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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 January 27, 2021 7 Expires: July 31, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-71 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 July 31, 2021. 41 Copyright Notice 43 Copyright (c) 2021 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 . . . . . . . . . . . . . . . . . . . . . . . . 9 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 14 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 19 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 20 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 20 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 22 67 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 23 68 10. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 24 69 10.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 26 70 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 27 71 10.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 27 72 10.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 28 73 10.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 29 74 10.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 33 75 10.1.6. Origin Indication . . . . . . . . . . . . . . . . . 34 76 10.1.7. MS-Register . . . . . . . . . . . . . . . . . . . . 35 77 10.1.8. MS-Release . . . . . . . . . . . . . . . . . . . . . 35 78 10.1.9. Geo Coordinates . . . . . . . . . . . . . . . . . . 36 79 10.1.10. Dynamic Host Configuration Protocol for IPv6 80 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 36 81 10.1.11. Host Identity Protocol (HIP) Message . . . . . . . . 37 82 11. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 38 83 12. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 38 84 12.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 39 85 12.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 39 86 13. Router Discovery and Prefix Registration . . . . . . . . . . 40 87 13.1. Router Discovery in IP Multihop and IPv4-Only Networks . 44 88 13.2. MS-Register and MS-Release List Processing . . . . . . . 45 89 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 47 90 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 48 91 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 48 92 16. Detecting and Responding to MSE Failures . . . . . . . . . . 48 93 17. Transition Considerations . . . . . . . . . . . . . . . . . . 49 94 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 50 95 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 51 96 20. Node Identification . . . . . . . . . . . . . . . . . . . . . 51 97 21. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52 98 22. Security Considerations . . . . . . . . . . . . . . . . . . . 53 99 23. Implementation Status . . . . . . . . . . . . . . . . . . . . 54 100 24. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 54 101 25. References . . . . . . . . . . . . . . . . . . . . . . . . . 55 102 25.1. Normative References . . . . . . . . . . . . . . . . . . 55 103 25.2. Informative References . . . . . . . . . . . . . . . . . 57 104 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 63 105 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 65 106 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 66 107 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 66 108 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 69 110 1. Introduction 112 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 113 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 114 pedestrians with cellphones, etc.) often have multiple interface 115 connections to wireless and/or wired-link data links used for 116 communicating with networked correspondents. These data links may 117 have diverse performance, cost and availability properties that can 118 change dynamically according to mobility patterns, flight phases, 119 proximity to infrastructure, etc. MNs coordinate their data links in 120 a discipline known as "multilink", in which a single virtual 121 interface is configured over the node's underlying interface 122 connections to the data links. 124 The MN configures a virtual interface (termed the "Overlay Multilink 125 Network (OMNI) interface") as a thin layer over the underlying 126 interfaces. The OMNI interface is therefore the only interface 127 abstraction exposed to the IP layer and behaves according to the Non- 128 Broadcast, Multiple Access (NBMA) interface principle, while 129 underlying interfaces appear as link layer communication channels in 130 the architecture. The OMNI interface connects to a virtual overlay 131 service known as the "OMNI link". The OMNI link spans one or more 132 Internetworks that may include private-use infrastructures and/or the 133 global public Internet itself. 135 Each MN receives a Mobile Network Prefix (MNP) for numbering 136 downstream-attached End User Networks (EUNs) independently of the 137 access network data links selected for data transport. The MN 138 performs router discovery over the OMNI interface (i.e., similar to 139 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 140 behalf of its EUNs. The router discovery process is iterated over 141 each of the OMNI interface's underlying interfaces in order to 142 register per-link parameters (see Section 13). 144 The OMNI interface provides a multilink nexus for exchanging inbound 145 and outbound traffic via the correct underlying interface(s). The IP 146 layer sees the OMNI interface as a point of connection to the OMNI 147 link. Each OMNI link has one or more associated Mobility Service 148 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 149 prefixes from which OMNI link MNPs are derived. If there are 150 multiple OMNI links, the IPv6 layer will see multiple OMNI 151 interfaces. 153 MNs may connect to multiple distinct OMNI links by configuring 154 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 155 interface is configured over a set of underlying interfaces and 156 provides a nexus for Safety-Based Multilink (SBM) operation. Each 157 OMNI SBM "domain" configures a common ULA prefix [ULA]::/48, and each 158 OMNI link within the domain configures a unique 16-bit Subnet ID '*' 159 to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 160 layer applies SBM routing to select an OMNI interface, which then 161 applies Performance-Based Multilink (PBM) to select the correct 162 underlying interface. Applications can apply Segment Routing 163 [RFC8402] to select independent SBM topologies for fault tolerance. 165 The OMNI interface interacts with a network-based Mobility Service 166 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 167 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 168 track MN movements and represent their MNPs in a global routing or 169 mapping system. 171 Many OMNI use cases are currently under active consideration. In 172 particular, the International Civil Aviation Organization (ICAO) 173 Working Group-I Mobility Subgroup is developing a future Aeronautical 174 Telecommunications Network with Internet Protocol Services (ATN/IPS) 175 and has issued a liaison statement requesting IETF adoption [ATN] in 176 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 177 in Vehicular Environments (ipwave) working group has further included 178 problem statement and use case analysis for OMNI in a document now in 179 AD evaluation for RFC publication 180 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 181 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 182 programs that examine commercial aviation, Urban Air Mobility (UAM) 183 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 184 represent another large class of potential OMNI users. 186 This document specifies the transmission of IP packets and MN/MS 187 control messages over OMNI interfaces. The OMNI interface supports 188 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 189 as the network layer in the data plane, while using IPv6 ND messaging 190 as the control plane independently of the data plane IP protocol(s). 191 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 192 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 193 discussed in the following sections. Support for both Vehicle-to- 194 Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) communications 195 outside the context of infrastructure are discussed. 197 2. Terminology 199 The terminology in the normative references applies; especially, the 200 terms "link" and "interface" are the same as defined in the IPv6 201 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 202 Additionally, this document assumes the following IPv6 ND message 203 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 204 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 206 The Protocol Constants defined in Section 10 of [RFC4861] are used in 207 their same format and meaning in this document. The terms "All- 208 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 209 are the same as defined in [RFC4291] (with Link-Local scope assumed). 211 The term "IP" is used to refer collectively to either Internet 212 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 213 specification at the layer in question applies equally to either 214 version. 216 The following terms are defined within the scope of this document: 218 Mobile Node (MN) 219 an end system with a mobile router having multiple distinct 220 upstream data link connections that are grouped together in one or 221 more logical units. The MN's data link connection parameters can 222 change over time due to, e.g., node mobility, link quality, etc. 223 The MN further connects a downstream-attached End User Network 224 (EUN). The term MN used here is distinct from uses in other 225 documents, and does not imply a particular mobility protocol. 227 End User Network (EUN) 228 a simple or complex downstream-attached mobile network that 229 travels with the MN as a single logical unit. The IP addresses 230 assigned to EUN devices remain stable even if the MN's upstream 231 data link connections change. 233 Mobility Service (MS) 234 a mobile routing service that tracks MN movements and ensures that 235 MNs remain continuously reachable even across mobility events. 236 Specific MS details are out of scope for this document. 238 Mobility Service Endpoint (MSE) 239 an entity in the MS (either singular or aggregate) that 240 coordinates the mobility events of one or more MN. 242 Mobility Service Prefix (MSP) 243 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 244 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 245 from which more-specific Mobile Network Prefixes (MNPs) are 246 delegated. OMNI link administrators typically obtain MSPs from an 247 Internet address registry, however private-use prefixes can 248 alternatively be used subject to certain limitations (see: 249 Section 9). OMNI links that connect to the global Internet 250 advertise their MSPs to their interdomain routing peers. 252 Mobile Network Prefix (MNP) 253 a longer IP prefix delegated from an MSP (e.g., 254 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 255 MNs sub-delegate the MNP to devices located in EUNs. 257 Access Network (ANET) 258 a data link service network (e.g., an aviation radio access 259 network, satellite service provider network, cellular operator 260 network, wifi network, etc.) that connects MNs. Physical and/or 261 data link level security is assumed, and sometimes referred to as 262 "protected spectrum". Private enterprise networks and ground 263 domain aviation service networks may provide multiple secured IP 264 hops between the MN's point of connection and the nearest Access 265 Router. 267 Access Router (AR) 268 a router in the ANET for connecting MNs to correspondents in 269 outside Internetworks. The AR may be located on the same physical 270 link as the MN, or may be located multiple IP hops away. In the 271 latter case, the MN uses encapsulation to communicate with the AR 272 as though it were on the same physical link. 274 ANET interface 275 a MN's attachment to a link in an ANET. 277 Internetwork (INET) 278 a connected network region with a coherent IP addressing plan that 279 provides transit forwarding services between ANETs and nodes that 280 connect directly to the open INET via unprotected media. No 281 physical and/or data link level security is assumed, therefore 282 security must be applied by upper layers. The global public 283 Internet itself is an example. 285 INET interface 286 a node's attachment to a link in an INET. 288 *NET 289 a "wildcard" term used when a given specification applies equally 290 to both ANET and INET cases. 292 OMNI link 293 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 294 over one or more INETs and their connected ANETs. An OMNI link 295 can comprise multiple INET segments joined by bridges the same as 296 for any link; the addressing plans in each segment may be mutually 297 exclusive and managed by different administrative entities. 299 OMNI interface 300 a node's attachment to an OMNI link, and configured over one or 301 more underlying *NET interfaces. If there are multiple OMNI links 302 in an OMNI domain, a separate OMNI interface is configured for 303 each link. 305 OMNI Adaptation Layer (OAL) 306 an OMNI interface process whereby packets admitted into the 307 interface are wrapped in a mid-layer IPv6 header and fragmented/ 308 reassembled if necessary to support the OMNI link Maximum 309 Transmission Unit (MTU). The OAL is also responsible for 310 generating MTU-related control messages as necessary, and for 311 providing addressing context for spanning multiple segments of a 312 bridged OMNI link. 314 OMNI Option 315 an IPv6 Neighbor Discovery option providing multilink parameters 316 for the OMNI interface as specified in Section 10. 318 Mobile Network Prefix Link Local Address (MNP-LLA) 319 an IPv6 Link Local Address that embeds the most significant 64 320 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 321 Section 7. 323 Mobile Network Prefix Unique Local Address (MNP-ULA) 324 an IPv6 Unique-Local Address derived from an MNP-LLA. 326 Administrative Link Local Address (ADM-LLA) 327 an IPv6 Link Local Address that embeds a 32-bit administratively- 328 assigned identification value in the lower 32 bits of fe80::/96, 329 as specified in Section 7. 331 Administrative Unique Local Address (ADM-ULA) 332 an IPv6 Unique-Local Address derived from an ADM-LLA. 334 Multilink 335 an OMNI interface's manner of managing diverse underlying 336 interface connections to data links as a single logical unit. The 337 OMNI interface provides a single unified interface to upper 338 layers, while underlying interface selections are performed on a 339 per-packet basis considering factors such as DSCP, flow label, 340 application policy, signal quality, cost, etc. Multilinking 341 decisions are coordinated in both the outbound (i.e. MN to 342 correspondent) and inbound (i.e., correspondent to MN) directions. 344 L2 345 The second layer in the OSI network model. Also known as "layer- 346 2", "link-layer", "sub-IP layer", "data link layer", etc. 348 L3 349 The third layer in the OSI network model. Also known as "layer- 350 3", "network-layer", "IP layer", etc. 352 underlying interface 353 a *NET interface over which an OMNI interface is configured. The 354 OMNI interface is seen as a L3 interface by the IP layer, and each 355 underlying interface is seen as a L2 interface by the OMNI 356 interface. The underlying interface either connects directly to 357 the physical communications media or coordinates with another node 358 where the physical media is hosted. 360 Mobility Service Identification (MSID) 361 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 362 (see: Section 7). IDs are assigned according to MS-specific 363 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 365 Safety-Based Multilink (SBM) 366 A means for ensuring fault tolerance through redundancy by 367 connecting multiple affiliated OMNI interfaces to independent 368 routing topologies (i.e., multiple independent OMNI links). 370 Performance Based Multilink (PBM) 371 A means for selecting underlying interface(s) for packet 372 transmission and reception within a single OMNI interface. 374 OMNI Domain 375 The set of all SBM/PBM OMNI links that collectively provides 376 services for a common set of MSPs. Each OMNI domain consists of a 377 set of affiliated OMNI links that all configure the same ::/48 ULA 378 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 380 3. Requirements 382 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 383 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 384 "OPTIONAL" in this document are to be interpreted as described in BCP 385 14 [RFC2119][RFC8174] when, and only when, they appear in all 386 capitals, as shown here. 388 OMNI links maintain a constant value "MAX_MSID" selected to provide 389 MNs with an acceptable level of MSE redundancy while minimizing 390 control message amplification. It is RECOMMENDED that MAX_MSID be 391 set to the default value 5; if a different value is chosen, it should 392 be set uniformly by all nodes on the OMNI link. 394 An implementation is not required to internally use the architectural 395 constructs described here so long as its external behavior is 396 consistent with that described in this document. 398 4. Overlay Multilink Network (OMNI) Interface Model 400 An OMNI interface is a MN virtual interface configured over one or 401 more underlying interfaces, which may be physical (e.g., an 402 aeronautical radio link) or virtual (e.g., an Internet or higher- 403 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 404 with the MS through IPv6 ND message exchanges. The MN uses the MNP 405 to construct a unique Link-Local Address (MNP-LLA) through the 406 algorithmic derivation specified in Section 7 and assigns the LLA to 407 the OMNI interface. 409 The OMNI interface architectural layering model is the same as in 410 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 411 therefore sees the OMNI interface as a single L3 interface with 412 multiple underlying interfaces that appear as L2 communication 413 channels in the architecture. 415 +----------------------------+ 416 | Upper Layer Protocol | 417 Session-to-IP +---->| | 418 Address Binding | +----------------------------+ 419 +---->| IP (L3) | 420 IP Address +---->| | 421 Binding | +----------------------------+ 422 +---->| OMNI Interface | 423 Logical-to- +---->| (LLA) | 424 Physical | +----------------------------+ 425 Interface +---->| L2 | L2 | | L2 | 426 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 427 +------+------+ +------+ 428 | L1 | L1 | | L1 | 429 | | | | | 430 +------+------+ +------+ 432 Figure 1: OMNI Interface Architectural Layering Model 434 Each underlying interface provides an L2/L1 abstraction according to 435 one of the following models: 437 o INET interfaces connect to an INET either natively or through one 438 or several IPv4 Network Address Translators (NATs). Native INET 439 interfaces have global IP addresses that are reachable from any 440 INET correspondent. NATed INET interfaces typically have private 441 IP addresses and connect to a private network behind one or more 442 NATs that provide INET access. 444 o ANET interfaces connect to a protected ANET that is separated from 445 the open INET by an AR acting as a proxy. The ANET interface may 446 be either on the same L2 link segment as the AR, or separated from 447 the AR by multiple IP hops. 449 o VPNed interfaces use security encapsulation over a *NET to a 450 Virtual Private Network (VPN) gateway. Other than the link-layer 451 encapsulation format, VPNed interfaces behave the same as for 452 Direct interfaces. 454 o Direct (aka "point-to-point") interfaces connect directly to a 455 peer without crossing any *NET paths. An example is a line-of- 456 sight link between a remote pilot and an unmanned aircraft. 458 The OMNI virtual interface model gives rise to a number of 459 opportunities: 461 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 462 Address Detection (DAD) or Multicast Listener Discovery (MLD) 463 messaging is necessary. 465 o since Temporary LLAs are statistically unique, they can be used 466 without DAD for short-term purposes, e.g. until an MNP-LLA is 467 obtained. 469 o *NET interfaces on the same L2 link segment as an AR do not 470 require any L3 addresses (i.e., not even link-local) in 471 environments where communications are coordinated entirely over 472 the OMNI interface. (An alternative would be to also assign the 473 same LLA to all *NET interfaces.) 475 o as underlying interface properties change (e.g., link quality, 476 cost, availability, etc.), any active interface can be used to 477 update the profiles of multiple additional interfaces in a single 478 message. This allows for timely adaptation and service continuity 479 under dynamically changing conditions. 481 o coordinating underlying interfaces in this way allows them to be 482 represented in a unified MS profile with provisions for mobility 483 and multilink operations. 485 o exposing a single virtual interface abstraction to the IPv6 layer 486 allows for multilink operation (including QoS based link 487 selection, packet replication, load balancing, etc.) at L2 while 488 still permitting L3 traffic shaping based on, e.g., DSCP, flow 489 label, etc. 491 o the OMNI interface allows inter-INET traversal when nodes located 492 in different INETs need to communicate with one another. This 493 mode of operation would not be possible via direct communications 494 over the underlying interfaces themselves. 496 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 497 lossless and adaptive path MTU mitigations not available for 498 communications directly over the underlying interfaces themselves. 500 o L3 sees the OMNI interface as a point of connection to the OMNI 501 link; if there are multiple OMNI links (i.e., multiple MS's), L3 502 will see multiple OMNI interfaces. 504 o Multiple independent OMNI interfaces can be used for increased 505 fault tolerance through Safety-Based Multilink (SBM), with 506 Performance-Based Multilink (PBM) applied within each interface. 508 Other opportunities are discussed in [RFC7847]. Note that even when 509 the OMNI virtual interface is present, applications can still access 510 underlying interfaces either through the network protocol stack using 511 an Internet socket or directly using a raw socket. This allows for 512 intra-network (or point-to-point) communications without invoking the 513 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 514 is configured over an underlying IPv4 interface, applications can 515 still invoke IPv4 intra-network communications as long as the 516 communicating endpoints are not subject to mobility dynamics. 517 However, the opportunities discussed above are not available when the 518 architectural layering is bypassed in this way. 520 Figure 2 depicts the architectural model for a MN with an attached 521 EUN connecting to the MS via multiple independent *NETs. When an 522 underlying interface becomes active, the MN's OMNI interface sends 523 IPv6 ND messages without encapsulation if the first-hop Access Router 524 (AR) is on the same underlying link; otherwise, the interface uses 525 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 526 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 527 then coordinates with an INET Mobility Service Endpoint (MSE#1, 528 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 529 The Hop Limit in IPv6 ND messages is not decremented due to 530 encapsulation; hence, the OMNI interface appears to be attached to an 531 ordinary link. 533 +--------------+ (:::)-. 534 | MN |<-->.-(::EUN:::) 535 +--------------+ `-(::::)-' 536 |OMNI interface| 537 +----+----+----+ 538 +--------|IF#1|IF#2|IF#n|------ + 539 / +----+----+----+ \ 540 / | \ 541 / | \ 542 v v v 543 (:::)-. (:::)-. (:::)-. 544 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 545 `-(::::)-' `-(::::)-' `-(::::)-' 546 +----+ +----+ +----+ 547 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 548 . +-|--+ +-|--+ +-|--+ . 549 . | | | 550 . v v v . 551 . <----- INET Encapsulation -----> . 552 . . 553 . +-----+ (:::)-. . 554 . |MSE#2| .-(::::::::) +-----+ . 555 . +-----+ .-(::: INET :::)-. |MSE#m| . 556 . (::::: Routing ::::) +-----+ . 557 . `-(::: System :::)-' . 558 . +-----+ `-(:::::::-' . 559 . |MSE#1| +-----+ +-----+ . 560 . +-----+ |MSE#3| |MSE#4| . 561 . +-----+ +-----+ . 562 . . 563 . . 564 . <----- Worldwide Connected Internetwork ----> . 565 ........................................................... 567 Figure 2: MN/MS Coordination via Multiple *NETs 569 After the initial IPv6 ND message exchange, the MN (and/or any nodes 570 on its attached EUNs) can send and receive IP data packets over the 571 OMNI interface. OMNI interface multilink services will forward the 572 packets via ARs in the correct underlying *NETs. The AR encapsulates 573 the packets according to the capabilities provided by the MS and 574 forwards them to the next hop within the worldwide connected 575 Internetwork via optimal routes. 577 OMNI links span one or more underlying Internetwork via the OMNI 578 Adaptation Layer (OAL) which is based on a mid-layer overlay 579 encapsulation using [RFC2473]. Each OMNI link corresponds to a 580 different overlay (differentiated by an address codepoint) which may 581 be carried over a completely separate underlying topology. Each MN 582 can facilitate SBM by connecting to multiple OMNI links using a 583 distinct OMNI interface for each link. 585 Note: OMNI interface underlying interfaces often connect directly to 586 physical media on the local platform (e.g., a laptop computer with 587 WiFi, etc.), but in some configurations the physical media may be 588 hosted on a separate Local Area Network (LAN) node. In that case, 589 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 590 tunnel (at a layer below the underlying interface) to the node 591 hosting the physical media. The OMNI interface may also apply 592 encapsulation at a layer above the underlying interface such that 593 packets would appear "double-encapsulated" on the LAN; the node 594 hosting the physical media in turn removes the LAN encapsulation 595 prior to transmission or inserts it following reception. Finally, 596 the underlying interface must monitor the node hosting the physical 597 media (e.g., through periodic keepalives) so that it can convey 598 up/down/status information to the OMNI interface. 600 5. The OMNI Adaptation Layer (OAL) 602 The OMNI interface observes the link nature of tunnels, including the 603 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 604 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 605 The OMNI interface is configured over one or more underlying 606 interfaces that may have diverse MTUs. OMNI interfaces accommodate 607 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 608 discussed in this section. 610 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 611 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 612 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 613 permitted to perform network fragmentation even though the 614 destination is required to reassemble more. The network therefore 615 MUST forward packets of at least 1280 bytes without generating an 616 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 617 [RFC8201]. (Note: the source can apply "source fragmentation" for 618 locally-generated IPv6 packets up to 1500 bytes and larger still if 619 it if has a way to determine that the destination configures a larger 620 MRU, but this does not affect the minimum IPv6 path MTU.) 622 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 623 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 624 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 625 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 626 support network fragmentation and the destination is required to 627 reassemble at least that much. The "Don't Fragment" (DF) bit in the 628 IPv4 encapsulation headers of packets sent over IPv4 underlying 629 interfaces therefore MUST be set to 0. (Note: even if the 630 encapsulation source has a way to determine that the encapsulation 631 destination configures an MRU larger than 576 bytes, it should not 632 assume a larger minimum IPv4 path MTU without careful consideration 633 of the issues discussed in Section 5.1.) 635 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 636 encapsulation may be prevalent, it may be prudent for the OAL to 637 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 638 of the underlying interface IP protocol version. Always assuming the 639 IPv4 minimum path MTU even for IPv6 underlying interfaces may produce 640 more fragments and additional header overhead, but will always 641 interoperate and never run the risk of presenting an IPv4 interface 642 with a packet that exceeds its MRU. 644 The OMNI interface configures both an MTU and MRU of 9180 bytes 645 [RFC2492]; the size is therefore not a reflection of the underlying 646 interface MTUs, but rather determines the largest packet the OMNI 647 interface can forward or reassemble. The OMNI interface uses the 648 OMNI Adaptation Layer (OAL) to admit packets from the network layer 649 that are no larger than the OMNI interface MTU while generating 650 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 651 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 652 document refers to both of these ICMPv4/ICMPv6 message types simply 653 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 654 errors as discussed below. 656 For IPv4 packets with DF=0, the network layer performs IPv4 657 fragmentation if necessary then admits the packets/fragments into the 658 OMNI interface; these fragments will be reassembled by the final 659 destination. For IPv4 packets with DF=1 and IPv6 packets, the 660 network layer admits the packet if it is no larger than the OMNI 661 interface MTU; otherwise, it drops the packet and returns a PTB hard 662 error message to the source. 664 For each admitted IP packet/fragment, the OMNI interface internally 665 employs the OAL when necessary by encapsulating the inner IP packet/ 666 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 667 outer IP encapsulations. (The OAL does not decrement the inner IP 668 Hop Limit/TTL during encapsulation since the insertion occurs at a 669 layer below IP forwarding.) The OAL then calculates the 32-bit CRC 670 over the entire mid-layer packet and writes the value in a trailing 671 4-octet field at the end of the packet. Next, the OAL fragments this 672 mid-layer IPv6 packet, forwards the fragments (using *NET 673 encapsulation if necessary), and returns an internally-generated PTB 674 soft error message (subject to rate limiting) if it deems the packet 675 too large according to factors such as link performance 676 characteristics, reassembly congestion, etc. This ensures that the 677 path MTU is adaptive and reflects the current path used for a given 678 data flow. 680 The OAL operates with respect to both the minimum IPv6 and IPv4 path 681 MTUs as follows: 683 o When an OMNI interface sends a packet toward a final destination 684 via an ANET peer, it sends without OAL encapsulation if the packet 685 (including any outer-layer ANET encapsulations) is no larger than 686 the underlying interface MTU for on-link ANET peers or the minimum 687 ANET path MTU for peers separated by multiple IP hops. Otherwise, 688 the OAL inserts an IPv6 header per [RFC2473] with source address 689 set to the node's own Unique-Local Address (ULA) (see: Section 8) 690 and destination set to either the Administrative ULA (ADM-ULA) of 691 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 692 corresponding to the final destination (see below). The OAL then 693 calculates and appends the trailing 32-bit CRC, then uses IPv6 694 fragmentation to break the packet into a minimum number of non- 695 overlapping fragments where the size of each non-final fragment 696 (including both the OMNI and any outer-layer ANET encapsulations) 697 is determined by the underlying interface MTU for on-link ANET 698 peers or the minimum ANET path MTU for peers separated by multiple 699 IP hops. The OAL then encapsulates the fragments in any ANET 700 headers and sends them to the ANET peer, which either reassembles 701 before forwarding if the OAL destination is its own ADM-ULA or 702 forwards the fragments toward the final destination without first 703 reassembling otherwise. 705 o When an OMNI interface sends a packet toward a final destination 706 via an INET interface, it sends packets (including any outer-layer 707 INET encapsulations) no larger than the minimum INET path MTU 708 without OAL encapsulation if the destination is reached via an 709 INET address within the same OMNI link segment. Otherwise, the 710 OAL inserts an IPv6 header per [RFC2473] with source address set 711 to the node's ULA, destination set to the ULA of the next hop OMNI 712 node toward the final destination and (if necessary) with an OMNI 713 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 714 final segment addressing information. The OAL then calculates and 715 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 716 break the packet into a minimum number of non-overlapping 717 fragments where the size of each non-final fragment (including 718 both the OMNI and outer-layer INET encapsulations) is determined 719 by the minimum INET path MTU. The OAL then encapsulates the 720 fragments in any INET headers and sends them to the OMNI link 721 neighbor, which reassembles before forwarding toward the final 722 destination. 724 In light of the above considerations, the OAL should assume a minimum 725 path MTU of 576 bytes for the purpose of generating OAL fragments. 726 Each OAL fragment will undergo *NET encapsulation including either a 727 20 byte IPv4 or 40 byte IPv6 header plus an 8 byte UDP header, 728 leaving a minimum of 528 bytes for each fragment. Each OAL fragment 729 must accommodate 40 bytes for the OAL IPv6 header plus 8 bytes for 730 the fragment header (while reserving 40 additional bytes in case a 731 maximum-length ORH is inserted during re-encapsulation), leaving 440 732 bytes to accommodate the actual inner IP packet fragment. OAL 733 fragmentation algorithms therefore MUST produce non-final fragments 734 with the OAL IPv6 header Payload Length set to no less than 448 bytes 735 (8 bytes for the fragment header plus 440 bytes for the inner packet 736 fragment), while the Payload Length of the final fragment may be 737 smaller. OAL reassembly algorithms MUST drop any non-final fragments 738 with Payload Length less than 448 bytes. 740 Note that OAL fragmentation algorithms MAY produce larger non-final 741 fragments if better path MTU information is available. For example, 742 when two ANET peers share a common physical or virtual link with a 743 larger MTU such as 1500 bytes or larger, OAL fragmentation may use 744 this larger MTU size as long as the receiving ANET peer reassembles 745 (and possibly also refragments) before forwarding. This is important 746 for accommodating links where performance is highly dependent on 747 maximum use of the available link MTU, e.g. for wireless aviation 748 data links. Additionally, in order to set the correct context for 749 reassembly, the OMNI interface that inserts the OAL header MUST also 750 be the one that inserts the IPv6 fragment header Identification 751 value. While not strictly required, sending all fragments of the 752 same fragmented OAL packet consecutively over the same underlying 753 interface with minimal inter-fragment delay may increase the 754 likelihood of successful reassembly. 756 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 757 header Code field value 0 are hard errors that always indicate that a 758 packet has been dropped due to a real MTU restriction. However, the 759 OAL can also forward large packets via encapsulation and 760 fragmentation while at the same time returning PTB soft error 761 messages (subject to rate limiting) indicating that a forwarded 762 packet was uncomfortably large. The OMNI interface can therefore 763 continuously forward large packets without loss while returning PTB 764 soft error messages recommending a smaller size. Original sources 765 that receive the soft errors in turn reduce the size of the packets 766 they send, i.e., the same as for hard errors. 768 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 769 field to the value 1 in PTB soft error messages. The OAL sets the 770 PTB destination address to the source address of the original packet, 771 and sets the source address to the MNP Subnet Router Anycast address 772 of the MN (i.e., whether the MN was the source or target of the 773 original packet). The OAL then sets the MTU field to a value no 774 smaller than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB 775 soft error to the original source. 777 When the original source receives the PTB, it reduces its path MTU 778 estimate the same as for hard errors but does not regard the message 779 as a loss indication. (If the original source does not recognize the 780 soft error code, it regards the PTB the same as a hard error but 781 should heed the retransmission advice given in [RFC8201] suggesting 782 retransmission based on normal packetization layer retransmission 783 timers.) This document therefore updates [RFC1191][RFC4443] and 784 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 785 that PTB hard or soft errors may arrive at any time even if after a 786 successful MTU probe (this is the same consideration as for an 787 ordinary path fluctuation following a successful probe). 789 In summary, the OAL supports continuous transmission and reception of 790 packets of various sizes in the face of dynamically changing network 791 conditions. Moreover, since PTB soft errors do not indicate loss, 792 original sources that receive soft errors can quickly scan for path 793 MTU increases without waiting for the minimum 10 minutes specified 794 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 795 therefore provides a lossless and adaptive service that accommodates 796 MTU diversity especially well-suited for dynamic multilink 797 environments. 799 Note: An OMNI interface that reassembles OAL fragments may experience 800 congestion-oriented loss in its reassembly cache and can optionally 801 send PTB soft errors to the original source and/or ICMP "Time 802 Exceeded" messages to the source of the OAL fragments. In 803 environments where the messages may contribute to unacceptable 804 additional congestion, however, the OMNI interface can simply regard 805 the loss as an ordinary unreported congestion event for which the 806 original source will eventually compensate. 808 Note: When the network layer forwards an IPv4 packet/fragment with 809 DF=0 into the OMNI interface, the interface can optionally perform 810 (further) IPv4 fragmentation before invoking the OAL so that the 811 fragments will be reassembled by the final destination. When the 812 network layer performs IPv6 fragmentation for locally-generated IPv6 813 packets, the OMNI interface typically invokes the OAL without first 814 applying (further) IPv6 fragmentation; the network layer should 815 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 816 push the reassembly burden to the final destination and avoid 817 receiving PTB soft errors from the OMNI interface. Aside from these 818 non-normative guidelines, the manner in which any IP fragmentation is 819 invoked prior to OAL encapsulation/fragmentation is an implementation 820 matter. 822 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 823 the receiving OAL will discard any packets with incorrect CRC values 824 following reassembly. The 32-bit CRC is sufficient to detect 825 reassembly misassociations for packet sizes up to the OMNI interface 826 MTU 9180 but may not be sufficient to detect errors for larger sizes 827 [CRC]. 829 Note: Some underlying interface types (e.g., VPNs) may already 830 provide their own robust fragmentation and reassembly services even 831 without OAL encapsulation. In those cases, the OAL can invoke the 832 inherent underlying interface schemes instead while employing PTB 833 soft errors in the same fashion as described above. Other underlying 834 interface properties such as header/message compression can also be 835 harnessed in a similar fashion. 837 Note: Applications can dynamically tune the size of the packets they 838 to send to produce the best possible throughput and latency, with the 839 understanding that these parameters may change over time due to 840 factors such as congestion, mobility, network path changes, etc. The 841 receipt or absence of soft errors should be seen as hints of when 842 increasing or decreasing packet sizes may be beneficial. 844 5.1. Fragmentation Security Implications 846 As discussed in Section 3.7 of [RFC8900], there are four basic 847 threats concerning IPv6 fragmentation; each of which is addressed by 848 effective mitigations as follows: 850 1. Overlapping fragment attacks - reassembly of overlapping 851 fragments is forbidden by [RFC8200]; therefore, this threat does 852 not apply to the OAL. 854 2. Resource exhaustion attacks - this threat is mitigated by 855 providing a sufficiently large OAL reassembly cache and 856 instituting "fast discard" of incomplete reassemblies that may be 857 part of a buffer exhaustion attack. The reassembly cache should 858 be sufficiently large so that a sustained attack does not cause 859 excessive loss of good reassemblies but not so large that (timer- 860 based) data structure management becomes computationally 861 expensive. The cache should also be indexed based on the arrival 862 underlying interface such that congestion experienced over a 863 first underlying interface does not cause discard of incomplete 864 reassemblies for uncongested underlying interfaces. 866 3. Attacks based on predictable fragment identification values - 867 this threat is mitigated by selecting a suitably random ID value 868 per [RFC7739]. 870 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 871 threat is mitigated by disallowing "tiny fragments" per the OAL 872 fragmentation procedures specified above. 874 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 875 ID) field with only 65535 unique values such that at high data rates 876 the field could wrap and apply to new packets while the fragments of 877 old packets using the same ID are still alive in the network 878 [RFC4963]. However, since the largest OAL fragment that will be sent 879 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 880 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 881 recommendations suggest that such links will have low data rates. 882 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 883 at high data rates is not a concern for IPv6 fragmentation. 885 Finally, [RFC6980] documents fragmentation security concerns for 886 large IPv6 ND messages. These concerns are addressed when OAL 887 fragmentation is used without invoking direct fragmentation of the 888 IPv6 ND message itself. For this reason, OMNI interfaces MUST NOT 889 send IPv6 ND messages larger than the OMNI interface MTU. 891 6. Frame Format 893 The OMNI interface transmits IPv6 packets according to the native 894 frame format of each underlying interface. For example, for 895 Ethernet-compatible interfaces the frame format is specified in 896 [RFC2464], for aeronautical radio interfaces the frame format is 897 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 898 Manual), for tunnels over IPv6 the frame format is specified in 899 [RFC2473], etc. 901 7. Link-Local Addresses (LLAs) 903 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 904 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 905 the MNP assigned to the mobile node, while "ADM-LLAs" include an 906 administratively-unique ID that is guaranteed to be unique on the 907 link. LLAs are configured as follows: 909 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 910 the least-significant 64 bits of the IPv6 link-local prefix 911 fe80::/64, i.e., in the LLA "interface identifier" portion. The 912 prefix length for the LLA is determined by adding 64 to the MNP 913 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 914 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 916 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 917 i.e., the interface identifier consists of 16 '0' bits, followed 918 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 919 prefix length for the LLA is determined by adding 96 to the MNP 920 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 921 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 922 fe80::ffff:c000:0200/120). 924 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 925 uniqueness. The lower 32 bits of the LLA includes a unique 926 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 927 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 928 prefix length is determined by adding 96 to the MSID prefix 929 length. For example, if the prefix length for MSID 0x10012001 is 930 16 then the ADM-LLA prefix length is set to 112 and the LLA is 931 written as fe80::1001:2001/112. The "zero" address for each ADM- 932 LLA prefix is the Subnet-Router anycast address for that prefix 933 [RFC4291]; for example, the Subnet-Router anycast address for 934 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 935 0xff000000 through 0xffffffff is reserved for future use. 937 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 938 used by MNs for the short-term purpose of procuring an actual MNP- 939 LLA upon startup or (re)connecting to the network. MNs may use 940 Temporary LLAs as the IPv6 source address of an RS message in 941 order to request a MNP-LLA from the MS. 943 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 944 MNPs can be allocated from that block ensuring that there is no 945 possibility for overlap between the various LLA constructs discussed 946 above. 948 Since MNP-LLAs are based on the distribution of administratively 949 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 950 administrative assignment, OMNI interfaces set the autoconfiguration 951 variable DupAddrDetectTransmits to 0 [RFC4862]. 953 Temporary LLAs employ optimistic DAD principles [RFC4429] since they 954 are probabilistically unique and their use is short-duration in 955 nature. 957 Note: If future protocol extensions relax the 64-bit boundary in IPv6 958 addressing, the additional prefix bits of an MNP could be encoded in 959 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 960 would therefore still be in bits 64-127, and the remaining bits would 961 appear in bits 16 through 48.) However, the analysis provided in 962 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 963 architecture for the foreseeable future. 965 Note: Even though this document honors the 64-bit boundary in IPv6 966 addressing per [RFC7421], it suggests prefix lengths longer than /64 967 for routing purposes. This effectively extends IPv6 routing 968 determination into the interface identifier portion of the IPv6 969 address, but it does not redefine the 64-bit boundary. 971 8. Unique-Local Addresses (ULAs) 973 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 974 destination addresses in OAL IPv6 encapsulation headers. ULAs are 975 only routable within the scope of a an OMNI domain, and are derived 976 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 977 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 978 Global ID to produce the prefix [ULA]::/48, which is then followed by 979 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 980 specified in Section 3 of [RFC4193]. The statistic uniqueness of the 981 40-bit pseudo-random Global ID allows different OMNI domains to be 982 joined together in the future without requiring OMNI link 983 renumbering. 985 Each OMNI link instance is identified by a value between 0x0000 and 986 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xffff 987 are reserved for future use). For example, OMNI ULAs associated with 988 instance 0 are configured from the prefix [ULA]:0000::/64, instance 1 989 from [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 990 their associated prefix lengths are configured in correspondence with 991 LLAs through stateless prefix translation where "MNP-ULAs" are 992 assigned in correspondence to MNP-LLAs and "ADM-ULAs" are assigned in 993 correspondence to ADM-LLAs. For example, for OMNI link instance 994 [ULA]:1010::/64: 996 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 997 56-bit MNP length is derived by copying the lower 64 bits of the 998 LLA into the lower 64 bits of the ULA as 999 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1000 64 plus the IPv6 MNP length). 1002 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1003 MNP length is derived by simply writing the LLA interface ID into 1004 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1005 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1007 o the ADM-ULA corresponding to fe80::1000/112 is simply 1008 [ULA]:1010::1000/112. 1010 o the ADM-ULA corresponding to fe80::/128 is simply 1011 [ULA]:1010::/128. 1013 o the Temporary ULA corresponding to a Temporary LLA is simply 1014 [ULA]:1010:[64-bit Temporary Interface ID]/128. 1016 o etc. 1018 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1019 link instance. For example, the OMNI interface connected to instance 1020 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1021 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1022 [ULA]:0003::/64) into the local routing system so that applications 1023 can direct traffic according to SBM requirements. 1025 The ULA presents an IPv6 address format that is routable within the 1026 OMNI routing system and can be used to convey link-scoped IPv6 ND 1027 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1028 The OMNI link extends across one or more underling Internetworks to 1029 include all ARs and MSEs. All MNs are also considered to be 1030 connected to the OMNI link, however OAL encapsulation is omitted 1031 whenever possible to conserve bandwidth (see: Section 12). 1033 Each OMNI link can be subdivided into "segments" that often 1034 correspond to different administrative domains or physical 1035 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1036 necessary to support efficient packet forwarding to destinations 1037 located in other OMNI link segments. A full discussion of Segment 1038 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1040 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1041 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1042 however the range could be used for MSP and MNP addressing under 1043 certain limiting conditions (see: Section 9). 1045 9. Global Unicast Addresses (GUAs) 1047 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1048 as Mobility Service Prefixes (MSPs) from which Mobile Network 1049 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1051 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1052 associated regional assigned numbers authority such that the OMNI 1053 domain can be interconnected to the global IPv6 Internet without 1054 causing inconsistencies in the routing system. An OMNI domain could 1055 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1056 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1057 were ever connected to the global IPv6 Internet. 1059 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1060 associated regional assigned numbers authority such that the OMNI 1061 domain can be interconnected to the global IPv4 Internet without 1062 causing routing inconsistencies. An OMNI domain could instead use 1063 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1064 this would require IPv4 NAT if the domain were ever connected to the 1065 global IPv4 Internet. 1067 10. Address Mapping - Unicast 1069 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1070 state and use the link-local address format specified in Section 7. 1071 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1072 over physical underlying interfaces without encapsulation observe the 1073 native underlying interface Source/Target Link-Layer Address Option 1074 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1075 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1076 interfaces via encapsulation do not include S/TLLAOs which were 1077 intended for encoding physical L2 media address formats and not 1078 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1079 for encoding additional interface attributes needed for multilink 1080 coordination. Hence, this document does not define an S/TLLAO format 1081 but instead defines a new option type termed the "OMNI option" 1082 designed for these purposes. 1084 MNs such as aircraft typically have many wireless data link types 1085 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1086 etc.) with diverse performance, cost and availability properties. 1087 The OMNI interface would therefore appear to have multiple L2 1088 connections, and may include information for multiple underlying 1089 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1090 an IPv6 ND option called the OMNI option formatted as shown in 1091 Figure 3: 1093 0 1 2 3 1094 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 1095 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 | Type | Length |T| Preflen | S/T-omIndex | 1097 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1098 | | 1099 ~ Sub-Options ~ 1100 | | 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1103 Figure 3: OMNI Option Format 1105 In this format: 1107 o Type is set to TBD. 1109 o Length is set to the number of 8 octet blocks in the option. 1111 o T is a 1-bit flag set to 1 for Temporary LLAs (otherwise, set to 1112 0) and Preflen is a 7 bit field that determines the length of 1113 prefix associated with an LLA. Values 1 through 127 specify a 1114 prefix length, while the value 0 indicates "unspecified". For 1115 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1116 the IPv6 source LLA and provide the length that the MN is 1117 requesting or asserting to the MS. For IPv6 ND messages sent from 1118 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1119 and indicate the length that the MS is granting to the MN. For 1120 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1121 Preflen provides the length associated with the source/target MN 1122 that is subject of the ND message. 1124 o S/T-omIndex corresponds to the omIndex value for source or target 1125 underlying interface used to convey this IPv6 ND message. OMNI 1126 interfaces MUST number each distinct underlying interface with an 1127 omIndex value between '1' and '255' that represents a MN-specific 1128 8-bit mapping for the actual ifIndex value assigned by network 1129 management [RFC2863] (the omIndex value '0' is reserved for use by 1130 the MS). For RS and NS messages, S/T-omIndex corresponds to the 1131 source underlying interface the message originated from. For RA 1132 and NA messages, S/T-omIndex corresponds to the target underlying 1133 interface that the message is destined to. (For NS messages used 1134 for Neighbor Unreachability Detection (NUD), S/T-omIndex instead 1135 identifies the neighbor's underlying interface to be used as the 1136 target interface to return the NA.) 1138 o Sub-Options is a Variable-length field, of length such that the 1139 complete OMNI Option is an integer multiple of 8 octets long. 1140 Contains one or more Sub-Options, as described in Section 10.1. 1142 The OMNI option may appear in any IPv6 ND message type; it is 1143 processed by interfaces that recognize the option and ignored by all 1144 other interfaces. If multiple OMNI option instances appear in the 1145 same IPv6 ND message, the interface processes the T, Preflen and S/ 1146 T-omIndex fields in the first instance and ignores those fields in 1147 all other instances. The interface processes the Sub-Options of all 1148 OMNI option instances in the consecutive order in which they appear 1149 in the IPv6 ND message, beginning with the first instance and 1150 continuing consecutively through any additional instances to the end 1151 of the message. 1153 The OMNI option(s) in each IPv6 ND message may include full or 1154 partial information for the neighbor. The union of the information 1155 in the most recently received OMNI options is therefore retained, and 1156 the information is aged/removed in conjunction with the corresponding 1157 neighbor cache entry. 1159 10.1. Sub-Options 1161 The OMNI option includes zero or more Sub-Options. Each consecutive 1162 Sub-Option is concatenated immediately after its predecessor. All 1163 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1164 encoded in the following format: 1166 0 1 2 1167 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 1168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1169 | Sub-Type| Sub-length | Sub-Option Data ... 1170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1172 Figure 4: Sub-Option Format 1174 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1175 Options defined in this document are: 1177 Option Name Sub-Type 1178 Pad1 0 1179 PadN 1 1180 Interface Attributes (Type 1) 2 1181 Interface Attributes (Type 2) 3 1182 Traffic Selector 4 1183 Origin Indication 5 1184 MS-Register 6 1185 MS-Release 7 1186 Geo Coordinates 8 1187 DHCPv6 Message 9 1188 HIP Message 10 1190 Figure 5 1192 Sub-Types 11-29 are available for future assignment. Sub-Type 30 1193 is reserved for experimentation, as recommended in [RFC3692]. 1194 Sub-Type 31 is reserved by IANA. 1196 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1197 Option Data (i.e., ranging from 0 to 2047 octets). 1199 o Sub-Option Data is a block of data with format determined by Sub- 1200 Type and length determined by Sub-Length. 1202 Note that Sub-Type and Sub-Length are coded together in network byte 1203 order in two consecutive octets. Note also that Sub-Option Data may 1204 be up to 2047 bytes in length. This allows ample space for encoding 1205 large objects (e.g., ascii character strings, protocol messages, 1206 security codes, etc.), while a single OMNI option is limited to 2048 1207 bytes the same as for any IPv6 ND option. If the Sub-Options to be 1208 coded would cause an OMNI option to exceed 2048 bytes, any remaining 1209 Sub-Options are encoded in additional OMNI options in the consecutive 1210 order of intended processing. Implementations must therefore be 1211 mindful of size limitations, and must refrain from sending IPv6 ND 1212 messages larger than the OMNI interface MTU. 1214 During processing, unrecognized Sub-Options are ignored and the next 1215 Sub-Option processed until the end of the OMNI option is reached. 1217 The following Sub-Option types and formats are defined in this 1218 document: 1220 10.1.1. Pad1 1222 0 1223 0 1 2 3 4 5 6 7 1224 +-+-+-+-+-+-+-+-+ 1225 | S-Type=0|x|x|x| 1226 +-+-+-+-+-+-+-+-+ 1228 Figure 6: Pad1 1230 o Sub-Type is set to 0. If multiple instances appear in OMNI 1231 options of the same message all are processed. 1233 o Sub-Type is followed by three 'x' bits, set randomly on 1234 transmission and ignored on receipt. Pad1 therefore consists of a 1235 whole single octet with the most significant 5 bits set to 0, and 1236 with no Sub-Length or Sub-Option Data fields following. 1238 10.1.2. PadN 1240 0 1 2 1241 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 1242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1243 | S-Type=1| Sub-length=N | N padding octets ... 1244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1246 Figure 7: PadN 1248 o Sub-Type is set to 1. If multiple instances appear in OMNI 1249 options of the same message all are processed. 1251 o Sub-Length is set to N (from 0 to 2047 being the number of padding 1252 octets that follow. 1254 o Sub-Option Data consists of N zero-valued octets. 1256 10.1.3. Interface Attributes (Type 1) 1258 The Interface Attributes (Type 1) sub-option provides a basic set of 1259 attributes for underlying interfaces. Interface Attributes (Type 1) 1260 is deprecated throughout the rest of this specification, and 1261 Interface Attributes (Type 2) (see: Section 10.1.4) are indicated 1262 wherever the term "Interface Attributes" appears without an 1263 associated Type designation. 1265 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1266 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1267 they receive. If an Interface Attributes (Type 1) is included, it 1268 must have the following format: 1270 0 1 2 3 1271 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 1272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1273 | Sub-Type=2| Sub-length=N | omIndex | omType | 1274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1275 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1277 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1279 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1281 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1283 |P56|P57|P58|P59|P60|P61|P62|P63| 1284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1286 Figure 8: Interface Attributes (Type 1) 1288 o Sub-Type is set to 2. If multiple instances with different 1289 omIndex values appear in OMNI option of the same message all are 1290 processed; if multiple instances with the same omIndex value 1291 appear, the first is processed and all others are ignored 1293 o Sub-Length is set to N (from 1 to 2047 that encodes the number of 1294 Sub-Option Data octets that follow. 1296 o omIndex is a 1-octet field containing a value from 0 to 255 1297 identifying the underlying interface for which the attributes 1298 apply. 1300 o omType is a 1-octet field containing a value from 0 to 255 1301 corresponding to the underlying interface identified by omIndex. 1303 o Provider ID is a 1-octet field containing a value from 0 to 255 1304 corresponding to the underlying interface identified by omIndex. 1306 o Link encodes a 4-bit link metric. The value '0' means the link is 1307 DOWN, and the remaining values mean the link is UP with metric 1308 ranging from '1' ("lowest") to '15' ("highest"). 1310 o Resvd is reserved for future use. 1312 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1313 values P[00] through P[63] corresponding to the 64 Differentiated 1314 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1315 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1316 or '3' ("high") to indicate a QoS preference for underlying 1317 interface selection purposes. 1319 10.1.4. Interface Attributes (Type 2) 1321 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1322 information for the multilink conceptual sending algorithm discussed 1323 in Section 12. The L2 information is used for selecting among 1324 potentially multiple candidate underlying interfaces that can be used 1325 to forward packets to the neighbor based on factors such as DSCP 1326 preferences and link quality. Interface Attributes (Type 2) further 1327 includes link-layer address information to be used for either OAL 1328 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1329 can be avoided). 1331 Interface Attributes (Type 2) are the sole Interface Attributes 1332 format in this specification that all OMNI nodes must honor. 1333 Wherever the term "Interface Attributes" occurs throughout this 1334 specification without a "Type" designation, the format given below is 1335 indicated: 1337 0 1 2 3 1338 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 1339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1340 | S-Type=3| Sub-length=N | omIndex | omType | 1341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1342 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1344 | LHS (bits 8 - 31) | ~ 1345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1346 ~ ~ 1347 ~ Link Layer Address (L2ADDR) ~ 1348 ~ ~ 1349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1350 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1352 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1354 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1357 Figure 9: Interface Attributes (Type 2) 1359 o Sub-Type is set to 3. If multiple instances with different 1360 omIndex values appear in OMNI options of the same message all are 1361 processed; if multiple instances with the same omIndex value 1362 appear, the first is processed and all others are ignored. 1364 o Sub-Length is set to N (from 4 to 2047) that encodes the number of 1365 Sub-Option Data octets that follow. 1367 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1368 encoded as follows (note that the first four octets must be 1369 present): 1371 * omIndex is set to an 8-bit integer value corresponding to a 1372 specific underlying interface the same as specified above for 1373 the OMNI option header S/T-omIndex. The OMNI options of a same 1374 message may include multiple Interface Attributes Sub-Options, 1375 with each distinct omIndex value pertaining to a different 1376 underlying interface. The OMNI option will often include an 1377 Interface Attributes Sub-Option with the same omIndex value 1378 that appears in the S/T-omIndex. In that case, the actual 1379 encapsulation address of the received IPv6 ND message should be 1380 compared with the L2ADDR encoded in the Sub-Option (see below); 1381 if the addresses are different (or, if L2ADDR is absent) the 1382 presence of a NAT is assumed. 1384 * omType is set to an 8-bit integer value corresponding to the 1385 underlying interface identified by omIndex. The value 1386 represents an OMNI interface-specific 8-bit mapping for the 1387 actual IANA ifType value registered in the 'IANAifType-MIB' 1388 registry [http://www.iana.org]. 1390 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1391 for the network service provider associated with this omIndex. 1393 * Link encodes a 4-bit link metric. The value '0' means the link 1394 is DOWN, and the remaining values mean the link is UP with 1395 metric ranging from '1' ("lowest") to '15' ("highest"). 1397 * R is reserved for future use. 1399 * API - a 3-bit "Address/Preferences/Indexed" code that 1400 determines the contents of the remainder of the sub-option as 1401 follows: 1403 + When the most significant bit (i.e., "Address") is set to 1, 1404 the SRT, FMT, LHS and L2ADDR fields are included immediately 1405 following the API code; else, they are omitted. 1407 + When the next most significant bit (i.e., "Preferences") is 1408 set to 1, a preferences block is included next; else, it is 1409 omitted. (Note that if "Address" is set the preferences 1410 block immediately follows L2ADDR; else, it immediately 1411 follows the API code.) 1413 + When a preferences block is present and the least 1414 significant bit (i.e., "Indexed") is set to 0, the block is 1415 encoded in "Simplex" form as shown in Figure 8; else it is 1416 encoded in "Indexed" form as discussed below. 1418 * When API indicates that an "Address" is included, the following 1419 fields appear in consecutive order (else, they are omitted): 1421 + SRT - a 5-bit Segment Routing Topology prefix length value 1422 that (when added to 96) determines the prefix length to 1423 apply to the ULA formed from concatenating [ULA*]::/96 with 1424 the 32 bit LHS MSID value that follows. For example, the 1425 value 16 corresponds to the prefix length 112. 1427 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1428 the included Link Layer Address as follows: 1430 - When the most significant bit (i.e., "Framework") is set 1431 to 0, L2ADDR is the INET encapsulation address of a 1432 Proxy/Server; otherwise, it is the address for the 1433 Source/Target itself 1435 - When the next most significant bit (i.e., "Mode") is set 1436 to 0, the Source/Target L2ADDR is on the open INET; 1437 otherwise, it is (likely) located behind one or more 1438 NATs. 1440 - When the least significant bit (i.e., "Type") is set to 1441 0, L2ADDR includes a UDP Port Number followed by an IPv4 1442 address; else, a UDP Port Number followed by an IPv6 1443 address. 1445 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1446 path to the target. When SRT and LHS are both set to 0, the 1447 LHS is considered unspecified in this IPv6 ND message. When 1448 SRT is set to 0 and LHS is non-zero, the prefix length is 1449 set to 128. SRT and LHS together provide guidance to the 1450 OMNI interface forwarding algorithm. Specifically, if SRT/ 1451 LHS is located in the local OMNI link segment then the OMNI 1452 interface can encapsulate according to FMT/L2ADDR (following 1453 any necessary NAT traversal messaging); else, it must 1454 forward according to the OMNI link spanning tree. See 1455 [I-D.templin-intarea-6706bis] for further discussion. 1457 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1458 and identifies the link-layer address (i.e., the 1459 encapsulation address) of the source/target. The UDP Port 1460 Number appears in the first two octets and the IP address 1461 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1462 The Port Number and IP address are recorded in ones- 1463 compliment "obfuscated" form per [RFC4380]. The OMNI 1464 interface forwarding algorithm uses FMT/L2ADDR to determine 1465 the encapsulation address for forwarding when SRT/LHS is 1466 located in the local OMNI link segment. Note that if the 1467 target is behind a NAT, L2ADDR will contain the mapped INET 1468 address stored in the NAT; otherwise, L2ADDR will contain 1469 the native INET information of the target itself. 1471 * When API indicates that "Preferences" are included, a 1472 preferences block appears as the remainder of the Sub-Option as 1473 a series of Bitmaps and P[*] values. In "Simplex" form, the 1474 index for each singleton Bitmap octet is inferred from its 1475 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1476 In "Indexed" form, each Bitmap is preceded by an Index octet 1477 that encodes a value "i" = (0 - 255) as the index for its 1478 companion Bitmap as follows: 1480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1481 | Index=i | Bitmap(i) |P[*] values ... 1482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1484 Figure 10 1486 * The preferences consist of a first (simplex/indexed) Bitmap 1487 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1488 2-bit P[*] values, followed by a second Bitmap (i), followed by 1489 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1490 the bits of each Bitmap(i) that are set to '1'' indicate the 1491 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1492 that follow; if any Bitmap(i) bits are '0', then the 1493 corresponding P[*] block is instead omitted. For example, if 1494 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1495 followed by the block with P[04]-P[07], etc., and ending with 1496 the block with P[28]-P[31] are included (as shown in Figure 8). 1497 The next Bitmap(i) is then consulted with its bits indicating 1498 which P[*] blocks follow, etc. out to the end of the Sub- 1499 Option. 1501 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1502 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1503 preference for underlying interface selection purposes. Not 1504 all P[*] values need to be included in the OMNI option of each 1505 IPv6 ND message received. Any P[*] values represented in an 1506 earlier OMNI option but omitted in the current OMNI option 1507 remain unchanged. Any P[*] values not yet represented in any 1508 OMNI option default to "medium". 1510 * The first 16 P[*] blocks correspond to the 64 Differentiated 1511 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1512 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1513 traffic classifier values P[64], P[65], P[66], etc. See 1514 Appendix A for further discussion and examples. 1516 10.1.5. Traffic Selector 1517 0 1 2 3 1518 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 1519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1520 | S-Type=4| Sub-length=N | omIndex | ~ 1521 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1522 ~ ~ 1523 ~ RFC 6088 Format Traffic Selector ~ 1524 ~ ~ 1525 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1527 Figure 11: Traffic Selector 1529 o Sub-Type is set to 4. If multiple instances appear in OMNI 1530 options of the same message all are processed, i.e., even if the 1531 same omIndex value appears multiple times. 1533 o Sub-Length is set to N (the number of Sub-Option Data octets that 1534 follow). 1536 o Sub-Option Data contains a 1-octet omIndex encoded exactly as 1537 specified in Section 10.1.3, followed by an N-1 octet traffic 1538 selector formatted per [RFC6088] beginning with the "TS Format" 1539 field. The largest traffic selector for a given omIndex is 1540 therefore 2046 octets. 1542 10.1.6. Origin Indication 1544 0 1 2 3 1545 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 1546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1547 | S-Type=5| Sub-length=6/18 | Origin Port Number | 1548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1549 ~ Origin IPv4/IPv6 Address ~ 1550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1552 Figure 12: Origin Indication 1554 o Sub-Type is set to 5. If multiple instances appear in OMNI 1555 options of the same message the first instance is processed and 1556 all others are ignored. 1558 o Sub-Length is set to either 6 or 18; if Sub-Length encodes any 1559 other value, the Sub-Option is ignored. 1561 o Sub-Option Data contains a 2-octet Port Number followed by a 1562 4-octet IPv4 address if Sub-Length encodes 6 or a 16-octet IPv6 1563 address if Sub-Length encodes 18. 1565 10.1.7. MS-Register 1567 0 1 2 3 1568 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 1569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1570 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1572 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1576 ... ... ... ... ... ... 1577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1578 | MSID [n] (bits 16 - 32) | 1579 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1581 Figure 13: MS-Register Sub-option 1583 o Sub-Type is set to 6. If multiple instances appear in OMNI 1584 options of the same message all are processed. Only the first 1585 MAX_MSID values processed (whether in a single instance or 1586 multiple) are retained and all other MSIDs are ignored. 1588 o Sub-Length is set to 4n. 1590 o A list of n 4-octet MSIDs is included in the following 4n octets. 1591 The Anycast MSID value '0' in an RS message MS-Register sub-option 1592 requests the recipient to return the MSID of a nearby MSE in a 1593 corresponding RA response. 1595 10.1.8. MS-Release 1597 0 1 2 3 1598 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 1599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1600 | S-Type=7| Sub-length=4n | MSID[1] (bits 0 - 15) | 1601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1602 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1606 ... ... ... ... ... ... 1607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1608 | MSID [n] (bits 16 - 32) | 1609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1611 Figure 14: MS-Release Sub-option 1613 o Sub-Type is set to 7. If multiple instances appear in OMNI 1614 options of the same message all are processed. Only the first 1615 MAX_MSID values processed (whether in a single instance or 1616 multiple) are retained and all other MSIDs are ignored. 1618 o Sub-Length is set to 4n. 1620 o A list of n 4 octet MSIDs is included in the following 4n octets. 1621 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1622 i.e., only non-zero values are processed. 1624 10.1.9. Geo Coordinates 1626 0 1 2 3 1627 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 1628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1629 | S-Type=8| Sub-length=N | Geo Coordinates 1630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1632 Figure 15: Geo Coordinates Sub-option 1634 o Sub-Type is set to 8. If multiple instances appear in OMNI 1635 options of the same message the first is processed and all others 1636 are ignored. 1638 o Sub-Length is set to N (i.e., the length of the encoded Geo 1639 Coordinates). 1641 o A set of Geo Coordinates up to 2047 octets in length (format TBD). 1642 Includes Latitude/Longitude at a minimum; may also include 1643 additional attributes such as altitude, heading, speed, etc.). 1645 10.1.10. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1647 0 1 2 3 1648 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 1649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1650 | S-Type=9| Sub-length=N | msg-type | id (octet 0) | 1651 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1652 | transaction-id (octets 1-2) | | 1653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1654 | | 1655 . DHCPv6 options . 1656 . (variable number and length) . 1657 | | 1658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1660 Figure 16: DHCPv6 Message Sub-option 1662 o Sub-Type is set to 9. If multiple instances appear in OMNI 1663 options of the same message the first is processed and all others 1664 are ignored. 1666 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1667 beginning with 'msg-type' and continuing to the end of the DHCPv6 1668 options). The length of the entire DHCPv6 message is therefore 1669 restricted to 2047 octets. 1671 o 'msg-type' and 'transaction-id' are coded according to Section 8 1672 of [RFC8415]. 1674 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1675 follows. 1677 10.1.11. Host Identity Protocol (HIP) Message 1679 0 1 2 3 1680 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 1681 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1682 |S-Type=10| Sub-length=N |0| Packet Type |Version| RES.|1| 1683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1684 | Checksum | Controls | 1685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1686 | Sender's Host Identity Tag (HIT) | 1687 | | 1688 | | 1689 | | 1690 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1691 | Receiver's Host Identity Tag (HIT) | 1692 | | 1693 | | 1694 | | 1695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1696 | | 1697 / HIP Parameters / 1698 / / 1699 | | 1700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1702 Figure 17: HIP Message Sub-option 1704 o Sub-Type is set to 10. If multiple instances appear in OMNI 1705 options of the same message the first is processed and all others 1706 are ignored. 1708 o Sub-Length is set to N (i.e., the length of the option in bytes 1709 beginning immediately following the Sub-Length field and extending 1710 to the end of the HIP parameters. 1712 o The HIP message is coded exactly as specified in Section 5 of 1713 [RFC7401], with the exception that the OMNI "Sub-Type" and "Sub- 1714 Length" fields replace the first two header octets of the HIP 1715 message (i.e., the Next Header and Header Length fields). 1717 11. Address Mapping - Multicast 1719 The multicast address mapping of the native underlying interface 1720 applies. The mobile router on board the MN also serves as an IGMP/ 1721 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1722 using the L2 address of the AR as the L2 address for all multicast 1723 packets. 1725 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1726 coordinate with the AR, and *NET L2 elements use MLD snooping 1727 [RFC4541]. 1729 12. Multilink Conceptual Sending Algorithm 1731 The MN's IPv6 layer selects the outbound OMNI interface according to 1732 SBM considerations when forwarding data packets from local or EUN 1733 applications to external correspondents. Each OMNI interface 1734 maintains a neighbor cache the same as for any IPv6 interface, but 1735 with additional state for multilink coordination. Each OMNI 1736 interface maintains default routes via ARs discovered as discussed in 1737 Section 13, and may configure more-specific routes discovered through 1738 means outside the scope of this specification. 1740 After a packet enters the OMNI interface, one or more outbound 1741 underlying interfaces are selected based on PBM traffic attributes, 1742 and one or more neighbor underlying interfaces are selected based on 1743 the receipt of Interface Attributes sub-options in IPv6 ND messages 1744 (see: Figure 8). Underlying interface selection for the nodes own 1745 local interfaces are based on attributes such as DSCP, application 1746 port number, cost, performance, message size, etc. OMNI interface 1747 multilink selections could also be configured to perform replication 1748 across multiple underlying interfaces for increased reliability at 1749 the expense of packet duplication. The set of all Interface 1750 Attributes received in IPv6 ND messages determine the multilink 1751 forwarding profile for selecting the neighbor's underlying 1752 interfaces. 1754 When the OMNI interface sends a packet over a selected outbound 1755 underlying interface, the OAL includes or omits a mid-layer 1756 encapsulation header as necessary as discussed in Section 5 and as 1757 determined by the L2 address information received in Interface 1758 Attributes. The OAL also performs encapsulation when the nearest AR 1759 is located multiple hops away as discussed in Section 13.1. 1761 OMNI interface multilink service designers MUST observe the BCP 1762 guidance in Section 15 [RFC3819] in terms of implications for 1763 reordering when packets from the same flow may be spread across 1764 multiple underlying interfaces having diverse properties. 1766 12.1. Multiple OMNI Interfaces 1768 MNs may connect to multiple independent OMNI links concurrently in 1769 support of SBM. Each OMNI interface is distinguished by its Anycast 1770 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1771 configures a separate OMNI interface for each link so that multiple 1772 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1773 layer. A different Anycast ULA is assigned to each interface, and 1774 the MN injects the service prefixes for the OMNI link instances into 1775 the EUN routing system. 1777 Applications in EUNs can use Segment Routing to select the desired 1778 OMNI interface based on SBM considerations. The Anycast ULA is 1779 written into the IPv6 destination address, and the actual destination 1780 (along with any additional intermediate hops) is written into the 1781 Segment Routing Header. Standard IP routing directs the packets to 1782 the MN's mobile router entity, and the Anycast ULA identifies the 1783 OMNI interface to be used for transmission to the next hop. When the 1784 MN receives the message, it replaces the IPv6 destination address 1785 with the next hop found in the routing header and transmits the 1786 message over the OMNI interface identified by the Anycast ULA. 1788 Multiple distinct OMNI links can therefore be used to support fault 1789 tolerance, load balancing, reliability, etc. The architectural model 1790 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1792 12.2. MN<->AR Traffic Loop Prevention 1794 After an AR has registered an MNP for a MN (see: Section 13), the AR 1795 will forward packets destined to an address within the MNP to the MN. 1796 The MN will under normal circumstances then forward the packet to the 1797 correct destination within its internal networks. 1799 If at some later time the MN loses state (e.g., after a reboot), it 1800 may begin returning packets destined to an MNP address to the AR as 1801 its default router. The AR therefore must drop any packets 1802 originating from the MN and destined to an address within the MN's 1803 registered MNP. To do so, the AR institutes the following check: 1805 o if the IP destination address belongs to a neighbor on the same 1806 OMNI interface, and if the link-layer source address is the same 1807 as one of the neighbor's link-layer addresses, drop the packet. 1809 13. Router Discovery and Prefix Registration 1811 MNs interface with the MS by sending RS messages with OMNI options 1812 under the assumption that one or more AR on the *NET will process the 1813 message and respond. The MN then configures default routes for the 1814 OMNI interface via the discovered ARs as the next hop. The manner in 1815 which the *NET ensures AR coordination is link-specific and outside 1816 the scope of this document (however, considerations for *NETs that do 1817 not provide ARs that recognize the OMNI option are discussed in 1818 Section 18). 1820 For each underlying interface, the MN sends an RS message with an 1821 OMNI option to coordinate with MSEs identified by MSID values. 1822 Example MSID discovery methods are given in [RFC5214] and include 1823 data link login parameters, name service lookups, static 1824 configuration, a static "hosts" file, etc. The MN can also send an 1825 RS with an MS-Register sub-option that includes the Anycast MSID 1826 value '0', i.e., instead of or in addition to any non-zero MSIDs. 1827 When the AR receives an RS with a MSID '0', it selects a nearby MSE 1828 (which may be itself) and returns an RA with the selected MSID in an 1829 MS-Register sub-option. The AR selects only a single wildcard MSE 1830 (i.e., even if the RS MS-Register sub-option included multiple '0' 1831 MSIDs) while also soliciting the MSEs corresponding to any non-zero 1832 MSIDs. 1834 MNs configure OMNI interfaces that observe the properties discussed 1835 in the previous section. The OMNI interface and its underlying 1836 interfaces are said to be in either the "UP" or "DOWN" state 1837 according to administrative actions in conjunction with the interface 1838 connectivity status. An OMNI interface transitions to UP or DOWN 1839 through administrative action and/or through state transitions of the 1840 underlying interfaces. When a first underlying interface transitions 1841 to UP, the OMNI interface also transitions to UP. When all 1842 underlying interfaces transition to DOWN, the OMNI interface also 1843 transitions to DOWN. 1845 When an OMNI interface transitions to UP, the MN sends RS messages to 1846 register its MNP and an initial set of underlying interfaces that are 1847 also UP. The MN sends additional RS messages to refresh lifetimes 1848 and to register/deregister underlying interfaces as they transition 1849 to UP or DOWN. The MN sends initial RS messages over an UP 1850 underlying interface with its MNP-LLA as the source and with 1851 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1852 messages include an OMNI option per Section 10 with a Preflen 1853 assertion, Interface Attributes appropriate for underlying 1854 interfaces, MS-Register/Release sub-options containing MSID values, 1855 and with any other necessary OMNI sub-options (e.g., a DUID sub- 1856 option as an identity for the MN). The S/T-omIndex field is set to 1857 the index of the underlying interface over which the RS message is 1858 sent. 1860 ARs process IPv6 ND messages with OMNI options and act as an MSE 1861 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1862 and create a neighbor cache entry for the MN, then coordinate with 1863 any MSEs named in the Register/Release lists in a manner outside the 1864 scope of this document. When an MSE processes the OMNI information, 1865 it first validates the prefix registration information then injects/ 1866 withdraws the MNP in the routing/mapping system and caches/discards 1867 the new Preflen, MNP and Interface Attributes. The MSE then informs 1868 the AR of registration success/failure, and the AR returns an RA 1869 message to the MN with an OMNI option per Section 10. 1871 The AR returns the RA message via the same underlying interface of 1872 the MN over which the RS was received, and with destination address 1873 set to the MNP-LLA (i.e., unicast), with source address set to its 1874 own LLA, and with an OMNI option with S/T-omIndex set to the value 1875 included in the RS. The OMNI option also includes a Preflen 1876 confirmation, Interface Attributes, MS-Register/Release and any other 1877 necessary OMNI sub-options (e.g., a DUID sub-option as an identity 1878 for the AR). The RA also includes any information for the link, 1879 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 1880 Time and Retrans Timer values, and includes any necessary options 1881 such as: 1883 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1885 o RIOs [RFC4191] with more-specific routes. 1887 o an MTU option that specifies the maximum acceptable packet size 1888 for this underlying interface. 1890 The AR MAY also send periodic and/or event-driven unsolicited RA 1891 messages per [RFC4861]. In that case, the S/T-omIndex field in the 1892 OMNI header of the unsolicited RA message identifies the target 1893 underlying interface of the destination MN. 1895 The AR can combine the information from multiple MSEs into one or 1896 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 1897 Each aggregate RA includes an OMNI option with MS-Register/Release 1898 sub-options with the MSEs represented by the aggregate. If an 1899 aggregate is sent, the RA message contents must consistently 1900 represent the combined information advertised by all represented 1901 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 1902 address, the MN determines the addresses of the represented MSEs by 1903 examining the MS-Register/Release OMNI sub-options. 1905 When the MN receives the RA message, it creates an OMNI interface 1906 neighbor cache entry for each MSID that has confirmed MNP 1907 registration via the L2 address of this AR. If the MN connects to 1908 multiple *NETs, it records the additional L2 AR addresses in each 1909 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1910 then configures a default route via the MSE that returned the RA 1911 message, and assigns the Subnet Router Anycast address corresponding 1912 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 1913 manages its underlying interfaces according to their states as 1914 follows: 1916 o When an underlying interface transitions to UP, the MN sends an RS 1917 over the underlying interface with an OMNI option. The OMNI 1918 option contains at least one Interface Attribute sub-option with 1919 values specific to this underlying interface, and may contain 1920 additional Interface Attributes specific to other underlying 1921 interfaces. The option also includes any MS-Register/Release sub- 1922 options. 1924 o When an underlying interface transitions to DOWN, the MN sends an 1925 RS or unsolicited NA message over any UP underlying interface with 1926 an OMNI option containing an Interface Attribute sub-option for 1927 the DOWN underlying interface with Link set to '0'. The MN sends 1928 an RS when an acknowledgement is required, or an unsolicited NA 1929 when reliability is not thought to be a concern (e.g., if 1930 redundant transmissions are sent on multiple underlying 1931 interfaces). 1933 o When the Router Lifetime for a specific AR nears expiration, the 1934 MN sends an RS over the underlying interface to receive a fresh 1935 RA. If no RA is received, the MN can send RS messages to an 1936 alternate MSID in case the current MSID has failed. If no RS 1937 messages are received even after trying to contact alternate 1938 MSIDs, the MN marks the underlying interface as DOWN. 1940 o When a MN wishes to release from one or more current MSIDs, it 1941 sends an RS or unsolicited NA message over any UP underlying 1942 interfaces with an OMNI option with a Release MSID. Each MSID 1943 then withdraws the MNP from the routing/mapping system and informs 1944 the AR that the release was successful. 1946 o When all of a MNs underlying interfaces have transitioned to DOWN 1947 (or if the prefix registration lifetime expires), any associated 1948 MSEs withdraw the MNP the same as if they had received a message 1949 with a release indication. 1951 The MN is responsible for retrying each RS exchange up to 1952 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1953 seconds until an RA is received. If no RA is received over an UP 1954 underlying interface (i.e., even after attempting to contact 1955 alternate MSEs), the MN declares this underlying interface as DOWN. 1957 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1958 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1959 returns an internally-generated RA message as though the message 1960 originated from an IPv6 router. The internally-generated RA message 1961 contains configuration information that is consistent with the 1962 information received from the RAs generated by the MS. Whether the 1963 OMNI interface IPv6 ND messaging process is initiated from the 1964 receipt of an RS message from the IPv6 layer is an implementation 1965 matter. Some implementations may elect to defer the IPv6 ND 1966 messaging process until an RS is received from the IPv6 layer, while 1967 others may elect to initiate the process proactively. Still other 1968 deployments may elect to administratively disable the ordinary RS/RA 1969 messaging used by the IPv6 layer over the OMNI interface, since they 1970 are not required to drive the internal RS/RA processing. (Note that 1971 this same logic applies to IPv4 implementations that employ ICMP- 1972 based Router Discovery per [RFC1256].) 1974 Note: The Router Lifetime value in RA messages indicates the time 1975 before which the MN must send another RS message over this underlying 1976 interface (e.g., 600 seconds), however that timescale may be 1977 significantly longer than the lifetime the MS has committed to retain 1978 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1979 therefore responsible for keeping MS state alive on a shorter 1980 timescale than the MN is required to do on its own behalf. 1982 Note: On multicast-capable underlying interfaces, MNs should send 1983 periodic unsolicited multicast NA messages and ARs should send 1984 periodic unsolicited multicast RA messages as "beacons" that can be 1985 heard by other nodes on the link. If a node fails to receive a 1986 beacon after a timeout value specific to the link, it can initiate a 1987 unicast exchange to test reachability. 1989 Note: if an AR acting as a proxy forwards a MN's RS message to 1990 another node acting as an MSE using UDP/IP encapsulation, it must use 1991 a distinct UDP source port number for each MN. This allows the MSE 1992 to distinguish different MNs behind the same AR at the link-layer, 1993 whereas the link-layer addresses would otherwise be 1994 indistinguishable. 1996 Note: when an AR acting as an MSE returns an RA to an INET Client, it 1997 includes an OMNI option with an Interface Attributes sub-option with 1998 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 1999 its INET interface. This provides the Client with partition prefix 2000 context regarding the local OMNI link segment. 2002 13.1. Router Discovery in IP Multihop and IPv4-Only Networks 2004 On some *NETs, a MN may be located multiple IP hops away from the 2005 nearest AR. Forwarding through IP multihop *NETs is conducted 2006 through the application of a routing protocol (e.g., a Mobile Ad-hoc 2007 Network (MANET) routing protocol over omni-directional wireless 2008 interfaces, an inter-domain routing protocol in an enterprise 2009 network, etc.). These *NETs could be either IPv6-enabled or 2010 IPv4-only, while IPv4-only *NETs could be either multicast-capable or 2011 unicast-only (note that for IPv4-only *NETs the following procedures 2012 apply for both single-hop and multihop cases). 2014 A MN located potentially multiple *NET hops away from the nearest AR 2015 prepares an RS message with source address set to either its MNP-LLA 2016 or a Temporary LLA, and with destination set to link-scoped All- 2017 Routers multicast the same as discussed above. For IPv6-enabled 2018 *NETs, the MN then encapsulates the message in an IPv6 header with 2019 source address set to the ULA corresponding to the LLA source address 2020 and with destination set to either a unicast or anycast ADM-ULA. For 2021 IPv4-only *NETs, the MN instead encapsulates the RS message in an 2022 IPv4 header with source address set to the node's own IPv4 address 2023 and with destination address set to either the unicast IPv4 address 2024 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 2025 MN then sends the encapsulated RS message via the *NET interface, 2026 where it will be forwarded by zero or more intermediate *NET hops. 2028 When an intermediate *NET hop that participates in the routing 2029 protocol receives the encapsulated RS, it forwards the message 2030 according to its routing tables (note that an intermediate node could 2031 be a fixed infrastructure element or another MN). This process 2032 repeats iteratively until the RS message is received by a penultimate 2033 *NET hop within single-hop communications range of an AR, which 2034 forwards the message to the AR. 2036 When the AR receives the message, it decapsulates the RS and 2037 coordinates with the MS the same as for an ordinary link-local RS, 2038 since the inner Hop Limit will not have been decremented by the 2039 multihop forwarding process. The AR then prepares an RA message with 2040 source address set to its own ADM-LLA and destination address set to 2041 the LLA of the original MN, then encapsulates the message in an IPv4/ 2042 IPv6 header with source address set to its own IPv4/ULA address and 2043 with destination set to the encapsulation source of the RS. 2045 The AR then forwards the message to an *NET node within 2046 communications range, which forwards the message according to its 2047 routing tables to an intermediate node. The multihop forwarding 2048 process within the *NET continues repetitively until the message is 2049 delivered to the original MN, which decapsulates the message and 2050 performs autoconfiguration the same as if it had received the RA 2051 directly from the AR as an on-link neighbor. 2053 Note: An alternate approach to multihop forwarding via IPv6 2054 encapsulation would be to statelessly translate the IPv6 LLAs into 2055 ULAs and forward the messages without encapsulation. This would 2056 violate the [RFC4861] requirement that certain IPv6 ND messages must 2057 use link-local addresses and must not be accepted if received with 2058 Hop Limit less than 255. This document therefore advocates 2059 encapsulation since the overhead is nominal considering the 2060 infrequent nature and small size of IPv6 ND messages. Future 2061 documents may consider encapsulation avoidance through translation 2062 while updating [RFC4861]. 2064 Note: An alternate approach to multihop forwarding via IPv4 2065 encapsulation would be to employ IPv6/IPv4 protocol translation. 2066 However, for IPv6 ND messages the LLAs would be truncated due to 2067 translation and the OMNI Router and Prefix Discovery services would 2068 not be able to function. The use of IPv4 encapsulation is therefore 2069 indicated. 2071 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2072 of a new IPv4 /24 prefix allocation, but this may be difficult to 2073 obtain given IPv4 address exhaustion. An alternative would be to re- 2074 purpose the prefix 192.88.99.0 which has been set aside from its 2075 former use by [RFC7526]. 2077 13.2. MS-Register and MS-Release List Processing 2079 When a MN sends an RS message with an OMNI option via an underlying 2080 interface to an AR, the MN must convey its knowledge of its 2081 currently-associated MSEs. Initially, the MN will have no associated 2082 MSEs and should therefore include an MS-Register sub-option with the 2083 single MSID value 0 which requests the AR to select and assign an 2084 MSE. The AR will then return an RA message with source address set 2085 to the ADM-LLA of the selected MSE. 2087 As the MN activates additional underlying interfaces, it can 2088 optionally include an MS-Register sub-option with MSID value 0, or 2089 with non-zero MSIDs for MSEs discovered from previous RS/RA 2090 exchanges. The MN will thus eventually begin to learn and manage its 2091 currently active set of MSEs, and can register with new MSEs or 2092 release from former MSEs with each successive RS/RA exchange. As the 2093 MN's MSE constituency grows, it alone is responsible for including or 2094 omitting MSIDs in the MS-Register/Release lists it sends in RS 2095 messages. The inclusion or omission of MSIDs determines the MN's 2096 interface to the MS and defines the manner in which MSEs will 2097 respond. The only limiting factor is that the MN should include no 2098 more than MAX_MSID values in each list per each IPv6 ND message, and 2099 should avoid duplication of entries in each list unless it wants to 2100 increase likelihood of control message delivery. 2102 When an AR receives an RS message sent by a MN with an OMNI option, 2103 the option will contain zero or more MS-Register and MS-Release sub- 2104 options containing MSIDs. After processing the OMNI option, the AR 2105 will have a list of zero or more MS-Register MSIDs and a list of zero 2106 or more of MS-Release MSIDs. The AR then processes the lists as 2107 follows: 2109 o For each list, retain the first MAX_MSID values in the list and 2110 discard any additional MSIDs (i.e., even if there are duplicates 2111 within a list). 2113 o Next, for each MSID in the MS-Register list, remove all matching 2114 MSIDs from the MS-Release list. 2116 o Next, proceed according to whether the AR's own MSID or the value 2117 0 appears in the MS-Register list as follows: 2119 * If yes, send an RA message directly back to the MN and send a 2120 proxy copy of the RS message to each additional MSID in the MS- 2121 Register list with the MS-Register/Release lists omitted. 2122 Then, send a uNA message to each MSID in the MS-Release list 2123 with the MS-Register/Release lists omitted and with an OMNI 2124 header with S/T-omIndex set to 0. 2126 * If no, send a proxy copy of the RS message to each additional 2127 MSID in the MS-Register list with the MS-Register list omitted. 2128 For the first MSID, include the original MS-Release list; for 2129 all other MSIDs, omit the MS-Release list. 2131 Each proxy copy of the RS message will include an OMNI option and 2132 encapsulation header with the ADM-ULA of the AR as the source and the 2133 ADM-ULA of the Register MSE as the destination. When the Register 2134 MSE receives the proxy RS message, if the message includes an MS- 2135 Release list the MSE sends a uNA message to each additional MSID in 2136 the Release list. The Register MSE then sends an RA message back to 2137 the (Proxy) AR wrapped in an OMNI encapsulation header with source 2138 and destination addresses reversed, and with RA destination set to 2139 the MNP-LLA of the MN. When the AR receives this RA message, it 2140 sends a proxy copy of the RA to the MN. 2142 Each uNA message (whether send by the first-hop AR or by a Register 2143 MSE) will include an OMNI option and an encapsulation header with the 2144 ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2145 Release ME as the destination. The uNA informs the Release MSE that 2146 its previous relationship with the MN has been released and that the 2147 source of the uNA message is now registered. The Release MSE must 2148 then note that the subject MN of the uNA message is now "departed", 2149 and forward any subsequent packets destined to the MN to the Register 2150 MSE. 2152 Note that it is not an error for the MS-Register/Release lists to 2153 include duplicate entries. If duplicates occur within a list, the AR 2154 will generate multiple proxy RS and/or uNA messages - one for each 2155 copy of the duplicate entries. 2157 13.3. DHCPv6-based Prefix Registration 2159 When a MN is not pre-provisioned with an MNP-LLA (or, when multiple 2160 MNPs are needed), it will require the AR to select MNPs on its behalf 2161 and set up the correct routing state within the MS. The DHCPv6 2162 service [RFC8415] supports this requirement. 2164 When an MN needs to have the AR select MNPs, it sends an RS message 2165 with a Temporary LLA as the source and with DHCPv6 Message sub-option 2166 containing a Client Identifier, one or more IA_PD options and a Rapid 2167 Commit option. The MN also sets the 'msg-type' field to "Solicit", 2168 and includes a 3-octet 'transaction-id'. 2170 When the AR receives the RS message, it extracts the DHCPv6 message 2171 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 2172 a message exchange with the locally-resident DHCPv6 server, which 2173 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2174 (If the AR wishes to defer creation of MN state until the DHCPv6 2175 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2176 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2177 forward/reply exchange with Relay Message and Interface ID options.) 2179 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2180 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2181 sends an RA back to the MN with the DHCPv6 Reply message included in 2182 an OMNI DHCPv6 message sub-option. If the RS message source address 2183 was a Temporary address, the AR includes one of the (newly-created) 2184 MNP-LLAs as the RA destination address. The MN then creates a 2185 default route, assigns Subnet Router Anycast addresses and uses the 2186 RA destination address as its primary MNP-LLA. The MN will then use 2187 this primary MNP-LLA as the source address of any IPv6 ND messages it 2188 sends as long as it retains ownership of the MNP. 2190 Note: After a MN performs a DHCPv6-based prefix registration exchange 2191 with a first AR, it would need to repeat the exchange with each 2192 additional MSE it registers with. In that case, the MN supplies the 2193 MNP delegations received from the first AR in the IA_PD fields of a 2194 DHCPv6 message when it engages the additional MSEs. 2196 14. Secure Redirection 2198 If the *NET link model is multiple access, the AR is responsible for 2199 assuring that address duplication cannot corrupt the neighbor caches 2200 of other nodes on the link. When the MN sends an RS message on a 2201 multiple access *NET link, the AR verifies that the MN is authorized 2202 to use the address and returns an RA with a non-zero Router Lifetime 2203 only if the MN is authorized. 2205 After verifying MN authorization and returning an RA, the AR MAY 2206 return IPv6 ND Redirect messages to direct MNs located on the same 2207 *NET link to exchange packets directly without transiting the AR. In 2208 that case, the MNs can exchange packets according to their unicast L2 2209 addresses discovered from the Redirect message instead of using the 2210 dogleg path through the AR. In some *NET links, however, such direct 2211 communications may be undesirable and continued use of the dogleg 2212 path through the AR may provide better performance. In that case, 2213 the AR can refrain from sending Redirects, and/or MNs can ignore 2214 them. 2216 15. AR and MSE Resilience 2218 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2219 [RFC5798] configurations so that service continuity is maintained 2220 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2221 the (redundant) ARs is currently providing service, and any service 2222 discontinuity will be limited to the failover time supported by VRRP. 2223 Widely deployed public domain implementations of VRRP are available. 2225 MSEs SHOULD use high availability clustering services so that 2226 multiple redundant systems can provide coordinated response to 2227 failures. As with VRRP, widely deployed public domain 2228 implementations of high availability clustering services are 2229 available. Note that special-purpose and expensive dedicated 2230 hardware is not necessary, and public domain implementations can be 2231 used even between lightweight virtual machines in cloud deployments. 2233 16. Detecting and Responding to MSE Failures 2235 In environments where fast recovery from MSE failure is required, ARs 2236 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2237 manner that parallels Bidirectional Forwarding Detection (BFD) 2239 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2240 react to failures so that cached information is re-established 2241 through alternate paths. Proactive NUD control messaging is carried 2242 only over well-connected ground domain networks (i.e., and not low- 2243 end *NET links such as aeronautical radios) and can therefore be 2244 tuned for rapid response. 2246 ARs perform proactive NUD for MSEs for which there are currently 2247 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2248 of the outage by sending multicast RA messages on the *NET interface. 2249 The AR sends RA messages to MNs via the *NET interface with an OMNI 2250 option with a Release ID for the failed MSE, and with destination 2251 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2253 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2254 by small delays [RFC4861]. Any MNs on the *NET interface that have 2255 been using the (now defunct) MSE will receive the RA messages and 2256 associate with a new MSE. 2258 17. Transition Considerations 2260 When a MN connects to an *NET link for the first time, it sends an RS 2261 message with an OMNI option. If the first hop AR recognizes the 2262 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2263 as the destination and with an OMNI option included. The MN then 2264 engages the AR according to the OMNI link model specified above. If 2265 the first hop AR is a legacy IPv6 router, however, it instead returns 2266 an RA message with no OMNI option and with a non-OMNI unicast source 2267 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2268 according to the legacy IPv6 link model and without the OMNI 2269 extensions specified in this document. 2271 If the *NET link model is multiple access, there must be assurance 2272 that address duplication cannot corrupt the neighbor caches of other 2273 nodes on the link. When the MN sends an RS message on a multiple 2274 access *NET link with an LLA source address and an OMNI option, ARs 2275 that recognize the option ensure that the MN is authorized to use the 2276 address and return an RA with a non-zero Router Lifetime only if the 2277 MN is authorized. ARs that do not recognize the option instead 2278 return an RA that makes no statement about the MN's authorization to 2279 use the source address. In that case, the MN should perform 2280 Duplicate Address Detection to ensure that it does not interfere with 2281 other nodes on the link. 2283 An alternative approach for multiple access *NET links to ensure 2284 isolation for MN / AR communications is through L2 address mappings 2285 as discussed in Appendix C. This arrangement imparts a (virtual) 2286 point-to-point link model over the (physical) multiple access link. 2288 18. OMNI Interfaces on the Open Internet 2290 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2291 the open Internet without an OMNI-aware first-hop AR receive RA 2292 messages that do not include an OMNI option, while OMNI interfaces 2293 configured over IPv4-only underlying interfaces do not receive any 2294 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2295 without an OMNI option configure addresses, on-link prefixes, etc. on 2296 the underlying interface that received the RA according to standard 2297 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2298 interfaces configured over IPv4-only underlying interfaces configure 2299 IPv4 address information on the underlying interfaces using 2300 mechanisms such as DHCPv4 [RFC2131]. 2302 OMNI interfaces configured over underlying interfaces that connect to 2303 the open Internet can apply security services such as VPNs to connect 2304 to an MSE, or can establish a direct link to an MSE through some 2305 other means (see Section 4). In environments where an explicit VPN 2306 or direct link may be impractical, OMNI interfaces can instead use 2307 UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2308 authentication per [RFC7401]. 2310 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes the 2311 HIP messages in an OMNI option of an IPv6 RS message and the MSE 2312 responds with HIP messages coded in an OMNI option of an IPv6 RA 2313 message. The standard HIP security services are applied per 2314 [RFC7401], using the RS/RA messages as simple "shipping containers" 2315 to convey the HIP parameters. In that case, a "two-message HIP 2316 exchange" through a single RS/RA exchange may be sufficient for 2317 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2318 two MNs can coordinate directly with one another with HIP messages 2319 coded in OMNI options of IPv6 NS/NA messages. In that case, a four- 2320 message HIP exchange (i.e., two back-to-back NS/NA exchanges) may be 2321 necessary for the two MNs to attain mutual authentication. 2323 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2324 interfaces send control plane messages to interface with the MS, 2325 including RS/RA messages used according to Section 13 and Neighbor 2326 Solicitation (NS) and Neighbor Advertisement (NA) messages used for 2327 address resolution / route optimization (see: 2328 [I-D.templin-intarea-6706bis]). The control plane messages must be 2329 authenticated while data plane messages are delivered the same as for 2330 ordinary best-effort Internet traffic with basic source address-based 2331 data origin verification. Data plane communications via OMNI 2332 interfaces that connect over the open Internet without an explicit 2333 VPN should therefore employ transport- or higher-layer security to 2334 ensure integrity and/or confidentiality. 2336 OMNI interfaces in the open Internet are often located behind NATs. 2337 The OMNI interface accommodates NAT traversal using UDP/IP 2338 encapsulation and the mechanisms discussed in 2339 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2341 19. Time-Varying MNPs 2343 In some use cases, it is desirable, beneficial and efficient for the 2344 MN to receive a constant MNP that travels with the MN wherever it 2345 moves. For example, this would allow air traffic controllers to 2346 easily track aircraft, etc. In other cases, however (e.g., 2347 intelligent transportation systems), the MN may be willing to 2348 sacrifice a modicum of efficiency in order to have time-varying MNPs 2349 that can be changed every so often to defeat adversarial tracking. 2351 The prefix delegation services discussed in Section 13.3 allows OMNI 2352 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2353 use a Temporary LLA as the source address of an RS message with an 2354 OMNI option with DHCPv6 Option sub-options. The MN would then be 2355 obligated to renumber its internal networks whenever its MNP (and 2356 therefore also its OMNI address) changes. This should not present a 2357 challenge for MNs with automated network renumbering services, 2358 however presents limits for the durations of ongoing sessions that 2359 would prefer to use a constant address. 2361 20. Node Identification 2363 MNs and MSEs that connect over the open Internet generate a Host 2364 Identity Tag (HIT) using the procedures specified in [RFC7401] and 2365 use the value as a robust general-purpose node ID. Emerging work on 2366 Hierarchical HITs (HHITs) [I-D.ietf-drip-rid] may also produce node 2367 IDs for use in specific domains such as the Unmanned (Air) Traffic 2368 Management (UTM) service for Unmanned Air Systems (UAS). 2370 After generating a (H)HIT, the node may use it in both HIP and DHCPv6 2371 protocol message exchanges. In the latter case, the (H)HIT is coded 2372 as a DHCP Unique IDentifer (DUID) using the DUID-EN format with 2373 enterprise number 45282 registered to "LinkUp Networks" in the IANA 2374 Private Enterprise Numbers registry. The DUID-EN has the following 2375 format: 2377 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 2378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2379 | DUID-Type (2) | EN (high bits == 0) | 2380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2381 | EN (low bits = 45282) | | 2382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 2383 . (Hierarchical) Host Identity Tag (128 bits) . 2384 . . 2385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2387 Figure 18: DUID-EN for (H)HIT Format 2389 This document therefore permanently associates Private Enterprise 2390 Number 45282 with the (H)HIT DUID format shown in Figure 18. 2392 When a MN is truly outside the context of any infrastructure, it may 2393 have no MNP information at all. In that case, it may be able to use 2394 its (H)HIT as the IPv6 source address in packets used for ongoing 2395 communications with other vehicles in V2V scenarios. The (H)HIT 2396 could also be propagated into the multihop routing protocol tables of 2397 (collective) Vehicular Ad-hoc Networks (VANETs) using only the 2398 vehicles themselves as communications relays. 2400 21. IANA Considerations 2402 The IANA has assigned a 4-octet Private Enterprise Number (PEN) code 2403 "45282" in the "enterprise-numbers" registry. This document is the 2404 normative reference for using this code in DHCP Unique IDentifiers 2405 based on Enterprise Numbers (DUID-EN) for (Hierarchical) Host 2406 Identity Tags ((H)HITs) (see: Section 20). 2408 The IANA is instructed to allocate an official Type number TBD from 2409 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2410 option. Implementations set Type to 253 as an interim value 2411 [RFC4727]. 2413 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2414 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2415 read as follows: 2417 Code Name Reference 2418 --- ---- --------- 2419 0 Diagnostic Packet Too Big [RFC4443] 2420 1 Advisory Packet Too Big [RFCXXXX] 2422 Figure 19: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2424 The IANA is instructed to allocate one Ethernet unicast address TBD2 2425 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2426 Address Block - Unicast Use". 2428 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 2429 instructed to create and maintain a new registry entitled "OMNI 2430 option Sub-Type values". Initial values for the OMNI option Sub-Type 2431 values registry are given below; future assignments are to be made 2432 through Expert Review [RFC8126]. 2434 Value Sub-Type name Reference 2435 ----- ------------- ---------- 2436 0 Pad1 [RFCXXXX] 2437 1 PadN [RFCXXXX] 2438 2 Interface Attributes (Type 1) [RFCXXXX] 2439 3 Interface Attributes (Type 2) [RFCXXXX] 2440 4 Traffic Selector [RFCXXXX] 2441 5 Origin Indication [RFCXXXX] 2442 6 MS-Register [RFCXXXX] 2443 7 MS-Release [RFCXXXX] 2444 8 Geo Coordinates [RFCXXXX] 2445 9 DHCPv6 Message [RFCXXXX] 2446 10 HIP Message [RFCXXXX] 2447 11-29 Unassigned 2448 30 Experimental [RFCXXXX] 2449 31 Reserved [RFCXXXX] 2451 Figure 20: OMNI Option Sub-Type Values 2453 22. Security Considerations 2455 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2456 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2457 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2458 confirmation and/or time synchronization is needed. 2460 MN OMNI interfaces configured over secured ANET interfaces inherit 2461 the physical and/or link-layer security properties (i.e., "protected 2462 spectrum") of the connected ANETs. MN OMNI interfaces configured 2463 over open INET interfaces can use symmetric securing services such as 2464 VPNs or can by some other means establish a direct link. When a VPN 2465 or direct link may be impractical, however, the security services 2466 specified in [RFC7401] can be employed. While the OMNI link protects 2467 control plane messaging, applications must still employ end-to-end 2468 transport- or higher-layer security services to protect the data 2469 plane. 2471 Strong network layer security for control plane messages and 2472 forwarding path integrity for data plane messages between MSEs MUST 2473 be supported. In one example, the AERO service 2474 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 2475 and secures the links in the spanning tree with network layer 2476 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 2477 plane messages are then constrained to travel only over the secured 2478 spanning tree paths and are therefore protected from attack or 2479 eavesdropping. Since data plane messages can travel over route 2480 optimized paths that do not strictly follow the spanning tree, 2481 however, end-to-end transport- or higher-layer security services are 2482 still required. 2484 Identity-based key verification infrastructure services such as iPSK 2485 may be necessary for verifying the identities claimed by MNs. This 2486 requirement should be harmonized with the manner in which (H)HITs are 2487 attested in a given operational environment. 2489 Security considerations for specific access network interface types 2490 are covered under the corresponding IP-over-(foo) specification 2491 (e.g., [RFC2464], [RFC2492], etc.). 2493 Security considerations for IPv6 fragmentation and reassembly are 2494 discussed in Section 5.1. 2496 23. Implementation Status 2498 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2499 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2500 Newer specification versions will be tagged in upcoming releases. 2501 First public release expected before the end of 2020. 2503 24. Acknowledgements 2505 The first version of this document was prepared per the consensus 2506 decision at the 7th Conference of the International Civil Aviation 2507 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2508 2019. Consensus to take the document forward to the IETF was reached 2509 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2510 Attendees and contributors included: Guray Acar, Danny Bharj, 2511 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2512 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2513 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2514 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2515 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2516 Fryderyk Wrobel and Dongsong Zeng. 2518 The following individuals are acknowledged for their useful comments: 2519 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 2520 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are especially 2521 recognized for their many helpful ideas and suggestions. Madhuri 2522 Madhava Badgandi, Sean Dickson, Don Dillenburg, Joe Dudkowski, 2523 Vijayasarathy Rajagopalan and Katherine Tran are acknowledged for 2524 their hard work on the implementation and technical insights that led 2525 to improvements for the spec. 2527 Discussions on the IETF 6man and atn mailing lists during the fall of 2528 2020 suggested additional points to consider. The authors gratefully 2529 acknowledge the list members who contributed valuable insights 2530 through those discussions. Eric Vyncke and Erik Kline were the 2531 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2532 at the time the document was developed; they are all gratefully 2533 acknowledged for their many helpful insights. 2535 This work is aligned with the NASA Safe Autonomous Systems Operation 2536 (SASO) program under NASA contract number NNA16BD84C. 2538 This work is aligned with the FAA as per the SE2025 contract number 2539 DTFAWA-15-D-00030. 2541 This work is aligned with the Boeing Information Technology (BIT) 2542 Mobility Vision Lab (MVL) program. 2544 25. References 2546 25.1. Normative References 2548 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2549 DOI 10.17487/RFC0791, September 1981, 2550 . 2552 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2553 Requirement Levels", BCP 14, RFC 2119, 2554 DOI 10.17487/RFC2119, March 1997, 2555 . 2557 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2558 "Definition of the Differentiated Services Field (DS 2559 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2560 DOI 10.17487/RFC2474, December 1998, 2561 . 2563 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2564 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2565 DOI 10.17487/RFC3971, March 2005, 2566 . 2568 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2569 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2570 November 2005, . 2572 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2573 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2574 . 2576 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2577 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2578 2006, . 2580 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2581 Control Message Protocol (ICMPv6) for the Internet 2582 Protocol Version 6 (IPv6) Specification", STD 89, 2583 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2584 . 2586 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2587 ICMPv6, UDP, and TCP Headers", RFC 4727, 2588 DOI 10.17487/RFC4727, November 2006, 2589 . 2591 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2592 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2593 DOI 10.17487/RFC4861, September 2007, 2594 . 2596 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2597 Address Autoconfiguration", RFC 4862, 2598 DOI 10.17487/RFC4862, September 2007, 2599 . 2601 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2602 "Traffic Selectors for Flow Bindings", RFC 6088, 2603 DOI 10.17487/RFC6088, January 2011, 2604 . 2606 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 2607 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 2608 RFC 7401, DOI 10.17487/RFC7401, April 2015, 2609 . 2611 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2612 Hosts in a Multi-Prefix Network", RFC 8028, 2613 DOI 10.17487/RFC8028, November 2016, 2614 . 2616 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2617 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2618 May 2017, . 2620 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2621 (IPv6) Specification", STD 86, RFC 8200, 2622 DOI 10.17487/RFC8200, July 2017, 2623 . 2625 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2626 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2627 DOI 10.17487/RFC8201, July 2017, 2628 . 2630 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2631 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2632 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2633 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2634 . 2636 25.2. Informative References 2638 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2639 Interface for Civil Aviation, IETF Liaison Statement 2640 #1676, https://datatracker.ietf.org/liaison/1676/", March 2641 2020. 2643 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2644 Aeronautical Telecommunication Network (ATN) using 2645 Internet Protocol Suite (IPS) Standards and Protocol), 2646 Draft Edition 3 (work-in-progress)", December 2020. 2648 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2649 Interface (FDDI), IEEE Transactions on Communications", 2650 August 1990. 2652 [I-D.ietf-6man-rfc4941bis] 2653 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2654 "Temporary Address Extensions for Stateless Address 2655 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2656 (work in progress), November 2020. 2658 [I-D.ietf-drip-rid] 2659 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 2660 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 2661 progress), December 2020. 2663 [I-D.ietf-intarea-tunnels] 2664 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2665 Architecture", draft-ietf-intarea-tunnels-10 (work in 2666 progress), September 2019. 2668 [I-D.ietf-ipwave-vehicular-networking] 2669 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2670 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2671 ipwave-vehicular-networking-19 (work in progress), July 2672 2020. 2674 [I-D.templin-6man-dhcpv6-ndopt] 2675 Templin, F., "A Unified Stateful/Stateless Configuration 2676 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 2677 (work in progress), January 2021. 2679 [I-D.templin-6man-lla-type] 2680 Templin, F., "The IPv6 Link-Local Address Type Field", 2681 draft-templin-6man-lla-type-02 (work in progress), 2682 November 2020. 2684 [I-D.templin-intarea-6706bis] 2685 Templin, F., "Asymmetric Extended Route Optimization 2686 (AERO)", draft-templin-intarea-6706bis-87 (work in 2687 progress), January 2021. 2689 [IPV4-GUA] 2690 Postel, J., "IPv4 Address Space Registry, 2691 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2692 address-space.xhtml", December 2020. 2694 [IPV6-GUA] 2695 Postel, J., "IPv6 Global Unicast Address Assignments, 2696 https://www.iana.org/assignments/ipv6-unicast-address- 2697 assignments/ipv6-unicast-address-assignments.xhtml", 2698 December 2020. 2700 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2701 Communication Layers", STD 3, RFC 1122, 2702 DOI 10.17487/RFC1122, October 1989, 2703 . 2705 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2706 DOI 10.17487/RFC1191, November 1990, 2707 . 2709 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2710 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2711 . 2713 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2714 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2715 . 2717 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2718 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2719 . 2721 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2722 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2723 . 2725 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2726 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2727 December 1998, . 2729 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2730 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2731 . 2733 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2734 Domains without Explicit Tunnels", RFC 2529, 2735 DOI 10.17487/RFC2529, March 1999, 2736 . 2738 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2739 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2740 . 2742 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2743 DOI 10.17487/RFC3330, September 2002, 2744 . 2746 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2747 Considered Useful", BCP 82, RFC 3692, 2748 DOI 10.17487/RFC3692, January 2004, 2749 . 2751 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2752 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2753 DOI 10.17487/RFC3810, June 2004, 2754 . 2756 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2757 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2758 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2759 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2760 . 2762 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2763 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2764 2004, . 2766 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2767 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2768 DOI 10.17487/RFC4271, January 2006, 2769 . 2771 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2772 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2773 December 2005, . 2775 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2776 Network Address Translations (NATs)", RFC 4380, 2777 DOI 10.17487/RFC4380, February 2006, 2778 . 2780 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2781 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2782 2006, . 2784 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2785 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2786 . 2788 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2789 "Considerations for Internet Group Management Protocol 2790 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2791 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2792 . 2794 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2795 "Internet Group Management Protocol (IGMP) / Multicast 2796 Listener Discovery (MLD)-Based Multicast Forwarding 2797 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2798 August 2006, . 2800 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2801 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2802 . 2804 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2805 Errors at High Data Rates", RFC 4963, 2806 DOI 10.17487/RFC4963, July 2007, 2807 . 2809 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2810 Advertisement Flags Option", RFC 5175, 2811 DOI 10.17487/RFC5175, March 2008, 2812 . 2814 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2815 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2816 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2817 . 2819 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2820 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2821 DOI 10.17487/RFC5214, March 2008, 2822 . 2824 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2825 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2826 . 2828 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2829 Version 3 for IPv4 and IPv6", RFC 5798, 2830 DOI 10.17487/RFC5798, March 2010, 2831 . 2833 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2834 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2835 . 2837 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2838 DOI 10.17487/RFC6081, January 2011, 2839 . 2841 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2842 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2843 DOI 10.17487/RFC6221, May 2011, 2844 . 2846 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2847 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2848 DOI 10.17487/RFC6355, August 2011, 2849 . 2851 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2852 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2853 2012, . 2855 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 2856 with IPv6 Neighbor Discovery", RFC 6980, 2857 DOI 10.17487/RFC6980, August 2013, 2858 . 2860 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2861 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2862 DOI 10.17487/RFC7084, November 2013, 2863 . 2865 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2866 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2867 Boundary in IPv6 Addressing", RFC 7421, 2868 DOI 10.17487/RFC7421, January 2015, 2869 . 2871 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 2872 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 2873 DOI 10.17487/RFC7526, May 2015, 2874 . 2876 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2877 DOI 10.17487/RFC7542, May 2015, 2878 . 2880 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2881 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2882 February 2016, . 2884 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2885 Support for IP Hosts with Multi-Access Support", RFC 7847, 2886 DOI 10.17487/RFC7847, May 2016, 2887 . 2889 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2890 Writing an IANA Considerations Section in RFCs", BCP 26, 2891 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2892 . 2894 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2895 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2896 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2897 July 2018, . 2899 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2900 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2901 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2902 . 2904 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2905 and F. Gont, "IP Fragmentation Considered Fragile", 2906 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2907 . 2909 Appendix A. Interface Attribute Preferences Bitmap Encoding 2911 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 2912 encoding to specific Internetworks such as the Aeronautical 2913 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2914 may include link selection preferences based on other traffic 2915 classifiers (e.g., transport port numbers, etc.) in addition to the 2916 existing DSCP-based preferences. Nodes on specific Internetworks 2917 maintain a map of traffic classifiers to additional P[*] preference 2918 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2919 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2921 Implementations use Simplex or Indexed encoding formats for P[*] 2922 encoding in order to encode a given set of traffic classifiers in the 2923 most efficient way. Some use cases may be more efficiently coded 2924 using Simplex form, while others may be more efficient using Indexed. 2925 Once a format is selected for preparation of a single Interface 2926 Attribute the same format must be used for the entire Interface 2927 Attribute sub-option. Different sub-options may use different 2928 formats. 2930 The following figures show coding examples for various Simplex and 2931 Indexed formats: 2933 0 1 2 3 2934 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 2935 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2936 | Sub-Type=3| Sub-length=N | omIndex | omType | 2937 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2938 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 2939 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2940 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2941 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2942 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2943 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2944 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2946 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2948 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2949 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2951 Figure 21: Example 1: Dense Simplex Encoding 2953 0 1 2 3 2954 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 2955 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2956 | Sub-Type=3| Sub-length=N | omIndex | omType | 2957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2958 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2960 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2961 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2962 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2963 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2964 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2966 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2967 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2968 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2969 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2970 |Bitmap(10)=0x00| ... 2971 +-+-+-+-+-+-+-+-+-+-+- 2973 Figure 22: Example 2: Sparse Simplex Encoding 2975 0 1 2 3 2976 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 2977 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2978 | Sub-Type=3| Sub-length=N | omIndex | omType | 2979 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2980 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 2981 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2982 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2983 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2984 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2986 | Bitmap = 0x01 |796|797|798|799| ... 2987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2989 Figure 23: Example 3: Indexed Encoding 2991 Appendix B. VDL Mode 2 Considerations 2993 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2994 (VDLM2) that specifies an essential radio frequency data link service 2995 for aircraft and ground stations in worldwide civil aviation air 2996 traffic management. The VDLM2 link type is "multicast capable" 2997 [RFC4861], but with considerable differences from common multicast 2998 links such as Ethernet and IEEE 802.11. 3000 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3001 magnitude less than most modern wireless networking gear. Second, 3002 due to the low available link bandwidth only VDLM2 ground stations 3003 (i.e., and not aircraft) are permitted to send broadcasts, and even 3004 so only as compact layer 2 "beacons". Third, aircraft employ the 3005 services of ground stations by performing unicast RS/RA exchanges 3006 upon receipt of beacons instead of listening for multicast RA 3007 messages and/or sending multicast RS messages. 3009 This beacon-oriented unicast RS/RA approach is necessary to conserve 3010 the already-scarce available link bandwidth. Moreover, since the 3011 numbers of beaconing ground stations operating within a given spatial 3012 range must be kept as sparse as possible, it would not be feasible to 3013 have different classes of ground stations within the same region 3014 observing different protocols. It is therefore highly desirable that 3015 all ground stations observe a common language of RS/RA as specified 3016 in this document. 3018 Note that links of this nature may benefit from compression 3019 techniques that reduce the bandwidth necessary for conveying the same 3020 amount of data. The IETF lpwan working group is considering possible 3021 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3023 Appendix C. MN / AR Isolation Through L2 Address Mapping 3025 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3026 unicast link-scoped IPv6 destination address. However, IPv6 ND 3027 messaging should be coordinated between the MN and AR only without 3028 invoking other nodes on the *NET. This implies that MN / AR control 3029 messaging should be isolated and not overheard by other nodes on the 3030 link. 3032 To support MN / AR isolation on some *NET links, ARs can maintain an 3033 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3034 *NETs, this specification reserves one Ethernet unicast address TBD2 3035 (see: Section 21). For non-Ethernet statically-addressed *NETs, 3036 MSADDR is reserved per the assigned numbers authority for the *NET 3037 addressing space. For still other *NETs, MSADDR may be dynamically 3038 discovered through other means, e.g., L2 beacons. 3040 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3041 both multicast and unicast) to MSADDR instead of to an ordinary 3042 unicast or multicast L2 address. In this way, all of the MN's IPv6 3043 ND messages will be received by ARs that are configured to accept 3044 packets destined to MSADDR. Note that multiple ARs on the link could 3045 be configured to accept packets destined to MSADDR, e.g., as a basis 3046 for supporting redundancy. 3048 Therefore, ARs must accept and process packets destined to MSADDR, 3049 while all other devices must not process packets destined to MSADDR. 3050 This model has well-established operational experience in Proxy 3051 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3053 Appendix D. Change Log 3055 << RFC Editor - remove prior to publication >> 3057 Differences from draft-templin-6man-omni-interface-35 to draft- 3058 templin-6man-omni-interface-36: 3060 o Major clarifications on aspects such as "hard/soft" PTB error 3061 messages 3063 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3064 be used in the data plane. 3066 Differences from draft-templin-6man-omni-interface-31 to draft- 3067 templin-6man-omni-interface-32: 3069 o MTU 3070 o Support for multi-hop ANETS such as ISATAP. 3072 Differences from draft-templin-6man-omni-interface-29 to draft- 3073 templin-6man-omni-interface-30: 3075 o Moved link-layer addressing information into the OMNI option on a 3076 per-ifIndex basis 3078 o Renamed "ifIndex-tuple" to "Interface Attributes" 3080 Differences from draft-templin-6man-omni-interface-27 to draft- 3081 templin-6man-omni-interface-28: 3083 o Updates based on implementation experience. 3085 Differences from draft-templin-6man-omni-interface-25 to draft- 3086 templin-6man-omni-interface-26: 3088 o Further clarification on "aggregate" RA messages. 3090 o Expanded Security Considerations to discuss expectations for 3091 security in the Mobility Service. 3093 Differences from draft-templin-6man-omni-interface-20 to draft- 3094 templin-6man-omni-interface-21: 3096 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3097 (PBM). 3099 Differences from draft-templin-6man-omni-interface-18 to draft- 3100 templin-6man-omni-interface-19: 3102 o SEND/CGA. 3104 Differences from draft-templin-6man-omni-interface-17 to draft- 3105 templin-6man-omni-interface-18: 3107 o Teredo 3109 Differences from draft-templin-6man-omni-interface-14 to draft- 3110 templin-6man-omni-interface-15: 3112 o Prefix length discussions removed. 3114 Differences from draft-templin-6man-omni-interface-12 to draft- 3115 templin-6man-omni-interface-13: 3117 o Teredo 3118 Differences from draft-templin-6man-omni-interface-11 to draft- 3119 templin-6man-omni-interface-12: 3121 o Major simplifications and clarifications on MTU and fragmentation. 3123 o Document now updates RFC4443 and RFC8201. 3125 Differences from draft-templin-6man-omni-interface-10 to draft- 3126 templin-6man-omni-interface-11: 3128 o Removed /64 assumption, resulting in new OMNI address format. 3130 Differences from draft-templin-6man-omni-interface-07 to draft- 3131 templin-6man-omni-interface-08: 3133 o OMNI MNs in the open Internet 3135 Differences from draft-templin-6man-omni-interface-06 to draft- 3136 templin-6man-omni-interface-07: 3138 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3139 L2 addressing. 3141 o Expanded "Transition Considerations". 3143 Differences from draft-templin-6man-omni-interface-05 to draft- 3144 templin-6man-omni-interface-06: 3146 o Brought back OMNI option "R" flag, and discussed its use. 3148 Differences from draft-templin-6man-omni-interface-04 to draft- 3149 templin-6man-omni-interface-05: 3151 o Transition considerations, and overhaul of RS/RA addressing with 3152 the inclusion of MSE addresses within the OMNI option instead of 3153 as RS/RA addresses (developed under FAA SE2025 contract number 3154 DTFAWA-15-D-00030). 3156 Differences from draft-templin-6man-omni-interface-02 to draft- 3157 templin-6man-omni-interface-03: 3159 o Added "advisory PTB messages" under FAA SE2025 contract number 3160 DTFAWA-15-D-00030. 3162 Differences from draft-templin-6man-omni-interface-01 to draft- 3163 templin-6man-omni-interface-02: 3165 o Removed "Primary" flag and supporting text. 3167 o Clarified that "Router Lifetime" applies to each ANET interface 3168 independently, and that the union of all ANET interface Router 3169 Lifetimes determines MSE lifetime. 3171 Differences from draft-templin-6man-omni-interface-00 to draft- 3172 templin-6man-omni-interface-01: 3174 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3175 for future use (most likely as "pseudo-multicast"). 3177 o Non-normative discussion of alternate OMNI LLA construction form 3178 made possible if the 64-bit assumption were relaxed. 3180 First draft version (draft-templin-atn-aero-interface-00): 3182 o Draft based on consensus decision of ICAO Working Group I Mobility 3183 Subgroup March 22, 2019. 3185 Authors' Addresses 3187 Fred L. Templin (editor) 3188 The Boeing Company 3189 P.O. Box 3707 3190 Seattle, WA 98124 3191 USA 3193 Email: fltemplin@acm.org 3195 Tony Whyman 3196 MWA Ltd c/o Inmarsat Global Ltd 3197 99 City Road 3198 London EC1Y 1AX 3199 England 3201 Email: tony.whyman@mccallumwhyman.com