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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, rfc4443, rfc8201 (if A. Whyman 5 approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track December 14, 2020 7 Expires: June 17, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-58 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 June 17, 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 8 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 13 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 17 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 18 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 18 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 20 67 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 21 68 10. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 22 69 10.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 23 70 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 24 71 10.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 25 72 10.1.3. Interface Attributes . . . . . . . . . . . . . . . . 25 73 10.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 29 74 10.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . 30 75 10.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 30 76 10.1.7. Network Access Identifier (NAI) . . . . . . . . . . 31 77 10.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 32 78 10.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . 32 79 10.1.10. DHCPv6 Message . . . . . . . . . . . . . . . . . . . 33 80 11. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 33 81 12. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 34 82 12.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 34 83 12.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 35 84 13. Router Discovery and Prefix Registration . . . . . . . . . . 35 85 13.1. Router Discovery in IP Multihop and IPv4-Only Access 86 Networks . . . . . . . . . . . . . . . . . . . . . . . . 39 87 13.2. MS-Register and MS-Release List Processing . . . . . . . 41 88 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 42 89 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 43 90 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 44 91 16. Detecting and Responding to MSE Failures . . . . . . . . . . 44 92 17. Transition Considerations . . . . . . . . . . . . . . . . . . 45 93 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 45 94 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 46 95 20. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47 96 21. Security Considerations . . . . . . . . . . . . . . . . . . . 48 97 22. Implementation Status . . . . . . . . . . . . . . . . . . . . 48 98 23. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 49 99 24. References . . . . . . . . . . . . . . . . . . . . . . . . . 49 100 24.1. Normative References . . . . . . . . . . . . . . . . . . 49 101 24.2. Informative References . . . . . . . . . . . . . . . . . 51 102 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 57 103 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 58 104 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 59 105 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 60 106 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 62 108 1. Introduction 110 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 111 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 112 etc.) often have multiple data links for communicating with networked 113 correspondents. These data links may have diverse performance, cost 114 and availability properties that can change dynamically according to 115 mobility patterns, flight phases, proximity to infrastructure, etc. 116 MNs coordinate their data links in a discipline known as "multilink", 117 in which a single virtual interface is configured over the underlying 118 data links. 120 The MN configures a virtual interface (termed the "Overlay Multilink 121 Network (OMNI) interface") as a thin layer over the underlying Access 122 Network (ANET) interfaces. The OMNI interface is therefore the only 123 interface abstraction exposed to the IP layer and behaves according 124 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 125 while underlying interfaces appear as link layer communication 126 channels in the architecture. The OMNI interface connects to a 127 virtual overlay service known as the "OMNI link". The OMNI link 128 spans one or more Internetworks that may include private-use 129 infrastructures and/or the global public Internet itself. 131 Each MN receives a Mobile Network Prefix (MNP) for numbering 132 downstream-attached End User Networks (EUNs) independently of the 133 access network data links selected for data transport. The MN 134 performs router discovery over the OMNI interface (i.e., similar to 135 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 136 behalf of its EUNs. The router discovery process is iterated over 137 each of the OMNI interface's underlying interfaces in order to 138 register per-link parameters (see Section 13). 140 The OMNI interface provides a multilink nexus for exchanging inbound 141 and outbound traffic via the correct underlying interface(s). The IP 142 layer sees the OMNI interface as a point of connection to the OMNI 143 link. Each OMNI link has one or more associated Mobility Service 144 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 145 prefixes from which OMNI link MNPs are derived. If there are 146 multiple OMNI links, the IPv6 layer will see multiple OMNI 147 interfaces. 149 MNs may connect to multiple distinct OMNI links by configuring 150 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 151 interface is configured over a set of underlying interfaces and 152 provides a nexus for Safety-Based Multilink (SBM) operation. Each 153 OMNI SBM "domain" configures a common OMNI ULA ::/48 prefix, and each 154 OMNI link within the domain configures a unique ::/64 sub-prefix 155 within the domain common ::/48 (see: Section 8). The IP layer 156 selects an OMNI interface based on SBM routing considerations, then 157 the selected interface applies Performance-Based Multilink (PBM) to 158 select the correct underlying interface. Applications can apply 159 Segment Routing [RFC8402] to select independent SBM topologies for 160 fault tolerance. 162 The OMNI interface interacts with a network-based Mobility Service 163 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 164 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 165 track MN movements and represent their MNPs in a global routing or 166 mapping system. 168 Many OMNI use cases are currently under active consideration. In 169 particular, the International Civil Aviation Organization (ICAO) 170 Working Group-I Mobility Subgroup is developing a future Aeronautical 171 Telecommunications Network with Internet Protocol Services (ATN/IPS) 172 and has issued a liaison statement requesting IETF adoption [ATN] in 173 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 174 in Vehicular Environments (ipwave) working group has further included 175 problem statement and use case analysis for OMNI in a document now in 176 AD evaluation for RFC publication 177 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 178 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 179 programs that examine commercial aviation, Urban Air Mobility (UAM) 180 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 181 represent another large class of potential OMNI users. 183 This document specifies the transmission of IP packets and MN/MS 184 control messages over OMNI interfaces. The OMNI interface supports 185 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 186 as the network layer in the data plane, while using IPv6 ND messaging 187 as the control plane independently of the data plane IP protocol(s). 188 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 189 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 190 discussed in the following sections. 192 2. Terminology 194 The terminology in the normative references applies; especially, the 195 terms "link" and "interface" are the same as defined in the IPv6 196 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 197 Additionally, this document assumes the following IPv6 ND message 198 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 199 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 201 The Protocol Constants defined in Section 10 of [RFC4861] are used in 202 their same format and meaning in this document. The terms "All- 203 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 204 are the same as defined in [RFC4291] (with Link-Local scope assumed). 206 The term "IP" is used to refer collectively to either Internet 207 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 208 specification at the layer in question applies equally to either 209 version. 211 The following terms are defined within the scope of this document: 213 Mobile Node (MN) 214 an end system with a mobile router having multiple distinct 215 upstream data link connections that are grouped together in one or 216 more logical units. The MN's data link connection parameters can 217 change over time due to, e.g., node mobility, link quality, etc. 218 The MN further connects a downstream-attached End User Network 219 (EUN). The term MN used here is distinct from uses in other 220 documents, and does not imply a particular mobility protocol. 222 End User Network (EUN) 223 a simple or complex downstream-attached mobile network that 224 travels with the MN as a single logical unit. The IP addresses 225 assigned to EUN devices remain stable even if the MN's upstream 226 data link connections change. 228 Mobility Service (MS) 229 a mobile routing service that tracks MN movements and ensures that 230 MNs remain continuously reachable even across mobility events. 231 Specific MS details are out of scope for this document. 233 Mobility Service Endpoint (MSE) 234 an entity in the MS (either singular or aggregate) that 235 coordinates the mobility events of one or more MN. 237 Mobility Service Prefix (MSP) 238 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 239 2001:db8::/32, 192.0.2.0/24, etc.) advertised to the rest of the 240 Internetwork by the MS, and from which more-specific Mobile 241 Network Prefixes (MNPs) are derived. OMNI link administrators 242 typically obtain MSPs from an Internet assigned numbers service, 243 however private-use prefixes can alternatively be used subject to 244 certain limitations (see: Section 9). 246 Mobile Network Prefix (MNP) 247 a longer IP prefix taken from an MSP (e.g., 248 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 249 MNs sub-delegate the MNP to devices located in EUNs. 251 Access Network (ANET) 252 a data link service network (e.g., an aviation radio access 253 network, satellite service provider network, cellular operator 254 network, wifi network, etc.) that connects MNs. Physical and/or 255 data link level security between the MN and ANET are assumed. 257 Access Router (AR) 258 a first-hop router in the ANET for connecting MNs to 259 correspondents in outside Internetworks. 261 ANET interface 262 a MN's attachment to a link in an ANET. 264 Internetwork (INET) 265 a connected network region with a coherent IP addressing plan that 266 provides transit forwarding services for ANET MNs and INET 267 correspondents. Examples include private enterprise networks, 268 ground domain aviation service networks and the global public 269 Internet itself. 271 INET interface 272 a node's attachment to a link in an INET. 274 OMNI link 275 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 276 over one or more INETs and their connected ANETs. An OMNI link 277 can comprise multiple INET segments joined by bridges the same as 278 for any link; the addressing plans in each segment may be mutually 279 exclusive and managed by different administrative entities. 281 OMNI interface 282 a node's attachment to an OMNI link, and configured over one or 283 more underlying ANET/INET interfaces. If there are multiple OMNI 284 links in an OMNI domain, a separate OMNI interface is configured 285 for each link. 287 OMNI Adaptation Layer (OAL) 288 an OMNI interface process whereby packets admitted into the 289 interface are wrapped in a mid-layer IPv6 header and fragmented/ 290 reassembled if necessary to support the OMNI link Maximum 291 Transmission Unit (MTU). The OAL is also responsible for 292 generating MTU-related control messages as necessary, and for 293 providing addressing context for spanning multiple segments of a 294 bridged OMNI link. 296 OMNI Link-Local Address (LLA) 297 a link local IPv6 address per [RFC4291] constructed as specified 298 in Section 7. 300 OMNI Unique-Local Address (DLA) 301 an IPv6 address from a /64 sub-prefix of fd00::/8 constructed as 302 specified in Section 3 of [RFC4193]. OMNI ULAs are statelessly 303 derived from OMNI LLAs, and vice-versa. 305 OMNI Option 306 an IPv6 Neighbor Discovery option providing multilink parameters 307 for the OMNI interface as specified in Section 10. 309 Multilink 310 an OMNI interface's manner of managing diverse underlying data 311 link interfaces as a single logical unit. The OMNI interface 312 provides a single unified interface to upper layers, while 313 underlying data link selections are performed on a per-packet 314 basis considering factors such as DSCP, flow label, application 315 policy, signal quality, cost, etc. Multilinking decisions are 316 coordinated in both the outbound (i.e. MN to correspondent) and 317 inbound (i.e., correspondent to MN) directions. 319 L2 320 The second layer in the OSI network model. Also known as "layer- 321 2", "link-layer", "sub-IP layer", "data link layer", etc. 323 L3 324 The third layer in the OSI network model. Also known as "layer- 325 3", "network-layer", "IP layer", etc. 327 underlying interface 328 an ANET/INET interface over which an OMNI interface is configured. 329 The OMNI interface is seen as a L3 interface by the IP layer, and 330 each underlying interface is seen as a L2 interface by the OMNI 331 interface. 333 Mobility Service Identification (MSID) 334 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 335 as specified in Section 7. 337 Safety-Based Multilink (SBM) 338 A means for ensuring fault tolerance through redundancy by 339 connecting multiple affiliated OMNI interfaces to independent 340 routing topologies (i.e., multiple independent OMNI links). 342 Performance Based Multilink (PBM) 343 A means for selecting underlying interface(s) for packet 344 transmission and reception within a single OMNI interface. 346 OMNI Domain 347 The set of all SBM/PBM OMNI links that collectively provides 348 services for a common set of MSPs. Each OMNI domain consists of a 349 set of affiliated OMNI links that all configure the same ::/48 ULA 350 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 352 3. Requirements 354 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 355 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 356 "OPTIONAL" in this document are to be interpreted as described in BCP 357 14 [RFC2119][RFC8174] when, and only when, they appear in all 358 capitals, as shown here. 360 OMNI links maintain a constant value "MAX_MSID" selected to provide 361 MNs with an acceptable level of MSE redundancy while minimizing 362 control message amplification. It is RECOMMENDED that MAX_MSID be 363 set to the default value 5; if a different value is chosen, it should 364 be set uniformly by all nodes on the OMNI link. 366 An implementation is not required to internally use the architectural 367 constructs described here so long as its external behavior is 368 consistent with that described in this document. 370 4. Overlay Multilink Network (OMNI) Interface Model 372 An OMNI interface is a MN virtual interface configured over one or 373 more underlying interfaces, which may be physical (e.g., an 374 aeronautical radio link) or virtual (e.g., an Internet or higher- 375 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 376 with the MS through IPv6 ND message exchanges. The MN uses the MNP 377 to construct a unique OMNI LLA through the algorithmic derivation 378 specified in Section 7 and assigns the LLA to the OMNI interface. 380 The OMNI interface architectural layering model is the same as in 381 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 382 therefore sees the OMNI interface as a single L3 interface with 383 multiple underlying interfaces that appear as L2 communication 384 channels in the architecture. 386 +----------------------------+ 387 | Upper Layer Protocol | 388 Session-to-IP +---->| | 389 Address Binding | +----------------------------+ 390 +---->| IP (L3) | 391 IP Address +---->| | 392 Binding | +----------------------------+ 393 +---->| OMNI Interface | 394 Logical-to- +---->| (OMNI LLA) | 395 Physical | +----------------------------+ 396 Interface +---->| L2 | L2 | | L2 | 397 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 398 +------+------+ +------+ 399 | L1 | L1 | | L1 | 400 | | | | | 401 +------+------+ +------+ 403 Figure 1: OMNI Interface Architectural Layering Model 405 Each underlying interface provides an L2/L1 abstraction according to 406 one of the following models: 408 o INET interfaces connect to an INET either natively or through one 409 or several IPv4 Network Address Translators (NATs). Native INET 410 interfaces have global IP addresses that are reachable from any 411 INET correspondent. NATed INET interfaces typically have private 412 IP addresses and connect to a private network behind one or more 413 NATs that provide INET access. 415 o ANET interfaces connect to a protected ANET that is separated from 416 the open INET by an AR acting as a proxy. The ANET interface may 417 be either on the same L2 link segment as the AR, or separated from 418 the AR by multiple IP hops. 420 o VPNed interfaces use security encapsulation over an INET/ANET to a 421 Virtual Private Network (VPN) gateway. Other than the link-layer 422 encapsulation format, VPNed interfaces behave the same as for 423 Direct interfaces. 425 o Direct (aka "point-to-point") interfaces connect directly to a 426 peer without crossing any ANET/INET paths. An example is a line- 427 of-sight link between a remote pilot and an unmanned aircraft. 429 The OMNI virtual interface model gives rise to a number of 430 opportunities: 432 o since MN OMNI LLAs are uniquely derived from an MNP, no Duplicate 433 Address Detection (DAD) or Multicast Listener Discovery (MLD) 434 messaging is necessary. 436 o since Temporary OMNI LLAs are statistically unique, they can be 437 used without DAD for short-term purposes, e.g. until an MN OMNI 438 LLA is obtained. 440 o ANET interfaces on the same L2 link segment as an AR do not 441 require any L3 addresses (i.e., not even link-local) in 442 environments where communications are coordinated entirely over 443 the OMNI interface. (An alternative would be to also assign the 444 same OMNI LLA to all ANET interfaces.) 446 o as underlying interface properties change (e.g., link quality, 447 cost, availability, etc.), any active interface can be used to 448 update the profiles of multiple additional interfaces in a single 449 message. This allows for timely adaptation and service continuity 450 under dynamically changing conditions. 452 o coordinating underlying interfaces in this way allows them to be 453 represented in a unified MS profile with provisions for mobility 454 and multilink operations. 456 o exposing a single virtual interface abstraction to the IPv6 layer 457 allows for multilink operation (including QoS based link 458 selection, packet replication, load balancing, etc.) at L2 while 459 still permitting L3 traffic shaping based on, e.g., DSCP, flow 460 label, etc. 462 o the OMNI interface allows inter-INET traversal when nodes located 463 in different INETs need to communicate with one another. This 464 mode of operation would not be possible via direct communications 465 over the underlying interfaces themselves. 467 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 468 lossless and adaptive path MTU mitigations not available for 469 communications directly over the underlying interfaces themselves. 471 o L3 sees the OMNI interface as a point of connection to the OMNI 472 link; if there are multiple OMNI links (i.e., multiple MS's), L3 473 will see multiple OMNI interfaces. 475 o Multiple independent OMNI interfaces can be used for increased 476 fault tolerance through Safety-Based Multilink (SBM), with 477 Performance-Based Multilink (PBM) applied within each interface. 479 Other opportunities are discussed in [RFC7847]. Note that even when 480 the OMNI virtual interface is present, applications can still access 481 underlying interfaces either through the network protocol stack using 482 an Internet socket or directly using a raw socket. This allows for 483 intra-network (or point-to-point) communications without invoking the 484 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 485 is configured over an underlying IPv4 interface, applications can 486 still invoke IPv4 intra-network communications as long as the 487 communicating endpoints are not subject to mobility dynamics. 488 However, the opportunities discussed above are not available when the 489 architectural layering is bypassed in this way. 491 Figure 2 depicts the architectural model for a MN with an attached 492 EUN connecting to the MS via multiple independent ANETs. When an 493 underlying interface becomes active, the MN's OMNI interface sends 494 IPv6 ND messages without encapsulation if the first-hop Access Router 495 (AR) is on the same underlying link; otherwise, the interface uses 496 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 497 domain ANETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 498 then coordinates with a Mobility Service Endpoint (MSE#1, MSE#2, ..., 499 MSE#m) in the INET and returns an IPv6 ND message response to the MN. 500 The Hop Limit in IPv6 ND messages is not decremented due to 501 encapsulation; hence, the OMNI interface appears to be attached to an 502 ordinary link. 504 +--------------+ (:::)-. 505 | MN |<-->.-(::EUN:::) 506 +--------------+ `-(::::)-' 507 |OMNI interface| 508 +----+----+----+ 509 +--------|IF#1|IF#2|IF#n|------ + 510 / +----+----+----+ \ 511 / | \ 512 / | \ 513 v v v 514 (:::)-. (:::)-. (:::)-. 515 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 516 `-(::::)-' `-(::::)-' `-(::::)-' 517 +----+ +----+ +----+ 518 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 519 . +-|--+ +-|--+ +-|--+ . 520 . | | | 521 . v v v . 522 . <----- INET Encapsulation -----> . 523 . . 524 . +-----+ (:::)-. . 525 . |MSE#2| .-(::::::::) +-----+ . 526 . +-----+ .-(::: INET :::)-. |MSE#m| . 527 . (::::: Routing ::::) +-----+ . 528 . `-(::: System :::)-' . 529 . +-----+ `-(:::::::-' . 530 . |MSE#1| +-----+ +-----+ . 531 . +-----+ |MSE#3| |MSE#4| . 532 . +-----+ +-----+ . 533 . . 534 . . 535 . <----- Worldwide Connected Internetwork ----> . 536 ........................................................... 538 Figure 2: MN/MS Coordination via Multiple ANETs 540 After the initial IPv6 ND message exchange, the MN (and/or any nodes 541 on its attached EUNs) can send and receive IP data packets over the 542 OMNI interface. OMNI interface multilink services will forward the 543 packets via ARs in the correct underlying ANETs. The AR encapsulates 544 the packets according to the capabilities provided by the MS and 545 forwards them to the next hop within the worldwide connected 546 Internetwork via optimal routes. 548 OMNI links span one or more underlying Internetwork via the OMNI 549 Adaptation Layer (OAL) which is based on a mid-layer overlay 550 encapsulation using [RFC2473]. Each OMNI link corresponds to a 551 different overlay (differentiated by an address codepoint) which may 552 be carried over a completely separate underlying topology. Each MN 553 can facilitate SBM by connecting to multiple OMNI links using a 554 distinct OMNI interface for each link. 556 5. The OMNI Adaptation Layer (OAL) 558 The OMNI interface observes the link nature of tunnels, including the 559 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 560 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 561 The OMNI interface is configured over one or more underlying 562 interfaces that may have diverse MTUs. OMNI interfaces accommodate 563 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 564 discussed in this section. 566 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 567 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 568 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 569 permitted to perform network fragmentation even though the 570 destination is required to reassemble more. The network therefore 571 MUST forward packets of at least 1280 bytes without generating an 572 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 573 [RFC8201]. (Note: the source can apply "source fragmentation" for 574 locally-generated IPv6 packets up to 1500 bytes and larger still if 575 it if has a way to determine that the destination configures a larger 576 MRU, but this does not affect the minimum IPv6 path MTU.) 578 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 579 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 580 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 581 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 582 support network fragmentation and the destination is required to 583 reassemble at least that much. The DF bit in the IPv4 encapsulation 584 headers of packets sent over IPv4 underlying interfaces therefore 585 MUST be set to 0. (Note: even if the encapsulation source has a way 586 to determine that the encapsulation destination configures an MRU 587 larger than 576 bytes, it should not assume a larger minimum IPv4 588 path MTU without careful consideration of the issues discussed in 589 Section 5.1.) 591 The OMNI interface configures both an MTU and MRU of 9180 bytes 592 [RFC2492]; the size is therefore not a reflection of the underlying 593 interface MTUs, but rather determines the largest packet the OMNI 594 interface can forward or reassemble. The OMNI interface uses the 595 OMNI Adaptation Layer (OAL) to admit packets from the network layer 596 that are no larger than the OMNI interface MTU while generating 597 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 598 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 599 document refers to both of these ICMPv4/ICMPv6 message types simply 600 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 601 errors as discussed below. 603 For IPv4 packets with DF=0, the network layer performs IPv4 604 fragmentation if necessary then admits the packets/fragments into the 605 OMNI interface; these fragments will be reassembled by the final 606 destination. For IPv4 packets with DF=1 and IPv6 packets, the 607 network layer admits the packet if it is no larger than the OMNI 608 interface MTU; otherwise, it drops the packet and returns a PTB hard 609 error message to the source. 611 For each admitted IP packet/fragment, the OMNI interface internally 612 employs the OAL when necessary by inserting a mid-layer IPv6 header 613 between the inner IP packet/fragment and any outer IP encapsulation 614 headers per [RFC2473]. (The OAL does not decrement the inner IP Hop 615 Limit/TTL during enapsulation since the insertion occurs at a layer 616 below IP forwarding.) The OAL then calculates the 32-bit CRC over 617 the entire mid-layer packet and writes the value in a trailing 618 4-octet field at the end of the packet. Next, the OAL fragments this 619 mid-layer IPv6 packet, forwards the fragments (using outer IP 620 encapsulation if necessary), and returns an internally-generated PTB 621 soft error message (subject to rate limiting) if it deems the packet 622 too large according to factors such as link performance 623 characteristics, reassembly congestion, etc. This ensures that the 624 path MTU is adaptive and reflects the current path used for a given 625 data flow. 627 The OAL operates with respect to both the minimum IPv6 and IPv4 path 628 MTUs as follows: 630 o When an OMNI interface sends a packet toward a final destination 631 via an ANET peer, it sends without OAL encapsulation if the packet 632 (including any outer-layer ANET encapsulations) is no larger than 633 the underlying interface MTU for on-link ANET peers or the minimum 634 ANET path MTU for peers separated by multiple IP hops. Otherwise, 635 the OAL inserts an IPv6 header per [RFC2473] with source address 636 set to the node's own OMNI Unique-Local Address (ULA) (see: 637 Section 8) and destination set to the OMNI ULA of the ANET peer. 638 The OAL then calculates and appends the trailing 32-bit CRC, then 639 uses IPv6 fragmentation to break the packet into a minimum number 640 of non-overlapping fragments where the largest fragment size 641 (including both the OMNI and any outer-layer ANET encapsulations) 642 is determined by the underlying interface MTU for on-link ANET 643 peers or the minimum ANET path MTU for peers separated by multiple 644 IP hops. The OAL then encapsulates the fragments in any ANET 645 headers and sends them to the ANET peer, which reassembles before 646 forwarding toward the final destination. 648 o When an OMNI interface sends a packet toward a final destination 649 via an INET interface, it sends packets (including any outer-layer 650 INET encapsulations) no larger than the minimum INET path MTU 651 without OAL encapsulation if the destination is reached via an 652 INET address within the same OMNI link segment. Otherwise, the 653 OAL inserts an IPv6 header per [RFC2473] with source address set 654 to the node's OMNI ULA, destination set to the ULA of the next hop 655 OMNI node toward the final destination and (if necessary) with a 656 Segment Routing Header with the remaining Segment IDs on the path 657 to the final destination. The OAL then calculates and appends the 658 trailing 32-bit CRC, then uses IPv6 fragmentation to break the 659 packet into a minimum number of non-overlapping fragments where 660 the largest fragment size (including both the OMNI and outer-layer 661 INET encapsulations) is the minimum INET path MTU, and the 662 smallest fragment size is no smaller than 256 bytes (i.e., 663 slightly less than half the minimum IPv4 path MTU). The OAL then 664 encapsulates the fragments in any INET headers and sends them to 665 the OMNI link neighbor, which reassembles before forwarding toward 666 the final destination. 668 The OAL unconditionally drops all OAL fragments received from an INET 669 peer that are smaller than 256 bytes (note that no minimum fragment 670 size is specified for ANET peers since the underlying ANET is secured 671 against tiny fragment attacks). In order to set the correct context 672 for reassembly, the OAL of the OMNI interface that inserts the IPv6 673 header MUST also be the one that inserts the IPv6 Fragment Header 674 Identification value. While not strictly required, sending all 675 fragments of the same fragmented OAL packet consecutively over the 676 same underlying interface with minimal inter-fragment delay may 677 increase the likelihood of successful reassembly. 679 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 680 header Code field value 0 are hard errors that always indicate that a 681 packet has been dropped due to a real MTU restriction. However, the 682 OAL can also forward large packets via encapsulation and 683 fragmentation while at the same time returning PTB soft error 684 messages (subject to rate limiting) indicating that a forwarded 685 packet was uncomfortably large. The OMNI interface can therefore 686 continuously forward large packets without loss while returning PTB 687 soft error messages recommending a smaller size. Original sources 688 that receive the soft errors in turn reduce the size of the packets 689 they send, i.e., the same as for hard errors. 691 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 692 field to the value 1 in PTB soft error messages. The OAL sets the 693 PTB destination address to the source address of the original packet, 694 and sets the source address to the MNP Subnet Router Anycast address 695 of the MN (i.e., whether the MN was the source or target of the 696 original packet). When the original source receives the PTB, it 697 reduces its path MTU estimate the same as for hard errors but does 698 not regard the message as a loss indication. (If the original source 699 does not recognize the soft error code, it regards the PTB the same 700 as a hard error but should heed the retransmission advice given in 701 [RFC8201] suggesting retransmission based on normal packetization 702 layer retransmission timers.) This document therefore updates 703 [RFC1191][RFC4443] and [RFC8201]. Furthermore, implementations of 704 [RFC4821] must be aware that PTB hard or soft errors may arrive at 705 any time even if after a successful MTU probe (this is the same 706 consideration as for an ordinary path fluctuation following a 707 successful probe). 709 In summary, the OAL supports continuous transmission and reception of 710 packets of various sizes in the face of dynamically changing network 711 conditions. Moreover, since PTB soft errors do not indicate loss, 712 original sources that receive soft errors can quickly scan for path 713 MTU increases without waiting for the minimum 10 minutes specified 714 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 715 therefore provides a lossless and adaptive service that accommodates 716 MTU diversity especially well-suited for dynamic multilink 717 environments. 719 Note: In network paths where IPv6/IPv4 protocol translation or IPv6- 720 in-IPv4 encapsulation may be prevalent, it may be prudent for the OAL 721 to always assume the IPv4 minimum path MTU (i.e., 576 bytes) 722 regardless of the underlying interface IP protocol version. Always 723 assuming the IPv4 minimum path MTU even for IPv6 underlying 724 interfaces may produce more fragments and additional header overhead, 725 but will always interoperate and never run the risk of presenting an 726 IPv4 interface with a packet that exceeds its MRU. 728 Note: An OMNI interface that reassembles OAL fragments may experience 729 congestion-oriented loss in its reassembly cache and can optionally 730 send PTB soft errors to the original source and/or ICMP "Time 731 Exceeded" messages to the source of the OAL fragments. In 732 environments where the messages may contribute to unacceptable 733 additional congestion, however, the OMNI interface can simply regard 734 the loss as an ordinary unreported congestion event for which the 735 original source will eventually compensate. 737 Note: When the network layer forwards an IPv4 packet/fragment with 738 DF=0 into the OMNI interface, the interface can optionally perform 739 (further) IPv4 fragmentation before invoking the OAL so that the 740 fragments will be reassembled by the final destination. When the 741 network layer performs IPv6 fragmentation for locally-generated IPv6 742 packets, the OMNI interface typically invokes the OAL without first 743 applying (further) IPv6 fragmentation; the network layer should 744 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 745 push the reassembly burden to the final destination and avoid 746 receiving PTB soft errors from the OMNI interface. Aside from these 747 non-normative guidelines, the manner in which any IP fragmentation is 748 invoked prior to OAL encapsulation/fragmentation is an implementation 749 matter. 751 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 752 the receiving OAL will discard any packets with incorrect CRC values 753 following reassembly. The 32-bit CRC is sufficient to detect 754 reassembly misassociations for packet sizes up to the OMNI interface 755 MTU 9180 but may not be sufficient to detect errors for larger sizes 756 [CRC]. 758 Note: Some underlying interface types (e.g., VPNs) may already 759 provide their own robust fragmentation and reassembly services even 760 without OAL encapsulation. In those cases, the OAL can invoke the 761 inherent underlying interface schemes instead while employing PTB 762 soft errors in the same fashion as described above. Other underlying 763 interface properties such as header/message compression can also be 764 harnessed in a similar fashion. 766 Note: Applications can dynamically tune the size of the packets they 767 to send to produce the best possible throughput and latency, with the 768 understanding that these parameters may change over time due to 769 factors such as congestion, mobility, network path changes, etc. The 770 receipt or absence of soft errors should be seen as hints of when 771 increasing or decreasing packet sizes may be beneficial. 773 5.1. Fragmentation Security Implications 775 As discussed in Section 3.7 of [RFC8900], there are four basic 776 threats concerning IPv6 fragmentation; each of which is addressed by 777 effective mitigations as follows: 779 1. Overlapping fragment attacks - reassembly of overlapping 780 fragments is forbidden by [RFC8200]; therefore, this threat does 781 not apply to the OAL. 783 2. Resource exhaustion attacks - this threat is mitigated by 784 providing a sufficiently large OAL reassembly cache and 785 instituting "fast discard" of incomplete reassemblies that may be 786 part of a buffer exhaustion attack. The reassembly cache should 787 be sufficiently large so that a sustained attack does not cause 788 excessive loss of good reassemblies but not so large that (timer- 789 based) data structure management becomes computationally 790 expensive. The cache should also be indexed based on the arrival 791 underlying interface such that congestion experienced over a 792 first underlying interface does not cause discard of incomplete 793 reassemblies for uncongested underlying interfaces. 795 3. Attacks based on predictable fragment identification values - 796 this threat is mitigated by selecting a suitably random ID value 797 per [RFC7739]. 799 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 800 threat is mitigated by disallowing "tiny fragments" per the OAL 801 fragmentation procedures specified above. 803 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 804 ID) field with only 65535 unique values such that at high data rates 805 the field could wrap and apply to new packets while the fragments of 806 old packets using the same ID are still alive in the network 807 [RFC4963]. However, since the largest OAL fragment that will be sent 808 via an IPv4 INET path is 576 bytes any IPv4 fragmentation would occur 809 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 810 recommendations suggest that such links will have low data rates. 811 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 812 at high data rates is not a concern for IPv6 fragmentation. 814 6. Frame Format 816 The OMNI interface transmits IPv6 packets according to the native 817 frame format of each underlying interface. For example, for 818 Ethernet-compatible interfaces the frame format is specified in 819 [RFC2464], for aeronautical radio interfaces the frame format is 820 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 821 Manual), for tunnels over IPv6 the frame format is specified in 822 [RFC2473], etc. 824 7. Link-Local Addresses (LLAs) 826 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 827 (i.e., "OMNI LLAs") through pre-service administrative actions. MN 828 OMNI LLAs embed the MNP assigned to the mobile node, while MS OMNI 829 LLAs include an administratively-unique ID that is guaranteed to be 830 unique on the link. OMNI LLAs are configured as follows: 832 o IPv6 MN OMNI LLAs encode the most-significant 64 bits of a MNP 833 within the least-significant 64 bits of the IPv6 link-local prefix 834 fe80::/64, i.e., in the LLA "interface identifier" portion. The 835 prefix length for the LLA is determined by adding 64 to the MNP 836 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 837 the corresponding MN OMNI LLA is fe80::2001:db8:1000:2000/120. 839 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 840 i.e., the interface identifier consists of 16 '0' bits, followed 841 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 842 prefix length for the LLA is determined by adding 96 to the MNP 843 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 844 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 845 fe80::ffff:c000:0200/120). 847 o MS OMNI LLAs are assigned to ARs and MSEs and MUST be managed for 848 uniqueness. The lower 32 bits of the LLA includes a unique 849 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 850 in fe80::1, fe80::2, fe80::3, etc., fe80::feff:ffff. The MS OMNI 851 LLA prefix length is determined by adding 96 to the MSID prefix 852 length. For example, if the MSID '0x10002000' prefix length is 16 853 then the MS OMNI LLA prefix length is set to 112 and the LLA is 854 written as fe80::1000:2000/112. The MSID 0x00000000 is the 855 "Anycast" MSID and corresponds to the link-local Subnet-Router 856 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 857 through 0xffffffff is reserved for future use. 859 o Temporary OMNI LLAs are constructed per [I-D.ietf-6man-rfc4941bis] 860 and used by MNs for the short-term purpose of procuring an actual 861 MN OMNI LLA upon startup or (re)connecting to the network. MNs 862 may use Temporary OMNI LLAs as the IPv6 source address of an RS 863 message in order to request a MN OMNI LLA from the MS. 865 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 866 MNPs can be allocated from that block ensuring that there is no 867 possibility for overlap between the various OMNI LLA constructs 868 discussed above. 870 Since MN OMNI LLAs are based on the distribution of administratively 871 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 872 through administrative assignment, OMNI interfaces set the 873 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 875 Temporary OMNI LLAs employ optimistic DAD principles [RFC4429] since 876 they are probabilistically unique and their use is short-duration in 877 nature. 879 Note: If future extensions of the IPv6 protocol permit extension of 880 the /64 boundary, the additional prefix bits of IPv6 MN OMNI LLAs 881 would be encoded in bits 16 through 63 of the LLA. (The most- 882 significant 64 bits would therefore still be in LLA bits 64-127, and 883 the remaining bits would be in bits 16 through 48 of the LLA. This 884 would permit encoding of IPv6 prefix lengths up to /112.) 886 8. Unique-Local Addresses (ULAs) 888 OMNI domains use IPv6 Unique-Local Addresses (i.e., "OMNI ULAs") as 889 the source and destination addresses in OAL IPv6 encapsulation 890 headers. OMNI ULAs are only routable within the scope of a an OMNI 891 domain, and are derived from the IPv6 Unique Local Address (ULA) 892 prefix fc00::/7 followed by the L bit set to 1 (i.e., as fd00::/8) 893 followed by a 40-bit pseudo-random Global ID to produce the prefix 894 [ULA]::/48, which is then followed by a 16-bit Subnet ID then finally 895 followed by a 64 bit Interface ID as specified in Section 3 of 896 [RFC4193]. The statistic uniqueness of the 40-bit pseudo-random 897 Global ID allows different OMNI domains to be joined together at a 898 later time. 900 Each OMNI link instance is identified by a value between 0x0000 and 901 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xfffe 902 are reserved for future use and the value 0xffff denotes a Temporary 903 OMNI ULA). For example, OMNI ULAs associated with instance 0 are 904 configured from the prefix [ULA]:0000::/64, instance 1 from 905 [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. OMNI ULAs and 906 their associated prefix lengths are configured in correspondence with 907 OMNI LLAs through stateless prefix translation. For example, for 908 OMNI link instance [ULA]:1010::/64: 910 o the OMNI ULA corresponding to the MN OMNI LLA fe80::2001:db8:1:2 911 with a 56-bit MNP length is derived by copying the lower 64 bits 912 of the LLA into the lower 64 bits of the ULA as 913 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 914 64 plus the IPv6 MNP length). 916 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 917 MNP length is derived by simply writing the LLA interface ID into 918 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 919 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 921 o the OMNI ULA corresponding to fe80::1000/112 is simply 922 [ULA]:1010::1000/112. 924 o the OMNI ULA corresponding to fe80::/128 is simply 925 [ULA]:1010::/128. 927 o the OMNI ULA corresponding to a Temporary OMNI LLA is simply 928 [ULA]:ffff:[64-bit Temporary Interface ID]/128. 930 o etc. 932 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 933 link instance. For example, the OMNI interface connected to instance 934 3 assigns the Anycast OMNI ULA [ULA]:0003::/128. Routers that 935 configure OMNI interfaces advertise the OMNI service prefix (e.g., 936 [ULA]:0003::/64) into the local routing system so that applications 937 can direct traffic according to SBM requirements. 939 The OMNI ULA presents an IPv6 address format that is routable within 940 the OMNI routing system and can be used to convey link-scoped IPv6 ND 941 messages across multiple hops using IPv6 encapsulation [RFC2473]. 942 The OMNI link extends across one or more underling Internetworks to 943 include all ARs and MSEs. All MNs are also considered to be 944 connected to the OMNI link, however OAL encapsulation is omitted over 945 ANET links when possible to conserve bandwidth (see: Section 12). 947 Each OMNI link can be subdivided into "segments" that often 948 correspond to different administrative domains or physical 949 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 950 necessary to support efficient packet forwarding to destinations 951 located in other OMNI link segments. A full discussion of Segment 952 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 954 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 955 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 956 however the range could be used for MSP and MNP addressing under 957 certain limiting conditions (see: Section 9). 959 9. Global Unicast Addresses (GUAs) 961 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 962 as Mobility Service Prefixes (MSPs) from which Mobile Network 963 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 965 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 966 associated regional assigned numbers authority such that the OMNI 967 domain can be interconnected to the global IPv6 Internet without 968 causing inconsistencies in the routing system. An OMNI domain could 969 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 970 fc00::/8)[RFC4193], however this would require IPv6 Network Address 971 Translation (NAT) if the domain were ever connected to the global 972 IPv6 Internet. 974 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 975 associated regional assigned numbers authority such that the OMNI 976 domain can be interconnected to the global IPv4 Internet without 977 causing routing inconsistencies. An OMNI domain could instead use 978 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 979 this would require IPv4 NAT if the domain were ever connected to the 980 global IPv4 Internet. 982 10. Address Mapping - Unicast 984 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 985 state and use the link-local address format specified in Section 7. 986 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 987 over physical underlying interfaces without encapsulation observe the 988 native underlying interface Source/Target Link-Layer Address Option 989 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 990 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 991 interfaces via encapsulation do not include S/TLLAOs which were 992 intended for encoding physical L2 media address formats and not 993 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 994 for encoding additional interface attributes needed for multilink 995 coordination. Hence, this document does not define an S/TLLAO format 996 but instead defines a new option type termed the "OMNI option" 997 designed for these purposes. 999 MNs such as aircraft typically have many wireless data link types 1000 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1001 etc.) with diverse performance, cost and availability properties. 1002 The OMNI interface would therefore appear to have multiple L2 1003 connections, and may include information for multiple underlying 1004 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1005 an IPv6 ND option called the OMNI option formatted as shown in 1006 Figure 3: 1008 0 1 2 3 1009 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 1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1011 | Type | Length |T| Preflen | S/T-ifIndex | 1012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1013 | | 1014 ~ Sub-Options ~ 1015 | | 1016 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1018 Figure 3: OMNI Option Format 1020 In this format: 1022 o Type is set to TBD. If multiple OMNI option instances appear in 1023 the same IPv6 ND message, the first instance is processed and all 1024 other instances are ignored. 1026 o Length is set to the number of 8 octet blocks in the option. 1028 o T is a 1-bit flag set to 1 for Temporary OMNI LLAs (otherwise, set 1029 to 0) and Preflen is a 7 bit field that determines the length of 1030 prefix associated with an MN OMNI LLA. Values 1 through 127 1031 specify a prefix length, while the value 0 indicates 1032 "unspecified". For IPv6 ND messages sent from a MN to the MS, T 1033 and Preflen apply to the IPv6 source LLA and provide the length 1034 that the MN is requesting or asserting to the MS. For IPv6 ND 1035 messages sent from the MS to the MN, T and Preflen apply to the 1036 IPv6 destination LLA and indicate the length that the MS is 1037 granting to the MN. For IPv6 ND messages sent between MS 1038 endpoints, T is set to 0 and Preflen provides the length 1039 associated with the source/target MN that is subject of the ND 1040 message. 1042 o S/T-ifIndex corresponds to the ifIndex value for source or target 1043 underlying interface used to convey this IPv6 ND message. OMNI 1044 interfaces MUST number each distinct underlying interface with an 1045 ifIndex value between '1' and '255' that represents a MN-specific 1046 8-bit mapping for the actual ifIndex value assigned by network 1047 management [RFC2863] (the ifIndex value '0' is reserved for use by 1048 the MS). For RS and NS messages, S/T-ifIndex corresponds to the 1049 source underlying interface the message originated from. For RA 1050 and NA messages, S/T-ifIndex corresponds to the target underlying 1051 interface that the message is destined to. 1053 o Sub-Options is a Variable-length field, of length such that the 1054 complete OMNI Option is an integer multiple of 8 octets long. 1055 Contains one or more Sub-Options, as described in Section 10.1. 1057 10.1. Sub-Options 1059 The OMNI option includes zero or more Sub-Options. Each consecutive 1060 Sub-Option is concatenated immediately after its predecessor. All 1061 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1062 encoded in the following format: 1064 0 1 2 1065 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 1066 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1067 | Sub-Type | Sub-length | Sub-Option Data ... 1068 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1070 Figure 4: Sub-Option Format 1072 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 1073 Sub-Options defined in this document are: 1075 Option Name Sub-Type 1076 Pad1 0 1077 PadN 1 1078 Interface Attributes 2 1079 Traffic Selector 3 1080 MS-Register 4 1081 MS-Release 5 1082 Network Access Identifier 6 1083 Geo Coordinates 7 1084 DHCP Unique Identifier (DUID) 8 1085 DHCPv6 Message 9 1087 Figure 5 1089 Sub-Types 253 and 254 are reserved for experimentation, as 1090 recommended in [RFC3692]. 1092 o Sub-Length is a 1-octet field that encodes the length of the Sub- 1093 Option Data (i.e., ranging from 0 to 255 octets). 1095 o Sub-Option Data is a block of data with format determined by Sub- 1096 Type. 1098 During processing, unrecognized Sub-Options are ignored and the next 1099 Sub-Option processed until the end of the OMNI option is reached. 1101 The following Sub-Option types and formats are defined in this 1102 document: 1104 10.1.1. Pad1 1106 0 1107 0 1 2 3 4 5 6 7 1108 +-+-+-+-+-+-+-+-+ 1109 | Sub-Type=0 | 1110 +-+-+-+-+-+-+-+-+ 1112 Figure 6: Pad1 1114 o Sub-Type is set to 0. If multiple instances appear in the same 1115 OMNI option all are processed. 1117 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 1118 consists of a single zero octet). 1120 10.1.2. PadN 1122 0 1 2 1123 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 1124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1125 | Sub-Type=1 | Sub-length=N | N padding octets ... 1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1128 Figure 7: PadN 1130 o Sub-Type is set to 1. If multiple instances appear in the same 1131 OMNI option all are processed. 1133 o Sub-Length is set to N (from 0 to 255) being the number of padding 1134 octets that follow. 1136 o Sub-Option Data consists of N zero-valued octets. 1138 10.1.3. Interface Attributes 1140 The Interface Attributes sub-option provides L2 forwarding 1141 information for the multilink conceptual sending algorithm discussed 1142 in Section 12. The L2 information is used for selecting among 1143 potentially multiple candidate underlying interfaces that can be used 1144 to forward packets to the neighbor based on factors such as DSCP 1145 preferences and link quality. Interface Attributes further include 1146 link-layer address information to be used for either OAL 1147 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1148 can be avoided). The Interface Attributes format and contents are 1149 given in Figure 8 below: 1151 0 1 2 3 1152 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 1153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1154 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 1155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1156 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1158 | LHS (bits 8 - 31) | ~ 1159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1160 ~ ~ 1161 ~ Link Layer Address (L2ADDR) ~ 1162 ~ ~ 1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1164 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1166 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1168 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1171 Figure 8: Interface Attributes 1173 o Sub-Type is set to 2. If multiple instances with different 1174 ifIndex values appear in the same OMNI option all are processed; 1175 if multiple instances with the same ifIndex value appear, the 1176 first is processed and all others are ignored. 1178 o Sub-Length is set to N (from 4 to 255) that encodes the number of 1179 Sub-Option Data octets that follow. 1181 o Sub-Option Data contains an "Interface Attribute" option encoded 1182 as follows (note that the first four octets must be present): 1184 * ifIndex is set to an 8-bit integer value corresponding to a 1185 specific underlying interface the same as specified above for 1186 the OMNI option header S/T-ifIndex. An OMNI option may include 1187 multiple Interface Attributes Sub-Options, with each distinct 1188 ifIndex value pertaining to a different underlying interface. 1189 The OMNI option will often include an Interface Attributes Sub- 1190 Option with the same ifIndex value that appears in the S/ 1191 T-ifIndex. In that case, the actual encapsulation address of 1192 the received IPv6 ND message should be compared with the L2ADDR 1193 encoded in the Sub-Option (see below); if the addresses are 1194 different (or, if L2ADDR absent) the presence of a Network 1195 Address Translator (NAT) is indicated. 1197 * ifType is set to an 8-bit integer value corresponding to the 1198 underlying interface identified by ifIndex. The value 1199 represents an OMNI interface-specific 8-bit mapping for the 1200 actual IANA ifType value registered in the 'IANAifType-MIB' 1201 registry [http://www.iana.org]. 1203 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1204 for the network service provider associated with this ifIndex. 1206 * Link encodes a 4-bit link metric. The value '0' means the link 1207 is DOWN, and the remaining values mean the link is UP with 1208 metric ranging from '1' ("lowest") to '15' ("highest"). 1210 * R is reserved for future use. 1212 * API - a 3-bit "Address/Preferences/Indexed" code that 1213 determines the contents of the remainder of the sub-option as 1214 follows: 1216 + When the most significant bit (i.e., "Address") is set to 1, 1217 the SRT, FMT, LHS and L2ADDR fields are included immediately 1218 following the API code; else, they are omitted. 1220 + When the next most significant bit (i.e., "Preferences") is 1221 set to 1, a preferences block is included next; else, it is 1222 omitted. (Note that if "Address" is set the preferences 1223 block immediately follows L2ADDR; else, it immediately 1224 follows the API code.) 1226 + When a preferences block is present and the least 1227 significant bit (i.e., "Indexed") is set to 0, the block is 1228 encoded in "Simplex" form as shown in Figure 8; else it is 1229 encoded in "Indexed" form as discussed below. 1231 * When API indicates that an "Address" is included, the following 1232 fields appear in consecutive order (else, they are omitted): 1234 + SRT - a 5-bit Segment Routing Topology prefix length value 1235 that (when added to 96) determines the prefix length to 1236 apply to the ULA formed from concatenating fe*::/96 with the 1237 32 bit LHS MSID value that follows. For example, the value 1238 16 corresponds to the prefix length 112. 1240 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1241 the included Link Layer Address as follows: 1243 - When the most significant bit (i.e., "Framework") is set 1244 to 0, L2ADDR is the INET encapsulation address of a 1245 Proxy/Server; otherwise, it is the address for the 1246 Source/Target itself 1248 - When the next most significant bit (i.e., "Mode") is set 1249 to 0, the Source/Target L2ADDR is on the open INET; 1250 otherwise, it is (likely) located behind a Network 1251 Address Translator (NAT). 1253 - When the least significant bit (i.e., "Type") is set to 1254 0, L2ADDR includes a UDP Port Number followed by an IPv4 1255 address; else, a UDP Port Number followed by an IPv6 1256 address. 1258 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1259 path to the target. When SRT and LHS are both set to 0, the 1260 LHS is considered unspecified in this IPv6 ND message. When 1261 SRT is set to 0 and LHS is non-zero, the prefix length is 1262 set to 128. SRT and LHS provide guidance to the OMNI 1263 interface forwarding algorithm. Specifically, if SRT/LHS is 1264 located in the local OMNI link segment then the OMNI 1265 interface can encapsulate according to FMT/L2ADDR; else, it 1266 must forward according to the OMNI link spanning tree. See 1267 [I-D.templin-intarea-6706bis] for further discussion. 1269 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1270 and identifies the link-layer address (i.e., the 1271 encapsulation address) of the source/target. The UDP Port 1272 Number appears in the first two octets and the IP address 1273 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1274 The Port Number and IP address are recorded in ones- 1275 compliment "obfuscated" form per [RFC4380]. The OMNI 1276 interface forwarding algorithm uses FMT/L2ADDR to determine 1277 the encapsulation address for forwarding when SRT/LHS is 1278 located in the local OMNI link segment. 1280 * When API indicates that "Preferences" are included, a 1281 preferences block appears as the remainder of the Sub-Option as 1282 a series of Bitmaps and P[*] values. In "Simplex" form, the 1283 index for each singleton Bitmap octet is inferred from its 1284 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1285 In "Indexed" form, each Bitmap is preceded by an Index octet 1286 that encodes a value "i" = (0 - 255) as the index for its 1287 companion Bitmap as follows: 1289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1290 | Index=i | Bitmap(i) |P[*] values ... 1291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1293 Figure 9 1295 * The preferences consist of a first (simplex/indexed) Bitmap 1296 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1297 2-bit P[*] values, followed by a second Bitmap (i), followed by 1298 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1299 the bits of each Bitmap(i) that are set to '1'' indicate the 1300 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1301 that follow; if any Bitmap(i) bits are '0', then the 1302 corresponding P[*] block is instead omitted. For example, if 1303 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1304 followed by the block with P[04]-P[07], etc., and ending with 1305 the block with P[28]-P[31] are included (as shown in Figure 8). 1306 The next Bitmap(i) is then consulted with its bits indicating 1307 which P[*] blocks follow, etc. out to the end of the Sub- 1308 Option. 1310 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1311 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1312 preference for underlying interface selection purposes. Not 1313 all P[*] values need to be included in the OMNI option of each 1314 IPv6 ND message received. Any P[*] values represented in an 1315 earlier OMNI option but omitted in the current OMNI option 1316 remain unchanged. Any P[*] values not yet represented in any 1317 OMNI option default to "medium". 1319 * The first 16 P[*] blocks correspond to the 64 Differentiated 1320 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1321 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1322 traffic classifier values P[64], P[65], P[66], etc. See 1323 Appendix A for further discussion and examples. 1325 10.1.4. Traffic Selector 1327 0 1 2 3 1328 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 1329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1330 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1332 ~ ~ 1333 ~ RFC 6088 Format Traffic Selector ~ 1334 ~ ~ 1335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1337 Figure 10: Traffic Selector 1339 o Sub-Type is set to 3. If multiple instances appear in the same 1340 OMNI option all are processed, i.e., even if the same ifIndex 1341 value appears multiple times. 1343 o Sub-Length is set to N (the number of Sub-Option Data octets that 1344 follow). 1346 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1347 specified in Section 10.1.3, followed by an N-1 octet traffic 1348 selector formatted per [RFC6088] beginning with the "TS Format" 1349 field. The largest traffic selector for a given ifIndex is 1350 therefore 254 octets. 1352 10.1.5. MS-Register 1354 0 1 2 3 1355 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 1356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1357 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1359 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1361 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1363 ... ... ... ... ... ... 1364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1365 | MSID [n] (bits 16 - 32) | 1366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1368 Figure 11: MS-Register Sub-option 1370 o Sub-Type is set to 4. If multiple instances appear in the same 1371 OMNI option all are processed. Only the first MAX_MSID values 1372 processed (whether in a single instance or multiple) are retained 1373 and all other MSIDs are ignored. 1375 o Sub-Length is set to 4n. 1377 o A list of n 4-octet MSIDs is included in the following 4n octets. 1378 The Anycast MSID value '0' in an RS message MS-Register sub-option 1379 requests the recipient to return the MSID of a nearby MSE in a 1380 corresponding RA response. 1382 10.1.6. MS-Release 1383 0 1 2 3 1384 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 1385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1386 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1388 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1390 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1392 ... ... ... ... ... ... 1393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1394 | MSID [n] (bits 16 - 32) | 1395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1397 Figure 12: MS-Release Sub-option 1399 o Sub-Type is set to 5. If multiple instances appear in the same 1400 IPv6 OMNI option all are processed. Only the first MAX_MSID 1401 values processed (whether in a single instance or multiple) are 1402 retained and all other MSIDs are ignored. 1404 o Sub-Length is set to 4n. 1406 o A list of n 4 octet MSIDs is included in the following 4n octets. 1407 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1408 i.e., only non-zero values are processed. 1410 10.1.7. Network Access Identifier (NAI) 1412 0 1 2 3 1413 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 1414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1415 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1418 Figure 13: Network Access Identifier (NAI) Sub-option 1420 o Sub-Type is set to 6. If multiple instances appear in the same 1421 OMNI option the first is processed and all others are ignored. 1423 o Sub-Length is set to N. 1425 o A Network Access Identifier (NAI) up to 255 octets in length is 1426 coded per [RFC7542]. 1428 10.1.8. Geo Coordinates 1430 0 1 2 3 1431 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 1432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1433 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1436 Figure 14: Geo Coordinates Sub-option 1438 o Sub-Type is set to 7. If multiple instances appear in the same 1439 OMNI option the first is processed and all others are ignored. 1441 o Sub-Length is set to N. 1443 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1444 Includes Latitude/Longitude at a minimum; may also include 1445 additional attributes such as altitude, heading, speed, etc.). 1447 10.1.9. DHCP Unique Identifier (DUID) 1449 0 1 2 3 1450 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 1451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1452 | Sub-Type=8 | Sub-length=N | DUID-Type | 1453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1454 . . 1455 . type-specific DUID body (variable length) . 1456 . . 1457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1459 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1461 o Sub-Type is set to 8. If multiple instances appear in the same 1462 OMNI option the first is processed and all others are ignored. 1464 o Sub-Length is set to N (i.e., the length of the option beginning 1465 with the DUID-Type and continuing to the end of the type-specific 1466 body). 1468 o DUID-Type is a two-octet field coded in network byte order that 1469 determines the format and contents of the type-specific body 1470 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1471 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1472 which will occur in common operational practice. 1474 o A type-specific DUID body up to 253 octets in length follows, 1475 formatted according to DUID-type. For example, for type 4 the 1476 body consists of a 128-bit UUID selected according to [RFC6355]. 1478 10.1.10. DHCPv6 Message 1480 0 1 2 3 1481 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 1482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1483 | Sub-Type=9 | Sub-length=N | msg-type | id (octet 0) | 1484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1485 | transaction-id (octets 1-2) | | 1486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1487 | | 1488 . DHCPv6 options . 1489 . (variable number and length) . 1490 | | 1491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1493 Figure 16: DHCPv6 Message Sub-option 1495 o Sub-Type is set to 9. If multiple instances appear in the same 1496 OMNI option the first is processed and all others are ignored. 1498 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1499 beginning with 'msg-type' and continuing to the end of the DHCPv6 1500 options). The length of the entire DHCPv6 message is therefore 1501 restricted to 255 octets. 1503 o 'msg-type' and 'transaction-id' are coded according to Section 8 1504 of [RFC8415]. 1506 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1507 follows. 1509 11. Address Mapping - Multicast 1511 The multicast address mapping of the native underlying interface 1512 applies. The mobile router on board the MN also serves as an IGMP/ 1513 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1514 using the L2 address of the AR as the L2 address for all multicast 1515 packets. 1517 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1518 coordinate with the AR, and ANET L2 elements use MLD snooping 1519 [RFC4541]. 1521 12. Multilink Conceptual Sending Algorithm 1523 The MN's IPv6 layer selects the outbound OMNI interface according to 1524 SBM considerations when forwarding data packets from local or EUN 1525 applications to external correspondents. Each OMNI interface 1526 maintains a neighbor cache the same as for any IPv6 interface, but 1527 with additional state for multilink coordination. Each OMNI 1528 interface maintains default routes via ARs discovered as discussed in 1529 Section 13, and may configure more-specific routes discovered through 1530 means outside the scope of this specification. 1532 After a packet enters the OMNI interface, one or more outbound 1533 underlying interfaces are selected based on PBM traffic attributes, 1534 and one or more neighbor underlying interfaces are selected based on 1535 the receipt of Interface Attributes sub-options in IPv6 ND messages 1536 (see: Figure 8). Underlying interface selection for the nodes own 1537 local interfaces are based on attributes such as DSCP, application 1538 port number, cost, performance, message size, etc. OMNI interface 1539 multilink selections could also be configured to perform replication 1540 across multiple underlying interfaces for increased reliability at 1541 the expense of packet duplication. The set of all Interface 1542 Attributes received in IPv6 ND messages determine the multilink 1543 forwarding profile for selecting the neighbor's underlying 1544 interfaces. 1546 When the OMNI interface sends a packet over a selected outbound 1547 underlying interface, the OAL includes or omits a mid-layer 1548 encapsulation header as necessary as discussed in Section 5 and as 1549 determined by the L2 address information received in Interface 1550 Attributes. The OAL also performs encapsulation when the nearest AR 1551 is located multiple hops away as discussed in Section 13.1. 1553 OMNI interface multilink service designers MUST observe the BCP 1554 guidance in Section 15 [RFC3819] in terms of implications for 1555 reordering when packets from the same flow may be spread across 1556 multiple underlying interfaces having diverse properties. 1558 12.1. Multiple OMNI Interfaces 1560 MNs may connect to multiple independent OMNI links concurrently in 1561 support of SBM. Each OMNI interface is distinguished by its Anycast 1562 OMNI ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The 1563 MN configures a separate OMNI interface for each link so that 1564 multiple interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to 1565 the IPv6 layer. A different Anycast OMNI ULA is assigned to each 1566 interface, and the MN injects the service prefixes for the OMNI link 1567 instances into the EUN routing system. 1569 Applications in EUNs can use Segment Routing to select the desired 1570 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1571 written into the IPv6 destination address, and the actual destination 1572 (along with any additional intermediate hops) is written into the 1573 Segment Routing Header. Standard IP routing directs the packets to 1574 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1575 the OMNI interface to be used for transmission to the next hop. When 1576 the MN receives the message, it replaces the IPv6 destination address 1577 with the next hop found in the routing header and transmits the 1578 message over the OMNI interface identified by the Anycast OMNI ULA. 1580 Multiple distinct OMNI links can therefore be used to support fault 1581 tolerance, load balancing, reliability, etc. The architectural model 1582 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1584 12.2. MN<->AR Traffic Loop Prevention 1586 After an AR has registered an MNP for a MN (see: Section 13), the AR 1587 will forward packets destined to an address within the MNP to the MN. 1588 The MN will under normal circumstances then forward the packet to the 1589 correct destination within its internal networks. 1591 If at some later time the MN loses state (e.g., after a reboot), it 1592 may begin returning packets destined to an MNP address to the AR as 1593 its default router. The AR therefore must drop any packets 1594 originating from the MN and destined to an address within the MN's 1595 registered MNP. To do so, the AR institutes the following check: 1597 o if the IP destination address belongs to a neighbor on the same 1598 OMNI interface, and if the link-layer source address is the same 1599 as one of the neighbor's link-layer addresses, drop the packet. 1601 13. Router Discovery and Prefix Registration 1603 MNs interface with the MS by sending RS messages with OMNI options 1604 under the assumption that one or more AR on the ANET will process the 1605 message and respond. The MN then configures default routes for the 1606 OMNI interface via the discovered ARs as the next hop. The manner in 1607 which the ANET ensures AR coordination is link-specific and outside 1608 the scope of this document (however, considerations for ANETs that do 1609 not provide ARs that recognize the OMNI option are discussed in 1610 Section 18). 1612 For each underlying interface, the MN sends an RS message with an 1613 OMNI option to coordinate with MSEs identified by MSID values. 1614 Example MSID discovery methods are given in [RFC5214] and include 1615 data link login parameters, name service lookups, static 1616 configuration, a static "hosts" file, etc. The MN can also send an 1617 RS with an MS-Register suboption that includes the Anycast MSID value 1618 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1619 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1620 be itself) and returns an RA with the selected MSID in an MS-Register 1621 suboption. The AR selects only a single wildcard MSE (i.e., even if 1622 the RS MS-Register suboption included multiple '0' MSIDs) while also 1623 soliciting the MSEs corresponding to any non-zero MSIDs. 1625 MNs configure OMNI interfaces that observe the properties discussed 1626 in the previous section. The OMNI interface and its underlying 1627 interfaces are said to be in either the "UP" or "DOWN" state 1628 according to administrative actions in conjunction with the interface 1629 connectivity status. An OMNI interface transitions to UP or DOWN 1630 through administrative action and/or through state transitions of the 1631 underlying interfaces. When a first underlying interface transitions 1632 to UP, the OMNI interface also transitions to UP. When all 1633 underlying interfaces transition to DOWN, the OMNI interface also 1634 transitions to DOWN. 1636 When an OMNI interface transitions to UP, the MN sends RS messages to 1637 register its MNP and an initial set of underlying interfaces that are 1638 also UP. The MN sends additional RS messages to refresh lifetimes 1639 and to register/deregister underlying interfaces as they transition 1640 to UP or DOWN. The MN sends initial RS messages over an UP 1641 underlying interface with its MN OMNI LLA as the source and with 1642 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1643 messages include an OMNI option per Section 10 with a Preflen 1644 assertion, Interface Attributes appropriate for underlying 1645 interfaces, MS-Register/Release sub-options containing MSID values, 1646 and with any other necessary OMNI sub-options (e.g., a DUID suboption 1647 as an identity for the MN). The S/T-ifIndex field is set to the 1648 index of the underlying interface over which the RS message is sent. 1650 ARs process IPv6 ND messages with OMNI options and act as an MSE 1651 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1652 and create a neighbor cache entry for the MN, then coordinate with 1653 any MSEs named in the Register/Release lists in a manner outside the 1654 scope of this document. When an MSE processes the OMNI information, 1655 it first validates the prefix registration information then injects/ 1656 withdraws the MNP in the routing/mapping system and caches/discards 1657 the new Preflen, MNP and Interface Attributes. The MSE then informs 1658 the AR of registration success/failure, and the AR returns an RA 1659 message to the MN with an OMNI option per Section 10. 1661 The AR returns the RA message via the same underlying interface of 1662 the MN over which the RS was received, and with destination address 1663 set to the MN OMNI LLA (i.e., unicast), with source address set to 1664 its own OMNI LLA, and with an OMNI option with S/T-ifIndex set to the 1665 value included in the RS. The OMNI option also includes a Preflen 1666 confirmation, Interface Attributes, MS-Register/Release and any other 1667 necessary OMNI sub-options (e.g., a DUID suboption as an identity for 1668 the AR). The RA also includes any information for the link, 1669 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 1670 Time and Retrans Timer values, and includes any necessary options 1671 such as: 1673 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1675 o RIOs [RFC4191] with more-specific routes. 1677 o an MTU option that specifies the maximum acceptable packet size 1678 for this ANET interface. 1680 The AR MAY also send periodic and/or event-driven unsolicited RA 1681 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1682 OMNI header of the unsolicited RA message identifies the target 1683 underlying interface of the destination MN. 1685 The AR can combine the information from multiple MSEs into one or 1686 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1687 Each aggregate RA includes an OMNI option with MS-Register/Release 1688 sub-options with the MSEs represented by the aggregate. If an 1689 aggregate is sent, the RA message contents must consistently 1690 represent the combined information advertised by all represented 1691 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1692 address, the MN determines the addresses of the represented MSEs by 1693 examining the MS-Register/Release OMNI sub-options. 1695 When the MN receives the RA message, it creates an OMNI interface 1696 neighbor cache entry for each MSID that has confirmed MNP 1697 registration via the L2 address of this AR. If the MN connects to 1698 multiple ANETs, it records the additional L2 AR addresses in each 1699 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1700 then configures a default route via the MSE that returned the RA 1701 message, and assigns the Subnet Router Anycast address corresponding 1702 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 1703 manages its underlying interfaces according to their states as 1704 follows: 1706 o When an underlying interface transitions to UP, the MN sends an RS 1707 over the underlying interface with an OMNI option. The OMNI 1708 option contains at least one Interface Attribute sub-option with 1709 values specific to this underlying interface, and may contain 1710 additional Interface Attributes specific to other underlying 1711 interfaces. The option also includes any MS-Register/Release sub- 1712 options. 1714 o When an underlying interface transitions to DOWN, the MN sends an 1715 RS or unsolicited NA message over any UP underlying interface with 1716 an OMNI option containing an Interface Attribute sub-option for 1717 the DOWN underlying interface with Link set to '0'. The MN sends 1718 an RS when an acknowledgement is required, or an unsolicited NA 1719 when reliability is not thought to be a concern (e.g., if 1720 redundant transmissions are sent on multiple underlying 1721 interfaces). 1723 o When the Router Lifetime for a specific AR nears expiration, the 1724 MN sends an RS over the underlying interface to receive a fresh 1725 RA. If no RA is received, the MN can send RS messages to an 1726 alternate MSID in case the current MSID has failed. If no RS 1727 messages are received even after trying to contact alternate 1728 MSIDs, the MN marks the underlying interface as DOWN. 1730 o When a MN wishes to release from one or more current MSIDs, it 1731 sends an RS or unsolicited NA message over any UP underlying 1732 interfaces with an OMNI option with a Release MSID. Each MSID 1733 then withdraws the MNP from the routing/mapping system and informs 1734 the AR that the release was successful. 1736 o When all of a MNs underlying interfaces have transitioned to DOWN 1737 (or if the prefix registration lifetime expires), any associated 1738 MSEs withdraw the MNP the same as if they had received a message 1739 with a release indication. 1741 The MN is responsible for retrying each RS exchange up to 1742 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1743 seconds until an RA is received. If no RA is received over an UP 1744 underlying interface (i.e., even after attempting to contact 1745 alternate MSEs), the MN declares this underlying interface as DOWN. 1747 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1748 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1749 returns an internally-generated RA message as though the message 1750 originated from an IPv6 router. The internally-generated RA message 1751 contains configuration information that is consistent with the 1752 information received from the RAs generated by the MS. Whether the 1753 OMNI interface IPv6 ND messaging process is initiated from the 1754 receipt of an RS message from the IPv6 layer is an implementation 1755 matter. Some implementations may elect to defer the IPv6 ND 1756 messaging process until an RS is received from the IPv6 layer, while 1757 others may elect to initiate the process proactively. Still other 1758 deployments may elect to administratively disable the ordinary RS/RA 1759 messaging used by the IPv6 layer over the OMNI interface, since they 1760 are not required to drive the internal RS/RA processing. (Note that 1761 this same logic applies to IPv4 implementations that employ ICMP- 1762 based Router Discovery per [RFC1256].) 1764 Note: The Router Lifetime value in RA messages indicates the time 1765 before which the MN must send another RS message over this underlying 1766 interface (e.g., 600 seconds), however that timescale may be 1767 significantly longer than the lifetime the MS has committed to retain 1768 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1769 therefore responsible for keeping MS state alive on a shorter 1770 timescale than the MN is required to do on its own behalf. 1772 Note: On multicast-capable underlying interfaces, MNs should send 1773 periodic unsolicited multicast NA messages and ARs should send 1774 periodic unsolicited multicast RA messages as "beacons" that can be 1775 heard by other nodes on the link. If a node fails to receive a 1776 beacon after a timeout value specific to the link, it can initiate a 1777 unicast exchange to test reachability. 1779 Note: if an AR acting as a proxy forwards a MN's RS message to 1780 another node acting as an MSE using UDP/IP encapsulation, it must use 1781 a distinct UDP source port number for each MN. This allows the MSE 1782 to distinguish different MNs behind the same AR at the link-layer, 1783 whereas the link-layer addresses would otherwise be 1784 indistinguishable. 1786 13.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1788 On some ANET types a MN may be located multiple IP hops away from the 1789 nearest AR. Forwarding through IP multihop ANETs is conducted 1790 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1791 Network (MANET) routing protocol over omni-directional wireless 1792 interfaces, an inter-domain routing protocol in an enterprise 1793 network, etc.). These ANETs could be either IPv6-enabled or 1794 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1795 unicast-only (note that for IPv4-only ANETs the following procedures 1796 apply for both single-hop and multihop cases). 1798 A MN located potentially multiple ANET hops away from the nearest AR 1799 prepares an RS message with source address set to either its MN OMNI 1800 LLA or a Temporary OMNI LLA, and with destination set to link-scoped 1801 All-Routers multicast the same as discussed above. For IPv6-enabled 1802 ANETs, the MN then encapsulates the message in an IPv6 header with 1803 source address set to the ULA corresponding to the LLA source address 1804 and with destination set to either a unicast or anycast ULA. For 1805 IPv4-only ANETs, the MN instead encapsulates the RS message in an 1806 IPv4 header with source address set to the node's own IPv4 address 1807 and with destination address set to either the unicast IPv4 address 1808 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 1809 MN then sends the encapsulated RS message via the ANET interface, 1810 where it will be forwarded by zero or more intermediate ANET hops. 1812 When an intermediate ANET hop that participates in the routing 1813 protocol receives the encapsulated RS, it forwards the message 1814 according to its routing tables (note that an intermediate node could 1815 be a fixed infrastructure element or another MN). This process 1816 repeats iteratively until the RS message is received by a penultimate 1817 ANET hop within single-hop communications range of an AR, which 1818 forwards the message to the AR. 1820 When the AR receives the message, it decapsulates the RS and 1821 coordinates with the MS the same as for an ordinary link-local RS, 1822 since the inner Hop Limit will not have been decremented by the 1823 multihop forwarding process. The AR then prepares an RA message with 1824 source address set to its own LLA and destination address set to the 1825 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1826 header with source address set to its own IPv4/ULA address and with 1827 destination set to the encapsulation source of the RS. 1829 The AR then forwards the message to an ANET node within 1830 communications range, which forwards the message according to its 1831 routing tables to an intermediate node. The multihop forwarding 1832 process within the ANET continues repetitively until the message is 1833 delivered to the original MN, which decapsulates the message and 1834 performs autoconfiguration the same as if it had received the RA 1835 directly from the AR as an on-link neighbor. 1837 Note: An alternate approach to multihop forwarding via IPv6 1838 encapsulation would be to statelessly translate the IPv6 LLAs into 1839 ULAs and forward the messages without encapsulation. This would 1840 violate the [RFC4861] requirement that certain IPv6 ND messages must 1841 use link-local addresses and must not be accepted if received with 1842 Hop Limit less than 255. This document therefore advocates 1843 encapsulation since the overhead is nominal considering the 1844 infrequent nature and small size of IPv6 ND messages. Future 1845 documents may consider encapsulation avoidance through translation 1846 while updating [RFC4861]. 1848 Note: An alternate approach to multihop forwarding via IPv4 1849 encapsulation would be to employ IPv6/IPv4 protocol translation. 1850 However, for IPv6 ND messages the OMNI LLA addresses would be 1851 truncated due to translation and the OMNI Router and Prefix Discovery 1852 services would not be able to function. The use of IPv4 1853 encapsulation is therefore indicated. 1855 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 1856 of a new IPv4 /24 prefix allocation, but this may be difficult to 1857 obtain given IPv4 address exhaustion. An alternative would be to re- 1858 purpose the prefix 192.88.99.0 which has been set aside from its 1859 former use by [RFC7526]. 1861 13.2. MS-Register and MS-Release List Processing 1863 When a MN sends an RS message with an OMNI option via an underlying 1864 interface to an AR, the MN must convey its knowledge of its 1865 currently-associated MSEs. Initially, the MN will have no associated 1866 MSEs and should therefore include an MS-Register sub-option with the 1867 single MSID value 0 which requests the AR to select and assign an 1868 MSE. The AR will then return an RA message with source address set 1869 to the OMNI LLA containing the MSE of the selected MSE. 1871 As the MN activates additional underlying interfaces, it can 1872 optionally include an MS-Register sub-option with MSID value 0, or 1873 with non-zero MSIDs for MSEs discovered from previous RS/RA 1874 exchanges. The MN will thus eventually begin to learn and manage its 1875 currently active set of MSEs, and can register with new MSEs or 1876 release from former MSEs with each successive RS/RA exchange. As the 1877 MN's MSE constituency grows, it alone is responsible for including or 1878 omitting MSIDs in the MS-Register/Release lists it sends in RS 1879 messages. The inclusion or omission of MSIDs determines the MN's 1880 interface to the MS and defines the manner in which MSEs will 1881 respond. The only limiting factor is that the MN should include no 1882 more than MAX_MSID values in each list per each IPv6 ND message, and 1883 should avoid duplication of entries in each list unless it wants to 1884 increase likelihood of control message delivery. 1886 When an AR receives an RS message sent by a MN with an OMNI option, 1887 the option will contain zero or more MS-Register and MS-Release sub- 1888 options containing MSIDs. After processing the OMNI option, the AR 1889 will have a list of zero or more MS-Register MSIDs and a list of zero 1890 or more of MS-Release MSIDs. The AR then processes the lists as 1891 follows: 1893 o For each list, retain the first MAX_MSID values in the list and 1894 discard any additional MSIDs (i.e., even if there are duplicates 1895 within a list). 1897 o Next, for each MSID in the MS-Register list, remove all matching 1898 MSIDs from the MS-Release list. 1900 o Next, proceed according to whether the AR's own MSID or the value 1901 0 appears in the MS-Register list as follows: 1903 * If yes, send an RA message directly back to the MN and send a 1904 proxy copy of the RS message to each additional MSID in the MS- 1905 Register list with the MS-Register/Release lists omitted. 1906 Then, send a uNA message to each MSID in the MS-Release list 1907 with the MS-Register/Release lists omitted and with an OMNI 1908 header with S/T-ifIndex set to 0. 1910 * If no, send a proxy copy of the RS message to each additional 1911 MSID in the MS-Register list with the MS-Register list omitted. 1912 For the first MSID, include the original MS-Release list; for 1913 all other MSIDs, omit the MS-Release list. 1915 Each proxy copy of the RS message will include an OMNI option and 1916 encapsulation header with the ULA of the AR as the source and the ULA 1917 of the Register MSE as the destination. When the Register MSE 1918 receives the proxy RS message, if the message includes an MS-Release 1919 list the MSE sends a uNA message to each additional MSID in the 1920 Release list. The Register MSE then sends an RA message back to the 1921 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1922 destination addresses reversed, and with RA destination set to the 1923 LLA of the MN. When the AR receives this RA message, it sends a 1924 proxy copy of the RA to the MN. 1926 Each uNA message (whether send by the first-hop AR or by a Register 1927 MSE) will include an OMNI option and an encapsulation header with the 1928 ULA of the Register MSE as the source and the ULA of the Release ME 1929 as the destination. The uNA informs the Release MSE that its 1930 previous relationship with the MN has been released and that the 1931 source of the uNA message is now registered. The Release MSE must 1932 then note that the subject MN of the uNA message is now "departed", 1933 and forward any subsequent packets destined to the MN to the Register 1934 MSE. 1936 Note that it is not an error for the MS-Register/Release lists to 1937 include duplicate entries. If duplicates occur within a list, the AR 1938 will generate multiple proxy RS and/or uNA messages - one for each 1939 copy of the duplicate entries. 1941 13.3. DHCPv6-based Prefix Registration 1943 When a MN is not pre-provisioned with an OMNI LLA containing a MNP 1944 (or, when multiple MNPs are needed), it will require the AR to select 1945 MNPs on its behalf and set up the correct routing state within the 1946 MS. The DHCPv6 service [RFC8415] supports this requirement. 1948 When an MN needs to have the AR select MNPs, it sends an RS message 1949 with a DHCPv6 Message suboption containing a Client Identifier, one 1950 or more IA_PD options and a Rapid Commit option. The MN also sets 1951 the 'msg-type' field to "Solicit", and includes a 3-octet 1952 'transaction-id'. 1954 When the AR receives the RS message, it extracts the DHCPv6 message 1955 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 1956 a message exchange with the locally-resident DHCPv6 server, which 1957 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 1958 (If the AR wishes to defer creation of MN state until the DHCPv6 1959 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 1960 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 1961 forward/reply exchange with Relay Message and Interface ID options.) 1963 When the AR receives the DHCPv6 Reply, it adds routes to the routing 1964 system and creates MN OMNI LLAs based on the delegated MNPs. The AR 1965 then sends an RA back to the MN with the DHCPv6 Reply message 1966 included in an OMNI DHCPv6 message sub-option. If the RS message 1967 source address was a Temporary address, the AR includes one of the 1968 (newly-created) MN OMNI LLAs as the RA destination address. The MN 1969 then creates a default route, assigns Subnet Router Anycast addresses 1970 and uses the RA destination address as its primary MN OMNI LLA. The 1971 MN will then use this primary MN OMNI LLA as the source address of 1972 any IPv6 ND messages it sends as long as it retains ownership of the 1973 MNP. 1975 Note: The single-octet OMNI sub-option length field restricts the 1976 DHCPv6 Message sub-option to a maximum of 255 octets for both the RS 1977 and RA messages. This provides sufficient room for the DHCPv6 1978 message header, a Client/Server Identifier option, a Rapid Commit 1979 option, at least 3 Identity Association for Prefix Delegation (IA_PD) 1980 options and any other supporting DHCPv6 options. A MN requiring more 1981 DHCPv6-based configuration information than this can either perform 1982 multiple independent RS/RA exchanges (with each exchange providing a 1983 subset of the total configuration information) or simply perform an 1984 actual DHCPv6 message exchange in addition to any RS/RA exchanges. 1986 Note: After a MN performs a DHCPv6-based prefix registration exchange 1987 with a first AR, it would need to repeat the exchange with each 1988 additional MSE it registers with. In that case, the MN supplies the 1989 MNP delegations received from the first AR in the IA_PD fields of a 1990 DHCPv6 message when it engages the additonal MSEs. 1992 14. Secure Redirection 1994 If the ANET link model is multiple access, the AR is responsible for 1995 assuring that address duplication cannot corrupt the neighbor caches 1996 of other nodes on the link. When the MN sends an RS message on a 1997 multiple access ANET link, the AR verifies that the MN is authorized 1998 to use the address and returns an RA with a non-zero Router Lifetime 1999 only if the MN is authorized. 2001 After verifying MN authorization and returning an RA, the AR MAY 2002 return IPv6 ND Redirect messages to direct MNs located on the same 2003 ANET link to exchange packets directly without transiting the AR. In 2004 that case, the MNs can exchange packets according to their unicast L2 2005 addresses discovered from the Redirect message instead of using the 2006 dogleg path through the AR. In some ANET links, however, such direct 2007 communications may be undesirable and continued use of the dogleg 2008 path through the AR may provide better performance. In that case, 2009 the AR can refrain from sending Redirects, and/or MNs can ignore 2010 them. 2012 15. AR and MSE Resilience 2014 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2015 [RFC5798] configurations so that service continuity is maintained 2016 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2017 the (redundant) ARs is currently providing service, and any service 2018 discontinuity will be limited to the failover time supported by VRRP. 2019 Widely deployed public domain implementations of VRRP are available. 2021 MSEs SHOULD use high availability clustering services so that 2022 multiple redundant systems can provide coordinated response to 2023 failures. As with VRRP, widely deployed public domain 2024 implementations of high availability clustering services are 2025 available. Note that special-purpose and expensive dedicated 2026 hardware is not necessary, and public domain implementations can be 2027 used even between lightweight virtual machines in cloud deployments. 2029 16. Detecting and Responding to MSE Failures 2031 In environments where fast recovery from MSE failure is required, ARs 2032 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2033 manner that parallels Bidirectional Forwarding Detection (BFD) 2034 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2035 react to failures so that cached information is re-established 2036 through alternate paths. Proactive NUD control messaging is carried 2037 only over well-connected ground domain networks (i.e., and not low- 2038 end ANET links such as aeronautical radios) and can therefore be 2039 tuned for rapid response. 2041 ARs perform proactive NUD for MSEs for which there are currently 2042 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 2043 of the outage by sending multicast RA messages on the ANET interface. 2044 The AR sends RA messages to MNs via the ANET interface with an OMNI 2045 option with a Release ID for the failed MSE, and with destination 2046 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2048 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2049 by small delays [RFC4861]. Any MNs on the ANET interface that have 2050 been using the (now defunct) MSE will receive the RA messages and 2051 associate with a new MSE. 2053 17. Transition Considerations 2055 When a MN connects to an ANET link for the first time, it sends an RS 2056 message with an OMNI option. If the first hop AR recognizes the 2057 option, it returns an RA with its MS OMNI LLA as the source, the MN 2058 OMNI LLA as the destination and with an OMNI option included. The MN 2059 then engages the AR according to the OMNI link model specified above. 2060 If the first hop AR is a legacy IPv6 router, however, it instead 2061 returns an RA message with no OMNI option and with a non-OMNI unicast 2062 source LLA as specified in [RFC4861]. In that case, the MN engages 2063 the ANET according to the legacy IPv6 link model and without the OMNI 2064 extensions specified in this document. 2066 If the ANET link model is multiple access, there must be assurance 2067 that address duplication cannot corrupt the neighbor caches of other 2068 nodes on the link. When the MN sends an RS message on a multiple 2069 access ANET link with an OMNI LLA source address and an OMNI option, 2070 ARs that recognize the option ensure that the MN is authorized to use 2071 the address and return an RA with a non-zero Router Lifetime only if 2072 the MN is authorized. ARs that do not recognize the option instead 2073 return an RA that makes no statement about the MN's authorization to 2074 use the source address. In that case, the MN should perform 2075 Duplicate Address Detection to ensure that it does not interfere with 2076 other nodes on the link. 2078 An alternative approach for multiple access ANET links to ensure 2079 isolation for MN / AR communications is through L2 address mappings 2080 as discussed in Appendix C. This arrangement imparts a (virtual) 2081 point-to-point link model over the (physical) multiple access link. 2083 18. OMNI Interfaces on the Open Internet 2085 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2086 the open Internet without an OMNI-aware first-hop AR receive RA 2087 messages that do not include an OMNI option, while OMNI interfaces 2088 configured over IPv4-only underlying interfaces do not receive any 2089 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2090 without an OMNI option configure addresses, on-link prefixes, etc. on 2091 the underlying interface that received the RA according to standard 2092 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2093 interfaces configured over IPv4-only underlying interfaces configure 2094 IPv4 address information on the underlying interfaces using 2095 mechanisms such as DHCPv4 [RFC2131]. 2097 OMNI interfaces configured over underlying interfaces that connect to 2098 the open Internet can apply security services such as VPNs to connect 2099 to an MSE or establish a direct link to an MSE through some other 2100 means (see Section 4). In environments where an explicit VPN or 2101 direct link may be impractical, OMNI interfaces can instead use UDP/ 2102 IP encapsulation and HMAC-based message authentication per 2103 [RFC6081][RFC4380]. 2105 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2106 interfaces send control plane messages to interface with the MS, 2107 including Neighbor Solicitation (NS) and Neighbor Advertisement (NA) 2108 messages used for address resolution / route optimization (see: 2109 [I-D.templin-intarea-6706bis]). The control plane messages must be 2110 authenticated while data plane messages are delivered the same as for 2111 ordinary best-effort Internet traffic with basic source address-based 2112 data origin verification. Data plane communications via OMNI 2113 interfaces that connect over the open Internet without an explicit 2114 VPN should therefore employ transport- or higher-layer security to 2115 ensure integrity and/or confidentiality. 2117 OMNI interfaces in the open Internet are often located behind Network 2118 Address Translators (NATs). The OMNI interface accommodates NAT 2119 traversal using UDP/IP encapsulation and the mechanisms discussed in 2120 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2122 19. Time-Varying MNPs 2124 In some use cases, it is desirable, beneficial and efficient for the 2125 MN to receive a constant MNP that travels with the MN wherever it 2126 moves. For example, this would allow air traffic controllers to 2127 easily track aircraft, etc. In other cases, however (e.g., 2128 intelligent transportation systems), the MN may be willing to 2129 sacrifice a modicum of efficiency in order to have time-varying MNPs 2130 that can be changed every so often to defeat adversarial tracking. 2132 The prefix delegation services discussed in Section 13.3 allows OMNI 2133 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2134 use a Temporary OMNI LLA as the source address of an RS message with 2135 an OMNI option with DHCPv6 Option sub-options. The MN would then be 2136 obligated to renumber its internal networks whenever its MNP (and 2137 therefore also its OMNI address) changes. This should not present a 2138 challenge for MNs with automated network renumbering services, 2139 however presents limits for the durations of ongoing sessions that 2140 would prefer to use a constant address. 2142 20. IANA Considerations 2144 The IANA is instructed to allocate an official Type number TBD from 2145 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2146 option. Implementations set Type to 253 as an interim value 2147 [RFC4727]. 2149 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2150 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2151 read as follows: 2153 Code Name Reference 2154 --- ---- --------- 2155 0 Diagnostic Packet Too Big [RFC4443] 2156 1 Advisory Packet Too Big [RFCXXXX] 2158 Figure 17: OMNI Option Sub-Type Values 2160 The IANA is instructed to allocate one Ethernet unicast address TBD2 2161 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2162 Address Block - Unicast Use". 2164 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 2165 is instructed to create and maintain a new registry entitled "OMNI 2166 option Sub-Type values". Initial values for the OMNI option Sub-Type 2167 values registry are given below; future assignments are to be made 2168 through Expert Review [RFC8126]. 2170 Value Sub-Type name Reference 2171 ----- ------------- ---------- 2172 0 Pad1 [RFCXXXX] 2173 1 PadN [RFCXXXX] 2174 2 Interface Attributes [RFCXXXX] 2175 3 Traffic Selector [RFCXXXX] 2176 4 MS-Register [RFCXXXX] 2177 5 MS-Release [RFCXXXX] 2178 6 Network Access Identifier [RFCXXXX] 2179 7 Geo Coordinates [RFCXXXX] 2180 8 DHCP Unique Identifier (DUID) [RFCXXXX] 2181 9 DHCPv6 Message [RFCXXXX] 2182 10-252 Unassigned 2183 253-254 Experimental [RFCXXXX] 2184 255 Reserved [RFCXXXX] 2186 Figure 18: OMNI Option Sub-Type Values 2188 21. Security Considerations 2190 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2191 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2192 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2193 confirmation and/or time synchronization is needed. 2195 OMNI interfaces configured over secured ANET interfaces inherit the 2196 physical and/or link-layer security properties of the connected 2197 ANETs. OMNI interfaces configured over open INET interfaces can use 2198 symmetric securing services such as VPNs or can by some other means 2199 establish a direct link. When a VPN or direct link may be 2200 impractical, however, an asymmetric security service such as the 2201 authentication option specified in [RFC4380] or other protocol 2202 control message security mechanisms may be necessary. While the OMNI 2203 link protects control plane messaging, applications must still employ 2204 end-to-end transport- or higher-layer security services to protect 2205 the data plane. 2207 The Mobility Service MUST provide strong network layer security for 2208 control plane messages and forwarding path integrity for data plane 2209 messages. In one example, the AERO service 2210 [I-D.templin-intarea-6706bis] constructs a spanning tree between 2211 mobility service elements and secures the links in the spanning tree 2212 with network layer security mechanisms such as IPsec [RFC4301] or 2213 Wireguard. Control plane messages are then constrained to travel 2214 only over the secured spanning tree paths and are therefore protected 2215 from attack or eavesdropping. Since data plane messages can travel 2216 over route optimized paths that do not strictly follow the spanning 2217 tree, however, end-to-end transport- or higher-layer security 2218 services are still required. 2220 Security considerations for specific access network interface types 2221 are covered under the corresponding IP-over-(foo) specification 2222 (e.g., [RFC2464], [RFC2492], etc.). 2224 Security considerations for IPv6 fragmentation and reassembly are 2225 discussed in Section 5.1. 2227 22. Implementation Status 2229 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2230 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2231 Newer specification versions will be tagged in upcoming releases. 2232 First public release expected before the end of 2020. 2234 23. Acknowledgements 2236 The first version of this document was prepared per the consensus 2237 decision at the 7th Conference of the International Civil Aviation 2238 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2239 2019. Consensus to take the document forward to the IETF was reached 2240 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2241 Attendees and contributors included: Guray Acar, Danny Bharj, 2242 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2243 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2244 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2245 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2246 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2247 Fryderyk Wrobel and Dongsong Zeng. 2249 The following individuals are acknowledged for their useful comments: 2250 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 2251 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized 2252 for their many helpful ideas and suggestions. Madhuri Madhava 2253 Badgandi, Katherine Tran, and Vijayasarathy Rajagopalan are 2254 acknowledged for their hard work on the implementation and insights 2255 that led to improvements to the spec. 2257 Discussions on the IETF 6man and atn mailing lists during the fall of 2258 2020 suggested additional points to consider. The authors gratefully 2259 acknowledge the list members who contributed valuable insights 2260 through those discussions. Eric Vyncke and Erik Kline were the 2261 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2262 at the time the document was developed; they are all gratefully 2263 acknowledged for their many helpful insights. 2265 This work is aligned with the NASA Safe Autonomous Systems Operation 2266 (SASO) program under NASA contract number NNA16BD84C. 2268 This work is aligned with the FAA as per the SE2025 contract number 2269 DTFAWA-15-D-00030. 2271 24. References 2273 24.1. Normative References 2275 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2276 DOI 10.17487/RFC0791, September 1981, 2277 . 2279 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2280 Requirement Levels", BCP 14, RFC 2119, 2281 DOI 10.17487/RFC2119, March 1997, 2282 . 2284 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2285 "Definition of the Differentiated Services Field (DS 2286 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2287 DOI 10.17487/RFC2474, December 1998, 2288 . 2290 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2291 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2292 DOI 10.17487/RFC3971, March 2005, 2293 . 2295 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2296 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2297 November 2005, . 2299 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2300 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2301 . 2303 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2304 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2305 2006, . 2307 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2308 Control Message Protocol (ICMPv6) for the Internet 2309 Protocol Version 6 (IPv6) Specification", STD 89, 2310 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2311 . 2313 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2314 ICMPv6, UDP, and TCP Headers", RFC 4727, 2315 DOI 10.17487/RFC4727, November 2006, 2316 . 2318 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2319 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2320 DOI 10.17487/RFC4861, September 2007, 2321 . 2323 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2324 Address Autoconfiguration", RFC 4862, 2325 DOI 10.17487/RFC4862, September 2007, 2326 . 2328 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2329 "Traffic Selectors for Flow Bindings", RFC 6088, 2330 DOI 10.17487/RFC6088, January 2011, 2331 . 2333 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2334 Hosts in a Multi-Prefix Network", RFC 8028, 2335 DOI 10.17487/RFC8028, November 2016, 2336 . 2338 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2339 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2340 May 2017, . 2342 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2343 (IPv6) Specification", STD 86, RFC 8200, 2344 DOI 10.17487/RFC8200, July 2017, 2345 . 2347 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2348 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2349 DOI 10.17487/RFC8201, July 2017, 2350 . 2352 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2353 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2354 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2355 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2356 . 2358 24.2. Informative References 2360 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2361 Interface for Civil Aviation, IETF Liaison Statement 2362 #1676, https://datatracker.ietf.org/liaison/1676/", March 2363 2020. 2365 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2366 Aeronautical Telecommunication Network (ATN) using 2367 Internet Protocol Suite (IPS) Standards and Protocol), 2368 Draft Edition 3 (work-in-progress)", December 2020. 2370 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2371 Interface (FDDI), IEEE Transactions on Communications", 2372 August 1990. 2374 [I-D.ietf-6man-rfc4941bis] 2375 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2376 "Temporary Address Extensions for Stateless Address 2377 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2378 (work in progress), November 2020. 2380 [I-D.ietf-intarea-tunnels] 2381 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2382 Architecture", draft-ietf-intarea-tunnels-10 (work in 2383 progress), September 2019. 2385 [I-D.ietf-ipwave-vehicular-networking] 2386 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2387 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2388 ipwave-vehicular-networking-19 (work in progress), July 2389 2020. 2391 [I-D.templin-6man-dhcpv6-ndopt] 2392 Templin, F., "A Unified Stateful/Stateless Configuration 2393 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2394 (work in progress), June 2020. 2396 [I-D.templin-6man-lla-type] 2397 Templin, F., "The IPv6 Link-Local Address Type Field", 2398 draft-templin-6man-lla-type-02 (work in progress), 2399 November 2020. 2401 [I-D.templin-intarea-6706bis] 2402 Templin, F., "Asymmetric Extended Route Optimization 2403 (AERO)", draft-templin-intarea-6706bis-76 (work in 2404 progress), December 2020. 2406 [IPV4-GUA] 2407 Postel, J., "IPv4 Address Space Registry, 2408 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2409 address-space.xhtml", December 2020. 2411 [IPV6-GUA] 2412 Postel, J., "IPv6 Global Unicast Address Assignments, 2413 https://www.iana.org/assignments/ipv6-unicast-address- 2414 assignments/ipv6-unicast-address-assignments.xhtml", 2415 December 2020. 2417 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2418 Communication Layers", STD 3, RFC 1122, 2419 DOI 10.17487/RFC1122, October 1989, 2420 . 2422 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2423 DOI 10.17487/RFC1191, November 1990, 2424 . 2426 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2427 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2428 . 2430 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2431 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2432 . 2434 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2435 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2436 . 2438 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2439 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2440 . 2442 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2443 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2444 December 1998, . 2446 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2447 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2448 . 2450 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2451 Domains without Explicit Tunnels", RFC 2529, 2452 DOI 10.17487/RFC2529, March 1999, 2453 . 2455 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2456 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2457 . 2459 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2460 DOI 10.17487/RFC3330, September 2002, 2461 . 2463 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2464 Considered Useful", BCP 82, RFC 3692, 2465 DOI 10.17487/RFC3692, January 2004, 2466 . 2468 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2469 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2470 DOI 10.17487/RFC3810, June 2004, 2471 . 2473 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2474 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2475 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2476 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2477 . 2479 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2480 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2481 2004, . 2483 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2484 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2485 December 2005, . 2487 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2488 Network Address Translations (NATs)", RFC 4380, 2489 DOI 10.17487/RFC4380, February 2006, 2490 . 2492 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2493 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2494 2006, . 2496 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2497 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2498 . 2500 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2501 "Considerations for Internet Group Management Protocol 2502 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2503 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2504 . 2506 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2507 "Internet Group Management Protocol (IGMP) / Multicast 2508 Listener Discovery (MLD)-Based Multicast Forwarding 2509 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2510 August 2006, . 2512 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2513 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2514 . 2516 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2517 Errors at High Data Rates", RFC 4963, 2518 DOI 10.17487/RFC4963, July 2007, 2519 . 2521 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2522 Advertisement Flags Option", RFC 5175, 2523 DOI 10.17487/RFC5175, March 2008, 2524 . 2526 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2527 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2528 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2529 . 2531 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2532 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2533 DOI 10.17487/RFC5214, March 2008, 2534 . 2536 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2537 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2538 . 2540 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2541 Version 3 for IPv4 and IPv6", RFC 5798, 2542 DOI 10.17487/RFC5798, March 2010, 2543 . 2545 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2546 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2547 . 2549 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2550 DOI 10.17487/RFC6081, January 2011, 2551 . 2553 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2554 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2555 DOI 10.17487/RFC6221, May 2011, 2556 . 2558 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2559 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2560 DOI 10.17487/RFC6355, August 2011, 2561 . 2563 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2564 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2565 2012, . 2567 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2568 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2569 DOI 10.17487/RFC7084, November 2013, 2570 . 2572 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2573 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2574 Boundary in IPv6 Addressing", RFC 7421, 2575 DOI 10.17487/RFC7421, January 2015, 2576 . 2578 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 2579 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 2580 DOI 10.17487/RFC7526, May 2015, 2581 . 2583 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2584 DOI 10.17487/RFC7542, May 2015, 2585 . 2587 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2588 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2589 February 2016, . 2591 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2592 Support for IP Hosts with Multi-Access Support", RFC 7847, 2593 DOI 10.17487/RFC7847, May 2016, 2594 . 2596 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2597 Writing an IANA Considerations Section in RFCs", BCP 26, 2598 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2599 . 2601 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2602 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2603 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2604 July 2018, . 2606 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2607 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2608 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2609 . 2611 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2612 and F. Gont, "IP Fragmentation Considered Fragile", 2613 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2614 . 2616 Appendix A. Interface Attribute Preferences Bitmap Encoding 2618 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 2619 encoding to specific Internetworks such as the Aeronautical 2620 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2621 may include link selection preferences based on other traffic 2622 classifiers (e.g., transport port numbers, etc.) in addition to the 2623 existing DSCP-based preferences. Nodes on specific Internetworks 2624 maintain a map of traffic classifiers to additional P[*] preference 2625 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2626 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2628 Implementations use Simplex or Indexed encoding formats for P[*] 2629 encoding in order to encode a given set of traffic classifiers in the 2630 most efficient way. Some use cases may be more efficiently coded 2631 using Simplex form, while others may be more efficient using Indexed. 2632 Once a format is selected for preparation of a single Interface 2633 Attribute the same format must be used for the entire Interface 2634 Attribute sub-option. Different sub-options may use different 2635 formats. 2637 The following figures show coding examples for various Simplex and 2638 Indexed formats: 2640 0 1 2 3 2641 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 2642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2643 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2645 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 2646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2647 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2648 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2649 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2650 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2651 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2653 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2655 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2658 Figure 19: Example 1: Dense Simplex Encoding 2660 0 1 2 3 2661 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 2662 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2663 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2665 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2666 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2667 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2668 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2669 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2671 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2673 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2675 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2677 |Bitmap(10)=0x00| ... 2678 +-+-+-+-+-+-+-+-+-+-+- 2680 Figure 20: Example 2: Sparse Simplex Encoding 2682 0 1 2 3 2683 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 2684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2685 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2687 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 2688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2689 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2690 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2691 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2692 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2693 | Bitmap = 0x01 |796|797|798|799| ... 2694 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2696 Figure 21: Example 3: Indexed Encoding 2698 Appendix B. VDL Mode 2 Considerations 2700 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2701 (VDLM2) that specifies an essential radio frequency data link service 2702 for aircraft and ground stations in worldwide civil aviation air 2703 traffic management. The VDLM2 link type is "multicast capable" 2704 [RFC4861], but with considerable differences from common multicast 2705 links such as Ethernet and IEEE 802.11. 2707 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2708 magnitude less than most modern wireless networking gear. Second, 2709 due to the low available link bandwidth only VDLM2 ground stations 2710 (i.e., and not aircraft) are permitted to send broadcasts, and even 2711 so only as compact layer 2 "beacons". Third, aircraft employ the 2712 services of ground stations by performing unicast RS/RA exchanges 2713 upon receipt of beacons instead of listening for multicast RA 2714 messages and/or sending multicast RS messages. 2716 This beacon-oriented unicast RS/RA approach is necessary to conserve 2717 the already-scarce available link bandwidth. Moreover, since the 2718 numbers of beaconing ground stations operating within a given spatial 2719 range must be kept as sparse as possible, it would not be feasible to 2720 have different classes of ground stations within the same region 2721 observing different protocols. It is therefore highly desirable that 2722 all ground stations observe a common language of RS/RA as specified 2723 in this document. 2725 Note that links of this nature may benefit from compression 2726 techniques that reduce the bandwidth necessary for conveying the same 2727 amount of data. The IETF lpwan working group is considering possible 2728 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2730 Appendix C. MN / AR Isolation Through L2 Address Mapping 2732 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2733 unicast link-scoped IPv6 destination address. However, IPv6 ND 2734 messaging should be coordinated between the MN and AR only without 2735 invoking other nodes on the ANET. This implies that MN / AR control 2736 messaging should be isolated and not overheard by other nodes on the 2737 link. 2739 To support MN / AR isolation on some ANET links, ARs can maintain an 2740 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2741 ANETs, this specification reserves one Ethernet unicast address TBD2 2742 (see: Section 20). For non-Ethernet statically-addressed ANETs, 2743 MSADDR is reserved per the assigned numbers authority for the ANET 2744 addressing space. For still other ANETs, MSADDR may be dynamically 2745 discovered through other means, e.g., L2 beacons. 2747 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2748 both multicast and unicast) to MSADDR instead of to an ordinary 2749 unicast or multicast L2 address. In this way, all of the MN's IPv6 2750 ND messages will be received by ARs that are configured to accept 2751 packets destined to MSADDR. Note that multiple ARs on the link could 2752 be configured to accept packets destined to MSADDR, e.g., as a basis 2753 for supporting redundancy. 2755 Therefore, ARs must accept and process packets destined to MSADDR, 2756 while all other devices must not process packets destined to MSADDR. 2757 This model has well-established operational experience in Proxy 2758 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2760 Appendix D. Change Log 2762 << RFC Editor - remove prior to publication >> 2764 Differences from draft-templin-6man-omni-interface-35 to draft- 2765 templin-6man-omni-interface-36: 2767 o Major clarifications on aspects such as "hard/soft" PTB error 2768 messages 2770 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2771 be used in the data plane. 2773 Differences from draft-templin-6man-omni-interface-31 to draft- 2774 templin-6man-omni-interface-32: 2776 o MTU 2778 o Support for multi-hop ANETS such as ISATAP. 2780 Differences from draft-templin-6man-omni-interface-29 to draft- 2781 templin-6man-omni-interface-30: 2783 o Moved link-layer addressing information into the OMNI option on a 2784 per-ifIndex basis 2786 o Renamed "ifIndex-tuple" to "Interface Attributes" 2788 Differences from draft-templin-6man-omni-interface-27 to draft- 2789 templin-6man-omni-interface-28: 2791 o Updates based on implementation expereince. 2793 Differences from draft-templin-6man-omni-interface-25 to draft- 2794 templin-6man-omni-interface-26: 2796 o Further clarification on "aggregate" RA messages. 2798 o Expanded Security Considerations to discuss expectations for 2799 security in the Mobility Service. 2801 Differences from draft-templin-6man-omni-interface-20 to draft- 2802 templin-6man-omni-interface-21: 2804 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2805 (PBM). 2807 Differences from draft-templin-6man-omni-interface-18 to draft- 2808 templin-6man-omni-interface-19: 2810 o SEND/CGA. 2812 Differences from draft-templin-6man-omni-interface-17 to draft- 2813 templin-6man-omni-interface-18: 2815 o Teredo 2817 Differences from draft-templin-6man-omni-interface-14 to draft- 2818 templin-6man-omni-interface-15: 2820 o Prefix length discussions removed. 2822 Differences from draft-templin-6man-omni-interface-12 to draft- 2823 templin-6man-omni-interface-13: 2825 o Teredo 2827 Differences from draft-templin-6man-omni-interface-11 to draft- 2828 templin-6man-omni-interface-12: 2830 o Major simplifications and clarifications on MTU and fragmentation. 2832 o Document now updates RFC4443 and RFC8201. 2834 Differences from draft-templin-6man-omni-interface-10 to draft- 2835 templin-6man-omni-interface-11: 2837 o Removed /64 assumption, resulting in new OMNI address format. 2839 Differences from draft-templin-6man-omni-interface-07 to draft- 2840 templin-6man-omni-interface-08: 2842 o OMNI MNs in the open Internet 2844 Differences from draft-templin-6man-omni-interface-06 to draft- 2845 templin-6man-omni-interface-07: 2847 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2848 L2 addressing. 2850 o Expanded "Transition Considerations". 2852 Differences from draft-templin-6man-omni-interface-05 to draft- 2853 templin-6man-omni-interface-06: 2855 o Brought back OMNI option "R" flag, and discussed its use. 2857 Differences from draft-templin-6man-omni-interface-04 to draft- 2858 templin-6man-omni-interface-05: 2860 o Transition considerations, and overhaul of RS/RA addressing with 2861 the inclusion of MSE addresses within the OMNI option instead of 2862 as RS/RA addresses (developed under FAA SE2025 contract number 2863 DTFAWA-15-D-00030). 2865 Differences from draft-templin-6man-omni-interface-02 to draft- 2866 templin-6man-omni-interface-03: 2868 o Added "advisory PTB messages" under FAA SE2025 contract number 2869 DTFAWA-15-D-00030. 2871 Differences from draft-templin-6man-omni-interface-01 to draft- 2872 templin-6man-omni-interface-02: 2874 o Removed "Primary" flag and supporting text. 2876 o Clarified that "Router Lifetime" applies to each ANET interface 2877 independently, and that the union of all ANET interface Router 2878 Lifetimes determines MSE lifetime. 2880 Differences from draft-templin-6man-omni-interface-00 to draft- 2881 templin-6man-omni-interface-01: 2883 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2884 for future use (most likely as "pseudo-multicast"). 2886 o Non-normative discussion of alternate OMNI LLA construction form 2887 made possible if the 64-bit assumption were relaxed. 2889 First draft version (draft-templin-atn-aero-interface-00): 2891 o Draft based on consensus decision of ICAO Working Group I Mobility 2892 Subgroup March 22, 2019. 2894 Authors' Addresses 2895 Fred L. Templin (editor) 2896 The Boeing Company 2897 P.O. Box 3707 2898 Seattle, WA 98124 2899 USA 2901 Email: fltemplin@acm.org 2903 Tony Whyman 2904 MWA Ltd c/o Inmarsat Global Ltd 2905 99 City Road 2906 London EC1Y 1AX 2907 England 2909 Email: tony.whyman@mccallumwhyman.com