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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 18, 2020 7 Expires: June 21, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-62 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 21, 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 . . . . . . . . . . . 18 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 18 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 19 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 . . . . . . . . . . . . . . . . . . . . . . 24 70 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 25 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 . . . . . . . . . . . . . . . . . . 31 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 . . . . . . . . . . . 33 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 Networks . 39 86 13.2. MS-Register and MS-Release List Processing . . . . . . . 41 87 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 42 88 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 43 89 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 44 90 16. Detecting and Responding to MSE Failures . . . . . . . . . . 44 91 17. Transition Considerations . . . . . . . . . . . . . . . . . . 45 92 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 45 93 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 46 94 20. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 95 21. Security Considerations . . . . . . . . . . . . . . . . . . . 47 96 22. Implementation Status . . . . . . . . . . . . . . . . . . . . 48 97 23. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48 98 24. References . . . . . . . . . . . . . . . . . . . . . . . . . 49 99 24.1. Normative References . . . . . . . . . . . . . . . . . . 49 100 24.2. Informative References . . . . . . . . . . . . . . . . . 51 101 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 57 102 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 58 103 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 59 104 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 60 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 62 107 1. Introduction 109 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 110 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 111 etc.) often have multiple interface connections to wireless and/or 112 wired-link data links used 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 node's 118 underlying interface connections to the data links. 120 The MN configures a virtual interface (termed the "Overlay Multilink 121 Network (OMNI) interface") as a thin layer over the underlying 122 interfaces. The OMNI interface is therefore the only interface 123 abstraction exposed to the IP layer and behaves according to the Non- 124 Broadcast, Multiple Access (NBMA) interface principle, while 125 underlying interfaces appear as link layer communication channels in 126 the architecture. The OMNI interface connects to a virtual overlay 127 service known as the "OMNI link". The OMNI link spans one or more 128 Internetworks that may include private-use infrastructures and/or the 129 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 ULA prefix [ULA]::/48 prefix, 154 and each OMNI link within the domain configures a unique 16-bit ID 155 '*' to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 156 layer applies SBM routing to select an OMNI interface, which then 157 applies Performance-Based Multilink (PBM) to select the correct 158 underlying interface. Applications can apply Segment Routing 159 [RFC8402] to select independent SBM topologies for fault tolerance. 161 The OMNI interface interacts with a network-based Mobility Service 162 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 163 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 164 track MN movements and represent their MNPs in a global routing or 165 mapping system. 167 Many OMNI use cases are currently under active consideration. In 168 particular, the International Civil Aviation Organization (ICAO) 169 Working Group-I Mobility Subgroup is developing a future Aeronautical 170 Telecommunications Network with Internet Protocol Services (ATN/IPS) 171 and has issued a liaison statement requesting IETF adoption [ATN] in 172 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 173 in Vehicular Environments (ipwave) working group has further included 174 problem statement and use case analysis for OMNI in a document now in 175 AD evaluation for RFC publication 176 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 177 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 178 programs that examine commercial aviation, Urban Air Mobility (UAM) 179 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 180 represent another large class of potential OMNI users. 182 This document specifies the transmission of IP packets and MN/MS 183 control messages over OMNI interfaces. The OMNI interface supports 184 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 185 as the network layer in the data plane, while using IPv6 ND messaging 186 as the control plane independently of the data plane IP protocol(s). 187 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 188 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 189 discussed in the following sections. 191 2. Terminology 193 The terminology in the normative references applies; especially, the 194 terms "link" and "interface" are the same as defined in the IPv6 195 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 196 Additionally, this document assumes the following IPv6 ND message 197 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 198 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 200 The Protocol Constants defined in Section 10 of [RFC4861] are used in 201 their same format and meaning in this document. The terms "All- 202 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 203 are the same as defined in [RFC4291] (with Link-Local scope assumed). 205 The term "IP" is used to refer collectively to either Internet 206 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 207 specification at the layer in question applies equally to either 208 version. 210 The following terms are defined within the scope of this document: 212 Mobile Node (MN) 213 an end system with a mobile router having multiple distinct 214 upstream data link connections that are grouped together in one or 215 more logical units. The MN's data link connection parameters can 216 change over time due to, e.g., node mobility, link quality, etc. 217 The MN further connects a downstream-attached End User Network 218 (EUN). The term MN used here is distinct from uses in other 219 documents, and does not imply a particular mobility protocol. 221 End User Network (EUN) 222 a simple or complex downstream-attached mobile network that 223 travels with the MN as a single logical unit. The IP addresses 224 assigned to EUN devices remain stable even if the MN's upstream 225 data link connections change. 227 Mobility Service (MS) 228 a mobile routing service that tracks MN movements and ensures that 229 MNs remain continuously reachable even across mobility events. 230 Specific MS details are out of scope for this document. 232 Mobility Service Endpoint (MSE) 233 an entity in the MS (either singular or aggregate) that 234 coordinates the mobility events of one or more MN. 236 Mobility Service Prefix (MSP) 237 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 238 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 239 from which more-specific Mobile Network Prefixes (MNPs) are 240 delegated. OMNI link administrators typically obtain MSPs from an 241 Internet address registry, however private-use prefixes can 242 alternatively be used subject to certain limitations (see: 243 Section 9). OMNI links that connect to the global Internet 244 advertise their MSPs to their interdomain routing peers. 246 Mobile Network Prefix (MNP) 247 a longer IP prefix delegated 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 is assumed, and sometimes referred to as 256 "protected spectrum". Private enterprise networks and ground 257 domain aviation service networks may provide multiple secured IP 258 hops between the MN's point of connection and the nearest Access 259 Router. 261 Access Router (AR) 262 a router in the ANET for connecting MNs to correspondents in 263 outside Internetworks. The AR may be located on the same physical 264 link as the MN, or may be located multiple IP hops away. In the 265 latter case, the MN uses encapsulation to communicate with the AR 266 as though it were on the same physical link. 268 ANET interface 269 a MN's attachment to a link in an ANET. 271 Internetwork (INET) 272 a connected network region with a coherent IP addressing plan that 273 provides transit forwarding services between ANETs and nodes that 274 connect directly to the open INET via unprotected media. No 275 physical and/or data link level security is assumed, therefore 276 security must be applied by upper layers. The global public 277 Internet itself is an example. 279 INET interface 280 a node's attachment to a link in an INET. 282 *NET 283 a "wildcard" term used when a given specification applies equally 284 to both ANET and INET cases. 286 OMNI link 287 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 288 over one or more INETs and their connected ANETs. An OMNI link 289 can comprise multiple INET segments joined by bridges the same as 290 for any link; the addressing plans in each segment may be mutually 291 exclusive and managed by different administrative entities. 293 OMNI interface 294 a node's attachment to an OMNI link, and configured over one or 295 more underlying *NET interfaces. If there are multiple OMNI links 296 in an OMNI domain, a separate OMNI interface is configured for 297 each link. 299 OMNI Adaptation Layer (OAL) 300 an OMNI interface process whereby packets admitted into the 301 interface are wrapped in a mid-layer IPv6 header and fragmented/ 302 reassembled if necessary to support the OMNI link Maximum 303 Transmission Unit (MTU). The OAL is also responsible for 304 generating MTU-related control messages as necessary, and for 305 providing addressing context for spanning multiple segments of a 306 bridged OMNI link. 308 OMNI Option 309 an IPv6 Neighbor Discovery option providing multilink parameters 310 for the OMNI interface as specified in Section 10. 312 Multilink 313 an OMNI interface's manner of managing diverse underlying 314 interface connections to data links as a single logical unit. The 315 OMNI interface provides a single unified interface to upper 316 layers, while underlying interface selections are performed on a 317 per-packet basis considering factors such as DSCP, flow label, 318 application policy, signal quality, cost, etc. Multilinking 319 decisions are coordinated in both the outbound (i.e. MN to 320 correspondent) and inbound (i.e., correspondent to MN) directions. 322 L2 323 The second layer in the OSI network model. Also known as "layer- 324 2", "link-layer", "sub-IP layer", "data link layer", etc. 326 L3 327 The third layer in the OSI network model. Also known as "layer- 328 3", "network-layer", "IP layer", etc. 330 underlying interface 331 a *NET interface over which an OMNI interface is configured. The 332 OMNI interface is seen as a L3 interface by the IP layer, and each 333 underlying interface is seen as a L2 interface by the OMNI 334 interface. The underlying interface either connects directly to 335 the physical communications media or coordinates with another node 336 where the physical media is hosted. 338 Mobility Service Identification (MSID) 339 Each MSE and AR is assigned a unique 16-bit Identification (MSID) 340 as specified in Section 7. The IDs is assigned based on the BGP 341 Autonomous System Number (ASN) [RFC4271] assigned to the MSE/AR by 342 the OMNI link administrative authority (see: 343 [I-D.templin-intarea-6706bis]. 345 Safety-Based Multilink (SBM) 346 A means for ensuring fault tolerance through redundancy by 347 connecting multiple affiliated OMNI interfaces to independent 348 routing topologies (i.e., multiple independent OMNI links). 350 Performance Based Multilink (PBM) 351 A means for selecting underlying interface(s) for packet 352 transmission and reception within a single OMNI interface. 354 OMNI Domain 355 The set of all SBM/PBM OMNI links that collectively provides 356 services for a common set of MSPs. Each OMNI domain consists of a 357 set of affiliated OMNI links that all configure the same ::/48 ULA 358 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 360 3. Requirements 362 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 363 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 364 "OPTIONAL" in this document are to be interpreted as described in BCP 365 14 [RFC2119][RFC8174] when, and only when, they appear in all 366 capitals, as shown here. 368 OMNI links maintain a constant value "MAX_MSID" selected to provide 369 MNs with an acceptable level of MSE redundancy while minimizing 370 control message amplification. It is RECOMMENDED that MAX_MSID be 371 set to the default value 5; if a different value is chosen, it should 372 be set uniformly by all nodes on the OMNI link. 374 An implementation is not required to internally use the architectural 375 constructs described here so long as its external behavior is 376 consistent with that described in this document. 378 4. Overlay Multilink Network (OMNI) Interface Model 380 An OMNI interface is a MN virtual interface configured over one or 381 more underlying interfaces, which may be physical (e.g., an 382 aeronautical radio link) or virtual (e.g., an Internet or higher- 383 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 384 with the MS through IPv6 ND message exchanges. The MN uses the MNP 385 to construct a unique Link-Local Address (LLA) through the 386 algorithmic derivation specified in Section 7 and assigns the LLA to 387 the OMNI interface. 389 The OMNI interface architectural layering model is the same as in 390 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 391 therefore sees the OMNI interface as a single L3 interface with 392 multiple underlying interfaces that appear as L2 communication 393 channels in the architecture. 395 +----------------------------+ 396 | Upper Layer Protocol | 397 Session-to-IP +---->| | 398 Address Binding | +----------------------------+ 399 +---->| IP (L3) | 400 IP Address +---->| | 401 Binding | +----------------------------+ 402 +---->| OMNI Interface | 403 Logical-to- +---->| (LLA) | 404 Physical | +----------------------------+ 405 Interface +---->| L2 | L2 | | L2 | 406 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 407 +------+------+ +------+ 408 | L1 | L1 | | L1 | 409 | | | | | 410 +------+------+ +------+ 412 Figure 1: OMNI Interface Architectural Layering Model 414 Each underlying interface provides an L2/L1 abstraction according to 415 one of the following models: 417 o INET interfaces connect to an INET either natively or through one 418 or several IPv4 Network Address Translators (NATs). Native INET 419 interfaces have global IP addresses that are reachable from any 420 INET correspondent. NATed INET interfaces typically have private 421 IP addresses and connect to a private network behind one or more 422 NATs that provide INET access. 424 o ANET interfaces connect to a protected ANET that is separated from 425 the open INET by an AR acting as a proxy. The ANET interface may 426 be either on the same L2 link segment as the AR, or separated from 427 the AR by multiple IP hops. 429 o VPNed interfaces use security encapsulation over a *NET to a 430 Virtual Private Network (VPN) gateway. Other than the link-layer 431 encapsulation format, VPNed interfaces behave the same as for 432 Direct interfaces. 434 o Direct (aka "point-to-point") interfaces connect directly to a 435 peer without crossing any *NET paths. An example is a line-of- 436 sight link between a remote pilot and an unmanned aircraft. 438 The OMNI virtual interface model gives rise to a number of 439 opportunities: 441 o since MN LLAs are uniquely derived from an MNP, no Duplicate 442 Address Detection (DAD) or Multicast Listener Discovery (MLD) 443 messaging is necessary. 445 o since Temporary LLAs are statistically unique, they can be used 446 without DAD for short-term purposes, e.g. until an MN LLA is 447 obtained. 449 o *NET interfaces on the same L2 link segment as an AR do not 450 require any L3 addresses (i.e., not even link-local) in 451 environments where communications are coordinated entirely over 452 the OMNI interface. (An alternative would be to also assign the 453 same LLA to all *NET interfaces.) 455 o as underlying interface properties change (e.g., link quality, 456 cost, availability, etc.), any active interface can be used to 457 update the profiles of multiple additional interfaces in a single 458 message. This allows for timely adaptation and service continuity 459 under dynamically changing conditions. 461 o coordinating underlying interfaces in this way allows them to be 462 represented in a unified MS profile with provisions for mobility 463 and multilink operations. 465 o exposing a single virtual interface abstraction to the IPv6 layer 466 allows for multilink operation (including QoS based link 467 selection, packet replication, load balancing, etc.) at L2 while 468 still permitting L3 traffic shaping based on, e.g., DSCP, flow 469 label, etc. 471 o the OMNI interface allows inter-INET traversal when nodes located 472 in different INETs need to communicate with one another. This 473 mode of operation would not be possible via direct communications 474 over the underlying interfaces themselves. 476 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 477 lossless and adaptive path MTU mitigations not available for 478 communications directly over the underlying interfaces themselves. 480 o L3 sees the OMNI interface as a point of connection to the OMNI 481 link; if there are multiple OMNI links (i.e., multiple MS's), L3 482 will see multiple OMNI interfaces. 484 o Multiple independent OMNI interfaces can be used for increased 485 fault tolerance through Safety-Based Multilink (SBM), with 486 Performance-Based Multilink (PBM) applied within each interface. 488 Other opportunities are discussed in [RFC7847]. Note that even when 489 the OMNI virtual interface is present, applications can still access 490 underlying interfaces either through the network protocol stack using 491 an Internet socket or directly using a raw socket. This allows for 492 intra-network (or point-to-point) communications without invoking the 493 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 494 is configured over an underlying IPv4 interface, applications can 495 still invoke IPv4 intra-network communications as long as the 496 communicating endpoints are not subject to mobility dynamics. 497 However, the opportunities discussed above are not available when the 498 architectural layering is bypassed in this way. 500 Figure 2 depicts the architectural model for a MN with an attached 501 EUN connecting to the MS via multiple independent *NETs. When an 502 underlying interface becomes active, the MN's OMNI interface sends 503 IPv6 ND messages without encapsulation if the first-hop Access Router 504 (AR) is on the same underlying link; otherwise, the interface uses 505 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 506 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 507 then coordinates with an INET Mobility Service Endpoint (MSE#1, 508 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 509 The Hop Limit in IPv6 ND messages is not decremented due to 510 encapsulation; hence, the OMNI interface appears to be attached to an 511 ordinary link. 513 +--------------+ (:::)-. 514 | MN |<-->.-(::EUN:::) 515 +--------------+ `-(::::)-' 516 |OMNI interface| 517 +----+----+----+ 518 +--------|IF#1|IF#2|IF#n|------ + 519 / +----+----+----+ \ 520 / | \ 521 / | \ 522 v v v 523 (:::)-. (:::)-. (:::)-. 524 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 525 `-(::::)-' `-(::::)-' `-(::::)-' 526 +----+ +----+ +----+ 527 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 528 . +-|--+ +-|--+ +-|--+ . 529 . | | | 530 . v v v . 531 . <----- INET Encapsulation -----> . 532 . . 533 . +-----+ (:::)-. . 534 . |MSE#2| .-(::::::::) +-----+ . 535 . +-----+ .-(::: INET :::)-. |MSE#m| . 536 . (::::: Routing ::::) +-----+ . 537 . `-(::: System :::)-' . 538 . +-----+ `-(:::::::-' . 539 . |MSE#1| +-----+ +-----+ . 540 . +-----+ |MSE#3| |MSE#4| . 541 . +-----+ +-----+ . 542 . . 543 . . 544 . <----- Worldwide Connected Internetwork ----> . 545 ........................................................... 547 Figure 2: MN/MS Coordination via Multiple *NETs 549 After the initial IPv6 ND message exchange, the MN (and/or any nodes 550 on its attached EUNs) can send and receive IP data packets over the 551 OMNI interface. OMNI interface multilink services will forward the 552 packets via ARs in the correct underlying *NETs. The AR encapsulates 553 the packets according to the capabilities provided by the MS and 554 forwards them to the next hop within the worldwide connected 555 Internetwork via optimal routes. 557 OMNI links span one or more underlying Internetwork via the OMNI 558 Adaptation Layer (OAL) which is based on a mid-layer overlay 559 encapsulation using [RFC2473]. Each OMNI link corresponds to a 560 different overlay (differentiated by an address codepoint) which may 561 be carried over a completely separate underlying topology. Each MN 562 can facilitate SBM by connecting to multiple OMNI links using a 563 distinct OMNI interface for each link. 565 Note: OMNI interface underlying interfaces often connect directly to 566 physical media on the local platform (e.g., a laptop computer with 567 WiFi, etc.), but in some configurations the physical media may be 568 hosted on a separate Local Area Network (LAN) node. In that case, 569 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 570 tunnel (at a layer below the underlying interface) to the node 571 hosting the physical media. The OMNI interface may also apply 572 encapsulation at a layer above the underlying interface such that 573 packets would appear "double-encapsulated" on the LAN; the node 574 hosting the physical media in turn removes the LAN encapsulation 575 prior to transmission or inserts it following reception. Finally, 576 the underlying interface must monitor the node hosting the physical 577 media (e.g., through active pinging) so that it can convey up/down/ 578 status information to the OMNI interface. 580 5. The OMNI Adaptation Layer (OAL) 582 The OMNI interface observes the link nature of tunnels, including the 583 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 584 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 585 The OMNI interface is configured over one or more underlying 586 interfaces that may have diverse MTUs. OMNI interfaces accommodate 587 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 588 discussed in this section. 590 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 591 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 592 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 593 permitted to perform network fragmentation even though the 594 destination is required to reassemble more. The network therefore 595 MUST forward packets of at least 1280 bytes without generating an 596 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 597 [RFC8201]. (Note: the source can apply "source fragmentation" for 598 locally-generated IPv6 packets up to 1500 bytes and larger still if 599 it if has a way to determine that the destination configures a larger 600 MRU, but this does not affect the minimum IPv6 path MTU.) 602 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 603 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 604 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 605 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 606 support network fragmentation and the destination is required to 607 reassemble at least that much. The DF bit in the IPv4 encapsulation 608 headers of packets sent over IPv4 underlying interfaces therefore 609 MUST be set to 0. (Note: even if the encapsulation source has a way 610 to determine that the encapsulation destination configures an MRU 611 larger than 576 bytes, it should not assume a larger minimum IPv4 612 path MTU without careful consideration of the issues discussed in 613 Section 5.1.) 615 The OMNI interface configures both an MTU and MRU of 9180 bytes 616 [RFC2492]; the size is therefore not a reflection of the underlying 617 interface MTUs, but rather determines the largest packet the OMNI 618 interface can forward or reassemble. The OMNI interface uses the 619 OMNI Adaptation Layer (OAL) to admit packets from the network layer 620 that are no larger than the OMNI interface MTU while generating 621 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 622 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 623 document refers to both of these ICMPv4/ICMPv6 message types simply 624 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 625 errors as discussed below. 627 For IPv4 packets with DF=0, the network layer performs IPv4 628 fragmentation if necessary then admits the packets/fragments into the 629 OMNI interface; these fragments will be reassembled by the final 630 destination. For IPv4 packets with DF=1 and IPv6 packets, the 631 network layer admits the packet if it is no larger than the OMNI 632 interface MTU; otherwise, it drops the packet and returns a PTB hard 633 error message to the source. 635 For each admitted IP packet/fragment, the OMNI interface internally 636 employs the OAL when necessary by inserting a mid-layer IPv6 header 637 between the inner IP packet/fragment and any outer IP encapsulation 638 headers per [RFC2473]. (The OAL does not decrement the inner IP Hop 639 Limit/TTL during encapsulation since the insertion occurs at a layer 640 below IP forwarding.) The OAL then calculates the 32-bit CRC over 641 the entire mid-layer packet and writes the value in a trailing 642 4-octet field at the end of the packet. Next, the OAL fragments this 643 mid-layer IPv6 packet, forwards the fragments (using outer IP 644 encapsulation if necessary), and returns an internally-generated PTB 645 soft error message (subject to rate limiting) if it deems the packet 646 too large according to factors such as link performance 647 characteristics, reassembly congestion, etc. This ensures that the 648 path MTU is adaptive and reflects the current path used for a given 649 data flow. 651 The OAL operates with respect to both the minimum IPv6 and IPv4 path 652 MTUs as follows: 654 o When an OMNI interface sends a packet toward a final destination 655 via an ANET peer, it sends without OAL encapsulation if the packet 656 (including any outer-layer ANET encapsulations) is no larger than 657 the underlying interface MTU for on-link ANET peers or the minimum 658 ANET path MTU for peers separated by multiple IP hops. Otherwise, 659 the OAL inserts an IPv6 header per [RFC2473] with source address 660 set to the node's own Unique-Local Address (ULA) (see: Section 8) 661 and destination set to the ULA of the ANET peer. The OAL then 662 calculates and appends the trailing 32-bit CRC, then uses IPv6 663 fragmentation to break the packet into a minimum number of non- 664 overlapping fragments where the largest fragment size (including 665 both the OMNI and any outer-layer ANET encapsulations) is 666 determined by the underlying interface MTU for on-link ANET peers 667 or the minimum ANET path MTU for peers separated by multiple IP 668 hops. The OAL then encapsulates the fragments in any ANET headers 669 and sends them to the ANET peer, which reassembles before 670 forwarding toward the final destination. 672 o When an OMNI interface sends a packet toward a final destination 673 via an INET interface, it sends packets (including any outer-layer 674 INET encapsulations) no larger than the minimum INET path MTU 675 without OAL encapsulation if the destination is reached via an 676 INET address within the same OMNI link segment. Otherwise, the 677 OAL inserts an IPv6 header per [RFC2473] with source address set 678 to the node's ULA, destination set to the ULA of the next hop OMNI 679 node toward the final destination and (if necessary) with a 680 Segment Routing Header with the remaining Segment IDs on the path 681 to the final destination. The OAL then calculates and appends the 682 trailing 32-bit CRC, then uses IPv6 fragmentation to break the 683 packet into a minimum number of non-overlapping fragments where 684 the largest fragment size (including both the OMNI and outer-layer 685 INET encapsulations) is the minimum INET path MTU, and the 686 smallest fragment size is no smaller than 256 bytes (i.e., 687 slightly less than half the minimum IPv4 path MTU). The OAL then 688 encapsulates the fragments in any INET headers and sends them to 689 the OMNI link neighbor, which reassembles before forwarding toward 690 the final destination. 692 The OAL unconditionally drops all OAL fragments received from an INET 693 peer that are smaller than 256 bytes (note that no minimum fragment 694 size is specified for ANET peers since the underlying ANET is secured 695 against tiny fragment attacks). In order to set the correct context 696 for reassembly, the OAL of the OMNI interface that inserts the IPv6 697 header MUST also be the one that inserts the IPv6 Fragment Header 698 Identification value. While not strictly required, sending all 699 fragments of the same fragmented OAL packet consecutively over the 700 same underlying interface with minimal inter-fragment delay may 701 increase the likelihood of successful reassembly. 703 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 704 header Code field value 0 are hard errors that always indicate that a 705 packet has been dropped due to a real MTU restriction. However, the 706 OAL can also forward large packets via encapsulation and 707 fragmentation while at the same time returning PTB soft error 708 messages (subject to rate limiting) indicating that a forwarded 709 packet was uncomfortably large. The OMNI interface can therefore 710 continuously forward large packets without loss while returning PTB 711 soft error messages recommending a smaller size. Original sources 712 that receive the soft errors in turn reduce the size of the packets 713 they send, i.e., the same as for hard errors. 715 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 716 field to the value 1 in PTB soft error messages. The OAL sets the 717 PTB destination address to the source address of the original packet, 718 and sets the source address to the MNP Subnet Router Anycast address 719 of the MN (i.e., whether the MN was the source or target of the 720 original packet). When the original source receives the PTB, it 721 reduces its path MTU estimate the same as for hard errors but does 722 not regard the message as a loss indication. (If the original source 723 does not recognize the soft error code, it regards the PTB the same 724 as a hard error but should heed the retransmission advice given in 725 [RFC8201] suggesting retransmission based on normal packetization 726 layer retransmission timers.) This document therefore updates 727 [RFC1191][RFC4443] and [RFC8201]. Furthermore, implementations of 728 [RFC4821] must be aware that PTB hard or soft errors may arrive at 729 any time even if after a successful MTU probe (this is the same 730 consideration as for an ordinary path fluctuation following a 731 successful probe). 733 In summary, the OAL supports continuous transmission and reception of 734 packets of various sizes in the face of dynamically changing network 735 conditions. Moreover, since PTB soft errors do not indicate loss, 736 original sources that receive soft errors can quickly scan for path 737 MTU increases without waiting for the minimum 10 minutes specified 738 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 739 therefore provides a lossless and adaptive service that accommodates 740 MTU diversity especially well-suited for dynamic multilink 741 environments. 743 Note: In network paths where IPv6/IPv4 protocol translation or IPv6- 744 in-IPv4 encapsulation may be prevalent, it may be prudent for the OAL 745 to always assume the IPv4 minimum path MTU (i.e., 576 bytes) 746 regardless of the underlying interface IP protocol version. Always 747 assuming the IPv4 minimum path MTU even for IPv6 underlying 748 interfaces may produce more fragments and additional header overhead, 749 but will always interoperate and never run the risk of presenting an 750 IPv4 interface with a packet that exceeds its MRU. 752 Note: An OMNI interface that reassembles OAL fragments may experience 753 congestion-oriented loss in its reassembly cache and can optionally 754 send PTB soft errors to the original source and/or ICMP "Time 755 Exceeded" messages to the source of the OAL fragments. In 756 environments where the messages may contribute to unacceptable 757 additional congestion, however, the OMNI interface can simply regard 758 the loss as an ordinary unreported congestion event for which the 759 original source will eventually compensate. 761 Note: When the network layer forwards an IPv4 packet/fragment with 762 DF=0 into the OMNI interface, the interface can optionally perform 763 (further) IPv4 fragmentation before invoking the OAL so that the 764 fragments will be reassembled by the final destination. When the 765 network layer performs IPv6 fragmentation for locally-generated IPv6 766 packets, the OMNI interface typically invokes the OAL without first 767 applying (further) IPv6 fragmentation; the network layer should 768 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 769 push the reassembly burden to the final destination and avoid 770 receiving PTB soft errors from the OMNI interface. Aside from these 771 non-normative guidelines, the manner in which any IP fragmentation is 772 invoked prior to OAL encapsulation/fragmentation is an implementation 773 matter. 775 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 776 the receiving OAL will discard any packets with incorrect CRC values 777 following reassembly. The 32-bit CRC is sufficient to detect 778 reassembly misassociations for packet sizes up to the OMNI interface 779 MTU 9180 but may not be sufficient to detect errors for larger sizes 780 [CRC]. 782 Note: Some underlying interface types (e.g., VPNs) may already 783 provide their own robust fragmentation and reassembly services even 784 without OAL encapsulation. In those cases, the OAL can invoke the 785 inherent underlying interface schemes instead while employing PTB 786 soft errors in the same fashion as described above. Other underlying 787 interface properties such as header/message compression can also be 788 harnessed in a similar fashion. 790 Note: Applications can dynamically tune the size of the packets they 791 to send to produce the best possible throughput and latency, with the 792 understanding that these parameters may change over time due to 793 factors such as congestion, mobility, network path changes, etc. The 794 receipt or absence of soft errors should be seen as hints of when 795 increasing or decreasing packet sizes may be beneficial. 797 5.1. Fragmentation Security Implications 799 As discussed in Section 3.7 of [RFC8900], there are four basic 800 threats concerning IPv6 fragmentation; each of which is addressed by 801 effective mitigations as follows: 803 1. Overlapping fragment attacks - reassembly of overlapping 804 fragments is forbidden by [RFC8200]; therefore, this threat does 805 not apply to the OAL. 807 2. Resource exhaustion attacks - this threat is mitigated by 808 providing a sufficiently large OAL reassembly cache and 809 instituting "fast discard" of incomplete reassemblies that may be 810 part of a buffer exhaustion attack. The reassembly cache should 811 be sufficiently large so that a sustained attack does not cause 812 excessive loss of good reassemblies but not so large that (timer- 813 based) data structure management becomes computationally 814 expensive. The cache should also be indexed based on the arrival 815 underlying interface such that congestion experienced over a 816 first underlying interface does not cause discard of incomplete 817 reassemblies for uncongested underlying interfaces. 819 3. Attacks based on predictable fragment identification values - 820 this threat is mitigated by selecting a suitably random ID value 821 per [RFC7739]. 823 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 824 threat is mitigated by disallowing "tiny fragments" per the OAL 825 fragmentation procedures specified above. 827 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 828 ID) field with only 65535 unique values such that at high data rates 829 the field could wrap and apply to new packets while the fragments of 830 old packets using the same ID are still alive in the network 831 [RFC4963]. However, since the largest OAL fragment that will be sent 832 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 833 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 834 recommendations suggest that such links will have low data rates. 835 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 836 at high data rates is not a concern for IPv6 fragmentation. 838 6. Frame Format 840 The OMNI interface transmits IPv6 packets according to the native 841 frame format of each underlying interface. For example, for 842 Ethernet-compatible interfaces the frame format is specified in 843 [RFC2464], for aeronautical radio interfaces the frame format is 844 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 845 Manual), for tunnels over IPv6 the frame format is specified in 846 [RFC2473], etc. 848 7. Link-Local Addresses (LLAs) 850 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 851 (i.e., "LLAs") through pre-service administrative actions. "MNP- 852 LLAs" embed the MNP assigned to the mobile node, while "ADM-LLAs" 853 include an administratively-unique ID that is guaranteed to be unique 854 on the link. LLAs are configured as follows: 856 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 857 the least-significant 64 bits of the IPv6 link-local prefix 858 fe80::/64, i.e., in the LLA "interface identifier" portion. The 859 prefix length for the LLA is determined by adding 64 to the MNP 860 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 861 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 863 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 864 i.e., the interface identifier consists of 16 '0' bits, followed 865 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 866 prefix length for the LLA is determined by adding 96 to the MNP 867 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 868 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 869 fe80::ffff:c000:0200/120). 871 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 872 uniqueness. The lower 16 bits of the LLA includes a unique 873 integer "MSID" value between 0x0001 and 0xfeff, e.g., as in 874 fe80::1, fe80::2, fe80::3, etc., fe80::feff. The ADM-LLA prefix 875 length is determined by adding 112 to the MSID prefix length. For 876 example, if the MSID '0x1020' prefix length is 8 then the ADM-LLA 877 prefix length is set to 120 and the LLA is written as 878 fe80::1020/120. The MSID 0x0000 is the "Anycast" MSID and 879 corresponds to the link-local Subnet-Router anycast address 880 (fe80::) [RFC4291]; the MSID range 0xff00 through 0xffff is 881 reserved for future use. 883 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 884 used by MNs for the short-term purpose of procuring an actual MNP- 885 LLA upon startup or (re)connecting to the network. MNs may use 886 Temporary LLAs as the IPv6 source address of an RS message in 887 order to request a MNP-LLA from the MS. 889 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 890 MNPs can be allocated from that block ensuring that there is no 891 possibility for overlap between the various OMNI LLA constructs 892 discussed above. 894 Since MNP-LLAs are based on the distribution of administratively 895 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 896 administrative assignment, OMNI interfaces set the autoconfiguration 897 variable DupAddrDetectTransmits to 0 [RFC4862]. 899 Temporary LLAs employ optimistic DAD principles [RFC4429] since they 900 are probabilistically unique and their use is short-duration in 901 nature. 903 Note: If future extensions of the IPv6 protocol permit extension of 904 the /64 boundary, the additional prefix bits of IPv6 MNP-LLAs could 905 be encoded in bits 16 through 63 of the LLA. (The most-significant 906 64 bits would therefore still be in LLA bits 64-127, and the 907 remaining bits would be in bits 16 through 48 of the LLA. This would 908 permit encoding of IPv6 prefix lengths up to /112.) 910 8. Unique-Local Addresses (ULAs) 912 OMNI domains use IPv6 Unique-Local Addresses as the source and 913 destination addresses in OAL IPv6 encapsulation headers. ULAs are 914 only routable within the scope of a an OMNI domain, and are derived 915 from the IPv6 Unique Local Address (ULA) prefix fc00::/7 followed by 916 the L bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo- 917 random Global ID to produce the prefix [ULA]::/48, which is then 918 followed by a 16-bit Subnet ID then finally followed by a 64 bit 919 Interface ID as specified in Section 3 of [RFC4193]. The statistic 920 uniqueness of the 40-bit pseudo-random Global ID allows different 921 OMNI domains to be joined together at a later time without conflict. 923 Each OMNI link instance is identified by a value between 0x0000 and 924 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xfffe 925 are reserved for future use and the value 0xffff denotes a Temporary 926 OMNI ULA). For example, OMNI ULAs associated with instance 0 are 927 configured from the prefix [ULA]:0000::/64, instance 1 from 928 [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 929 their associated prefix lengths are configured in correspondence with 930 LLAs through stateless prefix translation. For example, for OMNI 931 link instance [ULA]:1010::/64: 933 o the ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 934 56-bit MNP length is derived by copying the lower 64 bits of the 935 LLA into the lower 64 bits of the ULA as 936 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 937 64 plus the IPv6 MNP length). 939 o the ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit MNP 940 length is derived by simply writing the LLA interface ID into the 941 lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the ULA 942 prefix length is 64 plus 32 plus the IPv4 MNP length). 944 o the ULA corresponding to fe80::5500/120 is simply 945 [ULA]:1010::5500/120. 947 o the ULA corresponding to fe80::/128 is simply [ULA]:1010::/128. 949 o the ULA corresponding to a Temporary LLA is simply 950 [ULA]:1010:[64-bit Temporary Interface ID]/128. 952 o etc. 954 Each OMNI interface assigns the Anycast ULA specific to the OMNI link 955 instance. For example, the OMNI interface connected to instance 3 956 assigns the Anycast address [ULA]:0003::/128. Routers that configure 957 OMNI interfaces advertise the OMNI service prefix (e.g., 958 [ULA]:0003::/64) into the local routing system so that applications 959 can direct traffic according to SBM requirements. 961 The ULA presents an IPv6 address format that is routable within the 962 OMNI routing system and can be used to convey link-scoped IPv6 ND 963 messages across multiple hops using IPv6 encapsulation [RFC2473]. 964 The OMNI link extends across one or more underling Internetworks to 965 include all ARs and MSEs. All MNs are also considered to be 966 connected to the OMNI link, however OAL encapsulation is omitted 967 whenever possible to conserve bandwidth (see: Section 12). 969 Each OMNI link can be subdivided into "segments" that often 970 correspond to different administrative domains or physical 971 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 972 necessary to support efficient packet forwarding to destinations 973 located in other OMNI link segments. A full discussion of Segment 974 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 976 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 977 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 978 however the range could be used for MSP and MNP addressing under 979 certain limiting conditions (see: Section 9). 981 9. Global Unicast Addresses (GUAs) 983 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 984 as Mobility Service Prefixes (MSPs) from which Mobile Network 985 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 987 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 988 associated regional assigned numbers authority such that the OMNI 989 domain can be interconnected to the global IPv6 Internet without 990 causing inconsistencies in the routing system. An OMNI domain could 991 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 992 fc00::/8)[RFC4193], however this would require IPv6 Network Address 993 Translation (NAT) if the domain were ever connected to the global 994 IPv6 Internet. 996 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 997 associated regional assigned numbers authority such that the OMNI 998 domain can be interconnected to the global IPv4 Internet without 999 causing routing inconsistencies. An OMNI domain could instead use 1000 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1001 this would require IPv4 NAT if the domain were ever connected to the 1002 global IPv4 Internet. 1004 10. Address Mapping - Unicast 1006 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1007 state and use the link-local address format specified in Section 7. 1008 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1009 over physical underlying interfaces without encapsulation observe the 1010 native underlying interface Source/Target Link-Layer Address Option 1011 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1012 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1013 interfaces via encapsulation do not include S/TLLAOs which were 1014 intended for encoding physical L2 media address formats and not 1015 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1016 for encoding additional interface attributes needed for multilink 1017 coordination. Hence, this document does not define an S/TLLAO format 1018 but instead defines a new option type termed the "OMNI option" 1019 designed for these purposes. 1021 MNs such as aircraft typically have many wireless data link types 1022 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1023 etc.) with diverse performance, cost and availability properties. 1024 The OMNI interface would therefore appear to have multiple L2 1025 connections, and may include information for multiple underlying 1026 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1027 an IPv6 ND option called the OMNI option formatted as shown in 1028 Figure 3: 1030 0 1 2 3 1031 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 1032 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1033 | Type | Length |T| Preflen | S/T-ifIndex | 1034 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1035 | | 1036 ~ Sub-Options ~ 1037 | | 1038 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1040 Figure 3: OMNI Option Format 1042 In this format: 1044 o Type is set to TBD. If multiple OMNI option instances appear in 1045 the same IPv6 ND message, the first instance is processed and all 1046 other instances are ignored. 1048 o Length is set to the number of 8 octet blocks in the option. 1050 o T is a 1-bit flag set to 1 for Temporary LLAs (otherwise, set to 1051 0) and Preflen is a 7 bit field that determines the length of 1052 prefix associated with an LLA. Values 1 through 127 specify a 1053 prefix length, while the value 0 indicates "unspecified". For 1054 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1055 the IPv6 source LLA and provide the length that the MN is 1056 requesting or asserting to the MS. For IPv6 ND messages sent from 1057 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1058 and indicate the length that the MS is granting to the MN. For 1059 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1060 Preflen provides the length associated with the source/target MN 1061 that is subject of the ND message. 1063 o S/T-ifIndex corresponds to the ifIndex value for source or target 1064 underlying interface used to convey this IPv6 ND message. OMNI 1065 interfaces MUST number each distinct underlying interface with an 1066 ifIndex value between '1' and '255' that represents a MN-specific 1067 8-bit mapping for the actual ifIndex value assigned by network 1068 management [RFC2863] (the ifIndex value '0' is reserved for use by 1069 the MS). For RS and NS messages, S/T-ifIndex corresponds to the 1070 source underlying interface the message originated from. For RA 1071 and NA messages, S/T-ifIndex corresponds to the target underlying 1072 interface that the message is destined to. 1074 o Sub-Options is a Variable-length field, of length such that the 1075 complete OMNI Option is an integer multiple of 8 octets long. 1076 Contains one or more Sub-Options, as described in Section 10.1. 1078 10.1. Sub-Options 1080 The OMNI option includes zero or more Sub-Options. Each consecutive 1081 Sub-Option is concatenated immediately after its predecessor. All 1082 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1083 encoded in the following format: 1085 0 1 2 1086 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 1087 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1088 | Sub-Type | Sub-length | Sub-Option Data ... 1089 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1091 Figure 4: Sub-Option Format 1093 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 1094 Sub-Options defined in this document are: 1096 Option Name Sub-Type 1097 Pad1 0 1098 PadN 1 1099 Interface Attributes 2 1100 Traffic Selector 3 1101 MS-Register 4 1102 MS-Release 5 1103 Network Access Identifier 6 1104 Geo Coordinates 7 1105 DHCP Unique Identifier (DUID) 8 1106 DHCPv6 Message 9 1108 Figure 5 1110 Sub-Types 253 and 254 are reserved for experimentation, as 1111 recommended in [RFC3692]. 1113 o Sub-Length is a 1-octet field that encodes the length of the Sub- 1114 Option Data (i.e., ranging from 0 to 255 octets). 1116 o Sub-Option Data is a block of data with format determined by Sub- 1117 Type. 1119 During processing, unrecognized Sub-Options are ignored and the next 1120 Sub-Option processed until the end of the OMNI option is reached. 1122 The following Sub-Option types and formats are defined in this 1123 document: 1125 10.1.1. Pad1 1127 0 1128 0 1 2 3 4 5 6 7 1129 +-+-+-+-+-+-+-+-+ 1130 | Sub-Type=0 | 1131 +-+-+-+-+-+-+-+-+ 1133 Figure 6: Pad1 1135 o Sub-Type is set to 0. If multiple instances appear in the same 1136 OMNI option all are processed. 1138 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 1139 consists of a single zero octet). 1141 10.1.2. PadN 1143 0 1 2 1144 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1146 | Sub-Type=1 | Sub-length=N | N padding octets ... 1147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1149 Figure 7: PadN 1151 o Sub-Type is set to 1. If multiple instances appear in the same 1152 OMNI option all are processed. 1154 o Sub-Length is set to N (from 0 to 255) being the number of padding 1155 octets that follow. 1157 o Sub-Option Data consists of N zero-valued octets. 1159 10.1.3. Interface Attributes 1161 The Interface Attributes sub-option provides L2 forwarding 1162 information for the multilink conceptual sending algorithm discussed 1163 in Section 12. The L2 information is used for selecting among 1164 potentially multiple candidate underlying interfaces that can be used 1165 to forward packets to the neighbor based on factors such as DSCP 1166 preferences and link quality. Interface Attributes further include 1167 link-layer address information to be used for either OAL 1168 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1169 can be avoided). The Interface Attributes format and contents are 1170 given in Figure 8 below: 1172 0 1 2 3 1173 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1175 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 1176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1177 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1179 | LHS (8 - 15) | ~ 1180 +-+-+-+-+-+-+-+-+ ~ 1181 ~ ~ 1182 ~ Link Layer Address (L2ADDR) ~ 1183 ~ ~ 1184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1185 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1187 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1189 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1192 Figure 8: Interface Attributes 1194 o Sub-Type is set to 2. If multiple instances with different 1195 ifIndex values appear in the same OMNI option all are processed; 1196 if multiple instances with the same ifIndex value appear, the 1197 first is processed and all others are ignored. 1199 o Sub-Length is set to N (from 4 to 255) that encodes the number of 1200 Sub-Option Data octets that follow. 1202 o Sub-Option Data contains an "Interface Attribute" option encoded 1203 as follows (note that the first four octets must be present): 1205 * ifIndex is set to an 8-bit integer value corresponding to a 1206 specific underlying interface the same as specified above for 1207 the OMNI option header S/T-ifIndex. An OMNI option may include 1208 multiple Interface Attributes Sub-Options, with each distinct 1209 ifIndex value pertaining to a different underlying interface. 1210 The OMNI option will often include an Interface Attributes Sub- 1211 Option with the same ifIndex value that appears in the S/ 1212 T-ifIndex. In that case, the actual encapsulation address of 1213 the received IPv6 ND message should be compared with the L2ADDR 1214 encoded in the Sub-Option (see below); if the addresses are 1215 different (or, if L2ADDR absent) the presence of a Network 1216 Address Translator (NAT) is indicated. 1218 * ifType is set to an 8-bit integer value corresponding to the 1219 underlying interface identified by ifIndex. The value 1220 represents an OMNI interface-specific 8-bit mapping for the 1221 actual IANA ifType value registered in the 'IANAifType-MIB' 1222 registry [http://www.iana.org]. 1224 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1225 for the network service provider associated with this ifIndex. 1227 * Link encodes a 4-bit link metric. The value '0' means the link 1228 is DOWN, and the remaining values mean the link is UP with 1229 metric ranging from '1' ("lowest") to '15' ("highest"). 1231 * R is reserved for future use. 1233 * API - a 3-bit "Address/Preferences/Indexed" code that 1234 determines the contents of the remainder of the sub-option as 1235 follows: 1237 + When the most significant bit (i.e., "Address") is set to 1, 1238 the SRT, FMT, LHS and L2ADDR fields are included immediately 1239 following the API code; else, they are omitted. 1241 + When the next most significant bit (i.e., "Preferences") is 1242 set to 1, a preferences block is included next; else, it is 1243 omitted. (Note that if "Address" is set the preferences 1244 block immediately follows L2ADDR; else, it immediately 1245 follows the API code.) 1247 + When a preferences block is present and the least 1248 significant bit (i.e., "Indexed") is set to 0, the block is 1249 encoded in "Simplex" form as shown in Figure 8; else it is 1250 encoded in "Indexed" form as discussed below. 1252 * When API indicates that an "Address" is included, the following 1253 fields appear in consecutive order (else, they are omitted): 1255 + SRT - a 5-bit Segment Routing Topology prefix length value 1256 that (when added to 112) determines the prefix length to 1257 apply to the ULA formed from concatenating [ULA*]::/112 with 1258 the 16 bit LHS MSID value that follows. For example, the 1259 value 8 corresponds to the prefix length 120. 1261 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1262 the included Link Layer Address as follows: 1264 - When the most significant bit (i.e., "Framework") is set 1265 to 0, L2ADDR is the INET encapsulation address of a 1266 Proxy/Server; otherwise, it is the address for the 1267 Source/Target itself 1269 - When the next most significant bit (i.e., "Mode") is set 1270 to 0, the Source/Target L2ADDR is on the open INET; 1271 otherwise, it is (likely) located behind a Network 1272 Address Translator (NAT). 1274 - When the least significant bit (i.e., "Type") is set to 1275 0, L2ADDR includes a UDP Port Number followed by an IPv4 1276 address; else, a UDP Port Number followed by an IPv6 1277 address. 1279 + LHS - the 16 bit MSID of the Last Hop Server/Proxy on the 1280 path to the target. SRT and LHS together provide guidance 1281 to the OMNI interface forwarding algorithm. Specifically, 1282 if SRT/LHS is located in the local OMNI link segment then 1283 the OMNI interface can encapsulate according to FMT/L2ADDR; 1284 else, it must forward according to the OMNI link spanning 1285 tree. See [I-D.templin-intarea-6706bis] for further 1286 discussion. 1288 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1289 and identifies the link-layer address (i.e., the 1290 encapsulation address) of the source/target. The UDP Port 1291 Number appears in the first two octets and the IP address 1292 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1293 The Port Number and IP address are recorded in ones- 1294 compliment "obfuscated" form per [RFC4380]. The OMNI 1295 interface forwarding algorithm uses FMT/L2ADDR to determine 1296 the encapsulation address for forwarding when SRT/LHS is 1297 located in the local OMNI link segment. 1299 * When API indicates that "Preferences" are included, a 1300 preferences block appears as the remainder of the Sub-Option as 1301 a series of Bitmaps and P[*] values. In "Simplex" form, the 1302 index for each singleton Bitmap octet is inferred from its 1303 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1304 In "Indexed" form, each Bitmap is preceded by an Index octet 1305 that encodes a value "i" = (0 - 255) as the index for its 1306 companion Bitmap as follows: 1308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1309 | Index=i | Bitmap(i) |P[*] values ... 1310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1312 Figure 9 1314 * The preferences consist of a first (simplex/indexed) Bitmap 1315 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1316 2-bit P[*] values, followed by a second Bitmap (i), followed by 1317 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1318 the bits of each Bitmap(i) that are set to '1'' indicate the 1319 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1320 that follow; if any Bitmap(i) bits are '0', then the 1321 corresponding P[*] block is instead omitted. For example, if 1322 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1323 followed by the block with P[04]-P[07], etc., and ending with 1324 the block with P[28]-P[31] are included (as shown in Figure 8). 1325 The next Bitmap(i) is then consulted with its bits indicating 1326 which P[*] blocks follow, etc. out to the end of the Sub- 1327 Option. 1329 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1330 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1331 preference for underlying interface selection purposes. Not 1332 all P[*] values need to be included in the OMNI option of each 1333 IPv6 ND message received. Any P[*] values represented in an 1334 earlier OMNI option but omitted in the current OMNI option 1335 remain unchanged. Any P[*] values not yet represented in any 1336 OMNI option default to "medium". 1338 * The first 16 P[*] blocks correspond to the 64 Differentiated 1339 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1340 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1341 traffic classifier values P[64], P[65], P[66], etc. See 1342 Appendix A for further discussion and examples. 1344 10.1.4. Traffic Selector 1346 0 1 2 3 1347 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 1348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1349 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1351 ~ ~ 1352 ~ RFC 6088 Format Traffic Selector ~ 1353 ~ ~ 1354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1356 Figure 10: Traffic Selector 1358 o Sub-Type is set to 3. If multiple instances appear in the same 1359 OMNI option all are processed, i.e., even if the same ifIndex 1360 value appears multiple times. 1362 o Sub-Length is set to N (the number of Sub-Option Data octets that 1363 follow). 1365 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1366 specified in Section 10.1.3, followed by an N-1 octet traffic 1367 selector formatted per [RFC6088] beginning with the "TS Format" 1368 field. The largest traffic selector for a given ifIndex is 1369 therefore 254 octets. 1371 10.1.5. MS-Register 1373 0 1 2 3 1374 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 1375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1376 | Sub-Type=4 | Sub-length=4n | MSID[1] | 1377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1378 | MSID[2] | MSID[3] | 1379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1380 ... ... ... ... ... ... 1381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1382 | MSID [n] | 1383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1385 Figure 11: MS-Register Sub-option 1387 o Sub-Type is set to 4. If multiple instances appear in the same 1388 OMNI option all are processed. Only the first MAX_MSID values 1389 processed (whether in a single instance or multiple) are retained 1390 and all other MSIDs are ignored. 1392 o Sub-Length is set to 4n. 1394 o A list of n 4-octet MSIDs is included in the following 4n octets. 1395 The Anycast MSID value '0' in an RS message MS-Register sub-option 1396 requests the recipient to return the MSID of a nearby MSE in a 1397 corresponding RA response. 1399 10.1.6. MS-Release 1400 0 1 2 3 1401 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 1402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1403 | Sub-Type=5 | Sub-length=4n | MSID[1] | 1404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1405 | MSID[2] | MSID[3] | 1406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1407 ... ... ... ... ... ... 1408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1409 | MSID [n] | 1410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1412 Figure 12: MS-Release Sub-option 1414 o Sub-Type is set to 5. If multiple instances appear in the same 1415 IPv6 OMNI option all are processed. Only the first MAX_MSID 1416 values processed (whether in a single instance or multiple) are 1417 retained and all other MSIDs are ignored. 1419 o Sub-Length is set to 4n. 1421 o A list of n 4 octet MSIDs is included in the following 4n octets. 1422 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1423 i.e., only non-zero values are processed. 1425 10.1.7. Network Access Identifier (NAI) 1427 0 1 2 3 1428 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 1429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1430 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1433 Figure 13: Network Access Identifier (NAI) Sub-option 1435 o Sub-Type is set to 6. If multiple instances appear in the same 1436 OMNI option the first is processed and all others are ignored. 1438 o Sub-Length is set to N. 1440 o A Network Access Identifier (NAI) up to 255 octets in length is 1441 coded per [RFC7542]. 1443 10.1.8. Geo Coordinates 1444 0 1 2 3 1445 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 1446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1447 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1450 Figure 14: Geo Coordinates Sub-option 1452 o Sub-Type is set to 7. If multiple instances appear in the same 1453 OMNI option the first is processed and all others are ignored. 1455 o Sub-Length is set to N. 1457 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1458 Includes Latitude/Longitude at a minimum; may also include 1459 additional attributes such as altitude, heading, speed, etc.). 1461 10.1.9. DHCP Unique Identifier (DUID) 1463 0 1 2 3 1464 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 1465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1466 | Sub-Type=8 | Sub-length=N | DUID-Type | 1467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1468 . . 1469 . type-specific DUID body (variable length) . 1470 . . 1471 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1473 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1475 o Sub-Type is set to 8. If multiple instances appear in the same 1476 OMNI option the first is processed and all others are ignored. 1478 o Sub-Length is set to N (i.e., the length of the option beginning 1479 with the DUID-Type and continuing to the end of the type-specific 1480 body). 1482 o DUID-Type is a two-octet field coded in network byte order that 1483 determines the format and contents of the type-specific body 1484 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1485 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1486 which will occur in common operational practice. 1488 o A type-specific DUID body up to 253 octets in length follows, 1489 formatted according to DUID-type. For example, for type 4 the 1490 body consists of a 128-bit UUID selected according to [RFC6355]. 1492 10.1.10. DHCPv6 Message 1494 0 1 2 3 1495 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 1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1497 | Sub-Type=9 | Sub-length=N | msg-type | id (octet 0) | 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 | transaction-id (octets 1-2) | | 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1501 | | 1502 . DHCPv6 options . 1503 . (variable number and length) . 1504 | | 1505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1507 Figure 16: DHCPv6 Message Sub-option 1509 o Sub-Type is set to 9. If multiple instances appear in the same 1510 OMNI option the first is processed and all others are ignored. 1512 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1513 beginning with 'msg-type' and continuing to the end of the DHCPv6 1514 options). The length of the entire DHCPv6 message is therefore 1515 restricted to 255 octets. 1517 o 'msg-type' and 'transaction-id' are coded according to Section 8 1518 of [RFC8415]. 1520 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1521 follows. 1523 11. Address Mapping - Multicast 1525 The multicast address mapping of the native underlying interface 1526 applies. The mobile router on board the MN also serves as an IGMP/ 1527 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1528 using the L2 address of the AR as the L2 address for all multicast 1529 packets. 1531 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1532 coordinate with the AR, and *NET L2 elements use MLD snooping 1533 [RFC4541]. 1535 12. Multilink Conceptual Sending Algorithm 1537 The MN's IPv6 layer selects the outbound OMNI interface according to 1538 SBM considerations when forwarding data packets from local or EUN 1539 applications to external correspondents. Each OMNI interface 1540 maintains a neighbor cache the same as for any IPv6 interface, but 1541 with additional state for multilink coordination. Each OMNI 1542 interface maintains default routes via ARs discovered as discussed in 1543 Section 13, and may configure more-specific routes discovered through 1544 means outside the scope of this specification. 1546 After a packet enters the OMNI interface, one or more outbound 1547 underlying interfaces are selected based on PBM traffic attributes, 1548 and one or more neighbor underlying interfaces are selected based on 1549 the receipt of Interface Attributes sub-options in IPv6 ND messages 1550 (see: Figure 8). Underlying interface selection for the nodes own 1551 local interfaces are based on attributes such as DSCP, application 1552 port number, cost, performance, message size, etc. OMNI interface 1553 multilink selections could also be configured to perform replication 1554 across multiple underlying interfaces for increased reliability at 1555 the expense of packet duplication. The set of all Interface 1556 Attributes received in IPv6 ND messages determine the multilink 1557 forwarding profile for selecting the neighbor's underlying 1558 interfaces. 1560 When the OMNI interface sends a packet over a selected outbound 1561 underlying interface, the OAL includes or omits a mid-layer 1562 encapsulation header as necessary as discussed in Section 5 and as 1563 determined by the L2 address information received in Interface 1564 Attributes. The OAL also performs encapsulation when the nearest AR 1565 is located multiple hops away as discussed in Section 13.1. 1567 OMNI interface multilink service designers MUST observe the BCP 1568 guidance in Section 15 [RFC3819] in terms of implications for 1569 reordering when packets from the same flow may be spread across 1570 multiple underlying interfaces having diverse properties. 1572 12.1. Multiple OMNI Interfaces 1574 MNs may connect to multiple independent OMNI links concurrently in 1575 support of SBM. Each OMNI interface is distinguished by its Anycast 1576 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1577 configures a separate OMNI interface for each link so that multiple 1578 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1579 layer. A different Anycast ULA is assigned to each interface, and 1580 the MN injects the service prefixes for the OMNI link instances into 1581 the EUN routing system. 1583 Applications in EUNs can use Segment Routing to select the desired 1584 OMNI interface based on SBM considerations. The Anycast ULA is 1585 written into the IPv6 destination address, and the actual destination 1586 (along with any additional intermediate hops) is written into the 1587 Segment Routing Header. Standard IP routing directs the packets to 1588 the MN's mobile router entity, and the Anycast ULA identifies the 1589 OMNI interface to be used for transmission to the next hop. When the 1590 MN receives the message, it replaces the IPv6 destination address 1591 with the next hop found in the routing header and transmits the 1592 message over the OMNI interface identified by the Anycast ULA. 1594 Multiple distinct OMNI links can therefore be used to support fault 1595 tolerance, load balancing, reliability, etc. The architectural model 1596 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1598 12.2. MN<->AR Traffic Loop Prevention 1600 After an AR has registered an MNP for a MN (see: Section 13), the AR 1601 will forward packets destined to an address within the MNP to the MN. 1602 The MN will under normal circumstances then forward the packet to the 1603 correct destination within its internal networks. 1605 If at some later time the MN loses state (e.g., after a reboot), it 1606 may begin returning packets destined to an MNP address to the AR as 1607 its default router. The AR therefore must drop any packets 1608 originating from the MN and destined to an address within the MN's 1609 registered MNP. To do so, the AR institutes the following check: 1611 o if the IP destination address belongs to a neighbor on the same 1612 OMNI interface, and if the link-layer source address is the same 1613 as one of the neighbor's link-layer addresses, drop the packet. 1615 13. Router Discovery and Prefix Registration 1617 MNs interface with the MS by sending RS messages with OMNI options 1618 under the assumption that one or more AR on the *NET will process the 1619 message and respond. The MN then configures default routes for the 1620 OMNI interface via the discovered ARs as the next hop. The manner in 1621 which the *NET ensures AR coordination is link-specific and outside 1622 the scope of this document (however, considerations for *NETs that do 1623 not provide ARs that recognize the OMNI option are discussed in 1624 Section 18). 1626 For each underlying interface, the MN sends an RS message with an 1627 OMNI option to coordinate with MSEs identified by MSID values. 1628 Example MSID discovery methods are given in [RFC5214] and include 1629 data link login parameters, name service lookups, static 1630 configuration, a static "hosts" file, etc. The MN can also send an 1631 RS with an MS-Register suboption that includes the Anycast MSID value 1632 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1633 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1634 be itself) and returns an RA with the selected MSID in an MS-Register 1635 suboption. The AR selects only a single wildcard MSE (i.e., even if 1636 the RS MS-Register suboption included multiple '0' MSIDs) while also 1637 soliciting the MSEs corresponding to any non-zero MSIDs. 1639 MNs configure OMNI interfaces that observe the properties discussed 1640 in the previous section. The OMNI interface and its underlying 1641 interfaces are said to be in either the "UP" or "DOWN" state 1642 according to administrative actions in conjunction with the interface 1643 connectivity status. An OMNI interface transitions to UP or DOWN 1644 through administrative action and/or through state transitions of the 1645 underlying interfaces. When a first underlying interface transitions 1646 to UP, the OMNI interface also transitions to UP. When all 1647 underlying interfaces transition to DOWN, the OMNI interface also 1648 transitions to DOWN. 1650 When an OMNI interface transitions to UP, the MN sends RS messages to 1651 register its MNP and an initial set of underlying interfaces that are 1652 also UP. The MN sends additional RS messages to refresh lifetimes 1653 and to register/deregister underlying interfaces as they transition 1654 to UP or DOWN. The MN sends initial RS messages over an UP 1655 underlying interface with its MNP-LLA as the source and with 1656 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1657 messages include an OMNI option per Section 10 with a Preflen 1658 assertion, Interface Attributes appropriate for underlying 1659 interfaces, MS-Register/Release sub-options containing MSID values, 1660 and with any other necessary OMNI sub-options (e.g., a DUID suboption 1661 as an identity for the MN). The S/T-ifIndex field is set to the 1662 index of the underlying interface over which the RS message is sent. 1664 ARs process IPv6 ND messages with OMNI options and act as an MSE 1665 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1666 and create a neighbor cache entry for the MN, then coordinate with 1667 any MSEs named in the Register/Release lists in a manner outside the 1668 scope of this document. When an MSE processes the OMNI information, 1669 it first validates the prefix registration information then injects/ 1670 withdraws the MNP in the routing/mapping system and caches/discards 1671 the new Preflen, MNP and Interface Attributes. The MSE then informs 1672 the AR of registration success/failure, and the AR returns an RA 1673 message to the MN with an OMNI option per Section 10. 1675 The AR returns the RA message via the same underlying interface of 1676 the MN over which the RS was received, and with destination address 1677 set to the MNP-LLA (i.e., unicast), with source address set to its 1678 own LLA, and with an OMNI option with S/T-ifIndex set to the value 1679 included in the RS. The OMNI option also includes a Preflen 1680 confirmation, Interface Attributes, MS-Register/Release and any other 1681 necessary OMNI sub-options (e.g., a DUID suboption as an identity for 1682 the AR). The RA also includes any information for the link, 1683 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 1684 Time and Retrans Timer values, and includes any necessary options 1685 such as: 1687 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1689 o RIOs [RFC4191] with more-specific routes. 1691 o an MTU option that specifies the maximum acceptable packet size 1692 for this underlying interface. 1694 The AR MAY also send periodic and/or event-driven unsolicited RA 1695 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1696 OMNI header of the unsolicited RA message identifies the target 1697 underlying interface of the destination MN. 1699 The AR can combine the information from multiple MSEs into one or 1700 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 1701 Each aggregate RA includes an OMNI option with MS-Register/Release 1702 sub-options with the MSEs represented by the aggregate. If an 1703 aggregate is sent, the RA message contents must consistently 1704 represent the combined information advertised by all represented 1705 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 1706 address, the MN determines the addresses of the represented MSEs by 1707 examining the MS-Register/Release OMNI sub-options. 1709 When the MN receives the RA message, it creates an OMNI interface 1710 neighbor cache entry for each MSID that has confirmed MNP 1711 registration via the L2 address of this AR. If the MN connects to 1712 multiple *NETs, it records the additional L2 AR addresses in each 1713 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1714 then configures a default route via the MSE that returned the RA 1715 message, and assigns the Subnet Router Anycast address corresponding 1716 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 1717 manages its underlying interfaces according to their states as 1718 follows: 1720 o When an underlying interface transitions to UP, the MN sends an RS 1721 over the underlying interface with an OMNI option. The OMNI 1722 option contains at least one Interface Attribute sub-option with 1723 values specific to this underlying interface, and may contain 1724 additional Interface Attributes specific to other underlying 1725 interfaces. The option also includes any MS-Register/Release sub- 1726 options. 1728 o When an underlying interface transitions to DOWN, the MN sends an 1729 RS or unsolicited NA message over any UP underlying interface with 1730 an OMNI option containing an Interface Attribute sub-option for 1731 the DOWN underlying interface with Link set to '0'. The MN sends 1732 an RS when an acknowledgement is required, or an unsolicited NA 1733 when reliability is not thought to be a concern (e.g., if 1734 redundant transmissions are sent on multiple underlying 1735 interfaces). 1737 o When the Router Lifetime for a specific AR nears expiration, the 1738 MN sends an RS over the underlying interface to receive a fresh 1739 RA. If no RA is received, the MN can send RS messages to an 1740 alternate MSID in case the current MSID has failed. If no RS 1741 messages are received even after trying to contact alternate 1742 MSIDs, the MN marks the underlying interface as DOWN. 1744 o When a MN wishes to release from one or more current MSIDs, it 1745 sends an RS or unsolicited NA message over any UP underlying 1746 interfaces with an OMNI option with a Release MSID. Each MSID 1747 then withdraws the MNP from the routing/mapping system and informs 1748 the AR that the release was successful. 1750 o When all of a MNs underlying interfaces have transitioned to DOWN 1751 (or if the prefix registration lifetime expires), any associated 1752 MSEs withdraw the MNP the same as if they had received a message 1753 with a release indication. 1755 The MN is responsible for retrying each RS exchange up to 1756 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1757 seconds until an RA is received. If no RA is received over an UP 1758 underlying interface (i.e., even after attempting to contact 1759 alternate MSEs), the MN declares this underlying interface as DOWN. 1761 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1762 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1763 returns an internally-generated RA message as though the message 1764 originated from an IPv6 router. The internally-generated RA message 1765 contains configuration information that is consistent with the 1766 information received from the RAs generated by the MS. Whether the 1767 OMNI interface IPv6 ND messaging process is initiated from the 1768 receipt of an RS message from the IPv6 layer is an implementation 1769 matter. Some implementations may elect to defer the IPv6 ND 1770 messaging process until an RS is received from the IPv6 layer, while 1771 others may elect to initiate the process proactively. Still other 1772 deployments may elect to administratively disable the ordinary RS/RA 1773 messaging used by the IPv6 layer over the OMNI interface, since they 1774 are not required to drive the internal RS/RA processing. (Note that 1775 this same logic applies to IPv4 implementations that employ ICMP- 1776 based Router Discovery per [RFC1256].) 1778 Note: The Router Lifetime value in RA messages indicates the time 1779 before which the MN must send another RS message over this underlying 1780 interface (e.g., 600 seconds), however that timescale may be 1781 significantly longer than the lifetime the MS has committed to retain 1782 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1783 therefore responsible for keeping MS state alive on a shorter 1784 timescale than the MN is required to do on its own behalf. 1786 Note: On multicast-capable underlying interfaces, MNs should send 1787 periodic unsolicited multicast NA messages and ARs should send 1788 periodic unsolicited multicast RA messages as "beacons" that can be 1789 heard by other nodes on the link. If a node fails to receive a 1790 beacon after a timeout value specific to the link, it can initiate a 1791 unicast exchange to test reachability. 1793 Note: if an AR acting as a proxy forwards a MN's RS message to 1794 another node acting as an MSE using UDP/IP encapsulation, it must use 1795 a distinct UDP source port number for each MN. This allows the MSE 1796 to distinguish different MNs behind the same AR at the link-layer, 1797 whereas the link-layer addresses would otherwise be 1798 indistinguishable. 1800 13.1. Router Discovery in IP Multihop and IPv4-Only Networks 1802 On some *NETs, a MN may be located multiple IP hops away from the 1803 nearest AR. Forwarding through IP multihop *NETs is conducted 1804 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1805 Network (MANET) routing protocol over omni-directional wireless 1806 interfaces, an inter-domain routing protocol in an enterprise 1807 network, etc.). These *NETs could be either IPv6-enabled or 1808 IPv4-only, while IPv4-only *NETs could be either multicast-capable or 1809 unicast-only (note that for IPv4-only *NETs the following procedures 1810 apply for both single-hop and multihop cases). 1812 A MN located potentially multiple *NET hops away from the nearest AR 1813 prepares an RS message with source address set to either its MNP-LLA 1814 or a Temporary LLA, and with destination set to link-scoped All- 1815 Routers multicast the same as discussed above. For IPv6-enabled 1816 *NETs, the MN then encapsulates the message in an IPv6 header with 1817 source address set to the ULA corresponding to the LLA source address 1818 and with destination set to either a unicast or anycast ULA. For 1819 IPv4-only *NETs, the MN instead encapsulates the RS message in an 1820 IPv4 header with source address set to the node's own IPv4 address 1821 and with destination address set to either the unicast IPv4 address 1822 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 1823 MN then sends the encapsulated RS message via the *NET interface, 1824 where it will be forwarded by zero or more intermediate *NET hops. 1826 When an intermediate *NET hop that participates in the routing 1827 protocol receives the encapsulated RS, it forwards the message 1828 according to its routing tables (note that an intermediate node could 1829 be a fixed infrastructure element or another MN). This process 1830 repeats iteratively until the RS message is received by a penultimate 1831 *NET hop within single-hop communications range of an AR, which 1832 forwards the message to the AR. 1834 When the AR receives the message, it decapsulates the RS and 1835 coordinates with the MS the same as for an ordinary link-local RS, 1836 since the inner Hop Limit will not have been decremented by the 1837 multihop forwarding process. The AR then prepares an RA message with 1838 source address set to its own LLA and destination address set to the 1839 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1840 header with source address set to its own IPv4/ULA address and with 1841 destination set to the encapsulation source of the RS. 1843 The AR then forwards the message to an *NET node within 1844 communications range, which forwards the message according to its 1845 routing tables to an intermediate node. The multihop forwarding 1846 process within the *NET continues repetitively until the message is 1847 delivered to the original MN, which decapsulates the message and 1848 performs autoconfiguration the same as if it had received the RA 1849 directly from the AR as an on-link neighbor. 1851 Note: An alternate approach to multihop forwarding via IPv6 1852 encapsulation would be to statelessly translate the IPv6 LLAs into 1853 ULAs and forward the messages without encapsulation. This would 1854 violate the [RFC4861] requirement that certain IPv6 ND messages must 1855 use link-local addresses and must not be accepted if received with 1856 Hop Limit less than 255. This document therefore advocates 1857 encapsulation since the overhead is nominal considering the 1858 infrequent nature and small size of IPv6 ND messages. Future 1859 documents may consider encapsulation avoidance through translation 1860 while updating [RFC4861]. 1862 Note: An alternate approach to multihop forwarding via IPv4 1863 encapsulation would be to employ IPv6/IPv4 protocol translation. 1864 However, for IPv6 ND messages the LLAs would be truncated due to 1865 translation and the OMNI Router and Prefix Discovery services would 1866 not be able to function. The use of IPv4 encapsulation is therefore 1867 indicated. 1869 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 1870 of a new IPv4 /24 prefix allocation, but this may be difficult to 1871 obtain given IPv4 address exhaustion. An alternative would be to re- 1872 purpose the prefix 192.88.99.0 which has been set aside from its 1873 former use by [RFC7526]. 1875 13.2. MS-Register and MS-Release List Processing 1877 When a MN sends an RS message with an OMNI option via an underlying 1878 interface to an AR, the MN must convey its knowledge of its 1879 currently-associated MSEs. Initially, the MN will have no associated 1880 MSEs and should therefore include an MS-Register sub-option with the 1881 single MSID value 0 which requests the AR to select and assign an 1882 MSE. The AR will then return an RA message with source address set 1883 to the LLA containing the MSE of the selected MSE. 1885 As the MN activates additional underlying interfaces, it can 1886 optionally include an MS-Register sub-option with MSID value 0, or 1887 with non-zero MSIDs for MSEs discovered from previous RS/RA 1888 exchanges. The MN will thus eventually begin to learn and manage its 1889 currently active set of MSEs, and can register with new MSEs or 1890 release from former MSEs with each successive RS/RA exchange. As the 1891 MN's MSE constituency grows, it alone is responsible for including or 1892 omitting MSIDs in the MS-Register/Release lists it sends in RS 1893 messages. The inclusion or omission of MSIDs determines the MN's 1894 interface to the MS and defines the manner in which MSEs will 1895 respond. The only limiting factor is that the MN should include no 1896 more than MAX_MSID values in each list per each IPv6 ND message, and 1897 should avoid duplication of entries in each list unless it wants to 1898 increase likelihood of control message delivery. 1900 When an AR receives an RS message sent by a MN with an OMNI option, 1901 the option will contain zero or more MS-Register and MS-Release sub- 1902 options containing MSIDs. After processing the OMNI option, the AR 1903 will have a list of zero or more MS-Register MSIDs and a list of zero 1904 or more of MS-Release MSIDs. The AR then processes the lists as 1905 follows: 1907 o For each list, retain the first MAX_MSID values in the list and 1908 discard any additional MSIDs (i.e., even if there are duplicates 1909 within a list). 1911 o Next, for each MSID in the MS-Register list, remove all matching 1912 MSIDs from the MS-Release list. 1914 o Next, proceed according to whether the AR's own MSID or the value 1915 0 appears in the MS-Register list as follows: 1917 * If yes, send an RA message directly back to the MN and send a 1918 proxy copy of the RS message to each additional MSID in the MS- 1919 Register list with the MS-Register/Release lists omitted. 1920 Then, send a uNA message to each MSID in the MS-Release list 1921 with the MS-Register/Release lists omitted and with an OMNI 1922 header with S/T-ifIndex set to 0. 1924 * If no, send a proxy copy of the RS message to each additional 1925 MSID in the MS-Register list with the MS-Register list omitted. 1926 For the first MSID, include the original MS-Release list; for 1927 all other MSIDs, omit the MS-Release list. 1929 Each proxy copy of the RS message will include an OMNI option and 1930 encapsulation header with the ULA of the AR as the source and the ULA 1931 of the Register MSE as the destination. When the Register MSE 1932 receives the proxy RS message, if the message includes an MS-Release 1933 list the MSE sends a uNA message to each additional MSID in the 1934 Release list. The Register MSE then sends an RA message back to the 1935 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1936 destination addresses reversed, and with RA destination set to the 1937 LLA of the MN. When the AR receives this RA message, it sends a 1938 proxy copy of the RA to the MN. 1940 Each uNA message (whether send by the first-hop AR or by a Register 1941 MSE) will include an OMNI option and an encapsulation header with the 1942 ULA of the Register MSE as the source and the ULA of the Release ME 1943 as the destination. The uNA informs the Release MSE that its 1944 previous relationship with the MN has been released and that the 1945 source of the uNA message is now registered. The Release MSE must 1946 then note that the subject MN of the uNA message is now "departed", 1947 and forward any subsequent packets destined to the MN to the Register 1948 MSE. 1950 Note that it is not an error for the MS-Register/Release lists to 1951 include duplicate entries. If duplicates occur within a list, the AR 1952 will generate multiple proxy RS and/or uNA messages - one for each 1953 copy of the duplicate entries. 1955 13.3. DHCPv6-based Prefix Registration 1957 When a MN is not pre-provisioned with an LLA containing a MNP (or, 1958 when multiple MNPs are needed), it will require the AR to select MNPs 1959 on its behalf and set up the correct routing state within the MS. 1960 The DHCPv6 service [RFC8415] supports this requirement. 1962 When an MN needs to have the AR select MNPs, it sends an RS message 1963 with a DHCPv6 Message suboption containing a Client Identifier, one 1964 or more IA_PD options and a Rapid Commit option. The MN also sets 1965 the 'msg-type' field to "Solicit", and includes a 3-octet 1966 'transaction-id'. 1968 When the AR receives the RS message, it extracts the DHCPv6 message 1969 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 1970 a message exchange with the locally-resident DHCPv6 server, which 1971 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 1973 (If the AR wishes to defer creation of MN state until the DHCPv6 1974 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 1975 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 1976 forward/reply exchange with Relay Message and Interface ID options.) 1978 When the AR receives the DHCPv6 Reply, it adds routes to the routing 1979 system and creates MNP-LLAs based on the delegated MNPs. The AR then 1980 sends an RA back to the MN with the DHCPv6 Reply message included in 1981 an OMNI DHCPv6 message sub-option. If the RS message source address 1982 was a Temporary address, the AR includes one of the (newly-created) 1983 MNP-LLAs as the RA destination address. The MN then creates a 1984 default route, assigns Subnet Router Anycast addresses and uses the 1985 RA destination address as its primary MNP-LLA. The MN will then use 1986 this primary MNP-LLA as the source address of any IPv6 ND messages it 1987 sends as long as it retains ownership of the MNP. 1989 Note: The single-octet OMNI sub-option length field restricts the 1990 DHCPv6 Message sub-option to a maximum of 255 octets for both the RS 1991 and RA messages. This provides sufficient room for the DHCPv6 1992 message header, a Client/Server Identifier option, a Rapid Commit 1993 option, at least 3 Identity Association for Prefix Delegation (IA_PD) 1994 options and any other supporting DHCPv6 options. A MN requiring more 1995 DHCPv6-based configuration information than this can either perform 1996 multiple independent RS/RA exchanges (with each exchange providing a 1997 subset of the total configuration information) or simply perform an 1998 actual DHCPv6 message exchange in addition to any RS/RA exchanges. 2000 Note: After a MN performs a DHCPv6-based prefix registration exchange 2001 with a first AR, it would need to repeat the exchange with each 2002 additional MSE it registers with. In that case, the MN supplies the 2003 MNP delegations received from the first AR in the IA_PD fields of a 2004 DHCPv6 message when it engages the additional MSEs. 2006 14. Secure Redirection 2008 If the *NET link model is multiple access, the AR is responsible for 2009 assuring that address duplication cannot corrupt the neighbor caches 2010 of other nodes on the link. When the MN sends an RS message on a 2011 multiple access *NET link, the AR verifies that the MN is authorized 2012 to use the address and returns an RA with a non-zero Router Lifetime 2013 only if the MN is authorized. 2015 After verifying MN authorization and returning an RA, the AR MAY 2016 return IPv6 ND Redirect messages to direct MNs located on the same 2017 *NET link to exchange packets directly without transiting the AR. In 2018 that case, the MNs can exchange packets according to their unicast L2 2019 addresses discovered from the Redirect message instead of using the 2020 dogleg path through the AR. In some *NET links, however, such direct 2021 communications may be undesirable and continued use of the dogleg 2022 path through the AR may provide better performance. In that case, 2023 the AR can refrain from sending Redirects, and/or MNs can ignore 2024 them. 2026 15. AR and MSE Resilience 2028 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2029 [RFC5798] configurations so that service continuity is maintained 2030 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2031 the (redundant) ARs is currently providing service, and any service 2032 discontinuity will be limited to the failover time supported by VRRP. 2033 Widely deployed public domain implementations of VRRP are available. 2035 MSEs SHOULD use high availability clustering services so that 2036 multiple redundant systems can provide coordinated response to 2037 failures. As with VRRP, widely deployed public domain 2038 implementations of high availability clustering services are 2039 available. Note that special-purpose and expensive dedicated 2040 hardware is not necessary, and public domain implementations can be 2041 used even between lightweight virtual machines in cloud deployments. 2043 16. Detecting and Responding to MSE Failures 2045 In environments where fast recovery from MSE failure is required, ARs 2046 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2047 manner that parallels Bidirectional Forwarding Detection (BFD) 2048 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2049 react to failures so that cached information is re-established 2050 through alternate paths. Proactive NUD control messaging is carried 2051 only over well-connected ground domain networks (i.e., and not low- 2052 end *NET links such as aeronautical radios) and can therefore be 2053 tuned for rapid response. 2055 ARs perform proactive NUD for MSEs for which there are currently 2056 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2057 of the outage by sending multicast RA messages on the *NET interface. 2058 The AR sends RA messages to MNs via the *NET interface with an OMNI 2059 option with a Release ID for the failed MSE, and with destination 2060 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2062 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2063 by small delays [RFC4861]. Any MNs on the *NET interface that have 2064 been using the (now defunct) MSE will receive the RA messages and 2065 associate with a new MSE. 2067 17. Transition Considerations 2069 When a MN connects to an *NET link for the first time, it sends an RS 2070 message with an OMNI option. If the first hop AR recognizes the 2071 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2072 as the destination and with an OMNI option included. The MN then 2073 engages the AR according to the OMNI link model specified above. If 2074 the first hop AR is a legacy IPv6 router, however, it instead returns 2075 an RA message with no OMNI option and with a non-OMNI unicast source 2076 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2077 according to the legacy IPv6 link model and without the OMNI 2078 extensions specified in this document. 2080 If the *NET link model is multiple access, there must be assurance 2081 that address duplication cannot corrupt the neighbor caches of other 2082 nodes on the link. When the MN sends an RS message on a multiple 2083 access *NET link with an LLA source address and an OMNI option, ARs 2084 that recognize the option ensure that the MN is authorized to use the 2085 address and return an RA with a non-zero Router Lifetime only if the 2086 MN is authorized. ARs that do not recognize the option instead 2087 return an RA that makes no statement about the MN's authorization to 2088 use the source address. In that case, the MN should perform 2089 Duplicate Address Detection to ensure that it does not interfere with 2090 other nodes on the link. 2092 An alternative approach for multiple access *NET links to ensure 2093 isolation for MN / AR communications is through L2 address mappings 2094 as discussed in Appendix C. This arrangement imparts a (virtual) 2095 point-to-point link model over the (physical) multiple access link. 2097 18. OMNI Interfaces on the Open Internet 2099 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2100 the open Internet without an OMNI-aware first-hop AR receive RA 2101 messages that do not include an OMNI option, while OMNI interfaces 2102 configured over IPv4-only underlying interfaces do not receive any 2103 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2104 without an OMNI option configure addresses, on-link prefixes, etc. on 2105 the underlying interface that received the RA according to standard 2106 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2107 interfaces configured over IPv4-only underlying interfaces configure 2108 IPv4 address information on the underlying interfaces using 2109 mechanisms such as DHCPv4 [RFC2131]. 2111 OMNI interfaces configured over underlying interfaces that connect to 2112 the open Internet can apply security services such as VPNs to connect 2113 to an MSE or establish a direct link to an MSE through some other 2114 means (see Section 4). In environments where an explicit VPN or 2115 direct link may be impractical, OMNI interfaces can instead use UDP/ 2116 IP encapsulation and HMAC-based message authentication per 2117 [RFC6081][RFC4380]. 2119 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2120 interfaces send control plane messages to interface with the MS, 2121 including Neighbor Solicitation (NS) and Neighbor Advertisement (NA) 2122 messages used for address resolution / route optimization (see: 2123 [I-D.templin-intarea-6706bis]). The control plane messages must be 2124 authenticated while data plane messages are delivered the same as for 2125 ordinary best-effort Internet traffic with basic source address-based 2126 data origin verification. Data plane communications via OMNI 2127 interfaces that connect over the open Internet without an explicit 2128 VPN should therefore employ transport- or higher-layer security to 2129 ensure integrity and/or confidentiality. 2131 OMNI interfaces in the open Internet are often located behind Network 2132 Address Translators (NATs). The OMNI interface accommodates NAT 2133 traversal using UDP/IP encapsulation and the mechanisms discussed in 2134 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2136 19. Time-Varying MNPs 2138 In some use cases, it is desirable, beneficial and efficient for the 2139 MN to receive a constant MNP that travels with the MN wherever it 2140 moves. For example, this would allow air traffic controllers to 2141 easily track aircraft, etc. In other cases, however (e.g., 2142 intelligent transportation systems), the MN may be willing to 2143 sacrifice a modicum of efficiency in order to have time-varying MNPs 2144 that can be changed every so often to defeat adversarial tracking. 2146 The prefix delegation services discussed in Section 13.3 allows OMNI 2147 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2148 use a Temporary LLA as the source address of an RS message with an 2149 OMNI option with DHCPv6 Option sub-options. The MN would then be 2150 obligated to renumber its internal networks whenever its MNP (and 2151 therefore also its OMNI address) changes. This should not present a 2152 challenge for MNs with automated network renumbering services, 2153 however presents limits for the durations of ongoing sessions that 2154 would prefer to use a constant address. 2156 20. IANA Considerations 2158 The IANA is instructed to allocate an official Type number TBD from 2159 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2160 option. Implementations set Type to 253 as an interim value 2161 [RFC4727]. 2163 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2164 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2165 read as follows: 2167 Code Name Reference 2168 --- ---- --------- 2169 0 Diagnostic Packet Too Big [RFC4443] 2170 1 Advisory Packet Too Big [RFCXXXX] 2172 Figure 17: OMNI Option Sub-Type Values 2174 The IANA is instructed to allocate one Ethernet unicast address TBD2 2175 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2176 Address Block - Unicast Use". 2178 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 2179 is instructed to create and maintain a new registry entitled "OMNI 2180 option Sub-Type values". Initial values for the OMNI option Sub-Type 2181 values registry are given below; future assignments are to be made 2182 through Expert Review [RFC8126]. 2184 Value Sub-Type name Reference 2185 ----- ------------- ---------- 2186 0 Pad1 [RFCXXXX] 2187 1 PadN [RFCXXXX] 2188 2 Interface Attributes [RFCXXXX] 2189 3 Traffic Selector [RFCXXXX] 2190 4 MS-Register [RFCXXXX] 2191 5 MS-Release [RFCXXXX] 2192 6 Network Access Identifier [RFCXXXX] 2193 7 Geo Coordinates [RFCXXXX] 2194 8 DHCP Unique Identifier (DUID) [RFCXXXX] 2195 9 DHCPv6 Message [RFCXXXX] 2196 10-252 Unassigned 2197 253-254 Experimental [RFCXXXX] 2198 255 Reserved [RFCXXXX] 2200 Figure 18: OMNI Option Sub-Type Values 2202 21. Security Considerations 2204 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2205 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2206 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2207 confirmation and/or time synchronization is needed. 2209 OMNI interfaces configured over secured ANET interfaces inherit the 2210 physical and/or link-layer security properties (i.e., "protected 2211 spectrum") of the connected ANETs. OMNI interfaces configured over 2212 open INET interfaces can use symmetric securing services such as VPNs 2213 or can by some other means establish a direct link. When a VPN or 2214 direct link may be impractical, however, an asymmetric security 2215 service such as the authentication option specified in [RFC4380] or 2216 other protocol control message security mechanisms may be necessary. 2217 While the OMNI link protects control plane messaging, applications 2218 must still employ end-to-end transport- or higher-layer security 2219 services to protect the data plane. 2221 The Mobility Service MUST provide strong network layer security for 2222 control plane messages and forwarding path integrity for data plane 2223 messages. In one example, the AERO service 2224 [I-D.templin-intarea-6706bis] constructs a spanning tree between 2225 mobility service elements and secures the links in the spanning tree 2226 with network layer security mechanisms such as IPsec [RFC4301] or 2227 Wireguard. Control plane messages are then constrained to travel 2228 only over the secured spanning tree paths and are therefore protected 2229 from attack or eavesdropping. Since data plane messages can travel 2230 over route optimized paths that do not strictly follow the spanning 2231 tree, however, end-to-end transport- or higher-layer security 2232 services are still required. 2234 Security considerations for specific access network interface types 2235 are covered under the corresponding IP-over-(foo) specification 2236 (e.g., [RFC2464], [RFC2492], etc.). 2238 Security considerations for IPv6 fragmentation and reassembly are 2239 discussed in Section 5.1. 2241 22. Implementation Status 2243 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2244 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2245 Newer specification versions will be tagged in upcoming releases. 2246 First public release expected before the end of 2020. 2248 23. Acknowledgements 2250 The first version of this document was prepared per the consensus 2251 decision at the 7th Conference of the International Civil Aviation 2252 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2253 2019. Consensus to take the document forward to the IETF was reached 2254 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2255 Attendees and contributors included: Guray Acar, Danny Bharj, 2256 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2257 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2258 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2259 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2260 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2261 Fryderyk Wrobel and Dongsong Zeng. 2263 The following individuals are acknowledged for their useful comments: 2264 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 2265 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized 2266 for their many helpful ideas and suggestions. Madhuri Madhava 2267 Badgandi, Katherine Tran, and Vijayasarathy Rajagopalan are 2268 acknowledged for their hard work on the implementation and insights 2269 that led to improvements to the spec. 2271 Discussions on the IETF 6man and atn mailing lists during the fall of 2272 2020 suggested additional points to consider. The authors gratefully 2273 acknowledge the list members who contributed valuable insights 2274 through those discussions. Eric Vyncke and Erik Kline were the 2275 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2276 at the time the document was developed; they are all gratefully 2277 acknowledged for their many helpful insights. 2279 This work is aligned with the NASA Safe Autonomous Systems Operation 2280 (SASO) program under NASA contract number NNA16BD84C. 2282 This work is aligned with the FAA as per the SE2025 contract number 2283 DTFAWA-15-D-00030. 2285 24. References 2287 24.1. Normative References 2289 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2290 DOI 10.17487/RFC0791, September 1981, 2291 . 2293 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2294 Requirement Levels", BCP 14, RFC 2119, 2295 DOI 10.17487/RFC2119, March 1997, 2296 . 2298 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2299 "Definition of the Differentiated Services Field (DS 2300 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2301 DOI 10.17487/RFC2474, December 1998, 2302 . 2304 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2305 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2306 DOI 10.17487/RFC3971, March 2005, 2307 . 2309 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2310 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2311 November 2005, . 2313 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2314 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2315 . 2317 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2318 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2319 2006, . 2321 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2322 Control Message Protocol (ICMPv6) for the Internet 2323 Protocol Version 6 (IPv6) Specification", STD 89, 2324 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2325 . 2327 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2328 ICMPv6, UDP, and TCP Headers", RFC 4727, 2329 DOI 10.17487/RFC4727, November 2006, 2330 . 2332 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2333 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2334 DOI 10.17487/RFC4861, September 2007, 2335 . 2337 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2338 Address Autoconfiguration", RFC 4862, 2339 DOI 10.17487/RFC4862, September 2007, 2340 . 2342 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2343 "Traffic Selectors for Flow Bindings", RFC 6088, 2344 DOI 10.17487/RFC6088, January 2011, 2345 . 2347 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2348 Hosts in a Multi-Prefix Network", RFC 8028, 2349 DOI 10.17487/RFC8028, November 2016, 2350 . 2352 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2353 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2354 May 2017, . 2356 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2357 (IPv6) Specification", STD 86, RFC 8200, 2358 DOI 10.17487/RFC8200, July 2017, 2359 . 2361 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2362 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2363 DOI 10.17487/RFC8201, July 2017, 2364 . 2366 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2367 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2368 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2369 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2370 . 2372 24.2. Informative References 2374 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2375 Interface for Civil Aviation, IETF Liaison Statement 2376 #1676, https://datatracker.ietf.org/liaison/1676/", March 2377 2020. 2379 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2380 Aeronautical Telecommunication Network (ATN) using 2381 Internet Protocol Suite (IPS) Standards and Protocol), 2382 Draft Edition 3 (work-in-progress)", December 2020. 2384 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2385 Interface (FDDI), IEEE Transactions on Communications", 2386 August 1990. 2388 [I-D.ietf-6man-rfc4941bis] 2389 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2390 "Temporary Address Extensions for Stateless Address 2391 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2392 (work in progress), November 2020. 2394 [I-D.ietf-intarea-tunnels] 2395 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2396 Architecture", draft-ietf-intarea-tunnels-10 (work in 2397 progress), September 2019. 2399 [I-D.ietf-ipwave-vehicular-networking] 2400 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2401 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2402 ipwave-vehicular-networking-19 (work in progress), July 2403 2020. 2405 [I-D.templin-6man-dhcpv6-ndopt] 2406 Templin, F., "A Unified Stateful/Stateless Configuration 2407 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2408 (work in progress), June 2020. 2410 [I-D.templin-6man-lla-type] 2411 Templin, F., "The IPv6 Link-Local Address Type Field", 2412 draft-templin-6man-lla-type-02 (work in progress), 2413 November 2020. 2415 [I-D.templin-intarea-6706bis] 2416 Templin, F., "Asymmetric Extended Route Optimization 2417 (AERO)", draft-templin-intarea-6706bis-80 (work in 2418 progress), December 2020. 2420 [IPV4-GUA] 2421 Postel, J., "IPv4 Address Space Registry, 2422 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2423 address-space.xhtml", December 2020. 2425 [IPV6-GUA] 2426 Postel, J., "IPv6 Global Unicast Address Assignments, 2427 https://www.iana.org/assignments/ipv6-unicast-address- 2428 assignments/ipv6-unicast-address-assignments.xhtml", 2429 December 2020. 2431 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2432 Communication Layers", STD 3, RFC 1122, 2433 DOI 10.17487/RFC1122, October 1989, 2434 . 2436 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2437 DOI 10.17487/RFC1191, November 1990, 2438 . 2440 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2441 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2442 . 2444 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2445 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2446 . 2448 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2449 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2450 . 2452 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2453 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2454 . 2456 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2457 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2458 December 1998, . 2460 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2461 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2462 . 2464 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2465 Domains without Explicit Tunnels", RFC 2529, 2466 DOI 10.17487/RFC2529, March 1999, 2467 . 2469 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2470 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2471 . 2473 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2474 DOI 10.17487/RFC3330, September 2002, 2475 . 2477 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2478 Considered Useful", BCP 82, RFC 3692, 2479 DOI 10.17487/RFC3692, January 2004, 2480 . 2482 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2483 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2484 DOI 10.17487/RFC3810, June 2004, 2485 . 2487 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2488 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2489 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2490 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2491 . 2493 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2494 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2495 2004, . 2497 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2498 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2499 DOI 10.17487/RFC4271, January 2006, 2500 . 2502 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2503 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2504 December 2005, . 2506 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2507 Network Address Translations (NATs)", RFC 4380, 2508 DOI 10.17487/RFC4380, February 2006, 2509 . 2511 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2512 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2513 2006, . 2515 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2516 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2517 . 2519 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2520 "Considerations for Internet Group Management Protocol 2521 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2522 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2523 . 2525 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2526 "Internet Group Management Protocol (IGMP) / Multicast 2527 Listener Discovery (MLD)-Based Multicast Forwarding 2528 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2529 August 2006, . 2531 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2532 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2533 . 2535 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2536 Errors at High Data Rates", RFC 4963, 2537 DOI 10.17487/RFC4963, July 2007, 2538 . 2540 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2541 Advertisement Flags Option", RFC 5175, 2542 DOI 10.17487/RFC5175, March 2008, 2543 . 2545 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2546 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2547 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2548 . 2550 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2551 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2552 DOI 10.17487/RFC5214, March 2008, 2553 . 2555 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2556 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2557 . 2559 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2560 Version 3 for IPv4 and IPv6", RFC 5798, 2561 DOI 10.17487/RFC5798, March 2010, 2562 . 2564 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2565 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2566 . 2568 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2569 DOI 10.17487/RFC6081, January 2011, 2570 . 2572 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2573 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2574 DOI 10.17487/RFC6221, May 2011, 2575 . 2577 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2578 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2579 DOI 10.17487/RFC6355, August 2011, 2580 . 2582 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2583 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2584 2012, . 2586 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2587 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2588 DOI 10.17487/RFC7084, November 2013, 2589 . 2591 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2592 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2593 Boundary in IPv6 Addressing", RFC 7421, 2594 DOI 10.17487/RFC7421, January 2015, 2595 . 2597 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 2598 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 2599 DOI 10.17487/RFC7526, May 2015, 2600 . 2602 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2603 DOI 10.17487/RFC7542, May 2015, 2604 . 2606 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2607 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2608 February 2016, . 2610 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2611 Support for IP Hosts with Multi-Access Support", RFC 7847, 2612 DOI 10.17487/RFC7847, May 2016, 2613 . 2615 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2616 Writing an IANA Considerations Section in RFCs", BCP 26, 2617 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2618 . 2620 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2621 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2622 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2623 July 2018, . 2625 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2626 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2627 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2628 . 2630 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2631 and F. Gont, "IP Fragmentation Considered Fragile", 2632 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2633 . 2635 Appendix A. Interface Attribute Preferences Bitmap Encoding 2637 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 2638 encoding to specific Internetworks such as the Aeronautical 2639 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2640 may include link selection preferences based on other traffic 2641 classifiers (e.g., transport port numbers, etc.) in addition to the 2642 existing DSCP-based preferences. Nodes on specific Internetworks 2643 maintain a map of traffic classifiers to additional P[*] preference 2644 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2645 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2647 Implementations use Simplex or Indexed encoding formats for P[*] 2648 encoding in order to encode a given set of traffic classifiers in the 2649 most efficient way. Some use cases may be more efficiently coded 2650 using Simplex form, while others may be more efficient using Indexed. 2651 Once a format is selected for preparation of a single Interface 2652 Attribute the same format must be used for the entire Interface 2653 Attribute sub-option. Different sub-options may use different 2654 formats. 2656 The following figures show coding examples for various Simplex and 2657 Indexed formats: 2659 0 1 2 3 2660 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 2661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2662 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2664 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 2665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2666 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2668 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2670 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2672 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2674 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2677 Figure 19: Example 1: Dense Simplex Encoding 2679 0 1 2 3 2680 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 2681 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2682 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2684 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2686 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2688 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2690 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2692 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2694 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2696 |Bitmap(10)=0x00| ... 2697 +-+-+-+-+-+-+-+-+-+-+- 2699 Figure 20: Example 2: Sparse Simplex Encoding 2701 0 1 2 3 2702 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 2703 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2704 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2705 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2706 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 2707 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2708 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2710 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2712 | Bitmap = 0x01 |796|797|798|799| ... 2713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2715 Figure 21: Example 3: Indexed Encoding 2717 Appendix B. VDL Mode 2 Considerations 2719 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2720 (VDLM2) that specifies an essential radio frequency data link service 2721 for aircraft and ground stations in worldwide civil aviation air 2722 traffic management. The VDLM2 link type is "multicast capable" 2723 [RFC4861], but with considerable differences from common multicast 2724 links such as Ethernet and IEEE 802.11. 2726 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2727 magnitude less than most modern wireless networking gear. Second, 2728 due to the low available link bandwidth only VDLM2 ground stations 2729 (i.e., and not aircraft) are permitted to send broadcasts, and even 2730 so only as compact layer 2 "beacons". Third, aircraft employ the 2731 services of ground stations by performing unicast RS/RA exchanges 2732 upon receipt of beacons instead of listening for multicast RA 2733 messages and/or sending multicast RS messages. 2735 This beacon-oriented unicast RS/RA approach is necessary to conserve 2736 the already-scarce available link bandwidth. Moreover, since the 2737 numbers of beaconing ground stations operating within a given spatial 2738 range must be kept as sparse as possible, it would not be feasible to 2739 have different classes of ground stations within the same region 2740 observing different protocols. It is therefore highly desirable that 2741 all ground stations observe a common language of RS/RA as specified 2742 in this document. 2744 Note that links of this nature may benefit from compression 2745 techniques that reduce the bandwidth necessary for conveying the same 2746 amount of data. The IETF lpwan working group is considering possible 2747 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2749 Appendix C. MN / AR Isolation Through L2 Address Mapping 2751 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2752 unicast link-scoped IPv6 destination address. However, IPv6 ND 2753 messaging should be coordinated between the MN and AR only without 2754 invoking other nodes on the *NET. This implies that MN / AR control 2755 messaging should be isolated and not overheard by other nodes on the 2756 link. 2758 To support MN / AR isolation on some *NET links, ARs can maintain an 2759 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2760 *NETs, this specification reserves one Ethernet unicast address TBD2 2761 (see: Section 20). For non-Ethernet statically-addressed *NETs, 2762 MSADDR is reserved per the assigned numbers authority for the *NET 2763 addressing space. For still other *NETs, MSADDR may be dynamically 2764 discovered through other means, e.g., L2 beacons. 2766 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2767 both multicast and unicast) to MSADDR instead of to an ordinary 2768 unicast or multicast L2 address. In this way, all of the MN's IPv6 2769 ND messages will be received by ARs that are configured to accept 2770 packets destined to MSADDR. Note that multiple ARs on the link could 2771 be configured to accept packets destined to MSADDR, e.g., as a basis 2772 for supporting redundancy. 2774 Therefore, ARs must accept and process packets destined to MSADDR, 2775 while all other devices must not process packets destined to MSADDR. 2776 This model has well-established operational experience in Proxy 2777 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2779 Appendix D. Change Log 2781 << RFC Editor - remove prior to publication >> 2783 Differences from draft-templin-6man-omni-interface-35 to draft- 2784 templin-6man-omni-interface-36: 2786 o Major clarifications on aspects such as "hard/soft" PTB error 2787 messages 2789 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2790 be used in the data plane. 2792 Differences from draft-templin-6man-omni-interface-31 to draft- 2793 templin-6man-omni-interface-32: 2795 o MTU 2797 o Support for multi-hop ANETS such as ISATAP. 2799 Differences from draft-templin-6man-omni-interface-29 to draft- 2800 templin-6man-omni-interface-30: 2802 o Moved link-layer addressing information into the OMNI option on a 2803 per-ifIndex basis 2805 o Renamed "ifIndex-tuple" to "Interface Attributes" 2807 Differences from draft-templin-6man-omni-interface-27 to draft- 2808 templin-6man-omni-interface-28: 2810 o Updates based on implementation expereince. 2812 Differences from draft-templin-6man-omni-interface-25 to draft- 2813 templin-6man-omni-interface-26: 2815 o Further clarification on "aggregate" RA messages. 2817 o Expanded Security Considerations to discuss expectations for 2818 security in the Mobility Service. 2820 Differences from draft-templin-6man-omni-interface-20 to draft- 2821 templin-6man-omni-interface-21: 2823 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2824 (PBM). 2826 Differences from draft-templin-6man-omni-interface-18 to draft- 2827 templin-6man-omni-interface-19: 2829 o SEND/CGA. 2831 Differences from draft-templin-6man-omni-interface-17 to draft- 2832 templin-6man-omni-interface-18: 2834 o Teredo 2836 Differences from draft-templin-6man-omni-interface-14 to draft- 2837 templin-6man-omni-interface-15: 2839 o Prefix length discussions removed. 2841 Differences from draft-templin-6man-omni-interface-12 to draft- 2842 templin-6man-omni-interface-13: 2844 o Teredo 2846 Differences from draft-templin-6man-omni-interface-11 to draft- 2847 templin-6man-omni-interface-12: 2849 o Major simplifications and clarifications on MTU and fragmentation. 2851 o Document now updates RFC4443 and RFC8201. 2853 Differences from draft-templin-6man-omni-interface-10 to draft- 2854 templin-6man-omni-interface-11: 2856 o Removed /64 assumption, resulting in new OMNI address format. 2858 Differences from draft-templin-6man-omni-interface-07 to draft- 2859 templin-6man-omni-interface-08: 2861 o OMNI MNs in the open Internet 2863 Differences from draft-templin-6man-omni-interface-06 to draft- 2864 templin-6man-omni-interface-07: 2866 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2867 L2 addressing. 2869 o Expanded "Transition Considerations". 2871 Differences from draft-templin-6man-omni-interface-05 to draft- 2872 templin-6man-omni-interface-06: 2874 o Brought back OMNI option "R" flag, and discussed its use. 2876 Differences from draft-templin-6man-omni-interface-04 to draft- 2877 templin-6man-omni-interface-05: 2879 o Transition considerations, and overhaul of RS/RA addressing with 2880 the inclusion of MSE addresses within the OMNI option instead of 2881 as RS/RA addresses (developed under FAA SE2025 contract number 2882 DTFAWA-15-D-00030). 2884 Differences from draft-templin-6man-omni-interface-02 to draft- 2885 templin-6man-omni-interface-03: 2887 o Added "advisory PTB messages" under FAA SE2025 contract number 2888 DTFAWA-15-D-00030. 2890 Differences from draft-templin-6man-omni-interface-01 to draft- 2891 templin-6man-omni-interface-02: 2893 o Removed "Primary" flag and supporting text. 2895 o Clarified that "Router Lifetime" applies to each ANET interface 2896 independently, and that the union of all ANET interface Router 2897 Lifetimes determines MSE lifetime. 2899 Differences from draft-templin-6man-omni-interface-00 to draft- 2900 templin-6man-omni-interface-01: 2902 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2903 for future use (most likely as "pseudo-multicast"). 2905 o Non-normative discussion of alternate OMNI LLA construction form 2906 made possible if the 64-bit assumption were relaxed. 2908 First draft version (draft-templin-atn-aero-interface-00): 2910 o Draft based on consensus decision of ICAO Working Group I Mobility 2911 Subgroup March 22, 2019. 2913 Authors' Addresses 2914 Fred L. Templin (editor) 2915 The Boeing Company 2916 P.O. Box 3707 2917 Seattle, WA 98124 2918 USA 2920 Email: fltemplin@acm.org 2922 Tony Whyman 2923 MWA Ltd c/o Inmarsat Global Ltd 2924 99 City Road 2925 London EC1Y 1AX 2926 England 2928 Email: tony.whyman@mccallumwhyman.com