disjoint ranges of fragment ID, a BR using an anycast source address SHOULD fragment the IPv6 encapsulated packet correctly. For MAP-E domain traversal, IPv4 packets are encapsulated in IPv6 packets whose Next header is set to 4 (i.e. IPv4). If fragmentation of IPv6 packets is needed, it is performed according to [RFC2460]. Absent more specific information, the path MTU of a MAP-E Domain has to be set to 1280 [RFC2460]. In domains where IPv4 addresses are not shared, IPv6 destinations are derived from IPv4 addresses alone. Thus, each IPv4 packet can be encapsulated and decapsulated independently of each other. MAP-E processing is completely stateless. On the other hand, in domains where IPv4 addresses are shared, BR's and CE's can have to encapsulate IPv4 packets whose IPv6 destinations depend on destination ports. Precautions are needed, due to the fact that the destination port of a fragmented datagram is available only in its first fragment. A sufficient precaution consists in reassembling each datagram received in multiple packets, and to treat it as though it would have been received in single packet. This function is such that MAP-E is in this case stateful at the IP layer. (This is common with DS-lite and NAT64/DNS64 which, in addition, are stateful at the transport layer.) At Domain entrance, this ensures that all pieces of all received IPv4 datagrams go to the right IPv6 destinations. Another peculiarity of shared IPv4 addresses is that, without precaution, a destination could simultaneously receive from different sources fragmented datagrams that have the same Datagram ID (the Identification field of [RFC0791]. This would disturb the reassembly process. To eliminate this risk, CE MUST rewrite the datagram ID to an unique value among CEs having same shared IPv4 address upon sending the packets over MAP-E tunnel. This value SHOULD be generated locally within the port-range assigned to a given CE. Note that replacing a Datagram ID in an IPv4 header implies an update of its Header-checksum fieald, by adding to it the one's complement difference between the old and the new values. 8. Packet Forwarding Considerations Murakami, et al. Expires July 30, 2012 [Page 11] Internet-Draft MAP Encapsulation (MAP-E) January 2012 8.1. Mesh model Basically, MAP-E should allow the mesh model in order for all CEs to communicate each others directly. If one mapping rules is applied to a given MAP-E domain, all CEs can communicate each others directly. If multiple mapping rules are applied to a given MAP-E domain, or if multiple MAP-E domains are existed, CE can communicate each others directly only if all CEs know all mapping rules. When a CE receives an IPv4 packet from its LAN side, the CE looks up a mapping rule corresponding to an IPv4 destination address in the received IPv4 packet. If the corresponding mapping rule is found, CE can communicate to another CE directly based on the mapping rule defined as Forwarding mapping rule (FMR) in [I-D.mdt-softwire-mapping-address-and-port] . If the corresponding mapping rule is not found, CE must forward the packet to a given BR. 8.2. Hub & Spoke model In order to allow the mesh topology so that all CEs can communicate each others directly, all CE should know all mapping rules applied to a given MAP-E domain or MAP-E domains. However, if a CE knows only subset of mapping rules applied to a given MAP-E domain or MAP-E domains, a CE can not communicate to some CEs due to the lack of mapping rules. In this case, an IPv4 packet toward to these CEs must be forwarded to a given BR. In order to achieve the hub & spoke mode fully, Forwarding mapping rule (FMR) defined in [I-D.mdt-softwire-mapping-address-and-port] should be disabled. In this case, all CEs do not look up the mapping rules upon receiving an IPv4 packet from its LAN side and then CE must encapsulate the IPv4 packet with IPv6 whose destination must be a given BR. 9. NAT Considerations NAT44 should be implemented in CPE which has MAP-E CE function. The NAT44 must conform that best current practice documented in [RFC4787], [RFC5508] and [RFC5382]. When there are restricted available port numbers in a given MAP-E CE, the NAT44 must restrict mapping ports within the port-set. 10. ICMP Considerations ICMP message should be supported in MAP-E domain. Hence, the NAT44 in MAP-E CE must implement the behavior for ICMP message conforming to the best current practice documented in [RFC5508]. If a MAP-E CE receives an ICMP message having ICMP identifier field Murakami, et al. Expires July 30, 2012 [Page 12] Internet-Draft MAP Encapsulation (MAP-E) January 2012 in ICMP header, NAT44 in the MAP-E CE must rewrite this field to a specific value assigned from the port-set. BR and other CEs must handle this field similar to the port number in tcp/udp header upon receiving the ICMP message with ICMP identifier field. If a MAP-E BR and CE receives an ICMP error message without ICMP identifier field for some errors that is detected inside a IPv6 tunnel, a MAP-E BR and CE should replay the ICMP error message to the original source. This behavior should be implemented conforming to the section 8 of [RFC2473]. The MAP-E BR and CE obtain the origianl IPv6 tunnel packet storing in ICMP payload and then decapsulate IPv4 packet. Finally the MAP-E BR and CE generate a new ICMP error message from the decapsulated IPv4 packet and then forward it. If a MAP-E BR receives an ICMP error message on its IPv4 interface, the MAP-E BR should replay the ICMP message to an appropriate MAP-E CE. If IPv4 address is not shared, the MAP-E BR generates a CE IPv6 address from the IPv4 destination address in the ICMP error message and encapsulates the ICMP message in IPv6. If IPv4 address is shared, the MAP-E BR derives an original IPv4 packet from the ICMP payload and generates a CE IPv6 address from the source address and the source port in the original IPv4 packet. If the MAP-E BR can generate the CE IPv6 address, the MAP-E BR encapsulates the ICMP error message in IPv6 and then forward it to its IPv6 interface. 11. Security Considerations Spoofing attacks: With consistency checks between IPv4 and IPv6 sources that are performed on IPv4/IPv6 packets received by BR's and CE's (Section 5), MAP-E does not introduce any opportunity for spoofing attack that would not pre-exist in IPv6. Denial-of-service attacks: In MAP-E domains where IPv4 addresses are shared, the fact that IPv4 datagram reassembly may be necessary introduces an opportunity for DOS attacks. This is inherent to address sharing, and is common with other address sharing approaches such as DS-lite and NAT64/ DNS64. The best protection against such attacks is to accelerate IPv6 enablement in both clients and servers so that, where MAP-E is supported, it is less and less used. Murakami, et al. Expires July 30, 2012 [Page 13] Internet-Draft MAP Encapsulation (MAP-E) January 2012 Routing-loop attacks: This attack may exist in some automatic- tunneling scenarios are documented in [I-D.ietf-v6ops-tunnel-loops]. They cannot exist with MAP-E because each BRs checks that the IPv6 source address of a received IPv6 packet is a CE address. Attacks facilitated by restricted port set: From hosts that are not subject to ingress filtering of [RFC2827], some attacks are possible by intervening with faked packets during ongoing transport connections ([RFC4953], [RFC5961], [RFC6056]. The attacks depend on guessing which ports are currently used by target hosts. Using unrestricted port set which mean that are IPv6 is exactly preferable. To avoid this attacks using restricted port set, NAT44 filtering behavior SHOULD be "Address-Dependent Filtering". 12. IANA Consideration This document makes no request of IANA. 13. Acknowledgements This draft is based on original idea described in [I-D.despres-softwire-sam]. The authors would like to thank Remi Despres, Mark Townsley, Wojciech Dec and Olivier Vautrin. 14. References 14.1. Normative References [I-D.mdt-softwire-map-dhcp-option] Mrugalski, T., Boucadair, M., Troan, O., Deng, X., and C. Bao, "DHCPv6 Options for Mapping of Address and Port", draft-mdt-softwire-map-dhcp-option-01 (work in progress), October 2011. [I-D.mdt-softwire-mapping-address-and-port] Troan, O., "Mapping of Address and Port (MAP)", draft-mdt-softwire-mapping-address-and-port-01 (work in progress), October 2011. [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, Murakami, et al. Expires July 30, 2012 [Page 14] Internet-Draft MAP Encapsulation (MAP-E) January 2012 September 1981. [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. [RFC2491] Armitage, G., Schulter, P., Jork, M., and G. Harter, "IPv6 over Non-Broadcast Multiple Access (NBMA) networks", RFC 2491, January 1999. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. 14.2. Informative References [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.ietf-softwire-dual-stack-lite] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- Stack Lite Broadband Deployments Following IPv4 Exhaustion", draft-ietf-softwire-dual-stack-lite-11 (work in progress), May 2011. [I-D.ietf-v6ops-tunnel-loops] Nakibly, G. and F. Templin, "Routing Loop Attack using IPv6 Automatic Tunnels: Problem Statement and Proposed Mitigations", draft-ietf-v6ops-tunnel-loops-07 (work in progress), May 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. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. Murakami, et al. Expires July 30, 2012 [Page 15] Internet-Draft MAP Encapsulation (MAP-E) January 2012 [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network Address Translator (Traditional NAT)", RFC 3022, January 2001. [RFC4787] Audet, F. and C. Jennings, "Network Address Translation (NAT) Behavioral Requirements for Unicast UDP", BCP 127, RFC 4787, January 2007. [RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks", RFC 4953, July 2007. [RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142, RFC 5382, October 2008. [RFC5508] Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT Behavioral Requirements for ICMP", BCP 148, RFC 5508, April 2009. [RFC5961] Ramaiah, A., Stewart, R., and M. Dalal, "Improving TCP's Robustness to Blind In-Window Attacks", RFC 5961, August 2010. [RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) -- Protocol Specification", RFC 5969, August 2010. [RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport- Protocol Port Randomization", BCP 156, RFC 6056, January 2011. Authors' Addresses Tetsuya Murakami (editor) IP Infusion 1188 East Arques Avenue Sunnyvale USA Email: tetsuya@ipinfusion.com Murakami, et al. Expires July 30, 2012 [Page 16] Internet-Draft MAP Encapsulation (MAP-E) January 2012 Ole Troan cisco Oslo Norway Email: ot@cisco.com Satoru Matsushima SoftBank 1-9-1 Higashi-Shinbashi, Munato-ku Tokyo Japan Email: satoru.matsushima@tm.softbank.co.jp Murakami, et al. Expires July 30, 2012 [Page 17]