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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 3, 2021 7 Expires: August 7, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-75 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 7, 2021. 41 Copyright Notice 43 Copyright (c) 2021 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 14 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 19 64 5.2. OAL "Super-Packet" Packing . . . . . . . . . . . . . . . 20 65 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 22 66 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 22 67 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 24 68 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 25 69 10. Node Identification . . . . . . . . . . . . . . . . . . . . . 26 70 11. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 26 71 11.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 28 72 11.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 30 73 11.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 30 74 11.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 30 75 11.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 32 76 11.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 36 77 11.1.6. Origin Indication . . . . . . . . . . . . . . . . . 36 78 11.1.7. MS-Register . . . . . . . . . . . . . . . . . . . . 37 79 11.1.8. MS-Release . . . . . . . . . . . . . . . . . . . . . 37 80 11.1.9. Geo Coordinates . . . . . . . . . . . . . . . . . . 38 81 11.1.10. Dynamic Host Configuration Protocol for IPv6 82 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 39 83 11.1.11. Host Identity Protocol (HIP) Message . . . . . . . . 39 84 11.1.12. Node Identification . . . . . . . . . . . . . . . . 40 85 12. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 42 86 13. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 42 87 13.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 43 88 13.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 44 89 14. Router Discovery and Prefix Registration . . . . . . . . . . 44 90 14.1. Router Discovery in IP Multihop and IPv4-Only Networks . 48 91 14.2. MS-Register and MS-Release List Processing . . . . . . . 50 92 14.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 51 93 15. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 52 94 16. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 53 95 17. Detecting and Responding to MSE Failures . . . . . . . . . . 53 96 18. Transition Considerations . . . . . . . . . . . . . . . . . . 53 97 19. OMNI Interfaces on Open Internetworks . . . . . . . . . . . . 54 98 20. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 55 99 21. Using (H)HITs Instead of Temporary Addresses . . . . . . . . 56 100 22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56 101 23. Security Considerations . . . . . . . . . . . . . . . . . . . 58 102 24. Implementation Status . . . . . . . . . . . . . . . . . . . . 59 103 25. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 59 104 26. References . . . . . . . . . . . . . . . . . . . . . . . . . 60 105 26.1. Normative References . . . . . . . . . . . . . . . . . . 60 106 26.2. Informative References . . . . . . . . . . . . . . . . . 62 107 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 68 108 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 69 109 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 70 110 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 71 111 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 73 113 1. Introduction 115 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 116 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 117 pedestrians with cellphones, etc.) often have multiple interface 118 connections to wireless and/or wired-link data links used for 119 communicating with networked correspondents. These data links may 120 have diverse performance, cost and availability properties that can 121 change dynamically according to mobility patterns, flight phases, 122 proximity to infrastructure, etc. MNs coordinate their data links in 123 a discipline known as "multilink", in which a single virtual 124 interface is configured over the node's underlying interface 125 connections to the data links. 127 The MN configures a virtual interface (termed the "Overlay Multilink 128 Network (OMNI) interface") as a thin layer over the underlying 129 interfaces. The OMNI interface is therefore the only interface 130 abstraction exposed to the IP layer and behaves according to the Non- 131 Broadcast, Multiple Access (NBMA) interface principle, while 132 underlying interfaces appear as link layer communication channels in 133 the architecture. The OMNI interface connects to a virtual overlay 134 service known as the "OMNI link". The OMNI link spans one or more 135 Internetworks that may include private-use infrastructures and/or the 136 global public Internet itself. 138 Each MN receives a Mobile Network Prefix (MNP) for numbering 139 downstream-attached End User Networks (EUNs) independently of the 140 access network data links selected for data transport. The MN 141 performs router discovery over the OMNI interface (i.e., similar to 142 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 143 behalf of its EUNs. The router discovery process is iterated over 144 each of the OMNI interface's underlying interfaces in order to 145 register per-link parameters (see Section 14). 147 The OMNI interface provides a multilink nexus for exchanging inbound 148 and outbound traffic via the correct underlying interface(s). The IP 149 layer sees the OMNI interface as a point of connection to the OMNI 150 link. Each OMNI link has one or more associated Mobility Service 151 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 152 prefixes from which OMNI link MNPs are derived. If there are 153 multiple OMNI links, the IPv6 layer will see multiple OMNI 154 interfaces. 156 MNs may connect to multiple distinct OMNI links by configuring 157 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 158 interface is configured over a set of underlying interfaces and 159 provides a nexus for Safety-Based Multilink (SBM) operation. Each 160 OMNI SBM topology configures a common ULA prefix [ULA]::/48, and each 161 OMNI link within the topology configures a unique 16-bit Subnet ID 162 '*' to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 163 layer applies SBM routing to select an OMNI interface, which then 164 applies Performance-Based Multilink (PBM) to select the correct 165 underlying interface. Applications can apply Segment Routing 166 [RFC8402] to select independent SBM topologies for fault tolerance. 168 The OMNI interface interacts with a network-based Mobility Service 169 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 170 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 171 track MN movements and represent their MNPs in a global routing or 172 mapping system. 174 Many OMNI use cases are currently under active consideration. In 175 particular, the International Civil Aviation Organization (ICAO) 176 Working Group-I Mobility Subgroup is developing a future Aeronautical 177 Telecommunications Network with Internet Protocol Services (ATN/IPS) 178 and has issued a liaison statement requesting IETF adoption [ATN] in 179 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 180 in Vehicular Environments (ipwave) working group has further included 181 problem statement and use case analysis for OMNI in a document now in 182 AD evaluation for RFC publication 183 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 184 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 185 programs that examine commercial aviation, Urban Air Mobility (UAM) 186 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 187 represent another large class of potential OMNI users. 189 This document specifies the transmission of IP packets and MN/MS 190 control messages over OMNI interfaces. The OMNI interface supports 191 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 192 as the network layer in the data plane, while using IPv6 ND messaging 193 as the control plane independently of the data plane IP protocol(s). 194 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 195 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 196 discussed in the following sections. OMNI interfaces enable 197 multilink, mobility, multihop and multicast services, with provisions 198 for both Vehicle-to-Infrastructure (V2I) communications and Vehicle- 199 to-Vehicle (V2V) communications outside the context of 200 infrastructure. 202 2. Terminology 204 The terminology in the normative references applies; especially, the 205 terms "link" and "interface" are the same as defined in the IPv6 206 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 207 Additionally, this document assumes the following IPv6 ND message 208 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 209 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 211 The Protocol Constants defined in Section 10 of [RFC4861] are used in 212 their same format and meaning in this document. The terms "All- 213 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 214 are the same as defined in [RFC4291] (with Link-Local scope assumed). 216 The term "IP" is used to refer collectively to either Internet 217 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 218 specification at the layer in question applies equally to either 219 version. 221 The following terms are defined within the scope of this document: 223 Mobile Node (MN) 224 an end system with a mobile router having multiple distinct 225 upstream data link connections that are grouped together in one or 226 more logical units. The MN's data link connection parameters can 227 change over time due to, e.g., node mobility, link quality, etc. 228 The MN further connects a downstream-attached End User Network 229 (EUN). The term MN used here is distinct from uses in other 230 documents, and does not imply a particular mobility protocol. 232 End User Network (EUN) 233 a simple or complex downstream-attached mobile network that 234 travels with the MN as a single logical unit. The IP addresses 235 assigned to EUN devices remain stable even if the MN's upstream 236 data link connections change. 238 Mobility Service (MS) 239 a mobile routing service that tracks MN movements and ensures that 240 MNs remain continuously reachable even across mobility events. 241 Specific MS details are out of scope for this document. 243 Mobility Service Endpoint (MSE) 244 an entity in the MS (either singular or aggregate) that 245 coordinates the mobility events of one or more MN. 247 Mobility Service Prefix (MSP) 248 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 249 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 250 from which more-specific Mobile Network Prefixes (MNPs) are 251 delegated. OMNI link administrators typically obtain MSPs from an 252 Internet address registry, however private-use prefixes can 253 alternatively be used subject to certain limitations (see: 254 Section 9). OMNI links that connect to the global Internet 255 advertise their MSPs to their interdomain routing peers. 257 Mobile Network Prefix (MNP) 258 a longer IP prefix delegated from an MSP (e.g., 259 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 260 MNs sub-delegate the MNP to devices located in EUNs. 262 Access Network (ANET) 263 a data link service network (e.g., an aviation radio access 264 network, satellite service provider network, cellular operator 265 network, wifi network, etc.) that connects MNs. Physical and/or 266 data link level security is assumed, and sometimes referred to as 267 "protected spectrum". Private enterprise networks and ground 268 domain aviation service networks may provide multiple secured IP 269 hops between the MN's point of connection and the nearest Access 270 Router. 272 Access Router (AR) 273 a router in the ANET for connecting MNs to correspondents in 274 outside Internetworks. The AR may be located on the same physical 275 link as the MN, or may be located multiple IP hops away. In the 276 latter case, the MN uses encapsulation to communicate with the AR 277 as though it were on the same physical link. 279 ANET interface 280 a MN's attachment to a link in an ANET. 282 Internetwork (INET) 283 a connected network region with a coherent IP addressing plan that 284 provides transit forwarding services between ANETs and nodes that 285 connect directly to the open INET via unprotected media. No 286 physical and/or data link level security is assumed, therefore 287 security must be applied by upper layers. The global public 288 Internet itself is an example. 290 INET interface 291 a node's attachment to a link in an INET. 293 *NET 294 a "wildcard" term used when a given specification applies equally 295 to both ANET and INET cases. 297 OMNI link 298 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 299 over one or more INETs and their connected ANETs. An OMNI link 300 can comprise multiple INET segments joined by bridges the same as 301 for any link; the addressing plans in each segment may be mutually 302 exclusive and managed by different administrative entities. 304 OMNI interface 305 a node's attachment to an OMNI link, and configured over one or 306 more underlying *NET interfaces. If there are multiple OMNI links 307 in an OMNI domain, a separate OMNI interface is configured for 308 each link. 310 OMNI Adaptation Layer (OAL) 311 an OMNI interface process whereby packets admitted into the 312 interface are wrapped in a mid-layer IPv6 header and fragmented/ 313 reassembled if necessary to support the OMNI link Maximum 314 Transmission Unit (MTU). The OAL is also responsible for 315 generating MTU-related control messages as necessary, and for 316 providing addressing context for spanning multiple segments of a 317 bridged OMNI link. 319 OMNI Option 320 an IPv6 Neighbor Discovery option providing multilink parameters 321 for the OMNI interface as specified in Section 11. 323 Mobile Network Prefix Link Local Address (MNP-LLA) 324 an IPv6 Link Local Address that embeds the most significant 64 325 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 326 Section 7. 328 Mobile Network Prefix Unique Local Address (MNP-ULA) 329 an IPv6 Unique-Local Address derived from an MNP-LLA. 331 Administrative Link Local Address (ADM-LLA) 332 an IPv6 Link Local Address that embeds a 32-bit administratively- 333 assigned identification value in the lower 32 bits of fe80::/96, 334 as specified in Section 7. 336 Administrative Unique Local Address (ADM-ULA) 337 an IPv6 Unique-Local Address derived from an ADM-LLA. 339 Multilink 340 an OMNI interface's manner of managing diverse underlying 341 interface connections to data links as a single logical unit. The 342 OMNI interface provides a single unified interface to upper 343 layers, while underlying interface selections are performed on a 344 per-packet basis considering factors such as DSCP, flow label, 345 application policy, signal quality, cost, etc. Multilinking 346 decisions are coordinated in both the outbound (i.e. MN to 347 correspondent) and inbound (i.e., correspondent to MN) directions. 349 Multihop 350 an iterative relaying of IP packets between MNs over an OMNI 351 underlying interface technology (such as omnidirectional wireless) 352 without support of fixed infrastructure. Multihop services entail 353 node-to-node relaying within a Mobile/Vehicular Ad-hoc Network 354 (MANET/VANET) for MN-to-MN communications and/or for "range 355 extension" where MNs within range of communications infrastructure 356 elements provide forwarding services for other MNs. 358 L2 359 The second layer in the OSI network model. Also known as "layer- 360 2", "link-layer", "sub-IP layer", "data link layer", etc. 362 L3 363 The third layer in the OSI network model. Also known as "layer- 364 3", "network-layer", "IP layer", etc. 366 underlying interface 367 a *NET interface over which an OMNI interface is configured. The 368 OMNI interface is seen as a L3 interface by the IP layer, and each 369 underlying interface is seen as a L2 interface by the OMNI 370 interface. The underlying interface either connects directly to 371 the physical communications media or coordinates with another node 372 where the physical media is hosted. 374 Mobility Service Identification (MSID) 375 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 376 (see: Section 7). IDs are assigned according to MS-specific 377 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 379 Safety-Based Multilink (SBM) 380 A means for ensuring fault tolerance through redundancy by 381 connecting multiple affiliated OMNI interfaces to independent 382 routing topologies (i.e., multiple independent OMNI links). 384 Performance Based Multilink (PBM) 385 A means for selecting underlying interface(s) for packet 386 transmission and reception within a single OMNI interface. 388 OMNI Domain 389 The set of all SBM/PBM OMNI links that collectively provides 390 services for a common set of MSPs. Each OMNI domain consists of a 391 set of affiliated OMNI links that all configure the same ::/48 ULA 392 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 394 3. Requirements 396 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 397 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 398 "OPTIONAL" in this document are to be interpreted as described in BCP 399 14 [RFC2119][RFC8174] when, and only when, they appear in all 400 capitals, as shown here. 402 OMNI links maintain a constant value "MAX_MSID" selected to provide 403 MNs with an acceptable level of MSE redundancy while minimizing 404 control message amplification. It is RECOMMENDED that MAX_MSID be 405 set to the default value 5; if a different value is chosen, it should 406 be set uniformly by all nodes on the OMNI link. 408 An implementation is not required to internally use the architectural 409 constructs described here so long as its external behavior is 410 consistent with that described in this document. 412 4. Overlay Multilink Network (OMNI) Interface Model 414 An OMNI interface is a MN virtual interface configured over one or 415 more underlying interfaces, which may be physical (e.g., an 416 aeronautical radio link) or virtual (e.g., an Internet or higher- 417 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 418 with the MS through IPv6 ND message exchanges. The MN uses the MNP 419 to construct a unique Link-Local Address (MNP-LLA) through the 420 algorithmic derivation specified in Section 7 and assigns the LLA to 421 the OMNI interface. 423 The OMNI interface architectural layering model is the same as in 424 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 425 therefore sees the OMNI interface as a single L3 interface with 426 multiple underlying interfaces that appear as L2 communication 427 channels in the architecture. 429 +----------------------------+ 430 | Upper Layer Protocol | 431 Session-to-IP +---->| | 432 Address Binding | +----------------------------+ 433 +---->| IP (L3) | 434 IP Address +---->| | 435 Binding | +----------------------------+ 436 +---->| OMNI Interface | 437 Logical-to- +---->| (LLA) | 438 Physical | +----------------------------+ 439 Interface +---->| L2 | L2 | | L2 | 440 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 441 +------+------+ +------+ 442 | L1 | L1 | | L1 | 443 | | | | | 444 +------+------+ +------+ 446 Figure 1: OMNI Interface Architectural Layering Model 448 Each underlying interface provides an L2/L1 abstraction according to 449 one of the following models: 451 o INET interfaces connect to an INET either natively or through one 452 or several IPv4 Network Address Translators (NATs). Native INET 453 interfaces have global IP addresses that are reachable from any 454 INET correspondent. NATed INET interfaces typically have private 455 IP addresses and connect to a private network behind one or more 456 NATs that provide INET access. 458 o ANET interfaces connect to a protected ANET that is separated from 459 the open INET by an AR acting as a proxy. The ANET interface may 460 be either on the same L2 link segment as the AR, or separated from 461 the AR by multiple IP hops. 463 o VPNed interfaces use security encapsulation over a *NET to a 464 Virtual Private Network (VPN) gateway. Other than the link-layer 465 encapsulation format, VPNed interfaces behave the same as for 466 Direct interfaces. 468 o Direct (aka "point-to-point") interfaces connect directly to a 469 peer without crossing any *NET paths. An example is a line-of- 470 sight link between a remote pilot and an unmanned aircraft. 472 The OMNI virtual interface model gives rise to a number of 473 opportunities: 475 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 476 Address Detection (DAD) or Multicast Listener Discovery (MLD) 477 messaging is necessary. 479 o since Temporary LLAs are statistically unique, they can be used 480 without DAD for short-term purposes, e.g. until an MNP-LLA is 481 obtained. 483 o *NET interfaces on the same L2 link segment as an AR do not 484 require any L3 addresses (i.e., not even link-local) in 485 environments where communications are coordinated entirely over 486 the OMNI interface. (An alternative would be to also assign the 487 same LLA to all *NET interfaces.) 489 o as underlying interface properties change (e.g., link quality, 490 cost, availability, etc.), any active interface can be used to 491 update the profiles of multiple additional interfaces in a single 492 message. This allows for timely adaptation and service continuity 493 under dynamically changing conditions. 495 o coordinating underlying interfaces in this way allows them to be 496 represented in a unified MS profile with provisions for mobility 497 and multilink operations. 499 o exposing a single virtual interface abstraction to the IPv6 layer 500 allows for multilink operation (including QoS based link 501 selection, packet replication, load balancing, etc.) at L2 while 502 still permitting L3 traffic shaping based on, e.g., DSCP, flow 503 label, etc. 505 o the OMNI interface allows inter-INET traversal when nodes located 506 in different INETs need to communicate with one another. This 507 mode of operation would not be possible via direct communications 508 over the underlying interfaces themselves. 510 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 511 lossless and adaptive path MTU mitigations not available for 512 communications directly over the underlying interfaces themselves. 513 The OAL supports "packing" of multiple IP payload packets within a 514 single OAL packet. 516 o L3 sees the OMNI interface as a point of connection to the OMNI 517 link; if there are multiple OMNI links (i.e., multiple MS's), L3 518 will see multiple OMNI interfaces. 520 o Multiple independent OMNI interfaces can be used for increased 521 fault tolerance through Safety-Based Multilink (SBM), with 522 Performance-Based Multilink (PBM) applied within each interface. 524 Other opportunities are discussed in [RFC7847]. Note that even when 525 the OMNI virtual interface is present, applications can still access 526 underlying interfaces either through the network protocol stack using 527 an Internet socket or directly using a raw socket. This allows for 528 intra-network (or point-to-point) communications without invoking the 529 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 530 is configured over an underlying IPv4 interface, applications can 531 still invoke IPv4 intra-network communications as long as the 532 communicating endpoints are not subject to mobility dynamics. 533 However, the opportunities discussed above are not available when the 534 architectural layering is bypassed in this way. 536 Figure 2 depicts the architectural model for a MN with an attached 537 EUN connecting to the MS via multiple independent *NETs. When an 538 underlying interface becomes active, the MN's OMNI interface sends 539 IPv6 ND messages without encapsulation if the first-hop Access Router 540 (AR) is on the same underlying link; otherwise, the interface uses 541 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 542 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 543 then coordinates with an INET Mobility Service Endpoint (MSE#1, 544 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 545 The Hop Limit in IPv6 ND messages is not decremented due to 546 encapsulation; hence, the OMNI interface appears to be attached to an 547 ordinary link. 549 +--------------+ (:::)-. 550 | MN |<-->.-(::EUN:::) 551 +--------------+ `-(::::)-' 552 |OMNI interface| 553 +----+----+----+ 554 +--------|IF#1|IF#2|IF#n|------ + 555 / +----+----+----+ \ 556 / | \ 557 / | \ 558 v v v 559 (:::)-. (:::)-. (:::)-. 560 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 561 `-(::::)-' `-(::::)-' `-(::::)-' 562 +----+ +----+ +----+ 563 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 564 . +-|--+ +-|--+ +-|--+ . 565 . | | | 566 . v v v . 567 . <----- INET Encapsulation -----> . 568 . . 569 . +-----+ (:::)-. . 570 . |MSE#2| .-(::::::::) +-----+ . 571 . +-----+ .-(::: INET :::)-. |MSE#m| . 572 . (::::: Routing ::::) +-----+ . 573 . `-(::: System :::)-' . 574 . +-----+ `-(:::::::-' . 575 . |MSE#1| +-----+ +-----+ . 576 . +-----+ |MSE#3| |MSE#4| . 577 . +-----+ +-----+ . 578 . . 579 . . 580 . <----- Worldwide Connected Internetwork ----> . 581 ........................................................... 583 Figure 2: MN/MS Coordination via Multiple *NETs 585 After the initial IPv6 ND message exchange, the MN (and/or any nodes 586 on its attached EUNs) can send and receive IP data packets over the 587 OMNI interface. OMNI interface multilink services will forward the 588 packets via ARs in the correct underlying *NETs. The AR encapsulates 589 the packets according to the capabilities provided by the MS and 590 forwards them to the next hop within the worldwide connected 591 Internetwork via optimal routes. 593 OMNI links span one or more underlying Internetwork via the OMNI 594 Adaptation Layer (OAL) which is based on a mid-layer overlay 595 encapsulation using [RFC2473]. Each OMNI link corresponds to a 596 different overlay (differentiated by an address codepoint) which may 597 be carried over a completely separate underlying topology. Each MN 598 can facilitate SBM by connecting to multiple OMNI links using a 599 distinct OMNI interface for each link. 601 Note: OMNI interface underlying interfaces often connect directly to 602 physical media on the local platform (e.g., a laptop computer with 603 WiFi, etc.), but in some configurations the physical media may be 604 hosted on a separate Local Area Network (LAN) node. In that case, 605 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 606 tunnel (at a layer below the underlying interface) to the node 607 hosting the physical media. The OMNI interface may also apply 608 encapsulation at a layer above the underlying interface such that 609 packets would appear "double-encapsulated" on the LAN; the node 610 hosting the physical media in turn removes the LAN encapsulation 611 prior to transmission or inserts it following reception. Finally, 612 the underlying interface must monitor the node hosting the physical 613 media (e.g., through periodic keepalives) so that it can convey 614 up/down/status information to the OMNI interface. 616 5. The OMNI Adaptation Layer (OAL) 618 The OMNI interface observes the link nature of tunnels, including the 619 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 620 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 621 The OMNI interface is configured over one or more underlying 622 interfaces that may have diverse MTUs. OMNI interfaces accommodate 623 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 624 discussed in this section. 626 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 627 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 628 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 629 permitted to perform network fragmentation even though the 630 destination is required to reassemble more. The network therefore 631 MUST forward packets of at least 1280 bytes without generating an 632 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 633 [RFC8201]. (Note: the source can apply "source fragmentation" for 634 locally-generated IPv6 packets up to 1500 bytes and larger still if 635 it if has a way to determine that the destination configures a larger 636 MRU, but this does not affect the minimum IPv6 path MTU.) 638 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 639 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 640 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 641 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 642 support network fragmentation and the destination is required to 643 reassemble at least that much. The "Don't Fragment" (DF) bit in the 644 IPv4 encapsulation headers of packets sent over IPv4 underlying 645 interfaces therefore MUST be set to 0. (Note: even if the 646 encapsulation source has a way to determine that the encapsulation 647 destination configures an MRU larger than 576 bytes, it should not 648 assume a larger minimum IPv4 path MTU without careful consideration 649 of the issues discussed in Section 5.1.) 651 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 652 encapsulation may be prevalent, it may be prudent for the OAL to 653 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 654 of the underlying interface IP protocol version. By always assuming 655 the IPv4 minimum path MTU even for IPv6 underlying interfaces, the 656 OAL may produce smaller fragments and additional header overhead but 657 will always interoperate and never run the risk of presenting a 658 destination interface with a packet that exceeds its MRU. 660 The OMNI interface configures both an MTU and MRU of 9180 bytes 661 [RFC2492]; the size is therefore not a reflection of the underlying 662 interface MTUs, but rather determines the largest packet the OMNI 663 interface can forward or reassemble. The OMNI interface uses the 664 OMNI Adaptation Layer (OAL) to admit packets from the network layer 665 that are no larger than the OMNI interface MTU while generating 666 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 667 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 668 document refers to both of these ICMPv4/ICMPv6 message types simply 669 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 670 errors as discussed below. 672 For IPv4 packets with DF=0, the network layer performs IPv4 673 fragmentation if necessary then admits the packets/fragments into the 674 OMNI interface; these fragments will be reassembled by the final 675 destination. For IPv4 packets with DF=1 and IPv6 packets, the 676 network layer admits the packet if it is no larger than the OMNI 677 interface MTU; otherwise, it drops the packet and returns a PTB hard 678 error message to the source. 680 For each admitted IP packet/fragment, the OMNI interface internally 681 employs the OAL when necessary by encapsulating the inner IP packet/ 682 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 683 outer IP encapsulations. (The OAL does not decrement the inner IP 684 Hop Limit/TTL during encapsulation since the insertion occurs at a 685 layer below IP forwarding.) If the OAL packet will itself require 686 fragmentation, the OMNI interface then calculates the 32-bit CRC over 687 the entire mid-layer packet and writes the value in a trailing field 688 at the end of the packet. Next, the OAL fragments this mid-layer 689 IPv6 packet, forwards the fragments (using *NET encapsulation if 690 necessary), and returns an internally-generated PTB soft error 691 message (subject to rate limiting) if it deems the packet too large 692 according to factors such as link performance characteristics, 693 reassembly congestion, etc. This ensures that the path MTU is 694 adaptive and reflects the current path used for a given data flow. 696 The OAL operates with respect to both the minimum IPv6 and IPv4 path 697 MTUs as follows: 699 o When an OMNI interface sends a packet toward a final destination 700 via an ANET peer, it sends without OAL encapsulation if the packet 701 (including any outer-layer ANET encapsulations) is no larger than 702 the underlying interface MTU for on-link ANET peers or the minimum 703 ANET path MTU for peers separated by multiple IP hops. Otherwise, 704 the OAL inserts an IPv6 header per [RFC2473] with source address 705 set to the node's own Unique-Local Address (ULA) (see: Section 8) 706 and destination set to either the Administrative ULA (ADM-ULA) of 707 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 708 corresponding to the final destination (see below). The OAL then 709 calculates and appends the trailing 32-bit CRC, then uses IPv6 710 fragmentation to break the packet into a minimum number of non- 711 overlapping fragments where the size of each non-final fragment 712 (including both the OMNI and any outer-layer ANET encapsulations) 713 is determined by the underlying interface MTU for on-link ANET 714 peers or the minimum ANET path MTU for peers separated by multiple 715 IP hops. The OAL then encapsulates the fragments in any ANET 716 headers and sends them to the ANET peer, which either reassembles 717 before forwarding if the OAL destination is its own ADM-ULA or 718 forwards the fragments toward the final destination without first 719 reassembling otherwise. 721 o When an OMNI interface sends a packet toward a final destination 722 via an INET interface, it sends packets (including any outer-layer 723 INET encapsulations) no larger than the minimum INET path MTU 724 without OAL encapsulation if the destination is reached via an 725 INET address within the same OMNI link segment. Otherwise, the 726 OAL inserts an IPv6 header per [RFC2473] with source address set 727 to the node's ULA, destination set to the ULA of the next hop OMNI 728 node toward the final destination and (if necessary) with an OMNI 729 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 730 final segment addressing information. The OAL next calculates and 731 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 732 break the packet into a minimum number of non-overlapping 733 fragments where the size of each non-final fragment (including 734 both the OMNI and outer-layer INET encapsulations) is determined 735 by the minimum INET path MTU. The OAL then encapsulates the 736 fragments in any INET headers and sends them to the OMNI link 737 neighbor, which reassembles before forwarding toward the final 738 destination. 740 In light of the above considerations, the OAL should assume a minimum 741 path MTU of 576 bytes for the purpose of generating OAL fragments. 742 Each OAL fragment will undergo *NET encapsulation including either a 743 20 byte IPv4 or 40 byte IPv6 header (plus an 8 byte UDP header for 744 INETs), leaving a minimum of 528 bytes for each fragment. Each OAL 745 fragment must accommodate 40 bytes for the OAL IPv6 header plus 8 746 bytes for the fragment header (while reserving 40 additional bytes in 747 case a maximum-length ORH is inserted during re-encapsulation), 748 leaving 440 bytes to accommodate the actual inner IP packet fragment. 749 OAL fragmentation algorithms therefore MUST produce non-final 750 fragments with the OAL IPv6 header Payload Length set to no less than 751 448 bytes (8 bytes for the fragment header plus 440 bytes for the 752 inner packet fragment), while the Payload Length of the final 753 fragment may be smaller. OAL reassembly algorithms MUST drop any 754 non-final fragments with Payload Length less than 448 bytes. 756 Note that OAL fragmentation algorithms MAY produce larger non-final 757 OAL fragments if better path MTU information is available. For 758 example, for ANETs in which no UDP encapsulation header is needed the 759 algorithm can increase the minimum non-final fragment length by 8 760 bytes. In a second example, for ANETs in which no IPv6 hops will be 761 traversed over the path the algorithm can increase the minimum length 762 by 20 bytes. In a third example, if there is assurance that no ORH 763 will be inserted in the path the algorithm can increase the minimum 764 length by 40 bytes. In a final example, when two ANET peers share a 765 common physical or virtual link with a larger MTU (e.g., 1280 bytes 766 or larger), the OAL can base the minimum non-final fragment length on 767 this larger MTU size as long as the receiving ANET peer reassembles 768 (and possibly also refragments) before forwarding. (Other examples 769 are possible, and dependent on actual ANET/INET deployment 770 scenarios.) 772 In all of the above examples, optimizing the minimum OAL fragment 773 size may be important for accommodating links where performance is 774 dependent on maximum use of the available link MTU, e.g. for wireless 775 aviation data links. Additionally, in order to set the correct 776 context for reassembly, the OMNI interface that inserts the OAL 777 header MUST also be the one that inserts the IPv6 fragment header 778 Identification value. While not strictly required, sending all 779 fragments of the same fragmented OAL packet consecutively over the 780 same underlying interface with minimal inter-fragment delay may 781 increase the likelihood of successful reassembly. 783 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 784 header Code field value 0 are hard errors that always indicate that a 785 packet has been dropped due to a real MTU restriction. However, the 786 OAL can also forward large packets via encapsulation and 787 fragmentation while at the same time returning PTB soft error 788 messages (subject to rate limiting) indicating that a forwarded 789 packet was uncomfortably large. The OMNI interface can therefore 790 continuously forward large packets without loss while returning PTB 791 soft error messages recommending a smaller size. Original sources 792 that receive the soft errors in turn reduce the size of the packets 793 they send, i.e., the same as for hard errors. 795 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 796 field to the value 1 in PTB soft error messages. The OAL sets the 797 PTB destination address to the source address of the original packet, 798 and sets the source address to the MNP Subnet Router Anycast address 799 of the MN. The OAL then sets the MTU field to a value no smaller 800 than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB soft 801 error to the original source. 803 When the original source receives the PTB, it reduces its path MTU 804 estimate the same as for hard errors but does not regard the message 805 as a loss indication. (If the original source does not recognize the 806 soft error code, it regards the PTB the same as a hard error but 807 should heed the retransmission advice given in [RFC8201] suggesting 808 retransmission based on normal packetization layer retransmission 809 timers.) This document therefore updates [RFC1191][RFC4443] and 810 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 811 that PTB hard or soft errors may arrive at any time even if after a 812 successful MTU probe (this is the same consideration as for an 813 ordinary path fluctuation following a successful probe). 815 In summary, the OAL supports continuous transmission and reception of 816 packets of various sizes in the face of dynamically changing network 817 conditions. Moreover, since PTB soft errors do not indicate loss, 818 original sources that receive soft errors can quickly scan for path 819 MTU increases without waiting for the minimum 10 minutes specified 820 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 821 therefore provides a lossless and adaptive service that accommodates 822 MTU diversity especially well-suited for dynamic multilink 823 environments. 825 Note: An OMNI interface that reassembles OAL fragments may experience 826 congestion-oriented loss in its reassembly cache and can optionally 827 send PTB soft errors to the original source and/or ICMP "Time 828 Exceeded" messages to the source of the OAL fragments. In 829 environments where the messages may contribute to unacceptable 830 additional congestion, however, the OMNI interface can refrain from 831 sending PTB soft errors and simply regard the loss as an ordinary 832 unreported congestion event for which the original source will 833 eventually compensate. 835 Note: When the network layer forwards an IPv4 packet/fragment with 836 DF=0 into the OMNI interface, the interface can optionally perform 837 (further) IPv4 fragmentation before invoking the OAL so that the 838 fragments will be reassembled by the final destination. When the 839 network layer performs IPv6 fragmentation for locally-generated IPv6 840 packets, the OMNI interface typically invokes the OAL without first 841 applying (further) IPv6 fragmentation; the network layer should 842 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 843 push the reassembly burden to the final destination and avoid 844 receiving PTB soft errors from the OMNI interface. Aside from these 845 non-normative guidelines, the manner in which any IP fragmentation is 846 invoked prior to OAL encapsulation/fragmentation is an implementation 847 matter. 849 Note: The source OAL includes a trailing 32-bit CRC only for OAL 850 packets that require fragmentation, and the destination OAL discards 851 any OAL packets with incorrect CRC values following reassembly. (The 852 source OAL calculates the CRC over the entire packet, then appends 853 the CRC to the end of the packet and adds the CRC length to the OAL 854 Payload Length prior to fragmentation. The destination OAL subtracts 855 the CRC length from the OAL Payload Length and verifies the CRC 856 following reassembly.) A 32-bit CRC is sufficient for detecting 857 reassembly misassociations for packet sizes no larger than the OMNI 858 interface MTU but may not be sufficient to detect errors for larger 859 sizes [CRC]. 861 Note: Some underlying interface types (e.g., VPNs) may already 862 provide their own robust fragmentation and reassembly services even 863 without OAL encapsulation. In those cases, the OAL can invoke the 864 inherent underlying interface schemes instead while employing PTB 865 soft errors in the same fashion as described above. Other underlying 866 interface facilities such as header/message compression can also be 867 harnessed in a similar fashion. 869 Note: Applications can dynamically tune the size of the packets they 870 to send to produce the best possible throughput and latency, with the 871 understanding that these parameters may change over time due to 872 factors such as congestion, mobility, network path changes, etc. The 873 receipt or absence of soft errors should be seen as hints of when 874 increasing or decreasing packet sizes may be beneficial. 876 5.1. Fragmentation Security Implications 878 As discussed in Section 3.7 of [RFC8900], there are four basic 879 threats concerning IPv6 fragmentation; each of which is addressed by 880 effective mitigations as follows: 882 1. Overlapping fragment attacks - reassembly of overlapping 883 fragments is forbidden by [RFC8200]; therefore, this threat does 884 not apply to the OAL. 886 2. Resource exhaustion attacks - this threat is mitigated by 887 providing a sufficiently large OAL reassembly cache and 888 instituting "fast discard" of incomplete reassemblies that may be 889 part of a buffer exhaustion attack. The reassembly cache should 890 be sufficiently large so that a sustained attack does not cause 891 excessive loss of good reassemblies but not so large that (timer- 892 based) data structure management becomes computationally 893 expensive. The cache should also be indexed based on the arrival 894 underlying interface such that congestion experienced over a 895 first underlying interface does not cause discard of incomplete 896 reassemblies for uncongested underlying interfaces. 898 3. Attacks based on predictable fragment identification values - 899 this threat is mitigated by selecting a suitably random ID value 900 per [RFC7739]. 902 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 903 threat is mitigated by disallowing "tiny fragments" per the OAL 904 fragmentation procedures specified above. 906 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 907 ID) field with only 65535 unique values such that at high data rates 908 the field could wrap and apply to new packets while the fragments of 909 old packets using the same ID are still alive in the network 910 [RFC4963]. However, since the largest OAL fragment that will be sent 911 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 912 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 913 recommendations suggest that such links will have low data rates. 914 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 915 at high data rates is not a concern for IPv6 fragmentation. 917 Finally, [RFC6980] documents fragmentation security concerns for 918 large IPv6 ND messages. These concerns are addressed when the OMNI 919 interface employs the OAL instead of directly fragmenting the IPv6 ND 920 message itself. For this reason, OMNI interfaces MUST NOT admit IPv6 921 ND messages larger than the OMNI interface MTU, and MUST employ the 922 OAL for IPv6 ND messages admitted into the OMNI interface the same as 923 discussed above. 925 5.2. OAL "Super-Packet" Packing 927 By default, the source OAL includes a 40-byte IPv6 encapsulation 928 header for each inner IP payload packet during OAL encapsulation. 929 When fragmentation is needed, the source OAL also calculates and 930 includes a 32-bit trailing CRC for the entire packet then performs 931 fragmentation such that a copy of the 40-byte IPv6 header plus an 932 8-byte IPv6 Fragment Header is included in each fragment. However, 933 these encapsulations may represent excessive overhead in some 934 environments. A technique known as "packing" discussed in 935 [I-D.ietf-intarea-tunnels] is therefore supported so that multiple 936 inner IP payload packets can be included within a single OAL packet 937 known as a "super-packet". 939 When the source OAL has multiple inner IP payload packets with total 940 length no larger than the OMNI interface MTU to send to the same 941 destination, it can optionally concatenate them into a super-packet 942 encapsulated in a single OAL header. Within the super-packet, the IP 943 header of the first inner packet (iHa) followed by its data (iDa) is 944 concatenated immediately following the OAL header, then the inner IP 945 header of the next packet (iHb) followed by its data (iDb) is 946 concatenated immediately following the first packet, etc. The super- 947 packet format is transposed from [I-D.ietf-intarea-tunnels] and shown 948 in Figure 3: 950 <-- Multiple inner IP payload packets to be "packed" --> 951 +-----+-----+ 952 | iHa | iDa | 953 +-----+-----+ 954 | 955 | +-----+-----+ 956 | | iHb | iDb | 957 | +-----+-----+ 958 | | 959 | | +-----+-----+ 960 | | | iHc | iDc | 961 | | +-----+-----+ 962 | | | 963 v v v 964 +----------+-----+-----+-----+-----+-----+-----+ 965 | OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc | 966 +----------+-----+-----+-----+-----+-----+-----+ 967 <-- OMNI "Super-Packet" with single OAL hdr --> 969 Figure 3: OAL Super-Packet Format 971 When the source OAL sends a super-packet, it calculates a CRC and 972 applies OAL fragmentation if necessary then sends the packet or 973 fragments to the destination OAL. When the destination OAL receives 974 the super-packet as a whole packet or as fragments, it reassembles 975 and verifies the CRC if necessary then regards the OAL header Payload 976 Length (after subtracting the CRC length) as the sum of the lengths 977 of all payload packets. The destination OAL then selectively 978 extracts each individual payload packet (e.g., by setting pointers 979 into the buffer containing the super-packet and maintaining a 980 reference count, by copying each payload packet into its own buffer, 981 etc.) and forwards each payload packet or processes it locally as 982 appropriate. During extraction, the OAL determines the IP protocol 983 version of each successive inner payload packet 'j' by examining the 984 first four bits of iH(j), and determines the length of the inner 985 packet by examining the rest of iH(j) according to the IP protocol 986 version. 988 Note: OMNI interfaces must take care to avoid processing super-packet 989 payload elements that would subvert security. Specifically, if a 990 super-packet contains a mix of data and control payload packets 991 (which could include critical security codes), the node MUST NOT 992 process the data packets before processing the control packets. 994 6. Frame Format 996 The OMNI interface transmits IP packets according to the native frame 997 format of each underlying interface. For example, for Ethernet- 998 compatible interfaces the frame format is specified in [RFC2464], for 999 aeronautical radio interfaces the frame format is specified in 1000 standards such as ICAO Doc 9776 (VDL Mode 2 Technical Manual), for 1001 tunnels over IPv6 the frame format is specified in [RFC2473], etc. 1003 7. Link-Local Addresses (LLAs) 1005 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 1006 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 1007 the MNP assigned to the mobile node, while "ADM-LLAs" include an 1008 administratively-unique ID that is guaranteed to be unique on the 1009 link. LLAs are configured as follows: 1011 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 1012 the least-significant 64 bits of the IPv6 link-local prefix 1013 fe80::/64, i.e., in the LLA "interface identifier" portion. The 1014 prefix length for the LLA is determined by adding 64 to the MNP 1015 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 1016 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 1018 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 1019 i.e., the interface identifier consists of 16 '0' bits, followed 1020 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 1021 prefix length for the LLA is determined by adding 96 to the MNP 1022 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 1023 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 1024 fe80::ffff:c000:0200/120). 1026 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 1027 uniqueness. The lower 32 bits of the LLA includes a unique 1028 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 1029 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 1030 prefix length is determined by adding 96 to the MSID prefix 1031 length. For example, if the prefix length for MSID 0x10012001 is 1032 16 then the ADM-LLA prefix length is set to 112 and the LLA is 1033 written as fe80::1001:2001/112. The "zero" address for each ADM- 1034 LLA prefix is the Subnet-Router anycast address for that prefix 1035 [RFC4291]; for example, the Subnet-Router anycast address for 1036 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 1037 0xff000000 through 0xffffffff is reserved for future use. 1039 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 1040 used by MNs for the short-term purpose of procuring an actual MNP- 1041 LLA upon startup or (re)connecting to the network. MNs may use 1042 Temporary LLAs as the IPv6 source address of an RS message in 1043 order to request a MNP-LLA from the MS. 1045 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 1046 MNPs can be allocated from that block ensuring that there is no 1047 possibility for overlap between the MNP- and ADM-LLA constructs 1048 discussed above. 1050 Since MNP-LLAs are based on the distribution of administratively 1051 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 1052 administrative assignment, OMNI interfaces set the autoconfiguration 1053 variable DupAddrDetectTransmits to 0 [RFC4862]. 1055 Temporary LLAs are distinguished from MNP- and ADM-LLAs by examining 1056 the OMNI option T field (see: Section 11), and employ optimistic DAD 1057 principles [RFC4429] since they are probabilistically unique and 1058 their use is short-duration in nature. 1060 Note: If future protocol extensions relax the 64-bit boundary in IPv6 1061 addressing, the additional prefix bits of an MNP could be encoded in 1062 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 1063 would therefore still be in bits 64-127, and the remaining bits would 1064 appear in bits 16 through 48.) However, the analysis provided in 1065 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 1066 architecture for the foreseeable future. 1068 Note: Even though this document honors the 64-bit boundary in IPv6 1069 addressing per [RFC7421], it suggests prefix lengths longer than /64 1070 for routing purposes. This effectively extends IPv6 routing 1071 determination into the interface identifier portion of the IPv6 1072 address, but it does not redefine the 64-bit boundary. 1074 8. Unique-Local Addresses (ULAs) 1076 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 1077 destination addresses in OAL IPv6 encapsulation headers. ULAs are 1078 only routable within the scope of a an OMNI domain, and are derived 1079 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 1080 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 1081 Global ID to produce the prefix [ULA]::/48, which is then followed by 1082 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 1083 specified in Section 3 of [RFC4193]. All nodes in the same OMNI 1084 domain configure the same 40-bit Global ID as the OMNI domain 1085 identifier. The statistic uniqueness of the 40-bit pseudo-random 1086 Global ID allows different OMNI domains to be joined together in the 1087 future without requiring renumbering. 1089 Each OMNI link instance is identified by a value between 0x0000 and 1090 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xffff 1091 are reserved for future use). For example, OMNI ULAs associated with 1092 instance 0 are configured from the prefix [ULA]:0000::/64, instance 1 1093 from [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 1094 their associated prefix lengths are configured in correspondence with 1095 LLAs through stateless prefix translation where "MNP-ULAs" are 1096 assigned in correspondence to MNP-LLAs and "ADM-ULAs" are assigned in 1097 correspondence to ADM-LLAs. For example, for OMNI link instance 1098 [ULA]:1010::/64: 1100 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 1101 56-bit MNP length is derived by copying the lower 64 bits of the 1102 LLA into the lower 64 bits of the ULA as 1103 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1104 64 plus the IPv6 MNP length). 1106 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1107 MNP length is derived by simply writing the LLA interface ID into 1108 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1109 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1111 o the ADM-ULA corresponding to fe80::1000/112 is simply 1112 [ULA]:1010::1000/112. 1114 o the ADM-ULA corresponding to fe80::/128 is simply 1115 [ULA]:1010::/128. 1117 o the Temporary ULA corresponding to a Temporary LLA is simply 1118 [ULA]:1010:[64-bit Temporary Interface ID]/128. 1120 o etc. 1122 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1123 link instance. For example, the OMNI interface connected to instance 1124 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1125 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1126 [ULA]:0003::/64) into the local routing system so that applications 1127 can direct traffic according to SBM requirements. 1129 The ULA presents an IPv6 address format that is routable within the 1130 OMNI routing system and can be used to convey link-scoped IPv6 ND 1131 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1132 The OMNI link extends across one or more underling Internetworks to 1133 include all ARs and MSEs. All MNs are also considered to be 1134 connected to the OMNI link, however OAL encapsulation is omitted 1135 whenever possible to conserve bandwidth (see: Section 13). 1137 Each OMNI link can be subdivided into "segments" that often 1138 correspond to different administrative domains or physical 1139 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1140 necessary to support efficient packet forwarding to destinations 1141 located in other OMNI link segments. A full discussion of Segment 1142 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1144 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1145 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1146 however the range could be used for MSP and MNP addressing under 1147 certain limiting conditions (see: Section 9). 1149 9. Global Unicast Addresses (GUAs) 1151 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1152 as Mobility Service Prefixes (MSPs) from which Mobile Network 1153 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1155 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1156 associated regional assigned numbers authority such that the OMNI 1157 domain can be interconnected to the global IPv6 Internet without 1158 causing inconsistencies in the routing system. An OMNI domain could 1159 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1160 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1161 were ever connected to the global IPv6 Internet. 1163 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1164 associated regional assigned numbers authority such that the OMNI 1165 domain can be interconnected to the global IPv4 Internet without 1166 causing routing inconsistencies. An OMNI domain could instead use 1167 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1168 this would require IPv4 NAT if the domain were ever connected to the 1169 global IPv4 Internet. 1171 10. Node Identification 1173 OMNI MNs and MSEs that connect over open Internetworks generate a 1174 Host Identity Tag (HIT) as specified in [RFC7401] and use the value 1175 as a robust general-purpose node identification value. Hierarchical 1176 HITs (HHITs) [I-D.ietf-drip-rid] may provide a useful alternative in 1177 certain domains such as the Unmanned (Air) Traffic Management (UTM) 1178 service for Unmanned Air Systems (UAS). MNs and MSEs can then use 1179 their (H)HITs in IPv6 ND control message exchanges. 1181 When a MN is truly outside the context of any infrastructure, it may 1182 have no MNP information at all. In that case, the MN can use its 1183 (H)HIT as an IPv6 source/destination address for sustained 1184 communications in Vehicle-to-Vehicle (V2V) and (multihop) Vehicle-to- 1185 Infrastructure (V2I) scenarios. The MN can also propagate the (H)HIT 1186 into the multihop routing tables of (collective) Mobile/Vehicular Ad- 1187 hoc Networks (MANETs/VANETs) using only the vehicles themselves as 1188 communications relays. 1190 When a MN connects to ARs over (non-multihop) protected-spectrum 1191 ANETs, an alternate form of node identification (e.g., MAC address, 1192 serial number, airframe identification value, VIN, etc.) may be 1193 sufficient. In that case, the MN should still generate a (H)HIT and 1194 maintain it in conjunction with any other node identifiers. The MN 1195 can then include OMNI "Node Identification" sub-options (see: 1196 Section 11.1.12) in IPv6 ND messages should the need to transmit 1197 identification information over the network arise. 1199 11. Address Mapping - Unicast 1201 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1202 state and use the link-local address format specified in Section 7. 1203 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1204 over physical underlying interfaces without encapsulation observe the 1205 native underlying interface Source/Target Link-Layer Address Option 1206 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1207 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1208 interfaces via encapsulation do not include S/TLLAOs which were 1209 intended for encoding physical L2 media address formats and not 1210 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1211 for encoding additional interface attributes needed for multilink 1212 coordination. Hence, this document does not define an S/TLLAO format 1213 but instead defines a new option type termed the "OMNI option" 1214 designed for these purposes. 1216 MNs such as aircraft typically have many wireless data link types 1217 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1218 etc.) with diverse performance, cost and availability properties. 1220 The OMNI interface would therefore appear to have multiple L2 1221 connections, and may include information for multiple underlying 1222 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1223 an IPv6 ND option called the OMNI option formatted as shown in 1224 Figure 4: 1226 0 1 2 3 1227 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 1228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1229 | Type | Length |T| Preflen | S/T-omIndex | 1230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1231 | | 1232 ~ Sub-Options ~ 1233 | | 1234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1236 Figure 4: OMNI Option Format 1238 In this format: 1240 o Type is set to TBD1. 1242 o Length is set to the number of 8 octet blocks in the option. The 1243 value 0 is invalid, while the values 1 through 255 (i.e., 8 1244 through 2040 octets, respectively) indicate the total length of 1245 the OMNI option. 1247 o T is a 1 bit field set to 1 for Temporary LLAs (otherwise, set to 1248 0) and Preflen is a 7 bit field that determines the length of 1249 prefix associated with an LLA. Values 1 through 127 specify a 1250 prefix length, while the value 0 indicates "unspecified". For 1251 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1252 the IPv6 source LLA and provide the length that the MN is 1253 requesting or asserting to the MS. For IPv6 ND messages sent from 1254 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1255 and indicate the length that the MS is granting to the MN. For 1256 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1257 Preflen provides the length associated with the source/target MN 1258 that is subject of the ND message. 1260 o S/T-omIndex is an 8 bit field corresponds to the omIndex value for 1261 source or target underlying interface used to convey this IPv6 ND 1262 message. OMNI interfaces MUST number each distinct underlying 1263 interface with an omIndex value between '1' and '255' that 1264 represents a MN-specific 8-bit mapping for the actual ifIndex 1265 value assigned by network management [RFC2863] (the omIndex value 1266 '0' is reserved for use by the MS). For RS and NS messages, S/ 1267 T-omIndex corresponds to the source underlying interface the 1268 message originated from. For RA and NA messages, S/T-omIndex 1269 corresponds to the target underlying interface that the message is 1270 destined to. (For NS messages used for Neighbor Unreachability 1271 Detection (NUD), S/T-omIndex instead identifies the neighbor's 1272 underlying interface to be used as the target interface to return 1273 the NA.) 1275 o Sub-Options is a Variable-length field, of length such that the 1276 complete OMNI Option is an integer multiple of 8 octets long. 1277 Contains one or more Sub-Options, as described in Section 11.1. 1279 The OMNI option may appear in any IPv6 ND message type; it is 1280 processed by interfaces that recognize the option and ignored by all 1281 other interfaces. If multiple OMNI option instances appear in the 1282 same IPv6 ND message, the interface processes the T, Preflen and S/ 1283 T-omIndex fields in the first instance and ignores those fields in 1284 all other instances. The interface processes the Sub-Options of all 1285 OMNI option instances in the consecutive order in which they appear 1286 in the IPv6 ND message, beginning with the first instance and 1287 continuing consecutively through any additional instances to the end 1288 of the message. 1290 The OMNI option(s) in each IPv6 ND message may include full or 1291 partial information for the neighbor. The union of the information 1292 in the most recently received OMNI options is therefore retained, and 1293 the information is aged/removed in conjunction with the corresponding 1294 neighbor cache entry. 1296 11.1. Sub-Options 1298 The OMNI option includes zero or more Sub-Options. Each consecutive 1299 Sub-Option is concatenated immediately after its predecessor. All 1300 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1301 encoded in the following format: 1303 0 1 2 1304 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 1305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1306 | Sub-Type| Sub-length | Sub-Option Data ... 1307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1309 Figure 5: Sub-Option Format 1311 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1312 Options defined in this document are: 1314 Option Name Sub-Type 1315 Pad1 0 1316 PadN 1 1317 Interface Attributes (Type 1) 2 1318 Interface Attributes (Type 2) 3 1319 Traffic Selector 4 1320 Origin Indication 5 1321 MS-Register 6 1322 MS-Release 7 1323 Geo Coordinates 8 1324 DHCPv6 Message 9 1325 HIP Message 10 1326 Node Identification 11 1328 Figure 6 1330 Sub-Types 12-29 are available for future assignment. Sub-Type 30 1331 is reserved for experimentation, as recommended in [RFC3692]. 1332 Sub-Type 31 is reserved by IANA. 1334 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1335 Option Data ranging from 0 to 2034 octets (the values 2035 through 1336 2047 are invalid, since each OMNI option is limited to 2040 1337 octets). 1339 o Sub-Option Data is a block of data with format determined by Sub- 1340 Type and length determined by Sub-Length. 1342 Note that Sub-Type and Sub-Length are coded together in network byte 1343 order in two consecutive octets. Note also that Sub-Option Data may 1344 be up to 2034 octets in length. This allows ample space for encoding 1345 large objects (e.g., ascii character strings, protocol messages, 1346 security codes, etc.), while a single OMNI option is limited to 2040 1347 octets the same as for any IPv6 ND option. If the Sub-Options to be 1348 coded would cause an OMNI option to exceed 2040 octets, any remaining 1349 Sub-Options are encoded in additional OMNI options in the consecutive 1350 order of intended processing. Implementations must therefore be 1351 mindful of size limitations, and must refrain from sending IPv6 ND 1352 messages larger than the OMNI interface MTU. 1354 During processing, unrecognized Sub-Options are ignored and the next 1355 Sub-Option processed until the end of the OMNI option is reached. 1357 The following Sub-Option types and formats are defined in this 1358 document: 1360 11.1.1. Pad1 1362 0 1363 0 1 2 3 4 5 6 7 1364 +-+-+-+-+-+-+-+-+ 1365 | S-Type=0|x|x|x| 1366 +-+-+-+-+-+-+-+-+ 1368 Figure 7: Pad1 1370 o Sub-Type is set to 0. If multiple instances appear in OMNI 1371 options of the same message all are processed. 1373 o Sub-Type is followed by three 'x' bits, set randomly on 1374 transmission and ignored on receipt. Pad1 therefore consists of a 1375 whole single octet with the most significant 5 bits set to 0, and 1376 with no Sub-Length or Sub-Option Data fields following. 1378 11.1.2. PadN 1380 0 1 2 1381 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 1382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1383 | S-Type=1| Sub-length=N | N padding octets ... 1384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1386 Figure 8: PadN 1388 o Sub-Type is set to 1. If multiple instances appear in OMNI 1389 options of the same message all are processed. 1391 o Sub-Length is set to N (from 0 to 2034 being the number of padding 1392 octets that follow. 1394 o Sub-Option Data consists of N zero-valued octets. 1396 11.1.3. Interface Attributes (Type 1) 1398 The Interface Attributes (Type 1) sub-option provides a basic set of 1399 attributes for underlying interfaces. Interface Attributes (Type 1) 1400 is deprecated throughout the rest of this specification, and 1401 Interface Attributes (Type 2) (see: Section 11.1.4) are indicated 1402 wherever the term "Interface Attributes" appears without an 1403 associated Type designation. 1405 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1406 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1407 they receive. If an Interface Attributes (Type 1) is included, it 1408 must have the following format: 1410 0 1 2 3 1411 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 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1413 | Sub-Type=2| Sub-length=N | omIndex | omType | 1414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1415 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1417 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1419 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1421 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1423 |P56|P57|P58|P59|P60|P61|P62|P63| 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1426 Figure 9: Interface Attributes (Type 1) 1428 o Sub-Type is set to 2. If multiple instances with different 1429 omIndex values appear in OMNI option of the same message all are 1430 processed; if multiple instances with the same omIndex value 1431 appear, the first is processed and all others are ignored 1433 o Sub-Length is set to N (from 4 to 2034 that encodes the number of 1434 Sub-Option Data octets that follow. 1436 o omIndex is a 1-octet field containing a value from 0 to 255 1437 identifying the underlying interface for which the attributes 1438 apply. 1440 o omType is a 1-octet field containing a value from 0 to 255 1441 corresponding to the underlying interface identified by omIndex. 1443 o Provider ID is a 1-octet field containing a value from 0 to 255 1444 corresponding to the underlying interface identified by omIndex. 1446 o Link encodes a 4-bit link metric. The value '0' means the link is 1447 DOWN, and the remaining values mean the link is UP with metric 1448 ranging from '1' ("lowest") to '15' ("highest"). 1450 o Resvd is reserved for future use. 1452 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1453 values P[00] through P[63] corresponding to the 64 Differentiated 1454 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1455 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1456 or '3' ("high") to indicate a QoS preference for underlying 1457 interface selection purposes. 1459 11.1.4. Interface Attributes (Type 2) 1461 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1462 information for the multilink conceptual sending algorithm discussed 1463 in Section 13. The L2 information is used for selecting among 1464 potentially multiple candidate underlying interfaces that can be used 1465 to forward packets to the neighbor based on factors such as DSCP 1466 preferences and link quality. Interface Attributes (Type 2) further 1467 includes link-layer address information to be used for either OAL 1468 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1469 can be avoided). 1471 Interface Attributes (Type 2) are the sole Interface Attributes 1472 format in this specification that all OMNI nodes must honor. 1473 Wherever the term "Interface Attributes" occurs throughout this 1474 specification without a "Type" designation, the format given below is 1475 indicated: 1477 0 1 2 3 1478 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 1479 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1480 | S-Type=3| Sub-length=N | omIndex | omType | 1481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1482 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1484 | LHS (bits 8 - 31) | ~ 1485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1486 ~ ~ 1487 ~ Link Layer Address (L2ADDR) ~ 1488 ~ ~ 1489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1490 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1492 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1493 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1494 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1497 Figure 10: Interface Attributes (Type 2) 1499 o Sub-Type is set to 3. If multiple instances with different 1500 omIndex values appear in OMNI options of the same message all are 1501 processed; if multiple instances with the same omIndex value 1502 appear, the first is processed and all others are ignored. 1504 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1505 Sub-Option Data octets that follow. 1507 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1508 encoded as follows (note that the first four octets must be 1509 present): 1511 * omIndex is set to an 8-bit integer value corresponding to a 1512 specific underlying interface the same as specified above for 1513 the OMNI option S/T-omIndex field. The OMNI options of a same 1514 message may include multiple Interface Attributes Sub-Options, 1515 with each distinct omIndex value pertaining to a different 1516 underlying interface. The OMNI option will often include an 1517 Interface Attributes Sub-Option with the same omIndex value 1518 that appears in the S/T-omIndex. In that case, the actual 1519 encapsulation address of the received IPv6 ND message should be 1520 compared with the L2ADDR encoded in the Sub-Option (see below); 1521 if the addresses are different (or, if L2ADDR is absent) the 1522 presence of a NAT is assumed. 1524 * omType is set to an 8-bit integer value corresponding to the 1525 underlying interface identified by omIndex. The value 1526 represents an OMNI interface-specific 8-bit mapping for the 1527 actual IANA ifType value registered in the 'IANAifType-MIB' 1528 registry [http://www.iana.org]. 1530 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1531 for the network service provider associated with this omIndex. 1533 * Link encodes a 4-bit link metric. The value '0' means the link 1534 is DOWN, and the remaining values mean the link is UP with 1535 metric ranging from '1' ("lowest") to '15' ("highest"). 1537 * R is reserved for future use. 1539 * API - a 3-bit "Address/Preferences/Indexed" code that 1540 determines the contents of the remainder of the sub-option as 1541 follows: 1543 + When the most significant bit (i.e., "Address") is set to 1, 1544 the SRT, FMT, LHS and L2ADDR fields are included immediately 1545 following the API code; else, they are omitted. 1547 + When the next most significant bit (i.e., "Preferences") is 1548 set to 1, a preferences block is included next; else, it is 1549 omitted. (Note that if "Address" is set the preferences 1550 block immediately follows L2ADDR; else, it immediately 1551 follows the API code.) 1553 + When a preferences block is present and the least 1554 significant bit (i.e., "Indexed") is set to 0, the block is 1555 encoded in "Simplex" form as shown in Figure 9; else it is 1556 encoded in "Indexed" form as discussed below. 1558 * When API indicates that an "Address" is included, the following 1559 fields appear in consecutive order (else, they are omitted): 1561 + SRT - a 5-bit Segment Routing Topology prefix length value 1562 that (when added to 96) determines the prefix length to 1563 apply to the ULA formed from concatenating [ULA*]::/96 with 1564 the 32 bit LHS MSID value that follows. For example, the 1565 value 16 corresponds to the prefix length 112. 1567 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1568 the included Link Layer Address as follows: 1570 - When the most significant bit (i.e., "Framework") is set 1571 to 0, L2ADDR is the INET encapsulation address of a 1572 Proxy/Server; otherwise, it is the address for the 1573 Source/Target itself 1575 - When the next most significant bit (i.e., "Mode") is set 1576 to 0, the Source/Target L2ADDR is on the open INET; 1577 otherwise, it is (likely) located behind one or more 1578 NATs. 1580 - When the least significant bit (i.e., "Type") is set to 1581 0, L2ADDR includes a UDP Port Number followed by an IPv4 1582 address; else, a UDP Port Number followed by an IPv6 1583 address. 1585 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1586 path to the target. When SRT and LHS are both set to 0, the 1587 LHS is considered unspecified in this IPv6 ND message. When 1588 SRT is set to 0 and LHS is non-zero, the prefix length is 1589 set to 128. SRT and LHS together provide guidance to the 1590 OMNI interface forwarding algorithm. Specifically, if SRT/ 1591 LHS is located in the local OMNI link segment then the OMNI 1592 interface can encapsulate according to FMT/L2ADDR (following 1593 any necessary NAT traversal messaging); else, it must 1594 forward according to the OMNI link spanning tree. See 1595 [I-D.templin-intarea-6706bis] for further discussion. 1597 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1598 and identifies the link-layer address (i.e., the 1599 encapsulation address) of the source/target. The UDP Port 1600 Number appears in the first two octets and the IP address 1601 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1602 The Port Number and IP address are recorded in ones- 1603 compliment "obfuscated" form per [RFC4380]. The OMNI 1604 interface forwarding algorithm uses FMT/L2ADDR to determine 1605 the encapsulation address for forwarding when SRT/LHS is 1606 located in the local OMNI link segment. Note that if the 1607 target is behind a NAT, L2ADDR will contain the mapped INET 1608 address stored in the NAT; otherwise, L2ADDR will contain 1609 the native INET information of the target itself. 1611 * When API indicates that "Preferences" are included, a 1612 preferences block appears as the remainder of the Sub-Option as 1613 a series of Bitmaps and P[*] values. In "Simplex" form, the 1614 index for each singleton Bitmap octet is inferred from its 1615 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 9. 1616 In "Indexed" form, each Bitmap is preceded by an Index octet 1617 that encodes a value "i" = (0 - 255) as the index for its 1618 companion Bitmap as follows: 1620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1621 | Index=i | Bitmap(i) |P[*] values ... 1622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1624 Figure 11 1626 * The preferences consist of a first (simplex/indexed) Bitmap 1627 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1628 2-bit P[*] values, followed by a second Bitmap (i), followed by 1629 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1630 the bits of each Bitmap(i) that are set to '1'' indicate the 1631 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1632 that follow; if any Bitmap(i) bits are '0', then the 1633 corresponding P[*] block is instead omitted. For example, if 1634 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1635 followed by the block with P[04]-P[07], etc., and ending with 1636 the block with P[28]-P[31] are included (as shown in Figure 9). 1637 The next Bitmap(i) is then consulted with its bits indicating 1638 which P[*] blocks follow, etc. out to the end of the Sub- 1639 Option. 1641 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1642 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1643 preference for underlying interface selection purposes. Not 1644 all P[*] values need to be included in the OMNI option of each 1645 IPv6 ND message received. Any P[*] values represented in an 1646 earlier OMNI option but omitted in the current OMNI option 1647 remain unchanged. Any P[*] values not yet represented in any 1648 OMNI option default to "medium". 1650 * The first 16 P[*] blocks correspond to the 64 Differentiated 1651 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1652 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1653 traffic classifier values P[64], P[65], P[66], etc. See 1654 Appendix A for further discussion and examples. 1656 11.1.5. Traffic Selector 1658 0 1 2 3 1659 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 1660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1661 | S-Type=4| Sub-length=N | omIndex | ~ 1662 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1663 ~ ~ 1664 ~ RFC 6088 Format Traffic Selector ~ 1665 ~ ~ 1666 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1668 Figure 12: Traffic Selector 1670 o Sub-Type is set to 4. If multiple instances appear in OMNI 1671 options of the same message all are processed, i.e., even if the 1672 same omIndex value appears multiple times. 1674 o Sub-Length is set to N (the number of Sub-Option Data octets that 1675 follow). 1677 o Sub-Option Data contains a 1-octet omIndex encoded exactly as 1678 specified in Section 11.1.3, followed by an N-1 octet traffic 1679 selector formatted per [RFC6088] beginning with the "TS Format" 1680 field. The largest traffic selector for a given omIndex is 1681 therefore 2033 octets. 1683 11.1.6. Origin Indication 1685 0 1 2 3 1686 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 1687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1688 | S-Type=5| Sub-length=6/18 | Origin Port Number | 1689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1690 ~ Origin IPv4/IPv6 Address ~ 1691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1693 Figure 13: Origin Indication 1695 o Sub-Type is set to 5. If multiple instances appear in OMNI 1696 options of the same message the first instance is processed and 1697 all others are ignored. 1699 o Sub-Length is set to either 6 or 18; if Sub-Length encodes any 1700 other value, the Sub-Option is ignored. 1702 o Sub-Option Data contains a 2-octet Port Number followed by a 1703 4-octet IPv4 address if Sub-Length encodes 6 or a 16-octet IPv6 1704 address if Sub-Length encodes 18. 1706 11.1.7. MS-Register 1708 0 1 2 3 1709 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 1710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1711 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1713 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1715 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1717 ... ... ... ... ... ... 1718 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1719 | MSID [n] (bits 16 - 32) | 1720 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1722 Figure 14: MS-Register Sub-option 1724 o Sub-Type is set to 6. If multiple instances appear in OMNI 1725 options of the same message all are processed. Only the first 1726 MAX_MSID values processed (whether in a single instance or 1727 multiple) are retained and all other MSIDs are ignored. 1729 o Sub-Length is set to 4n, with 508 as the maximum value for n. 1731 o A list of n 4-octet MSIDs is included in the following 4n octets. 1732 The Anycast MSID value '0' in an RS message MS-Register sub-option 1733 requests the recipient to return the MSID of a nearby MSE in a 1734 corresponding RA response. 1736 11.1.8. MS-Release 1737 0 1 2 3 1738 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 1739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1740 | S-Type=7| Sub-length=4n | MSID[1] (bits 0 - 15) | 1741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1742 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1744 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1746 ... ... ... ... ... ... 1747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1748 | MSID [n] (bits 16 - 32) | 1749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1751 Figure 15: MS-Release Sub-option 1753 o Sub-Type is set to 7. If multiple instances appear in OMNI 1754 options of the same message all are processed. Only the first 1755 MAX_MSID values processed (whether in a single instance or 1756 multiple) are retained and all other MSIDs are ignored. 1758 o Sub-Length is set to 4n, with 508 as the maximum value for n. 1760 o A list of n 4 octet MSIDs is included in the following 4n octets. 1761 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1762 i.e., only non-zero values are processed. 1764 11.1.9. Geo Coordinates 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=8| Sub-length=N | Geo Coordinates 1770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1772 Figure 16: Geo Coordinates Sub-option 1774 o Sub-Type is set to 8. If multiple instances appear in OMNI 1775 options of the same message the first is processed and all others 1776 are ignored. 1778 o Sub-Length is set to N (i.e., the length of the encoded Geo 1779 Coordinates up to a maximum of 2034 octets). 1781 o A set of Geo Coordinates. Format(s) to be specified in future 1782 documents; should include Latitude/Longitude, plus any additional 1783 attributes such as altitude, heading, speed, etc. 1785 11.1.10. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1787 0 1 2 3 1788 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 1789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1790 | S-Type=9| Sub-length=N | msg-type | id (octet 0) | 1791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1792 | transaction-id (octets 1-2) | | 1793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1794 | | 1795 . DHCPv6 options . 1796 . (variable number and length) . 1797 | | 1798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1800 Figure 17: DHCPv6 Message Sub-option 1802 o Sub-Type is set to 9. If multiple instances appear in OMNI 1803 options of the same message the first is processed and all others 1804 are ignored. 1806 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1807 beginning with 'msg-type' and continuing to the end of the DHCPv6 1808 options). The length of the entire DHCPv6 message is therefore 1809 restricted to 2034 octets. 1811 o 'msg-type' and 'transaction-id' are coded according to Section 8 1812 of [RFC8415]. 1814 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1815 follows. 1817 11.1.11. Host Identity Protocol (HIP) Message 1818 0 1 2 3 1819 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 1820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1821 |S-Type=10| Sub-length=N |0| Packet Type |Version| RES.|1| 1822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1823 | Checksum | Controls | 1824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1825 | Sender's Host Identity Tag (HIT) | 1826 | | 1827 | | 1828 | | 1829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1830 | Receiver's Host Identity Tag (HIT) | 1831 | | 1832 | | 1833 | | 1834 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1835 | | 1836 / HIP Parameters / 1837 / / 1838 | | 1839 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1841 Figure 18: HIP Message Sub-option 1843 o Sub-Type is set to 10. If multiple instances appear in OMNI 1844 options of the same message the first is processed and all others 1845 are ignored. 1847 o Sub-Length is set to N, i.e., the length of the option in octets 1848 beginning immediately following the Sub-Length field and extending 1849 to the end of the HIP parameters. The length of the entire HIP 1850 message is therefore restricted to 2034 octets. 1852 o The HIP message is coded exactly as specified in Section 5 of 1853 [RFC7401], with the exception that the OMNI "Sub-Type" and "Sub- 1854 Length" fields replace the first two header octets of the HIP 1855 message (i.e., the Next Header and Header Length fields). 1857 11.1.12. Node Identification 1858 0 1 2 3 1859 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 1860 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1861 |S-Type=11| Sub-length=N | ID-Type | ~ 1862 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1863 ~ Node Identification Value (N-1 octets) ~ 1864 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1866 Figure 19: Node Identification 1868 o Sub-Type is set to 11. If multiple instances appear in OMNI 1869 options of the same IPv6 ND message the first instance of a 1870 specific ID-Type is processed and all other instances of the same 1871 ID-Type are ignored. (Note therefore that it is possible for a 1872 single IPv6 ND message to convey multiple Node Identifications - 1873 each having a different ID-Type.) 1875 o Sub-Length is set to N, i.e., the combined length of the ID-Type 1876 and Node Identification Value fields. The maximum Node 1877 Identification Value length is therefore 2033 octets. 1879 o ID-Type is a one-octet field that encodes the type of the Node 1880 Identification Value. The following ID-Type values are currently 1881 defined: 1883 * 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates 1884 that Node Identification Value contains a 16 octet UUID. 1886 * 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node 1887 Identification Value contains a 16 octet HIT. 1889 * 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates 1890 that Node Identification Value contains a 16 octet HHIT. 1892 * 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that 1893 Node Identification Value contains an N-1 octet NAI. 1895 * 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicates 1896 that Node Identification Value contains an N-1 octet FQDN. 1898 * 5 - 252 - Unassigned. 1900 * 253-254 - Reserved for experimentation, as recommended in 1901 [RFC3692]. 1903 * 255 - reserved by IANA. 1905 o Node Identification Value is an (N - 1)-octet field encoded 1906 according to the appropriate the "ID-Type" reference above. 1908 When a Node Identification Value is needed for DHCPv6 messaging 1909 purposes, it is encoded as a DHCP Unique IDentifier (DUID) using the 1910 "DUID-EN for OMNI" format with enterprise number 45282 (see: 1911 Section 22) as shown in Figure 20: 1913 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 1914 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1915 | DUID-Type (2) | EN (high bits == 0) | 1916 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1917 | EN (low bits = 45282) | ID-Type | | 1918 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1919 . Node Identification Value . 1920 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1922 Figure 20: DUID-EN for OMNI Format 1924 In this format, the ID-Type and Node Identification Value fields are 1925 coded exactly as in Figure 19 following the 6 octet DUID-EN header, 1926 and the entire "DUID-EN for OMNI" is included in a DHCPv6 message per 1927 [RFC8415]. 1929 12. Address Mapping - Multicast 1931 The multicast address mapping of the native underlying interface 1932 applies. The mobile router on board the MN also serves as an IGMP/ 1933 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1934 using the L2 address of the AR as the L2 address for all multicast 1935 packets. 1937 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1938 coordinate with the AR, and *NET L2 elements use MLD snooping 1939 [RFC4541]. 1941 13. Multilink Conceptual Sending Algorithm 1943 The MN's IPv6 layer selects the outbound OMNI interface according to 1944 SBM considerations when forwarding data packets from local or EUN 1945 applications to external correspondents. Each OMNI interface 1946 maintains a neighbor cache the same as for any IPv6 interface, but 1947 with additional state for multilink coordination. Each OMNI 1948 interface maintains default routes via ARs discovered as discussed in 1949 Section 14, and may configure more-specific routes discovered through 1950 means outside the scope of this specification. 1952 After a packet enters the OMNI interface, one or more outbound 1953 underlying interfaces are selected based on PBM traffic attributes, 1954 and one or more neighbor underlying interfaces are selected based on 1955 the receipt of Interface Attributes sub-options in IPv6 ND messages 1956 (see: Figure 9). Underlying interface selection for the nodes own 1957 local interfaces are based on attributes such as DSCP, application 1958 port number, cost, performance, message size, etc. OMNI interface 1959 multilink selections could also be configured to perform replication 1960 across multiple underlying interfaces for increased reliability at 1961 the expense of packet duplication. The set of all Interface 1962 Attributes received in IPv6 ND messages determines the multilink 1963 forwarding profile for selecting the neighbor's underlying 1964 interfaces. 1966 When the OMNI interface sends a packet over a selected outbound 1967 underlying interface, the OAL includes or omits a mid-layer 1968 encapsulation header as necessary as discussed in Section 5 and as 1969 determined by the L2 address information received in Interface 1970 Attributes. The OAL also performs encapsulation when the nearest AR 1971 is located multiple hops away as discussed in Section 14.1. (Note 1972 that the OAL MAY employ packing when multiple packets are available 1973 for forwarding to the same destination.) 1975 OMNI interface multilink service designers MUST observe the BCP 1976 guidance in Section 15 [RFC3819] in terms of implications for 1977 reordering when packets from the same flow may be spread across 1978 multiple underlying interfaces having diverse properties. 1980 13.1. Multiple OMNI Interfaces 1982 MNs may connect to multiple independent OMNI links concurrently in 1983 support of SBM. Each OMNI interface is distinguished by its Anycast 1984 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1985 configures a separate OMNI interface for each link so that multiple 1986 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1987 layer. A different Anycast ULA is assigned to each interface, and 1988 the MN injects the service prefixes for the OMNI link instances into 1989 the EUN routing system. 1991 Applications in EUNs can use Segment Routing to select the desired 1992 OMNI interface based on SBM considerations. The Anycast ULA is 1993 written into the IPv6 destination address, and the actual destination 1994 (along with any additional intermediate hops) is written into the 1995 Segment Routing Header. Standard IP routing directs the packets to 1996 the MN's mobile router entity, and the Anycast ULA identifies the 1997 OMNI interface to be used for transmission to the next hop. When the 1998 MN receives the message, it replaces the IPv6 destination address 1999 with the next hop found in the routing header and transmits the 2000 message over the OMNI interface identified by the Anycast ULA. 2002 Multiple distinct OMNI links can therefore be used to support fault 2003 tolerance, load balancing, reliability, etc. The architectural model 2004 is similar to Layer 2 Virtual Local Area Networks (VLANs). 2006 13.2. MN<->AR Traffic Loop Prevention 2008 After an AR has registered an MNP for a MN (see: Section 14), the AR 2009 will forward packets destined to an address within the MNP to the MN. 2010 The MN will under normal circumstances then forward the packet to the 2011 correct destination within its internal networks. 2013 If at some later time the MN loses state (e.g., after a reboot), it 2014 may begin returning packets destined to an MNP address to the AR as 2015 its default router. The AR therefore must drop any packets 2016 originating from the MN and destined to an address within the MN's 2017 registered MNP. To do so, the AR institutes the following check: 2019 o if the IP destination address belongs to a neighbor on the same 2020 OMNI interface, and if the link-layer source address is the same 2021 as one of the neighbor's link-layer addresses, drop the packet. 2023 14. Router Discovery and Prefix Registration 2025 MNs interface with the MS by sending RS messages with OMNI options 2026 under the assumption that one or more AR on the *NET will process the 2027 message and respond. The MN then configures default routes for the 2028 OMNI interface via the discovered ARs as the next hop. The manner in 2029 which the *NET ensures AR coordination is link-specific and outside 2030 the scope of this document (however, considerations for *NETs that do 2031 not provide ARs that recognize the OMNI option are discussed in 2032 Section 19). 2034 For each underlying interface, the MN sends an RS message with an 2035 OMNI option to coordinate with MSEs identified by MSID values. 2036 Example MSID discovery methods are given in [RFC5214] and include 2037 data link login parameters, name service lookups, static 2038 configuration, a static "hosts" file, etc. The MN can also send an 2039 RS with an MS-Register sub-option that includes the Anycast MSID 2040 value '0', i.e., instead of or in addition to any non-zero MSIDs. 2041 When the AR receives an RS with a MSID '0', it selects a nearby MSE 2042 (which may be itself) and returns an RA with the selected MSID in an 2043 MS-Register sub-option. The AR selects only a single wildcard MSE 2044 (i.e., even if the RS MS-Register sub-option included multiple '0' 2045 MSIDs) while also soliciting the MSEs corresponding to any non-zero 2046 MSIDs. 2048 MNs configure OMNI interfaces that observe the properties discussed 2049 in the previous section. The OMNI interface and its underlying 2050 interfaces are said to be in either the "UP" or "DOWN" state 2051 according to administrative actions in conjunction with the interface 2052 connectivity status. An OMNI interface transitions to UP or DOWN 2053 through administrative action and/or through state transitions of the 2054 underlying interfaces. When a first underlying interface transitions 2055 to UP, the OMNI interface also transitions to UP. When all 2056 underlying interfaces transition to DOWN, the OMNI interface also 2057 transitions to DOWN. 2059 When an OMNI interface transitions to UP, the MN sends RS messages to 2060 register its MNP and an initial set of underlying interfaces that are 2061 also UP. The MN sends additional RS messages to refresh lifetimes 2062 and to register/deregister underlying interfaces as they transition 2063 to UP or DOWN. The MN sends initial RS messages over an UP 2064 underlying interface with its MNP-LLA as the source and with 2065 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 2066 messages include an OMNI option per Section 11 with a Preflen 2067 assertion, Interface Attributes appropriate for underlying 2068 interfaces, MS-Register/Release sub-options containing MSID values, 2069 and with any other necessary OMNI sub-options (e.g., a DUID sub- 2070 option as an identity for the MN). The S/T-omIndex field is set to 2071 the index of the underlying interface over which the RS message is 2072 sent. 2074 ARs process IPv6 ND messages with OMNI options and act as an MSE 2075 themselves and/or as a proxy for other MSEs. ARs receive RS messages 2076 and create a neighbor cache entry for the MN, then coordinate with 2077 any MSEs named in the Register/Release lists in a manner outside the 2078 scope of this document. When an MSE processes the OMNI information, 2079 it first validates the prefix registration information then injects/ 2080 withdraws the MNP in the routing/mapping system and caches/discards 2081 the new Preflen, MNP and Interface Attributes. The MSE then informs 2082 the AR of registration success/failure, and the AR returns an RA 2083 message to the MN with an OMNI option per Section 11. 2085 The AR returns the RA message via the same underlying interface of 2086 the MN over which the RS was received, and with destination address 2087 set to the MNP-LLA (i.e., unicast), with source address set to its 2088 own LLA, and with an OMNI option with S/T-omIndex set to the value 2089 included in the RS. The OMNI option also includes a Preflen 2090 confirmation, Interface Attributes, MS-Register/Release and any other 2091 necessary OMNI sub-options (e.g., a DUID sub-option as an identity 2092 for the AR). The RA also includes any information for the link, 2093 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 2094 Time and Retrans Timer values, and includes any necessary options 2095 such as: 2097 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 2099 o RIOs [RFC4191] with more-specific routes. 2101 o an MTU option that specifies the maximum acceptable packet size 2102 for this underlying interface. 2104 The AR MAY also send periodic and/or event-driven unsolicited RA 2105 messages per [RFC4861]. In that case, the S/T-omIndex field in the 2106 OMNI option of the unsolicited RA message identifies the target 2107 underlying interface of the destination MN. 2109 The AR can combine the information from multiple MSEs into one or 2110 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 2111 Each aggregate RA includes an OMNI option with MS-Register/Release 2112 sub-options with the MSEs represented by the aggregate. If an 2113 aggregate is sent, the RA message contents must consistently 2114 represent the combined information advertised by all represented 2115 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 2116 address, the MN determines the addresses of the represented MSEs by 2117 examining the MS-Register/Release OMNI sub-options. 2119 When the MN receives the RA message, it creates an OMNI interface 2120 neighbor cache entry for each MSID that has confirmed MNP 2121 registration via the L2 address of this AR. If the MN connects to 2122 multiple *NETs, it records the additional L2 AR addresses in each 2123 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 2124 then configures a default route via the MSE that returned the RA 2125 message, and assigns the Subnet Router Anycast address corresponding 2126 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 2127 manages its underlying interfaces according to their states as 2128 follows: 2130 o When an underlying interface transitions to UP, the MN sends an RS 2131 over the underlying interface with an OMNI option. The OMNI 2132 option contains at least one Interface Attribute sub-option with 2133 values specific to this underlying interface, and may contain 2134 additional Interface Attributes specific to other underlying 2135 interfaces. The option also includes any MS-Register/Release sub- 2136 options. 2138 o When an underlying interface transitions to DOWN, the MN sends an 2139 RS or unsolicited NA message over any UP underlying interface with 2140 an OMNI option containing an Interface Attribute sub-option for 2141 the DOWN underlying interface with Link set to '0'. The MN sends 2142 an RS when an acknowledgement is required, or an unsolicited NA 2143 when reliability is not thought to be a concern (e.g., if 2144 redundant transmissions are sent on multiple underlying 2145 interfaces). 2147 o When the Router Lifetime for a specific AR nears expiration, the 2148 MN sends an RS over the underlying interface to receive a fresh 2149 RA. If no RA is received, the MN can send RS messages to an 2150 alternate MSID in case the current MSID has failed. If no RS 2151 messages are received even after trying to contact alternate 2152 MSIDs, the MN marks the underlying interface as DOWN. 2154 o When a MN wishes to release from one or more current MSIDs, it 2155 sends an RS or unsolicited NA message over any UP underlying 2156 interfaces with an OMNI option with a Release MSID. Each MSID 2157 then withdraws the MNP from the routing/mapping system and informs 2158 the AR that the release was successful. 2160 o When all of a MNs underlying interfaces have transitioned to DOWN 2161 (or if the prefix registration lifetime expires), any associated 2162 MSEs withdraw the MNP the same as if they had received a message 2163 with a release indication. 2165 The MN is responsible for retrying each RS exchange up to 2166 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 2167 seconds until an RA is received. If no RA is received over an UP 2168 underlying interface (i.e., even after attempting to contact 2169 alternate MSEs), the MN declares this underlying interface as DOWN. 2171 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 2172 Therefore, when the IPv6 layer sends an RS message the OMNI interface 2173 returns an internally-generated RA message as though the message 2174 originated from an IPv6 router. The internally-generated RA message 2175 contains configuration information that is consistent with the 2176 information received from the RAs generated by the MS. Whether the 2177 OMNI interface IPv6 ND messaging process is initiated from the 2178 receipt of an RS message from the IPv6 layer is an implementation 2179 matter. Some implementations may elect to defer the IPv6 ND 2180 messaging process until an RS is received from the IPv6 layer, while 2181 others may elect to initiate the process proactively. Still other 2182 deployments may elect to administratively disable the ordinary RS/RA 2183 messaging used by the IPv6 layer over the OMNI interface, since they 2184 are not required to drive the internal RS/RA processing. (Note that 2185 this same logic applies to IPv4 implementations that employ ICMP- 2186 based Router Discovery per [RFC1256].) 2188 Note: The Router Lifetime value in RA messages indicates the time 2189 before which the MN must send another RS message over this underlying 2190 interface (e.g., 600 seconds), however that timescale may be 2191 significantly longer than the lifetime the MS has committed to retain 2192 the prefix registration (e.g., REACHABLETIME seconds). ARs are 2193 therefore responsible for keeping MS state alive on a shorter 2194 timescale than the MN is required to do on its own behalf. 2196 Note: On multicast-capable underlying interfaces, MNs should send 2197 periodic unsolicited multicast NA messages and ARs should send 2198 periodic unsolicited multicast RA messages as "beacons" that can be 2199 heard by other nodes on the link. If a node fails to receive a 2200 beacon after a timeout value specific to the link, it can initiate a 2201 unicast exchange to test reachability. 2203 Note: if an AR acting as a proxy forwards a MN's RS message to 2204 another node acting as an MSE using UDP/IP encapsulation, it must use 2205 a distinct UDP source port number for each MN. This allows the MSE 2206 to distinguish different MNs behind the same AR at the link-layer, 2207 whereas the link-layer addresses would otherwise be 2208 indistinguishable. 2210 Note: when an AR acting as an MSE returns an RA to an INET Client, it 2211 includes an OMNI option with an Interface Attributes sub-option with 2212 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 2213 its INET interface. This provides the Client with partition prefix 2214 context regarding the local OMNI link segment. 2216 14.1. Router Discovery in IP Multihop and IPv4-Only Networks 2218 On some *NETs, a MN may be located multiple IP hops away from the 2219 nearest AR. Forwarding through IP multihop *NETs is conducted 2220 through the application of a routing protocol (e.g., a MANET/VANET 2221 routing protocol over omni-directional wireless interfaces, an inter- 2222 domain routing protocol in an enterprise network, etc.). These *NETs 2223 could be either IPv6-enabled or IPv4-only, while IPv4-only *NETs 2224 could be either multicast-capable or unicast-only (note that for 2225 IPv4-only *NETs the following procedures apply for both single-hop 2226 and multihop cases). 2228 A MN located potentially multiple *NET hops away from the nearest AR 2229 prepares an RS message with source address set to either its MNP-LLA 2230 or a Temporary LLA, and with destination set to link-scoped All- 2231 Routers multicast the same as discussed above. For IPv6-enabled 2232 *NETs, the MN then encapsulates the message in an IPv6 header with 2233 source address set to the ULA corresponding to the LLA source address 2234 and with destination set to either a unicast or anycast ADM-ULA. For 2235 IPv4-only *NETs, the MN instead encapsulates the RS message in an 2236 IPv4 header with source address set to the node's own IPv4 address 2237 and with destination address set to either the unicast IPv4 address 2238 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 2239 MN then sends the encapsulated RS message via the *NET interface, 2240 where it will be forwarded by zero or more intermediate *NET hops. 2242 When an intermediate *NET hop that participates in the routing 2243 protocol receives the encapsulated RS, it forwards the message 2244 according to its routing tables (note that an intermediate node could 2245 be a fixed infrastructure element or another MN). This process 2246 repeats iteratively until the RS message is received by a penultimate 2247 *NET hop within single-hop communications range of an AR, which 2248 forwards the message to the AR. 2250 When the AR receives the message, it decapsulates the RS and 2251 coordinates with the MS the same as for an ordinary link-local RS, 2252 since the inner Hop Limit will not have been decremented by the 2253 multihop forwarding process. The AR then prepares an RA message with 2254 source address set to its own ADM-LLA and destination address set to 2255 the LLA of the original MN, then encapsulates the message in an IPv4/ 2256 IPv6 header with source address set to its own IPv4/ULA address and 2257 with destination set to the encapsulation source of the RS. 2259 The AR then forwards the message to an *NET node within 2260 communications range, which forwards the message according to its 2261 routing tables to an intermediate node. The multihop forwarding 2262 process within the *NET continues repetitively until the message is 2263 delivered to the original MN, which decapsulates the message and 2264 performs autoconfiguration the same as if it had received the RA 2265 directly from the AR as an on-link neighbor. 2267 Note: An alternate approach to multihop forwarding via IPv6 2268 encapsulation would be to statelessly translate the IPv6 LLAs into 2269 ULAs and forward the messages without encapsulation. This would 2270 violate the [RFC4861] requirement that certain IPv6 ND messages must 2271 use link-local addresses and must not be accepted if received with 2272 Hop Limit less than 255. This document therefore advocates 2273 encapsulation since the overhead is nominal considering the 2274 infrequent nature and small size of IPv6 ND messages. Future 2275 documents may consider encapsulation avoidance through translation 2276 while updating [RFC4861]. 2278 Note: An alternate approach to multihop forwarding via IPv4 2279 encapsulation would be to employ IPv6/IPv4 protocol translation. 2280 However, for IPv6 ND messages the LLAs would be truncated due to 2281 translation and the OMNI Router and Prefix Discovery services would 2282 not be able to function. The use of IPv4 encapsulation is therefore 2283 indicated. 2285 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2286 of a new IPv4 /24 prefix allocation, but this may be difficult to 2287 obtain given IPv4 address exhaustion. An alternative would be to re- 2288 purpose the prefix 192.88.99.0 which has been set aside from its 2289 former use by [RFC7526]. 2291 14.2. MS-Register and MS-Release List Processing 2293 When a MN sends an RS message with an OMNI option via an underlying 2294 interface to an AR, the MN must convey its knowledge of its 2295 currently-associated MSEs. Initially, the MN will have no associated 2296 MSEs and should therefore include an MS-Register sub-option with the 2297 single MSID value 0 which requests the AR to select and assign an 2298 MSE. The AR will then return an RA message with source address set 2299 to the ADM-LLA of the selected MSE. 2301 As the MN activates additional underlying interfaces, it can 2302 optionally include an MS-Register sub-option with MSID value 0, or 2303 with non-zero MSIDs for MSEs discovered from previous RS/RA 2304 exchanges. The MN will thus eventually begin to learn and manage its 2305 currently active set of MSEs, and can register with new MSEs or 2306 release from former MSEs with each successive RS/RA exchange. As the 2307 MN's MSE constituency grows, it alone is responsible for including or 2308 omitting MSIDs in the MS-Register/Release lists it sends in RS 2309 messages. The inclusion or omission of MSIDs determines the MN's 2310 interface to the MS and defines the manner in which MSEs will 2311 respond. The only limiting factor is that the MN should include no 2312 more than MAX_MSID values in each list per each IPv6 ND message, and 2313 should avoid duplication of entries in each list unless it wants to 2314 increase likelihood of control message delivery. 2316 When an AR receives an RS message sent by a MN with an OMNI option, 2317 the option will contain zero or more MS-Register and MS-Release sub- 2318 options containing MSIDs. After processing the OMNI option, the AR 2319 will have a list of zero or more MS-Register MSIDs and a list of zero 2320 or more of MS-Release MSIDs. The AR then processes the lists as 2321 follows: 2323 o For each list, retain the first MAX_MSID values in the list and 2324 discard any additional MSIDs (i.e., even if there are duplicates 2325 within a list). 2327 o Next, for each MSID in the MS-Register list, remove all matching 2328 MSIDs from the MS-Release list. 2330 o Next, proceed according to whether the AR's own MSID or the value 2331 0 appears in the MS-Register list as follows: 2333 * If yes, send an RA message directly back to the MN and send a 2334 proxy copy of the RS message to each additional MSID in the MS- 2335 Register list with the MS-Register/Release lists omitted. 2336 Then, send an unsolicited NA (uNA) message to each MSID in the 2337 MS-Release list with the MS-Register/Release lists omitted and 2338 with an OMNI option with S/T-omIndex set to 0. 2340 * If no, send a proxy copy of the RS message to each additional 2341 MSID in the MS-Register list with the MS-Register list omitted. 2342 For the first MSID, include the original MS-Release list; for 2343 all other MSIDs, omit the MS-Release list. 2345 Each proxy copy of the RS message will include an OMNI option and 2346 encapsulation header with the ADM-ULA of the AR as the source and the 2347 ADM-ULA of the Register MSE as the destination. When the Register 2348 MSE receives the proxy RS message, if the message includes an MS- 2349 Release list the MSE sends a uNA message to each additional MSID in 2350 the Release list. The Register MSE then sends an RA message back to 2351 the (Proxy) AR wrapped in an OMNI encapsulation header with source 2352 and destination addresses reversed, and with RA destination set to 2353 the MNP-LLA of the MN. When the AR receives this RA message, it 2354 sends a proxy copy of the RA to the MN. 2356 Each uNA message (whether send by the first-hop AR or by a Register 2357 MSE) will include an OMNI option and an encapsulation header with the 2358 ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2359 Release ME as the destination. The uNA informs the Release MSE that 2360 its previous relationship with the MN has been released and that the 2361 source of the uNA message is now registered. The Release MSE must 2362 then note that the subject MN of the uNA message is now "departed", 2363 and forward any subsequent packets destined to the MN to the Register 2364 MSE. 2366 Note that it is not an error for the MS-Register/Release lists to 2367 include duplicate entries. If duplicates occur within a list, the AR 2368 will generate multiple proxy RS and/or uNA messages - one for each 2369 copy of the duplicate entries. 2371 14.3. DHCPv6-based Prefix Registration 2373 When a MN is not pre-provisioned with an MNP-LLA (or, when multiple 2374 MNPs are needed), it will require the AR to select MNPs on its behalf 2375 and set up the correct routing state within the MS. The DHCPv6 2376 service [RFC8415] supports this requirement. 2378 When an MN needs to have the AR select MNPs, it sends an RS message 2379 with a Temporary LLA as the source and with DHCPv6 Message sub-option 2380 containing a Client Identifier, one or more IA_PD options and a Rapid 2381 Commit option. The MN also sets the 'msg-type' field to "Solicit", 2382 and includes a 3-octet 'transaction-id'. 2384 When the AR receives the RS message, it extracts the DHCPv6 message 2385 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 2386 a message exchange with the locally-resident DHCPv6 server, which 2387 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2388 (If the AR wishes to defer creation of MN state until the DHCPv6 2389 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2390 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2391 forward/reply exchange with Relay Message and Interface ID options.) 2393 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2394 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2395 sends an RA back to the MN with the DHCPv6 Reply message included in 2396 an OMNI DHCPv6 message sub-option. If the RS message source address 2397 was a Temporary address, the AR includes one of the (newly-created) 2398 MNP-LLAs as the RA destination address. The MN then creates a 2399 default route, assigns Subnet Router Anycast addresses and uses the 2400 RA destination address as its primary MNP-LLA. The MN will then use 2401 this primary MNP-LLA as the source address of any IPv6 ND messages it 2402 sends as long as it retains ownership of the MNP. 2404 Note: After a MN performs a DHCPv6-based prefix registration exchange 2405 with a first AR, it would need to repeat the exchange with each 2406 additional MSE it registers with. In that case, the MN supplies the 2407 MNP delegations received from the first AR in the IA_PD fields of a 2408 DHCPv6 message when it engages the additional MSEs. 2410 15. Secure Redirection 2412 If the *NET link model is multiple access, the AR is responsible for 2413 assuring that address duplication cannot corrupt the neighbor caches 2414 of other nodes on the link. When the MN sends an RS message on a 2415 multiple access *NET link, the AR verifies that the MN is authorized 2416 to use the address and returns an RA with a non-zero Router Lifetime 2417 only if the MN is authorized. 2419 After verifying MN authorization and returning an RA, the AR MAY 2420 return IPv6 ND Redirect messages to direct MNs located on the same 2421 *NET link to exchange packets directly without transiting the AR. In 2422 that case, the MNs can exchange packets according to their unicast L2 2423 addresses discovered from the Redirect message instead of using the 2424 dogleg path through the AR. In some *NET links, however, such direct 2425 communications may be undesirable and continued use of the dogleg 2426 path through the AR may provide better performance. In that case, 2427 the AR can refrain from sending Redirects, and/or MNs can ignore 2428 them. 2430 16. AR and MSE Resilience 2432 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2433 [RFC5798] configurations so that service continuity is maintained 2434 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2435 the (redundant) ARs is currently providing service, and any service 2436 discontinuity will be limited to the failover time supported by VRRP. 2437 Widely deployed public domain implementations of VRRP are available. 2439 MSEs SHOULD use high availability clustering services so that 2440 multiple redundant systems can provide coordinated response to 2441 failures. As with VRRP, widely deployed public domain 2442 implementations of high availability clustering services are 2443 available. Note that special-purpose and expensive dedicated 2444 hardware is not necessary, and public domain implementations can be 2445 used even between lightweight virtual machines in cloud deployments. 2447 17. Detecting and Responding to MSE Failures 2449 In environments where fast recovery from MSE failure is required, ARs 2450 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2451 manner that parallels Bidirectional Forwarding Detection (BFD) 2452 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2453 react to failures so that cached information is re-established 2454 through alternate paths. Proactive NUD control messaging is carried 2455 only over well-connected ground domain networks (i.e., and not low- 2456 end *NET links such as aeronautical radios) and can therefore be 2457 tuned for rapid response. 2459 ARs perform proactive NUD for MSEs for which there are currently 2460 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2461 of the outage by sending multicast RA messages on the *NET interface. 2462 The AR sends RA messages to MNs via the *NET interface with an OMNI 2463 option with a Release ID for the failed MSE, and with destination 2464 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2466 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2467 by small delays [RFC4861]. Any MNs on the *NET interface that have 2468 been using the (now defunct) MSE will receive the RA messages and 2469 associate with a new MSE. 2471 18. Transition Considerations 2473 When a MN connects to an *NET link for the first time, it sends an RS 2474 message with an OMNI option. If the first hop AR recognizes the 2475 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2476 as the destination and with an OMNI option included. The MN then 2477 engages the AR according to the OMNI link model specified above. If 2478 the first hop AR is a legacy IPv6 router, however, it instead returns 2479 an RA message with no OMNI option and with a non-OMNI unicast source 2480 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2481 according to the legacy IPv6 link model and without the OMNI 2482 extensions specified in this document. 2484 If the *NET link model is multiple access, there must be assurance 2485 that address duplication cannot corrupt the neighbor caches of other 2486 nodes on the link. When the MN sends an RS message on a multiple 2487 access *NET link with an LLA source address and an OMNI option, ARs 2488 that recognize the option ensure that the MN is authorized to use the 2489 address and return an RA with a non-zero Router Lifetime only if the 2490 MN is authorized. ARs that do not recognize the option instead 2491 return an RA that makes no statement about the MN's authorization to 2492 use the source address. In that case, the MN should perform 2493 Duplicate Address Detection to ensure that it does not interfere with 2494 other nodes on the link. 2496 An alternative approach for multiple access *NET links to ensure 2497 isolation for MN / AR communications is through L2 address mappings 2498 as discussed in Appendix C. This arrangement imparts a (virtual) 2499 point-to-point link model over the (physical) multiple access link. 2501 19. OMNI Interfaces on Open Internetworks 2503 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2504 an open Internetwork without an OMNI-aware first-hop AR receive RA 2505 messages that do not include an OMNI option, while OMNI interfaces 2506 configured over IPv4-only underlying interfaces do not receive any 2507 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2508 without an OMNI option configure addresses, on-link prefixes, etc. on 2509 the underlying interface that received the RA according to standard 2510 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2511 interfaces configured over IPv4-only underlying interfaces configure 2512 IPv4 address information on the underlying interfaces using 2513 mechanisms such as DHCPv4 [RFC2131]. 2515 OMNI interfaces configured over underlying interfaces that connect to 2516 an open Internetwork can apply security services such as VPNs to 2517 connect to an MSE, or can establish a direct link to an MSE through 2518 some other means (see Section 4). In environments where an explicit 2519 VPN or direct link may be impractical, OMNI interfaces can instead 2520 use UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2521 authentication per [RFC7401]. 2523 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes a 2524 HIP "Initiator" message in an OMNI option of an IPv6 RS message and 2525 the MSE responds with a HIP "Responder" message coded in an OMNI 2526 option of an IPv6 RA message. HIP security services are applied per 2527 [RFC7401], using the RS/RA messages as simple "shipping containers" 2528 to convey the HIP parameters. In that case, a "two-message HIP 2529 exchange" through a single RS/RA exchange may be sufficient for 2530 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2531 two MNs can coordinate directly with one another with HIP "Initiator/ 2532 Responder" messages coded in OMNI options of IPv6 NS/NA messages. In 2533 that case, a four-message HIP exchange (i.e., two back-to-back NS/NA 2534 exchanges) may be necessary for the two MNs to attain mutual 2535 authentication. 2537 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2538 interfaces send control plane messages to interface with the MS, 2539 including RS/RA messages used according to Section 14 and NS/NA 2540 messages used for route optimization and mobility (see: 2541 [I-D.templin-intarea-6706bis]). The control plane messages must be 2542 authenticated while data plane messages are delivered the same as for 2543 ordinary best-effort traffic with basic source address-based data 2544 origin verification. Data plane communications via OMNI interfaces 2545 that connect over open Internetworks without an explicit VPN should 2546 therefore employ transport- or higher-layer security to ensure 2547 integrity and/or confidentiality. 2549 OMNI interfaces configured over open Internetworks are often located 2550 behind NATs. The OMNI interface accommodates NAT traversal using 2551 UDP/IP encapsulation and the mechanisms discussed in 2552 [I-D.templin-intarea-6706bis]. 2554 Note: Following the initial HIP Initiator/Responder exchange, OMNI 2555 interfaces configured over open Internetworks maintain HIP 2556 associations through the transmission of IPv6 ND messages that 2557 include OMNI options with HIP "Update" and "Notify" messages. OMNI 2558 interfaces use the HIP "Update" message when an acknowledgement is 2559 required, and use the "Notify" message in unacknowledged isolated 2560 IPv6 ND messages (e.g., unsolicited NAs). 2562 20. Time-Varying MNPs 2564 In some use cases, it is desirable, beneficial and efficient for the 2565 MN to receive a constant MNP that travels with the MN wherever it 2566 moves. For example, this would allow air traffic controllers to 2567 easily track aircraft, etc. In other cases, however (e.g., 2568 intelligent transportation systems), the MN may be willing to 2569 sacrifice a modicum of efficiency in order to have time-varying MNPs 2570 that can be changed every so often to defeat adversarial tracking. 2572 The prefix delegation services discussed in Section 14.3 allows OMNI 2573 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2574 use a Temporary LLA as the source address of an RS message with an 2575 OMNI option with DHCPv6 Option sub-options. The MN would then be 2576 obligated to renumber its internal networks whenever its MNP (and 2577 therefore also its OMNI address) changes. This should not present a 2578 challenge for MNs with automated network renumbering services, 2579 however presents limits for the durations of ongoing sessions that 2580 would prefer to use a constant address. 2582 21. Using (H)HITs Instead of Temporary Addresses 2584 MNs that generate (H)HITs but do not have pre-assigned MNPs can 2585 request MNP delegations by issuing IPv6 ND messages that use the 2586 (H)HIT instead of a Temporary address. In particular, when a MN 2587 creates an RS message it can set the source address to the 2588 unspecified address (::) and encapsulate the message in an IPv6 2589 header with the (H)HIT as the source address. The MN sets the T 2590 field in the OMNI option to 0 (since the address is not Temporary) 2591 and sends the message to the AR as specified in Section 14. 2593 When the AR receives the message, it examines the RS encapsulation 2594 source address to determine that the source is a (H)HIT and not a 2595 ULA. The AR next invokes the DHCPv6 protocol to request an MNP 2596 prefix delegation, then prepares an RA message with source address 2597 set to its own ADM-LLA and destination set to the MNP-LLA 2598 corresponding to the delegated MNP. The AR finally encapsulates the 2599 RA in an IPv6 header with source address set to its own ADM-ULA and 2600 destination set to the (H)HIT from the RS encapsulation source 2601 address, then returns the encapsulated RA to the MN. 2603 22. IANA Considerations 2605 The IANA has assigned a 4-octet Private Enterprise Number (PEN) code 2606 "45282" in the "enterprise-numbers" registry. This document is the 2607 normative reference for using this code in DHCP Unique IDentifiers 2608 based on Enterprise Numbers (DUID-EN) for OMNI Interfaces (see: 2609 Section 10). 2611 The IANA is instructed to allocate an official Type number TBD1 from 2612 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2613 option. Implementations set Type to 253 as an interim value 2614 [RFC4727]. 2616 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2617 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2618 read as follows: 2620 Code Name Reference 2621 --- ---- --------- 2622 0 Diagnostic Packet Too Big [RFC4443] 2623 1 Advisory Packet Too Big [RFCXXXX] 2625 Figure 21: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2627 The IANA is instructed to allocate one Ethernet unicast address TBD2 2628 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2629 Address Block - Unicast Use". 2631 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 2632 instructed to create and maintain a new registry entitled "OMNI 2633 option Sub-Type values". Initial values for the OMNI option Sub-Type 2634 values registry are given below; future assignments are to be made 2635 through Expert Review [RFC8126]. 2637 Value Sub-Type name Reference 2638 ----- ------------- ---------- 2639 0 Pad1 [RFCXXXX] 2640 1 PadN [RFCXXXX] 2641 2 Interface Attributes (Type 1) [RFCXXXX] 2642 3 Interface Attributes (Type 2) [RFCXXXX] 2643 4 Traffic Selector [RFCXXXX] 2644 5 Origin Indication [RFCXXXX] 2645 6 MS-Register [RFCXXXX] 2646 7 MS-Release [RFCXXXX] 2647 8 Geo Coordinates [RFCXXXX] 2648 9 DHCPv6 Message [RFCXXXX] 2649 10 HIP Message [RFCXXXX] 2650 11 Node Identification [RFCXXXX] 2651 12-29 Unassigned 2652 30 Experimental [RFCXXXX] 2653 31 Reserved [RFCXXXX] 2655 Figure 22: OMNI Option Sub-Type Values 2657 The OMNI Node Identification Sub-Option (see: Section 11.1.12) 2658 contains an 8-bit ID-Type field, for which IANA is instructed to 2659 create and maintain a new registry entitled "OMNI Node Identification 2660 Sub-Option ID-Type values". Initial values for the OMNI Node 2661 Identification Sub-Option ID Type values registry are given below; 2662 future assignments are to be made through Expert Review [RFC8126]. 2664 Value Sub-Type name Reference 2665 ----- ------------- ---------- 2666 0 UUID [RFCXXXX] 2667 1 HIT [RFCXXXX] 2668 2 HHIT [RFCXXXX] 2669 3 Network Access Identifier [RFCXXXX] 2670 4 FQDN [RFCXXXX] 2671 5-252 Unassigned [RFCXXXX] 2672 253-254 Experimental [RFCXXXX] 2673 255 Reserved [RFCXXXX] 2675 Figure 23: OMNI Node Identification Sub-Option ID-Type Values 2677 23. Security Considerations 2679 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2680 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2681 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2682 confirmation and/or time synchronization is needed. 2684 MN OMNI interfaces configured over secured ANET interfaces inherit 2685 the physical and/or link-layer security properties (i.e., "protected 2686 spectrum") of the connected ANETs. MN OMNI interfaces configured 2687 over open INET interfaces can use symmetric securing services such as 2688 VPNs or can by some other means establish a direct link. When a VPN 2689 or direct link may be impractical, however, the security services 2690 specified in [RFC7401] can be employed. While the OMNI link protects 2691 control plane messaging, applications must still employ end-to-end 2692 transport- or higher-layer security services to protect the data 2693 plane. 2695 Strong network layer security for control plane messages and 2696 forwarding path integrity for data plane messages between MSEs MUST 2697 be supported. In one example, the AERO service 2698 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 2699 and secures the links in the spanning tree with network layer 2700 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 2701 plane messages are then constrained to travel only over the secured 2702 spanning tree paths and are therefore protected from attack or 2703 eavesdropping. Since data plane messages can travel over route 2704 optimized paths that do not strictly follow the spanning tree, 2705 however, end-to-end transport- or higher-layer security services are 2706 still required. 2708 Identity-based key verification infrastructure services such as iPSK 2709 may be necessary for verifying the identities claimed by MNs. This 2710 requirement should be harmonized with the manner in which (H)HITs are 2711 attested in a given operational environment. 2713 Security considerations for specific access network interface types 2714 are covered under the corresponding IP-over-(foo) specification 2715 (e.g., [RFC2464], [RFC2492], etc.). 2717 Security considerations for IPv6 fragmentation and reassembly are 2718 discussed in Section 5.1. 2720 24. Implementation Status 2722 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2723 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2724 Newer specification versions will be tagged in upcoming releases. 2725 First public release expected before the end of 2020. 2727 25. Acknowledgements 2729 The first version of this document was prepared per the consensus 2730 decision at the 7th Conference of the International Civil Aviation 2731 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2732 2019. Consensus to take the document forward to the IETF was reached 2733 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2734 Attendees and contributors included: Guray Acar, Danny Bharj, 2735 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2736 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2737 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2738 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2739 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2740 Fryderyk Wrobel and Dongsong Zeng. 2742 The following individuals are acknowledged for their useful comments: 2743 Stuart Card, Michael Matyas, Robert Moskowitz, Madhu Niraula, Greg 2744 Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron 2745 and Michal Skorepa are especially recognized for their many helpful 2746 ideas and suggestions. Madhuri Madhava Badgandi, Sean Dickson, Don 2747 Dillenburg, Joe Dudkowski, Vijayasarathy Rajagopalan, Ron Sackman and 2748 Katherine Tran are acknowledged for their hard work on the 2749 implementation and technical insights that led to improvements for 2750 the spec. 2752 Discussions on the IETF 6man and atn mailing lists during the fall of 2753 2020 suggested additional points to consider. The authors gratefully 2754 acknowledge the list members who contributed valuable insights 2755 through those discussions. Eric Vyncke and Erik Kline were the 2756 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2757 at the time the document was developed; they are all gratefully 2758 acknowledged for their many helpful insights. 2760 This work is aligned with the NASA Safe Autonomous Systems Operation 2761 (SASO) program under NASA contract number NNA16BD84C. 2763 This work is aligned with the FAA as per the SE2025 contract number 2764 DTFAWA-15-D-00030. 2766 This work is aligned with the Boeing Information Technology (BIT) 2767 Mobility Vision Lab (MVL) program. 2769 26. References 2771 26.1. Normative References 2773 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2774 DOI 10.17487/RFC0791, September 1981, 2775 . 2777 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2778 Requirement Levels", BCP 14, RFC 2119, 2779 DOI 10.17487/RFC2119, March 1997, 2780 . 2782 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2783 "Definition of the Differentiated Services Field (DS 2784 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2785 DOI 10.17487/RFC2474, December 1998, 2786 . 2788 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2789 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2790 DOI 10.17487/RFC3971, March 2005, 2791 . 2793 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2794 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2795 November 2005, . 2797 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2798 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2799 . 2801 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2802 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2803 2006, . 2805 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2806 Control Message Protocol (ICMPv6) for the Internet 2807 Protocol Version 6 (IPv6) Specification", STD 89, 2808 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2809 . 2811 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2812 ICMPv6, UDP, and TCP Headers", RFC 4727, 2813 DOI 10.17487/RFC4727, November 2006, 2814 . 2816 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2817 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2818 DOI 10.17487/RFC4861, September 2007, 2819 . 2821 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2822 Address Autoconfiguration", RFC 4862, 2823 DOI 10.17487/RFC4862, September 2007, 2824 . 2826 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2827 "Traffic Selectors for Flow Bindings", RFC 6088, 2828 DOI 10.17487/RFC6088, January 2011, 2829 . 2831 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 2832 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 2833 RFC 7401, DOI 10.17487/RFC7401, April 2015, 2834 . 2836 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2837 Hosts in a Multi-Prefix Network", RFC 8028, 2838 DOI 10.17487/RFC8028, November 2016, 2839 . 2841 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2842 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2843 May 2017, . 2845 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2846 (IPv6) Specification", STD 86, RFC 8200, 2847 DOI 10.17487/RFC8200, July 2017, 2848 . 2850 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2851 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2852 DOI 10.17487/RFC8201, July 2017, 2853 . 2855 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2856 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2857 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2858 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2859 . 2861 26.2. Informative References 2863 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2864 Interface for Civil Aviation, IETF Liaison Statement 2865 #1676, https://datatracker.ietf.org/liaison/1676/", March 2866 2020. 2868 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2869 Aeronautical Telecommunication Network (ATN) using 2870 Internet Protocol Suite (IPS) Standards and Protocol), 2871 Draft Edition 3 (work-in-progress)", December 2020. 2873 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2874 Interface (FDDI), IEEE Transactions on Communications", 2875 August 1990. 2877 [I-D.ietf-6man-rfc4941bis] 2878 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2879 "Temporary Address Extensions for Stateless Address 2880 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2881 (work in progress), November 2020. 2883 [I-D.ietf-drip-rid] 2884 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 2885 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 2886 progress), December 2020. 2888 [I-D.ietf-intarea-tunnels] 2889 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2890 Architecture", draft-ietf-intarea-tunnels-10 (work in 2891 progress), September 2019. 2893 [I-D.ietf-ipwave-vehicular-networking] 2894 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2895 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2896 ipwave-vehicular-networking-19 (work in progress), July 2897 2020. 2899 [I-D.templin-6man-dhcpv6-ndopt] 2900 Templin, F., "A Unified Stateful/Stateless Configuration 2901 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 2902 (work in progress), January 2021. 2904 [I-D.templin-6man-lla-type] 2905 Templin, F., "The IPv6 Link-Local Address Type Field", 2906 draft-templin-6man-lla-type-02 (work in progress), 2907 November 2020. 2909 [I-D.templin-intarea-6706bis] 2910 Templin, F., "Asymmetric Extended Route Optimization 2911 (AERO)", draft-templin-intarea-6706bis-87 (work in 2912 progress), January 2021. 2914 [IPV4-GUA] 2915 Postel, J., "IPv4 Address Space Registry, 2916 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2917 address-space.xhtml", December 2020. 2919 [IPV6-GUA] 2920 Postel, J., "IPv6 Global Unicast Address Assignments, 2921 https://www.iana.org/assignments/ipv6-unicast-address- 2922 assignments/ipv6-unicast-address-assignments.xhtml", 2923 December 2020. 2925 [RFC1035] Mockapetris, P., "Domain names - implementation and 2926 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 2927 November 1987, . 2929 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2930 Communication Layers", STD 3, RFC 1122, 2931 DOI 10.17487/RFC1122, October 1989, 2932 . 2934 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2935 DOI 10.17487/RFC1191, November 1990, 2936 . 2938 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2939 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2940 . 2942 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2943 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2944 . 2946 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2947 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2948 . 2950 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2951 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2952 . 2954 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2955 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2956 December 1998, . 2958 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2959 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2960 . 2962 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2963 Domains without Explicit Tunnels", RFC 2529, 2964 DOI 10.17487/RFC2529, March 1999, 2965 . 2967 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2968 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2969 . 2971 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2972 DOI 10.17487/RFC3330, September 2002, 2973 . 2975 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2976 Considered Useful", BCP 82, RFC 3692, 2977 DOI 10.17487/RFC3692, January 2004, 2978 . 2980 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2981 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2982 DOI 10.17487/RFC3810, June 2004, 2983 . 2985 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2986 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2987 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2988 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2989 . 2991 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2992 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2993 2004, . 2995 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 2996 Unique IDentifier (UUID) URN Namespace", RFC 4122, 2997 DOI 10.17487/RFC4122, July 2005, 2998 . 3000 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 3001 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 3002 DOI 10.17487/RFC4271, January 2006, 3003 . 3005 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 3006 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 3007 December 2005, . 3009 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 3010 Network Address Translations (NATs)", RFC 4380, 3011 DOI 10.17487/RFC4380, February 2006, 3012 . 3014 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 3015 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 3016 2006, . 3018 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 3019 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 3020 . 3022 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 3023 "Considerations for Internet Group Management Protocol 3024 (IGMP) and Multicast Listener Discovery (MLD) Snooping 3025 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 3026 . 3028 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 3029 "Internet Group Management Protocol (IGMP) / Multicast 3030 Listener Discovery (MLD)-Based Multicast Forwarding 3031 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 3032 August 2006, . 3034 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3035 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 3036 . 3038 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 3039 Errors at High Data Rates", RFC 4963, 3040 DOI 10.17487/RFC4963, July 2007, 3041 . 3043 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 3044 Advertisement Flags Option", RFC 5175, 3045 DOI 10.17487/RFC5175, March 2008, 3046 . 3048 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 3049 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 3050 RFC 5213, DOI 10.17487/RFC5213, August 2008, 3051 . 3053 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 3054 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 3055 DOI 10.17487/RFC5214, March 2008, 3056 . 3058 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 3059 RFC 5558, DOI 10.17487/RFC5558, February 2010, 3060 . 3062 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 3063 Version 3 for IPv4 and IPv6", RFC 5798, 3064 DOI 10.17487/RFC5798, March 2010, 3065 . 3067 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 3068 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 3069 . 3071 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 3072 DOI 10.17487/RFC6081, January 2011, 3073 . 3075 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 3076 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 3077 DOI 10.17487/RFC6221, May 2011, 3078 . 3080 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 3081 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 3082 DOI 10.17487/RFC6355, August 2011, 3083 . 3085 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 3086 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 3087 2012, . 3089 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 3090 with IPv6 Neighbor Discovery", RFC 6980, 3091 DOI 10.17487/RFC6980, August 2013, 3092 . 3094 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 3095 Requirements for IPv6 Customer Edge Routers", RFC 7084, 3096 DOI 10.17487/RFC7084, November 2013, 3097 . 3099 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 3100 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 3101 Boundary in IPv6 Addressing", RFC 7421, 3102 DOI 10.17487/RFC7421, January 2015, 3103 . 3105 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 3106 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 3107 DOI 10.17487/RFC7526, May 2015, 3108 . 3110 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 3111 DOI 10.17487/RFC7542, May 2015, 3112 . 3114 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 3115 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 3116 February 2016, . 3118 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 3119 Support for IP Hosts with Multi-Access Support", RFC 7847, 3120 DOI 10.17487/RFC7847, May 2016, 3121 . 3123 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 3124 Writing an IANA Considerations Section in RFCs", BCP 26, 3125 RFC 8126, DOI 10.17487/RFC8126, June 2017, 3126 . 3128 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 3129 Decraene, B., Litkowski, S., and R. Shakir, "Segment 3130 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 3131 July 2018, . 3133 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 3134 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 3135 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 3136 . 3138 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 3139 and F. Gont, "IP Fragmentation Considered Fragile", 3140 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 3141 . 3143 Appendix A. Interface Attribute Preferences Bitmap Encoding 3145 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 3146 encoding to specific Internetworks such as the Aeronautical 3147 Telecommunications Network with Internet Protocol Services (ATN/IPS) 3148 may include link selection preferences based on other traffic 3149 classifiers (e.g., transport port numbers, etc.) in addition to the 3150 existing DSCP-based preferences. Nodes on specific Internetworks 3151 maintain a map of traffic classifiers to additional P[*] preference 3152 fields beyond the first 64. For example, TCP port 22 maps to P[67], 3153 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 3155 Implementations use Simplex or Indexed encoding formats for P[*] 3156 encoding in order to encode a given set of traffic classifiers in the 3157 most efficient way. Some use cases may be more efficiently coded 3158 using Simplex form, while others may be more efficient using Indexed. 3159 Once a format is selected for preparation of a single Interface 3160 Attribute the same format must be used for the entire Interface 3161 Attribute sub-option. Different sub-options may use different 3162 formats. 3164 The following figures show coding examples for various Simplex and 3165 Indexed formats: 3167 0 1 2 3 3168 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 3169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3170 | Sub-Type=3| Sub-length=N | omIndex | omType | 3171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3172 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 3173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3174 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 3175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3176 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 3177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3178 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 3179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3180 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3182 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 3183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3185 Figure 24: Example 1: Dense Simplex Encoding 3187 0 1 2 3 3188 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 3189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3190 | Sub-Type=3| Sub-length=N | omIndex | omType | 3191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3192 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 3193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3194 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3196 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 3197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3198 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 3199 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3200 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 3201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3202 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 3203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3204 |Bitmap(10)=0x00| ... 3205 +-+-+-+-+-+-+-+-+-+-+- 3207 Figure 25: Example 2: Sparse Simplex Encoding 3209 0 1 2 3 3210 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 3211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3212 | Sub-Type=3| Sub-length=N | omIndex | omType | 3213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3214 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 3215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3216 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 3217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3218 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 3219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3220 | Bitmap = 0x01 |796|797|798|799| ... 3221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3223 Figure 26: Example 3: Indexed Encoding 3225 Appendix B. VDL Mode 2 Considerations 3227 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 3228 (VDLM2) that specifies an essential radio frequency data link service 3229 for aircraft and ground stations in worldwide civil aviation air 3230 traffic management. The VDLM2 link type is "multicast capable" 3231 [RFC4861], but with considerable differences from common multicast 3232 links such as Ethernet and IEEE 802.11. 3234 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3235 magnitude less than most modern wireless networking gear. Second, 3236 due to the low available link bandwidth only VDLM2 ground stations 3237 (i.e., and not aircraft) are permitted to send broadcasts, and even 3238 so only as compact layer 2 "beacons". Third, aircraft employ the 3239 services of ground stations by performing unicast RS/RA exchanges 3240 upon receipt of beacons instead of listening for multicast RA 3241 messages and/or sending multicast RS messages. 3243 This beacon-oriented unicast RS/RA approach is necessary to conserve 3244 the already-scarce available link bandwidth. Moreover, since the 3245 numbers of beaconing ground stations operating within a given spatial 3246 range must be kept as sparse as possible, it would not be feasible to 3247 have different classes of ground stations within the same region 3248 observing different protocols. It is therefore highly desirable that 3249 all ground stations observe a common language of RS/RA as specified 3250 in this document. 3252 Note that links of this nature may benefit from compression 3253 techniques that reduce the bandwidth necessary for conveying the same 3254 amount of data. The IETF lpwan working group is considering possible 3255 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3257 Appendix C. MN / AR Isolation Through L2 Address Mapping 3259 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3260 unicast link-scoped IPv6 destination address. However, IPv6 ND 3261 messaging should be coordinated between the MN and AR only without 3262 invoking other nodes on the *NET. This implies that MN / AR control 3263 messaging should be isolated and not overheard by other nodes on the 3264 link. 3266 To support MN / AR isolation on some *NET links, ARs can maintain an 3267 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3268 *NETs, this specification reserves one Ethernet unicast address TBD2 3269 (see: Section 22). For non-Ethernet statically-addressed *NETs, 3270 MSADDR is reserved per the assigned numbers authority for the *NET 3271 addressing space. For still other *NETs, MSADDR may be dynamically 3272 discovered through other means, e.g., L2 beacons. 3274 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3275 both multicast and unicast) to MSADDR instead of to an ordinary 3276 unicast or multicast L2 address. In this way, all of the MN's IPv6 3277 ND messages will be received by ARs that are configured to accept 3278 packets destined to MSADDR. Note that multiple ARs on the link could 3279 be configured to accept packets destined to MSADDR, e.g., as a basis 3280 for supporting redundancy. 3282 Therefore, ARs must accept and process packets destined to MSADDR, 3283 while all other devices must not process packets destined to MSADDR. 3284 This model has well-established operational experience in Proxy 3285 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3287 Appendix D. Change Log 3289 << RFC Editor - remove prior to publication >> 3291 Differences from draft-templin-6man-omni-interface-35 to draft- 3292 templin-6man-omni-interface-36: 3294 o Major clarifications on aspects such as "hard/soft" PTB error 3295 messages 3297 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3298 be used in the data plane. 3300 Differences from draft-templin-6man-omni-interface-31 to draft- 3301 templin-6man-omni-interface-32: 3303 o MTU 3305 o Support for multi-hop ANETS such as ISATAP. 3307 Differences from draft-templin-6man-omni-interface-29 to draft- 3308 templin-6man-omni-interface-30: 3310 o Moved link-layer addressing information into the OMNI option on a 3311 per-ifIndex basis 3313 o Renamed "ifIndex-tuple" to "Interface Attributes" 3315 Differences from draft-templin-6man-omni-interface-27 to draft- 3316 templin-6man-omni-interface-28: 3318 o Updates based on implementation experience. 3320 Differences from draft-templin-6man-omni-interface-25 to draft- 3321 templin-6man-omni-interface-26: 3323 o Further clarification on "aggregate" RA messages. 3325 o Expanded Security Considerations to discuss expectations for 3326 security in the Mobility Service. 3328 Differences from draft-templin-6man-omni-interface-20 to draft- 3329 templin-6man-omni-interface-21: 3331 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3332 (PBM). 3334 Differences from draft-templin-6man-omni-interface-18 to draft- 3335 templin-6man-omni-interface-19: 3337 o SEND/CGA. 3339 Differences from draft-templin-6man-omni-interface-17 to draft- 3340 templin-6man-omni-interface-18: 3342 o Teredo 3344 Differences from draft-templin-6man-omni-interface-14 to draft- 3345 templin-6man-omni-interface-15: 3347 o Prefix length discussions removed. 3349 Differences from draft-templin-6man-omni-interface-12 to draft- 3350 templin-6man-omni-interface-13: 3352 o Teredo 3354 Differences from draft-templin-6man-omni-interface-11 to draft- 3355 templin-6man-omni-interface-12: 3357 o Major simplifications and clarifications on MTU and fragmentation. 3359 o Document now updates RFC4443 and RFC8201. 3361 Differences from draft-templin-6man-omni-interface-10 to draft- 3362 templin-6man-omni-interface-11: 3364 o Removed /64 assumption, resulting in new OMNI address format. 3366 Differences from draft-templin-6man-omni-interface-07 to draft- 3367 templin-6man-omni-interface-08: 3369 o OMNI MNs in the open Internet 3371 Differences from draft-templin-6man-omni-interface-06 to draft- 3372 templin-6man-omni-interface-07: 3374 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3375 L2 addressing. 3377 o Expanded "Transition Considerations". 3379 Differences from draft-templin-6man-omni-interface-05 to draft- 3380 templin-6man-omni-interface-06: 3382 o Brought back OMNI option "R" flag, and discussed its use. 3384 Differences from draft-templin-6man-omni-interface-04 to draft- 3385 templin-6man-omni-interface-05: 3387 o Transition considerations, and overhaul of RS/RA addressing with 3388 the inclusion of MSE addresses within the OMNI option instead of 3389 as RS/RA addresses (developed under FAA SE2025 contract number 3390 DTFAWA-15-D-00030). 3392 Differences from draft-templin-6man-omni-interface-02 to draft- 3393 templin-6man-omni-interface-03: 3395 o Added "advisory PTB messages" under FAA SE2025 contract number 3396 DTFAWA-15-D-00030. 3398 Differences from draft-templin-6man-omni-interface-01 to draft- 3399 templin-6man-omni-interface-02: 3401 o Removed "Primary" flag and supporting text. 3403 o Clarified that "Router Lifetime" applies to each ANET interface 3404 independently, and that the union of all ANET interface Router 3405 Lifetimes determines MSE lifetime. 3407 Differences from draft-templin-6man-omni-interface-00 to draft- 3408 templin-6man-omni-interface-01: 3410 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3411 for future use (most likely as "pseudo-multicast"). 3413 o Non-normative discussion of alternate OMNI LLA construction form 3414 made possible if the 64-bit assumption were relaxed. 3416 First draft version (draft-templin-atn-aero-interface-00): 3418 o Draft based on consensus decision of ICAO Working Group I Mobility 3419 Subgroup March 22, 2019. 3421 Authors' Addresses 3422 Fred L. Templin (editor) 3423 The Boeing Company 3424 P.O. Box 3707 3425 Seattle, WA 98124 3426 USA 3428 Email: fltemplin@acm.org 3430 Tony Whyman 3431 MWA Ltd c/o Inmarsat Global Ltd 3432 99 City Road 3433 London EC1Y 1AX 3434 England 3436 Email: tony.whyman@mccallumwhyman.com