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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin, Ed. 3 Internet-Draft The Boeing Company 4 Intended status: Standards Track A. Whyman 5 Expires: October 3, 2020 MWA Ltd c/o Inmarsat Global Ltd 6 April 1, 2020 8 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 9 Interfaces 10 draft-templin-6man-omni-interface-08 12 Abstract 14 Mobile nodes (e.g., aircraft of various configurations, terrestrial 15 vehicles, seagoing vessels, mobile enterprise devices, etc.) 16 communicate with networked correspondents over multiple access 17 network data links and configure mobile routers to connect end user 18 networks. A multilink interface specification is therefore needed 19 for coordination with the network-based mobility service. This 20 document specifies the transmission of IPv6 packets over Overlay 21 Multilink Network (OMNI) Interfaces. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on October 3, 2020. 40 Copyright Notice 42 Copyright (c) 2020 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6 60 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 6 61 5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 10 62 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 11 63 7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . 11 64 8. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 12 65 8.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 14 66 8.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 15 67 8.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 15 68 8.1.3. ifIndex-tuple (Type 1) . . . . . . . . . . . . . . . 15 69 8.1.4. ifIndex-tuple (Type 2) . . . . . . . . . . . . . . . 18 70 8.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 18 71 8.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 19 72 9. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 19 73 10. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 19 74 10.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 20 75 11. Router Discovery and Prefix Registration . . . . . . . . . . 20 76 12. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 23 77 13. Detecting and Responding to MSE Failures . . . . . . . . . . 23 78 14. Transition Considerations . . . . . . . . . . . . . . . . . . 24 79 15. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 24 80 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 81 17. Security Considerations . . . . . . . . . . . . . . . . . . . 26 82 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 83 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 84 19.1. Normative References . . . . . . . . . . . . . . . . . . 27 85 19.2. Informative References . . . . . . . . . . . . . . . . . 28 86 Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference 87 Encoding . . . . . . . . . . . . . . . . . . . . . . 30 88 Appendix B. Prefix Length Considerations . . . . . . . . . . . . 32 89 Appendix C. VDL Mode 2 Considerations . . . . . . . . . . . . . 33 90 Appendix D. MN / AR Isolation Through L2 Address Mapping . . . . 33 91 Appendix E. Change Log . . . . . . . . . . . . . . . . . . . . . 34 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 94 1. Introduction 96 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 97 terrestrial vehicles, seagoing vessels, mobile enterprise devices, 98 etc.) often have multiple data links for communicating with networked 99 correspondents. These data links may have diverse performance, cost 100 and availability properties that can change dynamically according to 101 mobility patterns, flight phases, proximity to infrastructure, etc. 102 MNs coordinate their data links in a discipline known as "multilink", 103 in which a single virtual interface is configured over the underlying 104 data links. 106 The MN configures a virtual interface (termed the "Overlay Multilink 107 Network (OMNI) interface") as a thin layer over the underlying Access 108 Network (ANET) interfaces. The OMNI interface is therefore the only 109 interface abstraction exposed to the IPv6 layer and behaves according 110 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 111 while underlying interfaces appear as link layer communication 112 channels in the architecture. The OMNI interface connects to a 113 virtual overlay service known as the "OMNI link". The OMNI link 114 spans a worldwide Internetwork that may include private-use 115 infrastructures and/or the global public Internet itself. 117 Each MN receives a Mobile Network Prefix (MNP) for numbering 118 downstream-attached End User Networks (EUNs) independently of the 119 access network data links selected for data transport. The MN 120 performs router discovery over the OMNI interface (i.e., similar to 121 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 122 behalf of its EUNs. The router discovery process is iterated over 123 each of the OMNI interface's underlying interfaces in order to 124 register per-link parameters (see Section 11). 126 The OMNI interface provides a multilink nexus for exchanging inbound 127 and outbound traffic via the correct underlying interface(s). The 128 IPv6 layer sees the OMNI interface as a point of connection to the 129 OMNI link. Each OMNI link has one or more associated Mobility 130 Service Prefixes (MSPs) from which OMNI link MNPs are derived. If 131 there are multiple OMNI links, the IPv6 layer will see multiple OMNI 132 interfaces. 134 The OMNI interface interacts with a network-based Mobility Service 135 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 136 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 137 track MN movements and represent their MNPs in a global routing or 138 mapping system. 140 This document specifies the transmission of IPv6 packets [RFC8200] 141 and MN/MS control messaging over OMNI interfaces. 143 2. Terminology 145 The terminology in the normative references applies; especially, the 146 terms "link" and "interface" are the same as defined in the IPv6 147 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 148 Also, the Protocol Constants defined in Section 10 of [RFC4861] are 149 used in their same format and meaning in this document. The terms 150 "All-Routers multicast", "All-Nodes multicast" and "Subnet-Router 151 anycast" are defined in [RFC4291] (with Link-Local scope assumed). 153 The following terms are defined within the scope of this document: 155 Mobile Node (MN) 156 an end system with multiple distinct upstream data link 157 connections that are managed together as a single logical unit. 158 The MN's data link connection parameters can change over time due 159 to, e.g., node mobility, link quality, etc. The MN further 160 connects a downstream-attached End User Network (EUN). The term 161 MN used here is distinct from uses in other documents, and does 162 not imply a particular mobility protocol. 164 End User Network (EUN) 165 a simple or complex downstream-attached mobile network that 166 travels with the MN as a single logical unit. The IPv6 addresses 167 assigned to EUN devices remain stable even if the MN's upstream 168 data link connections change. 170 Mobility Service (MS) 171 a mobile routing service that tracks MN movements and ensures that 172 MNs remain continuously reachable even across mobility events. 173 Specific MS details are out of scope for this document. 175 Mobility Service Endpoint (MSE) 176 an entity in the MS (either singluar or aggregate) that 177 coordinates the mobility events of one or more MN. 179 Mobility Service Prefix (MSP) 180 an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the 181 rest of the Internetwork by the MS, and from which more-specific 182 Mobile Network Prefixes (MNPs) are derived. 184 Mobile Network Prefix (MNP) 185 a longer IPv6 prefix taken from an MSP (e.g., 186 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate 187 the MNP to devices located in EUNs. 189 Access Network (ANET) 190 a data link service network (e.g., an aviation radio access 191 network, satellite service provider network, cellular operator 192 network, wifi network, etc.) that connects MNs. Physical and/or 193 data link level security between the MN and ANET are assumed. 195 Access Router (AR) 196 a first-hop router in the ANET for connecting MNs to 197 correspondents in outside Internetworks. 199 ANET interface 200 a MN's attachment to a link in an ANET. 202 Internetwork (INET) 203 a connected network region with a coherent IP addressing plan that 204 provides transit forwarding services for ANET MNs and INET 205 correspondents. Examples include private enterprise networks, 206 ground domain aviation service networks and the global public 207 Internet itself. 209 INET interface 210 a node's attachment to a link in an INET. 212 OMNI link 213 a virtual overlay configured over one or more INETs and their 214 connected ANETs. An OMNI link can comprise multiple INET segments 215 joined by bridges the same as for any link; the addressing plans 216 in each segment may be mutually exclusive and managed by different 217 administrative entities. 219 OMNI interface 220 a node's attachment to an OMNI link, and configured over one or 221 more underlying ANET/INET interfaces. 223 OMNI link local address (LLA) 224 an IPv6 link-local address constructed as specified in Section 7, 225 and assigned to an OMNI interface. 227 OMNI Option 228 an IPv6 Neighbor Discovery option providing multilink parameters 229 for the OMNI interface as specified in Section 8. 231 Multilink 232 an OMNI interface's manner of managing diverse underlying data 233 link interfaces as a single logical unit. The OMNI interface 234 provides a single unified interface to upper layers, while 235 underlying data link selections are performed on a per-packet 236 basis considering factors such as DSCP, flow label, application 237 policy, signal quality, cost, etc. Multilinking decisions are 238 coordinated in both the outbound (i.e. MN to correspondent) and 239 inbound (i.e., correspondent to MN) directions. 241 L2 242 The second layer in the OSI network model. Also known as "layer- 243 2", "link-layer", "sub-IP layer", "data link layer", etc. 245 L3 246 The third layer in the OSI network model. Also known as "layer- 247 3", "network-layer", "IPv6 layer", etc. 249 underlying interface 250 an ANET/INET interface over which an OMNI interface is configured. 251 The OMNI interface is seen as a L3 interface by the IP layer, and 252 each underlying interface is seen as a L2 interface by the OMNI 253 interface. 255 Mobility Service Identification (MSID) 256 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 257 as specified in Section 7. 259 3. Requirements 261 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 262 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 263 "OPTIONAL" in this document are to be interpreted as described in BCP 264 14 [RFC2119][RFC8174] when, and only when, they appear in all 265 capitals, as shown here. 267 An implementation is not required to internally use the architectural 268 constructs described here so long as its external behavior is 269 consistent with that described in this document. 271 4. Overlay Multilink Network (OMNI) Interface Model 273 An OMNI interface is a MN virtual interface configured over one or 274 more underlying interfaces, which may be physical (e.g., an 275 aeronautical radio link) or virtual (e.g., an Internet or higher- 276 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 277 with the MS through IPv6 ND message exchanges. The MN uses the MNP 278 to construct a unique OMNI LLA through the algorithmic derivation 279 specified in Section 7 and assigns the LLA to the OMNI interface. 281 The OMNI interface architectural layering model is the same as in 282 [RFC7847], and augmented as shown in Figure 1. The IP layer 283 therefore sees the OMNI interface as a single L3 interface with 284 multiple underlying interfaces that appear as L2 communication 285 channels in the architecture. 287 +----------------------------+ 288 | Upper Layer Protocol | 289 Session-to-IP +---->| | 290 Address Binding | +----------------------------+ 291 +---->| IP (L3) | 292 IP Address +---->| | 293 Binding | +----------------------------+ 294 +---->| OMNI Interface | 295 Logical-to- +---->| (OMNI LLA) | 296 Physical | +----------------------------+ 297 Interface +---->| L2 | L2 | | L2 | 298 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 299 +------+------+ +------+ 300 | L1 | L1 | | L1 | 301 | | | | | 302 +------+------+ +------+ 304 Figure 1: OMNI Interface Architectural Layering Model 306 The OMNI virtual interface model gives rise to a number of 307 opportunities: 309 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 310 Address Detection (DAD) or Muticast Listener Discovery (MLD) 311 messaging is necessary. 313 o ANET interfaces do not require any L3 addresses (i.e., not even 314 link-local) in environments where communications are coordinated 315 entirely over the OMNI interface. (An alternative would be to 316 also assign the same OMNI LLA to all ANET interfaces.) 318 o as ANET interface properties change (e.g., link quality, cost, 319 availability, etc.), any active ANET interface can be used to 320 update the profiles of multiple additional ANET interfaces in a 321 single message. This allows for timely adaptation and service 322 continuity under dynamically changing conditions. 324 o coordinating ANET interfaces in this way allows them to be 325 represented in a unified MS profile with provisions for mobility 326 and multilink operations. 328 o exposing a single virtual interface abstraction to the IPv6 layer 329 allows for multilink operation (including QoS based link 330 selection, packet replication, load balancing, etc.) at L2 while 331 still permitting L3 traffic shaping based on, e.g., DSCP, flow 332 label, etc. 334 o L3 sees the OMNI interface as a point of connection to the OMNI 335 link; if there are multiple OMNI links (i.e., multiple MS's), L3 336 will see multiple OMNI interfaces. 338 Other opportunities are discussed in [RFC7847]. 340 Figure 2 depicts the architectural model for a MN connecting to the 341 MS via multiple independent ANETs. When an underlying interface 342 becomes active, the MN's OMNI interface sends native (i.e., 343 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 344 ND messages traverse the ground domain ANETs until they reach an 345 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 346 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 347 returns an IPv6 ND message response to the MN. IPv6 ND messages 348 traverse the ANET at layer 2; hence, the Hop Limit is not 349 decremented. 351 +--------------+ 352 | MN | 353 +--------------+ 354 |OMNI interface| 355 +----+----+----+ 356 +--------|IF#1|IF#2|IF#n|------ + 357 / +----+----+----+ \ 358 / | \ 359 / <---- Native | IP ----> \ 360 v v v 361 (:::)-. (:::)-. (:::)-. 362 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 363 `-(::::)-' `-(::::)-' `-(::::)-' 364 +----+ +----+ +----+ 365 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 366 . +-|--+ +-|--+ +-|--+ . 367 . | | | 368 . v v v . 369 . <----- Encapsulation -----> . 370 . . 371 . +-----+ (:::)-. . 372 . |MSE#2| .-(::::::::) +-----+ . 373 . +-----+ .-(::: INET :::)-. |MSE#m| . 374 . (::::: Routing ::::) +-----+ . 375 . `-(::: System :::)-' . 376 . +-----+ `-(:::::::-' . 377 . |MSE#1| +-----+ +-----+ . 378 . +-----+ |MSE#3| |MSE#4| . 379 . +-----+ +-----+ . 380 . . 381 . . 382 . <----- Worldwide Connected Internetwork ----> . 383 ........................................................... 385 Figure 2: MN/MS Coordination via Multiple ANETs 387 After the initial IPv6 ND message exchange, the MN can send and 388 receive unencapsulated IPv6 data packets over the OMNI interface. 389 OMNI interface multilink services will forward the packets via ARs in 390 the correct underlying ANETs. The AR encapsulates the packets 391 according to the capabilities provided by the MS and forwards them to 392 the next hop within the worldwide connected Internetwork via optimal 393 routes. 395 5. Maximum Transmission Unit (MTU) and Fragmentation 397 All IPv6 interfaces are REQUIRED to configure a minimum Maximum 398 Transmission Unit (MTU) of 1280 bytes [RFC8200]. The network 399 therefore MUST forward packets of at least 1280 bytes without 400 generating an IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) 401 message [RFC8201]. 403 The OMNI interface configures an MTU of 9180 bytes [RFC2492]; the 404 size is therefore not a reflection of the underlying interface MTUs, 405 but rather determines the largest packet the OMNI interface can 406 forward or reassemble. 408 The OMNI interface can employ link-layer IPv6 encapsulation and 409 fragmentation/reassembly per [RFC2473], but its use is OPTIONAL since 410 correct operation will result in either case. Implementations that 411 omit link-layer IPv6 fragmentation/reassembly may be more prone to 412 dropping large packets and returning a PTB, while those that include 413 it may see improved performance at the expense of including 414 additional code. In both cases, MNs and ARs are responsible for 415 advertising their willingness to reassemble over the ANET, while all 416 ARs and MSEs MUST support fragmentation and reassembly up to 9180 417 bytes over the INET. 419 The OMNI interface returns internally-generated PTB messages for 420 packets admitted into the interface that it deems too large for the 421 outbound underlying interface (e.g., according to ANET performance 422 characteristics, MTU, etc). For all other packets, the OMNI 423 interface performs PMTUD even if the destination appears to be on the 424 same link since a proxy on the path could return a PTB message. This 425 ensures that the path MTU is adaptive and reflects the current path 426 used for a given data flow. 428 The MN's OMNI interface forwards packets that are no larger than the 429 MTU of the selected underlying interface according to the ANET L2 430 frame format. When the OMNI interface forwards a packet that is 431 larger than the underlying interface MTU, it drops the packet and 432 returns a PTB if the AR is not willing to reassemble. 434 Otherwise, the OMNI interface encapsulates the packet in an IPv6 435 header with source address set to the MN's link-local address and 436 destination address set to the link-local address of the AR (see: 437 Section 7). The OMNI interface then uses IPv6 fragmentation to break 438 the encapsulated packet into fragments that are no larger than the 439 underlying interface MTU and sends the fragments over the ANET where 440 they will be intercepted by the AR. The AR then reassembles and 441 conveys the packet toward the final destination. 443 When an AR receives a fragmented or whole packet from the INET 444 destined to an ANET MN, it first determines whether to forward or 445 drop and return a PTB. If the AR deems the packet to be of 446 acceptable size, it first reassembles locally (if necessary) then 447 forwards the packet to the MN. If the (reassembled) packet is no 448 larger than the ANET MTU, the AR forwards according to the ANET L2 449 frame format. If the packet is larger than the ANET MTU, the AR 450 instead uses link-layer IPv6 encapsulation and fragmentation as above 451 if the MN accepts fragments or drops and returns a PTB otherwise. 452 The MN then reassembles and discards the encapsulation header, then 453 forwards the whole packet to the final destination. 455 Applications that cannot tolerate loss due to MTU restrictions SHOULD 456 avoid sending packets larger than 1280 bytes, since dynamic path 457 changes can reduce the path MTU at any time. Applications that may 458 benefit from sending larger packets even though the path MTU may 459 change dynamically MAY use larger sizes (i.e., up to the OMNI 460 interface MTU). 462 Note that when the AR forwards a fragmented packet received from the 463 INET, it is imperative that the AR reassembles locally first instead 464 of blindly forwarding fragments directly to the MN to avoid attacks 465 such as tiny fragments, overlapping fragments, etc. 467 Note also that the OMNI interface can forward large packets via 468 encapsulation and fragmentation while at the same time returning 469 advisory PTB messages, e.g., subject to rate limiting. The receiving 470 node that performs reassembly can also send advisory PTB messages if 471 reassembly conditions become unfavorable. The OMNI interface can 472 therefore continuously forward large packets without loss while 473 returning advisory messages recommending a smaller size. 475 6. Frame Format 477 The OMNI interface transmits IPv6 packets according to the native 478 frame format of each underlying interface. For example, for 479 Ethernet-compatible interfaces the frame format is specified in 480 [RFC2464], for aeronautical radio interfaces the frame format is 481 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 482 Manual), for tunnels over IPv6 the frame format is specified in 483 [RFC2473], etc. 485 7. Link-Local Addresses 487 OMNI interfaces assign IPv6 Link-Local Addresses (i.e., "OMNI LLAs") 488 using the following constructs: 490 o IPv6 MN OMNI LLAs encode the most-significant 64 bits of a MNP 491 within the least-significant 64 bits (i.e., the interface ID) of a 492 Link-Local IPv6 Unicast Address (see: [RFC4291], Section 2.5.6). 493 For example, for the MNP 2001:db8:1000:2000::/56 the corresponding 494 LLA is fe80::2001:db8:1000:2000. 496 o IPv4-compatible MN OMNI LLAs are assigned as fe80::ffff:[v4addr], 497 i.e., the most significant 10 bits of the prefix fe80::/10, 498 followed by 70 '0' bits, followed by 16 '1' bits, followed by a 499 32bit IPv4 address. For example, the IPv4-Compatible MN OMNI LLA 500 for 192.0.2.1 is fe80::ffff:192.0.2.1 (also written as 501 fe80::ffff:c000:0201). 503 o MS OMNI LLAs are assigned to ARs and MSEs from the range 504 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 505 of the LLA includes a unique integer "MSID" value between 506 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 507 etc., fe80::feff:ffff. The MSID 0x00000000 corresponds to the 508 link-local Subnet-Router anycast address (fe80::) [RFC4291] and 509 the MSID 0xffffffff corresponds to the "All-MSEs" address 510 (fe80::ffff:ffff). The MSID range 0xff00000000 through 0xfffffffe 511 is reserved for future use. (Note that distinct OMNI link 512 segments can avoid overlap by assigning MS OMNI LLAs from unique 513 fe80::/96 sub-prefixes. For example, a first segment could assign 514 from fe80::1000/116, a second from fe80::2000/116, a third from 515 fe80::3000/116, etc.) 517 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 518 MNPs can be allocated from that block ensuring that there is no 519 possibility for overlap between the above OMNI LLA constructs. 521 Since MN OMNI LLAs are based on the distribution of administratively 522 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 523 through administrative assignment, OMNI interfaces set the 524 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 526 8. Address Mapping - Unicast 528 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 529 state and use the link-local address format specified in Section 7. 530 IPv6 Neighbor Discovery (ND) [RFC4861] messages on MN OMNI interfaces 531 observe the native Source/Target Link-Layer Address Option (S/TLLAO) 532 formats of the underlying interfaces (e.g., for Ethernet the S/TLLAO 533 is specified in [RFC2464]). 535 MNs such as aircraft typically have many wireless data link types 536 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 537 etc.) with diverse performance, cost and availability properties. 539 The OMNI interface would therefore appear to have multiple L2 540 connections, and may include information for multiple underlying 541 interfaces in a single IPv6 ND message exchange. 543 OMNI interfaces use an IPv6 ND option called the "OMNI option" 544 formatted as shown in Figure 3: 546 0 1 2 3 547 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 1 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 | Type | Length | Prefix Length |R|A| Reserved | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | | 552 ~ Sub-Options ~ 553 | | 554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 Figure 3: OMNI Option Format 558 In this format: 560 o Type is set to TBD. 562 o Length is set to the number of 8 octet blocks in the option. 564 o Prefix Length is set according to the IPv6 source address type. 565 For MN OMNI LLAs, the value is set to the length of the embedded 566 MNP. For IPv4-compatible MN OMNI LLAs, the value is set to 96 567 plus the length of the embedded IPv4 prefix. For MS OMNI LLAs, 568 the value is set to 128. 570 o R (the "Register/Release" bit) is set to 1/0 to request the 571 message recipient to register/release a MN's MNP. The OMNI option 572 may additionally include MSIDs for the recipient to contact to 573 also register/release the MNP. 575 o A (the "Accepts Fragments" bit) is set to '1' if the sender 576 accepts OMNI interface link-local fragments (see: Section 5); 577 otherwise, set to 0. Consulted only in RS and RA message 578 exchanges betweeen the MN and AR; ignored in all other IPv6 ND 579 messages. 581 o Reserved is set to the value '0' on transmission and ignored on 582 reception. 584 o Sub-Options is a Variable-length field, of length such that the 585 complete OMNI Option is an integer multiple of 8 octets long. 586 Contains one or more options, as described in Section 8.1. 588 8.1. Sub-Options 590 The OMNI option includes zero or more Sub-Options, some of which may 591 appear multiple times in the same message. Each consecutive Sub- 592 Option is concatenated immediately after its predecessor. All Sub- 593 Options except Pad1 (see below) are type-length-value (TLV) encoded 594 in the following format: 596 0 1 2 597 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 5 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 599 | Sub-Type | Sub-length | Sub-Option Data ... 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 602 Figure 4: Sub-Option Format 604 o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub- 605 Options defined in this document are: 607 Option Name Sub-Type 608 Pad1 0 609 PadN 1 610 ifIndex-tuple (Type 1) 2 611 ifIndex-tuple (Type 2) 3 612 MS-Register 4 613 MS-Release 5 615 Figure 5 617 Sub-Types 253 and 254 are reserved for experimentation, as 618 recommended in[RFC3692]]. 620 o Sub-Length is a 1-byte field that encodes the length of the Sub- 621 Option Data, in bytes 623 o Sub-Option Data is a byte string with format determined by Sub- 624 Type 626 During processing, unrecognized Sub-Options are ignored and the next 627 Sub-Option processed until the end of the OMNI option. 629 The following Sub-Option types and formats are defined in this 630 document: 632 8.1.1. Pad1 634 0 635 0 1 2 3 4 5 6 7 636 +-+-+-+-+-+-+-+-+ 637 | Sub-Type=0 | 638 +-+-+-+-+-+-+-+-+ 640 Figure 6: Pad1 642 o Sub-Type is set to 0. 644 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 645 consists of a single zero octet). 647 8.1.2. PadN 649 0 1 2 650 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 5 651 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 652 | Sub-Type=1 |Sub-length=N-2 | N-2 padding bytes ... 653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 655 Figure 7: PadN 657 o Sub-Type is set to 1. 659 o Sub-Length is set to N-2 being the number of padding bytes that 660 follow. 662 o Sub-Option Data consists of N-2 zero-valued octets. 664 8.1.3. ifIndex-tuple (Type 1) 665 0 1 2 3 666 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 1 667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | Provider ID | Link |S|I|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 674 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 676 |P32|P33|P34|P35|P36|P37|P38|P39| ... 677 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 679 Figure 8: ifIndex-tuple (Type 1) 681 o Sub-Type is set to 2. 683 o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that 684 follow). 686 o Sub-Option Data contains an "ifIndex-tuple" (Type 1) encoded as 687 follows (note that the first four bytes must be present): 689 * ifIndex is set to an 8-bit integer value corresponding to a 690 specific underlying interface. OMNI options MAY include 691 multiple ifIndex-tuples, and MUST number each with an ifIndex 692 value between '1' and '255' that represents a MN-specific 8-bit 693 mapping for the actual ifIndex value assigned to the underlying 694 interface by network management [RFC2863] (the ifIndex value 695 '0' is reserved for use by the MS). Multiple ifIndex-tuples 696 with the same ifIndex value MAY appear in the same OMNI option. 698 * ifType is set to an 8-bit integer value corresponding to the 699 underlying interface identified by ifIndex. The value 700 represents an OMNI interface-specific 8-bit mapping for the 701 actual IANA ifType value registered in the 'IANAifType-MIB' 702 registry [http://www.iana.org]. 704 * Provider ID is set to an OMNI interface-specific 8-bit ID value 705 for the network service provider associated with this ifIndex. 707 * Link encodes a 4-bit link metric. The value '0' means the link 708 is DOWN, and the remaining values mean the link is UP with 709 metric ranging from '1' ("lowest") to '15' ("highest"). 711 * S is set to '1' if this ifIndex-tuple corresponds to the 712 underlying interface that is the source of the ND message. Set 713 to '0' otherwise. 715 * I is set to '0' ("Simplex") if the index for each singleton 716 Bitmap byte in the Sub-Option Data is inferred from its 717 sequential position (i.e., 0, 1, 2, ...), or set to '1' 718 ("Indexed") if each Bitmap is preceded by an Index byte. 719 Figure 8 shows the simplex case for I set to '0'. For I set to 720 '1', each Bitmap is instead preceded by an Index byte that 721 encodes a value "i" = (0 - 255) as the index for its companion 722 Bitmap as follows: 724 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 725 | Index=i | Bitmap(i) |P[*] values ... 726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 728 Figure 9 730 * RSV is set to the value 0 on transmission and ignored on 731 reception. 733 * The remainder of the Sub-Option Data contains N = (0 - 251) 734 bytes of traffic classifier preferences consisting of a first 735 (indexed) Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte 736 blocks of 2-bit P[*] values, followed by a second Bitmap (i), 737 followed by 0-8 blocks of P[*] values, etc. Reading from bit 0 738 to bit 7, the bits of each Bitmap(i) that are set to '1'' 739 indicate the P[*] blocks from the range P[(i*32)] through 740 P[(i*32) + 31] that follow; if any Bitmap(i) bits are '0', then 741 the corresponding P[*] block is instead omitted. For example, 742 if Bitmap(0) contains 0xff then the block with P[00]-P[03], 743 followed by the block with P[04]-P[07], etc., and ending with 744 the block with P[28]-P[31] are included (as showin in 745 Figure 8). The next Bitmap(i) is then consulted with its bits 746 indicating which P[*] blocks follow, etc. out to the end of the 747 Sub-Option. The first 16 P[*] blocks correspond to the 64 748 Differentiated Service Code Point (DSCP) values P[00] - P[63] 749 [RFC2474]. If additional P[*] blocks follow, their values 750 correspond to "pseudo-DSCP" traffic classifier values P[64], 751 P[65], P[66], etc. See Appendix A for further discussion and 752 examples. 754 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 755 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 756 preference level for underlying interface selection purposes. 757 Not all P[*] values need to be included in all OMNI option 758 instances of a given ifIndex-tuple. Any P[*] values 759 represented in an earlier OMNI option but ommitted in the 760 current OMNI option remain unchanged. Any P[*] values not yet 761 represented in any OMNI option default to "medium". 763 8.1.4. ifIndex-tuple (Type 2) 765 0 1 2 3 766 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 1 767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 768 | Sub-Type=3 | Sub-length=4+N| ifIndex | ifType | 769 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 770 | Provider ID | Link |S|Resvd| ~ 771 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 772 ~ ~ 773 ~ RFC 6088 Format Traffic Selector ~ 774 ~ ~ 775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 777 Figure 10: ifIndex-tuple (Type 2) 779 o Sub-Type is set to 3. 781 o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that 782 follow). 784 o Sub-Option Data contains an "ifIndex-tuple" (Type 2) encoded as 785 follows (note that the first four bytes must be present): 787 * ifIndex, ifType, Provider ID, Link and S are set exactly as for 788 Type 1 ifIndex-tuples as specified in Section 8.1.3. 790 * the remainder of the Sub-Option body encodes a variable-length 791 traffic selector formatted per [RFC6088], beginning with the 792 "TS Format" field. 794 8.1.5. MS-Register 796 0 1 2 3 797 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 1 798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 799 | Sub-Type=4 | Sub-length=4 | MSID (bits 0 - 15) | 800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 801 | MSID (bits 16 - 32) | 802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 804 Figure 11: MS-Register Sub-option 806 o Sub-Type is set to 4. 808 o Sub-Length is set to 4. 810 o MSID contains the 32 bit ID of an MSE or AR, in network byte 811 order. OMNI options contain zero or more MS-Register sub-options. 813 8.1.6. MS-Release 815 0 1 2 3 816 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 1 817 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 818 | Sub-Type=5 | Sub-length=4 | MSID (bits 0 - 15) | 819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 820 | MSID (bits 16 - 32) | 821 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 823 Figure 12: MS-Release Sub-option 825 o Sub-Type is set to 5. 827 o Sub-Length is set to 4. 829 o MSIID contains the 32 bit ID of an MS or AR, in network byte 830 order. OMNI options contain zero or more MS-Release sub-options. 832 9. Address Mapping - Multicast 834 The multicast address mapping of the native underlying interface 835 applies. The mobile router on board the aircraft also serves as an 836 IGMP/MLD Proxy for its EUNs and/or hosted applications per [RFC4605] 837 while using the L2 address of the router as the L2 address for all 838 multicast packets. 840 10. Conceptual Sending Algorithm 842 The MN's IPv6 layer selects the outbound OMNI interface according to 843 standard IPv6 requirements when forwarding data packets from local or 844 EUN applications to external correspondents. The OMNI interface 845 maintains a neighbor cache the same as for any IPv6 interface, but 846 with additional state for multilink coordination. 848 After a packet enters the OMNI interface, an outbound underlying 849 interface is selected based on multilink parameters such as DSCP, 850 application port number, cost, performance, message size, etc. OMNI 851 interface multilink selections could also be configured to perform 852 replication across multiple underlying interfaces for increased 853 reliability at the expense of packet duplication. 855 OMNI interface multilink service designers MUST observe the BCP 856 guidance in Section 15 [RFC3819] in terms of implications for 857 reordering when packets from the same flow may be spread across 858 multiple underlying interfaces having diverse properties. 860 10.1. Multiple OMNI Interfaces 862 MNs may associate with multiple MS instances concurrently. Each MS 863 instance represents a distinct OMNI link distinguished by its 864 associated MSPs. The MN configures a separate OMNI interface for 865 each link so that multiple interfaces (e.g., omni0, omni1, omni2, 866 etc.) are exposed to the IPv6 layer. 868 Depending on local policy and configuration, an MN may choose between 869 alternative active OMNI interfaces using a packet's DSCP, routing 870 information or static configuration. Interface selection based on 871 per-packet source addresses is also enabled when the MSPs for each 872 OMNI interface are known (e.g., discovered through Prefix Information 873 Options (PIOs) and/or Route Information Options (RIOs)). 875 Each OMNI interface can be configured over the same or different sets 876 of underlying interfaces. Each ANET distinguishes between the 877 different OMNI links based on the MSPs represented in per-packet IPv6 878 addresses. 880 Multiple distinct OMNI links can therefore be used to support fault 881 tolerance, load balancing, reliability, etc. The architectural model 882 parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs 883 serve as (virtual) VLAN tags. 885 11. Router Discovery and Prefix Registration 887 MNs interface with the MS by sending RS messages with OMNI options 888 that include MSIDs. For each underlying interface, the MN sends an 889 RS message with an OMNI option with (R,A) flags, wth MS-Register/ 890 Release suboptions, and with destination address set to All-Routers 891 multicast (ff02::2) [RFC4291]. Example MSID discovery methods are 892 given in [RFC5214], including data link login parameters, name 893 service lookups, static configuration, etc. Alternatively, MNs can 894 discover indiviual MSIDs by sending an initial RS with MS-Register 895 MSID set to 0x00000000, or associate with all MSEs by sending an RS 896 with MS-Register MSID set to 0xffffffff. 898 MNs configure OMNI interfaces that observe the properties discussed 899 in the previous section. The OMNI interface and its underlying 900 interfaces are said to be in either the "UP" or "DOWN" state 901 according to administrative actions in conjunction with the interface 902 connectivity status. An OMNI interface transitions to UP or DOWN 903 through administrative action and/or through state transitions of the 904 underlying interfaces. When a first underlying interface transitions 905 to UP, the OMNI interface also transitions to UP. When all 906 underlying interfaces transition to DOWN, the OMNI interface also 907 transitions to DOWN. 909 When an OMNI interface transitions to UP, the MN sends RS messages to 910 register its MNP and an initial set of underlying interfaces that are 911 also UP. The MN sends additional RS messages to refresh lifetimes 912 and to register/deregister underlying interfaces as they transition 913 to UP or DOWN. The MN sends initial RS messages over an UP 914 underlying interface with its OMNI LLA as the source and with 915 destination set to All-Routers multicast. The RS messages include an 916 OMNI option per Section 8 with a valid Prefix Length, (R, A) flags, 917 ifIndex-tuples appropriate for underlying interfaces and with MS- 918 Register/Release sub-options. 920 ARs process IPv6 ND messages with OMNI options and act as a proxy for 921 MSEs. ARs receive RS messages and create a neighbor cache entry for 922 the MN, then coordinate with any named MSIDs in a manner outside the 923 scope of this document. The AR returns an RA message with 924 destination address set to the MN OMNI LLA (i.e., unicast), with 925 source address set to its MS OMNI LLA, with the P(roxy) bit set in 926 the RA flags [RFC4389], with an OMNI option with (R, A) flags, 927 ifIndex tuples and MS-Register/Release sub-options, and with any 928 information for the link that would normally be delivered in a 929 solicited RA message. ARs return RA messages with configuration 930 information in response to a MN's RS messages. The AR sets the RA 931 Cur Hop Limit, M and O flags, Router Lifetime, Reachable Time and 932 Retrans Timer values, and includes any necessary options such as: 934 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 936 o RIOs [RFC4191] with more-specific routes. 938 o an MTU option that specifies the maximum acceptable packet size 939 for this ANET interface. 941 The AR coordinates with each Register/Release MSID then sends an 942 immediate unicast RA response without delay; therefore, the IPv6 ND 943 MAX_RA_DELAY_TIME and MIN_DELAY_BETWEEN_RAS constants for multicast 944 RAs do not apply. The AR MAY send periodic and/or event-driven 945 unsolicited RA messages according to the standard [RFC4861]. 947 When the MSE processes the OMNI information, it first validates the 948 prefix registration information. The MSE then injects/withdraws the 949 MNP in the routing/mapping system and caches/discards the new Prefix 950 Length, MNP and ifIndex-tuples. The MSE then informs the AR of 951 registration success/failure, and the AR adds the MSE to the list of 952 Register/Release MSIDs to return in an RA message OMNI option per 953 Section 8. 955 When the MN receives the RA message, it creates an OMNI interface 956 neighbor cache entry with the AR's address as an L2 address and 957 records the MSIDs that have confirmed MNP registration via this AR. 958 If the MN connects to multiple ANETs, it establishes additional AR L2 959 addresses (i.e., as a Multilink neighbor). The MN then manages its 960 underlying interfaces according to their states as follows: 962 o When an underlying interface transitions to UP, the MN sends an RS 963 over the underlying interface with an OMNI option with R set to 1. 964 The OMNI option contains at least one ifIndex-tuple with values 965 specific to this underlying interface, and may contain additional 966 ifIndex-tuples specific to this and/or other underlying 967 interfaces. The option also includes any Register/Release MSIDs. 969 o When an underlying interface transitions to DOWN, the MN sends an 970 RS or unsolicited NA message over any UP underlying interface with 971 an OMNI option containing an ifIndex-tuple for the DOWN underlying 972 interface with Link set to '0'. The MN sends an RS when an 973 acknowledgement is required, or an unsolicited NA when reliability 974 is not thought to be a concern (e.g., if redundant transmissions 975 are sent on multiple underlying interfaces). 977 o When the Router Lifetime for a specific AR nears expiration, the 978 MN sends an RS over the underlying interface to receive a fresh 979 RA. If no RA is received, the MN marks the underlying interface 980 as DOWN. 982 o When a MN wishes to release from one or more current MSIDs, it 983 sends an RS or unsolicited NA message over any UP underlying 984 interfaces with an OMNI option with a Release MSID. Each MSID 985 then withdraws the MNP from the routing/mapping system and informs 986 the AR that the release was successful. 988 o When all of a MNs underlying interfaces have transitioned to DOWN 989 (or if the prefix registration lifetime expires), any associated 990 MSEs withdraw the MNP the same as if they had received a message 991 with a release indication. 993 The MN is responsible for retrying each RS exchange up to 994 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 995 seconds until an RA is received. If no RA is received over a an UP 996 underlying interface, the MN declares this underlying interface as 997 DOWN. 999 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1000 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1001 returns an internally-generated RA message as though the message 1002 originated from an IPv6 router. The internally-generated RA message 1003 contains configuration information that is consistent with the 1004 information received from the RAs generated by the MS. Whether the 1005 OMNI interface IPv6 ND messaging process is initiated from the 1006 receipt of an RS message from the IPv6 layer is an implementation 1007 matter. Some implementations may elect to defer the IPv6 ND 1008 messaging process until an RS is received from the IPv6 layer, while 1009 others may elect to initiate the process proactively. 1011 Note: The Router Lifetime value in RA messages indicates the time 1012 before which the MN must send another RS message over this underlying 1013 interface (e.g., 600 seconds), however that timescale may be 1014 significantly longer than the lifetime the MS has committed to retain 1015 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1016 therefore responsible for keeping MS state alive on a finer-grained 1017 timescale than the MN is required to do on its own behalf. 1019 12. AR and MSE Resilience 1021 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1022 [RFC5798] configurations so that service continuity is maintained 1023 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1024 the (redundant) ARs is currently providing service, and any service 1025 discontinuity will be limited to the failover time supported by VRRP. 1026 Widely deployed public domain implementations of VRRP are available. 1028 MSEs SHOULD use high availability clustering services so that 1029 multiple redundant systems can provide coordinated response to 1030 failures. As with VRRP, widely deployed public domain 1031 implementations of high availability clustering services are 1032 available. Note that special-purpose and expensive dedicated 1033 hardware is not necessary, and public domain implementations can be 1034 used even between lightweight virtual machines in cloud deployments. 1036 13. Detecting and Responding to MSE Failures 1038 In environments where fast recovery from MSE failure is required, ARs 1039 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1040 manner that parallels Bidirectional Forwarding Detection (BFD) 1041 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1042 react to failures so that cached information is re-established 1043 through alternate paths. Proactive NUD control messaging is carried 1044 only over well-connected ground domain networks (i.e., and not low- 1045 end ANET links such as aeronautical radios) and can therefore be 1046 tuned for rapid response. 1048 ARs perform proactive NUD for MSEs for which there are currently 1049 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1050 of the outage by sending multicast RA messages on the ANET interface. 1051 The AR sends RA messages to the MN via the ANET interface with an 1052 OMNI option with a Release ID for the failed MSE, and with 1053 destination address set to All-Nodes multicast (ff02::1) [RFC4291]. 1055 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1056 by small delays [RFC4861]. Any MNs on the ANET interface that have 1057 been using the (now defunct) MSE will receive the RA messages and 1058 associate with a new MSE. 1060 14. Transition Considerations 1062 When a MN connects to an ANET link for the first time, it sends an RS 1063 message with an OMNI option. If the first hop AR recognizes the 1064 option, it returns an RA with its MS OMNI LLA as the source, the MN 1065 OMNI LLA as the destination, the P(roxy) bit set in the RA flags and 1066 with an OMNI option included. The MN then engages the AR according 1067 to the OMNI link model specified above. If the first hop AR is a 1068 legacy IPv6 router, however, it instead returns an RA message with no 1069 OMNI option and with a non-OMNI unicast source LLA as specified in 1070 [RFC4861]. In that case, the MN engages the ANET according to the 1071 legacy IPv6 link model and without the OMNI extensions specified in 1072 this document. 1074 If the ANET link model is multiple access, there must be assurance 1075 that address duplication cannot corrupt the neighbor caches of other 1076 nodes on the link. When the MN sends an RS message on a multiple 1077 access ANET link with an OMNI LLA source address and an OMNI option, 1078 ARs that recognize the option ensure that the MN is authorized to use 1079 the address and return an RA with a non-zero Router Lifetime only if 1080 the MN is authorized. ARs that do not recognize the option instead 1081 return an RA that makes no statement about the MN's authorization to 1082 use the source address. In that case, the MN should perform 1083 Duplicate Address Detection to ensure that it does not interfere with 1084 other nodes on the link. 1086 An alternative approach for multiple access ANET links to ensure 1087 isolation for MN / AR communications is through L2 address mappings 1088 as discussed in Appendix D. This arrangement imparts a (virtual) 1089 point-to-point link model over the (physical) multiple access link. 1091 15. OMNI Interfaces on the Open Internet 1093 OMNI interfaces that connect to the open Internet via native and/or 1094 NATed underlying interfaces can apply symmetric security services 1095 such as VPNs to establish secured tunnels to MSEs. In environments 1096 where an explicit VPN may be too restrictive, OMNI interfaces can 1097 instead ensure neighbor cache integrity using SEcure Neighbor 1098 Discovery (SEND) [RFC3971] and Cryptographically Generated Addresses 1099 (CGAs) [RFC3972]. 1101 When SEND/CGA are used, the IPv6 ND control plane messages used to 1102 establish neighbor cache state are authenticated while data plane 1103 messages are delivered the same as for ordinary best-effort Internet 1104 traffic. Instead, data plane communications via OMNI interfaces that 1105 connect over the open Internet without an explicit VPN must emply 1106 transport- or higher-layer security to ensure integrity and/or 1107 confidentiality. 1109 In addition to secured OMNI interface RS/RA exchanges, SEND/CGA 1110 supports safe address resolution and neighbor unreachability 1111 detection as discused in Asymmetric Extended Route Optimization 1112 (AERO) [I-D.templin-intarea-6706bis]. This allows for efficient 1113 multilink operations over the open Internet with assured neighbor 1114 cache integrity. 1116 16. IANA Considerations 1118 The IANA is instructed to allocate an official Type number TBD from 1119 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1120 option. Implementations set Type to 253 as an interim value 1121 [RFC4727]. 1123 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1124 is instructed to create and maintain a new registry entitled "OMNI 1125 option Sub-Type values". Initial values for the OMNI option Sub-Type 1126 values registry are given below; future assignments are to be made 1127 through Expert Review [RFC8126]. 1129 Value Sub-Type name Reference 1130 ----- ------------- ---------- 1131 0 Pad1 [RFCXXXX] 1132 1 PadN [RFCXXXX] 1133 2 ifIndex-tuple (Type 1) [RFCXXXX] 1134 3 ifIndex-tuple (Type 2) [RFCXXXX] 1135 4 MS-Register [RFCXXXX] 1136 5 MS-Release [RFCXXXX] 1137 6-252 Unassigned 1138 253-254 Experimental [RFCXXXX] 1139 255 Reserved [RFCXXXX] 1141 Figure 13: OMNI Option Sub-Type Values 1143 The IANA is instructed to allocate one Ethernet unicast address TBD2 1144 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1145 Address Block - Unicast Use". 1147 17. Security Considerations 1149 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1150 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1151 include Nonce and Timestamp options [RFC3971] when synchronized 1152 transaction confirmation is needed. 1154 OMNI interfaces configured over secured underlying ANET interfaces 1155 inherit the physical and/or link-layer security aspects of the 1156 connected ANETs. OMNI interfaces configured over open Internet 1157 interfaces must use symmetric securing services such as VPNs or 1158 asymmetric services such as SEND/CGA [RFC3971][RFC3972]. 1160 Security considerations for specific access network interface types 1161 are covered under the corresponding IP-over-(foo) specification 1162 (e.g., [RFC2464], [RFC2492], etc.). 1164 18. Acknowledgements 1166 The first version of this document was prepared per the consensus 1167 decision at the 7th Conference of the International Civil Aviation 1168 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1169 2019. Consensus to take the document forward to the IETF was reached 1170 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1171 Attendees and contributors included: Guray Acar, Danny Bharj, 1172 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1173 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1174 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1175 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1176 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1177 Fryderyk Wrobel and Dongsong Zeng. 1179 The following individuals are acknowledged for their useful comments: 1180 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 1181 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized 1182 for their many helpful ideas and suggestions. 1184 This work is aligned with the NASA Safe Autonomous Systems Operation 1185 (SASO) program under NASA contract number NNA16BD84C. 1187 This work is aligned with the FAA as per the SE2025 contract number 1188 DTFAWA-15-D-00030. 1190 19. References 1192 19.1. Normative References 1194 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1195 Requirement Levels", BCP 14, RFC 2119, 1196 DOI 10.17487/RFC2119, March 1997, 1197 . 1199 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1200 "Definition of the Differentiated Services Field (DS 1201 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1202 DOI 10.17487/RFC2474, December 1998, 1203 . 1205 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1206 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1207 DOI 10.17487/RFC3971, March 2005, 1208 . 1210 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1211 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1212 . 1214 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1215 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1216 November 2005, . 1218 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1219 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1220 2006, . 1222 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1223 ICMPv6, UDP, and TCP Headers", RFC 4727, 1224 DOI 10.17487/RFC4727, November 2006, 1225 . 1227 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1228 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1229 DOI 10.17487/RFC4861, September 2007, 1230 . 1232 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1233 Address Autoconfiguration", RFC 4862, 1234 DOI 10.17487/RFC4862, September 2007, 1235 . 1237 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1238 "Traffic Selectors for Flow Bindings", RFC 6088, 1239 DOI 10.17487/RFC6088, January 2011, 1240 . 1242 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1243 Hosts in a Multi-Prefix Network", RFC 8028, 1244 DOI 10.17487/RFC8028, November 2016, 1245 . 1247 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1248 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1249 May 2017, . 1251 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1252 (IPv6) Specification", STD 86, RFC 8200, 1253 DOI 10.17487/RFC8200, July 2017, 1254 . 1256 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 1257 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 1258 DOI 10.17487/RFC8201, July 2017, 1259 . 1261 19.2. Informative References 1263 [I-D.templin-intarea-6706bis] 1264 Templin, F., "Asymmetric Extended Route Optimization 1265 (AERO)", draft-templin-intarea-6706bis-35 (work in 1266 progress), March 2020. 1268 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 1269 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 1270 . 1272 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 1273 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 1274 . 1276 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1277 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 1278 December 1998, . 1280 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 1281 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 1282 . 1284 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 1285 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 1286 . 1288 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 1289 Considered Useful", BCP 82, RFC 3692, 1290 DOI 10.17487/RFC3692, January 2004, 1291 . 1293 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 1294 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 1295 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 1296 RFC 3819, DOI 10.17487/RFC3819, July 2004, 1297 . 1299 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 1300 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 1301 2006, . 1303 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 1304 "Internet Group Management Protocol (IGMP) / Multicast 1305 Listener Discovery (MLD)-Based Multicast Forwarding 1306 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 1307 August 2006, . 1309 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1310 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1311 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1312 . 1314 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 1315 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 1316 DOI 10.17487/RFC5214, March 2008, 1317 . 1319 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 1320 Version 3 for IPv4 and IPv6", RFC 5798, 1321 DOI 10.17487/RFC5798, March 2010, 1322 . 1324 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1325 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 1326 . 1328 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 1329 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 1330 2012, . 1332 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 1333 Requirements for IPv6 Customer Edge Routers", RFC 7084, 1334 DOI 10.17487/RFC7084, November 2013, 1335 . 1337 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 1338 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 1339 Boundary in IPv6 Addressing", RFC 7421, 1340 DOI 10.17487/RFC7421, January 2015, 1341 . 1343 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 1344 Support for IP Hosts with Multi-Access Support", RFC 7847, 1345 DOI 10.17487/RFC7847, May 2016, 1346 . 1348 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1349 Writing an IANA Considerations Section in RFCs", BCP 26, 1350 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1351 . 1353 Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference Encoding 1355 Adaptation of the OMNI option Type 1 ifIndex-tuple's traffic 1356 classifier Bitmap to specific Internetworks such as the Aeronautical 1357 Telecommunications Network with Internet Protocol Services (ATN/IPS) 1358 may include link selection preferences based on other traffic 1359 classifiers (e.g., transport port numbers, etc.) in addition to the 1360 existing DSCP-based preferences. Nodes on specific Internetworks 1361 maintain a map of traffic classifiers to additional P[*] preference 1362 fields beyond the first 64. For example, TCP port 22 maps to P[67], 1363 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 1365 Implementations use Simplex or Indexed encoding formats for P[*] 1366 encoding in order to encode a given set of traffic classifiers in the 1367 most efficient way. Some use cases may be more efficiently coded 1368 using Simplex form, while others may be more efficient using Indexed. 1369 Once a format is selected for preparation of a single ifIndex-tuple 1370 the same format must be used for the entire Sub-Option. Different 1371 Sub-Options may use different formats. 1373 The following figures show coding examples for various Simplex and 1374 Indexed formats: 1376 0 1 2 3 1377 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 1378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1379 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 1380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1381 | Provider ID | Link |S|0|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| 1382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1383 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 1384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1385 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 1386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1387 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 1388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1389 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 1390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1391 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 1392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1394 Figure 14: Example 1: Dense Simplex Encoding 1396 0 1 2 3 1397 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 1398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1399 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 1400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1401 | Provider ID | Link |S|0|RSV| Bitmap(0)=0x00| Bitmap(1)=0x0f| 1402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1403 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 1404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1405 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 1406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1407 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 1408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1409 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 1410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1411 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1413 |Bitmap(10)=0x00| ... 1414 +-+-+-+-+-+-+-+-+-+-+- 1416 Figure 15: Example 2: Sparse Simplex Encoding 1418 0 1 2 3 1419 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 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1421 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1423 | Provider ID | Link |S|1|RSV| Index = 0x00 | Bitmap = 0x80 | 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1425 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 1426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1427 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 1428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1429 | Bitmap = 0x01 |796|797|798|799| ... 1430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1432 Figure 16: Example 3: Indexed Encoding 1434 Appendix B. Prefix Length Considerations 1436 The 64-bit boundary in IPv6 addresses [RFC7421] determines the MN 1437 OMNI LLA format for encoding the most-significant 64 MNP bits into 1438 the least-significant 64 bits of the prefix fe80::/64 as discussed in 1439 Section 7. 1441 [RFC4291] defines the link-local address format as the most 1442 significant 10 bits of the prefix fe80::/10, followed by 54 unused 1443 bits, followed by the least-significant 64 bits of the address. If 1444 the 64-bit boundary is relaxed through future standards activity, 1445 then the 54 unused bits can be employed for extended coding of MNPs 1446 of length /65 up to /118. 1448 The extended coding format would continue to encode MNP bits 0-63 in 1449 bits 64-127 of the OMNI LLA, while including MNP bits 64-117 in bits 1450 10-63. For example, the OMNI LLA corresponding to the MNP 1451 2001:db8:1111:2222:3333:4444:5555::/112 would be 1452 fe8c:ccd1:1115:5540:2001:db8:1111:2222/128, and would still be a 1453 valid IPv6 LLA per [RFC4291]. However, a prefix length shorter than 1454 /128 cannot be applied due to the non-sequential byte ordering. 1456 Note that if the 64-bit boundary were relaxed an alternate form of 1457 OMNI LLA construction could be employed by embedding the MNP 1458 beginning with the most significant bit immediately following bit 10 1459 of the prefix fe80::/10. For example, the OMNI LLA corresponding to 1460 the MNP 2001:db8:1111:2222:3333:4444:5555::/112 would be written as 1461 fe88:0043:6e04:4448:888c:ccd1:1115:5540/122. This alternate form may 1462 provide a more natural coding for the MS along with the ability to 1463 apply a fully-qualified prefix length. It has the disadvantages of 1464 requiring an unweildy 10-bit right-shift of a 16byte address, as well 1465 as presenting a non-human-readable form. 1467 Appendix C. VDL Mode 2 Considerations 1469 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 1470 (VDLM2) that specifies an essential radio frequency data link service 1471 for aircraft and ground stations in worldwide civil aviation air 1472 traffic management. The VDLM2 link type is "multicast capable" 1473 [RFC4861], but with considerable differences from common multicast 1474 links such as Ethernet and IEEE 802.11. 1476 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 1477 magnitude less than most modern wireless networking gear. Second, 1478 due to the low available link bandwidth only VDLM2 ground stations 1479 (i.e., and not aircraft) are permitted to send broadcasts, and even 1480 so only as compact layer 2 "beacons". Third, aircraft employ the 1481 services of ground stations by performing unicast RS/RA exchanges 1482 upon receipt of beacons instead of listening for multicast RA 1483 messages and/or sending multicast RS messages. 1485 This beacon-oriented unicast RS/RA approach is necessary to conserve 1486 the already-scarce available link bandwidth. Moreover, since the 1487 numbers of beaconing ground stations operating within a given spatial 1488 range must be kept as sparse as possible, it would not be feasible to 1489 have different classes of ground stations within the same region 1490 observing different protocols. It is therefore highly desirable that 1491 all ground stations observe a common language of RS/RA as specified 1492 in this document. 1494 Note that links of this nature may benefit from compression 1495 techniques that reduce the bandwidth necessary for conveying the same 1496 amount of data. The IETF lpwan working group is considering possible 1497 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 1499 Appendix D. MN / AR Isolation Through L2 Address Mapping 1501 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 1502 unicast link-scoped IPv6 destination address. However, IPv6 ND 1503 messaging should be coordinated between the MN and AR only without 1504 invoking other nodes on the ANET. This implies that MN / AR 1505 coordinations should be isolated and not overheard by other nodes on 1506 the link. 1508 To support MN / AR isolation on some ANET links, ARs can maintain an 1509 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 1510 ANETs, this specification reserves one Ethernet unicast address TBD2 1511 (see: Section 16). For non-Ethernet statically-addressed ANETs, 1512 MSADDR is reserved per the assigned numbers authority for the ANET 1513 addressing space. For still other ANETs, MSADDR may be dynamically 1514 discovered through other means, e.g., L2 beacons. 1516 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 1517 both multicast and unicast) to MSADDR instead of to an ordinary 1518 unicast or multicast L2 address. In this way, all of the MN's IPv6 1519 ND messages will be received by ARs that are configured to accept 1520 packets destined to MSADDR. Note that multiple ARs on the link could 1521 be configured to accept packets destined to MSADDR, e.g., as a basis 1522 for supporting redundancy. 1524 Therefore, ARs must accept and process packets destined to MSADDR, 1525 while all other devices must not process packets destined to MSADDR. 1526 This model has well-established operational experience in Proxy 1527 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 1529 Appendix E. Change Log 1531 << RFC Editor - remove prior to publication >> 1533 Differences from draft-templin-6man-omni-interface-07 to draft- 1534 templin-6man-omni-interface-08: 1536 o OMNI MNs in the open Internet 1538 Differences from draft-templin-6man-omni-interface-06 to draft- 1539 templin-6man-omni-interface-07: 1541 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 1542 L2 addressing. 1544 o Explanded "Transition Considerations". 1546 Differences from draft-templin-6man-omni-interface-05 to draft- 1547 templin-6man-omni-interface-06: 1549 o Brought back OMNI option "R" flag, and dicussed its use. 1551 Differences from draft-templin-6man-omni-interface-04 to draft- 1552 templin-6man-omni-interface-05: 1554 o Transition considerations, and overhaul of RS/RA addressing with 1555 the inclusion of MSE addresses within the OMNI option instead of 1556 as RS/RA addresses (developed under FAA SE2025 contract number 1557 DTFAWA-15-D-00030). 1559 Differences from draft-templin-6man-omni-interface-02 to draft- 1560 templin-6man-omni-interface-03: 1562 o Added "advisory PTB messages" under FAA SE2025 contract number 1563 DTFAWA-15-D-00030. 1565 Differences from draft-templin-6man-omni-interface-01 to draft- 1566 templin-6man-omni-interface-02: 1568 o Removed "Primary" flag and supporting text. 1570 o Clarified that "Router Lifetime" applies to each ANET interface 1571 independently, and that the union of all ANET interface Router 1572 Lifetimes determines MSE lifetime. 1574 Differences from draft-templin-6man-omni-interface-00 to draft- 1575 templin-6man-omni-interface-01: 1577 o "All-MSEs" OMNI LLA defined. Also reserverd fe80::ff00:0000/104 1578 for future use (most likely as "pseudo-multicast"). 1580 o Non-normative discussion of alternate OMNI LLA construction form 1581 made possible if the 64-bit assumption were relaxed. 1583 Differences from draft-templin-atn-aero-interface-21 to draft- 1584 templin-6man-omni-interface-00: 1586 o Minor clarification on Type-2 ifIndex-tuple encoding. 1588 o Draft filename change (replaces draft-templin-atn-aero-interface). 1590 Differences from draft-templin-atn-aero-interface-20 to draft- 1591 templin-atn-aero-interface-21: 1593 o OMNI option format 1595 o MTU 1597 Differences from draft-templin-atn-aero-interface-19 to draft- 1598 templin-atn-aero-interface-20: 1600 o MTU 1602 Differences from draft-templin-atn-aero-interface-18 to draft- 1603 templin-atn-aero-interface-19: 1605 o MTU 1607 Differences from draft-templin-atn-aero-interface-17 to draft- 1608 templin-atn-aero-interface-18: 1610 o MTU and RA configuration information updated. 1612 Differences from draft-templin-atn-aero-interface-16 to draft- 1613 templin-atn-aero-interface-17: 1615 o New "Primary" flag in OMNI option. 1617 Differences from draft-templin-atn-aero-interface-15 to draft- 1618 templin-atn-aero-interface-16: 1620 o New note on MSE OMNI LLA uniqueness assurance. 1622 o General cleanup. 1624 Differences from draft-templin-atn-aero-interface-14 to draft- 1625 templin-atn-aero-interface-15: 1627 o General cleanup. 1629 Differences from draft-templin-atn-aero-interface-13 to draft- 1630 templin-atn-aero-interface-14: 1632 o General cleanup. 1634 Differences from draft-templin-atn-aero-interface-12 to draft- 1635 templin-atn-aero-interface-13: 1637 o Minor re-work on "Notify-MSE" (changed to Notification ID). 1639 Differences from draft-templin-atn-aero-interface-11 to draft- 1640 templin-atn-aero-interface-12: 1642 o Removed "Request/Response" OMNI option formats. Now, there is 1643 only one OMNI option format that applies to all ND messages. 1645 o Added new OMNI option field and supporting text for "Notify-MSE". 1647 Differences from draft-templin-atn-aero-interface-10 to draft- 1648 templin-atn-aero-interface-11: 1650 o Changed name from "aero" to "OMNI" 1652 o Resolved AD review comments from Eric Vyncke (posted to atn list) 1654 Differences from draft-templin-atn-aero-interface-09 to draft- 1655 templin-atn-aero-interface-10: 1657 o Renamed ARO option to AERO option 1659 o Re-worked Section 13 text to discuss proactive NUD. 1661 Differences from draft-templin-atn-aero-interface-08 to draft- 1662 templin-atn-aero-interface-09: 1664 o Version and reference update 1666 Differences from draft-templin-atn-aero-interface-07 to draft- 1667 templin-atn-aero-interface-08: 1669 o Removed "Classic" and "MS-enabled" link model discussion 1671 o Added new figure for MN/AR/MSE model. 1673 o New Section on "Detecting and responding to MSE failure". 1675 Differences from draft-templin-atn-aero-interface-06 to draft- 1676 templin-atn-aero-interface-07: 1678 o Removed "nonce" field from AR option format. Applications that 1679 require a nonce can include a standard nonce option if they want 1680 to. 1682 o Various editorial cleanups. 1684 Differences from draft-templin-atn-aero-interface-05 to draft- 1685 templin-atn-aero-interface-06: 1687 o New Appendix C on "VDL Mode 2 Considerations" 1689 o New Appendix D on "RS/RA Messaging as a Single Standard API" 1691 o Various significant updates in Section 5, 10 and 12. 1693 Differences from draft-templin-atn-aero-interface-04 to draft- 1694 templin-atn-aero-interface-05: 1696 o Introduced RFC6543 precedent for focusing IPv6 ND messaging to a 1697 reserved unicast link-layer address 1699 o Introduced new IPv6 ND option for Aero Registration 1701 o Specification of MN-to-MSE message exchanges via the ANET access 1702 router as a proxy 1704 o IANA Considerations updated to include registration requests and 1705 set interim RFC4727 option type value. 1707 Differences from draft-templin-atn-aero-interface-03 to draft- 1708 templin-atn-aero-interface-04: 1710 o Removed MNP from aero option format - we already have RIOs and 1711 PIOs, and so do not need another option type to include a Prefix. 1713 o Clarified that the RA message response must include an aero option 1714 to indicate to the MN that the ANET provides a MS. 1716 o MTU interactions with link adaptation clarified. 1718 Differences from draft-templin-atn-aero-interface-02 to draft- 1719 templin-atn-aero-interface-03: 1721 o Sections re-arranged to match RFC4861 structure. 1723 o Multiple aero interfaces 1725 o Conceptual sending algorithm 1727 Differences from draft-templin-atn-aero-interface-01 to draft- 1728 templin-atn-aero-interface-02: 1730 o Removed discussion of encapsulation (out of scope) 1732 o Simplified MTU section 1734 o Changed to use a new IPv6 ND option (the "aero option") instead of 1735 S/TLLAO 1737 o Explained the nature of the interaction between the mobility 1738 management service and the air interface 1740 Differences from draft-templin-atn-aero-interface-00 to draft- 1741 templin-atn-aero-interface-01: 1743 o Updates based on list review comments on IETF 'atn' list from 1744 4/29/2019 through 5/7/2019 (issue tracker established) 1746 o added list of opportunities afforded by the single virtual link 1747 model 1749 o added discussion of encapsulation considerations to Section 6 1751 o noted that DupAddrDetectTransmits is set to 0 1753 o removed discussion of IPv6 ND options for prefix assertions. The 1754 aero address already includes the MNP, and there are many good 1755 reasons for it to continue to do so. Therefore, also including 1756 the MNP in an IPv6 ND option would be redundant. 1758 o Significant re-work of "Router Discovery" section. 1760 o New Appendix B on Prefix Length considerations 1762 First draft version (draft-templin-atn-aero-interface-00): 1764 o Draft based on consensus decision of ICAO Working Group I Mobility 1765 Subgroup March 22, 2019. 1767 Authors' Addresses 1769 Fred L. Templin (editor) 1770 The Boeing Company 1771 P.O. Box 3707 1772 Seattle, WA 98124 1773 USA 1775 Email: fltemplin@acm.org 1777 Tony Whyman 1778 MWA Ltd c/o Inmarsat Global Ltd 1779 99 City Road 1780 London EC1Y 1AX 1781 England 1783 Email: tony.whyman@mccallumwhyman.com