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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-12) exists of draft-ietf-softwire-map-dhcp-07 == Outdated reference: A later version (-09) exists of draft-ietf-dhc-dhcpv4-over-dhcpv6-06 == Outdated reference: A later version (-13) exists of draft-ietf-pcp-port-set-04 == Outdated reference: A later version (-13) exists of draft-ietf-softwire-map-10 == Outdated reference: A later version (-08) exists of draft-ietf-softwire-unified-cpe-01 Summary: 0 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--).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: September 19, 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 March 18, 2014 16 Lightweight 4over6: An Extension to the DS-Lite Architecture 17 draft-ietf-softwire-lw4over6-08 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 September 19, 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 . . . . . . . . . . . 8 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 . . . . . . . . . . . . . 12 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 . . . . . . . . . . . . . . . . . . 17 90 13.2. Informative References . . . . . . . . . . . . . . . . . 18 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. 361 In the event that the lwB4 receives an ICMPv6 error message (type 1, 362 code 5) originating from the lwAFTR, the lwB4 SHOULD interpret this 363 to mean that no matching entry in the lwAFTR's binding table has been 364 found. The lwB4 MAY then re-initiate the dynamic port-restricted 365 provisioning process. The lwB4's re-initiation policy SHOULD be 366 configurable. 368 The DNS considerations described in Section 5.5 and Section 6.4 of 369 [RFC6333] SHOULD be followed. 371 5.2. Lightweight B4 Data Plane Behavior 373 Several sections of [RFC6333] provide background information on the 374 B4's data plane functionality and MUST be implemented by the lwB4 as 375 they are common to both solutions. The relevant sections are: 377 5.2 Encapsulation Covering encapsulation and de- 378 capsulation of tunneled traffic 380 5.3 Fragmentation and Reassembly Covering MTU and fragmentation 381 considerations (referencing 382 [RFC2473]), with the exception 383 noted below. 385 7.1 Tunneling Covering tunneling and traffic 386 class mapping between IPv4 and IPv6 387 (referencing [RFC2473] and 388 [RFC4213]) 390 The lwB4 element performs IPv4 address translation (NAPT44) as well 391 as encapsulation and de-capsulation. It runs standard NAPT44 392 [RFC3022] using the allocated port-restricted address as its external 393 IPv4 address and port numbers. 395 The working flow of the lwB4 is illustrated in figure 4. 397 +-------------+ 398 | lwB4 | 399 +--------+ IPv4 |------+------| IPv4-in-IPv6 +----------+ 400 |IPv4 LAN|------->| |Encap.|-------------->|Configured| 401 | |<-------| NAPT | or |<--------------| lwAFTR | 402 +--------+ | |Decap.| +----------+ 403 +------+------+ 405 Figure 4 Working Flow of the lwB4 407 Internally connected hosts source IPv4 packets with an [RFC1918] 408 address. When the lwB4 receives such an IPv4 packet, it performs a 409 NAPT44 function on the source address and port by using the public 410 IPv4 address and a port number from the allocated port-set. Then, it 411 encapsulates the packet with an IPv6 header. The destination IPv6 412 address is the lwAFTR's IPv6 address and the source IPv6 address is 413 the lwB4's IPv6 tunnel endpoint address. Finally, the lwB4 forwards 414 the encapsulated packet to the configured lwAFTR. 416 When the lwB4 receives an IPv4-in-IPv6 packet from the lwAFTR, it de- 417 capsulates the IPv4 packet from the IPv6 packet. Then, it performs 418 NAPT44 translation on the destination address and port, based on the 419 available information in its local NAPT44 table. 421 If the IPv6 source address does not match the configured lwAFTR 422 address, then the packet MUST be discarded. If the decapsulated IPv4 423 packet does not match the lwB4's configuration (i.e. invalid 424 destination IPv4 address or port) then the packet MUST be dropped. 425 An ICMPv4 error message (type 13 - Communication Administratively 426 Prohibited) message MAY be sent back to the lwAFTR. The ICMP policy 427 SHOULD be configurable. 429 The lwB4 is responsible for performing ALG functions (e.g., SIP, 430 FTP), and other NAPT traversal mechanisms (e.g., UPnP, NAPT-PMP, 431 manual binding configuration, PCP) for the internal hosts. This 432 requirement is typical for NAPT44 gateways available today. 434 It is possible that a lwB4 is co-located in a host. In this case, 435 the functions of NAPT44 and encapsulation/de-capsulation are 436 implemented inside the host. 438 5.2.1. Changes to RFC2473 and RFC6333 Fragmentation Behaviour 440 For TCP and UDP traffic the NAPT44 implemented in the lwB4 SHOULD 441 conform with the behaviour and best current practices documented in 442 [RFC4787], [RFC5508], and [RFC5382]. If the lwB4 supports DCCP, then 443 the requirements in [RFC5597] SHOULD be implemented. 445 The NAPT44 in the lwB4 MUST implement ICMP message handling behaviour 446 conforming to the best current practice documented in [RFC5508]. If 447 the lwB4 receives an ICMP error (for errors detected inside the IPv6 448 tunnel), the node should relay the ICMP error message to the original 449 source (the lwAFTR). 451 This behaviour SHOULD be implemented conforming to the section 8 of 452 [RFC2473]. 454 6. Lightweight AFTR Behavior 456 6.1. Binding Table Maintenance 458 The lwAFTR maintains an address binding table containing the binding 459 between the lwB4's IPv6 address, the allocated IPv4 address and 460 restricted port-set. Unlike the DS-Lite extended binding table 461 defined in section 6.6 of [RFC6333] which is a 5-tuple NAPT table, 462 each entry in the Lightweight 4over6 binding table contains the 463 following 3-tuples: 465 o IPv6 Address for a single lwB4 467 o Public IPv4 Address 469 o Restricted port-set 471 The entry has two functions: the IPv6 encapsulation of inbound IPv4 472 packets destined to the lwB4 and the validation of outbound IPv4-in- 473 IPv6 packets received from the lwB4 for de-capsulation. 475 The lwAFTR does not perform NAPT and so does not need session 476 entries. 478 The lwAFTR MUST synchronize the binding information with the port- 479 restricted address provisioning process. If the lwAFTR does not 480 participate in the port-restricted address provisioning process, the 481 binding MUST be synchronized through other methods (e.g. out-of-band 482 static update). 484 If the lwAFTR participates in the port-restricted provisioning 485 process, then its binding table MUST be created as part of this 486 process. 488 For all provisioning processes, the lifetime of binding table entries 489 MUST be synchronized with the lifetime of address allocations. 491 6.2. lwAFTR Data Plane Behavior 493 Several sections of [RFC6333] provide background information on the 494 AFTR's data plane functionality and MUST be implemented by the lwAFTR 495 as they are common to both solutions. The relevant sections are: 497 6.2 Encapsulation Covering encapsulation and de- 498 capsulation of tunneled traffic 500 6.3 Fragmentation and Reassembly Fragmentation and re-assembly 501 considerations (referencing 502 [RFC2473]) 504 7.1 Tunneling Covering tunneling and traffic 505 class mapping between IPv4 and IPv6 506 (referencing [RFC2473] and 507 [RFC4213]) 509 When the lwAFTR receives an IPv4-in-IPv6 packet from an lwB4, it de- 510 capsulates the IPv6 header and verifies the source addresses and port 511 in the binding table. If both the source IPv4 and IPv6 addresses 512 match a single entry in the binding table and the source port is in 513 the allowed port-set for that entry, the lwAFTR forwards the packet 514 to the IPv4 destination. 516 If no match is found (e.g., no matching IPv4 address entry, port out 517 of range, etc.), the lwAFTR MUST discard or implement a policy (such 518 as redirection) on the packet. An ICMPv6 type 1, code 5 (source 519 address failed ingress/egress policy) error message MAY be sent back 520 to the requesting lwB4. The ICMP policy SHOULD be configurable. 522 When the lwAFTR receives an inbound IPv4 packet, it uses the IPv4 523 destination address and port to lookup the destination lwB4's IPv6 524 address in its binding table. If a match is found, the lwAFTR 525 encapsulates the IPv4 packet. The source is the lwAFTR's IPv6 526 address and the destination is the lwB4's IPv6 address from the 527 matched entry. Then, the lwAFTR forwards the packet to the lwB4 528 natively over the IPv6 network. 530 If no match is found, the lwAFTR MUST discard the packet. An ICMPv4 531 type 3, code 1 (Destination unreachable, host unreachable) error 532 message MAY be sent back. The ICMP policy SHOULD be configurable. 534 The lwAFTR MUST support hairpinning of traffic between two lwB4s, by 535 performing de-capsulation and re-encapsulation of packets. The 536 hairpinning policy MUST be configurable. 538 7. Additional IPv4 address and Port Set Provisioning Mechanisms 540 In addition to the DHCPv6 based mechanism described in section 5.1, 541 several other IPv4 provisioning protocols have been suggested. These 542 protocols MAY be implemented. These alternatives include: 544 o DHCPv4 over DHCPv6: [I-D.ietf-dhc-dhcpv4-over-dhcpv6] describes 545 implementing DHCPv4 messages over an IPv6 only service providers 546 network. This enables leasing of IPv4 addresses and makes DHCPv4 547 options available to the DHCPv4 over DHCPv6 client. 549 o PCP[RFC6887]: an lwB4 MAY use [I-D.ietf-pcp-port-set] to retrieve 550 a restricted IPv4 address and a set of ports. 552 In a Lightweight 4over6 domain, the binding information MUST be 553 aligned between the lwB4s, the lwAFTRs and the provisioning server. 555 8. ICMP Processing 557 For both the lwAFTR and the lwB4, ICMPv6 MUST be handled as described 558 in [RFC2473]. 560 ICMPv4 does not work in an address sharing environment without 561 special handling [RFC6269]. Due to the port-set style address 562 sharing, Lightweight 4over6 requires specific ICMP message handling 563 not required by DS-Lite. 565 8.1. ICMPv4 Processing by the lwAFTR 567 For inbound ICMP messages The following behavior SHOULD be 568 implemented by the lwAFTR to provide ICMP error handling and basic 569 remote IPv4 service diagnostics for a port restricted CPE: 571 1. Check the ICMP Type field. 573 2. If the ICMP type is set to 0 or 8 (echo reply or request), then 574 the lwAFTR MUST take the value of the ICMP identifier field as 575 the source port, and use this value to lookup the binding table 576 for an encapsulation destination. If a match is found, the 577 lwAFTR forwards the ICMP packet to the IPv6 address stored in the 578 entry; otherwise it MUST discard the packet. 580 3. If the ICMP type field is set to any other value, then the lwAFTR 581 MUST use the method described in REQ-3 of [RFC5508] to locate the 582 source port within the transport layer header in ICMP packet's 583 data field. The destination IPv4 address and source port 584 extracted from the ICMP packet are then used to make a lookup in 585 the binding table. If a match is found, it MUST forward the ICMP 586 reply packet to the IPv6 address stored in the entry; otherwise 587 it MUST discard the packet. 589 Additionally, the lwAFTR MAY implement: 591 o Discarding of all inbound ICMP messages. 593 The ICMP policy SHOULD be configurable. 595 8.2. ICMPv4 Processing by the lwB4 597 The lwB4 SHOULD implement the requirements defined in [RFC5508] for 598 ICMP forwarding. For ICMP echo request packets originating from the 599 private IPv4 network, the lwB4 SHOULD implement the method described 600 in [RFC6346] and use an available port from its port-set as the ICMP 601 Identifier. 603 9. Security Considerations 605 As the port space for a subscriber shrinks due to address sharing, 606 the randomness for the port numbers of the subscriber is decreased 607 significantly. This means it is much easier for an attacker to guess 608 the port number used, which could result in attacks ranging from 609 throughput reduction to broken connections or data corruption. 611 The port-set for a subscriber can be a set of contiguous ports or 612 non-contiguous ports. Contiguous port-sets do not reduce this 613 threat. However, with non-contiguous port-set (which may be 614 generated in a pseudo-random way [RFC6431]), the randomness of the 615 port number is improved, provided that the attacker is outside the 616 Lightweight 4over6 domain and hence does not know the port-set 617 generation algorithm. 619 More considerations about IP address sharing are discussed in 620 Section 13 of [RFC6269], which is applicable to this solution. 622 10. IANA Considerations 624 This document does not include an IANA request. 626 11. Author List 628 The following are extended authors who contributed to the effort: 630 Jianping Wu 632 Tsinghua University 634 Department of Computer Science, Tsinghua University 636 Beijing 100084 638 P.R.China 640 Phone: +86-10-62785983 642 Email: jianping@cernet.edu.cn 644 Peng Wu 646 Tsinghua University 648 Department of Computer Science, Tsinghua University 650 Beijing 100084 652 P.R.China 654 Phone: +86-10-62785822 656 Email: pengwu.thu@gmail.com 658 Qi Sun 660 Tsinghua University 662 Beijing 100084 664 P.R.China 665 Phone: +86-10-62785822 667 Email: sunqi@csnet1.cs.tsinghua.edu.cn 669 Chongfeng Xie 671 China Telecom 673 Room 708, No.118, Xizhimennei Street 675 Beijing 100035 677 P.R.China 679 Phone: +86-10-58552116 681 Email: xiechf@ctbri.com.cn 683 Xiaohong Deng 685 France Telecom 687 Email: xiaohong.deng@orange.com 689 Cathy Zhou 691 Huawei Technologies 693 Section B, Huawei Industrial Base, Bantian Longgang 695 Shenzhen 518129 697 P.R.China 699 Email: cathyzhou@huawei.com 701 Alain Durand 703 Juniper Networks 704 1194 North Mathilda Avenue 706 Sunnyvale, CA 94089-1206 708 USA 710 Email: adurand@juniper.net 712 Reinaldo Penno 714 Cisco Systems, Inc. 716 170 West Tasman Drive 718 San Jose, California 95134 720 USA 722 Email: repenno@cisco.com 724 Alex Clauberg 726 Deutsche Telekom AG 728 GTN-FM4 730 Landgrabenweg 151 732 Bonn, CA 53227 734 Germany 736 Email: axel.clauberg@telekom.de 738 Lionel Hoffmann 740 Bouygues Telecom 742 TECHNOPOLE 744 13/15 Avenue du Marechal Juin 745 Meudon 92360 747 France 749 Email: lhoffman@bouyguestelecom.fr 751 Maoke Chen 753 FreeBit Co., Ltd. 755 13F E-space Tower, Maruyama-cho 3-6 757 Shibuya-ku, Tokyo 150-0044 759 Japan 761 Email: fibrib@gmail.com 763 12. Acknowledgement 765 The authors would like to thank Ole Troan, Ralph Droms and Suresh 766 Krishnan for their comments and feedback. 768 This document is a merge of three documents: 769 [I-D.cui-softwire-b4-translated-ds-lite], [I-D.zhou-softwire-b4-nat] 770 and [I-D.penno-softwire-sdnat]. 772 13. References 774 13.1. Normative References 776 [I-D.ietf-softwire-map-dhcp] 777 Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec, 778 W., Bao, C., leaf.yeh.sdo@gmail.com, l., and X. Deng, 779 "DHCPv6 Options for configuration of Softwire Address and 780 Port Mapped Clients", draft-ietf-softwire-map-dhcp-07 781 (work in progress), March 2014. 783 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 784 E. Lear, "Address Allocation for Private Internets", BCP 785 5, RFC 1918, February 1996. 787 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 788 Requirement Levels", BCP 14, RFC 2119, March 1997. 790 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 791 2131, March 1997. 793 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 794 IPv6 Specification", RFC 2473, December 1998. 796 [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms 797 for IPv6 Hosts and Routers", RFC 4213, October 2005. 799 [RFC4787] Audet, F. and C. Jennings, "Network Address Translation 800 (NAT) Behavioral Requirements for Unicast UDP", BCP 127, 801 RFC 4787, January 2007. 803 [RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. 804 Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142, 805 RFC 5382, October 2008. 807 [RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P. 808 Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142, 809 RFC 5382, October 2008. 811 [RFC5508] Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT 812 Behavioral Requirements for ICMP", BCP 148, RFC 5508, 813 April 2009. 815 [RFC5597] Denis-Courmont, R., "Network Address Translation (NAT) 816 Behavioral Requirements for the Datagram Congestion 817 Control Protocol", BCP 150, RFC 5597, September 2009. 819 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 820 Stack Lite Broadband Deployments Following IPv4 821 Exhaustion", RFC 6333, August 2011. 823 13.2. Informative References 825 [I-D.cui-softwire-b4-translated-ds-lite] 826 Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I. 827 Farrer, "Lightweight 4over6: An Extension to the DS-Lite 828 Architecture", draft-cui-softwire-b4-translated-ds-lite-11 829 (work in progress), February 2013. 831 [I-D.ietf-dhc-dhcpv4-over-dhcpv6] 832 Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I. 833 Farrer, "DHCPv4 over DHCPv6 Transport", draft-ietf-dhc- 834 dhcpv4-over-dhcpv6-06 (work in progress), February 2014. 836 [I-D.ietf-pcp-port-set] 837 Qiong, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, 838 T., and S. Perreault, "Port Control Protocol (PCP) 839 Extension for Port Set Allocation", draft-ietf-pcp-port- 840 set-04 (work in progress), November 2013. 842 [I-D.ietf-softwire-map-dhcp] 843 Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec, 844 W., Bao, C., leaf.yeh.sdo@gmail.com, l., and X. Deng, 845 "DHCPv6 Options for configuration of Softwire Address and 846 Port Mapped Clients", draft-ietf-softwire-map-dhcp-07 847 (work in progress), March 2014. 849 [I-D.ietf-softwire-map] 850 Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S., 851 Murakami, T., and T. Taylor, "Mapping of Address and Port 852 with Encapsulation (MAP)", draft-ietf-softwire-map-10 853 (work in progress), January 2014. 855 [I-D.ietf-softwire-unified-cpe] 856 Boucadair, M., Farrer, I., Perreault, S., and S. 857 Sivakumar, "Unified IPv4-in-IPv6 Softwire CPE", draft- 858 ietf-softwire-unified-cpe-01 (work in progress), May 2013. 860 [I-D.penno-softwire-sdnat] 861 Penno, R., Durand, A., Hoffmann, L., and A. Clauberg, 862 "Stateless DS-Lite", draft-penno-softwire-sdnat-02 (work 863 in progress), March 2012. 865 [I-D.zhou-softwire-b4-nat] 866 Zhou, C., Boucadair, M., and X. Deng, "NAT offload 867 extension to Dual-Stack lite", draft-zhou- 868 softwire-b4-nat-04 (work in progress), October 2011. 870 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 871 Address Translator (Traditional NAT)", RFC 3022, January 872 2001. 874 [RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P. 875 Roberts, "Issues with IP Address Sharing", RFC 6269, June 876 2011. 878 [RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the 879 IPv4 Address Shortage", RFC 6346, August 2011. 881 [RFC6431] Boucadair, M., Levis, P., Bajko, G., Savolainen, T., and 882 T. Tsou, "Huawei Port Range Configuration Options for PPP 883 IP Control Protocol (IPCP)", RFC 6431, November 2011. 885 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 886 Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 887 2013. 889 [RFC7040] Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public 890 IPv4-over-IPv6 Access Network", RFC 7040, November 2013. 892 Authors' Addresses 894 Yong Cui 895 Tsinghua University 896 Beijing 100084 897 P.R.China 899 Phone: +86-10-62603059 900 Email: yong@csnet1.cs.tsinghua.edu.cn 902 Qiong Sun 903 China Telecom 904 Room 708, No.118, Xizhimennei Street 905 Beijing 100035 906 P.R.China 908 Phone: +86-10-58552936 909 Email: sunqiong@ctbri.com.cn 911 Mohamed Boucadair 912 France Telecom 913 Rennes 35000 914 France 916 Email: mohamed.boucadair@orange.com 918 Tina Tsou 919 Huawei Technologies 920 2330 Central Expressway 921 Santa Clara, CA 95050 922 USA 924 Phone: +1-408-330-4424 925 Email: tena@huawei.com 926 Yiu L. Lee 927 Comcast 928 One Comcast Center 929 Philadelphia, PA 19103 930 USA 932 Email: yiu_lee@cable.comcast.com 934 Ian Farrer 935 Deutsche Telekom AG 936 CTO-ATI, Landgrabenweg 151 937 Bonn, NRW 53227 938 Germany 940 Email: ian.farrer@telekom.de