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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 26, 2020 7 Expires: March 30, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-39 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 IP 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 30, 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 . . . . . . 8 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 . . . . . . . . . . . . . 50 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 51 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 104 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 IP 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 IP 138 layer sees the OMNI interface as a point of connection to the OMNI 139 link. Each OMNI link has one or more associated Mobility Service 140 Prefixes (MSPs) from which OMNI link MNPs are derived. If there are 141 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 IP packets and MN/MS 161 control messages over OMNI interfaces. The OMNI interface supports 162 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 163 as the network layer in the data plane, while using IPv6 ND messaging 164 as the control plane independently of the data plane IP protocol(s). 165 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 166 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 167 discussed in the following sections. 169 2. Terminology 171 The terminology in the normative references applies; especially, the 172 terms "link" and "interface" are the same as defined in the IPv6 173 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 174 Additionally, this document assumes the following IPv6 ND message 175 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 176 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 178 The Protocol Constants defined in Section 10 of [RFC4861] are used in 179 their same format and meaning in this document. The terms "All- 180 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 181 are the same as defined in [RFC4291] (with Link-Local scope assumed). 183 The term "IP" is used to refer collectively to either Internet 184 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 185 specification at the layer in question applies equally to either 186 version. 188 The following terms are defined within the scope of this document: 190 Mobile Node (MN) 191 an end system with a mobile router having multiple distinct 192 upstream data link connections that are grouped together in one or 193 more logical units. The MN's data link connection parameters can 194 change over time due to, e.g., node mobility, link quality, etc. 195 The MN further connects a downstream-attached End User Network 196 (EUN). The term MN used here is distinct from uses in other 197 documents, and does not imply a particular mobility protocol. 199 End User Network (EUN) 200 a simple or complex downstream-attached mobile network that 201 travels with the MN as a single logical unit. The IP addresses 202 assigned to EUN devices remain stable even if the MN's upstream 203 data link connections change. 205 Mobility Service (MS) 206 a mobile routing service that tracks MN movements and ensures that 207 MNs remain continuously reachable even across mobility events. 208 Specific MS details are out of scope for this document. 210 Mobility Service Endpoint (MSE) 211 an entity in the MS (either singular or aggregate) that 212 coordinates the mobility events of one or more MN. 214 Mobility Service Prefix (MSP) 215 an aggregated IP prefix (e.g., 2001:db8::/32, 192.0.2.0/24, etc.) 216 advertised to the rest of the Internetwork by the MS, and from 217 which more-specific Mobile Network Prefixes (MNPs) are derived. 219 Mobile Network Prefix (MNP) 220 a longer IP prefix taken from an MSP (e.g., 221 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 222 MNs sub-delegate the MNP to devices located in EUNs. 224 Access Network (ANET) 225 a data link service network (e.g., an aviation radio access 226 network, satellite service provider network, cellular operator 227 network, wifi network, etc.) that connects MNs. Physical and/or 228 data link level security between the MN and ANET are assumed. 230 Access Router (AR) 231 a first-hop router in the ANET for connecting MNs to 232 correspondents in outside Internetworks. 234 ANET interface 235 a MN's attachment to a link in an ANET. 237 Internetwork (INET) 238 a connected network region with a coherent IP addressing plan that 239 provides transit forwarding services for ANET MNs and INET 240 correspondents. Examples include private enterprise networks, 241 ground domain aviation service networks and the global public 242 Internet itself. 244 INET interface 245 a node's attachment to a link in an INET. 247 OMNI link 248 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 249 over one or more INETs and their connected ANETs. An OMNI link 250 can comprise multiple INET segments joined by bridges the same as 251 for any link; the addressing plans in each segment may be mutually 252 exclusive and managed by different administrative entities. 254 OMNI interface 255 a node's attachment to an OMNI link, and configured over one or 256 more underlying ANET/INET interfaces. 258 OMNI Adaptation Layer (OAL) 259 an OMNI interface process whereby packets admitted into the 260 interface are wrapped in a mid-layer IPv6 header and fragmented/ 261 reassembled if necessary to support the OMNI link Maximum 262 Transmission Unit (MTU). The OAL is also responsible for 263 generating MTU-related control messages as necessary, and for 264 providing addressing context for spanning multiple segments of a 265 bridged OMNI link. 267 OMNI Link-Local Address (LLA) 268 a link local IPv6 address per [RFC4291] constructed as specified 269 in Section 7. 271 OMNI Unique-Local Address (ULA) 272 a unique local IPv6 address per [RFC4193] constructed as specified 273 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 274 and vice-versa. 276 OMNI Option 277 an IPv6 Neighbor Discovery option providing multilink parameters 278 for the OMNI interface as specified in Section 9. 280 Multilink 281 an OMNI interface's manner of managing diverse underlying data 282 link interfaces as a single logical unit. The OMNI interface 283 provides a single unified interface to upper layers, while 284 underlying data link selections are performed on a per-packet 285 basis considering factors such as DSCP, flow label, application 286 policy, signal quality, cost, etc. Multilinking decisions are 287 coordinated in both the outbound (i.e. MN to correspondent) and 288 inbound (i.e., correspondent to MN) directions. 290 L2 291 The second layer in the OSI network model. Also known as "layer- 292 2", "link-layer", "sub-IP layer", "data link layer", etc. 294 L3 295 The third layer in the OSI network model. Also known as "layer- 296 3", "network-layer", "IP layer", etc. 298 underlying interface 299 an ANET/INET interface over which an OMNI interface is configured. 300 The OMNI interface is seen as a L3 interface by the IP layer, and 301 each underlying interface is seen as a L2 interface by the OMNI 302 interface. 304 Mobility Service Identification (MSID) 305 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 306 as specified in Section 7. 308 Safety-Based Multilink (SBM) 309 A means for ensuring fault tolerance through redundancy by 310 connecting multiple independent OMNI interfaces to independent 311 routing topologies (i.e., multiple independent OMNI links). 313 Performance Based Multilink (PBM) 314 A means for selecting underlying interface(s) for packet 315 trasnmission and reception within a single OMNI interface. 317 3. Requirements 319 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 320 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 321 "OPTIONAL" in this document are to be interpreted as described in BCP 322 14 [RFC2119][RFC8174] when, and only when, they appear in all 323 capitals, as shown here. 325 OMNI links maintain a constant value "MAX_MSID" selected to provide 326 MNs with an acceptable level of MSE redundancy while minimizing 327 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 328 set to the default value 5; if a different value is chosen, it should 329 be set uniformly by all nodes on the OMNI link. 331 An implementation is not required to internally use the architectural 332 constructs described here so long as its external behavior is 333 consistent with that described in this document. 335 4. Overlay Multilink Network (OMNI) Interface Model 337 An OMNI interface is a MN virtual interface configured over one or 338 more underlying interfaces, which may be physical (e.g., an 339 aeronautical radio link) or virtual (e.g., an Internet or higher- 340 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 341 with the MS through IPv6 ND message exchanges. The MN uses the MNP 342 to construct a unique OMNI LLA through the algorithmic derivation 343 specified in Section 7 and assigns the LLA to the OMNI interface. 345 The OMNI interface architectural layering model is the same as in 346 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 347 therefore sees the OMNI interface as a single L3 interface with 348 multiple underlying interfaces that appear as L2 communication 349 channels in the architecture. 351 +----------------------------+ 352 | Upper Layer Protocol | 353 Session-to-IP +---->| | 354 Address Binding | +----------------------------+ 355 +---->| IP (L3) | 356 IP Address +---->| | 357 Binding | +----------------------------+ 358 +---->| OMNI Interface | 359 Logical-to- +---->| (OMNI LLA) | 360 Physical | +----------------------------+ 361 Interface +---->| L2 | L2 | | L2 | 362 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 363 +------+------+ +------+ 364 | L1 | L1 | | L1 | 365 | | | | | 366 +------+------+ +------+ 368 Figure 1: OMNI Interface Architectural Layering Model 370 The OMNI virtual interface model gives rise to a number of 371 opportunities: 373 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 374 Address Detection (DAD) or Muticast Listener Discovery (MLD) 375 messaging is necessary. 377 o ANET interfaces do not require any L3 addresses (i.e., not even 378 link-local) in environments where communications are coordinated 379 entirely over the OMNI interface. (An alternative would be to 380 also assign the same OMNI LLA to all ANET interfaces.) 382 o as ANET interface properties change (e.g., link quality, cost, 383 availability, etc.), any active ANET interface can be used to 384 update the profiles of multiple additional ANET interfaces in a 385 single message. This allows for timely adaptation and service 386 continuity under dynamically changing conditions. 388 o coordinating ANET interfaces in this way allows them to be 389 represented in a unified MS profile with provisions for mobility 390 and multilink operations. 392 o exposing a single virtual interface abstraction to the IPv6 layer 393 allows for multilink operation (including QoS based link 394 selection, packet replication, load balancing, etc.) at L2 while 395 still permitting L3 traffic shaping based on, e.g., DSCP, flow 396 label, etc. 398 o L3 sees the OMNI interface as a point of connection to the OMNI 399 link; if there are multiple OMNI links (i.e., multiple MS's), L3 400 will see multiple OMNI interfaces. 402 o Multiple independent OMNI interfaces can be used for increased 403 fault tolerance through Safety-Based Multilink (SBM), with 404 Performance-Based Multilink (PBM) applied within each interface. 406 Other opportunities are discussed in [RFC7847]. 408 Figure 2 depicts the architectural model for a MN connecting to the 409 MS via multiple independent ANETs. When an underlying interface 410 becomes active, the MN's OMNI interface sends native (i.e., 411 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 412 ND messages traverse the ground domain ANETs until they reach an 413 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 414 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 415 returns an IPv6 ND message response to the MN. IPv6 ND messages 416 traverse the ANET at layer 2; hence, the Hop Limit is not 417 decremented. 419 +--------------+ 420 | MN | 421 +--------------+ 422 |OMNI interface| 423 +----+----+----+ 424 +--------|IF#1|IF#2|IF#n|------ + 425 / +----+----+----+ \ 426 / | \ 427 / <---- Native | IP ----> \ 428 v v v 429 (:::)-. (:::)-. (:::)-. 430 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 431 `-(::::)-' `-(::::)-' `-(::::)-' 432 +----+ +----+ +----+ 433 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 434 . +-|--+ +-|--+ +-|--+ . 435 . | | | 436 . v v v . 437 . <----- Encapsulation -----> . 438 . . 439 . +-----+ (:::)-. . 440 . |MSE#2| .-(::::::::) +-----+ . 441 . +-----+ .-(::: INET :::)-. |MSE#m| . 442 . (::::: Routing ::::) +-----+ . 443 . `-(::: System :::)-' . 444 . +-----+ `-(:::::::-' . 445 . |MSE#1| +-----+ +-----+ . 446 . +-----+ |MSE#3| |MSE#4| . 447 . +-----+ +-----+ . 448 . . 449 . . 450 . <----- Worldwide Connected Internetwork ----> . 451 ........................................................... 453 Figure 2: MN/MS Coordination via Multiple ANETs 455 After the initial IPv6 ND message exchange, the MN can send and 456 receive unencapsulated IP data packets over the OMNI interface. OMNI 457 interface multilink services will forward the packets via ARs in the 458 correct underlying ANETs. The AR encapsulates the packets according 459 to the capabilities provided by the MS and forwards them to the next 460 hop within the worldwide connected Internetwork via optimal routes. 462 OMNI links span one or more underlying Internetwork via the OMNI 463 Adaptation Layer (OAL) which is based on a mid-layer overlay 464 encapsulation using [RFC2473] with [RFC4193] addressing. Each OMNI 465 link corresponds to a different overlay (differentiated by an address 466 codepoint) which may be carried over a completely separate underlying 467 topology. Each MN can facilitate SBM by connecting to multiple OMNI 468 links using a distinct OMNI interface for each link. 470 5. The OMNI Adaptation Layer (OAL) 472 The OMNI interface observes the link nature of tunnels, including the 473 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 474 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 475 The OMNI interface is configured over one or more underlying 476 interfaces that may have diverse MTUs. OMNI interfaces accommodate 477 MTU diversity through the use of the OMNI Adpatation Layer (OAL) as 478 discussed in this section. 480 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 481 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 482 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 483 not permitted to perform network fragmentation even though the 484 destination is required to reassemble more. The network therefore 485 MUST forward packets of at least 1280 bytes without generating an 486 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 487 [RFC8201]. (Note: the source can apply "source fragmentation" for 488 locally-generated IPv6 packets up to 1500 bytes and larger still if 489 it if has a way to determine that the destination configures a larger 490 MRU, but this does not affect the minimum IPv6 path MTU.) 492 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 493 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 494 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 495 minimum IPv4 path MTU is 576 bytes since routers on the path support 496 network fragmentation and the destination is required to reassemble 497 at least that much. The DF bit in the IPv4 encapsulation headers of 498 packets sent over IPv4 underlying interfaces therefore MUST be set to 499 0. (Note: even if the encapsulation source has a way to determine 500 that the encapsulation destination configures an MRU larger than 576 501 bytes, a larger minimum IPv4 path MTU should not be assumed without 502 careful consderation of the issues discussed in Section 5.1.) 504 The OMNI interface configures both an MTU and MRU of 9180 bytes 505 [RFC2492]; the size is therefore not a reflection of the underlying 506 interface MTUs, but rather determines the largest packet the OMNI 507 interface can forward or reassemble. The OMNI interface uses the 508 OMNI Adaptation Layer (OAL) to admit packets from the network layer 509 that are no larger than the OMNI interface MTU while generating 510 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 511 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. We 512 refer to both of these ICMPv4/ICMPv6 message types simply as "PTBs". 514 For IPv4 packets with DF=0 and locally-generated IPv6 packets, the 515 network layer performs IP fragmentation according to the OMNI 516 interface MTU if necessary then admits the fragments into the 517 interface; the OAL may then internally apply further IP fragmentation 518 prior to encapsulation. These fragments will be reassembled by the 519 final destination. (Note: Implementations normally apply 520 fragmentation prior to encapsulation according to the minimum IPv4/ 521 IPv6 path MTU in order to avoid further fragmentation in the network, 522 however they can optionally apply a larger size according to the 523 underlying interface MTU if the node that will reassemble is an on- 524 link neighbor on the underlying interface.) 526 Following any fragmentation of the original packet, OMNI interfaces 527 internally employ the OAL by either inserting or omitting a mid-layer 528 IPv6 header between the inner IP packet and any outer IP 529 encapsulation headers per [RFC2473], then performing fragmentation on 530 the mid-layer IPv6 packet when necessary. The OAL returns 531 internally-generated PTB "hard" or "soft" error messages for packets 532 admitted into the interface that it deems too large (e.g., according 533 to link performance characteristics, reassembly congestion, etc.) 534 while either dropping or forwarding the packet, respectively. The 535 OAL performs PMTUD even if the destination appears to be on the same 536 link since an OMNI link node on the path may return a PTB. This 537 ensures that the path MTU is adaptive and reflects the current path 538 used for a given data flow. 540 The OAL operates with respect to both the minimum IPv6 and IPv4 path 541 MTUs as follows: 543 o When an OMNI interface sends a packet toward a final destination 544 via an ANET peer, it sends without OAL encapsulation if the packet 545 (including any outer-layer ANET encapsulations) is no larger than 546 the underlying interface MTU for on-link ANET peers or the minimum 547 ANET path MTU for peers separated by multiple IP hops. Otherwise, 548 the OAL inserts an IPv6 header with source address set to the 549 node's own OMNI Unique Local Address (ULA) (see: Section 8) and 550 destination set to the OMNI ULA of the ANET peer. The OAL then 551 uses IPv6 fragmentation to break the packet into a minimum number 552 of non-overlapping fragments, where the largest fragment size 553 (including both the OMNI and any outer-layer ANET encapsulations) 554 is determined by the (path) MTU for the ANET peer. The OAL then 555 encapsulates the fragements in any ANET headers and sends them to 556 the ANET peer, which reassembles before forwarding toward the 557 final destination. 559 o When an OMNI interface sends a packet toward a final destination 560 via an INET interface, it sends packets (including any outer-layer 561 INET encapsulations) no larger than the minimum INET path MTU 562 without OAL encapsulation if the destination is reached via an 563 INET address within the same OMNI link segment. Otherwise, the 564 OAL inserts an IPv6 header with source address set to the node's 565 OMNI ULA, destination set to the ULA of the next hop OMNI node 566 toward the final destination and (if necessary) with a Segment 567 Routing Header with the remaining Segment IDs on the path to the 568 final destination. The OAL then uses IPv6 fragmentation to break 569 the packet into a minimum number of non-overlapping fragments, 570 where the largest fragment size (including both the OMNI and 571 outer-layer INET encapsulations) is the minimum INET path MTU, and 572 the smallest fragment size is no smaller than 256 bytes (i.e., 573 slightly less than half the minimum IPv4 path MTU). The OAL then 574 encapsulates the fragments in any INET headers and sends them to 575 the OMNI link neighbor, which reassembles before forwarding toward 576 the final destination. 578 The OAL unconditionally drops all OAL fragments received from an INET 579 peer that are smaller than 256 bytes (note that no minimum fragment 580 size is specified for ANET peers since the underlying ANET is secured 581 against tiny fragment attacks). In order to set the correct context 582 for reassembly, the OAL of the OMNI interface that inserts the IPv6 583 header MUST also be the one that inserts the IPv6 Fragment Header 584 Identification value. While not strictly required, sending all 585 fragments of the same fragmented OAL packet consecutively over the 586 same underlying interface with minimal inter-fragment delay may 587 increase the likelihood of successful reassembly. 589 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 590 header Code field value 0 are "hard errors" that always indicate that 591 a packet has been dropped due to a real MTU restriction. However, 592 the OAL can selectively forward large packets via encapsulation and 593 fragmentation while at the same time returning PTB "soft error" 594 messages (subject to rate limiting) indicating that a forwarded 595 packet was uncomfortably large. The OMNI interface can therefore 596 continuously forward large packets without loss while returning PTB 597 soft error messages recommending a smaller size. Original sources 598 that receive the soft errors in turn reduce the size of the packets 599 they send, i.e., the same as for hard errors. 601 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 602 field to the value 1 in PTB soft error messages. Receiving nodes 603 that recognize the code reduce their estimate of the path MTU the 604 same as for hard errors but do not regard the message as a loss 605 indication. Nodes that do not recognize the code treat the message 606 the same as a hard error, but should heed the retransmission advice 607 given in [RFC8201] which suggests retransmission based on normal 608 packetization layer retransmission timers. This document therefore 609 updates [RFC1191][RFC4443] and [RFC8201]. Furthermore, 610 implementations of [RFC4821] must be aware that PTB hard or soft 611 errors may arrive at any time even if after a successful MTU probe. 613 Note: In networks where IPv6/IPv4 protocol translation may be 614 prevalent, it may be prudent for the OAL to always assume the IPv4 615 minimum path MTU (i.e., 576 bytes) regardless of the underlying 616 interface IP protocol version. Always assuming the IPv4 minimum path 617 MTU even for IPv6 networks may produce more fragments and additional 618 header overhead, but will always interoperate and never run the risk 619 of presenting an IPv4 node with a packet that exceeds its MRU. 621 Note: An OMNI interface that reassembles OAL fragments may experience 622 congestion-oriented loss in its reassembly cache and can optionally 623 send PTB soft errors to the original source and/or ICMP "Time 624 Exceeded" messages to the source of the OAL fragments. In 625 environments where the messages may contribute to unacceptable 626 additional congestion, however, the OMNI interface can simply regard 627 the loss as an ordinary unreported congestion event for which the 628 original source will eventually compensate. 630 5.1. Fragmentation Security Implications 632 As discussed in Section 3.7 of [RFC8900], there are four basic 633 threats concerning IPv6 fragmentation; each of which is addressed by 634 effective mitigations as follows: 636 1. Overlapping fragment attacks - reassembly of overlapping 637 fragments is forbidden by [RFC8200]; therefore, this threat does 638 not apply to the OAL. 640 2. Resource exhaustion attacks - this threat is mitigated by 641 providing a sufficiently large OAL reassembly cache and 642 instituting "fast discard" of incomplete reassemblies that may be 643 part of a buffer exhaustion attack. The reassembly cache should 644 be sufficiently large so that a sustained attack does not cause 645 excessive loss of good reassemblies but not so large that (timer- 646 based) data structure management becomes computationally 647 expensive. 649 3. Attacks based on predictable fragment identification values - 650 this threat is mitigated by selecting a suitably random ID value 651 per [RFC7739]. 653 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 654 threat is mitigated by disallowing "tiny fragments" per the OAL 655 fragmentation procedures specified above. 657 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 658 ID) field with only 65535 unique values such that at high data rates 659 the field could wrap and apply to new packets while the fragments of 660 old packets using the same ID are still alive in the network 661 [RFC4963]. However, since the largest OAL fragment that will be sent 662 via an IPv4 INET path is 576 bytes any IPv4 fragmentation would occur 663 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 664 recommendations suggest that such links will have low data rates. 665 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 666 at high data rates is not a concern for IPv6 fragmentation. 668 6. Frame Format 670 The OMNI interface transmits IPv6 packets according to the native 671 frame format of each underlying interface. For example, for 672 Ethernet-compatible interfaces the frame format is specified in 673 [RFC2464], for aeronautical radio interfaces the frame format is 674 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 675 Manual), for tunnels over IPv6 the frame format is specified in 676 [RFC2473], etc. 678 7. Link-Local Addresses (LLAs) 680 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 681 LLAs") as follows: 683 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 684 within the least-significant 112 bits of the IPv6 link-local 685 prefix fe80::/16. The Prefix Length is determined by adding 16 to 686 the length of the embedded MNP. For example, for the MNP 687 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 688 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 689 link-local address format specified in Section 2.5.6 of [RFC4291] 690 by defining a use for bits 11 - 63. 692 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 693 i.e., the most significant 16 bits of the prefix fe80::/16, 694 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 695 32bit IPv4 address/prefix. The Prefix Length is determined by 696 adding 96 to the length of the embedded IPv4 address/prefix. For 697 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 698 fe80::ffff:192.0.2.0/120 (also written as 699 fe80::ffff:c000:0200/120). 701 o MS OMNI LLAs are assigned to ARs and MSEs from the range 702 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 703 of the LLA includes a unique integer "MSID" value between 704 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 705 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 706 determined by adding 96 to the MSID prefix length. For example, 707 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 708 Prefix Length is set to 112 and the LLA is written as 709 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 710 "Anycast" MSID and corresponds to the link-local Subnet-Router 711 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 712 through 0xffffffff is reserved for future use. 714 o The OMNI LLA range fe80::/32 is used as the service prefix for the 715 address format specified in Section 4 of [RFC4380] (see Section 17 716 for further discussion). 718 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 719 MNPs can be allocated from that block ensuring that there is no 720 possibility for overlap between the above OMNI LLA constructs. 722 Since MN OMNI LLAs are based on the distribution of administratively 723 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 724 through administrative assignment, OMNI interfaces set the 725 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 727 8. Unique-Local Addresses (ULAs) 729 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 730 [RFC4193] as the source and destination addresses in OAL IPv6 731 encapsulation headers. This document currently assumes use of the 732 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 733 (however, see the note at the end of this section). 735 Each OMNI link instance is identified by bits 10-15 of the OMNI 736 service prefix fc80::/10. For example, OMNI ULAs associated with 737 instance 0 are configured from the prefix fc80::/16, instance 1 from 738 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 739 their associated prefix lengths are configured in one-to-one 740 correspondence with OMNI LLAs through stateless prefix translation. 741 For example, for OMNI link instance fc80::/16: 743 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 744 fc80:2001:db8:1:2::/80 746 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 747 fc80::ffff:192.0.2.0/120 749 o the OMNI ULA corresponding to fe80::1000/112 is simply 750 fc80::1000/112 752 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 754 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 755 link instance, e.g., the OMNI interface connected to instance 3 756 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 757 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 758 the local routing system so that applications can direct traffic 759 according to SBM requirements. 761 The OMNI ULA presents an IPv6 address format that is routable within 762 the OMNI link routing system and can be used to convey link-scoped 763 messages across multiple hops using IPv6 encapsulation [RFC2473]. 764 The OMNI link extends across one or more underling Internetworks to 765 include all ARs and MSEs. All MNs are also considered to be 766 connected to the OMNI link, however OAL encapsulation is omitted over 767 ANET links when possible to conserve bandwidth (see: Section 11). 769 The OMNI link can be subdivided into "segments" that often correspond 770 to different administrative domains or physical partitions. OMNI 771 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 772 support efficient packet forwarding to destinations located in other 773 OMNI link segments. A full discussion of Segment Routing over the 774 OMNI link appears in [I-D.templin-intarea-6706bis]. 776 NOTE: An alternative to the application of ULAs as discussed in this 777 document would be to re-purpose the deprectated IPv6 Site-Local 778 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 779 SLAs would be a more natural fit since both LLA and SLA prefix 780 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 781 single bit setting, and LLAs and SLAs can be unambiguously allocated 782 in one-to-one correspondence with one another. Re-purposing SLAs 783 would also make good use of an otherwise-wasted address range that 784 has been "parked" since the 2004 deprecation. However, moving from 785 ULAs to SLAs would require an IETF standards action acknowledging 786 this document as obsoleting [RFC3879] and updating [RFC4291]. The 787 authors therefore defer to IETF consensus as to the proper way 788 forward. 790 9. Address Mapping - Unicast 792 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 793 state and use the link-local address format specified in Section 7. 794 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 795 over physical underlying interfaces without encapsulation observe the 796 native underlying interface Source/Target Link-Layer Address Option 797 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 798 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 799 interfaces via encapsulation do not include S/TLLAOs which were 800 intended for encoding physical L2 media address formats and not 801 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 802 for encoding additional interface attributes. Hence, this document 803 does not define an S/TLLAO format but instead defines a new option 804 type termed the "OMNI option" designed for these purposes. 806 MNs such as aircraft typically have many wireless data link types 807 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 808 etc.) with diverse performance, cost and availability properties. 809 The OMNI interface would therefore appear to have multiple L2 810 connections, and may include information for multiple underlying 811 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 812 an IPv6 ND option called the OMNI option formatted as shown in 813 Figure 3: 815 0 1 2 3 816 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 817 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 818 | Type | Length | Prefix Length | S/T-ifIndex | 819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 820 | | 821 ~ Sub-Options ~ 822 | | 823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 825 Figure 3: OMNI Option Format 827 In this format: 829 o Type is set to TBD. If multiple OMNI option instances appear in 830 the same IPv6 ND message, the first instance is processed and all 831 other instances are ignored. 833 o Length is set to the number of 8 octet blocks in the option. 835 o Prefix Length is determines the length of prefix to be applied to 836 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 837 MS, Prefix Length is the length that the MN is requesting or 838 asserting to the MS. For IPv6 ND messages sent from the MS to the 839 MN, Prefix Length indicates the length that the MS is granting to 840 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 841 Length indicates the length associated with the target MN that is 842 subject of the ND message. 844 o S/T-ifIndex corresponds to the ifIndex value for source or target 845 underlying interface used to convey this IPv6 ND message. OMNI 846 interfaces MUST number each distinct underlying interface with an 847 ifIndex value between '1' and '255' that represents a MN-specific 848 8-bit mapping for the actual ifIndex value assigned by network 849 management [RFC2863] (the ifIndex value '0' is reserved for use by 850 the MS). For RS and NS messages,S/T-ifIndex corresponds to the 851 source underlying interface the message originated from. For RA 852 and NA messages, S/T-ifIndex corresponds to the target underlying 853 interface that the message is destined to. 855 o Sub-Options is a Variable-length field, of length such that the 856 complete OMNI Option is an integer multiple of 8 octets long. 857 Contains one or more Sub-Options, as described in Section 9.1. 859 9.1. Sub-Options 861 The OMNI option includes zero or more Sub-Options. Each consecutive 862 Sub-Option is concatenated immediately after its predecessor. All 863 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 864 encoded in the following format: 866 0 1 2 867 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 5 868 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 869 | Sub-Type | Sub-length | Sub-Option Data ... 870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 872 Figure 4: Sub-Option Format 874 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 875 Sub-Options defined in this document are: 877 Option Name Sub-Type 878 Pad1 0 879 PadN 1 880 Interface Attributes 2 881 Traffic Selector 3 882 MS-Register 4 883 MS-Release 5 884 Network Access Identifier 6 885 Geo Coordinates 7 886 DHCP Unique Identifier (DUID) 8 888 Figure 5 890 Sub-Types 253 and 254 are reserved for experimentation, as 891 recommended in [RFC3692]. 893 o Sub-Length is a 1-octet field that encodes the length of the Sub- 894 Option Data (i.e., ranging from 0 to 255 octets). 896 o Sub-Option Data is a block of data with format determined by Sub- 897 Type. 899 During processing, unrecognized Sub-Options are ignored and the next 900 Sub-Option processed until the end of the OMNI option is reached. 902 The following Sub-Option types and formats are defined in this 903 document: 905 9.1.1. Pad1 907 0 908 0 1 2 3 4 5 6 7 909 +-+-+-+-+-+-+-+-+ 910 | Sub-Type=0 | 911 +-+-+-+-+-+-+-+-+ 913 Figure 6: Pad1 915 o Sub-Type is set to 0. If multiple instances appear in the same 916 OMNI option all are processed. 918 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 919 consists of a single zero octet). 921 9.1.2. PadN 923 0 1 2 924 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 5 925 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 926 | Sub-Type=1 | Sub-length=N | N padding octets ... 927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 929 Figure 7: PadN 931 o Sub-Type is set to 1. If multiple instances appear in the same 932 OMNI option all are processed. 934 o Sub-Length is set to N (from 0 to 255) being the number of padding 935 octets that follow. 937 o Sub-Option Data consists of N zero-valued octets. 939 9.1.3. Interface Attributes 940 0 1 2 3 941 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 1 942 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 943 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 945 | Provider ID | Link |R| APS | SRT | FMT | LHS (0 - 7) | 946 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 947 | LHS (bits 8 - 31) | ~ 948 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 949 ~ ~ 950 ~ Link Layer Address (L2ADDR) ~ 951 ~ ~ 952 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 953 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 955 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 957 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 958 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 960 Figure 8: Interface Attributes 962 o Sub-Type is set to 2. If multiple instances with different 963 ifIndex values appear in the same OMNI option all are processed; 964 if multiple instances with the same ifIndex value appear, the 965 first is processed and all others are ignored. 967 o Sub-Length is set to N (from 4 to 255) that encodes the number of 968 Sub-Option Data octets that follow. 970 o Sub-Option Data contains an "Interface Attribute" option encoded 971 as follows (note that the first four octets must be present): 973 * ifIndex is set to an 8-bit integer value corresponding to a 974 specific underlying interface the same as specified above for 975 the OMNI option header S/T-ifIndex. An OMNI option may include 976 multiple Interface Attributes Sub-Options, with each distinct 977 ifIndex value pertaining to a different underlying interface. 978 The OMNI option will often include an Interface Attributes Sub- 979 Option with the same ifIndex value that appears in the S/ 980 T-ifIndex. In that case, the actual encapsulation address of 981 the received IPv6 ND message should be compared with the L2ADDR 982 encoded in the Sub-Option (see below); if the addresses are 983 different (or, if L2ADDR absent) the presence of a Network 984 Address Translator (NAT) is indicated. 986 * ifType is set to an 8-bit integer value corresponding to the 987 underlying interface identified by ifIndex. The value 988 represents an OMNI interface-specific 8-bit mapping for the 989 actual IANA ifType value registered in the 'IANAifType-MIB' 990 registry [http://www.iana.org]. 992 * Provider ID is set to an OMNI interface-specific 8-bit ID value 993 for the network service provider associated with this ifIndex. 995 * Link encodes a 4-bit link metric. The value '0' means the link 996 is DOWN, and the remaining values mean the link is UP with 997 metric ranging from '1' ("lowest") to '15' ("highest"). 999 * R is reserved for future use. 1001 * APS - a 3-bit "Address/Preferences/Simplex" code that 1002 determines the contents of the remainder of the sub-option as 1003 follows: 1005 + When the most significant bit (i.e., "Address") is set to 1, 1006 the SRT, FMT, LHS and L2ADDR fields are included immediately 1007 following the APS code; else, they are omitted. 1009 + When the next most significant bit (i.e., "Preferences") is 1010 set to 1, a preferences block is included next; else, it is 1011 omitted. (Note that if "Address" is set the preferences 1012 block immediately follows L2ADDR; else, it immediately 1013 follows the APS code.) 1015 + When a preferences block is present and the least 1016 significant bit (i.e., "Simplex") is set to 1, the block is 1017 encoded in "Simplex" form as shown in Figure 8; else it is 1018 encoded in "Indexed" form as discussed below. 1020 * When APS indicates that an "Address" is included, the following 1021 fields appear in consecutive order (else, they are omitted): 1023 + SRT - a 5-bit Segment Routing Topology prefix length value 1024 that (when added to 96) determines the prefix length to 1025 apply to the ULA formed from concatenating fc*::/96 with the 1026 32 bit LHS MSID value that follows. For example, the value 1027 16 corresponds to the prefix length 112. 1029 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1030 the included Link Layer Address as follows: 1032 - When the most significant bit (i.e., "Framework") is set 1033 to 0, L2ADDR is the INET encapsulation address of a 1034 Proxy/Server; otherwise, it is the addresss for the 1035 Source/Target itself 1037 - When the next most significant bit (i.e., "Mode") is set 1038 to 0, the Source/Target L2ADDR is on the open INET; 1039 otherwise, it is (likely) located behind a Network 1040 Address Translator (NAT). 1042 - When the least significant bit (i.e., "Type") is set to 1043 0, L2ADDR includes a UDP Port Number followed by an IPv4 1044 address; else, a UDP Port Number followed by an IPv6 1045 address. 1047 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1048 path to the target. When SRT and LHS are both set to 0, the 1049 LHS is considered unspecified in this IPv6 ND message. When 1050 SRT is set to 0 and LHS is non-zero, the prefix length is 1051 set to 128. SRT and LHS provide guidance to the OMNI 1052 interface forwarding algorithm. Specifically, if SRT/LHS is 1053 located in the local OMNI link segment then the OMNI 1054 interface can encapsulate according to FMT/L2ADDR; else, it 1055 must forward according to the OMNI link spanning tree. See 1056 [I-D.templin-intarea-6706bis] for further discussion. 1058 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1059 and identifies the link-layer address (i.e., the 1060 encapsulation address) of the source/target. The UDP Port 1061 Number appears in the first two octets and the IP address 1062 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1063 The Port Number and IP address are recorded in ones- 1064 compliment "obfuscated" form per [RFC4380]. The OMNI 1065 interface forwarding algoritherm uses FMT/L2ADDR to 1066 determine the encapsulation address for forwarding when SRT/ 1067 LHS is located in the local OMNI link segment. 1069 * When APS indicates that "Preferences" are included, a 1070 preferences block appears as the remainder of the Sub-Option as 1071 a series of Bitmaps and P[*] values. In "Simplex" form, the 1072 index for each singleton Bitmap octet is inferred from its 1073 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1074 In "Indexed" form, each Bitmap is preceded by an Index octet 1075 that encodes a value "i" = (0 - 255) as the index for its 1076 companion Bitmap as follows: 1078 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1079 | Index=i | Bitmap(i) |P[*] values ... 1080 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1082 Figure 9 1084 * The preferences consist of a first (simplex/indexed) Bitmap 1085 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1086 2-bit P[*] values, followed by a second Bitmap (i), followed by 1087 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1088 the bits of each Bitmap(i) that are set to '1'' indicate the 1089 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1090 that follow; if any Bitmap(i) bits are '0', then the 1091 corresponding P[*] block is instead omitted. For example, if 1092 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1093 followed by the block with P[04]-P[07], etc., and ending with 1094 the block with P[28]-P[31] are included (as shown in Figure 8). 1095 The next Bitmap(i) is then consulted with its bits indicating 1096 which P[*] blocks follow, etc. out to the end of the Sub- 1097 Option. 1099 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1100 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1101 preference for underlying interface selection purposes. Not 1102 all P[*] values need to be included in the OMNI option of each 1103 IPv6 ND message received. Any P[*] values represented in an 1104 earlier OMNI option but omitted in the current OMNI option 1105 remain unchanged. Any P[*] values not yet represented in any 1106 OMNI option default to "medium". 1108 * The first 16 P[*] blocks correspond to the 64 Differentiated 1109 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1110 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1111 traffic classifier values P[64], P[65], P[66], etc. See 1112 Appendix A for further discussion and examples. 1114 9.1.4. Traffic Selector 1116 0 1 2 3 1117 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 1118 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1119 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1121 ~ ~ 1122 ~ RFC 6088 Format Traffic Selector ~ 1123 ~ ~ 1124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1126 Figure 10: Traffic Selector 1128 o Sub-Type is set to 3. If multiple instances appear in the same 1129 OMNI option all are processed, i.e., even if the same ifIndex 1130 value appears multiple times. 1132 o Sub-Length is set to N (the number of Sub-Option Data octets that 1133 follow). 1135 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1136 specified in Section 9.1.3, followed by an N-1 octet traffic 1137 selector formatted per [RFC6088] beginning with the "TS Format" 1138 field. The largest traffic selector for a given ifIndex is 1139 therefore 254 octets. 1141 9.1.5. MS-Register 1143 0 1 2 3 1144 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 1145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1146 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1148 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1150 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1152 ... ... ... ... ... ... 1153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1154 | MSID [n] (bits 16 - 32) | 1155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1157 Figure 11: MS-Register Sub-option 1159 o Sub-Type is set to 4. If multiple instances appear in the same 1160 OMNI option all are processed. Only the first MAX_MSID values 1161 processed (whether in a single instance or multiple) are retained 1162 and all other MSIDs are ignored. 1164 o Sub-Length is set to 4n. 1166 o A list of n 4-octet MSIDs is included in the following 4n octets. 1167 The Anycast MSID value '0' in an RS message MS-Register sub-option 1168 requests the recipient to return the MSID of a nearby MSE in a 1169 corresponding RA response. 1171 9.1.6. MS-Release 1172 0 1 2 3 1173 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 1174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1175 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1177 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1179 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1181 ... ... ... ... ... ... 1182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1183 | MSID [n] (bits 16 - 32) | 1184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1186 Figure 12: MS-Release Sub-option 1188 o Sub-Type is set to 5. If multiple instances appear in the same 1189 IPv6 OMNI option all are processed. Only the first MAX_MSID 1190 values processed (whether in a single instance or multiple) are 1191 retained and all other MSIDs are ignored. 1193 o Sub-Length is set to 4n. 1195 o A list of n 4 octet MSIDs is included in the following 4n octets. 1196 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1197 i.e., only non-zero values are processed. 1199 9.1.7. Network Access Identifier (NAI) 1201 0 1 2 3 1202 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 1203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1204 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1207 Figure 13: Network Access Identifier (NAI) Sub-option 1209 o Sub-Type is set to 6. If multiple instances appear in the same 1210 OMNI option the first is processed and all others are ignored. 1212 o Sub-Length is set to N. 1214 o A Network Access Identifier (NAI) up to 255 octets in length is 1215 coded per [RFC7542]. 1217 9.1.8. Geo Coordinates 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=7 | Sub-length=N | Geo Coordinates 1223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1225 Figure 14: Geo Coordinates Sub-option 1227 o Sub-Type is set to 7. If multiple instances appear in the same 1228 OMNI option the first is processed and all others are ignored. 1230 o Sub-Length is set to N. 1232 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1233 Includes Latitude/Longitude at a minimum; may also include 1234 additional attributes such as altitude, heading, speed, etc.). 1236 9.1.9. DHCP Unique Identifier (DUID) 1238 0 1 2 3 1239 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 1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1241 | Sub-Type=8 | Sub-length=N | DUID-Type | 1242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1243 . . 1244 . type-specific DUID body (variable length) . 1245 . . 1246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1248 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1250 o Sub-Type is set to 8. If multiple instances appear in the same 1251 OMNI option the first is processed and all others are ignored. 1253 o Sub-Length is set to N (i.e., the length of the option beginning 1254 with the DUID-Type and continuing to the end of the type-specifc 1255 body). 1257 o DUID-Type is a two-octet field coded in network byte order that 1258 determines the format and contents of the type-specific body 1259 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1260 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1261 which will occur in common operational practice. 1263 o A type-specific DUID body up to 253 octets in length follows, 1264 formatted according to DUID-type. For example, for type 4 the 1265 body consists of a 128-bit UUID selected according to [RFC6355]. 1267 10. Address Mapping - Multicast 1269 The multicast address mapping of the native underlying interface 1270 applies. The mobile router on board the MN also serves as an IGMP/ 1271 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1272 using the L2 address of the AR as the L2 address for all multicast 1273 packets. 1275 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1276 coordinate with the AR, and ANET L2 elements use MLD snooping 1277 [RFC4541]. 1279 11. Conceptual Sending Algorithm 1281 The MN's IPv6 layer selects the outbound OMNI interface according to 1282 SBM considerations when forwarding data packets from local or EUN 1283 applications to external correspondents. Each OMNI interface 1284 maintains a neighbor cache the same as for any IPv6 interface, but 1285 with additional state for multilink coordination. 1287 After a packet enters the OMNI interface, an outbound underlying 1288 interface is selected based on PBM traffic attributes such as DSCP, 1289 application port number, cost, performance, message size, etc. OMNI 1290 interface multilink selections could also be configured to perform 1291 replication across multiple underlying interfaces for increased 1292 reliability at the expense of packet duplication. 1294 When the OMNI interface sends a packet over a selected outbound 1295 underlying interface, the OAL includes or omits a mid-layer 1296 encapsulation header as necessary as discussed in Section 5. The OAL 1297 also performs encapsulation when the nearest AR is located multiple 1298 hops away as discussed in Section 12.1. 1300 OMNI interface multilink service designers MUST observe the BCP 1301 guidance in Section 15 [RFC3819] in terms of implications for 1302 reordering when packets from the same flow may be spread across 1303 multiple underlying interfaces having diverse properties. 1305 11.1. Multiple OMNI Interfaces 1307 MNs may connect to multiple independent OMNI links concurrently in 1308 support of SBM. Each OMNI interface is distinguished by its Anycast 1309 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1310 separate OMNI interface for each link so that multiple interfaces 1311 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1312 different Anycast OMNI ULA is assigned to each interface, and the MN 1313 injects the service prefixes for the OMNI link instances into the EUN 1314 routing system. 1316 Applications in EUNs can use Segment Routing to select the desired 1317 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1318 written into the IPv6 destination address, and the actual destination 1319 (along with any additional intermediate hops) is written into the 1320 Segment Routing Header. Standard IP routing directs the packets to 1321 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1322 the OMNI interface to be used for transmission to the next hop. When 1323 the MN receives the message, it replaces the IPv6 destination address 1324 with the next hop found in the routing header and transmits the 1325 message over the OMNI interface identified by the Anycast OMNI ULA. 1327 Multiple distinct OMNI links can therefore be used to support fault 1328 tolerance, load balancing, reliability, etc. The architectural model 1329 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1331 12. Router Discovery and Prefix Registration 1333 MNs interface with the MS by sending RS messages with OMNI options 1334 under the assumption that one or more AR on the ANET will process the 1335 message and respond. The manner in which the ANET ensures AR 1336 coordination is link-specific and outside the scope of this document 1337 (however, considerations for ANETs that do not provide ARs that 1338 recognize the OMNI option are discussed in Section 17). 1340 For each underlying interface, the MN sends an RS message with an 1341 OMNI option to coordinate with MSEs identified by MSID values. 1342 Example MSID discovery methods are given in [RFC5214] and include 1343 data link login parameters, name service lookups, static 1344 configuration, a static "hosts" file, etc. The MN can also send an 1345 RS with an MS-Register suboption that includes the Anycast MSID value 1346 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1347 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1348 be itself) and returns an RA with the selected MSID in an MS-Register 1349 suboption. The AR selects only a single wildcard MSE (i.e., even if 1350 the RS MS-Register suboption included multiple '0' MSIDs) while also 1351 soliciting the MSEs corresponding to any non-zero MSIDs. 1353 MNs configure OMNI interfaces that observe the properties discussed 1354 in the previous section. The OMNI interface and its underlying 1355 interfaces are said to be in either the "UP" or "DOWN" state 1356 according to administrative actions in conjunction with the interface 1357 connectivity status. An OMNI interface transitions to UP or DOWN 1358 through administrative action and/or through state transitions of the 1359 underlying interfaces. When a first underlying interface transitions 1360 to UP, the OMNI interface also transitions to UP. When all 1361 underlying interfaces transition to DOWN, the OMNI interface also 1362 transitions to DOWN. 1364 When an OMNI interface transitions to UP, the MN sends RS messages to 1365 register its MNP and an initial set of underlying interfaces that are 1366 also UP. The MN sends additional RS messages to refresh lifetimes 1367 and to register/deregister underlying interfaces as they transition 1368 to UP or DOWN. The MN sends initial RS messages over an UP 1369 underlying interface with its OMNI LLA as the source and with 1370 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1371 messages include an OMNI option per Section 9 with valid prefix 1372 registration information, Interface Attributes appropriate for 1373 underlying interfaces, MS-Register/Release sub-options containing 1374 MSID values, and with any other necessary OMNI sub-options. The S/ 1375 T-ifIndex field is set to the index of the underlying interface over 1376 which the RS message is sent. 1378 ARs process IPv6 ND messages with OMNI options and act as an MSE 1379 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1380 and create a neighbor cache entry for the MN, then coordinate with 1381 any MSEs named in the Register/Release lists in a manner outside the 1382 scope of this document. When an MSE processes the OMNI information, 1383 it first validates the prefix registration information then injects/ 1384 withdraws the MNP in the routing/mapping system and caches/discards 1385 the new Prefix Length, MNP and Interface Attributes. The MSE then 1386 informs the AR of registration success/failure, and the AR returns an 1387 RA message to the MN with an OMNI option per Section 9. 1389 The AR returns the RA message via the same underlying interface of 1390 the MN over which the RS was received, and with destination address 1391 set to the MN OMNI LLA (i.e., unicast), with source address set to 1392 its own OMNI LLA, and with an OMNI option with S/T-ifIndex set to the 1393 value included in the RS. The OMNI option also includes valid prefix 1394 registration information, Interface Attributes, MS-Register/Release 1395 and any other necessary OMNI sub-options. The RA also includes any 1396 information for the link, including RA Cur Hop Limit, M and O flags, 1397 Router Lifetime, Reachable Time and Retrans Timer values, and 1398 includes any necessary options such as: 1400 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1402 o RIOs [RFC4191] with more-specific routes. 1404 o an MTU option that specifies the maximum acceptable packet size 1405 for this ANET interface. 1407 The AR MAY also send periodic and/or event-driven unsolicited RA 1408 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1409 OMNI header of the unsolicited RA message identifies the target 1410 underlying interface of the destination MN. 1412 The AR can combine the information from multiple MSEs into one or 1413 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1414 Each aggregate RA includes an OMNI option with MS-Register/Release 1415 sub-options with the MSEs represented by the aggregate. If an 1416 aggregate is sent, the RA message contents must consistently 1417 represent the combined information advertised by all represented 1418 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1419 address, the MN determines the addresses of the represented MSEs by 1420 examining the MS-Register/Release OMNI sub-options. 1422 When the MN receives the RA message, it creates an OMNI interface 1423 neighbor cache entry for each MSID that has confirmed MNP 1424 registration via the L2 address of this AR. If the MN connects to 1425 multiple ANETs, it records the additional L2 AR addresses in each 1426 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1427 then manages its underlying interfaces according to their states as 1428 follows: 1430 o When an underlying interface transitions to UP, the MN sends an RS 1431 over the underlying interface with an OMNI option. The OMNI 1432 option contains at least one Interface Attribute sub-option with 1433 values specific to this underlying interface, and may contain 1434 additional Interface Attributes specific to other underlying 1435 interfaces. The option also includes any MS-Register/Release sub- 1436 options. 1438 o When an underlying interface transitions to DOWN, the MN sends an 1439 RS or unsolicited NA message over any UP underlying interface with 1440 an OMNI option containing an Interface Attribute sub-option for 1441 the DOWN underlying interface with Link set to '0'. The MN sends 1442 an RS when an acknowledgement is required, or an unsolicited NA 1443 when reliability is not thought to be a concern (e.g., if 1444 redundant transmissions are sent on multiple underlying 1445 interfaces). 1447 o When the Router Lifetime for a specific AR nears expiration, the 1448 MN sends an RS over the underlying interface to receive a fresh 1449 RA. If no RA is received, the MN can send RS messages to an 1450 alternate MSID in case the current MSID has failed. If no RS 1451 messages are received even after trying to contact alternate 1452 MSIDs, the MN marks the underlying interface as DOWN. 1454 o When a MN wishes to release from one or more current MSIDs, it 1455 sends an RS or unsolicited NA message over any UP underlying 1456 interfaces with an OMNI option with a Release MSID. Each MSID 1457 then withdraws the MNP from the routing/mapping system and informs 1458 the AR that the release was successful. 1460 o When all of a MNs underlying interfaces have transitioned to DOWN 1461 (or if the prefix registration lifetime expires), any associated 1462 MSEs withdraw the MNP the same as if they had received a message 1463 with a release indication. 1465 The MN is responsible for retrying each RS exchange up to 1466 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1467 seconds until an RA is received. If no RA is received over a an UP 1468 underlying interface (i.e., even after attempting to contact 1469 alternate MSEs), the MN declares this underlying interface as DOWN. 1471 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1472 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1473 returns an internally-generated RA message as though the message 1474 originated from an IPv6 router. The internally-generated RA message 1475 contains configuration information that is consistent with the 1476 information received from the RAs generated by the MS. Whether the 1477 OMNI interface IPv6 ND messaging process is initiated from the 1478 receipt of an RS message from the IPv6 layer is an implementation 1479 matter. Some implementations may elect to defer the IPv6 ND 1480 messaging process until an RS is received from the IPv6 layer, while 1481 others may elect to initiate the process proactively. Still other 1482 deployments may elect to administratively disable the ordinary RS/RA 1483 messaging used by the IPv6 layer over the OMNI interface, since they 1484 are not required to drive the internal RS/RA processing. (Note that 1485 this same logic applies to IPv4 implementations that employ ICMP- 1486 based Router Discovery per [RFC1256].) 1488 Note: The Router Lifetime value in RA messages indicates the time 1489 before which the MN must send another RS message over this underlying 1490 interface (e.g., 600 seconds), however that timescale may be 1491 significantly longer than the lifetime the MS has committed to retain 1492 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1493 therefore responsible for keeping MS state alive on a shorter 1494 timescale than the MN is required to do on its own behalf. 1496 Note: On multicast-capable underlying interfaces, MNs should send 1497 periodic unsolicited multicast NA messages and ARs should send 1498 periodic unsolicited multicast RA messages as "beacons" that can be 1499 heard by other nodes on the link. If a node fails to receive a 1500 beacon after a timeout value specific to the link, it can initiate a 1501 unicast exchange to test reachability. 1503 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1505 On some ANET types a MN may be located multiple IP hops away from the 1506 nearest AR. Forwarding through IP multihop ANETs is conducted 1507 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1508 Network (MANET) routing protocol over omni-directional wireless 1509 interfaces, an inter-domain routing protocol in an enterprise 1510 network, etc.). These ANETs could be either IPv6-enabled or 1511 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1512 unicast-only (note that for IPv4-only ANETs the following procedures 1513 apply for both single-hop and multhop cases). 1515 A MN located potentially multiple ANET hops away from the nearst AR 1516 prepares an RS message with source address set to its OMNI LLA and 1517 with destination set to link-scoped All-Routers multicast the same as 1518 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1519 the message in an IPv6 header with source address set to the ULA 1520 corresponding to the LLA source address and with destination set to 1521 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1522 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1523 with source address set to the node's own IPv4 address. For 1524 multicast-capable IPv4-only ANETs, the MN then sets the destination 1525 address to the site-scoped IPv4 multicast address corresponding to 1526 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1527 IPv4-only ANETs, the MN instead sets the destination address to the 1528 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1529 encapsulated RS message via the ANET interface, where it will be 1530 forwarded by zero or more intermediate ANET hops. 1532 When an intermediate ANET hop that particpates in the routing 1533 protocol receives the encapsulated RS, it forwards the message 1534 according to its routing tables (note that an intermediate node could 1535 be a fixed infrastructure element or another MN). This process 1536 repeats iteratively until the RS message is received by a penultimate 1537 ANET hop within single-hop communications range of an AR, which 1538 forwards the message to the AR. 1540 When the AR receives the message, it decapsulates the RS and 1541 coordinates with the MS the same as for an ordinary link-local RS, 1542 since the inner Hop Limit will not have been decremented by the 1543 multihop forwarding process. The AR then prepares an RA message with 1544 source address set to its own LLA and destination address set to the 1545 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1546 header with source address set to its own IPv4/ULA address and with 1547 destination set to the encapsulation source of the RS. 1549 The AR then forwards the message to an ANET node within 1550 communications range, which forwards the message according to its 1551 routing tables to an intermediate node. The multihop forwarding 1552 process within the ANET continues repetitively until the message is 1553 delivered to the original MN, which decapsulates the message and 1554 performs autoconfiguration the same as if it had received the RA 1555 directly from the AR as an on-link neighbor. 1557 Note: An alternate approach to multihop forwarding via IPv6 1558 encapsulation would be to statelessly translate the IPv6 LLAs into 1559 ULAs and forward the messages without encapsulation. This would 1560 violate the [RFC4861] requirement that certain IPv6 ND messages must 1561 use link-local addresses and must not be accepted if received with 1562 Hop Limit less than 255. This document therefore advocates 1563 encapsulation since the overhead is nominal considering the 1564 infrequent nature and small size of IPv6 ND messages. Future 1565 documents may consider encapsulation avoidance through translation 1566 while updating [RFC4861]. 1568 Note: An alternate approach to multihop forwarding via IPv4 1569 encapsulation would be to employ IPv6/IPv4 protocol translation. 1570 However, for IPv6 ND messages the OMNI LLA addresses would be 1571 truncated due to translation and the OMNI Router and Prefix Discovery 1572 services would not be able to function. The use of IPv4 1573 encapsulation is therefore indicated. 1575 12.2. MS-Register and MS-Release List Processing 1577 When a MN sends an RS message with an OMNI option via an underlying 1578 interface to an AR, the MN must convey its knowledge of its 1579 currently-associated MSEs. Initially, the MN will have no associated 1580 MSEs and should therefore include an MS-Register sub-option with the 1581 single MSID value 0 which requests the AR to select and assign an 1582 MSE. The AR will then return an RA message with source address set 1583 to the OMNI LLA containing the MSE of the selected MSE. 1585 As the MN activates additional underlying interfaces, it can 1586 optionally include an MS-Register sub-option with MSID value 0, or 1587 with non-zero MSIDs for MSEs discovered from previous RS/RA 1588 exchanges. The MN will thus eventually begin to learn and manage its 1589 currently active set of MSEs, and can register with new MSEs or 1590 release from former MSEs with each successive RS/RA exchange. As the 1591 MN's MSE constituency grows, it alone is responsible for including or 1592 omitting MSIDs in the MS-Register/Release lists it sends in RS 1593 messages. The inclusion or omission of MSIDs determines the MN's 1594 interface to the MS and defines the manner in which MSEs will 1595 respond. The only limiting factor is that the MN should include no 1596 more than MAX_MSID values in each list per each IPv6 ND message, and 1597 should avoid duplication of entries in each list unless it wants to 1598 increase likelihood of control message delivery. 1600 When an AR receives an RS message sent by a MN with an OMNI option, 1601 the option will contain zero or more MS-Register and MS-Release sub- 1602 options containing MSIDs. After processing the OMNI option, the AR 1603 will have a list of zero or more MS-Register MSIDs and a list of zero 1604 or more of MS-Release MSIDs. The AR then processes the lists as 1605 follows: 1607 o For each list, retain the first MAX_MSID values in the list and 1608 discard any additional MSIDs (i.e., even if there are duplicates 1609 within a list). 1611 o Next, for each MSID in the MS-Register list, remove all matching 1612 MSIDs from the MS-Release list. 1614 o Next, proceed according to whether the AR's own MSID or the value 1615 0 appears in the MS-Register list as folllows: 1617 * If yes, send an RA message directly back to the MN and send a 1618 proxy copy of the RS message to each additional MSID in the MS- 1619 Register list with the MS-Register/Release lists omitted. 1620 Then, send a uNA message to each MSID in the MS-Release list 1621 with the MS-Register/Release lists omitted and with an OMNI 1622 header with S/T-ifIndex set to 0. 1624 * If no, send a proxy copy of the RS message to each additional 1625 MSID in the MS-Register list with the MS-Register list omitted. 1626 For the first MSID, include the original MS-Release list; for 1627 all other MSIDs, omit the MS-Release list. 1629 Each proxy copy of the RS message will include an OMNI option and 1630 encapsulation header with the ULA of the AR as the source and the ULA 1631 of the Register MSE as the destination. When the Register MSE 1632 receives the proxy RS message, if the message includes an MS-Release 1633 list the MSE sends a uNA message to each additional MSID in the 1634 Release list. The Register MSE then sends an RA message back to the 1635 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1636 destination addresses reversed, and with RA destination set to the 1637 LLA of the MN. When the AR receives this RA message, it sends a 1638 proxy copy of the RA to the MN. 1640 Each uNA message (whether send by the first-hop AR or by a Register 1641 MSE) will include an OMNI option and an encapsulation header with the 1642 ULA of the Register MSE as the source and the ULA of the Release ME 1643 as the destination. The uNA informs the Release MSE that its 1644 previous relationship with the MN has been released and that the 1645 source of the uNA message is now registered. The Release MSE must 1646 then note that the subject MN of the uNA message is now "departed", 1647 and forward any subsequent packets destined to the MN to the Register 1648 MSE. 1650 Note that it is not an error for the MS-Register/Release lists to 1651 include duplicate entries. If duplicates occur within a list, the 1652 the AR will generate multiple proxy RS and/or uNA messages - one for 1653 each copy of the duplicate entries. 1655 13. Secure Redirection 1657 If the ANET link model is multiple access, the AR is responsible for 1658 assuring that address duplication cannot corrupt the neighbor caches 1659 of other nodes on the link. When the MN sends an RS message on a 1660 multiple access ANET link, the AR verifies that the MN is authorized 1661 to use the address and returns an RA with a non-zero Router Lifetime 1662 only if the MN is authorized. 1664 After verifying MN authorization and returning an RA, the AR MAY 1665 return IPv6 ND Redirect messages to direct MNs located on the same 1666 ANET link to exchange packets directly without transiting the AR. In 1667 that case, the MNs can exchange packets according to their unicast L2 1668 addresses discovered from the Redirect message instead of using the 1669 dogleg path through the AR. In some ANET links, however, such direct 1670 communications may be undesirable and continued use of the dogleg 1671 path through the AR may provide better performance. In that case, 1672 the AR can refrain from sending Redirects, and/or MNs can ignore 1673 them. 1675 14. AR and MSE Resilience 1677 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1678 [RFC5798] configurations so that service continuity is maintained 1679 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1680 the (redundant) ARs is currently providing service, and any service 1681 discontinuity will be limited to the failover time supported by VRRP. 1682 Widely deployed public domain implementations of VRRP are available. 1684 MSEs SHOULD use high availability clustering services so that 1685 multiple redundant systems can provide coordinated response to 1686 failures. As with VRRP, widely deployed public domain 1687 implementations of high availability clustering services are 1688 available. Note that special-purpose and expensive dedicated 1689 hardware is not necessary, and public domain implementations can be 1690 used even between lightweight virtual machines in cloud deployments. 1692 15. Detecting and Responding to MSE Failures 1694 In environments where fast recovery from MSE failure is required, ARs 1695 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1696 manner that parallels Bidirectional Forwarding Detection (BFD) 1697 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1698 react to failures so that cached information is re-established 1699 through alternate paths. Proactive NUD control messaging is carried 1700 only over well-connected ground domain networks (i.e., and not low- 1701 end ANET links such as aeronautical radios) and can therefore be 1702 tuned for rapid response. 1704 ARs perform proactive NUD for MSEs for which there are currently 1705 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1706 of the outage by sending multicast RA messages on the ANET interface. 1707 The AR sends RA messages to MNs via the ANET interface with an OMNI 1708 option with a Release ID for the failed MSE, and with destination 1709 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1711 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1712 by small delays [RFC4861]. Any MNs on the ANET interface that have 1713 been using the (now defunct) MSE will receive the RA messages and 1714 associate with a new MSE. 1716 16. Transition Considerations 1718 When a MN connects to an ANET link for the first time, it sends an RS 1719 message with an OMNI option. If the first hop AR recognizes the 1720 option, it returns an RA with its MS OMNI LLA as the source, the MN 1721 OMNI LLA as the destination and with an OMNI option included. The MN 1722 then engages the AR according to the OMNI link model specified above. 1723 If the first hop AR is a legacy IPv6 router, however, it instead 1724 returns an RA message with no OMNI option and with a non-OMNI unicast 1725 source LLA as specified in [RFC4861]. In that case, the MN engages 1726 the ANET according to the legacy IPv6 link model and without the OMNI 1727 extensions specified in this document. 1729 If the ANET link model is multiple access, there must be assurance 1730 that address duplication cannot corrupt the neighbor caches of other 1731 nodes on the link. When the MN sends an RS message on a multiple 1732 access ANET link with an OMNI LLA source address and an OMNI option, 1733 ARs that recognize the option ensure that the MN is authorized to use 1734 the address and return an RA with a non-zero Router Lifetime only if 1735 the MN is authorized. ARs that do not recognize the option instead 1736 return an RA that makes no statement about the MN's authorization to 1737 use the source address. In that case, the MN should perform 1738 Duplicate Address Detection to ensure that it does not interfere with 1739 other nodes on the link. 1741 An alternative approach for multiple access ANET links to ensure 1742 isolation for MN / AR communications is through L2 address mappings 1743 as discussed in Appendix C. This arrangement imparts a (virtual) 1744 point-to-point link model over the (physical) multiple access link. 1746 17. OMNI Interfaces on the Open Internet 1748 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1749 the open Internet without an OMNI-aware first-hop AR receive RA 1750 messages that do not include an OMNI option, while OMNI interfaces 1751 configured over IPv4-only underlying interfaces do not receive any 1752 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1753 without an OMNI option configure addresses, on-link prefxies, etc. on 1754 the underlying interface that received the RA according to standard 1755 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1756 interfaces configured over IPv4-only underlying interfaces configure 1757 IPv4 address information on the underlying interfaces using 1758 mechanisms such as DHCPv4 [RFC2131]. 1760 OMNI interfaces configured over underlying interfaces that connect to 1761 the open Internet can apply security services such as VPNs to connect 1762 to an MSE or establish a direct link to an MSE through some other 1763 means. In environments where an explicit VPN or direct link may be 1764 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1765 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1766 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1767 other protocol-specific security services can can also be used if 1768 additional authentication is necessary.) 1770 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1771 interfaces send control plane messages to interface with the MS. The 1772 control plane messages must be authenticated while data plane 1773 messages are delivered the same as for ordinary best-effort Internet 1774 traffic with basic source address-based data origin verification. 1775 Data plane communications via OMNI interfaces that connect over the 1776 open Internet without an explicit VPN should therefore employ 1777 transport- or higher-layer security to ensure integrity and/or 1778 confidentiality. 1780 When SEND/CGA are used over an open Internet underlying interfaces, 1781 each OMNI node configures a link-local CGA for use as the source 1782 address of IPv6 ND messages. The node then employs OMNI link 1783 encapsualation and sets the IPv6 source address of the OMNI header to 1784 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1785 the IPv6 ND message OMNI option then apply to the ULA found in the 1786 OMNI header, i.e., and not to the CGA found in the IPv6 ND message 1787 source address. 1789 OMNI interfaces in the open Internet are often located behind Network 1790 Address Translators (NATs). The OMNI interface accommodates NAT 1791 traversal using UDP/IP encapsulation and the mechanisms discussed in 1792 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1794 18. Time-Varying MNPs 1796 In some use cases, it is desirable, beneficial and efficient for the 1797 MN to receive a constant MNP that travels with the MN wherever it 1798 moves. For example, this would allow air traffic controllers to 1799 easily track aircraft, etc. In other cases, however (e.g., 1800 intelligent transportation systems), the MN may be willing to 1801 sacrifice a modicum of efficiency in order to have time-varying MNPs 1802 that can be changed every so often to defeat adversarial tracking. 1804 Prefix delegation services such as those discussed in 1805 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1806 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1807 prefixes. In that case, the identity of the MN can be used as a 1808 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1809 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1810 internal networks whenever its MNP (and therefore also its OMNI 1811 address) changes. This should not present a challenge for MNs with 1812 automated network renumbering services, however presents limits for 1813 the durations of ongoing sessions that would prefer to use a constant 1814 address. 1816 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1817 sets the source address of an RS message to fe80:: and includes a 1818 DUID sub-option and a desired Prefix Length value in the RS message 1819 OMNI option. When the first-hop AR receives the RS message, it 1820 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1821 of the requested length then returns an RA message with the OMNI LLA 1822 corresponding to the MNP as the destination address. When the MN 1823 receives the RA message, it provisons the PD to its downstream- 1824 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1825 messaging. 1827 19. IANA Considerations 1829 The IANA is instructed to allocate an official Type number TBD from 1830 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1831 option. Implementations set Type to 253 as an interim value 1832 [RFC4727]. 1834 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1835 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1836 read as follows: 1838 Code Name Reference 1839 --- ---- --------- 1840 0 Diagnostic Packet Too Big [RFC4443] 1841 1 Advisory Packet Too Big [RFCXXXX] 1843 Figure 16: OMNI Option Sub-Type Values 1845 The IANA is instructed to allocate one Ethernet unicast address TBD2 1846 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1847 Address Block - Unicast Use". 1849 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1850 is instructed to create and maintain a new registry entitled "OMNI 1851 option Sub-Type values". Initial values for the OMNI option Sub-Type 1852 values registry are given below; future assignments are to be made 1853 through Expert Review [RFC8126]. 1855 Value Sub-Type name Reference 1856 ----- ------------- ---------- 1857 0 Pad1 [RFCXXXX] 1858 1 PadN [RFCXXXX] 1859 2 Interface Attributes [RFCXXXX] 1860 3 Traffic Selector [RFCXXXX] 1861 4 MS-Register [RFCXXXX] 1862 5 MS-Release [RFCXXXX] 1863 6 Network Acceess Identifier [RFCXXXX] 1864 7 Geo Coordinates [RFCXXXX] 1865 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1866 9-252 Unassigned 1867 253-254 Experimental [RFCXXXX] 1868 255 Reserved [RFCXXXX] 1870 Figure 17: OMNI Option Sub-Type Values 1872 20. Security Considerations 1874 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 1875 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 1876 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 1877 confirmation and/or time synchronization is needed. 1879 OMNI interfaces configured over secured ANET interfaces inherit the 1880 physical and/or link-layer security properties of the connected 1881 ANETs. OMNI interfaces configured over open INET interfaces can use 1882 symmetric securing services such as VPNs or can by some other means 1883 establish a direct link. When a VPN or direct link may be 1884 impractical, however, an asymmetric security service such as SEcure 1885 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1886 Addresses (CGAs) [RFC3972], the authentication option specified in 1887 [RFC4380] or other protocol control message security mechanisms may 1888 be necessary. While the OMNI link protects control plane messaging, 1889 applications must still employ end-to-end transport- or higher-layer 1890 security services to protect the data plane. 1892 The Mobility Service MUST provide strong network layer security for 1893 control plane messages and forwading path integrity for data plane 1894 messages. In one example, the AERO service 1895 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1896 mobility service elements and secures the links in the spanning tree 1897 with network layer security mechanisms such as IPsec [RFC4301] or 1898 Wireguard. Control plane messages are then constrained to travel 1899 only over the secured spanning tree paths and are therefore protected 1900 from attack or eavesdropping. Since data plane messages can travel 1901 over route optimized paths that do not strictly follow the spanning 1902 tree, however, end-to-end transport- or higher-layer security 1903 services are still required. 1905 Security considerations for specific access network interface types 1906 are covered under the corresponding IP-over-(foo) specification 1907 (e.g., [RFC2464], [RFC2492], etc.). 1909 Security considerations for IPv6 fragmentation and reassembly are 1910 discussed in Section 5.1. 1912 21. Implementation Status 1914 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 1915 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 1916 Newer specification versions will be tagged in upcoming releases. 1917 First public release expected before the end of 2020. 1919 22. Acknowledgements 1921 The first version of this document was prepared per the consensus 1922 decision at the 7th Conference of the International Civil Aviation 1923 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1924 2019. Consensus to take the document forward to the IETF was reached 1925 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1926 Attendees and contributors included: Guray Acar, Danny Bharj, 1927 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1928 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1929 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1930 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1931 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1932 Fryderyk Wrobel and Dongsong Zeng. 1934 The following individuals are acknowledged for their useful comments: 1935 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1936 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1937 Skorepa are recognized for their many helpful ideas and suggestions. 1938 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 1939 Rajagopalan are acknowledged for their hard work on the 1940 implementation and insights that led to improvements to the spec. 1942 This work is aligned with the NASA Safe Autonomous Systems Operation 1943 (SASO) program under NASA contract number NNA16BD84C. 1945 This work is aligned with the FAA as per the SE2025 contract number 1946 DTFAWA-15-D-00030. 1948 23. References 1950 23.1. Normative References 1952 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1953 DOI 10.17487/RFC0791, September 1981, 1954 . 1956 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1957 Requirement Levels", BCP 14, RFC 2119, 1958 DOI 10.17487/RFC2119, March 1997, 1959 . 1961 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1962 "Definition of the Differentiated Services Field (DS 1963 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1964 DOI 10.17487/RFC2474, December 1998, 1965 . 1967 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1968 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1969 DOI 10.17487/RFC3971, March 2005, 1970 . 1972 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1973 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1974 . 1976 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1977 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1978 November 2005, . 1980 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1981 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1982 . 1984 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1985 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1986 2006, . 1988 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1989 Control Message Protocol (ICMPv6) for the Internet 1990 Protocol Version 6 (IPv6) Specification", STD 89, 1991 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1992 . 1994 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1995 ICMPv6, UDP, and TCP Headers", RFC 4727, 1996 DOI 10.17487/RFC4727, November 2006, 1997 . 1999 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2000 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2001 DOI 10.17487/RFC4861, September 2007, 2002 . 2004 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2005 Address Autoconfiguration", RFC 4862, 2006 DOI 10.17487/RFC4862, September 2007, 2007 . 2009 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2010 "Traffic Selectors for Flow Bindings", RFC 6088, 2011 DOI 10.17487/RFC6088, January 2011, 2012 . 2014 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2015 Hosts in a Multi-Prefix Network", RFC 8028, 2016 DOI 10.17487/RFC8028, November 2016, 2017 . 2019 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2020 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2021 May 2017, . 2023 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2024 (IPv6) Specification", STD 86, RFC 8200, 2025 DOI 10.17487/RFC8200, July 2017, 2026 . 2028 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2029 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2030 DOI 10.17487/RFC8201, July 2017, 2031 . 2033 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2034 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2035 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2036 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2037 . 2039 23.2. Informative References 2041 [I-D.ietf-intarea-tunnels] 2042 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2043 Architecture", draft-ietf-intarea-tunnels-10 (work in 2044 progress), September 2019. 2046 [I-D.templin-6man-dhcpv6-ndopt] 2047 Templin, F., "A Unified Stateful/Stateless Configuration 2048 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2049 (work in progress), June 2020. 2051 [I-D.templin-intarea-6706bis] 2052 Templin, F., "Asymmetric Extended Route Optimization 2053 (AERO)", draft-templin-intarea-6706bis-62 (work in 2054 progress), September 2020. 2056 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2057 Communication Layers", STD 3, RFC 1122, 2058 DOI 10.17487/RFC1122, October 1989, 2059 . 2061 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2062 DOI 10.17487/RFC1191, November 1990, 2063 . 2065 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2066 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2067 . 2069 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2070 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2071 . 2073 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2074 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2075 . 2077 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2078 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2079 . 2081 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2082 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2083 December 1998, . 2085 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2086 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2087 . 2089 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2090 Domains without Explicit Tunnels", RFC 2529, 2091 DOI 10.17487/RFC2529, March 1999, 2092 . 2094 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2095 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2096 . 2098 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2099 Considered Useful", BCP 82, RFC 3692, 2100 DOI 10.17487/RFC3692, January 2004, 2101 . 2103 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2104 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2105 DOI 10.17487/RFC3810, June 2004, 2106 . 2108 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2109 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2110 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2111 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2112 . 2114 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2115 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2116 2004, . 2118 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2119 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2120 December 2005, . 2122 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2123 Network Address Translations (NATs)", RFC 4380, 2124 DOI 10.17487/RFC4380, February 2006, 2125 . 2127 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2128 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2129 2006, . 2131 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2132 "Considerations for Internet Group Management Protocol 2133 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2134 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2135 . 2137 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2138 "Internet Group Management Protocol (IGMP) / Multicast 2139 Listener Discovery (MLD)-Based Multicast Forwarding 2140 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2141 August 2006, . 2143 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2144 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2145 . 2147 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2148 Errors at High Data Rates", RFC 4963, 2149 DOI 10.17487/RFC4963, July 2007, 2150 . 2152 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2153 Advertisement Flags Option", RFC 5175, 2154 DOI 10.17487/RFC5175, March 2008, 2155 . 2157 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2158 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2159 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2160 . 2162 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2163 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2164 DOI 10.17487/RFC5214, March 2008, 2165 . 2167 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2168 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2169 . 2171 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2172 Version 3 for IPv4 and IPv6", RFC 5798, 2173 DOI 10.17487/RFC5798, March 2010, 2174 . 2176 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2177 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2178 . 2180 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2181 DOI 10.17487/RFC6081, January 2011, 2182 . 2184 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2185 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2186 DOI 10.17487/RFC6355, August 2011, 2187 . 2189 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2190 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2191 2012, . 2193 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2194 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2195 DOI 10.17487/RFC7084, November 2013, 2196 . 2198 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2199 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2200 Boundary in IPv6 Addressing", RFC 7421, 2201 DOI 10.17487/RFC7421, January 2015, 2202 . 2204 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2205 DOI 10.17487/RFC7542, May 2015, 2206 . 2208 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2209 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2210 February 2016, . 2212 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2213 Support for IP Hosts with Multi-Access Support", RFC 7847, 2214 DOI 10.17487/RFC7847, May 2016, 2215 . 2217 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2218 Writing an IANA Considerations Section in RFCs", BCP 26, 2219 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2220 . 2222 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2223 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2224 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2225 July 2018, . 2227 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2228 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2229 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2230 . 2232 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2233 and F. Gont, "IP Fragmentation Considered Fragile", 2234 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2235 . 2237 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2239 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2240 encoding to specific Internetworks such as the Aeronautical 2241 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2242 may include link selection preferences based on other traffic 2243 classifiers (e.g., transport port numbers, etc.) in addition to the 2244 existing DSCP-based preferences. Nodes on specific Internetworks 2245 maintain a map of traffic classifiers to additional P[*] preference 2246 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2247 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2249 Implementations use Simplex or Indexed encoding formats for P[*] 2250 encoding in order to encode a given set of traffic classifiers in the 2251 most efficient way. Some use cases may be more efficiently coded 2252 using Simplex form, while others may be more efficient using Indexed. 2253 Once a format is selected for preparation of a single Interface 2254 Attribute the same format must be used for the entire Interface 2255 Attribute sub-option. Different sub-options may use different 2256 formats. 2258 The following figures show coding examples for various Simplex and 2259 Indexed formats: 2261 0 1 2 3 2262 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 2263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2264 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2266 | Provider ID | Link |R| APS | Bitmap(0)=0xff|P00|P01|P02|P03| 2267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2268 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2270 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2272 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2274 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2276 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2279 Figure 18: Example 1: Dense Simplex Encoding 2281 0 1 2 3 2282 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 2283 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2284 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2285 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2286 | Provider ID | Link |R| APS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2288 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2290 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2292 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2294 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2296 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2298 |Bitmap(10)=0x00| ... 2299 +-+-+-+-+-+-+-+-+-+-+- 2301 Figure 19: Example 2: Sparse Simplex Encoding 2303 0 1 2 3 2304 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 2305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2306 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2308 | Provider ID | Link |R| APS | Index = 0x00 | Bitmap = 0x80 | 2309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2310 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2312 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2314 | Bitmap = 0x01 |796|797|798|799| ... 2315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2317 Figure 20: Example 3: Indexed Encoding 2319 Appendix B. VDL Mode 2 Considerations 2321 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2322 (VDLM2) that specifies an essential radio frequency data link service 2323 for aircraft and ground stations in worldwide civil aviation air 2324 traffic management. The VDLM2 link type is "multicast capable" 2325 [RFC4861], but with considerable differences from common multicast 2326 links such as Ethernet and IEEE 802.11. 2328 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2329 magnitude less than most modern wireless networking gear. Second, 2330 due to the low available link bandwidth only VDLM2 ground stations 2331 (i.e., and not aircraft) are permitted to send broadcasts, and even 2332 so only as compact layer 2 "beacons". Third, aircraft employ the 2333 services of ground stations by performing unicast RS/RA exchanges 2334 upon receipt of beacons instead of listening for multicast RA 2335 messages and/or sending multicast RS messages. 2337 This beacon-oriented unicast RS/RA approach is necessary to conserve 2338 the already-scarce available link bandwidth. Moreover, since the 2339 numbers of beaconing ground stations operating within a given spatial 2340 range must be kept as sparse as possible, it would not be feasible to 2341 have different classes of ground stations within the same region 2342 observing different protocols. It is therefore highly desirable that 2343 all ground stations observe a common language of RS/RA as specified 2344 in this document. 2346 Note that links of this nature may benefit from compression 2347 techniques that reduce the bandwidth necessary for conveying the same 2348 amount of data. The IETF lpwan working group is considering possible 2349 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2351 Appendix C. MN / AR Isolation Through L2 Address Mapping 2353 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2354 unicast link-scoped IPv6 destination address. However, IPv6 ND 2355 messaging should be coordinated between the MN and AR only without 2356 invoking other nodes on the ANET. This implies that MN / AR control 2357 messaging should be isolated and not overheard by other nodes on the 2358 link. 2360 To support MN / AR isolation on some ANET links, ARs can maintain an 2361 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2362 ANETs, this specification reserves one Ethernet unicast address TBD2 2363 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2364 MSADDR is reserved per the assigned numbers authority for the ANET 2365 addressing space. For still other ANETs, MSADDR may be dynamically 2366 discovered through other means, e.g., L2 beacons. 2368 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2369 both multicast and unicast) to MSADDR instead of to an ordinary 2370 unicast or multicast L2 address. In this way, all of the MN's IPv6 2371 ND messages will be received by ARs that are configured to accept 2372 packets destined to MSADDR. Note that multiple ARs on the link could 2373 be configured to accept packets destined to MSADDR, e.g., as a basis 2374 for supporting redundancy. 2376 Therefore, ARs must accept and process packets destined to MSADDR, 2377 while all other devices must not process packets destined to MSADDR. 2378 This model has well-established operational experience in Proxy 2379 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2381 Appendix D. Change Log 2383 << RFC Editor - remove prior to publication >> 2385 Differences from draft-templin-6man-omni-interface-35 to draft- 2386 templin-6man-omni-interface-36: 2388 o Major clarifications on aspects such as "hard/soft" PTB error 2389 messages 2391 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2392 be used in the data plane. 2394 Differences from draft-templin-6man-omni-interface-31 to draft- 2395 templin-6man-omni-interface-32: 2397 o MTU 2398 o Support for multi-hop ANETS such as ISATAP. 2400 Differences from draft-templin-6man-omni-interface-29 to draft- 2401 templin-6man-omni-interface-30: 2403 o Moved link-layer addressing information into the OMNI option on a 2404 per-ifIndex basis 2406 o Renamed "ifIndex-tuple" to "Interface Attributes" 2408 Differences from draft-templin-6man-omni-interface-27 to draft- 2409 templin-6man-omni-interface-28: 2411 o Updates based on implementation expereince. 2413 Differences from draft-templin-6man-omni-interface-25 to draft- 2414 templin-6man-omni-interface-26: 2416 o Further clarification on "aggregate" RA messages. 2418 o Expanded Security Considerations to discuss expectations for 2419 security in the Mobility Service. 2421 Differences from draft-templin-6man-omni-interface-20 to draft- 2422 templin-6man-omni-interface-21: 2424 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2425 (PBM). 2427 Differences from draft-templin-6man-omni-interface-18 to draft- 2428 templin-6man-omni-interface-19: 2430 o SEND/CGA. 2432 Differences from draft-templin-6man-omni-interface-17 to draft- 2433 templin-6man-omni-interface-18: 2435 o Teredo 2437 Differences from draft-templin-6man-omni-interface-14 to draft- 2438 templin-6man-omni-interface-15: 2440 o Prefix length discussions removed. 2442 Differences from draft-templin-6man-omni-interface-12 to draft- 2443 templin-6man-omni-interface-13: 2445 o Teredo 2446 Differences from draft-templin-6man-omni-interface-11 to draft- 2447 templin-6man-omni-interface-12: 2449 o Major simplifications and clarifications on MTU and fragmentation. 2451 o Document now updates RFC4443 and RFC8201. 2453 Differences from draft-templin-6man-omni-interface-10 to draft- 2454 templin-6man-omni-interface-11: 2456 o Removed /64 assumption, resulting in new OMNI address format. 2458 Differences from draft-templin-6man-omni-interface-07 to draft- 2459 templin-6man-omni-interface-08: 2461 o OMNI MNs in the open Internet 2463 Differences from draft-templin-6man-omni-interface-06 to draft- 2464 templin-6man-omni-interface-07: 2466 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2467 L2 addressing. 2469 o Expanded "Transition Considerations". 2471 Differences from draft-templin-6man-omni-interface-05 to draft- 2472 templin-6man-omni-interface-06: 2474 o Brought back OMNI option "R" flag, and discussed its use. 2476 Differences from draft-templin-6man-omni-interface-04 to draft- 2477 templin-6man-omni-interface-05: 2479 o Transition considerations, and overhaul of RS/RA addressing with 2480 the inclusion of MSE addresses within the OMNI option instead of 2481 as RS/RA addresses (developed under FAA SE2025 contract number 2482 DTFAWA-15-D-00030). 2484 Differences from draft-templin-6man-omni-interface-02 to draft- 2485 templin-6man-omni-interface-03: 2487 o Added "advisory PTB messages" under FAA SE2025 contract number 2488 DTFAWA-15-D-00030. 2490 Differences from draft-templin-6man-omni-interface-01 to draft- 2491 templin-6man-omni-interface-02: 2493 o Removed "Primary" flag and supporting text. 2495 o Clarified that "Router Lifetime" applies to each ANET interface 2496 independently, and that the union of all ANET interface Router 2497 Lifetimes determines MSE lifetime. 2499 Differences from draft-templin-6man-omni-interface-00 to draft- 2500 templin-6man-omni-interface-01: 2502 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2503 for future use (most likely as "pseudo-multicast"). 2505 o Non-normative discussion of alternate OMNI LLA construction form 2506 made possible if the 64-bit assumption were relaxed. 2508 First draft version (draft-templin-atn-aero-interface-00): 2510 o Draft based on consensus decision of ICAO Working Group I Mobility 2511 Subgroup March 22, 2019. 2513 Authors' Addresses 2515 Fred L. Templin (editor) 2516 The Boeing Company 2517 P.O. Box 3707 2518 Seattle, WA 98124 2519 USA 2521 Email: fltemplin@acm.org 2523 Tony Whyman 2524 MWA Ltd c/o Inmarsat Global Ltd 2525 99 City Road 2526 London EC1Y 1AX 2527 England 2529 Email: tony.whyman@mccallumwhyman.com