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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 September 14, 2020 7 Expires: March 18, 2021 9 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-31 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 March 18, 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. Interface Attributes . . . . . . . . . . . . . . . . 19 72 9.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 23 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 23 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 24 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 25 76 9.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . . 25 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 26 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 26 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 26 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 27 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 28 82 12.1. Router Discovery in IP Multihop and IPv4-Only Access 83 Networks . . . . . . . . . . . . . . . . . . . . . . . . 31 84 12.2. MS-Register and MS-Release List Processing . . . . . . . 33 85 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 34 86 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 35 87 15. Detecting and Responding to MSE Failures . . . . . . . . . . 35 88 16. Transition Considerations . . . . . . . . . . . . . . . . . . 36 89 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 36 90 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 37 91 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 92 20. Security Considerations . . . . . . . . . . . . . . . . . . . 39 93 21. Implementation Status . . . . . . . . . . . . . . . . . . . . 40 94 22. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 40 95 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 41 96 23.1. Normative References . . . . . . . . . . . . . . . . . . 41 97 23.2. Informative References . . . . . . . . . . . . . . . . . 42 98 Appendix A. Interface Attribute Heuristic Bitmap Encoding . . . 46 99 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 48 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 49 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 50 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 104 1. Introduction 106 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 107 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 108 etc.) often have multiple data links for communicating with networked 109 correspondents. These data links may have diverse performance, cost 110 and availability properties that can change dynamically according to 111 mobility patterns, flight phases, proximity to infrastructure, etc. 112 MNs coordinate their data links in a discipline known as "multilink", 113 in which a single virtual interface is configured over the underlying 114 data links. 116 The MN configures a virtual interface (termed the "Overlay Multilink 117 Network (OMNI) interface") as a thin layer over the underlying Access 118 Network (ANET) interfaces. The OMNI interface is therefore the only 119 interface abstraction exposed to the IPv6 layer and behaves according 120 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 121 while underlying interfaces appear as link layer communication 122 channels in the architecture. The OMNI interface connects to a 123 virtual overlay service known as the "OMNI link". The OMNI link 124 spans one or more Internetworks that may include private-use 125 infrastructures and/or the global public Internet itself. 127 Each MN receives a Mobile Network Prefix (MNP) for numbering 128 downstream-attached End User Networks (EUNs) independently of the 129 access network data links selected for data transport. The MN 130 performs router discovery over the OMNI interface (i.e., similar to 131 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 132 behalf of its EUNs. The router discovery process is iterated over 133 each of the OMNI interface's underlying interfaces in order to 134 register per-link parameters (see Section 12). 136 The OMNI interface provides a multilink nexus for exchanging inbound 137 and outbound traffic via the correct underlying interface(s). The 138 IPv6 layer sees the OMNI interface as a point of connection to the 139 OMNI link. Each OMNI link has one or more associated Mobility 140 Service Prefixes (MSPs) from which OMNI link MNPs are derived. If 141 there are multiple OMNI links, the IPv6 layer will see multiple OMNI 142 interfaces. 144 MNs may connect to multiple distinct OMNI links by configuring 145 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 146 interface is configured over a set of underlying interfaces and 147 provides a nexus for Safety-Based Multilink (SBM) operation. The IP 148 layer selects an OMNI interface based on SBM routing considerations, 149 then the selected interface applies Performance-Based Multilink (PBM) 150 to select the correct underlying interface. Applications can apply 151 Segment Routing [RFC8402] to select independent SBM topologies for 152 fault tolerance. 154 The OMNI interface interacts with a network-based Mobility Service 155 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 156 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 157 track MN movements and represent their MNPs in a global routing or 158 mapping system. 160 This document specifies the transmission of IPv6 packets [RFC8200] 161 and MN/MS control messaging over OMNI interfaces. 163 2. Terminology 165 The terminology in the normative references applies; especially, the 166 terms "link" and "interface" are the same as defined in the IPv6 167 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 168 Additionally, this document assumes the following IPv6 ND message 169 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 170 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 172 The Protocol Constants defined in Section 10 of [RFC4861] are used in 173 their same format and meaning in this document. The terms "All- 174 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 175 are the same as defined in [RFC4291] (with Link-Local scope assumed). 177 The following terms are defined within the scope of this document: 179 Mobile Node (MN) 180 an end system with a mobile router having multiple distinct 181 upstream data link connections that are grouped together in one or 182 more logical units. The MN's data link connection parameters can 183 change over time due to, e.g., node mobility, link quality, etc. 184 The MN further connects a downstream-attached End User Network 185 (EUN). The term MN used here is distinct from uses in other 186 documents, and does not imply a particular mobility protocol. 188 End User Network (EUN) 189 a simple or complex downstream-attached mobile network that 190 travels with the MN as a single logical unit. The IPv6 addresses 191 assigned to EUN devices remain stable even if the MN's upstream 192 data link connections change. 194 Mobility Service (MS) 195 a mobile routing service that tracks MN movements and ensures that 196 MNs remain continuously reachable even across mobility events. 197 Specific MS details are out of scope for this document. 199 Mobility Service Endpoint (MSE) 200 an entity in the MS (either singular or aggregate) that 201 coordinates the mobility events of one or more MN. 203 Mobility Service Prefix (MSP) 204 an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the 205 rest of the Internetwork by the MS, and from which more-specific 206 Mobile Network Prefixes (MNPs) are derived. 208 Mobile Network Prefix (MNP) 209 a longer IPv6 prefix taken from an MSP (e.g., 210 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate 211 the MNP to devices located in EUNs. 213 Access Network (ANET) 214 a data link service network (e.g., an aviation radio access 215 network, satellite service provider network, cellular operator 216 network, wifi network, etc.) that connects MNs. Physical and/or 217 data link level security between the MN and ANET are assumed. 219 Access Router (AR) 220 a first-hop router in the ANET for connecting MNs to 221 correspondents in outside Internetworks. 223 ANET interface 224 a MN's attachment to a link in an ANET. 226 Internetwork (INET) 227 a connected network region with a coherent IP addressing plan that 228 provides transit forwarding services for ANET MNs and INET 229 correspondents. Examples include private enterprise networks, 230 ground domain aviation service networks and the global public 231 Internet itself. 233 INET interface 234 a node's attachment to a link in an INET. 236 OMNI link 237 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 238 over one or more INETs and their connected ANETs. An OMNI link 239 can comprise multiple INET segments joined by bridges the same as 240 for any link; the addressing plans in each segment may be mutually 241 exclusive and managed by different administrative entities. 243 OMNI interface 244 a node's attachment to an OMNI link, and configured over one or 245 more underlying ANET/INET interfaces. 247 OMNI Link-Local Address (LLA) 248 a link local IPv6 address per [RFC4291] constructed as specified 249 in Section 7. 251 OMNI Unique-Local Address (ULA) 252 a unique local IPv6 address per [RFC4193] constructed as specified 253 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 254 and vice-versa. 256 OMNI Option 257 an IPv6 Neighbor Discovery option providing multilink parameters 258 for the OMNI interface as specified in Section 9. 260 Multilink 261 an OMNI interface's manner of managing diverse underlying data 262 link interfaces as a single logical unit. The OMNI interface 263 provides a single unified interface to upper layers, while 264 underlying data link selections are performed on a per-packet 265 basis considering factors such as DSCP, flow label, application 266 policy, signal quality, cost, etc. Multilinking decisions are 267 coordinated in both the outbound (i.e. MN to correspondent) and 268 inbound (i.e., correspondent to MN) directions. 270 L2 271 The second layer in the OSI network model. Also known as "layer- 272 2", "link-layer", "sub-IP layer", "data link layer", etc. 274 L3 275 The third layer in the OSI network model. Also known as "layer- 276 3", "network-layer", "IPv6 layer", etc. 278 underlying interface 279 an ANET/INET interface over which an OMNI interface is configured. 280 The OMNI interface is seen as a L3 interface by the IP layer, and 281 each underlying interface is seen as a L2 interface by the OMNI 282 interface. 284 Mobility Service Identification (MSID) 285 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 286 as specified in Section 7. 288 Safety-Based Multilink (SBM) 289 A means for ensuring fault tolerance through redundancy by 290 connecting multiple independent OMNI interfaces to independent 291 routing topologies (i.e., multiple independent OMNI links). 293 Performance Based Multilink (PBM) 294 A means for selecting underlying interface(s) for packet 295 trasnmission and reception within a single OMNI interface. 297 3. Requirements 299 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 300 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 301 "OPTIONAL" in this document are to be interpreted as described in BCP 302 14 [RFC2119][RFC8174] when, and only when, they appear in all 303 capitals, as shown here. 305 OMNI links maintain a constant value "MAX_MSID" selected to provide 306 MNs with an acceptable level of MSE redundancy while minimizing 307 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 308 set to the default value 5; if a different value is chosen, it should 309 be set uniformly by all nodes on the OMNI link. 311 An implementation is not required to internally use the architectural 312 constructs described here so long as its external behavior is 313 consistent with that described in this document. 315 4. Overlay Multilink Network (OMNI) Interface Model 317 An OMNI interface is a MN virtual interface configured over one or 318 more underlying interfaces, which may be physical (e.g., an 319 aeronautical radio link) or virtual (e.g., an Internet or higher- 320 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 321 with the MS through IPv6 ND message exchanges. The MN uses the MNP 322 to construct a unique OMNI LLA through the algorithmic derivation 323 specified in Section 7 and assigns the LLA to the OMNI interface. 325 The OMNI interface architectural layering model is the same as in 326 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 327 therefore sees the OMNI interface as a single L3 interface with 328 multiple underlying interfaces that appear as L2 communication 329 channels in the architecture. 331 +----------------------------+ 332 | Upper Layer Protocol | 333 Session-to-IP +---->| | 334 Address Binding | +----------------------------+ 335 +---->| IP (L3) | 336 IP Address +---->| | 337 Binding | +----------------------------+ 338 +---->| OMNI Interface | 339 Logical-to- +---->| (OMNI LLA) | 340 Physical | +----------------------------+ 341 Interface +---->| L2 | L2 | | L2 | 342 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 343 +------+------+ +------+ 344 | L1 | L1 | | L1 | 345 | | | | | 346 +------+------+ +------+ 348 Figure 1: OMNI Interface Architectural Layering Model 350 The OMNI virtual interface model gives rise to a number of 351 opportunities: 353 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 354 Address Detection (DAD) or Muticast Listener Discovery (MLD) 355 messaging is necessary. 357 o ANET interfaces do not require any L3 addresses (i.e., not even 358 link-local) in environments where communications are coordinated 359 entirely over the OMNI interface. (An alternative would be to 360 also assign the same OMNI LLA to all ANET interfaces.) 362 o as ANET interface properties change (e.g., link quality, cost, 363 availability, etc.), any active ANET interface can be used to 364 update the profiles of multiple additional ANET interfaces in a 365 single message. This allows for timely adaptation and service 366 continuity under dynamically changing conditions. 368 o coordinating ANET interfaces in this way allows them to be 369 represented in a unified MS profile with provisions for mobility 370 and multilink operations. 372 o exposing a single virtual interface abstraction to the IPv6 layer 373 allows for multilink operation (including QoS based link 374 selection, packet replication, load balancing, etc.) at L2 while 375 still permitting L3 traffic shaping based on, e.g., DSCP, flow 376 label, etc. 378 o L3 sees the OMNI interface as a point of connection to the OMNI 379 link; if there are multiple OMNI links (i.e., multiple MS's), L3 380 will see multiple OMNI interfaces. 382 o Multiple independent OMNI interfaces can be used for increased 383 fault tolerance through Safety-Based Multilink (SBM), with 384 Performance-Based Multilink (PBM) applied within each interface. 386 Other opportunities are discussed in [RFC7847]. 388 Figure 2 depicts the architectural model for a MN connecting to the 389 MS via multiple independent ANETs. When an underlying interface 390 becomes active, the MN's OMNI interface sends native (i.e., 391 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 392 ND messages traverse the ground domain ANETs until they reach an 393 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 394 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 395 returns an IPv6 ND message response to the MN. IPv6 ND messages 396 traverse the ANET at layer 2; hence, the Hop Limit is not 397 decremented. 399 +--------------+ 400 | MN | 401 +--------------+ 402 |OMNI interface| 403 +----+----+----+ 404 +--------|IF#1|IF#2|IF#n|------ + 405 / +----+----+----+ \ 406 / | \ 407 / <---- Native | IP ----> \ 408 v v v 409 (:::)-. (:::)-. (:::)-. 410 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 411 `-(::::)-' `-(::::)-' `-(::::)-' 412 +----+ +----+ +----+ 413 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 414 . +-|--+ +-|--+ +-|--+ . 415 . | | | 416 . v v v . 417 . <----- Encapsulation -----> . 418 . . 419 . +-----+ (:::)-. . 420 . |MSE#2| .-(::::::::) +-----+ . 421 . +-----+ .-(::: INET :::)-. |MSE#m| . 422 . (::::: Routing ::::) +-----+ . 423 . `-(::: System :::)-' . 424 . +-----+ `-(:::::::-' . 425 . |MSE#1| +-----+ +-----+ . 426 . +-----+ |MSE#3| |MSE#4| . 427 . +-----+ +-----+ . 428 . . 429 . . 430 . <----- Worldwide Connected Internetwork ----> . 431 ........................................................... 433 Figure 2: MN/MS Coordination via Multiple ANETs 435 After the initial IPv6 ND message exchange, the MN can send and 436 receive unencapsulated IPv6 data packets over the OMNI interface. 437 OMNI interface multilink services will forward the packets via ARs in 438 the correct underlying ANETs. The AR encapsulates the packets 439 according to the capabilities provided by the MS and forwards them to 440 the next hop within the worldwide connected Internetwork via optimal 441 routes. 443 OMNI links span one or more underlying Internetwork via a mid-layer 444 overlay encapsulation based on [RFC2473] and using [RFC4193] 445 addressing. Each OMNI link corresponds to a different overlay 446 (differentiated by an address codepoint) which may be carried over a 447 completely separate underlying topology. Each MN can facilitate SBM 448 by connecting to multiple OMNI links using a distinct OMNI interface 449 for each link. 451 5. Maximum Transmission Unit (MTU) and Fragmentation 453 The OMNI interface observes the link nature of tunnels, including the 454 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 455 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 456 The OMNI interface is configured over one or more underlying 457 interfaces that may have diverse MTUs. 459 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 460 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 461 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 462 not permitted to perform fragmentation even though the destination is 463 required to reassemble more. The network therefore MUST forward 464 packets of at least 1280 bytes without generating an IPv6 Path MTU 465 Discovery (PMTUD) Packet Too Big (PTB) message [RFC8201]. 467 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 468 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 469 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 470 minimum IPv4 path MTU is 576 bytes since routers on the path are 471 permitted to perform fragmentation and the destination is required to 472 reassemble at least that much. The DF bit in the IPv4 encapsulation 473 headers of packets sent over IPv4 underlying interfaces therefore 474 MUST be set to 0. 476 The OMNI interface configures both an MTU and MRU of 9180 bytes 477 [RFC2492]; the size is therefore not a reflection of the underlying 478 interface MTUs, but rather determines the largest packet the OMNI 479 interface can forward or reassemble. The OMNI interface accommodates 480 packets as large as the OMNI interface MTU while generating IPv6 Path 481 MTU Discovery (PMTUD) Packet Too Big (PTB) messages [RFC8201] as 482 necessary (see below). For original IPv4 packets with DF=0, the IP 483 layer performs IPv4 fragmentation according to the OMNI interface MTU 484 if necessary to admit the fragments into the interface. The 485 interface may then internally apply further IPv4 fragmentation 486 according to the underlying interface MTU prior to encapsulation to 487 ensure that the fragments are delivered to the final destination. 489 OMNI interfaces internally employ OMNI link adaptation when necessary 490 by inserting a mid-layer IPv6 header between the inner IP packet and 491 any outer IP encapsulation headers per [RFC2473] then performing 492 fragmentation on the mid-layer IPv6 packet. The OMNI interface can 493 instead return internally-generated PTB messages for packets admitted 494 into the interface that it deems too large (e.g., according to link 495 performance characteristics, reassembly congestion, etc.) while 496 either dropping or forwarding the packet. The OMNI interface 497 performs PMTUD even if the destination appears to be on the same link 498 since an OMNI link node on the path may return a PTB. This ensures 499 that the path MTU is adaptive and reflects the current path used for 500 a given data flow. 502 OMNI interfaces perform encapsulation and fragmentation/reassembly 503 with respect to both the minimum IPv6 and IPv4 path MTUs as follows: 505 o When an OMNI interface sends a packet toward a final destination 506 via an ANET peer, it sends without OMNI link encapsulation if the 507 packet is no larger than the underlying interface MTU. Otherwise, 508 it inserts an IPv6 header with source address set to the node's 509 own OMNI Unique Local Address (ULA) (see: Section 8) and 510 destination set to the OMNI ULA of the ANET peer. The OMNI 511 interface then uses IPv6 fragmentation to break the packet into a 512 minimum number of non-overlapping fragments, where the largest 513 fragment size is determined by the underlying interface MTU. The 514 OMNI interface then sends the fragments to the ANET peer, which 515 reassembles before forwarding toward the final destination. 517 o When an OMNI interface sends a packet toward a final destination 518 via an INET interface, it sends packets (including any outer-layer 519 INET encapsulations) no larger than the minimum INET path MTU 520 without OMNI link adaptation if the destination is reached via an 521 INET address within the same OMNI link segment. Otherwise, it 522 inserts an IPv6 header with source address set to the node's OMNI 523 ULA, destination set to the ULA of the next hop OMNI node toward 524 the final destination and (if necessary) with a Segment Routing 525 Header with the remaining Segment IDs on the path to the final 526 destination. The OMNI interface then uses IPv6 fragmentation to 527 break the encapsulated packet into a minimum number of non- 528 overlapping fragments, where the largest fragment size (including 529 both the OMNI and outer-layer INET encapsulations) is the minimum 530 INET path MTU, and the smallest fragment size is no smaller than 531 256 bytes (i.e., slightly less than half the minimum IPv4 path 532 MTU). The OMNI interface then encapsulates the fragments in any 533 INET headers and sends them to the OMNI link neighbor, which 534 reassembles before forwarding toward the final destination. 536 OMNI interfaces unconditionally drop all OMNI link fragments received 537 from an INET peer that are smaller than 256 bytes. In order to set 538 the correct context for reassembly, the OMNI interface that inserts 539 the IPv6 header MUST also be the one that inserts the IPv6 Fragment 540 Header Identification value. While not strictly required, sending 541 all fragments of the same fragmented OMNI-encapsulated packet 542 consecutively over the same underlying interface with minimal inter- 543 fragment delay may increase the likelihood of successful reassembly. 545 Note that the OMNI interface can forward large packets via 546 encapsulation and fragmentation while at the same time returning 547 "advisory" PTB messages (subject to rate limiting). The receiving 548 node that performs reassembly can also send advisory PTB messages if 549 reassembly conditions become unfavorable. The OMNI interface can 550 therefore continuously forward large packets without loss while 551 returning advisory PTB messages recommending a smaller size. 553 OMNI interfaces that send advisory PTB messages set the ICMPv6 554 message header Code field to the value 1. Receiving nodes that 555 recognize the code reduce their estimate of the path MTU the same as 556 for ordinary "diagnistic" PTBs but do not regard the message as a 557 loss indication. Nodes that do not recognize the code treat the 558 message the same as a diagnostic PTB, but should heed the 559 retransmission advice given in [RFC8201]. This document therefore 560 updates [RFC4443] and [RFC8201]. 562 5.1. Fragmentation Security Implications 564 As discussed in Section 3.7 of [I-D.ietf-intarea-frag-fragile], there 565 are four basic threats concerning IPv6 fragmentation; each of which 566 is addressed by a suitable mitigation as follows: 568 1. Overlapping fragment attacks - reassembly of overlapping 569 fragments is forbidden by [RFC8200]; therefore, this threat does 570 not apply to OMNI interfaces. 572 2. Resource exhaustion attacks - this threat is mitigated by 573 providing a sufficiently large OMNI interface reassembly cache 574 and instituting "fast discard" of incomplete reassemblies that 575 may be part of a buffer exhaustion attack. The reassembly cache 576 should be sufficiently large so that a sustained attack does not 577 cause excessive loss of good reassemblies but not so large that 578 (timer-based) data structure management becomes computationally 579 expensive. 581 3. Attacks based on predictable fragment identification values - 582 this threat is mitigated by selecting a suitably random ID value 583 per [RFC7739]. 585 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 586 threat is mitigated by disallowing "tiny fragments" per the OMNI 587 interface fragmentation procedures specified above. 589 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 590 ID) field with only 65535 unique values such that at high data rates 591 the field could wrap and apply to new packets while the fragments of 592 old packets using the same ID are still alive in the network 593 [RFC4963]. However, since the largest OMNI fragment that will be 594 sent via an IPv4 INET path is 576 bytes any IPv4 fragmentation would 595 occur only on links with an IPv4 MTU smaller than this size, and 596 [RFC3819] recommendations suggest that such links will have low data 597 rates. Since IPv6 provides a 32-bit Identification value, IP ID 598 wraparound at high data rates is not a concern for IPv6 599 fragmentation. 601 6. Frame Format 603 The OMNI interface transmits IPv6 packets according to the native 604 frame format of each underlying interface. For example, for 605 Ethernet-compatible interfaces the frame format is specified in 606 [RFC2464], for aeronautical radio interfaces the frame format is 607 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 608 Manual), for tunnels over IPv6 the frame format is specified in 609 [RFC2473], etc. 611 7. Link-Local Addresses (LLAs) 613 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 614 LLAs") as follows: 616 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 617 within the least-significant 112 bits of the IPv6 link-local 618 prefix fe80::/16. The Prefix Length is determined by adding 16 to 619 the length of the embedded MNP. For example, for the MNP 620 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 621 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 622 link-local address format specified in Section 2.5.6 of [RFC4291] 623 by defining a use for bits 11 - 63. 625 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 626 i.e., the most significant 16 bits of the prefix fe80::/16, 627 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 628 32bit IPv4 address/prefix. The Prefix Length is determined by 629 adding 96 to the length of the embedded IPv4 address/prefix. For 630 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 631 fe80::ffff:192.0.2.0/120 (also written as 632 fe80::ffff:c000:0200/120). 634 o MS OMNI LLAs are assigned to ARs and MSEs from the range 635 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 636 of the LLA includes a unique integer "MSID" value between 637 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 638 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 639 determined by adding 96 to the MSID prefix length. For example, 640 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 641 Prefix Length is set to 112 and the LLA is written as 642 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 643 "Anycast" MSID and corresponds to the link-local Subnet-Router 644 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 645 through 0xffffffff is reserved for future use. 647 o The OMNI LLA range fe80::/32 is used as the service prefix for the 648 address format specified in Section 4 of [RFC4380] (see Section 17 649 for further discussion). 651 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 652 MNPs can be allocated from that block ensuring that there is no 653 possibility for overlap between the above OMNI LLA constructs. 655 Since MN OMNI LLAs are based on the distribution of administratively 656 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 657 through administrative assignment, OMNI interfaces set the 658 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 660 8. Unique-Local Addresses (ULAs) 662 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 663 [RFC4193] as the source and destination addresses in OMNI link IPv6 664 encapsulation headers. This document currently assumes use of the 665 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 666 (however, see the note at the end of this section). 668 Each OMNI link instance is identified by bits 10-15 of the OMNI 669 service prefix fc80::/10. For example, OMNI ULAs associated with 670 instance 0 are configured from the prefix fc80::/16, instance 1 from 671 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 672 their associated prefix lengths are configured in one-to-one 673 correspondence with OMNI LLAs through stateless prefix translation. 674 For example, for OMNI link instance fc80::/16: 676 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 677 fc80:2001:db8:1:2::/80 679 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 680 fc80::ffff:192.0.2.0/120 682 o the OMNI ULA corresponding to fe80::1000/112 is simply 683 fc80::1000/112 685 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 687 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 688 link instance, e.g., the OMNI interface connected to instance 3 689 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 690 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 691 the local routing system so that applications can direct traffic 692 according to SBM requirements. 694 The OMNI ULA presents an IPv6 address format that is routable within 695 the OMNI link routing system and can be used to convey link-scoped 696 messages across multiple hops using IPv6 encapsulation [RFC2473]. 697 The OMNI link extends across one or more underling Internetworks to 698 include all ARs and MSEs. All MNs are also considered to be 699 connected to the OMNI link, however OMNI link encapsulation is 700 omitted over ANET links when possible to conserve bandwidth (see: 701 Section 11). 703 The OMNI link can be subdivided into "segments" that often correspond 704 to different administrative domains or physical partitions. OMNI 705 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 706 support efficient packet forwarding to destinations located in other 707 OMNI link segments. A full discussion of Segment Routing over the 708 OMNI link appears in [I-D.templin-intarea-6706bis]. 710 NOTE: An alternative to the application of ULAs as discussed in this 711 document would be to re-purpose the deprectated IPv6 Site-Local 712 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 713 SLAs would be a more natural fit since both LLA and SLA prefix 714 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 715 single bit setting, and LLAs and SLAs can be unambiguously allocated 716 in one-to-one correspondence with one another. Re-purposing SLAs 717 would also make good use of an otherwise-wasted address range that 718 has been "parked" since the 2004 deprecation. However, moving from 719 ULAs to SLAs would require an IETF standards action acknowledging 720 this document as obsoleting [RFC3879] and updating [RFC4291]. The 721 authors therefore defer to IETF consensus as to the proper way 722 forward. 724 9. Address Mapping - Unicast 726 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 727 state and use the link-local address format specified in Section 7. 728 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 729 over physical underlying interfaces without encapsulation observe the 730 native underlying interface Source/Target Link-Layer Address Option 731 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 732 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 733 interfaces via encapsulation do not include S/TLLAOs which were 734 intended for encoding physical L2 media address formats and not 735 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 736 for encoding additional interface attributes. Hence, this document 737 does not define an S/TLLAO format but instead defines a new option 738 type termed the "OMNI option" designed for these purposes. 740 MNs such as aircraft typically have many wireless data link types 741 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 742 etc.) with diverse performance, cost and availability properties. 743 The OMNI interface would therefore appear to have multiple L2 744 connections, and may include information for multiple underlying 745 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 746 an IPv6 ND option called the OMNI option formatted as shown in 747 Figure 3: 749 0 1 2 3 750 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 1 751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 752 | Type | Length | Prefix Length | ifIndex | 753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 754 | | 755 ~ Sub-Options ~ 756 | | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 759 Figure 3: OMNI Option Format 761 In this format: 763 o Type is set to TBD. If multiple OMNI option instances appear in 764 the same IPv6 ND message, the first instance is processed and all 765 other instances are ignored. 767 o Length is set to the number of 8 octet blocks in the option. 769 o Prefix Length is determines the length of prefix to be applied to 770 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 771 MS, Prefix Length is the length that the MN is requesting or 772 asserting to the MS. For IPv6 ND messages sent from the MS to the 773 MN, Prefix Length indicates the length that the MS is granting to 774 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 775 Length indicates the length associated with the target MN that is 776 subject of the ND message. 778 o ifIndex corresponds to the source or target underlying interface 779 for this IPv6 ND message, with a value between 0 and 255 encoded 780 as specified in Section 9.1.3. For RS and NS messages, ifIndex 781 corresponds to the source underlying interface over which the 782 message originated. For RA and NA messages, ifIndex corresponds 783 to the target underlying interface that the message is destined 784 to. 786 o Sub-Options is a Variable-length field, of length such that the 787 complete OMNI Option is an integer multiple of 8 octets long. 788 Contains one or more options, as described in Section 9.1. 790 9.1. Sub-Options 792 The OMNI option includes zero or more Sub-Options. Each consecutive 793 Sub-Option is concatenated immediately after its predecessor. All 794 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 795 encoded in the following format: 797 0 1 2 798 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 5 799 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 800 | Sub-Type | Sub-length | Sub-Option Data ... 801 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 803 Figure 4: Sub-Option Format 805 o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub- 806 Options defined in this document are: 808 Option Name Sub-Type 809 Pad1 0 810 PadN 1 811 Interface Attributes 2 812 Traffic Selector 3 813 MS-Register 4 814 MS-Release 5 815 Network Access Identifier 6 816 Geo Coordinates 7 817 DHCP Unique Identifier (DUID) 8 819 Figure 5 821 Sub-Types 253 and 254 are reserved for experimentation, as 822 recommended in [RFC3692]. 824 o Sub-Length is a 1-byte field that encodes the length of the Sub- 825 Option Data, in bytes (I.e., ranging from 0 to 255). 827 o Sub-Option Data is a byte string with format determined by Sub- 828 Type. 830 During processing, unrecognized Sub-Options are ignored and the next 831 Sub-Option processed until the end of the OMNI option is reached. 833 The following Sub-Option types and formats are defined in this 834 document: 836 9.1.1. Pad1 838 0 839 0 1 2 3 4 5 6 7 840 +-+-+-+-+-+-+-+-+ 841 | Sub-Type=0 | 842 +-+-+-+-+-+-+-+-+ 844 Figure 6: Pad1 846 o Sub-Type is set to 0. If multiple instances appear in the same 847 OMNI option all are processed. 849 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 850 consists of a single zero octet). 852 9.1.2. PadN 854 0 1 2 855 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 5 856 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 857 | Sub-Type=1 | Sub-length=N | N padding bytes ... 858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 860 Figure 7: PadN 862 o Sub-Type is set to 1. If multiple instances appear in the same 863 OMNI option all are processed. 865 o Sub-Length is set to N (from 0 to 255) being the number of padding 866 bytes that follow. 868 o Sub-Option Data consists of N zero-valued octets. 870 9.1.3. Interface Attributes 871 0 1 2 3 872 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 1 873 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 874 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 875 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 876 | Provider ID | Link |R| LHS | SRT | FMT | MSID (0 - 7) | 877 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 878 | MSID (bits 8 - 31) | ~ 879 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 880 ~ ~ 881 ~ Link Layer Address (L2ADDR) ~ 882 ~ ~ 883 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 884 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 885 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 886 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 887 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 888 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 889 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 891 Figure 8: Interface Attributes 893 o Sub-Type is set to 2. If multiple instances with different 894 ifIndex values appear in the same OMNI option all are processed; 895 if multiple instances with the same ifIndex value appear, the 896 first is processed and all others are ignored. 898 o Sub-Length is set to N (from 4 to 255) that encodes the number of 899 Sub-Option Data bytes that follow. 901 o Sub-Option Data contains an "Interface Attribute" option encoded 902 as follows (note that the first four octets must be present): 904 * ifIndex is set to an 8-bit integer value corresponding to a 905 specific underlying interface. OMNI interfaces MUST number 906 each distinct underlying interface with an ifIndex value 907 between '1' and '255' that represents a MN-specific 8-bit 908 mapping for the actual ifIndex value assigned by network 909 management [RFC2863] (the ifIndex value '0' is reserved for use 910 by the MS). 912 * ifType is set to an 8-bit integer value corresponding to the 913 underlying interface identified by ifIndex. The value 914 represents an OMNI interface-specific 8-bit mapping for the 915 actual IANA ifType value registered in the 'IANAifType-MIB' 916 registry [http://www.iana.org]. 918 * Provider ID is set to an OMNI interface-specific 8-bit ID value 919 for the network service provider associated with this ifIndex. 921 * Link encodes a 4-bit link metric. The value '0' means the link 922 is DOWN, and the remaining values mean the link is UP with 923 metric ranging from '1' ("lowest") to '15' ("highest"). 925 * R is reserved for future use. 927 * LHS - a 3-bit "Link-Address/Heuristics/Simplex" code that 928 indicates which other fields appear in the sub-option as 929 follows: 931 + When the most significant bit (i.e., "Link-Address") is set 932 to 1, the SRT, FMT, MSID and L2ADDR fields are included 933 immediately following the LHS code; else, they are omitted. 935 + When the next most significant bit (i.e., "Heuristics") is 936 set to 1, a trailing Heuristics Bitmap is included next; 937 else, it is omitted. (Note that if "Link-Address" is set 938 the Bitmap immediately follows L2ADDR; else, it immediately 939 follows LHS.) 941 + When the Heuristics Bitmap is present and the least 942 significant bit (i.e., "Simplex") is set to 1, the Bitmap is 943 encoded in Simplex form as shown in Figure 8; else it is 944 encoded in Indexed form as discussed below. 946 * SRT - a 5-bit Segment Routing Topology prefix length value that 947 (when added to 96) determines the prefix length to apply to the 948 ULA formed from concatenating fc*::/96 with the 32 bit MSID 949 value that follows. For example, the value 16 corresponds to 950 the prefix length 112. 952 * FMT - a 3-bit "Framework/Mode/Type" code corresponding to the 953 included Link Layer Address as follows: 955 + When the most significant bit (i.e., "Framework") is set to 956 0, L2ADDR is the INET encapsulation address of a Proxy/ 957 Server; otherwise, it is the addresss for the Source/Target 958 itself 960 + When the next most significant bit (i.e., "Mode") is set to 961 0, the Source/Target L2ADDR is on the open INET; otherwise, 962 it is (likely) located behind a NAT. 964 + When the least significant bit (i.e., "Type") is set to 0, 965 L2ADDR is an IPv4 address; else, it is an IPv6 address. 967 * MSID includes the 32 bit ID of the last hop Proxy/Server ULA on 968 the path to the target according to LHS. When SRT and LHS are 969 both set to 0, the last hop Proxy/Server ULA is considered 970 unspecified in this IPv6 ND message. When SRT is set to 0 and 971 LHS is non-zero, the prefix length is set to 128. 973 * Link Layer Address (L2ADDR) - Included according to FMT, and 974 identifies the link-layer address (i.e., the encapsulation 975 address) of the source/target. The Port Number and IP address 976 are recorded in ones-compliment "obfuscated" form per 977 [RFC4380]. 979 * When LHS indicates that a Hueristics Bitmap is present, the 980 Bitmap appears as the remainder of the suboption. In "Simplex" 981 form, the index for each singleton Bitmap byte is inferred from 982 its sequential position (i.e., 0, 1, 2, ...) as shown in 983 Figure 8. In "Indexed" form, each Bitmap is preceded by an 984 Index byte that encodes a value "i" = (0 - 255) as the index 985 for its companion Bitmap as follows: 987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 988 | Index=i | Bitmap(i) |P[*] values ... 989 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 991 Figure 9 993 * The remainder of the Sub-Option Data contains traffic 994 classifier heuristics consisting of a first (simplex/indexed) 995 Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte blocks of 996 2-bit P[*] values, followed by a second Bitmap (i), followed by 997 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 998 the bits of each Bitmap(i) that are set to '1'' indicate the 999 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1000 that follow; if any Bitmap(i) bits are '0', then the 1001 corresponding P[*] block is instead omitted. For example, if 1002 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1003 followed by the block with P[04]-P[07], etc., and ending with 1004 the block with P[28]-P[31] are included (as shown in Figure 8). 1005 The next Bitmap(i) is then consulted with its bits indicating 1006 which P[*] blocks follow, etc. out to the end of the Sub- 1007 Option. 1009 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1010 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1011 heuristics preference for underlying interface selection 1012 purposes. Not all P[*] values need to be included in the OMNI 1013 option of each IPv6 ND message received. Any P[*] values 1014 represented in an earlier OMNI option but omitted in the 1015 current OMNI option remain unchanged. Any P[*] values not yet 1016 represented in any OMNI option default to "medium". 1018 * The first 16 P[*] blocks correspond to the 64 Differentiated 1019 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1020 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1021 traffic classifier values P[64], P[65], P[66], etc. See 1022 Appendix A for further discussion and examples. 1024 9.1.4. Traffic Selector 1026 0 1 2 3 1027 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 1028 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1029 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1030 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1031 ~ ~ 1032 ~ RFC 6088 Format Traffic Selector ~ 1033 ~ ~ 1034 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 Figure 10: Traffic Selector 1038 o Sub-Type is set to 3. If multiple instances appear in the same 1039 OMNI option all are processed, i.e., even if the same ifIndex 1040 value appears multiple times. 1042 o Sub-Length is set to N (the number of Sub-Option Data bytes that 1043 follow). 1045 o Sub-Option Data contains a 1 byte ifIndex encoded exactly as 1046 specified in Section 9.1.3, followed by an N-1 byte traffic 1047 selector formatted per [RFC6088] beginning with the "TS Format" 1048 field. The largest traffic selector for a given ifIndex is 1049 therefore 254 bytes. 1051 9.1.5. MS-Register 1052 0 1 2 3 1053 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 1054 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1055 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1056 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1057 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1058 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1059 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1060 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1061 ... ... ... ... ... ... 1062 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1063 | MSID [n] (bits 16 - 32) | 1064 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1066 Figure 11: MS-Register Sub-option 1068 o Sub-Type is set to 4. If multiple instances appear in the same 1069 OMNI option all are processed. Only the first MAX_MSID values 1070 processed (whether in a single instance or multiple) are retained 1071 and all other MSIDs are ignored. 1073 o Sub-Length is set to 4n. 1075 o A list of n 4-octet MSIDs is included in the following 4n octets. 1076 The Anycast MSID value '0' in an RS message MS-Register sub-option 1077 requests the recipient to return the MSID of a nearby MSE in a 1078 corresponding RA response. 1080 9.1.6. MS-Release 1082 0 1 2 3 1083 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 1084 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1085 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1087 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1090 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1091 ... ... ... ... ... ... 1092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1093 | MSID [n] (bits 16 - 32) | 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 Figure 12: MS-Release Sub-option 1098 o Sub-Type is set to 5. If multiple instances appear in the same 1099 IPv6 OMNI option all are processed. Only the first MAX_MSID 1100 values processed (whether in a single instance or multiple) are 1101 retained and all other MSIDs are ignored. 1103 o Sub-Length is set to 4n. 1105 o A list of n 4 octet MSIDs is included in the following 4n octets. 1106 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1107 i.e., only non-zero values are processed. 1109 9.1.7. Network Access Identifier (NAI) 1111 0 1 2 3 1112 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 1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1114 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1117 Figure 13: Network Access Identifier (NAI) Sub-option 1119 o Sub-Type is set to 6. If multiple instances appear in the same 1120 OMNI option the first is processed and all others are ignored. 1122 o Sub-Length is set to N. 1124 o A Network Access Identifier (NAI) up to 255 bytes in length is 1125 coded per [RFC7542]. 1127 9.1.8. Geo Coordinates 1129 0 1 2 3 1130 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 1131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1135 Figure 14: Geo Coordinates Sub-option 1137 o Sub-Type is set to 7. If multiple instances appear in the same 1138 OMNI option the first is processed and all others are ignored. 1140 o Sub-Length is set to N. 1142 o A set of Geo Coordinates up to 255 bytes in length (format TBD). 1143 Includes Latitude/Longitude at a minimum; may also include 1144 additional attributes such as altitude, heading, speed, etc.). 1146 9.1.9. DHCP Unique Identifier (DUID) 1148 0 1 2 3 1149 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 1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1151 | Sub-Type=8 | Sub-length=N | DUID-Type | 1152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1153 . . 1154 . type-specific DUID body (variable length) . 1155 . . 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1158 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1160 o Sub-Type is set to 8. If multiple instances appear in the same 1161 OMNI option the first is processed and all others are ignored. 1163 o Sub-Length is set to N (i.e., the length of the option beginning 1164 with the DUID-Type and continuing to the end of the type-specifc 1165 body). 1167 o DUID-Type is a two-octet field coded in network byte order that 1168 determines the format and contents of the type-specific body 1169 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1170 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1171 which will occur in common operational practice. 1173 o A type-specific DUID body up to 253 bytes in length follows, 1174 formatted according to DUID-type. For example, for type 4 the 1175 body consists of a 128-bit UUID selected according to [RFC6355]. 1177 10. Address Mapping - Multicast 1179 The multicast address mapping of the native underlying interface 1180 applies. The mobile router on board the MN also serves as an IGMP/ 1181 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1182 using the L2 address of the AR as the L2 address for all multicast 1183 packets. 1185 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1186 coordinate with the AR, and ANET L2 elements use MLD snooping 1187 [RFC4541]. 1189 11. Conceptual Sending Algorithm 1191 The MN's IPv6 layer selects the outbound OMNI interface according to 1192 SBM considerations when forwarding data packets from local or EUN 1193 applications to external correspondents. Each OMNI interface 1194 maintains a neighbor cache the same as for any IPv6 interface, but 1195 with additional state for multilink coordination. 1197 After a packet enters the OMNI interface, an outbound underlying 1198 interface is selected based on PBM traffic attributes such as DSCP, 1199 application port number, cost, performance, message size, etc. OMNI 1200 interface multilink selections could also be configured to perform 1201 replication across multiple underlying interfaces for increased 1202 reliability at the expense of packet duplication. 1204 When an OMNI interface sends a packet over a selected outbound 1205 underlying interface, it omits or employs OMNI link adaptation as 1206 necessary as discussed in Section 5. The OMNI interface also 1207 performs encapsulation when the nearest AR is located multiple hops 1208 away as discussed in Section 12.1. 1210 OMNI interface multilink service designers MUST observe the BCP 1211 guidance in Section 15 [RFC3819] in terms of implications for 1212 reordering when packets from the same flow may be spread across 1213 multiple underlying interfaces having diverse properties. 1215 11.1. Multiple OMNI Interfaces 1217 MNs may connect to multiple independent OMNI links concurrently in 1218 support of SBM. Each OMNI interface is distinguished by its Anycast 1219 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1220 separate OMNI interface for each link so that multiple interfaces 1221 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1222 different Anycast OMNI ULA is assigned to each interface, and the MN 1223 injects the service prefixes for the OMNI link instances into the EUN 1224 routing system. 1226 Applications in EUNs can use Segment Routing to select the desired 1227 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1228 written into the IPv6 destination address, and the actual destination 1229 (along with any additional intermediate hops) is written into the 1230 Segment Routing Header. Standard IP routing directs the packets to 1231 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1232 the OMNI interface to be used for transmission to the next hop. When 1233 the MN receives the message, it replaces the IPv6 destination address 1234 with the next hop found in the routing header and transmits the 1235 message over the OMNI interface identified by the Anycast OMNI ULA. 1237 Multiple distinct OMNI links can therefore be used to support fault 1238 tolerance, load balancing, reliability, etc. The architectural model 1239 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1241 12. Router Discovery and Prefix Registration 1243 MNs interface with the MS by sending RS messages with OMNI options 1244 under the assumption that a single AR on the ANET will process the 1245 message and respond. This places a requirement on each ANET, which 1246 may be enforced by physical/logical partitioning, L2 AR beaconing, 1247 etc. The manner in which the ANET ensures single AR coordination is 1248 link-specific and outside the scope of this document (however, 1249 considerations for ANETs that do not provide ARs that recognize the 1250 OMNI option are discussed in Section 17). 1252 For each underlying interface, the MN sends an RS message with an 1253 OMNI option to coordinate with MSEs identified by MSID values. 1254 Example MSID discovery methods are given in [RFC5214] and include 1255 data link login parameters, name service lookups, static 1256 configuration, a static "hosts" file, etc. The MN can also send an 1257 RS with an MS-Register suboption that includes the Anycast MSID value 1258 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1259 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1260 be itself) and returns an RA with the selected MSID in an MS-Register 1261 suboption. The AR selects only a single wildcard MSE (i.e., even if 1262 the RS MS-Register suboption included multiple '0' MSIDs) while also 1263 soliciting the MSEs corresponding to any non-zero MSIDs. 1265 MNs configure OMNI interfaces that observe the properties discussed 1266 in the previous section. The OMNI interface and its underlying 1267 interfaces are said to be in either the "UP" or "DOWN" state 1268 according to administrative actions in conjunction with the interface 1269 connectivity status. An OMNI interface transitions to UP or DOWN 1270 through administrative action and/or through state transitions of the 1271 underlying interfaces. When a first underlying interface transitions 1272 to UP, the OMNI interface also transitions to UP. When all 1273 underlying interfaces transition to DOWN, the OMNI interface also 1274 transitions to DOWN. 1276 When an OMNI interface transitions to UP, the MN sends RS messages to 1277 register its MNP and an initial set of underlying interfaces that are 1278 also UP. The MN sends additional RS messages to refresh lifetimes 1279 and to register/deregister underlying interfaces as they transition 1280 to UP or DOWN. The MN sends initial RS messages over an UP 1281 underlying interface with its OMNI LLA as the source and with 1282 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1283 messages include an OMNI option per Section 9 with valid prefix 1284 registration information, Interface Attributes appropriate for 1285 underlying interfaces, MS-Register/Release sub-options containing 1286 MSID values, and with any other necessary OMNI sub-options. The OMNI 1287 header ifIndex field is set to the index of the underlying interface 1288 over which the RS message is sent. 1290 ARs process IPv6 ND messages with OMNI options and act as an MSE 1291 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1292 and create a neighbor cache entry for the MN, then coordinate with 1293 any MSEs named in the Register/Release lists in a manner outside the 1294 scope of this document. When an MSE processes the OMNI information, 1295 it first validates the prefix registration information then injects/ 1296 withdraws the MNP in the routing/mapping system and caches/discards 1297 the new Prefix Length, MNP and Interface Attributes. The MSE then 1298 informs the AR of registration success/failure, and the AR returns an 1299 RA message to the MN with an OMNI option per Section 9. 1301 The AR returns the RA message via the same underlying interface of 1302 the MN over which the RS was received, and with destination address 1303 set to the MN OMNI LLA (i.e., unicast), with source address set to 1304 its own OMNI LLA, and with an OMNI option with ifIndex set to the 1305 value included in the RS. The OMNI option also includes valid prefix 1306 registration information, Interface Attributes, MS-Register/Release 1307 and any other necessary OMNI sub-options. The RA also includes any 1308 information for the link, including RA Cur Hop Limit, M and O flags, 1309 Router Lifetime, Reachable Time and Retrans Timer values, and 1310 includes any necessary options such as: 1312 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1314 o RIOs [RFC4191] with more-specific routes. 1316 o an MTU option that specifies the maximum acceptable packet size 1317 for this ANET interface. 1319 The AR MAY also send periodic and/or event-driven unsolicited RA 1320 messages per [RFC4861]. In that case, the ifIndex field in the OMNI 1321 header of the unsolicited RA message identifies the target underlying 1322 interface of the destination MN. 1324 The AR can combine the information from multiple MSEs into one or 1325 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1326 Each aggregate RA includes an OMNI option with MS-Register/Release 1327 sub-options with the MSEs represented by the aggregate. If an 1328 aggregate is sent, the RA message contents must consistently 1329 represent the combined information advertised by all represented 1330 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1331 address, the MN determines the addresses of the represented MSEs by 1332 examining the MS-Register/Release OMNI sub-options. 1334 When the MN receives the RA message, it creates an OMNI interface 1335 neighbor cache entry for each MSID that has confirmed MNP 1336 registration via the L2 address of this AR. If the MN connects to 1337 multiple ANETs, it records the additional L2 AR addresses in each 1338 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1339 then manages its underlying interfaces according to their states as 1340 follows: 1342 o When an underlying interface transitions to UP, the MN sends an RS 1343 over the underlying interface with an OMNI option. The OMNI 1344 option contains at least one Interface Attribute sub-option with 1345 values specific to this underlying interface, and may contain 1346 additional Interface Attributes specific to other underlying 1347 interfaces. The option also includes any MS-Register/Release sub- 1348 options. 1350 o When an underlying interface transitions to DOWN, the MN sends an 1351 RS or unsolicited NA message over any UP underlying interface with 1352 an OMNI option containing an Interface Attribute sub-option for 1353 the DOWN underlying interface with Link set to '0'. The MN sends 1354 an RS when an acknowledgement is required, or an unsolicited NA 1355 when reliability is not thought to be a concern (e.g., if 1356 redundant transmissions are sent on multiple underlying 1357 interfaces). 1359 o When the Router Lifetime for a specific AR nears expiration, the 1360 MN sends an RS over the underlying interface to receive a fresh 1361 RA. If no RA is received, the MN can send RS messages to an 1362 alternate MSID in case the current MSID has failed. If no RS 1363 messages are received even after trying to contact alternate 1364 MSIDs, the MN marks the underlying interface as DOWN. 1366 o When a MN wishes to release from one or more current MSIDs, it 1367 sends an RS or unsolicited NA message over any UP underlying 1368 interfaces with an OMNI option with a Release MSID. Each MSID 1369 then withdraws the MNP from the routing/mapping system and informs 1370 the AR that the release was successful. 1372 o When all of a MNs underlying interfaces have transitioned to DOWN 1373 (or if the prefix registration lifetime expires), any associated 1374 MSEs withdraw the MNP the same as if they had received a message 1375 with a release indication. 1377 The MN is responsible for retrying each RS exchange up to 1378 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1379 seconds until an RA is received. If no RA is received over a an UP 1380 underlying interface (i.e., even after attempting to contact 1381 alternate MSEs), the MN declares this underlying interface as DOWN. 1383 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1384 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1385 returns an internally-generated RA message as though the message 1386 originated from an IPv6 router. The internally-generated RA message 1387 contains configuration information that is consistent with the 1388 information received from the RAs generated by the MS. Whether the 1389 OMNI interface IPv6 ND messaging process is initiated from the 1390 receipt of an RS message from the IPv6 layer is an implementation 1391 matter. Some implementations may elect to defer the IPv6 ND 1392 messaging process until an RS is received from the IPv6 layer, while 1393 others may elect to initiate the process proactively. Still other 1394 deployments may elect to administratively disable the ordinary RS/RA 1395 messaging used by the IPv6 layer over the OMNI interface, since they 1396 are not required to drive the internal RS/RA processing. 1398 Note: The Router Lifetime value in RA messages indicates the time 1399 before which the MN must send another RS message over this underlying 1400 interface (e.g., 600 seconds), however that timescale may be 1401 significantly longer than the lifetime the MS has committed to retain 1402 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1403 therefore responsible for keeping MS state alive on a shorter 1404 timescale than the MN is required to do on its own behalf. 1406 Note: On multicast-capable underlying interfaces, MNs should send 1407 periodic unsolicited multicast NA messages and ARs should send 1408 periodic unsolicited multicast RA messages as "beacons" that can be 1409 heard by other nodes on the link. If a node fails to receive a 1410 beacon after a timeout value specific to the link, it can initiate a 1411 unicast exchange to test reachability. 1413 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1415 On some ANET types a MN may be located multiple IP hops away from the 1416 nearest AR. Forwarding through IP multihop ANETs is conducted 1417 through the application of a routing protocol, e.g., a Mobile Ad-hoc 1418 Network (MANET) routing protocol over omni-directional wireless 1419 interfaces. These ANETs could be either IPv6-enabled or IPv4-only, 1420 while IPv4-only ANETs could be either multicast-capable or unicast- 1421 only (note that for IPv4-only ANETs the following procedures apply 1422 for both single-hop and multhop cases). 1424 A MN located potentially multiple ANET hops away from the nearst AR 1425 prepares an RS message with source address set to its OMNI LLA and 1426 with destination set to link-scoped All-Routers multicast the same as 1427 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1428 the message in an IPv6 header with source address set to the ULA 1429 corresponding to the LLA source address and with destination set to 1430 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1431 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1432 with source address set to the node's own IPv4 address. For 1433 multicast-capable IPv4-only ANETs, the MN then sets the destination 1434 address to the site-scoped IPv4 multicast address corresponding to 1435 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1436 IPv4-only ANETs, the MN instead sets the destination address to the 1437 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1438 encapsulated RS message via the ANET interface, where it will be 1439 forwarded by zero or more intermediate ANET hops. 1441 When an intermediate ANET hop that particpates in the routing 1442 protocol receives the encapsulated RS, it forwards the message 1443 according to its routing tables (note that an intermediate node could 1444 be a fixed infrastructure element or another MN). This process 1445 repeats iteratively until the RS message is received by a penultimate 1446 ANET hop within single-hop communications range of an AR, which 1447 forwards the message to the AR. 1449 When the AR receives the message, it decapsulates the RS and 1450 coordinates with the MS the same as for an ordinary link-local RS, 1451 since the inner Hop Limit will not have been decremented by the 1452 multihop forwarding process. The AR then prepares an RA message with 1453 source address set to its own LLA and destination address set to the 1454 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1455 header with source address set to its own IPv4/ULA address and with 1456 destination set to the encapsulation source of the RS. 1458 The AR then forwards the message to an ANET node within 1459 communications range, which forwards the message according to its 1460 routing tables to an intermediate node. The multihop forwarding 1461 process within the ANET continues repetitively until the message is 1462 delivered to the original MN, which decapsulates the message and 1463 performs autoconfiguration the same as if it had received the RA 1464 directly from the AR as an on-link neighbor. 1466 Note: An alternate approach to multihop forwarding via IPv6 1467 encapsulation would be to statelessly translate the IPv6 LLAs into 1468 ULAs and forward the messages without encapsulation. This would 1469 violate the [RFC4861] requirement that certain IPv6 ND messages must 1470 use link-local addresses and must not be accepted if received with 1471 Hop Limit less than 255. This document therefore advocates 1472 encapsulation since the overhead is nominal considering the 1473 infrequent nature and small size of IPv6 ND messages. Future 1474 documents may consider encapsulation avoidance through translation 1475 while updating [RFC4861]. 1477 Note: An alternate approach to multihop forwarding via IPv4 1478 encapsulation would be to employ IPv6/IPv4 protocol translation. 1479 However, for IPv6 ND messages the OMNI LLA addresses would be 1480 truncated due to translation and the OMNI Router and Prefix Discovery 1481 services would not be able to function. The use of IPv4 1482 encapsulation is therefore indicated. 1484 Note: The Section 5 procedures for encapsulation and fragmentation of 1485 large packets across MTU-constrained ANETs applies equally in the IP 1486 multihop and IPv4-only cases. In particular, mid-layer IPv6 1487 encapsulation and fragmentation are used to convey large packets, 1488 i.e., instead of using outer IPv4 fragmentation or inner IPv6 1489 fragmentation. 1491 12.2. MS-Register and MS-Release List Processing 1493 When a MN sends an RS message with an OMNI option via an underlying 1494 interface to an AR, the MN must convey its knowledge of its 1495 currently-associated MSEs. Initially, the MN will have no associated 1496 MSEs and should therefore include an MS-Register sub-option with the 1497 single MSID value 0 which requests the AR to select and assign an 1498 MSE. The AR will then return an RA message with source address set 1499 to the OMNI LLA containing the MSE of the selected MSE. 1501 As the MN activates additional underlying interfaces, it can 1502 optionally include an MS-Register sub-option with MSID value 0, or 1503 with non-zero MSIDs for MSEs discovered from previous RS/RA 1504 exchanges. The MN will thus eventually begin to learn and manage its 1505 currently active set of MSEs, and can register with new MSEs or 1506 release from former MSEs with each successive RS/RA exchange. As the 1507 MN's MSE constituency grows, it alone is responsible for including or 1508 omitting MSIDs in the MS-Register/Release lists it sends in RS 1509 messages. The inclusion or omission of MSIDs determines the MN's 1510 interface to the MS and defines the manner in which MSEs will 1511 respond. The only limiting factor is that the MN should include no 1512 more than MAX_MSID values in each list per each IPv6 ND message, and 1513 should avoid duplication of entries in each list unless it wants to 1514 increase likelihood of control message delivery. 1516 When an AR receives an RS message sent by a MN with an OMNI option, 1517 the option will contain zero or more MS-Register and MS-Release sub- 1518 options containing MSIDs. After processing the OMNI option, the AR 1519 will have a list of zero or more MS-Register MSIDs and a list of zero 1520 or more of MS-Release MSIDs. The AR then processes the lists as 1521 follows: 1523 o For each list, retain the first MAX_MSID values in the list and 1524 discard any additional MSIDs (i.e., even if there are duplicates 1525 within a list). 1527 o Next, for each MSID in the MS-Register list, remove all matching 1528 MSIDs from the MS-Release list. 1530 o Next, proceed according to whether the AR's own MSID or the value 1531 0 appears in the MS-Register list as folllows: 1533 * If yes, send an RA message directly back to the MN and send a 1534 proxy copy of the RS message to each additional MSID in the MS- 1535 Register list with the MS-Register/Release lists omitted. 1536 Then, send a uNA message to each MSID in the MS-Release list 1537 with the MS-Register/Release lists omitted and with an 1538 Interface Attributes sub-option with ifIndex set to 0. 1540 * If no, send a proxy copy of the RS message to each additional 1541 MSID in the MS-Register list with the MS-Register list omitted. 1542 For the first MSID, include the original MS-Release list; for 1543 all other MSIDs, omit the MS-Release list. 1545 Each proxy copy of the RS message will include an OMNI option and 1546 encapsulation header with the ULA of the AR as the source and the ULA 1547 of the Register MSE as the destination. When the Register MSE 1548 receives the proxy RS message, if the message includes an MS-Release 1549 list the MSE sends a uNA message to each additional MSID in the 1550 Release list. The Register MSE then sends an RA message back to the 1551 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1552 destination addresses reversed, and with RA destination set to the 1553 LLA of the MN. When the AR receives this RA message, it sends a 1554 proxy copy of the RA to the MN. 1556 Each uNA message (whether send by the first-hop AR or by a Register 1557 MSE) will include an OMNI option and an encapsulation header with the 1558 ULA of the Register MSE as the source and the ULA of the Release ME 1559 as the destination. The uNA informs the Release MSE that its 1560 previous relationship with the MN has been released and that the 1561 source of the uNA message is now registered. The Release MSE must 1562 then note that the subject MN of the uNA message is now "departed", 1563 and forward any subsequent packets destined to the MN to the Register 1564 MSE. 1566 Note that it is not an error for the MS-Register/Release lists to 1567 include duplicate entries. If duplicates occur within a list, the 1568 the AR will generate multiple proxy RS and/or uNA messages - one for 1569 each copy of the duplicate entries. 1571 13. Secure Redirection 1573 If the ANET link model is multiple access, the AR is responsible for 1574 assuring that address duplication cannot corrupt the neighbor caches 1575 of other nodes on the link. When the MN sends an RS message on a 1576 multiple access ANET link, the AR verifies that the MN is authorized 1577 to use the address and returns an RA with a non-zero Router Lifetime 1578 only if the MN is authorized. 1580 After verifying MN authorization and returning an RA, the AR MAY 1581 return IPv6 ND Redirect messages to direct MNs located on the same 1582 ANET link to exchange packets directly without transiting the AR. In 1583 that case, the MNs can exchange packets according to their unicast L2 1584 addresses discovered from the Redirect message instead of using the 1585 dogleg path through the AR. In some ANET links, however, such direct 1586 communications may be undesirable and continued use of the dogleg 1587 path through the AR may provide better performance. In that case, 1588 the AR can refrain from sending Redirects, and/or MNs can ignore 1589 them. 1591 14. AR and MSE Resilience 1593 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1594 [RFC5798] configurations so that service continuity is maintained 1595 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1596 the (redundant) ARs is currently providing service, and any service 1597 discontinuity will be limited to the failover time supported by VRRP. 1598 Widely deployed public domain implementations of VRRP are available. 1600 MSEs SHOULD use high availability clustering services so that 1601 multiple redundant systems can provide coordinated response to 1602 failures. As with VRRP, widely deployed public domain 1603 implementations of high availability clustering services are 1604 available. Note that special-purpose and expensive dedicated 1605 hardware is not necessary, and public domain implementations can be 1606 used even between lightweight virtual machines in cloud deployments. 1608 15. Detecting and Responding to MSE Failures 1610 In environments where fast recovery from MSE failure is required, ARs 1611 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1612 manner that parallels Bidirectional Forwarding Detection (BFD) 1613 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1614 react to failures so that cached information is re-established 1615 through alternate paths. Proactive NUD control messaging is carried 1616 only over well-connected ground domain networks (i.e., and not low- 1617 end ANET links such as aeronautical radios) and can therefore be 1618 tuned for rapid response. 1620 ARs perform proactive NUD for MSEs for which there are currently 1621 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1622 of the outage by sending multicast RA messages on the ANET interface. 1623 The AR sends RA messages to MNs via the ANET interface with an OMNI 1624 option with a Release ID for the failed MSE, and with destination 1625 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1627 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1628 by small delays [RFC4861]. Any MNs on the ANET interface that have 1629 been using the (now defunct) MSE will receive the RA messages and 1630 associate with a new MSE. 1632 16. Transition Considerations 1634 When a MN connects to an ANET link for the first time, it sends an RS 1635 message with an OMNI option. If the first hop AR recognizes the 1636 option, it returns an RA with its MS OMNI LLA as the source, the MN 1637 OMNI LLA as the destination and with an OMNI option included. The MN 1638 then engages the AR according to the OMNI link model specified above. 1639 If the first hop AR is a legacy IPv6 router, however, it instead 1640 returns an RA message with no OMNI option and with a non-OMNI unicast 1641 source LLA as specified in [RFC4861]. In that case, the MN engages 1642 the ANET according to the legacy IPv6 link model and without the OMNI 1643 extensions specified in this document. 1645 If the ANET link model is multiple access, there must be assurance 1646 that address duplication cannot corrupt the neighbor caches of other 1647 nodes on the link. When the MN sends an RS message on a multiple 1648 access ANET link with an OMNI LLA source address and an OMNI option, 1649 ARs that recognize the option ensure that the MN is authorized to use 1650 the address and return an RA with a non-zero Router Lifetime only if 1651 the MN is authorized. ARs that do not recognize the option instead 1652 return an RA that makes no statement about the MN's authorization to 1653 use the source address. In that case, the MN should perform 1654 Duplicate Address Detection to ensure that it does not interfere with 1655 other nodes on the link. 1657 An alternative approach for multiple access ANET links to ensure 1658 isolation for MN / AR communications is through L2 address mappings 1659 as discussed in Appendix C. This arrangement imparts a (virtual) 1660 point-to-point link model over the (physical) multiple access link. 1662 17. OMNI Interfaces on the Open Internet 1664 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1665 the open Internet without an OMNI-aware first-hop AR receive RA 1666 messages that do not include an OMNI option, while OMNI interfaces 1667 configured over IPv4-only underlying interfaces do not receive any 1668 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1669 without an OMNI option configure addresses, on-link prefxies, etc. on 1670 the underlying interface that received the RA according to standard 1671 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1672 interfaces configured over IPv4-only underlying interfaces configure 1673 IPv4 address information on the underlying interfaces using 1674 mechanisms such as DHCPv4 [RFC2131]. 1676 OMNI interfaces configured over underlying interfaces that connect to 1677 the open Internet can apply security services such as VPNs to connect 1678 to an MSE or establish a direct link to an MSE through some other 1679 means. In environments where an explicit VPN or direct link may be 1680 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1681 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1682 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1683 other protocol-specific security services can can also be used if 1684 additional authentication is necessary.) 1686 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1687 interfaces send control plane messages to interface with the MS. The 1688 control plane messages must be authenticated while data plane 1689 messages are delivered the same as for ordinary best-effort Internet 1690 traffic with basic source address-based data origin verification. 1691 Data plane communications via OMNI interfaces that connect over the 1692 open Internet without an explicit VPN should therefore employ 1693 transport- or higher-layer security to ensure integrity and/or 1694 confidentiality. 1696 When SEND/CGA are used over an open Internet underlying interfaces, 1697 each OMNI node configures a link-local CGA for use as the source 1698 address of IPv6 ND messages. The node then employs OMNI link 1699 encapsualation and sets the IPv6 source address of the OMNI header to 1700 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1701 the IPv6 ND message OMNI option then apply to the ULA found in the 1702 OMNI header, i.e., and not to the CGA found in the IPv6 ND source 1703 address. 1705 OMNI interfaces in the open Internet are often located behind Network 1706 Address Translators (NATs). The OMNI interface accommodates NAT 1707 traversal using UDP/IP encapsulation and the mechanisms discussed in 1708 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1710 18. Time-Varying MNPs 1712 In some use cases, it is desirable, beneficial and efficient for the 1713 MN to receive a constant MNP that travels with the MN wherever it 1714 moves. For example, this would allow air traffic controllers to 1715 easily track aircraft, etc. In other cases, however (e.g., 1716 intelligent transportation systems), the MN may be willing to 1717 sacrifice a modicum of efficiency in order to have time-varying MNPs 1718 that can be changed every so often to defeat adversarial tracking. 1720 Prefix delegation services such as those discussed in 1721 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1722 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1723 prefixes. In that case, the identity of the MN can be used as a 1724 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1725 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1726 internal networks whenever its MNP (and therefore also its OMNI 1727 address) changes. This should not present a challenge for MNs with 1728 automated network renumbering services, however presents limits for 1729 the durations of ongoing sessions that would prefer to use a constant 1730 address. 1732 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1733 sets the source address of an RS message to fe80:: and includes a 1734 DUID sub-option and a desired Prefix Length value in the RS message 1735 OMNI option. When the first-hop AR receives the RS message, it 1736 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1737 of the requested length then returns an RA message with the OMNI LLA 1738 corresponding to the MNP as the destination address. When the MN 1739 receives the RA message, it provisons the PD to its downstream- 1740 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1741 messaging. 1743 19. IANA Considerations 1745 The IANA is instructed to allocate an official Type number TBD from 1746 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1747 option. Implementations set Type to 253 as an interim value 1748 [RFC4727]. 1750 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1751 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1752 read as follows: 1754 Code Name Reference 1755 --- ---- --------- 1756 0 Diagnostic Packet Too Big [RFC4443] 1757 1 Advisory Packet Too Big [RFCXXXX] 1759 Figure 16: OMNI Option Sub-Type Values 1761 The IANA is instructed to allocate one Ethernet unicast address TBD2 1762 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1763 Address Block - Unicast Use". 1765 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1766 is instructed to create and maintain a new registry entitled "OMNI 1767 option Sub-Type values". Initial values for the OMNI option Sub-Type 1768 values registry are given below; future assignments are to be made 1769 through Expert Review [RFC8126]. 1771 Value Sub-Type name Reference 1772 ----- ------------- ---------- 1773 0 Pad1 [RFCXXXX] 1774 1 PadN [RFCXXXX] 1775 2 Interface Attributes [RFCXXXX] 1776 3 Traffic Selector [RFCXXXX] 1777 4 MS-Register [RFCXXXX] 1778 5 MS-Release [RFCXXXX] 1779 6 Network Acceess Identifier [RFCXXXX] 1780 7 Geo Coordinates [RFCXXXX] 1781 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1782 9-252 Unassigned 1783 253-254 Experimental [RFCXXXX] 1784 255 Reserved [RFCXXXX] 1786 Figure 17: OMNI Option Sub-Type Values 1788 20. Security Considerations 1790 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1791 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1792 include Nonce and Timestamp options [RFC3971] when transaction 1793 confirmation and/or time synchronization is needed. 1795 OMNI interfaces configured over secured ANET interfaces inherit the 1796 physical and/or link-layer security properties of the connected 1797 ANETs. OMNI interfaces configured over open INET interfaces can use 1798 symmetric securing services such as VPNs or can by some other means 1799 establish a direct link. When a VPN or direct link may be 1800 impractical, however, an asymmetric security service such as SEcure 1801 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1802 Addresses (CGAs) [RFC3972], the authentication option specified in 1803 [RFC4380] or other protocol control message security mechanisms may 1804 be necessary. While the OMNI link protects control plane messaging, 1805 applications must still employ end-to-end transport- or higher-layer 1806 security services to protect the data plane. 1808 The Mobility Service MUST provide strong network layer security for 1809 control plane messages and forwading path integrity for data plane 1810 messages. In one example, the AERO service 1811 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1812 mobility service elements and secures the links in the spanning tree 1813 with network layer security mechanisms such as IPsec [RFC4301] or 1814 Wireguard. Control plane messages are then constrained to travel 1815 only over the secured spanning tree paths and are therefore protected 1816 from attack or eavesdropping. Since data plane messages can travel 1817 over route optimized paths that do not strictly follow the spanning 1818 tree, however, end-to-end transport- or higher-layer security 1819 services are still required. 1821 Security considerations for specific access network interface types 1822 are covered under the corresponding IP-over-(foo) specification 1823 (e.g., [RFC2464], [RFC2492], etc.). 1825 Security considerations for IPv6 fragmentation and reassembly are 1826 discussed in Section 5.1. 1828 21. Implementation Status 1830 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 1831 internal release, while Draft -30 is scheduled for implementation in 1832 the soon-to-be-tagged AERO/OMNI 3.0.1 internal release. First public 1833 release expected before the end of 2020. 1835 22. Acknowledgements 1837 The first version of this document was prepared per the consensus 1838 decision at the 7th Conference of the International Civil Aviation 1839 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1840 2019. Consensus to take the document forward to the IETF was reached 1841 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1842 Attendees and contributors included: Guray Acar, Danny Bharj, 1843 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1844 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1845 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1846 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1847 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1848 Fryderyk Wrobel and Dongsong Zeng. 1850 The following individuals are acknowledged for their useful comments: 1851 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1852 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1853 Skorepa are recognized for their many helpful ideas and suggestions. 1854 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 1855 Rajagopalan are acknowledged for their hard work on the 1856 implementation and insights that led to improvements to the spec. 1858 This work is aligned with the NASA Safe Autonomous Systems Operation 1859 (SASO) program under NASA contract number NNA16BD84C. 1861 This work is aligned with the FAA as per the SE2025 contract number 1862 DTFAWA-15-D-00030. 1864 23. References 1866 23.1. Normative References 1868 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1869 Requirement Levels", BCP 14, RFC 2119, 1870 DOI 10.17487/RFC2119, March 1997, 1871 . 1873 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1874 "Definition of the Differentiated Services Field (DS 1875 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1876 DOI 10.17487/RFC2474, December 1998, 1877 . 1879 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1880 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1881 DOI 10.17487/RFC3971, March 2005, 1882 . 1884 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1885 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1886 . 1888 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1889 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1890 November 2005, . 1892 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1893 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1894 . 1896 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1897 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1898 2006, . 1900 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1901 Control Message Protocol (ICMPv6) for the Internet 1902 Protocol Version 6 (IPv6) Specification", STD 89, 1903 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1904 . 1906 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1907 ICMPv6, UDP, and TCP Headers", RFC 4727, 1908 DOI 10.17487/RFC4727, November 2006, 1909 . 1911 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1912 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1913 DOI 10.17487/RFC4861, September 2007, 1914 . 1916 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1917 Address Autoconfiguration", RFC 4862, 1918 DOI 10.17487/RFC4862, September 2007, 1919 . 1921 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1922 "Traffic Selectors for Flow Bindings", RFC 6088, 1923 DOI 10.17487/RFC6088, January 2011, 1924 . 1926 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1927 Hosts in a Multi-Prefix Network", RFC 8028, 1928 DOI 10.17487/RFC8028, November 2016, 1929 . 1931 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1932 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1933 May 2017, . 1935 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1936 (IPv6) Specification", STD 86, RFC 8200, 1937 DOI 10.17487/RFC8200, July 2017, 1938 . 1940 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 1941 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 1942 DOI 10.17487/RFC8201, July 2017, 1943 . 1945 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1946 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1947 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1948 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1949 . 1951 23.2. Informative References 1953 [I-D.ietf-intarea-frag-fragile] 1954 Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 1955 and F. Gont, "IP Fragmentation Considered Fragile", draft- 1956 ietf-intarea-frag-fragile-17 (work in progress), September 1957 2019. 1959 [I-D.ietf-intarea-tunnels] 1960 Touch, J. and M. Townsley, "IP Tunnels in the Internet 1961 Architecture", draft-ietf-intarea-tunnels-10 (work in 1962 progress), September 2019. 1964 [I-D.templin-6man-dhcpv6-ndopt] 1965 Templin, F., "A Unified Stateful/Stateless Configuration 1966 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 1967 (work in progress), June 2020. 1969 [I-D.templin-intarea-6706bis] 1970 Templin, F., "Asymmetric Extended Route Optimization 1971 (AERO)", draft-templin-intarea-6706bis-59 (work in 1972 progress), August 2020. 1974 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 1975 Communication Layers", STD 3, RFC 1122, 1976 DOI 10.17487/RFC1122, October 1989, 1977 . 1979 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1980 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1981 . 1983 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 1984 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 1985 . 1987 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 1988 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 1989 . 1991 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1992 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 1993 December 1998, . 1995 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 1996 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 1997 . 1999 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2000 Domains without Explicit Tunnels", RFC 2529, 2001 DOI 10.17487/RFC2529, March 1999, 2002 . 2004 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2005 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2006 . 2008 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2009 Considered Useful", BCP 82, RFC 3692, 2010 DOI 10.17487/RFC3692, January 2004, 2011 . 2013 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2014 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2015 DOI 10.17487/RFC3810, June 2004, 2016 . 2018 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2019 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2020 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2021 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2022 . 2024 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2025 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2026 2004, . 2028 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2029 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2030 December 2005, . 2032 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2033 Network Address Translations (NATs)", RFC 4380, 2034 DOI 10.17487/RFC4380, February 2006, 2035 . 2037 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2038 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2039 2006, . 2041 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2042 "Considerations for Internet Group Management Protocol 2043 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2044 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2045 . 2047 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2048 "Internet Group Management Protocol (IGMP) / Multicast 2049 Listener Discovery (MLD)-Based Multicast Forwarding 2050 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2051 August 2006, . 2053 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2054 Errors at High Data Rates", RFC 4963, 2055 DOI 10.17487/RFC4963, July 2007, 2056 . 2058 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2059 Advertisement Flags Option", RFC 5175, 2060 DOI 10.17487/RFC5175, March 2008, 2061 . 2063 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2064 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2065 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2066 . 2068 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2069 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2070 DOI 10.17487/RFC5214, March 2008, 2071 . 2073 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2074 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2075 . 2077 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2078 Version 3 for IPv4 and IPv6", RFC 5798, 2079 DOI 10.17487/RFC5798, March 2010, 2080 . 2082 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2083 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2084 . 2086 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2087 DOI 10.17487/RFC6081, January 2011, 2088 . 2090 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2091 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2092 DOI 10.17487/RFC6355, August 2011, 2093 . 2095 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2096 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2097 2012, . 2099 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2100 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2101 DOI 10.17487/RFC7084, November 2013, 2102 . 2104 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2105 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2106 Boundary in IPv6 Addressing", RFC 7421, 2107 DOI 10.17487/RFC7421, January 2015, 2108 . 2110 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2111 DOI 10.17487/RFC7542, May 2015, 2112 . 2114 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2115 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2116 February 2016, . 2118 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2119 Support for IP Hosts with Multi-Access Support", RFC 7847, 2120 DOI 10.17487/RFC7847, May 2016, 2121 . 2123 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2124 Writing an IANA Considerations Section in RFCs", BCP 26, 2125 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2126 . 2128 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2129 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2130 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2131 July 2018, . 2133 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2134 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2135 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2136 . 2138 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2140 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2141 encoding to specific Internetworks such as the Aeronautical 2142 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2143 may include link selection preferences based on other traffic 2144 classifiers (e.g., transport port numbers, etc.) in addition to the 2145 existing DSCP-based preferences. Nodes on specific Internetworks 2146 maintain a map of traffic classifiers to additional P[*] preference 2147 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2148 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2150 Implementations use Simplex or Indexed encoding formats for P[*] 2151 encoding in order to encode a given set of traffic classifiers in the 2152 most efficient way. Some use cases may be more efficiently coded 2153 using Simplex form, while others may be more efficient using Indexed. 2154 Once a format is selected for preparation of a single Interface 2155 Attribute the same format must be used for the entire Interface 2156 Attribute sub-option. Different sub-options may use different 2157 formats. 2159 The following figures show coding examples for various Simplex and 2160 Indexed formats: 2162 0 1 2 3 2163 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 2164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2165 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2167 | Provider ID | Link |R| LHS | Bitmap(0)=0xff|P00|P01|P02|P03| 2168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2169 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2171 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2173 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2175 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2177 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2180 Figure 18: Example 1: Dense Simplex Encoding 2182 0 1 2 3 2183 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 2184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2185 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2187 | Provider ID | Link |R| LHS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2189 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2191 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2193 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2195 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2197 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2199 |Bitmap(10)=0x00| ... 2200 +-+-+-+-+-+-+-+-+-+-+- 2202 Figure 19: Example 2: Sparse Simplex Encoding 2204 0 1 2 3 2205 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 2206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2207 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2209 | Provider ID | Link |R| LHS | Index = 0x00 | Bitmap = 0x80 | 2210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2211 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2213 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2215 | Bitmap = 0x01 |796|797|798|799| ... 2216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2218 Figure 20: Example 3: Indexed Encoding 2220 Appendix B. VDL Mode 2 Considerations 2222 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2223 (VDLM2) that specifies an essential radio frequency data link service 2224 for aircraft and ground stations in worldwide civil aviation air 2225 traffic management. The VDLM2 link type is "multicast capable" 2226 [RFC4861], but with considerable differences from common multicast 2227 links such as Ethernet and IEEE 802.11. 2229 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2230 magnitude less than most modern wireless networking gear. Second, 2231 due to the low available link bandwidth only VDLM2 ground stations 2232 (i.e., and not aircraft) are permitted to send broadcasts, and even 2233 so only as compact layer 2 "beacons". Third, aircraft employ the 2234 services of ground stations by performing unicast RS/RA exchanges 2235 upon receipt of beacons instead of listening for multicast RA 2236 messages and/or sending multicast RS messages. 2238 This beacon-oriented unicast RS/RA approach is necessary to conserve 2239 the already-scarce available link bandwidth. Moreover, since the 2240 numbers of beaconing ground stations operating within a given spatial 2241 range must be kept as sparse as possible, it would not be feasible to 2242 have different classes of ground stations within the same region 2243 observing different protocols. It is therefore highly desirable that 2244 all ground stations observe a common language of RS/RA as specified 2245 in this document. 2247 Note that links of this nature may benefit from compression 2248 techniques that reduce the bandwidth necessary for conveying the same 2249 amount of data. The IETF lpwan working group is considering possible 2250 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2252 Appendix C. MN / AR Isolation Through L2 Address Mapping 2254 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2255 unicast link-scoped IPv6 destination address. However, IPv6 ND 2256 messaging should be coordinated between the MN and AR only without 2257 invoking other nodes on the ANET. This implies that MN / AR control 2258 messaging should be isolated and not overheard by other nodes on the 2259 link. 2261 To support MN / AR isolation on some ANET links, ARs can maintain an 2262 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2263 ANETs, this specification reserves one Ethernet unicast address TBD2 2264 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2265 MSADDR is reserved per the assigned numbers authority for the ANET 2266 addressing space. For still other ANETs, MSADDR may be dynamically 2267 discovered through other means, e.g., L2 beacons. 2269 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2270 both multicast and unicast) to MSADDR instead of to an ordinary 2271 unicast or multicast L2 address. In this way, all of the MN's IPv6 2272 ND messages will be received by ARs that are configured to accept 2273 packets destined to MSADDR. Note that multiple ARs on the link could 2274 be configured to accept packets destined to MSADDR, e.g., as a basis 2275 for supporting redundancy. 2277 Therefore, ARs must accept and process packets destined to MSADDR, 2278 while all other devices must not process packets destined to MSADDR. 2279 This model has well-established operational experience in Proxy 2280 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2282 Appendix D. Change Log 2284 << RFC Editor - remove prior to publication >> 2286 Differences from draft-templin-6man-omni-interface-29 to draft- 2287 templin-6man-omni-interface-30: 2289 o Moved link-layer addressing information into the OMNI option on a 2290 per-ifIndex basis 2292 o Renamed "ifIndex-tuple" to "Interface Attributes" 2294 Differences from draft-templin-6man-omni-interface-27 to draft- 2295 templin-6man-omni-interface-28: 2297 o Updates based on implementation expereince. 2299 Differences from draft-templin-6man-omni-interface-25 to draft- 2300 templin-6man-omni-interface-26: 2302 o Further clarification on "aggregate" RA messages. 2304 o Expanded Security Considerations to discuss expectations for 2305 security in the Mobility Service. 2307 Differences from draft-templin-6man-omni-interface-20 to draft- 2308 templin-6man-omni-interface-21: 2310 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2311 (PBM). 2313 Differences from draft-templin-6man-omni-interface-18 to draft- 2314 templin-6man-omni-interface-19: 2316 o SEND/CGA. 2318 Differences from draft-templin-6man-omni-interface-17 to draft- 2319 templin-6man-omni-interface-18: 2321 o Teredo 2323 Differences from draft-templin-6man-omni-interface-14 to draft- 2324 templin-6man-omni-interface-15: 2326 o Prefix length discussions removed. 2328 Differences from draft-templin-6man-omni-interface-12 to draft- 2329 templin-6man-omni-interface-13: 2331 o Teredo 2333 Differences from draft-templin-6man-omni-interface-11 to draft- 2334 templin-6man-omni-interface-12: 2336 o Major simplifications and clarifications on MTU and fragmentation. 2338 o Document now updates RFC4443 and RFC8201. 2340 Differences from draft-templin-6man-omni-interface-10 to draft- 2341 templin-6man-omni-interface-11: 2343 o Removed /64 assumption, resulting in new OMNI address format. 2345 Differences from draft-templin-6man-omni-interface-07 to draft- 2346 templin-6man-omni-interface-08: 2348 o OMNI MNs in the open Internet 2350 Differences from draft-templin-6man-omni-interface-06 to draft- 2351 templin-6man-omni-interface-07: 2353 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2354 L2 addressing. 2356 o Expanded "Transition Considerations". 2358 Differences from draft-templin-6man-omni-interface-05 to draft- 2359 templin-6man-omni-interface-06: 2361 o Brought back OMNI option "R" flag, and discussed its use. 2363 Differences from draft-templin-6man-omni-interface-04 to draft- 2364 templin-6man-omni-interface-05: 2366 o Transition considerations, and overhaul of RS/RA addressing with 2367 the inclusion of MSE addresses within the OMNI option instead of 2368 as RS/RA addresses (developed under FAA SE2025 contract number 2369 DTFAWA-15-D-00030). 2371 Differences from draft-templin-6man-omni-interface-02 to draft- 2372 templin-6man-omni-interface-03: 2374 o Added "advisory PTB messages" under FAA SE2025 contract number 2375 DTFAWA-15-D-00030. 2377 Differences from draft-templin-6man-omni-interface-01 to draft- 2378 templin-6man-omni-interface-02: 2380 o Removed "Primary" flag and supporting text. 2382 o Clarified that "Router Lifetime" applies to each ANET interface 2383 independently, and that the union of all ANET interface Router 2384 Lifetimes determines MSE lifetime. 2386 Differences from draft-templin-6man-omni-interface-00 to draft- 2387 templin-6man-omni-interface-01: 2389 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2390 for future use (most likely as "pseudo-multicast"). 2392 o Non-normative discussion of alternate OMNI LLA construction form 2393 made possible if the 64-bit assumption were relaxed. 2395 First draft version (draft-templin-atn-aero-interface-00): 2397 o Draft based on consensus decision of ICAO Working Group I Mobility 2398 Subgroup March 22, 2019. 2400 Authors' Addresses 2402 Fred L. Templin (editor) 2403 The Boeing Company 2404 P.O. Box 3707 2405 Seattle, WA 98124 2406 USA 2408 Email: fltemplin@acm.org 2410 Tony Whyman 2411 MWA Ltd c/o Inmarsat Global Ltd 2412 99 City Road 2413 London EC1Y 1AX 2414 England 2416 Email: tony.whyman@mccallumwhyman.com