idnits 2.17.1 draft-wbeebee-ipv6-cpe-router-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** The document seems to lack a License Notice according IETF Trust Provisions of 28 Dec 2009, Section 6.b.ii or Provisions of 12 Sep 2009 Section 6.b -- however, there's a paragraph with a matching beginning. Boilerplate error? (You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Feb 2009 rather than one of the newer Notices. See https://trustee.ietf.org/license-info/.) Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 124: '... and, therefore, MUST follow IPv6 Node...' RFC 2119 keyword, line 213: '... The CPE Router SHOULD support the ab...' RFC 2119 keyword, line 228: '... The CPE Router MUST support at least...' RFC 2119 keyword, line 512: '... router MUST support a DHCPv6 server...' RFC 2119 keyword, line 513: '...Provider or user MUST allocate an IA_P...' (17 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: It is possible that in future, IPv6 global unicast prefix can expand beyond 2000::/3. Therefore the CPE Router MUST not have hard coded filters tied to only allow prefixes in a given range. The CPE Router SHOULD be capable of treating any address not already reserved for a specific use by the IETF (such as Link-Local and Multicast addresses) as a potential global unicast address. -- The document seems to contain a disclaimer for pre-RFC5378 work, and may have content which was first submitted before 10 November 2008. The disclaimer is necessary when there are original authors that you have been unable to contact, or if some do not wish to grant the BCP78 rights to the IETF Trust. If you are able to get all authors (current and original) to grant those rights, you can and should remove the disclaimer; otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (March 6, 2009) is 5501 days in the past. Is this intentional? 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group H. Singh 3 Internet-Draft W. Beebee 4 Intended status: BCP Cisco Systems, Inc. 5 Expires: September 7, 2009 March 6, 2009 7 IPv6 CPE Router Recommendations 8 draft-wbeebee-ipv6-cpe-router-04 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. This document may contain material 14 from IETF Documents or IETF Contributions published or made publicly 15 available before November 10, 2008. The person(s) controlling the 16 copyright in some of this material may not have granted the IETF 17 Trust the right to allow modifications of such material outside the 18 IETF Standards Process. Without obtaining an adequate license from 19 the person(s) controlling the copyright in such materials, this 20 document may not be modified outside the IETF Standards Process, and 21 derivative works of it may not be created outside the IETF Standards 22 Process, except to format it for publication as an RFC or to 23 translate it into languages other than English. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF), its areas, and its working groups. Note that 27 other groups may also distribute working documents as Internet- 28 Drafts. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 The list of current Internet-Drafts can be accessed at 36 http://www.ietf.org/ietf/1id-abstracts.txt. 38 The list of Internet-Draft Shadow Directories can be accessed at 39 http://www.ietf.org/shadow.html. 41 This Internet-Draft will expire on September 7, 2009. 43 Copyright Notice 45 Copyright (c) 2009 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents in effect on the date of 50 publication of this document (http://trustee.ietf.org/license-info). 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. 54 Abstract 56 This document recommends IPv6 behavior for Customer Premises 57 Equipment (CPE) routers in Internet-enabled homes and small offices. 58 The CPE Router may be a standalone device. The CPE Router may also 59 be embedded in a device such as a cable modem, DSL modem, cellular 60 phone, etc. This document describes the router portion of such a 61 device. The purpose behind this document is to provide minimal 62 functionality for interoperability and create consistency in the 63 customer experience and satisfy customer expectations for the device. 64 Further, the document also provide some guidance for implementers to 65 expedite availability of IPv6 CPE router products in the marketplace. 66 It is expected that standards bodies other than the IETF developing 67 standards for specific products in this area (e.g. CableLabs 68 eRouter, DSL Forum, Home Gateway Initiative, etc.) may reference this 69 work for basic functionality and provide value-added or linktype- 70 specific customizations and enhancements which are beyond the scope 71 of this document. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4 77 3. Operational Behavior . . . . . . . . . . . . . . . . . . . . . 5 78 3.1. Conceptual Configuration Variables . . . . . . . . . . . . 5 79 4. Router Initialization . . . . . . . . . . . . . . . . . . . . 6 80 5. Basic IPv6 Provisioning . . . . . . . . . . . . . . . . . . . 6 81 5.1. Construct Link-Local Address . . . . . . . . . . . . . . . 7 82 5.2. Process RAs . . . . . . . . . . . . . . . . . . . . . . . 7 83 5.3. Acquire IPv6 Address and Other Configuration Parameters . 7 84 5.3.1. Numbered Model . . . . . . . . . . . . . . . . . . . . 7 85 5.3.2. Unnumbered Model . . . . . . . . . . . . . . . . . . . 8 86 5.3.3. Both Models . . . . . . . . . . . . . . . . . . . . . 8 87 5.4. Details for DHCPv6 Address Acquisition . . . . . . . . . . 8 88 5.5. IPv6 Provisioning of Home Devices . . . . . . . . . . . . 9 89 5.5.1. LAN Initialization before WAN Initialization . . . . . 9 90 5.5.2. WAN initialization before LAN Initialization . . . . . 10 91 5.6. IPv6 over PPP . . . . . . . . . . . . . . . . . . . . . . 11 92 5.6.1. Softwire Support . . . . . . . . . . . . . . . . . . . 11 93 5.7. Stateful DHCPv6 Server . . . . . . . . . . . . . . . . . . 12 94 6. Cascading of Routers behind the CPE Router . . . . . . . . . . 12 95 7. IPv6 Data Forwarding . . . . . . . . . . . . . . . . . . . . . 12 96 7.1. IPv6 ND Proxy Behavior . . . . . . . . . . . . . . . . . . 13 97 7.2. IPv6 Multicast Behavior . . . . . . . . . . . . . . . . . 13 98 8. Other IPv6 Features . . . . . . . . . . . . . . . . . . . . . 14 99 8.1. Path MTU Discovery Support . . . . . . . . . . . . . . . . 14 100 8.2. Optional RIPng Support . . . . . . . . . . . . . . . . . . 14 101 8.3. Firewall . . . . . . . . . . . . . . . . . . . . . . . . . 14 102 8.3.1. Packet Filters . . . . . . . . . . . . . . . . . . . . 14 103 8.4. Zero Configuration Support . . . . . . . . . . . . . . . . 15 104 8.5. 6to4 Automated Tunneling/Dual-Stack Lite/ISATAP . . . . . 15 105 8.6. DNS Support . . . . . . . . . . . . . . . . . . . . . . . 16 106 8.7. Quality Of Service(QoS) . . . . . . . . . . . . . . . . . 16 107 9. IPv4 Support . . . . . . . . . . . . . . . . . . . . . . . . . 16 108 10. Protocol Constants . . . . . . . . . . . . . . . . . . . . . . 17 109 11. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 17 110 12. Security Considerations . . . . . . . . . . . . . . . . . . . 17 111 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 112 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 113 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 114 15.1. Normative References . . . . . . . . . . . . . . . . . . . 17 115 15.2. Informative References . . . . . . . . . . . . . . . . . . 18 116 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 118 1. Introduction 120 This document defines IPv6 features for a residential or small office 121 router referred to as a CPE Router. Typically, CPE Router devices 122 support IPv4, as discussed in the "IPv4 Support" section. Also, this 123 document does not go into configuration details for the CPE Router. 124 A CPE Router is an IPv6 Node and, therefore, MUST follow IPv6 Node 125 Requirements draft-ietf-6man-node-req-bis-01 126 [I-D.ietf-6man-node-req-bis]. 128 The document discusses IPv6 implications for the attached Service 129 Provider network. The document notes that the CPE Router may be 130 deployed in home in one of two ways. Either the Service Provider or 131 the home user may manage this device. When the CPE Router is managed 132 by the Service Provider, the router may need additional management 133 and routing properties like a new MIB definition and routing 134 protocols communicating between the CPE Router and the Service 135 Provider network. The CPE router has one or more WAN interface(s) to 136 connect to the Service Provider and zero or more LAN interfaces to 137 the home network devices. The WAN interface is preferred to be 138 Ethernet encapsulated but it may support other encapsulations such as 139 PPP. 141 2. Terminology and Abbreviations 143 Host - this is a personal computer or any other network device in 144 a home that connects to the Internet via the CPE Router. 146 LAN interface(s) - an optional set of network interfaces on the 147 CPE Router that are used to connect hosts in the home. This set 148 of ports could be switched, bridged, or routed. If no LAN 149 interface is present, then there is no need for the CPE router to 150 provide LAN side services such as DHCPv6 PD or ULA's. 152 WLAN interface - an optional wireless access point interface on 153 the CPE Router used to connect wireless hosts in the home in 154 either managed or ad-hoc modes. 156 WAN interface - usually a single physical network interface on the 157 standalone CPE Router that is used to connect the router to the 158 access network of the Service Provider. When the CPE Router is 159 embedded in a device that connects to the WAN, this interface is a 160 logical network interface that bridges the device to the CPE 161 Router. Some devices which can have an embedded CPE router are: a 162 cable or DSL modem, or a cellular telephone, etc. A CPE router 163 with more than one WAN interface will need a more complicated 164 provisioning and multicast model than is described in this 165 document. 167 GRE tunnel - Generic Routing Encapsulation tunnel. 169 SLAAC - StateLess Address Auto Configuration. 171 IPTV - Internet Protocol TeleVision. 173 mDNS - Multicast Domain Name System - see http://www.zeroconf.org. 175 3. Operational Behavior 177 The CPE Router is a gateway to the Internet for a home. The router 178 is also intended to provide home networking functionality. The CPE 179 Router may have a console or web interface for configuration. This 180 document defines the core set of features that are supported by the 181 CPE Router, however individual implementations may include value- 182 added features such as WLAN capability. 184 The core set of IPv6 features for the CPE Router includes 185 provisioning the CPE Router for IPv6, IPv6 data forwarding including 186 IPv6 multicast, CPE Router provisioning hosts on its LAN 187 interface(s), firewall, and QoS behavior. An IPv6 firewall is 188 discussed briefly in the Firewall section where the section refers 189 the draft-ietf-v6ops-cpe-simple-security 190 [I-D.ietf-v6ops-cpe-simple-security] for more details. 192 3.1. Conceptual Configuration Variables 194 The CPE Router maintains such a list of conceptual optional 195 configuration variables. 197 1. Loopback interface enable. 199 2. PPPOE enable. 201 3. Softwire enable. 203 4. RIPng enable. 205 5. If DHCPv6 fails, the CPE Router may initiate PPPOE, L2TPv2 206 Softwire tunnel, or 6to4 [RFC3056] operation. 208 6. 210 4. Router Initialization 212 Before the CPE Router is initialized, the device must have IPv6 213 enabled. The CPE Router SHOULD support the ability to disable its 214 IPv6 stack. The CPE Router also has the ability to block or forward 215 IPv6 traffic to and from the router's LAN interface(s). [RFC2669] 216 includes a MIB definition to block the IPv4 or IPv6 Ethertype in the 217 upstream or downstream interface(s) of a device such as the CPE 218 Router. Some portion of this MIB may need to be modified for use 219 with the CPE Router. 221 The CPE Router supports at least one of two modes of initialization: 222 either the LAN interface(s) become operational first or the WAN 223 interface becomes operational first. More details have been provided 224 in the Basic IPv6 Provisioning section. 226 5. Basic IPv6 Provisioning 228 The CPE Router MUST support at least one of two WAN interface models, 229 one of which will be active on the CPE Router at any given time. In 230 the Numbered model, the WAN interface acquires a global unicast 231 address (GUA) using a combination of SLAAC and stateful DHCPv6 for 232 IA_PD (no IA_NA) or uses only stateful DHCPv6 for GUA (IA_NA) and 233 IA_PD. IA_PD is acquired using stateful DHCPv6 as described in 234 [RFC3633]. A Loopback interface (which can be used as a stable 235 peering point for routing protocols or to respond to the anycast 236 address) is optional. If stateful DHCPv6 is not used to obtain other 237 IPv6 configuration, then stateless DHCPv6 [RFC3736] must be initiated 238 by the WAN interface to obtain other IPv6 configuration. Further, in 239 the numbered model, we recommend the CPE Router WAN interface acquire 240 its global IPv6 address using stateful DHCPv6 for administrative 241 control of the router. Manual configuration may be supported by the 242 CPE router for IPv6 address configuration of the WAN interface. 243 However, manual configuration is beyond the scope of this document. 245 In the Unnumbered model, the WAN interface only constructs a LLA, 246 then the WAN interface initiates stateful DHCPv6 for IA_PD. The 247 IA_PD is sub-delegated to the LAN interface(s) and an optional 248 Loopback interface (or the addresses for the LAN/Loopback interfaces 249 could come from IA_NAs). Either the Loopback or the LAN interface 250 can be used to source WAN-facing traffic. Other IPv6 configuration 251 information is obtained using stateless DHCPv6. 253 The CPE Router acquires its IPv6 addresses from the Service Provider 254 along with any other IPv6 configuration any time the WAN interface is 255 connected to the Service Provider network. Thereafter the CPE Router 256 provisions its LAN interface(s) for IPv6 router functionality 257 including provisioning global IPv6 addresses on the LAN interface(s). 258 Even if LAN interface(s) have been operational and provisioned 259 earlier, the global IPv6 configuration of LAN interface(s) is still 260 required. More details for provisioning the CPE Router are given in 261 the following sections. 263 5.1. Construct Link-Local Address 265 If an interface of the CPE Router is configured for IPv6, when the 266 interface initializes itself, as per [RFC4862], the CPE Router must 267 create a link-local address for the interface. We recommend the CPE 268 Router use the EUI-64 identifier as a link-local address for each of 269 its interfaces. Refer to EUI-64 details in [RFC4291]. Further, as 270 per [RFC4862], the CPE Router must perform Duplicate Address 271 Detection (DAD) on all unicast addresses unless a layer 2-specific 272 document specifies that DupAddrDetectTransmits is zero for that 273 linktype. If the CPE Router detects a duplicate address assigned to 274 an interface, the CPE Router must not send IPv6 packets from the 275 interface. 277 5.2. Process RAs 279 The CPE Router must process incoming RAs received on the WAN 280 interface as specified in section 6.3 of [RFC4861]. The CPE Router 281 locates routers that reside on the attached WAN link from the 282 received RAs. 284 5.3. Acquire IPv6 Address and Other Configuration Parameters 286 The CPE Router must process RAs received on the WAN interface. As 287 per [RFC4861] if the M bit is set in the RA, the WAN interface must 288 perform stateful DHCPv6- if the O bit is set in the RA, the WAN 289 interface acquires other configuration information. If stateful 290 DHCPv6 is not used to obtain other IPv6 configuration, then stateless 291 must be initiated by the WAN interface to obtain other IPV6 292 configuration. If the A bit in the RA is clear or the RA does not 293 include any Prefix Information Option (PIO), the WAN interface must 294 not perform SLAAC. IPv6 deployments that configure RA to not include 295 any PIO are discussed in draft-ietf-6man-ipv6-subnet-model 296 [I-D.ietf-6man-ipv6-subnet-model]. 298 5.3.1. Numbered Model 300 As instructed by the RA message, the WAN interface acquires global 301 IPv6 address using stateful DHCPv6. 303 5.3.2. Unnumbered Model 305 When the CPE router is configured for Unnumbered model, the WAN 306 interface only constructs a LLA, then the WAN interface initiates 307 stateful DHCPv6 for IA_PD. Then the IA_PD is sub-delegated to the 308 LAN interface(s) and an optional Loopback interface (or the addresses 309 for the LAN/Loopback interfaces could come from IA_NAs). Either the 310 Loopback or the LAN interface can be used to source WAN-facing 311 traffic. When the Loopback or the LAN interface is used to source 312 WAN-facing traffic, both the CPE Router and the Service Provider 313 Router must consider the traffic to be off-link to the link 314 connecting the CPE Router with the Service Provider Router. Other 315 IPv6 configuration information is obtained using stateless DHCPv6. A 316 CPE Router acts as a host for packets originating from or destined 317 for the CPE Router. Such packets may include SNMP or web-based 318 router configuration, tunnel encapsulation/decapsulation, or PPP 319 endpoint packets. The Unnumbered model is incompatible with the 320 strong host model on the CPE router. The unnumbered model may be 321 inappropriate for use with certain deployments where a device that 322 uses the strong host model can operate as a CPE Router. 324 5.3.3. Both Models 326 At any instance in time of the CPE Router operation, the router does 327 not forward any traffic between its WAN and LAN interface(s) if the 328 router has not completed IPv6 provisioning process that involves the 329 acquisition of a global IPv6 address by the WAN or if the WAN is 330 unnumbered and there is no GUA available to source WAN packets. The 331 LAN interface(s) must also be provisioned for a global or Unique 332 Local Address. 334 5.4. Details for DHCPv6 Address Acquisition 336 If the WAN interface uses stateful DHCPv6, the interface sends a 337 DHCPv6 Solicit message as described in section 17.1.1 of [RFC3315]. 338 The Solicit message must include an IA_NA option as specified by 339 [RFC3315]. If the WAN interfaces uses stateless DHCPv6, the WAN 340 interface sends an Information Request. Both the DHCPv6 SOLICIT and 341 Information Request also include other options like a Reconfigure 342 Accept option to inform the server that client is willing to accept 343 Reconfigure message from server, and the Options Request option that 344 includes the DNS Recursive Name server option as specified in 345 [RFC3646]. The Solicit may also include the Rapid Commit option if 346 the CPE Router is willing to accept a 2-message DHCPv6 exchange with 347 the server. 349 When the CPE Router processes a DHCPv6 response from the server, if 350 the response message (e.g. ADVERTISE or REPLY) received does not 351 include an IA_PD option (if stateful DHCPv6 was initiated), or 352 Reconfigure Accept option, then the CPE Router has failed DHCPv6 353 address acquisition. If stateful DHCPv6 succeeds, the CPE Router 354 must perform DAD for any IPv6 address acquired from DHCPv6. If the 355 CPE Router detects a duplicate, the CPE Router must send a DHCPv6 356 Decline message to the DHCPv6 server. 358 The CPE Router may support the Reconfigure Key Authentication 359 Protocol, as described in section 21.5 of [RFC3315]. The CPE Router 360 may also support prefix sub-delegation. Prefix sub-delegation 361 involves DHCPv6 server support with IA_PD on the CPE router and the 362 ability to provision the server from a DHCPv6 REPLY with IA_PD option 363 received on the WAN interface. 365 5.5. IPv6 Provisioning of Home Devices 367 The CPE Router may include a stateful DHCPv6 server to assign 368 addresses to home devices connected via the LAN interface(s) of the 369 CPE Router. The home devices can also acquire addresses via SLAAC. 371 If the LAN interface(s) are switched or bridged ports, then the CPE 372 Router assigns a single global IPv6 address to a conceptual virtual 373 interface serving all the LAN interface(s). If each LAN interface is 374 a routed port, then the CPE router will assign a global IPv6 address 375 and unique subnet to each LAN interface. In either case, when the 376 CPE Router needs to assign a single IPv6 address to LAN interface(s) 377 or multiple IPv6 addresses, the CPE Router redistributes the 378 addresses and subnets from the prefix received in IA_PD option by the 379 WAN interface. If the IA_PD changes, the CPE Router must reconfigure 380 the LAN interface(s) with new IPv6 addresses derived from the new 381 IA_PD and then also renumber the IPv6 ND RA configuration on the LAN 382 interface(s). 384 This document recommends the RA sent out by LAN Interface(S) to be 385 configured for SLAAC so that the prefix advertised in the RA is 386 derived from the IA_PD assigned to the CPE Router by the Service 387 Provider; the O-bit is also set so that the CPE Router can pass 388 Domain Name Server(s) IPv6 address(es) to home devices. The CPE 389 Router obtained the Domain Name Server(s) in OPTION_DNS_SERVERS 390 option from the DHCPv6 server when the CPE Router WAN interface 391 completed DHCPv6. 393 5.5.1. LAN Initialization before WAN Initialization 395 On power up, the LAN interface(s) of the CPE Router may become 396 operational before the WAN interface. This mode is appropriate for 397 manual user configuration of the CPE Router. After any LAN interface 398 has constructed a link-local address, the address can be used for 399 user configuration via the network. The interface can assign itself 400 a Unique Local Address automatically through the pseudo-random number 401 generation algorithm described in [RFC4193]. Note that the ULA must 402 have a larger subnet than a /64 if multiple routers are cascaded 403 behind the CPE router and prefix sub-delegation is used (see the 404 Cascading of Routers behind the CPE Router section below). Once the 405 IPv6 address configuration of the LAN interface(s) is complete with a 406 ULA, as per [RFC4862], the CPE Router sends Router Advertisements 407 (RA) to devices in the home. Hosts receiving the RA from LAN 408 interface(s) will process the RA and perform IPv6 address 409 acquisition. After all the LAN interface(s) have become operational, 410 if the WAN interface is connected to the Service Provider network, 411 then the WAN interface provisions itself and may acquire an IA_PD. 412 If an IA_PD is acquired, it may be sub-delegated to any cascaded 413 routers or used for SLAAC provisioning of hosts in the home. Based 414 on the IA_PD, the CPE Router configures global address(es) on the LAN 415 interface(s) and sends an RA containing the global address and unique 416 local prefixes out the LAN interface(s). After this process, every 417 LAN interface has a link-local unicast address, a ULA, and a GUA. 418 Therefore, the interface has to apply source address selection to 419 determine which address to use as a source for outgoing packets. 420 Since the GUA has a larger scope than the link-local address, or the 421 ULA (rule #2 of [RFC3484]), the GUA will be used as a source address 422 of outgoing packets that are not subject to rule #1. If a user 423 desires to keep CPE Router configuration traffic local to the home 424 network, the user can do the following: 426 Use the ULA of the CPE Router as the destination of the 427 configuration traffic. 429 Use access control lists (ACL)s to block any ULA sourced packet 430 from being sent out the WAN interface. 432 Rule #1 of [RFC3484] and the ACLs ensure that the traffic does not 433 escape the home network. 435 After the WAN interface initializes, then the LAN interface(s) can 436 acquire global unicast addresses. 438 5.5.2. WAN initialization before LAN Initialization 440 On power up, the WAN interface of the CPE Router may become 441 operational before the LAN interface(s). This mode is appropriate 442 for Service Provider configuration of the CPE Router. After the IPv6 443 address configuration for WAN interface is completed, the CPE Router 444 configures IPv6 address for LAN interface(s). 446 Once IPv6 address configuration of the LAN interface(s) is complete, 447 as per [RFC4862], the CPE Router sends Router Advertisements (RA) to 448 devices in the home. Hosts receiving the RA from LAN interface(s) 449 will process the RA and perform IPv6 address acquisition. 451 5.6. IPv6 over PPP 453 In some deployments IPv6 over PPP is preferred to connect the home to 454 the Service Provider. For such a deployment, another configuration 455 variable on the CPE Router enables optional IPv6 over PPP support. 456 After IPv6CP negotiates IPv6 over PPP and the WAN interface has 457 constructed a LLA, steps mentioned in the "Acquire IPv6 Address and 458 Other Configuration Parameters" section above are followed to acquire 459 a GUA for WAN interface and also an IA_PD. If an IA_PD is acquired 460 by the WAN interface, the CPE Router assigns global address(es) to 461 its LAN interface(s) and sub-delegates the IA_PD to hosts connected 462 to the LAN interface(s). IPv6 over PPP follows [RFC5072]. As per 463 [RFC5072], the CPE router does not initiate any DAD for unicast IPv6 464 addresses since DupAddrDetectTransmits variable from [RFC4862] is 465 zero for IPv6 over PPP. 467 If the Service Provider deployment supports dual-stack PPP support, 468 then the CPE Router WAN interface may initiate one PPP logical 469 channel and support NCP IPv4 and IPv6 control protocols over one PPP 470 logical channel. [RFC4241] describes such behavior. The IPv4 and 471 IPv6 NCP's are independent of each other and start and terminate 472 independently. 474 5.6.1. Softwire Support 476 If the CPE Router is deployed in a deployment where the home includes 477 IPv6 hosts but the Service Provider network does not support IPv6, an 478 optional softwire feature may be enabled on the CPE Router. The 479 softwire draft-ietf-softwire-hs-framework-l2tpv2 480 [I-D.ietf-softwire-hs-framework-l2tpv2] initiates L2TPv2 tunnel from 481 the CPE Router to tunnel IPv6 data from the home over an IPv4 482 network. The feature is enabled before any IPv6 host in the home is 483 connected to the CPE Router or the WAN interface of the CPE Router is 484 operational. If the CPE Router supports the Softwire feature, then 485 the CPE Router must support the deployment scenario of Router CPE as 486 Softwire Initiator described in section 3.1.2 of 487 draft-ietf-softwire-hs-framework-l2tpv2 488 [I-D.ietf-softwire-hs-framework-l2tpv2]. IPV6CP negotiates IPv6 over 489 PPP which also provides the capability for the Service Provider to 490 assign the 64-bit Interface-Identifier to the WAN interface of the 491 CPE Router. After the WAN interface has acquired an IA_PD option, 492 global addresses from the IA_PD are assigned to the LAN interface(s) 493 and the IA_PD is also sub-delegated to clients connected to the LAN 494 interface(s). 496 5.7. Stateful DHCPv6 Server 498 The CPE Router may support a stateful DHCPv6 server to serve clients 499 on the CPE Router LAN interface(s). If the CPE Router needs to 500 support a stateful DHCPv6 server, then more details will be added to 501 this section specifying the minimal functionality that the stateful 502 DHCPv6 server needs to support. 504 6. Cascading of Routers behind the CPE Router 506 To support cascading routers behind the CPE Router this document 507 recommends using prefix sub-delegation of the prefix obtained either 508 via IA_PD from WAN interface or a ULA from the LAN interface. The 509 network interface of the downstream router may obtain an IA_PD either 510 via stateful DHCPv6 or stateless DHCPv6. If the CPE router supports 511 cascading of routers through automatic prefix sub-delegation, the CPE 512 router MUST support a DHCPv6 server or DHCPv6 relay agent. If an 513 IA_PD is used, the Service Provider or user MUST allocate an IA_PD or 514 ULA prefix short enough to be sub-delegated and subsequently used for 515 SLAAC. Therefore, a prefix length shorter than /64 is needed. The 516 CPE Router MAY support RIPng in the home network. 518 7. IPv6 Data Forwarding 520 Each of the WAN and LAN interface(s) of the CPE Router must have its 521 own L2 (e.g. MAC) address. The CPE Router supports ND protocol on 522 both the WAN interface and LAN interface(s) to advertise itself as a 523 router to neighbors in the Service Provider and home networks. 525 The CPE Router forwards packets between the Service Provider and the 526 home network. To do this, the CPE Router looks up the destination 527 address of the packet in the routing table and decide which route to 528 use to forward the packet. The CPE Router routing table will be 529 initialized during CPE Router initialization. The routing table is 530 filled by directly connected, static, and routing protocol routes. 532 The CPE Router consumes any packet destined to its WAN or LAN 533 interface. The CPE Router forwards other packets destined to hosts 534 attached to CPE Router LAN interface(s). Any packet that is not 535 routable by the CPE Router must be dropped. 537 The CPE Router must support the ND protocol specified by [RFC4861]. 538 Proxy Neighbor Advertisements as described in Section 7.2.8 of 539 [RFC4861] as applicable to the CPE Router are discussed in the IPv6 540 ND Proxy Behavior section. Also note, as per section 6.2.8 of 541 [RFC4861] the link-local address on a router should rarely change, if 542 ever. As per [RFC2460], the CPE Router decrements the Hop Limit by 1 543 for any packet it forwards. The packet is discarded if Hop Limit is 544 decremented to zero and the CPE Router also sends an ICMP Time 545 Exceeded message to the source of the packet. 547 A route SHOULD be added to the routing table (to prevent routing 548 loops) that is lower priority than any route except the default 549 route. The choice to drop the packet or send an ICMPv6 Destination 550 Unreachable to the source address of the packet is implementation- 551 dependent. The installation of the null route MAY be automatic. 553 7.1. IPv6 ND Proxy Behavior 555 If the CPE Router has only one /64 prefix to be used across multiple 556 LAN interfaces and the CPE Router supports any two LAN interfaces 557 that cannot bridge data between them because the two interfaces have 558 disparate MAC layer, then the CPE Router MUST support ND Proxy. If 559 any two disparate LAN interfaces support bridging between the 560 interfaces, then ND Proxy may be supported, although the support is 561 not necessary. However, if the CPE Router has more than multiple 562 prefixes available for use on LAN interfaces(s), and still any two 563 interfaces on the LAN have disparate MAC layer, the CPE Router MUST 564 NOT support ND Proxy. 566 7.2. IPv6 Multicast Behavior 568 The CPE Router SHOULD follow the model described for MLD Proxy in 569 [RFC4605] to implement multicast. The MLD Proxy model was chosen 570 because it is simpler to implement than more complicated multicast 571 routing functionality. 573 Querier Election rules as described in section 7.6.2 of [RFC3810] do 574 not apply to the CPE Router (even when the home has multiple cascaded 575 routers) since every CPE Router in the cascade is the only router in 576 its own multicast domain. Every CPE Router in the cascade will send 577 MLDv2 Reports with aggregated multicast Group Membership information 578 to the next upstream router. 580 If the CPE Router hardware includes a network bridge between the WAN 581 interface and the LAN interface(s), then the CPE Router MUST support 582 MLDv2 snooping as per [RFC4541]. 584 Consistent with [RFC4605], the CPE Router must not implement the 585 router portion of MLDv2 for the WAN interface. Likewise, the LAN 586 interfaces on the CPE router must not implement an MLDv2 Multicast 587 Listener. However, if a user at home wants to create a new multicast 588 group and send multicast data to other nodes on the Service Provider 589 network, then Protocol Independent Multicast-Source Specific 590 Multicast (PIM-SSM) [RFC3569] is recommended to handle multicast 591 traffic flowing in the upstream direction as a one-to-many multicast 592 flow. 594 8. Other IPv6 Features 596 8.1. Path MTU Discovery Support 598 GRE tunnels, such as IPv6 to IPv4 tunnels (which may be terminated on 599 the CPE Router), can modify the default Ethernet MTU of 1500 bytes. 600 Also, in the future, Ethernet Jumbo frames (9000+ bytes) may also be 601 supported. Since the MTU can vary, a newly initiated TCP stream must 602 detect the largest packet that can be sent to the destination without 603 fragmentation. This can be detected using Path MTU Discovery 604 [RFC1981]. Routers which may encounter a packet too large to be 605 forwarded from source to destination may drop the packet and send an 606 ICMPv6 Packet Too Big message to the source. The CPE Router must 607 route back to the source any ICMPv6 Packet Too Big messages generated 608 anywhere on this path. 610 8.2. Optional RIPng Support 612 The CPE Router may support RIPng routing protocol [RFC2080] so that 613 RIPng operates between the CPE Router and the Service Provider 614 network. RIPng has scaling and security implications for the Service 615 Provider network where one Service Provider router may terminate 616 several tens of thousands of CPE routers. However, RIPng does 617 provide one solution from the CPE Router to the Service Provider 618 network for prefix route injection. 620 8.3. Firewall 622 The CPE Router must support an IPv6 Firewall feature. The firewall 623 may include features like access-control lists. The firewall may 624 support interpretation or recognition of most IPv6 extension header 625 information including inspecting fragmentation header. The firewall 626 must support stateful and stateless Packet Filters as follows. 628 8.3.1. Packet Filters 630 The CPE Router must support packet filtering based on IP headers, 631 extended headers, UDP and TCP ports etc. There are numerous filters 632 mentioned (section 3.2) in draft-ietf-v6ops-cpe-simple-security 633 [I-D.ietf-v6ops-cpe-simple-security], like some that allow IKE, IPSec 634 packets while another filter may block Teredo packets. 636 It is possible that in future, IPv6 global unicast prefix can expand 637 beyond 2000::/3. Therefore the CPE Router MUST not have hard coded 638 filters tied to only allow prefixes in a given range. The CPE Router 639 SHOULD be capable of treating any address not already reserved for a 640 specific use by the IETF (such as Link-Local and Multicast addresses) 641 as a potential global unicast address. 643 6to4 and ISATAP tunnels may be initiated by hosts behind the CPE 644 Router. The CPE Router MUST NOT block 6to4 or ISATAP packets without 645 a configurable override. 647 8.4. Zero Configuration Support 649 The CPE Router MAY support manual configuration via the web using a 650 URL string like http://router.local as per mDNS described in the 651 Terminology and Abbreviations section. Note that mDNS is a link- 652 local protocol, so extra functionality is required if configuration 653 is to be supported over cascaded routers. Support of configuration 654 through cascaded routers is beyond the scope of this document. 656 8.5. 6to4 Automated Tunneling/Dual-Stack Lite/ISATAP 658 If the IPv4 address assigned to the WAN interface of the CPE Router 659 is a non-[RFC1918] IPv4 address, and the CPE Router fails to acquire 660 an IPv6 address before WAN_IP_ACQUIRE_TIMEOUT seconds after acquiring 661 the IPv4 address, then the 6to4 tunneling protocol [RFC3056] SHOULD 662 be enabled automatically, allowing tunneling of IPv6 packets over 663 IPv4 without requiring user configuration. If an anycast 6to4 server 664 cannot be located, the CPE Router MAY initiate ISATAP [RFC4214] to 665 establish IPv6 connectivity over the IPv4 network. If an IPv6 666 address is acquired, but no IPv4 address is acquired before 667 WAN_IP_ACQUIRE_TIMEOUT seconds after the IPv6 address was acquired, 668 then the CPE Router SHOULD use DS-Lite and disable NAT44 in the CPE 669 Router. If both IPv6 and IPv4 addresses are acquired within 670 WAN_IP_ACQUIRE_TIMEOUT seconds of each other, then the CPE Router 671 operates in dual stack mode, and does not need either 6to4 or DS- 672 Lite. If no IPv4 and no IPv6 address has been acquired, then the CPE 673 Router retries acquisition. 675 6to4 can be useful in the scenario where the Service Provider does 676 not yet support IPv6, but devices in the home use IPv6. An IPv6 677 address is constructed automatically from the IPv4 address (V4ADDR) 678 configured on the interface using the prefix 2002:V4ADDR::/48. A 679 6to4 tunnel can be automatically created using a pre-configured 6to4 680 gateway end-point for the tunnel. 682 Several proposals are being considered by IETF related to the problem 683 of IPv4 address depletion, but have not yet achieved working group 684 consensus for publication as an RFC. Dual-stack lite ietf-softwire- 685 dual-stack-lite-00 [I-D.ietf-softwire-dual-stack-lite] requires the 686 CPE Router to support features such as v4 in v6 encapsulation and 687 softwires. Further, any approach which requires the use of a tunnel 688 MUST take into account the reduced MTU. The tunnel software on the 689 CPE Router MUST be capable of fragmenting data packets. 691 For DS-Lite, the CPE Router also discovers the IPv6 address of the 692 Carrier Grade NAT node in the deployment. The ietf-softwire-dual- 693 stack-lite-00 [I-D.ietf-softwire-dual-stack-lite] draft has yet to 694 fully describe the method of discovery. 696 8.6. DNS Support 698 For local DNS queries for configuration, the CPE Router may include a 699 DNS server to handle local queries. Non-local queries can be 700 forwarded unchanged to a DNS server specified in the DNS server 701 DHCPv6 option. The CPE Router may also include DNS64 functionality. 702 In that case, the prefix used is either a well-known prefix or 703 configured through DHCPv6 or SNMP. An A record is simply passed 704 through untouched. An AAAA record is relayed to the server. If the 705 CPE Router receives no response, then an A query is used. If the A 706 query returns a response, then an AAAA record is synthesized using 707 the prefix and sent to the host. If DNSSEC is used, then both an A 708 record (authenticated with DNSSEC), and the synthesized AAAA record 709 (possibly tagged as synthetic with an EDNS0 option, IDENT bit(s), or 710 using a well-known prefix) is returned. This allows unmodified hosts 711 to simply use the synthetic AAAA record (without DNSSEC). Modified 712 hosts can look at the DNSSEC A record, authenticate it, then 713 synthesize its own AAAA record in a stub resolver located in the 714 host. Therefore, unmodified hosts can get connectivity, but modified 715 hosts can also authenticate DNS records. 717 8.7. Quality Of Service(QoS) 719 The CPE router MAY support differentiated services [RFC2474]. 721 9. IPv4 Support 723 IPv4 support is largely out of scope for this document. However, a 724 brief overview of current practice in the market may be helpful since 725 the CPE Router may support both IPv4 and IPv6. This section does NOT 726 require the CPE Router to support IPv4. For background information 727 on IPv4 routing capabilities, please refer to [RFC1812]. Typically, 728 CPE Routers which support IPv4, also support IPv4 NAT for translating 729 private [RFC1918] addresses (e.g. 192.168.x.x) into a single non- 730 [RFC1918] WAN address assigned through DHCPv4 or manually configured. 731 In addition to NAT, CPE Routers that support IPv4 typically also 732 support Application Layer Gateway functionality (ALG), such as the 733 FTP ALG. The IPv4 NAT functionality typically has a built-in DHCPv4 734 server. A CPE Router which supports IPv4 also supports ARP and basic 735 unicast IPv4 forwarding. Some CPE Routers which support IPv4 also 736 support IPv4 multicast forwarding ([RFC5135]) and basic firewall 737 capabilities. A stateful firewall can enhance security by examining 738 the state of each connection and only allow traffic which conforms to 739 an expected packet flow. 741 10. Protocol Constants 743 WAN_IP_ACQUIRE_TIMEOUT 180 seconds. 745 11. Open Issues 747 12. Security Considerations 749 Security considerations of a CPE router are covered by 750 draft-ietf-v6ops-cpe-simple-security 751 [I-D.ietf-v6ops-cpe-simple-security]. 753 13. IANA Considerations 755 None. 757 14. Acknowledgements 759 Thanks (in alphabetical order) to Antonio Querubin, Bernie Volz, 760 Carlos Pignataro, Dan Wing, David Miles, Francois-Xavier Le Bail, 761 Fred Baker, James Woodyatt, Mark Townsley, Mikael Abrahamsson, Ole 762 Troan, Remi Denis-Courmont, Shin Miyakawa, and Tony Hain for their 763 input on the document. 765 15. References 767 15.1. Normative References 769 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 770 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 771 September 2007. 773 15.2. Informative References 775 [I-D.ietf-6man-ipv6-subnet-model] 776 Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet 777 Model: the Relationship between Links and Subnet 778 Prefixes", draft-ietf-6man-ipv6-subnet-model-02 (work in 779 progress), October 2008. 781 [I-D.ietf-6man-node-req-bis] 782 Loughney, J., "IPv6 Node Requirements RFC 4294-bis", 783 draft-ietf-6man-node-req-bis-02 (work in progress), 784 November 2008. 786 [I-D.ietf-softwire-dual-stack-lite] 787 Durand, A., Droms, R., Haberman, B., and J. Woodyatt, 788 "Dual-stack lite broadband deployments post IPv4 789 exhaustion", draft-ietf-softwire-dual-stack-lite-00 (work 790 in progress), March 2009. 792 [I-D.ietf-softwire-hs-framework-l2tpv2] 793 Storer, B., Pignataro, C., Santos, M., Stevant, B., and J. 794 Tremblay, "Softwire Hub & Spoke Deployment Framework with 795 L2TPv2", draft-ietf-softwire-hs-framework-l2tpv2-11 (work 796 in progress), February 2009. 798 [I-D.ietf-v6ops-cpe-simple-security] 799 Woodyatt, J., "Recommended Simple Security Capabilities in 800 Customer Premises Equipment for Providing Residential 801 IPv6 Internet Service", 802 draft-ietf-v6ops-cpe-simple-security-03 (work in 803 progress), July 2008. 805 [RFC1122] Braden, R., "Requirements for Internet Hosts - 806 Communication Layers", STD 3, RFC 1122, October 1989. 808 [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", 809 RFC 1812, June 1995. 811 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 812 E. Lear, "Address Allocation for Private Internets", 813 BCP 5, RFC 1918, February 1996. 815 [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery 816 for IP version 6", RFC 1981, August 1996. 818 [RFC2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080, 819 January 1997. 821 [RFC2453] Malkin, G., "RIP Version 2", STD 56, RFC 2453, 822 November 1998. 824 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 825 (IPv6) Specification", RFC 2460, December 1998. 827 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 828 "Definition of the Differentiated Services Field (DS 829 Field) in the IPv4 and IPv6 Headers", RFC 2474, 830 December 1998. 832 [RFC2669] St. Johns, M., "DOCSIS Cable Device MIB Cable Device 833 Management Information Base for DOCSIS compliant Cable 834 Modems and Cable Modem Termination Systems", RFC 2669, 835 August 1999. 837 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 838 via IPv4 Clouds", RFC 3056, February 2001. 840 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 841 and M. Carney, "Dynamic Host Configuration Protocol for 842 IPv6 (DHCPv6)", RFC 3315, July 2003. 844 [RFC3484] Draves, R., "Default Address Selection for Internet 845 Protocol version 6 (IPv6)", RFC 3484, February 2003. 847 [RFC3569] Bhattacharyya, S., "An Overview of Source-Specific 848 Multicast (SSM)", RFC 3569, July 2003. 850 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 851 Host Configuration Protocol (DHCP) version 6", RFC 3633, 852 December 2003. 854 [RFC3646] Droms, R., "DNS Configuration options for Dynamic Host 855 Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, 856 December 2003. 858 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 859 (DHCP) Service for IPv6", RFC 3736, April 2004. 861 [RFC3769] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix 862 Delegation", RFC 3769, June 2004. 864 [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery 865 Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. 867 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 868 Addresses", RFC 4193, October 2005. 870 [RFC4214] Templin, F., Gleeson, T., Talwar, M., and D. Thaler, 871 "Intra-Site Automatic Tunnel Addressing Protocol 872 (ISATAP)", RFC 4214, October 2005. 874 [RFC4241] Shirasaki, Y., Miyakawa, S., Yamasaki, T., and A. 875 Takenouchi, "A Model of IPv6/IPv4 Dual Stack Internet 876 Access Service", RFC 4241, December 2005. 878 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 879 Architecture", RFC 4291, February 2006. 881 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 882 "Considerations for Internet Group Management Protocol 883 (IGMP) and Multicast Listener Discovery (MLD) Snooping 884 Switches", RFC 4541, May 2006. 886 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 887 "Internet Group Management Protocol (IGMP) / Multicast 888 Listener Discovery (MLD)-Based Multicast Forwarding 889 ("IGMP/MLD Proxying")", RFC 4605, August 2006. 891 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 892 Address Autoconfiguration", RFC 4862, September 2007. 894 [RFC5072] S.Varada, Haskin, D., and E. Allen, "IP Version 6 over 895 PPP", RFC 5072, September 2007. 897 [RFC5135] Wing, D. and T. Eckert, "IP Multicast Requirements for a 898 Network Address Translator (NAT) and a Network Address 899 Port Translator (NAPT)", BCP 135, RFC 5135, February 2008. 901 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 902 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 903 March 2008. 905 Authors' Addresses 907 Hemant Singh 908 Cisco Systems, Inc. 909 1414 Massachusetts Ave. 910 Boxborough, MA 01719 911 USA 913 Phone: +1 978 936 1622 914 Email: shemant@cisco.com 915 URI: http://www.cisco.com/ 916 Wes Beebee 917 Cisco Systems, Inc. 918 1414 Massachusetts Ave. 919 Boxborough, MA 01719 920 USA 922 Phone: +1 978 936 2030 923 Email: wbeebee@cisco.com 924 URI: http://www.cisco.com/