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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 Updates: rfc4193, rfc4291, rfc4443, A. Whyman 5 rfc8201 (if approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track August 27, 2020 7 Expires: February 28, 2021 9 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-28 13 Abstract 15 Mobile nodes (e.g., aircraft of various configurations, terrestrial 16 vehicles, seagoing vessels, enterprise wireless devices, etc.) 17 communicate with networked correspondents over multiple access 18 network data links and configure mobile routers to connect end user 19 networks. A multilink interface specification is therefore needed 20 for coordination with the network-based mobility service. This 21 document specifies the transmission of IPv6 packets over Overlay 22 Multilink Network (OMNI) Interfaces. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on February 28, 2021. 41 Copyright Notice 43 Copyright (c) 2020 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 7 62 5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 11 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 13 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 14 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 14 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 15 67 9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 16 68 9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 18 69 9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 19 70 9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 19 71 9.1.3. ifIndex-tuple (Type 1) . . . . . . . . . . . . . . . 19 72 9.1.4. ifIndex-tuple (Type 2) . . . . . . . . . . . . . . . 22 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 22 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 23 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 24 76 9.1.8. Geo Coordiantes . . . . . . . . . . . . . . . . . . . 24 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 25 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 25 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 25 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 26 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 27 82 12.1. Multihop Router Discovery . . . . . . . . . . . . . . . 30 83 12.2. MS-Register and MS-Release List Processing . . . . . . . 31 84 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 33 85 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 33 86 15. Detecting and Responding to MSE Failures . . . . . . . . . . 33 87 16. Transition Considerations . . . . . . . . . . . . . . . . . . 34 88 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 34 89 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 35 90 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 91 20. Security Considerations . . . . . . . . . . . . . . . . . . . 37 92 21. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 38 93 22. References . . . . . . . . . . . . . . . . . . . . . . . . . 39 94 22.1. Normative References . . . . . . . . . . . . . . . . . . 39 95 22.2. Informative References . . . . . . . . . . . . . . . . . 40 96 Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference 97 Encoding . . . . . . . . . . . . . . . . . . . . . . 44 98 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 46 99 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 47 100 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 48 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50 103 1. Introduction 105 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 106 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 107 etc.) often have multiple data links for communicating with networked 108 correspondents. These data links may have diverse performance, cost 109 and availability properties that can change dynamically according to 110 mobility patterns, flight phases, proximity to infrastructure, etc. 111 MNs coordinate their data links in a discipline known as "multilink", 112 in which a single virtual interface is configured over the underlying 113 data links. 115 The MN configures a virtual interface (termed the "Overlay Multilink 116 Network (OMNI) interface") as a thin layer over the underlying Access 117 Network (ANET) interfaces. The OMNI interface is therefore the only 118 interface abstraction exposed to the IPv6 layer and behaves according 119 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 120 while underlying interfaces appear as link layer communication 121 channels in the architecture. The OMNI interface connects to a 122 virtual overlay service known as the "OMNI link". The OMNI link 123 spans one or more Internetworks that may include private-use 124 infrastructures and/or the global public Internet itself. 126 Each MN receives a Mobile Network Prefix (MNP) for numbering 127 downstream-attached End User Networks (EUNs) independently of the 128 access network data links selected for data transport. The MN 129 performs router discovery over the OMNI interface (i.e., similar to 130 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 131 behalf of its EUNs. The router discovery process is iterated over 132 each of the OMNI interface's underlying interfaces in order to 133 register per-link parameters (see Section 12). 135 The OMNI interface provides a multilink nexus for exchanging inbound 136 and outbound traffic via the correct underlying interface(s). The 137 IPv6 layer sees the OMNI interface as a point of connection to the 138 OMNI link. Each OMNI link has one or more associated Mobility 139 Service Prefixes (MSPs) from which OMNI link MNPs are derived. If 140 there are multiple OMNI links, the IPv6 layer will see multiple OMNI 141 interfaces. 143 MNs may connect to multiple distinct OMNI links by configuring 144 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 145 interface is configured over a set of underlying interfaces and 146 provides a nexus for Safety-Based Multilink (SBM) operation. The IP 147 layer selects an OMNI interface based on SBM routing considerations, 148 then the selected interface applies Performance-Based Multilink (PBM) 149 to select the correct underlying interface. Applications can apply 150 Segment Routing [RFC8402] to select independent SBM topologies for 151 fault tolerance. 153 The OMNI interface interacts with a network-based Mobility Service 154 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 155 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 156 track MN movements and represent their MNPs in a global routing or 157 mapping system. 159 This document specifies the transmission of IPv6 packets [RFC8200] 160 and MN/MS control messaging over OMNI interfaces. 162 2. Terminology 164 The terminology in the normative references applies; especially, the 165 terms "link" and "interface" are the same as defined in the IPv6 166 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 167 Also, the Protocol Constants defined in Section 10 of [RFC4861] are 168 used in their same format and meaning in this document. The terms 169 "All-Routers multicast", "All-Nodes multicast" and "Subnet-Router 170 anycast" are the same as defined in [RFC4291] (with Link-Local scope 171 assumed). 173 The following terms are defined within the scope of this document: 175 Mobile Node (MN) 176 an end system with a mobile router having multiple distinct 177 upstream data link connections that are grouped together in one or 178 more logical units. The MN's data link connection parameters can 179 change over time due to, e.g., node mobility, link quality, etc. 180 The MN further connects a downstream-attached End User Network 181 (EUN). The term MN used here is distinct from uses in other 182 documents, and does not imply a particular mobility protocol. 184 End User Network (EUN) 185 a simple or complex downstream-attached mobile network that 186 travels with the MN as a single logical unit. The IPv6 addresses 187 assigned to EUN devices remain stable even if the MN's upstream 188 data link connections change. 190 Mobility Service (MS) 191 a mobile routing service that tracks MN movements and ensures that 192 MNs remain continuously reachable even across mobility events. 193 Specific MS details are out of scope for this document. 195 Mobility Service Endpoint (MSE) 196 an entity in the MS (either singular or aggregate) that 197 coordinates the mobility events of one or more MN. 199 Mobility Service Prefix (MSP) 200 an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the 201 rest of the Internetwork by the MS, and from which more-specific 202 Mobile Network Prefixes (MNPs) are derived. 204 Mobile Network Prefix (MNP) 205 a longer IPv6 prefix taken from an MSP (e.g., 206 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate 207 the MNP to devices located in EUNs. 209 Access Network (ANET) 210 a data link service network (e.g., an aviation radio access 211 network, satellite service provider network, cellular operator 212 network, wifi network, etc.) that connects MNs. Physical and/or 213 data link level security between the MN and ANET are assumed. 215 Access Router (AR) 216 a first-hop router in the ANET for connecting MNs to 217 correspondents in outside Internetworks. 219 ANET interface 220 a MN's attachment to a link in an ANET. 222 Internetwork (INET) 223 a connected network region with a coherent IP addressing plan that 224 provides transit forwarding services for ANET MNs and INET 225 correspondents. Examples include private enterprise networks, 226 ground domain aviation service networks and the global public 227 Internet itself. 229 INET interface 230 a node's attachment to a link in an INET. 232 OMNI link 233 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 234 over one or more INETs and their connected ANETs. An OMNI link 235 can comprise multiple INET segments joined by bridges the same as 236 for any link; the addressing plans in each segment may be mutually 237 exclusive and managed by different administrative entities. 239 OMNI interface 240 a node's attachment to an OMNI link, and configured over one or 241 more underlying ANET/INET interfaces. 243 OMNI Link-Local Address (LLA) 244 a link local IPv6 address per [RFC4291] constructed as specified 245 in Section 7. 247 OMNI Unique-Local Address (ULA) 248 a unique local IPv6 address per [RFC4193] constructed as specified 249 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 250 and vice-versa. 252 OMNI Option 253 an IPv6 Neighbor Discovery option providing multilink parameters 254 for the OMNI interface as specified in Section 9. 256 Multilink 257 an OMNI interface's manner of managing diverse underlying data 258 link interfaces as a single logical unit. The OMNI interface 259 provides a single unified interface to upper layers, while 260 underlying data link selections are performed on a per-packet 261 basis considering factors such as DSCP, flow label, application 262 policy, signal quality, cost, etc. Multilinking decisions are 263 coordinated in both the outbound (i.e. MN to correspondent) and 264 inbound (i.e., correspondent to MN) directions. 266 L2 267 The second layer in the OSI network model. Also known as "layer- 268 2", "link-layer", "sub-IP layer", "data link layer", etc. 270 L3 271 The third layer in the OSI network model. Also known as "layer- 272 3", "network-layer", "IPv6 layer", etc. 274 underlying interface 275 an ANET/INET interface over which an OMNI interface is configured. 276 The OMNI interface is seen as a L3 interface by the IP layer, and 277 each underlying interface is seen as a L2 interface by the OMNI 278 interface. 280 Mobility Service Identification (MSID) 281 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 282 as specified in Section 7. 284 Safety-Based Multilink (SBM) 285 A means for ensuring fault tolerance through redundancy by 286 connecting multiple independent OMNI interfaces to independent 287 routing topologies (i.e., multiple independent OMNI links). 289 Performance Based Multilink (PBM) 290 A means for selecting underlying interface(s) for packet 291 trasnmission and reception within a single OMNI interface. 293 3. Requirements 295 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 296 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 297 "OPTIONAL" in this document are to be interpreted as described in BCP 298 14 [RFC2119][RFC8174] when, and only when, they appear in all 299 capitals, as shown here. 301 An implementation is not required to internally use the architectural 302 constructs described here so long as its external behavior is 303 consistent with that described in this document. 305 4. Overlay Multilink Network (OMNI) Interface Model 307 An OMNI interface is a MN virtual interface configured over one or 308 more underlying interfaces, which may be physical (e.g., an 309 aeronautical radio link) or virtual (e.g., an Internet or higher- 310 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 311 with the MS through IPv6 ND message exchanges. The MN uses the MNP 312 to construct a unique OMNI LLA through the algorithmic derivation 313 specified in Section 7 and assigns the LLA to the OMNI interface. 315 The OMNI interface architectural layering model is the same as in 316 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 317 therefore sees the OMNI interface as a single L3 interface with 318 multiple underlying interfaces that appear as L2 communication 319 channels in the architecture. 321 +----------------------------+ 322 | Upper Layer Protocol | 323 Session-to-IP +---->| | 324 Address Binding | +----------------------------+ 325 +---->| IP (L3) | 326 IP Address +---->| | 327 Binding | +----------------------------+ 328 +---->| OMNI Interface | 329 Logical-to- +---->| (OMNI LLA) | 330 Physical | +----------------------------+ 331 Interface +---->| L2 | L2 | | L2 | 332 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 333 +------+------+ +------+ 334 | L1 | L1 | | L1 | 335 | | | | | 336 +------+------+ +------+ 338 Figure 1: OMNI Interface Architectural Layering Model 340 The OMNI virtual interface model gives rise to a number of 341 opportunities: 343 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 344 Address Detection (DAD) or Muticast Listener Discovery (MLD) 345 messaging is necessary. 347 o ANET interfaces do not require any L3 addresses (i.e., not even 348 link-local) in environments where communications are coordinated 349 entirely over the OMNI interface. (An alternative would be to 350 also assign the same OMNI LLA to all ANET interfaces.) 352 o as ANET interface properties change (e.g., link quality, cost, 353 availability, etc.), any active ANET interface can be used to 354 update the profiles of multiple additional ANET interfaces in a 355 single message. This allows for timely adaptation and service 356 continuity under dynamically changing conditions. 358 o coordinating ANET interfaces in this way allows them to be 359 represented in a unified MS profile with provisions for mobility 360 and multilink operations. 362 o exposing a single virtual interface abstraction to the IPv6 layer 363 allows for multilink operation (including QoS based link 364 selection, packet replication, load balancing, etc.) at L2 while 365 still permitting L3 traffic shaping based on, e.g., DSCP, flow 366 label, etc. 368 o L3 sees the OMNI interface as a point of connection to the OMNI 369 link; if there are multiple OMNI links (i.e., multiple MS's), L3 370 will see multiple OMNI interfaces. 372 o Multiple independent OMNI interfaces can be used for increased 373 fault tolerance through Safety-Based Multilink (SBM), with 374 Performance-Based Multilink (PBM) applied within each interface. 376 Other opportunities are discussed in [RFC7847]. 378 Figure 2 depicts the architectural model for a MN connecting to the 379 MS via multiple independent ANETs. When an underlying interface 380 becomes active, the MN's OMNI interface sends native (i.e., 381 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 382 ND messages traverse the ground domain ANETs until they reach an 383 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 384 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 385 returns an IPv6 ND message response to the MN. IPv6 ND messages 386 traverse the ANET at layer 2; hence, the Hop Limit is not 387 decremented. 389 +--------------+ 390 | MN | 391 +--------------+ 392 |OMNI interface| 393 +----+----+----+ 394 +--------|IF#1|IF#2|IF#n|------ + 395 / +----+----+----+ \ 396 / | \ 397 / <---- Native | IP ----> \ 398 v v v 399 (:::)-. (:::)-. (:::)-. 400 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 401 `-(::::)-' `-(::::)-' `-(::::)-' 402 +----+ +----+ +----+ 403 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 404 . +-|--+ +-|--+ +-|--+ . 405 . | | | 406 . v v v . 407 . <----- Encapsulation -----> . 408 . . 409 . +-----+ (:::)-. . 410 . |MSE#2| .-(::::::::) +-----+ . 411 . +-----+ .-(::: INET :::)-. |MSE#m| . 412 . (::::: Routing ::::) +-----+ . 413 . `-(::: System :::)-' . 414 . +-----+ `-(:::::::-' . 415 . |MSE#1| +-----+ +-----+ . 416 . +-----+ |MSE#3| |MSE#4| . 417 . +-----+ +-----+ . 418 . . 419 . . 420 . <----- Worldwide Connected Internetwork ----> . 421 ........................................................... 423 Figure 2: MN/MS Coordination via Multiple ANETs 425 After the initial IPv6 ND message exchange, the MN can send and 426 receive unencapsulated IPv6 data packets over the OMNI interface. 427 OMNI interface multilink services will forward the packets via ARs in 428 the correct underlying ANETs. The AR encapsulates the packets 429 according to the capabilities provided by the MS and forwards them to 430 the next hop within the worldwide connected Internetwork via optimal 431 routes. 433 OMNI links span one or more underlying Internetwork via a mid-layer 434 overlay encapsulation based on [RFC2473] and using [RFC4193] 435 addressing. Each OMNI link corresponds to a different overlay 436 (differentiated by an address codepoint) which may be carried over a 437 completely separate underlying topology. Each MN can facilitate SBM 438 by connecting to multiple OMNI links using a distinct OMNI interface 439 for each link. 441 5. Maximum Transmission Unit (MTU) and Fragmentation 443 The OMNI interface observes the link nature of tunnels, including the 444 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 445 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 446 The OMNI interface is configured over one or more underlying 447 interfaces that may have diverse MTUs. 449 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 450 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 451 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 452 not permitted to perform fragmentation even though the destination is 453 required to reassemble more. The network therefore MUST forward 454 packets of at least 1280 bytes without generating an IPv6 Path MTU 455 Discovery (PMTUD) Packet Too Big (PTB) message [RFC8201]. 457 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 458 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 459 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 460 minimum IPv4 path MTU is 576 bytes since routers on the path are 461 permitted to perform fragmentation and the destination is required to 462 reassemble at least that much. The DF bit in the IPv4 encapsulation 463 headers of packets sent over IPv4 underlying interfaces therefore 464 MUST be set to 0. 466 The OMNI interface configures both an MTU and MRU of 9180 bytes 467 [RFC2492]; the size is therefore not a reflection of the underlying 468 interface MTUs, but rather determines the largest packet the OMNI 469 interface can forward or reassemble. The OMNI interface accommodates 470 packets as large as the OMNI interface MTU while generating IPv6 Path 471 MTU Discovery (PMTUD) Packet Too Big (PTB) messages [RFC8201] as 472 necessary (see below). For original IPv4 packets with DF=0, the IP 473 layer performs IPv4 fragmentation according to the OMNI interface MTU 474 if necessary to admit the fragments into the interface. The 475 interface may then internally apply further IPv4 fragmentation 476 according to the underlying interface MTU prior to encapsulation to 477 ensure that the fragments are delivered to the final destination. 479 OMNI interfaces internally employ OMNI link adaptation when necessary 480 by inserting a mid-layer IPv6 header between the inner IP packet and 481 any outer IP encapsulation headers per [RFC2473] then performing 482 fragmentation on the mid-layer IPv6 packet. The OMNI interface can 483 instead return internally-generated PTB messages for packets admitted 484 into the interface that it deems too large (e.g., according to link 485 performance characteristics, reassembly congestion, etc.) while 486 either dropping or forwarding the packet. The OMNI interface 487 performs PMTUD even if the destination appears to be on the same link 488 since an OMNI link node on the path may return a PTB. This ensures 489 that the path MTU is adaptive and reflects the current path used for 490 a given data flow. 492 OMNI interfaces perform encapsulation and fragmentation/reassembly 493 with respect to both the minimum IPv6 and IPv4 path MTUs as follows: 495 o When an OMNI interface sends a packet toward a final destination 496 via an ANET peer, it sends without OMNI link encapsulation if the 497 packet is no larger than the underlying interface MTU. Otherwise, 498 it inserts an IPv6 header with source address set to the node's 499 own OMNI Unique Local Address (ULA) (see: Section 8) and 500 destination set to the OMNI ULA of the ANET peer. The OMNI 501 interface then uses IPv6 fragmentation to break the packet into a 502 minimum number of non-overlapping fragments, where the largest 503 fragment size is determined by the underlying interface MTU. The 504 OMNI interface then sends the fragments to the ANET peer, which 505 reassembles before forwarding toward the final destination. 507 o When an OMNI interface sends a packet toward a final destination 508 via an INET interface, it sends packets (including any outer-layer 509 INET encapsulations) no larger than the minimum INET path MTU 510 without OMNI link adaptation if the destination is reached via an 511 INET address within the same OMNI link segment. Otherwise, it 512 inserts an IPv6 header with source address set to the node's OMNI 513 ULA, destination set to the ULA of the next hop OMNI node toward 514 the final destination and (if necessary) with a Segment Routing 515 Header with the remaining Segment IDs on the path to the final 516 destination. The OMNI interface then uses IPv6 fragmentation to 517 break the encapsulated packet into a minimum number of non- 518 overlapping fragments, where the largest fragment size (including 519 both the OMNI and outer-layer INET encapsulations) is the minimum 520 INET path MTU, and the smallest fragment size is no smaller than 521 half the minimum IPv4 path MTU (i.e., 288 bytes). The OMNI 522 interface then encapsulates the fragments in any INET headers and 523 sends them to the OMNI link neighbor, which reassembles before 524 forwarding toward the final destination. 526 OMNI interfaces unconditionally drop all OMNI link fragments received 527 from an INET peer that are smaller than 288 bytes. In order to set 528 the correct context for reassembly, the OMNI interface that inserts 529 the IPv6 header MUST also be the one that inserts the IPv6 Fragment 530 Header Identification value. While not strictly required, sending 531 all fragments of the same fragmented OMNI-encapsulated packet 532 consecutively over the same underlying interface with minimal inter- 533 fragment delay may increase the likelihood of successful reassembly. 535 Note that the OMNI interface can forward large packets via 536 encapsulation and fragmentation while at the same time returning 537 "advisory" PTB messages (subject to rate limiting). The receiving 538 node that performs reassembly can also send advisory PTB messages if 539 reassembly conditions become unfavorable. The OMNI interface can 540 therefore continuously forward large packets without loss while 541 returning advisory PTB messages recommending a smaller size. 543 OMNI interfaces that send advisory PTB messages set the ICMPv6 544 message header Code field to the value 1. Receiving nodes that 545 recognize the code reduce their estimate of the path MTU the same as 546 for ordinary "diagnistic" PTBs but do not regard the message as a 547 loss indication. Nodes that do not recognize the code treat the 548 message the same as a diagnostic PTB, but should heed the 549 retransmission advice given in [RFC8201]. This document therefore 550 updates [RFC4443] and [RFC8201]. 552 5.1. Fragmentation Security Implications 554 As discussed in Section 3.7 of [I-D.ietf-intarea-frag-fragile], there 555 are four basic threats concerning IPv6 fragmentation; each of which 556 is addressed by a suitable mitigation as follows: 558 1. Overlapping fragment attacks - reassembly of overlapping 559 fragments is forbidden by [RFC8200]; therefore, this threat does 560 not apply to OMNI interfaces. 562 2. Resource exhaustion attacks - this threat is mitigated by 563 providing a sufficiently large OMNI interface reassembly cache 564 and instituting "fast discard" of incomplete reassemblies that 565 may be part of a buffer exhaustion attack. The reassembly cache 566 should be sufficiently large so that a sustained attack does not 567 cause excessive loss of good reassemblies but not so large that 568 (timer-based) data structure management becomes computationally 569 expensive. 571 3. Attacks based on predictable fragment identification values - 572 this threat is mitigated by selecting a suitably random ID value 573 per [RFC7739]. 575 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 576 threat is mitigated by disallowing "tiny fragments" per the OMNI 577 interface fragmentation procedures specified above. 579 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 580 ID) field with only 65535 unique values such that at high data rates 581 the field could wrap and apply to new packets while the fragments of 582 old packets using the same ID are still alive in the network 583 [RFC4963]. However, since the largest OMNI fragment that will be 584 sent via an IPv4 INET path is 576 bytes any IPv4 fragmentation would 585 occur only on links with an IPv4 MTU smaller than this size, and 586 [RFC3819] recommendations suggest that such links will have low data 587 rates. Since IPv6 provides a 32-bit Identification value, IP ID 588 wraparound at high data rates is not a concern for IPv6 589 fragmentation. 591 6. Frame Format 593 The OMNI interface transmits IPv6 packets according to the native 594 frame format of each underlying interface. For example, for 595 Ethernet-compatible interfaces the frame format is specified in 596 [RFC2464], for aeronautical radio interfaces the frame format is 597 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 598 Manual), for tunnels over IPv6 the frame format is specified in 599 [RFC2473], etc. 601 7. Link-Local Addresses (LLAs) 603 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 604 LLAs") as follows: 606 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 607 within the least-significant 112 bits of the IPv6 link-local 608 prefix fe80::/16. The Prefix Length is determined by adding 16 to 609 the length of the embedded MNP. For example, for the MNP 610 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 611 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 612 link-local address format specified in Section 2.5.6 of [RFC4291] 613 by defining a use for bits 11 - 63. 615 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 616 i.e., the most significant 16 bits of the prefix fe80::/16, 617 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 618 32bit IPv4 address/prefix. The Prefix Length is determined by 619 adding 96 to the length of the embedded IPv4 address/prefix. For 620 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 621 fe80::ffff:192.0.2.0/120 (also written as 622 fe80::ffff:c000:0200/120). 624 o MS OMNI LLAs are assigned to ARs and MSEs from the range 625 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 626 of the LLA includes a unique integer "MSID" value between 627 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 628 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 629 determined by adding 96 to the MSID prefix length. For example, 630 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 631 Prefix Length is set to 112 and the LLA is written as 632 fe80::1000:2000/112. Finally, the MSID 0x00000000 corresponds to 633 the link-local Subnet-Router anycast address (fe80::) [RFC4291], 634 and the MSID range 0xff000000 through 0xffffffff is reserved for 635 future use. 637 o The OMNI LLA range fe80::/32 is used as the service prefix for the 638 address format specified in Section 4 of [RFC4380] (see Section 17 639 for further discussion). 641 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 642 MNPs can be allocated from that block ensuring that there is no 643 possibility for overlap between the above OMNI LLA constructs. 645 Since MN OMNI LLAs are based on the distribution of administratively 646 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 647 through administrative assignment, OMNI interfaces set the 648 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 650 8. Unique-Local Addresses (ULAs) 652 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 653 [RFC4193] as the source and destination addresses in OMNI link IPv6 654 encapsulation headers. This document currently assumes use of the 655 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 656 (however, see the note at the end of this section). 658 Each OMNI link instance is identified by bits 10-15 of the OMNI 659 service prefix fc80::/10. For example, OMNI ULAs associated with 660 instance 0 are configured from the prefix fc80::/16, instance 1 from 661 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 662 their associated prefix lengths are configured in one-to-one 663 correspondence with OMNI LLAs through stateless prefix translation. 664 For example, for OMNI link instance fc80::/16: 666 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 667 fc80:2001:db8:1:2::/80 669 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 670 fc80::ffff:192.0.2.0/120 672 o the OMNI ULA corresponding to fe80::1000/112 is simply 673 fc80::1000/112 675 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 677 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 678 link instance, e.g., the OMNI interface connected to instance 3 679 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 680 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 681 the local routing system so that applications can direct traffic 682 according to SBM requirements. 684 The OMNI ULA presents an IPv6 address format that is routable within 685 the OMNI link routing system and can be used to convey link-scoped 686 messages across multiple hops using IPv6 encapsulation [RFC2473]. 687 The OMNI link extends across one or more underling Internetworks to 688 include all ARs and MSEs. All MNs are also considered to be 689 connected to the OMNI link, however OMNI link encapsulation is 690 omitted over ANET links when possible to conserve bandwidth (see: 691 Section 11). 693 The OMNI link can be subdivided into "segments" that often correspond 694 to different administrative domains or physical partitions. OMNI 695 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 696 support efficient packet forwarding to destinations located in other 697 OMNI link segments. A full discussion of Segment Routing over the 698 OMNI link appears in [I-D.templin-intarea-6706bis]. 700 NOTE: An alternative to the application of ULAs as discussed in this 701 document would be to re-purpose the deprectated IPv6 Site-Local 702 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 703 SLAs would be a more natural fit since both LLA and SLA prefix 704 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 705 single bit setting, and LLAs and SLAs can be unambiguously allocated 706 in one-to-one correspondence with one another. Re-purposing SLAs 707 would also make good use of an otherwise-wasted address range that 708 has been "parked" since the 2004 deprecation. However, moving from 709 ULAs to SLAs would require an IETF standards action acknowledging 710 this document as obsoleting [RFC3879] and updating [RFC4291]. The 711 authors therefore defer to IETF consensus as to the proper way 712 forward. 714 9. Address Mapping - Unicast 716 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 717 state and use the link-local address format specified in Section 7. 718 IPv6 Neighbor Discovery (ND) [RFC4861] messages on MN OMNI interfaces 719 observe the native Source/Target Link-Layer Address Option (S/TLLAO) 720 formats of the underlying interfaces (e.g., for Ethernet the S/TLLAO 721 is specified in [RFC2464]). 723 MNs such as aircraft typically have many wireless data link types 724 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 725 etc.) with diverse performance, cost and availability properties. 726 The OMNI interface would therefore appear to have multiple L2 727 connections, and may include information for multiple underlying 728 interfaces in a single IPv6 ND message exchange. 730 OMNI interfaces use an IPv6 ND option called the "OMNI option" 731 formatted as shown in Figure 3: 733 0 1 2 3 734 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 1 735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 | Type | Length | Prefix Length | Reserved | 737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 738 | | 739 ~ Sub-Options ~ 740 | | 741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 743 Figure 3: OMNI Option Format 745 In this format: 747 o Type is set to TBD. If multiple OMNI option instances appear in 748 the same IPv6 ND message, the first instance is processed and all 749 other instances are ignored. 751 o Length is set to the number of 8 octet blocks in the option. 753 o Prefix Length is determines the length of prefix to be applied to 754 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 755 MS, Prefix Length is the length that the MN is requesting or 756 asserting to the MS. For IPv6 ND messages sent from the MS to the 757 MN, Prefix Length indicates the length that the MS is granting to 758 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 759 Length indicates the length associated with the target MN that is 760 subject of the ND message. 762 o Reserved is set to the value '0' on transmission and ignored on 763 reception. 765 o Sub-Options is a Variable-length field, of length such that the 766 complete OMNI Option is an integer multiple of 8 octets long. 767 Contains one or more options, as described in Section 9.1. 769 9.1. Sub-Options 771 The OMNI option includes zero or more Sub-Options. Each consecutive 772 Sub-Option is concatenated immediately after its predecessor. All 773 Sub-Options except Pad1 (see below) are type-length-value (TLV) 774 encoded in the following format: 776 0 1 2 777 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 5 778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 779 | Sub-Type | Sub-length | Sub-Option Data ... 780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 782 Figure 4: Sub-Option Format 784 o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub- 785 Options defined in this document are: 787 Option Name Sub-Type 788 Pad1 0 789 PadN 1 790 ifIndex-tuple (Type 1) 2 791 ifIndex-tuple (Type 2) 3 792 MS-Register 4 793 MS-Release 5 794 Network Access Identifier 6 795 Geo Coordinates 7 796 DHCP Unique Identifier (DUID) 8 798 Figure 5 800 Sub-Types 253 and 254 are reserved for experimentation, as 801 recommended in [RFC3692]. 803 o Sub-Length is a 1-byte field that encodes the length of the Sub- 804 Option Data, in bytes 806 o Sub-Option Data is a byte string with format determined by Sub- 807 Type 809 During processing, unrecognized Sub-Options are ignored and the next 810 Sub-Option processed until the end of the OMNI option is reached. 812 The following Sub-Option types and formats are defined in this 813 document: 815 9.1.1. Pad1 817 0 818 0 1 2 3 4 5 6 7 819 +-+-+-+-+-+-+-+-+ 820 | Sub-Type=0 | 821 +-+-+-+-+-+-+-+-+ 823 Figure 6: Pad1 825 o Sub-Type is set to 0. If multiple instances appear in the same 826 OMNI option all are processed. 828 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 829 consists of a single zero octet). 831 9.1.2. PadN 833 0 1 2 834 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 5 835 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 836 | Sub-Type=1 |Sub-length=N-2 | N-2 padding bytes ... 837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 839 Figure 7: PadN 841 o Sub-Type is set to 1. If multiple instances appear in the same 842 OMNI option all are processed. 844 o Sub-Length is set to N-2 being the number of padding bytes that 845 follow. 847 o Sub-Option Data consists of N-2 zero-valued octets. 849 9.1.3. ifIndex-tuple (Type 1) 850 0 1 2 3 851 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 1 852 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 853 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 855 | Provider ID | Link |S|I|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| 856 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 857 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 859 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 860 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 861 |P32|P33|P34|P35|P36|P37|P38|P39| ... 862 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 864 Figure 8: ifIndex-tuple (Type 1) 866 o Sub-Type is set to 2. If multiple instances appear in the same 867 OMNI option all are processed. 869 o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that 870 follow). 872 o Sub-Option Data contains an "ifIndex-tuple" (Type 1) encoded as 873 follows (note that the first four bytes must be present): 875 * ifIndex is set to an 8-bit integer value corresponding to a 876 specific underlying interface. OMNI options MAY include 877 multiple ifIndex-tuples, and MUST number each with an ifIndex 878 value between '1' and '255' that represents a MN-specific 8-bit 879 mapping for the actual ifIndex value assigned to the underlying 880 interface by network management [RFC2863] (the ifIndex value 881 '0' is reserved for use by the MS). Multiple ifIndex-tuples 882 with the same ifIndex value MAY appear in the same OMNI option. 884 * ifType is set to an 8-bit integer value corresponding to the 885 underlying interface identified by ifIndex. The value 886 represents an OMNI interface-specific 8-bit mapping for the 887 actual IANA ifType value registered in the 'IANAifType-MIB' 888 registry [http://www.iana.org]. 890 * Provider ID is set to an OMNI interface-specific 8-bit ID value 891 for the network service provider associated with this ifIndex. 893 * Link encodes a 4-bit link metric. The value '0' means the link 894 is DOWN, and the remaining values mean the link is UP with 895 metric ranging from '1' ("lowest") to '15' ("highest"). 897 * S is set to '1' if this ifIndex-tuple corresponds to the 898 underlying interface that is the source of the ND message. Set 899 to '0' otherwise. 901 * I is set to '0' ("Simplex") if the index for each singleton 902 Bitmap byte in the Sub-Option Data is inferred from its 903 sequential position (i.e., 0, 1, 2, ...), or set to '1' 904 ("Indexed") if each Bitmap is preceded by an Index byte. 905 Figure 8 shows the simplex case for I set to '0'. For I set to 906 '1', each Bitmap is instead preceded by an Index byte that 907 encodes a value "i" = (0 - 255) as the index for its companion 908 Bitmap as follows: 910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 911 | Index=i | Bitmap(i) |P[*] values ... 912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 914 Figure 9 916 * RSV is set to the value 0 on transmission and ignored on 917 reception. 919 * The remainder of the Sub-Option Data contains N = (0 - 251) 920 bytes of traffic classifier preferences consisting of a first 921 (indexed) Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte 922 blocks of 2-bit P[*] values, followed by a second Bitmap (i), 923 followed by 0-8 blocks of P[*] values, etc. Reading from bit 0 924 to bit 7, the bits of each Bitmap(i) that are set to '1'' 925 indicate the P[*] blocks from the range P[(i*32)] through 926 P[(i*32) + 31] that follow; if any Bitmap(i) bits are '0', then 927 the corresponding P[*] block is instead omitted. For example, 928 if Bitmap(0) contains 0xff then the block with P[00]-P[03], 929 followed by the block with P[04]-P[07], etc., and ending with 930 the block with P[28]-P[31] are included (as shown in Figure 8). 931 The next Bitmap(i) is then consulted with its bits indicating 932 which P[*] blocks follow, etc. out to the end of the Sub- 933 Option. The first 16 P[*] blocks correspond to the 64 934 Differentiated Service Code Point (DSCP) values P[00] - P[63] 935 [RFC2474]. Any additional P[*] blocks that follow correspond 936 to "pseudo-DSCP" traffic classifier values P[64], P[65], P[66], 937 etc. See Appendix A for further discussion and examples. 939 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 940 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 941 preference level for underlying interface selection purposes. 942 Not all P[*] values need to be included in all OMNI option 943 instances of a given ifIndex-tuple. Any P[*] values 944 represented in an earlier OMNI option but omitted in the 945 current OMNI option remain unchanged. Any P[*] values not yet 946 represented in any OMNI option default to "medium". 948 9.1.4. ifIndex-tuple (Type 2) 950 0 1 2 3 951 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 1 952 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 953 | Sub-Type=3 | Sub-length=4+N| ifIndex | ifType | 954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 955 | Provider ID | Link |S|Resvd| ~ 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 957 ~ ~ 958 ~ RFC 6088 Format Traffic Selector ~ 959 ~ ~ 960 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 962 Figure 10: ifIndex-tuple (Type 2) 964 o Sub-Type is set to 3. If multiple instances appear in the same 965 OMNI option all are processed. 967 o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that 968 follow). 970 o Sub-Option Data contains an "ifIndex-tuple" (Type 2) encoded as 971 follows (note that the first four bytes must be present): 973 * ifIndex, ifType, Provider ID, Link and S are set exactly as for 974 Type 1 ifIndex-tuples as specified in Section 9.1.3. 976 * the remainder of the Sub-Option body encodes a variable-length 977 traffic selector formatted per [RFC6088], beginning with the 978 "TS Format" field. 980 9.1.5. MS-Register 981 0 1 2 3 982 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 1 983 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 984 | Sub-Type=4 | Sub-length=4N | MSID[1] (bits 0 - 15) | 985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 986 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 988 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 989 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 990 ... ... ... ... ... ... 991 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 992 | MSID [N] (bits 16 - 32) | 993 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 995 Figure 11: MS-Register Sub-option 997 o Sub-Type is set to 4. If multiple instances appear in the same 998 OMNI option all are processed. However, only the first 5 MS- 999 Register MSIDs encountered (whether in a single instance or 1000 multiple) are retained and all other MSIDs are ignored. 1002 o Sub-Length is set to 4N. 1004 o A list of N 4 octet MSIDs is included in the following 4N octets. 1005 The "wildcard" MSID value '0' in a Router Solicitation (RS) 1006 message MS-Register sub-option requests the recipient to return 1007 the MSID of a nearby MSE in a corresponding Router Advertisement 1008 (RA) response. 1010 9.1.6. MS-Release 1012 0 1 2 3 1013 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 1014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1015 | Sub-Type=5 | Sub-length=4N | MSID[1] (bits 0 - 15) | 1016 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1017 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1019 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1020 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1021 ... ... ... ... ... ... 1022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1023 | MSID [N] (bits 16 - 32) | 1024 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1026 Figure 12: MS-Release Sub-option 1028 o Sub-Type is set to 5. If multiple instances appear in the same 1029 IPv6 OMNI option all are processed. However, only the first 5 MS- 1030 Release MSIDs encountered (whether in a single instance or 1031 multiple) are retained and all other MSIDs are ignored. 1033 o Sub-Length is set to 4N. 1035 o A list of N 4 octet MSIDs is included in the following 4N octets. 1036 The wildcard MSID value '0' is ignored in MS-Release sub-options, 1037 i.e., only non-zero values are processed. 1039 9.1.7. Network Access Identifier (NAI) 1041 0 1 2 3 1042 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 1043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1047 Figure 13: Network Access Identifier (NAI) Sub-option 1049 o Sub-Type is set to 6. If multiple instances appear in the same 1050 OMNI option the first is processed and all others are ignored. 1052 o Sub-Length is set to N. 1054 o A Network Access Identifier (NAI) up to 253 bytes in length is 1055 coded per [RFC7542]. 1057 9.1.8. Geo Coordiantes 1059 0 1 2 3 1060 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 1061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1062 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1063 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1065 Figure 14: Geo Coordinates Sub-option 1067 o Sub-Type is set to 7. If multiple instances appear in the same 1068 OMNI option the first is processed and all others are ignored. 1070 o Sub-Length is set to N. 1072 o A set of Geo Coordinates up to 253 bytes in length (format TBD). 1073 Includes Latitude/Longitude at a minimum; may also include 1074 additional attributes such as altitude, heading, speed, etc.). 1076 9.1.9. DHCP Unique Identifier (DUID) 1078 0 1 2 3 1079 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 1080 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1081 | Sub-Type=7 | Sub-length=N | DUID-Type | 1082 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1083 . . 1084 . type-specific DUID body (variable length) . 1085 . . 1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1088 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1090 o Sub-Type is set to 8. If multiple instances appear in the same 1091 OMNI option the first is processed and all others are ignored. 1093 o Sub-Length is set to N (i.e., the length of the option beginning 1094 with the DUID-Type and continuing to the end of the type-specifc 1095 body). 1097 o DUID-Type is a two-octet field coded in network byte order that 1098 determines the format and contents of the type-specific body 1099 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1100 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1101 which will occur in common operational practice. 1103 o A type-specific DUID body up to 251 bytes in length follows, 1104 formatted according to DUID-type. For example, for type 4 the 1105 body consists of a 128-bit UUID selected according to [RFC6355]. 1107 10. Address Mapping - Multicast 1109 The multicast address mapping of the native underlying interface 1110 applies. The mobile router on board the MN also serves as an IGMP/ 1111 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1112 using the L2 address of the AR as the L2 address for all multicast 1113 packets. 1115 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1116 coordinate with the AR, and ANET L2 elements use MLD snooping 1117 [RFC4541]. 1119 11. Conceptual Sending Algorithm 1121 The MN's IPv6 layer selects the outbound OMNI interface according to 1122 SBM considerations when forwarding data packets from local or EUN 1123 applications to external correspondents. Each OMNI interface 1124 maintains a neighbor cache the same as for any IPv6 interface, but 1125 with additional state for multilink coordination. 1127 After a packet enters the OMNI interface, an outbound underlying 1128 interface is selected based on PBM traffic selectors such as DSCP, 1129 application port number, cost, performance, message size, etc. OMNI 1130 interface multilink selections could also be configured to perform 1131 replication across multiple underlying interfaces for increased 1132 reliability at the expense of packet duplication. 1134 When an OMNI interface sends a packet over a selected outbound 1135 underlying interface, it omits or employs OMNI link adaptation as 1136 necessary as discussed in Section 5. The OMNI interface also 1137 performs encapsulation when the nearest AR is located multiple hops 1138 away as discussed in Section 12.1. 1140 OMNI interface multilink service designers MUST observe the BCP 1141 guidance in Section 15 [RFC3819] in terms of implications for 1142 reordering when packets from the same flow may be spread across 1143 multiple underlying interfaces having diverse properties. 1145 11.1. Multiple OMNI Interfaces 1147 MNs may connect to multiple independent OMNI links concurrently in 1148 support of SBM. Each OMNI interface is distinguished by its Anycast 1149 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1150 separate OMNI interface for each link so that multiple interfaces 1151 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1152 different Anycast OMNI ULA is assigned to each interface, and the MN 1153 injects the service prefixes for the OMNI link instances into the EUN 1154 routing system. 1156 Applications in EUNs can use Segment Routing to select the desired 1157 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1158 written into the IPv6 destination address, and the actual destination 1159 (along with any additional intermediate hops) is written into the 1160 Segment Routing Header. Standard IP routing directs the packets to 1161 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1162 the OMNI interface to be used for transmission to the next hop. When 1163 the MN receives the message, it replaces the IPv6 destination address 1164 with the next hop found in the routing header and transmits the 1165 message over the OMNI interface identified by the Anycast OMNI ULA. 1167 Multiple distinct OMNI links can therefore be used to support fault 1168 tolerance, load balancing, reliability, etc. The architectural model 1169 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1171 12. Router Discovery and Prefix Registration 1173 MNs interface with the MS by sending RS messages with OMNI options 1174 under the assumption that a single AR on the ANET will process the 1175 message and respond. This places a requirement on each ANET, which 1176 may be enforced by physical/logical partitioning, L2 AR beaconing, 1177 etc. The manner in which the ANET ensures single AR coordination is 1178 link-specific and outside the scope of this document (however, 1179 considerations for ANETs that do not provide ARs that recognize the 1180 OMNI option are discussed in Section 17). 1182 For each underlying interface, the MN sends an RS message with an 1183 OMNI option with prefix registration information, ifIndex-tuples, MS- 1184 Register/Release suboptions, and with destination address set to 1185 link-scoped All-Routers multicast (ff02::2) [RFC4291]. Example MSID 1186 discovery methods are given in [RFC5214] and include data link login 1187 parameters, name service lookups, static configuration, a static 1188 "hosts" file, etc. The MN can also send an RS with an MS-Register 1189 suboption that includes a wildcard '0' MSID, i.e., instead of or in 1190 addition to any non-zero MSIDs. When the AR receives an RS with a 1191 wildcard MSID, it selects a nearby MSE (which may be itself) and 1192 returns an RA with the selected MSID in an MS-Register suboption. 1193 The AR selects only a single wildcard MSE (i.e., even if the RS MS- 1194 Register suboption included multiple '0' MSIDs) while also soliciting 1195 the MSEs corresponding to any non-zero MSIDs. 1197 MNs configure OMNI interfaces that observe the properties discussed 1198 in the previous section. The OMNI interface and its underlying 1199 interfaces are said to be in either the "UP" or "DOWN" state 1200 according to administrative actions in conjunction with the interface 1201 connectivity status. An OMNI interface transitions to UP or DOWN 1202 through administrative action and/or through state transitions of the 1203 underlying interfaces. When a first underlying interface transitions 1204 to UP, the OMNI interface also transitions to UP. When all 1205 underlying interfaces transition to DOWN, the OMNI interface also 1206 transitions to DOWN. 1208 When an OMNI interface transitions to UP, the MN sends RS messages to 1209 register its MNP and an initial set of underlying interfaces that are 1210 also UP. The MN sends additional RS messages to refresh lifetimes 1211 and to register/deregister underlying interfaces as they transition 1212 to UP or DOWN. The MN sends initial RS messages over an UP 1213 underlying interface with its OMNI LLA as the source and with 1214 destination set to All-Routers multicast. The RS messages include an 1215 OMNI option per Section 9 with valid prefix registration information, 1216 ifIndex-tuples appropriate for underlying interfaces and MS-Register/ 1217 Release sub-options. 1219 ARs process IPv6 ND messages with OMNI options and act as an MSE 1220 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1221 and create a neighbor cache entry for the MN, then coordinate with 1222 any named MSEs in a manner outside the scope of this document. The 1223 AR returns RA messages with destination address set to the MN OMNI 1224 LLA (i.e., unicast), with source address set to its own OMNI LLA, 1225 with an OMNI option with valid prefix registration information, 1226 ifIndex-tuples, MS-Register/Release sub-options and with any 1227 information for the link that would normally be delivered in a 1228 solicited RA message. The AR sets the RA Cur Hop Limit, M and O 1229 flags, Router Lifetime, Reachable Time and Retrans Timer values, and 1230 includes any necessary options such as: 1232 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1234 o RIOs [RFC4191] with more-specific routes. 1236 o an MTU option that specifies the maximum acceptable packet size 1237 for this ANET interface. 1239 The AR coordinates with each Register/Release MSE then sends unicast 1240 RA responses to the MN without delay (therefore, the IPv6 ND 1241 MAX_RA_DELAY_TIME and MIN_DELAY_BETWEEN_RAS constants for multicast 1242 RAs do not apply). When the MSE processes the OMNI information, it 1243 first validates the prefix registration information then injects/ 1244 withdraws the MNP in the routing/mapping system and caches/discards 1245 the new Prefix Length, MNP and ifIndex-tuples. The MSE then informs 1246 the AR of registration success/failure, and the AR returns an RA 1247 message with an OMNI option per Section 9. The AR MAY also send 1248 periodic and/or event-driven unsolicited RA messages per [RFC4861]. 1250 The AR can combine the information from multiple MSEs into one or 1251 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1252 Each aggregate RA includes an OMNI option with MS-Register/Release 1253 sub-options with the MSEs represented by the aggregate. If an 1254 aggregate is sent, the RA message contents must consistently 1255 represent the combined information advertised by all represented 1256 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1257 address, the MN determines the addresses of the represented MSEs by 1258 examining the MS-Register/Release OMNI sub-options. Since these 1259 values already represent the MSEs for which the AR is acting as a 1260 proxy, OMNI nodes ignore the P(roxy) bit in the RA flags [RFC4389]. 1262 When the MN receives the RA message, it creates an OMNI interface 1263 neighbor cache entry for each MSID that has confirmed MNP 1264 registration via the L2 address of this AR. If the MN connects to 1265 multiple ANETs, it records the additional L2 AR addresses in each 1266 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1267 then manages its underlying interfaces according to their states as 1268 follows: 1270 o When an underlying interface transitions to UP, the MN sends an RS 1271 over the underlying interface with an OMNI option. The OMNI 1272 option contains at least one ifIndex-tuple with values specific to 1273 this underlying interface, and may contain additional ifIndex- 1274 tuples specific to this and/or other underlying interfaces. The 1275 option also includes any Register/Release MSIDs. 1277 o When an underlying interface transitions to DOWN, the MN sends an 1278 RS or unsolicited NA message over any UP underlying interface with 1279 an OMNI option containing an ifIndex-tuple for the DOWN underlying 1280 interface with Link set to '0'. The MN sends an RS when an 1281 acknowledgement is required, or an unsolicited NA when reliability 1282 is not thought to be a concern (e.g., if redundant transmissions 1283 are sent on multiple underlying interfaces). 1285 o When the Router Lifetime for a specific AR nears expiration, the 1286 MN sends an RS over the underlying interface to receive a fresh 1287 RA. If no RA is received, the MN marks the underlying interface 1288 as DOWN. 1290 o When a MN wishes to release from one or more current MSIDs, it 1291 sends an RS or unsolicited NA message over any UP underlying 1292 interfaces with an OMNI option with a Release MSID. Each MSID 1293 then withdraws the MNP from the routing/mapping system and informs 1294 the AR that the release was successful. 1296 o When all of a MNs underlying interfaces have transitioned to DOWN 1297 (or if the prefix registration lifetime expires), any associated 1298 MSEs withdraw the MNP the same as if they had received a message 1299 with a release indication. 1301 The MN is responsible for retrying each RS exchange up to 1302 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1303 seconds until an RA is received. If no RA is received over a an UP 1304 underlying interface, the MN declares this underlying interface as 1305 DOWN. 1307 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1308 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1309 returns an internally-generated RA message as though the message 1310 originated from an IPv6 router. The internally-generated RA message 1311 contains configuration information that is consistent with the 1312 information received from the RAs generated by the MS. Whether the 1313 OMNI interface IPv6 ND messaging process is initiated from the 1314 receipt of an RS message from the IPv6 layer is an implementation 1315 matter. Some implementations may elect to defer the IPv6 ND 1316 messaging process until an RS is received from the IPv6 layer, while 1317 others may elect to initiate the process proactively. 1319 Note: The Router Lifetime value in RA messages indicates the time 1320 before which the MN must send another RS message over this underlying 1321 interface (e.g., 600 seconds), however that timescale may be 1322 significantly longer than the lifetime the MS has committed to retain 1323 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1324 therefore responsible for keeping MS state alive on a shorter 1325 timescale than the MN is required to do on its own behalf. 1327 Note: On multicast-capable underlying interfaces, MNs should send 1328 periodic unsolicited multicast NA messages and ARs should send 1329 periodic unsolicited multicast RA messages as "beacons" that can be 1330 heard by other nodes on the link. If a node fails to receive a 1331 beacon after a timeout value specific to the link, it can initiate a 1332 unicast exchange to test reachability. 1334 12.1. Multihop Router Discovery 1336 On some ANET types (e.g., omni-directional ad-hoc wireless) a MN may 1337 be located multiple hops away from a node which has connectivity to 1338 the nearest ANET/INET service. Forwarding through these multiple 1339 hops would be conducted through the application of a Mobile Ad-hoc 1340 Network (MANET) routing protocol operating across the ANET 1341 interfaces. 1343 A MN located potentially multiple ANET hops away from the nearst AR 1344 prepares an RS message as normal then encapsulates the message in an 1345 IPv6 header with source address set to the ULA corresponding to the 1346 RS LLA source address, and with destination set to site-scoped All- 1347 Routers multicast (ff05::2)[RFC4291]. The MN then sends the 1348 encapsulated RS message via the ANET interface, where it will be 1349 received by zero or more nearby intermediate MNs. 1351 When an intermediate MN that particpates in the MANET routing 1352 protocol receives the encapsulated RS, it forwards the message 1353 according to its (ULA-based) MANET routing tables. This process 1354 repeats iteratively until the RS message is received by an ultimate 1355 MN that is within communications range of an AR, which forwards the 1356 message to the AR. 1358 When the AR receives the RS message, it coordinates with the MS the 1359 same as if the message were received as an ordinary link-local RS, 1360 since the inner Hop Limit will not have been decremented by the MANET 1361 multihop forwarding process. The AR then prepares an RA message with 1362 source address set to its own LLA and destination address set to the 1363 LLA of the original MN, then encapsulates the message in an IPv6 1364 header with source and destination set to the ULAs corresponding to 1365 the inner header. 1367 The AR then forwards the message to an MN within communications 1368 range, which forwards the message according to its MANET routing 1369 tables to an intermediate MN. The MANET forwarding process continues 1370 repetitively until the message is delivered to the original MN, which 1371 decapsulates the message and performs autoconfiguration the same as 1372 if it had received the RA directly from an AR. 1374 Note: An alternate approach to encapsulation of IPv6 ND messages for 1375 multihop forwarding would be to statelessly translate the IPv6 LLAs 1376 into ULAs and forward the messages without encapsulation. This would 1377 violate the [RFC4861] requirement that certain IPv6 ND messages must 1378 use link-local addresses and must not be accepted if received with 1379 Hop Limit less than 255. This document therefore advocates 1380 encapsulation since the overhead is nominal considering the 1381 infrequent nature and small size of IPv6 ND messages. Future 1382 documents may consider encapsulation avoidance through translation 1383 while updating [RFC4861]. 1385 12.2. MS-Register and MS-Release List Processing 1387 When a MN sends an RS message with an OMNI option via an underlying 1388 interface to an AR, the MN must convey its knowledge of its 1389 currently-associated MSIDs. Initially, the MN will have no 1390 associated MSIDs and should therefore include an MS-Register sub- 1391 option with the single MSID value 0 which requests the AR to select 1392 and assign an MSID. The AR will then return an RA message with 1393 source address set to the OMNI LLA corresponding to the selected 1394 MSID. 1396 As the MN activates additional underlying interfaces, it can 1397 optionally include an MS-Register sub-option with MSID value 0, or 1398 with non-zero MSIDs discovered from previous RS/RA exchanges. The MN 1399 will thus eventually begin to learn and manage its currently active 1400 set of MSIDs, and can register with new MSIDs or release from former 1401 MSIDs with each successive RS/RA exchange. As the MN's MSID 1402 constituency grows, it alone is responsible for including or omitting 1403 MSIDs in the MS-Register/Release lists it sends in RS messages. The 1404 inclusion or omission of MSIDs determines the MN's interface to the 1405 MS and defines the manner in which the MS will respond. The only 1406 limiting factor is that the MN should include no more than 5 MSIDs in 1407 each list per each RS message, and should avoid duplication of 1408 entries in each list unless it wants to increase likelihood of 1409 control message delivery. 1411 When an AR receives an RS message sent by a MN with an OMNI option, 1412 the option will contain zero or more MS-Register and MS-Release sub- 1413 options. After processing the OMNI option, the AR will have a list 1414 of zero or more MS-Register and a list of zero or more of MS-Release 1415 MSIDs. The AR then processes the lists as follows: 1417 o For each list, retain the first 5 MSIDs in the list and discard 1418 any additional MSIDs beyond the first 5. 1420 o Next, for each MSID in the MS-Register list, remove all matching 1421 MSIDs from the MS-Release list. 1423 o Next, proceed according to whether the AR's own MSID or the value 1424 0 appears in the MS-Register list as folllows: 1426 * If yes, send an RA message directly back to the MN and send a 1427 proxy copy of the RS message to each additional MSID in the MS- 1428 Register list with the MS-Register/Release lists omitted. 1429 Then, send a uNA message to each MSID in the MS-Release list 1430 with the MS-Register/Release lists omitted and with an ifIndex- 1431 tuple with ifIndex set to 0. 1433 * If no, send a proxy copy of the RS message to each additional 1434 MSID in the MS-Register list with the MS-Register list omitted. 1435 For the first MSID, include the original MS-Release list; for 1436 all other MSIDs, omit the MS-Release list. 1438 Each proxy copy of the RS message will include an OMNI option and 1439 encapsulation header with the ULA of the AR as the source and the ULA 1440 of the register MSID as the destination. When the register MSID 1441 receives the proxy RS message, if the message includes an MS-Release 1442 list the MSID sends a uNA message to each additional MSID in the 1443 list. The register MSID then sends an RA message back to the AR 1444 wrapped in an OMNI encapsulation header with source and destination 1445 addresses reversed, and with RA destination set to the LLA of the MN. 1446 When the AR receives this RA message, it sends a proxy copy of the RA 1447 to the MN. 1449 Each uNA message (whether send by the first-hop AR or by a register 1450 MSID) will include an OMNI option and an encapsulation header with 1451 the ULA of the register MSID as the source and the ULA of the release 1452 MSID as the destination. The uNA informs the release MSID that its 1453 previous relationship with the MN has been released and that the 1454 source of the uNA message is now registered. The release MSID must 1455 then note that the subject MN of the uNA message is now "departed", 1456 and forward any subsequent packets destined to the MN to the register 1457 MSID. 1459 13. Secure Redirection 1461 If the ANET link model is multiple access, the AR is responsible for 1462 assuring that address duplication cannot corrupt the neighbor caches 1463 of other nodes on the link. When the MN sends an RS message on a 1464 multiple access ANET link, the AR verifies that the MN is authorized 1465 to use the address and returns an RA with a non-zero Router Lifetime 1466 only if the MN is authorized. 1468 After verifying MN authorization and returning an RA, the AR MAY 1469 return IPv6 ND Redirect messages to direct MNs located on the same 1470 ANET link to exchange packets directly without transiting the AR. In 1471 that case, the MNs can exchange packets according to their unicast L2 1472 addresses discovered from the Redirect message instead of using the 1473 dogleg path through the AR. In some ANET links, however, such direct 1474 communications may be undesirable and continued use of the dogleg 1475 path through the AR may provide better performance. In that case, 1476 the AR can refrain from sending Redirects, and/or MNs can ignore 1477 them. 1479 14. AR and MSE Resilience 1481 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1482 [RFC5798] configurations so that service continuity is maintained 1483 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1484 the (redundant) ARs is currently providing service, and any service 1485 discontinuity will be limited to the failover time supported by VRRP. 1486 Widely deployed public domain implementations of VRRP are available. 1488 MSEs SHOULD use high availability clustering services so that 1489 multiple redundant systems can provide coordinated response to 1490 failures. As with VRRP, widely deployed public domain 1491 implementations of high availability clustering services are 1492 available. Note that special-purpose and expensive dedicated 1493 hardware is not necessary, and public domain implementations can be 1494 used even between lightweight virtual machines in cloud deployments. 1496 15. Detecting and Responding to MSE Failures 1498 In environments where fast recovery from MSE failure is required, ARs 1499 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1500 manner that parallels Bidirectional Forwarding Detection (BFD) 1501 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1502 react to failures so that cached information is re-established 1503 through alternate paths. Proactive NUD control messaging is carried 1504 only over well-connected ground domain networks (i.e., and not low- 1505 end ANET links such as aeronautical radios) and can therefore be 1506 tuned for rapid response. 1508 ARs perform proactive NUD for MSEs for which there are currently 1509 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1510 of the outage by sending multicast RA messages on the ANET interface. 1511 The AR sends RA messages to MNs via the ANET interface with an OMNI 1512 option with a Release ID for the failed MSE, and with destination 1513 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1515 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1516 by small delays [RFC4861]. Any MNs on the ANET interface that have 1517 been using the (now defunct) MSE will receive the RA messages and 1518 associate with a new MSE. 1520 16. Transition Considerations 1522 When a MN connects to an ANET link for the first time, it sends an RS 1523 message with an OMNI option. If the first hop AR recognizes the 1524 option, it returns an RA with its MS OMNI LLA as the source, the MN 1525 OMNI LLA as the destination, the P(roxy) bit set in the RA flags and 1526 with an OMNI option included. The MN then engages the AR according 1527 to the OMNI link model specified above. If the first hop AR is a 1528 legacy IPv6 router, however, it instead returns an RA message with no 1529 OMNI option and with a non-OMNI unicast source LLA as specified in 1530 [RFC4861]. In that case, the MN engages the ANET according to the 1531 legacy IPv6 link model and without the OMNI extensions specified in 1532 this document. 1534 If the ANET link model is multiple access, there must be assurance 1535 that address duplication cannot corrupt the neighbor caches of other 1536 nodes on the link. When the MN sends an RS message on a multiple 1537 access ANET link with an OMNI LLA source address and an OMNI option, 1538 ARs that recognize the option ensure that the MN is authorized to use 1539 the address and return an RA with a non-zero Router Lifetime only if 1540 the MN is authorized. ARs that do not recognize the option instead 1541 return an RA that makes no statement about the MN's authorization to 1542 use the source address. In that case, the MN should perform 1543 Duplicate Address Detection to ensure that it does not interfere with 1544 other nodes on the link. 1546 An alternative approach for multiple access ANET links to ensure 1547 isolation for MN / AR communications is through L2 address mappings 1548 as discussed in Appendix C. This arrangement imparts a (virtual) 1549 point-to-point link model over the (physical) multiple access link. 1551 17. OMNI Interfaces on the Open Internet 1553 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1554 the open Internet without an OMNI-aware first-hop AR receive RA 1555 messages that do not include an OMNI option, while OMNI interfaces 1556 configured over IPv4-only underlying interfaces do not receive any 1557 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1558 without an OMNI option configure addresses, on-link prefxies, etc. on 1559 the underlying interface that received the RA according to standard 1560 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1561 interfaces configured over IPv4-only underlying interfaces configure 1562 IPv4 address information on the underlying interfaces using 1563 mechanisms such as DHCPv4 [RFC2131]. 1565 OMNI interfaces configured over underlying interfaces that connect to 1566 the open Internet can apply security services such as VPNs to connect 1567 to an MSE or establish a direct link to an MSE through some other 1568 means. In environments where an explicit VPN or direct link may be 1569 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1570 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1571 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1572 other protocol-specific security services can can also be used if 1573 additional authentication is necessary.) 1575 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1576 interfaces send control plane messages to interface with the MS. The 1577 control plane messages must be authenticated while data plane 1578 messages are delivered the same as for ordinary best-effort Internet 1579 traffic with basic source address-based data origin verification. 1580 Data plane communications via OMNI interfaces that connect over the 1581 open Internet without an explicit VPN should therefore employ 1582 transport- or higher-layer security to ensure integrity and/or 1583 confidentiality. 1585 When SEND/CGA are used over an open Internet underlying interfaces, 1586 each OMNI node configures a link-local CGA for use as the source 1587 address of IPv6 ND messages. The node then employs OMNI link 1588 encapsualation and sets the IPv6 source address of the OMNI header to 1589 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1590 the IPv6 ND message OMNI option then apply to the ULA found in the 1591 OMNI header, i.e., and not to the CGA found in the IPv6 ND source 1592 address. 1594 OMNI interfaces in the open Internet are often located behind Network 1595 Address Translators (NATs). The OMNI interface accommodates NAT 1596 traversal using UDP/IP encapsulation and the mechanisms discussed in 1597 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1599 18. Time-Varying MNPs 1601 In some use cases, it is desirable, beneficial and efficient for the 1602 MN to receive a constant MNP that travels with the MN wherever it 1603 moves. For example, this would allow air traffic controllers to 1604 easily track aircraft, etc. In other cases, however (e.g., 1605 intelligent transportation systems), the MN may be willing to 1606 sacrifice a modicum of efficiency in order to have time-varying MNPs 1607 that can be changed every so often to defeat adversarial tracking. 1609 Prefix delegation services such as those discussed in 1610 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1611 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1612 prefixes. In that case, the identity of the MN can be used as a 1613 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1614 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1615 internal networks whenever its MNP (and therefore also its OMNI 1616 address) changes. This should not present a challenge for MNs with 1617 automated network renumbering services, however presents limits for 1618 the durations of ongoing sessions that would prefer to use a constant 1619 address. 1621 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1622 sets the source address of an RS message to fe80:: and includes a 1623 DUID sub-option and a desired Prefix Length value in the RS message 1624 OMNI option. When the first-hop AR receives the RS message, it 1625 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1626 of the requested length then returns an RA message with the OMNI LLA 1627 corresponding to the MNP as the destination address. When the MN 1628 receives the RA message, it provisons the PD to its downstream- 1629 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1630 messaging. 1632 19. IANA Considerations 1634 The IANA is instructed to allocate an official Type number TBD from 1635 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1636 option. Implementations set Type to 253 as an interim value 1637 [RFC4727]. 1639 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1640 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1641 read as follows: 1643 Code Name Reference 1644 --- ---- --------- 1645 0 Diagnostic Packet Too Big [RFC4443] 1646 1 Advisory Packet Too Big [RFCXXXX] 1648 Figure 16: OMNI Option Sub-Type Values 1650 The IANA is instructed to allocate one Ethernet unicast address TBD2 1651 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1652 Address Block - Unicast Use". 1654 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1655 is instructed to create and maintain a new registry entitled "OMNI 1656 option Sub-Type values". Initial values for the OMNI option Sub-Type 1657 values registry are given below; future assignments are to be made 1658 through Expert Review [RFC8126]. 1660 Value Sub-Type name Reference 1661 ----- ------------- ---------- 1662 0 Pad1 [RFCXXXX] 1663 1 PadN [RFCXXXX] 1664 2 ifIndex-tuple (Type 1) [RFCXXXX] 1665 3 ifIndex-tuple (Type 2) [RFCXXXX] 1666 4 MS-Register [RFCXXXX] 1667 5 MS-Release [RFCXXXX] 1668 6 Network Acceess Identifier [RFCXXXX] 1669 7 Geo Coordinates [RFCXXXX] 1670 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1671 9-252 Unassigned 1672 253-254 Experimental [RFCXXXX] 1673 255 Reserved [RFCXXXX] 1675 Figure 17: OMNI Option Sub-Type Values 1677 20. Security Considerations 1679 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1680 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1681 include Nonce and Timestamp options [RFC3971] when transaction 1682 confirmation and/or time synchronization is needed. 1684 OMNI interfaces configured over secured ANET interfaces inherit the 1685 physical and/or link-layer security properties of the connected 1686 ANETs. OMNI interfaces configured over open INET interfaces can use 1687 symmetric securing services such as VPNs or can by some other means 1688 establish a direct link. When a VPN or direct link may be 1689 impractical, however, an asymmetric security service such as SEcure 1690 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1691 Addresses (CGAs) [RFC3972], the authentication option specified in 1692 [RFC4380] or other protocol control message security mechanisms may 1693 be necessary. While the OMNI link protects control plane messaging, 1694 applications must still employ end-to-end transport- or higher-layer 1695 security services to protect the data plane. 1697 The Mobility Service MUST provide strong network layer security for 1698 control plane messages and forwading path integrity for data plane 1699 messages. In one example, the AERO service 1700 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1701 mobility service elements and secures the links in the spanning tree 1702 with network layer security mechanisms such as IPsec [RFC4301] or 1703 Wireguard. Control plane messages are then constrained to travel 1704 only over the secured spanning tree paths and are therefore protected 1705 from attack or eavesdropping. Since data plane messages can travel 1706 over route optimized paths that do not strictly follow the spanning 1707 tree, however, end-to-end transport- or higher-layer security 1708 services are still required. 1710 Security considerations for specific access network interface types 1711 are covered under the corresponding IP-over-(foo) specification 1712 (e.g., [RFC2464], [RFC2492], etc.). 1714 Security considerations for IPv6 fragmentation and reassembly are 1715 discussed in Section 5.1. 1717 21. Acknowledgements 1719 The first version of this document was prepared per the consensus 1720 decision at the 7th Conference of the International Civil Aviation 1721 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1722 2019. Consensus to take the document forward to the IETF was reached 1723 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1724 Attendees and contributors included: Guray Acar, Danny Bharj, 1725 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1726 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1727 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1728 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1729 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1730 Fryderyk Wrobel and Dongsong Zeng. 1732 The following individuals are acknowledged for their useful comments: 1733 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1734 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1735 Skorepa are recognized for their many helpful ideas and suggestions. 1737 This work is aligned with the NASA Safe Autonomous Systems Operation 1738 (SASO) program under NASA contract number NNA16BD84C. 1740 This work is aligned with the FAA as per the SE2025 contract number 1741 DTFAWA-15-D-00030. 1743 22. References 1745 22.1. Normative References 1747 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1748 Requirement Levels", BCP 14, RFC 2119, 1749 DOI 10.17487/RFC2119, March 1997, 1750 . 1752 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1753 "Definition of the Differentiated Services Field (DS 1754 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1755 DOI 10.17487/RFC2474, December 1998, 1756 . 1758 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1759 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1760 DOI 10.17487/RFC3971, March 2005, 1761 . 1763 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1764 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1765 . 1767 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1768 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1769 November 2005, . 1771 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1772 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1773 . 1775 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1776 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1777 2006, . 1779 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1780 Control Message Protocol (ICMPv6) for the Internet 1781 Protocol Version 6 (IPv6) Specification", STD 89, 1782 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1783 . 1785 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1786 ICMPv6, UDP, and TCP Headers", RFC 4727, 1787 DOI 10.17487/RFC4727, November 2006, 1788 . 1790 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1791 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1792 DOI 10.17487/RFC4861, September 2007, 1793 . 1795 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1796 Address Autoconfiguration", RFC 4862, 1797 DOI 10.17487/RFC4862, September 2007, 1798 . 1800 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1801 "Traffic Selectors for Flow Bindings", RFC 6088, 1802 DOI 10.17487/RFC6088, January 2011, 1803 . 1805 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1806 Hosts in a Multi-Prefix Network", RFC 8028, 1807 DOI 10.17487/RFC8028, November 2016, 1808 . 1810 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1811 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1812 May 2017, . 1814 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1815 (IPv6) Specification", STD 86, RFC 8200, 1816 DOI 10.17487/RFC8200, July 2017, 1817 . 1819 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 1820 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 1821 DOI 10.17487/RFC8201, July 2017, 1822 . 1824 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1825 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1826 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1827 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1828 . 1830 22.2. Informative References 1832 [I-D.ietf-intarea-frag-fragile] 1833 Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 1834 and F. Gont, "IP Fragmentation Considered Fragile", draft- 1835 ietf-intarea-frag-fragile-17 (work in progress), September 1836 2019. 1838 [I-D.ietf-intarea-tunnels] 1839 Touch, J. and M. Townsley, "IP Tunnels in the Internet 1840 Architecture", draft-ietf-intarea-tunnels-10 (work in 1841 progress), September 2019. 1843 [I-D.templin-6man-dhcpv6-ndopt] 1844 Templin, F., "A Unified Stateful/Stateless Configuration 1845 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 1846 (work in progress), June 2020. 1848 [I-D.templin-intarea-6706bis] 1849 Templin, F., "Asymmetric Extended Route Optimization 1850 (AERO)", draft-templin-intarea-6706bis-59 (work in 1851 progress), August 2020. 1853 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 1854 Communication Layers", STD 3, RFC 1122, 1855 DOI 10.17487/RFC1122, October 1989, 1856 . 1858 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1859 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1860 . 1862 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 1863 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 1864 . 1866 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 1867 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 1868 . 1870 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1871 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 1872 December 1998, . 1874 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 1875 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 1876 . 1878 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 1879 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 1880 . 1882 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 1883 Considered Useful", BCP 82, RFC 3692, 1884 DOI 10.17487/RFC3692, January 2004, 1885 . 1887 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 1888 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 1889 DOI 10.17487/RFC3810, June 2004, 1890 . 1892 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 1893 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 1894 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 1895 RFC 3819, DOI 10.17487/RFC3819, July 2004, 1896 . 1898 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 1899 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 1900 2004, . 1902 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1903 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 1904 December 2005, . 1906 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 1907 Network Address Translations (NATs)", RFC 4380, 1908 DOI 10.17487/RFC4380, February 2006, 1909 . 1911 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 1912 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 1913 2006, . 1915 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 1916 "Considerations for Internet Group Management Protocol 1917 (IGMP) and Multicast Listener Discovery (MLD) Snooping 1918 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 1919 . 1921 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 1922 "Internet Group Management Protocol (IGMP) / Multicast 1923 Listener Discovery (MLD)-Based Multicast Forwarding 1924 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 1925 August 2006, . 1927 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 1928 Errors at High Data Rates", RFC 4963, 1929 DOI 10.17487/RFC4963, July 2007, 1930 . 1932 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 1933 Advertisement Flags Option", RFC 5175, 1934 DOI 10.17487/RFC5175, March 2008, 1935 . 1937 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1938 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1939 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1940 . 1942 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 1943 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 1944 DOI 10.17487/RFC5214, March 2008, 1945 . 1947 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 1948 RFC 5558, DOI 10.17487/RFC5558, February 2010, 1949 . 1951 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 1952 Version 3 for IPv4 and IPv6", RFC 5798, 1953 DOI 10.17487/RFC5798, March 2010, 1954 . 1956 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1957 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 1958 . 1960 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 1961 DOI 10.17487/RFC6081, January 2011, 1962 . 1964 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 1965 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 1966 DOI 10.17487/RFC6355, August 2011, 1967 . 1969 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 1970 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 1971 2012, . 1973 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 1974 Requirements for IPv6 Customer Edge Routers", RFC 7084, 1975 DOI 10.17487/RFC7084, November 2013, 1976 . 1978 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 1979 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 1980 Boundary in IPv6 Addressing", RFC 7421, 1981 DOI 10.17487/RFC7421, January 2015, 1982 . 1984 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 1985 DOI 10.17487/RFC7542, May 2015, 1986 . 1988 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 1989 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 1990 February 2016, . 1992 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 1993 Support for IP Hosts with Multi-Access Support", RFC 7847, 1994 DOI 10.17487/RFC7847, May 2016, 1995 . 1997 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1998 Writing an IANA Considerations Section in RFCs", BCP 26, 1999 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2000 . 2002 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2003 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2004 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2005 July 2018, . 2007 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2008 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2009 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2010 . 2012 Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference Encoding 2014 Adaptation of the OMNI option Type 1 ifIndex-tuple's traffic 2015 classifier Bitmap to specific Internetworks such as the Aeronautical 2016 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2017 may include link selection preferences based on other traffic 2018 classifiers (e.g., transport port numbers, etc.) in addition to the 2019 existing DSCP-based preferences. Nodes on specific Internetworks 2020 maintain a map of traffic classifiers to additional P[*] preference 2021 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2022 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2024 Implementations use Simplex or Indexed encoding formats for P[*] 2025 encoding in order to encode a given set of traffic classifiers in the 2026 most efficient way. Some use cases may be more efficiently coded 2027 using Simplex form, while others may be more efficient using Indexed. 2028 Once a format is selected for preparation of a single ifIndex-tuple 2029 the same format must be used for the entire Sub-Option. Different 2030 Sub-Options may use different formats. 2032 The following figures show coding examples for various Simplex and 2033 Indexed formats: 2035 0 1 2 3 2036 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 2037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2038 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 2039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2040 | Provider ID | Link |S|0|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| 2041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2042 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2044 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2046 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2048 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2050 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2051 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2053 Figure 18: Example 1: Dense Simplex Encoding 2055 0 1 2 3 2056 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 2057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2058 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 2059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2060 | Provider ID | Link |S|0|RSV| Bitmap(0)=0x00| Bitmap(1)=0x0f| 2061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2062 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2063 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2064 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2065 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2066 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2067 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2068 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2069 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2070 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2072 |Bitmap(10)=0x00| ... 2073 +-+-+-+-+-+-+-+-+-+-+- 2075 Figure 19: Example 2: Sparse Simplex Encoding 2077 0 1 2 3 2078 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 2079 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2080 | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | 2081 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2082 | Provider ID | Link |S|1|RSV| Index = 0x00 | Bitmap = 0x80 | 2083 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2084 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2085 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2086 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2087 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2088 | Bitmap = 0x01 |796|797|798|799| ... 2089 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2091 Figure 20: Example 3: Indexed Encoding 2093 Appendix B. VDL Mode 2 Considerations 2095 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2096 (VDLM2) that specifies an essential radio frequency data link service 2097 for aircraft and ground stations in worldwide civil aviation air 2098 traffic management. The VDLM2 link type is "multicast capable" 2099 [RFC4861], but with considerable differences from common multicast 2100 links such as Ethernet and IEEE 802.11. 2102 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2103 magnitude less than most modern wireless networking gear. Second, 2104 due to the low available link bandwidth only VDLM2 ground stations 2105 (i.e., and not aircraft) are permitted to send broadcasts, and even 2106 so only as compact layer 2 "beacons". Third, aircraft employ the 2107 services of ground stations by performing unicast RS/RA exchanges 2108 upon receipt of beacons instead of listening for multicast RA 2109 messages and/or sending multicast RS messages. 2111 This beacon-oriented unicast RS/RA approach is necessary to conserve 2112 the already-scarce available link bandwidth. Moreover, since the 2113 numbers of beaconing ground stations operating within a given spatial 2114 range must be kept as sparse as possible, it would not be feasible to 2115 have different classes of ground stations within the same region 2116 observing different protocols. It is therefore highly desirable that 2117 all ground stations observe a common language of RS/RA as specified 2118 in this document. 2120 Note that links of this nature may benefit from compression 2121 techniques that reduce the bandwidth necessary for conveying the same 2122 amount of data. The IETF lpwan working group is considering possible 2123 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2125 Appendix C. MN / AR Isolation Through L2 Address Mapping 2127 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2128 unicast link-scoped IPv6 destination address. However, IPv6 ND 2129 messaging should be coordinated between the MN and AR only without 2130 invoking other nodes on the ANET. This implies that MN / AR control 2131 messaging should be isolated and not overheard by other nodes on the 2132 link. 2134 To support MN / AR isolation on some ANET links, ARs can maintain an 2135 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2136 ANETs, this specification reserves one Ethernet unicast address TBD2 2137 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2138 MSADDR is reserved per the assigned numbers authority for the ANET 2139 addressing space. For still other ANETs, MSADDR may be dynamically 2140 discovered through other means, e.g., L2 beacons. 2142 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2143 both multicast and unicast) to MSADDR instead of to an ordinary 2144 unicast or multicast L2 address. In this way, all of the MN's IPv6 2145 ND messages will be received by ARs that are configured to accept 2146 packets destined to MSADDR. Note that multiple ARs on the link could 2147 be configured to accept packets destined to MSADDR, e.g., as a basis 2148 for supporting redundancy. 2150 Therefore, ARs must accept and process packets destined to MSADDR, 2151 while all other devices must not process packets destined to MSADDR. 2152 This model has well-established operational experience in Proxy 2153 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2155 Appendix D. Change Log 2157 << RFC Editor - remove prior to publication >> 2159 Differences from draft-templin-6man-omni-interface-27 to draft- 2160 templin-6man-omni-interface-28: 2162 o Updates based on implementation expereince. 2164 Differences from draft-templin-6man-omni-interface-25 to draft- 2165 templin-6man-omni-interface-26: 2167 o Further clarification on "aggregate" RA messages. 2169 o Expanded Security Considerations to discuss expectations for 2170 security in the Mobility Service. 2172 Differences from draft-templin-6man-omni-interface-20 to draft- 2173 templin-6man-omni-interface-21: 2175 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2176 (PBM). 2178 Differences from draft-templin-6man-omni-interface-18 to draft- 2179 templin-6man-omni-interface-19: 2181 o SEND/CGA. 2183 Differences from draft-templin-6man-omni-interface-17 to draft- 2184 templin-6man-omni-interface-18: 2186 o Teredo 2188 Differences from draft-templin-6man-omni-interface-14 to draft- 2189 templin-6man-omni-interface-15: 2191 o Prefix length discussions removed. 2193 Differences from draft-templin-6man-omni-interface-12 to draft- 2194 templin-6man-omni-interface-13: 2196 o Teredo 2197 Differences from draft-templin-6man-omni-interface-11 to draft- 2198 templin-6man-omni-interface-12: 2200 o Major simplifications and clarifications on MTU and fragmentation. 2202 o Document now updates RFC4443 and RFC8201. 2204 Differences from draft-templin-6man-omni-interface-10 to draft- 2205 templin-6man-omni-interface-11: 2207 o Removed /64 assumption, resulting in new OMNI address format. 2209 Differences from draft-templin-6man-omni-interface-07 to draft- 2210 templin-6man-omni-interface-08: 2212 o OMNI MNs in the open Internet 2214 Differences from draft-templin-6man-omni-interface-06 to draft- 2215 templin-6man-omni-interface-07: 2217 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2218 L2 addressing. 2220 o Expanded "Transition Considerations". 2222 Differences from draft-templin-6man-omni-interface-05 to draft- 2223 templin-6man-omni-interface-06: 2225 o Brought back OMNI option "R" flag, and discussed its use. 2227 Differences from draft-templin-6man-omni-interface-04 to draft- 2228 templin-6man-omni-interface-05: 2230 o Transition considerations, and overhaul of RS/RA addressing with 2231 the inclusion of MSE addresses within the OMNI option instead of 2232 as RS/RA addresses (developed under FAA SE2025 contract number 2233 DTFAWA-15-D-00030). 2235 Differences from draft-templin-6man-omni-interface-02 to draft- 2236 templin-6man-omni-interface-03: 2238 o Added "advisory PTB messages" under FAA SE2025 contract number 2239 DTFAWA-15-D-00030. 2241 Differences from draft-templin-6man-omni-interface-01 to draft- 2242 templin-6man-omni-interface-02: 2244 o Removed "Primary" flag and supporting text. 2246 o Clarified that "Router Lifetime" applies to each ANET interface 2247 independently, and that the union of all ANET interface Router 2248 Lifetimes determines MSE lifetime. 2250 Differences from draft-templin-6man-omni-interface-00 to draft- 2251 templin-6man-omni-interface-01: 2253 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2254 for future use (most likely as "pseudo-multicast"). 2256 o Non-normative discussion of alternate OMNI LLA construction form 2257 made possible if the 64-bit assumption were relaxed. 2259 First draft version (draft-templin-atn-aero-interface-00): 2261 o Draft based on consensus decision of ICAO Working Group I Mobility 2262 Subgroup March 22, 2019. 2264 Authors' Addresses 2266 Fred L. Templin (editor) 2267 The Boeing Company 2268 P.O. Box 3707 2269 Seattle, WA 98124 2270 USA 2272 Email: fltemplin@acm.org 2274 Tony Whyman 2275 MWA Ltd c/o Inmarsat Global Ltd 2276 99 City Road 2277 London EC1Y 1AX 2278 England 2280 Email: tony.whyman@mccallumwhyman.com