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Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-12) exists of draft-ietf-softwire-map-dhcp-07 == Outdated reference: A later version (-09) exists of draft-ietf-dhc-dhcpv4-over-dhcpv6-08 == Outdated reference: A later version (-13) exists of draft-ietf-pcp-port-set-05 == Outdated reference: A later version (-13) exists of draft-ietf-softwire-map-10 == Outdated reference: A later version (-08) exists of draft-ietf-softwire-unified-cpe-01 Summary: 0 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Softwire Working Group Y. Cui 3 Internet-Draft Tsinghua University 4 Intended status: Standards Track Q. Sun 5 Expires: December 6, 2014 China Telecom 6 M. Boucadair 7 France Telecom 8 T. Tsou 9 Huawei Technologies 10 Y. Lee 11 Comcast 12 I. Farrer 13 Deutsche Telekom AG 14 June 04, 2014 16 Lightweight 4over6: An Extension to the DS-Lite Architecture 17 draft-ietf-softwire-lw4over6-09 19 Abstract 21 Dual-Stack Lite (RFC 6333) describes an architecture for transporting 22 IPv4 packets over an IPv6 network. This document specifies an 23 extension to DS-Lite called Lightweight 4over6 which moves the 24 Network Address and Port Translation (NAPT) function from the 25 centralized DS-Lite tunnel concentrator to the tunnel client located 26 in the Customer Premises Equipment (CPE). This removes the 27 requirement for a Carrier Grade NAT function in the tunnel 28 concentrator and reduces the amount of centralized state that must be 29 held to a per-subscriber level. In order to delegate the NAPT 30 function and make IPv4 Address sharing possible, port-restricted IPv4 31 addresses are allocated to the CPEs. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on December 6, 2014. 50 Copyright Notice 52 Copyright (c) 2014 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 4. Lightweight 4over6 Architecture . . . . . . . . . . . . . . . 5 71 5. Lightweight B4 Behavior . . . . . . . . . . . . . . . . . . . 7 72 5.1. Lightweight B4 Provisioning with DHCPv6 . . . . . . . . . 7 73 5.2. Lightweight B4 Data Plane Behavior . . . . . . . . . . . 9 74 5.2.1. Changes to RFC2473 and RFC6333 Fragmentation 75 Behaviour . . . . . . . . . . . . . . . . . . . . . . 10 76 6. Lightweight AFTR Behavior . . . . . . . . . . . . . . . . . . 10 77 6.1. Binding Table Maintenance . . . . . . . . . . . . . . . . 10 78 6.2. lwAFTR Data Plane Behavior . . . . . . . . . . . . . . . 11 79 7. Additional IPv4 address and Port Set Provisioning 80 Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . 12 81 8. ICMP Processing . . . . . . . . . . . . . . . . . . . . . . . 12 82 8.1. ICMPv4 Processing by the lwAFTR . . . . . . . . . . . . . 13 83 8.2. ICMPv4 Processing by the lwB4 . . . . . . . . . . . . . . 13 84 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 85 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 86 11. Author List . . . . . . . . . . . . . . . . . . . . . . . . . 14 87 12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 17 88 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 89 13.1. Normative References . . . . . . . . . . . . . . . . . . 18 90 13.2. Informative References . . . . . . . . . . . . . . . . . 19 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 93 1. Introduction 95 Dual-Stack Lite (DS-Lite, [RFC6333]) defines a model for providing 96 IPv4 access over an IPv6 network using two well-known technologies: 98 IP in IP [RFC2473] and Network Address Translation (NAT). The DS- 99 Lite architecture defines two major functional elements as follows: 101 Basic Bridging BroadBand element: A B4 element is a function 102 implemented on a dual-stack capable 103 node, either a directly connected 104 device or a CPE, that creates a 105 tunnel to an AFTR. 107 Address Family Transition Router: An AFTR element is the combination 108 of an IPv4-in-IPv6 tunnel endpoint 109 and an IPv4-IPv4 NAT implemented on 110 the same node. 112 As the AFTR performs the centralized NAT44 function, it dynamically 113 assigns public IPv4 addresses and ports to requesting host's traffic 114 (as described in [RFC3022]). To achieve this, the AFTR must 115 dynamically maintain per-flow state in the form of active NAPT 116 sessions. For service providers with a large number of B4 clients, 117 the size and associated costs for scaling the AFTR can quickly become 118 prohibitive. It can also place a large NAPT logging overhead upon 119 the service provider in countries where legal requirements mandate 120 this. 122 This document describes a mechanism called Lightweight 4 over 6 123 (lw4o6), which provides a solution for these problems. By relocating 124 the NAPT functionality from the centralized AFTR to the distributed 125 B4s, a number of benefits can be realised: 127 o NAPT44 functionality is already widely supported and used in 128 today's CPE devices. Lw4o6 uses this to provide private<->public 129 NAPT44, meaning that the service provider does not need a 130 centralized NAT44 function. 132 o The amount of state that must be maintained centrally in the AFTR 133 can be reduced from per-flow to per-subscriber. This reduces the 134 amount of resources (memory and processing power) necessary in the 135 AFTR. 137 o The reduction of maintained state results in a greatly reduced 138 logging overhead on the service provider. 140 Operator's IPv6 and IPv4 addressing architectures remain independent 141 of each other. Therefore, flexible IPv4/IPv6 addressing schemes can 142 be deployed. 144 Lightweight 4over6 is a solution designed specifically for complete 145 independence between IPv6 subnet prefix and IPv4 address with or 146 without IPv4 address sharing. This is accomplished by maintaining 147 state for each softwire (per-subscriber state) in the central lwAFTR 148 and a hub-and-spoke forwarding architecture. [I-D.ietf-softwire-map] 149 also offers these capabilities or, alternatively, allows for a 150 reduction of the amount of centralized state using rules to express 151 IPv4/IPv6 address mappings. This introduces an algorithmic 152 relationship between the IPv6 subnet and IPv4 address. This 153 relationship also allows the option of direct, meshed connectivity 154 between users. 156 The tunneling mechanism remains the same for DS-Lite and Lightweight 157 4over6. This document describes the changes to DS-Lite that are 158 necessary to implement Lightweight 4over6. These changes mainly 159 concern the configuration parameters and provisioning method 160 necessary for the functional elements. 162 Lightweight 4over6 features keeping per-subscriber state in the 163 service provider's network. It is categorized as Binding approach in 164 [I-D.ietf-softwire-unified-cpe] which defines a unified IPv4-in-IPv6 165 Softwire CPE. 167 This document is an extended case, which covers address sharing for 168 [RFC7040]. It is also a variant of A+P called Binding Table Mode 169 (see Section 4.4 of [RFC6346]). 171 This document focuses on architectural considerations and 172 particularly on the expected behavior of the involved functional 173 elements and their interfaces. Deployment-specific issues are 174 discussed in a companion document. As such, discussions about 175 redundancy and provisioning policy are out of scope. 177 2. Conventions 179 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 180 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 181 document are to be interpreted as described in [RFC2119]. 183 3. Terminology 185 The document defines the following terms: 187 Lightweight 4over6 (lw4o6): An IPv4-over-IPv6 hub and spoke 188 mechanism, which extends DS-Lite by 189 moving the IPv4 translation (NAPT44) 190 function from the AFTR to the B4. 192 Lightweight B4 (lwB4): A B4 element (Basic Bridging BroadBand 193 element [RFC6333]), which supports 194 Lightweight 4over6 extensions. An lwB4 195 is a function implemented on a dual- 196 stack capable node, (either a directly 197 connected device or a CPE), that 198 supports port-restricted IPv4 address 199 allocation, implements NAPT44 200 functionality and creates a tunnel to 201 an lwAFTR. 203 Lightweight AFTR (lwAFTR): An AFTR element (Address Family 204 Transition Router element [RFC6333]), 205 which supports Lightweight 4over6 206 extension. An lwAFTR is an IPv4-in- 207 IPv6 tunnel endpoint which maintains 208 per-subscriber address binding only and 209 does not perform a NAPT44 function. 211 Restricted Port-Set: A non-overlapping range of allowed 212 external ports allocated to the lwB4 to 213 use for NAPT44. Source ports of IPv4 214 packets sent by the B4 must belong to 215 the assigned port-set. The port set is 216 used for all port aware IP protocols 217 (TCP, UDP, SCTP etc.). 219 Port-restricted IPv4 Address: A public IPv4 address with a restricted 220 port-set. In Lightweight 4over6, 221 multiple B4s may share the same IPv4 222 address, however, their port-sets must 223 be non-overlapping. 225 Throughout the remainder of this document, the terms B4/AFTR should 226 be understood to refer specifically to a DS-Lite implementation. The 227 terms lwB4/lwAFTR refer to a Lightweight 4over6 implementation. 229 4. Lightweight 4over6 Architecture 231 The Lightweight 4over6 architecture is functionally similar to DS- 232 Lite. lwB4s and an lwAFTR are connected through an IPv6-enabled 233 network. Both approaches use an IPv4-in-IPv6 encapsulation scheme to 234 deliver IPv4 connectivity. The following figure shows the data plane 235 with the main functional change between DS-Lite and lw4o6: 237 +--------+ +---------+ IPv4-in-IPv6 +------+ +-------------+ 238 |IPv4 LAN|---|lwB4/NAPT|==================|lwAFTR|----|IPv4 Internet| 239 +--------+ +---------+ +------+ +-------------+ 240 ^ | 241 +-------------------------+ 242 NAPT function relocated 243 to lwB4 in lw4o6 245 Figure 1 Lightweight 4over6 Data Plane Overview 247 There are three main components in the Lightweight 4over6 248 architecture: 250 o The lwB4, which performs the NAPT function and encapsulation/de- 251 capsulation IPv4/IPv6. 253 o The lwAFTR, which performs the encapsulation/de-capsulation IPv4/ 254 IPv6. 256 o The provisioning system, which tells the lwB4 which IPv4 address 257 and port set to use. 259 The lwB4 differs from a regular B4 in that it now performs the NAPT 260 functionality. This means that it needs to be provisioned with the 261 public IPv4 address and port set it is allowed to use. This 262 information is provided though a provisioning mechanism such as DHCP, 263 PCP or TR-69. 265 The lwAFTR needs to know the binding between the IPv6 address of each 266 subscriber and the IPv4 address and port set allocated to that 267 subscriber. This information is used to perform ingress filtering 268 upstream and encapsulation downstream. Note that this is per- 269 subscriber state as opposed to per-flow state in the regular AFTR 270 case. 272 The consequence of this architecture is that the information 273 maintained by the provisioning mechanism and the one maintained by 274 the lwAFTR MUST be synchronized (See figure 2). The details of this 275 synchronization depend on the exact provisioning mechanism and will 276 be discussed in a companion document. 278 The solution specified in this document allows the assignment of 279 either a full or a shared IPv4 address requesting CPEs. [RFC7040] 280 provides a mechanism for assigning a full IPv4 address only. 282 +------------+ 283 /-------|Provisioning|<-----\ 284 | +------------+ | 285 | | 286 V V 287 +--------+ +---------+ IPv4/IPv6 +------+ +-------------+ 288 |IPv4 LAN|---|lwB4/NAPT|==================|lwAFTR|----|IPv4 Internet| 289 +--------+ +---------+ +------+ +-------------+ 291 Figure 2 Lightweight 4over6 Provisioning Synchronization 293 5. Lightweight B4 Behavior 295 5.1. Lightweight B4 Provisioning with DHCPv6 297 With DS-Lite, the B4 element only needs to be configured with a 298 single DS-Lite specific parameter so that it can set up the softwire 299 (the IPv6 address of the AFTR). Its IPv4 address can be taken from 300 the well-known range 192.0.0.0/29. 302 In lw4o6, a number of lw4o6 specific configuration parameters must be 303 provisioned to the lwB4. These are: 305 o IPv6 Address for the lwAFTR 307 o IPv4 External (Public) Address for NAPT44 309 o Restricted port-set to use for NAPT44 311 o IPv6 Binding Prefix 313 For DHCPv6 based configuration of these parameters, the lwB4 SHOULD 314 implement OPTION_S46_CONT_LW as described in section 5.3 of 315 [I-D.ietf-softwire-map-dhcp]. This means that the lifetime of the 316 softwire and the derived configuration information (e.g. IPv4 shared 317 address, IPv4 address) is bound to the lifetime of the DHCPv6 lease. 318 If stateful IPv4 configuration or additional IPv4 configuration 319 information is required, DHCPv4 [RFC2131] must be used. 321 Although it would be possible to extend lw4o6 to have more than one 322 active lw4o6 tunnel configured simultaneously, this document is only 323 concerned with the use of a single tunnel. 325 On receipt of the necessary configuration parameters, the lwB4 326 performs a longest prefix match between the IPv6 binding prefix and 327 its currently active IPv6 prefixes. The result forms the subnet to 328 be used for sourcing the lw4o6 tunnel. The full /128 prefix is then 329 constructed in the same manner as [I-D.ietf-softwire-map]. 331 0 1 2 3 332 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 | Operator assigned | 335 . . 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | Zero Padding | IPv4 Address | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | IPv4 Addr cont. | PSID | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 Figure 3 Construction of the lw4o6 /128 Prefix 344 Padding: Padding (all zeros) 346 IPv4 Address: Public IPv4 address allocated to the client 348 PSID: Port Set ID allocated to the client, left padded with 349 zeros to 16-bits. If no PSID is provisioned, all 350 zeros. 352 In the event that the lwB4's encapsulation source address is changed 353 for any reason (such as the DHCPv6 lease expiring), the lwB4's 354 dynamic provisioning process must be re-initiated. 356 An lwB4 MUST support dynamic port-restricted IPv4 address 357 provisioning. The port set algorithm for provisioning this is 358 described in Section 5.1 of [I-D.ietf-softwire-map]. For lw4o6, the 359 number of a-bits SHOULD be 0, thus allocating a single contiguous 360 port set to each lwB4. 362 Unless an lwB4 is being allocated a full IPv4 address, it is 363 RECOMMENDED that PSIDs containing the well-known ports (0-1023) are 364 not allocated to lwB4s. 366 In the event that the lwB4 receives an ICMPv6 error message (type 1, 367 code 5) originating from the lwAFTR, the lwB4 SHOULD interpret this 368 to mean that no matching entry in the lwAFTR's binding table has been 369 found. The lwB4 MAY then re-initiate the dynamic port-restricted 370 provisioning process. The lwB4's re-initiation policy SHOULD be 371 configurable. 373 The DNS considerations described in Section 5.5 and Section 6.4 of 374 [RFC6333] SHOULD be followed. 376 5.2. Lightweight B4 Data Plane Behavior 378 Several sections of [RFC6333] provide background information on the 379 B4's data plane functionality and MUST be implemented by the lwB4 as 380 they are common to both solutions. The relevant sections are: 382 5.2 Encapsulation Covering encapsulation and de- 383 capsulation of tunneled traffic 385 5.3 Fragmentation and Reassembly Covering MTU and fragmentation 386 considerations (referencing 387 [RFC2473]), with the exception 388 noted below. 390 7.1 Tunneling Covering tunneling and traffic 391 class mapping between IPv4 and IPv6 392 (referencing [RFC2473] and 393 [RFC4213]) 395 The lwB4 element performs IPv4 address translation (NAPT44) as well 396 as encapsulation and de-capsulation. It runs standard NAPT44 397 [RFC3022] using the allocated port-restricted address as its external 398 IPv4 address and port numbers. 400 The working flow of the lwB4 is illustrated in figure 4. 402 +-------------+ 403 | lwB4 | 404 +--------+ IPv4 |------+------| IPv4-in-IPv6 +----------+ 405 |IPv4 LAN|------->| |Encap.|-------------->|Configured| 406 | |<-------| NAPT | or |<--------------| lwAFTR | 407 +--------+ | |Decap.| +----------+ 408 +------+------+ 410 Figure 4 Working Flow of the lwB4 412 Internally connected hosts source IPv4 packets with an [RFC1918] 413 address. When the lwB4 receives such an IPv4 packet, it performs a 414 NAPT44 function on the source address and port by using the public 415 IPv4 address and a port number from the allocated port-set. Then, it 416 encapsulates the packet with an IPv6 header. The destination IPv6 417 address is the lwAFTR's IPv6 address and the source IPv6 address is 418 the lwB4's IPv6 tunnel endpoint address. Finally, the lwB4 forwards 419 the encapsulated packet to the configured lwAFTR. 421 When the lwB4 receives an IPv4-in-IPv6 packet from the lwAFTR, it de- 422 capsulates the IPv4 packet from the IPv6 packet. Then, it performs 423 NAPT44 translation on the destination address and port, based on the 424 available information in its local NAPT44 table. 426 If the IPv6 source address does not match the configured lwAFTR 427 address, then the packet MUST be discarded. If the decapsulated IPv4 428 packet does not match the lwB4's configuration (i.e. invalid 429 destination IPv4 address or port) then the packet MUST be dropped. 430 An ICMPv4 error message (type 13 - Communication Administratively 431 Prohibited) message MAY be sent back to the lwAFTR. The ICMP policy 432 SHOULD be configurable. 434 The lwB4 is responsible for performing ALG functions (e.g., SIP, 435 FTP), and other NAPT traversal mechanisms (e.g., UPnP, NAPT-PMP, 436 manual binding configuration, PCP) for the internal hosts. This 437 requirement is typical for NAPT44 gateways available today. 439 It is possible that a lwB4 is co-located in a host. In this case, 440 the functions of NAPT44 and encapsulation/de-capsulation are 441 implemented inside the host. 443 5.2.1. Changes to RFC2473 and RFC6333 Fragmentation Behaviour 445 For TCP and UDP traffic the NAPT44 implemented in the lwB4 SHOULD 446 conform with the behaviour and best current practices documented in 447 [RFC4787], [RFC5508], and [RFC5382]. If the lwB4 supports DCCP, then 448 the requirements in [RFC5597] SHOULD be implemented. 450 The NAPT44 in the lwB4 MUST implement ICMP message handling behaviour 451 conforming to the best current practice documented in [RFC5508]. If 452 the lwB4 receives an ICMP error (for errors detected inside the IPv6 453 tunnel), the node should relay the ICMP error message to the original 454 source (the lwAFTR). 456 This behaviour SHOULD be implemented conforming to the section 8 of 457 [RFC2473]. 459 6. Lightweight AFTR Behavior 461 6.1. Binding Table Maintenance 463 The lwAFTR maintains an address binding table containing the binding 464 between the lwB4's IPv6 address, the allocated IPv4 address and 465 restricted port-set. Unlike the DS-Lite extended binding table 466 defined in section 6.6 of [RFC6333] which is a 5-tuple NAPT table, 467 each entry in the Lightweight 4over6 binding table contains the 468 following 3-tuples: 470 o IPv6 Address for a single lwB4 471 o Public IPv4 Address 473 o Restricted port-set 475 The entry has two functions: the IPv6 encapsulation of inbound IPv4 476 packets destined to the lwB4 and the validation of outbound IPv4-in- 477 IPv6 packets received from the lwB4 for de-capsulation. 479 The lwAFTR does not perform NAPT and so does not need session 480 entries. 482 The lwAFTR MUST synchronize the binding information with the port- 483 restricted address provisioning process. If the lwAFTR does not 484 participate in the port-restricted address provisioning process, the 485 binding MUST be synchronized through other methods (e.g. out-of-band 486 static update). 488 If the lwAFTR participates in the port-restricted provisioning 489 process, then its binding table MUST be created as part of this 490 process. 492 For all provisioning processes, the lifetime of binding table entries 493 MUST be synchronized with the lifetime of address allocations. 495 6.2. lwAFTR Data Plane Behavior 497 Several sections of [RFC6333] provide background information on the 498 AFTR's data plane functionality and MUST be implemented by the lwAFTR 499 as they are common to both solutions. The relevant sections are: 501 6.2 Encapsulation Covering encapsulation and de- 502 capsulation of tunneled traffic 504 6.3 Fragmentation and Reassembly Fragmentation and re-assembly 505 considerations (referencing 506 [RFC2473]) 508 7.1 Tunneling Covering tunneling and traffic 509 class mapping between IPv4 and IPv6 510 (referencing [RFC2473] and 511 [RFC4213]) 513 When the lwAFTR receives an IPv4-in-IPv6 packet from an lwB4, it de- 514 capsulates the IPv6 header and verifies the source addresses and port 515 in the binding table. If both the source IPv4 and IPv6 addresses 516 match a single entry in the binding table and the source port is in 517 the allowed port-set for that entry, the lwAFTR forwards the packet 518 to the IPv4 destination. 520 If no match is found (e.g., no matching IPv4 address entry, port out 521 of range, etc.), the lwAFTR MUST discard or implement a policy (such 522 as redirection) on the packet. An ICMPv6 type 1, code 5 (source 523 address failed ingress/egress policy) error message MAY be sent back 524 to the requesting lwB4. The ICMP policy SHOULD be configurable. 526 When the lwAFTR receives an inbound IPv4 packet, it uses the IPv4 527 destination address and port to lookup the destination lwB4's IPv6 528 address in its binding table. If a match is found, the lwAFTR 529 encapsulates the IPv4 packet. The source is the lwAFTR's IPv6 530 address and the destination is the lwB4's IPv6 address from the 531 matched entry. Then, the lwAFTR forwards the packet to the lwB4 532 natively over the IPv6 network. 534 If no match is found, the lwAFTR MUST discard the packet. An ICMPv4 535 type 3, code 1 (Destination unreachable, host unreachable) error 536 message MAY be sent back. The ICMP policy SHOULD be configurable. 538 The lwAFTR MUST support hairpinning of traffic between two lwB4s, by 539 performing de-capsulation and re-encapsulation of packets. The 540 hairpinning policy MUST be configurable. 542 7. Additional IPv4 address and Port Set Provisioning Mechanisms 544 In addition to the DHCPv6 based mechanism described in section 5.1, 545 several other IPv4 provisioning protocols have been suggested. These 546 protocols MAY be implemented. These alternatives include: 548 o DHCPv4 over DHCPv6: [I-D.ietf-dhc-dhcpv4-over-dhcpv6] describes 549 implementing DHCPv4 messages over an IPv6 only service providers 550 network. This enables leasing of IPv4 addresses and makes DHCPv4 551 options available to the DHCPv4 over DHCPv6 client. 553 o PCP[RFC6887]: an lwB4 MAY use [I-D.ietf-pcp-port-set] to retrieve 554 a restricted IPv4 address and a set of ports. 556 In a Lightweight 4over6 domain, the binding information MUST be 557 aligned between the lwB4s, the lwAFTRs and the provisioning server. 559 8. ICMP Processing 561 For both the lwAFTR and the lwB4, ICMPv6 MUST be handled as described 562 in [RFC2473]. 564 ICMPv4 does not work in an address sharing environment without 565 special handling [RFC6269]. Due to the port-set style address 566 sharing, Lightweight 4over6 requires specific ICMP message handling 567 not required by DS-Lite. 569 8.1. ICMPv4 Processing by the lwAFTR 571 For inbound ICMP messages The following behavior SHOULD be 572 implemented by the lwAFTR to provide ICMP error handling and basic 573 remote IPv4 service diagnostics for a port restricted CPE: 575 1. Check the ICMP Type field. 577 2. If the ICMP type is set to 0 or 8 (echo reply or request), then 578 the lwAFTR MUST take the value of the ICMP identifier field as 579 the source port, and use this value to lookup the binding table 580 for an encapsulation destination. If a match is found, the 581 lwAFTR forwards the ICMP packet to the IPv6 address stored in the 582 entry; otherwise it MUST discard the packet. 584 3. If the ICMP type field is set to any other value, then the lwAFTR 585 MUST use the method described in REQ-3 of [RFC5508] to locate the 586 source port within the transport layer header in ICMP packet's 587 data field. The destination IPv4 address and source port 588 extracted from the ICMP packet are then used to make a lookup in 589 the binding table. If a match is found, it MUST forward the ICMP 590 reply packet to the IPv6 address stored in the entry; otherwise 591 it MUST discard the packet. 593 Additionally, the lwAFTR MAY implement: 595 o Discarding of all inbound ICMP messages. 597 The ICMP policy SHOULD be configurable. 599 8.2. ICMPv4 Processing by the lwB4 601 The lwB4 SHOULD implement the requirements defined in [RFC5508] for 602 ICMP forwarding. For ICMP echo request packets originating from the 603 private IPv4 network, the lwB4 SHOULD implement the method described 604 in [RFC6346] and use an available port from its port-set as the ICMP 605 Identifier. 607 9. Security Considerations 609 As the port space for a subscriber shrinks due to address sharing, 610 the randomness for the port numbers of the subscriber is decreased 611 significantly. This means it is much easier for an attacker to guess 612 the port number used, which could result in attacks ranging from 613 throughput reduction to broken connections or data corruption. 615 The port-set for a subscriber can be a set of contiguous ports or 616 non-contiguous ports. Contiguous port-sets do not reduce this 617 threat. However, with non-contiguous port-set (which may be 618 generated in a pseudo-random way [RFC6431]), the randomness of the 619 port number is improved, provided that the attacker is outside the 620 Lightweight 4over6 domain and hence does not know the port-set 621 generation algorithm. 623 More considerations about IP address sharing are discussed in 624 Section 13 of [RFC6269], which is applicable to this solution. 626 10. IANA Considerations 628 This document does not include an IANA request. 630 11. Author List 632 The following are extended authors who contributed to the effort: 634 Jianping Wu 636 Tsinghua University 638 Department of Computer Science, Tsinghua University 640 Beijing 100084 642 P.R.China 644 Phone: +86-10-62785983 646 Email: jianping@cernet.edu.cn 648 Peng Wu 650 Tsinghua University 652 Department of Computer Science, Tsinghua University 654 Beijing 100084 656 P.R.China 657 Phone: +86-10-62785822 659 Email: pengwu.thu@gmail.com 661 Qi Sun 663 Tsinghua University 665 Beijing 100084 667 P.R.China 669 Phone: +86-10-62785822 671 Email: sunqi@csnet1.cs.tsinghua.edu.cn 673 Chongfeng Xie 675 China Telecom 677 Room 708, No.118, Xizhimennei Street 679 Beijing 100035 681 P.R.China 683 Phone: +86-10-58552116 685 Email: xiechf@ctbri.com.cn 687 Xiaohong Deng 689 France Telecom 691 Email: xiaohong.deng@orange.com 693 Cathy Zhou 695 Huawei Technologies 696 Section B, Huawei Industrial Base, Bantian Longgang 698 Shenzhen 518129 700 P.R.China 702 Email: cathyzhou@huawei.com 704 Alain Durand 706 Juniper Networks 708 1194 North Mathilda Avenue 710 Sunnyvale, CA 94089-1206 712 USA 714 Email: adurand@juniper.net 716 Reinaldo Penno 718 Cisco Systems, Inc. 720 170 West Tasman Drive 722 San Jose, California 95134 724 USA 726 Email: repenno@cisco.com 728 Alex Clauberg 730 Deutsche Telekom AG 732 GTN-FM4 734 Landgrabenweg 151 736 Bonn, CA 53227 737 Germany 739 Email: axel.clauberg@telekom.de 741 Lionel Hoffmann 743 Bouygues Telecom 745 TECHNOPOLE 747 13/15 Avenue du Marechal Juin 749 Meudon 92360 751 France 753 Email: lhoffman@bouyguestelecom.fr 755 Maoke Chen 757 FreeBit Co., Ltd. 759 13F E-space Tower, Maruyama-cho 3-6 761 Shibuya-ku, Tokyo 150-0044 763 Japan 765 Email: fibrib@gmail.com 767 12. Acknowledgement 769 The authors would like to thank Ole Troan, Ralph Droms and Suresh 770 Krishnan for their comments and feedback. 772 This document is a merge of three documents: 773 [I-D.cui-softwire-b4-translated-ds-lite], [I-D.zhou-softwire-b4-nat] 774 and [I-D.penno-softwire-sdnat]. 776 13. References 777 13.1. Normative References 779 [I-D.ietf-softwire-map-dhcp] 780 Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec, 781 W., Bao, C., leaf.yeh.sdo@gmail.com, l., and X. Deng, 782 "DHCPv6 Options for configuration of Softwire Address and 783 Port Mapped Clients", draft-ietf-softwire-map-dhcp-07 784 (work in progress), March 2014. 786 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 787 E. Lear, "Address Allocation for Private Internets", BCP 788 5, RFC 1918, February 1996. 790 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 791 Requirement Levels", BCP 14, RFC 2119, March 1997. 793 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 794 2131, March 1997. 796 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 797 IPv6 Specification", RFC 2473, December 1998. 799 [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms 800 for IPv6 Hosts and Routers", RFC 4213, October 2005. 802 [RFC4787] Audet, F. and C. Jennings, "Network Address Translation 803 (NAT) Behavioral Requirements for Unicast UDP", BCP 127, 804 RFC 4787, January 2007. 806 [RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. 807 Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142, 808 RFC 5382, October 2008. 810 [RFC5508] Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT 811 Behavioral Requirements for ICMP", BCP 148, RFC 5508, 812 April 2009. 814 [RFC5597] Denis-Courmont, R., "Network Address Translation (NAT) 815 Behavioral Requirements for the Datagram Congestion 816 Control Protocol", BCP 150, RFC 5597, September 2009. 818 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 819 Stack Lite Broadband Deployments Following IPv4 820 Exhaustion", RFC 6333, August 2011. 822 13.2. Informative References 824 [I-D.cui-softwire-b4-translated-ds-lite] 825 Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I. 826 Farrer, "Lightweight 4over6: An Extension to the DS-Lite 827 Architecture", draft-cui-softwire-b4-translated-ds-lite-11 828 (work in progress), February 2013. 830 [I-D.ietf-dhc-dhcpv4-over-dhcpv6] 831 Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I. 832 Farrer, "DHCPv4 over DHCPv6 Transport", draft-ietf-dhc- 833 dhcpv4-over-dhcpv6-08 (work in progress), May 2014. 835 [I-D.ietf-pcp-port-set] 836 Qiong, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, 837 T., and S. Perreault, "Port Control Protocol (PCP) 838 Extension for Port Set Allocation", draft-ietf-pcp-port- 839 set-05 (work in progress), May 2014. 841 [I-D.ietf-softwire-map] 842 Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S., 843 Murakami, T., and T. Taylor, "Mapping of Address and Port 844 with Encapsulation (MAP)", draft-ietf-softwire-map-10 845 (work in progress), January 2014. 847 [I-D.ietf-softwire-unified-cpe] 848 Boucadair, M., Farrer, I., Perreault, S., and S. 849 Sivakumar, "Unified IPv4-in-IPv6 Softwire CPE", draft- 850 ietf-softwire-unified-cpe-01 (work in progress), May 2013. 852 [I-D.penno-softwire-sdnat] 853 Penno, R., Durand, A., Hoffmann, L., and A. Clauberg, 854 "Stateless DS-Lite", draft-penno-softwire-sdnat-02 (work 855 in progress), March 2012. 857 [I-D.zhou-softwire-b4-nat] 858 Zhou, C., Boucadair, M., and X. Deng, "NAT offload 859 extension to Dual-Stack lite", draft-zhou- 860 softwire-b4-nat-04 (work in progress), October 2011. 862 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 863 Address Translator (Traditional NAT)", RFC 3022, January 864 2001. 866 [RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P. 867 Roberts, "Issues with IP Address Sharing", RFC 6269, June 868 2011. 870 [RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the 871 IPv4 Address Shortage", RFC 6346, August 2011. 873 [RFC6431] Boucadair, M., Levis, P., Bajko, G., Savolainen, T., and 874 T. Tsou, "Huawei Port Range Configuration Options for PPP 875 IP Control Protocol (IPCP)", RFC 6431, November 2011. 877 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 878 Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 879 2013. 881 [RFC7040] Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public 882 IPv4-over-IPv6 Access Network", RFC 7040, November 2013. 884 Authors' Addresses 886 Yong Cui 887 Tsinghua University 888 Beijing 100084 889 P.R.China 891 Phone: +86-10-62603059 892 Email: yong@csnet1.cs.tsinghua.edu.cn 894 Qiong Sun 895 China Telecom 896 Room 708, No.118, Xizhimennei Street 897 Beijing 100035 898 P.R.China 900 Phone: +86-10-58552936 901 Email: sunqiong@ctbri.com.cn 903 Mohamed Boucadair 904 France Telecom 905 Rennes 35000 906 France 908 Email: mohamed.boucadair@orange.com 909 Tina Tsou 910 Huawei Technologies 911 2330 Central Expressway 912 Santa Clara, CA 95050 913 USA 915 Phone: +1-408-330-4424 916 Email: tena@huawei.com 918 Yiu L. Lee 919 Comcast 920 One Comcast Center 921 Philadelphia, PA 19103 922 USA 924 Email: yiu_lee@cable.comcast.com 926 Ian Farrer 927 Deutsche Telekom AG 928 CTO-ATI, Landgrabenweg 151 929 Bonn, NRW 53227 930 Germany 932 Email: ian.farrer@telekom.de