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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-09) exists of draft-ietf-dhc-mac-assign-06 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DHC WG CJ. Bernardos 3 Internet-Draft UC3M 4 Intended status: Standards Track A. Mourad 5 Expires: November 14, 2020 InterDigital 6 May 13, 2020 8 SLAP quadrant selection options for DHCPv6 9 draft-ietf-dhc-slap-quadrant-08 11 Abstract 13 The IEEE originally structured the 48-bit MAC address space in such a 14 way that half of it was reserved for local use. Recently, the IEEE 15 has been working on a new specification (IEEE 802c) which defines a 16 new optional "Structured Local Address Plan" (SLAP) that specifies 17 different assignment approaches in four specified regions of the 18 local MAC address space. 20 The IEEE is working on mechanisms to allocate addresses in the one of 21 these quadrants (IEEE 802.1CQ). There is work also in the IETF on 22 specifying a new mechanism that extends DHCPv6 operation to handle 23 the local MAC address assignments. We complement this work by 24 defining a mechanism to allow choosing the SLAP quadrant to use in 25 the allocation of the MAC address to the requesting device/client. 27 This document proposes extensions to DHCPv6 protocols to enable a 28 DHCPv6 client or a DHCPv6 relay to indicate a preferred SLAP quadrant 29 to the server, so that the server allocates the MAC addresses to the 30 given client out of the quadrant requested by relay or client. A new 31 DHCPv6 option (OPTION_SLAP_QUAD, or QUAD) is defined for this 32 purpose. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on November 14, 2020. 50 Copyright Notice 52 Copyright (c) 2020 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 (https://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 1.1. Problem statement . . . . . . . . . . . . . . . . . . . . 4 69 1.1.1. WiFi devices . . . . . . . . . . . . . . . . . . . . 4 70 1.1.2. Hypervisor: migratable vs non-migratable functions . 5 71 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 72 3. Quadrant Selection Mechanisms examples . . . . . . . . . . . 7 73 4. DHCPv6 Extensions . . . . . . . . . . . . . . . . . . . . . . 9 74 4.1. Address Assignment from the Preferred SLAP Quadrant 75 Indicated by the Client . . . . . . . . . . . . . . . . . 9 76 4.2. Address Assignment from the SLAP Quadrant Indicated by 77 the Relay . . . . . . . . . . . . . . . . . . . . . . . . 11 78 5. DHCPv6 Options Definitions . . . . . . . . . . . . . . . . . 14 79 5.1. Quad (IA_LL) option . . . . . . . . . . . . . . . . . . . 14 80 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 81 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 82 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 83 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 84 9.1. Normative References . . . . . . . . . . . . . . . . . . 16 85 9.2. Informative References . . . . . . . . . . . . . . . . . 17 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 88 1. Introduction 90 The IEEE originally structured the 48-bit MAC address space in such a 91 way that half of it was reserved for local use (where the U/L bit is 92 set to 1). Recently, the IEEE has been working on a new 93 specification (IEEE 802c [IEEEStd802c-2017]) which defines a new 94 "optional Structured Local Address Plan" (SLAP) that specifies 95 different assignment approaches in four specified regions of the 96 local MAC address space. These four regions, called SLAP quadrants, 97 are briefly described below (see Figure 1 and Figure 2 for details): 99 o Quadrant "Extended Local Identifier" (ELI) MAC addresses are 100 assigned based on a Company ID (CID), which takes 24-bits, leaving 101 the remaining 24-bits for the locally assigned address for each 102 CID for unicast (M-bit = 0) and also for multicast (M-bit = 1). 103 The CID is assigned by the IEEE Registration Authority (RA). 105 o Quadrant "Standard Assigned Identifier" (SAI) MAC addresses are 106 assigned based on a protocol specified in an IEEE 802 standard. 107 For 48-bit MAC addresses, 44 bits are available. Multiple 108 protocols for assigning SAIs may be specified in IEEE standards. 109 Coexistence of multiple protocols may be supported by limiting the 110 subspace available for assignment by each protocol. 112 o Quadrant "Administratively Assigned Identifier" (AAI) MAC 113 addresses are assigned locally by an administrator. Multicast 114 IPv6 packets use a destination address starting in 33-33 and this 115 falls within this space and therefore should not be used to avoid 116 conflict with the MAC addresses used for use with IPv6 multicast 117 addresses. For 48-bit MAC addresses, 44 bits are available. 119 o Quadrant "Reserved for future use" where MAC addresses may be 120 assigned using new methods yet to be defined, or by an 121 administrator like in the AAI quadrant. For 48-bit MAC addresses, 122 44 bits would be available. 124 LSB MSB 125 M X Y Z - - - - 126 | | | | 127 | | | +------------ SLAP Z-bit 128 | | +--------------- SLAP Y-bit 129 | +------------------ X-bit (U/L) = 1 for locally assigned 130 +--------------------- M-bit (I/G) (unicast/group) 132 Figure 1: IEEE 48-bit MAC address structure 134 +----------+-------+-------+-----------------------+----------------+ 135 | Quadrant | Y-bit | Z-bit | Local Identifier Type | Local | 136 | | | | | Identifier | 137 +----------+-------+-------+-----------------------+----------------+ 138 | 01 | 0 | 1 | Extended Local | ELI | 139 | 11 | 1 | 1 | Standard Assigned | SAI | 140 | 00 | 0 | 0 | Administratively | AAI | 141 | | | | Assigned | | 142 | 10 | 1 | 0 | Reserved | Reserved | 143 +----------+-------+-------+-----------------------+----------------+ 145 Figure 2: SLAP quadrants 147 1.1. Problem statement 149 The IEEE is working on mechanisms to allocate addresses in the SAI 150 quadrant (IEEE 802.1CQ project). There is also ongoing work in the 151 IETF [I-D.ietf-dhc-mac-assign] specifying a new mechanism that 152 extends DHCPv6 operation to handle the local MAC address assignments. 153 We complement this work by defining a mechanism to allow choosing the 154 SLAP quadrant to use in the allocation of the MAC address to the 155 requesting device/client. This document proposes extensions to 156 DHCPv6 protocols to enable a DHCPv6 client or a DHCPv6 relay to 157 indicate a preferred SLAP quadrant to the server, so that the server 158 allocates the MAC address to the given client out of the quadrant 159 requested by relay or client. 161 In the following, we describe two application scenarios where a need 162 arises to assign local MAC addresses according to preferred SLAP 163 quadrants. 165 1.1.1. WiFi devices 167 Today, most WiFi devices come with interfaces that have a "burned in" 168 MAC address, allocated from the universal address space using a 169 24-bit Organizationally Unique Identifier (OUI, assigned to IEEE 802 170 interface vendors). However, recently, the need to assign local 171 (instead of universal) MAC addresses has emerged in particular in the 172 following two scenarios: 174 o IoT (Internet of Things): where there are a lot of cheap, 175 sometimes short lived and disposable devices. Examples of this 176 include: sensors and actuators for health or home automation 177 applications. In this scenario, it is common that upon a first 178 boot, the device uses a temporary MAC address, to send initial 179 DHCP packets to available DHCP servers. IoT devices typically 180 request a single MAC address for each available network interface. 181 Once the server assigns a MAC address, the device abandons its 182 temporary MAC address. This type of device is typically not 183 moving. In general, any type of SLAP quadrant would be good for 184 assigning addresses from, but ELI/SAI quadrants might be more 185 suitable in some scenarios, such as if the addresses need to 186 belong to the CID assigned to the IoT communication device vendor. 188 o Privacy: Today, MAC addresses allow the exposure of users' 189 locations making it relatively easy to track users' movement. One 190 of the mechanisms considered to mitigate this problem is the use 191 of local random MAC addresses, changing them every time the user 192 connects to a different network. In this scenario, devices are 193 typically mobile. Here, AAI is probably the best SLAP quadrant to 194 assign addresses from, as it is the best fit for randomization of 195 addresses, and it is not required for the addresses to survive 196 when changing networks. 198 1.1.2. Hypervisor: migratable vs non-migratable functions 200 In large scale virtualization environments, thousands of virtual 201 machines (VMs) are active. These VMs are typically managed by a 202 hypervisor, in charge of spawning and stopping VMs as needed. The 203 hypervisor is also typically in charge of assigning new MAC addresses 204 to the VMs. If a DHCP solution is in place for that, the hypervisor 205 acts as a DHCP client and requests available DHCP servers to assign 206 one or more MAC addresses (an address block). The hypervisor does 207 not use those addresses for itself, but rather uses them to create 208 new VMs with appropriate MAC addresses. If we assume very large data 209 center environments, such as the ones that are typically used 210 nowadays, it is expected that the data center is divided in different 211 network regions, each one managing its own local address space. In 212 this scenario, there are two possible situations that need to be 213 tackled: 215 o Migratable functions. If a VM (providing a given function) needs 216 to be migrated to another region of the data center (e.g., for 217 maintenance, resilience, end-user mobility, etc.), the VM's 218 networking context needs to migrate with the VM. This includes 219 the VM's MAC address(es). Therefore, for this case, it is better 220 to allocate addresses from the ELI/SAI SLAP quadrant, which can be 221 centrally allocated by the DHCP server. 223 o Non-migratable functions. If a VM will not be migrated to 224 another region of the data center, there are no requirements 225 associated with its MAC address. In this case, it is more 226 efficient to allocate it from the AAI SLAP quadrant, that does not 227 need to be unique across multiple data centers (i.e., each region 228 can manage its own MAC address assignment, without checking for 229 duplicates globally). 231 2. Terminology 233 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 234 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 235 "OPTIONAL" in this document are to be interpreted as described in BCP 236 14 [RFC2119] [RFC8174] when, and only when, they appear in all 237 capitals, as shown here. 239 Where relevant, the DHCPv6 terminology from the DHCPv6 Protocol 240 [RFC8415] also applies here. Additionally, the following definitions 241 are updated for this document. 243 client A device that is interested in obtaining link-layer 244 addresses. It implements the basic DHCPv6 mechanisms 245 needed by a DHCPv6 client as described in [RFC8415] and 246 supports the new options (IA_LL and LLADDR) specified 247 in [I-D.ietf-dhc-mac-assign]. The client may or may 248 not support address assignment and prefix delegation as 249 specified in [RFC8415]. 251 server Software that manages link-layer address allocation and 252 is able to respond to client queries. It implements 253 basic DHCPv6 server functionality as described in 254 [RFC8415] and supports the new options (IA_LL and 255 LLADDR) specified in [I-D.ietf-dhc-mac-assign]. The 256 server may or may not support address assignment and 257 prefix delegation as specified in [RFC8415]. 259 relay A node that acts as an intermediary to deliver DHCP 260 messages between clients and servers. A relay, based 261 on local knowledge and policies, may include the 262 preferred SLAP quadrant in a QUAD option sent to the 263 server. The relay implements basic DHCPv6 relay agent 264 functionality as described in in [RFC8415]. 266 address Unless specified otherwise, an address means a link- 267 layer (or MAC) address, as defined in IEEE802. The 268 address is typically 6 bytes long, but some network 269 architectures may use different lengths. 271 address block A number of consecutive link-layer addresses. An 272 address block is expressed as a first address plus a 273 number that designates the number of additional (extra) 274 addresses. A single address can be represented by the 275 address itself and zero extra addresses. 277 3. Quadrant Selection Mechanisms examples 279 The following section describes some examples of how the quadrant 280 preference mechanisms could be used. 282 Let's take first an IoT scenario as an example. An IoT device might 283 decide on its own the SLAP quadrant it wants to use to obtain a local 284 MAC address, using the following information to take the decision: 286 o Type of IoT deployment: e.g., industrial, domestic, rural, etc. 287 For small deployments, such as domestic ones, the IoT itself can 288 decide to use the AAI quadrant (this might not even involve the 289 use of DHCP, by the device just configuring a random address 290 computed by the device itself). For large deployments, such as 291 industrial or rural ones, where thousands of devices might co- 292 exist, the IoT can decide to use the ELI or SAI quadrants. 294 o Mobility: if the IoT device can move, then it might prefer to 295 select the SAI or AAI quadrants to minimize address collisions 296 when moving to another network. If the device is known to remain 297 fixed, then the ELI is probably the most suitable one to use. 299 o Managed/unmanaged: depending on whether the IoT device is managed 300 during its lifetime or cannot be re-configured, the selected 301 quadrant might be different. For example, it can be managed, this 302 means that network topology changes might occur during its 303 lifetime (e.g., due to changes on the deployment, such as 304 extensions involving additional devices), and this might have an 305 impact on the preferred quadrant (e.g., to avoid potential 306 collisions in the future). 308 o Operation/battery lifetime: depending on the expected lifetime of 309 the device a different quadrant might be preferred (as before, to 310 minimize potential address collisions in the future). 312 The previous parameters are considerations that the device vendor/ 313 administrator may wish to use when defining the IoT device's 314 MAC address request policy (i.e., how to select a given SLAP 315 quadrant). IoT devices are typically very resource constrained, so 316 there may only be simple decision making process based on pre- 317 configured preferences. 319 If we now take the WiFi device scenario, considering for example that 320 a laptop or smartphone connects to a network using its built in MAC 321 address. Due to privacy/security concerns, the device might want to 322 configure a local MAC address. The device might use different 323 parameters and context information to decide, not only which SLAP 324 quadrant to use for the local MAC address configuration, but also 325 when to perform a change of address (e.g., it might be needed to 326 change address several times). This information includes, but it is 327 not limited to: 329 o Type of network the device is connected: public, work, home. 331 o Trusted network? Y/N. 333 o First time visited network? Y/N. 335 o Network geographical location. 337 o Mobility? Y/N. 339 o Operating System (OS) network profile, including security/trust 340 related parameters. Most modern OSs keep metadata associated to 341 the networks they can attach to, as for example the level of trust 342 the user or administrator assigns to the network. This 343 information is used to configure how the device behaves in terms 344 of advertising itself on the network, firewall settings, etc. But 345 this information can also be used to decide whether to configure a 346 local MAC address or not, from which SLAP quadrant and how often. 348 o Triggers coming from applications regarding location privacy. An 349 app might request to the OS to maximize location privacy (due to 350 the nature of the application) and this might require that the OS 351 forces the use of a local MAC address, or that the local MAC 352 address is changed. 354 This information can be used by the device to select the SLAP 355 quadrant. For example, if the device is moving around (e.g., while 356 connected to a public network in an airport), it is likely that it 357 might change access point several times, and therefore it is best to 358 minimize the chances of address collision, using the SAI or AAI 359 quadrants. If the device is not moving and attached to a trusted 360 network (e.g. at work), then it is probably best to select the ELI 361 quadrant. These are just some examples of how to use this 362 information to select the quadrant. 364 Additionally, the information can also be used to trigger subsequent 365 changes of MAC address, to enhance location privacy. Besides, 366 changing the SLAP quadrant used might also be used as an additional 367 enhancement to make it harder to track the user location. 369 Last, if we consider the data center scenario, a hypervisor might 370 request local MAC addresses to be assigned to virtual machines. As 371 in the previous scenarios, the hypervisor might select the preferred 372 SLAP quadrant using information provided by the cloud management 373 system (CMS) or virtualization infrastructure manager (VIM) running 374 on top of the hypervisor. This information might include, but is not 375 limited to: 377 o Migratable VM. If the function implemented by the VM is subject 378 to be moved to another physical server or not. This has an impact 379 on the preference for the SLAP quadrant, as some quadrants are 380 better suited (e.g., ELI/SAI) for supporting migration in a large 381 data center. 383 o VM connectivity characteristics , e.g.,: standalone, part of a 384 pool, part of a service graph/chain. If the connectivity 385 characteristics of the VM are known, this can be used by the 386 hypervisor to select the best SLAP quadrant. 388 4. DHCPv6 Extensions 390 4.1. Address Assignment from the Preferred SLAP Quadrant Indicated by 391 the Client 393 Next, we describe the protocol operations for a client to select a 394 preferred SLAP quadrant using the DHCPv6 signaling procedures 395 described in [I-D.ietf-dhc-mac-assign]. The signaling flow is shown 396 in Figure 3. 398 +--------+ +--------+ 399 | DHCPv6 | | DHCPv6 | 400 | client | | server | 401 +--------+ +--------+ 402 | | 403 +-------1. Solicit(IA_LL(QUAD))------->| 404 | | 405 |<--2. Advertise(IA_LL(LLADDR,QUAD))--+| 406 | | 407 +---3. Request(IA_LL(LLADDR,QUAD))---->| 408 | | 409 |<------4. Reply(IA_LL(LLADDR))--------+ 410 | | 411 . . 412 . (timer expiring) . 413 . . 414 | | 415 +---5. Renew(IA_LL(LLADDR,QUAD))------>| 416 | | 417 |<-----6. Reply(IA_LL(LLADDR))---------+ 418 | | 420 Figure 3: DHCPv6 signaling flow (client-server) 422 1. Link-layer addresses (i.e., MAC addresses) are assigned in 423 blocks. The smallest block is a single address. To request an 424 assignment, the client sends a Solicit message with an IA_LL 425 option in the message. The IA_LL option MUST contain a LLADDR 426 option. In order to indicate the preferred SLAP quadrant(s), the 427 IA_LL option includes the new OPTION_SLAP_QUAD option in the 428 IA_LL-option field (with the LLAADR option). 430 2. The server, upon receiving an IA_LL option, inspects its 431 contents. For each of the entries in OPTION_SLAP_QUAD, in order 432 of the preference field (highest to lowest), the server checks if 433 it has a configured MAC address pool matching the requested 434 quadrant identifier, and an available range of addresses of the 435 requested size. If suitable addresses are found, the server 436 sends back an Advertise message with an IA_LL option containing 437 an LLADDR option that specifies the addresses being offered. If 438 the server supports the new QUAD IA_LL-option, and manages a 439 block of addresses belonging to the requested quadrant(s), the 440 addresses being offered MUST belong to the requested quadrant(s). 441 If the server does not have a configured address pool matching 442 the client's request, it MUST return the IA_LL option containing 443 a Status Code option with status set to NoQuadAvail (IANA-2). If 444 the client specified more than one SLAP quadrant, the server MUST 445 only return a NoQuadAvail status code if no address pool(s) 446 configured at the server match any of the specified SLAP 447 quadrants. If the server has a configured address pool of the 448 correct quadrant, but no available addresses, it MUST return the 449 IA_LL option containing a Status Code option with status set to 450 NoAddrsAvail. 452 3. The client waits for available servers to send Advertise 453 responses and picks one server as defined in Section 18.2.9 of 454 [RFC8415]. The client SHOULD NOT pick a server that does not 455 advertise an address in the requested quadrant. The client then 456 sends a Request message that includes the IA_LL container option 457 with the LLADDR option copied from the Advertise message sent by 458 the chosen server. It includes the preferred SLAP quadrant(s) in 459 the new QUAD IA_LL-option. 461 4. Upon reception of a Request message with IA_LL container option, 462 the server assigns requested addresses. The server MAY alter the 463 allocation at this time. It then generates and sends a Reply 464 message back to the client. Upon receiving a Reply message, the 465 client parses the IA_LL container option and may start using all 466 provided addresses. Note that a client that has included a Rapid 467 Commit option in the Solicit, may receive a Reply in response to 468 the Solicit and skip the Advertise and Request steps above 469 (following standard DHCPv6 procedures). 471 5. When the assigned addresses are about to expire, the client sends 472 a Renew message. It includes the preferred SLAP quadrant(s) in 473 the new QUAD IA_LL-option, so in case the server is unable to 474 extend the lifetime on the existing address(es), the preferred 475 quadrants are known for the allocation of any "new" addresses. 477 6. The server responds with a Reply message, including an LLADDR 478 option with extended lifetime. 480 The client SHOULD check if the received MAC address comes from one of 481 the requested quadrants. Otherwise, the client SHOULD NOT configure 482 the obtained address. It MAY repeat the process selecting a 483 different DHCP server. 485 4.2. Address Assignment from the SLAP Quadrant Indicated by the Relay 487 Next, we describe the protocol operations for a relay to select a 488 preferred SLAP quadrant using the DHCPv6 signaling procedures 489 described in [I-D.ietf-dhc-mac-assign]. This is useful when a DHCPv6 490 server is operating over a large infrastructure split in different 491 network regions, where each region might have different requirements. 492 The signaling flow is shown in Figure 4. 494 +--------+ +--------+ +--------+ 495 | DHCPv6 | | DHCPv6 | | DHCPv6 | 496 | client | | relay | | server | 497 +--------+ +--------+ +--------+ 498 | | | 499 +-----1. Solicit(IA_LL)----->| | 500 | +----2. Relay-forward | 501 | | (Solicit(IA_LL),QUAD)------>| 502 | | | 503 | |<---3. Relay-reply | 504 | | (Advertise(IA_LL(LLADDR)))--+ 505 |<4. Advertise(IA_LL(LLADDR))+ | 506 |-5. Request(IA_LL(LLADDR))->| | 507 | +-6. Relay-forward | 508 | | (Request(IA_LL(LLADDR)),QUAD)->| 509 | | | 510 | |<--7. Relay-reply | 511 | | (Reply(IA_LL(LLADDR)))-------+ 512 |<--8. Reply(IA_LL(LLADDR))--+ | 513 | | | 514 . . . 515 . (timer expiring) . 516 . . . 517 | | | 518 +--9. Renew(IA_LL(LLADDR))-->| | 519 | |--10. Relay-forward | 520 | | (Renew(IA_LL(LLADDR)),QUAD)-->| 521 | | | 522 | |<---11. Relay-reply | 523 | | (Reply(IA_LL(LLADDR)))-----+ 524 |<--12. Reply(IA_LL(LLADDR)--+ | 525 | | | 527 Figure 4: DHCPv6 signaling flow (client-relay-server) 529 1. Link-layer addresses (i.e., MAC addresses) are assigned in 530 blocks. The smallest block is a single address. To request an 531 assignment, the client sends a Solicit message with an IA_LL 532 option in the message. The IA_LL option MUST contain a LLADDR 533 option. 535 2. The DHCP relay receives the Solicit message and encapsulates it 536 in a Relay-forward message. The relay, based on local knowledge 537 and policies, includes in the Relay-forward message the QUAD 538 option with the preferred quadrant. The relay might know which 539 quadrant to request based on local configuration (e.g., the 540 served network contains IoT devices only, thus requiring ELI/ 541 SAI) or other means. Note that if a client sends multiple 542 instances of the IA_LL option in the same message, the DHCP 543 relay MUST only add a single instance of the QUAD option. 545 3. Upon receiving a relayed message containing an IA_LL option, the 546 server inspects the contents for instances of OPTION_SLAP_QUAD 547 in both the Relay Forward message and the client's message 548 payload. Depending on the server's policy, the instance(s) of 549 the option to process is selected. For each of the entries in 550 OPTION_SLAP_QUAD, in order of the preference field (highest to 551 lowest), the server checks if it has a configured MAC address 552 pool matching the requested quadrant identifier, and an 553 available range of addresses of the requested size. If suitable 554 addresses are found, the server sends back an Advertise message 555 with an IA_LL option containing an LLADDR option that specifies 556 the addresses being offered. This message is sent to the Relay 557 in a Relay-reply message. If the server supports the semantics 558 of the preferred quadrant included in the QUAD option, and 559 manages a block of addresses belonging to the requested 560 quadrant(s), then the addresses being offered MUST belong to the 561 requested quadrant(s). The server SHOULD apply the contents of 562 the relay's supplied QUAD option for all of the client's IA_LLs, 563 unless configured to do otherwise. 565 4. The relay sends the received Advertise message to the client. 567 5. The client waits for available servers to send Advertise 568 responses and picks one server as defined in Section 18.2.9 of 569 [RFC8415]. The client then sends a Request message that 570 includes the IA_LL container option with the LLADDR option 571 copied from the Advertise message sent by the chosen server. 573 6. The relay forwards the received Request in a Relay-forward 574 message. It adds in the Relay-forward a QUAD IA_LL-option with 575 the preferred quadrant. 577 7. Upon reception of the forwarded Request message with IA_LL 578 container option, the server assigns requested addresses. The 579 server MAY alter the allocation at this time. It then generates 580 and sends a Reply message, in a Relay-reply back to the relay. 582 8. Upon receiving a Reply message, the client parses the IA_LL 583 container option and may start using all provided addresses. 585 9. When the assigned addresses are about to expire, the client 586 sends a Renew message. 588 10. This message is forwarded by the Relay in a Relay-forward 589 message, including a QUAD IA_LL-option with the preferred 590 quadrant. 592 11. The server responds with a Reply message, including an LLADDR 593 option with extended lifetime. This message is sent in a Relay- 594 reply message. 596 12. The relay sends the Reply message back to the client. 598 The server SHOULD implement a configuration parameter to deal 599 with the case where the client's DHCP message contains an instance of 600 OPTION_SLAP_QUAD, and the relay adds a second instance in its relay- 601 forward message. This parameter configures the server to process 602 either the client's, or the relay's instance of option QUAD. It is 603 RECOMMENDED that the default for such a parameter is to process the 604 client's instance of the option. 606 The client MAY check if the received MAC address belongs to a 607 quadrant it is willing to use/configure, and MAY decide based on that 608 whether to use configure the received address. 610 5. DHCPv6 Options Definitions 612 5.1. Quad (IA_LL) option 614 The QUAD option is used to specify the preferences for the selected 615 quadrants within an IA_LL. The option MUST either be encapsulated in 616 the IA_LL-options field of an IA_LL option or in a Relay-forward 617 message. 619 The format of the QUAD option is: 621 0 1 2 3 622 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 1 623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 | OPTION_SLAP_QUAD | option-len | 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 | quadrant-1 | pref-1 | quadrant-2 | pref-2 | 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 628 . . 629 . . 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 Figure 5: Quad Option Format 634 option-code OPTION_SLAP_QUAD (IANA-1). 636 option-len 2 * number of included (quadrant, preference). A 637 2-byte field containing the total length of all 638 (quadrant, preference) pairs included in the option. 640 quadrant-n Identifier of the quadrant (0: AAI, 1: ELI, 2: 641 Reserved, 3: SAI). Each quadrant MUST only appear 642 once at most in the option. A 1-byte field. 644 pref-n Preference associated to quadrant-n. A higher value 645 means a more preferred quadrant. A 1-byte field. 647 A quadrant identifier value MUST only appear at most once in the 648 option. If an option includes more than one occurrence of the same 649 quadrant identifier, only the first occurence is processed and the 650 rest MUST be ignored by the server. 652 If the same preference value is used for more than one quadrant, the 653 server MAY select which quadrant should be preferred (if the server 654 can assign addresses from all or some of the quadrants with the same 655 assigned preference). Note that a quadrant - preference tuple is 656 used in this option (instead of using a list of quadrants ordered by 657 preference) to support the case whereby a client really has no 658 preference between two or three quadrants, leaving the decision to 659 the server. 661 If the client or relay agent provide the OPTION_SLAP_QUAD, the server 662 MUST use the quadrant-n/pref-n values to order the selection of the 663 quadrants. If the server can provide an assignment from one of the 664 specified quadrants, it SHOULD proceed with the assignment. If the 665 server cannot provide an assignment from one of the specified 666 quadrant-n fields, it MUST NOT assign any addresses and return a 667 status of NoQuadAvail (IANA-2) in the IA_LL Option. 669 There is no requirement that the client or relay agent order the 670 quadrant/pref values in any specific order; hence servers MUST NOT 671 assume that quadrant-1/pref-1 have the highest preference (except if 672 there is only 1 set of values). 674 6. IANA Considerations 676 IANA is requested to assign the QUAD (IANA-1) option code from the 677 DHCPv6 "Option Codes" registry maintained at 678 http://www.iana.org/assignments/dhcpv6-parameters and use the 679 following data when adding the option to the registry: 681 Value: IANA-1 682 Description: OPTION_SLAP_QUAD 683 Client ORO: No 684 Singleton Option: No 685 Reference: this document 687 IANA is requested to assign the NoQuadAvail (IANA-2) code from the 688 DHCPv6 "Status Codes" registry maintained 689 athttp://www.iana.org/assignments/dhcpv6-parameters and use the 690 following data when adding the option to the registry: 692 Value: IANA-2 693 Description: NoQuadAvail 694 Reference: this document 696 7. Security Considerations 698 See [RFC8415] for the DHCPv6 security considerations. See [RFC8200] 699 for the IPv6 security considerations. 701 See also [I-D.ietf-dhc-mac-assign] for security considerations 702 regarding link-layer address assignments using DHCP. 704 8. Acknowledgments 706 The authors would like to thank Bernie Volz for his very valuable 707 comments on this document. We also want to thank Ian Farrer, Tomek 708 Mrugalski and Eric Vyncke for their very detailed and helpful 709 reviews. 711 The work in this draft will be further developed and explored under 712 the framework of the H2020 5Growth (Grant 856709) and 5G-DIVE 713 projects (Grant 859881). 715 9. References 717 9.1. Normative References 719 [I-D.ietf-dhc-mac-assign] 720 Volz, B., Mrugalski, T., and C. Bernardos, "Link-Layer 721 Addresses Assignment Mechanism for DHCPv6", draft-ietf- 722 dhc-mac-assign-06 (work in progress), May 2020. 724 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 725 Requirement Levels", BCP 14, RFC 2119, 726 DOI 10.17487/RFC2119, March 1997, 727 . 729 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 730 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 731 May 2017, . 733 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 734 (IPv6) Specification", STD 86, RFC 8200, 735 DOI 10.17487/RFC8200, July 2017, 736 . 738 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 739 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 740 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 741 RFC 8415, DOI 10.17487/RFC8415, November 2018, 742 . 744 9.2. Informative References 746 [IEEEStd802c-2017] 747 IEEE Computer Society, "IEEE Standard for Local and 748 Metropolitan Area Networks: Overview and Architecture, 749 Amendment 2: Local Medium Access Control (MAC) Address 750 Usage, IEEE Std 802c-2017". 752 Authors' Addresses 754 Carlos J. Bernardos 755 Universidad Carlos III de Madrid 756 Av. Universidad, 30 757 Leganes, Madrid 28911 758 Spain 760 Phone: +34 91624 6236 761 Email: cjbc@it.uc3m.es 762 URI: http://www.it.uc3m.es/cjbc/ 764 Alain Mourad 765 InterDigital Europe 767 Email: Alain.Mourad@InterDigital.com 768 URI: http://www.InterDigital.com/