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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: rfc1191, rfc4193, rfc4291, A. Whyman 5 rfc4443, rfc8201 (if approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track September 23, 2020 7 Expires: March 27, 2021 9 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-36 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 27, 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. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 11 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 14 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 15 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 15 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 16 67 9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 17 68 9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 19 69 9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 20 70 9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 20 71 9.1.3. Interface Attributes . . . . . . . . . . . . . . . . 20 72 9.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 24 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 25 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 25 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 26 76 9.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . . 27 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 27 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 28 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 28 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 28 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 29 82 12.1. Router Discovery in IP Multihop and IPv4-Only Access 83 Networks . . . . . . . . . . . . . . . . . . . . . . . . 33 84 12.2. MS-Register and MS-Release List Processing . . . . . . . 34 85 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 36 86 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 36 87 15. Detecting and Responding to MSE Failures . . . . . . . . . . 37 88 16. Transition Considerations . . . . . . . . . . . . . . . . . . 37 89 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 38 90 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 39 91 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 92 20. Security Considerations . . . . . . . . . . . . . . . . . . . 40 93 21. Implementation Status . . . . . . . . . . . . . . . . . . . . 41 94 22. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41 95 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 96 23.1. Normative References . . . . . . . . . . . . . . . . . . 42 97 23.2. Informative References . . . . . . . . . . . . . . . . . 44 98 Appendix A. Interface Attribute Heuristic Bitmap Encoding . . . 48 99 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 49 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 50 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 104 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 Adaptation Layer (OAL) 248 an OMNI interface process whereby packets admitted into the 249 interface are wrapped in a mid-layer IPv6 header and fragmented/ 250 reassembled if necessary to support the OMNI link Maximum 251 Transmission Unit (MTU). The OAL is also responsible for 252 generating MTU-related control messages as necessary, and for 253 providing addressing context for spanning multiple segments of a 254 bridged OMNI link. 256 OMNI Link-Local Address (LLA) 257 a link local IPv6 address per [RFC4291] constructed as specified 258 in Section 7. 260 OMNI Unique-Local Address (ULA) 261 a unique local IPv6 address per [RFC4193] constructed as specified 262 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 263 and vice-versa. 265 OMNI Option 266 an IPv6 Neighbor Discovery option providing multilink parameters 267 for the OMNI interface as specified in Section 9. 269 Multilink 270 an OMNI interface's manner of managing diverse underlying data 271 link interfaces as a single logical unit. The OMNI interface 272 provides a single unified interface to upper layers, while 273 underlying data link selections are performed on a per-packet 274 basis considering factors such as DSCP, flow label, application 275 policy, signal quality, cost, etc. Multilinking decisions are 276 coordinated in both the outbound (i.e. MN to correspondent) and 277 inbound (i.e., correspondent to MN) directions. 279 L2 280 The second layer in the OSI network model. Also known as "layer- 281 2", "link-layer", "sub-IP layer", "data link layer", etc. 283 L3 284 The third layer in the OSI network model. Also known as "layer- 285 3", "network-layer", "IPv6 layer", etc. 287 underlying interface 288 an ANET/INET interface over which an OMNI interface is configured. 289 The OMNI interface is seen as a L3 interface by the IP layer, and 290 each underlying interface is seen as a L2 interface by the OMNI 291 interface. 293 Mobility Service Identification (MSID) 294 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 295 as specified in Section 7. 297 Safety-Based Multilink (SBM) 298 A means for ensuring fault tolerance through redundancy by 299 connecting multiple independent OMNI interfaces to independent 300 routing topologies (i.e., multiple independent OMNI links). 302 Performance Based Multilink (PBM) 303 A means for selecting underlying interface(s) for packet 304 trasnmission and reception within a single OMNI interface. 306 3. Requirements 308 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 309 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 310 "OPTIONAL" in this document are to be interpreted as described in BCP 311 14 [RFC2119][RFC8174] when, and only when, they appear in all 312 capitals, as shown here. 314 OMNI links maintain a constant value "MAX_MSID" selected to provide 315 MNs with an acceptable level of MSE redundancy while minimizing 316 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 317 set to the default value 5; if a different value is chosen, it should 318 be set uniformly by all nodes on the OMNI link. 320 An implementation is not required to internally use the architectural 321 constructs described here so long as its external behavior is 322 consistent with that described in this document. 324 4. Overlay Multilink Network (OMNI) Interface Model 326 An OMNI interface is a MN virtual interface configured over one or 327 more underlying interfaces, which may be physical (e.g., an 328 aeronautical radio link) or virtual (e.g., an Internet or higher- 329 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 330 with the MS through IPv6 ND message exchanges. The MN uses the MNP 331 to construct a unique OMNI LLA through the algorithmic derivation 332 specified in Section 7 and assigns the LLA to the OMNI interface. 334 The OMNI interface architectural layering model is the same as in 335 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 336 therefore sees the OMNI interface as a single L3 interface with 337 multiple underlying interfaces that appear as L2 communication 338 channels in the architecture. 340 +----------------------------+ 341 | Upper Layer Protocol | 342 Session-to-IP +---->| | 343 Address Binding | +----------------------------+ 344 +---->| IP (L3) | 345 IP Address +---->| | 346 Binding | +----------------------------+ 347 +---->| OMNI Interface | 348 Logical-to- +---->| (OMNI LLA) | 349 Physical | +----------------------------+ 350 Interface +---->| L2 | L2 | | L2 | 351 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 352 +------+------+ +------+ 353 | L1 | L1 | | L1 | 354 | | | | | 355 +------+------+ +------+ 357 Figure 1: OMNI Interface Architectural Layering Model 359 The OMNI virtual interface model gives rise to a number of 360 opportunities: 362 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 363 Address Detection (DAD) or Muticast Listener Discovery (MLD) 364 messaging is necessary. 366 o ANET interfaces do not require any L3 addresses (i.e., not even 367 link-local) in environments where communications are coordinated 368 entirely over the OMNI interface. (An alternative would be to 369 also assign the same OMNI LLA to all ANET interfaces.) 371 o as ANET interface properties change (e.g., link quality, cost, 372 availability, etc.), any active ANET interface can be used to 373 update the profiles of multiple additional ANET interfaces in a 374 single message. This allows for timely adaptation and service 375 continuity under dynamically changing conditions. 377 o coordinating ANET interfaces in this way allows them to be 378 represented in a unified MS profile with provisions for mobility 379 and multilink operations. 381 o exposing a single virtual interface abstraction to the IPv6 layer 382 allows for multilink operation (including QoS based link 383 selection, packet replication, load balancing, etc.) at L2 while 384 still permitting L3 traffic shaping based on, e.g., DSCP, flow 385 label, etc. 387 o L3 sees the OMNI interface as a point of connection to the OMNI 388 link; if there are multiple OMNI links (i.e., multiple MS's), L3 389 will see multiple OMNI interfaces. 391 o Multiple independent OMNI interfaces can be used for increased 392 fault tolerance through Safety-Based Multilink (SBM), with 393 Performance-Based Multilink (PBM) applied within each interface. 395 Other opportunities are discussed in [RFC7847]. 397 Figure 2 depicts the architectural model for a MN connecting to the 398 MS via multiple independent ANETs. When an underlying interface 399 becomes active, the MN's OMNI interface sends native (i.e., 400 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 401 ND messages traverse the ground domain ANETs until they reach an 402 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 403 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 404 returns an IPv6 ND message response to the MN. IPv6 ND messages 405 traverse the ANET at layer 2; hence, the Hop Limit is not 406 decremented. 408 +--------------+ 409 | MN | 410 +--------------+ 411 |OMNI interface| 412 +----+----+----+ 413 +--------|IF#1|IF#2|IF#n|------ + 414 / +----+----+----+ \ 415 / | \ 416 / <---- Native | IP ----> \ 417 v v v 418 (:::)-. (:::)-. (:::)-. 419 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 420 `-(::::)-' `-(::::)-' `-(::::)-' 421 +----+ +----+ +----+ 422 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 423 . +-|--+ +-|--+ +-|--+ . 424 . | | | 425 . v v v . 426 . <----- Encapsulation -----> . 427 . . 428 . +-----+ (:::)-. . 429 . |MSE#2| .-(::::::::) +-----+ . 430 . +-----+ .-(::: INET :::)-. |MSE#m| . 431 . (::::: Routing ::::) +-----+ . 432 . `-(::: System :::)-' . 433 . +-----+ `-(:::::::-' . 434 . |MSE#1| +-----+ +-----+ . 435 . +-----+ |MSE#3| |MSE#4| . 436 . +-----+ +-----+ . 437 . . 438 . . 439 . <----- Worldwide Connected Internetwork ----> . 440 ........................................................... 442 Figure 2: MN/MS Coordination via Multiple ANETs 444 After the initial IPv6 ND message exchange, the MN can send and 445 receive unencapsulated IPv6 data packets over the OMNI interface. 446 OMNI interface multilink services will forward the packets via ARs in 447 the correct underlying ANETs. The AR encapsulates the packets 448 according to the capabilities provided by the MS and forwards them to 449 the next hop within the worldwide connected Internetwork via optimal 450 routes. 452 OMNI links span one or more underlying Internetwork via the OMNI 453 Adaptation Layer (OAL) which is based on a mid-layer overlay 454 encapsulation using [RFC2473] with [RFC4193] addressing. Each OMNI 455 link corresponds to a different overlay (differentiated by an address 456 codepoint) which may be carried over a completely separate underlying 457 topology. Each MN can facilitate SBM by connecting to multiple OMNI 458 links using a distinct OMNI interface for each link. 460 5. The OMNI Adaptation Layer (OAL) 462 The OMNI interface observes the link nature of tunnels, including the 463 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 464 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 465 The OMNI interface is configured over one or more underlying 466 interfaces that may have diverse MTUs. OMNI interfaces accommodate 467 MTU diversity through the use of the OMNI Adpatation Layer (OAL) as 468 discussed in this section. 470 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 471 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 472 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 473 not permitted to perform network fragmentation even though the 474 destination is required to reassemble more. The network therefore 475 MUST forward packets of at least 1280 bytes without generating an 476 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 477 [RFC8201]. (Note: the source can apply IPv6 "source fragmentation" 478 for locally-generated IPv6 packets up to 1500 bytes and larger still 479 if it if has a way to determine that the destination configures a 480 larger MRU, but this does not affect the minimum IPv6 path MTU.) 482 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 483 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 484 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 485 minimum IPv4 path MTU is 576 bytes since routers on the path support 486 network fragmentation and the destination is required to reassemble 487 at least that much. The DF bit in the IPv4 encapsulation headers of 488 packets sent over IPv4 underlying interfaces therefore MUST be set to 489 0. (Note: even if the encapsulation source has a way to determine 490 that the encapsulation destination configures an MRU larger than 576 491 bytes, a larger minimum IPv4 path MTU should not be assumed without 492 careful consderation of the issues discussed in Section 5.1.) 494 The OMNI interface configures both an MTU and MRU of 9180 bytes 495 [RFC2492]; the size is therefore not a reflection of the underlying 496 interface MTUs, but rather determines the largest packet the OMNI 497 interface can forward or reassemble. The OMNI interface uses the 498 OMNI Adaptation Layer (OAL) to admit packets from the network layer 499 that are no larger than the OMNI interface MTU while generating 500 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 501 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. We 502 refer to both of these ICMPv4/ICMPv6 message types simply as "PTBs". 504 For IPv4 packets with DF=0 and locally-generated IPv6 packets, the 505 network layer performs IP fragmentation according to the OMNI 506 interface MTU if necessary then admits the fragments into the 507 interface; the OAL may then internally apply further IP fragmentation 508 prior to encapsulation. These fragments will be reassembled by the 509 final destination. (Note: Implementations normally apply 510 fragmentation prior to encapsulation according to the minimum IPv4/ 511 IPv6 path MTU in order to avoid further fragmentation in the network, 512 however they can optionally apply a larger size according to the 513 underlying interface MTU if the node that will reassemble is an on- 514 link neighbor on the underlying interface.) 516 Following any fragmentation of the original packet, OMNI interfaces 517 internally employ the OAL by either inserting or omitting a mid-layer 518 IPv6 header between the inner IP packet and any outer IP 519 encapsulation headers per [RFC2473], then performing fragmentation on 520 the mid-layer IPv6 packet when necessary. The OAL returns 521 internally-generated PTB "hard" or "soft" error messages for packets 522 admitted into the interface that it deems too large (e.g., according 523 to link performance characteristics, reassembly congestion, etc.) 524 while either dropping or forwarding the packet, respectively. The 525 OAL performs PMTUD even if the destination appears to be on the same 526 link since an OMNI link node on the path may return a PTB. This 527 ensures that the path MTU is adaptive and reflects the current path 528 used for a given data flow. 530 The OAL operates with respect to both the minimum IPv6 and IPv4 path 531 MTUs as follows: 533 o When an OMNI interface sends a packet toward a final destination 534 via an ANET peer, it sends without OAL encapsulation if the packet 535 (including any outer-layer ANET encapsulations) is no larger than 536 the underlying interface MTU for on-link ANET peers or the minimum 537 ANET path MTU for peers separated by multiple IP hops. Otherwise, 538 the OAL inserts an IPv6 header with source address set to the 539 node's own OMNI Unique Local Address (ULA) (see: Section 8) and 540 destination set to the OMNI ULA of the ANET peer. The OAL then 541 uses IPv6 fragmentation to break the packet into a minimum number 542 of non-overlapping fragments, where the largest fragment size 543 (including both the OMNI and any outer-layer ANET encapsulations) 544 is determined by the (path) MTU for the ANET peer. The OAL then 545 encapsulates the fragements in any ANET headers and sends them to 546 the ANET peer, which reassembles before forwarding toward the 547 final destination. 549 o When an OMNI interface sends a packet toward a final destination 550 via an INET interface, it sends packets (including any outer-layer 551 INET encapsulations) no larger than the minimum INET path MTU 552 without OAL encapsulation if the destination is reached via an 553 INET address within the same OMNI link segment. Otherwise, the 554 OAL inserts an IPv6 header with source address set to the node's 555 OMNI ULA, destination set to the ULA of the next hop OMNI node 556 toward the final destination and (if necessary) with a Segment 557 Routing Header with the remaining Segment IDs on the path to the 558 final destination. The OAL then uses IPv6 fragmentation to break 559 the packet into a minimum number of non-overlapping fragments, 560 where the largest fragment size (including both the OMNI and 561 outer-layer INET encapsulations) is the minimum INET path MTU, and 562 the smallest fragment size is no smaller than 256 bytes (i.e., 563 slightly less than half the minimum IPv4 path MTU). The OAL then 564 encapsulates the fragments in any INET headers and sends them to 565 the OMNI link neighbor, which reassembles before forwarding toward 566 the final destination. 568 The OAL unconditionally drops all OAL fragments received from an INET 569 peer that are smaller than 256 bytes (note that no minimum fragment 570 size is specified for ANET peers since the underlying ANET is secured 571 against tiny fragment attacks). In order to set the correct context 572 for reassembly, the OAL of the OMNI interface that inserts the IPv6 573 header MUST also be the one that inserts the IPv6 Fragment Header 574 Identification value. While not strictly required, sending all 575 fragments of the same fragmented OAL packet consecutively over the 576 same underlying interface with minimal inter-fragment delay may 577 increase the likelihood of successful reassembly. 579 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 580 header Code field value 0 are "hard errors" that always indicate that 581 a packet has been dropped. However, the OAL can selectively forward 582 large packets via encapsulation and fragmentation while at the same 583 time returning "soft error" PTB messages (subject to rate limiting) 584 indicating that a forwarded packet was uncomfortably large. (The 585 receiving node that performs reassembly can also send soft errors if 586 reassembly conditions become unfavorable.) The OMNI interface can 587 therefore continuously forward large packets without loss while 588 returning soft error PTB messages recommending a smaller size. 589 Original sources that receive the soft errors in turn reduce the size 590 of the packets they send, i.e., the same as for hard errors. 592 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 593 field to the value 1 in PTB soft error messages. Receiving nodes 594 that recognize the code reduce their estimate of the path MTU the 595 same as for ordinary hard errors but do not regard the message as a 596 loss indication. Nodes that do not recognize the code treat the 597 message the same as a hard error, but should heed the retransmission 598 advice given in [RFC8201] which suggests retransmission based on 599 normal packetization layer retransmission timers. This document 600 therefore updates [RFC1191][RFC4443] and [RFC8201]. 602 Note: In networks where IPv6/IPv4 protocol translation may be 603 prevalent, it may be prudent for the OAL to always assume the IPv4 604 minimum path MTU (i.e., 576 bytes) regardless of the underlying 605 interface IP protocol version. Always assuming the IPv4 minimum path 606 MTU even for IPv6 networks may produce more fragments and additional 607 header overhead, but will always interoperate and never run the risk 608 of presenting an IPv4 node with a packet that exceeds its MRU. 610 5.1. Fragmentation Security Implications 612 As discussed in Section 3.7 of [RFC8900], there are four basic 613 threats concerning IPv6 fragmentation; each of which is addressed by 614 effective mitigations as follows: 616 1. Overlapping fragment attacks - reassembly of overlapping 617 fragments is forbidden by [RFC8200]; therefore, this threat does 618 not apply to the OAL. 620 2. Resource exhaustion attacks - this threat is mitigated by 621 providing a sufficiently large OAL reassembly cache and 622 instituting "fast discard" of incomplete reassemblies that may be 623 part of a buffer exhaustion attack. The reassembly cache should 624 be sufficiently large so that a sustained attack does not cause 625 excessive loss of good reassemblies but not so large that (timer- 626 based) data structure management becomes computationally 627 expensive. 629 3. Attacks based on predictable fragment identification values - 630 this threat is mitigated by selecting a suitably random ID value 631 per [RFC7739]. 633 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 634 threat is mitigated by disallowing "tiny fragments" per the OAL 635 fragmentation procedures specified above. 637 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 638 ID) field with only 65535 unique values such that at high data rates 639 the field could wrap and apply to new packets while the fragments of 640 old packets using the same ID are still alive in the network 641 [RFC4963]. However, since the largest OAL fragment that will be sent 642 via an IPv4 INET path is 576 bytes any IPv4 fragmentation would occur 643 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 644 recommendations suggest that such links will have low data rates. 645 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 646 at high data rates is not a concern for IPv6 fragmentation. 648 6. Frame Format 650 The OMNI interface transmits IPv6 packets according to the native 651 frame format of each underlying interface. For example, for 652 Ethernet-compatible interfaces the frame format is specified in 653 [RFC2464], for aeronautical radio interfaces the frame format is 654 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 655 Manual), for tunnels over IPv6 the frame format is specified in 656 [RFC2473], etc. 658 7. Link-Local Addresses (LLAs) 660 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 661 LLAs") as follows: 663 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 664 within the least-significant 112 bits of the IPv6 link-local 665 prefix fe80::/16. The Prefix Length is determined by adding 16 to 666 the length of the embedded MNP. For example, for the MNP 667 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 668 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 669 link-local address format specified in Section 2.5.6 of [RFC4291] 670 by defining a use for bits 11 - 63. 672 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 673 i.e., the most significant 16 bits of the prefix fe80::/16, 674 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 675 32bit IPv4 address/prefix. The Prefix Length is determined by 676 adding 96 to the length of the embedded IPv4 address/prefix. For 677 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 678 fe80::ffff:192.0.2.0/120 (also written as 679 fe80::ffff:c000:0200/120). 681 o MS OMNI LLAs are assigned to ARs and MSEs from the range 682 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 683 of the LLA includes a unique integer "MSID" value between 684 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 685 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 686 determined by adding 96 to the MSID prefix length. For example, 687 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 688 Prefix Length is set to 112 and the LLA is written as 689 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 690 "Anycast" MSID and corresponds to the link-local Subnet-Router 691 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 692 through 0xffffffff is reserved for future use. 694 o The OMNI LLA range fe80::/32 is used as the service prefix for the 695 address format specified in Section 4 of [RFC4380] (see Section 17 696 for further discussion). 698 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 699 MNPs can be allocated from that block ensuring that there is no 700 possibility for overlap between the above OMNI LLA constructs. 702 Since MN OMNI LLAs are based on the distribution of administratively 703 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 704 through administrative assignment, OMNI interfaces set the 705 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 707 8. Unique-Local Addresses (ULAs) 709 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 710 [RFC4193] as the source and destination addresses in OAL IPv6 711 encapsulation headers. This document currently assumes use of the 712 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 713 (however, see the note at the end of this section). 715 Each OMNI link instance is identified by bits 10-15 of the OMNI 716 service prefix fc80::/10. For example, OMNI ULAs associated with 717 instance 0 are configured from the prefix fc80::/16, instance 1 from 718 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 719 their associated prefix lengths are configured in one-to-one 720 correspondence with OMNI LLAs through stateless prefix translation. 721 For example, for OMNI link instance fc80::/16: 723 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 724 fc80:2001:db8:1:2::/80 726 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 727 fc80::ffff:192.0.2.0/120 729 o the OMNI ULA corresponding to fe80::1000/112 is simply 730 fc80::1000/112 732 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 734 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 735 link instance, e.g., the OMNI interface connected to instance 3 736 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 737 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 738 the local routing system so that applications can direct traffic 739 according to SBM requirements. 741 The OMNI ULA presents an IPv6 address format that is routable within 742 the OMNI link routing system and can be used to convey link-scoped 743 messages across multiple hops using IPv6 encapsulation [RFC2473]. 744 The OMNI link extends across one or more underling Internetworks to 745 include all ARs and MSEs. All MNs are also considered to be 746 connected to the OMNI link, however OAL encapsulation is omitted over 747 ANET links when possible to conserve bandwidth (see: Section 11). 749 The OMNI link can be subdivided into "segments" that often correspond 750 to different administrative domains or physical partitions. OMNI 751 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 752 support efficient packet forwarding to destinations located in other 753 OMNI link segments. A full discussion of Segment Routing over the 754 OMNI link appears in [I-D.templin-intarea-6706bis]. 756 NOTE: An alternative to the application of ULAs as discussed in this 757 document would be to re-purpose the deprectated IPv6 Site-Local 758 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 759 SLAs would be a more natural fit since both LLA and SLA prefix 760 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 761 single bit setting, and LLAs and SLAs can be unambiguously allocated 762 in one-to-one correspondence with one another. Re-purposing SLAs 763 would also make good use of an otherwise-wasted address range that 764 has been "parked" since the 2004 deprecation. However, moving from 765 ULAs to SLAs would require an IETF standards action acknowledging 766 this document as obsoleting [RFC3879] and updating [RFC4291]. The 767 authors therefore defer to IETF consensus as to the proper way 768 forward. 770 9. Address Mapping - Unicast 772 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 773 state and use the link-local address format specified in Section 7. 774 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 775 over physical underlying interfaces without encapsulation observe the 776 native underlying interface Source/Target Link-Layer Address Option 777 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 778 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 779 interfaces via encapsulation do not include S/TLLAOs which were 780 intended for encoding physical L2 media address formats and not 781 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 782 for encoding additional interface attributes. Hence, this document 783 does not define an S/TLLAO format but instead defines a new option 784 type termed the "OMNI option" designed for these purposes. 786 MNs such as aircraft typically have many wireless data link types 787 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 788 etc.) with diverse performance, cost and availability properties. 790 The OMNI interface would therefore appear to have multiple L2 791 connections, and may include information for multiple underlying 792 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 793 an IPv6 ND option called the OMNI option formatted as shown in 794 Figure 3: 796 0 1 2 3 797 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 799 | Type | Length | Prefix Length | S/T-ifIndex | 800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 801 | | 802 ~ Sub-Options ~ 803 | | 804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 806 Figure 3: OMNI Option Format 808 In this format: 810 o Type is set to TBD. If multiple OMNI option instances appear in 811 the same IPv6 ND message, the first instance is processed and all 812 other instances are ignored. 814 o Length is set to the number of 8 octet blocks in the option. 816 o Prefix Length is determines the length of prefix to be applied to 817 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 818 MS, Prefix Length is the length that the MN is requesting or 819 asserting to the MS. For IPv6 ND messages sent from the MS to the 820 MN, Prefix Length indicates the length that the MS is granting to 821 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 822 Length indicates the length associated with the target MN that is 823 subject of the ND message. 825 o S/T-ifIndex corresponds to the ifIndex value for source or target 826 underlying interface used to convey this IPv6 ND message. OMNI 827 interfaces MUST number each distinct underlying interface with an 828 ifIndex value between '1' and '255' that represents a MN-specific 829 8-bit mapping for the actual ifIndex value assigned by network 830 management [RFC2863] (the ifIndex value '0' is reserved for use by 831 the MS). For RS and NS messages,S/T-ifIndex corresponds to the 832 source underlying interface the message originated from. For RA 833 and NA messages, S/T-ifIndex corresponds to the target underlying 834 interface that the message is destined to. 836 o Sub-Options is a Variable-length field, of length such that the 837 complete OMNI Option is an integer multiple of 8 octets long. 838 Contains one or more Sub-Options, as described in Section 9.1. 840 9.1. Sub-Options 842 The OMNI option includes zero or more Sub-Options. Each consecutive 843 Sub-Option is concatenated immediately after its predecessor. All 844 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 845 encoded in the following format: 847 0 1 2 848 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 5 849 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 850 | Sub-Type | Sub-length | Sub-Option Data ... 851 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 853 Figure 4: Sub-Option Format 855 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 856 Sub-Options defined in this document are: 858 Option Name Sub-Type 859 Pad1 0 860 PadN 1 861 Interface Attributes 2 862 Traffic Selector 3 863 MS-Register 4 864 MS-Release 5 865 Network Access Identifier 6 866 Geo Coordinates 7 867 DHCP Unique Identifier (DUID) 8 869 Figure 5 871 Sub-Types 253 and 254 are reserved for experimentation, as 872 recommended in [RFC3692]. 874 o Sub-Length is a 1-octet field that encodes the length of the Sub- 875 Option Data (i.e., ranging from 0 to 255 octets). 877 o Sub-Option Data is a block of data with format determined by Sub- 878 Type. 880 During processing, unrecognized Sub-Options are ignored and the next 881 Sub-Option processed until the end of the OMNI option is reached. 883 The following Sub-Option types and formats are defined in this 884 document: 886 9.1.1. Pad1 888 0 889 0 1 2 3 4 5 6 7 890 +-+-+-+-+-+-+-+-+ 891 | Sub-Type=0 | 892 +-+-+-+-+-+-+-+-+ 894 Figure 6: Pad1 896 o Sub-Type is set to 0. If multiple instances appear in the same 897 OMNI option all are processed. 899 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 900 consists of a single zero octet). 902 9.1.2. PadN 904 0 1 2 905 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 5 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 907 | Sub-Type=1 | Sub-length=N | N padding octets ... 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 910 Figure 7: PadN 912 o Sub-Type is set to 1. If multiple instances appear in the same 913 OMNI option all are processed. 915 o Sub-Length is set to N (from 0 to 255) being the number of padding 916 octets that follow. 918 o Sub-Option Data consists of N zero-valued octets. 920 9.1.3. Interface Attributes 921 0 1 2 3 922 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 1 923 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 924 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 925 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 926 | Provider ID | Link |R| APS | SRT | FMT | LHS (0 - 7) | 927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 928 | LHS (bits 8 - 31) | ~ 929 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 930 ~ ~ 931 ~ Link Layer Address (L2ADDR) ~ 932 ~ ~ 933 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 934 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 935 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 936 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 937 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 938 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 939 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 941 Figure 8: Interface Attributes 943 o Sub-Type is set to 2. If multiple instances with different 944 ifIndex values appear in the same OMNI option all are processed; 945 if multiple instances with the same ifIndex value appear, the 946 first is processed and all others are ignored. 948 o Sub-Length is set to N (from 4 to 255) that encodes the number of 949 Sub-Option Data octets that follow. 951 o Sub-Option Data contains an "Interface Attribute" option encoded 952 as follows (note that the first four octets must be present): 954 * ifIndex is set to an 8-bit integer value corresponding to a 955 specific underlying interface the same as specified above for 956 the OMNI option header S/T-ifIndex. An OMNI option may include 957 multiple Interface Attributes Sub-Options, with each distinct 958 ifIndex value pertaining to a different underlying interface. 959 The OMNI option will often include an Interface Attributes Sub- 960 Option with the same ifIndex value that appears in the S/ 961 T-ifIndex. In that case, the actual encapsulation address of 962 the received IPv6 ND message should be compared with the L2ADDR 963 encoded in the Sub-Option (see below); if the addresses are 964 different (or, if L2ADDR absent) the presence of a Network 965 Address Translator (NAT) is indicated. 967 * ifType is set to an 8-bit integer value corresponding to the 968 underlying interface identified by ifIndex. The value 969 represents an OMNI interface-specific 8-bit mapping for the 970 actual IANA ifType value registered in the 'IANAifType-MIB' 971 registry [http://www.iana.org]. 973 * Provider ID is set to an OMNI interface-specific 8-bit ID value 974 for the network service provider associated with this ifIndex. 976 * Link encodes a 4-bit link metric. The value '0' means the link 977 is DOWN, and the remaining values mean the link is UP with 978 metric ranging from '1' ("lowest") to '15' ("highest"). 980 * R is reserved for future use. 982 * APS - a 3-bit "Address/Preferences/Simplex" code that 983 determines the contents of the remainder of the sub-option as 984 follows: 986 + When the most significant bit (i.e., "Address") is set to 1, 987 the SRT, FMT, LHS and L2ADDR fields are included immediately 988 following the APS code; else, they are omitted. 990 + When the next most significant bit (i.e., "Preferences") is 991 set to 1, a preferences block is included next; else, it is 992 omitted. (Note that if "Address" is set the preferences 993 block immediately follows L2ADDR; else, it immediately 994 follows the APS code.) 996 + When a preferences block is present and the least 997 significant bit (i.e., "Simplex") is set to 1, the block is 998 encoded in "Simplex" form as shown in Figure 8; else it is 999 encoded in "Indexed" form as discussed below. 1001 * When APS indicates that an "Address" is included, the following 1002 fields appear in consecutive order (else, they are omitted): 1004 + SRT - a 5-bit Segment Routing Topology prefix length value 1005 that (when added to 96) determines the prefix length to 1006 apply to the ULA formed from concatenating fc*::/96 with the 1007 32 bit LHS MSID value that follows. For example, the value 1008 16 corresponds to the prefix length 112. 1010 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1011 the included Link Layer Address as follows: 1013 - When the most significant bit (i.e., "Framework") is set 1014 to 0, L2ADDR is the INET encapsulation address of a 1015 Proxy/Server; otherwise, it is the addresss for the 1016 Source/Target itself 1018 - When the next most significant bit (i.e., "Mode") is set 1019 to 0, the Source/Target L2ADDR is on the open INET; 1020 otherwise, it is (likely) located behind a Network 1021 Address Translator (NAT). 1023 - When the least significant bit (i.e., "Type") is set to 1024 0, L2ADDR includes a UDP Port Number followed by an IPv4 1025 address; else, a UDP Port Number followed by an IPv6 1026 address. 1028 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1029 path to the target. When SRT and LHS are both set to 0, the 1030 LHS is considered unspecified in this IPv6 ND message. When 1031 SRT is set to 0 and LHS is non-zero, the prefix length is 1032 set to 128. SRT and LHS provide guidance to the OMNI 1033 interface forwarding algorithm. Specifically, if SRT/LHS is 1034 located in the local OMNI link segment then the OMNI 1035 interface can encapsulate according to FMT/L2ADDR; else, it 1036 must forward according to the OMNI link spanning tree. See 1037 [I-D.templin-intarea-6706bis] for further discussion. 1039 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1040 and identifies the link-layer address (i.e., the 1041 encapsulation address) of the source/target. The UDP Port 1042 Number appears in the first two octets and the IP address 1043 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1044 The Port Number and IP address are recorded in ones- 1045 compliment "obfuscated" form per [RFC4380]. The OMNI 1046 interface forwarding algoritherm uses FMT/L2ADDR to 1047 determine the encapsulation address for forwarding when SRT/ 1048 LHS is located in the local OMNI link segment. 1050 * When APS indicates that "Preferences" are included, a 1051 preferences block appears as the remainder of the Sub-Option as 1052 a series of Bitmaps and P[*] values. In "Simplex" form, the 1053 index for each singleton Bitmap octet is inferred from its 1054 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1055 In "Indexed" form, each Bitmap is preceded by an Index octet 1056 that encodes a value "i" = (0 - 255) as the index for its 1057 companion Bitmap as follows: 1059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1060 | Index=i | Bitmap(i) |P[*] values ... 1061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1063 Figure 9 1065 * The preferences consist of a first (simplex/indexed) Bitmap 1066 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1067 2-bit P[*] values, followed by a second Bitmap (i), followed by 1068 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1069 the bits of each Bitmap(i) that are set to '1'' indicate the 1070 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1071 that follow; if any Bitmap(i) bits are '0', then the 1072 corresponding P[*] block is instead omitted. For example, if 1073 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1074 followed by the block with P[04]-P[07], etc., and ending with 1075 the block with P[28]-P[31] are included (as shown in Figure 8). 1076 The next Bitmap(i) is then consulted with its bits indicating 1077 which P[*] blocks follow, etc. out to the end of the Sub- 1078 Option. 1080 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1081 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1082 preference for underlying interface selection purposes. Not 1083 all P[*] values need to be included in the OMNI option of each 1084 IPv6 ND message received. Any P[*] values represented in an 1085 earlier OMNI option but omitted in the current OMNI option 1086 remain unchanged. Any P[*] values not yet represented in any 1087 OMNI option default to "medium". 1089 * The first 16 P[*] blocks correspond to the 64 Differentiated 1090 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1091 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1092 traffic classifier values P[64], P[65], P[66], etc. See 1093 Appendix A for further discussion and examples. 1095 9.1.4. Traffic Selector 1097 0 1 2 3 1098 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 1099 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1100 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1102 ~ ~ 1103 ~ RFC 6088 Format Traffic Selector ~ 1104 ~ ~ 1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1107 Figure 10: Traffic Selector 1109 o Sub-Type is set to 3. If multiple instances appear in the same 1110 OMNI option all are processed, i.e., even if the same ifIndex 1111 value appears multiple times. 1113 o Sub-Length is set to N (the number of Sub-Option Data octets that 1114 follow). 1116 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1117 specified in Section 9.1.3, followed by an N-1 octet traffic 1118 selector formatted per [RFC6088] beginning with the "TS Format" 1119 field. The largest traffic selector for a given ifIndex is 1120 therefore 254 octets. 1122 9.1.5. MS-Register 1124 0 1 2 3 1125 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 1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1127 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1129 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1131 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1133 ... ... ... ... ... ... 1134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1135 | MSID [n] (bits 16 - 32) | 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1138 Figure 11: MS-Register Sub-option 1140 o Sub-Type is set to 4. If multiple instances appear in the same 1141 OMNI option all are processed. Only the first MAX_MSID values 1142 processed (whether in a single instance or multiple) are retained 1143 and all other MSIDs are ignored. 1145 o Sub-Length is set to 4n. 1147 o A list of n 4-octet MSIDs is included in the following 4n octets. 1148 The Anycast MSID value '0' in an RS message MS-Register sub-option 1149 requests the recipient to return the MSID of a nearby MSE in a 1150 corresponding RA response. 1152 9.1.6. MS-Release 1153 0 1 2 3 1154 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 1155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1156 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1158 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1160 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1162 ... ... ... ... ... ... 1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1164 | MSID [n] (bits 16 - 32) | 1165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1167 Figure 12: MS-Release Sub-option 1169 o Sub-Type is set to 5. If multiple instances appear in the same 1170 IPv6 OMNI option all are processed. Only the first MAX_MSID 1171 values processed (whether in a single instance or multiple) are 1172 retained and all other MSIDs are ignored. 1174 o Sub-Length is set to 4n. 1176 o A list of n 4 octet MSIDs is included in the following 4n octets. 1177 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1178 i.e., only non-zero values are processed. 1180 9.1.7. Network Access Identifier (NAI) 1182 0 1 2 3 1183 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 1184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1185 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1188 Figure 13: Network Access Identifier (NAI) Sub-option 1190 o Sub-Type is set to 6. If multiple instances appear in the same 1191 OMNI option the first is processed and all others are ignored. 1193 o Sub-Length is set to N. 1195 o A Network Access Identifier (NAI) up to 255 octets in length is 1196 coded per [RFC7542]. 1198 9.1.8. Geo Coordinates 1200 0 1 2 3 1201 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 1202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1203 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1206 Figure 14: Geo Coordinates Sub-option 1208 o Sub-Type is set to 7. If multiple instances appear in the same 1209 OMNI option the first is processed and all others are ignored. 1211 o Sub-Length is set to N. 1213 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1214 Includes Latitude/Longitude at a minimum; may also include 1215 additional attributes such as altitude, heading, speed, etc.). 1217 9.1.9. DHCP Unique Identifier (DUID) 1219 0 1 2 3 1220 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 1221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1222 | Sub-Type=8 | Sub-length=N | DUID-Type | 1223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1224 . . 1225 . type-specific DUID body (variable length) . 1226 . . 1227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1229 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1231 o Sub-Type is set to 8. If multiple instances appear in the same 1232 OMNI option the first is processed and all others are ignored. 1234 o Sub-Length is set to N (i.e., the length of the option beginning 1235 with the DUID-Type and continuing to the end of the type-specifc 1236 body). 1238 o DUID-Type is a two-octet field coded in network byte order that 1239 determines the format and contents of the type-specific body 1240 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1241 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1242 which will occur in common operational practice. 1244 o A type-specific DUID body up to 253 octets in length follows, 1245 formatted according to DUID-type. For example, for type 4 the 1246 body consists of a 128-bit UUID selected according to [RFC6355]. 1248 10. Address Mapping - Multicast 1250 The multicast address mapping of the native underlying interface 1251 applies. The mobile router on board the MN also serves as an IGMP/ 1252 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1253 using the L2 address of the AR as the L2 address for all multicast 1254 packets. 1256 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1257 coordinate with the AR, and ANET L2 elements use MLD snooping 1258 [RFC4541]. 1260 11. Conceptual Sending Algorithm 1262 The MN's IPv6 layer selects the outbound OMNI interface according to 1263 SBM considerations when forwarding data packets from local or EUN 1264 applications to external correspondents. Each OMNI interface 1265 maintains a neighbor cache the same as for any IPv6 interface, but 1266 with additional state for multilink coordination. 1268 After a packet enters the OMNI interface, an outbound underlying 1269 interface is selected based on PBM traffic attributes such as DSCP, 1270 application port number, cost, performance, message size, etc. OMNI 1271 interface multilink selections could also be configured to perform 1272 replication across multiple underlying interfaces for increased 1273 reliability at the expense of packet duplication. 1275 When the OMNI interface sends a packet over a selected outbound 1276 underlying interface, the OAL includes or omits a mid-layer 1277 encapsulation header as necessary as discussed in Section 5. The OAL 1278 also performs encapsulation when the nearest AR is located multiple 1279 hops away as discussed in Section 12.1. 1281 OMNI interface multilink service designers MUST observe the BCP 1282 guidance in Section 15 [RFC3819] in terms of implications for 1283 reordering when packets from the same flow may be spread across 1284 multiple underlying interfaces having diverse properties. 1286 11.1. Multiple OMNI Interfaces 1288 MNs may connect to multiple independent OMNI links concurrently in 1289 support of SBM. Each OMNI interface is distinguished by its Anycast 1290 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1291 separate OMNI interface for each link so that multiple interfaces 1292 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1293 different Anycast OMNI ULA is assigned to each interface, and the MN 1294 injects the service prefixes for the OMNI link instances into the EUN 1295 routing system. 1297 Applications in EUNs can use Segment Routing to select the desired 1298 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1299 written into the IPv6 destination address, and the actual destination 1300 (along with any additional intermediate hops) is written into the 1301 Segment Routing Header. Standard IP routing directs the packets to 1302 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1303 the OMNI interface to be used for transmission to the next hop. When 1304 the MN receives the message, it replaces the IPv6 destination address 1305 with the next hop found in the routing header and transmits the 1306 message over the OMNI interface identified by the Anycast OMNI ULA. 1308 Multiple distinct OMNI links can therefore be used to support fault 1309 tolerance, load balancing, reliability, etc. The architectural model 1310 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1312 12. Router Discovery and Prefix Registration 1314 MNs interface with the MS by sending RS messages with OMNI options 1315 under the assumption that one or more AR on the ANET will process the 1316 message and respond. The manner in which the ANET ensures AR 1317 coordination is link-specific and outside the scope of this document 1318 (however, considerations for ANETs that do not provide ARs that 1319 recognize the OMNI option are discussed in Section 17). 1321 For each underlying interface, the MN sends an RS message with an 1322 OMNI option to coordinate with MSEs identified by MSID values. 1323 Example MSID discovery methods are given in [RFC5214] and include 1324 data link login parameters, name service lookups, static 1325 configuration, a static "hosts" file, etc. The MN can also send an 1326 RS with an MS-Register suboption that includes the Anycast MSID value 1327 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1328 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1329 be itself) and returns an RA with the selected MSID in an MS-Register 1330 suboption. The AR selects only a single wildcard MSE (i.e., even if 1331 the RS MS-Register suboption included multiple '0' MSIDs) while also 1332 soliciting the MSEs corresponding to any non-zero MSIDs. 1334 MNs configure OMNI interfaces that observe the properties discussed 1335 in the previous section. The OMNI interface and its underlying 1336 interfaces are said to be in either the "UP" or "DOWN" state 1337 according to administrative actions in conjunction with the interface 1338 connectivity status. An OMNI interface transitions to UP or DOWN 1339 through administrative action and/or through state transitions of the 1340 underlying interfaces. When a first underlying interface transitions 1341 to UP, the OMNI interface also transitions to UP. When all 1342 underlying interfaces transition to DOWN, the OMNI interface also 1343 transitions to DOWN. 1345 When an OMNI interface transitions to UP, the MN sends RS messages to 1346 register its MNP and an initial set of underlying interfaces that are 1347 also UP. The MN sends additional RS messages to refresh lifetimes 1348 and to register/deregister underlying interfaces as they transition 1349 to UP or DOWN. The MN sends initial RS messages over an UP 1350 underlying interface with its OMNI LLA as the source and with 1351 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1352 messages include an OMNI option per Section 9 with valid prefix 1353 registration information, Interface Attributes appropriate for 1354 underlying interfaces, MS-Register/Release sub-options containing 1355 MSID values, and with any other necessary OMNI sub-options. The S/ 1356 T-ifIndex field is set to the index of the underlying interface over 1357 which the RS message is sent. 1359 ARs process IPv6 ND messages with OMNI options and act as an MSE 1360 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1361 and create a neighbor cache entry for the MN, then coordinate with 1362 any MSEs named in the Register/Release lists in a manner outside the 1363 scope of this document. When an MSE processes the OMNI information, 1364 it first validates the prefix registration information then injects/ 1365 withdraws the MNP in the routing/mapping system and caches/discards 1366 the new Prefix Length, MNP and Interface Attributes. The MSE then 1367 informs the AR of registration success/failure, and the AR returns an 1368 RA message to the MN with an OMNI option per Section 9. 1370 The AR returns the RA message via the same underlying interface of 1371 the MN over which the RS was received, and with destination address 1372 set to the MN OMNI LLA (i.e., unicast), with source address set to 1373 its own OMNI LLA, and with an OMNI option with S/T-ifIndex set to the 1374 value included in the RS. The OMNI option also includes valid prefix 1375 registration information, Interface Attributes, MS-Register/Release 1376 and any other necessary OMNI sub-options. The RA also includes any 1377 information for the link, including RA Cur Hop Limit, M and O flags, 1378 Router Lifetime, Reachable Time and Retrans Timer values, and 1379 includes any necessary options such as: 1381 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1383 o RIOs [RFC4191] with more-specific routes. 1385 o an MTU option that specifies the maximum acceptable packet size 1386 for this ANET interface. 1388 The AR MAY also send periodic and/or event-driven unsolicited RA 1389 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1390 OMNI header of the unsolicited RA message identifies the target 1391 underlying interface of the destination MN. 1393 The AR can combine the information from multiple MSEs into one or 1394 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1395 Each aggregate RA includes an OMNI option with MS-Register/Release 1396 sub-options with the MSEs represented by the aggregate. If an 1397 aggregate is sent, the RA message contents must consistently 1398 represent the combined information advertised by all represented 1399 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1400 address, the MN determines the addresses of the represented MSEs by 1401 examining the MS-Register/Release OMNI sub-options. 1403 When the MN receives the RA message, it creates an OMNI interface 1404 neighbor cache entry for each MSID that has confirmed MNP 1405 registration via the L2 address of this AR. If the MN connects to 1406 multiple ANETs, it records the additional L2 AR addresses in each 1407 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1408 then manages its underlying interfaces according to their states as 1409 follows: 1411 o When an underlying interface transitions to UP, the MN sends an RS 1412 over the underlying interface with an OMNI option. The OMNI 1413 option contains at least one Interface Attribute sub-option with 1414 values specific to this underlying interface, and may contain 1415 additional Interface Attributes specific to other underlying 1416 interfaces. The option also includes any MS-Register/Release sub- 1417 options. 1419 o When an underlying interface transitions to DOWN, the MN sends an 1420 RS or unsolicited NA message over any UP underlying interface with 1421 an OMNI option containing an Interface Attribute sub-option for 1422 the DOWN underlying interface with Link set to '0'. The MN sends 1423 an RS when an acknowledgement is required, or an unsolicited NA 1424 when reliability is not thought to be a concern (e.g., if 1425 redundant transmissions are sent on multiple underlying 1426 interfaces). 1428 o When the Router Lifetime for a specific AR nears expiration, the 1429 MN sends an RS over the underlying interface to receive a fresh 1430 RA. If no RA is received, the MN can send RS messages to an 1431 alternate MSID in case the current MSID has failed. If no RS 1432 messages are received even after trying to contact alternate 1433 MSIDs, the MN marks the underlying interface as DOWN. 1435 o When a MN wishes to release from one or more current MSIDs, it 1436 sends an RS or unsolicited NA message over any UP underlying 1437 interfaces with an OMNI option with a Release MSID. Each MSID 1438 then withdraws the MNP from the routing/mapping system and informs 1439 the AR that the release was successful. 1441 o When all of a MNs underlying interfaces have transitioned to DOWN 1442 (or if the prefix registration lifetime expires), any associated 1443 MSEs withdraw the MNP the same as if they had received a message 1444 with a release indication. 1446 The MN is responsible for retrying each RS exchange up to 1447 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1448 seconds until an RA is received. If no RA is received over a an UP 1449 underlying interface (i.e., even after attempting to contact 1450 alternate MSEs), the MN declares this underlying interface as DOWN. 1452 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1453 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1454 returns an internally-generated RA message as though the message 1455 originated from an IPv6 router. The internally-generated RA message 1456 contains configuration information that is consistent with the 1457 information received from the RAs generated by the MS. Whether the 1458 OMNI interface IPv6 ND messaging process is initiated from the 1459 receipt of an RS message from the IPv6 layer is an implementation 1460 matter. Some implementations may elect to defer the IPv6 ND 1461 messaging process until an RS is received from the IPv6 layer, while 1462 others may elect to initiate the process proactively. Still other 1463 deployments may elect to administratively disable the ordinary RS/RA 1464 messaging used by the IPv6 layer over the OMNI interface, since they 1465 are not required to drive the internal RS/RA processing. 1467 Note: The Router Lifetime value in RA messages indicates the time 1468 before which the MN must send another RS message over this underlying 1469 interface (e.g., 600 seconds), however that timescale may be 1470 significantly longer than the lifetime the MS has committed to retain 1471 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1472 therefore responsible for keeping MS state alive on a shorter 1473 timescale than the MN is required to do on its own behalf. 1475 Note: On multicast-capable underlying interfaces, MNs should send 1476 periodic unsolicited multicast NA messages and ARs should send 1477 periodic unsolicited multicast RA messages as "beacons" that can be 1478 heard by other nodes on the link. If a node fails to receive a 1479 beacon after a timeout value specific to the link, it can initiate a 1480 unicast exchange to test reachability. 1482 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1484 On some ANET types a MN may be located multiple IP hops away from the 1485 nearest AR. Forwarding through IP multihop ANETs is conducted 1486 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1487 Network (MANET) routing protocol over omni-directional wireless 1488 interfaces, an inter-domain routing protocol in an enterprise 1489 network, etc.). These ANETs could be either IPv6-enabled or 1490 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1491 unicast-only (note that for IPv4-only ANETs the following procedures 1492 apply for both single-hop and multhop cases). 1494 A MN located potentially multiple ANET hops away from the nearst AR 1495 prepares an RS message with source address set to its OMNI LLA and 1496 with destination set to link-scoped All-Routers multicast the same as 1497 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1498 the message in an IPv6 header with source address set to the ULA 1499 corresponding to the LLA source address and with destination set to 1500 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1501 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1502 with source address set to the node's own IPv4 address. For 1503 multicast-capable IPv4-only ANETs, the MN then sets the destination 1504 address to the site-scoped IPv4 multicast address corresponding to 1505 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1506 IPv4-only ANETs, the MN instead sets the destination address to the 1507 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1508 encapsulated RS message via the ANET interface, where it will be 1509 forwarded by zero or more intermediate ANET hops. 1511 When an intermediate ANET hop that particpates in the routing 1512 protocol receives the encapsulated RS, it forwards the message 1513 according to its routing tables (note that an intermediate node could 1514 be a fixed infrastructure element or another MN). This process 1515 repeats iteratively until the RS message is received by a penultimate 1516 ANET hop within single-hop communications range of an AR, which 1517 forwards the message to the AR. 1519 When the AR receives the message, it decapsulates the RS and 1520 coordinates with the MS the same as for an ordinary link-local RS, 1521 since the inner Hop Limit will not have been decremented by the 1522 multihop forwarding process. The AR then prepares an RA message with 1523 source address set to its own LLA and destination address set to the 1524 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1525 header with source address set to its own IPv4/ULA address and with 1526 destination set to the encapsulation source of the RS. 1528 The AR then forwards the message to an ANET node within 1529 communications range, which forwards the message according to its 1530 routing tables to an intermediate node. The multihop forwarding 1531 process within the ANET continues repetitively until the message is 1532 delivered to the original MN, which decapsulates the message and 1533 performs autoconfiguration the same as if it had received the RA 1534 directly from the AR as an on-link neighbor. 1536 Note: An alternate approach to multihop forwarding via IPv6 1537 encapsulation would be to statelessly translate the IPv6 LLAs into 1538 ULAs and forward the messages without encapsulation. This would 1539 violate the [RFC4861] requirement that certain IPv6 ND messages must 1540 use link-local addresses and must not be accepted if received with 1541 Hop Limit less than 255. This document therefore advocates 1542 encapsulation since the overhead is nominal considering the 1543 infrequent nature and small size of IPv6 ND messages. Future 1544 documents may consider encapsulation avoidance through translation 1545 while updating [RFC4861]. 1547 Note: An alternate approach to multihop forwarding via IPv4 1548 encapsulation would be to employ IPv6/IPv4 protocol translation. 1549 However, for IPv6 ND messages the OMNI LLA addresses would be 1550 truncated due to translation and the OMNI Router and Prefix Discovery 1551 services would not be able to function. The use of IPv4 1552 encapsulation is therefore indicated. 1554 12.2. MS-Register and MS-Release List Processing 1556 When a MN sends an RS message with an OMNI option via an underlying 1557 interface to an AR, the MN must convey its knowledge of its 1558 currently-associated MSEs. Initially, the MN will have no associated 1559 MSEs and should therefore include an MS-Register sub-option with the 1560 single MSID value 0 which requests the AR to select and assign an 1561 MSE. The AR will then return an RA message with source address set 1562 to the OMNI LLA containing the MSE of the selected MSE. 1564 As the MN activates additional underlying interfaces, it can 1565 optionally include an MS-Register sub-option with MSID value 0, or 1566 with non-zero MSIDs for MSEs discovered from previous RS/RA 1567 exchanges. The MN will thus eventually begin to learn and manage its 1568 currently active set of MSEs, and can register with new MSEs or 1569 release from former MSEs with each successive RS/RA exchange. As the 1570 MN's MSE constituency grows, it alone is responsible for including or 1571 omitting MSIDs in the MS-Register/Release lists it sends in RS 1572 messages. The inclusion or omission of MSIDs determines the MN's 1573 interface to the MS and defines the manner in which MSEs will 1574 respond. The only limiting factor is that the MN should include no 1575 more than MAX_MSID values in each list per each IPv6 ND message, and 1576 should avoid duplication of entries in each list unless it wants to 1577 increase likelihood of control message delivery. 1579 When an AR receives an RS message sent by a MN with an OMNI option, 1580 the option will contain zero or more MS-Register and MS-Release sub- 1581 options containing MSIDs. After processing the OMNI option, the AR 1582 will have a list of zero or more MS-Register MSIDs and a list of zero 1583 or more of MS-Release MSIDs. The AR then processes the lists as 1584 follows: 1586 o For each list, retain the first MAX_MSID values in the list and 1587 discard any additional MSIDs (i.e., even if there are duplicates 1588 within a list). 1590 o Next, for each MSID in the MS-Register list, remove all matching 1591 MSIDs from the MS-Release list. 1593 o Next, proceed according to whether the AR's own MSID or the value 1594 0 appears in the MS-Register list as folllows: 1596 * If yes, send an RA message directly back to the MN and send a 1597 proxy copy of the RS message to each additional MSID in the MS- 1598 Register list with the MS-Register/Release lists omitted. 1599 Then, send a uNA message to each MSID in the MS-Release list 1600 with the MS-Register/Release lists omitted and with an OMNI 1601 header with S/T-ifIndex set to 0. 1603 * If no, send a proxy copy of the RS message to each additional 1604 MSID in the MS-Register list with the MS-Register list omitted. 1605 For the first MSID, include the original MS-Release list; for 1606 all other MSIDs, omit the MS-Release list. 1608 Each proxy copy of the RS message will include an OMNI option and 1609 encapsulation header with the ULA of the AR as the source and the ULA 1610 of the Register MSE as the destination. When the Register MSE 1611 receives the proxy RS message, if the message includes an MS-Release 1612 list the MSE sends a uNA message to each additional MSID in the 1613 Release list. The Register MSE then sends an RA message back to the 1614 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1615 destination addresses reversed, and with RA destination set to the 1616 LLA of the MN. When the AR receives this RA message, it sends a 1617 proxy copy of the RA to the MN. 1619 Each uNA message (whether send by the first-hop AR or by a Register 1620 MSE) will include an OMNI option and an encapsulation header with the 1621 ULA of the Register MSE as the source and the ULA of the Release ME 1622 as the destination. The uNA informs the Release MSE that its 1623 previous relationship with the MN has been released and that the 1624 source of the uNA message is now registered. The Release MSE must 1625 then note that the subject MN of the uNA message is now "departed", 1626 and forward any subsequent packets destined to the MN to the Register 1627 MSE. 1629 Note that it is not an error for the MS-Register/Release lists to 1630 include duplicate entries. If duplicates occur within a list, the 1631 the AR will generate multiple proxy RS and/or uNA messages - one for 1632 each copy of the duplicate entries. 1634 13. Secure Redirection 1636 If the ANET link model is multiple access, the AR is responsible for 1637 assuring that address duplication cannot corrupt the neighbor caches 1638 of other nodes on the link. When the MN sends an RS message on a 1639 multiple access ANET link, the AR verifies that the MN is authorized 1640 to use the address and returns an RA with a non-zero Router Lifetime 1641 only if the MN is authorized. 1643 After verifying MN authorization and returning an RA, the AR MAY 1644 return IPv6 ND Redirect messages to direct MNs located on the same 1645 ANET link to exchange packets directly without transiting the AR. In 1646 that case, the MNs can exchange packets according to their unicast L2 1647 addresses discovered from the Redirect message instead of using the 1648 dogleg path through the AR. In some ANET links, however, such direct 1649 communications may be undesirable and continued use of the dogleg 1650 path through the AR may provide better performance. In that case, 1651 the AR can refrain from sending Redirects, and/or MNs can ignore 1652 them. 1654 14. AR and MSE Resilience 1656 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1657 [RFC5798] configurations so that service continuity is maintained 1658 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1659 the (redundant) ARs is currently providing service, and any service 1660 discontinuity will be limited to the failover time supported by VRRP. 1661 Widely deployed public domain implementations of VRRP are available. 1663 MSEs SHOULD use high availability clustering services so that 1664 multiple redundant systems can provide coordinated response to 1665 failures. As with VRRP, widely deployed public domain 1666 implementations of high availability clustering services are 1667 available. Note that special-purpose and expensive dedicated 1668 hardware is not necessary, and public domain implementations can be 1669 used even between lightweight virtual machines in cloud deployments. 1671 15. Detecting and Responding to MSE Failures 1673 In environments where fast recovery from MSE failure is required, ARs 1674 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1675 manner that parallels Bidirectional Forwarding Detection (BFD) 1676 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1677 react to failures so that cached information is re-established 1678 through alternate paths. Proactive NUD control messaging is carried 1679 only over well-connected ground domain networks (i.e., and not low- 1680 end ANET links such as aeronautical radios) and can therefore be 1681 tuned for rapid response. 1683 ARs perform proactive NUD for MSEs for which there are currently 1684 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1685 of the outage by sending multicast RA messages on the ANET interface. 1686 The AR sends RA messages to MNs via the ANET interface with an OMNI 1687 option with a Release ID for the failed MSE, and with destination 1688 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1690 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1691 by small delays [RFC4861]. Any MNs on the ANET interface that have 1692 been using the (now defunct) MSE will receive the RA messages and 1693 associate with a new MSE. 1695 16. Transition Considerations 1697 When a MN connects to an ANET link for the first time, it sends an RS 1698 message with an OMNI option. If the first hop AR recognizes the 1699 option, it returns an RA with its MS OMNI LLA as the source, the MN 1700 OMNI LLA as the destination and with an OMNI option included. The MN 1701 then engages the AR according to the OMNI link model specified above. 1702 If the first hop AR is a legacy IPv6 router, however, it instead 1703 returns an RA message with no OMNI option and with a non-OMNI unicast 1704 source LLA as specified in [RFC4861]. In that case, the MN engages 1705 the ANET according to the legacy IPv6 link model and without the OMNI 1706 extensions specified in this document. 1708 If the ANET link model is multiple access, there must be assurance 1709 that address duplication cannot corrupt the neighbor caches of other 1710 nodes on the link. When the MN sends an RS message on a multiple 1711 access ANET link with an OMNI LLA source address and an OMNI option, 1712 ARs that recognize the option ensure that the MN is authorized to use 1713 the address and return an RA with a non-zero Router Lifetime only if 1714 the MN is authorized. ARs that do not recognize the option instead 1715 return an RA that makes no statement about the MN's authorization to 1716 use the source address. In that case, the MN should perform 1717 Duplicate Address Detection to ensure that it does not interfere with 1718 other nodes on the link. 1720 An alternative approach for multiple access ANET links to ensure 1721 isolation for MN / AR communications is through L2 address mappings 1722 as discussed in Appendix C. This arrangement imparts a (virtual) 1723 point-to-point link model over the (physical) multiple access link. 1725 17. OMNI Interfaces on the Open Internet 1727 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1728 the open Internet without an OMNI-aware first-hop AR receive RA 1729 messages that do not include an OMNI option, while OMNI interfaces 1730 configured over IPv4-only underlying interfaces do not receive any 1731 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1732 without an OMNI option configure addresses, on-link prefxies, etc. on 1733 the underlying interface that received the RA according to standard 1734 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1735 interfaces configured over IPv4-only underlying interfaces configure 1736 IPv4 address information on the underlying interfaces using 1737 mechanisms such as DHCPv4 [RFC2131]. 1739 OMNI interfaces configured over underlying interfaces that connect to 1740 the open Internet can apply security services such as VPNs to connect 1741 to an MSE or establish a direct link to an MSE through some other 1742 means. In environments where an explicit VPN or direct link may be 1743 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1744 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1745 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1746 other protocol-specific security services can can also be used if 1747 additional authentication is necessary.) 1749 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1750 interfaces send control plane messages to interface with the MS. The 1751 control plane messages must be authenticated while data plane 1752 messages are delivered the same as for ordinary best-effort Internet 1753 traffic with basic source address-based data origin verification. 1754 Data plane communications via OMNI interfaces that connect over the 1755 open Internet without an explicit VPN should therefore employ 1756 transport- or higher-layer security to ensure integrity and/or 1757 confidentiality. 1759 When SEND/CGA are used over an open Internet underlying interfaces, 1760 each OMNI node configures a link-local CGA for use as the source 1761 address of IPv6 ND messages. The node then employs OMNI link 1762 encapsualation and sets the IPv6 source address of the OMNI header to 1763 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1764 the IPv6 ND message OMNI option then apply to the ULA found in the 1765 OMNI header, i.e., and not to the CGA found in the IPv6 ND source 1766 address. 1768 OMNI interfaces in the open Internet are often located behind Network 1769 Address Translators (NATs). The OMNI interface accommodates NAT 1770 traversal using UDP/IP encapsulation and the mechanisms discussed in 1771 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1773 18. Time-Varying MNPs 1775 In some use cases, it is desirable, beneficial and efficient for the 1776 MN to receive a constant MNP that travels with the MN wherever it 1777 moves. For example, this would allow air traffic controllers to 1778 easily track aircraft, etc. In other cases, however (e.g., 1779 intelligent transportation systems), the MN may be willing to 1780 sacrifice a modicum of efficiency in order to have time-varying MNPs 1781 that can be changed every so often to defeat adversarial tracking. 1783 Prefix delegation services such as those discussed in 1784 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1785 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1786 prefixes. In that case, the identity of the MN can be used as a 1787 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1788 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1789 internal networks whenever its MNP (and therefore also its OMNI 1790 address) changes. This should not present a challenge for MNs with 1791 automated network renumbering services, however presents limits for 1792 the durations of ongoing sessions that would prefer to use a constant 1793 address. 1795 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1796 sets the source address of an RS message to fe80:: and includes a 1797 DUID sub-option and a desired Prefix Length value in the RS message 1798 OMNI option. When the first-hop AR receives the RS message, it 1799 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1800 of the requested length then returns an RA message with the OMNI LLA 1801 corresponding to the MNP as the destination address. When the MN 1802 receives the RA message, it provisons the PD to its downstream- 1803 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1804 messaging. 1806 19. IANA Considerations 1808 The IANA is instructed to allocate an official Type number TBD from 1809 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1810 option. Implementations set Type to 253 as an interim value 1811 [RFC4727]. 1813 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1814 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1815 read as follows: 1817 Code Name Reference 1818 --- ---- --------- 1819 0 Diagnostic Packet Too Big [RFC4443] 1820 1 Advisory Packet Too Big [RFCXXXX] 1822 Figure 16: OMNI Option Sub-Type Values 1824 The IANA is instructed to allocate one Ethernet unicast address TBD2 1825 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1826 Address Block - Unicast Use". 1828 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1829 is instructed to create and maintain a new registry entitled "OMNI 1830 option Sub-Type values". Initial values for the OMNI option Sub-Type 1831 values registry are given below; future assignments are to be made 1832 through Expert Review [RFC8126]. 1834 Value Sub-Type name Reference 1835 ----- ------------- ---------- 1836 0 Pad1 [RFCXXXX] 1837 1 PadN [RFCXXXX] 1838 2 Interface Attributes [RFCXXXX] 1839 3 Traffic Selector [RFCXXXX] 1840 4 MS-Register [RFCXXXX] 1841 5 MS-Release [RFCXXXX] 1842 6 Network Acceess Identifier [RFCXXXX] 1843 7 Geo Coordinates [RFCXXXX] 1844 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1845 9-252 Unassigned 1846 253-254 Experimental [RFCXXXX] 1847 255 Reserved [RFCXXXX] 1849 Figure 17: OMNI Option Sub-Type Values 1851 20. Security Considerations 1853 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1854 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1855 include Nonce and Timestamp options [RFC3971] when transaction 1856 confirmation and/or time synchronization is needed. 1858 OMNI interfaces configured over secured ANET interfaces inherit the 1859 physical and/or link-layer security properties of the connected 1860 ANETs. OMNI interfaces configured over open INET interfaces can use 1861 symmetric securing services such as VPNs or can by some other means 1862 establish a direct link. When a VPN or direct link may be 1863 impractical, however, an asymmetric security service such as SEcure 1864 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1865 Addresses (CGAs) [RFC3972], the authentication option specified in 1866 [RFC4380] or other protocol control message security mechanisms may 1867 be necessary. While the OMNI link protects control plane messaging, 1868 applications must still employ end-to-end transport- or higher-layer 1869 security services to protect the data plane. 1871 The Mobility Service MUST provide strong network layer security for 1872 control plane messages and forwading path integrity for data plane 1873 messages. In one example, the AERO service 1874 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1875 mobility service elements and secures the links in the spanning tree 1876 with network layer security mechanisms such as IPsec [RFC4301] or 1877 Wireguard. Control plane messages are then constrained to travel 1878 only over the secured spanning tree paths and are therefore protected 1879 from attack or eavesdropping. Since data plane messages can travel 1880 over route optimized paths that do not strictly follow the spanning 1881 tree, however, end-to-end transport- or higher-layer security 1882 services are still required. 1884 Security considerations for specific access network interface types 1885 are covered under the corresponding IP-over-(foo) specification 1886 (e.g., [RFC2464], [RFC2492], etc.). 1888 Security considerations for IPv6 fragmentation and reassembly are 1889 discussed in Section 5.1. 1891 21. Implementation Status 1893 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 1894 internal release, while Draft -30 is scheduled for implementation in 1895 the soon-to-be-tagged AERO/OMNI 3.0.1 internal release. First public 1896 release expected before the end of 2020. 1898 22. Acknowledgements 1900 The first version of this document was prepared per the consensus 1901 decision at the 7th Conference of the International Civil Aviation 1902 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1903 2019. Consensus to take the document forward to the IETF was reached 1904 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1905 Attendees and contributors included: Guray Acar, Danny Bharj, 1906 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1907 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1908 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1909 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1910 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1911 Fryderyk Wrobel and Dongsong Zeng. 1913 The following individuals are acknowledged for their useful comments: 1914 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1915 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1916 Skorepa are recognized for their many helpful ideas and suggestions. 1917 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 1918 Rajagopalan are acknowledged for their hard work on the 1919 implementation and insights that led to improvements to the spec. 1921 This work is aligned with the NASA Safe Autonomous Systems Operation 1922 (SASO) program under NASA contract number NNA16BD84C. 1924 This work is aligned with the FAA as per the SE2025 contract number 1925 DTFAWA-15-D-00030. 1927 23. References 1929 23.1. Normative References 1931 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1932 Requirement Levels", BCP 14, RFC 2119, 1933 DOI 10.17487/RFC2119, March 1997, 1934 . 1936 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1937 "Definition of the Differentiated Services Field (DS 1938 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1939 DOI 10.17487/RFC2474, December 1998, 1940 . 1942 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1943 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1944 DOI 10.17487/RFC3971, March 2005, 1945 . 1947 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1948 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1949 . 1951 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1952 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1953 November 2005, . 1955 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1956 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1957 . 1959 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1960 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1961 2006, . 1963 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1964 Control Message Protocol (ICMPv6) for the Internet 1965 Protocol Version 6 (IPv6) Specification", STD 89, 1966 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1967 . 1969 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1970 ICMPv6, UDP, and TCP Headers", RFC 4727, 1971 DOI 10.17487/RFC4727, November 2006, 1972 . 1974 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1975 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1976 DOI 10.17487/RFC4861, September 2007, 1977 . 1979 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1980 Address Autoconfiguration", RFC 4862, 1981 DOI 10.17487/RFC4862, September 2007, 1982 . 1984 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1985 "Traffic Selectors for Flow Bindings", RFC 6088, 1986 DOI 10.17487/RFC6088, January 2011, 1987 . 1989 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1990 Hosts in a Multi-Prefix Network", RFC 8028, 1991 DOI 10.17487/RFC8028, November 2016, 1992 . 1994 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1995 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1996 May 2017, . 1998 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1999 (IPv6) Specification", STD 86, RFC 8200, 2000 DOI 10.17487/RFC8200, July 2017, 2001 . 2003 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2004 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2005 DOI 10.17487/RFC8201, July 2017, 2006 . 2008 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2009 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2010 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2011 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2012 . 2014 23.2. Informative References 2016 [I-D.ietf-intarea-tunnels] 2017 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2018 Architecture", draft-ietf-intarea-tunnels-10 (work in 2019 progress), September 2019. 2021 [I-D.templin-6man-dhcpv6-ndopt] 2022 Templin, F., "A Unified Stateful/Stateless Configuration 2023 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2024 (work in progress), June 2020. 2026 [I-D.templin-intarea-6706bis] 2027 Templin, F., "Asymmetric Extended Route Optimization 2028 (AERO)", draft-templin-intarea-6706bis-62 (work in 2029 progress), September 2020. 2031 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2032 Communication Layers", STD 3, RFC 1122, 2033 DOI 10.17487/RFC1122, October 1989, 2034 . 2036 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2037 DOI 10.17487/RFC1191, November 1990, 2038 . 2040 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2041 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2042 . 2044 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2045 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2046 . 2048 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2049 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2050 . 2052 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2053 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2054 December 1998, . 2056 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2057 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2058 . 2060 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2061 Domains without Explicit Tunnels", RFC 2529, 2062 DOI 10.17487/RFC2529, March 1999, 2063 . 2065 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2066 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2067 . 2069 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2070 Considered Useful", BCP 82, RFC 3692, 2071 DOI 10.17487/RFC3692, January 2004, 2072 . 2074 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2075 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2076 DOI 10.17487/RFC3810, June 2004, 2077 . 2079 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2080 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2081 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2082 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2083 . 2085 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2086 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2087 2004, . 2089 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2090 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2091 December 2005, . 2093 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2094 Network Address Translations (NATs)", RFC 4380, 2095 DOI 10.17487/RFC4380, February 2006, 2096 . 2098 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2099 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2100 2006, . 2102 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2103 "Considerations for Internet Group Management Protocol 2104 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2105 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2106 . 2108 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2109 "Internet Group Management Protocol (IGMP) / Multicast 2110 Listener Discovery (MLD)-Based Multicast Forwarding 2111 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2112 August 2006, . 2114 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2115 Errors at High Data Rates", RFC 4963, 2116 DOI 10.17487/RFC4963, July 2007, 2117 . 2119 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2120 Advertisement Flags Option", RFC 5175, 2121 DOI 10.17487/RFC5175, March 2008, 2122 . 2124 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2125 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2126 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2127 . 2129 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2130 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2131 DOI 10.17487/RFC5214, March 2008, 2132 . 2134 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2135 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2136 . 2138 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2139 Version 3 for IPv4 and IPv6", RFC 5798, 2140 DOI 10.17487/RFC5798, March 2010, 2141 . 2143 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2144 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2145 . 2147 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2148 DOI 10.17487/RFC6081, January 2011, 2149 . 2151 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2152 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2153 DOI 10.17487/RFC6355, August 2011, 2154 . 2156 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2157 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2158 2012, . 2160 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2161 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2162 DOI 10.17487/RFC7084, November 2013, 2163 . 2165 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2166 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2167 Boundary in IPv6 Addressing", RFC 7421, 2168 DOI 10.17487/RFC7421, January 2015, 2169 . 2171 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2172 DOI 10.17487/RFC7542, May 2015, 2173 . 2175 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2176 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2177 February 2016, . 2179 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2180 Support for IP Hosts with Multi-Access Support", RFC 7847, 2181 DOI 10.17487/RFC7847, May 2016, 2182 . 2184 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2185 Writing an IANA Considerations Section in RFCs", BCP 26, 2186 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2187 . 2189 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2190 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2191 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2192 July 2018, . 2194 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2195 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2196 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2197 . 2199 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2200 and F. Gont, "IP Fragmentation Considered Fragile", 2201 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2202 . 2204 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2206 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2207 encoding to specific Internetworks such as the Aeronautical 2208 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2209 may include link selection preferences based on other traffic 2210 classifiers (e.g., transport port numbers, etc.) in addition to the 2211 existing DSCP-based preferences. Nodes on specific Internetworks 2212 maintain a map of traffic classifiers to additional P[*] preference 2213 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2214 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2216 Implementations use Simplex or Indexed encoding formats for P[*] 2217 encoding in order to encode a given set of traffic classifiers in the 2218 most efficient way. Some use cases may be more efficiently coded 2219 using Simplex form, while others may be more efficient using Indexed. 2220 Once a format is selected for preparation of a single Interface 2221 Attribute the same format must be used for the entire Interface 2222 Attribute sub-option. Different sub-options may use different 2223 formats. 2225 The following figures show coding examples for various Simplex and 2226 Indexed formats: 2228 0 1 2 3 2229 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 2230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2231 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2233 | Provider ID | Link |R| APS | Bitmap(0)=0xff|P00|P01|P02|P03| 2234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2235 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2237 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2239 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2241 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2243 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2246 Figure 18: Example 1: Dense Simplex Encoding 2248 0 1 2 3 2249 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 2250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2251 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2253 | Provider ID | Link |R| APS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2255 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2257 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2259 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2261 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2263 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2265 |Bitmap(10)=0x00| ... 2266 +-+-+-+-+-+-+-+-+-+-+- 2268 Figure 19: Example 2: Sparse Simplex Encoding 2270 0 1 2 3 2271 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 2272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2273 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2275 | Provider ID | Link |R| APS | Index = 0x00 | Bitmap = 0x80 | 2276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2277 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2279 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2281 | Bitmap = 0x01 |796|797|798|799| ... 2282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2284 Figure 20: Example 3: Indexed Encoding 2286 Appendix B. VDL Mode 2 Considerations 2288 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2289 (VDLM2) that specifies an essential radio frequency data link service 2290 for aircraft and ground stations in worldwide civil aviation air 2291 traffic management. The VDLM2 link type is "multicast capable" 2292 [RFC4861], but with considerable differences from common multicast 2293 links such as Ethernet and IEEE 802.11. 2295 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2296 magnitude less than most modern wireless networking gear. Second, 2297 due to the low available link bandwidth only VDLM2 ground stations 2298 (i.e., and not aircraft) are permitted to send broadcasts, and even 2299 so only as compact layer 2 "beacons". Third, aircraft employ the 2300 services of ground stations by performing unicast RS/RA exchanges 2301 upon receipt of beacons instead of listening for multicast RA 2302 messages and/or sending multicast RS messages. 2304 This beacon-oriented unicast RS/RA approach is necessary to conserve 2305 the already-scarce available link bandwidth. Moreover, since the 2306 numbers of beaconing ground stations operating within a given spatial 2307 range must be kept as sparse as possible, it would not be feasible to 2308 have different classes of ground stations within the same region 2309 observing different protocols. It is therefore highly desirable that 2310 all ground stations observe a common language of RS/RA as specified 2311 in this document. 2313 Note that links of this nature may benefit from compression 2314 techniques that reduce the bandwidth necessary for conveying the same 2315 amount of data. The IETF lpwan working group is considering possible 2316 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2318 Appendix C. MN / AR Isolation Through L2 Address Mapping 2320 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2321 unicast link-scoped IPv6 destination address. However, IPv6 ND 2322 messaging should be coordinated between the MN and AR only without 2323 invoking other nodes on the ANET. This implies that MN / AR control 2324 messaging should be isolated and not overheard by other nodes on the 2325 link. 2327 To support MN / AR isolation on some ANET links, ARs can maintain an 2328 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2329 ANETs, this specification reserves one Ethernet unicast address TBD2 2330 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2331 MSADDR is reserved per the assigned numbers authority for the ANET 2332 addressing space. For still other ANETs, MSADDR may be dynamically 2333 discovered through other means, e.g., L2 beacons. 2335 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2336 both multicast and unicast) to MSADDR instead of to an ordinary 2337 unicast or multicast L2 address. In this way, all of the MN's IPv6 2338 ND messages will be received by ARs that are configured to accept 2339 packets destined to MSADDR. Note that multiple ARs on the link could 2340 be configured to accept packets destined to MSADDR, e.g., as a basis 2341 for supporting redundancy. 2343 Therefore, ARs must accept and process packets destined to MSADDR, 2344 while all other devices must not process packets destined to MSADDR. 2345 This model has well-established operational experience in Proxy 2346 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2348 Appendix D. Change Log 2350 << RFC Editor - remove prior to publication >> 2352 Differences from draft-templin-6man-omni-interface-31 to draft- 2353 templin-6man-omni-interface-32: 2355 o MTU 2357 o Support for multi-hop ANETS such as ISATAP. 2359 Differences from draft-templin-6man-omni-interface-29 to draft- 2360 templin-6man-omni-interface-30: 2362 o Moved link-layer addressing information into the OMNI option on a 2363 per-ifIndex basis 2365 o Renamed "ifIndex-tuple" to "Interface Attributes" 2367 Differences from draft-templin-6man-omni-interface-27 to draft- 2368 templin-6man-omni-interface-28: 2370 o Updates based on implementation expereince. 2372 Differences from draft-templin-6man-omni-interface-25 to draft- 2373 templin-6man-omni-interface-26: 2375 o Further clarification on "aggregate" RA messages. 2377 o Expanded Security Considerations to discuss expectations for 2378 security in the Mobility Service. 2380 Differences from draft-templin-6man-omni-interface-20 to draft- 2381 templin-6man-omni-interface-21: 2383 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2384 (PBM). 2386 Differences from draft-templin-6man-omni-interface-18 to draft- 2387 templin-6man-omni-interface-19: 2389 o SEND/CGA. 2391 Differences from draft-templin-6man-omni-interface-17 to draft- 2392 templin-6man-omni-interface-18: 2394 o Teredo 2396 Differences from draft-templin-6man-omni-interface-14 to draft- 2397 templin-6man-omni-interface-15: 2399 o Prefix length discussions removed. 2401 Differences from draft-templin-6man-omni-interface-12 to draft- 2402 templin-6man-omni-interface-13: 2404 o Teredo 2406 Differences from draft-templin-6man-omni-interface-11 to draft- 2407 templin-6man-omni-interface-12: 2409 o Major simplifications and clarifications on MTU and fragmentation. 2411 o Document now updates RFC4443 and RFC8201. 2413 Differences from draft-templin-6man-omni-interface-10 to draft- 2414 templin-6man-omni-interface-11: 2416 o Removed /64 assumption, resulting in new OMNI address format. 2418 Differences from draft-templin-6man-omni-interface-07 to draft- 2419 templin-6man-omni-interface-08: 2421 o OMNI MNs in the open Internet 2423 Differences from draft-templin-6man-omni-interface-06 to draft- 2424 templin-6man-omni-interface-07: 2426 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2427 L2 addressing. 2429 o Expanded "Transition Considerations". 2431 Differences from draft-templin-6man-omni-interface-05 to draft- 2432 templin-6man-omni-interface-06: 2434 o Brought back OMNI option "R" flag, and discussed its use. 2436 Differences from draft-templin-6man-omni-interface-04 to draft- 2437 templin-6man-omni-interface-05: 2439 o Transition considerations, and overhaul of RS/RA addressing with 2440 the inclusion of MSE addresses within the OMNI option instead of 2441 as RS/RA addresses (developed under FAA SE2025 contract number 2442 DTFAWA-15-D-00030). 2444 Differences from draft-templin-6man-omni-interface-02 to draft- 2445 templin-6man-omni-interface-03: 2447 o Added "advisory PTB messages" under FAA SE2025 contract number 2448 DTFAWA-15-D-00030. 2450 Differences from draft-templin-6man-omni-interface-01 to draft- 2451 templin-6man-omni-interface-02: 2453 o Removed "Primary" flag and supporting text. 2455 o Clarified that "Router Lifetime" applies to each ANET interface 2456 independently, and that the union of all ANET interface Router 2457 Lifetimes determines MSE lifetime. 2459 Differences from draft-templin-6man-omni-interface-00 to draft- 2460 templin-6man-omni-interface-01: 2462 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2463 for future use (most likely as "pseudo-multicast"). 2465 o Non-normative discussion of alternate OMNI LLA construction form 2466 made possible if the 64-bit assumption were relaxed. 2468 First draft version (draft-templin-atn-aero-interface-00): 2470 o Draft based on consensus decision of ICAO Working Group I Mobility 2471 Subgroup March 22, 2019. 2473 Authors' Addresses 2475 Fred L. Templin (editor) 2476 The Boeing Company 2477 P.O. Box 3707 2478 Seattle, WA 98124 2479 USA 2481 Email: fltemplin@acm.org 2482 Tony Whyman 2483 MWA Ltd c/o Inmarsat Global Ltd 2484 99 City Road 2485 London EC1Y 1AX 2486 England 2488 Email: tony.whyman@mccallumwhyman.com