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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 19, 2021 7 Expires: August 23, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-83 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 23, 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 . . . . . . . . . . . 20 64 5.2. OAL "Super-Packet" Packing . . . . . . . . . . . . . . . 21 65 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 23 66 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 23 67 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 24 68 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 26 69 10. Node Identification . . . . . . . . . . . . . . . . . . . . . 26 70 11. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 27 71 11.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 29 72 11.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 31 73 11.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 31 74 11.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 32 75 11.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 33 76 11.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 37 77 11.1.6. MS-Register . . . . . . . . . . . . . . . . . . . . 38 78 11.1.7. MS-Release . . . . . . . . . . . . . . . . . . . . . 39 79 11.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 39 80 11.1.9. Dynamic Host Configuration Protocol for IPv6 81 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 40 82 11.1.10. Host Identity Protocol (HIP) Message . . . . . . . . 41 83 11.1.11. Node Identification . . . . . . . . . . . . . . . . 42 84 11.1.12. Sub-Type Extension . . . . . . . . . . . . . . . . . 43 85 12. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 46 86 13. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 47 87 13.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 47 88 13.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 48 89 14. Router Discovery and Prefix Registration . . . . . . . . . . 48 90 14.1. Router Discovery in IP Multihop and IPv4-Only Networks . 53 91 14.2. MS-Register and MS-Release List Processing . . . . . . . 54 92 14.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 56 93 15. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 58 94 16. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 58 95 17. Detecting and Responding to MSE Failures . . . . . . . . . . 58 96 18. Transition Considerations . . . . . . . . . . . . . . . . . . 59 97 19. OMNI Interfaces on Open Internetworks . . . . . . . . . . . . 59 98 20. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 61 99 21. (H)HITs and Temporary ULAs . . . . . . . . . . . . . . . . . 62 100 22. Address Selection . . . . . . . . . . . . . . . . . . . . . . 63 101 23. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 63 102 23.1. "IPv6 Neighbor Discovery Option Formats" Registry . . . 63 103 23.2. "Ethernet Numbers" Registry . . . . . . . . . . . . . . 63 104 23.3. "ICMPv6 Code Fields: Type 2 - Packet Too Big" Registry . 64 105 23.4. "OMNI Option Sub-Type Values" (New Registry) . . . . . . 64 106 23.5. "OMNI Node Identification ID-Type Values" (New Registry) 64 107 23.6. "OMNI Option Sub-Type Extension Values" (New Registry) . 65 108 23.7. "OMNI RFC4380 UDP/IP Header Option" (New Registry) . . . 65 109 23.8. "OMNI RFC6081 UDP/IP Trailer Option" (New Registry) . . 66 110 23.9. Additional Considerations . . . . . . . . . . . . . . . 66 111 24. Security Considerations . . . . . . . . . . . . . . . . . . . 67 112 25. Implementation Status . . . . . . . . . . . . . . . . . . . . 68 113 26. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 68 114 27. References . . . . . . . . . . . . . . . . . . . . . . . . . 69 115 27.1. Normative References . . . . . . . . . . . . . . . . . . 69 116 27.2. Informative References . . . . . . . . . . . . . . . . . 71 117 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 77 118 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 79 119 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 80 120 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 80 121 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 83 123 1. Introduction 125 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 126 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 127 pedestrians with cellphones, etc.) often have multiple interface 128 connections to wireless and/or wired-link data links used for 129 communicating with networked correspondents. These data links may 130 have diverse performance, cost and availability properties that can 131 change dynamically according to mobility patterns, flight phases, 132 proximity to infrastructure, etc. MNs coordinate their data links in 133 a discipline known as "multilink", in which a single virtual 134 interface is configured over the node's underlying interface 135 connections to the data links. 137 The MN configures a virtual interface (termed the "Overlay Multilink 138 Network (OMNI) interface") as a thin layer over the underlying 139 interfaces. The OMNI interface is therefore the only interface 140 abstraction exposed to the IP layer and behaves according to the Non- 141 Broadcast, Multiple Access (NBMA) interface principle, while 142 underlying interfaces appear as link layer communication channels in 143 the architecture. The OMNI interface connects to a virtual overlay 144 service known as the "OMNI link". The OMNI link spans one or more 145 Internetworks that may include private-use infrastructures and/or the 146 global public Internet itself. 148 Each MN receives a Mobile Network Prefix (MNP) for numbering 149 downstream-attached End User Networks (EUNs) independently of the 150 access network data links selected for data transport. The MN 151 performs router discovery over the OMNI interface (i.e., similar to 152 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 153 behalf of its EUNs. The router discovery process is iterated over 154 each of the OMNI interface's underlying interfaces in order to 155 register per-link parameters (see Section 14). 157 The OMNI interface provides a multilink nexus for exchanging inbound 158 and outbound traffic via the correct underlying interface(s). The IP 159 layer sees the OMNI interface as a point of connection to the OMNI 160 link. Each OMNI link has one or more associated Mobility Service 161 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 162 prefixes from which OMNI link MNPs are derived. If there are 163 multiple OMNI links, the IPv6 layer will see multiple OMNI 164 interfaces. 166 MNs may connect to multiple distinct OMNI links within the same OMNI 167 domain by configuring multiple OMNI interfaces, e.g., omni0, omni1, 168 omni2, etc. Each OMNI interface is configured over a set of 169 underlying interfaces and provides a nexus for Safety-Based Multilink 170 (SBM) operation. Each OMNI interface within the same OMNI domain 171 configures a common ULA prefix [ULA]::/48, and configures a unique 172 16-bit Subnet ID '*' to construct the sub-prefix [ULA*]::/64 (see: 173 Section 8). The IP layer applies SBM routing to select an OMNI 174 interface, which then applies Performance-Based Multilink (PBM) to 175 select the correct underlying interface. Applications can apply 176 Segment Routing [RFC8402] to select independent SBM topologies for 177 fault tolerance. 179 The OMNI interface interacts with a network-based Mobility Service 180 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 181 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 182 track MN movements and represent their MNPs in a global routing or 183 mapping system. 185 Many OMNI use cases have been proposed. In particular, the 186 International Civil Aviation Organization (ICAO) Working Group-I 187 Mobility Subgroup is developing a future Aeronautical 188 Telecommunications Network with Internet Protocol Services (ATN/IPS) 189 and has issued a liaison statement requesting IETF adoption [ATN] in 190 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 191 in Vehicular Environments (ipwave) working group has further included 192 problem statement and use case analysis for OMNI in a document now in 193 AD evaluation for RFC publication 194 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 195 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 196 programs that examine commercial aviation, Urban Air Mobility (UAM) 197 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 198 represent another large class of potential OMNI users. 200 This document specifies the transmission of IP packets and MN/MS 201 control messages over OMNI interfaces. The OMNI interface supports 202 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 203 as the network layer in the data plane, while using IPv6 ND messaging 204 as the control plane independently of the data plane IP protocol(s). 205 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 206 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 207 discussed in the following sections. OMNI interfaces enable 208 multilink, mobility, multihop and multicast services, with provisions 209 for both Vehicle-to-Infrastructure (V2I) communications and Vehicle- 210 to-Vehicle (V2V) communications outside the context of 211 infrastructure. 213 2. Terminology 215 The terminology in the normative references applies; especially, the 216 terms "link" and "interface" are the same as defined in the IPv6 217 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 218 Additionally, this document assumes the following IPv6 ND message 219 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 220 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 222 The Protocol Constants defined in Section 10 of [RFC4861] are used in 223 their same format and meaning in this document. The terms "All- 224 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 225 are the same as defined in [RFC4291] (with Link-Local scope assumed). 227 The term "IP" is used to refer collectively to either Internet 228 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 229 specification at the layer in question applies equally to either 230 version. 232 The following terms are defined within the scope of this document: 234 Mobile Node (MN) 235 an end system with a mobile router having multiple distinct 236 upstream data link connections that are grouped together in one or 237 more logical units. The MN's data link connection parameters can 238 change over time due to, e.g., node mobility, link quality, etc. 239 The MN further connects a downstream-attached End User Network 240 (EUN). The term MN used here is distinct from uses in other 241 documents, and does not imply a particular mobility protocol. 243 End User Network (EUN) 244 a simple or complex downstream-attached mobile network that 245 travels with the MN as a single logical unit. The IP addresses 246 assigned to EUN devices remain stable even if the MN's upstream 247 data link connections change. 249 Mobility Service (MS) 250 a mobile routing service that tracks MN movements and ensures that 251 MNs remain continuously reachable even across mobility events. 252 Specific MS details are out of scope for this document. 254 Mobility Service Endpoint (MSE) 255 an entity in the MS (either singular or aggregate) that 256 coordinates the mobility events of one or more MN. 258 Mobility Service Prefix (MSP) 259 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 260 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 261 from which more-specific Mobile Network Prefixes (MNPs) are 262 delegated. OMNI link administrators typically obtain MSPs from an 263 Internet address registry, however private-use prefixes can 264 alternatively be used subject to certain limitations (see: 265 Section 9). OMNI links that connect to the global Internet 266 advertise their MSPs to their interdomain routing peers. 268 Mobile Network Prefix (MNP) 269 a longer IP prefix delegated from an MSP (e.g., 270 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 271 MNs sub-delegate the MNP to devices located in EUNs. 273 Access Network (ANET) 274 a data link service network (e.g., an aviation radio access 275 network, satellite service provider network, cellular operator 276 network, WiFi network, etc.) that connects MNs. Physical and/or 277 data link level security is assumed, and sometimes referred to as 278 "protected spectrum". Private enterprise networks and ground 279 domain aviation service networks may provide multiple secured IP 280 hops between the MN's point of connection and the nearest Access 281 Router. 283 Access Router (AR) 284 a router in the ANET for connecting MNs to correspondents in 285 outside Internetworks. The AR may be located on the same physical 286 link as the MN, or may be located multiple IP hops away. In the 287 latter case, the MN uses encapsulation to communicate with the AR 288 as though it were on the same physical link. 290 ANET interface 291 a MN's attachment to a link in an ANET. 293 Internetwork (INET) 294 a connected network region with a coherent IP addressing plan that 295 provides transit forwarding services between ANETs and nodes that 296 connect directly to the open INET via unprotected media. No 297 physical and/or data link level security is assumed, therefore 298 security must be applied by upper layers. The global public 299 Internet itself is an example. 301 INET interface 302 a node's attachment to a link in an INET. 304 *NET 305 a "wildcard" term used when a given specification applies equally 306 to both ANET and INET cases. 308 OMNI link 309 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 310 over one or more INETs and their connected ANETs. An OMNI link 311 can comprise multiple INET segments joined by bridges the same as 312 for any link; the addressing plans in each segment may be mutually 313 exclusive and managed by different administrative entities. 315 OMNI interface 316 a node's attachment to an OMNI link, and configured over one or 317 more underlying *NET interfaces. If there are multiple OMNI links 318 in an OMNI domain, a separate OMNI interface is configured for 319 each link. 321 OMNI Adaptation Layer (OAL) 322 an OMNI interface process whereby packets admitted into the 323 interface are wrapped in a mid-layer IPv6 header and fragmented/ 324 reassembled if necessary to support the OMNI link Maximum 325 Transmission Unit (MTU). The OAL is also responsible for 326 generating MTU-related control messages as necessary, and for 327 providing addressing context for spanning multiple segments of a 328 bridged OMNI link. 330 OMNI Option 331 an IPv6 Neighbor Discovery option providing multilink parameters 332 for the OMNI interface as specified in Section 11. 334 Mobile Network Prefix Link Local Address (MNP-LLA) 335 an IPv6 Link Local Address that embeds the most significant 64 336 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 337 Section 7. 339 Mobile Network Prefix Unique Local Address (MNP-ULA) 340 an IPv6 Unique-Local Address derived from an MNP-LLA. 342 Administrative Link Local Address (ADM-LLA) 343 an IPv6 Link Local Address that embeds a 32-bit administratively- 344 assigned identification value in the lower 32 bits of fe80::/96, 345 as specified in Section 7. 347 Administrative Unique Local Address (ADM-ULA) 348 an IPv6 Unique-Local Address derived from an ADM-LLA. 350 Multilink 351 an OMNI interface's manner of managing diverse underlying 352 interface connections to data links as a single logical unit. The 353 OMNI interface provides a single unified interface to upper 354 layers, while underlying interface selections are performed on a 355 per-packet basis considering factors such as DSCP, flow label, 356 application policy, signal quality, cost, etc. Multilinking 357 decisions are coordinated in both the outbound (i.e. MN to 358 correspondent) and inbound (i.e., correspondent to MN) directions. 360 Multihop 361 an iterative relaying of IP packets between MNs over an OMNI 362 underlying interface technology (such as omnidirectional wireless) 363 without support of fixed infrastructure. Multihop services entail 364 node-to-node relaying within a Mobile/Vehicular Ad-hoc Network 365 (MANET/VANET) for MN-to-MN communications and/or for "range 366 extension" where MNs within range of communications infrastructure 367 elements provide forwarding services for other MNs. 369 L2 370 The second layer in the OSI network model. Also known as "layer- 371 2", "link-layer", "sub-IP layer", "data link layer", etc. 373 L3 374 The third layer in the OSI network model. Also known as "layer- 375 3", "network-layer", "IP layer", etc. 377 underlying interface 378 a *NET interface over which an OMNI interface is configured. The 379 OMNI interface is seen as a L3 interface by the IP layer, and each 380 underlying interface is seen as a L2 interface by the OMNI 381 interface. The underlying interface either connects directly to 382 the physical communications media or coordinates with another node 383 where the physical media is hosted. 385 Mobility Service Identification (MSID) 386 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 387 (see: Section 7). IDs are assigned according to MS-specific 388 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 390 Safety-Based Multilink (SBM) 391 A means for ensuring fault tolerance through redundancy by 392 connecting multiple affiliated OMNI interfaces to independent 393 routing topologies (i.e., multiple independent OMNI links). 395 Performance Based Multilink (PBM) 396 A means for selecting underlying interface(s) for packet 397 transmission and reception within a single OMNI interface. 399 OMNI Domain 400 The set of all SBM/PBM OMNI links that collectively provides 401 services for a common set of MSPs. Each OMNI domain consists of a 402 set of affiliated OMNI links that all configure the same ::/48 ULA 403 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 405 3. Requirements 407 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 408 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 409 "OPTIONAL" in this document are to be interpreted as described in BCP 410 14 [RFC2119][RFC8174] when, and only when, they appear in all 411 capitals, as shown here. 413 An implementation is not required to internally use the architectural 414 constructs described here so long as its external behavior is 415 consistent with that described in this document. 417 4. Overlay Multilink Network (OMNI) Interface Model 419 An OMNI interface is a MN virtual interface configured over one or 420 more underlying interfaces, which may be physical (e.g., an 421 aeronautical radio link) or virtual (e.g., an Internet or higher- 422 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 423 with the MS through IPv6 ND message exchanges. The MN uses the MNP 424 to construct a unique Link-Local Address (MNP-LLA) through the 425 algorithmic derivation specified in Section 7 and assigns the LLA to 426 the OMNI interface. 428 The OMNI interface architectural layering model is the same as in 429 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 430 therefore sees the OMNI interface as a single L3 interface with 431 multiple underlying interfaces that appear as L2 communication 432 channels in the architecture. 434 +----------------------------+ 435 | Upper Layer Protocol | 436 Session-to-IP +---->| | 437 Address Binding | +----------------------------+ 438 +---->| IP (L3) | 439 IP Address +---->| | 440 Binding | +----------------------------+ 441 +---->| OMNI Interface | 442 Logical-to- +---->| (LLA) | 443 Physical | +----------------------------+ 444 Interface +---->| L2 | L2 | | L2 | 445 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 446 +------+------+ +------+ 447 | L1 | L1 | | L1 | 448 | | | | | 449 +------+------+ +------+ 451 Figure 1: OMNI Interface Architectural Layering Model 453 Each underlying interface provides an L2/L1 abstraction according to 454 one of the following models: 456 o INET interfaces connect to an INET either natively or through one 457 or several IPv4 Network Address Translators (NATs). Native INET 458 interfaces have global IP addresses that are reachable from any 459 INET correspondent. NATed INET interfaces typically have private 460 IP addresses and connect to a private network behind one or more 461 NATs that provide INET access. 463 o ANET interfaces connect to a protected ANET that is separated from 464 the open INET by an AR acting as a proxy. The ANET interface may 465 be either on the same L2 link segment as the AR, or separated from 466 the AR by multiple IP hops. 468 o VPNed interfaces use security encapsulation over a *NET to a 469 Virtual Private Network (VPN) gateway. Other than the link-layer 470 encapsulation format, VPNed interfaces behave the same as for 471 Direct interfaces. 473 o Direct (aka "point-to-point") interfaces connect directly to a 474 peer without crossing any *NET paths. An example is a line-of- 475 sight link between a remote pilot and an unmanned aircraft. 477 The OMNI virtual interface model gives rise to a number of 478 opportunities: 480 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 481 Address Detection (DAD) or Multicast Listener Discovery (MLD) 482 messaging is necessary. 484 o since Temporary ULAs are statistically unique, they can be used 485 without DAD, e.g. for MN-to-MN communications until an MNP-LLA is 486 obtained. 488 o *NET interfaces on the same L2 link segment as an AR do not 489 require any L3 addresses (i.e., not even link-local) in 490 environments where communications are coordinated entirely over 491 the OMNI interface. (An alternative would be to also assign the 492 same LLA to all *NET interfaces.) 494 o as underlying interface properties change (e.g., link quality, 495 cost, availability, etc.), any active interface can be used to 496 update the profiles of multiple additional interfaces in a single 497 message. This allows for timely adaptation and service continuity 498 under dynamically changing conditions. 500 o coordinating underlying interfaces in this way allows them to be 501 represented in a unified MS profile with provisions for mobility 502 and multilink operations. 504 o exposing a single virtual interface abstraction to the IPv6 layer 505 allows for multilink operation (including QoS based link 506 selection, packet replication, load balancing, etc.) at L2 while 507 still permitting L3 traffic shaping based on, e.g., DSCP, flow 508 label, etc. 510 o the OMNI interface allows inter-INET traversal when nodes located 511 in different INETs need to communicate with one another. This 512 mode of operation would not be possible via direct communications 513 over the underlying interfaces themselves. 515 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 516 lossless and adaptive path MTU mitigations not available for 517 communications directly over the underlying interfaces themselves. 518 The OAL supports "packing" of multiple IP payload packets within a 519 single OAL packet. 521 o L3 sees the OMNI interface as a point of connection to the OMNI 522 link; if there are multiple OMNI links (i.e., multiple MS's), L3 523 will see multiple OMNI interfaces. 525 o Multiple independent OMNI interfaces can be used for increased 526 fault tolerance through Safety-Based Multilink (SBM), with 527 Performance-Based Multilink (PBM) applied within each interface. 529 Other opportunities are discussed in [RFC7847]. Note that even when 530 the OMNI virtual interface is present, applications can still access 531 underlying interfaces either through the network protocol stack using 532 an Internet socket or directly using a raw socket. This allows for 533 intra-network (or point-to-point) communications without invoking the 534 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 535 is configured over an underlying IPv4 interface, applications can 536 still invoke IPv4 intra-network communications as long as the 537 communicating endpoints are not subject to mobility dynamics. 538 However, the opportunities discussed above are not available when the 539 architectural layering is bypassed in this way. 541 Figure 2 depicts the architectural model for a MN with an attached 542 EUN connecting to the MS via multiple independent *NETs. When an 543 underlying interface becomes active, the MN's OMNI interface sends 544 IPv6 ND messages without encapsulation if the first-hop Access Router 545 (AR) is on the same underlying link; otherwise, the interface uses 546 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 547 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 548 then coordinates with an INET Mobility Service Endpoint (MSE#1, 549 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 550 The Hop Limit in IPv6 ND messages is not decremented due to 551 encapsulation; hence, the OMNI interface appears to be attached to an 552 ordinary link. 554 +--------------+ (:::)-. 555 | MN |<-->.-(::EUN:::) 556 +--------------+ `-(::::)-' 557 |OMNI interface| 558 +----+----+----+ 559 +--------|IF#1|IF#2|IF#n|------ + 560 / +----+----+----+ \ 561 / | \ 562 / | \ 563 v v v 564 (:::)-. (:::)-. (:::)-. 565 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 566 `-(::::)-' `-(::::)-' `-(::::)-' 567 +----+ +----+ +----+ 568 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 569 . +-|--+ +-|--+ +-|--+ . 570 . | | | 571 . v v v . 572 . <----- INET Encapsulation -----> . 573 . . 574 . +-----+ (:::)-. . 575 . |MSE#2| .-(::::::::) +-----+ . 576 . +-----+ .-(::: INET :::)-. |MSE#m| . 577 . (::::: Routing ::::) +-----+ . 578 . `-(::: System :::)-' . 579 . +-----+ `-(:::::::-' . 580 . |MSE#1| +-----+ +-----+ . 581 . +-----+ |MSE#3| |MSE#4| . 582 . +-----+ +-----+ . 583 . . 584 . . 585 . <----- Worldwide Connected Internetwork ----> . 586 ........................................................... 588 Figure 2: MN/MS Coordination via Multiple *NETs 590 After the initial IPv6 ND message exchange, the MN (and/or any nodes 591 on its attached EUNs) can send and receive IP data packets over the 592 OMNI interface. OMNI interface multilink services will forward the 593 packets via ARs in the correct underlying *NETs. The AR encapsulates 594 the packets according to the capabilities provided by the MS and 595 forwards them to the next hop within the worldwide connected 596 Internetwork via optimal routes. 598 OMNI links span one or more underlying Internetwork via the OMNI 599 Adaptation Layer (OAL) which is based on a mid-layer overlay 600 encapsulation using [RFC2473]. Each OMNI link corresponds to a 601 different overlay (differentiated by an address codepoint) which may 602 be carried over a completely separate underlying topology. Each MN 603 can facilitate SBM by connecting to multiple OMNI links using a 604 distinct OMNI interface for each link. 606 Note: OMNI interface underlying interfaces often connect directly to 607 physical media on the local platform (e.g., a laptop computer with 608 WiFi, etc.), but in some configurations the physical media may be 609 hosted on a separate Local Area Network (LAN) node. In that case, 610 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 611 tunnel (at a layer below the underlying interface) to the node 612 hosting the physical media. The OMNI interface may also apply 613 encapsulation at a layer above the underlying interface such that 614 packets would appear "double-encapsulated" on the LAN; the node 615 hosting the physical media in turn removes the LAN encapsulation 616 prior to transmission or inserts it following reception. Finally, 617 the underlying interface must monitor the node hosting the physical 618 media (e.g., through periodic keepalives) so that it can convey 619 up/down/status information to the OMNI interface. 621 5. The OMNI Adaptation Layer (OAL) 623 The OMNI interface observes the link nature of tunnels, including the 624 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 625 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 626 The OMNI interface is configured over one or more underlying 627 interfaces that may have diverse MTUs. OMNI interfaces accommodate 628 MTU diversity using the OMNI Adaptation Layer (OAL) which provides a 629 mid-layer encapsulation and fragmentation/reassembly service as 630 discussed in this section. 632 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 633 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 634 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 635 permitted to perform network fragmentation even though the 636 destination is required to reassemble more. The network therefore 637 MUST forward packets of at least 1280 bytes without generating an 638 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 639 [RFC8201]. (Note: the source can apply "source fragmentation" for 640 locally-generated IPv6 packets up to 1500 bytes and larger still if 641 it if has a way to determine that the destination configures a larger 642 MRU, but this does not affect the minimum IPv6 path MTU.) 644 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 645 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 646 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 647 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 648 support network fragmentation and the destination is required to 649 reassemble at least that much. The "Don't Fragment" (DF) bit in the 650 IPv4 encapsulation headers of packets sent over IPv4 underlying 651 interfaces therefore MUST be set to 0. (Note: even if the 652 encapsulation source has a way to determine that the encapsulation 653 destination configures an MRU larger than 576 bytes, it should not 654 assume a larger minimum IPv4 path MTU without careful consideration 655 of the issues discussed in Section 5.1.) 657 Since IPv6/IPv4 protocol translation and/or IPv6-in-IPv4 658 encapsulation may occur in any *NET path, the OAL should always 659 assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless of the 660 underlying interface IP protocol version. By always assuming the 661 IPv4 minimum path MTU even for IPv6 underlying interfaces, the OAL 662 may produce smaller fragments with additional encapsulation overhead 663 but will always interoperate and never run the risk of presenting a 664 destination interface with a packet that exceeds its MRU. 665 Additionally, the OAL path could traverse multiple *NET "segments" 666 with intermediate OAL forwarding nodes performing re-encapsulation 667 between segments. Re-encapsulation at each successive intermediate 668 node could introduce a larger encapsualtion overhead than that which 669 appeared in previous segments; hence, the worst-case encapsulation 670 overhead must be assumed. 672 The OMNI interface configures both an MTU and MRU of 9180 bytes 673 [RFC2492]; the size is therefore not a reflection of the underlying 674 interface or *NET path MTUs, but rather determines the largest packet 675 the OMNI interface can forward or reassemble. The OMNI interface 676 uses the OAL to admit packets from the network layer that are no 677 larger than the OMNI interface MTU while generating ICMPv4 678 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery (PMTUD) 679 Packet Too Big (PTB) [RFC8201] messages as necessary. This document 680 refers to both of these ICMPv4/ICMPv6 message types simply as "PTBs", 681 and introduces a distinction between PTB "hard" and "soft" errors as 682 discussed below. 684 For IPv4 packets with DF=0, the network layer performs IPv4 685 fragmentation if necessary then admits the packets/fragments into the 686 OMNI interface; these fragments will be reassembled by the final 687 destination. For IPv4 packets with DF=1 and IPv6 packets, the 688 network layer admits the packet if it is no larger than the OMNI 689 interface MTU; otherwise, it drops the packet and returns a PTB hard 690 error message to the source. 692 For each admitted IP packet/fragment, the OAL inserts a mid-layer 693 IPv6 encapsulation header per [RFC2473] before adding any outer *NET 694 encapsulations. (The OAL does not decrement the inner IP Hop Limit/ 695 TTL during encapsulation since the insertion occurs at a layer below 696 IP forwarding.) If the OAL-encapsulated packet requires 697 fragmentation, the OMNI interface then calculates the 32-bit CRC over 698 the entire mid-layer packet and writes the value in a trailing field 699 at the end of the packet. The OAL next inserts a single OMNI Routing 700 Header (ORH) if necessary (see: [I-D.templin-intarea-6706bis]), 701 fragments the mid-layer IPv6 packet if necessary, forwards the 702 packet/fragments using *NET encapsulation, and returns an internally- 703 generated PTB soft error message (subject to rate limiting) if it 704 deems the packet too large according to factors such as link 705 performance characteristics, reassembly congestion, etc. This 706 ensures that the path MTU is adaptive and reflects the current path 707 used for a given data flow. 709 The OAL operates with respect to both the minimum IPv6 and IPv4 path 710 MTUs as follows: 712 o When an OMNI interface sends a packet toward a final destination 713 via an ANET peer, it sends without OAL encapsulation if the packet 714 (including any outer-layer ANET encapsulations) is no larger than 715 the underlying interface MTU for on-link ANET peers or the minimum 716 ANET path MTU for peers separated by multiple IP hops. Otherwise, 717 the OAL inserts an IPv6 header per [RFC2473] with source address 718 set to the node's own Unique-Local Address (ULA) (see: Section 8) 719 and destination set to either the Administrative ULA (ADM-ULA) of 720 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 721 corresponding to the final destination (see below). The OAL then 722 calculates and appends the trailing 32-bit CRC, then uses IPv6 723 fragmentation to break the packet into a minimum number of non- 724 overlapping fragments where the size of each non-final fragment 725 (including both the OMNI and any outer-layer ANET encapsulations) 726 is determined by the underlying interface MTU for on-link ANET 727 peers or the Maximum Cell Size (MCS) for peers separated by 728 multiple IP hops (see below). The OAL then encapsulates the 729 fragments in any ANET headers and sends them to the ANET peer, 730 which either reassembles before forwarding if the OAL destination 731 is its own ADM-ULA or forwards the fragments toward the final 732 destination without first reassembling otherwise. 734 o When an OMNI interface sends a packet toward a final destination 735 via an INET interface, it sends packets (including any outer-layer 736 INET encapsulations) no larger than the minimum INET path MTU 737 without OAL encapsulation if the destination is reached via an 738 INET address within the same OMNI link segment. Otherwise, the 739 OAL inserts an IPv6 header per [RFC2473] with source address set 740 to the node's ULA, destination set to the ULA of an OMNI node on 741 the final *NET segment. The OAL next calculates and appends the 742 trailing 32-bit CRC, then inserts an OMNI Routing Header (ORH) if 743 necessary (see: [I-D.templin-intarea-6706bis]), then uses IPv6 744 fragmentation to break the packet into a minimum number of non- 745 overlapping fragments where the size of each non-final fragment is 746 determined by the Maximum Cell Size (MCS) as discussed below. The 747 OAL then encapsulates the fragments in any INET headers and sends 748 them toward the final segment OMNI node, which reassembles before 749 forwarding toward the final destination. 751 In light of the above considerations, the OAL assumes an absolute 752 minimum path MTU of 576 bytes at each *NET segment for the purpose of 753 generating OAL fragments. Each *NET segment will apply encapsulation 754 including either a 20 byte IPv4 or 40 byte IPv6 header, plus an 8 755 byte UDP header for INETs. Each *NET segment may also insert an IP 756 security encapsulation (40 bytes maximum assumed), and may add a 757 maximum-length (40 byte) ORH as an OAL header extension if one was 758 not included by the original OAL source. Assuming therefore an 759 absolute worst case of (40 + 8 + 40) = 88 bytes for *NET 760 encapsulation plus (40 + 8 + 40) = 88 bytes for OAL encapsulation, 761 this leaves 400 bytes to accommodate the actual inner IP packet 762 fragment. OMNI interfaces therefore set a minimum Maximum Cell Size 763 (MCS) of 400 bytes as the basis for the minimum-sized OAL fragment 764 that can be assured of traversing all segments without loss due to an 765 MTU/MRU restriction. The fragment size for OAL IPv6 fragmentation is 766 therefore determined by adding the size of the encapsulating OAL 767 header plus extension headers to the MCS. 769 The OAL therefore MUST NOT perform fragmentation for IP packets 770 smaller than the minimum MCS. Instead, OAL fragmentation algorithms 771 MUST produce non-final fragments containing a portion of the original 772 packet at least as large as the minimum MCS, and OAL reassembly 773 algorithms MUST unconditionally drop any non-final OAL fragments 774 containing less than the minimum MCS. Additionally, intermediate 775 nodes MUST NOT perform further OAL fragmentation, and OAL 776 destinations MUST unconditionally drop OAL packets/fragments that 777 include any extension headers other than a single ORH and a single 778 Fragment Header. 780 For selected underlying paths, the OAL MAY maintain a "path MCS" 781 value initialized to the minimum MCS and increased to larger values 782 if better information is known or discovered. For example: 784 o the OAL can increase path MCS by 8 bytes for ANET paths in which 785 no UDP encapsulation header is needed. 787 o the OAL can increase path MCS by 20 bytes for ANET paths in which 788 no IPv6 hops will occur. 790 o the OAL can increase path MCS by 40 bytes if there is assurance 791 that no ORH will be inserted in the path. 793 o when ANET peers share a common physical link or a fixed path with 794 a known larger MTU, the OAL can base path MCS on this larger size 795 (i.e., instead of 576 bytes) as long as the ANET peer reassembles 796 before re-encapsulating and forwarding (while re-fragmenting if 797 necessary). 799 o etc. 801 The OAL can also actively probe underlying paths to discover larger 802 path MCS values (e.g., per [RFC4821]), but care must be taken to 803 avoid setting static values for dynamically changing paths leading to 804 black holes. While observing the minimum MCS will always result in 805 robust and secure behavior, the OAL should optimize path MCS values 806 for underlying paths where more efficient utilization may result in 807 better performance (e.g. for wireless aviation data links). 809 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 810 header Code field value 0 are hard errors that always indicate that a 811 packet has been dropped due to a real MTU restriction. However, the 812 OAL can also forward large packets via encapsulation and 813 fragmentation while at the same time returning PTB soft error 814 messages (subject to rate limiting) indicating that a forwarded 815 packet was uncomfortably large. The OMNI interface can therefore 816 continuously forward large packets without loss while returning PTB 817 soft error messages recommending a smaller size. Original sources 818 that receive the soft errors in turn reduce the size of the packets 819 they send, i.e., the same as for hard errors. 821 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 822 field to the value 1 in PTB soft error messages. The OAL sets the 823 PTB destination address to the source address of the original packet, 824 and sets the source address to the MNP Subnet Router Anycast address 825 of the MN. The OAL then sets the MTU field to a value no smaller 826 than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB soft 827 error to the original source. 829 When the original source receives the PTB, it reduces its path MTU 830 estimate the same as for hard errors but does not regard the message 831 as a loss indication. (If the original source does not recognize the 832 soft error code, it regards the PTB the same as a hard error but 833 should heed the retransmission advice given in [RFC8201] suggesting 834 retransmission based on normal packetization layer retransmission 835 timers.) This document therefore updates [RFC1191][RFC4443] and 836 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 837 that PTB hard or soft errors may arrive at any time even if after a 838 successful MTU probe (this is the same consideration as for an 839 ordinary path fluctuation following a successful probe). 841 In summary, the OAL supports continuous transmission and reception of 842 packets of various sizes in the face of dynamically changing network 843 conditions. Moreover, since PTB soft errors do not indicate loss, 844 original sources that receive soft errors can quickly scan for path 845 MTU increases without waiting for the minimum 10 minutes specified 846 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 847 therefore provides a lossless and adaptive service that accommodates 848 MTU diversity especially well-suited for dynamic multilink 849 environments. 851 Note: An OMNI interface that reassembles OAL fragments may experience 852 congestion-oriented loss in its reassembly cache and can optionally 853 send PTB soft errors to the original source and/or ICMP "Time 854 Exceeded" messages to the source of the OAL fragments. In 855 environments where the messages may contribute to unacceptable 856 additional congestion, however, the OMNI interface can refrain from 857 sending PTB soft errors and simply regard the loss as an ordinary 858 unreported congestion event for which the original source will 859 eventually compensate. 861 Note: When the network layer forwards an IPv4 packet/fragment with 862 DF=0 into the OMNI interface, the interface can optionally perform 863 (further) IPv4 fragmentation before invoking the OAL so that the 864 fragments will be reassembled by the final destination. When the 865 network layer performs IPv6 fragmentation for locally-generated IPv6 866 packets, the OMNI interface typically invokes the OAL without first 867 applying (further) IPv6 fragmentation; the network layer should 868 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 869 push the reassembly burden to the final destination and avoid 870 receiving PTB soft errors from the OMNI interface. Aside from these 871 non-normative guidelines, the manner in which any IP fragmentation is 872 invoked prior to OAL encapsulation/fragmentation is an implementation 873 matter. 875 Note: The source OAL includes a trailing 32-bit CRC only for OAL 876 packets that require fragmentation, and the destination OAL discards 877 any OAL packets with incorrect CRC values following reassembly. (The 878 source OAL calculates the CRC over the entire packet before inserting 879 the ORH, then appends the CRC to the end of the packet and adds the 880 CRC length to the OAL Payload Length prior to fragmentation. The 881 destination OAL removes the ORH (if present) and subtracts the CRC 882 length from the OAL Payload Length then verifies the CRC following 883 reassembly.) A 32-bit CRC is sufficient for detecting reassembly 884 misassociations for packet sizes no larger than the OMNI interface 885 MTU but may not be sufficient to detect errors for larger sizes 886 [CRC]. 888 Note: Some underlying interface types (e.g., VPNs) may already 889 provide their own robust fragmentation and reassembly services even 890 without OAL encapsulation. In those cases, the OAL can invoke the 891 inherent underlying interface schemes instead while employing PTB 892 soft errors in the same fashion as described above. Other underlying 893 interface facilities such as header/message compression can also be 894 harnessed in a similar fashion. 896 Note: Applications can dynamically tune the size of the packets they 897 to send to produce the best possible throughput and latency, with the 898 understanding that these parameters may change over time due to 899 factors such as congestion, mobility, network path changes, etc. The 900 receipt or absence of soft errors should be seen as hints of when 901 increasing or decreasing packet sizes may be beneficial. 903 Note: While not strictly required, sending all fragments of the same 904 fragmented OAL packet consecutively over the same underlying 905 interface with minimal inter-fragment delay may increase the 906 likelihood of successful reassembly. 908 Note: By way of example, under the minimum MCS each non-final OAL 909 fragment would include a 400 byte fragment of the original inner IP 910 packet. Therefore, a 1500 byte inner IP packet would require 4 OAL 911 fragments, with each non-final fragment containing 400 bytes and the 912 final fragment containing 300 bytes of the original packet. 914 5.1. Fragmentation Security Implications 916 As discussed in Section 3.7 of [RFC8900], there are four basic 917 threats concerning IPv6 fragmentation; each of which is addressed by 918 effective mitigations as follows: 920 1. Overlapping fragment attacks - reassembly of overlapping 921 fragments is forbidden by [RFC8200]; therefore, this threat does 922 not apply to the OAL. 924 2. Resource exhaustion attacks - this threat is mitigated by 925 providing a sufficiently large OAL reassembly cache and 926 instituting "fast discard" of incomplete reassemblies that may be 927 part of a buffer exhaustion attack. The reassembly cache should 928 be sufficiently large so that a sustained attack does not cause 929 excessive loss of good reassemblies but not so large that (timer- 930 based) data structure management becomes computationally 931 expensive. The cache should also be indexed based on the arrival 932 underlying interface such that congestion experienced over a 933 first underlying interface does not cause discard of incomplete 934 reassemblies for uncongested underlying interfaces. 936 3. Attacks based on predictable fragment identification values - 937 this threat is mitigated by selecting a suitably random ID value 938 per [RFC7739]. 940 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 941 threat is mitigated by setting a minimum MCS for OAL 942 fragmentation, which defeats all "tiny fragment"-based attacks. 944 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 945 ID) field with only 65535 unique values such that at high data rates 946 the field could wrap and apply to new packets while the fragments of 947 old packets using the same ID are still alive in the network 948 [RFC4963]. However, since the largest OAL fragment that will be sent 949 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 950 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 951 recommendations suggest that such links will have low data rates. 952 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 953 at high data rates is not a concern for IPv6 fragmentation. 955 Finally, [RFC6980] documents fragmentation security concerns for 956 large IPv6 ND messages. These concerns are addressed when the OMNI 957 interface employs the OAL instead of directly fragmenting the IPv6 ND 958 message itself. For this reason, OMNI interfaces MUST NOT admit IPv6 959 ND messages larger than the OMNI interface MTU, and MUST employ the 960 OAL for IPv6 ND messages admitted into the OMNI interface the same as 961 discussed above. 963 5.2. OAL "Super-Packet" Packing 965 By default, the source OAL includes a 40-byte IPv6 encapsulation 966 header for each inner IP payload packet during OAL encapsulation. 967 When fragmentation is needed, the source OAL also calculates and 968 includes a 32-bit trailing CRC for the entire packet then performs 969 fragmentation such that a copy of the 40-byte IPv6 header plus an 970 8-byte IPv6 Fragment Header is included in each fragment (when an ORH 971 is added, the OAL encapsulation headers become larger still). 972 However, these encapsulations may represent excessive overhead in 973 some environments. A technique known as "packing" discussed in 974 [I-D.ietf-intarea-tunnels] is therefore supported so that multiple 975 inner IP payload packets can be included within a single OAL packet 976 known as a "super-packet". 978 When the source OAL has multiple inner IP payload packets with total 979 length no larger than the OMNI interface MTU to send to the same 980 destination, it can optionally concatenate them into a super-packet 981 encapsulated in a single OAL header. Within the super-packet, the IP 982 header of the first inner packet (iHa) followed by its data (iDa) is 983 concatenated immediately following the OAL header, then the inner IP 984 header of the next packet (iHb) followed by its data (iDb) is 985 concatenated immediately following the first packet, etc. The super- 986 packet format is transposed from [I-D.ietf-intarea-tunnels] and shown 987 in Figure 3: 989 <-- Multiple inner IP payload packets to be "packed" --> 990 +-----+-----+ 991 | iHa | iDa | 992 +-----+-----+ 993 | 994 | +-----+-----+ 995 | | iHb | iDb | 996 | +-----+-----+ 997 | | 998 | | +-----+-----+ 999 | | | iHc | iDc | 1000 | | +-----+-----+ 1001 | | | 1002 v v v 1003 +----------+-----+-----+-----+-----+-----+-----+ 1004 | OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc | 1005 +----------+-----+-----+-----+-----+-----+-----+ 1006 <-- OMNI "Super-Packet" with single OAL Hdr --> 1008 Figure 3: OAL Super-Packet Format 1010 When the source OAL sends a super-packet, it calculates a CRC and 1011 applies OAL fragmentation if necessary then sends the packet or 1012 fragments to the destination OAL. When the destination OAL receives 1013 the super-packet as a whole packet or as fragments, it reassembles 1014 and verifies the CRC if necessary then regards the OAL header Payload 1015 Length (after subtracting the CRC length) as the sum of the lengths 1016 of all payload packets. The destination OAL then selectively 1017 extracts each individual payload packet (e.g., by setting pointers 1018 into the buffer containing the super-packet and maintaining a 1019 reference count, by copying each payload packet into its own buffer, 1020 etc.) and forwards each payload packet or processes it locally as 1021 appropriate. During extraction, the OAL determines the IP protocol 1022 version of each successive inner payload packet 'j' by examining the 1023 first four bits of iH(j), and determines the length of the inner 1024 packet by examining the rest of iH(j) according to the IP protocol 1025 version. 1027 Note: OMNI interfaces must take care to avoid processing super-packet 1028 payload elements that would subvert security. Specifically, if a 1029 super-packet contains a mix of data and control payload packets 1030 (which could include critical security codes), the node MUST NOT 1031 process the data packets before processing the control packets. 1033 6. Frame Format 1035 The OMNI interface transmits IP packets according to the native frame 1036 format of each underlying interface. For example, for Ethernet- 1037 compatible interfaces the frame format is specified in [RFC2464], for 1038 aeronautical radio interfaces the frame format is specified in 1039 standards such as ICAO Doc 9776 (VDL Mode 2 Technical Manual), for 1040 tunnels over IPv6 the frame format is specified in [RFC2473], etc. 1042 7. Link-Local Addresses (LLAs) 1044 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 1045 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 1046 the MNP assigned to the mobile node, while "ADM-LLAs" include an 1047 administratively-unique ID that is guaranteed to be unique on the 1048 link. LLAs are configured as follows: 1050 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 1051 the least-significant 64 bits of the IPv6 link-local prefix 1052 fe80::/64, i.e., in the LLA "interface identifier" portion. The 1053 prefix length for the LLA is determined by adding 64 to the MNP 1054 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 1055 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 1057 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 1058 i.e., the interface identifier consists of 16 '0' bits, followed 1059 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 1060 prefix length for the LLA is determined by adding 96 to the MNP 1061 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 1062 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 1063 fe80::ffff:c000:0200/120). 1065 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 1066 uniqueness. The lower 32 bits of the LLA includes a unique 1067 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 1068 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 1069 prefix length is determined by adding 96 to the MSID prefix 1070 length. For example, if the prefix length for MSID 0x10012001 is 1071 16 then the ADM-LLA prefix length is set to 112 and the LLA is 1072 written as fe80::1001:2001/112. The "zero" address for each ADM- 1073 LLA prefix is the Subnet-Router anycast address for that prefix 1074 [RFC4291]; for example, the Subnet-Router anycast address for 1075 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 1076 0xff000000 through 0xffffffff is reserved for future use. 1078 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 1079 MNPs can be allocated from that block ensuring that there is no 1080 possibility for overlap between the different MNP- and ADM-LLA 1081 constructs discussed above. 1083 Since MNP-LLAs are based on the distribution of administratively 1084 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 1085 administrative assignment, OMNI interfaces set the autoconfiguration 1086 variable DupAddrDetectTransmits to 0 [RFC4862]. 1088 Note: If future protocol extensions relax the 64-bit boundary in IPv6 1089 addressing, the additional prefix bits of an MNP could be encoded in 1090 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 1091 would therefore still be in bits 64-127, and the remaining bits would 1092 appear in bits 16 through 48.) However, the analysis provided in 1093 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 1094 architecture for the foreseeable future. 1096 Note: Even though this document honors the 64-bit boundary in IPv6 1097 addressing, it specifies prefix lengths longer than /64 for routing 1098 purposes. This effectively extends IPv6 routing determination into 1099 the interface identifier portion of the IPv6 address, but it does not 1100 redefine the 64-bit boundary. Modern routing protocol 1101 implementations honor IPv6 prefixes of all lengths, up to and 1102 including /128. 1104 8. Unique-Local Addresses (ULAs) 1106 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 1107 destination addresses in OAL IPv6 encapsulation headers. ULAs are 1108 only routable within the scope of a an OMNI domain, and are derived 1109 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 1110 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 1111 Global ID to produce the prefix [ULA]::/48, which is then followed by 1112 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 1113 specified in Section 3 of [RFC4193]. All nodes in the same OMNI 1114 domain configure the same 40-bit Global ID as the OMNI domain 1115 identifier. The statistic uniqueness of the 40-bit pseudo-random 1116 Global ID allows different OMNI domains to be joined together in the 1117 future without requiring renumbering. 1119 Each OMNI link instance is identified by a value between 0x0000 and 1120 0xfeff in bits 48-63 of [ULA]::/48; the values 0xff00 through 0xfffe 1121 are reserved for future use, and the value 0xffff denotes the 1122 presence of a Temporary ULA (see below). For example, OMNI ULAs 1123 associated with instance 0 are configured from the prefix 1124 [ULA]:0000::/64, instance 1 from [ULA]:0001::/64, instance 2 from 1125 [ULA]:0002::/64, etc. ULAs and their associated prefix lengths are 1126 configured in correspondence with LLAs through stateless prefix 1127 translation where "MNP-ULAs" are assigned in correspondence to MNP- 1128 LLAs and "ADM-ULAs" are assigned in correspondence to ADM-LLAs. For 1129 example, for OMNI link instance [ULA]:1010::/64: 1131 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 1132 56-bit MNP length is derived by copying the lower 64 bits of the 1133 LLA into the lower 64 bits of the ULA as 1134 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1135 64 plus the IPv6 MNP length). 1137 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1138 MNP length is derived by simply writing the LLA interface ID into 1139 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1140 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1142 o the ADM-ULA corresponding to fe80::1000/112 is simply 1143 [ULA]:1010::1000/112. 1145 o the ADM-ULA corresponding to fe80::/128 is simply 1146 [ULA]:1010::/128. 1148 o etc. 1150 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1151 link instance. For example, the OMNI interface connected to instance 1152 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1153 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1154 [ULA]:0003::/64) into the local routing system so that applications 1155 can direct traffic according to SBM requirements. 1157 The ULA presents an IPv6 address format that is routable within the 1158 OMNI routing system and can be used to convey link-scoped IPv6 ND 1159 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1160 The OMNI link extends across one or more underling Internetworks to 1161 include all ARs and MSEs. All MNs are also considered to be 1162 connected to the OMNI link, however OAL encapsulation is omitted 1163 whenever possible to conserve bandwidth (see: Section 13). 1165 Each OMNI link can be subdivided into "segments" that often 1166 correspond to different administrative domains or physical 1167 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1168 necessary to support efficient packet forwarding to destinations 1169 located in other OMNI link segments. A full discussion of Segment 1170 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1172 Temporary ULAs are constructed per [I-D.ietf-6man-rfc4941bis] based 1173 on the prefix [ULA]:ffff::/64 and used by MNs when they have no other 1174 addresses. Temporary ULAs can be used for MN-to-MN communications 1175 outside the context of any supporting OMNI link infrastructure, and 1176 can also be used as an initial address while the MN is in the process 1177 of procuring an MNP. Temporary ULAs are not routable within the OMNI 1178 routing system, and are therefore useful only for OMNI link "edge" 1179 communications. Temporary ULAs employ optimistic DAD principles 1180 [RFC4429] since they are probabilistically unique. 1182 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1183 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1184 however the range could be used for MSP and MNP addressing under 1185 certain limiting conditions (see: Section 9). 1187 9. Global Unicast Addresses (GUAs) 1189 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1190 as Mobility Service Prefixes (MSPs) from which Mobile Network 1191 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1193 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1194 associated regional assigned numbers authority such that the OMNI 1195 domain can be interconnected to the global IPv6 Internet without 1196 causing inconsistencies in the routing system. An OMNI domain could 1197 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1198 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1199 were ever connected to the global IPv6 Internet. 1201 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1202 associated regional assigned numbers authority such that the OMNI 1203 domain can be interconnected to the global IPv4 Internet without 1204 causing routing inconsistencies. An OMNI domain could instead use 1205 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1206 this would require IPv4 NAT if the domain were ever connected to the 1207 global IPv4 Internet. 1209 10. Node Identification 1211 OMNI MNs and MSEs that connect over open Internetworks generate a 1212 Host Identity Tag (HIT) as specified in [RFC7401] and use the value 1213 as a robust general-purpose node identification value. Hierarchical 1214 HITs (HHITs) [I-D.ietf-drip-rid] may provide a useful alternative in 1215 certain domains such as the Unmanned (Air) Traffic Management (UTM) 1216 service for Unmanned Air Systems (UAS). MNs and MSEs can then use 1217 their (H)HITs in IPv6 ND control message exchanges. 1219 When a MN is truly outside the context of any infrastructure, it may 1220 have no MNP information at all. In that case, the MN can use its 1221 (H)HIT as an IPv6 source/destination address for sustained 1222 communications in Vehicle-to-Vehicle (V2V) and (multihop) Vehicle-to- 1223 Infrastructure (V2I) scenarios. The MN can also propagate the (H)HIT 1224 into the multihop routing tables of (collective) Mobile/Vehicular Ad- 1225 hoc Networks (MANETs/VANETs) using only the vehicles themselves as 1226 communications relays. 1228 When a MN connects to ARs over (non-multihop) protected-spectrum 1229 ANETs, an alternate form of node identification (e.g., MAC address, 1230 serial number, airframe identification value, VIN, etc.) may be 1231 sufficient. In that case, the MN should still generate a (H)HIT and 1232 maintain it in conjunction with any other node identifiers. The MN 1233 can then include OMNI "Node Identification" sub-options (see: 1234 Section 11.1.11) in IPv6 ND messages should the need to transmit 1235 identification information over the network arise. 1237 11. Address Mapping - Unicast 1239 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1240 state and use the link-local address format specified in Section 7. 1241 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1242 over physical underlying interfaces without encapsulation observe the 1243 native underlying interface Source/Target Link-Layer Address Option 1244 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1245 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1246 interfaces via encapsulation do not include S/TLLAOs which were 1247 intended for encoding physical L2 media address formats and not 1248 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1249 for encoding additional interface attributes needed for multilink 1250 coordination. Hence, this document does not define an S/TLLAO format 1251 but instead defines a new option type termed the "OMNI option" 1252 designed for these purposes. 1254 MNs such as aircraft typically have many wireless data link types 1255 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1256 etc.) with diverse performance, cost and availability properties. 1257 The OMNI interface would therefore appear to have multiple L2 1258 connections, and may include information for multiple underlying 1259 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1260 an IPv6 ND option called the OMNI option formatted as shown in 1261 Figure 4: 1263 0 1 2 3 1264 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 1265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1266 | Type | Length | Preflen | S/T-omIndex | 1267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1268 | | 1269 ~ Sub-Options ~ 1270 | | 1271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1273 Figure 4: OMNI Option Format 1275 In this format: 1277 o Type is set to TBD1. 1279 o Length is set to the number of 8 octet blocks in the option. The 1280 value 0 is invalid, while the values 1 through 255 (i.e., 8 1281 through 2040 octets, respectively) indicate the total length of 1282 the OMNI option. 1284 o Preflen is an 8 bit field that determines the length of prefix 1285 associated with an LLA. Values 0 through 128 specify a valid 1286 prefix length (all other values are invalid). For IPv6 ND 1287 messages sent from a MN to the MS, Preflen applies to the IPv6 1288 source LLA and provides the length that the MN is requesting or 1289 asserting to the MS. For IPv6 ND messages sent from the MS to the 1290 MN, Preflen applies to the IPv6 destination LLA and indicates the 1291 length that the MS is granting to the MN. For IPv6 ND messages 1292 sent between MS endpoints, Preflen provides the length associated 1293 with the source/target MN that is subject of the ND message. 1295 o S/T-omIndex is an 8 bit field corresponds to the omIndex value for 1296 source or target underlying interface used to convey this IPv6 ND 1297 message. OMNI interfaces MUST number each distinct underlying 1298 interface with an omIndex value between '1' and '255' that 1299 represents a MN-specific 8-bit mapping for the actual ifIndex 1300 value assigned by network management [RFC2863] (the omIndex value 1301 '0' is reserved for use by the MS). For RS and NS messages, S/ 1302 T-omIndex corresponds to the source underlying interface the 1303 message originated from. For RA and NA messages, S/T-omIndex 1304 corresponds to the target underlying interface that the message is 1305 destined to. (For NS messages used for Neighbor Unreachability 1306 Detection (NUD), S/T-omIndex instead identifies the neighbor's 1307 underlying interface to be used as the target interface to return 1308 the NA.) 1310 o Sub-Options is a Variable-length field, of length such that the 1311 complete OMNI Option is an integer multiple of 8 octets long. 1312 Contains one or more Sub-Options, as described in Section 11.1. 1314 The OMNI option may appear in any IPv6 ND message type; it is 1315 processed by interfaces that recognize the option and ignored by all 1316 other interfaces. If multiple OMNI option instances appear in the 1317 same IPv6 ND message, the interface processes the Preflen and S/ 1318 T-omIndex fields in the first instance and ignores those fields in 1319 all other instances. The interface processes the Sub-Options of all 1320 OMNI option instances in the same IPv6 ND message in the consecutive 1321 order in which they occur. 1323 The OMNI option(s) in each IPv6 ND message may include full or 1324 partial information for the neighbor. The union of the information 1325 in the most recently received OMNI options is therefore retained, and 1326 the information is aged/removed in conjunction with the corresponding 1327 neighbor cache entry. 1329 11.1. Sub-Options 1331 Each OMNI option includes zero or more Sub-Options. Each consecutive 1332 Sub-Option is concatenated immediately after its predecessor. All 1333 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1334 encoded in the following format: 1336 0 1 2 1337 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 1338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1339 | Sub-Type| Sub-length | Sub-Option Data ... 1340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1342 Figure 5: Sub-Option Format 1344 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1345 Options defined in this document are: 1347 Sub-Option Name Sub-Type 1348 Pad1 0 1349 PadN 1 1350 Interface Attributes (Type 1) 2 1351 Interface Attributes (Type 2) 3 1352 Traffic Selector 4 1353 MS-Register 5 1354 MS-Release 6 1355 Geo Coordinates 7 1356 DHCPv6 Message 8 1357 HIP Message 9 1358 Node Identification 10 1359 Sub-Type Extension 30 1361 Figure 6 1363 Sub-Types 11-29 are available for future assignment for major 1364 protocol functions. Sub-Type 31 is reserved by IANA. 1366 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1367 Option Data ranging from 0 to 2034 octets. 1369 o Sub-Option Data is a block of data with format determined by Sub- 1370 Type and length determined by Sub-Length. 1372 During transmission, the OMNI interface codes Sub-Type and Sub-Length 1373 together in network byte order in 2 consecutive octets, where Sub- 1374 Option Data may be up to 2034 octets in length. This allows ample 1375 space for coding large objects (e.g., ascii character strings, 1376 protocol messages, security codes, etc.), while a single OMNI option 1377 is limited to 2040 octets the same as for any IPv6 ND option. If the 1378 Sub-Options to be coded would cause an OMNI option to exceed 2040 1379 octets, the OMNI interface codes any remaining Sub-Options in 1380 additional OMNI option instances in the intended order of processing 1381 in the same IPv6 ND message. Implementations must therefore observe 1382 size limitations, and must refrain from sending IPv6 ND messages 1383 larger than the OMNI interface MTU. 1385 During reception, the OMNI interface processes each OMNI option Sub- 1386 Option while skipping over and ignoring any unrecognized Sub-Options. 1387 The OMNI interface processes the Sub-Options of all OMNI option 1388 instances in the consecutive order in which they appear in the IPv6 1389 ND message, beginning with the first instance and continuing through 1390 any additional instances to the end of the message. If a Sub-Option 1391 length would cause the running total for that OMNI option to exceed 1392 the length coded in the option header, the interface accepts any Sub- 1393 Options already processed and ignores the remainder of that OMNI 1394 option. The interface then processes any remaining OMNI options in 1395 the same fashion to the end of the IPv6 ND message. 1397 Note: large objects that exceed the Sub-Option Data limit of 2034 1398 octets are not supported under the current specification; if this 1399 proves to be limiting in practice, future specifications may define 1400 support for fragmenting large objects across multiple OMNI options 1401 within the same IPv6 ND message. 1403 The following Sub-Option types and formats are defined in this 1404 document: 1406 11.1.1. Pad1 1408 0 1409 0 1 2 3 4 5 6 7 1410 +-+-+-+-+-+-+-+-+ 1411 | S-Type=0|x|x|x| 1412 +-+-+-+-+-+-+-+-+ 1414 Figure 7: Pad1 1416 o Sub-Type is set to 0. If multiple instances appear in OMNI 1417 options of the same message all are processed. 1419 o Sub-Type is followed by three 'x' bits, set randomly on 1420 transmission and ignored on receipt. Pad1 therefore consists of a 1421 1 octet with the most significant 5 bits set to 0, and with no 1422 Sub-Length or Sub-Option Data fields following. 1424 11.1.2. PadN 1426 0 1 2 1427 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 1428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1429 | S-Type=1| Sub-length=N | N padding octets ... 1430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1432 Figure 8: PadN 1434 o Sub-Type is set to 1. If multiple instances appear in OMNI 1435 options of the same message all are processed. 1437 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1438 padding octets that follow. 1440 o Sub-Option Data consists of N zero-valued octets. 1442 11.1.3. Interface Attributes (Type 1) 1444 The Interface Attributes (Type 1) sub-option provides a basic set of 1445 attributes for underlying interfaces. Interface Attributes (Type 1) 1446 is deprecated throughout the rest of this specification, and 1447 Interface Attributes (Type 2) (see: Section 11.1.4) are indicated 1448 wherever the term "Interface Attributes" appears without an 1449 associated Type designation. 1451 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1452 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1453 they receive. If an Interface Attributes (Type 1) is included, it 1454 must have the following format: 1456 0 1 2 3 1457 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 1458 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1459 | Sub-Type=2| Sub-length=N | omIndex | omType | 1460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1461 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1463 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1465 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1467 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1469 |P56|P57|P58|P59|P60|P61|P62|P63| 1470 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1472 Figure 9: Interface Attributes (Type 1) 1474 o Sub-Type is set to 2. If multiple instances with different 1475 omIndex values appear in OMNI option of the same message all are 1476 processed; if multiple instances with the same omIndex value 1477 appear, the first is processed and all others are ignored 1479 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1480 Sub-Option Data octets that follow. 1482 o omIndex is a 1-octet field containing a value from 0 to 255 1483 identifying the underlying interface for which the attributes 1484 apply. 1486 o omType is a 1-octet field containing a value from 0 to 255 1487 corresponding to the underlying interface identified by omIndex. 1489 o Provider ID is a 1-octet field containing a value from 0 to 255 1490 corresponding to the underlying interface identified by omIndex. 1492 o Link encodes a 4-bit link metric. The value '0' means the link is 1493 DOWN, and the remaining values mean the link is UP with metric 1494 ranging from '1' ("lowest") to '15' ("highest"). 1496 o Resvd is reserved for future use. Set to 0 on transmission and 1497 ignored on reception. 1499 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1500 values P[00] through P[63] corresponding to the 64 Differentiated 1501 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1502 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1503 or '3' ("high") to indicate a QoS preference for underlying 1504 interface selection purposes. 1506 11.1.4. Interface Attributes (Type 2) 1508 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1509 information for the multilink conceptual sending algorithm discussed 1510 in Section 13. The L2 information is used for selecting among 1511 potentially multiple candidate underlying interfaces that can be used 1512 to forward packets to the neighbor based on factors such as DSCP 1513 preferences and link quality. Interface Attributes (Type 2) further 1514 includes link-layer address information to be used for either OAL 1515 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1516 can be avoided). 1518 Interface Attributes (Type 2) are the sole Interface Attributes 1519 format in this specification that all OMNI nodes must honor. 1520 Wherever the term "Interface Attributes" occurs throughout this 1521 specification without a "Type" designation, the format given below is 1522 indicated: 1524 0 1 2 3 1525 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 1526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1527 | S-Type=3| Sub-length=N | omIndex | omType | 1528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1529 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1531 | LHS (bits 8 - 31) | ~ 1532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1533 ~ ~ 1534 ~ Link Layer Address (L2ADDR) ~ 1535 ~ ~ 1536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1537 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1539 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1541 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1544 Figure 10: Interface Attributes (Type 2) 1546 o Sub-Type is set to 3. If multiple instances with different 1547 omIndex values appear in OMNI options of the same message all are 1548 processed; if multiple instances with the same omIndex value 1549 appear, the first is processed and all others are ignored. 1551 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1552 Sub-Option Data octets that follow. The 'omIndex', 'omType', 1553 'Provider ID', 'Link', 'R' and 'API' fields are always present; 1554 hence, the remainder of the Sub-Option Data is limited to 2030 1555 octets. 1557 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1558 encoded as follows: 1560 * omIndex is set to an 8-bit integer value corresponding to a 1561 specific underlying interface the same as specified above for 1562 the OMNI option S/T-omIndex field. The OMNI options of a same 1563 message may include multiple Interface Attributes Sub-Options, 1564 with each distinct omIndex value pertaining to a different 1565 underlying interface. The OMNI option will often include an 1566 Interface Attributes Sub-Option with the same omIndex value 1567 that appears in the S/T-omIndex. In that case, the actual 1568 encapsulation address of the received IPv6 ND message should be 1569 compared with the L2ADDR encoded in the Sub-Option (see below); 1570 if the addresses are different (or, if L2ADDR is absent) the 1571 presence of a NAT is assumed. 1573 * omType is set to an 8-bit integer value corresponding to the 1574 underlying interface identified by omIndex. The value 1575 represents an OMNI interface-specific 8-bit mapping for the 1576 actual IANA ifType value registered in the 'IANAifType-MIB' 1577 registry [http://www.iana.org]. 1579 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1580 for the network service provider associated with this omIndex. 1582 * Link encodes a 4-bit link metric. The value '0' means the link 1583 is DOWN, and the remaining values mean the link is UP with 1584 metric ranging from '1' ("lowest") to '15' ("highest"). 1586 * R is reserved for future use. 1588 * API - a 3-bit "Address/Preferences/Indexed" code that 1589 determines the contents of the remainder of the sub-option as 1590 follows: 1592 + When the most significant bit (i.e., "Address") is set to 1, 1593 the SRT, FMT, LHS and L2ADDR fields are included immediately 1594 following the API code; else, they are omitted. 1596 + When the next most significant bit (i.e., "Preferences") is 1597 set to 1, a preferences block is included next; else, it is 1598 omitted. (Note that if "Address" is set the preferences 1599 block immediately follows L2ADDR; else, it immediately 1600 follows the API code.) 1602 + When a preferences block is present and the least 1603 significant bit (i.e., "Indexed") is set to 0, the block is 1604 encoded in "Simplex" form as shown in Figure 9; else it is 1605 encoded in "Indexed" form as discussed below. 1607 * When API indicates that an "Address" is included, the following 1608 fields appear in consecutive order (else, they are omitted): 1610 + SRT - a 5-bit Segment Routing Topology prefix length value 1611 that (when added to 96) determines the prefix length to 1612 apply to the ULA formed from concatenating [ULA*]::/96 with 1613 the 32 bit LHS MSID value that follows. For example, the 1614 value 16 corresponds to the prefix length 112. 1616 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1617 the included Link Layer Address as follows: 1619 - When the most significant bit (i.e., "Framework") is set 1620 to 1, L2ADDR is the INET encapsulation address for the 1621 Source/Target Client itself; otherwise L2ADDR is the 1622 address of the Server/Proxy named in the LHS. 1624 - When the next most significant bit (i.e., "Mode") is set 1625 to 1, the Framework node is (likely) located behind an 1626 INET Network Address Translator (NAT); otherwise, it is 1627 on the open INET. 1629 - When the least significant bit (i.e., "Type") is set to 1630 0, L2ADDR includes a UDP Port Number followed by an IPv4 1631 address; otherwise, it includes a UDP Port Number 1632 followed by an IPv6 address. 1634 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1635 path to the target. When SRT and LHS are both set to 0, the 1636 LHS is considered unspecified in this IPv6 ND message. When 1637 SRT is set to 0 and LHS is non-zero, the prefix length is 1638 set to 128. SRT and LHS together provide guidance to the 1639 OMNI interface forwarding algorithm. Specifically, if SRT/ 1640 LHS is located in the local OMNI link segment then the OMNI 1641 interface can encapsulate according to FMT/L2ADDR (following 1642 any necessary NAT traversal messaging); else, it must 1643 forward according to the OMNI link spanning tree. See 1644 [I-D.templin-intarea-6706bis] for further discussion. 1646 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1647 and identifies the link-layer address (i.e., the 1648 encapsulation address) of the source/target. The UDP Port 1649 Number appears in the first 2 octets and the IP address 1650 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1651 The Port Number and IP address are recorded in network byte 1652 order, and in ones-compliment "obfuscated" form per 1653 [RFC4380]. The OMNI interface forwarding algorithm uses 1654 FMT/L2ADDR to determine the encapsulation address for 1655 forwarding when SRT/LHS is located in the local OMNI link 1656 segment. Note that if the target is behind a NAT, L2ADDR 1657 will contain the mapped INET address stored in the NAT; 1658 otherwise, L2ADDR will contain the native INET information 1659 of the target itself. 1661 * When API indicates that "Preferences" are included, a 1662 preferences block appears as the remainder of the Sub-Option as 1663 a series of Bitmaps and P[*] values. In "Simplex" form, the 1664 index for each singleton Bitmap octet is inferred from its 1665 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 10. 1666 In "Indexed" form, each Bitmap is preceded by an Index octet 1667 that encodes a value "i" = (0 - 255) as the index for its 1668 companion Bitmap as follows: 1670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1671 | Index=i | Bitmap(i) |P[*] values ... 1672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1674 Figure 11 1676 * The preferences consist of a first (simplex/indexed) Bitmap 1677 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1678 2-bit P[*] values, followed by a second Bitmap (i), followed by 1679 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1680 the bits of each Bitmap(i) that are set to '1'' indicate the 1681 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1682 that follow; if any Bitmap(i) bits are '0', then the 1683 corresponding P[*] block is instead omitted. For example, if 1684 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1685 followed by the block with P[04]-P[07], etc., and ending with 1686 the block with P[28]-P[31] are included (as shown in Figure 9). 1687 The next Bitmap(i) is then consulted with its bits indicating 1688 which P[*] blocks follow, etc. out to the end of the Sub- 1689 Option. 1691 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1692 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1693 preference for underlying interface selection purposes. Not 1694 all P[*] values need to be included in the OMNI option of each 1695 IPv6 ND message received. Any P[*] values represented in an 1696 earlier OMNI option but omitted in the current OMNI option 1697 remain unchanged. Any P[*] values not yet represented in any 1698 OMNI option default to "medium". 1700 * The first 16 P[*] blocks correspond to the 64 Differentiated 1701 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1702 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1703 traffic classifier values P[64], P[65], P[66], etc. See 1704 Appendix A for further discussion and examples. 1706 11.1.5. Traffic Selector 1707 0 1 2 3 1708 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 1709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1710 | S-Type=4| Sub-length=N | omIndex | ~ 1711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1712 ~ ~ 1713 ~ RFC 6088 Format Traffic Selector ~ 1714 ~ ~ 1715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1717 Figure 12: Traffic Selector 1719 o Sub-Type is set to 4. If multiple instances appear in OMNI 1720 options of the same message all are processed, i.e., even if the 1721 same omIndex value appears multiple times. 1723 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1724 Sub-Option Data octets that follow. 1726 o Sub-Option Data contains a 1 octet omIndex encoded exactly as 1727 specified in Section 11.1.3, followed by an N-1 octet traffic 1728 selector formatted per [RFC6088] beginning with the "TS Format" 1729 field. The largest traffic selector for a given omIndex is 1730 therefore 2033 octets. 1732 11.1.6. MS-Register 1734 0 1 2 3 1735 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 1736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1737 | S-Type=5| Sub-length=4n | MSID[1] (bits 0 - 15) | 1738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1739 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1740 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1741 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1743 ... ... ... ... ... ... 1744 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1745 | MSID [n] (bits 16 - 32) | 1746 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1748 Figure 13: MS-Register Sub-option 1750 o Sub-Type is set to 5. If multiple instances appear in OMNI 1751 options of the same message all are processed. Only the first 1752 MAX_MSID values processed (whether in a single instance or 1753 multiple) are retained and all other MSIDs are ignored. 1755 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1756 length of the Sub-Option Data section is therefore limited to 2032 1757 octets. 1759 o A list of n 4 octet MSIDs is included in the following 4n octets. 1760 The Anycast MSID value '0' in an RS message MS-Register sub-option 1761 requests the recipient to return the MSID of a nearby MSE in a 1762 corresponding RA response. 1764 11.1.7. MS-Release 1766 0 1 2 3 1767 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 1768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1769 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1771 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1773 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1775 ... ... ... ... ... ... 1776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1777 | MSID [n] (bits 16 - 32) | 1778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1780 Figure 14: MS-Release Sub-option 1782 o Sub-Type is set to 6. If multiple instances appear in OMNI 1783 options of the same message all are processed. Only the first 1784 MAX_MSID values processed (whether in a single instance or 1785 multiple) are retained and all other MSIDs are ignored. 1787 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1788 length of the Sub-Option Data section is therefore limited to 2032 1789 octets. 1791 o A list of n 4 octet MSIDs is included in the following 4n octets. 1792 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1793 i.e., only non-zero values are processed. 1795 11.1.8. Geo Coordinates 1796 0 1 2 3 1797 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 1798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1799 | S-Type=7| Sub-length=N | Geo Coordinates 1800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1802 Figure 15: Geo Coordinates Sub-option 1804 o Sub-Type is set to 7. If multiple instances appear in OMNI 1805 options of the same message the first is processed and all others 1806 are ignored. 1808 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1809 Sub-Option Data octets that follow. 1811 o A set of Geo Coordinates of maximum length 2034 octets. Format(s) 1812 to be specified in future documents; should include Latitude/ 1813 Longitude, plus any additional attributes such as altitude, 1814 heading, speed, etc. 1816 11.1.9. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1818 The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) sub-option 1819 may be included in the OMNI options of RS messages sent by MNs and RA 1820 messages returned by MSEs. ARs that act as proxys to forward RS/RA 1821 messages between MNs and MSEs also forward DHCPv6 sub-options 1822 unchanged and do not process DHCPv6 sub-options themselves. 1824 0 1 2 3 1825 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 1826 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1827 | S-Type=8| Sub-length=N | msg-type | id (octet 0) | 1828 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1829 | transaction-id (octets 1-2) | | 1830 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1831 | | 1832 . DHCPv6 options . 1833 . (variable number and length) . 1834 | | 1835 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1837 Figure 16: DHCPv6 Message Sub-option 1839 o Sub-Type is set to 8. If multiple instances appear in OMNI 1840 options of the same message the first is processed and all others 1841 are ignored. 1843 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1844 Sub-Option Data octets that follow. The 'msg-type' and 1845 'transaction-id' fields are always present; hence, the length of 1846 the DHCPv6 options is restricted to 2030 octets. 1848 o 'msg-type' and 'transaction-id' are coded according to Section 8 1849 of [RFC8415]. 1851 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1852 follows. 1854 11.1.10. Host Identity Protocol (HIP) Message 1856 The Host Identity Protocol (HIP) Message sub-option may be included 1857 in the OMNI options of RS messages sent by MNs and RA messages 1858 returned by ARs. ARs that act as proxys authenticate and remove HIP 1859 messages in RS messages they forward from a MN to an MSE. ARs that 1860 act as proxys insert and sign HIP messages in the RA messages they 1861 forward from an MSE to a MN. 1863 0 1 2 3 1864 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 1865 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1866 | S-Type=9| Sub-length=N |0| Packet Type |Version| RES.|1| 1867 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1868 | Checksum | Controls | 1869 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1870 | Sender's Host Identity Tag (HIT) | 1871 | | 1872 | | 1873 | | 1874 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1875 | Receiver's Host Identity Tag (HIT) | 1876 | | 1877 | | 1878 | | 1879 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1880 | | 1881 / HIP Parameters / 1882 / / 1883 | | 1884 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1886 Figure 17: HIP Message Sub-option 1888 o Sub-Type is set to 9. If multiple instances appear in OMNI 1889 options of the same message the first is processed and all others 1890 are ignored. 1892 o Sub-Length is set to N, i.e., the length of the option in octets 1893 beginning immediately following the Sub-Length field and extending 1894 to the end of the HIP parameters. The length of the entire HIP 1895 message is therefore restricted to 2034 octets. 1897 o The HIP message is coded exactly as specified in Section 5 of 1898 [RFC7401], except that the OMNI "Sub-Type" and "Sub-Length" fields 1899 replace the first 2 octets of the HIP message header (i.e., the 1900 Next Header and Header Length fields). 1902 11.1.11. Node Identification 1904 0 1 2 3 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 |S-Type=10| Sub-length=N | ID-Type | ~ 1908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1909 ~ Node Identification Value (N-1 octets) ~ 1910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1912 Figure 18: Node Identification 1914 o Sub-Type is set to 10. If multiple instances appear in OMNI 1915 options of the same IPv6 ND message the first instance of a 1916 specific ID-Type is processed and all other instances of the same 1917 ID-Type are ignored. (Note therefore that it is possible for a 1918 single IPv6 ND message to convey multiple Node Identifications - 1919 each having a different ID-Type.) 1921 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1922 Sub-Option Data octets that follow. The ID-Type field is always 1923 present; hence, the maximum Node Identification Value length is 1924 2033 octets. 1926 o ID-Type is a 1 octet field that encodes the type of the Node 1927 Identification Value. The following ID-Type values are currently 1928 defined: 1930 * 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates 1931 that Node Identification Value contains a 16 octet UUID. 1933 * 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node 1934 Identification Value contains a 16 octet HIT. 1936 * 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates 1937 that Node Identification Value contains a 16 octet HHIT. 1939 * 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that 1940 Node Identification Value contains an N-1 octet NAI. 1942 * 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicates 1943 that Node Identification Value contains an N-1 octet FQDN. 1945 * 5 - 252 - Unassigned. 1947 * 253-254 - Reserved for experimentation, as recommended in 1948 [RFC3692]. 1950 * 255 - reserved by IANA. 1952 o Node Identification Value is an (N - 1) octet field encoded 1953 according to the appropriate the "ID-Type" reference above. 1955 When a Node Identification Value is needed for DHCPv6 messaging 1956 purposes, it is encoded as a DHCP Unique IDentifier (DUID) using the 1957 "DUID-EN for OMNI" format with enterprise number 45282 (see: 1958 Section 23) as shown in Figure 19: 1960 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 1961 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1962 | DUID-Type (2) | EN (high bits == 0) | 1963 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1964 | EN (low bits = 45282) | ID-Type | | 1965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1966 . Node Identification Value . 1967 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1969 Figure 19: DUID-EN for OMNI Format 1971 In this format, the ID-Type and Node Identification Value fields are 1972 coded exactly as in Figure 18 following the 6 octet DUID-EN header, 1973 and the entire "DUID-EN for OMNI" is included in a DHCPv6 message per 1974 [RFC8415]. 1976 11.1.12. Sub-Type Extension 1978 Since the Sub-Type field is only 5 bits in length, future 1979 specifications of major protocol functions may exhaust the remaining 1980 Sub-Type values available for assignment. This document therefore 1981 defines Sub-Type 30 as an "extension", meaning that the actual sub- 1982 option type is determined by examining a 1 octet "Extension-Type" 1983 field immediately following the Sub-Length field. The Sub-Type 1984 Extension is formatted as shown in Figure 20: 1986 0 1 2 3 1987 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 1988 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1989 |S-Type=30| Sub-length=N | Extension-Type| ~ 1990 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1991 ~ ~ 1992 ~ Extension-Type Body ~ 1993 ~ ~ 1994 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1996 Figure 20: Sub-Type Extension 1998 o Sub-Type is set to 30. If multiple instances appear in OMNI 1999 options of the same message all are processed, where each 2000 individual extension defines its own policy for processing 2001 multiple of that type. 2003 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 2004 Sub-Option Data octets that follow. The Extension-Type field is 2005 always present; hence, the maximum Extension-Type Body length is 2006 2033 octets. 2008 o Extension-Type contains a 1 octet Sub-Type Extension value between 2009 0 and 255. 2011 o Extension-Type Body contains an N-1 octet block with format 2012 defined by the given extension specification. 2014 Extension-Type values 2 through 252 are available for assignment by 2015 future specifications, which must also define the format of the 2016 Extension-Type Body and its processing rules. Extension-Type values 2017 253 and 254 are reserved for experimentation, as recommended in 2018 [RFC3692], and value 255 is reserved by IANA. Extension-Type values 2019 0 and 1 are defined in the following subsections: 2021 11.1.12.1. RFC4380 UDP/IP Header Option 2023 0 1 2 3 2024 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 2025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2026 |S-Type=30| Sub-length=N | Ext-Type=0 | Header Type | 2027 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2028 ~ Header Option Value ~ 2029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2031 Figure 21: RFC4380 UDP/IP Header Option (Extension-Type 0) 2033 o Sub-Type is set to 30. 2035 o Sub-Length is set to N (from 2 to 2034) that encodes the number of 2036 Sub-Option Data octets that follow. The Extension-Type and Header 2037 Type fields are always present; hence, the maximum-length Header 2038 Option Value is 2032 octets. 2040 o Extension-Type is set to 0. Each instance encodes exactly one 2041 header option per Section 5.1.1 of [RFC4380], with the leading '0' 2042 octet omitted and the following octet coded as Header Type. If 2043 multiple instances of the same Header Type appear in OMNI options 2044 of the same message the first instance is processed and all others 2045 are ignored. 2047 o Header Type and Header Option Value are coded exactly as specified 2048 in Section 5.1.1 of [RFC4380]; the following types are currently 2049 defined: 2051 * 0 - Origin Indication (IPv4) - value coded per Section 5.1.1 of 2052 [RFC4380]. 2054 * 1 - Authentication Encapsulation - value coded per 2055 Section 5.1.1 of [RFC4380]. 2057 * 2 - Origin Indication (IPv6) - value coded per Section 5.1.1 of 2058 [RFC4380], except that the address is a 16-octet IPv6 address 2059 instead of a 4-octet IPv4 address. 2061 o Header Type values 3 through 252 are available for assignment by 2062 future specifications, which must also define the format of the 2063 Header Option Value and its processing rules. Header Type values 2064 253 and 254 are reserved for experimentation, as recommended in 2065 [RFC3692], and value 255 is Reserved by IANA. 2067 11.1.12.2. RFC6081 UDP/IP Trailer Option 2069 0 1 2 3 2070 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 2071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2072 |S-Type=30| Sub-length=N | Ext-Type=1 | Trailer Type | 2073 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2074 ~ Trailer Option Value ~ 2075 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2077 Figure 22: RFC6081 UDP/IP Trailer Option (Extension-Type 1) 2079 o Sub-Type is set to 30. 2081 o Sub-Length is set to N (from 2 to 2034) that encodes the number of 2082 Sub-Option Data octets that follow. The Extension-Type and 2083 Trailer Type fields are always present; hence, the maximum-length 2084 Trailer Option Value is 2032 octets. 2086 o Extension-Type is set to 1. Each instance encodes exactly one 2087 trailer option per Section 4 of [RFC6081]. If multiple instances 2088 of the same trailer type appear in OMNI options of the same 2089 message the first instance is processed and all others ignored. 2091 o Trailer Type and Trailer Option Value are coded exactly as 2092 specified in Section 4 of [RFC6081]; the following Trailer Types 2093 are currently defined: 2095 * 0 - Unassigned 2097 * 1 - Nonce Trailer - value coded per Section 4.2 of [RFC6081]. 2099 * 2 - Unassigned 2101 * 3 - Alternate Address Trailer (IPv4) - value coded per 2102 Section 4.3 of [RFC6081]. 2104 * 4 - Neighbor Discovery Option Trailer - value coded per 2105 Section 4.4 of [RFC6081]. 2107 * 5 - Random Port Trailer - value coded per Section 4.5 of 2108 [RFC6081]. 2110 * 6 - Alternate Address Trailer (IPv6) - value coded per 2111 Section 4.3 of [RFC6081], except that each address is a 2112 16-octet IPv6 address instead of a 4-octet IPv4 address. 2114 o Trailer Type values 7 through 252 are available for assignment by 2115 future specifications, which must also define the format of the 2116 Trailer Option Value and its processing rules. Trailer Type 2117 values 253 and 254 are reserved for experimentation, as 2118 recommended in [RFC3692], and value 255 is Reserved by IANA. 2120 12. Address Mapping - Multicast 2122 The multicast address mapping of the native underlying interface 2123 applies. The mobile router on board the MN also serves as an IGMP/ 2124 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 2125 using the L2 address of the AR as the L2 address for all multicast 2126 packets. 2128 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 2129 coordinate with the AR, and *NET L2 elements use MLD snooping 2130 [RFC4541]. 2132 13. Multilink Conceptual Sending Algorithm 2134 The MN's IPv6 layer selects the outbound OMNI interface according to 2135 SBM considerations when forwarding data packets from local or EUN 2136 applications to external correspondents. Each OMNI interface 2137 maintains a neighbor cache the same as for any IPv6 interface, but 2138 with additional state for multilink coordination. Each OMNI 2139 interface maintains default routes via ARs discovered as discussed in 2140 Section 14, and may configure more-specific routes discovered through 2141 means outside the scope of this specification. 2143 After a packet enters the OMNI interface, one or more outbound 2144 underlying interfaces are selected based on PBM traffic attributes, 2145 and one or more neighbor underlying interfaces are selected based on 2146 the receipt of Interface Attributes sub-options in IPv6 ND messages 2147 (see: Figure 9). Underlying interface selection for the nodes own 2148 local interfaces are based on attributes such as DSCP, application 2149 port number, cost, performance, message size, etc. OMNI interface 2150 multilink selections could also be configured to perform replication 2151 across multiple underlying interfaces for increased reliability at 2152 the expense of packet duplication. The set of all Interface 2153 Attributes received in IPv6 ND messages determines the multilink 2154 forwarding profile for selecting the neighbor's underlying 2155 interfaces. 2157 When the OMNI interface sends a packet over a selected outbound 2158 underlying interface, the OAL includes or omits a mid-layer 2159 encapsulation header as necessary as discussed in Section 5 and as 2160 determined by the L2 address information received in Interface 2161 Attributes. The OAL also performs encapsulation when the nearest AR 2162 is located multiple hops away as discussed in Section 14.1. (Note 2163 that the OAL MAY employ packing when multiple packets are available 2164 for forwarding to the same destination.) 2166 OMNI interface multilink service designers MUST observe the BCP 2167 guidance in Section 15 [RFC3819] in terms of implications for 2168 reordering when packets from the same flow may be spread across 2169 multiple underlying interfaces having diverse properties. 2171 13.1. Multiple OMNI Interfaces 2173 MNs may connect to multiple independent OMNI links concurrently in 2174 support of SBM. Each OMNI interface is distinguished by its Anycast 2175 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 2176 configures a separate OMNI interface for each link so that multiple 2177 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 2178 layer. A different Anycast ULA is assigned to each interface, and 2179 the MN injects the service prefixes for the OMNI link instances into 2180 the EUN routing system. 2182 Applications in EUNs can use Segment Routing to select the desired 2183 OMNI interface based on SBM considerations. The Anycast ULA is 2184 written into the IPv6 destination address, and the actual destination 2185 (along with any additional intermediate hops) is written into the 2186 Segment Routing Header. Standard IP routing directs the packets to 2187 the MN's mobile router entity, and the Anycast ULA identifies the 2188 OMNI interface to be used for transmission to the next hop. When the 2189 MN receives the message, it replaces the IPv6 destination address 2190 with the next hop found in the routing header and transmits the 2191 message over the OMNI interface identified by the Anycast ULA. 2193 Multiple distinct OMNI links can therefore be used to support fault 2194 tolerance, load balancing, reliability, etc. The architectural model 2195 is similar to Layer 2 Virtual Local Area Networks (VLANs). 2197 13.2. MN<->AR Traffic Loop Prevention 2199 After an AR has registered an MNP for a MN (see: Section 14), the AR 2200 will forward packets destined to an address within the MNP to the MN. 2201 The MN will under normal circumstances then forward the packet to the 2202 correct destination within its internal networks. 2204 If at some later time the MN loses state (e.g., after a reboot), it 2205 may begin returning packets destined to an MNP address to the AR as 2206 its default router. The AR therefore must drop any packets 2207 originating from the MN and destined to an address within the MN's 2208 registered MNP. To do so, the AR institutes the following check: 2210 o if the IP destination address belongs to a neighbor on the same 2211 OMNI interface, and if the link-layer source address is the same 2212 as one of the neighbor's link-layer addresses, drop the packet. 2214 14. Router Discovery and Prefix Registration 2216 MNs interface with the MS by sending RS messages with OMNI options 2217 under the assumption that one or more AR on the *NET will process the 2218 message and respond. The MN then configures default routes for the 2219 OMNI interface via the discovered ARs as the next hop. The manner in 2220 which the *NET ensures AR coordination is link-specific and outside 2221 the scope of this document (however, considerations for *NETs that do 2222 not provide ARs that recognize the OMNI option are discussed in 2223 Section 19). 2225 For each underlying interface, the MN sends an RS message with an 2226 OMNI option to coordinate with MSEs identified by MSID values. 2228 Example MSID discovery methods are given in [RFC5214] and include 2229 data link login parameters, name service lookups, static 2230 configuration, a static "hosts" file, etc. The MN can also send an 2231 RS with an MS-Register sub-option that includes the Anycast MSID 2232 value '0', i.e., instead of or in addition to any non-zero MSIDs. 2233 When the AR receives an RS with a MSID '0', it selects a nearby MSE 2234 (which may be itself) and returns an RA with the selected MSID in an 2235 MS-Register sub-option. The AR selects only a single wildcard MSE 2236 (i.e., even if the RS MS-Register sub-option included multiple '0' 2237 MSIDs) while also soliciting the MSEs corresponding to any non-zero 2238 MSIDs. 2240 MNs configure OMNI interfaces that observe the properties discussed 2241 in the previous section. The OMNI interface and its underlying 2242 interfaces are said to be in either the "UP" or "DOWN" state 2243 according to administrative actions in conjunction with the interface 2244 connectivity status. An OMNI interface transitions to UP or DOWN 2245 through administrative action and/or through state transitions of the 2246 underlying interfaces. When a first underlying interface transitions 2247 to UP, the OMNI interface also transitions to UP. When all 2248 underlying interfaces transition to DOWN, the OMNI interface also 2249 transitions to DOWN. 2251 When an OMNI interface transitions to UP, the MN sends RS messages to 2252 register its MNP and an initial set of underlying interfaces that are 2253 also UP. The MN sends additional RS messages to refresh lifetimes 2254 and to register/deregister underlying interfaces as they transition 2255 to UP or DOWN. The MN's OMNI interface sends initial RS messages 2256 over an UP underlying interface with its MNP-LLA as the source and 2257 with destination set to link-scoped All-Routers multicast (ff02::2) 2258 [RFC4291]. The OMNI interface includes an OMNI option per Section 11 2259 with a Preflen assertion, Interface Attributes appropriate for 2260 underlying interfaces, MS-Register/Release sub-options containing 2261 MSID values, and with any other necessary OMNI sub-options (e.g., a 2262 Node Identification sub-option as an identity for the MN). The OMNI 2263 interface then sets the S/T-omIndex field to the index of the 2264 underlying interface over which the RS message is sent. The OMNI 2265 interface then sends the RS over the underlying interface, using OAL 2266 encapsulation and fragmentation if necessary. If OAL encapsulation 2267 is used, the OMNI interface sets the OAL source address to the ULA 2268 corresponding to the RS source and sets the OAL destination to site- 2269 scoped All-Routers multicast (ff05::2). 2271 ARs process IPv6 ND messages with OMNI options and act as an MSE 2272 themselves and/or as a proxy for other MSEs. ARs receive RS messages 2273 (while performing OAL reassembly if necessary) and create a neighbor 2274 cache entry for the MN, then coordinate with any MSEs named in the 2275 Register/Release lists in a manner outside the scope of this 2276 document. When an MSE processes the OMNI information, it first 2277 validates the prefix registration information then injects/withdraws 2278 the MNP in the routing/mapping system and caches/discards the new 2279 Preflen, MNP and Interface Attributes. The MSE then informs the AR 2280 of registration success/failure, and the AR returns an RA message to 2281 the MN with an OMNI option per Section 11. 2283 The AR's OMNI interface returns the RA message via the same 2284 underlying interface of the MN over which the RS was received, and 2285 with destination address set to the MNP-LLA (i.e., unicast), with 2286 source address set to its own LLA, and with an OMNI option with S/ 2287 T-omIndex set to the value included in the RS. The OMNI option also 2288 includes a Preflen confirmation, Interface Attributes, MS-Register/ 2289 Release and any other necessary OMNI sub-options (e.g., a Node 2290 Identification sub-option as an identity for the AR). The RA also 2291 includes any information for the link, including RA Cur Hop Limit, M 2292 and O flags, Router Lifetime, Reachable Time and Retrans Timer 2293 values, and includes any necessary options such as: 2295 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 2297 o RIOs [RFC4191] with more-specific routes. 2299 o an MTU option that specifies the maximum acceptable packet size 2300 for this underlying interface. 2302 The OMNI interface then sends the RA, using OAL encapsulation and 2303 fragmentation if necessary. If OAL encapsulation is used, the OMNI 2304 interface sets the OAL source address to the ULA corresponding to the 2305 RA source and sets the OAL destination to the ULA corresponding to 2306 the RA destination. The AR MAY also send periodic and/or event- 2307 driven unsolicited RA messages per [RFC4861]. In that case, the S/ 2308 T-omIndex field in the OMNI option of the unsolicited RA message 2309 identifies the target underlying interface of the destination MN. 2311 The AR can combine the information from multiple MSEs into one or 2312 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 2313 Each aggregate RA includes an OMNI option with MS-Register/Release 2314 sub-options with the MSEs represented by the aggregate. If an 2315 aggregate is sent, the RA message contents must consistently 2316 represent the combined information advertised by all represented 2317 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 2318 address, the MN determines the addresses of the represented MSEs by 2319 examining the MS-Register/Release OMNI sub-options. 2321 When the MN receives the RA message, it creates an OMNI interface 2322 neighbor cache entry for each MSID that has confirmed MNP 2323 registration via the L2 address of this AR. If the MN connects to 2324 multiple *NETs, it records the additional L2 AR addresses in each 2325 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 2326 then configures a default route via the MSE that returned the RA 2327 message, and assigns the Subnet Router Anycast address corresponding 2328 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 2329 manages its underlying interfaces according to their states as 2330 follows: 2332 o When an underlying interface transitions to UP, the MN sends an RS 2333 over the underlying interface with an OMNI option. The OMNI 2334 option contains at least one Interface Attribute sub-option with 2335 values specific to this underlying interface, and may contain 2336 additional Interface Attributes specific to other underlying 2337 interfaces. The option also includes any MS-Register/Release sub- 2338 options. 2340 o When an underlying interface transitions to DOWN, the MN sends an 2341 RS or unsolicited NA message over any UP underlying interface with 2342 an OMNI option containing an Interface Attribute sub-option for 2343 the DOWN underlying interface with Link set to '0'. The MN sends 2344 an RS when an acknowledgement is required, or an unsolicited NA 2345 when reliability is not thought to be a concern (e.g., if 2346 redundant transmissions are sent on multiple underlying 2347 interfaces). 2349 o When the Router Lifetime for a specific AR nears expiration, the 2350 MN sends an RS over the underlying interface to receive a fresh 2351 RA. If no RA is received, the MN can send RS messages to an 2352 alternate MSID in case the current MSID has failed. If no RS 2353 messages are received even after trying to contact alternate 2354 MSIDs, the MN marks the underlying interface as DOWN. 2356 o When a MN wishes to release from one or more current MSIDs, it 2357 sends an RS or unsolicited NA message over any UP underlying 2358 interfaces with an OMNI option with a Release MSID. Each MSID 2359 then withdraws the MNP from the routing/mapping system and informs 2360 the AR that the release was successful. 2362 o When all of a MNs underlying interfaces have transitioned to DOWN 2363 (or if the prefix registration lifetime expires), any associated 2364 MSEs withdraw the MNP the same as if they had received a message 2365 with a release indication. 2367 The MN is responsible for retrying each RS exchange up to 2368 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 2369 seconds until an RA is received. If no RA is received over an UP 2370 underlying interface (i.e., even after attempting to contact 2371 alternate MSEs), the MN declares this underlying interface as DOWN. 2373 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 2374 Therefore, when the IPv6 layer sends an RS message the OMNI interface 2375 returns an internally-generated RA message as though the message 2376 originated from an IPv6 router. The internally-generated RA message 2377 contains configuration information that is consistent with the 2378 information received from the RAs generated by the MS. Whether the 2379 OMNI interface IPv6 ND messaging process is initiated from the 2380 receipt of an RS message from the IPv6 layer is an implementation 2381 matter. Some implementations may elect to defer the IPv6 ND 2382 messaging process until an RS is received from the IPv6 layer, while 2383 others may elect to initiate the process proactively. Still other 2384 deployments may elect to administratively disable the ordinary RS/RA 2385 messaging used by the IPv6 layer over the OMNI interface, since they 2386 are not required to drive the internal RS/RA processing. (Note that 2387 this same logic applies to IPv4 implementations that employ ICMP- 2388 based Router Discovery per [RFC1256].) 2390 Note: The Router Lifetime value in RA messages indicates the time 2391 before which the MN must send another RS message over this underlying 2392 interface (e.g., 600 seconds), however that timescale may be 2393 significantly longer than the lifetime the MS has committed to retain 2394 the prefix registration (e.g., REACHABLETIME seconds). ARs are 2395 therefore responsible for keeping MS state alive on a shorter 2396 timescale than the MN is required to do on its own behalf. 2398 Note: On multicast-capable underlying interfaces, MNs should send 2399 periodic unsolicited multicast NA messages and ARs should send 2400 periodic unsolicited multicast RA messages as "beacons" that can be 2401 heard by other nodes on the link. If a node fails to receive a 2402 beacon after a timeout value specific to the link, it can initiate a 2403 unicast exchange to test reachability. 2405 Note: if an AR acting as a proxy forwards a MN's RS message to 2406 another node acting as an MSE using UDP/IP encapsulation, it must use 2407 a distinct UDP source port number for each MN. This allows the MSE 2408 to distinguish different MNs behind the same AR at the link-layer, 2409 whereas the link-layer addresses would otherwise be 2410 indistinguishable. 2412 Note: when an AR acting as an MSE returns an RA to an INET Client, it 2413 includes an OMNI option with an Interface Attributes sub-option with 2414 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 2415 its INET interface. This provides the Client with partition prefix 2416 context regarding the local OMNI link segment. 2418 14.1. Router Discovery in IP Multihop and IPv4-Only Networks 2420 On some *NETs, a MN may be located multiple IP hops away from the 2421 nearest AR. Forwarding through IP multihop *NETs is conducted 2422 through the application of a routing protocol (e.g., a MANET/VANET 2423 routing protocol over omni-directional wireless interfaces, an inter- 2424 domain routing protocol in an enterprise network, etc.). These *NETs 2425 could be either IPv6-enabled or IPv4-only, while IPv4-only *NETs 2426 could be either multicast-capable or unicast-only (note that for 2427 IPv4-only *NETs the following procedures apply for both single-hop 2428 and multihop cases). 2430 A MN located potentially multiple *NET hops away from the nearest AR 2431 prepares an RS message with source address set to its MNP-LLA (or to 2432 the unspecified address (::) if it does not yet have an MNP-LLA), and 2433 with destination set to link-scoped All-Routers multicast the same as 2434 discussed above. If OAL encapsulation and fragmentation are 2435 necessary, the OMNI interface sets the OAL source address to the ULA 2436 corresponding to the RS source (or to a Temporary ULA if the RS 2437 source was the unspecified address (::)) and sets the OAL destination 2438 to site-scoped All-Routers multicast (ff05::2). For IPv6-enabled 2439 *NETs, the MN then encapsulates the message in UDP/IPv6 headers with 2440 source address set to the underlying interface address (or to the ULA 2441 that would be used for OAL encapsulation if the underlying interface 2442 does not yet have an address) and sets the destination to either a 2443 unicast or anycast address of an AR. For IPv4-only *NETs, the MN 2444 instead encapsulates the RS message in an IPv4 header with source 2445 address set to the IPv4 address of the underlying interface and with 2446 destination address set to either the unicast IPv4 address of an AR 2447 [RFC5214] or an IPv4 anycast address reserved for OMNI. The MN then 2448 sends the encapsulated RS message via the *NET interface, where it 2449 will be forwarded by zero or more intermediate *NET hops. 2451 When an intermediate *NET hop that participates in the routing 2452 protocol receives the encapsulated RS, it forwards the message 2453 according to its routing tables (note that an intermediate node could 2454 be a fixed infrastructure element or another MN). This process 2455 repeats iteratively until the RS message is received by a penultimate 2456 *NET hop within single-hop communications range of an AR, which 2457 forwards the message to the AR. 2459 When the AR receives the message, it decapsulates the RS (while 2460 performing OAL reassembly, if necessary) and coordinates with the MS 2461 the same as for an ordinary link-local RS, since the inner Hop Limit 2462 will not have been decremented by the multihop forwarding process. 2463 The AR then prepares an RA message with source address set to its own 2464 ADM-LLA and destination address set to the LLA of the original MN. 2465 The AR then performs OAL encapsulation and fragmentation if 2466 necessary, with OAL source set to its own ADM-ULA and destination set 2467 to the ULA corresponding to the RA source. The AR then encapsulates 2468 the message in an IPv4/IPv6 header with source address set to its own 2469 IPv4/ULA address and with destination set to the encapsulation source 2470 of the RS. 2472 The AR then forwards the message to an *NET node within 2473 communications range, which forwards the message according to its 2474 routing tables to an intermediate node. The multihop forwarding 2475 process within the *NET continues repetitively until the message is 2476 delivered to the original MN, which decapsulates the message and 2477 performs autoconfiguration the same as if it had received the RA 2478 directly from the AR as an on-link neighbor. 2480 Note: An alternate approach to multihop forwarding via IPv6 2481 encapsulation would be for the MN and AR to statelessly translate the 2482 IPv6 LLAs into ULAs and forward the RS/RA messages without 2483 encapsulation. This would violate the [RFC4861] requirement that 2484 certain IPv6 ND messages must use link-local addresses and must not 2485 be accepted if received with Hop Limit less than 255. This document 2486 therefore mandates encapsulation since the overhead is nominal 2487 considering the infrequent nature and small size of IPv6 ND messages. 2488 Future documents may consider encapsulation avoidance through 2489 translation while updating [RFC4861]. 2491 Note: An alternate approach to multihop forwarding via IPv4 2492 encapsulation would be to employ IPv6/IPv4 protocol translation. 2493 However, for IPv6 ND messages the LLAs would be truncated due to 2494 translation and the OMNI Router and Prefix Discovery services would 2495 not be able to function. The use of IPv4 encapsulation is therefore 2496 indicated. 2498 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2499 of a new IPv4 /24 prefix allocation, but this may be difficult to 2500 obtain given IPv4 address exhaustion. An alternative would be to re- 2501 purpose the prefix 192.88.99.0 which has been set aside from its 2502 former use by [RFC7526]. 2504 14.2. MS-Register and MS-Release List Processing 2506 OMNI links maintain a constant value "MAX_MSID" selected to provide 2507 MNs with an acceptable level of MSE redundancy while minimizing 2508 control message amplification. It is RECOMMENDED that MAX_MSID be 2509 set to the default value 5; if a different value is chosen, it should 2510 be set uniformly by all nodes on the OMNI link. 2512 When a MN sends an RS message with an OMNI option via an underlying 2513 interface to an AR, the MN must convey its knowledge of its 2514 currently-associated MSEs. Initially, the MN will have no associated 2515 MSEs and should therefore include an MS-Register sub-option with the 2516 single "anycast" MSID value 0 which requests the AR to select and 2517 assign an MSE. The AR will then return an RA message with source 2518 address set to the ADM-LLA of the selected MSE. 2520 As the MN activates additional underlying interfaces, it can 2521 optionally include an MS-Register sub-option with MSID value 0, or 2522 with non-zero MSIDs for MSEs discovered from previous RS/RA 2523 exchanges. The MN will thus eventually begin to learn and manage its 2524 currently active set of MSEs, and can register with new MSEs or 2525 release from former MSEs with each successive RS/RA exchange. As the 2526 MN's MSE constituency grows, it alone is responsible for including or 2527 omitting MSIDs in the MS-Register/Release lists it sends in RS 2528 messages. The inclusion or omission of MSIDs determines the MN's 2529 interface to the MS and defines the manner in which MSEs will 2530 respond. The only limiting factor is that the MN should include no 2531 more than MAX_MSID values in each list per each IPv6 ND message, and 2532 should avoid duplication of entries in each list unless it wants to 2533 increase likelihood of control message delivery. 2535 When an AR receives an RS message sent by a MN with an OMNI option, 2536 the option will contain zero or more MS-Register and MS-Release sub- 2537 options containing MSIDs. After processing the OMNI option, the AR 2538 will have a list of zero or more MS-Register MSIDs and a list of zero 2539 or more of MS-Release MSIDs. The AR then processes the lists as 2540 follows: 2542 o For each list, retain the first MAX_MSID values in the list and 2543 discard any additional MSIDs (i.e., even if there are duplicates 2544 within a list). 2546 o Next, for each MSID in the MS-Register list, remove all matching 2547 MSIDs from the MS-Release list. 2549 o Next, proceed according to whether the AR's own MSID or the value 2550 0 appears in the MS-Register list as follows: 2552 * If yes, send an RA message directly back to the MN and send a 2553 proxy copy of the RS message to each additional MSID in the MS- 2554 Register list with the MS-Register/Release lists omitted. 2555 Then, send an unsolicited NA (uNA) message to each MSID in the 2556 MS-Release list with the MS-Register/Release lists omitted and 2557 with an OMNI option with S/T-omIndex set to 0. 2559 * If no, send a proxy copy of the RS message to each additional 2560 MSID in the MS-Register list with the MS-Register list omitted. 2562 For the first MSID, include the original MS-Release list; for 2563 all other MSIDs, omit the MS-Release list. 2565 Each proxy copy of the RS message will include an OMNI option and OAL 2566 encapsulation header with the ADM-ULA of the AR as the source and the 2567 ADM-ULA of the Register MSE as the destination. When the Register 2568 MSE receives the proxy RS message, if the message includes an MS- 2569 Release list the MSE sends a uNA message to each additional MSID in 2570 the Release list with an OMNI option with S/T-omIndex set to 0. The 2571 Register MSE then sends an RA message back to the (Proxy) AR wrapped 2572 in an OAL encapsulation header with source and destination addresses 2573 reversed, and with RA destination set to the MNP-LLA of the MN. When 2574 the AR receives this RA message, it sends a proxy copy of the RA to 2575 the MN. 2577 Each uNA message (whether sent by the first-hop AR or by a Register 2578 MSE) will include an OMNI option and an OAL encapsulation header with 2579 the ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2580 Release MSE as the destination. The uNA informs the Release MSE that 2581 its previous relationship with the MN has been released and that the 2582 source of the uNA message is now registered. The Release MSE must 2583 then note that the subject MN of the uNA message is now "departed", 2584 and forward any subsequent packets destined to the MN to the Register 2585 MSE. 2587 Note that it is not an error for the MS-Register/Release lists to 2588 include duplicate entries. If duplicates occur within a list, the AR 2589 will generate multiple proxy RS and/or uNA messages - one for each 2590 copy of the duplicate entries. 2592 14.3. DHCPv6-based Prefix Registration 2594 When a MN is not pre-provisioned with an MNP-LLA (or, when the MN 2595 requires additional MNP delegations), it requests the MSE to select 2596 MNPs on its behalf and set up the correct routing state within the 2597 MS. The DHCPv6 service [RFC8415] supports this requirement. 2599 When an MN needs to have the MSE select MNPs, it sends an RS message 2600 with source set to the unspecified address (::) if it has no 2601 MNP_LLAs. If the MN requires only a single MNP delegation, it can 2602 then include a Node Identification sub-option in the OMNI option and 2603 set Preflen to the length of the desired MNP. If the MN requires 2604 multiple MNP delegations and/or more complex DHCPv6 services, it 2605 instead includes a DHCPv6 Message sub-option containing a Client 2606 Identifier, one or more IA_PD options and a Rapid Commit option then 2607 sets the 'msg-type' field to "Solicit", and includes a 3 octet 2608 'transaction-id'. The MN then sets the RS destination to All-Routers 2609 multicast and sends the message using OAL encapsulation and 2610 fragmentation if necessary as discussed above. 2612 When the MSE receives the RS message, it performs OAL reassembly if 2613 necessary. Next, if the RS source is the unspecified address (::) 2614 and/or the OMNI option includes a DHCPv6 message sub-option, the MSE 2615 acts as a "Proxy DHCPv6 Client" in a message exchange with the 2616 locally-resident DHCPv6 server. If the RS did not contain a DHCPv6 2617 message sub-option, the MSE generates a DHCPv6 Solicit message on 2618 behalf of the MN using an IA_PD option with the prefix length set to 2619 the OMNI header Preflen value and with a Client Identifier formed 2620 from the OMNI option Node Identification sub-option; otherwise, the 2621 MSE uses the DHCPv6 Solicit message contained in the OMNI option. 2622 The MSE then sends the DHCPv6 message to the DHCPv6 Server, which 2623 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2624 (If the MSE wishes to defer creation of MN state until the DHCPv6 2625 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2626 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2627 forward/reply exchange with Relay Message and Interface ID options. 2628 In the process, the MSE packs any state information needed to return 2629 an RA to the MN in the Relay-forward Interface ID option so that the 2630 information will be echoed back in the Relay-reply.) 2632 When the MSE receives the DHCPv6 Reply, it adds routes to the routing 2633 system and creates MNP-LLAs based on the delegated MNPs. The MSE 2634 then sends an RA back to the MN with the DHCPv6 Reply message 2635 included in an OMNI DHCPv6 message sub-option if and only if the RS 2636 message had included an explicit DHCPv6 Solicit. If the RS message 2637 source was the unspecified address (::), the MSE includes one of the 2638 (newly-created) MNP-LLAs as the RA destination address and sets the 2639 OMNI option Preflen accordingly; otherwise, the MSE includes the RS 2640 source address as the RA destination address. The MSE then sets the 2641 RA source address to its own ADM-LLA then performs OAL encapsulation 2642 and fragmentation if necessary and sends the RA to the MN. When the 2643 MN receives the RA, it reassembles and discards the OAL encapsulation 2644 if necessary, then creates a default route, assigns Subnet Router 2645 Anycast addresses and uses the RA destination address as its primary 2646 MNP-LLA. The MN will then use this primary MNP-LLA as the source 2647 address of any IPv6 ND messages it sends as long as it retains 2648 ownership of the MNP. 2650 Note: After a MN performs a DHCPv6-based prefix registration exchange 2651 with a first MSE, it would need to repeat the exchange with each 2652 additional MSE it registers with. In that case, the MN supplies the 2653 MNP delegation information received from the first MSE when it 2654 engages the additional MSEs. 2656 15. Secure Redirection 2658 If the *NET link model is multiple access, the AR is responsible for 2659 assuring that address duplication cannot corrupt the neighbor caches 2660 of other nodes on the link. When the MN sends an RS message on a 2661 multiple access *NET link, the AR verifies that the MN is authorized 2662 to use the address and returns an RA with a non-zero Router Lifetime 2663 only if the MN is authorized. 2665 After verifying MN authorization and returning an RA, the AR MAY 2666 return IPv6 ND Redirect messages to direct MNs located on the same 2667 *NET link to exchange packets directly without transiting the AR. In 2668 that case, the MNs can exchange packets according to their unicast L2 2669 addresses discovered from the Redirect message instead of using the 2670 dogleg path through the AR. In some *NET links, however, such direct 2671 communications may be undesirable and continued use of the dogleg 2672 path through the AR may provide better performance. In that case, 2673 the AR can refrain from sending Redirects, and/or MNs can ignore 2674 them. 2676 16. AR and MSE Resilience 2678 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2679 [RFC5798] configurations so that service continuity is maintained 2680 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2681 the (redundant) ARs is currently providing service, and any service 2682 discontinuity will be limited to the failover time supported by VRRP. 2683 Widely deployed public domain implementations of VRRP are available. 2685 MSEs SHOULD use high availability clustering services so that 2686 multiple redundant systems can provide coordinated response to 2687 failures. As with VRRP, widely deployed public domain 2688 implementations of high availability clustering services are 2689 available. Note that special-purpose and expensive dedicated 2690 hardware is not necessary, and public domain implementations can be 2691 used even between lightweight virtual machines in cloud deployments. 2693 17. Detecting and Responding to MSE Failures 2695 In environments where fast recovery from MSE failure is required, ARs 2696 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2697 manner that parallels Bidirectional Forwarding Detection (BFD) 2698 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2699 react to failures so that cached information is re-established 2700 through alternate paths. Proactive NUD control messaging is carried 2701 only over well-connected ground domain networks (i.e., and not low- 2702 end *NET links such as aeronautical radios) and can therefore be 2703 tuned for rapid response. 2705 ARs perform proactive NUD for MSEs for which there are currently 2706 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2707 of the outage by sending multicast RA messages on the *NET interface. 2708 The AR sends RA messages to MNs via the *NET interface with an OMNI 2709 option with a Release ID for the failed MSE, and with destination 2710 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2712 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2713 by small delays [RFC4861]. Any MNs on the *NET interface that have 2714 been using the (now defunct) MSE will receive the RA messages and 2715 associate with a new MSE. 2717 18. Transition Considerations 2719 When a MN connects to an *NET link for the first time, it sends an RS 2720 message with an OMNI option. If the first hop AR recognizes the 2721 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2722 as the destination and with an OMNI option included. The MN then 2723 engages the AR according to the OMNI link model specified above. If 2724 the first hop AR is a legacy IPv6 router, however, it instead returns 2725 an RA message with no OMNI option and with a non-OMNI unicast source 2726 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2727 according to the legacy IPv6 link model and without the OMNI 2728 extensions specified in this document. 2730 If the *NET link model is multiple access, there must be assurance 2731 that address duplication cannot corrupt the neighbor caches of other 2732 nodes on the link. When the MN sends an RS message on a multiple 2733 access *NET link with an LLA source address and an OMNI option, ARs 2734 that recognize the option ensure that the MN is authorized to use the 2735 address and return an RA with a non-zero Router Lifetime only if the 2736 MN is authorized. ARs that do not recognize the option instead 2737 return an RA that makes no statement about the MN's authorization to 2738 use the source address. In that case, the MN should perform 2739 Duplicate Address Detection to ensure that it does not interfere with 2740 other nodes on the link. 2742 An alternative approach for multiple access *NET links to ensure 2743 isolation for MN / AR communications is through L2 address mappings 2744 as discussed in Appendix C. This arrangement imparts a (virtual) 2745 point-to-point link model over the (physical) multiple access link. 2747 19. OMNI Interfaces on Open Internetworks 2749 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2750 an open Internetwork without an OMNI-aware first-hop AR receive RA 2751 messages that do not include an OMNI option, while OMNI interfaces 2752 configured over IPv4-only underlying interfaces do not receive any 2753 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2754 without an OMNI option configure addresses, on-link prefixes, etc. on 2755 the underlying interface that received the RA according to standard 2756 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2757 interfaces configured over IPv4-only underlying interfaces configure 2758 IPv4 address information on the underlying interfaces using 2759 mechanisms such as DHCPv4 [RFC2131]. 2761 OMNI interfaces configured over underlying interfaces that connect to 2762 an open Internetwork can apply security services such as VPNs to 2763 connect to an MSE, or can establish a direct link to an MSE through 2764 some other means (see Section 4). In environments where an explicit 2765 VPN or direct link may be impractical, OMNI interfaces can instead 2766 use UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2767 authentication per [RFC7401]. 2769 OMNI interfaces that use UDP/IP encapsulation use the UDP service 2770 port number 8060 for 'aero' (see: Section 23), but do not include 2771 [RFC4380] header nor [RFC6081] trailer extension options (the 2772 interface instead includes them as OMNI sub-options when needed). 2773 OMNI interfaces therefore unconditionally drop any UDP encapsulated 2774 messages that include any such header/trailer extension options. 2775 Furthermore, OMNI UDP/IP encapsulation over IPv6 underlying 2776 interfaces uses the encapsulation format specified in [RFC4380] with 2777 the exception that IPv6 is used as the outer IP protocol instead of 2778 IPv4. 2780 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes a 2781 HIP "Initiator" message in an OMNI option of an IPv6 RS message and 2782 the AR responds with a HIP "Responder" message coded in an OMNI 2783 option of an IPv6 RA message. HIP security services are applied per 2784 [RFC7401], using the RS/RA messages as simple "shipping containers" 2785 to convey the HIP parameters. In that case, a "two-message HIP 2786 exchange" through a single RS/RA exchange may be sufficient for 2787 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2788 two MNs can coordinate directly with one another with HIP "Initiator/ 2789 Responder" messages coded in OMNI options of IPv6 NS/NA messages. In 2790 that case, a four-message HIP exchange (i.e., two back-to-back NS/NA 2791 exchanges) may be necessary for the two MNs to attain mutual 2792 authentication. 2794 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2795 interfaces send control plane messages to interface with the MS, 2796 including RS/RA messages used according to Section 14 and NS/NA 2797 messages used for route optimization and mobility (see: 2798 [I-D.templin-intarea-6706bis]). The control plane messages must be 2799 authenticated while data plane messages are delivered the same as for 2800 ordinary best-effort traffic with basic source address-based data 2801 origin verification. Data plane communications via OMNI interfaces 2802 that connect over open Internetworks without an explicit VPN should 2803 therefore employ transport- or higher-layer security to ensure 2804 integrity and/or confidentiality. 2806 OMNI interfaces configured over open Internetworks are often located 2807 behind NATs. The OMNI interface accommodates NAT traversal using 2808 UDP/IP encapsulation and the mechanisms discussed in 2809 [I-D.templin-intarea-6706bis]. To support NAT determination, ARs 2810 include an Origin Indication sub-option in RA messages sent in 2811 response to RS messages received from a Client via UDP/IP 2812 encapsulation. 2814 Note: Following the initial HIP Initiator/Responder exchange, OMNI 2815 interfaces configured over open Internetworks maintain HIP 2816 associations through the transmission of IPv6 ND messages that 2817 include OMNI options with HIP "Update" and "Notify" messages. OMNI 2818 interfaces use the HIP "Update" message when an acknowledgement is 2819 required, and use the "Notify" message in unacknowledged isolated 2820 IPv6 ND messages (e.g., unsolicited NAs). 2822 Note: ARs that act as proxys on an open Internetwork authenticate and 2823 remove HIP message OMNI sub-options from RSes they forward from a MN 2824 to an MSE, and insert and sign HIP message and Origin Indication sub- 2825 options in RAs they forward from an MSE to an MN. Conversely, ARs 2826 that act as proxys forward without processing any DHCPv6 information 2827 in RS/RA message exchanges between MNs and MSEs. The AR is therefore 2828 responsible for MN authentication while the MSE is responsible for 2829 registering/delegating MNPs. 2831 20. Time-Varying MNPs 2833 In some use cases, it is desirable, beneficial and efficient for the 2834 MN to receive a constant MNP that travels with the MN wherever it 2835 moves. For example, this would allow air traffic controllers to 2836 easily track aircraft, etc. In other cases, however (e.g., 2837 intelligent transportation systems), the MN may be willing to 2838 sacrifice a modicum of efficiency in order to have time-varying MNPs 2839 that can be changed every so often to defeat adversarial tracking. 2841 The prefix delegation services discussed in Section 14.3 allows OMNI 2842 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2843 send RS messages with source set to the unspecified address (::) and/ 2844 or with an OMNI option with DHCPv6 Option sub-options. The MN would 2845 then be obligated to renumber its internal networks whenever its MNP 2846 (and therefore also its OMNI address) changes. This should not 2847 present a challenge for MNs with automated network renumbering 2848 services, however presents limits for the durations of ongoing 2849 sessions that would prefer to use a constant address. 2851 21. (H)HITs and Temporary ULAs 2853 MNs that generate (H)HITs but do not have pre-assigned MNPs can 2854 request MNP delegations by issuing IPv6 ND messages that use the 2855 (H)HIT instead of a Temporary ULA. In particular, when a MN creates 2856 an RS message it can set the source to the unspecified address (::) 2857 and destination to All-Routers multicast. The IPv6 ND message 2858 includes an OMNI option with a HIP "Initiator" message sub-option, 2859 and need not include a Node Identification sub-option since the MN's 2860 HIT appears in the HIP message. The MN then encapsulates the message 2861 in an IPv6 header with the (H)HIT as the source address and with 2862 destination set to either a unicast or anycast ADM-ULA. The MN then 2863 sends the message to the AR as specified in Section 14.1. 2865 When the AR receives the message, it notes that the RS source was the 2866 unspecified address (::), then examines the RS encapsulation source 2867 address to determine that the source is a (H)HIT and not a Temporary 2868 ULA. The AR next invokes the DHCPv6 protocol to request an MNP 2869 prefix delegation while using the HIT as the Client Identifier, then 2870 prepares an RA message with source address set to its own ADM-LLA and 2871 destination set to the MNP-LLA corresponding to the delegated MNP. 2872 The AR next includes an OMNI option with a HIP "Responder" message 2873 and any DHCPv6 prefix delegation parameters. The AR then finally 2874 encapsulates the RA in an IPv6 header with source address set to its 2875 own ADM-ULA and destination set to the (H)HIT from the RS 2876 encapsulation source address, then returns the encapsulated RA to the 2877 MN. 2879 MNs can also use (H)HITs and/or Temporary ULAs for direct MN-to-MN 2880 communications outside the context of any OMNI link supporting 2881 infrastructure. When two MNs encounter one another they can use 2882 their (H)HITs and/or Temporary ULAs as IPv6 packet source and 2883 destination addresses to support direct communications. MNs can also 2884 inject their (H)HITs and/or Temporary ULAs into a MANET/VANET routing 2885 protocol to enable multihop communications. MNs can further exchange 2886 IPv6 ND messages (such as NS/NA) using their (H)HITs and/or Temporary 2887 ULAs as source and destination addresses. Note that the HIP security 2888 protocols for establishing secure neighbor relationships are based on 2889 (H)HITs; therefore, Temporary ULAs would presumably utilize some 2890 alternate form of message authentication such as the [RFC4380] 2891 authentication service. 2893 Lastly, when MNs are within the coverage range of OMNI link 2894 infrastructure a case could be made for injecting (H)HITs and/or 2895 Temporary ULAs into the global MS routing system. For example, when 2896 the MN sends an RS to a MSE it could include a request to inject the 2897 (H)HIT / Temporary ULA into the routing system instead of requesting 2898 an MNP prefix delegation. This would potentially enable OMNI link- 2899 wide communications using only (H)HITs or Temporary ULAs, and not 2900 MNPs. This document notes the opportunity, but makes no 2901 recommendation. 2903 22. Address Selection 2905 OMNI MNs use LLAs only for link-scoped communications on the OMNI 2906 link. Typically, MNs use LLAs as source/destination IPv6 addresses 2907 of IPv6 ND messages, but may also use them for addressing ordinary 2908 data packets exchanged with an OMNI link neighbor. 2910 OMNI MNs use MNP-ULAs as source/destination IPv6 addresses in the OAL 2911 headers of OAL-encapsulated packets. OMNI MNs use Temporary ULAs for 2912 OAL addressing when an MNP-ULA is not available, or as source/ 2913 destination IPv6 addresses for communications within a MANET/VANET 2914 local area. OMNI MNs use HITs instead of Temporary ULAs when 2915 operation outside the context of a specific ULA domain and/or source 2916 address attestation is necessary. 2918 OMNI MNs use MNP-based GUAs for communications with Internet 2919 destinations when they are within range of OMNI link supporting 2920 infrastructure that can inject the MNP into the routing system. 2922 23. IANA Considerations 2924 The following IANA actions are requested: 2926 23.1. "IPv6 Neighbor Discovery Option Formats" Registry 2928 The IANA is instructed to allocate an official Type number TBD1 from 2929 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2930 option. Implementations set Type to 253 as an interim value 2931 [RFC4727]. 2933 23.2. "Ethernet Numbers" Registry 2935 The IANA is instructed to allocate one Ethernet unicast address TBD2 2936 (suggested value '00-52-14') in the 'ethernet-numbers' registry under 2937 "IANA Unicast 48-bit MAC Addresses" as follows: 2939 Addresses Usage Reference 2940 --------- ----- --------- 2941 00-52-14 Overlay Multilink Network (OMNI) Interface [RFCXXXX] 2943 Figure 23: IANA Unicast 48-bit MAC Addresses 2945 23.3. "ICMPv6 Code Fields: Type 2 - Packet Too Big" Registry 2947 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2948 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2949 appear as follows: 2951 Code Name Reference 2952 --- ---- --------- 2953 0 Diagnostic Packet Too Big [RFC4443] 2954 1 Advisory Packet Too Big [RFCXXXX] 2956 Figure 24: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2958 23.4. "OMNI Option Sub-Type Values" (New Registry) 2960 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 2961 instructed to create and maintain a new registry entitled "OMNI 2962 Option Sub-Type Values". Initial values are given below (future 2963 assignments are to be made through Standards Action [RFC8126]): 2965 Value Sub-Type name Reference 2966 ----- ------------- ---------- 2967 0 Pad1 [RFCXXXX] 2968 1 PadN [RFCXXXX] 2969 2 Interface Attributes (Type 1) [RFCXXXX] 2970 3 Interface Attributes (Type 2) [RFCXXXX] 2971 4 Traffic Selector [RFCXXXX] 2972 5 MS-Register [RFCXXXX] 2973 6 MS-Release [RFCXXXX] 2974 7 Geo Coordinates [RFCXXXX] 2975 8 DHCPv6 Message [RFCXXXX] 2976 9 HIP Message [RFCXXXX] 2977 10 Node Identification [RFCXXXX] 2978 11-29 Unassigned 2979 30 Sub-Type Extension [RFCXXXX] 2980 31 Reserved by IANA [RFCXXXX] 2982 Figure 25: OMNI Option Sub-Type Values 2984 23.5. "OMNI Node Identification ID-Type Values" (New Registry) 2986 The OMNI Node Identification Sub-Option (see: Section 11.1.11) 2987 contains an 8-bit ID-Type field, for which IANA is instructed to 2988 create and maintain a new registry entitled "OMNI Node Identification 2989 ID-Type Values". Initial values are given below (future assignments 2990 are to be made through Expert Review [RFC8126]): 2992 Value Sub-Type name Reference 2993 ----- ------------- ---------- 2994 0 UUID [RFCXXXX] 2995 1 HIT [RFCXXXX] 2996 2 HHIT [RFCXXXX] 2997 3 Network Access Identifier [RFCXXXX] 2998 4 FQDN [RFCXXXX] 2999 5-252 Unassigned [RFCXXXX] 3000 253-254 Reserved for Experimentation [RFCXXXX] 3001 255 Reserved by IANA [RFCXXXX] 3003 Figure 26: OMNI Node Identification ID-Type Values 3005 23.6. "OMNI Option Sub-Type Extension Values" (New Registry) 3007 The OMNI option defines an 8-bit Extension-Type field for Sub-Type 30 3008 (Sub-Type Extension), for which IANA is instructed to create and 3009 maintain a new registry entitled "OMNI Option Sub-Type Extension 3010 Values". Initial values are given below (future assignments are to 3011 be made through Expert Review [RFC8126]): 3013 Value Sub-Type name Reference 3014 ----- ------------- ---------- 3015 0 RFC4380 UDP/IP Header Option [RFCXXXX] 3016 1 RFC6081 UDP/IP Trailer Option [RFCXXXX] 3017 2-252 Unassigned 3018 253-254 Reserved for Experimentation [RFCXXXX] 3019 255 Reserved by IANA [RFCXXXX] 3021 Figure 27: OMNI Option Sub-Type Extension Values 3023 23.7. "OMNI RFC4380 UDP/IP Header Option" (New Registry) 3025 The OMNI Sub-Type Extension "RFC4380 UDP/IP Header Option" defines an 3026 8-bit Header Type field, for which IANA is instructed to create and 3027 maintain a new registry entitled "OMNI RFC4380 UDP/IP Header Option". 3028 Initial registry values are given below (future assignments are to be 3029 made through Expert Review [RFC8126]): 3031 Value Sub-Type name Reference 3032 ----- ------------- ---------- 3033 0 Origin Indication (IPv4) [RFC4380] 3034 1 Authentication Encapsulation [RFC4380] 3035 2 Origin Indication (IPv6) [RFCXXXX] 3036 3-252 Unassigned 3037 253-254 Reserved for Experimentation [RFCXXXX] 3038 255 Reserved by IANA [RFCXXXX] 3040 Figure 28: OMNI RFC4380 UDP/IP Header Option 3042 23.8. "OMNI RFC6081 UDP/IP Trailer Option" (New Registry) 3044 The OMNI Sub-Type Extension for "RFC6081 UDP/IP Trailer Option" 3045 defines an 8-bit Trailer Type field, for which IANA is instructed to 3046 create and maintain a new registry entitled "OMNI RFC6081 UDP/IP 3047 Trailer Option". Initial registry values are given below (future 3048 assignments are to be made through Expert Review [RFC8126]): 3050 Value Sub-Type name Reference 3051 ----- ------------- ---------- 3052 0 Unassigned 3053 1 Nonce [RFC6081] 3054 2 Unassigned 3055 3 Alternate Address (IPv4) [RFC6081] 3056 4 Neighbor Discovery Option [RFC6081] 3057 5 Random Port [RFC6081] 3058 6 Alternate Address (IPv6) [RFCXXXX] 3059 7-252 Unassigned 3060 253-254 Reserved for Experimentation [RFCXXXX] 3061 255 Reserved by IANA [RFCXXXX] 3063 Figure 29: OMNI RFC6081 Trailer Option 3065 23.9. Additional Considerations 3067 The IANA has assigned the UDP port number "8060" for an earlier 3068 experimental version of AERO [RFC6706]. This document together with 3069 [I-D.templin-intarea-6706bis] reclaims the UDP port number "8060" for 3070 'aero' as the service port for UDP/IP encapsulation. (Note that, 3071 although [RFC6706] was not widely implemented or deployed, any 3072 messages coded to that specification can be easily distinguished and 3073 ignored since they use the invalid ICMPv6 message type number '0'.) 3074 The IANA is therefore instructed to update the reference for UDP port 3075 number "8060" from "RFC6706" to "RFCXXXX" (i.e., this document). 3077 The IANA has assigned a 4 octet Private Enterprise Number (PEN) code 3078 "45282" in the "enterprise-numbers" registry. This document is the 3079 normative reference for using this code in DHCP Unique IDentifiers 3080 based on Enterprise Numbers ("DUID-EN for OMNI Interfaces") (see: 3081 Section 10). The IANA is therefore instructed to change the 3082 enterprise designation for PEN code "45282" from "LinkUp Networks" to 3083 "Overlay Multilink Network Interface (OMNI)". 3085 The IANA has assigned the ifType code "301 - omni - Overlay Multilink 3086 Network Interface (OMNI)" in accordance with Section 6 of [RFC8892]. 3087 The registration appears under the IANA "Structure of Management 3088 Information (SMI) Numbers (MIB Module Registrations) - Interface 3089 Types (ifType)" registry. 3091 No further IANA actions are required. 3093 24. Security Considerations 3095 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 3096 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 3097 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 3098 confirmation and/or time synchronization is needed. 3100 MN OMNI interfaces configured over secured ANET interfaces inherit 3101 the physical and/or link-layer security properties (i.e., "protected 3102 spectrum") of the connected ANETs. MN OMNI interfaces configured 3103 over open INET interfaces can use symmetric securing services such as 3104 VPNs or can by some other means establish a direct link. When a VPN 3105 or direct link may be impractical, however, the security services 3106 specified in [RFC7401] and/or [RFC4380] can be employed. While the 3107 OMNI link protects control plane messaging, applications must still 3108 employ end-to-end transport- or higher-layer security services to 3109 protect the data plane. 3111 Strong network layer security for control plane messages and 3112 forwarding path integrity for data plane messages between MSEs MUST 3113 be supported. In one example, the AERO service 3114 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 3115 and secures the links in the spanning tree with network layer 3116 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 3117 plane messages are then constrained to travel only over the secured 3118 spanning tree paths and are therefore protected from attack or 3119 eavesdropping. Since data plane messages can travel over route 3120 optimized paths that do not strictly follow the spanning tree, 3121 however, end-to-end transport- or higher-layer security services are 3122 still required. 3124 Identity-based key verification infrastructure services such as iPSK 3125 may be necessary for verifying the identities claimed by MNs. This 3126 requirement should be harmonized with the manner in which (H)HITs are 3127 attested in a given operational environment. 3129 Security considerations for specific access network interface types 3130 are covered under the corresponding IP-over-(foo) specification 3131 (e.g., [RFC2464], [RFC2492], etc.). 3133 Security considerations for IPv6 fragmentation and reassembly are 3134 discussed in Section 5.1. 3136 25. Implementation Status 3138 AERO/OMNI Release-3.0.2 was tagged on October 15, 2020, and is 3139 undergoing internal testing. Additional internal releases expected 3140 within the coming months, with first public release expected end of 3141 1H2021. 3143 26. Acknowledgements 3145 The first version of this document was prepared per the consensus 3146 decision at the 7th Conference of the International Civil Aviation 3147 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 3148 2019. Consensus to take the document forward to the IETF was reached 3149 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 3150 Attendees and contributors included: Guray Acar, Danny Bharj, 3151 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 3152 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 3153 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 3154 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 3155 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 3156 Fryderyk Wrobel and Dongsong Zeng. 3158 The following individuals are acknowledged for their useful comments: 3159 Stuart Card, Michael Matyas, Robert Moskowitz, Madhu Niraula, Greg 3160 Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron 3161 and Michal Skorepa are especially recognized for their many helpful 3162 ideas and suggestions. Madhuri Madhava Badgandi, Sean Dickson, Don 3163 Dillenburg, Joe Dudkowski, Vijayasarathy Rajagopalan, Ron Sackman and 3164 Katherine Tran are acknowledged for their hard work on the 3165 implementation and technical insights that led to improvements for 3166 the spec. 3168 Discussions on the IETF 6man and atn mailing lists during the fall of 3169 2020 suggested additional points to consider. The authors gratefully 3170 acknowledge the list members who contributed valuable insights 3171 through those discussions. Eric Vyncke and Erik Kline were the 3172 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 3173 at the time the document was developed; they are all gratefully 3174 acknowledged for their many helpful insights. 3176 This work is aligned with the NASA Safe Autonomous Systems Operation 3177 (SASO) program under NASA contract number NNA16BD84C. 3179 This work is aligned with the FAA as per the SE2025 contract number 3180 DTFAWA-15-D-00030. 3182 This work is aligned with the Boeing Information Technology (BIT) 3183 Mobility Vision Lab (MVL) program. 3185 27. References 3187 27.1. Normative References 3189 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 3190 DOI 10.17487/RFC0791, September 1981, 3191 . 3193 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3194 Requirement Levels", BCP 14, RFC 2119, 3195 DOI 10.17487/RFC2119, March 1997, 3196 . 3198 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3199 "Definition of the Differentiated Services Field (DS 3200 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3201 DOI 10.17487/RFC2474, December 1998, 3202 . 3204 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 3205 "SEcure Neighbor Discovery (SEND)", RFC 3971, 3206 DOI 10.17487/RFC3971, March 2005, 3207 . 3209 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 3210 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 3211 November 2005, . 3213 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 3214 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 3215 . 3217 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3218 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3219 2006, . 3221 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 3222 Control Message Protocol (ICMPv6) for the Internet 3223 Protocol Version 6 (IPv6) Specification", STD 89, 3224 RFC 4443, DOI 10.17487/RFC4443, March 2006, 3225 . 3227 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 3228 ICMPv6, UDP, and TCP Headers", RFC 4727, 3229 DOI 10.17487/RFC4727, November 2006, 3230 . 3232 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 3233 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 3234 DOI 10.17487/RFC4861, September 2007, 3235 . 3237 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 3238 Address Autoconfiguration", RFC 4862, 3239 DOI 10.17487/RFC4862, September 2007, 3240 . 3242 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 3243 "Traffic Selectors for Flow Bindings", RFC 6088, 3244 DOI 10.17487/RFC6088, January 2011, 3245 . 3247 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 3248 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 3249 RFC 7401, DOI 10.17487/RFC7401, April 2015, 3250 . 3252 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 3253 Hosts in a Multi-Prefix Network", RFC 8028, 3254 DOI 10.17487/RFC8028, November 2016, 3255 . 3257 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 3258 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 3259 May 2017, . 3261 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3262 (IPv6) Specification", STD 86, RFC 8200, 3263 DOI 10.17487/RFC8200, July 2017, 3264 . 3266 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 3267 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 3268 DOI 10.17487/RFC8201, July 2017, 3269 . 3271 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 3272 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 3273 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 3274 RFC 8415, DOI 10.17487/RFC8415, November 2018, 3275 . 3277 27.2. Informative References 3279 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 3280 Interface for Civil Aviation, IETF Liaison Statement 3281 #1676, https://datatracker.ietf.org/liaison/1676/", March 3282 2020. 3284 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 3285 Aeronautical Telecommunication Network (ATN) using 3286 Internet Protocol Suite (IPS) Standards and Protocol), 3287 Draft Edition 3 (work-in-progress)", December 2020. 3289 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 3290 Interface (FDDI), IEEE Transactions on Communications", 3291 August 1990. 3293 [I-D.ietf-6man-rfc4941bis] 3294 Gont, F., Krishnan, S., Narten, T., and R. Draves, 3295 "Temporary Address Extensions for Stateless Address 3296 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 3297 (work in progress), November 2020. 3299 [I-D.ietf-drip-rid] 3300 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 3301 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 3302 progress), December 2020. 3304 [I-D.ietf-intarea-tunnels] 3305 Touch, J. and M. Townsley, "IP Tunnels in the Internet 3306 Architecture", draft-ietf-intarea-tunnels-10 (work in 3307 progress), September 2019. 3309 [I-D.ietf-ipwave-vehicular-networking] 3310 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 3311 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 3312 ipwave-vehicular-networking-19 (work in progress), July 3313 2020. 3315 [I-D.templin-6man-dhcpv6-ndopt] 3316 Templin, F., "A Unified Stateful/Stateless Configuration 3317 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 3318 (work in progress), January 2021. 3320 [I-D.templin-6man-lla-type] 3321 Templin, F., "The IPv6 Link-Local Address Type Field", 3322 draft-templin-6man-lla-type-02 (work in progress), 3323 November 2020. 3325 [I-D.templin-intarea-6706bis] 3326 Templin, F., "Asymmetric Extended Route Optimization 3327 (AERO)", draft-templin-intarea-6706bis-87 (work in 3328 progress), January 2021. 3330 [IPV4-GUA] 3331 Postel, J., "IPv4 Address Space Registry, 3332 https://www.iana.org/assignments/ipv4-address-space/ipv4- 3333 address-space.xhtml", December 2020. 3335 [IPV6-GUA] 3336 Postel, J., "IPv6 Global Unicast Address Assignments, 3337 https://www.iana.org/assignments/ipv6-unicast-address- 3338 assignments/ipv6-unicast-address-assignments.xhtml", 3339 December 2020. 3341 [RFC1035] Mockapetris, P., "Domain names - implementation and 3342 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 3343 November 1987, . 3345 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 3346 Communication Layers", STD 3, RFC 1122, 3347 DOI 10.17487/RFC1122, October 1989, 3348 . 3350 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 3351 DOI 10.17487/RFC1191, November 1990, 3352 . 3354 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 3355 RFC 1256, DOI 10.17487/RFC1256, September 1991, 3356 . 3358 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 3359 RFC 2131, DOI 10.17487/RFC2131, March 1997, 3360 . 3362 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 3363 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 3364 . 3366 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 3367 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 3368 . 3370 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 3371 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 3372 December 1998, . 3374 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 3375 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 3376 . 3378 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 3379 Domains without Explicit Tunnels", RFC 2529, 3380 DOI 10.17487/RFC2529, March 1999, 3381 . 3383 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 3384 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 3385 . 3387 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 3388 DOI 10.17487/RFC3330, September 2002, 3389 . 3391 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 3392 Considered Useful", BCP 82, RFC 3692, 3393 DOI 10.17487/RFC3692, January 2004, 3394 . 3396 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 3397 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 3398 DOI 10.17487/RFC3810, June 2004, 3399 . 3401 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 3402 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 3403 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 3404 RFC 3819, DOI 10.17487/RFC3819, July 2004, 3405 . 3407 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 3408 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 3409 2004, . 3411 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 3412 Unique IDentifier (UUID) URN Namespace", RFC 4122, 3413 DOI 10.17487/RFC4122, July 2005, 3414 . 3416 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 3417 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 3418 DOI 10.17487/RFC4271, January 2006, 3419 . 3421 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 3422 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 3423 December 2005, . 3425 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 3426 Network Address Translations (NATs)", RFC 4380, 3427 DOI 10.17487/RFC4380, February 2006, 3428 . 3430 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 3431 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 3432 2006, . 3434 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 3435 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 3436 . 3438 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 3439 "Considerations for Internet Group Management Protocol 3440 (IGMP) and Multicast Listener Discovery (MLD) Snooping 3441 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 3442 . 3444 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 3445 "Internet Group Management Protocol (IGMP) / Multicast 3446 Listener Discovery (MLD)-Based Multicast Forwarding 3447 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 3448 August 2006, . 3450 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3451 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 3452 . 3454 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 3455 Errors at High Data Rates", RFC 4963, 3456 DOI 10.17487/RFC4963, July 2007, 3457 . 3459 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 3460 Advertisement Flags Option", RFC 5175, 3461 DOI 10.17487/RFC5175, March 2008, 3462 . 3464 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 3465 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 3466 RFC 5213, DOI 10.17487/RFC5213, August 2008, 3467 . 3469 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 3470 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 3471 DOI 10.17487/RFC5214, March 2008, 3472 . 3474 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 3475 RFC 5558, DOI 10.17487/RFC5558, February 2010, 3476 . 3478 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 3479 Version 3 for IPv4 and IPv6", RFC 5798, 3480 DOI 10.17487/RFC5798, March 2010, 3481 . 3483 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 3484 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 3485 . 3487 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 3488 DOI 10.17487/RFC6081, January 2011, 3489 . 3491 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 3492 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 3493 DOI 10.17487/RFC6221, May 2011, 3494 . 3496 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 3497 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 3498 DOI 10.17487/RFC6355, August 2011, 3499 . 3501 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 3502 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 3503 2012, . 3505 [RFC6706] Templin, F., Ed., "Asymmetric Extended Route Optimization 3506 (AERO)", RFC 6706, DOI 10.17487/RFC6706, August 2012, 3507 . 3509 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 3510 with IPv6 Neighbor Discovery", RFC 6980, 3511 DOI 10.17487/RFC6980, August 2013, 3512 . 3514 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 3515 Requirements for IPv6 Customer Edge Routers", RFC 7084, 3516 DOI 10.17487/RFC7084, November 2013, 3517 . 3519 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 3520 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 3521 Boundary in IPv6 Addressing", RFC 7421, 3522 DOI 10.17487/RFC7421, January 2015, 3523 . 3525 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 3526 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 3527 DOI 10.17487/RFC7526, May 2015, 3528 . 3530 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 3531 DOI 10.17487/RFC7542, May 2015, 3532 . 3534 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 3535 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 3536 February 2016, . 3538 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 3539 Support for IP Hosts with Multi-Access Support", RFC 7847, 3540 DOI 10.17487/RFC7847, May 2016, 3541 . 3543 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 3544 Writing an IANA Considerations Section in RFCs", BCP 26, 3545 RFC 8126, DOI 10.17487/RFC8126, June 2017, 3546 . 3548 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 3549 Decraene, B., Litkowski, S., and R. Shakir, "Segment 3550 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 3551 July 2018, . 3553 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 3554 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 3555 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 3556 . 3558 [RFC8892] Thaler, D. and D. Romascanu, "Guidelines and Registration 3559 Procedures for Interface Types and Tunnel Types", 3560 RFC 8892, DOI 10.17487/RFC8892, August 2020, 3561 . 3563 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 3564 and F. Gont, "IP Fragmentation Considered Fragile", 3565 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 3566 . 3568 Appendix A. Interface Attribute Preferences Bitmap Encoding 3570 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 3571 encoding to specific Internetworks such as the Aeronautical 3572 Telecommunications Network with Internet Protocol Services (ATN/IPS) 3573 may include link selection preferences based on other traffic 3574 classifiers (e.g., transport port numbers, etc.) in addition to the 3575 existing DSCP-based preferences. Nodes on specific Internetworks 3576 maintain a map of traffic classifiers to additional P[*] preference 3577 fields beyond the first 64. For example, TCP port 22 maps to P[67], 3578 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 3580 Implementations use Simplex or Indexed encoding formats for P[*] 3581 encoding in order to encode a given set of traffic classifiers in the 3582 most efficient way. Some use cases may be more efficiently coded 3583 using Simplex form, while others may be more efficient using Indexed. 3584 Once a format is selected for preparation of a single Interface 3585 Attribute the same format must be used for the entire Interface 3586 Attribute sub-option. Different sub-options may use different 3587 formats. 3589 The following figures show coding examples for various Simplex and 3590 Indexed formats: 3592 0 1 2 3 3593 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 3594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3595 | Sub-Type=3| Sub-length=N | omIndex | omType | 3596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3597 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 3598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3599 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 3600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3601 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 3602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3603 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 3604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3605 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3607 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 3608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3610 Figure 30: Example 1: Dense Simplex Encoding 3612 0 1 2 3 3613 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 3614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3615 | Sub-Type=3| Sub-length=N | omIndex | omType | 3616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3617 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 3618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3619 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3621 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 3622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3623 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 3624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3625 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 3626 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3627 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 3628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3629 |Bitmap(10)=0x00| ... 3630 +-+-+-+-+-+-+-+-+-+-+- 3632 Figure 31: Example 2: Sparse Simplex Encoding 3634 0 1 2 3 3635 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 3636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3637 | Sub-Type=3| Sub-length=N | omIndex | omType | 3638 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3639 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 3640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3641 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 3642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3643 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 3644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3645 | Bitmap = 0x01 |796|797|798|799| ... 3646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3648 Figure 32: Example 3: Indexed Encoding 3650 Appendix B. VDL Mode 2 Considerations 3652 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 3653 (VDLM2) that specifies an essential radio frequency data link service 3654 for aircraft and ground stations in worldwide civil aviation air 3655 traffic management. The VDLM2 link type is "multicast capable" 3656 [RFC4861], but with considerable differences from common multicast 3657 links such as Ethernet and IEEE 802.11. 3659 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3660 magnitude less than most modern wireless networking gear. Second, 3661 due to the low available link bandwidth only VDLM2 ground stations 3662 (i.e., and not aircraft) are permitted to send broadcasts, and even 3663 so only as compact layer 2 "beacons". Third, aircraft employ the 3664 services of ground stations by performing unicast RS/RA exchanges 3665 upon receipt of beacons instead of listening for multicast RA 3666 messages and/or sending multicast RS messages. 3668 This beacon-oriented unicast RS/RA approach is necessary to conserve 3669 the already-scarce available link bandwidth. Moreover, since the 3670 numbers of beaconing ground stations operating within a given spatial 3671 range must be kept as sparse as possible, it would not be feasible to 3672 have different classes of ground stations within the same region 3673 observing different protocols. It is therefore highly desirable that 3674 all ground stations observe a common language of RS/RA as specified 3675 in this document. 3677 Note that links of this nature may benefit from compression 3678 techniques that reduce the bandwidth necessary for conveying the same 3679 amount of data. The IETF lpwan working group is considering possible 3680 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3682 Appendix C. MN / AR Isolation Through L2 Address Mapping 3684 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3685 unicast link-scoped IPv6 destination address. However, IPv6 ND 3686 messaging should be coordinated between the MN and AR only without 3687 invoking other nodes on the *NET. This implies that MN / AR control 3688 messaging should be isolated and not overheard by other nodes on the 3689 link. 3691 To support MN / AR isolation on some *NET links, ARs can maintain an 3692 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3693 *NETs, this specification reserves one Ethernet unicast address TBD2 3694 (see: Section 23). For non-Ethernet statically-addressed *NETs, 3695 MSADDR is reserved per the assigned numbers authority for the *NET 3696 addressing space. For still other *NETs, MSADDR may be dynamically 3697 discovered through other means, e.g., L2 beacons. 3699 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3700 both multicast and unicast) to MSADDR instead of to an ordinary 3701 unicast or multicast L2 address. In this way, all of the MN's IPv6 3702 ND messages will be received by ARs that are configured to accept 3703 packets destined to MSADDR. Note that multiple ARs on the link could 3704 be configured to accept packets destined to MSADDR, e.g., as a basis 3705 for supporting redundancy. 3707 Therefore, ARs must accept and process packets destined to MSADDR, 3708 while all other devices must not process packets destined to MSADDR. 3709 This model has well-established operational experience in Proxy 3710 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3712 Appendix D. Change Log 3714 << RFC Editor - remove prior to publication >> 3716 Differences from draft-templin-6man-omni-interface-35 to draft- 3717 templin-6man-omni-interface-36: 3719 o Major clarifications on aspects such as "hard/soft" PTB error 3720 messages 3722 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3723 be used in the data plane. 3725 Differences from draft-templin-6man-omni-interface-31 to draft- 3726 templin-6man-omni-interface-32: 3728 o MTU 3729 o Support for multi-hop ANETS such as ISATAP. 3731 Differences from draft-templin-6man-omni-interface-29 to draft- 3732 templin-6man-omni-interface-30: 3734 o Moved link-layer addressing information into the OMNI option on a 3735 per-ifIndex basis 3737 o Renamed "ifIndex-tuple" to "Interface Attributes" 3739 Differences from draft-templin-6man-omni-interface-27 to draft- 3740 templin-6man-omni-interface-28: 3742 o Updates based on implementation experience. 3744 Differences from draft-templin-6man-omni-interface-25 to draft- 3745 templin-6man-omni-interface-26: 3747 o Further clarification on "aggregate" RA messages. 3749 o Expanded Security Considerations to discuss expectations for 3750 security in the Mobility Service. 3752 Differences from draft-templin-6man-omni-interface-20 to draft- 3753 templin-6man-omni-interface-21: 3755 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3756 (PBM). 3758 Differences from draft-templin-6man-omni-interface-18 to draft- 3759 templin-6man-omni-interface-19: 3761 o SEND/CGA. 3763 Differences from draft-templin-6man-omni-interface-17 to draft- 3764 templin-6man-omni-interface-18: 3766 o Teredo 3768 Differences from draft-templin-6man-omni-interface-14 to draft- 3769 templin-6man-omni-interface-15: 3771 o Prefix length discussions removed. 3773 Differences from draft-templin-6man-omni-interface-12 to draft- 3774 templin-6man-omni-interface-13: 3776 o Teredo 3777 Differences from draft-templin-6man-omni-interface-11 to draft- 3778 templin-6man-omni-interface-12: 3780 o Major simplifications and clarifications on MTU and fragmentation. 3782 o Document now updates RFC4443 and RFC8201. 3784 Differences from draft-templin-6man-omni-interface-10 to draft- 3785 templin-6man-omni-interface-11: 3787 o Removed /64 assumption, resulting in new OMNI address format. 3789 Differences from draft-templin-6man-omni-interface-07 to draft- 3790 templin-6man-omni-interface-08: 3792 o OMNI MNs in the open Internet 3794 Differences from draft-templin-6man-omni-interface-06 to draft- 3795 templin-6man-omni-interface-07: 3797 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3798 L2 addressing. 3800 o Expanded "Transition Considerations". 3802 Differences from draft-templin-6man-omni-interface-05 to draft- 3803 templin-6man-omni-interface-06: 3805 o Brought back OMNI option "R" flag, and discussed its use. 3807 Differences from draft-templin-6man-omni-interface-04 to draft- 3808 templin-6man-omni-interface-05: 3810 o Transition considerations, and overhaul of RS/RA addressing with 3811 the inclusion of MSE addresses within the OMNI option instead of 3812 as RS/RA addresses (developed under FAA SE2025 contract number 3813 DTFAWA-15-D-00030). 3815 Differences from draft-templin-6man-omni-interface-02 to draft- 3816 templin-6man-omni-interface-03: 3818 o Added "advisory PTB messages" under FAA SE2025 contract number 3819 DTFAWA-15-D-00030. 3821 Differences from draft-templin-6man-omni-interface-01 to draft- 3822 templin-6man-omni-interface-02: 3824 o Removed "Primary" flag and supporting text. 3826 o Clarified that "Router Lifetime" applies to each ANET interface 3827 independently, and that the union of all ANET interface Router 3828 Lifetimes determines MSE lifetime. 3830 Differences from draft-templin-6man-omni-interface-00 to draft- 3831 templin-6man-omni-interface-01: 3833 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3834 for future use (most likely as "pseudo-multicast"). 3836 o Non-normative discussion of alternate OMNI LLA construction form 3837 made possible if the 64-bit assumption were relaxed. 3839 First draft version (draft-templin-atn-aero-interface-00): 3841 o Draft based on consensus decision of ICAO Working Group I Mobility 3842 Subgroup March 22, 2019. 3844 Authors' Addresses 3846 Fred L. Templin (editor) 3847 The Boeing Company 3848 P.O. Box 3707 3849 Seattle, WA 98124 3850 USA 3852 Email: fltemplin@acm.org 3854 Tony Whyman 3855 MWA Ltd c/o Inmarsat Global Ltd 3856 99 City Road 3857 London EC1Y 1AX 3858 England 3860 Email: tony.whyman@mccallumwhyman.com