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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 February 5, 2021 7 Expires: August 9, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-77 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 August 9, 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 5.2. OAL "Super-Packet" Packing . . . . . . . . . . . . . . . 20 65 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 22 66 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 22 67 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 23 68 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 25 69 10. Node Identification . . . . . . . . . . . . . . . . . . . . . 26 70 11. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 26 71 11.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 28 72 11.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 30 73 11.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 30 74 11.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 31 75 11.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 32 76 11.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 36 77 11.1.6. MS-Register . . . . . . . . . . . . . . . . . . . . 37 78 11.1.7. MS-Release . . . . . . . . . . . . . . . . . . . . . 38 79 11.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 38 80 11.1.9. Dynamic Host Configuration Protocol for IPv6 81 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 39 82 11.1.10. Host Identity Protocol (HIP) Message . . . . . . . . 40 83 11.1.11. Node Identification . . . . . . . . . . . . . . . . 41 84 11.1.12. Sub-Type Extension . . . . . . . . . . . . . . . . . 42 85 12. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 44 86 13. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 44 87 13.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 45 88 13.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 45 89 14. Router Discovery and Prefix Registration . . . . . . . . . . 46 90 14.1. Router Discovery in IP Multihop and IPv4-Only Networks . 50 91 14.2. MS-Register and MS-Release List Processing . . . . . . . 52 92 14.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 53 93 15. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 54 94 16. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 55 95 17. Detecting and Responding to MSE Failures . . . . . . . . . . 55 96 18. Transition Considerations . . . . . . . . . . . . . . . . . . 56 97 19. OMNI Interfaces on Open Internetworks . . . . . . . . . . . . 56 98 20. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 58 99 21. (H)HITs and Temporary ULAs . . . . . . . . . . . . . . . . . 58 100 22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59 101 23. Security Considerations . . . . . . . . . . . . . . . . . . . 61 102 24. Implementation Status . . . . . . . . . . . . . . . . . . . . 62 103 25. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 62 104 26. References . . . . . . . . . . . . . . . . . . . . . . . . . 63 105 26.1. Normative References . . . . . . . . . . . . . . . . . . 63 106 26.2. Informative References . . . . . . . . . . . . . . . . . 65 107 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 71 108 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 72 109 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 73 110 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 74 111 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 76 113 1. Introduction 115 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 116 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 117 pedestrians with cellphones, etc.) often have multiple interface 118 connections to wireless and/or wired-link data links used for 119 communicating with networked correspondents. These data links may 120 have diverse performance, cost and availability properties that can 121 change dynamically according to mobility patterns, flight phases, 122 proximity to infrastructure, etc. MNs coordinate their data links in 123 a discipline known as "multilink", in which a single virtual 124 interface is configured over the node's underlying interface 125 connections to the data links. 127 The MN configures a virtual interface (termed the "Overlay Multilink 128 Network (OMNI) interface") as a thin layer over the underlying 129 interfaces. The OMNI interface is therefore the only interface 130 abstraction exposed to the IP layer and behaves according to the Non- 131 Broadcast, Multiple Access (NBMA) interface principle, while 132 underlying interfaces appear as link layer communication channels in 133 the architecture. The OMNI interface connects to a virtual overlay 134 service known as the "OMNI link". The OMNI link spans one or more 135 Internetworks that may include private-use infrastructures and/or the 136 global public Internet itself. 138 Each MN receives a Mobile Network Prefix (MNP) for numbering 139 downstream-attached End User Networks (EUNs) independently of the 140 access network data links selected for data transport. The MN 141 performs router discovery over the OMNI interface (i.e., similar to 142 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 143 behalf of its EUNs. The router discovery process is iterated over 144 each of the OMNI interface's underlying interfaces in order to 145 register per-link parameters (see Section 14). 147 The OMNI interface provides a multilink nexus for exchanging inbound 148 and outbound traffic via the correct underlying interface(s). The IP 149 layer sees the OMNI interface as a point of connection to the OMNI 150 link. Each OMNI link has one or more associated Mobility Service 151 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 152 prefixes from which OMNI link MNPs are derived. If there are 153 multiple OMNI links, the IPv6 layer will see multiple OMNI 154 interfaces. 156 MNs may connect to multiple distinct OMNI links within the same OMNI 157 domain by configuring multiple OMNI interfaces, e.g., omni0, omni1, 158 omni2, etc. Each OMNI interface is configured over a set of 159 underlying interfaces and provides a nexus for Safety-Based Multilink 160 (SBM) operation. Each OMNI interface within the same OMNI domain 161 configures a common ULA prefix [ULA]::/48, and configures a unique 162 16-bit Subnet ID '*' to construct the sub-prefix [ULA*]::/64 (see: 163 Section 8). The IP layer applies SBM routing to select an OMNI 164 interface, which then applies Performance-Based Multilink (PBM) to 165 select the correct underlying interface. Applications can apply 166 Segment Routing [RFC8402] to select independent SBM topologies for 167 fault tolerance. 169 The OMNI interface interacts with a network-based Mobility Service 170 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 171 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 172 track MN movements and represent their MNPs in a global routing or 173 mapping system. 175 Many OMNI use cases have been proposed. In particular, the 176 International Civil Aviation Organization (ICAO) Working Group-I 177 Mobility Subgroup is developing a future Aeronautical 178 Telecommunications Network with Internet Protocol Services (ATN/IPS) 179 and has issued a liaison statement requesting IETF adoption [ATN] in 180 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 181 in Vehicular Environments (ipwave) working group has further included 182 problem statement and use case analysis for OMNI in a document now in 183 AD evaluation for RFC publication 184 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 185 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 186 programs that examine commercial aviation, Urban Air Mobility (UAM) 187 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 188 represent another large class of potential OMNI users. 190 This document specifies the transmission of IP packets and MN/MS 191 control messages over OMNI interfaces. The OMNI interface supports 192 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 193 as the network layer in the data plane, while using IPv6 ND messaging 194 as the control plane independently of the data plane IP protocol(s). 195 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 196 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 197 discussed in the following sections. OMNI interfaces enable 198 multilink, mobility, multihop and multicast services, with provisions 199 for both Vehicle-to-Infrastructure (V2I) communications and Vehicle- 200 to-Vehicle (V2V) communications outside the context of 201 infrastructure. 203 2. Terminology 205 The terminology in the normative references applies; especially, the 206 terms "link" and "interface" are the same as defined in the IPv6 207 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 208 Additionally, this document assumes the following IPv6 ND message 209 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 210 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 212 The Protocol Constants defined in Section 10 of [RFC4861] are used in 213 their same format and meaning in this document. The terms "All- 214 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 215 are the same as defined in [RFC4291] (with Link-Local scope assumed). 217 The term "IP" is used to refer collectively to either Internet 218 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 219 specification at the layer in question applies equally to either 220 version. 222 The following terms are defined within the scope of this document: 224 Mobile Node (MN) 225 an end system with a mobile router having multiple distinct 226 upstream data link connections that are grouped together in one or 227 more logical units. The MN's data link connection parameters can 228 change over time due to, e.g., node mobility, link quality, etc. 229 The MN further connects a downstream-attached End User Network 230 (EUN). The term MN used here is distinct from uses in other 231 documents, and does not imply a particular mobility protocol. 233 End User Network (EUN) 234 a simple or complex downstream-attached mobile network that 235 travels with the MN as a single logical unit. The IP addresses 236 assigned to EUN devices remain stable even if the MN's upstream 237 data link connections change. 239 Mobility Service (MS) 240 a mobile routing service that tracks MN movements and ensures that 241 MNs remain continuously reachable even across mobility events. 242 Specific MS details are out of scope for this document. 244 Mobility Service Endpoint (MSE) 245 an entity in the MS (either singular or aggregate) that 246 coordinates the mobility events of one or more MN. 248 Mobility Service Prefix (MSP) 249 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 250 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 251 from which more-specific Mobile Network Prefixes (MNPs) are 252 delegated. OMNI link administrators typically obtain MSPs from an 253 Internet address registry, however private-use prefixes can 254 alternatively be used subject to certain limitations (see: 255 Section 9). OMNI links that connect to the global Internet 256 advertise their MSPs to their interdomain routing peers. 258 Mobile Network Prefix (MNP) 259 a longer IP prefix delegated from an MSP (e.g., 260 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 261 MNs sub-delegate the MNP to devices located in EUNs. 263 Access Network (ANET) 264 a data link service network (e.g., an aviation radio access 265 network, satellite service provider network, cellular operator 266 network, WiFi network, etc.) that connects MNs. Physical and/or 267 data link level security is assumed, and sometimes referred to as 268 "protected spectrum". Private enterprise networks and ground 269 domain aviation service networks may provide multiple secured IP 270 hops between the MN's point of connection and the nearest Access 271 Router. 273 Access Router (AR) 274 a router in the ANET for connecting MNs to correspondents in 275 outside Internetworks. The AR may be located on the same physical 276 link as the MN, or may be located multiple IP hops away. In the 277 latter case, the MN uses encapsulation to communicate with the AR 278 as though it were on the same physical link. 280 ANET interface 281 a MN's attachment to a link in an ANET. 283 Internetwork (INET) 284 a connected network region with a coherent IP addressing plan that 285 provides transit forwarding services between ANETs and nodes that 286 connect directly to the open INET via unprotected media. No 287 physical and/or data link level security is assumed, therefore 288 security must be applied by upper layers. The global public 289 Internet itself is an example. 291 INET interface 292 a node's attachment to a link in an INET. 294 *NET 295 a "wildcard" term used when a given specification applies equally 296 to both ANET and INET cases. 298 OMNI link 299 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 300 over one or more INETs and their connected ANETs. An OMNI link 301 can comprise multiple INET segments joined by bridges the same as 302 for any link; the addressing plans in each segment may be mutually 303 exclusive and managed by different administrative entities. 305 OMNI interface 306 a node's attachment to an OMNI link, and configured over one or 307 more underlying *NET interfaces. If there are multiple OMNI links 308 in an OMNI domain, a separate OMNI interface is configured for 309 each link. 311 OMNI Adaptation Layer (OAL) 312 an OMNI interface process whereby packets admitted into the 313 interface are wrapped in a mid-layer IPv6 header and fragmented/ 314 reassembled if necessary to support the OMNI link Maximum 315 Transmission Unit (MTU). The OAL is also responsible for 316 generating MTU-related control messages as necessary, and for 317 providing addressing context for spanning multiple segments of a 318 bridged OMNI link. 320 OMNI Option 321 an IPv6 Neighbor Discovery option providing multilink parameters 322 for the OMNI interface as specified in Section 11. 324 Mobile Network Prefix Link Local Address (MNP-LLA) 325 an IPv6 Link Local Address that embeds the most significant 64 326 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 327 Section 7. 329 Mobile Network Prefix Unique Local Address (MNP-ULA) 330 an IPv6 Unique-Local Address derived from an MNP-LLA. 332 Administrative Link Local Address (ADM-LLA) 333 an IPv6 Link Local Address that embeds a 32-bit administratively- 334 assigned identification value in the lower 32 bits of fe80::/96, 335 as specified in Section 7. 337 Administrative Unique Local Address (ADM-ULA) 338 an IPv6 Unique-Local Address derived from an ADM-LLA. 340 Multilink 341 an OMNI interface's manner of managing diverse underlying 342 interface connections to data links as a single logical unit. The 343 OMNI interface provides a single unified interface to upper 344 layers, while underlying interface selections are performed on a 345 per-packet basis considering factors such as DSCP, flow label, 346 application policy, signal quality, cost, etc. Multilinking 347 decisions are coordinated in both the outbound (i.e. MN to 348 correspondent) and inbound (i.e., correspondent to MN) directions. 350 Multihop 351 an iterative relaying of IP packets between MNs over an OMNI 352 underlying interface technology (such as omnidirectional wireless) 353 without support of fixed infrastructure. Multihop services entail 354 node-to-node relaying within a Mobile/Vehicular Ad-hoc Network 355 (MANET/VANET) for MN-to-MN communications and/or for "range 356 extension" where MNs within range of communications infrastructure 357 elements provide forwarding services for other MNs. 359 L2 360 The second layer in the OSI network model. Also known as "layer- 361 2", "link-layer", "sub-IP layer", "data link layer", etc. 363 L3 364 The third layer in the OSI network model. Also known as "layer- 365 3", "network-layer", "IP layer", etc. 367 underlying interface 368 a *NET interface over which an OMNI interface is configured. The 369 OMNI interface is seen as a L3 interface by the IP layer, and each 370 underlying interface is seen as a L2 interface by the OMNI 371 interface. The underlying interface either connects directly to 372 the physical communications media or coordinates with another node 373 where the physical media is hosted. 375 Mobility Service Identification (MSID) 376 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 377 (see: Section 7). IDs are assigned according to MS-specific 378 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 380 Safety-Based Multilink (SBM) 381 A means for ensuring fault tolerance through redundancy by 382 connecting multiple affiliated OMNI interfaces to independent 383 routing topologies (i.e., multiple independent OMNI links). 385 Performance Based Multilink (PBM) 386 A means for selecting underlying interface(s) for packet 387 transmission and reception within a single OMNI interface. 389 OMNI Domain 390 The set of all SBM/PBM OMNI links that collectively provides 391 services for a common set of MSPs. Each OMNI domain consists of a 392 set of affiliated OMNI links that all configure the same ::/48 ULA 393 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 395 3. Requirements 397 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 398 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 399 "OPTIONAL" in this document are to be interpreted as described in BCP 400 14 [RFC2119][RFC8174] when, and only when, they appear in all 401 capitals, as shown here. 403 An implementation is not required to internally use the architectural 404 constructs described here so long as its external behavior is 405 consistent with that described in this document. 407 4. Overlay Multilink Network (OMNI) Interface Model 409 An OMNI interface is a MN virtual interface configured over one or 410 more underlying interfaces, which may be physical (e.g., an 411 aeronautical radio link) or virtual (e.g., an Internet or higher- 412 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 413 with the MS through IPv6 ND message exchanges. The MN uses the MNP 414 to construct a unique Link-Local Address (MNP-LLA) through the 415 algorithmic derivation specified in Section 7 and assigns the LLA to 416 the OMNI interface. 418 The OMNI interface architectural layering model is the same as in 419 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 420 therefore sees the OMNI interface as a single L3 interface with 421 multiple underlying interfaces that appear as L2 communication 422 channels in the architecture. 424 +----------------------------+ 425 | Upper Layer Protocol | 426 Session-to-IP +---->| | 427 Address Binding | +----------------------------+ 428 +---->| IP (L3) | 429 IP Address +---->| | 430 Binding | +----------------------------+ 431 +---->| OMNI Interface | 432 Logical-to- +---->| (LLA) | 433 Physical | +----------------------------+ 434 Interface +---->| L2 | L2 | | L2 | 435 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 436 +------+------+ +------+ 437 | L1 | L1 | | L1 | 438 | | | | | 439 +------+------+ +------+ 441 Figure 1: OMNI Interface Architectural Layering Model 443 Each underlying interface provides an L2/L1 abstraction according to 444 one of the following models: 446 o INET interfaces connect to an INET either natively or through one 447 or several IPv4 Network Address Translators (NATs). Native INET 448 interfaces have global IP addresses that are reachable from any 449 INET correspondent. NATed INET interfaces typically have private 450 IP addresses and connect to a private network behind one or more 451 NATs that provide INET access. 453 o ANET interfaces connect to a protected ANET that is separated from 454 the open INET by an AR acting as a proxy. The ANET interface may 455 be either on the same L2 link segment as the AR, or separated from 456 the AR by multiple IP hops. 458 o VPNed interfaces use security encapsulation over a *NET to a 459 Virtual Private Network (VPN) gateway. Other than the link-layer 460 encapsulation format, VPNed interfaces behave the same as for 461 Direct interfaces. 463 o Direct (aka "point-to-point") interfaces connect directly to a 464 peer without crossing any *NET paths. An example is a line-of- 465 sight link between a remote pilot and an unmanned aircraft. 467 The OMNI virtual interface model gives rise to a number of 468 opportunities: 470 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 471 Address Detection (DAD) or Multicast Listener Discovery (MLD) 472 messaging is necessary. 474 o since Temporary ULAs are statistically unique, they can be used 475 without DAD, e.g. for MN-to-MN communications until an MNP-LLA is 476 obtained. 478 o *NET interfaces on the same L2 link segment as an AR do not 479 require any L3 addresses (i.e., not even link-local) in 480 environments where communications are coordinated entirely over 481 the OMNI interface. (An alternative would be to also assign the 482 same LLA to all *NET interfaces.) 484 o as underlying interface properties change (e.g., link quality, 485 cost, availability, etc.), any active interface can be used to 486 update the profiles of multiple additional interfaces in a single 487 message. This allows for timely adaptation and service continuity 488 under dynamically changing conditions. 490 o coordinating underlying interfaces in this way allows them to be 491 represented in a unified MS profile with provisions for mobility 492 and multilink operations. 494 o exposing a single virtual interface abstraction to the IPv6 layer 495 allows for multilink operation (including QoS based link 496 selection, packet replication, load balancing, etc.) at L2 while 497 still permitting L3 traffic shaping based on, e.g., DSCP, flow 498 label, etc. 500 o the OMNI interface allows inter-INET traversal when nodes located 501 in different INETs need to communicate with one another. This 502 mode of operation would not be possible via direct communications 503 over the underlying interfaces themselves. 505 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 506 lossless and adaptive path MTU mitigations not available for 507 communications directly over the underlying interfaces themselves. 508 The OAL supports "packing" of multiple IP payload packets within a 509 single OAL packet. 511 o L3 sees the OMNI interface as a point of connection to the OMNI 512 link; if there are multiple OMNI links (i.e., multiple MS's), L3 513 will see multiple OMNI interfaces. 515 o Multiple independent OMNI interfaces can be used for increased 516 fault tolerance through Safety-Based Multilink (SBM), with 517 Performance-Based Multilink (PBM) applied within each interface. 519 Other opportunities are discussed in [RFC7847]. Note that even when 520 the OMNI virtual interface is present, applications can still access 521 underlying interfaces either through the network protocol stack using 522 an Internet socket or directly using a raw socket. This allows for 523 intra-network (or point-to-point) communications without invoking the 524 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 525 is configured over an underlying IPv4 interface, applications can 526 still invoke IPv4 intra-network communications as long as the 527 communicating endpoints are not subject to mobility dynamics. 528 However, the opportunities discussed above are not available when the 529 architectural layering is bypassed in this way. 531 Figure 2 depicts the architectural model for a MN with an attached 532 EUN connecting to the MS via multiple independent *NETs. When an 533 underlying interface becomes active, the MN's OMNI interface sends 534 IPv6 ND messages without encapsulation if the first-hop Access Router 535 (AR) is on the same underlying link; otherwise, the interface uses 536 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 537 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 538 then coordinates with an INET Mobility Service Endpoint (MSE#1, 539 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 540 The Hop Limit in IPv6 ND messages is not decremented due to 541 encapsulation; hence, the OMNI interface appears to be attached to an 542 ordinary link. 544 +--------------+ (:::)-. 545 | MN |<-->.-(::EUN:::) 546 +--------------+ `-(::::)-' 547 |OMNI interface| 548 +----+----+----+ 549 +--------|IF#1|IF#2|IF#n|------ + 550 / +----+----+----+ \ 551 / | \ 552 / | \ 553 v v v 554 (:::)-. (:::)-. (:::)-. 555 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 556 `-(::::)-' `-(::::)-' `-(::::)-' 557 +----+ +----+ +----+ 558 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 559 . +-|--+ +-|--+ +-|--+ . 560 . | | | 561 . v v v . 562 . <----- INET Encapsulation -----> . 563 . . 564 . +-----+ (:::)-. . 565 . |MSE#2| .-(::::::::) +-----+ . 566 . +-----+ .-(::: INET :::)-. |MSE#m| . 567 . (::::: Routing ::::) +-----+ . 568 . `-(::: System :::)-' . 569 . +-----+ `-(:::::::-' . 570 . |MSE#1| +-----+ +-----+ . 571 . +-----+ |MSE#3| |MSE#4| . 572 . +-----+ +-----+ . 573 . . 574 . . 575 . <----- Worldwide Connected Internetwork ----> . 576 ........................................................... 578 Figure 2: MN/MS Coordination via Multiple *NETs 580 After the initial IPv6 ND message exchange, the MN (and/or any nodes 581 on its attached EUNs) can send and receive IP data packets over the 582 OMNI interface. OMNI interface multilink services will forward the 583 packets via ARs in the correct underlying *NETs. The AR encapsulates 584 the packets according to the capabilities provided by the MS and 585 forwards them to the next hop within the worldwide connected 586 Internetwork via optimal routes. 588 OMNI links span one or more underlying Internetwork via the OMNI 589 Adaptation Layer (OAL) which is based on a mid-layer overlay 590 encapsulation using [RFC2473]. Each OMNI link corresponds to a 591 different overlay (differentiated by an address codepoint) which may 592 be carried over a completely separate underlying topology. Each MN 593 can facilitate SBM by connecting to multiple OMNI links using a 594 distinct OMNI interface for each link. 596 Note: OMNI interface underlying interfaces often connect directly to 597 physical media on the local platform (e.g., a laptop computer with 598 WiFi, etc.), but in some configurations the physical media may be 599 hosted on a separate Local Area Network (LAN) node. In that case, 600 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 601 tunnel (at a layer below the underlying interface) to the node 602 hosting the physical media. The OMNI interface may also apply 603 encapsulation at a layer above the underlying interface such that 604 packets would appear "double-encapsulated" on the LAN; the node 605 hosting the physical media in turn removes the LAN encapsulation 606 prior to transmission or inserts it following reception. Finally, 607 the underlying interface must monitor the node hosting the physical 608 media (e.g., through periodic keepalives) so that it can convey 609 up/down/status information to the OMNI interface. 611 5. The OMNI Adaptation Layer (OAL) 613 The OMNI interface observes the link nature of tunnels, including the 614 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 615 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 616 The OMNI interface is configured over one or more underlying 617 interfaces that may have diverse MTUs. OMNI interfaces accommodate 618 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 619 discussed in this section. 621 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 622 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 623 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 624 permitted to perform network fragmentation even though the 625 destination is required to reassemble more. The network therefore 626 MUST forward packets of at least 1280 bytes without generating an 627 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 628 [RFC8201]. (Note: the source can apply "source fragmentation" for 629 locally-generated IPv6 packets up to 1500 bytes and larger still if 630 it if has a way to determine that the destination configures a larger 631 MRU, but this does not affect the minimum IPv6 path MTU.) 633 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 634 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 635 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 636 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 637 support network fragmentation and the destination is required to 638 reassemble at least that much. The "Don't Fragment" (DF) bit in the 639 IPv4 encapsulation headers of packets sent over IPv4 underlying 640 interfaces therefore MUST be set to 0. (Note: even if the 641 encapsulation source has a way to determine that the encapsulation 642 destination configures an MRU larger than 576 bytes, it should not 643 assume a larger minimum IPv4 path MTU without careful consideration 644 of the issues discussed in Section 5.1.) 646 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 647 encapsulation may be prevalent, it may be prudent for the OAL to 648 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 649 of the underlying interface IP protocol version. By always assuming 650 the IPv4 minimum path MTU even for IPv6 underlying interfaces, the 651 OAL may produce smaller fragments and additional header overhead but 652 will always interoperate and never run the risk of presenting a 653 destination interface with a packet that exceeds its MRU. 655 The OMNI interface configures both an MTU and MRU of 9180 bytes 656 [RFC2492]; the size is therefore not a reflection of the underlying 657 interface MTUs, but rather determines the largest packet the OMNI 658 interface can forward or reassemble. The OMNI interface uses the 659 OMNI Adaptation Layer (OAL) to admit packets from the network layer 660 that are no larger than the OMNI interface MTU while generating 661 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 662 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 663 document refers to both of these ICMPv4/ICMPv6 message types simply 664 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 665 errors as discussed below. 667 For IPv4 packets with DF=0, the network layer performs IPv4 668 fragmentation if necessary then admits the packets/fragments into the 669 OMNI interface; these fragments will be reassembled by the final 670 destination. For IPv4 packets with DF=1 and IPv6 packets, the 671 network layer admits the packet if it is no larger than the OMNI 672 interface MTU; otherwise, it drops the packet and returns a PTB hard 673 error message to the source. 675 For each admitted IP packet/fragment, the OMNI interface internally 676 employs the OAL when necessary by encapsulating the inner IP packet/ 677 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 678 outer IP encapsulations. (The OAL does not decrement the inner IP 679 Hop Limit/TTL during encapsulation since the insertion occurs at a 680 layer below IP forwarding.) If the OAL packet will itself require 681 fragmentation, the OMNI interface then calculates the 32-bit CRC over 682 the entire mid-layer packet and writes the value in a trailing field 683 at the end of the packet. Next, the OAL fragments this mid-layer 684 IPv6 packet, forwards the fragments (using *NET encapsulation if 685 necessary), and returns an internally-generated PTB soft error 686 message (subject to rate limiting) if it deems the packet too large 687 according to factors such as link performance characteristics, 688 reassembly congestion, etc. This ensures that the path MTU is 689 adaptive and reflects the current path used for a given data flow. 691 The OAL operates with respect to both the minimum IPv6 and IPv4 path 692 MTUs as follows: 694 o When an OMNI interface sends a packet toward a final destination 695 via an ANET peer, it sends without OAL encapsulation if the packet 696 (including any outer-layer ANET encapsulations) is no larger than 697 the underlying interface MTU for on-link ANET peers or the minimum 698 ANET path MTU for peers separated by multiple IP hops. Otherwise, 699 the OAL inserts an IPv6 header per [RFC2473] with source address 700 set to the node's own Unique-Local Address (ULA) (see: Section 8) 701 and destination set to either the Administrative ULA (ADM-ULA) of 702 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 703 corresponding to the final destination (see below). The OAL then 704 calculates and appends the trailing 32-bit CRC, then uses IPv6 705 fragmentation to break the packet into a minimum number of non- 706 overlapping fragments where the size of each non-final fragment 707 (including both the OMNI and any outer-layer ANET encapsulations) 708 is determined by the underlying interface MTU for on-link ANET 709 peers or the minimum ANET path MTU for peers separated by multiple 710 IP hops. The OAL then encapsulates the fragments in any ANET 711 headers and sends them to the ANET peer, which either reassembles 712 before forwarding if the OAL destination is its own ADM-ULA or 713 forwards the fragments toward the final destination without first 714 reassembling otherwise. 716 o When an OMNI interface sends a packet toward a final destination 717 via an INET interface, it sends packets (including any outer-layer 718 INET encapsulations) no larger than the minimum INET path MTU 719 without OAL encapsulation if the destination is reached via an 720 INET address within the same OMNI link segment. Otherwise, the 721 OAL inserts an IPv6 header per [RFC2473] with source address set 722 to the node's ULA, destination set to the ULA of the next hop OMNI 723 node toward the final destination and (if necessary) with an OMNI 724 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 725 final segment addressing information. The OAL next calculates and 726 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 727 break the packet into a minimum number of non-overlapping 728 fragments where the size of each non-final fragment (including 729 both the OMNI and outer-layer INET encapsulations) is determined 730 by the minimum INET path MTU. The OAL then encapsulates the 731 fragments in any INET headers and sends them to the OMNI link 732 neighbor, which reassembles before forwarding toward the final 733 destination. 735 In light of the above considerations, the OAL SHOULD assume a minimum 736 path MTU of 576 bytes for the purpose of generating OAL fragments. 737 Each OAL fragment will undergo *NET encapsulation including either a 738 20 byte IPv4 or 40 byte IPv6 header (plus an 8 byte UDP header for 739 INETs), leaving a minimum of 528 bytes for each fragment. Each OAL 740 fragment must reserve 40 bytes for the OAL IPv6 header plus 8 bytes 741 for the fragment header (while reserving 40 additional bytes in case 742 a maximum-length ORH is inserted during re-encapsulation), leaving 743 440 bytes to accommodate the actual inner IP packet fragment. OAL 744 fragmentation algorithms therefore MUST produce non-final fragments 745 with the OAL IPv6 header Payload Length set to no less than 448 bytes 746 (8 bytes for the fragment header plus 440 bytes for the inner packet 747 fragment), while the Payload Length of the final fragment may be 748 smaller. OAL reassembly algorithms MUST drop any non-final fragments 749 with Payload Length less than 448 bytes. 751 Note that OAL fragmentation algorithms MAY produce larger non-final 752 OAL fragments if better path MTU information is available. For 753 example, for ANETs in which no UDP encapsulation header is needed the 754 algorithm can increase the minimum non-final fragment length by 8 755 bytes. In a second example, for ANETs in which no IPv6 hops will be 756 traversed over the path the algorithm can increase the minimum length 757 by 20 bytes. In a third example, if there is assurance that no ORH 758 will be inserted in the path the algorithm can increase the minimum 759 length by 40 bytes. In a final example, when two ANET peers share a 760 common physical or virtual link with a larger MTU (e.g., 1280 bytes 761 or larger), the OAL can base the minimum non-final fragment length on 762 this larger MTU size as long as the receiving ANET peer reassembles 763 (and possibly also refragments) before forwarding. (Other examples 764 are possible, and dependent on actual ANET/INET deployment 765 scenarios.) 767 In all of the above examples, optimizing the minimum OAL fragment 768 size may be important for accommodating links where performance is 769 dependent on maximum use of the available link MTU, e.g. for wireless 770 aviation data links. Additionally, the OMNI interface that inserts 771 the OAL header MUST also be the one that inserts the IPv6 fragment 772 header Identification value in order to set the correct context for 773 reassembly. While not strictly required, sending all fragments of 774 the same fragmented OAL packet consecutively over the same underlying 775 interface with minimal inter-fragment delay may increase the 776 likelihood of successful reassembly. 778 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 779 header Code field value 0 are hard errors that always indicate that a 780 packet has been dropped due to a real MTU restriction. However, the 781 OAL can also forward large packets via encapsulation and 782 fragmentation while at the same time returning PTB soft error 783 messages (subject to rate limiting) indicating that a forwarded 784 packet was uncomfortably large. The OMNI interface can therefore 785 continuously forward large packets without loss while returning PTB 786 soft error messages recommending a smaller size. Original sources 787 that receive the soft errors in turn reduce the size of the packets 788 they send, i.e., the same as for hard errors. 790 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 791 field to the value 1 in PTB soft error messages. The OAL sets the 792 PTB destination address to the source address of the original packet, 793 and sets the source address to the MNP Subnet Router Anycast address 794 of the MN. The OAL then sets the MTU field to a value no smaller 795 than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB soft 796 error to the original source. 798 When the original source receives the PTB, it reduces its path MTU 799 estimate the same as for hard errors but does not regard the message 800 as a loss indication. (If the original source does not recognize the 801 soft error code, it regards the PTB the same as a hard error but 802 should heed the retransmission advice given in [RFC8201] suggesting 803 retransmission based on normal packetization layer retransmission 804 timers.) This document therefore updates [RFC1191][RFC4443] and 805 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 806 that PTB hard or soft errors may arrive at any time even if after a 807 successful MTU probe (this is the same consideration as for an 808 ordinary path fluctuation following a successful probe). 810 In summary, the OAL supports continuous transmission and reception of 811 packets of various sizes in the face of dynamically changing network 812 conditions. Moreover, since PTB soft errors do not indicate loss, 813 original sources that receive soft errors can quickly scan for path 814 MTU increases without waiting for the minimum 10 minutes specified 815 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 816 therefore provides a lossless and adaptive service that accommodates 817 MTU diversity especially well-suited for dynamic multilink 818 environments. 820 Note: An OMNI interface that reassembles OAL fragments may experience 821 congestion-oriented loss in its reassembly cache and can optionally 822 send PTB soft errors to the original source and/or ICMP "Time 823 Exceeded" messages to the source of the OAL fragments. In 824 environments where the messages may contribute to unacceptable 825 additional congestion, however, the OMNI interface can refrain from 826 sending PTB soft errors and simply regard the loss as an ordinary 827 unreported congestion event for which the original source will 828 eventually compensate. 830 Note: When the network layer forwards an IPv4 packet/fragment with 831 DF=0 into the OMNI interface, the interface can optionally perform 832 (further) IPv4 fragmentation before invoking the OAL so that the 833 fragments will be reassembled by the final destination. When the 834 network layer performs IPv6 fragmentation for locally-generated IPv6 835 packets, the OMNI interface typically invokes the OAL without first 836 applying (further) IPv6 fragmentation; the network layer should 837 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 838 push the reassembly burden to the final destination and avoid 839 receiving PTB soft errors from the OMNI interface. Aside from these 840 non-normative guidelines, the manner in which any IP fragmentation is 841 invoked prior to OAL encapsulation/fragmentation is an implementation 842 matter. 844 Note: The source OAL includes a trailing 32-bit CRC only for OAL 845 packets that require fragmentation, and the destination OAL discards 846 any OAL packets with incorrect CRC values following reassembly. (The 847 source OAL calculates the CRC over the entire packet, then appends 848 the CRC to the end of the packet and adds the CRC length to the OAL 849 Payload Length prior to fragmentation. The destination OAL subtracts 850 the CRC length from the OAL Payload Length and verifies the CRC 851 following reassembly.) A 32-bit CRC is sufficient for detecting 852 reassembly misassociations for packet sizes no larger than the OMNI 853 interface MTU but may not be sufficient to detect errors for larger 854 sizes [CRC]. 856 Note: Some underlying interface types (e.g., VPNs) may already 857 provide their own robust fragmentation and reassembly services even 858 without OAL encapsulation. In those cases, the OAL can invoke the 859 inherent underlying interface schemes instead while employing PTB 860 soft errors in the same fashion as described above. Other underlying 861 interface facilities such as header/message compression can also be 862 harnessed in a similar fashion. 864 Note: Applications can dynamically tune the size of the packets they 865 to send to produce the best possible throughput and latency, with the 866 understanding that these parameters may change over time due to 867 factors such as congestion, mobility, network path changes, etc. The 868 receipt or absence of soft errors should be seen as hints of when 869 increasing or decreasing packet sizes may be beneficial. 871 5.1. Fragmentation Security Implications 873 As discussed in Section 3.7 of [RFC8900], there are four basic 874 threats concerning IPv6 fragmentation; each of which is addressed by 875 effective mitigations as follows: 877 1. Overlapping fragment attacks - reassembly of overlapping 878 fragments is forbidden by [RFC8200]; therefore, this threat does 879 not apply to the OAL. 881 2. Resource exhaustion attacks - this threat is mitigated by 882 providing a sufficiently large OAL reassembly cache and 883 instituting "fast discard" of incomplete reassemblies that may be 884 part of a buffer exhaustion attack. The reassembly cache should 885 be sufficiently large so that a sustained attack does not cause 886 excessive loss of good reassemblies but not so large that (timer- 887 based) data structure management becomes computationally 888 expensive. The cache should also be indexed based on the arrival 889 underlying interface such that congestion experienced over a 890 first underlying interface does not cause discard of incomplete 891 reassemblies for uncongested underlying interfaces. 893 3. Attacks based on predictable fragment identification values - 894 this threat is mitigated by selecting a suitably random ID value 895 per [RFC7739]. 897 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 898 threat is mitigated by disallowing "tiny fragments" per the OAL 899 fragmentation procedures specified above. 901 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 902 ID) field with only 65535 unique values such that at high data rates 903 the field could wrap and apply to new packets while the fragments of 904 old packets using the same ID are still alive in the network 905 [RFC4963]. However, since the largest OAL fragment that will be sent 906 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 907 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 908 recommendations suggest that such links will have low data rates. 909 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 910 at high data rates is not a concern for IPv6 fragmentation. 912 Finally, [RFC6980] documents fragmentation security concerns for 913 large IPv6 ND messages. These concerns are addressed when the OMNI 914 interface employs the OAL instead of directly fragmenting the IPv6 ND 915 message itself. For this reason, OMNI interfaces MUST NOT admit IPv6 916 ND messages larger than the OMNI interface MTU, and MUST employ the 917 OAL for IPv6 ND messages admitted into the OMNI interface the same as 918 discussed above. 920 5.2. OAL "Super-Packet" Packing 922 By default, the source OAL includes a 40-byte IPv6 encapsulation 923 header for each inner IP payload packet during OAL encapsulation. 924 When fragmentation is needed, the source OAL also calculates and 925 includes a 32-bit trailing CRC for the entire packet then performs 926 fragmentation such that a copy of the 40-byte IPv6 header plus an 927 8-byte IPv6 Fragment Header is included in each fragment. However, 928 these encapsulations may represent excessive overhead in some 929 environments. A technique known as "packing" discussed in 930 [I-D.ietf-intarea-tunnels] is therefore supported so that multiple 931 inner IP payload packets can be included within a single OAL packet 932 known as a "super-packet". 934 When the source OAL has multiple inner IP payload packets with total 935 length no larger than the OMNI interface MTU to send to the same 936 destination, it can optionally concatenate them into a super-packet 937 encapsulated in a single OAL header. Within the super-packet, the IP 938 header of the first inner packet (iHa) followed by its data (iDa) is 939 concatenated immediately following the OAL header, then the inner IP 940 header of the next packet (iHb) followed by its data (iDb) is 941 concatenated immediately following the first packet, etc. The super- 942 packet format is transposed from [I-D.ietf-intarea-tunnels] and shown 943 in Figure 3: 945 <-- Multiple inner IP payload packets to be "packed" --> 946 +-----+-----+ 947 | iHa | iDa | 948 +-----+-----+ 949 | 950 | +-----+-----+ 951 | | iHb | iDb | 952 | +-----+-----+ 953 | | 954 | | +-----+-----+ 955 | | | iHc | iDc | 956 | | +-----+-----+ 957 | | | 958 v v v 959 +----------+-----+-----+-----+-----+-----+-----+ 960 | OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc | 961 +----------+-----+-----+-----+-----+-----+-----+ 962 <-- OMNI "Super-Packet" with single OAL Hdr --> 964 Figure 3: OAL Super-Packet Format 966 When the source OAL sends a super-packet, it calculates a CRC and 967 applies OAL fragmentation if necessary then sends the packet or 968 fragments to the destination OAL. When the destination OAL receives 969 the super-packet as a whole packet or as fragments, it reassembles 970 and verifies the CRC if necessary then regards the OAL header Payload 971 Length (after subtracting the CRC length) as the sum of the lengths 972 of all payload packets. The destination OAL then selectively 973 extracts each individual payload packet (e.g., by setting pointers 974 into the buffer containing the super-packet and maintaining a 975 reference count, by copying each payload packet into its own buffer, 976 etc.) and forwards each payload packet or processes it locally as 977 appropriate. During extraction, the OAL determines the IP protocol 978 version of each successive inner payload packet 'j' by examining the 979 first four bits of iH(j), and determines the length of the inner 980 packet by examining the rest of iH(j) according to the IP protocol 981 version. 983 Note: OMNI interfaces must take care to avoid processing super-packet 984 payload elements that would subvert security. Specifically, if a 985 super-packet contains a mix of data and control payload packets 986 (which could include critical security codes), the node MUST NOT 987 process the data packets before processing the control packets. 989 6. Frame Format 991 The OMNI interface transmits IP packets according to the native frame 992 format of each underlying interface. For example, for Ethernet- 993 compatible interfaces the frame format is specified in [RFC2464], for 994 aeronautical radio interfaces the frame format is specified in 995 standards such as ICAO Doc 9776 (VDL Mode 2 Technical Manual), for 996 tunnels over IPv6 the frame format is specified in [RFC2473], etc. 998 7. Link-Local Addresses (LLAs) 1000 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 1001 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 1002 the MNP assigned to the mobile node, while "ADM-LLAs" include an 1003 administratively-unique ID that is guaranteed to be unique on the 1004 link. LLAs are configured as follows: 1006 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 1007 the least-significant 64 bits of the IPv6 link-local prefix 1008 fe80::/64, i.e., in the LLA "interface identifier" portion. The 1009 prefix length for the LLA is determined by adding 64 to the MNP 1010 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 1011 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 1013 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 1014 i.e., the interface identifier consists of 16 '0' bits, followed 1015 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 1016 prefix length for the LLA is determined by adding 96 to the MNP 1017 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 1018 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 1019 fe80::ffff:c000:0200/120). 1021 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 1022 uniqueness. The lower 32 bits of the LLA includes a unique 1023 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 1024 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 1025 prefix length is determined by adding 96 to the MSID prefix 1026 length. For example, if the prefix length for MSID 0x10012001 is 1027 16 then the ADM-LLA prefix length is set to 112 and the LLA is 1028 written as fe80::1001:2001/112. The "zero" address for each ADM- 1029 LLA prefix is the Subnet-Router anycast address for that prefix 1030 [RFC4291]; for example, the Subnet-Router anycast address for 1031 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 1032 0xff000000 through 0xffffffff is reserved for future use. 1034 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 1035 MNPs can be allocated from that block ensuring that there is no 1036 possibility for overlap between the different MNP- and ADM-LLA 1037 constructs discussed above. 1039 Since MNP-LLAs are based on the distribution of administratively 1040 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 1041 administrative assignment, OMNI interfaces set the autoconfiguration 1042 variable DupAddrDetectTransmits to 0 [RFC4862]. 1044 Note: If future protocol extensions relax the 64-bit boundary in IPv6 1045 addressing, the additional prefix bits of an MNP could be encoded in 1046 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 1047 would therefore still be in bits 64-127, and the remaining bits would 1048 appear in bits 16 through 48.) However, the analysis provided in 1049 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 1050 architecture for the foreseeable future. 1052 Note: Even though this document honors the 64-bit boundary in IPv6 1053 addressing, it specifies prefix lengths longer than /64 for routing 1054 purposes. This effectively extends IPv6 routing determination into 1055 the interface identifier portion of the IPv6 address, but it does not 1056 redefine the 64-bit boundary. Modern routing protocol 1057 implementations honor IPv6 prefixes of all lengths, up to and 1058 including /128. 1060 8. Unique-Local Addresses (ULAs) 1062 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 1063 destination addresses in OAL IPv6 encapsulation headers. ULAs are 1064 only routable within the scope of a an OMNI domain, and are derived 1065 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 1066 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 1067 Global ID to produce the prefix [ULA]::/48, which is then followed by 1068 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 1069 specified in Section 3 of [RFC4193]. All nodes in the same OMNI 1070 domain configure the same 40-bit Global ID as the OMNI domain 1071 identifier. The statistic uniqueness of the 40-bit pseudo-random 1072 Global ID allows different OMNI domains to be joined together in the 1073 future without requiring renumbering. 1075 Each OMNI link instance is identified by a value between 0x0000 and 1076 0xfeff in bits 48-63 of [ULA]::/48; the values 0xff00 through 0xfffe 1077 are reserved for future use, and the value 0xffff denotes the 1078 presence of a Temporary ULA (see below). For example, OMNI ULAs 1079 associated with instance 0 are configured from the prefix 1080 [ULA]:0000::/64, instance 1 from [ULA]:0001::/64, instance 2 from 1081 [ULA]:0002::/64, etc. ULAs and their associated prefix lengths are 1082 configured in correspondence with LLAs through stateless prefix 1083 translation where "MNP-ULAs" are assigned in correspondence to MNP- 1084 LLAs and "ADM-ULAs" are assigned in correspondence to ADM-LLAs. For 1085 example, for OMNI link instance [ULA]:1010::/64: 1087 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 1088 56-bit MNP length is derived by copying the lower 64 bits of the 1089 LLA into the lower 64 bits of the ULA as 1090 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1091 64 plus the IPv6 MNP length). 1093 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1094 MNP length is derived by simply writing the LLA interface ID into 1095 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1096 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1098 o the ADM-ULA corresponding to fe80::1000/112 is simply 1099 [ULA]:1010::1000/112. 1101 o the ADM-ULA corresponding to fe80::/128 is simply 1102 [ULA]:1010::/128. 1104 o etc. 1106 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1107 link instance. For example, the OMNI interface connected to instance 1108 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1109 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1110 [ULA]:0003::/64) into the local routing system so that applications 1111 can direct traffic according to SBM requirements. 1113 The ULA presents an IPv6 address format that is routable within the 1114 OMNI routing system and can be used to convey link-scoped IPv6 ND 1115 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1116 The OMNI link extends across one or more underling Internetworks to 1117 include all ARs and MSEs. All MNs are also considered to be 1118 connected to the OMNI link, however OAL encapsulation is omitted 1119 whenever possible to conserve bandwidth (see: Section 13). 1121 Each OMNI link can be subdivided into "segments" that often 1122 correspond to different administrative domains or physical 1123 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1124 necessary to support efficient packet forwarding to destinations 1125 located in other OMNI link segments. A full discussion of Segment 1126 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1128 Temporary ULAs are constructed per [I-D.ietf-6man-rfc4941bis] based 1129 on the prefix [ULA]:ffff::/64 and used by MNs when they have no other 1130 addresses. Temporary ULAs can be used for MN-to-MN communications 1131 outside the context of any supporting OMNI link infrastructure, and 1132 can also be used as an initial address while the MN is in the process 1133 of procuring an MNP. Temporary ULAs are not routable within the OMNI 1134 routing system, and are therefore useful only for OMNI link "edge" 1135 communications. Temporary ULAs employ optimistic DAD principles 1136 [RFC4429] since they are probabilistically unique. 1138 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1139 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1140 however the range could be used for MSP and MNP addressing under 1141 certain limiting conditions (see: Section 9). 1143 9. Global Unicast Addresses (GUAs) 1145 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1146 as Mobility Service Prefixes (MSPs) from which Mobile Network 1147 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1149 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1150 associated regional assigned numbers authority such that the OMNI 1151 domain can be interconnected to the global IPv6 Internet without 1152 causing inconsistencies in the routing system. An OMNI domain could 1153 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1154 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1155 were ever connected to the global IPv6 Internet. 1157 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1158 associated regional assigned numbers authority such that the OMNI 1159 domain can be interconnected to the global IPv4 Internet without 1160 causing routing inconsistencies. An OMNI domain could instead use 1161 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1162 this would require IPv4 NAT if the domain were ever connected to the 1163 global IPv4 Internet. 1165 10. Node Identification 1167 OMNI MNs and MSEs that connect over open Internetworks generate a 1168 Host Identity Tag (HIT) as specified in [RFC7401] and use the value 1169 as a robust general-purpose node identification value. Hierarchical 1170 HITs (HHITs) [I-D.ietf-drip-rid] may provide a useful alternative in 1171 certain domains such as the Unmanned (Air) Traffic Management (UTM) 1172 service for Unmanned Air Systems (UAS). MNs and MSEs can then use 1173 their (H)HITs in IPv6 ND control message exchanges. 1175 When a MN is truly outside the context of any infrastructure, it may 1176 have no MNP information at all. In that case, the MN can use its 1177 (H)HIT as an IPv6 source/destination address for sustained 1178 communications in Vehicle-to-Vehicle (V2V) and (multihop) Vehicle-to- 1179 Infrastructure (V2I) scenarios. The MN can also propagate the (H)HIT 1180 into the multihop routing tables of (collective) Mobile/Vehicular Ad- 1181 hoc Networks (MANETs/VANETs) using only the vehicles themselves as 1182 communications relays. 1184 When a MN connects to ARs over (non-multihop) protected-spectrum 1185 ANETs, an alternate form of node identification (e.g., MAC address, 1186 serial number, airframe identification value, VIN, etc.) may be 1187 sufficient. In that case, the MN should still generate a (H)HIT and 1188 maintain it in conjunction with any other node identifiers. The MN 1189 can then include OMNI "Node Identification" sub-options (see: 1190 Section 11.1.11) in IPv6 ND messages should the need to transmit 1191 identification information over the network arise. 1193 11. Address Mapping - Unicast 1195 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1196 state and use the link-local address format specified in Section 7. 1197 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1198 over physical underlying interfaces without encapsulation observe the 1199 native underlying interface Source/Target Link-Layer Address Option 1200 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1201 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1202 interfaces via encapsulation do not include S/TLLAOs which were 1203 intended for encoding physical L2 media address formats and not 1204 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1205 for encoding additional interface attributes needed for multilink 1206 coordination. Hence, this document does not define an S/TLLAO format 1207 but instead defines a new option type termed the "OMNI option" 1208 designed for these purposes. 1210 MNs such as aircraft typically have many wireless data link types 1211 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1212 etc.) with diverse performance, cost and availability properties. 1214 The OMNI interface would therefore appear to have multiple L2 1215 connections, and may include information for multiple underlying 1216 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1217 an IPv6 ND option called the OMNI option formatted as shown in 1218 Figure 4: 1220 0 1 2 3 1221 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 1222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1223 | Type | Length | Preflen | S/T-omIndex | 1224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1225 | | 1226 ~ Sub-Options ~ 1227 | | 1228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1230 Figure 4: OMNI Option Format 1232 In this format: 1234 o Type is set to TBD1. 1236 o Length is set to the number of 8 octet blocks in the option. The 1237 value 0 is invalid, while the values 1 through 255 (i.e., 8 1238 through 2040 octets, respectively) indicate the total length of 1239 the OMNI option. 1241 o Preflen is an 8 bit field that determines the length of prefix 1242 associated with an LLA. Values 0 through 128 specify a valid 1243 prefix length (all other values are invalid). For IPv6 ND 1244 messages sent from a MN to the MS, Preflen applies to the IPv6 1245 source LLA and provides the length that the MN is requesting or 1246 asserting to the MS. For IPv6 ND messages sent from the MS to the 1247 MN, Preflen applies to the IPv6 destination LLA and indicates the 1248 length that the MS is granting to the MN. For IPv6 ND messages 1249 sent between MS endpoints, Preflen provides the length associated 1250 with the source/target MN that is subject of the ND message. 1252 o S/T-omIndex is an 8 bit field corresponds to the omIndex value for 1253 source or target underlying interface used to convey this IPv6 ND 1254 message. OMNI interfaces MUST number each distinct underlying 1255 interface with an omIndex value between '1' and '255' that 1256 represents a MN-specific 8-bit mapping for the actual ifIndex 1257 value assigned by network management [RFC2863] (the omIndex value 1258 '0' is reserved for use by the MS). For RS and NS messages, S/ 1259 T-omIndex corresponds to the source underlying interface the 1260 message originated from. For RA and NA messages, S/T-omIndex 1261 corresponds to the target underlying interface that the message is 1262 destined to. (For NS messages used for Neighbor Unreachability 1263 Detection (NUD), S/T-omIndex instead identifies the neighbor's 1264 underlying interface to be used as the target interface to return 1265 the NA.) 1267 o Sub-Options is a Variable-length field, of length such that the 1268 complete OMNI Option is an integer multiple of 8 octets long. 1269 Contains one or more Sub-Options, as described in Section 11.1. 1271 The OMNI option may appear in any IPv6 ND message type; it is 1272 processed by interfaces that recognize the option and ignored by all 1273 other interfaces. If multiple OMNI option instances appear in the 1274 same IPv6 ND message, the interface processes the Preflen and S/ 1275 T-omIndex fields in the first instance and ignores those fields in 1276 all other instances. The interface processes the Sub-Options of all 1277 OMNI option instances in the same IPv6 ND message in the consecutive 1278 order in which they occur. 1280 The OMNI option(s) in each IPv6 ND message may include full or 1281 partial information for the neighbor. The union of the information 1282 in the most recently received OMNI options is therefore retained, and 1283 the information is aged/removed in conjunction with the corresponding 1284 neighbor cache entry. 1286 11.1. Sub-Options 1288 Each OMNI option includes zero or more Sub-Options. Each consecutive 1289 Sub-Option is concatenated immediately after its predecessor. All 1290 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1291 encoded in the following format: 1293 0 1 2 1294 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 1295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1296 | Sub-Type| Sub-length | Sub-Option Data ... 1297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1299 Figure 5: Sub-Option Format 1301 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1302 Options defined in this document are: 1304 Sub-Option Name Sub-Type 1305 Pad1 0 1306 PadN 1 1307 Interface Attributes (Type 1) 2 1308 Interface Attributes (Type 2) 3 1309 Traffic Selector 4 1310 MS-Register 5 1311 MS-Release 6 1312 Geo Coordinates 7 1313 DHCPv6 Message 8 1314 HIP Message 9 1315 Node Identification 10 1316 Sub-Type Extension 30 1318 Figure 6 1320 Sub-Types 11-29 are available for future assignment for major 1321 protocol functions. Sub-Type 31 is reserved by IANA. 1323 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1324 Option Data ranging from 0 to 2034 octets. 1326 o Sub-Option Data is a block of data with format determined by Sub- 1327 Type and length determined by Sub-Length. 1329 During transmission, the OMNI interface codes Sub-Type and Sub-Length 1330 together in network byte order in 2 consecutive octets, where Sub- 1331 Option Data may be up to 2034 octets in length. This allows ample 1332 space for coding large objects (e.g., ascii character strings, 1333 protocol messages, security codes, etc.), while a single OMNI option 1334 is limited to 2040 octets the same as for any IPv6 ND option. If the 1335 Sub-Options to be coded would cause an OMNI option to exceed 2040 1336 octets, the OMNI interface codes any remaining Sub-Options in 1337 additional OMNI option instances in the intended order of processing 1338 in the same IPv6 ND message. Implementations must therefore observe 1339 size limitations, and must refrain from sending IPv6 ND messages 1340 larger than the OMNI interface MTU. 1342 During reception, the OMNI interface processes each OMNI option Sub- 1343 Option while skipping over and ignoring any unrecognized Sub-Options. 1344 The OMNI interface processes the Sub-Options of all OMNI option 1345 instances in the consecutive order in which they appear in the IPv6 1346 ND message, beginning with the first instance and continuing through 1347 any additional instances to the end of the message. If a Sub-Option 1348 length would cause the running total for that OMNI option to exceed 1349 the length coded in the option header, the interface accepts any Sub- 1350 Options already processed and ignores the remainder of that option. 1352 The interface then processes any remaining OMNI options in the same 1353 fashion to the end of the IPv6 ND message. 1355 Note: individual large objects that would on their own cause an OMNI 1356 option to exceed 2040 octets are not supported under the current 1357 specification; if this proves to be limiting in practice, future 1358 specifications may define support for fragmenting large objects 1359 across multiple OMNI options within the same IPv6 ND message. 1361 The following Sub-Option types and formats are defined in this 1362 document: 1364 11.1.1. Pad1 1366 0 1367 0 1 2 3 4 5 6 7 1368 +-+-+-+-+-+-+-+-+ 1369 | S-Type=0|x|x|x| 1370 +-+-+-+-+-+-+-+-+ 1372 Figure 7: Pad1 1374 o Sub-Type is set to 0. If multiple instances appear in OMNI 1375 options of the same message all are processed. 1377 o Sub-Type is followed by three 'x' bits, set randomly on 1378 transmission and ignored on receipt. Pad1 therefore consists of a 1379 1 octet with the most significant 5 bits set to 0, and with no 1380 Sub-Length or Sub-Option Data fields following. 1382 11.1.2. PadN 1384 0 1 2 1385 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 1386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1387 | S-Type=1| Sub-length=N | N padding octets ... 1388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1390 Figure 8: PadN 1392 o Sub-Type is set to 1. If multiple instances appear in OMNI 1393 options of the same message all are processed. 1395 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1396 padding octets that follow. 1398 o Sub-Option Data consists of N zero-valued octets. 1400 11.1.3. Interface Attributes (Type 1) 1402 The Interface Attributes (Type 1) sub-option provides a basic set of 1403 attributes for underlying interfaces. Interface Attributes (Type 1) 1404 is deprecated throughout the rest of this specification, and 1405 Interface Attributes (Type 2) (see: Section 11.1.4) are indicated 1406 wherever the term "Interface Attributes" appears without an 1407 associated Type designation. 1409 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1410 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1411 they receive. If an Interface Attributes (Type 1) is included, it 1412 must have the following format: 1414 0 1 2 3 1415 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 1416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1417 | Sub-Type=2| Sub-length=N | omIndex | omType | 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1419 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1421 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1423 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1425 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1427 |P56|P57|P58|P59|P60|P61|P62|P63| 1428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1430 Figure 9: Interface Attributes (Type 1) 1432 o Sub-Type is set to 2. If multiple instances with different 1433 omIndex values appear in OMNI option of the same message all are 1434 processed; if multiple instances with the same omIndex value 1435 appear, the first is processed and all others are ignored 1437 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1438 Sub-Option Data octets that follow. 1440 o omIndex is a 1-octet field containing a value from 0 to 255 1441 identifying the underlying interface for which the attributes 1442 apply. 1444 o omType is a 1-octet field containing a value from 0 to 255 1445 corresponding to the underlying interface identified by omIndex. 1447 o Provider ID is a 1-octet field containing a value from 0 to 255 1448 corresponding to the underlying interface identified by omIndex. 1450 o Link encodes a 4-bit link metric. The value '0' means the link is 1451 DOWN, and the remaining values mean the link is UP with metric 1452 ranging from '1' ("lowest") to '15' ("highest"). 1454 o Resvd is reserved for future use. Set to 0 on transmission and 1455 ignored on reception. 1457 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1458 values P[00] through P[63] corresponding to the 64 Differentiated 1459 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1460 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1461 or '3' ("high") to indicate a QoS preference for underlying 1462 interface selection purposes. 1464 11.1.4. Interface Attributes (Type 2) 1466 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1467 information for the multilink conceptual sending algorithm discussed 1468 in Section 13. The L2 information is used for selecting among 1469 potentially multiple candidate underlying interfaces that can be used 1470 to forward packets to the neighbor based on factors such as DSCP 1471 preferences and link quality. Interface Attributes (Type 2) further 1472 includes link-layer address information to be used for either OAL 1473 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1474 can be avoided). 1476 Interface Attributes (Type 2) are the sole Interface Attributes 1477 format in this specification that all OMNI nodes must honor. 1478 Wherever the term "Interface Attributes" occurs throughout this 1479 specification without a "Type" designation, the format given below is 1480 indicated: 1482 0 1 2 3 1483 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 1484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1485 | S-Type=3| Sub-length=N | omIndex | omType | 1486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1487 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1489 | LHS (bits 8 - 31) | ~ 1490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1491 ~ ~ 1492 ~ Link Layer Address (L2ADDR) ~ 1493 ~ ~ 1494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1495 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1497 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1502 Figure 10: Interface Attributes (Type 2) 1504 o Sub-Type is set to 3. If multiple instances with different 1505 omIndex values appear in OMNI options of the same message all are 1506 processed; if multiple instances with the same omIndex value 1507 appear, the first is processed and all others are ignored. 1509 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1510 Sub-Option Data octets that follow. The 'omIndex', 'omType', 1511 'Provider ID', 'Link', 'R' and 'API' fields are always present; 1512 hence, the remainder of the Sub-Option Data is limited to 2030 1513 octets. 1515 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1516 encoded as follows: 1518 * omIndex is set to an 8-bit integer value corresponding to a 1519 specific underlying interface the same as specified above for 1520 the OMNI option S/T-omIndex field. The OMNI options of a same 1521 message may include multiple Interface Attributes Sub-Options, 1522 with each distinct omIndex value pertaining to a different 1523 underlying interface. The OMNI option will often include an 1524 Interface Attributes Sub-Option with the same omIndex value 1525 that appears in the S/T-omIndex. In that case, the actual 1526 encapsulation address of the received IPv6 ND message should be 1527 compared with the L2ADDR encoded in the Sub-Option (see below); 1528 if the addresses are different (or, if L2ADDR is absent) the 1529 presence of a NAT is assumed. 1531 * omType is set to an 8-bit integer value corresponding to the 1532 underlying interface identified by omIndex. The value 1533 represents an OMNI interface-specific 8-bit mapping for the 1534 actual IANA ifType value registered in the 'IANAifType-MIB' 1535 registry [http://www.iana.org]. 1537 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1538 for the network service provider associated with this omIndex. 1540 * Link encodes a 4-bit link metric. The value '0' means the link 1541 is DOWN, and the remaining values mean the link is UP with 1542 metric ranging from '1' ("lowest") to '15' ("highest"). 1544 * R is reserved for future use. 1546 * API - a 3-bit "Address/Preferences/Indexed" code that 1547 determines the contents of the remainder of the sub-option as 1548 follows: 1550 + When the most significant bit (i.e., "Address") is set to 1, 1551 the SRT, FMT, LHS and L2ADDR fields are included immediately 1552 following the API code; else, they are omitted. 1554 + When the next most significant bit (i.e., "Preferences") is 1555 set to 1, a preferences block is included next; else, it is 1556 omitted. (Note that if "Address" is set the preferences 1557 block immediately follows L2ADDR; else, it immediately 1558 follows the API code.) 1560 + When a preferences block is present and the least 1561 significant bit (i.e., "Indexed") is set to 0, the block is 1562 encoded in "Simplex" form as shown in Figure 9; else it is 1563 encoded in "Indexed" form as discussed below. 1565 * When API indicates that an "Address" is included, the following 1566 fields appear in consecutive order (else, they are omitted): 1568 + SRT - a 5-bit Segment Routing Topology prefix length value 1569 that (when added to 96) determines the prefix length to 1570 apply to the ULA formed from concatenating [ULA*]::/96 with 1571 the 32 bit LHS MSID value that follows. For example, the 1572 value 16 corresponds to the prefix length 112. 1574 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1575 the included Link Layer Address as follows: 1577 - When the most significant bit (i.e., "Framework") is set 1578 to 1, L2ADDR is the INET encapsulation address for the 1579 Source/Target Client itself; otherwise L2ADDR is the 1580 address of the Server/Proxy named in the LHS. 1582 - When the next most significant bit (i.e., "Mode") is set 1583 to 1, the Framework node is (likely) located behind an 1584 INET Network Address Translator (NAT); otherwise, it is 1585 on the open INET. 1587 - When the least significant bit (i.e., "Type") is set to 1588 0, L2ADDR includes a UDP Port Number followed by an IPv4 1589 address; otherwise, it includes a UDP Port Number 1590 followed by an IPv6 address. 1592 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1593 path to the target. When SRT and LHS are both set to 0, the 1594 LHS is considered unspecified in this IPv6 ND message. When 1595 SRT is set to 0 and LHS is non-zero, the prefix length is 1596 set to 128. SRT and LHS together provide guidance to the 1597 OMNI interface forwarding algorithm. Specifically, if SRT/ 1598 LHS is located in the local OMNI link segment then the OMNI 1599 interface can encapsulate according to FMT/L2ADDR (following 1600 any necessary NAT traversal messaging); else, it must 1601 forward according to the OMNI link spanning tree. See 1602 [I-D.templin-intarea-6706bis] for further discussion. 1604 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1605 and identifies the link-layer address (i.e., the 1606 encapsulation address) of the source/target. The UDP Port 1607 Number appears in the first 2 octets and the IP address 1608 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1609 The Port Number and IP address are recorded in network byte 1610 order, and in ones-compliment "obfuscated" form per 1611 [RFC4380]. The OMNI interface forwarding algorithm uses 1612 FMT/L2ADDR to determine the encapsulation address for 1613 forwarding when SRT/LHS is located in the local OMNI link 1614 segment. Note that if the target is behind a NAT, L2ADDR 1615 will contain the mapped INET address stored in the NAT; 1616 otherwise, L2ADDR will contain the native INET information 1617 of the target itself. 1619 * When API indicates that "Preferences" are included, a 1620 preferences block appears as the remainder of the Sub-Option as 1621 a series of Bitmaps and P[*] values. In "Simplex" form, the 1622 index for each singleton Bitmap octet is inferred from its 1623 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 10. 1624 In "Indexed" form, each Bitmap is preceded by an Index octet 1625 that encodes a value "i" = (0 - 255) as the index for its 1626 companion Bitmap as follows: 1628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1629 | Index=i | Bitmap(i) |P[*] values ... 1630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1632 Figure 11 1634 * The preferences consist of a first (simplex/indexed) Bitmap 1635 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1636 2-bit P[*] values, followed by a second Bitmap (i), followed by 1637 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1638 the bits of each Bitmap(i) that are set to '1'' indicate the 1639 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1640 that follow; if any Bitmap(i) bits are '0', then the 1641 corresponding P[*] block is instead omitted. For example, if 1642 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1643 followed by the block with P[04]-P[07], etc., and ending with 1644 the block with P[28]-P[31] are included (as shown in Figure 9). 1645 The next Bitmap(i) is then consulted with its bits indicating 1646 which P[*] blocks follow, etc. out to the end of the Sub- 1647 Option. 1649 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1650 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1651 preference for underlying interface selection purposes. Not 1652 all P[*] values need to be included in the OMNI option of each 1653 IPv6 ND message received. Any P[*] values represented in an 1654 earlier OMNI option but omitted in the current OMNI option 1655 remain unchanged. Any P[*] values not yet represented in any 1656 OMNI option default to "medium". 1658 * The first 16 P[*] blocks correspond to the 64 Differentiated 1659 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1660 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1661 traffic classifier values P[64], P[65], P[66], etc. See 1662 Appendix A for further discussion and examples. 1664 11.1.5. Traffic Selector 1665 0 1 2 3 1666 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 1667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1668 | S-Type=4| Sub-length=N | omIndex | ~ 1669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1670 ~ ~ 1671 ~ RFC 6088 Format Traffic Selector ~ 1672 ~ ~ 1673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1675 Figure 12: Traffic Selector 1677 o Sub-Type is set to 4. If multiple instances appear in OMNI 1678 options of the same message all are processed, i.e., even if the 1679 same omIndex value appears multiple times. 1681 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1682 Sub-Option Data octets that follow. 1684 o Sub-Option Data contains a 1 octet omIndex encoded exactly as 1685 specified in Section 11.1.3, followed by an N-1 octet traffic 1686 selector formatted per [RFC6088] beginning with the "TS Format" 1687 field. The largest traffic selector for a given omIndex is 1688 therefore 2033 octets. 1690 11.1.6. MS-Register 1692 0 1 2 3 1693 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 1694 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1695 | S-Type=5| Sub-length=4n | MSID[1] (bits 0 - 15) | 1696 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1697 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 ... ... ... ... ... ... 1702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 | MSID [n] (bits 16 - 32) | 1704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1706 Figure 13: MS-Register Sub-option 1708 o Sub-Type is set to 5. If multiple instances appear in OMNI 1709 options of the same message all are processed. Only the first 1710 MAX_MSID values processed (whether in a single instance or 1711 multiple) are retained and all other MSIDs are ignored. 1713 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1714 length of the Sub-Option Data section is therefore limited to 2032 1715 octets. 1717 o A list of n 4 octet MSIDs is included in the following 4n octets. 1718 The Anycast MSID value '0' in an RS message MS-Register sub-option 1719 requests the recipient to return the MSID of a nearby MSE in a 1720 corresponding RA response. 1722 11.1.7. MS-Release 1724 0 1 2 3 1725 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 1726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1727 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1728 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1729 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1731 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1733 ... ... ... ... ... ... 1734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1735 | MSID [n] (bits 16 - 32) | 1736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 Figure 14: MS-Release Sub-option 1740 o Sub-Type is set to 6. If multiple instances appear in OMNI 1741 options of the same message all are processed. Only the first 1742 MAX_MSID values processed (whether in a single instance or 1743 multiple) are retained and all other MSIDs are ignored. 1745 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1746 length of the Sub-Option Data section is therefore limited to 2032 1747 octets. 1749 o A list of n 4 octet MSIDs is included in the following 4n octets. 1750 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1751 i.e., only non-zero values are processed. 1753 11.1.8. Geo Coordinates 1754 0 1 2 3 1755 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 1756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1757 | S-Type=7| Sub-length=N | Geo Coordinates 1758 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1760 Figure 15: Geo Coordinates Sub-option 1762 o Sub-Type is set to 7. If multiple instances appear in OMNI 1763 options of the same message the first is processed and all others 1764 are ignored. 1766 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1767 Sub-Option Data octets that follow. 1769 o A set of Geo Coordinates of maximum length 2034 octets. Format(s) 1770 to be specified in future documents; should include Latitude/ 1771 Longitude, plus any additional attributes such as altitude, 1772 heading, speed, etc. 1774 11.1.9. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1776 0 1 2 3 1777 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 1778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1779 | S-Type=8| Sub-length=N | msg-type | id (octet 0) | 1780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1781 | transaction-id (octets 1-2) | | 1782 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1783 | | 1784 . DHCPv6 options . 1785 . (variable number and length) . 1786 | | 1787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1789 Figure 16: DHCPv6 Message Sub-option 1791 o Sub-Type is set to 8. If multiple instances appear in OMNI 1792 options of the same message the first is processed and all others 1793 are ignored. 1795 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1796 Sub-Option Data octets that follow. The 'msg-type' and 1797 'transaction-id' fields are always present; hence, the length of 1798 the DHCPv6 options is restricted to 2030 octets. 1800 o 'msg-type' and 'transaction-id' are coded according to Section 8 1801 of [RFC8415]. 1803 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1804 follows. 1806 11.1.10. Host Identity Protocol (HIP) Message 1808 0 1 2 3 1809 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 1810 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1811 | S-Type=9| Sub-length=N |0| Packet Type |Version| RES.|1| 1812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1813 | Checksum | Controls | 1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1815 | Sender's Host Identity Tag (HIT) | 1816 | | 1817 | | 1818 | | 1819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1820 | Receiver's Host Identity Tag (HIT) | 1821 | | 1822 | | 1823 | | 1824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1825 | | 1826 / HIP Parameters / 1827 / / 1828 | | 1829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1831 Figure 17: HIP Message Sub-option 1833 o Sub-Type is set to 9. If multiple instances appear in OMNI 1834 options of the same message the first is processed and all others 1835 are ignored. 1837 o Sub-Length is set to N, i.e., the length of the option in octets 1838 beginning immediately following the Sub-Length field and extending 1839 to the end of the HIP parameters. The length of the entire HIP 1840 message is therefore restricted to 2034 octets. 1842 o The HIP message is coded exactly as specified in Section 5 of 1843 [RFC7401], except that the OMNI "Sub-Type" and "Sub-Length" fields 1844 replace the first 2 octets of the HIP message header (i.e., the 1845 Next Header and Header Length fields). 1847 11.1.11. Node Identification 1849 0 1 2 3 1850 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 1851 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1852 |S-Type=10| Sub-length=N | ID-Type | ~ 1853 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1854 ~ Node Identification Value (N-1 octets) ~ 1855 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1857 Figure 18: Node Identification 1859 o Sub-Type is set to 10. If multiple instances appear in OMNI 1860 options of the same IPv6 ND message the first instance of a 1861 specific ID-Type is processed and all other instances of the same 1862 ID-Type are ignored. (Note therefore that it is possible for a 1863 single IPv6 ND message to convey multiple Node Identifications - 1864 each having a different ID-Type.) 1866 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1867 Sub-Option Data octets that follow. The ID-Type field is always 1868 present; hence, the maximum Node Identification Value length is 1869 2033 octets. 1871 o ID-Type is a 1 octet field that encodes the type of the Node 1872 Identification Value. The following ID-Type values are currently 1873 defined: 1875 * 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates 1876 that Node Identification Value contains a 16 octet UUID. 1878 * 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node 1879 Identification Value contains a 16 octet HIT. 1881 * 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates 1882 that Node Identification Value contains a 16 octet HHIT. 1884 * 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that 1885 Node Identification Value contains an N-1 octet NAI. 1887 * 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicates 1888 that Node Identification Value contains an N-1 octet FQDN. 1890 * 5 - 252 - Unassigned. 1892 * 253-254 - Reserved for experimentation, as recommended in 1893 [RFC3692]. 1895 * 255 - reserved by IANA. 1897 o Node Identification Value is an (N - 1) octet field encoded 1898 according to the appropriate the "ID-Type" reference above. 1900 When a Node Identification Value is needed for DHCPv6 messaging 1901 purposes, it is encoded as a DHCP Unique IDentifier (DUID) using the 1902 "DUID-EN for OMNI" format with enterprise number 45282 (see: 1903 Section 22) as shown in Figure 19: 1905 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 1906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1907 | DUID-Type (2) | EN (high bits == 0) | 1908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1909 | EN (low bits = 45282) | ID-Type | | 1910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1911 . Node Identification Value . 1912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1914 Figure 19: DUID-EN for OMNI Format 1916 In this format, the ID-Type and Node Identification Value fields are 1917 coded exactly as in Figure 18 following the 6 octet DUID-EN header, 1918 and the entire "DUID-EN for OMNI" is included in a DHCPv6 message per 1919 [RFC8415]. 1921 11.1.12. Sub-Type Extension 1923 Since the Sub-Type field is only 5 bits in length, future 1924 specifications of major protocol functions may exhaust the remaining 1925 Sub-Type values available for assignment. This document therefore 1926 defines Sub-Type 30 as an "extension", meaning that the actual sub- 1927 option type is determined by examining a 1 octet "Extension-Type" 1928 field immediately following the Sub-Length field. The Sub-Type 1929 Extension is formatted as shown in Figure 20: 1931 0 1 2 3 1932 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 1933 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1934 |S-Type=30| Sub-length=N | Extension-Type| ~ 1935 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1936 ~ ~ 1937 ~ Extension-Type Body ~ 1938 ~ ~ 1939 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1941 Figure 20: Sub-Type Extension 1943 o Sub-Type is set to 30. If multiple instances appear in OMNI 1944 options of the same message all are processed, where each 1945 individual extension defines its own policy for processing 1946 multiple of that type. 1948 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1949 Sub-Option Data octets that follow. The Extension-Type field is 1950 always present; hence, the maximum Extension-Type Body length is 1951 2033 octets. 1953 o Extension-Type contains a 1 octet Sub-Type Extension value between 1954 0 and 255. 1956 o Extension-Type Body contains an N-1 octet block with format 1957 defined by the given extension specification. 1959 Extension-Type values 1 through 252 are available for assignment by 1960 future specifications, which must also define the format of the 1961 Extension-Type Body and its processing rules. Extension-Type values 1962 253 and 254 are reserved for experimentation, as recommended in 1963 [RFC3692]. Extension-Type value 255 is reserved by IANA. 1965 Extension-Type value 0 ("Origin Indication") is defined in this 1966 document according to Section 11.1.12.1: 1968 11.1.12.1. Origin Indication 1970 0 1 2 3 1971 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 1972 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1973 |S-Type=30| Sub-length=7/19 | Ext-Type=0 | Origin Port # | 1974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1975 | Origin Port # | Origin IPv4/IPv6 Address ~ 1976 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1978 Figure 21: Origin Indication (Extension-Type 0) 1980 o Sub-Type is set to 30. 1982 o Sub-Length is set to either 7 or 19; if Sub-Length encodes any 1983 other value, the Sub-Option is ignored. 1985 o Extension-Type is set to 0. If multiple instances appear in OMNI 1986 options of the same message the first instance is processed and 1987 all others are ignored. 1989 o Extension-Type Body contains a 2 octet Origin Port Number followed 1990 immediately by a 4 octet Origin IPv4 address if Sub-Length encodes 1991 7, or by a 16 octet Origin IPv6 address if Sub-Length encodes 19. 1992 The Port Number and IP address are recorded in ones-compliment 1993 "obfuscated" form per [RFC4380]. 1995 12. Address Mapping - Multicast 1997 The multicast address mapping of the native underlying interface 1998 applies. The mobile router on board the MN also serves as an IGMP/ 1999 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 2000 using the L2 address of the AR as the L2 address for all multicast 2001 packets. 2003 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 2004 coordinate with the AR, and *NET L2 elements use MLD snooping 2005 [RFC4541]. 2007 13. Multilink Conceptual Sending Algorithm 2009 The MN's IPv6 layer selects the outbound OMNI interface according to 2010 SBM considerations when forwarding data packets from local or EUN 2011 applications to external correspondents. Each OMNI interface 2012 maintains a neighbor cache the same as for any IPv6 interface, but 2013 with additional state for multilink coordination. Each OMNI 2014 interface maintains default routes via ARs discovered as discussed in 2015 Section 14, and may configure more-specific routes discovered through 2016 means outside the scope of this specification. 2018 After a packet enters the OMNI interface, one or more outbound 2019 underlying interfaces are selected based on PBM traffic attributes, 2020 and one or more neighbor underlying interfaces are selected based on 2021 the receipt of Interface Attributes sub-options in IPv6 ND messages 2022 (see: Figure 9). Underlying interface selection for the nodes own 2023 local interfaces are based on attributes such as DSCP, application 2024 port number, cost, performance, message size, etc. OMNI interface 2025 multilink selections could also be configured to perform replication 2026 across multiple underlying interfaces for increased reliability at 2027 the expense of packet duplication. The set of all Interface 2028 Attributes received in IPv6 ND messages determines the multilink 2029 forwarding profile for selecting the neighbor's underlying 2030 interfaces. 2032 When the OMNI interface sends a packet over a selected outbound 2033 underlying interface, the OAL includes or omits a mid-layer 2034 encapsulation header as necessary as discussed in Section 5 and as 2035 determined by the L2 address information received in Interface 2036 Attributes. The OAL also performs encapsulation when the nearest AR 2037 is located multiple hops away as discussed in Section 14.1. (Note 2038 that the OAL MAY employ packing when multiple packets are available 2039 for forwarding to the same destination.) 2041 OMNI interface multilink service designers MUST observe the BCP 2042 guidance in Section 15 [RFC3819] in terms of implications for 2043 reordering when packets from the same flow may be spread across 2044 multiple underlying interfaces having diverse properties. 2046 13.1. Multiple OMNI Interfaces 2048 MNs may connect to multiple independent OMNI links concurrently in 2049 support of SBM. Each OMNI interface is distinguished by its Anycast 2050 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 2051 configures a separate OMNI interface for each link so that multiple 2052 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 2053 layer. A different Anycast ULA is assigned to each interface, and 2054 the MN injects the service prefixes for the OMNI link instances into 2055 the EUN routing system. 2057 Applications in EUNs can use Segment Routing to select the desired 2058 OMNI interface based on SBM considerations. The Anycast ULA is 2059 written into the IPv6 destination address, and the actual destination 2060 (along with any additional intermediate hops) is written into the 2061 Segment Routing Header. Standard IP routing directs the packets to 2062 the MN's mobile router entity, and the Anycast ULA identifies the 2063 OMNI interface to be used for transmission to the next hop. When the 2064 MN receives the message, it replaces the IPv6 destination address 2065 with the next hop found in the routing header and transmits the 2066 message over the OMNI interface identified by the Anycast ULA. 2068 Multiple distinct OMNI links can therefore be used to support fault 2069 tolerance, load balancing, reliability, etc. The architectural model 2070 is similar to Layer 2 Virtual Local Area Networks (VLANs). 2072 13.2. MN<->AR Traffic Loop Prevention 2074 After an AR has registered an MNP for a MN (see: Section 14), the AR 2075 will forward packets destined to an address within the MNP to the MN. 2076 The MN will under normal circumstances then forward the packet to the 2077 correct destination within its internal networks. 2079 If at some later time the MN loses state (e.g., after a reboot), it 2080 may begin returning packets destined to an MNP address to the AR as 2081 its default router. The AR therefore must drop any packets 2082 originating from the MN and destined to an address within the MN's 2083 registered MNP. To do so, the AR institutes the following check: 2085 o if the IP destination address belongs to a neighbor on the same 2086 OMNI interface, and if the link-layer source address is the same 2087 as one of the neighbor's link-layer addresses, drop the packet. 2089 14. Router Discovery and Prefix Registration 2091 MNs interface with the MS by sending RS messages with OMNI options 2092 under the assumption that one or more AR on the *NET will process the 2093 message and respond. The MN then configures default routes for the 2094 OMNI interface via the discovered ARs as the next hop. The manner in 2095 which the *NET ensures AR coordination is link-specific and outside 2096 the scope of this document (however, considerations for *NETs that do 2097 not provide ARs that recognize the OMNI option are discussed in 2098 Section 19). 2100 For each underlying interface, the MN sends an RS message with an 2101 OMNI option to coordinate with MSEs identified by MSID values. 2102 Example MSID discovery methods are given in [RFC5214] and include 2103 data link login parameters, name service lookups, static 2104 configuration, a static "hosts" file, etc. The MN can also send an 2105 RS with an MS-Register sub-option that includes the Anycast MSID 2106 value '0', i.e., instead of or in addition to any non-zero MSIDs. 2107 When the AR receives an RS with a MSID '0', it selects a nearby MSE 2108 (which may be itself) and returns an RA with the selected MSID in an 2109 MS-Register sub-option. The AR selects only a single wildcard MSE 2110 (i.e., even if the RS MS-Register sub-option included multiple '0' 2111 MSIDs) while also soliciting the MSEs corresponding to any non-zero 2112 MSIDs. 2114 MNs configure OMNI interfaces that observe the properties discussed 2115 in the previous section. The OMNI interface and its underlying 2116 interfaces are said to be in either the "UP" or "DOWN" state 2117 according to administrative actions in conjunction with the interface 2118 connectivity status. An OMNI interface transitions to UP or DOWN 2119 through administrative action and/or through state transitions of the 2120 underlying interfaces. When a first underlying interface transitions 2121 to UP, the OMNI interface also transitions to UP. When all 2122 underlying interfaces transition to DOWN, the OMNI interface also 2123 transitions to DOWN. 2125 When an OMNI interface transitions to UP, the MN sends RS messages to 2126 register its MNP and an initial set of underlying interfaces that are 2127 also UP. The MN sends additional RS messages to refresh lifetimes 2128 and to register/deregister underlying interfaces as they transition 2129 to UP or DOWN. The MN's OMNI interface sends initial RS messages 2130 over an UP underlying interface with its MNP-LLA as the source and 2131 with destination set to link-scoped All-Routers multicast (ff02::2) 2132 [RFC4291]. The OMNI interface includes an OMNI option per Section 11 2133 with a Preflen assertion, Interface Attributes appropriate for 2134 underlying interfaces, MS-Register/Release sub-options containing 2135 MSID values, and with any other necessary OMNI sub-options (e.g., a 2136 Node Identification sub-option as an identity for the MN). The OMNI 2137 interface then sets the S/T-omIndex field to the index of the 2138 underlying interface over which the RS message is sent. The OMNI 2139 interface then sends the RS over the underlying interface, using OAL 2140 encapsulation and fragmentation if necessary. If OAL encapsulation 2141 is used, the OMNI interface sets the OAL source address to the ULA 2142 corresponding to the RS source and sets the OAL destination to site- 2143 scoped All-Routers multicast (ff05::2). 2145 ARs process IPv6 ND messages with OMNI options and act as an MSE 2146 themselves and/or as a proxy for other MSEs. ARs receive RS messages 2147 (while performing OAL reassembly if necessary) and create a neighbor 2148 cache entry for the MN, then coordinate with any MSEs named in the 2149 Register/Release lists in a manner outside the scope of this 2150 document. When an MSE processes the OMNI information, it first 2151 validates the prefix registration information then injects/withdraws 2152 the MNP in the routing/mapping system and caches/discards the new 2153 Preflen, MNP and Interface Attributes. The MSE then informs the AR 2154 of registration success/failure, and the AR returns an RA message to 2155 the MN with an OMNI option per Section 11. 2157 The AR's OMNI interface returns the RA message via the same 2158 underlying interface of the MN over which the RS was received, and 2159 with destination address set to the MNP-LLA (i.e., unicast), with 2160 source address set to its own LLA, and with an OMNI option with S/ 2161 T-omIndex set to the value included in the RS. The OMNI option also 2162 includes a Preflen confirmation, Interface Attributes, MS-Register/ 2163 Release and any other necessary OMNI sub-options (e.g., a Node 2164 Identification sub-option as an identity for the AR). The RA also 2165 includes any information for the link, including RA Cur Hop Limit, M 2166 and O flags, Router Lifetime, Reachable Time and Retrans Timer 2167 values, and includes any necessary options such as: 2169 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 2171 o RIOs [RFC4191] with more-specific routes. 2173 o an MTU option that specifies the maximum acceptable packet size 2174 for this underlying interface. 2176 The OMNI interface then sends the RA, using OAL encapsulation and 2177 fragmentation if necessary. If OAL encapsulation is used, the OMNI 2178 interface sets the OAL source address to the ULA corresponding to the 2179 RA source and sets the OAL destination to the ULA corresponding to 2180 the RA destination. The AR MAY also send periodic and/or event- 2181 driven unsolicited RA messages per [RFC4861]. In that case, the S/ 2182 T-omIndex field in the OMNI option of the unsolicited RA message 2183 identifies the target underlying interface of the destination MN. 2185 The AR can combine the information from multiple MSEs into one or 2186 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 2187 Each aggregate RA includes an OMNI option with MS-Register/Release 2188 sub-options with the MSEs represented by the aggregate. If an 2189 aggregate is sent, the RA message contents must consistently 2190 represent the combined information advertised by all represented 2191 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 2192 address, the MN determines the addresses of the represented MSEs by 2193 examining the MS-Register/Release OMNI sub-options. 2195 When the MN receives the RA message, it creates an OMNI interface 2196 neighbor cache entry for each MSID that has confirmed MNP 2197 registration via the L2 address of this AR. If the MN connects to 2198 multiple *NETs, it records the additional L2 AR addresses in each 2199 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 2200 then configures a default route via the MSE that returned the RA 2201 message, and assigns the Subnet Router Anycast address corresponding 2202 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 2203 manages its underlying interfaces according to their states as 2204 follows: 2206 o When an underlying interface transitions to UP, the MN sends an RS 2207 over the underlying interface with an OMNI option. The OMNI 2208 option contains at least one Interface Attribute sub-option with 2209 values specific to this underlying interface, and may contain 2210 additional Interface Attributes specific to other underlying 2211 interfaces. The option also includes any MS-Register/Release sub- 2212 options. 2214 o When an underlying interface transitions to DOWN, the MN sends an 2215 RS or unsolicited NA message over any UP underlying interface with 2216 an OMNI option containing an Interface Attribute sub-option for 2217 the DOWN underlying interface with Link set to '0'. The MN sends 2218 an RS when an acknowledgement is required, or an unsolicited NA 2219 when reliability is not thought to be a concern (e.g., if 2220 redundant transmissions are sent on multiple underlying 2221 interfaces). 2223 o When the Router Lifetime for a specific AR nears expiration, the 2224 MN sends an RS over the underlying interface to receive a fresh 2225 RA. If no RA is received, the MN can send RS messages to an 2226 alternate MSID in case the current MSID has failed. If no RS 2227 messages are received even after trying to contact alternate 2228 MSIDs, the MN marks the underlying interface as DOWN. 2230 o When a MN wishes to release from one or more current MSIDs, it 2231 sends an RS or unsolicited NA message over any UP underlying 2232 interfaces with an OMNI option with a Release MSID. Each MSID 2233 then withdraws the MNP from the routing/mapping system and informs 2234 the AR that the release was successful. 2236 o When all of a MNs underlying interfaces have transitioned to DOWN 2237 (or if the prefix registration lifetime expires), any associated 2238 MSEs withdraw the MNP the same as if they had received a message 2239 with a release indication. 2241 The MN is responsible for retrying each RS exchange up to 2242 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 2243 seconds until an RA is received. If no RA is received over an UP 2244 underlying interface (i.e., even after attempting to contact 2245 alternate MSEs), the MN declares this underlying interface as DOWN. 2247 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 2248 Therefore, when the IPv6 layer sends an RS message the OMNI interface 2249 returns an internally-generated RA message as though the message 2250 originated from an IPv6 router. The internally-generated RA message 2251 contains configuration information that is consistent with the 2252 information received from the RAs generated by the MS. Whether the 2253 OMNI interface IPv6 ND messaging process is initiated from the 2254 receipt of an RS message from the IPv6 layer is an implementation 2255 matter. Some implementations may elect to defer the IPv6 ND 2256 messaging process until an RS is received from the IPv6 layer, while 2257 others may elect to initiate the process proactively. Still other 2258 deployments may elect to administratively disable the ordinary RS/RA 2259 messaging used by the IPv6 layer over the OMNI interface, since they 2260 are not required to drive the internal RS/RA processing. (Note that 2261 this same logic applies to IPv4 implementations that employ ICMP- 2262 based Router Discovery per [RFC1256].) 2264 Note: The Router Lifetime value in RA messages indicates the time 2265 before which the MN must send another RS message over this underlying 2266 interface (e.g., 600 seconds), however that timescale may be 2267 significantly longer than the lifetime the MS has committed to retain 2268 the prefix registration (e.g., REACHABLETIME seconds). ARs are 2269 therefore responsible for keeping MS state alive on a shorter 2270 timescale than the MN is required to do on its own behalf. 2272 Note: On multicast-capable underlying interfaces, MNs should send 2273 periodic unsolicited multicast NA messages and ARs should send 2274 periodic unsolicited multicast RA messages as "beacons" that can be 2275 heard by other nodes on the link. If a node fails to receive a 2276 beacon after a timeout value specific to the link, it can initiate a 2277 unicast exchange to test reachability. 2279 Note: if an AR acting as a proxy forwards a MN's RS message to 2280 another node acting as an MSE using UDP/IP encapsulation, it must use 2281 a distinct UDP source port number for each MN. This allows the MSE 2282 to distinguish different MNs behind the same AR at the link-layer, 2283 whereas the link-layer addresses would otherwise be 2284 indistinguishable. 2286 Note: when an AR acting as an MSE returns an RA to an INET Client, it 2287 includes an OMNI option with an Interface Attributes sub-option with 2288 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 2289 its INET interface. This provides the Client with partition prefix 2290 context regarding the local OMNI link segment. 2292 14.1. Router Discovery in IP Multihop and IPv4-Only Networks 2294 On some *NETs, a MN may be located multiple IP hops away from the 2295 nearest AR. Forwarding through IP multihop *NETs is conducted 2296 through the application of a routing protocol (e.g., a MANET/VANET 2297 routing protocol over omni-directional wireless interfaces, an inter- 2298 domain routing protocol in an enterprise network, etc.). These *NETs 2299 could be either IPv6-enabled or IPv4-only, while IPv4-only *NETs 2300 could be either multicast-capable or unicast-only (note that for 2301 IPv4-only *NETs the following procedures apply for both single-hop 2302 and multihop cases). 2304 A MN located potentially multiple *NET hops away from the nearest AR 2305 prepares an RS message with source address set to its MNP-LLA (or to 2306 the unspecified address (::) if it does not yet have an MNP-LLA), and 2307 with destination set to link-scoped All-Routers multicast the same as 2308 discussed above. If OAL encapsulation and fragmentation are 2309 necessary, the OMNI interface sets the OAL source address to the ULA 2310 corresponding to the RS source (or to a Temporary ULA if the RS 2311 source was unspecified) and sets the OAL destination to site-scoped 2312 All-Routers multicast (ff05::2). For IPv6-enabled *NETs, the MN then 2313 encapsulates the message in UDP/IPv6 headers with source address set 2314 to the underlying interface address (or to the ULA that would be used 2315 for OAL encapsulation if the underlying interface does not yet have 2316 an address) and sets the destination to either a unicast or anycast 2317 address of an AR. For IPv4-only *NETs, the MN instead encapsulates 2318 the RS message in an IPv4 header with source address set to the IPv4 2319 address of the underlying interface and with destination address set 2320 to either the unicast IPv4 address of an AR [RFC5214] or an IPv4 2321 anycast address reserved for OMNI. The MN then sends the 2322 encapsulated RS message via the *NET interface, where it will be 2323 forwarded by zero or more intermediate *NET hops. 2325 When an intermediate *NET hop that participates in the routing 2326 protocol receives the encapsulated RS, it forwards the message 2327 according to its routing tables (note that an intermediate node could 2328 be a fixed infrastructure element or another MN). This process 2329 repeats iteratively until the RS message is received by a penultimate 2330 *NET hop within single-hop communications range of an AR, which 2331 forwards the message to the AR. 2333 When the AR receives the message, it decapsulates the RS (while 2334 performing OAL reassembly, if necessary) and coordinates with the MS 2335 the same as for an ordinary link-local RS, since the inner Hop Limit 2336 will not have been decremented by the multihop forwarding process. 2337 The AR then prepares an RA message with source address set to its own 2338 ADM-LLA and destination address set to the LLA of the original MN. 2339 The AR then performs OAL encapsulation and fragmentation if 2340 necessary, with OAL source set to its own ADM-ULA and destination set 2341 to the ULA corresponding to the RA source. The AR then encapsulates 2342 the message in an IPv4/IPv6 header with source address set to its own 2343 IPv4/ULA address and with destination set to the encapsulation source 2344 of the RS. 2346 The AR then forwards the message to an *NET node within 2347 communications range, which forwards the message according to its 2348 routing tables to an intermediate node. The multihop forwarding 2349 process within the *NET continues repetitively until the message is 2350 delivered to the original MN, which decapsulates the message and 2351 performs autoconfiguration the same as if it had received the RA 2352 directly from the AR as an on-link neighbor. 2354 Note: An alternate approach to multihop forwarding via IPv6 2355 encapsulation would be for the MN and AR to statelessly translate the 2356 IPv6 LLAs into ULAs and forward the RS/RA messages without 2357 encapsulation. This would violate the [RFC4861] requirement that 2358 certain IPv6 ND messages must use link-local addresses and must not 2359 be accepted if received with Hop Limit less than 255. This document 2360 therefore mandates encapsulation since the overhead is nominal 2361 considering the infrequent nature and small size of IPv6 ND messages. 2362 Future documents may consider encapsulation avoidance through 2363 translation while updating [RFC4861]. 2365 Note: An alternate approach to multihop forwarding via IPv4 2366 encapsulation would be to employ IPv6/IPv4 protocol translation. 2367 However, for IPv6 ND messages the LLAs would be truncated due to 2368 translation and the OMNI Router and Prefix Discovery services would 2369 not be able to function. The use of IPv4 encapsulation is therefore 2370 indicated. 2372 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2373 of a new IPv4 /24 prefix allocation, but this may be difficult to 2374 obtain given IPv4 address exhaustion. An alternative would be to re- 2375 purpose the prefix 192.88.99.0 which has been set aside from its 2376 former use by [RFC7526]. 2378 14.2. MS-Register and MS-Release List Processing 2380 OMNI links maintain a constant value "MAX_MSID" selected to provide 2381 MNs with an acceptable level of MSE redundancy while minimizing 2382 control message amplification. It is RECOMMENDED that MAX_MSID be 2383 set to the default value 5; if a different value is chosen, it should 2384 be set uniformly by all nodes on the OMNI link. 2386 When a MN sends an RS message with an OMNI option via an underlying 2387 interface to an AR, the MN must convey its knowledge of its 2388 currently-associated MSEs. Initially, the MN will have no associated 2389 MSEs and should therefore include an MS-Register sub-option with the 2390 single "anycast" MSID value 0 which requests the AR to select and 2391 assign an MSE. The AR will then return an RA message with source 2392 address set to the ADM-LLA of the selected MSE. 2394 As the MN activates additional underlying interfaces, it can 2395 optionally include an MS-Register sub-option with MSID value 0, or 2396 with non-zero MSIDs for MSEs discovered from previous RS/RA 2397 exchanges. The MN will thus eventually begin to learn and manage its 2398 currently active set of MSEs, and can register with new MSEs or 2399 release from former MSEs with each successive RS/RA exchange. As the 2400 MN's MSE constituency grows, it alone is responsible for including or 2401 omitting MSIDs in the MS-Register/Release lists it sends in RS 2402 messages. The inclusion or omission of MSIDs determines the MN's 2403 interface to the MS and defines the manner in which MSEs will 2404 respond. The only limiting factor is that the MN should include no 2405 more than MAX_MSID values in each list per each IPv6 ND message, and 2406 should avoid duplication of entries in each list unless it wants to 2407 increase likelihood of control message delivery. 2409 When an AR receives an RS message sent by a MN with an OMNI option, 2410 the option will contain zero or more MS-Register and MS-Release sub- 2411 options containing MSIDs. After processing the OMNI option, the AR 2412 will have a list of zero or more MS-Register MSIDs and a list of zero 2413 or more of MS-Release MSIDs. The AR then processes the lists as 2414 follows: 2416 o For each list, retain the first MAX_MSID values in the list and 2417 discard any additional MSIDs (i.e., even if there are duplicates 2418 within a list). 2420 o Next, for each MSID in the MS-Register list, remove all matching 2421 MSIDs from the MS-Release list. 2423 o Next, proceed according to whether the AR's own MSID or the value 2424 0 appears in the MS-Register list as follows: 2426 * If yes, send an RA message directly back to the MN and send a 2427 proxy copy of the RS message to each additional MSID in the MS- 2428 Register list with the MS-Register/Release lists omitted. 2429 Then, send an unsolicited NA (uNA) message to each MSID in the 2430 MS-Release list with the MS-Register/Release lists omitted and 2431 with an OMNI option with S/T-omIndex set to 0. 2433 * If no, send a proxy copy of the RS message to each additional 2434 MSID in the MS-Register list with the MS-Register list omitted. 2435 For the first MSID, include the original MS-Release list; for 2436 all other MSIDs, omit the MS-Release list. 2438 Each proxy copy of the RS message will include an OMNI option and OAL 2439 encapsulation header with the ADM-ULA of the AR as the source and the 2440 ADM-ULA of the Register MSE as the destination. When the Register 2441 MSE receives the proxy RS message, if the message includes an MS- 2442 Release list the MSE sends a uNA message to each additional MSID in 2443 the Release list with an OMNI option with S/T-omIndex set to 0. The 2444 Register MSE then sends an RA message back to the (Proxy) AR wrapped 2445 in an OAL encapsulation header with source and destination addresses 2446 reversed, and with RA destination set to the MNP-LLA of the MN. When 2447 the AR receives this RA message, it sends a proxy copy of the RA to 2448 the MN. 2450 Each uNA message (whether sent by the first-hop AR or by a Register 2451 MSE) will include an OMNI option and an OAL encapsulation header with 2452 the ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2453 Release MSE as the destination. The uNA informs the Release MSE that 2454 its previous relationship with the MN has been released and that the 2455 source of the uNA message is now registered. The Release MSE must 2456 then note that the subject MN of the uNA message is now "departed", 2457 and forward any subsequent packets destined to the MN to the Register 2458 MSE. 2460 Note that it is not an error for the MS-Register/Release lists to 2461 include duplicate entries. If duplicates occur within a list, the AR 2462 will generate multiple proxy RS and/or uNA messages - one for each 2463 copy of the duplicate entries. 2465 14.3. DHCPv6-based Prefix Registration 2467 When a MN is not pre-provisioned with an MNP-LLA (or, when the MN 2468 requires additional MNP delegations), it requests the AR to select 2469 MNPs on its behalf and set up the correct routing state within the 2470 MS. The DHCPv6 service [RFC8415] supports this requirement. 2472 When an MN needs to have the AR select MNPs, it sends an RS message 2473 with the unspecified address (::) as the source and with DHCPv6 2474 Message sub-option containing a Client Identifier, one or more IA_PD 2475 options and a Rapid Commit option. The MN also sets the 'msg-type' 2476 field to "Solicit", and includes a 3 octet 'transaction-id'. The MN 2477 sets the RS destination to All-Routers multicast and applies OAL 2478 encapsulation and fragmentation if necessary as discussed above. 2480 When the AR receives the RS message, it performs OAL reassembly if 2481 necessary and extracts the DHCPv6 message from the OMNI option. The 2482 AR then acts as a "Proxy DHCPv6 Client" in a message exchange with 2483 the locally-resident DHCPv6 server, which delegates MNPs and returns 2484 a DHCPv6 Reply message with PD parameters. (If the AR wishes to 2485 defer creation of MN state until the DHCPv6 Reply is received, it can 2486 instead act as a Lightweight DHCPv6 Relay Agent per [RFC6221] by 2487 encapsulating the DHCPv6 message in a Relay-forward/reply exchange 2488 with Relay Message and Interface ID options.) 2490 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2491 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2492 sends an RA back to the MN with the DHCPv6 Reply message included in 2493 an OMNI DHCPv6 message sub-option. If the RS message source address 2494 was unspecified, the AR includes one of the (newly-created) MNP-LLAs 2495 as the RA destination address; otherwise, it includes the RS source 2496 address as the RA destination address. The AR then sets the RA 2497 source address to its own ADM-LLA then performs OAL encapsulation and 2498 fragmentation if necessary and sends the RA to the MN. When the MN 2499 receives the RA, it reassembles and discards the OAL encapsulation if 2500 necessary, then creates a default route, assigns Subnet Router 2501 Anycast addresses and uses the RA destination address as its primary 2502 MNP-LLA. The MN will then use this primary MNP-LLA as the source 2503 address of any IPv6 ND messages it sends as long as it retains 2504 ownership of the MNP. 2506 Note: After a MN performs a DHCPv6-based prefix registration exchange 2507 with a first AR, it would need to repeat the exchange with each 2508 additional MSE it registers with. In that case, the MN supplies the 2509 MNP delegations received from the first AR in the IA_PD fields of a 2510 DHCPv6 message when it engages the additional MSEs. 2512 15. Secure Redirection 2514 If the *NET link model is multiple access, the AR is responsible for 2515 assuring that address duplication cannot corrupt the neighbor caches 2516 of other nodes on the link. When the MN sends an RS message on a 2517 multiple access *NET link, the AR verifies that the MN is authorized 2518 to use the address and returns an RA with a non-zero Router Lifetime 2519 only if the MN is authorized. 2521 After verifying MN authorization and returning an RA, the AR MAY 2522 return IPv6 ND Redirect messages to direct MNs located on the same 2523 *NET link to exchange packets directly without transiting the AR. In 2524 that case, the MNs can exchange packets according to their unicast L2 2525 addresses discovered from the Redirect message instead of using the 2526 dogleg path through the AR. In some *NET links, however, such direct 2527 communications may be undesirable and continued use of the dogleg 2528 path through the AR may provide better performance. In that case, 2529 the AR can refrain from sending Redirects, and/or MNs can ignore 2530 them. 2532 16. AR and MSE Resilience 2534 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2535 [RFC5798] configurations so that service continuity is maintained 2536 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2537 the (redundant) ARs is currently providing service, and any service 2538 discontinuity will be limited to the failover time supported by VRRP. 2539 Widely deployed public domain implementations of VRRP are available. 2541 MSEs SHOULD use high availability clustering services so that 2542 multiple redundant systems can provide coordinated response to 2543 failures. As with VRRP, widely deployed public domain 2544 implementations of high availability clustering services are 2545 available. Note that special-purpose and expensive dedicated 2546 hardware is not necessary, and public domain implementations can be 2547 used even between lightweight virtual machines in cloud deployments. 2549 17. Detecting and Responding to MSE Failures 2551 In environments where fast recovery from MSE failure is required, ARs 2552 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2553 manner that parallels Bidirectional Forwarding Detection (BFD) 2554 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2555 react to failures so that cached information is re-established 2556 through alternate paths. Proactive NUD control messaging is carried 2557 only over well-connected ground domain networks (i.e., and not low- 2558 end *NET links such as aeronautical radios) and can therefore be 2559 tuned for rapid response. 2561 ARs perform proactive NUD for MSEs for which there are currently 2562 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2563 of the outage by sending multicast RA messages on the *NET interface. 2564 The AR sends RA messages to MNs via the *NET interface with an OMNI 2565 option with a Release ID for the failed MSE, and with destination 2566 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2568 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2569 by small delays [RFC4861]. Any MNs on the *NET interface that have 2570 been using the (now defunct) MSE will receive the RA messages and 2571 associate with a new MSE. 2573 18. Transition Considerations 2575 When a MN connects to an *NET link for the first time, it sends an RS 2576 message with an OMNI option. If the first hop AR recognizes the 2577 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2578 as the destination and with an OMNI option included. The MN then 2579 engages the AR according to the OMNI link model specified above. If 2580 the first hop AR is a legacy IPv6 router, however, it instead returns 2581 an RA message with no OMNI option and with a non-OMNI unicast source 2582 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2583 according to the legacy IPv6 link model and without the OMNI 2584 extensions specified in this document. 2586 If the *NET link model is multiple access, there must be assurance 2587 that address duplication cannot corrupt the neighbor caches of other 2588 nodes on the link. When the MN sends an RS message on a multiple 2589 access *NET link with an LLA source address and an OMNI option, ARs 2590 that recognize the option ensure that the MN is authorized to use the 2591 address and return an RA with a non-zero Router Lifetime only if the 2592 MN is authorized. ARs that do not recognize the option instead 2593 return an RA that makes no statement about the MN's authorization to 2594 use the source address. In that case, the MN should perform 2595 Duplicate Address Detection to ensure that it does not interfere with 2596 other nodes on the link. 2598 An alternative approach for multiple access *NET links to ensure 2599 isolation for MN / AR communications is through L2 address mappings 2600 as discussed in Appendix C. This arrangement imparts a (virtual) 2601 point-to-point link model over the (physical) multiple access link. 2603 19. OMNI Interfaces on Open Internetworks 2605 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2606 an open Internetwork without an OMNI-aware first-hop AR receive RA 2607 messages that do not include an OMNI option, while OMNI interfaces 2608 configured over IPv4-only underlying interfaces do not receive any 2609 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2610 without an OMNI option configure addresses, on-link prefixes, etc. on 2611 the underlying interface that received the RA according to standard 2612 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2613 interfaces configured over IPv4-only underlying interfaces configure 2614 IPv4 address information on the underlying interfaces using 2615 mechanisms such as DHCPv4 [RFC2131]. 2617 OMNI interfaces configured over underlying interfaces that connect to 2618 an open Internetwork can apply security services such as VPNs to 2619 connect to an MSE, or can establish a direct link to an MSE through 2620 some other means (see Section 4). In environments where an explicit 2621 VPN or direct link may be impractical, OMNI interfaces can instead 2622 use UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2623 authentication per [RFC7401]. 2625 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes a 2626 HIP "Initiator" message in an OMNI option of an IPv6 RS message and 2627 the MSE responds with a HIP "Responder" message coded in an OMNI 2628 option of an IPv6 RA message. HIP security services are applied per 2629 [RFC7401], using the RS/RA messages as simple "shipping containers" 2630 to convey the HIP parameters. In that case, a "two-message HIP 2631 exchange" through a single RS/RA exchange may be sufficient for 2632 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2633 two MNs can coordinate directly with one another with HIP "Initiator/ 2634 Responder" messages coded in OMNI options of IPv6 NS/NA messages. In 2635 that case, a four-message HIP exchange (i.e., two back-to-back NS/NA 2636 exchanges) may be necessary for the two MNs to attain mutual 2637 authentication. 2639 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2640 interfaces send control plane messages to interface with the MS, 2641 including RS/RA messages used according to Section 14 and NS/NA 2642 messages used for route optimization and mobility (see: 2643 [I-D.templin-intarea-6706bis]). The control plane messages must be 2644 authenticated while data plane messages are delivered the same as for 2645 ordinary best-effort traffic with basic source address-based data 2646 origin verification. Data plane communications via OMNI interfaces 2647 that connect over open Internetworks without an explicit VPN should 2648 therefore employ transport- or higher-layer security to ensure 2649 integrity and/or confidentiality. 2651 OMNI interfaces configured over open Internetworks are often located 2652 behind NATs. The OMNI interface accommodates NAT traversal using 2653 UDP/IP encapsulation and the mechanisms discussed in 2654 [I-D.templin-intarea-6706bis]. 2656 Note: Following the initial HIP Initiator/Responder exchange, OMNI 2657 interfaces configured over open Internetworks maintain HIP 2658 associations through the transmission of IPv6 ND messages that 2659 include OMNI options with HIP "Update" and "Notify" messages. OMNI 2660 interfaces use the HIP "Update" message when an acknowledgement is 2661 required, and use the "Notify" message in unacknowledged isolated 2662 IPv6 ND messages (e.g., unsolicited NAs). 2664 20. Time-Varying MNPs 2666 In some use cases, it is desirable, beneficial and efficient for the 2667 MN to receive a constant MNP that travels with the MN wherever it 2668 moves. For example, this would allow air traffic controllers to 2669 easily track aircraft, etc. In other cases, however (e.g., 2670 intelligent transportation systems), the MN may be willing to 2671 sacrifice a modicum of efficiency in order to have time-varying MNPs 2672 that can be changed every so often to defeat adversarial tracking. 2674 The prefix delegation services discussed in Section 14.3 allows OMNI 2675 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2676 use the unspecified address (::) as the source address of an RS 2677 message with an OMNI option with DHCPv6 Option sub-options. The MN 2678 would then be obligated to renumber its internal networks whenever 2679 its MNP (and therefore also its OMNI address) changes. This should 2680 not present a challenge for MNs with automated network renumbering 2681 services, however presents limits for the durations of ongoing 2682 sessions that would prefer to use a constant address. 2684 21. (H)HITs and Temporary ULAs 2686 MNs that generate (H)HITs but do not have pre-assigned MNPs can 2687 request MNP delegations by issuing IPv6 ND messages that use the 2688 (H)HIT instead of a Temporary ULA. In particular, when a MN creates 2689 an RS message it can set the source address to the unspecified 2690 address (::) and destination address to All-Routers multicast. The 2691 MN then encapsulates the message in an IPv6 header with the (H)HIT as 2692 the source address and with destination set to either a unicast or 2693 anycast ADM-ULA. The MN then sends the message to the AR as 2694 specified in Section 14.1. 2696 When the AR receives the message, it notes that the RS source address 2697 was unspecified, then examines the RS encapsulation source address to 2698 determine that the source is a (H)HIT and not a Temporary ULA. The 2699 AR next invokes the DHCPv6 protocol to request an MNP prefix 2700 delegation, then prepares an RA message with source address set to 2701 its own ADM-LLA and destination set to the MNP-LLA corresponding to 2702 the delegated MNP. The AR finally encapsulates the RA in an IPv6 2703 header with source address set to its own ADM-ULA and destination set 2704 to the (H)HIT from the RS encapsulation source address, then returns 2705 the encapsulated RA to the MN. 2707 MNs can also use (H)HITs and/or Temporary ULAs for direct MN-to-MN 2708 communications outside the context of any OMNI link supporting 2709 infrastructure. When two MNs encounter one another they can use 2710 their (H)HITs and/or Temporary ULAs as IPv6 packet source and 2711 destination addresses to support direct communications. MNs can also 2712 inject their (H)HITs and/or Temporary ULAs into a MANET/VANET routing 2713 protocol to enable multihop communications. MNs can further exchange 2714 IPv6 ND messages (such as NS/NA) using their (H)HITs and/or Temporary 2715 ULAs as source and destination addresses, however the HIP security 2716 protocols for establishing secure neighbor relationships are based on 2717 (H)HITs. 2719 Lastly, when MNs are within the coverage range of OMNI link 2720 infrastructure a case could be made for injecting (H)HITs and/or 2721 Temporary ULAs into the global MS routing system. For example, when 2722 the MN sends an RS to a MSE it could include a request to inject the 2723 (H)HIT / Temporary ULA into the routing system instead of requesting 2724 an MNP prefix delegation. This would potentially enable OMNI link- 2725 wide communications using only (H)HITs or Temporary ULAs, and not 2726 MNPs. This document notes the opportunity, but makes no 2727 recommendation. 2729 22. IANA Considerations 2731 The IANA has assigned a 4 octet Private Enterprise Number (PEN) code 2732 "45282" in the "enterprise-numbers" registry. This document is the 2733 normative reference for using this code in DHCP Unique IDentifiers 2734 based on Enterprise Numbers ("DUID-EN for OMNI Interfaces") (see: 2735 Section 10). 2737 The IANA is instructed to allocate an official Type number TBD1 from 2738 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2739 option. Implementations set Type to 253 as an interim value 2740 [RFC4727]. 2742 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2743 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2744 read as follows: 2746 Code Name Reference 2747 --- ---- --------- 2748 0 Diagnostic Packet Too Big [RFC4443] 2749 1 Advisory Packet Too Big [RFCXXXX] 2751 Figure 22: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2753 The IANA is instructed to allocate one Ethernet unicast address TBD2 2754 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2755 Address Block - Unicast Use". 2757 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 2758 instructed to create and maintain a new registry entitled "OMNI 2759 Option Sub-Type Values". Initial values for the OMNI Option Sub-Type 2760 Values registry are given below (future assignments are to be made 2761 through Standards Action [RFC8126]): 2763 Value Sub-Type name Reference 2764 ----- ------------- ---------- 2765 0 Pad1 [RFCXXXX] 2766 1 PadN [RFCXXXX] 2767 2 Interface Attributes (Type 1) [RFCXXXX] 2768 3 Interface Attributes (Type 2) [RFCXXXX] 2769 4 Traffic Selector [RFCXXXX] 2770 5 MS-Register [RFCXXXX] 2771 6 MS-Release [RFCXXXX] 2772 7 Geo Coordinates [RFCXXXX] 2773 8 DHCPv6 Message [RFCXXXX] 2774 9 HIP Message [RFCXXXX] 2775 10 Node Identification [RFCXXXX] 2776 11-29 Unassigned 2777 30 Sub-Type Extension [RFCXXXX] 2778 31 Reserved by IANA [RFCXXXX] 2780 Figure 23: OMNI Option Sub-Type Values 2782 The OMNI option defines an 8-bit Extension-Type field for Sub-Type 30 2783 (Sub-Type Extension), for which IANA is instructed to create and 2784 maintain a new registry entitled "OMNI Option Extension-Type Values". 2785 Initial values for the OMNI Option Extension-Type Values registry are 2786 given below (future assignments are to be made through Expert Review 2787 [RFC8126]): 2789 Value Sub-Type name Reference 2790 ----- ------------- ---------- 2791 0 Origin Indication [RFCXXXX] 2792 1-252 Unassigned 2793 253-254 Reserved for Experimentation [RFCXXXX] 2794 255 Reserved by IANA [RFCXXXX] 2796 Figure 24: OMNI Option Extension-Type Values 2798 The OMNI Node Identification Sub-Option (see: Section 11.1.11) 2799 contains an 8-bit ID-Type field, for which IANA is instructed to 2800 create and maintain a new registry entitled "OMNI Node Identification 2801 Sub-Option ID-Type values". Initial values for the OMNI Node 2802 Identification Sub-Option ID Type values registry are given below 2803 (future assignments are to be made through Expert Review [RFC8126]): 2805 Value Sub-Type name Reference 2806 ----- ------------- ---------- 2807 0 UUID [RFCXXXX] 2808 1 HIT [RFCXXXX] 2809 2 HHIT [RFCXXXX] 2810 3 Network Access Identifier [RFCXXXX] 2811 4 FQDN [RFCXXXX] 2812 5-252 Unassigned [RFCXXXX] 2813 253-254 Reserved for Experimentation [RFCXXXX] 2814 255 Reserved by IANA [RFCXXXX] 2816 Figure 25: OMNI Node Identification Sub-Option ID-Type Values 2818 23. Security Considerations 2820 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2821 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2822 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2823 confirmation and/or time synchronization is needed. 2825 MN OMNI interfaces configured over secured ANET interfaces inherit 2826 the physical and/or link-layer security properties (i.e., "protected 2827 spectrum") of the connected ANETs. MN OMNI interfaces configured 2828 over open INET interfaces can use symmetric securing services such as 2829 VPNs or can by some other means establish a direct link. When a VPN 2830 or direct link may be impractical, however, the security services 2831 specified in [RFC7401] can be employed. While the OMNI link protects 2832 control plane messaging, applications must still employ end-to-end 2833 transport- or higher-layer security services to protect the data 2834 plane. 2836 Strong network layer security for control plane messages and 2837 forwarding path integrity for data plane messages between MSEs MUST 2838 be supported. In one example, the AERO service 2839 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 2840 and secures the links in the spanning tree with network layer 2841 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 2842 plane messages are then constrained to travel only over the secured 2843 spanning tree paths and are therefore protected from attack or 2844 eavesdropping. Since data plane messages can travel over route 2845 optimized paths that do not strictly follow the spanning tree, 2846 however, end-to-end transport- or higher-layer security services are 2847 still required. 2849 Identity-based key verification infrastructure services such as iPSK 2850 may be necessary for verifying the identities claimed by MNs. This 2851 requirement should be harmonized with the manner in which (H)HITs are 2852 attested in a given operational environment. 2854 Security considerations for specific access network interface types 2855 are covered under the corresponding IP-over-(foo) specification 2856 (e.g., [RFC2464], [RFC2492], etc.). 2858 Security considerations for IPv6 fragmentation and reassembly are 2859 discussed in Section 5.1. 2861 24. Implementation Status 2863 AERO/OMNI Release-3.0.2 was tagged on October 15, 2020, and is 2864 undergoing internal testing. Additional internal releases expected 2865 within the coming months, with first public release expected end of 2866 1H2021. 2868 25. Acknowledgements 2870 The first version of this document was prepared per the consensus 2871 decision at the 7th Conference of the International Civil Aviation 2872 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2873 2019. Consensus to take the document forward to the IETF was reached 2874 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2875 Attendees and contributors included: Guray Acar, Danny Bharj, 2876 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2877 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2878 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2879 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2880 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2881 Fryderyk Wrobel and Dongsong Zeng. 2883 The following individuals are acknowledged for their useful comments: 2884 Stuart Card, Michael Matyas, Robert Moskowitz, Madhu Niraula, Greg 2885 Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron 2886 and Michal Skorepa are especially recognized for their many helpful 2887 ideas and suggestions. Madhuri Madhava Badgandi, Sean Dickson, Don 2888 Dillenburg, Joe Dudkowski, Vijayasarathy Rajagopalan, Ron Sackman and 2889 Katherine Tran are acknowledged for their hard work on the 2890 implementation and technical insights that led to improvements for 2891 the spec. 2893 Discussions on the IETF 6man and atn mailing lists during the fall of 2894 2020 suggested additional points to consider. The authors gratefully 2895 acknowledge the list members who contributed valuable insights 2896 through those discussions. Eric Vyncke and Erik Kline were the 2897 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2898 at the time the document was developed; they are all gratefully 2899 acknowledged for their many helpful insights. 2901 This work is aligned with the NASA Safe Autonomous Systems Operation 2902 (SASO) program under NASA contract number NNA16BD84C. 2904 This work is aligned with the FAA as per the SE2025 contract number 2905 DTFAWA-15-D-00030. 2907 This work is aligned with the Boeing Information Technology (BIT) 2908 Mobility Vision Lab (MVL) program. 2910 26. References 2912 26.1. Normative References 2914 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2915 DOI 10.17487/RFC0791, September 1981, 2916 . 2918 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2919 Requirement Levels", BCP 14, RFC 2119, 2920 DOI 10.17487/RFC2119, March 1997, 2921 . 2923 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2924 "Definition of the Differentiated Services Field (DS 2925 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2926 DOI 10.17487/RFC2474, December 1998, 2927 . 2929 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2930 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2931 DOI 10.17487/RFC3971, March 2005, 2932 . 2934 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2935 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2936 November 2005, . 2938 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2939 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2940 . 2942 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2943 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2944 2006, . 2946 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2947 Control Message Protocol (ICMPv6) for the Internet 2948 Protocol Version 6 (IPv6) Specification", STD 89, 2949 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2950 . 2952 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2953 ICMPv6, UDP, and TCP Headers", RFC 4727, 2954 DOI 10.17487/RFC4727, November 2006, 2955 . 2957 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2958 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2959 DOI 10.17487/RFC4861, September 2007, 2960 . 2962 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2963 Address Autoconfiguration", RFC 4862, 2964 DOI 10.17487/RFC4862, September 2007, 2965 . 2967 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2968 "Traffic Selectors for Flow Bindings", RFC 6088, 2969 DOI 10.17487/RFC6088, January 2011, 2970 . 2972 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 2973 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 2974 RFC 7401, DOI 10.17487/RFC7401, April 2015, 2975 . 2977 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2978 Hosts in a Multi-Prefix Network", RFC 8028, 2979 DOI 10.17487/RFC8028, November 2016, 2980 . 2982 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2983 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2984 May 2017, . 2986 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2987 (IPv6) Specification", STD 86, RFC 8200, 2988 DOI 10.17487/RFC8200, July 2017, 2989 . 2991 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2992 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2993 DOI 10.17487/RFC8201, July 2017, 2994 . 2996 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2997 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2998 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2999 RFC 8415, DOI 10.17487/RFC8415, November 2018, 3000 . 3002 26.2. Informative References 3004 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 3005 Interface for Civil Aviation, IETF Liaison Statement 3006 #1676, https://datatracker.ietf.org/liaison/1676/", March 3007 2020. 3009 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 3010 Aeronautical Telecommunication Network (ATN) using 3011 Internet Protocol Suite (IPS) Standards and Protocol), 3012 Draft Edition 3 (work-in-progress)", December 2020. 3014 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 3015 Interface (FDDI), IEEE Transactions on Communications", 3016 August 1990. 3018 [I-D.ietf-6man-rfc4941bis] 3019 Gont, F., Krishnan, S., Narten, T., and R. Draves, 3020 "Temporary Address Extensions for Stateless Address 3021 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 3022 (work in progress), November 2020. 3024 [I-D.ietf-drip-rid] 3025 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 3026 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 3027 progress), December 2020. 3029 [I-D.ietf-intarea-tunnels] 3030 Touch, J. and M. Townsley, "IP Tunnels in the Internet 3031 Architecture", draft-ietf-intarea-tunnels-10 (work in 3032 progress), September 2019. 3034 [I-D.ietf-ipwave-vehicular-networking] 3035 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 3036 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 3037 ipwave-vehicular-networking-19 (work in progress), July 3038 2020. 3040 [I-D.templin-6man-dhcpv6-ndopt] 3041 Templin, F., "A Unified Stateful/Stateless Configuration 3042 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 3043 (work in progress), January 2021. 3045 [I-D.templin-6man-lla-type] 3046 Templin, F., "The IPv6 Link-Local Address Type Field", 3047 draft-templin-6man-lla-type-02 (work in progress), 3048 November 2020. 3050 [I-D.templin-intarea-6706bis] 3051 Templin, F., "Asymmetric Extended Route Optimization 3052 (AERO)", draft-templin-intarea-6706bis-87 (work in 3053 progress), January 2021. 3055 [IPV4-GUA] 3056 Postel, J., "IPv4 Address Space Registry, 3057 https://www.iana.org/assignments/ipv4-address-space/ipv4- 3058 address-space.xhtml", December 2020. 3060 [IPV6-GUA] 3061 Postel, J., "IPv6 Global Unicast Address Assignments, 3062 https://www.iana.org/assignments/ipv6-unicast-address- 3063 assignments/ipv6-unicast-address-assignments.xhtml", 3064 December 2020. 3066 [RFC1035] Mockapetris, P., "Domain names - implementation and 3067 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 3068 November 1987, . 3070 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 3071 Communication Layers", STD 3, RFC 1122, 3072 DOI 10.17487/RFC1122, October 1989, 3073 . 3075 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 3076 DOI 10.17487/RFC1191, November 1990, 3077 . 3079 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 3080 RFC 1256, DOI 10.17487/RFC1256, September 1991, 3081 . 3083 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 3084 RFC 2131, DOI 10.17487/RFC2131, March 1997, 3085 . 3087 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 3088 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 3089 . 3091 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 3092 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 3093 . 3095 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 3096 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 3097 December 1998, . 3099 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 3100 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 3101 . 3103 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 3104 Domains without Explicit Tunnels", RFC 2529, 3105 DOI 10.17487/RFC2529, March 1999, 3106 . 3108 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 3109 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 3110 . 3112 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 3113 DOI 10.17487/RFC3330, September 2002, 3114 . 3116 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 3117 Considered Useful", BCP 82, RFC 3692, 3118 DOI 10.17487/RFC3692, January 2004, 3119 . 3121 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 3122 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 3123 DOI 10.17487/RFC3810, June 2004, 3124 . 3126 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 3127 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 3128 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 3129 RFC 3819, DOI 10.17487/RFC3819, July 2004, 3130 . 3132 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 3133 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 3134 2004, . 3136 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 3137 Unique IDentifier (UUID) URN Namespace", RFC 4122, 3138 DOI 10.17487/RFC4122, July 2005, 3139 . 3141 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 3142 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 3143 DOI 10.17487/RFC4271, January 2006, 3144 . 3146 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 3147 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 3148 December 2005, . 3150 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 3151 Network Address Translations (NATs)", RFC 4380, 3152 DOI 10.17487/RFC4380, February 2006, 3153 . 3155 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 3156 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 3157 2006, . 3159 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 3160 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 3161 . 3163 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 3164 "Considerations for Internet Group Management Protocol 3165 (IGMP) and Multicast Listener Discovery (MLD) Snooping 3166 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 3167 . 3169 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 3170 "Internet Group Management Protocol (IGMP) / Multicast 3171 Listener Discovery (MLD)-Based Multicast Forwarding 3172 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 3173 August 2006, . 3175 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3176 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 3177 . 3179 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 3180 Errors at High Data Rates", RFC 4963, 3181 DOI 10.17487/RFC4963, July 2007, 3182 . 3184 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 3185 Advertisement Flags Option", RFC 5175, 3186 DOI 10.17487/RFC5175, March 2008, 3187 . 3189 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 3190 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 3191 RFC 5213, DOI 10.17487/RFC5213, August 2008, 3192 . 3194 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 3195 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 3196 DOI 10.17487/RFC5214, March 2008, 3197 . 3199 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 3200 RFC 5558, DOI 10.17487/RFC5558, February 2010, 3201 . 3203 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 3204 Version 3 for IPv4 and IPv6", RFC 5798, 3205 DOI 10.17487/RFC5798, March 2010, 3206 . 3208 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 3209 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 3210 . 3212 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 3213 DOI 10.17487/RFC6081, January 2011, 3214 . 3216 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 3217 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 3218 DOI 10.17487/RFC6221, May 2011, 3219 . 3221 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 3222 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 3223 DOI 10.17487/RFC6355, August 2011, 3224 . 3226 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 3227 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 3228 2012, . 3230 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 3231 with IPv6 Neighbor Discovery", RFC 6980, 3232 DOI 10.17487/RFC6980, August 2013, 3233 . 3235 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 3236 Requirements for IPv6 Customer Edge Routers", RFC 7084, 3237 DOI 10.17487/RFC7084, November 2013, 3238 . 3240 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 3241 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 3242 Boundary in IPv6 Addressing", RFC 7421, 3243 DOI 10.17487/RFC7421, January 2015, 3244 . 3246 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 3247 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 3248 DOI 10.17487/RFC7526, May 2015, 3249 . 3251 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 3252 DOI 10.17487/RFC7542, May 2015, 3253 . 3255 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 3256 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 3257 February 2016, . 3259 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 3260 Support for IP Hosts with Multi-Access Support", RFC 7847, 3261 DOI 10.17487/RFC7847, May 2016, 3262 . 3264 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 3265 Writing an IANA Considerations Section in RFCs", BCP 26, 3266 RFC 8126, DOI 10.17487/RFC8126, June 2017, 3267 . 3269 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 3270 Decraene, B., Litkowski, S., and R. Shakir, "Segment 3271 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 3272 July 2018, . 3274 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 3275 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 3276 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 3277 . 3279 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 3280 and F. Gont, "IP Fragmentation Considered Fragile", 3281 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 3282 . 3284 Appendix A. Interface Attribute Preferences Bitmap Encoding 3286 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 3287 encoding to specific Internetworks such as the Aeronautical 3288 Telecommunications Network with Internet Protocol Services (ATN/IPS) 3289 may include link selection preferences based on other traffic 3290 classifiers (e.g., transport port numbers, etc.) in addition to the 3291 existing DSCP-based preferences. Nodes on specific Internetworks 3292 maintain a map of traffic classifiers to additional P[*] preference 3293 fields beyond the first 64. For example, TCP port 22 maps to P[67], 3294 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 3296 Implementations use Simplex or Indexed encoding formats for P[*] 3297 encoding in order to encode a given set of traffic classifiers in the 3298 most efficient way. Some use cases may be more efficiently coded 3299 using Simplex form, while others may be more efficient using Indexed. 3300 Once a format is selected for preparation of a single Interface 3301 Attribute the same format must be used for the entire Interface 3302 Attribute sub-option. Different sub-options may use different 3303 formats. 3305 The following figures show coding examples for various Simplex and 3306 Indexed formats: 3308 0 1 2 3 3309 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 3310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3311 | Sub-Type=3| Sub-length=N | omIndex | omType | 3312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3313 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 3314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3315 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 3316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3317 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 3318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3319 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 3320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3321 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3323 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 3324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3326 Figure 26: Example 1: Dense Simplex Encoding 3328 0 1 2 3 3329 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 3330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3331 | Sub-Type=3| Sub-length=N | omIndex | omType | 3332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3333 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 3334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3335 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3337 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 3338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3339 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 3340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3341 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 3342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3343 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 3344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3345 |Bitmap(10)=0x00| ... 3346 +-+-+-+-+-+-+-+-+-+-+- 3348 Figure 27: Example 2: Sparse Simplex Encoding 3350 0 1 2 3 3351 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 3352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3353 | Sub-Type=3| Sub-length=N | omIndex | omType | 3354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3355 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 3356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3357 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 3358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3359 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 3360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3361 | Bitmap = 0x01 |796|797|798|799| ... 3362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3364 Figure 28: Example 3: Indexed Encoding 3366 Appendix B. VDL Mode 2 Considerations 3368 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 3369 (VDLM2) that specifies an essential radio frequency data link service 3370 for aircraft and ground stations in worldwide civil aviation air 3371 traffic management. The VDLM2 link type is "multicast capable" 3372 [RFC4861], but with considerable differences from common multicast 3373 links such as Ethernet and IEEE 802.11. 3375 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3376 magnitude less than most modern wireless networking gear. Second, 3377 due to the low available link bandwidth only VDLM2 ground stations 3378 (i.e., and not aircraft) are permitted to send broadcasts, and even 3379 so only as compact layer 2 "beacons". Third, aircraft employ the 3380 services of ground stations by performing unicast RS/RA exchanges 3381 upon receipt of beacons instead of listening for multicast RA 3382 messages and/or sending multicast RS messages. 3384 This beacon-oriented unicast RS/RA approach is necessary to conserve 3385 the already-scarce available link bandwidth. Moreover, since the 3386 numbers of beaconing ground stations operating within a given spatial 3387 range must be kept as sparse as possible, it would not be feasible to 3388 have different classes of ground stations within the same region 3389 observing different protocols. It is therefore highly desirable that 3390 all ground stations observe a common language of RS/RA as specified 3391 in this document. 3393 Note that links of this nature may benefit from compression 3394 techniques that reduce the bandwidth necessary for conveying the same 3395 amount of data. The IETF lpwan working group is considering possible 3396 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3398 Appendix C. MN / AR Isolation Through L2 Address Mapping 3400 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3401 unicast link-scoped IPv6 destination address. However, IPv6 ND 3402 messaging should be coordinated between the MN and AR only without 3403 invoking other nodes on the *NET. This implies that MN / AR control 3404 messaging should be isolated and not overheard by other nodes on the 3405 link. 3407 To support MN / AR isolation on some *NET links, ARs can maintain an 3408 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3409 *NETs, this specification reserves one Ethernet unicast address TBD2 3410 (see: Section 22). For non-Ethernet statically-addressed *NETs, 3411 MSADDR is reserved per the assigned numbers authority for the *NET 3412 addressing space. For still other *NETs, MSADDR may be dynamically 3413 discovered through other means, e.g., L2 beacons. 3415 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3416 both multicast and unicast) to MSADDR instead of to an ordinary 3417 unicast or multicast L2 address. In this way, all of the MN's IPv6 3418 ND messages will be received by ARs that are configured to accept 3419 packets destined to MSADDR. Note that multiple ARs on the link could 3420 be configured to accept packets destined to MSADDR, e.g., as a basis 3421 for supporting redundancy. 3423 Therefore, ARs must accept and process packets destined to MSADDR, 3424 while all other devices must not process packets destined to MSADDR. 3425 This model has well-established operational experience in Proxy 3426 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3428 Appendix D. Change Log 3430 << RFC Editor - remove prior to publication >> 3432 Differences from draft-templin-6man-omni-interface-35 to draft- 3433 templin-6man-omni-interface-36: 3435 o Major clarifications on aspects such as "hard/soft" PTB error 3436 messages 3438 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3439 be used in the data plane. 3441 Differences from draft-templin-6man-omni-interface-31 to draft- 3442 templin-6man-omni-interface-32: 3444 o MTU 3446 o Support for multi-hop ANETS such as ISATAP. 3448 Differences from draft-templin-6man-omni-interface-29 to draft- 3449 templin-6man-omni-interface-30: 3451 o Moved link-layer addressing information into the OMNI option on a 3452 per-ifIndex basis 3454 o Renamed "ifIndex-tuple" to "Interface Attributes" 3456 Differences from draft-templin-6man-omni-interface-27 to draft- 3457 templin-6man-omni-interface-28: 3459 o Updates based on implementation experience. 3461 Differences from draft-templin-6man-omni-interface-25 to draft- 3462 templin-6man-omni-interface-26: 3464 o Further clarification on "aggregate" RA messages. 3466 o Expanded Security Considerations to discuss expectations for 3467 security in the Mobility Service. 3469 Differences from draft-templin-6man-omni-interface-20 to draft- 3470 templin-6man-omni-interface-21: 3472 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3473 (PBM). 3475 Differences from draft-templin-6man-omni-interface-18 to draft- 3476 templin-6man-omni-interface-19: 3478 o SEND/CGA. 3480 Differences from draft-templin-6man-omni-interface-17 to draft- 3481 templin-6man-omni-interface-18: 3483 o Teredo 3485 Differences from draft-templin-6man-omni-interface-14 to draft- 3486 templin-6man-omni-interface-15: 3488 o Prefix length discussions removed. 3490 Differences from draft-templin-6man-omni-interface-12 to draft- 3491 templin-6man-omni-interface-13: 3493 o Teredo 3495 Differences from draft-templin-6man-omni-interface-11 to draft- 3496 templin-6man-omni-interface-12: 3498 o Major simplifications and clarifications on MTU and fragmentation. 3500 o Document now updates RFC4443 and RFC8201. 3502 Differences from draft-templin-6man-omni-interface-10 to draft- 3503 templin-6man-omni-interface-11: 3505 o Removed /64 assumption, resulting in new OMNI address format. 3507 Differences from draft-templin-6man-omni-interface-07 to draft- 3508 templin-6man-omni-interface-08: 3510 o OMNI MNs in the open Internet 3512 Differences from draft-templin-6man-omni-interface-06 to draft- 3513 templin-6man-omni-interface-07: 3515 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3516 L2 addressing. 3518 o Expanded "Transition Considerations". 3520 Differences from draft-templin-6man-omni-interface-05 to draft- 3521 templin-6man-omni-interface-06: 3523 o Brought back OMNI option "R" flag, and discussed its use. 3525 Differences from draft-templin-6man-omni-interface-04 to draft- 3526 templin-6man-omni-interface-05: 3528 o Transition considerations, and overhaul of RS/RA addressing with 3529 the inclusion of MSE addresses within the OMNI option instead of 3530 as RS/RA addresses (developed under FAA SE2025 contract number 3531 DTFAWA-15-D-00030). 3533 Differences from draft-templin-6man-omni-interface-02 to draft- 3534 templin-6man-omni-interface-03: 3536 o Added "advisory PTB messages" under FAA SE2025 contract number 3537 DTFAWA-15-D-00030. 3539 Differences from draft-templin-6man-omni-interface-01 to draft- 3540 templin-6man-omni-interface-02: 3542 o Removed "Primary" flag and supporting text. 3544 o Clarified that "Router Lifetime" applies to each ANET interface 3545 independently, and that the union of all ANET interface Router 3546 Lifetimes determines MSE lifetime. 3548 Differences from draft-templin-6man-omni-interface-00 to draft- 3549 templin-6man-omni-interface-01: 3551 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3552 for future use (most likely as "pseudo-multicast"). 3554 o Non-normative discussion of alternate OMNI LLA construction form 3555 made possible if the 64-bit assumption were relaxed. 3557 First draft version (draft-templin-atn-aero-interface-00): 3559 o Draft based on consensus decision of ICAO Working Group I Mobility 3560 Subgroup March 22, 2019. 3562 Authors' Addresses 3563 Fred L. Templin (editor) 3564 The Boeing Company 3565 P.O. Box 3707 3566 Seattle, WA 98124 3567 USA 3569 Email: fltemplin@acm.org 3571 Tony Whyman 3572 MWA Ltd c/o Inmarsat Global Ltd 3573 99 City Road 3574 London EC1Y 1AX 3575 England 3577 Email: tony.whyman@mccallumwhyman.com