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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 March 8, 2021 7 Expires: September 9, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-85 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 September 9, 2021. 41 Copyright Notice 43 Copyright (c) 2021 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. OMNI Interface Maximum Transmission Unit (MTU) . . . . . . . 14 63 5.1. OMNI Interface MTU/MRU . . . . . . . . . . . . . . . . . 14 64 5.2. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . 15 65 5.3. OAL Addressing Considerations . . . . . . . . . . . . . . 19 66 5.4. OMNI Interface MTU Feedback Messaging . . . . . . . . . . 20 67 5.5. OAL Fragmentation Security Implications . . . . . . . . . 21 68 5.6. OAL Super-Packets . . . . . . . . . . . . . . . . . . . . 22 69 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 24 70 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 24 71 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 25 72 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 27 73 10. Node Identification . . . . . . . . . . . . . . . . . . . . . 28 74 11. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 28 75 11.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 30 76 11.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 32 77 11.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 32 78 11.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 33 79 11.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 34 80 11.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 38 81 11.1.6. MS-Register . . . . . . . . . . . . . . . . . . . . 39 82 11.1.7. MS-Release . . . . . . . . . . . . . . . . . . . . . 40 83 11.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 40 84 11.1.9. Dynamic Host Configuration Protocol for IPv6 85 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 41 86 11.1.10. Host Identity Protocol (HIP) Message . . . . . . . . 42 87 11.1.11. Node Identification . . . . . . . . . . . . . . . . 43 88 11.1.12. Sub-Type Extension . . . . . . . . . . . . . . . . . 44 89 12. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 47 90 13. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 48 91 13.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 48 92 13.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 49 93 14. Router Discovery and Prefix Registration . . . . . . . . . . 49 94 14.1. Router Discovery in IP Multihop and IPv4-Only Networks . 54 95 14.2. MS-Register and MS-Release List Processing . . . . . . . 55 96 14.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 57 98 15. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 59 99 16. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 59 100 17. Detecting and Responding to MSE Failures . . . . . . . . . . 59 101 18. Transition Considerations . . . . . . . . . . . . . . . . . . 60 102 19. OMNI Interfaces on Open Internetworks . . . . . . . . . . . . 60 103 20. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 62 104 21. (H)HITs and Temporary ULAs . . . . . . . . . . . . . . . . . 63 105 22. Address Selection . . . . . . . . . . . . . . . . . . . . . . 64 106 23. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 64 107 23.1. "IPv6 Neighbor Discovery Option Formats" Registry . . . 64 108 23.2. "Ethernet Numbers" Registry . . . . . . . . . . . . . . 64 109 23.3. "ICMPv6 Code Fields: Type 2 - Packet Too Big" Registry . 65 110 23.4. "OMNI Option Sub-Type Values" (New Registry) . . . . . . 65 111 23.5. "OMNI Node Identification ID-Type Values" (New Registry) 66 112 23.6. "OMNI Option Sub-Type Extension Values" (New Registry) . 66 113 23.7. "OMNI RFC4380 UDP/IP Header Option" (New Registry) . . . 66 114 23.8. "OMNI RFC6081 UDP/IP Trailer Option" (New Registry) . . 67 115 23.9. Additional Considerations . . . . . . . . . . . . . . . 67 116 24. Security Considerations . . . . . . . . . . . . . . . . . . . 68 117 25. Implementation Status . . . . . . . . . . . . . . . . . . . . 69 118 26. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 69 119 27. References . . . . . . . . . . . . . . . . . . . . . . . . . 70 120 27.1. Normative References . . . . . . . . . . . . . . . . . . 70 121 27.2. Informative References . . . . . . . . . . . . . . . . . 72 122 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 79 123 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 81 124 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 82 125 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 82 126 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 85 128 1. Introduction 130 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 131 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 132 pedestrians with cellphones, etc.) often have multiple interface 133 connections to wireless and/or wired-link data links used for 134 communicating with networked correspondents. These data links may 135 have diverse performance, cost and availability properties that can 136 change dynamically according to mobility patterns, flight phases, 137 proximity to infrastructure, etc. MNs coordinate their data links in 138 a discipline known as "multilink", in which a single virtual 139 interface is configured over the node's underlying interface 140 connections to the data links. 142 The MN configures a virtual interface (termed the "Overlay Multilink 143 Network Interface (OMNI)") as a thin layer over the underlying 144 interfaces. The OMNI interface is therefore the only interface 145 abstraction exposed to the IP layer and behaves according to the Non- 146 Broadcast, Multiple Access (NBMA) interface principle, while 147 underlying interfaces appear as link layer communication channels in 148 the architecture. The OMNI interface internally employs the "OMNI 149 Adaptation Layer (OAL)" to ensure that packets are delivered without 150 loss due to size restrictions. The OMNI interface connects to a 151 virtual overlay service known as the "OMNI link". The OMNI link 152 spans one or more Internetworks that may include private-use 153 infrastructures and/or the global public Internet itself. 155 Each MN receives a Mobile Network Prefix (MNP) for numbering 156 downstream-attached End User Networks (EUNs) independently of the 157 access network data links selected for data transport. The MN 158 performs router discovery over the OMNI interface (i.e., similar to 159 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 160 behalf of its EUNs. The router discovery process is iterated over 161 each of the OMNI interface's underlying interfaces in order to 162 register per-link parameters (see Section 14). 164 The OMNI interface provides a multilink nexus for exchanging inbound 165 and outbound traffic via the correct underlying interface(s). The IP 166 layer sees the OMNI interface as a point of connection to the OMNI 167 link. Each OMNI link has one or more associated Mobility Service 168 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 169 prefixes from which OMNI link MNPs are derived. If there are 170 multiple OMNI links, the IPv6 layer will see multiple OMNI 171 interfaces. 173 MNs may connect to multiple distinct OMNI links within the same OMNI 174 domain by configuring multiple OMNI interfaces, e.g., omni0, omni1, 175 omni2, etc. Each OMNI interface is configured over a set of 176 underlying interfaces and provides a nexus for Safety-Based Multilink 177 (SBM) operation. Each OMNI interface within the same OMNI domain 178 configures a common ULA prefix [ULA]::/48, and configures a unique 179 16-bit Subnet ID '*' to construct the sub-prefix [ULA*]::/64 (see: 180 Section 8). The IP layer applies SBM routing to select an OMNI 181 interface, which then applies Performance-Based Multilink (PBM) to 182 select the correct underlying interface. Applications can apply 183 Segment Routing [RFC8402] to select independent SBM topologies for 184 fault tolerance. 186 The OMNI interface interacts with a network-based Mobility Service 187 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 188 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 189 track MN movements and represent their MNPs in a global routing or 190 mapping system. 192 Many OMNI use cases have been proposed. In particular, the 193 International Civil Aviation Organization (ICAO) Working Group-I 194 Mobility Subgroup is developing a future Aeronautical 195 Telecommunications Network with Internet Protocol Services (ATN/IPS) 196 and has issued a liaison statement requesting IETF adoption [ATN] in 197 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 198 in Vehicular Environments (ipwave) working group has further included 199 problem statement and use case analysis for OMNI in a document now in 200 AD evaluation for RFC publication 201 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 202 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 203 programs that examine commercial aviation, Urban Air Mobility (UAM) 204 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 205 represent another large class of potential OMNI users. 207 This document specifies the transmission of IP packets and MN/MS 208 control messages over OMNI interfaces. The OMNI interface supports 209 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 210 as the network layer in the data plane, while using IPv6 ND messaging 211 as the control plane independently of the data plane IP protocol(s). 212 The OAL operates as a mid-layer between L3 and L2 based on IP-in-IPv6 213 encapsulation per [RFC2473] as discussed in the following sections. 214 OMNI interfaces enable multilink, mobility, multihop and multicast 215 services, with provisions for both Vehicle-to-Infrastructure (V2I) 216 communications and Vehicle-to-Vehicle (V2V) communications outside 217 the context of infrastructure. 219 2. Terminology 221 The terminology in the normative references applies; especially, the 222 terms "link" and "interface" are the same as defined in the IPv6 223 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 224 Additionally, this document assumes the following IPv6 ND message 225 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 226 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 228 The Protocol Constants defined in Section 10 of [RFC4861] are used in 229 their same format and meaning in this document. The terms "All- 230 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 231 are the same as defined in [RFC4291] (with Link-Local scope assumed). 233 The term "IP" is used to refer collectively to either Internet 234 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 235 specification at the layer in question applies equally to either 236 version. 238 The following terms are defined within the scope of this document: 240 Mobile Node (MN) 241 an end system with a mobile router having multiple distinct 242 upstream data link connections that are grouped together in one or 243 more logical units. The MN's data link connection parameters can 244 change over time due to, e.g., node mobility, link quality, etc. 245 The MN further connects a downstream-attached End User Network 246 (EUN). The term MN used here is distinct from uses in other 247 documents, and does not imply a particular mobility protocol. 249 End User Network (EUN) 250 a simple or complex downstream-attached mobile network that 251 travels with the MN as a single logical unit. The IP addresses 252 assigned to EUN devices remain stable even if the MN's upstream 253 data link connections change. 255 Mobility Service (MS) 256 a mobile routing service that tracks MN movements and ensures that 257 MNs remain continuously reachable even across mobility events. 258 Specific MS details are out of scope for this document. 260 Mobility Service Endpoint (MSE) 261 an entity in the MS (either singular or aggregate) that 262 coordinates the mobility events of one or more MN. 264 Mobility Service Prefix (MSP) 265 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 266 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 267 from which more-specific Mobile Network Prefixes (MNPs) are 268 delegated. OMNI link administrators typically obtain MSPs from an 269 Internet address registry, however private-use prefixes can 270 alternatively be used subject to certain limitations (see: 271 Section 9). OMNI links that connect to the global Internet 272 advertise their MSPs to their interdomain routing peers. 274 Mobile Network Prefix (MNP) 275 a longer IP prefix delegated from an MSP (e.g., 276 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 277 MNs sub-delegate the MNP to devices located in EUNs. 279 Access Network (ANET) 280 a data link service network (e.g., an aviation radio access 281 network, satellite service provider network, cellular operator 282 network, WiFi network, etc.) that connects MNs. Physical and/or 283 data link level security is assumed, and sometimes referred to as 284 "protected spectrum". Private enterprise networks and ground 285 domain aviation service networks may provide multiple secured IP 286 hops between the MN's point of connection and the nearest Access 287 Router. 289 Access Router (AR) 290 a router in the ANET for connecting MNs to correspondents in 291 outside Internetworks. The AR may be located on the same physical 292 link as the MN, or may be located multiple IP hops away. In the 293 latter case, the MN uses encapsulation to communicate with the AR 294 as though it were on the same physical link. 296 ANET interface 297 a MN's attachment to a link in an ANET. 299 Internetwork (INET) 300 a connected network region with a coherent IP addressing plan that 301 provides transit forwarding services between ANETs and nodes that 302 connect directly to the open INET via unprotected media. No 303 physical and/or data link level security is assumed, therefore 304 security must be applied by upper layers. The global public 305 Internet itself is an example. 307 INET interface 308 a node's attachment to a link in an INET. 310 *NET 311 a "wildcard" term used when a given specification applies equally 312 to both ANET and INET cases. 314 OMNI link 315 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 316 over one or more INETs and their connected ANETs. An OMNI link 317 can comprise multiple INET segments joined by bridges the same as 318 for any link; the addressing plans in each segment may be mutually 319 exclusive and managed by different administrative entities. 321 OMNI interface 322 a node's attachment to an OMNI link, and configured over one or 323 more underlying *NET interfaces. If there are multiple OMNI links 324 in an OMNI domain, a separate OMNI interface is configured for 325 each link. 327 OMNI Adaptation Layer (OAL) 328 an OMNI interface process whereby packets admitted into the 329 interface are wrapped in a mid-layer IPv6 header and fragmented/ 330 reassembled if necessary to support the OMNI link Maximum 331 Transmission Unit (MTU). The OAL is also responsible for 332 generating MTU-related control messages as necessary, and for 333 providing addressing context for spanning multiple segments of a 334 bridged OMNI link. 336 OMNI Option 337 an IPv6 Neighbor Discovery option providing multilink parameters 338 for the OMNI interface as specified in Section 11. 340 Mobile Network Prefix Link Local Address (MNP-LLA) 341 an IPv6 Link Local Address that embeds the most significant 64 342 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 343 Section 7. 345 Mobile Network Prefix Unique Local Address (MNP-ULA) 346 an IPv6 Unique-Local Address derived from an MNP-LLA. 348 Administrative Link Local Address (ADM-LLA) 349 an IPv6 Link Local Address that embeds a 32-bit administratively- 350 assigned identification value in the lower 32 bits of fe80::/96, 351 as specified in Section 7. 353 Administrative Unique Local Address (ADM-ULA) 354 an IPv6 Unique-Local Address derived from an ADM-LLA. 356 Multilink 357 an OMNI interface's manner of managing diverse underlying 358 interface connections to data links as a single logical unit. The 359 OMNI interface provides a single unified interface to upper 360 layers, while underlying interface selections are performed on a 361 per-packet basis considering factors such as DSCP, flow label, 362 application policy, signal quality, cost, etc. Multilinking 363 decisions are coordinated in both the outbound (i.e. MN to 364 correspondent) and inbound (i.e., correspondent to MN) directions. 366 Multihop 367 an iterative relaying of IP packets between MNs over an OMNI 368 underlying interface technology (such as omnidirectional wireless) 369 without support of fixed infrastructure. Multihop services entail 370 node-to-node relaying within a Mobile/Vehicular Ad-hoc Network 371 (MANET/VANET) for MN-to-MN communications and/or for "range 372 extension" where MNs within range of communications infrastructure 373 elements provide forwarding services for other MNs. 375 L2 376 The second layer in the OSI network model. Also known as "layer- 377 2", "link-layer", "sub-IP layer", "data link layer", etc. 379 L3 380 The third layer in the OSI network model. Also known as "layer- 381 3", "network-layer", "IP layer", etc. 383 underlying interface 384 a *NET interface over which an OMNI interface is configured. The 385 OMNI interface is seen as a L3 interface by the IP layer, and each 386 underlying interface is seen as a L2 interface by the OMNI 387 interface. The underlying interface either connects directly to 388 the physical communications media or coordinates with another node 389 where the physical media is hosted. 391 Mobility Service Identification (MSID) 392 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 393 (see: Section 7). IDs are assigned according to MS-specific 394 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 396 Safety-Based Multilink (SBM) 397 A means for ensuring fault tolerance through redundancy by 398 connecting multiple affiliated OMNI interfaces to independent 399 routing topologies (i.e., multiple independent OMNI links). 401 Performance Based Multilink (PBM) 402 A means for selecting underlying interface(s) for packet 403 transmission and reception within a single OMNI interface. 405 OMNI Domain 406 The set of all SBM/PBM OMNI links that collectively provides 407 services for a common set of MSPs. Each OMNI domain consists of a 408 set of affiliated OMNI links that all configure the same ::/48 ULA 409 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 411 3. Requirements 413 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 414 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 415 "OPTIONAL" in this document are to be interpreted as described in BCP 416 14 [RFC2119][RFC8174] when, and only when, they appear in all 417 capitals, as shown here. 419 An implementation is not required to internally use the architectural 420 constructs described here so long as its external behavior is 421 consistent with that described in this document. 423 4. Overlay Multilink Network (OMNI) Interface Model 425 An OMNI interface is a MN virtual interface configured over one or 426 more underlying interfaces, which may be physical (e.g., an 427 aeronautical radio link) or virtual (e.g., an Internet or higher- 428 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 429 with the MS through IPv6 ND message exchanges. The MN uses the MNP 430 to construct a unique Link-Local Address (MNP-LLA) through the 431 algorithmic derivation specified in Section 7 and assigns the LLA to 432 the OMNI interface. 434 The OMNI interface architectural layering model is the same as in 435 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 436 therefore sees the OMNI interface as a single L3 interface with 437 multiple underlying interfaces that appear as L2 communication 438 channels in the architecture. 440 +----------------------------+ 441 | Upper Layer Protocol | 442 Session-to-IP +---->| | 443 Address Binding | +----------------------------+ 444 +---->| IP (L3) | 445 IP Address +---->| | 446 Binding | +----------------------------+ 447 +---->| OMNI Interface | 448 Logical-to- +---->| (LLA) | 449 Physical | +----------------------------+ 450 Interface +---->| L2 | L2 | | L2 | 451 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 452 +------+------+ +------+ 453 | L1 | L1 | | L1 | 454 | | | | | 455 +------+------+ +------+ 457 Figure 1: OMNI Interface Architectural Layering Model 459 Each underlying interface provides an L2/L1 abstraction according to 460 one of the following models: 462 o INET interfaces connect to an INET either natively or through one 463 or several IPv4 Network Address Translators (NATs). Native INET 464 interfaces have global IP addresses that are reachable from any 465 INET correspondent. NATed INET interfaces typically have private 466 IP addresses and connect to a private network behind one or more 467 NATs that provide INET access. 469 o ANET interfaces connect to a protected ANET that is separated from 470 the open INET by an AR acting as a proxy. The ANET interface may 471 be either on the same L2 link segment as the AR, or separated from 472 the AR by multiple IP hops. 474 o VPNed interfaces use security encapsulation over a *NET to a 475 Virtual Private Network (VPN) gateway. Other than the link-layer 476 encapsulation format, VPNed interfaces behave the same as for 477 Direct interfaces. 479 o Direct (aka "point-to-point") interfaces connect directly to a 480 peer without crossing any *NET paths. An example is a line-of- 481 sight link between a remote pilot and an unmanned aircraft. 483 The OMNI virtual interface model gives rise to a number of 484 opportunities: 486 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 487 Address Detection (DAD) or Multicast Listener Discovery (MLD) 488 messaging is necessary. 490 o since Temporary ULAs are statistically unique, they can be used 491 without DAD, e.g. for MN-to-MN communications until an MNP-LLA is 492 obtained. 494 o *NET interfaces on the same L2 link segment as an AR do not 495 require any L3 addresses (i.e., not even link-local) in 496 environments where communications are coordinated entirely over 497 the OMNI interface. (An alternative would be to also assign the 498 same LLA to all *NET interfaces.) 500 o as underlying interface properties change (e.g., link quality, 501 cost, availability, etc.), any active interface can be used to 502 update the profiles of multiple additional interfaces in a single 503 message. This allows for timely adaptation and service continuity 504 under dynamically changing conditions. 506 o coordinating underlying interfaces in this way allows them to be 507 represented in a unified MS profile with provisions for mobility 508 and multilink operations. 510 o exposing a single virtual interface abstraction to the IPv6 layer 511 allows for multilink operation (including QoS based link 512 selection, packet replication, load balancing, etc.) at L2 while 513 still permitting L3 traffic shaping based on, e.g., DSCP, flow 514 label, etc. 516 o the OMNI interface allows inter-INET traversal when nodes located 517 in different INETs need to communicate with one another. This 518 mode of operation would not be possible via direct communications 519 over the underlying interfaces themselves. 521 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 522 lossless and adaptive path MTU mitigations not available for 523 communications directly over the underlying interfaces themselves. 524 The OAL supports "packing" of multiple IP payload packets within a 525 single OAL packet. 527 o L3 sees the OMNI interface as a point of connection to the OMNI 528 link; if there are multiple OMNI links (i.e., multiple MS's), L3 529 will see multiple OMNI interfaces. 531 o Multiple independent OMNI interfaces can be used for increased 532 fault tolerance through Safety-Based Multilink (SBM), with 533 Performance-Based Multilink (PBM) applied within each interface. 535 Other opportunities are discussed in [RFC7847]. Note that even when 536 the OMNI virtual interface is present, applications can still access 537 underlying interfaces either through the network protocol stack using 538 an Internet socket or directly using a raw socket. This allows for 539 intra-network (or point-to-point) communications without invoking the 540 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 541 is configured over an underlying IPv4 interface, applications can 542 still invoke IPv4 intra-network communications as long as the 543 communicating endpoints are not subject to mobility dynamics. 544 However, the opportunities discussed above are not available when the 545 architectural layering is bypassed in this way. 547 Figure 2 depicts the architectural model for a MN with an attached 548 EUN connecting to the MS via multiple independent *NETs. When an 549 underlying interface becomes active, the MN's OMNI interface sends 550 IPv6 ND messages without encapsulation if the first-hop Access Router 551 (AR) is on the same underlying link; otherwise, the interface uses 552 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 553 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 554 then coordinates with an INET Mobility Service Endpoint (MSE#1, 555 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 556 The Hop Limit in IPv6 ND messages is not decremented due to 557 encapsulation; hence, the OMNI interface appears to be attached to an 558 ordinary link. 560 +--------------+ (:::)-. 561 | MN |<-->.-(::EUN:::) 562 +--------------+ `-(::::)-' 563 |OMNI interface| 564 +----+----+----+ 565 +--------|IF#1|IF#2|IF#n|------ + 566 / +----+----+----+ \ 567 / | \ 568 / | \ 569 v v v 570 (:::)-. (:::)-. (:::)-. 571 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 572 `-(::::)-' `-(::::)-' `-(::::)-' 573 +----+ +----+ +----+ 574 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 575 . +-|--+ +-|--+ +-|--+ . 576 . | | | 577 . v v v . 578 . <----- INET Encapsulation -----> . 579 . . 580 . +-----+ (:::)-. . 581 . |MSE#2| .-(::::::::) +-----+ . 582 . +-----+ .-(::: INET :::)-. |MSE#m| . 583 . (::::: Routing ::::) +-----+ . 584 . `-(::: System :::)-' . 585 . +-----+ `-(:::::::-' . 586 . |MSE#1| +-----+ +-----+ . 587 . +-----+ |MSE#3| |MSE#4| . 588 . +-----+ +-----+ . 589 . . 590 . . 591 . <----- Worldwide Connected Internetwork ----> . 592 ........................................................... 594 Figure 2: MN/MS Coordination via Multiple *NETs 596 After the initial IPv6 ND message exchange, the MN (and/or any nodes 597 on its attached EUNs) can send and receive IP data packets over the 598 OMNI interface. OMNI interface multilink services will forward the 599 packets via ARs in the correct underlying *NETs. The AR encapsulates 600 the packets according to the capabilities provided by the MS and 601 forwards them to the next hop within the worldwide connected 602 Internetwork via optimal routes. 604 OMNI links span one or more underlying Internetwork via the OMNI 605 Adaptation Layer (OAL) which is based on a mid-layer overlay 606 encapsulation using [RFC2473]. Each OMNI link corresponds to a 607 different overlay (differentiated by an address codepoint) which may 608 be carried over a completely separate underlying topology. Each MN 609 can facilitate SBM by connecting to multiple OMNI links using a 610 distinct OMNI interface for each link. 612 Note: OMNI interface underlying interfaces often connect directly to 613 physical media on the local platform (e.g., a laptop computer with 614 WiFi, etc.), but in some configurations the physical media may be 615 hosted on a separate Local Area Network (LAN) node. In that case, 616 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 617 tunnel (at a layer below the underlying interface) to the node 618 hosting the physical media. The OMNI interface may also apply 619 encapsulation at a layer above the underlying interface such that 620 packets would appear "double-encapsulated" on the LAN; the node 621 hosting the physical media in turn removes the LAN encapsulation 622 prior to transmission or inserts it following reception. Finally, 623 the underlying interface must monitor the node hosting the physical 624 media (e.g., through periodic keepalives) so that it can convey 625 up/down/status information to the OMNI interface. 627 5. OMNI Interface Maximum Transmission Unit (MTU) 629 The OMNI interface observes the link nature of tunnels, including the 630 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 631 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 632 The OMNI interface is configured over one or more underlying 633 interfaces as discussed in Section 4, where the interfaces (and their 634 associated *NET paths) may have diverse MTUs. The OMNI interface 635 accommodates MTU diversity by encapsulating original IP packets using 636 the OMNI Adaptation Layer (OAL) mid-layer encapsulation and 637 fragmentation/reassembly service. The OAL then further encapsulates 638 the resulting OAL packets/fragments in *NET headers for transmission 639 over underlying interfaces. OMNI interface considerations for 640 accommodating original IP packets of various sizes are discussed in 641 the following sections. 643 5.1. OMNI Interface MTU/MRU 645 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 646 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 647 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 648 permitted to perform network fragmentation even though the 649 destination is required to reassemble more. The network therefore 650 MUST forward packets of at least 1280 bytes without generating an 651 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 652 [RFC8201]. (Note: the source can apply "source fragmentation" for 653 locally-generated IPv6 packets up to 1500 bytes and larger still if 654 it if has a way to determine that the destination configures a larger 655 MRU, but this does not affect the minimum IPv6 path MTU.) 656 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 657 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 658 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 659 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 660 support network fragmentation and the destination is required to 661 reassemble at least that much. The OMNI interface therefore MUST set 662 DF to 0 in the IPv4 encapsulation headers of OAL/*NET packets that 663 are no larger than 576 bytes, and MUST set DF to 1 in larger packets. 664 (Note: even if the encapsulation source has a way to determine that 665 the encapsulation destination configures an MRU larger than 576 666 bytes, it should not assume a larger minimum IPv4 path MTU without 667 careful consideration of the issues discussed in Section 5.5.) 669 The OMNI interface configures both an MTU and MRU of 9180 bytes 670 [RFC2492]; the size is therefore not a reflection of the underlying 671 interface or *NET path MTUs, but rather determines the largest 672 original "inner-layer" IP packet the OMNI interface can forward or 673 reassemble. The OMNI interface employs the OAL as a "mid-layer" 674 encapsulation, fragmentation and reassembly service for original IP 675 packets, and the OAL in turn uses "outer-layer" *NET encapsulation to 676 forward OAL/*NET packets/fragments over the underlying interfaces 677 (see: Section 5.2). 679 5.2. The OMNI Adaptation Layer (OAL) 681 When the network layer admits an original inner IP packet/fragment 682 into the OMNI interface, the OAL inserts a mid-layer IPv6 683 encapsulation per [RFC2473] if fragmentation, integrity verification 684 and/or explicit OAL addressing is required. In other cases (e.g., 685 for packet transmissions between ANET peers that share a common 686 underlying link), the OAL MAY omit the encapsulation. When OAL 687 encapsulation is used, the OAL sets the header fields per standard 688 IPv6 procedures but does not decrement the inner IP header Hop Limit/ 689 TTL since encapsulation occurs at a layer below IP forwarding. The 690 OAL next inserts a 2 octet trailer (initialized to 0) at the end of 691 the packet while incrementing the OAL header Payload Length to 692 reflect the addition of the trailer. The OAL then calculates the 2's 693 complement (mod 256) Fletcher's checksum [CKSUM][RFC2328][RFC0905] 694 over the entire OAL packet beginning with an IPv6 pseudo-header based 695 on the OAL header Payload Length (see Section 8.1 of [RFC8200]), then 696 writes the results over the trailer octets. The OAL then inserts a 697 single OMNI Routing Header (ORH) if necessary (see: 698 [I-D.templin-intarea-6706bis]) while incrementing Payload Length to 699 reflect the addition of the ORH, then fragments the OAL packet if 700 necessary. The OAL finally forwards the packet/fragments over an 701 underlying interface while adding any necessary *NET encapsulations. 702 The formats of OAL packets and fragments are shown in Figure 3. 704 +----------+-----+-----+-----+-----+-----+-----+----+ 705 | OAL Hdr | Original IP packet |Csum| 706 +----------+-----+-----+-----+-----+-----+-----+----+ 707 a) OAL packet after encapsulation but before fragmentation 709 +--------+----------+--+---------+ 710 |*NET Hdr| OAL Hdr |FH| Frag #1 | 711 +--------+----------+--+---------+ 712 +--------+----------+--+---------+ 713 |*NET Hdr| OAL Hdr |FH| Frag #2 | 714 +--------+----------+--+---------+ 715 +--------+----------+--+---------+ 716 |*NET Hdr| OAL Hdr |FH| Frag #3 | 717 +--------+----------+--+---------+ 718 .... 719 +--------+----------+--+---------+----+ 720 |*NET hdr| OAL Hdr |FH| Frag #n |Csum| 721 +--------+----------+--+---------+----+ 722 b) Fragments after OAL fragmentation and *NET encapsulation 723 (FH = Fragment Header; Csum appears only in final fragment) 725 Figure 3: OAL Packets and Fragments 727 When an OMNI interface receives a *NET encapsulated packet from an 728 underlying interface, the OAL discards the *NET encapsulation headers 729 and examines the OAL header if present. If the packet is addressed 730 to a different node, the OAL re-encapsulates and forwards as 731 discussed below; otherwise, the OAL performs reassembly if necessary 732 then removes the ORH if present while decrementing Payload Length to 733 reflect the removal of the ORH. If the OAL header is present, the 734 OAL next verifies the checksum and discards the packet if the 735 checksum is incorrect. If the packet was accepted, the OAL then 736 removes the OAL header/trailer, then delivers the original packet to 737 the IP layer. Note that link layers include a CRC-32 integrity check 738 which provides effective hop-by-hop error detection in the underlying 739 network for packet/fragment sizes up to the OMNI interface MTU [CRC], 740 but that some hops may traverse intermediate layers such as tunnels 741 over IPv4 that do not include integrity checks. The OAL source 742 therefore includes a trailing Fletcher checksum to allow the OAL 743 destination to detect packet splicing errors for fragmented OAL 744 packets and/or to verify integrity for packets that may have 745 traversed unprotected underlying network hops [CKSUM]. The Fletcher 746 checksum also provides diversity with respect to both lower layer 747 CRCs and upper layer Internet checksums as part of a complimentary 748 multi-layer integrity assurance architecture. 750 The OMNI interface assumes the IPv4 minimum path MTU (i.e., 576 751 bytes) as the worst case for OAL fragmentation regardless of the 752 underlying interface IP protocol version since IPv6/IPv4 protocol 753 translation and/or IPv6-in-IPv4 encapsulation may occur in any *NET 754 path. By always assuming the IPv4 minimum even for IPv6 underlying 755 interfaces, the OAL may produce smaller fragments with additional 756 encapsulation overhead but will always interoperate and never run the 757 risk of loss due to an MTU restriction or due to presenting a 758 destination interface with a packet that exceeds its MRU. 759 Additionally, the OAL path could traverse multiple *NET "segments" 760 with intermediate OAL forwarding nodes performing re-encapsulation 761 where the *NET encapsulation of the previous segment is replaced by 762 the *NET encapsulation of the next segment which may be based on a 763 different IP protocol version and/or encapsulation sizes. 765 The OAL therefore assumes a default minimum path MTU of 576 bytes at 766 each *NET segment for the purpose of generating OAL fragments. In 767 the worst case, each successive *NET segment may re-encapsulate with 768 either a 20 byte IPv4 or 40 byte IPv6 header, an 8 byte UDP header 769 and in some cases an IP security encapsulation (40 bytes maximum 770 assumed). Any *NET segment may also insert a maximum-length (40 771 byte) ORH as an extension to the existing 40 byte OAL IPv6 header 772 plus 8 byte Fragment Header if an ORH was not already present. 773 Assuming therefore an absolute worst case of (40 + 40 + 8) = 88 bytes 774 for *NET encapsulation plus (40 + 40 + 8) = 88 bytes for OAL 775 encapsulation leaves (576 - 88 - 88) = 400 bytes to accommodate a 776 portion of the original IP packet/fragment. OMNI interfaces 777 therefore set a minimum Maximum Payload Size (MPS) of 400 bytes as 778 the basis for the minimum-sized OAL fragment that can be assured of 779 traversing all segments without loss due to an MTU/MRU restriction. 780 The OAL fragmentation Maximum Fragment Size (MFS) is therefore 781 determined by the MPS plus the size of the OAL encapsulation headers. 782 (Note that the OAL source must include the 2 octet trailer as part of 783 the payload during fragmentation, and the OAL destination must regard 784 it as ordinary payload until reassembly and checksum verification are 785 complete.) 787 In light of the above, OAL source, intermediate and destination nodes 788 observe the following normative requirements: 790 o OAL sources MUST NOT send OAL packets/fragments including original 791 IP packets larger than the OMNI interface MTU, i.e., whether or 792 not fragmentation is needed. 794 o OAL sources MUST NOT perform OAL fragmentation for original IP 795 packets smaller than the minimum MPS minus the trailer size, and 796 MUST produce non-final fragments that contain a payload no smaller 797 than the minimum MPS when performing fragmentation. 799 o OAL sources MUST NOT send OAL packets/fragments that include any 800 extension headers other than a single ORH and a single Fragment 801 Header. 803 o OAL intermediate nodes SHOULD and OAL destinations MUST 804 unconditionally drop OAL packets/fragments including original IP 805 packets larger than the OMNI interface MRU, i.e., whether or not 806 reassembly is needed. 808 o OAL intermediate nodes SHOULD and OAL destinations MUST 809 unconditionally drop any non-final OAL fragments containing a 810 payload smaller than the minimum MPS. 812 o OAL intermediate nodes SHOULD and OAL destinations MUST 813 unconditionally drop OAL packets/fragments that include any 814 extension headers other than a single ORH and a single Fragment 815 Header. 817 The OAL source MAY maintain "path MPS" values for selected OAL 818 destinations initialized to the minimum MPS and increased to larger 819 values (up to the OMNI interface MTU) if better information is known 820 or discovered. For example, when *NET peers share a common 821 underlying link or a fixed path with a known larger MTU, the OAL can 822 base path MPS on this larger size (i.e., instead of 576 bytes) as 823 long as the *NET peer reassembles before re-encapsulating and 824 forwarding (while re-fragmenting if necessary). Also, if the OAL 825 source has a way of knowing the maximum *NET encapsulation size for 826 all segments along the path it may be able to increase path MPS to 827 reserve additional room for payload data. 829 The OAL source can also actively probe OAL destinations to discover 830 larger path MPS values (e.g., per [RFC4821][RFC8899]), but care must 831 be taken to avoid setting static values for dynamically changing 832 paths leading to black holes. The probe involves sending an OAL 833 packet larger than the current path MPS and receiving a small 834 acknowledgement message in response. For this purpose, the OAL 835 source can send a large NS message with OMNI options with PadN sub- 836 options (see: Section 11) in order to receive a small NA response 837 from the OAL destination. While observing the minimum MPS will 838 always result in robust and secure behavior, the OAL should optimize 839 path MPS values when more efficient utilization may result in better 840 performance (e.g. for wireless aviation data links). 842 Under the minimum MPS, a common 1500 byte inner IP packet would 843 require 4 OAL fragments, with each non-final fragment containing 400 844 payload bytes and the final fragment containing 302 payload bytes 845 (i.e., the final 300 bytes of the original IP packet plus the 2 octet 846 trailer). For all packet sizes, the likelihood of successful 847 reassembly may improve when the OMNI interface sends all fragments of 848 the same fragmented OAL packet consecutively over the same underlying 849 interface; the OMNI interface can also impose an inter-fragment delay 850 and either increase the delay if loss is detected or decrease the 851 delay to improve performance when there is little/no loss. Finally, 852 an assured minimum/path MPS allows continuous operation over all 853 paths including those that traverse bridged L2 media with dissimilar 854 MTUs. 856 5.3. OAL Addressing Considerations 858 The OMNI interface performs OAL encapsulation and selects source and 859 destination addresses for the OAL IPv6 header according to the node's 860 *NET orientation. The OMNI interface sets the OAL IPv6 header 861 addresses to Unique Local Addresses (ULAs) based on either 862 Administrative (ADM-ULA) or Mobile Network Prefix (MNP-ULA) values 863 (see: Section 8). When an ADM-ULA or MNP-ULA is not available, the 864 OMNI interface can use Temporary ULAs and/or Host Identity Tags 865 (HITs) instead (see: Section 21). The following sections discuss the 866 addressing considerations for OMNI Interfaces configured over *NET 867 interfaces. 869 When an OMNI interface sends an original IP packet toward a final 870 destination via an ANET interface, it sends without OAL encapsulation 871 if the packet (including any outer-layer ANET encapsulations) is no 872 larger than the underlying interface MTU for on-link ANET peers or 873 the minimum ANET path MTU for peers separated by multiple IP hops. 874 Otherwise, the OAL inserts an IPv6 header per [RFC2473] with source 875 address set to the node's own ULA and destination set to either the 876 Administrative ULA (ADM-ULA) of the ANET peer or the Mobile Network 877 Prefix ULA (MNP-ULA) corresponding to the final destination (see 878 below). The OAL then fragments if necessary, encapsulates the OAL 879 packet/fragments in any ANET headers and sends them to the ANET peer 880 which either reassembles before forwarding if the OAL destination is 881 its own ULA or forwards the fragments toward the final destination 882 without first reassembling otherwise. 884 When an OMNI interface sends an original IP packet toward a final 885 destination via an INET interface, it sends packets (including any 886 outer-layer INET encapsulations) no larger than the minimum INET path 887 MTU without OAL encapsulation if the destination is reached via an 888 INET address within the same OMNI link segment. Otherwise, the OAL 889 inserts an IPv6 header per [RFC2473] with source address set to the 890 node's ULA and destination set to the ULA of an OMNI node on the 891 final *NET segment. The OAL then fragments if necessary, 892 encapsulates the OAL packet/fragments in any INET headers and sends 893 them toward the final segment OMNI node, which reassembles before 894 forwarding toward the final destination. 896 5.4. OMNI Interface MTU Feedback Messaging 898 When the OMNI interface admits original IP packets, it invokes the 899 OAL and returns internally-generated ICMPv4 Fragmentation Needed 900 [RFC1191] or ICMPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) 901 [RFC8201] messages as necessary. This document refers to both of 902 these ICMPv4/ICMPv6 message types simply as "PTBs", and introduces a 903 distinction between PTB "hard" and "soft" errors as discussed below. 905 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 906 header Code field value 0 are hard errors that always indicate that a 907 packet has been dropped due to a real MTU restriction. However, the 908 OMNI interface can also forward large original IP packets via OAL 909 encapsulation and fragmentation while at the same time returning PTB 910 soft error messages (subject to rate limiting) if it deems the 911 original IP packet too large according to factors such as link 912 performance characteristics, reassembly congestion, etc. This 913 ensures that the path MTU is adaptive and reflects the current path 914 used for a given data flow. The OMNI interface can therefore 915 continuously forward packets without loss while returning PTB soft 916 error messages recommending a smaller size if necessary. Original 917 sources that receive the soft errors in turn reduce the size of the 918 packets they send, i.e., the same as for hard errors. 920 The OMNI interface sets the ICMPv4 header "unused" field or ICMPv6 921 header Code field to the value 1 in PTB soft error messages. The 922 OMNI interface sets the PTB destination address to the source address 923 of the original packet, and sets the source address to the MNP Subnet 924 Router Anycast address of the MN. The OMNI interface then sets the 925 MTU field to a value no smaller than 576 for ICMPv4 or 1280 for 926 ICMPv6, and returns the PTB soft error to the original source. 928 When the original source receives the PTB, it reduces its path MTU 929 estimate the same as for hard errors but does not regard the message 930 as a loss indication. (If the original source does not recognize the 931 soft error code, it regards the PTB the same as a hard error but 932 should heed the retransmission advice given in [RFC8201] suggesting 933 retransmission based on normal packetization layer retransmission 934 timers.) This document therefore updates [RFC1191][RFC4443] and 935 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 936 that PTB hard or soft errors may arrive at any time even if after a 937 successful MTU probe (this is the same consideration as for an 938 ordinary path fluctuation following a successful probe). 940 An OMNI interface that reassembles OAL fragments may experience 941 congestion-oriented loss in its reassembly cache and can optionally 942 send PTB soft errors to the original source and/or ICMP "Time 943 Exceeded" messages to the source of the OAL fragments. In 944 environments where the messages may contribute to unacceptable 945 additional congestion, however, the OMNI interface can refrain from 946 sending PTB soft errors and simply regard the loss as an ordinary 947 unreported congestion event for which the original source will 948 eventually compensate. 950 Applications that receive PT soft errors can dynamically tune the 951 size of the packets they to send to produce the best possible 952 throughput and latency, with the understanding that these parameters 953 may change over time due to factors such as congestion, mobility, 954 network path changes, etc. The receipt or absence of soft errors 955 should be seen as hints of when increasing or decreasing packet sizes 956 may be beneficial. 958 In summary, the OMNI interface supports continuous transmission and 959 reception of packets of various sizes in the face of dynamically 960 changing network conditions. Moreover, since PTB soft errors do not 961 indicate loss, original sources that receive soft errors can quickly 962 scan for path MTU increases without waiting for the minimum 10 963 minutes specified for loss-oriented PTB hard errors 964 [RFC1191][RFC8201]. The OMNI interface therefore provides a lossless 965 and adaptive service that accommodates MTU diversity especially well- 966 suited for dynamic multilink environments. 968 5.5. OAL Fragmentation Security Implications 970 As discussed in Section 3.7 of [RFC8900], there are four basic 971 threats concerning IPv6 fragmentation; each of which is addressed by 972 effective mitigations as follows: 974 1. Overlapping fragment attacks - reassembly of overlapping 975 fragments is forbidden by [RFC8200]; therefore, this threat does 976 not apply to the OAL. 978 2. Resource exhaustion attacks - this threat is mitigated by 979 providing a sufficiently large OAL reassembly cache and 980 instituting "fast discard" of incomplete reassemblies that may be 981 part of a buffer exhaustion attack. The reassembly cache should 982 be sufficiently large so that a sustained attack does not cause 983 excessive loss of good reassemblies but not so large that (timer- 984 based) data structure management becomes computationally 985 expensive. The cache should also be indexed based on the arrival 986 underlying interface such that congestion experienced over a 987 first underlying interface does not cause discard of incomplete 988 reassemblies for uncongested underlying interfaces. 990 3. Attacks based on predictable fragment identification values - 991 this threat is mitigated by selecting a suitably random ID value 992 per [RFC7739]. Additionally, inclusion of the trailing Fletcher 993 checksum would make it very difficult for an attacker who could 994 somehow predict a fragment identification value to inject 995 malicious fragments resulting in undetected reassemblies of bad 996 data. 998 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 999 threat is mitigated by setting a minimum MPS for OAL 1000 fragmentation, which defeats all "tiny fragment"-based attacks. 1002 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 1003 ID) field with only 65535 unique values such that at high data rates 1004 the field could wrap and apply to new packets while the fragments of 1005 old packets using the same ID are still alive in the network 1006 [RFC4963]. However, since the largest OAL fragment that will be sent 1007 via an IPv4 *NET path with DF = 0 is 576 bytes any IPv4 fragmentation 1008 would occur only on links with an IPv4 MTU smaller than this size, 1009 and [RFC3819] recommendations suggest that such links will have low 1010 data rates. Since IPv6 provides a 32-bit Identification value, IP ID 1011 wraparound at high data rates is not a concern for IPv6 1012 fragmentation. 1014 Finally, [RFC6980] documents fragmentation security concerns for 1015 large IPv6 ND messages. These concerns are addressed when the OMNI 1016 interface employs the OAL instead of directly fragmenting the IPv6 ND 1017 message itself. For this reason, OMNI interfaces MUST NOT admit IPv6 1018 ND messages larger than the OMNI interface MTU, and MUST employ the 1019 OAL for IPv6 ND messages admitted into the OMNI interface the same as 1020 discussed above. 1022 5.6. OAL Super-Packets 1024 By default, the OAL source includes a 40-byte IPv6 encapsulation 1025 header for each original IP packet during OAL encapsulation. The OAL 1026 source also calculates and appends a 2 octet trailing Fletcher 1027 checksum then performs fragmentation such that a copy of the 40-byte 1028 IPv6 header plus an 8-byte IPv6 Fragment Header is included in each 1029 OAL fragment (when an ORH is added, the OAL encapsulation headers 1030 become larger still). However, these encapsulations may represent 1031 excessive overhead in some environments. A technique known as 1032 "packing" discussed in [I-D.ietf-intarea-tunnels] is therefore 1033 supported so that multiple original IP packets can be included within 1034 a single OAL "super-packet". 1036 When the OAL source has multiple original IP packets with total 1037 length no larger than the OMNI interface MTU to send to the same 1038 destination, it can concatenate them into a super-packet encapsulated 1039 in a single OAL header and trailing checksum. Within the OAL super- 1040 packet, the IP header of the first original packet (iHa) followed by 1041 its data (iDa) is concatenated immediately following the OAL header, 1042 then the IP header of the next original packet (iHb) followed by its 1043 data (iDb) is concatenated immediately following the first original 1044 packet, etc. with the trailing checksum included last. The OAL 1045 super-packet format is transposed from [I-D.ietf-intarea-tunnels] and 1046 shown in Figure 4: 1048 <------- Original IP packets -------> 1049 +-----+-----+ 1050 | iHa | iDa | 1051 +-----+-----+ 1052 | 1053 | +-----+-----+ 1054 | | iHb | iDb | 1055 | +-----+-----+ 1056 | | 1057 | | +-----+-----+ 1058 | | | iHc | iDc | 1059 | | +-----+-----+ 1060 | | | 1061 v v v 1062 +----------+-----+-----+-----+-----+-----+-----+----+ 1063 | OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc |Csum| 1064 +----------+-----+-----+-----+-----+-----+-----+----+ 1065 <--- OAL "Super-Packet" with single OAL Hdr/Csum ---> 1067 Figure 4: OAL Super-Packet Format 1069 When the OAL source prepares a super-packet, it applies OAL 1070 fragmentation if necessary then sends the packet or fragments to the 1071 OAL destination. When the OAL destination receives the super-packet 1072 it reassembles if necessary, verifies and removes the trailing 1073 checksum, then regards the remaining OAL header Payload Length as the 1074 sum of the lengths of all payload packets. The OAL destination then 1075 selectively extracts each original IP packet (e.g., by setting 1076 pointers into the super-packet buffer and maintaining a reference 1077 count, by copying each packet into a separate buffer, etc.) and 1078 forwards each packet or processes it locally as appropriate. During 1079 extraction, the OAL determines the IP protocol version of each 1080 successive original IP packet 'j' by examining the four most- 1081 significant bits of iH(j), and determines the length of the packet by 1082 examining the rest of iH(j) according to the IP protocol version. 1084 Note that OMNI interfaces must take care to avoid processing super- 1085 packet payload elements that would subvert security. Specifically, 1086 if a super-packet contains a mix of data and control payload packets 1087 (which could include critical security codes), the node MUST NOT 1088 process the data packets before processing the control packets 1090 6. Frame Format 1092 The OMNI interface transmits original IP packets by first invoking 1093 the OAL, next including any *NET encapsulations and finally engaging 1094 the native frame format of the underlying interface. For example, 1095 for Ethernet-compatible interfaces the frame format is specified in 1096 [RFC2464], for aeronautical radio interfaces the frame format is 1097 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 1098 Manual), for various forms of tunnels the frame format is found in 1099 the appropriate tunneling specification, etc. 1101 The OMNI interface SHOULD minimize the amount of *NET encapsulation 1102 for increased efficiency. For example, while an OMNI node may need 1103 to use UDP/IP as a *NET encapsulation over underlying interfaces 1104 connected to an open Internetwork, it may be able to omit the UDP 1105 header over underlying interfaces connected to *NETs that do not 1106 include NATs or packet filtering gateways. Similarly, when an OMNI 1107 MN shares a common underlying link with an AR, the MN may be able to 1108 avoid including any *NET encapsulations and instead directly engage 1109 the underlying interface native frame format. Further considerations 1110 for *NET encapsulation are discussed throughout the document and in 1111 [I-D.templin-intarea-6706bis]. 1113 7. Link-Local Addresses (LLAs) 1115 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 1116 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 1117 the MNP assigned to the mobile node, while "ADM-LLAs" include an 1118 administratively-unique ID that is guaranteed to be unique on the 1119 link. LLAs are configured as follows: 1121 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 1122 the least-significant 64 bits of the IPv6 link-local prefix 1123 fe80::/64, i.e., in the LLA "interface identifier" portion. The 1124 prefix length for the LLA is determined by adding 64 to the MNP 1125 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 1126 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 1128 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 1129 i.e., the interface identifier consists of 16 '0' bits, followed 1130 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 1131 prefix length for the LLA is determined by adding 96 to the MNP 1132 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 1133 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 1134 fe80::ffff:c000:0200/120). 1136 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 1137 uniqueness. The lower 32 bits of the LLA includes a unique 1138 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 1139 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 1140 prefix length is determined by adding 96 to the MSID prefix 1141 length. For example, if the prefix length for MSID 0x10012001 is 1142 16 then the ADM-LLA prefix length is set to 112 and the LLA is 1143 written as fe80::1001:2001/112. The "zero" address for each ADM- 1144 LLA prefix is the Subnet-Router anycast address for that prefix 1145 [RFC4291]; for example, the Subnet-Router anycast address for 1146 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 1147 0xff000000 through 0xffffffff is reserved for future use. 1149 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 1150 MNPs can be allocated from that block ensuring that there is no 1151 possibility for overlap between the different MNP- and ADM-LLA 1152 constructs discussed above. 1154 Since MNP-LLAs are based on the distribution of administratively 1155 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 1156 administrative assignment, OMNI interfaces set the autoconfiguration 1157 variable DupAddrDetectTransmits to 0 [RFC4862]. 1159 Note: If future protocol extensions relax the 64-bit boundary in IPv6 1160 addressing, the additional prefix bits of an MNP could be encoded in 1161 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 1162 would therefore still be in bits 64-127, and the remaining bits would 1163 appear in bits 16 through 48.) However, the analysis provided in 1164 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 1165 architecture for the foreseeable future. 1167 Note: Even though this document honors the 64-bit boundary in IPv6 1168 addressing, it specifies prefix lengths longer than /64 for routing 1169 purposes. This effectively extends IPv6 routing determination into 1170 the interface identifier portion of the IPv6 address, but it does not 1171 redefine the 64-bit boundary. Modern routing protocol 1172 implementations honor IPv6 prefixes of all lengths, up to and 1173 including /128. 1175 8. Unique-Local Addresses (ULAs) 1177 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 1178 destination addresses in OAL IPv6 encapsulation headers. ULAs are 1179 only routable within the scope of a an OMNI domain, and are derived 1180 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 1181 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 1182 Global ID to produce the prefix [ULA]::/48, which is then followed by 1183 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 1184 specified in Section 3 of [RFC4193]. All nodes in the same OMNI 1185 domain configure the same 40-bit Global ID as the OMNI domain 1186 identifier. The statistic uniqueness of the 40-bit pseudo-random 1187 Global ID allows different OMNI domains to be joined together in the 1188 future without requiring renumbering. 1190 Each OMNI link instance is identified by a value between 0x0000 and 1191 0xfeff in bits 48-63 of [ULA]::/48; the values 0xff00 through 0xfffe 1192 are reserved for future use, and the value 0xffff denotes the 1193 presence of a Temporary ULA (see below). For example, OMNI ULAs 1194 associated with instance 0 are configured from the prefix 1195 [ULA]:0000::/64, instance 1 from [ULA]:0001::/64, instance 2 from 1196 [ULA]:0002::/64, etc. ULAs and their associated prefix lengths are 1197 configured in correspondence with LLAs through stateless prefix 1198 translation where "MNP-ULAs" are assigned in correspondence to MNP- 1199 LLAs and "ADM-ULAs" are assigned in correspondence to ADM-LLAs. For 1200 example, for OMNI link instance [ULA]:1010::/64: 1202 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 1203 56-bit MNP length is derived by copying the lower 64 bits of the 1204 LLA into the lower 64 bits of the ULA as 1205 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1206 64 plus the IPv6 MNP length). 1208 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1209 MNP length is derived by simply writing the LLA interface ID into 1210 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1211 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1213 o the ADM-ULA corresponding to fe80::1000/112 is simply 1214 [ULA]:1010::1000/112. 1216 o the ADM-ULA corresponding to fe80::/128 is simply 1217 [ULA]:1010::/128. 1219 o etc. 1221 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1222 link instance. For example, the OMNI interface connected to instance 1223 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1224 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1225 [ULA]:0003::/64) into the local routing system so that applications 1226 can direct traffic according to SBM requirements. 1228 The ULA presents an IPv6 address format that is routable within the 1229 OMNI routing system and can be used to convey link-scoped IPv6 ND 1230 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1231 The OMNI link extends across one or more underling Internetworks to 1232 include all ARs and MSEs. All MNs are also considered to be 1233 connected to the OMNI link, however OAL encapsulation is omitted 1234 whenever possible to conserve bandwidth (see: Section 13). 1236 Each OMNI link can be subdivided into "segments" that often 1237 correspond to different administrative domains or physical 1238 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1239 necessary to support efficient packet forwarding to destinations 1240 located in other OMNI link segments. A full discussion of Segment 1241 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1243 Temporary ULAs are constructed per [RFC8981] based on the prefix 1244 [ULA]:ffff::/64 and used by MNs when they have no other addresses. 1245 Temporary ULAs can be used for MN-to-MN communications outside the 1246 context of any supporting OMNI link infrastructure, and can also be 1247 used as an initial address while the MN is in the process of 1248 procuring an MNP. Temporary ULAs are not routable within the OMNI 1249 routing system, and are therefore useful only for OMNI link "edge" 1250 communications. Temporary ULAs employ optimistic DAD principles 1251 [RFC4429] since they are probabilistically unique. 1253 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1254 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1255 however the range could be used for MSP and MNP addressing under 1256 certain limiting conditions (see: Section 9). 1258 9. Global Unicast Addresses (GUAs) 1260 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1261 as Mobility Service Prefixes (MSPs) from which Mobile Network 1262 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1264 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1265 associated regional assigned numbers authority such that the OMNI 1266 domain can be interconnected to the global IPv6 Internet without 1267 causing inconsistencies in the routing system. An OMNI domain could 1268 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1269 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1270 were ever connected to the global IPv6 Internet. 1272 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1273 associated regional assigned numbers authority such that the OMNI 1274 domain can be interconnected to the global IPv4 Internet without 1275 causing routing inconsistencies. An OMNI domain could instead use 1276 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1277 this would require IPv4 NAT if the domain were ever connected to the 1278 global IPv4 Internet. 1280 10. Node Identification 1282 OMNI MNs and MSEs that connect over open Internetworks generate a 1283 Host Identity Tag (HIT) as specified in [RFC7401] and use the value 1284 as a robust general-purpose node identification value. Hierarchical 1285 HITs (HHITs) [I-D.ietf-drip-rid] may provide a useful alternative in 1286 certain domains such as the Unmanned (Air) Traffic Management (UTM) 1287 service for Unmanned Air Systems (UAS). MNs and MSEs can then use 1288 their (H)HITs in IPv6 ND control message exchanges. 1290 When a MN is truly outside the context of any infrastructure, it may 1291 have no MNP information at all. In that case, the MN can use its 1292 (H)HIT as an IPv6 source/destination address for sustained 1293 communications in Vehicle-to-Vehicle (V2V) and (multihop) Vehicle-to- 1294 Infrastructure (V2I) scenarios. The MN can also propagate the (H)HIT 1295 into the multihop routing tables of (collective) Mobile/Vehicular Ad- 1296 hoc Networks (MANETs/VANETs) using only the vehicles themselves as 1297 communications relays. 1299 When a MN connects to ARs over (non-multihop) protected-spectrum 1300 ANETs, an alternate form of node identification (e.g., MAC address, 1301 serial number, airframe identification value, VIN, etc.) may be 1302 sufficient. In that case, the MN should still generate a (H)HIT and 1303 maintain it in conjunction with any other node identifiers. The MN 1304 can then include OMNI "Node Identification" sub-options (see: 1305 Section 11.1.11) in IPv6 ND messages should the need to transmit 1306 identification information over the network arise. 1308 11. Address Mapping - Unicast 1310 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1311 state and use the link-local address format specified in Section 7. 1312 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1313 over physical underlying interfaces without encapsulation observe the 1314 native underlying interface Source/Target Link-Layer Address Option 1315 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1316 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1317 interfaces via encapsulation do not include S/TLLAOs which were 1318 intended for encoding physical L2 media address formats and not 1319 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1320 for encoding additional interface attributes needed for multilink 1321 coordination. Hence, this document does not define an S/TLLAO format 1322 but instead defines a new option type termed the "OMNI option" 1323 designed for these purposes. 1325 MNs such as aircraft typically have many wireless data link types 1326 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1327 etc.) with diverse performance, cost and availability properties. 1329 The OMNI interface would therefore appear to have multiple L2 1330 connections, and may include information for multiple underlying 1331 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1332 an IPv6 ND option called the OMNI option formatted as shown in 1333 Figure 5: 1335 0 1 2 3 1336 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 1337 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1338 | Type | Length | Preflen | S/T-omIndex | 1339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1340 | | 1341 ~ Sub-Options ~ 1342 | | 1343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1345 Figure 5: OMNI Option Format 1347 In this format: 1349 o Type is set to TBD1. 1351 o Length is set to the number of 8 octet blocks in the option. The 1352 value 0 is invalid, while the values 1 through 255 (i.e., 8 1353 through 2040 octets, respectively) indicate the total length of 1354 the OMNI option. 1356 o Preflen is an 8 bit field that determines the length of prefix 1357 associated with an LLA. Values 0 through 128 specify a valid 1358 prefix length (all other values are invalid). For IPv6 ND 1359 messages sent from a MN to the MS, Preflen applies to the IPv6 1360 source LLA and provides the length that the MN is requesting or 1361 asserting to the MS. For IPv6 ND messages sent from the MS to the 1362 MN, Preflen applies to the IPv6 destination LLA and indicates the 1363 length that the MS is granting to the MN. For IPv6 ND messages 1364 sent between MS endpoints, Preflen provides the length associated 1365 with the source/target MN that is subject of the ND message. 1367 o S/T-omIndex is an 8 bit field corresponds to the omIndex value for 1368 source or target underlying interface used to convey this IPv6 ND 1369 message. OMNI interfaces MUST number each distinct underlying 1370 interface with an omIndex value between '1' and '255' that 1371 represents a MN-specific 8-bit mapping for the actual ifIndex 1372 value assigned by network management [RFC2863] (the omIndex value 1373 '0' is reserved for use by the MS). For RS and NS messages, S/ 1374 T-omIndex corresponds to the source underlying interface the 1375 message originated from. For RA and NA messages, S/T-omIndex 1376 corresponds to the target underlying interface that the message is 1377 destined to. (For NS messages used for Neighbor Unreachability 1378 Detection (NUD), S/T-omIndex instead identifies the neighbor's 1379 underlying interface to be used as the target interface to return 1380 the NA.) 1382 o Sub-Options is a Variable-length field, of length such that the 1383 complete OMNI Option is an integer multiple of 8 octets long. 1384 Contains one or more Sub-Options, as described in Section 11.1. 1386 The OMNI option may appear in any IPv6 ND message type; it is 1387 processed by interfaces that recognize the option and ignored by all 1388 other interfaces. If multiple OMNI option instances appear in the 1389 same IPv6 ND message, the interface processes the Preflen and S/ 1390 T-omIndex fields in the first instance and ignores those fields in 1391 all other instances. The interface processes the Sub-Options of all 1392 OMNI option instances in the same IPv6 ND message in the consecutive 1393 order in which they appear. 1395 The OMNI option(s) in each IPv6 ND message may include full or 1396 partial information for the neighbor. The union of the information 1397 in the most recently received OMNI options is therefore retained, and 1398 the information is aged/removed in conjunction with the corresponding 1399 neighbor cache entry. 1401 11.1. Sub-Options 1403 Each OMNI option includes zero or more Sub-Options. Each consecutive 1404 Sub-Option is concatenated immediately after its predecessor. All 1405 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1406 encoded in the following format: 1408 0 1 2 1409 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 1410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1411 | Sub-Type| Sub-length | Sub-Option Data ... 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1414 Figure 6: Sub-Option Format 1416 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1417 Options defined in this document are: 1419 Sub-Option Name Sub-Type 1420 Pad1 0 1421 PadN 1 1422 Interface Attributes (Type 1) 2 1423 Interface Attributes (Type 2) 3 1424 Traffic Selector 4 1425 MS-Register 5 1426 MS-Release 6 1427 Geo Coordinates 7 1428 DHCPv6 Message 8 1429 HIP Message 9 1430 Node Identification 10 1431 Sub-Type Extension 30 1433 Figure 7 1435 Sub-Types 11-29 are available for future assignment for major 1436 protocol functions. Sub-Type 31 is reserved by IANA. 1438 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1439 Option Data ranging from 0 to 2034 octets. 1441 o Sub-Option Data is a block of data with format determined by Sub- 1442 Type and length determined by Sub-Length. 1444 During transmission, the OMNI interface codes Sub-Type and Sub-Length 1445 together in network byte order in 2 consecutive octets, where Sub- 1446 Option Data may be up to 2034 octets in length. This allows ample 1447 space for coding large objects (e.g., ASCII strings, domain names, 1448 protocol messages, security codes, etc.), while a single OMNI option 1449 is limited to 2040 octets the same as for any IPv6 ND option. If the 1450 Sub-Options to be coded would cause an OMNI option to exceed 2040 1451 octets, the OMNI interface codes any remaining Sub-Options in 1452 additional OMNI option instances in the intended order of processing 1453 in the same IPv6 ND message. Implementations must therefore observe 1454 size limitations, and must refrain from sending IPv6 ND messages 1455 larger than the OMNI interface MTU. If the available OMNI 1456 information would cause a single IPv6 ND message to exceed the OMNI 1457 interface MTU, the OMNI interface codes as much as possible in a 1458 first IPv6 ND message and codes the remainder in additional IPv6 ND 1459 messages. 1461 During reception, the OMNI interface processes each OMNI option Sub- 1462 Option while skipping over and ignoring any unrecognized Sub-Options. 1463 The OMNI interface processes the Sub-Options of all OMNI option 1464 instances in the consecutive order in which they appear in the IPv6 1465 ND message, beginning with the first instance and continuing through 1466 any additional instances to the end of the message. If a Sub-Option 1467 length would cause processing to exceed the OMNI option total length, 1468 the OMNI interface accepts any Sub-Options already processed and 1469 ignores the final Sub-Option. The interface then processes any 1470 remaining OMNI options in the same fashion to the end of the IPv6 ND 1471 message. 1473 Note: large objects that exceed the Sub-Option Data limit of 2034 1474 octets are not supported under the current specification; if this 1475 proves to be limiting in practice, future specifications may define 1476 support for fragmenting large objects across multiple OMNI options 1477 within the same IPv6 ND message. 1479 The following Sub-Option types and formats are defined in this 1480 document: 1482 11.1.1. Pad1 1484 0 1485 0 1 2 3 4 5 6 7 1486 +-+-+-+-+-+-+-+-+ 1487 | S-Type=0|x|x|x| 1488 +-+-+-+-+-+-+-+-+ 1490 Figure 8: Pad1 1492 o Sub-Type is set to 0. If multiple instances appear in OMNI 1493 options of the same message all are processed. 1495 o Sub-Type is followed by 3 'x' bits, set to any value on 1496 transmission (typically all-zeros) and ignored on receipt. Pad1 1497 therefore consists of 1 octet with the most significant 5 bits set 1498 to 0, and with no Sub-Length or Sub-Option Data fields following. 1500 11.1.2. PadN 1502 0 1 2 1503 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 1504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1505 | S-Type=1| Sub-length=N | N padding octets ... 1506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1508 Figure 9: PadN 1510 o Sub-Type is set to 1. If multiple instances appear in OMNI 1511 options of the same message all are processed. 1513 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1514 padding octets that follow. 1516 o Sub-Option Data consists of N octets, set to any value on 1517 transmission (typically all-zeros) and ignored on receipt. 1519 11.1.3. Interface Attributes (Type 1) 1521 The Interface Attributes (Type 1) sub-option provides a basic set of 1522 attributes for underlying interfaces. Interface Attributes (Type 1) 1523 is deprecated throughout the rest of this specification, and 1524 Interface Attributes (Type 2) (see: Section 11.1.4) are indicated 1525 wherever the term "Interface Attributes" appears without an 1526 associated Type designation. 1528 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1529 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1530 they receive. If an Interface Attributes (Type 1) is included, it 1531 must have the following format: 1533 0 1 2 3 1534 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 1535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1536 | Sub-Type=2| Sub-length=N | omIndex | omType | 1537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1538 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1540 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1542 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1544 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1546 |P56|P57|P58|P59|P60|P61|P62|P63| 1547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1549 Figure 10: Interface Attributes (Type 1) 1551 o Sub-Type is set to 2. If multiple instances with different 1552 omIndex values appear in OMNI option of the same message all are 1553 processed; if multiple instances with the same omIndex value 1554 appear, the first is processed and all others are ignored 1556 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1557 Sub-Option Data octets that follow. 1559 o omIndex is a 1-octet field containing a value from 0 to 255 1560 identifying the underlying interface for which the attributes 1561 apply. 1563 o omType is a 1-octet field containing a value from 0 to 255 1564 corresponding to the underlying interface identified by omIndex. 1566 o Provider ID is a 1-octet field containing a value from 0 to 255 1567 corresponding to the underlying interface identified by omIndex. 1569 o Link encodes a 4-bit link metric. The value '0' means the link is 1570 DOWN, and the remaining values mean the link is UP with metric 1571 ranging from '1' ("lowest") to '15' ("highest"). 1573 o Resvd is reserved for future use. Set to 0 on transmission and 1574 ignored on reception. 1576 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1577 values P[00] through P[63] corresponding to the 64 Differentiated 1578 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1579 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1580 or '3' ("high") to indicate a QoS preference for underlying 1581 interface selection purposes. 1583 11.1.4. Interface Attributes (Type 2) 1585 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1586 information for the multilink conceptual sending algorithm discussed 1587 in Section 13. The L2 information is used for selecting among 1588 potentially multiple candidate underlying interfaces that can be used 1589 to forward packets to the neighbor based on factors such as DSCP 1590 preferences and link quality. Interface Attributes (Type 2) further 1591 includes link-layer address information to be used for either OAL 1592 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1593 can be avoided). 1595 Interface Attributes (Type 2) are the sole Interface Attributes 1596 format in this specification that all OMNI nodes must honor. 1597 Wherever the term "Interface Attributes" occurs throughout this 1598 specification without a "Type" designation, the format given below is 1599 indicated: 1601 0 1 2 3 1602 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 1603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 | S-Type=3| Sub-length=N | omIndex | omType | 1605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1606 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1608 | LHS (bits 8 - 31) | ~ 1609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1610 ~ ~ 1611 ~ Link Layer Address (L2ADDR) ~ 1612 ~ ~ 1613 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1614 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1616 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1618 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1621 Figure 11: Interface Attributes (Type 2) 1623 o Sub-Type is set to 3. If multiple instances with different 1624 omIndex values appear in OMNI options of the same message all are 1625 processed; if multiple instances with the same omIndex value 1626 appear, the first is processed and all others are ignored. 1628 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1629 Sub-Option Data octets that follow. The 'omIndex', 'omType', 1630 'Provider ID', 'Link', 'R' and 'API' fields are always present; 1631 hence, the remainder of the Sub-Option Data is limited to 2030 1632 octets. 1634 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1635 encoded as follows: 1637 * omIndex is set to an 8-bit integer value corresponding to a 1638 specific underlying interface the same as specified above for 1639 the OMNI option S/T-omIndex field. The OMNI options of a same 1640 message may include multiple Interface Attributes Sub-Options, 1641 with each distinct omIndex value pertaining to a different 1642 underlying interface. The OMNI option will often include an 1643 Interface Attributes Sub-Option with the same omIndex value 1644 that appears in the S/T-omIndex. In that case, the actual 1645 encapsulation address of the received IPv6 ND message should be 1646 compared with the L2ADDR encoded in the Sub-Option (see below); 1647 if the addresses are different (or, if L2ADDR is absent) the 1648 presence of a NAT is assumed. 1650 * omType is set to an 8-bit integer value corresponding to the 1651 underlying interface identified by omIndex. The value 1652 represents an OMNI interface-specific 8-bit mapping for the 1653 actual IANA ifType value registered in the 'IANAifType-MIB' 1654 registry [http://www.iana.org]. 1656 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1657 for the network service provider associated with this omIndex. 1659 * Link encodes a 4-bit link metric. The value '0' means the link 1660 is DOWN, and the remaining values mean the link is UP with 1661 metric ranging from '1' ("lowest") to '15' ("highest"). 1663 * R is reserved for future use. 1665 * API - a 3-bit "Address/Preferences/Indexed" code that 1666 determines the contents of the remainder of the sub-option as 1667 follows: 1669 + When the most significant bit (i.e., "Address") is set to 1, 1670 the SRT, FMT, LHS and L2ADDR fields are included immediately 1671 following the API code; else, they are omitted. 1673 + When the next most significant bit (i.e., "Preferences") is 1674 set to 1, a preferences block is included next; else, it is 1675 omitted. (Note that if "Address" is set the preferences 1676 block immediately follows L2ADDR; else, it immediately 1677 follows the API code.) 1679 + When a preferences block is present and the least 1680 significant bit (i.e., "Indexed") is set to 0, the block is 1681 encoded in "Simplex" form as shown in Figure 10; else it is 1682 encoded in "Indexed" form as discussed below. 1684 * When API indicates that an "Address" is included, the following 1685 fields appear in consecutive order (else, they are omitted): 1687 + SRT - a 5-bit Segment Routing Topology prefix length value 1688 that (when added to 96) determines the prefix length to 1689 apply to the ULA formed from concatenating [ULA*]::/96 with 1690 the 32 bit LHS MSID value that follows. For example, the 1691 value 16 corresponds to the prefix length 112. 1693 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1694 the included Link Layer Address as follows: 1696 - When the most significant bit (i.e., "Framework") is set 1697 to 1, L2ADDR is the INET encapsulation address for the 1698 Source/Target Client itself; otherwise L2ADDR is the 1699 address of the Server/Proxy named in the LHS. 1701 - When the next most significant bit (i.e., "Mode") is set 1702 to 1, the Framework node is (likely) located behind an 1703 INET Network Address Translator (NAT); otherwise, it is 1704 on the open INET. 1706 - When the least significant bit (i.e., "Type") is set to 1707 0, L2ADDR includes a UDP Port Number followed by an IPv4 1708 address; otherwise, it includes a UDP Port Number 1709 followed by an IPv6 address. 1711 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1712 path to the target. When SRT and LHS are both set to 0, the 1713 LHS is considered unspecified in this IPv6 ND message. When 1714 SRT is set to 0 and LHS is non-zero, the prefix length is 1715 set to 128. SRT and LHS together provide guidance to the 1716 OMNI interface forwarding algorithm. Specifically, if SRT/ 1717 LHS is located in the local OMNI link segment then the OMNI 1718 interface can encapsulate according to FMT/L2ADDR (following 1719 any necessary NAT traversal messaging); else, it must 1720 forward according to the OMNI link spanning tree. See 1721 [I-D.templin-intarea-6706bis] for further discussion. 1723 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1724 and identifies the link-layer address (i.e., the 1725 encapsulation address) of the source/target. The UDP Port 1726 Number appears in the first 2 octets and the IP address 1727 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1728 The Port Number and IP address are recorded in network byte 1729 order, and in ones-compliment "obfuscated" form per 1730 [RFC4380]. The OMNI interface forwarding algorithm uses 1731 FMT/L2ADDR to determine the encapsulation address for 1732 forwarding when SRT/LHS is located in the local OMNI link 1733 segment. Note that if the target is behind a NAT, L2ADDR 1734 will contain the mapped INET address stored in the NAT; 1735 otherwise, L2ADDR will contain the native INET information 1736 of the target itself. 1738 * When API indicates that "Preferences" are included, a 1739 preferences block appears as the remainder of the Sub-Option as 1740 a series of Bitmaps and P[*] values. In "Simplex" form, the 1741 index for each singleton Bitmap octet is inferred from its 1742 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 11. 1743 In "Indexed" form, each Bitmap is preceded by an Index octet 1744 that encodes a value "i" = (0 - 255) as the index for its 1745 companion Bitmap as follows: 1747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1748 | Index=i | Bitmap(i) |P[*] values ... 1749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1751 Figure 12 1753 * The preferences consist of a first (simplex/indexed) Bitmap 1754 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1755 2-bit P[*] values, followed by a second Bitmap (i), followed by 1756 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1757 the bits of each Bitmap(i) that are set to '1'' indicate the 1758 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1759 that follow; if any Bitmap(i) bits are '0', then the 1760 corresponding P[*] block is instead omitted. For example, if 1761 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1762 followed by the block with P[04]-P[07], etc., and ending with 1763 the block with P[28]-P[31] are included (as shown in 1764 Figure 10). The next Bitmap(i) is then consulted with its bits 1765 indicating which P[*] blocks follow, etc. out to the end of the 1766 Sub-Option. 1768 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1769 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1770 preference for underlying interface selection purposes. Not 1771 all P[*] values need to be included in the OMNI option of each 1772 IPv6 ND message received. Any P[*] values represented in an 1773 earlier OMNI option but omitted in the current OMNI option 1774 remain unchanged. Any P[*] values not yet represented in any 1775 OMNI option default to "medium". 1777 * The first 16 P[*] blocks correspond to the 64 Differentiated 1778 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1779 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1780 traffic classifier values P[64], P[65], P[66], etc. See 1781 Appendix A for further discussion and examples. 1783 11.1.5. Traffic Selector 1784 0 1 2 3 1785 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 1786 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1787 | S-Type=4| Sub-length=N | omIndex | ~ 1788 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1789 ~ ~ 1790 ~ RFC 6088 Format Traffic Selector ~ 1791 ~ ~ 1792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1794 Figure 13: Traffic Selector 1796 o Sub-Type is set to 4. If multiple instances appear in OMNI 1797 options of the same message all are processed, i.e., even if the 1798 same omIndex value appears multiple times. 1800 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1801 Sub-Option Data octets that follow. 1803 o Sub-Option Data contains a 1 octet omIndex encoded exactly as 1804 specified in Section 11.1.3, followed by an N-1 octet traffic 1805 selector formatted per [RFC6088] beginning with the "TS Format" 1806 field. The largest traffic selector for a given omIndex is 1807 therefore 2033 octets. 1809 11.1.6. MS-Register 1811 0 1 2 3 1812 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 1813 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1814 | S-Type=5| Sub-length=4n | MSID[1] (bits 0 - 15) | 1815 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1816 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1817 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1818 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1820 ... ... ... ... ... ... 1821 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1822 | MSID [n] (bits 16 - 32) | 1823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1825 Figure 14: MS-Register Sub-option 1827 o Sub-Type is set to 5. If multiple instances appear in OMNI 1828 options of the same message all are processed. Only the first 1829 MAX_MSID values processed (whether in a single instance or 1830 multiple) are retained and all other MSIDs are ignored. 1832 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1833 length of the Sub-Option Data section is therefore limited to 2032 1834 octets. 1836 o A list of n 4 octet MSIDs is included in the following 4n octets. 1837 The Anycast MSID value '0' in an RS message MS-Register sub-option 1838 requests the recipient to return the MSID of a nearby MSE in a 1839 corresponding RA response. 1841 11.1.7. MS-Release 1843 0 1 2 3 1844 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 1845 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1846 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1847 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1848 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1849 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1850 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1851 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1852 ... ... ... ... ... ... 1853 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1854 | MSID [n] (bits 16 - 32) | 1855 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1857 Figure 15: MS-Release Sub-option 1859 o Sub-Type is set to 6. If multiple instances appear in OMNI 1860 options of the same message all are processed. Only the first 1861 MAX_MSID values processed (whether in a single instance or 1862 multiple) are retained and all other MSIDs are ignored. 1864 o Sub-Length is set to 4n, with 508 as the maximum value for n. The 1865 length of the Sub-Option Data section is therefore limited to 2032 1866 octets. 1868 o A list of n 4 octet MSIDs is included in the following 4n octets. 1869 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1870 i.e., only non-zero values are processed. 1872 11.1.8. Geo Coordinates 1873 0 1 2 3 1874 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 1875 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1876 | S-Type=7| Sub-length=N | Geo Coordinates 1877 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1879 Figure 16: Geo Coordinates Sub-option 1881 o Sub-Type is set to 7. If multiple instances appear in OMNI 1882 options of the same message the first is processed and all others 1883 are ignored. 1885 o Sub-Length is set to N (from 0 to 2034) that encodes the number of 1886 Sub-Option Data octets that follow. 1888 o A set of Geo Coordinates of maximum length 2034 octets. Format(s) 1889 to be specified in future documents; should include Latitude/ 1890 Longitude, plus any additional attributes such as altitude, 1891 heading, speed, etc. 1893 11.1.9. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1895 The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) sub-option 1896 may be included in the OMNI options of RS messages sent by MNs and RA 1897 messages returned by MSEs. ARs that act as proxys to forward RS/RA 1898 messages between MNs and MSEs also forward DHCPv6 sub-options 1899 unchanged and do not process DHCPv6 sub-options themselves. 1901 0 1 2 3 1902 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 1903 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1904 | S-Type=8| Sub-length=N | msg-type | id (octet 0) | 1905 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1906 | transaction-id (octets 1-2) | | 1907 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1908 | | 1909 . DHCPv6 options . 1910 . (variable number and length) . 1911 | | 1912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1914 Figure 17: DHCPv6 Message Sub-option 1916 o Sub-Type is set to 8. If multiple instances appear in OMNI 1917 options of the same message the first is processed and all others 1918 are ignored. 1920 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1921 Sub-Option Data octets that follow. The 'msg-type' and 1922 'transaction-id' fields are always present; hence, the length of 1923 the DHCPv6 options is restricted to 2030 octets. 1925 o 'msg-type' and 'transaction-id' are coded according to Section 8 1926 of [RFC8415]. 1928 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1929 follows. 1931 11.1.10. Host Identity Protocol (HIP) Message 1933 The Host Identity Protocol (HIP) Message sub-option may be included 1934 in the OMNI options of RS messages sent by MNs and RA messages 1935 returned by ARs. ARs that act as proxys authenticate and remove HIP 1936 messages in RS messages they forward from a MN to an MSE. ARs that 1937 act as proxys insert and sign HIP messages in the RA messages they 1938 forward from an MSE to a MN. 1940 0 1 2 3 1941 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 1942 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1943 | S-Type=9| Sub-length=N |0| Packet Type |Version| RES.|1| 1944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1945 | Checksum | Controls | 1946 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1947 | Sender's Host Identity Tag (HIT) | 1948 | | 1949 | | 1950 | | 1951 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1952 | Receiver's Host Identity Tag (HIT) | 1953 | | 1954 | | 1955 | | 1956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1957 | | 1958 / HIP Parameters / 1959 / / 1960 | | 1961 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1963 Figure 18: HIP Message Sub-option 1965 o Sub-Type is set to 9. If multiple instances appear in OMNI 1966 options of the same message the first is processed and all others 1967 are ignored. 1969 o Sub-Length is set to N, i.e., the length of the option in octets 1970 beginning immediately following the Sub-Length field and extending 1971 to the end of the HIP parameters. The length of the entire HIP 1972 message is therefore restricted to 2034 octets. 1974 o The HIP message is coded exactly as specified in Section 5 of 1975 [RFC7401], except that the OMNI "Sub-Type" and "Sub-Length" fields 1976 replace the first 2 octets of the HIP message header (i.e., the 1977 Next Header and Header Length fields). 1979 11.1.11. Node Identification 1981 0 1 2 3 1982 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 1983 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1984 |S-Type=10| Sub-length=N | ID-Type | ~ 1985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1986 ~ Node Identification Value (N-1 octets) ~ 1987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1989 Figure 19: Node Identification 1991 o Sub-Type is set to 10. If multiple instances appear in OMNI 1992 options of the same IPv6 ND message the first instance of a 1993 specific ID-Type is processed and all other instances of the same 1994 ID-Type are ignored. (Note therefore that it is possible for a 1995 single IPv6 ND message to convey multiple Node Identifications - 1996 each having a different ID-Type.) 1998 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 1999 Sub-Option Data octets that follow. The ID-Type field is always 2000 present; hence, the maximum Node Identification Value length is 2001 2033 octets. 2003 o ID-Type is a 1 octet field that encodes the type of the Node 2004 Identification Value. The following ID-Type values are currently 2005 defined: 2007 * 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates 2008 that Node Identification Value contains a 16 octet UUID. 2010 * 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node 2011 Identification Value contains a 16 octet HIT. 2013 * 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates 2014 that Node Identification Value contains a 16 octet HHIT. 2016 * 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that 2017 Node Identification Value contains an N-1 octet NAI. 2019 * 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicates 2020 that Node Identification Value contains an N-1 octet FQDN. 2022 * 5 - 252 - Unassigned. 2024 * 253-254 - Reserved for experimentation, as recommended in 2025 [RFC3692]. 2027 * 255 - reserved by IANA. 2029 o Node Identification Value is an (N - 1) octet field encoded 2030 according to the appropriate the "ID-Type" reference above. 2032 When a Node Identification Value is needed for DHCPv6 messaging 2033 purposes, it is encoded as a DHCP Unique IDentifier (DUID) using the 2034 "DUID-EN for OMNI" format with enterprise number 45282 (see: 2035 Section 23) as shown in Figure 20: 2037 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 2038 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2039 | DUID-Type (2) | EN (high bits == 0) | 2040 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2041 | EN (low bits = 45282) | ID-Type | | 2042 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 2043 . Node Identification Value . 2044 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2046 Figure 20: DUID-EN for OMNI Format 2048 In this format, the ID-Type and Node Identification Value fields are 2049 coded exactly as in Figure 19 following the 6 octet DUID-EN header, 2050 and the entire "DUID-EN for OMNI" is included in a DHCPv6 message per 2051 [RFC8415]. 2053 11.1.12. Sub-Type Extension 2055 Since the Sub-Type field is only 5 bits in length, future 2056 specifications of major protocol functions may exhaust the remaining 2057 Sub-Type values available for assignment. This document therefore 2058 defines Sub-Type 30 as an "extension", meaning that the actual sub- 2059 option type is determined by examining a 1 octet "Extension-Type" 2060 field immediately following the Sub-Length field. The Sub-Type 2061 Extension is formatted as shown in Figure 21: 2063 0 1 2 3 2064 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 2065 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2066 |S-Type=30| Sub-length=N | Extension-Type| ~ 2067 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 2068 ~ ~ 2069 ~ Extension-Type Body ~ 2070 ~ ~ 2071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2073 Figure 21: Sub-Type Extension 2075 o Sub-Type is set to 30. If multiple instances appear in OMNI 2076 options of the same message all are processed, where each 2077 individual extension defines its own policy for processing 2078 multiple of that type. 2080 o Sub-Length is set to N (from 1 to 2034) that encodes the number of 2081 Sub-Option Data octets that follow. The Extension-Type field is 2082 always present; hence, the maximum Extension-Type Body length is 2083 2033 octets. 2085 o Extension-Type contains a 1 octet Sub-Type Extension value between 2086 0 and 255. 2088 o Extension-Type Body contains an N-1 octet block with format 2089 defined by the given extension specification. 2091 Extension-Type values 2 through 252 are available for assignment by 2092 future specifications, which must also define the format of the 2093 Extension-Type Body and its processing rules. Extension-Type values 2094 253 and 254 are reserved for experimentation, as recommended in 2095 [RFC3692], and value 255 is reserved by IANA. Extension-Type values 2096 0 and 1 are defined in the following subsections: 2098 11.1.12.1. RFC4380 UDP/IP Header Option 2100 0 1 2 3 2101 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 2102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2103 |S-Type=30| Sub-length=N | Ext-Type=0 | Header Type | 2104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2105 ~ Header Option Value ~ 2106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2108 Figure 22: RFC4380 UDP/IP Header Option (Extension-Type 0) 2110 o Sub-Type is set to 30. 2112 o Sub-Length is set to N (from 2 to 2034) that encodes the number of 2113 Sub-Option Data octets that follow. The Extension-Type and Header 2114 Type fields are always present; hence, the maximum-length Header 2115 Option Value is 2032 octets. 2117 o Extension-Type is set to 0. Each instance encodes exactly one 2118 header option per Section 5.1.1 of [RFC4380], with the leading '0' 2119 octet omitted and the following octet coded as Header Type. If 2120 multiple instances of the same Header Type appear in OMNI options 2121 of the same message the first instance is processed and all others 2122 are ignored. 2124 o Header Type and Header Option Value are coded exactly as specified 2125 in Section 5.1.1 of [RFC4380]; the following types are currently 2126 defined: 2128 * 0 - Origin Indication (IPv4) - value coded per Section 5.1.1 of 2129 [RFC4380]. 2131 * 1 - Authentication Encapsulation - value coded per 2132 Section 5.1.1 of [RFC4380]. 2134 * 2 - Origin Indication (IPv6) - value coded per Section 5.1.1 of 2135 [RFC4380], except that the address is a 16-octet IPv6 address 2136 instead of a 4-octet IPv4 address. 2138 o Header Type values 3 through 252 are available for assignment by 2139 future specifications, which must also define the format of the 2140 Header Option Value and its processing rules. Header Type values 2141 253 and 254 are reserved for experimentation, as recommended in 2142 [RFC3692], and value 255 is Reserved by IANA. 2144 11.1.12.2. RFC6081 UDP/IP Trailer Option 2146 0 1 2 3 2147 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 2148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2149 |S-Type=30| Sub-length=N | Ext-Type=1 | Trailer Type | 2150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2151 ~ Trailer Option Value ~ 2152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2154 Figure 23: RFC6081 UDP/IP Trailer Option (Extension-Type 1) 2156 o Sub-Type is set to 30. 2158 o Sub-Length is set to N (from 2 to 2034) that encodes the number of 2159 Sub-Option Data octets that follow. The Extension-Type and 2160 Trailer Type fields are always present; hence, the maximum-length 2161 Trailer Option Value is 2032 octets. 2163 o Extension-Type is set to 1. Each instance encodes exactly one 2164 trailer option per Section 4 of [RFC6081]. If multiple instances 2165 of the same trailer type appear in OMNI options of the same 2166 message the first instance is processed and all others ignored. 2168 o Trailer Type and Trailer Option Value are coded exactly as 2169 specified in Section 4 of [RFC6081]; the following Trailer Types 2170 are currently defined: 2172 * 0 - Unassigned 2174 * 1 - Nonce Trailer - value coded per Section 4.2 of [RFC6081]. 2176 * 2 - Unassigned 2178 * 3 - Alternate Address Trailer (IPv4) - value coded per 2179 Section 4.3 of [RFC6081]. 2181 * 4 - Neighbor Discovery Option Trailer - value coded per 2182 Section 4.4 of [RFC6081]. 2184 * 5 - Random Port Trailer - value coded per Section 4.5 of 2185 [RFC6081]. 2187 * 6 - Alternate Address Trailer (IPv6) - value coded per 2188 Section 4.3 of [RFC6081], except that each address is a 2189 16-octet IPv6 address instead of a 4-octet IPv4 address. 2191 o Trailer Type values 7 through 252 are available for assignment by 2192 future specifications, which must also define the format of the 2193 Trailer Option Value and its processing rules. Trailer Type 2194 values 253 and 254 are reserved for experimentation, as 2195 recommended in [RFC3692], and value 255 is Reserved by IANA. 2197 12. Address Mapping - Multicast 2199 The multicast address mapping of the native underlying interface 2200 applies. The mobile router on board the MN also serves as an IGMP/ 2201 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 2202 using the L2 address of the AR as the L2 address for all multicast 2203 packets. 2205 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 2206 coordinate with the AR, and *NET L2 elements use MLD snooping 2207 [RFC4541]. 2209 13. Multilink Conceptual Sending Algorithm 2211 The MN's IPv6 layer selects the outbound OMNI interface according to 2212 SBM considerations when forwarding data packets from local or EUN 2213 applications to external correspondents. Each OMNI interface 2214 maintains a neighbor cache the same as for any IPv6 interface, but 2215 with additional state for multilink coordination. Each OMNI 2216 interface maintains default routes via ARs discovered as discussed in 2217 Section 14, and may configure more-specific routes discovered through 2218 means outside the scope of this specification. 2220 After a packet enters the OMNI interface, one or more outbound 2221 underlying interfaces are selected based on PBM traffic attributes, 2222 and one or more neighbor underlying interfaces are selected based on 2223 the receipt of Interface Attributes sub-options in IPv6 ND messages 2224 (see: Figure 10). Underlying interface selection for the nodes own 2225 local interfaces are based on attributes such as DSCP, application 2226 port number, cost, performance, message size, etc. OMNI interface 2227 multilink selections could also be configured to perform replication 2228 across multiple underlying interfaces for increased reliability at 2229 the expense of packet duplication. The set of all Interface 2230 Attributes received in IPv6 ND messages determines the multilink 2231 forwarding profile for selecting the neighbor's underlying 2232 interfaces. 2234 When the OMNI interface sends a packet over a selected outbound 2235 underlying interface, the OAL includes or omits a mid-layer 2236 encapsulation header as necessary as discussed in Section 5 and as 2237 determined by the L2 address information received in Interface 2238 Attributes. The OAL also performs encapsulation when the nearest AR 2239 is located multiple hops away as discussed in Section 14.1. (Note 2240 that the OAL MAY employ packing when multiple packets are available 2241 for forwarding to the same destination.) 2243 OMNI interface multilink service designers MUST observe the BCP 2244 guidance in Section 15 [RFC3819] in terms of implications for 2245 reordering when packets from the same flow may be spread across 2246 multiple underlying interfaces having diverse properties. 2248 13.1. Multiple OMNI Interfaces 2250 MNs may connect to multiple independent OMNI links concurrently in 2251 support of SBM. Each OMNI interface is distinguished by its Anycast 2252 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 2253 configures a separate OMNI interface for each link so that multiple 2254 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 2255 layer. A different Anycast ULA is assigned to each interface, and 2256 the MN injects the service prefixes for the OMNI link instances into 2257 the EUN routing system. 2259 Applications in EUNs can use Segment Routing to select the desired 2260 OMNI interface based on SBM considerations. The Anycast ULA is 2261 written into the IPv6 destination address, and the actual destination 2262 (along with any additional intermediate hops) is written into the 2263 Segment Routing Header. Standard IP routing directs the packets to 2264 the MN's mobile router entity, and the Anycast ULA identifies the 2265 OMNI interface to be used for transmission to the next hop. When the 2266 MN receives the message, it replaces the IPv6 destination address 2267 with the next hop found in the routing header and transmits the 2268 message over the OMNI interface identified by the Anycast ULA. 2270 Multiple distinct OMNI links can therefore be used to support fault 2271 tolerance, load balancing, reliability, etc. The architectural model 2272 is similar to Layer 2 Virtual Local Area Networks (VLANs). 2274 13.2. MN<->AR Traffic Loop Prevention 2276 After an AR has registered an MNP for a MN (see: Section 14), the AR 2277 will forward packets destined to an address within the MNP to the MN. 2278 The MN will under normal circumstances then forward the packet to the 2279 correct destination within its internal networks. 2281 If at some later time the MN loses state (e.g., after a reboot), it 2282 may begin returning packets destined to an MNP address to the AR as 2283 its default router. The AR therefore must drop any packets 2284 originating from the MN and destined to an address within the MN's 2285 registered MNP. To do so, the AR institutes the following check: 2287 o if the IP destination address belongs to a neighbor on the same 2288 OMNI interface, and if the link-layer source address is the same 2289 as one of the neighbor's link-layer addresses, drop the packet. 2291 14. Router Discovery and Prefix Registration 2293 MNs interface with the MS by sending RS messages with OMNI options 2294 under the assumption that one or more AR on the *NET will process the 2295 message and respond. The MN then configures default routes for the 2296 OMNI interface via the discovered ARs as the next hop. The manner in 2297 which the *NET ensures AR coordination is link-specific and outside 2298 the scope of this document (however, considerations for *NETs that do 2299 not provide ARs that recognize the OMNI option are discussed in 2300 Section 19). 2302 For each underlying interface, the MN sends an RS message with an 2303 OMNI option to coordinate with MSEs identified by MSID values. 2305 Example MSID discovery methods are given in [RFC5214] and include 2306 data link login parameters, name service lookups, static 2307 configuration, a static "hosts" file, etc. The MN can also send an 2308 RS with an MS-Register sub-option that includes the Anycast MSID 2309 value '0', i.e., instead of or in addition to any non-zero MSIDs. 2310 When the AR receives an RS with a MSID '0', it selects a nearby MSE 2311 (which may be itself) and returns an RA with the selected MSID in an 2312 MS-Register sub-option. The AR selects only a single wildcard MSE 2313 (i.e., even if the RS MS-Register sub-option included multiple '0' 2314 MSIDs) while also soliciting the MSEs corresponding to any non-zero 2315 MSIDs. 2317 MNs configure OMNI interfaces that observe the properties discussed 2318 in the previous section. The OMNI interface and its underlying 2319 interfaces are said to be in either the "UP" or "DOWN" state 2320 according to administrative actions in conjunction with the interface 2321 connectivity status. An OMNI interface transitions to UP or DOWN 2322 through administrative action and/or through state transitions of the 2323 underlying interfaces. When a first underlying interface transitions 2324 to UP, the OMNI interface also transitions to UP. When all 2325 underlying interfaces transition to DOWN, the OMNI interface also 2326 transitions to DOWN. 2328 When an OMNI interface transitions to UP, the MN sends RS messages to 2329 register its MNP and an initial set of underlying interfaces that are 2330 also UP. The MN sends additional RS messages to refresh lifetimes 2331 and to register/deregister underlying interfaces as they transition 2332 to UP or DOWN. The MN's OMNI interface sends initial RS messages 2333 over an UP underlying interface with its MNP-LLA as the source and 2334 with destination set to link-scoped All-Routers multicast (ff02::2) 2335 [RFC4291]. The OMNI interface includes an OMNI option per Section 11 2336 with a Preflen assertion, Interface Attributes appropriate for 2337 underlying interfaces, MS-Register/Release sub-options containing 2338 MSID values, and with any other necessary OMNI sub-options (e.g., a 2339 Node Identification sub-option as an identity for the MN). The OMNI 2340 interface then sets the S/T-omIndex field to the index of the 2341 underlying interface over which the RS message is sent. The OMNI 2342 interface then sends the RS over the underlying interface, using OAL 2343 encapsulation and fragmentation if necessary. If OAL encapsulation 2344 is used, the OMNI interface sets the OAL source address to the ULA 2345 corresponding to the RS source and sets the OAL destination to site- 2346 scoped All-Routers multicast (ff05::2). 2348 ARs process IPv6 ND messages with OMNI options and act as an MSE 2349 themselves and/or as a proxy for other MSEs. ARs receive RS messages 2350 (while performing OAL reassembly if necessary) and create a neighbor 2351 cache entry for the MN, then coordinate with any MSEs named in the 2352 Register/Release lists in a manner outside the scope of this 2353 document. When an MSE processes the OMNI information, it first 2354 validates the prefix registration information then injects/withdraws 2355 the MNP in the routing/mapping system and caches/discards the new 2356 Preflen, MNP and Interface Attributes. The MSE then informs the AR 2357 of registration success/failure, and the AR returns an RA message to 2358 the MN with an OMNI option per Section 11. 2360 The AR's OMNI interface returns the RA message via the same 2361 underlying interface of the MN over which the RS was received, and 2362 with destination address set to the MNP-LLA (i.e., unicast), with 2363 source address set to its own LLA, and with an OMNI option with S/ 2364 T-omIndex set to the value included in the RS. The OMNI option also 2365 includes a Preflen confirmation, Interface Attributes, MS-Register/ 2366 Release and any other necessary OMNI sub-options (e.g., a Node 2367 Identification sub-option as an identity for the AR). The RA also 2368 includes any information for the link, including RA Cur Hop Limit, M 2369 and O flags, Router Lifetime, Reachable Time and Retrans Timer 2370 values, and includes any necessary options such as: 2372 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 2374 o RIOs [RFC4191] with more-specific routes. 2376 o an MTU option that specifies the maximum acceptable packet size 2377 for this underlying interface. 2379 The OMNI interface then sends the RA, using OAL encapsulation and 2380 fragmentation if necessary. If OAL encapsulation is used, the OMNI 2381 interface sets the OAL source address to the ULA corresponding to the 2382 RA source and sets the OAL destination to the ULA corresponding to 2383 the RA destination. The AR MAY also send periodic and/or event- 2384 driven unsolicited RA messages per [RFC4861]. In that case, the S/ 2385 T-omIndex field in the OMNI option of the unsolicited RA message 2386 identifies the target underlying interface of the destination MN. 2388 The AR can combine the information from multiple MSEs into one or 2389 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 2390 Each aggregate RA includes an OMNI option with MS-Register/Release 2391 sub-options with the MSEs represented by the aggregate. If an 2392 aggregate is sent, the RA message contents must consistently 2393 represent the combined information advertised by all represented 2394 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 2395 address, the MN determines the addresses of the represented MSEs by 2396 examining the MS-Register/Release OMNI sub-options. 2398 When the MN receives the RA message, it creates an OMNI interface 2399 neighbor cache entry for each MSID that has confirmed MNP 2400 registration via the L2 address of this AR. If the MN connects to 2401 multiple *NETs, it records the additional L2 AR addresses in each 2402 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 2403 then configures a default route via the MSE that returned the RA 2404 message, and assigns the Subnet Router Anycast address corresponding 2405 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 2406 manages its underlying interfaces according to their states as 2407 follows: 2409 o When an underlying interface transitions to UP, the MN sends an RS 2410 over the underlying interface with an OMNI option. The OMNI 2411 option contains at least one Interface Attribute sub-option with 2412 values specific to this underlying interface, and may contain 2413 additional Interface Attributes specific to other underlying 2414 interfaces. The option also includes any MS-Register/Release sub- 2415 options. 2417 o When an underlying interface transitions to DOWN, the MN sends an 2418 RS or unsolicited NA message over any UP underlying interface with 2419 an OMNI option containing an Interface Attribute sub-option for 2420 the DOWN underlying interface with Link set to '0'. The MN sends 2421 an RS when an acknowledgement is required, or an unsolicited NA 2422 when reliability is not thought to be a concern (e.g., if 2423 redundant transmissions are sent on multiple underlying 2424 interfaces). 2426 o When the Router Lifetime for a specific AR nears expiration, the 2427 MN sends an RS over the underlying interface to receive a fresh 2428 RA. If no RA is received, the MN can send RS messages to an 2429 alternate MSID in case the current MSID has failed. If no RS 2430 messages are received even after trying to contact alternate 2431 MSIDs, the MN marks the underlying interface as DOWN. 2433 o When a MN wishes to release from one or more current MSIDs, it 2434 sends an RS or unsolicited NA message over any UP underlying 2435 interfaces with an OMNI option with a Release MSID. Each MSID 2436 then withdraws the MNP from the routing/mapping system and informs 2437 the AR that the release was successful. 2439 o When all of a MNs underlying interfaces have transitioned to DOWN 2440 (or if the prefix registration lifetime expires), any associated 2441 MSEs withdraw the MNP the same as if they had received a message 2442 with a release indication. 2444 The MN is responsible for retrying each RS exchange up to 2445 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 2446 seconds until an RA is received. If no RA is received over an UP 2447 underlying interface (i.e., even after attempting to contact 2448 alternate MSEs), the MN declares this underlying interface as DOWN. 2450 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 2451 Therefore, when the IPv6 layer sends an RS message the OMNI interface 2452 returns an internally-generated RA message as though the message 2453 originated from an IPv6 router. The internally-generated RA message 2454 contains configuration information that is consistent with the 2455 information received from the RAs generated by the MS. Whether the 2456 OMNI interface IPv6 ND messaging process is initiated from the 2457 receipt of an RS message from the IPv6 layer is an implementation 2458 matter. Some implementations may elect to defer the IPv6 ND 2459 messaging process until an RS is received from the IPv6 layer, while 2460 others may elect to initiate the process proactively. Still other 2461 deployments may elect to administratively disable the ordinary RS/RA 2462 messaging used by the IPv6 layer over the OMNI interface, since they 2463 are not required to drive the internal RS/RA processing. (Note that 2464 this same logic applies to IPv4 implementations that employ ICMP- 2465 based Router Discovery per [RFC1256].) 2467 Note: The Router Lifetime value in RA messages indicates the time 2468 before which the MN must send another RS message over this underlying 2469 interface (e.g., 600 seconds), however that timescale may be 2470 significantly longer than the lifetime the MS has committed to retain 2471 the prefix registration (e.g., REACHABLETIME seconds). ARs are 2472 therefore responsible for keeping MS state alive on a shorter 2473 timescale than the MN is required to do on its own behalf. 2475 Note: On multicast-capable underlying interfaces, MNs should send 2476 periodic unsolicited multicast NA messages and ARs should send 2477 periodic unsolicited multicast RA messages as "beacons" that can be 2478 heard by other nodes on the link. If a node fails to receive a 2479 beacon after a timeout value specific to the link, it can initiate a 2480 unicast exchange to test reachability. 2482 Note: if an AR acting as a proxy forwards a MN's RS message to 2483 another node acting as an MSE using UDP/IP encapsulation, it must use 2484 a distinct UDP source port number for each MN. This allows the MSE 2485 to distinguish different MNs behind the same AR at the link-layer, 2486 whereas the link-layer addresses would otherwise be 2487 indistinguishable. 2489 Note: when an AR acting as an MSE returns an RA to an INET Client, it 2490 includes an OMNI option with an Interface Attributes sub-option with 2491 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 2492 its INET interface. This provides the Client with partition prefix 2493 context regarding the local OMNI link segment. 2495 14.1. Router Discovery in IP Multihop and IPv4-Only Networks 2497 On some *NETs, a MN may be located multiple IP hops away from the 2498 nearest AR. Forwarding through IP multihop *NETs is conducted 2499 through the application of a routing protocol (e.g., a MANET/VANET 2500 routing protocol over omni-directional wireless interfaces, an inter- 2501 domain routing protocol in an enterprise network, etc.). These *NETs 2502 could be either IPv6-enabled or IPv4-only, while IPv4-only *NETs 2503 could be either multicast-capable or unicast-only (note that for 2504 IPv4-only *NETs the following procedures apply for both single-hop 2505 and multihop cases). 2507 A MN located potentially multiple *NET hops away from the nearest AR 2508 prepares an RS message with source address set to its MNP-LLA (or to 2509 the unspecified address (::) if it does not yet have an MNP-LLA), and 2510 with destination set to link-scoped All-Routers multicast the same as 2511 discussed above. If OAL encapsulation and fragmentation are 2512 necessary, the OMNI interface sets the OAL source address to the ULA 2513 corresponding to the RS source (or to a Temporary ULA if the RS 2514 source was the unspecified address (::)) and sets the OAL destination 2515 to site-scoped All-Routers multicast (ff05::2). For IPv6-enabled 2516 *NETs, the MN then encapsulates the message in UDP/IPv6 headers with 2517 source address set to the underlying interface address (or to the ULA 2518 that would be used for OAL encapsulation if the underlying interface 2519 does not yet have an address) and sets the destination to either a 2520 unicast or anycast address of an AR. For IPv4-only *NETs, the MN 2521 instead encapsulates the RS message in an IPv4 header with source 2522 address set to the IPv4 address of the underlying interface and with 2523 destination address set to either the unicast IPv4 address of an AR 2524 [RFC5214] or an IPv4 anycast address reserved for OMNI. The MN then 2525 sends the encapsulated RS message via the *NET interface, where it 2526 will be forwarded by zero or more intermediate *NET hops. 2528 When an intermediate *NET hop that participates in the routing 2529 protocol receives the encapsulated RS, it forwards the message 2530 according to its routing tables (note that an intermediate node could 2531 be a fixed infrastructure element or another MN). This process 2532 repeats iteratively until the RS message is received by a penultimate 2533 *NET hop within single-hop communications range of an AR, which 2534 forwards the message to the AR. 2536 When the AR receives the message, it decapsulates the RS (while 2537 performing OAL reassembly, if necessary) and coordinates with the MS 2538 the same as for an ordinary link-local RS, since the inner Hop Limit 2539 will not have been decremented by the multihop forwarding process. 2540 The AR then prepares an RA message with source address set to its own 2541 ADM-LLA and destination address set to the LLA of the original MN. 2542 The AR then performs OAL encapsulation and fragmentation if 2543 necessary, with OAL source set to its own ADM-ULA and destination set 2544 to the ULA corresponding to the RA source. The AR then encapsulates 2545 the message in an IPv4/IPv6 header with source address set to its own 2546 IPv4/ULA address and with destination set to the encapsulation source 2547 of the RS. 2549 The AR then forwards the message to an *NET node within 2550 communications range, which forwards the message according to its 2551 routing tables to an intermediate node. The multihop forwarding 2552 process within the *NET continues repetitively until the message is 2553 delivered to the original MN, which decapsulates the message and 2554 performs autoconfiguration the same as if it had received the RA 2555 directly from the AR as an on-link neighbor. 2557 Note: An alternate approach to multihop forwarding via IPv6 2558 encapsulation would be for the MN and AR to statelessly translate the 2559 IPv6 LLAs into ULAs and forward the RS/RA messages without 2560 encapsulation. This would violate the [RFC4861] requirement that 2561 certain IPv6 ND messages must use link-local addresses and must not 2562 be accepted if received with Hop Limit less than 255. This document 2563 therefore mandates encapsulation since the overhead is nominal 2564 considering the infrequent nature and small size of IPv6 ND messages. 2565 Future documents may consider encapsulation avoidance through 2566 translation while updating [RFC4861]. 2568 Note: An alternate approach to multihop forwarding via IPv4 2569 encapsulation would be to employ IPv6/IPv4 protocol translation. 2570 However, for IPv6 ND messages the LLAs would be truncated due to 2571 translation and the OMNI Router and Prefix Discovery services would 2572 not be able to function. The use of IPv4 encapsulation is therefore 2573 indicated. 2575 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2576 of a new IPv4 /24 prefix allocation, but this may be difficult to 2577 obtain given IPv4 address exhaustion. An alternative would be to re- 2578 purpose the prefix 192.88.99.0 which has been set aside from its 2579 former use by [RFC7526]. 2581 14.2. MS-Register and MS-Release List Processing 2583 OMNI links maintain a constant value "MAX_MSID" selected to provide 2584 MNs with an acceptable level of MSE redundancy while minimizing 2585 control message amplification. It is RECOMMENDED that MAX_MSID be 2586 set to the default value 5; if a different value is chosen, it should 2587 be set uniformly by all nodes on the OMNI link. 2589 When a MN sends an RS message with an OMNI option via an underlying 2590 interface to an AR, the MN must convey its knowledge of its 2591 currently-associated MSEs. Initially, the MN will have no associated 2592 MSEs and should therefore include an MS-Register sub-option with the 2593 single "anycast" MSID value 0 which requests the AR to select and 2594 assign an MSE. The AR will then return an RA message with source 2595 address set to the ADM-LLA of the selected MSE. 2597 As the MN activates additional underlying interfaces, it can 2598 optionally include an MS-Register sub-option with MSID value 0, or 2599 with non-zero MSIDs for MSEs discovered from previous RS/RA 2600 exchanges. The MN will thus eventually begin to learn and manage its 2601 currently active set of MSEs, and can register with new MSEs or 2602 release from former MSEs with each successive RS/RA exchange. As the 2603 MN's MSE constituency grows, it alone is responsible for including or 2604 omitting MSIDs in the MS-Register/Release lists it sends in RS 2605 messages. The inclusion or omission of MSIDs determines the MN's 2606 interface to the MS and defines the manner in which MSEs will 2607 respond. The only limiting factor is that the MN should include no 2608 more than MAX_MSID values in each list per each IPv6 ND message, and 2609 should avoid duplication of entries in each list unless it wants to 2610 increase likelihood of control message delivery. 2612 When an AR receives an RS message sent by a MN with an OMNI option, 2613 the option will contain zero or more MS-Register and MS-Release sub- 2614 options containing MSIDs. After processing the OMNI option, the AR 2615 will have a list of zero or more MS-Register MSIDs and a list of zero 2616 or more of MS-Release MSIDs. The AR then processes the lists as 2617 follows: 2619 o For each list, retain the first MAX_MSID values in the list and 2620 discard any additional MSIDs (i.e., even if there are duplicates 2621 within a list). 2623 o Next, for each MSID in the MS-Register list, remove all matching 2624 MSIDs from the MS-Release list. 2626 o Next, proceed according to whether the AR's own MSID or the value 2627 0 appears in the MS-Register list as follows: 2629 * If yes, send an RA message directly back to the MN and send a 2630 proxy copy of the RS message to each additional MSID in the MS- 2631 Register list with the MS-Register/Release lists omitted. 2632 Then, send an unsolicited NA (uNA) message to each MSID in the 2633 MS-Release list with the MS-Register/Release lists omitted and 2634 with an OMNI option with S/T-omIndex set to 0. 2636 * If no, send a proxy copy of the RS message to each additional 2637 MSID in the MS-Register list with the MS-Register list omitted. 2639 For the first MSID, include the original MS-Release list; for 2640 all other MSIDs, omit the MS-Release list. 2642 Each proxy copy of the RS message will include an OMNI option and OAL 2643 encapsulation header with the ADM-ULA of the AR as the source and the 2644 ADM-ULA of the Register MSE as the destination. When the Register 2645 MSE receives the proxy RS message, if the message includes an MS- 2646 Release list the MSE sends a uNA message to each additional MSID in 2647 the Release list with an OMNI option with S/T-omIndex set to 0. The 2648 Register MSE then sends an RA message back to the (Proxy) AR wrapped 2649 in an OAL encapsulation header with source and destination addresses 2650 reversed, and with RA destination set to the MNP-LLA of the MN. When 2651 the AR receives this RA message, it sends a proxy copy of the RA to 2652 the MN. 2654 Each uNA message (whether sent by the first-hop AR or by a Register 2655 MSE) will include an OMNI option and an OAL encapsulation header with 2656 the ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2657 Release MSE as the destination. The uNA informs the Release MSE that 2658 its previous relationship with the MN has been released and that the 2659 source of the uNA message is now registered. The Release MSE must 2660 then note that the subject MN of the uNA message is now "departed", 2661 and forward any subsequent packets destined to the MN to the Register 2662 MSE. 2664 Note that it is not an error for the MS-Register/Release lists to 2665 include duplicate entries. If duplicates occur within a list, the AR 2666 will generate multiple proxy RS and/or uNA messages - one for each 2667 copy of the duplicate entries. 2669 14.3. DHCPv6-based Prefix Registration 2671 When a MN is not pre-provisioned with an MNP-LLA (or, when the MN 2672 requires additional MNP delegations), it requests the MSE to select 2673 MNPs on its behalf and set up the correct routing state within the 2674 MS. The DHCPv6 service [RFC8415] supports this requirement. 2676 When an MN needs to have the MSE select MNPs, it sends an RS message 2677 with source set to the unspecified address (::) if it has no 2678 MNP_LLAs. If the MN requires only a single MNP delegation, it can 2679 then include a Node Identification sub-option in the OMNI option and 2680 set Preflen to the length of the desired MNP. If the MN requires 2681 multiple MNP delegations and/or more complex DHCPv6 services, it 2682 instead includes a DHCPv6 Message sub-option containing a Client 2683 Identifier, one or more IA_PD options and a Rapid Commit option then 2684 sets the 'msg-type' field to "Solicit", and includes a 3 octet 2685 'transaction-id'. The MN then sets the RS destination to All-Routers 2686 multicast and sends the message using OAL encapsulation and 2687 fragmentation if necessary as discussed above. 2689 When the MSE receives the RS message, it performs OAL reassembly if 2690 necessary. Next, if the RS source is the unspecified address (::) 2691 and/or the OMNI option includes a DHCPv6 message sub-option, the MSE 2692 acts as a "Proxy DHCPv6 Client" in a message exchange with the 2693 locally-resident DHCPv6 server. If the RS did not contain a DHCPv6 2694 message sub-option, the MSE generates a DHCPv6 Solicit message on 2695 behalf of the MN using an IA_PD option with the prefix length set to 2696 the OMNI header Preflen value and with a Client Identifier formed 2697 from the OMNI option Node Identification sub-option; otherwise, the 2698 MSE uses the DHCPv6 Solicit message contained in the OMNI option. 2699 The MSE then sends the DHCPv6 message to the DHCPv6 Server, which 2700 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2701 (If the MSE wishes to defer creation of MN state until the DHCPv6 2702 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2703 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2704 forward/reply exchange with Relay Message and Interface ID options. 2705 In the process, the MSE packs any state information needed to return 2706 an RA to the MN in the Relay-forward Interface ID option so that the 2707 information will be echoed back in the Relay-reply.) 2709 When the MSE receives the DHCPv6 Reply, it adds routes to the routing 2710 system and creates MNP-LLAs based on the delegated MNPs. The MSE 2711 then sends an RA back to the MN with the DHCPv6 Reply message 2712 included in an OMNI DHCPv6 message sub-option if and only if the RS 2713 message had included an explicit DHCPv6 Solicit. If the RS message 2714 source was the unspecified address (::), the MSE includes one of the 2715 (newly-created) MNP-LLAs as the RA destination address and sets the 2716 OMNI option Preflen accordingly; otherwise, the MSE includes the RS 2717 source address as the RA destination address. The MSE then sets the 2718 RA source address to its own ADM-LLA then performs OAL encapsulation 2719 and fragmentation if necessary and sends the RA to the MN. When the 2720 MN receives the RA, it reassembles and discards the OAL encapsulation 2721 if necessary, then creates a default route, assigns Subnet Router 2722 Anycast addresses and uses the RA destination address as its primary 2723 MNP-LLA. The MN will then use this primary MNP-LLA as the source 2724 address of any IPv6 ND messages it sends as long as it retains 2725 ownership of the MNP. 2727 Note: After a MN performs a DHCPv6-based prefix registration exchange 2728 with a first MSE, it would need to repeat the exchange with each 2729 additional MSE it registers with. In that case, the MN supplies the 2730 MNP delegation information received from the first MSE when it 2731 engages the additional MSEs. 2733 15. Secure Redirection 2735 If the *NET link model is multiple access, the AR is responsible for 2736 assuring that address duplication cannot corrupt the neighbor caches 2737 of other nodes on the link. When the MN sends an RS message on a 2738 multiple access *NET link, the AR verifies that the MN is authorized 2739 to use the address and returns an RA with a non-zero Router Lifetime 2740 only if the MN is authorized. 2742 After verifying MN authorization and returning an RA, the AR MAY 2743 return IPv6 ND Redirect messages to direct MNs located on the same 2744 *NET link to exchange packets directly without transiting the AR. In 2745 that case, the MNs can exchange packets according to their unicast L2 2746 addresses discovered from the Redirect message instead of using the 2747 dogleg path through the AR. In some *NET links, however, such direct 2748 communications may be undesirable and continued use of the dogleg 2749 path through the AR may provide better performance. In that case, 2750 the AR can refrain from sending Redirects, and/or MNs can ignore 2751 them. 2753 16. AR and MSE Resilience 2755 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2756 [RFC5798] configurations so that service continuity is maintained 2757 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2758 the (redundant) ARs is currently providing service, and any service 2759 discontinuity will be limited to the failover time supported by VRRP. 2760 Widely deployed public domain implementations of VRRP are available. 2762 MSEs SHOULD use high availability clustering services so that 2763 multiple redundant systems can provide coordinated response to 2764 failures. As with VRRP, widely deployed public domain 2765 implementations of high availability clustering services are 2766 available. Note that special-purpose and expensive dedicated 2767 hardware is not necessary, and public domain implementations can be 2768 used even between lightweight virtual machines in cloud deployments. 2770 17. Detecting and Responding to MSE Failures 2772 In environments where fast recovery from MSE failure is required, ARs 2773 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2774 manner that parallels Bidirectional Forwarding Detection (BFD) 2775 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2776 react to failures so that cached information is re-established 2777 through alternate paths. Proactive NUD control messaging is carried 2778 only over well-connected ground domain networks (i.e., and not low- 2779 end *NET links such as aeronautical radios) and can therefore be 2780 tuned for rapid response. 2782 ARs perform proactive NUD for MSEs for which there are currently 2783 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2784 of the outage by sending multicast RA messages on the *NET interface. 2785 The AR sends RA messages to MNs via the *NET interface with an OMNI 2786 option with a Release ID for the failed MSE, and with destination 2787 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2789 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2790 by small delays [RFC4861]. Any MNs on the *NET interface that have 2791 been using the (now defunct) MSE will receive the RA messages and 2792 associate with a new MSE. 2794 18. Transition Considerations 2796 When a MN connects to an *NET link for the first time, it sends an RS 2797 message with an OMNI option. If the first hop AR recognizes the 2798 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2799 as the destination and with an OMNI option included. The MN then 2800 engages the AR according to the OMNI link model specified above. If 2801 the first hop AR is a legacy IPv6 router, however, it instead returns 2802 an RA message with no OMNI option and with a non-OMNI unicast source 2803 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2804 according to the legacy IPv6 link model and without the OMNI 2805 extensions specified in this document. 2807 If the *NET link model is multiple access, there must be assurance 2808 that address duplication cannot corrupt the neighbor caches of other 2809 nodes on the link. When the MN sends an RS message on a multiple 2810 access *NET link with an LLA source address and an OMNI option, ARs 2811 that recognize the option ensure that the MN is authorized to use the 2812 address and return an RA with a non-zero Router Lifetime only if the 2813 MN is authorized. ARs that do not recognize the option instead 2814 return an RA that makes no statement about the MN's authorization to 2815 use the source address. In that case, the MN should perform 2816 Duplicate Address Detection to ensure that it does not interfere with 2817 other nodes on the link. 2819 An alternative approach for multiple access *NET links to ensure 2820 isolation for MN / AR communications is through L2 address mappings 2821 as discussed in Appendix C. This arrangement imparts a (virtual) 2822 point-to-point link model over the (physical) multiple access link. 2824 19. OMNI Interfaces on Open Internetworks 2826 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2827 an open Internetwork without an OMNI-aware first-hop AR receive RA 2828 messages that do not include an OMNI option, while OMNI interfaces 2829 configured over IPv4-only underlying interfaces do not receive any 2830 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2831 without an OMNI option configure addresses, on-link prefixes, etc. on 2832 the underlying interface that received the RA according to standard 2833 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2834 interfaces configured over IPv4-only underlying interfaces configure 2835 IPv4 address information on the underlying interfaces using 2836 mechanisms such as DHCPv4 [RFC2131]. 2838 OMNI interfaces configured over underlying interfaces that connect to 2839 an open Internetwork can apply security services such as VPNs to 2840 connect to an MSE, or can establish a direct link to an MSE through 2841 some other means (see Section 4). In environments where an explicit 2842 VPN or direct link may be impractical, OMNI interfaces can instead 2843 use UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2844 authentication per [RFC7401]. 2846 OMNI interfaces use UDP service port number 8060 (see: Section 23.9 2847 and Section 3.6 of [I-D.templin-intarea-6706bis]) according to the 2848 simple UDP/IP encapsulation format specified in [RFC4380] for both 2849 IPv4 and IPv6 underlying interfaces. OMNI interfaces do not include 2850 the UDP/IP header/trailer extensions specified in [RFC4380][RFC6081], 2851 but may include them as OMNI sub-options instead when necessary. 2852 Since the OAL includes an integrity check over the OAL packet, OAL 2853 sources selectively disable UDP checksums for OAL packets that do not 2854 require UDP/IP address integrity, but enable UDP checksums for others 2855 including non-OAL packets, IPv6 ND messages used to establish link- 2856 layer addresses, etc. If the OAL source discovers that packets with 2857 UDP checksums disabled are being dropped in the path it should enable 2858 UDP checksums in future packets. Further considerations for UDP 2859 encapsulation checksums are found in [RFC6935][RFC6936]. 2861 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes a 2862 HIP "Initiator" message in an OMNI option of an IPv6 RS message and 2863 the AR responds with a HIP "Responder" message coded in an OMNI 2864 option of an IPv6 RA message. HIP security services are applied per 2865 [RFC7401], using the RS/RA messages as simple "shipping containers" 2866 to convey the HIP parameters. In that case, a "two-message HIP 2867 exchange" through a single RS/RA exchange may be sufficient for 2868 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2869 two MNs can coordinate directly with one another with HIP "Initiator/ 2870 Responder" messages coded in OMNI options of IPv6 NS/NA messages. In 2871 that case, a four-message HIP exchange (i.e., two back-to-back NS/NA 2872 exchanges) may be necessary for the two MNs to attain mutual 2873 authentication. 2875 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2876 interfaces send control plane messages to interface with the MS, 2877 including RS/RA messages used according to Section 14 and NS/NA 2878 messages used for route optimization and mobility (see: 2879 [I-D.templin-intarea-6706bis]). The control plane messages must be 2880 authenticated while data plane messages are delivered the same as for 2881 ordinary best-effort traffic with basic source address-based data 2882 origin verification. Data plane communications via OMNI interfaces 2883 that connect over open Internetworks without an explicit VPN should 2884 therefore employ transport- or higher-layer security to ensure 2885 integrity and/or confidentiality. 2887 OMNI interfaces configured over open Internetworks are often located 2888 behind NATs. The OMNI interface accommodates NAT traversal using 2889 UDP/IP encapsulation and the mechanisms discussed in 2890 [I-D.templin-intarea-6706bis]. To support NAT determination, ARs 2891 include an Origin Indication sub-option in RA messages sent in 2892 response to RS messages received from a Client via UDP/IP 2893 encapsulation. 2895 Note: Following the initial HIP Initiator/Responder exchange, OMNI 2896 interfaces configured over open Internetworks maintain HIP 2897 associations through the transmission of IPv6 ND messages that 2898 include OMNI options with HIP "Update" and "Notify" messages. OMNI 2899 interfaces use the HIP "Update" message when an acknowledgement is 2900 required, and use the "Notify" message in unacknowledged isolated 2901 IPv6 ND messages (e.g., unsolicited NAs). 2903 Note: ARs that act as proxys on an open Internetwork authenticate and 2904 remove HIP message OMNI sub-options from RSes they forward from a MN 2905 to an MSE, and insert and sign HIP message and Origin Indication sub- 2906 options in RAs they forward from an MSE to an MN. Conversely, ARs 2907 that act as proxys forward without processing any DHCPv6 information 2908 in RS/RA message exchanges between MNs and MSEs. The AR is therefore 2909 responsible for MN authentication while the MSE is responsible for 2910 registering/delegating MNPs. 2912 20. Time-Varying MNPs 2914 In some use cases, it is desirable, beneficial and efficient for the 2915 MN to receive a constant MNP that travels with the MN wherever it 2916 moves. For example, this would allow air traffic controllers to 2917 easily track aircraft, etc. In other cases, however (e.g., 2918 intelligent transportation systems), the MN may be willing to 2919 sacrifice a modicum of efficiency in order to have time-varying MNPs 2920 that can be changed every so often to defeat adversarial tracking. 2922 The prefix delegation services discussed in Section 14.3 allows OMNI 2923 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2924 send RS messages with source set to the unspecified address (::) and/ 2925 or with an OMNI option with DHCPv6 Option sub-options. The MN would 2926 then be obligated to renumber its internal networks whenever its MNP 2927 (and therefore also its OMNI address) changes. This should not 2928 present a challenge for MNs with automated network renumbering 2929 services, however presents limits for the durations of ongoing 2930 sessions that would prefer to use a constant address. 2932 21. (H)HITs and Temporary ULAs 2934 MNs that generate (H)HITs but do not have pre-assigned MNPs can 2935 request MNP delegations by issuing IPv6 ND messages that use the 2936 (H)HIT instead of a Temporary ULA. In particular, when a MN creates 2937 an RS message it can set the source to the unspecified address (::) 2938 and destination to All-Routers multicast. The IPv6 ND message 2939 includes an OMNI option with a HIP "Initiator" message sub-option, 2940 and need not include a Node Identification sub-option since the MN's 2941 HIT appears in the HIP message. The MN then encapsulates the message 2942 in an IPv6 header with the (H)HIT as the source address and with 2943 destination set to either a unicast or anycast ADM-ULA. The MN then 2944 sends the message to the AR as specified in Section 14.1. 2946 When the AR receives the message, it notes that the RS source was the 2947 unspecified address (::), then examines the RS encapsulation source 2948 address to determine that the source is a (H)HIT and not a Temporary 2949 ULA. The AR next invokes the DHCPv6 protocol to request an MNP 2950 prefix delegation while using the HIT as the Client Identifier, then 2951 prepares an RA message with source address set to its own ADM-LLA and 2952 destination set to the MNP-LLA corresponding to the delegated MNP. 2953 The AR next includes an OMNI option with a HIP "Responder" message 2954 and any DHCPv6 prefix delegation parameters. The AR then finally 2955 encapsulates the RA in an IPv6 header with source address set to its 2956 own ADM-ULA and destination set to the (H)HIT from the RS 2957 encapsulation source address, then returns the encapsulated RA to the 2958 MN. 2960 MNs can also use (H)HITs and/or Temporary ULAs for direct MN-to-MN 2961 communications outside the context of any OMNI link supporting 2962 infrastructure. When two MNs encounter one another they can use 2963 their (H)HITs and/or Temporary ULAs as IPv6 packet source and 2964 destination addresses to support direct communications. MNs can also 2965 inject their (H)HITs and/or Temporary ULAs into a MANET/VANET routing 2966 protocol to enable multihop communications. MNs can further exchange 2967 IPv6 ND messages (such as NS/NA) using their (H)HITs and/or Temporary 2968 ULAs as source and destination addresses. Note that the HIP security 2969 protocols for establishing secure neighbor relationships are based on 2970 (H)HITs; therefore, Temporary ULAs would presumably utilize some 2971 alternate form of message authentication such as the [RFC4380] 2972 authentication service. 2974 Lastly, when MNs are within the coverage range of OMNI link 2975 infrastructure a case could be made for injecting (H)HITs and/or 2976 Temporary ULAs into the global MS routing system. For example, when 2977 the MN sends an RS to a MSE it could include a request to inject the 2978 (H)HIT / Temporary ULA into the routing system instead of requesting 2979 an MNP prefix delegation. This would potentially enable OMNI link- 2980 wide communications using only (H)HITs or Temporary ULAs, and not 2981 MNPs. This document notes the opportunity, but makes no 2982 recommendation. 2984 22. Address Selection 2986 OMNI MNs use LLAs only for link-scoped communications on the OMNI 2987 link. Typically, MNs use LLAs as source/destination IPv6 addresses 2988 of IPv6 ND messages, but may also use them for addressing ordinary 2989 data packets exchanged with an OMNI link neighbor. 2991 OMNI MNs use MNP-ULAs as source/destination IPv6 addresses in the OAL 2992 headers of OAL-encapsulated packets. OMNI MNs use Temporary ULAs for 2993 OAL addressing when an MNP-ULA is not available, or as source/ 2994 destination IPv6 addresses for communications within a MANET/VANET 2995 local area. OMNI MNs use HITs instead of Temporary ULAs when 2996 operation outside the context of a specific ULA domain and/or source 2997 address attestation is necessary. 2999 OMNI MNs use MNP-based GUAs for communications with Internet 3000 destinations when they are within range of OMNI link supporting 3001 infrastructure that can inject the MNP into the routing system. 3003 23. IANA Considerations 3005 The following IANA actions are requested: 3007 23.1. "IPv6 Neighbor Discovery Option Formats" Registry 3009 The IANA is instructed to allocate an official Type number TBD1 from 3010 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 3011 option. Implementations set Type to 253 as an interim value 3012 [RFC4727]. 3014 23.2. "Ethernet Numbers" Registry 3016 The IANA is instructed to allocate one Ethernet unicast address TBD2 3017 (suggested value '00-52-14') in the 'ethernet-numbers' registry under 3018 "IANA Unicast 48-bit MAC Addresses" as follows: 3020 Addresses Usage Reference 3021 --------- ----- --------- 3022 00-52-14 Overlay Multilink Network (OMNI) Interface [RFCXXXX] 3024 Figure 24: IANA Unicast 48-bit MAC Addresses 3026 23.3. "ICMPv6 Code Fields: Type 2 - Packet Too Big" Registry 3028 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 3029 Code Fields: Type 2 - Packet Too Big" registry. The registry should 3030 appear as follows: 3032 Code Name Reference 3033 --- ---- --------- 3034 0 Diagnostic Packet Too Big [RFC4443] 3035 1 Advisory Packet Too Big [RFCXXXX] 3037 Figure 25: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 3039 23.4. "OMNI Option Sub-Type Values" (New Registry) 3041 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 3042 instructed to create and maintain a new registry entitled "OMNI 3043 Option Sub-Type Values". Initial values are given below (future 3044 assignments are to be made through Standards Action [RFC8126]): 3046 Value Sub-Type name Reference 3047 ----- ------------- ---------- 3048 0 Pad1 [RFCXXXX] 3049 1 PadN [RFCXXXX] 3050 2 Interface Attributes (Type 1) [RFCXXXX] 3051 3 Interface Attributes (Type 2) [RFCXXXX] 3052 4 Traffic Selector [RFCXXXX] 3053 5 MS-Register [RFCXXXX] 3054 6 MS-Release [RFCXXXX] 3055 7 Geo Coordinates [RFCXXXX] 3056 8 DHCPv6 Message [RFCXXXX] 3057 9 HIP Message [RFCXXXX] 3058 10 Node Identification [RFCXXXX] 3059 11-29 Unassigned 3060 30 Sub-Type Extension [RFCXXXX] 3061 31 Reserved by IANA [RFCXXXX] 3063 Figure 26: OMNI Option Sub-Type Values 3065 23.5. "OMNI Node Identification ID-Type Values" (New Registry) 3067 The OMNI Node Identification Sub-Option (see: Section 11.1.11) 3068 contains an 8-bit ID-Type field, for which IANA is instructed to 3069 create and maintain a new registry entitled "OMNI Node Identification 3070 ID-Type Values". Initial values are given below (future assignments 3071 are to be made through Expert Review [RFC8126]): 3073 Value Sub-Type name Reference 3074 ----- ------------- ---------- 3075 0 UUID [RFCXXXX] 3076 1 HIT [RFCXXXX] 3077 2 HHIT [RFCXXXX] 3078 3 Network Access Identifier [RFCXXXX] 3079 4 FQDN [RFCXXXX] 3080 5-252 Unassigned [RFCXXXX] 3081 253-254 Reserved for Experimentation [RFCXXXX] 3082 255 Reserved by IANA [RFCXXXX] 3084 Figure 27: OMNI Node Identification ID-Type Values 3086 23.6. "OMNI Option Sub-Type Extension Values" (New Registry) 3088 The OMNI option defines an 8-bit Extension-Type field for Sub-Type 30 3089 (Sub-Type Extension), for which IANA is instructed to create and 3090 maintain a new registry entitled "OMNI Option Sub-Type Extension 3091 Values". Initial values are given below (future assignments are to 3092 be made through Expert Review [RFC8126]): 3094 Value Sub-Type name Reference 3095 ----- ------------- ---------- 3096 0 RFC4380 UDP/IP Header Option [RFCXXXX] 3097 1 RFC6081 UDP/IP Trailer Option [RFCXXXX] 3098 2-252 Unassigned 3099 253-254 Reserved for Experimentation [RFCXXXX] 3100 255 Reserved by IANA [RFCXXXX] 3102 Figure 28: OMNI Option Sub-Type Extension Values 3104 23.7. "OMNI RFC4380 UDP/IP Header Option" (New Registry) 3106 The OMNI Sub-Type Extension "RFC4380 UDP/IP Header Option" defines an 3107 8-bit Header Type field, for which IANA is instructed to create and 3108 maintain a new registry entitled "OMNI RFC4380 UDP/IP Header Option". 3109 Initial registry values are given below (future assignments are to be 3110 made through Expert Review [RFC8126]): 3112 Value Sub-Type name Reference 3113 ----- ------------- ---------- 3114 0 Origin Indication (IPv4) [RFC4380] 3115 1 Authentication Encapsulation [RFC4380] 3116 2 Origin Indication (IPv6) [RFCXXXX] 3117 3-252 Unassigned 3118 253-254 Reserved for Experimentation [RFCXXXX] 3119 255 Reserved by IANA [RFCXXXX] 3121 Figure 29: OMNI RFC4380 UDP/IP Header Option 3123 23.8. "OMNI RFC6081 UDP/IP Trailer Option" (New Registry) 3125 The OMNI Sub-Type Extension for "RFC6081 UDP/IP Trailer Option" 3126 defines an 8-bit Trailer Type field, for which IANA is instructed to 3127 create and maintain a new registry entitled "OMNI RFC6081 UDP/IP 3128 Trailer Option". Initial registry values are given below (future 3129 assignments are to be made through Expert Review [RFC8126]): 3131 Value Sub-Type name Reference 3132 ----- ------------- ---------- 3133 0 Unassigned 3134 1 Nonce [RFC6081] 3135 2 Unassigned 3136 3 Alternate Address (IPv4) [RFC6081] 3137 4 Neighbor Discovery Option [RFC6081] 3138 5 Random Port [RFC6081] 3139 6 Alternate Address (IPv6) [RFCXXXX] 3140 7-252 Unassigned 3141 253-254 Reserved for Experimentation [RFCXXXX] 3142 255 Reserved by IANA [RFCXXXX] 3144 Figure 30: OMNI RFC6081 Trailer Option 3146 23.9. Additional Considerations 3148 The IANA has assigned the UDP port number "8060" for an earlier 3149 experimental version of AERO [RFC6706]. This document together with 3150 [I-D.templin-intarea-6706bis] reclaims the UDP port number "8060" for 3151 'aero' as the service port for UDP/IP encapsulation. (Note that, 3152 although [RFC6706] was not widely implemented or deployed, any 3153 messages coded to that specification can be easily distinguished and 3154 ignored since they use the invalid ICMPv6 message type number '0'.) 3155 The IANA is therefore instructed to update the reference for UDP port 3156 number "8060" from "RFC6706" to "RFCXXXX" (i.e., this document). 3158 The IANA has assigned a 4 octet Private Enterprise Number (PEN) code 3159 "45282" in the "enterprise-numbers" registry. This document is the 3160 normative reference for using this code in DHCP Unique IDentifiers 3161 based on Enterprise Numbers ("DUID-EN for OMNI Interfaces") (see: 3162 Section 10). The IANA is therefore instructed to change the 3163 enterprise designation for PEN code "45282" from "LinkUp Networks" to 3164 "Overlay Multilink Network Interface (OMNI)". 3166 The IANA has assigned the ifType code "301 - omni - Overlay Multilink 3167 Network Interface (OMNI)" in accordance with Section 6 of [RFC8892]. 3168 The registration appears under the IANA "Structure of Management 3169 Information (SMI) Numbers (MIB Module Registrations) - Interface 3170 Types (ifType)" registry. 3172 No further IANA actions are required. 3174 24. Security Considerations 3176 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 3177 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 3178 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 3179 confirmation and/or time synchronization is needed. 3181 MN OMNI interfaces configured over secured ANET interfaces inherit 3182 the physical and/or link-layer security properties (i.e., "protected 3183 spectrum") of the connected ANETs. MN OMNI interfaces configured 3184 over open INET interfaces can use symmetric securing services such as 3185 VPNs or can by some other means establish a direct link. When a VPN 3186 or direct link may be impractical, however, the security services 3187 specified in [RFC7401] and/or [RFC4380] can be employed. While the 3188 OMNI link protects control plane messaging, applications must still 3189 employ end-to-end transport- or higher-layer security services to 3190 protect the data plane. 3192 Strong network layer security for control plane messages and 3193 forwarding path integrity for data plane messages between MSEs MUST 3194 be supported. In one example, the AERO service 3195 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 3196 and secures the links in the spanning tree with network layer 3197 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 3198 plane messages are then constrained to travel only over the secured 3199 spanning tree paths and are therefore protected from attack or 3200 eavesdropping. Since data plane messages can travel over route 3201 optimized paths that do not strictly follow the spanning tree, 3202 however, end-to-end transport- or higher-layer security services are 3203 still required. 3205 Identity-based key verification infrastructure services such as iPSK 3206 may be necessary for verifying the identities claimed by MNs. This 3207 requirement should be harmonized with the manner in which (H)HITs are 3208 attested in a given operational environment. 3210 Security considerations for specific access network interface types 3211 are covered under the corresponding IP-over-(foo) specification 3212 (e.g., [RFC2464], [RFC2492], etc.). 3214 Security considerations for IPv6 fragmentation and reassembly are 3215 discussed in Section 5.5. 3217 25. Implementation Status 3219 AERO/OMNI Release-3.0.2 was tagged on October 15, 2020, and is 3220 undergoing internal testing. Additional internal releases expected 3221 within the coming months, with first public release expected end of 3222 1H2021. 3224 26. Acknowledgements 3226 The first version of this document was prepared per the consensus 3227 decision at the 7th Conference of the International Civil Aviation 3228 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 3229 2019. Consensus to take the document forward to the IETF was reached 3230 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 3231 Attendees and contributors included: Guray Acar, Danny Bharj, 3232 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 3233 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 3234 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 3235 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 3236 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 3237 Fryderyk Wrobel and Dongsong Zeng. 3239 The following individuals are acknowledged for their useful comments: 3240 Stuart Card, Michael Matyas, Robert Moskowitz, Madhu Niraula, Greg 3241 Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron 3242 and Michal Skorepa are especially recognized for their many helpful 3243 ideas and suggestions. Madhuri Madhava Badgandi, Sean Dickson, Don 3244 Dillenburg, Joe Dudkowski, Vijayasarathy Rajagopalan, Ron Sackman and 3245 Katherine Tran are acknowledged for their hard work on the 3246 implementation and technical insights that led to improvements for 3247 the spec. 3249 Discussions on the IETF 6man and atn mailing lists during the fall of 3250 2020 suggested additional points to consider. The authors gratefully 3251 acknowledge the list members who contributed valuable insights 3252 through those discussions. Eric Vyncke and Erik Kline were the 3253 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 3254 at the time the document was developed; they are all gratefully 3255 acknowledged for their many helpful insights. 3257 Early observations on IP fragmentation performance implications were 3258 noted in the 1986 Digital Equipment Corporation (DEC) "qe reset" 3259 investigation, where fragment bursts from NFS traffic caused hardware 3260 resets resulting in sustained retransmission storms. Jeff Chase and 3261 Chet Juzsczak of the Ultrix Engineering Group supported the 3262 investigation. Early observations on L2 media MTU mismatch issues 3263 were noted in the 1988 DEC FDDI investigation, where Raj Jain and KK 3264 Ramakrishnan represented architectural considerations for the FDDI/ 3265 Ethernet bridge. 3267 This work is aligned with the NASA Safe Autonomous Systems Operation 3268 (SASO) program under NASA contract number NNA16BD84C. 3270 This work is aligned with the FAA as per the SE2025 contract number 3271 DTFAWA-15-D-00030. 3273 This work is aligned with the Boeing Information Technology (BIT) 3274 Mobility Vision Lab (MVL) program. 3276 27. References 3278 27.1. Normative References 3280 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 3281 DOI 10.17487/RFC0791, September 1981, 3282 . 3284 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3285 Requirement Levels", BCP 14, RFC 2119, 3286 DOI 10.17487/RFC2119, March 1997, 3287 . 3289 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3290 "Definition of the Differentiated Services Field (DS 3291 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3292 DOI 10.17487/RFC2474, December 1998, 3293 . 3295 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 3296 "SEcure Neighbor Discovery (SEND)", RFC 3971, 3297 DOI 10.17487/RFC3971, March 2005, 3298 . 3300 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 3301 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 3302 November 2005, . 3304 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 3305 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 3306 . 3308 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3309 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3310 2006, . 3312 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 3313 Control Message Protocol (ICMPv6) for the Internet 3314 Protocol Version 6 (IPv6) Specification", STD 89, 3315 RFC 4443, DOI 10.17487/RFC4443, March 2006, 3316 . 3318 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 3319 ICMPv6, UDP, and TCP Headers", RFC 4727, 3320 DOI 10.17487/RFC4727, November 2006, 3321 . 3323 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 3324 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 3325 DOI 10.17487/RFC4861, September 2007, 3326 . 3328 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 3329 Address Autoconfiguration", RFC 4862, 3330 DOI 10.17487/RFC4862, September 2007, 3331 . 3333 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 3334 "Traffic Selectors for Flow Bindings", RFC 6088, 3335 DOI 10.17487/RFC6088, January 2011, 3336 . 3338 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 3339 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 3340 RFC 7401, DOI 10.17487/RFC7401, April 2015, 3341 . 3343 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 3344 Hosts in a Multi-Prefix Network", RFC 8028, 3345 DOI 10.17487/RFC8028, November 2016, 3346 . 3348 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 3349 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 3350 May 2017, . 3352 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3353 (IPv6) Specification", STD 86, RFC 8200, 3354 DOI 10.17487/RFC8200, July 2017, 3355 . 3357 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 3358 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 3359 DOI 10.17487/RFC8201, July 2017, 3360 . 3362 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 3363 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 3364 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 3365 RFC 8415, DOI 10.17487/RFC8415, November 2018, 3366 . 3368 27.2. Informative References 3370 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 3371 Interface for Civil Aviation, IETF Liaison Statement 3372 #1676, https://datatracker.ietf.org/liaison/1676/", March 3373 2020. 3375 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 3376 Aeronautical Telecommunication Network (ATN) using 3377 Internet Protocol Suite (IPS) Standards and Protocol), 3378 Draft Edition 3 (work-in-progress)", December 2020. 3380 [CKSUM] Stone, J., Greenwald, M., Partridge, C., and J. Hughes, 3381 "Performance of Checksums and CRC's Over Real Data, IEEE/ 3382 ACM Transactions on Networking, Vol. 6, No. 5", October 3383 1998. 3385 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 3386 Interface (FDDI), IEEE Transactions on Communications", 3387 August 1990. 3389 [I-D.ietf-drip-rid] 3390 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 3391 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 3392 progress), December 2020. 3394 [I-D.ietf-intarea-tunnels] 3395 Touch, J. and M. Townsley, "IP Tunnels in the Internet 3396 Architecture", draft-ietf-intarea-tunnels-10 (work in 3397 progress), September 2019. 3399 [I-D.ietf-ipwave-vehicular-networking] 3400 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 3401 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 3402 ipwave-vehicular-networking-19 (work in progress), July 3403 2020. 3405 [I-D.templin-6man-dhcpv6-ndopt] 3406 Templin, F., "A Unified Stateful/Stateless Configuration 3407 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 3408 (work in progress), January 2021. 3410 [I-D.templin-6man-lla-type] 3411 Templin, F., "The IPv6 Link-Local Address Type Field", 3412 draft-templin-6man-lla-type-02 (work in progress), 3413 November 2020. 3415 [I-D.templin-intarea-6706bis] 3416 Templin, F., "Asymmetric Extended Route Optimization 3417 (AERO)", draft-templin-intarea-6706bis-87 (work in 3418 progress), January 2021. 3420 [IPV4-GUA] 3421 Postel, J., "IPv4 Address Space Registry, 3422 https://www.iana.org/assignments/ipv4-address-space/ipv4- 3423 address-space.xhtml", December 2020. 3425 [IPV6-GUA] 3426 Postel, J., "IPv6 Global Unicast Address Assignments, 3427 https://www.iana.org/assignments/ipv6-unicast-address- 3428 assignments/ipv6-unicast-address-assignments.xhtml", 3429 December 2020. 3431 [RFC0905] "ISO Transport Protocol specification ISO DP 8073", 3432 RFC 905, DOI 10.17487/RFC0905, April 1984, 3433 . 3435 [RFC1035] Mockapetris, P., "Domain names - implementation and 3436 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 3437 November 1987, . 3439 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 3440 Communication Layers", STD 3, RFC 1122, 3441 DOI 10.17487/RFC1122, October 1989, 3442 . 3444 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 3445 DOI 10.17487/RFC1191, November 1990, 3446 . 3448 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 3449 RFC 1256, DOI 10.17487/RFC1256, September 1991, 3450 . 3452 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 3453 RFC 2131, DOI 10.17487/RFC2131, March 1997, 3454 . 3456 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 3457 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 3458 . 3460 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 3461 DOI 10.17487/RFC2328, April 1998, 3462 . 3464 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 3465 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 3466 . 3468 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 3469 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 3470 December 1998, . 3472 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 3473 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 3474 . 3476 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 3477 Domains without Explicit Tunnels", RFC 2529, 3478 DOI 10.17487/RFC2529, March 1999, 3479 . 3481 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 3482 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 3483 . 3485 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 3486 DOI 10.17487/RFC3330, September 2002, 3487 . 3489 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 3490 Considered Useful", BCP 82, RFC 3692, 3491 DOI 10.17487/RFC3692, January 2004, 3492 . 3494 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 3495 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 3496 DOI 10.17487/RFC3810, June 2004, 3497 . 3499 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 3500 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 3501 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 3502 RFC 3819, DOI 10.17487/RFC3819, July 2004, 3503 . 3505 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 3506 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 3507 2004, . 3509 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 3510 Unique IDentifier (UUID) URN Namespace", RFC 4122, 3511 DOI 10.17487/RFC4122, July 2005, 3512 . 3514 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 3515 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 3516 DOI 10.17487/RFC4271, January 2006, 3517 . 3519 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 3520 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 3521 December 2005, . 3523 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 3524 Network Address Translations (NATs)", RFC 4380, 3525 DOI 10.17487/RFC4380, February 2006, 3526 . 3528 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 3529 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 3530 2006, . 3532 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 3533 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 3534 . 3536 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 3537 "Considerations for Internet Group Management Protocol 3538 (IGMP) and Multicast Listener Discovery (MLD) Snooping 3539 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 3540 . 3542 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 3543 "Internet Group Management Protocol (IGMP) / Multicast 3544 Listener Discovery (MLD)-Based Multicast Forwarding 3545 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 3546 August 2006, . 3548 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3549 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 3550 . 3552 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 3553 Errors at High Data Rates", RFC 4963, 3554 DOI 10.17487/RFC4963, July 2007, 3555 . 3557 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 3558 Advertisement Flags Option", RFC 5175, 3559 DOI 10.17487/RFC5175, March 2008, 3560 . 3562 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 3563 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 3564 RFC 5213, DOI 10.17487/RFC5213, August 2008, 3565 . 3567 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 3568 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 3569 DOI 10.17487/RFC5214, March 2008, 3570 . 3572 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 3573 RFC 5558, DOI 10.17487/RFC5558, February 2010, 3574 . 3576 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 3577 Version 3 for IPv4 and IPv6", RFC 5798, 3578 DOI 10.17487/RFC5798, March 2010, 3579 . 3581 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 3582 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 3583 . 3585 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 3586 DOI 10.17487/RFC6081, January 2011, 3587 . 3589 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 3590 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 3591 DOI 10.17487/RFC6221, May 2011, 3592 . 3594 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 3595 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 3596 DOI 10.17487/RFC6355, August 2011, 3597 . 3599 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 3600 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 3601 2012, . 3603 [RFC6706] Templin, F., Ed., "Asymmetric Extended Route Optimization 3604 (AERO)", RFC 6706, DOI 10.17487/RFC6706, August 2012, 3605 . 3607 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 3608 UDP Checksums for Tunneled Packets", RFC 6935, 3609 DOI 10.17487/RFC6935, April 2013, 3610 . 3612 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 3613 for the Use of IPv6 UDP Datagrams with Zero Checksums", 3614 RFC 6936, DOI 10.17487/RFC6936, April 2013, 3615 . 3617 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 3618 with IPv6 Neighbor Discovery", RFC 6980, 3619 DOI 10.17487/RFC6980, August 2013, 3620 . 3622 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 3623 Requirements for IPv6 Customer Edge Routers", RFC 7084, 3624 DOI 10.17487/RFC7084, November 2013, 3625 . 3627 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 3628 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 3629 Boundary in IPv6 Addressing", RFC 7421, 3630 DOI 10.17487/RFC7421, January 2015, 3631 . 3633 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 3634 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 3635 DOI 10.17487/RFC7526, May 2015, 3636 . 3638 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 3639 DOI 10.17487/RFC7542, May 2015, 3640 . 3642 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 3643 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 3644 February 2016, . 3646 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 3647 Support for IP Hosts with Multi-Access Support", RFC 7847, 3648 DOI 10.17487/RFC7847, May 2016, 3649 . 3651 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 3652 Writing an IANA Considerations Section in RFCs", BCP 26, 3653 RFC 8126, DOI 10.17487/RFC8126, June 2017, 3654 . 3656 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 3657 Decraene, B., Litkowski, S., and R. Shakir, "Segment 3658 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 3659 July 2018, . 3661 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 3662 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 3663 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 3664 . 3666 [RFC8892] Thaler, D. and D. Romascanu, "Guidelines and Registration 3667 Procedures for Interface Types and Tunnel Types", 3668 RFC 8892, DOI 10.17487/RFC8892, August 2020, 3669 . 3671 [RFC8899] Fairhurst, G., Jones, T., Tuexen, M., Ruengeler, I., and 3672 T. Voelker, "Packetization Layer Path MTU Discovery for 3673 Datagram Transports", RFC 8899, DOI 10.17487/RFC8899, 3674 September 2020, . 3676 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 3677 and F. Gont, "IP Fragmentation Considered Fragile", 3678 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 3679 . 3681 [RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves, 3682 "Temporary Address Extensions for Stateless Address 3683 Autoconfiguration in IPv6", RFC 8981, 3684 DOI 10.17487/RFC8981, February 2021, 3685 . 3687 Appendix A. Interface Attribute Preferences Bitmap Encoding 3689 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 3690 encoding to specific Internetworks such as the Aeronautical 3691 Telecommunications Network with Internet Protocol Services (ATN/IPS) 3692 may include link selection preferences based on other traffic 3693 classifiers (e.g., transport port numbers, etc.) in addition to the 3694 existing DSCP-based preferences. Nodes on specific Internetworks 3695 maintain a map of traffic classifiers to additional P[*] preference 3696 fields beyond the first 64. For example, TCP port 22 maps to P[67], 3697 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 3699 Implementations use Simplex or Indexed encoding formats for P[*] 3700 encoding in order to encode a given set of traffic classifiers in the 3701 most efficient way. Some use cases may be more efficiently coded 3702 using Simplex form, while others may be more efficient using Indexed. 3703 Once a format is selected for preparation of a single Interface 3704 Attribute the same format must be used for the entire Interface 3705 Attribute sub-option. Different sub-options may use different 3706 formats. 3708 The following figures show coding examples for various Simplex and 3709 Indexed formats: 3711 0 1 2 3 3712 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 3713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3714 | Sub-Type=3| Sub-length=N | omIndex | omType | 3715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3716 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 3717 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3718 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 3719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3720 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 3721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3722 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 3723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3724 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3726 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 3727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3729 Figure 31: Example 1: Dense Simplex Encoding 3731 0 1 2 3 3732 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 3733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3734 | Sub-Type=3| Sub-length=N | omIndex | omType | 3735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3736 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 3737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3738 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3740 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 3741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3742 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 3743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3744 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 3745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3746 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 3747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3748 |Bitmap(10)=0x00| ... 3749 +-+-+-+-+-+-+-+-+-+-+- 3751 Figure 32: Example 2: Sparse Simplex Encoding 3753 0 1 2 3 3754 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 3755 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3756 | Sub-Type=3| Sub-length=N | omIndex | omType | 3757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3758 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 3759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3760 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 3761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3762 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 3763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3764 | Bitmap = 0x01 |796|797|798|799| ... 3765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3767 Figure 33: Example 3: Indexed Encoding 3769 Appendix B. VDL Mode 2 Considerations 3771 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 3772 (VDLM2) that specifies an essential radio frequency data link service 3773 for aircraft and ground stations in worldwide civil aviation air 3774 traffic management. The VDLM2 link type is "multicast capable" 3775 [RFC4861], but with considerable differences from common multicast 3776 links such as Ethernet and IEEE 802.11. 3778 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3779 magnitude less than most modern wireless networking gear. Second, 3780 due to the low available link bandwidth only VDLM2 ground stations 3781 (i.e., and not aircraft) are permitted to send broadcasts, and even 3782 so only as compact layer 2 "beacons". Third, aircraft employ the 3783 services of ground stations by performing unicast RS/RA exchanges 3784 upon receipt of beacons instead of listening for multicast RA 3785 messages and/or sending multicast RS messages. 3787 This beacon-oriented unicast RS/RA approach is necessary to conserve 3788 the already-scarce available link bandwidth. Moreover, since the 3789 numbers of beaconing ground stations operating within a given spatial 3790 range must be kept as sparse as possible, it would not be feasible to 3791 have different classes of ground stations within the same region 3792 observing different protocols. It is therefore highly desirable that 3793 all ground stations observe a common language of RS/RA as specified 3794 in this document. 3796 Note that links of this nature may benefit from compression 3797 techniques that reduce the bandwidth necessary for conveying the same 3798 amount of data. The IETF lpwan working group is considering possible 3799 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3801 Appendix C. MN / AR Isolation Through L2 Address Mapping 3803 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3804 unicast link-scoped IPv6 destination address. However, IPv6 ND 3805 messaging should be coordinated between the MN and AR only without 3806 invoking other nodes on the *NET. This implies that MN / AR control 3807 messaging should be isolated and not overheard by other nodes on the 3808 link. 3810 To support MN / AR isolation on some *NET links, ARs can maintain an 3811 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3812 *NETs, this specification reserves one Ethernet unicast address TBD2 3813 (see: Section 23). For non-Ethernet statically-addressed *NETs, 3814 MSADDR is reserved per the assigned numbers authority for the *NET 3815 addressing space. For still other *NETs, MSADDR may be dynamically 3816 discovered through other means, e.g., L2 beacons. 3818 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3819 both multicast and unicast) to MSADDR instead of to an ordinary 3820 unicast or multicast L2 address. In this way, all of the MN's IPv6 3821 ND messages will be received by ARs that are configured to accept 3822 packets destined to MSADDR. Note that multiple ARs on the link could 3823 be configured to accept packets destined to MSADDR, e.g., as a basis 3824 for supporting redundancy. 3826 Therefore, ARs must accept and process packets destined to MSADDR, 3827 while all other devices must not process packets destined to MSADDR. 3828 This model has well-established operational experience in Proxy 3829 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3831 Appendix D. Change Log 3833 << RFC Editor - remove prior to publication >> 3835 Differences from draft-templin-6man-omni-interface-35 to draft- 3836 templin-6man-omni-interface-36: 3838 o Major clarifications on aspects such as "hard/soft" PTB error 3839 messages 3841 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3842 be used in the data plane. 3844 Differences from draft-templin-6man-omni-interface-31 to draft- 3845 templin-6man-omni-interface-32: 3847 o MTU 3848 o Support for multi-hop ANETS such as ISATAP. 3850 Differences from draft-templin-6man-omni-interface-29 to draft- 3851 templin-6man-omni-interface-30: 3853 o Moved link-layer addressing information into the OMNI option on a 3854 per-ifIndex basis 3856 o Renamed "ifIndex-tuple" to "Interface Attributes" 3858 Differences from draft-templin-6man-omni-interface-27 to draft- 3859 templin-6man-omni-interface-28: 3861 o Updates based on implementation experience. 3863 Differences from draft-templin-6man-omni-interface-25 to draft- 3864 templin-6man-omni-interface-26: 3866 o Further clarification on "aggregate" RA messages. 3868 o Expanded Security Considerations to discuss expectations for 3869 security in the Mobility Service. 3871 Differences from draft-templin-6man-omni-interface-20 to draft- 3872 templin-6man-omni-interface-21: 3874 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3875 (PBM). 3877 Differences from draft-templin-6man-omni-interface-18 to draft- 3878 templin-6man-omni-interface-19: 3880 o SEND/CGA. 3882 Differences from draft-templin-6man-omni-interface-17 to draft- 3883 templin-6man-omni-interface-18: 3885 o Teredo 3887 Differences from draft-templin-6man-omni-interface-14 to draft- 3888 templin-6man-omni-interface-15: 3890 o Prefix length discussions removed. 3892 Differences from draft-templin-6man-omni-interface-12 to draft- 3893 templin-6man-omni-interface-13: 3895 o Teredo 3896 Differences from draft-templin-6man-omni-interface-11 to draft- 3897 templin-6man-omni-interface-12: 3899 o Major simplifications and clarifications on MTU and fragmentation. 3901 o Document now updates RFC4443 and RFC8201. 3903 Differences from draft-templin-6man-omni-interface-10 to draft- 3904 templin-6man-omni-interface-11: 3906 o Removed /64 assumption, resulting in new OMNI address format. 3908 Differences from draft-templin-6man-omni-interface-07 to draft- 3909 templin-6man-omni-interface-08: 3911 o OMNI MNs in the open Internet 3913 Differences from draft-templin-6man-omni-interface-06 to draft- 3914 templin-6man-omni-interface-07: 3916 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3917 L2 addressing. 3919 o Expanded "Transition Considerations". 3921 Differences from draft-templin-6man-omni-interface-05 to draft- 3922 templin-6man-omni-interface-06: 3924 o Brought back OMNI option "R" flag, and discussed its use. 3926 Differences from draft-templin-6man-omni-interface-04 to draft- 3927 templin-6man-omni-interface-05: 3929 o Transition considerations, and overhaul of RS/RA addressing with 3930 the inclusion of MSE addresses within the OMNI option instead of 3931 as RS/RA addresses (developed under FAA SE2025 contract number 3932 DTFAWA-15-D-00030). 3934 Differences from draft-templin-6man-omni-interface-02 to draft- 3935 templin-6man-omni-interface-03: 3937 o Added "advisory PTB messages" under FAA SE2025 contract number 3938 DTFAWA-15-D-00030. 3940 Differences from draft-templin-6man-omni-interface-01 to draft- 3941 templin-6man-omni-interface-02: 3943 o Removed "Primary" flag and supporting text. 3945 o Clarified that "Router Lifetime" applies to each ANET interface 3946 independently, and that the union of all ANET interface Router 3947 Lifetimes determines MSE lifetime. 3949 Differences from draft-templin-6man-omni-interface-00 to draft- 3950 templin-6man-omni-interface-01: 3952 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3953 for future use (most likely as "pseudo-multicast"). 3955 o Non-normative discussion of alternate OMNI LLA construction form 3956 made possible if the 64-bit assumption were relaxed. 3958 First draft version (draft-templin-atn-aero-interface-00): 3960 o Draft based on consensus decision of ICAO Working Group I Mobility 3961 Subgroup March 22, 2019. 3963 Authors' Addresses 3965 Fred L. Templin (editor) 3966 The Boeing Company 3967 P.O. Box 3707 3968 Seattle, WA 98124 3969 USA 3971 Email: fltemplin@acm.org 3973 Tony Whyman 3974 MWA Ltd c/o Inmarsat Global Ltd 3975 99 City Road 3976 London EC1Y 1AX 3977 England 3979 Email: tony.whyman@mccallumwhyman.com