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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, rfc3879, rfc4291, A. Whyman 5 rfc4443, rfc8201 (if approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track October 5, 2020 7 Expires: April 8, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-45 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 April 8, 2021. 41 Copyright Notice 43 Copyright (c) 2020 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 8 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 12 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 16 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 17 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 17 66 8. Site-Local Addresses (SLAs) . . . . . . . . . . . . . . . . . 18 67 9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 19 68 9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 21 69 9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 22 70 9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 22 71 9.1.3. Interface Attributes . . . . . . . . . . . . . . . . 22 72 9.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 26 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 27 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 27 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 28 76 9.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . . 29 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 29 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 30 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 30 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 30 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 31 82 12.1. Router Discovery in IP Multihop and IPv4-Only Access 83 Networks . . . . . . . . . . . . . . . . . . . . . . . . 35 84 12.2. MS-Register and MS-Release List Processing . . . . . . . 36 85 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 38 86 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 38 87 15. Detecting and Responding to MSE Failures . . . . . . . . . . 39 88 16. Transition Considerations . . . . . . . . . . . . . . . . . . 39 89 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 40 90 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 41 91 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 92 20. Security Considerations . . . . . . . . . . . . . . . . . . . 42 93 21. Implementation Status . . . . . . . . . . . . . . . . . . . . 43 94 22. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43 95 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 44 96 23.1. Normative References . . . . . . . . . . . . . . . . . . 44 97 23.2. Informative References . . . . . . . . . . . . . . . . . 46 98 Appendix A. Interface Attribute Heuristic Bitmap Encoding . . . 50 99 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 52 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 53 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 53 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56 104 1. Introduction 106 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 107 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 108 etc.) often have multiple data links for communicating with networked 109 correspondents. These data links may have diverse performance, cost 110 and availability properties that can change dynamically according to 111 mobility patterns, flight phases, proximity to infrastructure, etc. 112 MNs coordinate their data links in a discipline known as "multilink", 113 in which a single virtual interface is configured over the underlying 114 data links. 116 The MN configures a virtual interface (termed the "Overlay Multilink 117 Network (OMNI) interface") as a thin layer over the underlying Access 118 Network (ANET) interfaces. The OMNI interface is therefore the only 119 interface abstraction exposed to the IP layer and behaves according 120 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 121 while underlying interfaces appear as link layer communication 122 channels in the architecture. The OMNI interface connects to a 123 virtual overlay service known as the "OMNI link". The OMNI link 124 spans one or more Internetworks that may include private-use 125 infrastructures and/or the global public Internet itself. 127 Each MN receives a Mobile Network Prefix (MNP) for numbering 128 downstream-attached End User Networks (EUNs) independently of the 129 access network data links selected for data transport. The MN 130 performs router discovery over the OMNI interface (i.e., similar to 131 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 132 behalf of its EUNs. The router discovery process is iterated over 133 each of the OMNI interface's underlying interfaces in order to 134 register per-link parameters (see Section 12). 136 The OMNI interface provides a multilink nexus for exchanging inbound 137 and outbound traffic via the correct underlying interface(s). The IP 138 layer sees the OMNI interface as a point of connection to the OMNI 139 link. Each OMNI link has one or more associated Mobility Service 140 Prefixes (MSPs) from which OMNI link MNPs are derived. If there are 141 multiple OMNI links, the IPv6 layer will see multiple OMNI 142 interfaces. 144 MNs may connect to multiple distinct OMNI links by configuring 145 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 146 interface is configured over a set of underlying interfaces and 147 provides a nexus for Safety-Based Multilink (SBM) operation. The IP 148 layer selects an OMNI interface based on SBM routing considerations, 149 then the selected interface applies Performance-Based Multilink (PBM) 150 to select the correct underlying interface. Applications can apply 151 Segment Routing [RFC8402] to select independent SBM topologies for 152 fault tolerance. 154 The OMNI interface interacts with a network-based Mobility Service 155 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 156 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 157 track MN movements and represent their MNPs in a global routing or 158 mapping system. 160 This document specifies the transmission of IP packets and MN/MS 161 control messages over OMNI interfaces. The OMNI interface supports 162 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 163 as the network layer in the data plane, while using IPv6 ND messaging 164 as the control plane independently of the data plane IP protocol(s). 165 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 166 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 167 discussed in the following sections. 169 2. Terminology 171 The terminology in the normative references applies; especially, the 172 terms "link" and "interface" are the same as defined in the IPv6 173 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 174 Additionally, this document assumes the following IPv6 ND message 175 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 176 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 178 The Protocol Constants defined in Section 10 of [RFC4861] are used in 179 their same format and meaning in this document. The terms "All- 180 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 181 are the same as defined in [RFC4291] (with Link-Local scope assumed). 183 The term "IP" is used to refer collectively to either Internet 184 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 185 specification at the layer in question applies equally to either 186 version. 188 The following terms are defined within the scope of this document: 190 Mobile Node (MN) 191 an end system with a mobile router having multiple distinct 192 upstream data link connections that are grouped together in one or 193 more logical units. The MN's data link connection parameters can 194 change over time due to, e.g., node mobility, link quality, etc. 195 The MN further connects a downstream-attached End User Network 196 (EUN). The term MN used here is distinct from uses in other 197 documents, and does not imply a particular mobility protocol. 199 End User Network (EUN) 200 a simple or complex downstream-attached mobile network that 201 travels with the MN as a single logical unit. The IP addresses 202 assigned to EUN devices remain stable even if the MN's upstream 203 data link connections change. 205 Mobility Service (MS) 206 a mobile routing service that tracks MN movements and ensures that 207 MNs remain continuously reachable even across mobility events. 208 Specific MS details are out of scope for this document. 210 Mobility Service Endpoint (MSE) 211 an entity in the MS (either singular or aggregate) that 212 coordinates the mobility events of one or more MN. 214 Mobility Service Prefix (MSP) 215 an aggregated IP prefix (e.g., 2001:db8::/32, 192.0.2.0/24, etc.) 216 advertised to the rest of the Internetwork by the MS, and from 217 which more-specific Mobile Network Prefixes (MNPs) are derived. 219 Mobile Network Prefix (MNP) 220 a longer IP prefix taken from an MSP (e.g., 221 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 222 MNs sub-delegate the MNP to devices located in EUNs. 224 Access Network (ANET) 225 a data link service network (e.g., an aviation radio access 226 network, satellite service provider network, cellular operator 227 network, wifi network, etc.) that connects MNs. Physical and/or 228 data link level security between the MN and ANET are assumed. 230 Access Router (AR) 231 a first-hop router in the ANET for connecting MNs to 232 correspondents in outside Internetworks. 234 ANET interface 235 a MN's attachment to a link in an ANET. 237 Internetwork (INET) 238 a connected network region with a coherent IP addressing plan that 239 provides transit forwarding services for ANET MNs and INET 240 correspondents. Examples include private enterprise networks, 241 ground domain aviation service networks and the global public 242 Internet itself. 244 INET interface 245 a node's attachment to a link in an INET. 247 OMNI link 248 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 249 over one or more INETs and their connected ANETs. An OMNI link 250 can comprise multiple INET segments joined by bridges the same as 251 for any link; the addressing plans in each segment may be mutually 252 exclusive and managed by different administrative entities. 254 OMNI interface 255 a node's attachment to an OMNI link, and configured over one or 256 more underlying ANET/INET interfaces. 258 OMNI Adaptation Layer (OAL) 259 an OMNI interface process whereby packets admitted into the 260 interface are wrapped in a mid-layer IPv6 header and fragmented/ 261 reassembled if necessary to support the OMNI link Maximum 262 Transmission Unit (MTU). The OAL is also responsible for 263 generating MTU-related control messages as necessary, and for 264 providing addressing context for spanning multiple segments of a 265 bridged OMNI link. 267 OMNI Link-Local Address (LLA) 268 a link local IPv6 address per [RFC4291] constructed as specified 269 in Section 7. 271 OMNI Site-Local Address (SLA) 272 a site-local IPv6 address per [RFC4291] constructed as specified 273 in Section 8. OMNI SLAs are statelessly derived from OMNI LLAs, 274 and vice-versa. 276 OMNI Option 277 an IPv6 Neighbor Discovery option providing multilink parameters 278 for the OMNI interface as specified in Section 9. 280 Multilink 281 an OMNI interface's manner of managing diverse underlying data 282 link interfaces as a single logical unit. The OMNI interface 283 provides a single unified interface to upper layers, while 284 underlying data link selections are performed on a per-packet 285 basis considering factors such as DSCP, flow label, application 286 policy, signal quality, cost, etc. Multilinking decisions are 287 coordinated in both the outbound (i.e. MN to correspondent) and 288 inbound (i.e., correspondent to MN) directions. 290 L2 291 The second layer in the OSI network model. Also known as "layer- 292 2", "link-layer", "sub-IP layer", "data link layer", etc. 294 L3 295 The third layer in the OSI network model. Also known as "layer- 296 3", "network-layer", "IP layer", etc. 298 underlying interface 299 an ANET/INET interface over which an OMNI interface is configured. 300 The OMNI interface is seen as a L3 interface by the IP layer, and 301 each underlying interface is seen as a L2 interface by the OMNI 302 interface. 304 Mobility Service Identification (MSID) 305 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 306 as specified in Section 7. 308 Safety-Based Multilink (SBM) 309 A means for ensuring fault tolerance through redundancy by 310 connecting multiple independent OMNI interfaces to independent 311 routing topologies (i.e., multiple independent OMNI links). 313 Performance Based Multilink (PBM) 314 A means for selecting underlying interface(s) for packet 315 trasnmission and reception within a single OMNI interface. 317 3. Requirements 319 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 320 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 321 "OPTIONAL" in this document are to be interpreted as described in BCP 322 14 [RFC2119][RFC8174] when, and only when, they appear in all 323 capitals, as shown here. 325 OMNI links maintain a constant value "MAX_MSID" selected to provide 326 MNs with an acceptable level of MSE redundancy while minimizing 327 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 328 set to the default value 5; if a different value is chosen, it should 329 be set uniformly by all nodes on the OMNI link. 331 An implementation is not required to internally use the architectural 332 constructs described here so long as its external behavior is 333 consistent with that described in this document. 335 4. Overlay Multilink Network (OMNI) Interface Model 337 An OMNI interface is a MN virtual interface configured over one or 338 more underlying interfaces, which may be physical (e.g., an 339 aeronautical radio link) or virtual (e.g., an Internet or higher- 340 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 341 with the MS through IPv6 ND message exchanges. The MN uses the MNP 342 to construct a unique OMNI LLA through the algorithmic derivation 343 specified in Section 7 and assigns the LLA to the OMNI interface. 345 The OMNI interface architectural layering model is the same as in 346 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 347 therefore sees the OMNI interface as a single L3 interface with 348 multiple underlying interfaces that appear as L2 communication 349 channels in the architecture. 351 +----------------------------+ 352 | Upper Layer Protocol | 353 Session-to-IP +---->| | 354 Address Binding | +----------------------------+ 355 +---->| IP (L3) | 356 IP Address +---->| | 357 Binding | +----------------------------+ 358 +---->| OMNI Interface | 359 Logical-to- +---->| (OMNI LLA) | 360 Physical | +----------------------------+ 361 Interface +---->| L2 | L2 | | L2 | 362 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 363 +------+------+ +------+ 364 | L1 | L1 | | L1 | 365 | | | | | 366 +------+------+ +------+ 368 Figure 1: OMNI Interface Architectural Layering Model 370 Each underlying interface provides an L2/L1 abstraction according to 371 one of the following models: 373 o INET interfaces connect to an INET either natively or through one 374 or several IPv4 Network Address Translators (NATs). Native INET 375 interfaces have global IP addresses that are reachable from any 376 INET correspondent. NATed INET interfaces typically have private 377 IP addresses and connect to a private network behind one or more 378 NATs that provide INET access. 380 o ANET interfaces connect to a protected ANET that is separated from 381 the open INET by an AR acting as a proxy. The ANET interface may 382 be either on the same L2 link segment as the AR, or separated from 383 the AR by multiple IP hops. 385 o VPNed interfaces use security encapsulation over an INET/ANET to a 386 Virtual Private Network (VPN) gateway. Other than the link-layer 387 encapsulation format, VPNed interfaces behave the same as for 388 Direct interfaces. 390 o Direct (aka "point-to-point") interfaces connect directly to a 391 peer without crossing any ANET/INET paths. An example is a line- 392 of-sight link between a remote pilot and an unmanned aircraft. 394 The OMNI virtual interface model gives rise to a number of 395 opportunities: 397 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 398 Address Detection (DAD) or Muticast Listener Discovery (MLD) 399 messaging is necessary. 401 o ANET interfaces on the same L2 link segment as an AR do not 402 require any L3 addresses (i.e., not even link-local) in 403 environments where communications are coordinated entirely over 404 the OMNI interface. (An alternative would be to also assign the 405 same OMNI LLA to all ANET interfaces.) 407 o as underlying interface properties change (e.g., link quality, 408 cost, availability, etc.), any active interface can be used to 409 update the profiles of multiple additional interfaces in a single 410 message. This allows for timely adaptation and service continuity 411 under dynamically changing conditions. 413 o coordinating underlying interfaces in this way allows them to be 414 represented in a unified MS profile with provisions for mobility 415 and multilink operations. 417 o exposing a single virtual interface abstraction to the IPv6 layer 418 allows for multilink operation (including QoS based link 419 selection, packet replication, load balancing, etc.) at L2 while 420 still permitting L3 traffic shaping based on, e.g., DSCP, flow 421 label, etc. 423 o the OMNI interface allows inter-INET traversal when nodes located 424 in different INETs need to communicate with one another. This 425 mode of operation would not be possible via direct communications 426 over the underlying interfaces themselves. 428 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 429 lossless and adaptive path MTU mitigations not available for 430 communications directly over the underlying interfaces themselves. 432 o L3 sees the OMNI interface as a point of connection to the OMNI 433 link; if there are multiple OMNI links (i.e., multiple MS's), L3 434 will see multiple OMNI interfaces. 436 o Multiple independent OMNI interfaces can be used for increased 437 fault tolerance through Safety-Based Multilink (SBM), with 438 Performance-Based Multilink (PBM) applied within each interface. 440 Other opportunities are discussed in [RFC7847]. Note that even when 441 the OMNI virtual interface is present, applications can still access 442 underlying interfaces either through the network protocol stack using 443 an Internet socket or directly using a raw socket. This allows for 444 intra-network (or point-to-point) communications without invoking the 445 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 446 is configured over an underlying IPv4 interface, applications can 447 still invoke IPv4 intra-network communications as long as the 448 communicating endpoints are not subject to mobility dynamics. 449 However, the opportunities discussed above are not available when the 450 architectural layering is bypassed in this way. 452 Figure 2 depicts the architectural model for a MN connecting to the 453 MS via multiple independent ANETs. When an underlying interface 454 becomes active, the MN's OMNI interface sends native (i.e., 455 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 456 ND messages traverse the ground domain ANETs until they reach an 457 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 458 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 459 returns an IPv6 ND message response to the MN. IPv6 ND messages 460 traverse the ANET at layer 2; hence, the Hop Limit is not 461 decremented. 463 +--------------+ 464 | MN | 465 +--------------+ 466 |OMNI interface| 467 +----+----+----+ 468 +--------|IF#1|IF#2|IF#n|------ + 469 / +----+----+----+ \ 470 / | \ 471 / <---- Native | IP ----> \ 472 v v v 473 (:::)-. (:::)-. (:::)-. 474 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 475 `-(::::)-' `-(::::)-' `-(::::)-' 476 +----+ +----+ +----+ 477 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 478 . +-|--+ +-|--+ +-|--+ . 479 . | | | 480 . v v v . 481 . <----- Encapsulation -----> . 482 . . 483 . +-----+ (:::)-. . 484 . |MSE#2| .-(::::::::) +-----+ . 485 . +-----+ .-(::: INET :::)-. |MSE#m| . 486 . (::::: Routing ::::) +-----+ . 487 . `-(::: System :::)-' . 488 . +-----+ `-(:::::::-' . 489 . |MSE#1| +-----+ +-----+ . 490 . +-----+ |MSE#3| |MSE#4| . 491 . +-----+ +-----+ . 492 . . 493 . . 494 . <----- Worldwide Connected Internetwork ----> . 495 ........................................................... 497 Figure 2: MN/MS Coordination via Multiple ANETs 499 After the initial IPv6 ND message exchange, the MN can send and 500 receive unencapsulated IP data packets over the OMNI interface. OMNI 501 interface multilink services will forward the packets via ARs in the 502 correct underlying ANETs. The AR encapsulates the packets according 503 to the capabilities provided by the MS and forwards them to the next 504 hop within the worldwide connected Internetwork via optimal routes. 506 OMNI links span one or more underlying Internetwork via the OMNI 507 Adaptation Layer (OAL) which is based on a mid-layer overlay 508 encapsulation using [RFC2473] with IPv6 Site-Local Addressing (SLA) 509 [RFC4291]. Each OMNI link corresponds to a different overlay 510 (differentiated by an address codepoint) which may be carried over a 511 completely separate underlying topology. Each MN can facilitate SBM 512 by connecting to multiple OMNI links using a distinct OMNI interface 513 for each link. 515 5. The OMNI Adaptation Layer (OAL) 517 The OMNI interface observes the link nature of tunnels, including the 518 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 519 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 520 The OMNI interface is configured over one or more underlying 521 interfaces that may have diverse MTUs. OMNI interfaces accommodate 522 MTU diversity through the use of the OMNI Adpatation Layer (OAL) as 523 discussed in this section. 525 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 526 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 527 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 528 not permitted to perform network fragmentation even though the 529 destination is required to reassemble more. The network therefore 530 MUST forward packets of at least 1280 bytes without generating an 531 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 532 [RFC8201]. (Note: the source can apply "source fragmentation" for 533 locally-generated IPv6 packets up to 1500 bytes and larger still if 534 it if has a way to determine that the destination configures a larger 535 MRU, but this does not affect the minimum IPv6 path MTU.) 537 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 538 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 539 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 540 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 541 support network fragmentation and the destination is required to 542 reassemble at least that much. The DF bit in the IPv4 encapsulation 543 headers of packets sent over IPv4 underlying interfaces therefore 544 MUST be set to 0. (Note: even if the encapsulation source has a way 545 to determine that the encapsulation destination configures an MRU 546 larger than 576 bytes, it should not assume a larger minimum IPv4 547 path MTU without careful consderation of the issues discussed in 548 Section 5.1.) 550 The OMNI interface configures both an MTU and MRU of 9180 bytes 551 [RFC2492]; the size is therefore not a reflection of the underlying 552 interface MTUs, but rather determines the largest packet the OMNI 553 interface can forward or reassemble. The OMNI interface uses the 554 OMNI Adaptation Layer (OAL) to admit packets from the network layer 555 that are no larger than the OMNI interface MTU while generating 556 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 557 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 558 document refers to both of these ICMPv4/ICMPv6 message types simply 559 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 560 errors as discussed below. 562 For IPv4 packets with DF=0, the network layer performs IPv4 563 fragmentation if necessary then admits the packets/fragments into the 564 OMNI interface; these fragments will be reassembled by the final 565 destination. For IPv4 packets with DF=1 and IPv6 packets, the 566 network layer admits the packet if it is no larger than the OMNI 567 interface MTU; otherwise, it drops the packet and returns a PTB hard 568 error message to the source. 570 For each admitted IP packet/fragment, the OMNI interface internally 571 employs the OAL by either inserting or omitting a mid-layer IPv6 572 header between the inner IP packet/fragment and any outer IP 573 encapsulation headers per [RFC2473]. When the OAL inserts a mid- 574 layer IPv6 header, it calculates the 32-bit CRC over the entire 575 packet and writes the value in a trailing 4-octet field at the end of 576 the packet. The OAL then fragments this mid-layer IPv6 packet when 577 necessary, and returns internally-generated PTB soft error messages 578 for packets that it deems too large (e.g., according to link 579 performance characteristics, reassembly congestion, etc.) while 580 forwarding the packets/fragments without loss. This ensures that the 581 path MTU is adaptive and reflects the current path used for a given 582 data flow. 584 The OAL operates with respect to both the minimum IPv6 and IPv4 path 585 MTUs as follows: 587 o When an OMNI interface sends a packet toward a final destination 588 via an ANET peer, it sends without OAL encapsulation if the packet 589 (including any outer-layer ANET encapsulations) is no larger than 590 the underlying interface MTU for on-link ANET peers or the minimum 591 ANET path MTU for peers separated by multiple IP hops. Otherwise, 592 the OAL inserts an IPv6 header per [RFC2473] with source address 593 set to the node's own OMNI Site Local Address (SLA) (see: 594 Section 8) and destination set to the OMNI SLA of the ANET peer. 595 The OAL then calculates and appends the trailing 32-bit CRC, then 596 uses IPv6 fragmentation to break the packet into a minimum number 597 of non-overlapping fragments where the largest fragment size 598 (including both the OMNI and any outer-layer ANET encapsulations) 599 is determined by the underlying interface MTU for on-link ANET 600 peers or the minimum ANET path MTU for peers separated by multiple 601 IP hops. The OAL then encapsulates the fragements in any ANET 602 headers and sends them to the ANET peer, which reassembles before 603 forwarding toward the final destination. 605 o When an OMNI interface sends a packet toward a final destination 606 via an INET interface, it sends packets (including any outer-layer 607 INET encapsulations) no larger than the minimum INET path MTU 608 without OAL encapsulation if the destination is reached via an 609 INET address within the same OMNI link segment. Otherwise, the 610 OAL inserts an IPv6 header per [RFC2473] with source address set 611 to the node's OMNI SLA, destination set to the SLA of the next hop 612 OMNI node toward the final destination and (if necessary) with a 613 Segment Routing Header with the remaining Segment IDs on the path 614 to the final destination. The OAL then calculates and appends the 615 trailing 32-bit CRC, then uses IPv6 fragmentation to break the 616 packet into a minimum number of non-overlapping fragments where 617 the largest fragment size (including both the OMNI and outer-layer 618 INET encapsulations) is the minimum INET path MTU, and the 619 smallest fragment size is no smaller than 256 bytes (i.e., 620 slightly less than half the minimum IPv4 path MTU). The OAL then 621 encapsulates the fragments in any INET headers and sends them to 622 the OMNI link neighbor, which reassembles before forwarding toward 623 the final destination. 625 The OAL unconditionally drops all OAL fragments received from an INET 626 peer that are smaller than 256 bytes (note that no minimum fragment 627 size is specified for ANET peers since the underlying ANET is secured 628 against tiny fragment attacks). In order to set the correct context 629 for reassembly, the OAL of the OMNI interface that inserts the IPv6 630 header MUST also be the one that inserts the IPv6 Fragment Header 631 Identification value. While not strictly required, sending all 632 fragments of the same fragmented OAL packet consecutively over the 633 same underlying interface with minimal inter-fragment delay may 634 increase the likelihood of successful reassembly. 636 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 637 header Code field value 0 are hard errors that always indicate that a 638 packet has been dropped due to a real MTU restriction. However, the 639 OAL can also forward large packets via encapsulation and 640 fragmentation while at the same time returning PTB soft error 641 messages (subject to rate limiting) indicating that a forwarded 642 packet was uncomfortably large. The OMNI interface can therefore 643 continuously forward large packets without loss while returning PTB 644 soft error messages recommending a smaller size. Original sources 645 that receive the soft errors in turn reduce the size of the packets 646 they send, i.e., the same as for hard errors. 648 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 649 field to the value 1 in PTB soft error messages. Receiving nodes 650 that recognize the code reduce their estimate of the path MTU the 651 same as for hard errors but do not regard the message as a loss 652 indication. Nodes that do not recognize the code treat the message 653 the same as a hard error, but should heed the retransmission advice 654 given in [RFC8201] which suggests retransmission based on normal 655 packetization layer retransmission timers. This document therefore 656 updates [RFC1191][RFC4443] and [RFC8201]. Furthermore, 657 implementations of [RFC4821] must be aware that PTB hard or soft 658 errors may arrive at any time even if after a successful MTU probe 659 (this is the same consideration as for an ordinary path fluctuation 660 following a successful probe). 662 In summary, the OAL supports continuous transmission and reception of 663 packets of various sizes in the face of dynamically changing network 664 conditions. Moreover, since PTB soft errors do not indicate loss, 665 original sources that receive soft errors can quickly scan for path 666 MTU increases without waiting for the minimum 10 minutes specified 667 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 668 therefore provides a lossless and adaptive service that accommodates 669 MTU diversity especially well suited for dynamic multilink 670 environments. 672 Note: In network paths where IPv6/IPv4 protocol translation or IPv6- 673 in-IPv4 encapsulation may be prevalent, it may be prudent for the OAL 674 to always assume the IPv4 minimum path MTU (i.e., 576 bytes) 675 regardless of the underlying interface IP protocol version. Always 676 assuming the IPv4 minimum path MTU even for IPv6 underlying 677 interfaces may produce more fragments and additional header overhead, 678 but will always interoperate and never run the risk of presenting an 679 IPv4 node with a packet that exceeds its MRU. 681 Note: An OMNI interface that reassembles OAL fragments may experience 682 congestion-oriented loss in its reassembly cache and can optionally 683 send PTB soft errors to the original source and/or ICMP "Time 684 Exceeded" messages to the source of the OAL fragments. In 685 environments where the messages may contribute to unacceptable 686 additional congestion, however, the OMNI interface can simply regard 687 the loss as an ordinary unreported congestion event for which the 688 original source will eventually compensate. 690 Note: When the network layer forwards an IPv4 packet/fragment with 691 DF=0 into the OMNI interface, the interface can optionally perform 692 (further) IPv4 fragmentation before invoking the OAL so that the 693 fragments will be reassembled by the final destination. When the 694 network layer performs IPv6 fragmentation for locally-generated IPv6 695 packets, the OMNI interface typically invokes the OAL without first 696 applying (further) IPv6 fragmentation; the network layer should 697 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 698 push the reassembly burden to the final destination and avoid 699 receiving PTB soft errors from the OMNI interface. Aside from these 700 non-normative guidelines, the manner in which any IP fragmentation is 701 invoked prior to OAL encapsulation/fragmentation is an implementation 702 matter. 704 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 705 the receiving OAL will discard any packets with incorrect CRC values 706 following reassembly. The 32-bit CRC is sufficient to detect 707 reassembly misassociations for packet sizes up to the OMNI interface 708 MTU 9180 but may not be sufficient to detect errors for larger sizes 709 [CRC]. 711 Note: Some underlying interface types (e.g., VPNs) may already 712 provide their own robust fragmentation and reassembly services even 713 without OAL encapsulation. In those cases, the OAL can invoke the 714 inherent underlying interface schemes instead while employing PTB 715 soft errors in the same fashion as described above. Other underlying 716 interface properties such as header/message compression can also be 717 harnessed in a similar fashion. 719 5.1. Fragmentation Security Implications 721 As discussed in Section 3.7 of [RFC8900], there are four basic 722 threats concerning IPv6 fragmentation; each of which is addressed by 723 effective mitigations as follows: 725 1. Overlapping fragment attacks - reassembly of overlapping 726 fragments is forbidden by [RFC8200]; therefore, this threat does 727 not apply to the OAL. 729 2. Resource exhaustion attacks - this threat is mitigated by 730 providing a sufficiently large OAL reassembly cache and 731 instituting "fast discard" of incomplete reassemblies that may be 732 part of a buffer exhaustion attack. The reassembly cache should 733 be sufficiently large so that a sustained attack does not cause 734 excessive loss of good reassemblies but not so large that (timer- 735 based) data structure management becomes computationally 736 expensive. The cache should also be indexed based on the arrival 737 underlying interface such that congestion experienced over a 738 first underlying interface does not cause discard of incomplete 739 reassemblies for uncongested underlying interfaces. 741 3. Attacks based on predictable fragment identification values - 742 this threat is mitigated by selecting a suitably random ID value 743 per [RFC7739]. 745 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 746 threat is mitigated by disallowing "tiny fragments" per the OAL 747 fragmentation procedures specified above. 749 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 750 ID) field with only 65535 unique values such that at high data rates 751 the field could wrap and apply to new packets while the fragments of 752 old packets using the same ID are still alive in the network 753 [RFC4963]. However, since the largest OAL fragment that will be sent 754 via an IPv4 INET path is 576 bytes any IPv4 fragmentation would occur 755 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 756 recommendations suggest that such links will have low data rates. 757 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 758 at high data rates is not a concern for IPv6 fragmentation. 760 6. Frame Format 762 The OMNI interface transmits IPv6 packets according to the native 763 frame format of each underlying interface. For example, for 764 Ethernet-compatible interfaces the frame format is specified in 765 [RFC2464], for aeronautical radio interfaces the frame format is 766 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 767 Manual), for tunnels over IPv6 the frame format is specified in 768 [RFC2473], etc. 770 7. Link-Local Addresses (LLAs) 772 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 773 LLAs") as follows: 775 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 776 within the least-significant 112 bits of the IPv6 link-local 777 prefix fe80::/16. The Prefix Length is determined by adding 16 to 778 the length of the embedded MNP. For example, for the MNP 779 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 780 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 781 link-local address format specified in Section 2.5.6 of [RFC4291] 782 by defining a use for bits 11 - 63. 784 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 785 i.e., the most significant 16 bits of the prefix fe80::/16, 786 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 787 32bit IPv4 address/prefix. The Prefix Length is determined by 788 adding 96 to the length of the embedded IPv4 address/prefix. For 789 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 790 fe80::ffff:192.0.2.0/120 (also written as 791 fe80::ffff:c000:0200/120). 793 o MS OMNI LLAs are assigned to ARs and MSEs from the range 794 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 795 of the LLA includes a unique integer "MSID" value between 796 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 797 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 798 determined by adding 96 to the MSID prefix length. For example, 799 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 800 Prefix Length is set to 112 and the LLA is written as 801 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 802 "Anycast" MSID and corresponds to the link-local Subnet-Router 803 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 804 through 0xffffffff is reserved for future use. 806 o The OMNI LLA range fe80::/32 is used as the service prefix for the 807 address format specified in Section 4 of [RFC4380] (see Section 17 808 for further discussion). 810 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 811 MNPs can be allocated from that block ensuring that there is no 812 possibility for overlap between the above OMNI LLA constructs. 814 Since MN OMNI LLAs are based on the distribution of administratively 815 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 816 through administrative assignment, OMNI interfaces set the 817 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 819 8. Site-Local Addresses (SLAs) 821 OMNI links use IPv6 Site Local Addresses (i.e., "OMNI SLAs") 822 [RFC4291] as the source and destination addresses in OAL IPv6 823 encapsulation headers. This document assumes use of the SLA prefix 824 fec0::/10 for mapping OMNI LLAs to routable OMNI SLAs. 826 Each OMNI link instance is identified by bits 10-15 of the OMNI 827 service prefix fec0::/10. For example, OMNI SLAs associated with 828 instance 0 are configured from the prefix fec0::/16, instance 1 from 829 fec1::/16, etc., up to instance 63 from feff::/16. OMNI SLAs and 830 their associated prefix lengths are configured in one-to-one 831 correspondence with OMNI LLAs through stateless prefix translation. 832 For example, for OMNI link instance fec0::/16: 834 o the OMNI SLA corresponding to fe80:2001:db8:1:2::/80 is simply 835 fec0:2001:db8:1:2::/80 837 o the OMNI SLA corresponding to fe80::ffff:192.0.2.0/120 is simply 838 fec0::ffff:192.0.2.0/120 840 o the OMNI SLA corresponding to fe80::1000/112 is simply 841 fec0::1000/112 843 o the OMNI SLA corresponding to fe80::/128 is simply fec0::/128. 845 Each OMNI interface assigns the Anycast OMNI SLA specific to the OMNI 846 link instance, e.g., the OMNI interface connected to instance 3 847 assigns the Anycast OMNI SLA fec3:. Routers that configure OMNI 848 interfaces advertise the OMNI service prefix (e.g., fec3::/16) into 849 the local routing system so that applications can direct traffic 850 according to SBM requirements. 852 The OMNI SLA presents an IPv6 address format that is routable within 853 the OMNI link routing system and can be used to convey link-scoped 854 messages across multiple hops using IPv6 encapsulation [RFC2473]. 855 The OMNI link extends across one or more underling Internetworks to 856 include all ARs and MSEs. All MNs are also considered to be 857 connected to the OMNI link, however OAL encapsulation is omitted over 858 ANET links when possible to conserve bandwidth (see: Section 11). 860 The OMNI link can be subdivided into "segments" that often correspond 861 to different administrative domains or physical partitions. OMNI 862 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 863 support efficient packet forwarding to destinations located in other 864 OMNI link segments. A full discussion of Segment Routing over the 865 OMNI link appears in [I-D.templin-intarea-6706bis]. 867 NOTE: This document re-purposes the deprectated IPv6 Site-Local 868 Address (SLA) range fec0::/10 [RFC3879]. Re-purposing SLAs is a 869 natural fit since both LLA and SLA prefix lengths are ::/10, the 870 prefixes fe80:: and fec0:: differ only in a single bit setting, and 871 LLAs and SLAs can be unambiguously allocated in one-to-one 872 correspondence with one another. Re-purposing SLAs would also make 873 good use of an otherwise-wasted address range that has been "parked" 874 since the 2004 deprecation. However, this use of SLAs would require 875 an IETF standards action acknowledging this document as obsoleting 876 [RFC3879] and updating [RFC4291]. The authors therefore defer to 877 IETF consensus as to the proper way forward. 879 9. Address Mapping - Unicast 881 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 882 state and use the link-local address format specified in Section 7. 883 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 884 over physical underlying interfaces without encapsulation observe the 885 native underlying interface Source/Target Link-Layer Address Option 886 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 887 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 888 interfaces via encapsulation do not include S/TLLAOs which were 889 intended for encoding physical L2 media address formats and not 890 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 891 for encoding additional interface attributes. Hence, this document 892 does not define an S/TLLAO format but instead defines a new option 893 type termed the "OMNI option" designed for these purposes. 895 MNs such as aircraft typically have many wireless data link types 896 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 897 etc.) with diverse performance, cost and availability properties. 898 The OMNI interface would therefore appear to have multiple L2 899 connections, and may include information for multiple underlying 900 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 901 an IPv6 ND option called the OMNI option formatted as shown in 902 Figure 3: 904 0 1 2 3 905 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 1 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 907 | Type | Length | Prefix Length | S/T-ifIndex | 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 909 | | 910 ~ Sub-Options ~ 911 | | 912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 914 Figure 3: OMNI Option Format 916 In this format: 918 o Type is set to TBD. If multiple OMNI option instances appear in 919 the same IPv6 ND message, the first instance is processed and all 920 other instances are ignored. 922 o Length is set to the number of 8 octet blocks in the option. 924 o Prefix Length is determines the length of prefix to be applied to 925 an OMNI MN LLA/SLA. For IPv6 ND messages sent from a MN to the 926 MS, Prefix Length is the length that the MN is requesting or 927 asserting to the MS. For IPv6 ND messages sent from the MS to the 928 MN, Prefix Length indicates the length that the MS is granting to 929 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 930 Length indicates the length associated with the target MN that is 931 subject of the ND message. 933 o S/T-ifIndex corresponds to the ifIndex value for source or target 934 underlying interface used to convey this IPv6 ND message. OMNI 935 interfaces MUST number each distinct underlying interface with an 936 ifIndex value between '1' and '255' that represents a MN-specific 937 8-bit mapping for the actual ifIndex value assigned by network 938 management [RFC2863] (the ifIndex value '0' is reserved for use by 939 the MS). For RS and NS messages,S/T-ifIndex corresponds to the 940 source underlying interface the message originated from. For RA 941 and NA messages, S/T-ifIndex corresponds to the target underlying 942 interface that the message is destined to. 944 o Sub-Options is a Variable-length field, of length such that the 945 complete OMNI Option is an integer multiple of 8 octets long. 946 Contains one or more Sub-Options, as described in Section 9.1. 948 9.1. Sub-Options 950 The OMNI option includes zero or more Sub-Options. Each consecutive 951 Sub-Option is concatenated immediately after its predecessor. All 952 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 953 encoded in the following format: 955 0 1 2 956 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 5 957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 958 | Sub-Type | Sub-length | Sub-Option Data ... 959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 961 Figure 4: Sub-Option Format 963 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 964 Sub-Options defined in this document are: 966 Option Name Sub-Type 967 Pad1 0 968 PadN 1 969 Interface Attributes 2 970 Traffic Selector 3 971 MS-Register 4 972 MS-Release 5 973 Network Access Identifier 6 974 Geo Coordinates 7 975 DHCP Unique Identifier (DUID) 8 977 Figure 5 979 Sub-Types 253 and 254 are reserved for experimentation, as 980 recommended in [RFC3692]. 982 o Sub-Length is a 1-octet field that encodes the length of the Sub- 983 Option Data (i.e., ranging from 0 to 255 octets). 985 o Sub-Option Data is a block of data with format determined by Sub- 986 Type. 988 During processing, unrecognized Sub-Options are ignored and the next 989 Sub-Option processed until the end of the OMNI option is reached. 991 The following Sub-Option types and formats are defined in this 992 document: 994 9.1.1. Pad1 996 0 997 0 1 2 3 4 5 6 7 998 +-+-+-+-+-+-+-+-+ 999 | Sub-Type=0 | 1000 +-+-+-+-+-+-+-+-+ 1002 Figure 6: Pad1 1004 o Sub-Type is set to 0. If multiple instances appear in the same 1005 OMNI option all are processed. 1007 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 1008 consists of a single zero octet). 1010 9.1.2. PadN 1012 0 1 2 1013 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 1014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1015 | Sub-Type=1 | Sub-length=N | N padding octets ... 1016 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1018 Figure 7: PadN 1020 o Sub-Type is set to 1. If multiple instances appear in the same 1021 OMNI option all are processed. 1023 o Sub-Length is set to N (from 0 to 255) being the number of padding 1024 octets that follow. 1026 o Sub-Option Data consists of N zero-valued octets. 1028 9.1.3. Interface Attributes 1029 0 1 2 3 1030 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 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 | Provider ID | Link |R| APS | SRT | FMT | LHS (0 - 7) | 1035 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 | LHS (bits 8 - 31) | ~ 1037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1038 ~ ~ 1039 ~ Link Layer Address (L2ADDR) ~ 1040 ~ ~ 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1042 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1046 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1049 Figure 8: Interface Attributes 1051 o Sub-Type is set to 2. If multiple instances with different 1052 ifIndex values appear in the same OMNI option all are processed; 1053 if multiple instances with the same ifIndex value appear, the 1054 first is processed and all others are ignored. 1056 o Sub-Length is set to N (from 4 to 255) that encodes the number of 1057 Sub-Option Data octets that follow. 1059 o Sub-Option Data contains an "Interface Attribute" option encoded 1060 as follows (note that the first four octets must be present): 1062 * ifIndex is set to an 8-bit integer value corresponding to a 1063 specific underlying interface the same as specified above for 1064 the OMNI option header S/T-ifIndex. An OMNI option may include 1065 multiple Interface Attributes Sub-Options, with each distinct 1066 ifIndex value pertaining to a different underlying interface. 1067 The OMNI option will often include an Interface Attributes Sub- 1068 Option with the same ifIndex value that appears in the S/ 1069 T-ifIndex. In that case, the actual encapsulation address of 1070 the received IPv6 ND message should be compared with the L2ADDR 1071 encoded in the Sub-Option (see below); if the addresses are 1072 different (or, if L2ADDR absent) the presence of a Network 1073 Address Translator (NAT) is indicated. 1075 * ifType is set to an 8-bit integer value corresponding to the 1076 underlying interface identified by ifIndex. The value 1077 represents an OMNI interface-specific 8-bit mapping for the 1078 actual IANA ifType value registered in the 'IANAifType-MIB' 1079 registry [http://www.iana.org]. 1081 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1082 for the network service provider associated with this ifIndex. 1084 * Link encodes a 4-bit link metric. The value '0' means the link 1085 is DOWN, and the remaining values mean the link is UP with 1086 metric ranging from '1' ("lowest") to '15' ("highest"). 1088 * R is reserved for future use. 1090 * APS - a 3-bit "Address/Preferences/Simplex" code that 1091 determines the contents of the remainder of the sub-option as 1092 follows: 1094 + When the most significant bit (i.e., "Address") is set to 1, 1095 the SRT, FMT, LHS and L2ADDR fields are included immediately 1096 following the APS code; else, they are omitted. 1098 + When the next most significant bit (i.e., "Preferences") is 1099 set to 1, a preferences block is included next; else, it is 1100 omitted. (Note that if "Address" is set the preferences 1101 block immediately follows L2ADDR; else, it immediately 1102 follows the APS code.) 1104 + When a preferences block is present and the least 1105 significant bit (i.e., "Simplex") is set to 1, the block is 1106 encoded in "Simplex" form as shown in Figure 8; else it is 1107 encoded in "Indexed" form as discussed below. 1109 * When APS indicates that an "Address" is included, the following 1110 fields appear in consecutive order (else, they are omitted): 1112 + SRT - a 5-bit Segment Routing Topology prefix length value 1113 that (when added to 96) determines the prefix length to 1114 apply to the SLA formed from concatenating fe*::/96 with the 1115 32 bit LHS MSID value that follows. For example, the value 1116 16 corresponds to the prefix length 112. 1118 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1119 the included Link Layer Address as follows: 1121 - When the most significant bit (i.e., "Framework") is set 1122 to 0, L2ADDR is the INET encapsulation address of a 1123 Proxy/Server; otherwise, it is the addresss for the 1124 Source/Target itself 1126 - When the next most significant bit (i.e., "Mode") is set 1127 to 0, the Source/Target L2ADDR is on the open INET; 1128 otherwise, it is (likely) located behind a Network 1129 Address Translator (NAT). 1131 - When the least significant bit (i.e., "Type") is set to 1132 0, L2ADDR includes a UDP Port Number followed by an IPv4 1133 address; else, a UDP Port Number followed by an IPv6 1134 address. 1136 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1137 path to the target. When SRT and LHS are both set to 0, the 1138 LHS is considered unspecified in this IPv6 ND message. When 1139 SRT is set to 0 and LHS is non-zero, the prefix length is 1140 set to 128. SRT and LHS provide guidance to the OMNI 1141 interface forwarding algorithm. Specifically, if SRT/LHS is 1142 located in the local OMNI link segment then the OMNI 1143 interface can encapsulate according to FMT/L2ADDR; else, it 1144 must forward according to the OMNI link spanning tree. See 1145 [I-D.templin-intarea-6706bis] for further discussion. 1147 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1148 and identifies the link-layer address (i.e., the 1149 encapsulation address) of the source/target. The UDP Port 1150 Number appears in the first two octets and the IP address 1151 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1152 The Port Number and IP address are recorded in ones- 1153 compliment "obfuscated" form per [RFC4380]. The OMNI 1154 interface forwarding algoritherm uses FMT/L2ADDR to 1155 determine the encapsulation address for forwarding when SRT/ 1156 LHS is located in the local OMNI link segment. 1158 * When APS indicates that "Preferences" are included, a 1159 preferences block appears as the remainder of the Sub-Option as 1160 a series of Bitmaps and P[*] values. In "Simplex" form, the 1161 index for each singleton Bitmap octet is inferred from its 1162 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1163 In "Indexed" form, each Bitmap is preceded by an Index octet 1164 that encodes a value "i" = (0 - 255) as the index for its 1165 companion Bitmap as follows: 1167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1168 | Index=i | Bitmap(i) |P[*] values ... 1169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1171 Figure 9 1173 * The preferences consist of a first (simplex/indexed) Bitmap 1174 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1175 2-bit P[*] values, followed by a second Bitmap (i), followed by 1176 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1177 the bits of each Bitmap(i) that are set to '1'' indicate the 1178 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1179 that follow; if any Bitmap(i) bits are '0', then the 1180 corresponding P[*] block is instead omitted. For example, if 1181 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1182 followed by the block with P[04]-P[07], etc., and ending with 1183 the block with P[28]-P[31] are included (as shown in Figure 8). 1184 The next Bitmap(i) is then consulted with its bits indicating 1185 which P[*] blocks follow, etc. out to the end of the Sub- 1186 Option. 1188 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1189 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1190 preference for underlying interface selection purposes. Not 1191 all P[*] values need to be included in the OMNI option of each 1192 IPv6 ND message received. Any P[*] values represented in an 1193 earlier OMNI option but omitted in the current OMNI option 1194 remain unchanged. Any P[*] values not yet represented in any 1195 OMNI option default to "medium". 1197 * The first 16 P[*] blocks correspond to the 64 Differentiated 1198 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1199 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1200 traffic classifier values P[64], P[65], P[66], etc. See 1201 Appendix A for further discussion and examples. 1203 9.1.4. Traffic Selector 1205 0 1 2 3 1206 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 1207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1208 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1210 ~ ~ 1211 ~ RFC 6088 Format Traffic Selector ~ 1212 ~ ~ 1213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1215 Figure 10: Traffic Selector 1217 o Sub-Type is set to 3. If multiple instances appear in the same 1218 OMNI option all are processed, i.e., even if the same ifIndex 1219 value appears multiple times. 1221 o Sub-Length is set to N (the number of Sub-Option Data octets that 1222 follow). 1224 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1225 specified in Section 9.1.3, followed by an N-1 octet traffic 1226 selector formatted per [RFC6088] beginning with the "TS Format" 1227 field. The largest traffic selector for a given ifIndex is 1228 therefore 254 octets. 1230 9.1.5. MS-Register 1232 0 1 2 3 1233 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 1234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1235 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1237 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1239 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1241 ... ... ... ... ... ... 1242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1243 | MSID [n] (bits 16 - 32) | 1244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1246 Figure 11: MS-Register Sub-option 1248 o Sub-Type is set to 4. If multiple instances appear in the same 1249 OMNI option all are processed. Only the first MAX_MSID values 1250 processed (whether in a single instance or multiple) are retained 1251 and all other MSIDs are ignored. 1253 o Sub-Length is set to 4n. 1255 o A list of n 4-octet MSIDs is included in the following 4n octets. 1256 The Anycast MSID value '0' in an RS message MS-Register sub-option 1257 requests the recipient to return the MSID of a nearby MSE in a 1258 corresponding RA response. 1260 9.1.6. MS-Release 1261 0 1 2 3 1262 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 1263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1264 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1266 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1268 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1270 ... ... ... ... ... ... 1271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1272 | MSID [n] (bits 16 - 32) | 1273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1275 Figure 12: MS-Release Sub-option 1277 o Sub-Type is set to 5. If multiple instances appear in the same 1278 IPv6 OMNI option all are processed. Only the first MAX_MSID 1279 values processed (whether in a single instance or multiple) are 1280 retained and all other MSIDs are ignored. 1282 o Sub-Length is set to 4n. 1284 o A list of n 4 octet MSIDs is included in the following 4n octets. 1285 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1286 i.e., only non-zero values are processed. 1288 9.1.7. Network Access Identifier (NAI) 1290 0 1 2 3 1291 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 1292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1296 Figure 13: Network Access Identifier (NAI) Sub-option 1298 o Sub-Type is set to 6. If multiple instances appear in the same 1299 OMNI option the first is processed and all others are ignored. 1301 o Sub-Length is set to N. 1303 o A Network Access Identifier (NAI) up to 255 octets in length is 1304 coded per [RFC7542]. 1306 9.1.8. Geo Coordinates 1308 0 1 2 3 1309 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 1310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1311 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1314 Figure 14: Geo Coordinates Sub-option 1316 o Sub-Type is set to 7. If multiple instances appear in the same 1317 OMNI option the first is processed and all others are ignored. 1319 o Sub-Length is set to N. 1321 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1322 Includes Latitude/Longitude at a minimum; may also include 1323 additional attributes such as altitude, heading, speed, etc.). 1325 9.1.9. DHCP Unique Identifier (DUID) 1327 0 1 2 3 1328 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 1329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1330 | Sub-Type=8 | Sub-length=N | DUID-Type | 1331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1332 . . 1333 . type-specific DUID body (variable length) . 1334 . . 1335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1337 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1339 o Sub-Type is set to 8. If multiple instances appear in the same 1340 OMNI option the first is processed and all others are ignored. 1342 o Sub-Length is set to N (i.e., the length of the option beginning 1343 with the DUID-Type and continuing to the end of the type-specific 1344 body). 1346 o DUID-Type is a two-octet field coded in network byte order that 1347 determines the format and contents of the type-specific body 1348 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1349 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1350 which will occur in common operational practice. 1352 o A type-specific DUID body up to 253 octets in length follows, 1353 formatted according to DUID-type. For example, for type 4 the 1354 body consists of a 128-bit UUID selected according to [RFC6355]. 1356 10. Address Mapping - Multicast 1358 The multicast address mapping of the native underlying interface 1359 applies. The mobile router on board the MN also serves as an IGMP/ 1360 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1361 using the L2 address of the AR as the L2 address for all multicast 1362 packets. 1364 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1365 coordinate with the AR, and ANET L2 elements use MLD snooping 1366 [RFC4541]. 1368 11. Conceptual Sending Algorithm 1370 The MN's IPv6 layer selects the outbound OMNI interface according to 1371 SBM considerations when forwarding data packets from local or EUN 1372 applications to external correspondents. Each OMNI interface 1373 maintains a neighbor cache the same as for any IPv6 interface, but 1374 with additional state for multilink coordination. 1376 After a packet enters the OMNI interface, an outbound underlying 1377 interface is selected based on PBM traffic attributes such as DSCP, 1378 application port number, cost, performance, message size, etc. OMNI 1379 interface multilink selections could also be configured to perform 1380 replication across multiple underlying interfaces for increased 1381 reliability at the expense of packet duplication. 1383 When the OMNI interface sends a packet over a selected outbound 1384 underlying interface, the OAL includes or omits a mid-layer 1385 encapsulation header as necessary as discussed in Section 5. The OAL 1386 also performs encapsulation when the nearest AR is located multiple 1387 hops away as discussed in Section 12.1. 1389 OMNI interface multilink service designers MUST observe the BCP 1390 guidance in Section 15 [RFC3819] in terms of implications for 1391 reordering when packets from the same flow may be spread across 1392 multiple underlying interfaces having diverse properties. 1394 11.1. Multiple OMNI Interfaces 1396 MNs may connect to multiple independent OMNI links concurrently in 1397 support of SBM. Each OMNI interface is distinguished by its Anycast 1398 OMNI SLA (e.g., fec0::, fec1::, fec2::). The MN configures a 1399 separate OMNI interface for each link so that multiple interfaces 1400 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1401 different Anycast OMNI SLA is assigned to each interface, and the MN 1402 injects the service prefixes for the OMNI link instances into the EUN 1403 routing system. 1405 Applications in EUNs can use Segment Routing to select the desired 1406 OMNI interface based on SBM considerations. The Anycast OMNI SLA is 1407 written into the IPv6 destination address, and the actual destination 1408 (along with any additional intermediate hops) is written into the 1409 Segment Routing Header. Standard IP routing directs the packets to 1410 the MN's mobile router entity, and the Anycast OMNI SLA identifies 1411 the OMNI interface to be used for transmission to the next hop. When 1412 the MN receives the message, it replaces the IPv6 destination address 1413 with the next hop found in the routing header and transmits the 1414 message over the OMNI interface identified by the Anycast OMNI SLA. 1416 Multiple distinct OMNI links can therefore be used to support fault 1417 tolerance, load balancing, reliability, etc. The architectural model 1418 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1420 12. Router Discovery and Prefix Registration 1422 MNs interface with the MS by sending RS messages with OMNI options 1423 under the assumption that one or more AR on the ANET will process the 1424 message and respond. The manner in which the ANET ensures AR 1425 coordination is link-specific and outside the scope of this document 1426 (however, considerations for ANETs that do not provide ARs that 1427 recognize the OMNI option are discussed in Section 17). 1429 For each underlying interface, the MN sends an RS message with an 1430 OMNI option to coordinate with MSEs identified by MSID values. 1431 Example MSID discovery methods are given in [RFC5214] and include 1432 data link login parameters, name service lookups, static 1433 configuration, a static "hosts" file, etc. The MN can also send an 1434 RS with an MS-Register suboption that includes the Anycast MSID value 1435 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1436 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1437 be itself) and returns an RA with the selected MSID in an MS-Register 1438 suboption. The AR selects only a single wildcard MSE (i.e., even if 1439 the RS MS-Register suboption included multiple '0' MSIDs) while also 1440 soliciting the MSEs corresponding to any non-zero MSIDs. 1442 MNs configure OMNI interfaces that observe the properties discussed 1443 in the previous section. The OMNI interface and its underlying 1444 interfaces are said to be in either the "UP" or "DOWN" state 1445 according to administrative actions in conjunction with the interface 1446 connectivity status. An OMNI interface transitions to UP or DOWN 1447 through administrative action and/or through state transitions of the 1448 underlying interfaces. When a first underlying interface transitions 1449 to UP, the OMNI interface also transitions to UP. When all 1450 underlying interfaces transition to DOWN, the OMNI interface also 1451 transitions to DOWN. 1453 When an OMNI interface transitions to UP, the MN sends RS messages to 1454 register its MNP and an initial set of underlying interfaces that are 1455 also UP. The MN sends additional RS messages to refresh lifetimes 1456 and to register/deregister underlying interfaces as they transition 1457 to UP or DOWN. The MN sends initial RS messages over an UP 1458 underlying interface with its OMNI LLA as the source and with 1459 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1460 messages include an OMNI option per Section 9 with valid prefix 1461 registration information, Interface Attributes appropriate for 1462 underlying interfaces, MS-Register/Release sub-options containing 1463 MSID values, and with any other necessary OMNI sub-options. The S/ 1464 T-ifIndex field is set to the index of the underlying interface over 1465 which the RS message is sent. 1467 ARs process IPv6 ND messages with OMNI options and act as an MSE 1468 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1469 and create a neighbor cache entry for the MN, then coordinate with 1470 any MSEs named in the Register/Release lists in a manner outside the 1471 scope of this document. When an MSE processes the OMNI information, 1472 it first validates the prefix registration information then injects/ 1473 withdraws the MNP in the routing/mapping system and caches/discards 1474 the new Prefix Length, MNP and Interface Attributes. The MSE then 1475 informs the AR of registration success/failure, and the AR returns an 1476 RA message to the MN with an OMNI option per Section 9. 1478 The AR returns the RA message via the same underlying interface of 1479 the MN over which the RS was received, and with destination address 1480 set to the MN OMNI LLA (i.e., unicast), with source address set to 1481 its own OMNI LLA, and with an OMNI option with S/T-ifIndex set to the 1482 value included in the RS. The OMNI option also includes valid prefix 1483 registration information, Interface Attributes, MS-Register/Release 1484 and any other necessary OMNI sub-options. The RA also includes any 1485 information for the link, including RA Cur Hop Limit, M and O flags, 1486 Router Lifetime, Reachable Time and Retrans Timer values, and 1487 includes any necessary options such as: 1489 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1491 o RIOs [RFC4191] with more-specific routes. 1493 o an MTU option that specifies the maximum acceptable packet size 1494 for this ANET interface. 1496 The AR MAY also send periodic and/or event-driven unsolicited RA 1497 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1498 OMNI header of the unsolicited RA message identifies the target 1499 underlying interface of the destination MN. 1501 The AR can combine the information from multiple MSEs into one or 1502 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1503 Each aggregate RA includes an OMNI option with MS-Register/Release 1504 sub-options with the MSEs represented by the aggregate. If an 1505 aggregate is sent, the RA message contents must consistently 1506 represent the combined information advertised by all represented 1507 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1508 address, the MN determines the addresses of the represented MSEs by 1509 examining the MS-Register/Release OMNI sub-options. 1511 When the MN receives the RA message, it creates an OMNI interface 1512 neighbor cache entry for each MSID that has confirmed MNP 1513 registration via the L2 address of this AR. If the MN connects to 1514 multiple ANETs, it records the additional L2 AR addresses in each 1515 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1516 then manages its underlying interfaces according to their states as 1517 follows: 1519 o When an underlying interface transitions to UP, the MN sends an RS 1520 over the underlying interface with an OMNI option. The OMNI 1521 option contains at least one Interface Attribute sub-option with 1522 values specific to this underlying interface, and may contain 1523 additional Interface Attributes specific to other underlying 1524 interfaces. The option also includes any MS-Register/Release sub- 1525 options. 1527 o When an underlying interface transitions to DOWN, the MN sends an 1528 RS or unsolicited NA message over any UP underlying interface with 1529 an OMNI option containing an Interface Attribute sub-option for 1530 the DOWN underlying interface with Link set to '0'. The MN sends 1531 an RS when an acknowledgement is required, or an unsolicited NA 1532 when reliability is not thought to be a concern (e.g., if 1533 redundant transmissions are sent on multiple underlying 1534 interfaces). 1536 o When the Router Lifetime for a specific AR nears expiration, the 1537 MN sends an RS over the underlying interface to receive a fresh 1538 RA. If no RA is received, the MN can send RS messages to an 1539 alternate MSID in case the current MSID has failed. If no RS 1540 messages are received even after trying to contact alternate 1541 MSIDs, the MN marks the underlying interface as DOWN. 1543 o When a MN wishes to release from one or more current MSIDs, it 1544 sends an RS or unsolicited NA message over any UP underlying 1545 interfaces with an OMNI option with a Release MSID. Each MSID 1546 then withdraws the MNP from the routing/mapping system and informs 1547 the AR that the release was successful. 1549 o When all of a MNs underlying interfaces have transitioned to DOWN 1550 (or if the prefix registration lifetime expires), any associated 1551 MSEs withdraw the MNP the same as if they had received a message 1552 with a release indication. 1554 The MN is responsible for retrying each RS exchange up to 1555 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1556 seconds until an RA is received. If no RA is received over a an UP 1557 underlying interface (i.e., even after attempting to contact 1558 alternate MSEs), the MN declares this underlying interface as DOWN. 1560 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1561 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1562 returns an internally-generated RA message as though the message 1563 originated from an IPv6 router. The internally-generated RA message 1564 contains configuration information that is consistent with the 1565 information received from the RAs generated by the MS. Whether the 1566 OMNI interface IPv6 ND messaging process is initiated from the 1567 receipt of an RS message from the IPv6 layer is an implementation 1568 matter. Some implementations may elect to defer the IPv6 ND 1569 messaging process until an RS is received from the IPv6 layer, while 1570 others may elect to initiate the process proactively. Still other 1571 deployments may elect to administratively disable the ordinary RS/RA 1572 messaging used by the IPv6 layer over the OMNI interface, since they 1573 are not required to drive the internal RS/RA processing. (Note that 1574 this same logic applies to IPv4 implementations that employ ICMP- 1575 based Router Discovery per [RFC1256].) 1577 Note: The Router Lifetime value in RA messages indicates the time 1578 before which the MN must send another RS message over this underlying 1579 interface (e.g., 600 seconds), however that timescale may be 1580 significantly longer than the lifetime the MS has committed to retain 1581 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1582 therefore responsible for keeping MS state alive on a shorter 1583 timescale than the MN is required to do on its own behalf. 1585 Note: On multicast-capable underlying interfaces, MNs should send 1586 periodic unsolicited multicast NA messages and ARs should send 1587 periodic unsolicited multicast RA messages as "beacons" that can be 1588 heard by other nodes on the link. If a node fails to receive a 1589 beacon after a timeout value specific to the link, it can initiate a 1590 unicast exchange to test reachability. 1592 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1594 On some ANET types a MN may be located multiple IP hops away from the 1595 nearest AR. Forwarding through IP multihop ANETs is conducted 1596 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1597 Network (MANET) routing protocol over omni-directional wireless 1598 interfaces, an inter-domain routing protocol in an enterprise 1599 network, etc.). These ANETs could be either IPv6-enabled or 1600 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1601 unicast-only (note that for IPv4-only ANETs the following procedures 1602 apply for both single-hop and multhop cases). 1604 A MN located potentially multiple ANET hops away from the nearst AR 1605 prepares an RS message with source address set to its OMNI LLA and 1606 with destination set to link-scoped All-Routers multicast the same as 1607 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1608 the message in an IPv6 header with source address set to the SLA 1609 corresponding to the LLA source address and with destination set to 1610 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1611 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1612 with source address set to the node's own IPv4 address. For 1613 multicast-capable IPv4-only ANETs, the MN then sets the destination 1614 address to the site-scoped IPv4 multicast address corresponding to 1615 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1616 IPv4-only ANETs, the MN instead sets the destination address to the 1617 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1618 encapsulated RS message via the ANET interface, where it will be 1619 forwarded by zero or more intermediate ANET hops. 1621 When an intermediate ANET hop that particpates in the routing 1622 protocol receives the encapsulated RS, it forwards the message 1623 according to its routing tables (note that an intermediate node could 1624 be a fixed infrastructure element or another MN). This process 1625 repeats iteratively until the RS message is received by a penultimate 1626 ANET hop within single-hop communications range of an AR, which 1627 forwards the message to the AR. 1629 When the AR receives the message, it decapsulates the RS and 1630 coordinates with the MS the same as for an ordinary link-local RS, 1631 since the inner Hop Limit will not have been decremented by the 1632 multihop forwarding process. The AR then prepares an RA message with 1633 source address set to its own LLA and destination address set to the 1634 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1635 header with source address set to its own IPv4/SLA address and with 1636 destination set to the encapsulation source of the RS. 1638 The AR then forwards the message to an ANET node within 1639 communications range, which forwards the message according to its 1640 routing tables to an intermediate node. The multihop forwarding 1641 process within the ANET continues repetitively until the message is 1642 delivered to the original MN, which decapsulates the message and 1643 performs autoconfiguration the same as if it had received the RA 1644 directly from the AR as an on-link neighbor. 1646 Note: An alternate approach to multihop forwarding via IPv6 1647 encapsulation would be to statelessly translate the IPv6 LLAs into 1648 SLAs and forward the messages without encapsulation. This would 1649 violate the [RFC4861] requirement that certain IPv6 ND messages must 1650 use link-local addresses and must not be accepted if received with 1651 Hop Limit less than 255. This document therefore advocates 1652 encapsulation since the overhead is nominal considering the 1653 infrequent nature and small size of IPv6 ND messages. Future 1654 documents may consider encapsulation avoidance through translation 1655 while updating [RFC4861]. 1657 Note: An alternate approach to multihop forwarding via IPv4 1658 encapsulation would be to employ IPv6/IPv4 protocol translation. 1659 However, for IPv6 ND messages the OMNI LLA addresses would be 1660 truncated due to translation and the OMNI Router and Prefix Discovery 1661 services would not be able to function. The use of IPv4 1662 encapsulation is therefore indicated. 1664 12.2. MS-Register and MS-Release List Processing 1666 When a MN sends an RS message with an OMNI option via an underlying 1667 interface to an AR, the MN must convey its knowledge of its 1668 currently-associated MSEs. Initially, the MN will have no associated 1669 MSEs and should therefore include an MS-Register sub-option with the 1670 single MSID value 0 which requests the AR to select and assign an 1671 MSE. The AR will then return an RA message with source address set 1672 to the OMNI LLA containing the MSE of the selected MSE. 1674 As the MN activates additional underlying interfaces, it can 1675 optionally include an MS-Register sub-option with MSID value 0, or 1676 with non-zero MSIDs for MSEs discovered from previous RS/RA 1677 exchanges. The MN will thus eventually begin to learn and manage its 1678 currently active set of MSEs, and can register with new MSEs or 1679 release from former MSEs with each successive RS/RA exchange. As the 1680 MN's MSE constituency grows, it alone is responsible for including or 1681 omitting MSIDs in the MS-Register/Release lists it sends in RS 1682 messages. The inclusion or omission of MSIDs determines the MN's 1683 interface to the MS and defines the manner in which MSEs will 1684 respond. The only limiting factor is that the MN should include no 1685 more than MAX_MSID values in each list per each IPv6 ND message, and 1686 should avoid duplication of entries in each list unless it wants to 1687 increase likelihood of control message delivery. 1689 When an AR receives an RS message sent by a MN with an OMNI option, 1690 the option will contain zero or more MS-Register and MS-Release sub- 1691 options containing MSIDs. After processing the OMNI option, the AR 1692 will have a list of zero or more MS-Register MSIDs and a list of zero 1693 or more of MS-Release MSIDs. The AR then processes the lists as 1694 follows: 1696 o For each list, retain the first MAX_MSID values in the list and 1697 discard any additional MSIDs (i.e., even if there are duplicates 1698 within a list). 1700 o Next, for each MSID in the MS-Register list, remove all matching 1701 MSIDs from the MS-Release list. 1703 o Next, proceed according to whether the AR's own MSID or the value 1704 0 appears in the MS-Register list as folllows: 1706 * If yes, send an RA message directly back to the MN and send a 1707 proxy copy of the RS message to each additional MSID in the MS- 1708 Register list with the MS-Register/Release lists omitted. 1709 Then, send a uNA message to each MSID in the MS-Release list 1710 with the MS-Register/Release lists omitted and with an OMNI 1711 header with S/T-ifIndex set to 0. 1713 * If no, send a proxy copy of the RS message to each additional 1714 MSID in the MS-Register list with the MS-Register list omitted. 1715 For the first MSID, include the original MS-Release list; for 1716 all other MSIDs, omit the MS-Release list. 1718 Each proxy copy of the RS message will include an OMNI option and 1719 encapsulation header with the SLA of the AR as the source and the SLA 1720 of the Register MSE as the destination. When the Register MSE 1721 receives the proxy RS message, if the message includes an MS-Release 1722 list the MSE sends a uNA message to each additional MSID in the 1723 Release list. The Register MSE then sends an RA message back to the 1724 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1725 destination addresses reversed, and with RA destination set to the 1726 LLA of the MN. When the AR receives this RA message, it sends a 1727 proxy copy of the RA to the MN. 1729 Each uNA message (whether send by the first-hop AR or by a Register 1730 MSE) will include an OMNI option and an encapsulation header with the 1731 SLA of the Register MSE as the source and the SLA of the Release ME 1732 as the destination. The uNA informs the Release MSE that its 1733 previous relationship with the MN has been released and that the 1734 source of the uNA message is now registered. The Release MSE must 1735 then note that the subject MN of the uNA message is now "departed", 1736 and forward any subsequent packets destined to the MN to the Register 1737 MSE. 1739 Note that it is not an error for the MS-Register/Release lists to 1740 include duplicate entries. If duplicates occur within a list, the 1741 the AR will generate multiple proxy RS and/or uNA messages - one for 1742 each copy of the duplicate entries. 1744 13. Secure Redirection 1746 If the ANET link model is multiple access, the AR is responsible for 1747 assuring that address duplication cannot corrupt the neighbor caches 1748 of other nodes on the link. When the MN sends an RS message on a 1749 multiple access ANET link, the AR verifies that the MN is authorized 1750 to use the address and returns an RA with a non-zero Router Lifetime 1751 only if the MN is authorized. 1753 After verifying MN authorization and returning an RA, the AR MAY 1754 return IPv6 ND Redirect messages to direct MNs located on the same 1755 ANET link to exchange packets directly without transiting the AR. In 1756 that case, the MNs can exchange packets according to their unicast L2 1757 addresses discovered from the Redirect message instead of using the 1758 dogleg path through the AR. In some ANET links, however, such direct 1759 communications may be undesirable and continued use of the dogleg 1760 path through the AR may provide better performance. In that case, 1761 the AR can refrain from sending Redirects, and/or MNs can ignore 1762 them. 1764 14. AR and MSE Resilience 1766 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1767 [RFC5798] configurations so that service continuity is maintained 1768 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1769 the (redundant) ARs is currently providing service, and any service 1770 discontinuity will be limited to the failover time supported by VRRP. 1771 Widely deployed public domain implementations of VRRP are available. 1773 MSEs SHOULD use high availability clustering services so that 1774 multiple redundant systems can provide coordinated response to 1775 failures. As with VRRP, widely deployed public domain 1776 implementations of high availability clustering services are 1777 available. Note that special-purpose and expensive dedicated 1778 hardware is not necessary, and public domain implementations can be 1779 used even between lightweight virtual machines in cloud deployments. 1781 15. Detecting and Responding to MSE Failures 1783 In environments where fast recovery from MSE failure is required, ARs 1784 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1785 manner that parallels Bidirectional Forwarding Detection (BFD) 1786 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1787 react to failures so that cached information is re-established 1788 through alternate paths. Proactive NUD control messaging is carried 1789 only over well-connected ground domain networks (i.e., and not low- 1790 end ANET links such as aeronautical radios) and can therefore be 1791 tuned for rapid response. 1793 ARs perform proactive NUD for MSEs for which there are currently 1794 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1795 of the outage by sending multicast RA messages on the ANET interface. 1796 The AR sends RA messages to MNs via the ANET interface with an OMNI 1797 option with a Release ID for the failed MSE, and with destination 1798 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1800 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1801 by small delays [RFC4861]. Any MNs on the ANET interface that have 1802 been using the (now defunct) MSE will receive the RA messages and 1803 associate with a new MSE. 1805 16. Transition Considerations 1807 When a MN connects to an ANET link for the first time, it sends an RS 1808 message with an OMNI option. If the first hop AR recognizes the 1809 option, it returns an RA with its MS OMNI LLA as the source, the MN 1810 OMNI LLA as the destination and with an OMNI option included. The MN 1811 then engages the AR according to the OMNI link model specified above. 1812 If the first hop AR is a legacy IPv6 router, however, it instead 1813 returns an RA message with no OMNI option and with a non-OMNI unicast 1814 source LLA as specified in [RFC4861]. In that case, the MN engages 1815 the ANET according to the legacy IPv6 link model and without the OMNI 1816 extensions specified in this document. 1818 If the ANET link model is multiple access, there must be assurance 1819 that address duplication cannot corrupt the neighbor caches of other 1820 nodes on the link. When the MN sends an RS message on a multiple 1821 access ANET link with an OMNI LLA source address and an OMNI option, 1822 ARs that recognize the option ensure that the MN is authorized to use 1823 the address and return an RA with a non-zero Router Lifetime only if 1824 the MN is authorized. ARs that do not recognize the option instead 1825 return an RA that makes no statement about the MN's authorization to 1826 use the source address. In that case, the MN should perform 1827 Duplicate Address Detection to ensure that it does not interfere with 1828 other nodes on the link. 1830 An alternative approach for multiple access ANET links to ensure 1831 isolation for MN / AR communications is through L2 address mappings 1832 as discussed in Appendix C. This arrangement imparts a (virtual) 1833 point-to-point link model over the (physical) multiple access link. 1835 17. OMNI Interfaces on the Open Internet 1837 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1838 the open Internet without an OMNI-aware first-hop AR receive RA 1839 messages that do not include an OMNI option, while OMNI interfaces 1840 configured over IPv4-only underlying interfaces do not receive any 1841 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1842 without an OMNI option configure addresses, on-link prefxies, etc. on 1843 the underlying interface that received the RA according to standard 1844 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1845 interfaces configured over IPv4-only underlying interfaces configure 1846 IPv4 address information on the underlying interfaces using 1847 mechanisms such as DHCPv4 [RFC2131]. 1849 OMNI interfaces configured over underlying interfaces that connect to 1850 the open Internet can apply security services such as VPNs to connect 1851 to an MSE or establish a direct link to an MSE through some other 1852 means. In environments where an explicit VPN or direct link may be 1853 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1854 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1855 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1856 other protocol-specific security services can can also be used if 1857 additional authentication is necessary.) 1859 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1860 interfaces send control plane messages to interface with the MS. The 1861 control plane messages must be authenticated while data plane 1862 messages are delivered the same as for ordinary best-effort Internet 1863 traffic with basic source address-based data origin verification. 1864 Data plane communications via OMNI interfaces that connect over the 1865 open Internet without an explicit VPN should therefore employ 1866 transport- or higher-layer security to ensure integrity and/or 1867 confidentiality. 1869 When SEND/CGA are used over an open Internet underlying interfaces, 1870 each OMNI node configures a link-local CGA for use as the source 1871 address of IPv6 ND messages. The node then employs OMNI link 1872 encapsualation and sets the IPv6 source address of the OMNI header to 1873 the SLA corresponding to its OMNI LLA. Any Prefix Length values in 1874 the IPv6 ND message OMNI option then apply to the SLA found in the 1875 OMNI header, i.e., and not to the CGA found in the IPv6 ND message 1876 source address. 1878 OMNI interfaces in the open Internet are often located behind Network 1879 Address Translators (NATs). The OMNI interface accommodates NAT 1880 traversal using UDP/IP encapsulation and the mechanisms discussed in 1881 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1883 18. Time-Varying MNPs 1885 In some use cases, it is desirable, beneficial and efficient for the 1886 MN to receive a constant MNP that travels with the MN wherever it 1887 moves. For example, this would allow air traffic controllers to 1888 easily track aircraft, etc. In other cases, however (e.g., 1889 intelligent transportation systems), the MN may be willing to 1890 sacrifice a modicum of efficiency in order to have time-varying MNPs 1891 that can be changed every so often to defeat adversarial tracking. 1893 Prefix delegation services such as those discussed in 1894 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1895 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1896 prefixes. In that case, the identity of the MN can be used as a 1897 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1898 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1899 internal networks whenever its MNP (and therefore also its OMNI 1900 address) changes. This should not present a challenge for MNs with 1901 automated network renumbering services, however presents limits for 1902 the durations of ongoing sessions that would prefer to use a constant 1903 address. 1905 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1906 sets the source address of an RS message to fe80:: and includes a 1907 DUID sub-option and a desired Prefix Length value in the RS message 1908 OMNI option. When the first-hop AR receives the RS message, it 1909 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1910 of the requested length then returns an RA message with the OMNI LLA 1911 corresponding to the MNP as the destination address. When the MN 1912 receives the RA message, it provisons the PD to its downstream- 1913 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1914 messaging. 1916 19. IANA Considerations 1918 The IANA is instructed to allocate an official Type number TBD from 1919 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1920 option. Implementations set Type to 253 as an interim value 1921 [RFC4727]. 1923 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1924 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1925 read as follows: 1927 Code Name Reference 1928 --- ---- --------- 1929 0 Diagnostic Packet Too Big [RFC4443] 1930 1 Advisory Packet Too Big [RFCXXXX] 1932 Figure 16: OMNI Option Sub-Type Values 1934 The IANA is instructed to allocate one Ethernet unicast address TBD2 1935 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1936 Address Block - Unicast Use". 1938 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1939 is instructed to create and maintain a new registry entitled "OMNI 1940 option Sub-Type values". Initial values for the OMNI option Sub-Type 1941 values registry are given below; future assignments are to be made 1942 through Expert Review [RFC8126]. 1944 Value Sub-Type name Reference 1945 ----- ------------- ---------- 1946 0 Pad1 [RFCXXXX] 1947 1 PadN [RFCXXXX] 1948 2 Interface Attributes [RFCXXXX] 1949 3 Traffic Selector [RFCXXXX] 1950 4 MS-Register [RFCXXXX] 1951 5 MS-Release [RFCXXXX] 1952 6 Network Acceess Identifier [RFCXXXX] 1953 7 Geo Coordinates [RFCXXXX] 1954 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1955 9-252 Unassigned 1956 253-254 Experimental [RFCXXXX] 1957 255 Reserved [RFCXXXX] 1959 Figure 17: OMNI Option Sub-Type Values 1961 20. Security Considerations 1963 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 1964 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 1965 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 1966 confirmation and/or time synchronization is needed. 1968 OMNI interfaces configured over secured ANET interfaces inherit the 1969 physical and/or link-layer security properties of the connected 1970 ANETs. OMNI interfaces configured over open INET interfaces can use 1971 symmetric securing services such as VPNs or can by some other means 1972 establish a direct link. When a VPN or direct link may be 1973 impractical, however, an asymmetric security service such as SEcure 1974 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1975 Addresses (CGAs) [RFC3972], the authentication option specified in 1976 [RFC4380] or other protocol control message security mechanisms may 1977 be necessary. While the OMNI link protects control plane messaging, 1978 applications must still employ end-to-end transport- or higher-layer 1979 security services to protect the data plane. 1981 The Mobility Service MUST provide strong network layer security for 1982 control plane messages and forwading path integrity for data plane 1983 messages. In one example, the AERO service 1984 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1985 mobility service elements and secures the links in the spanning tree 1986 with network layer security mechanisms such as IPsec [RFC4301] or 1987 Wireguard. Control plane messages are then constrained to travel 1988 only over the secured spanning tree paths and are therefore protected 1989 from attack or eavesdropping. Since data plane messages can travel 1990 over route optimized paths that do not strictly follow the spanning 1991 tree, however, end-to-end transport- or higher-layer security 1992 services are still required. 1994 Security considerations for specific access network interface types 1995 are covered under the corresponding IP-over-(foo) specification 1996 (e.g., [RFC2464], [RFC2492], etc.). 1998 Security considerations for IPv6 fragmentation and reassembly are 1999 discussed in Section 5.1. 2001 21. Implementation Status 2003 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2004 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2005 Newer specification versions will be tagged in upcoming releases. 2006 First public release expected before the end of 2020. 2008 22. Acknowledgements 2010 The first version of this document was prepared per the consensus 2011 decision at the 7th Conference of the International Civil Aviation 2012 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2013 2019. Consensus to take the document forward to the IETF was reached 2014 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2015 Attendees and contributors included: Guray Acar, Danny Bharj, 2016 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2017 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2018 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2019 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2020 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2021 Fryderyk Wrobel and Dongsong Zeng. 2023 The following individuals are acknowledged for their useful comments: 2024 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 2025 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 2026 Skorepa are recognized for their many helpful ideas and suggestions. 2027 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 2028 Rajagopalan are acknowledged for their hard work on the 2029 implementation and insights that led to improvements to the spec. 2031 This work is aligned with the NASA Safe Autonomous Systems Operation 2032 (SASO) program under NASA contract number NNA16BD84C. 2034 This work is aligned with the FAA as per the SE2025 contract number 2035 DTFAWA-15-D-00030. 2037 23. References 2039 23.1. Normative References 2041 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2042 DOI 10.17487/RFC0791, September 1981, 2043 . 2045 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2046 Requirement Levels", BCP 14, RFC 2119, 2047 DOI 10.17487/RFC2119, March 1997, 2048 . 2050 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2051 "Definition of the Differentiated Services Field (DS 2052 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2053 DOI 10.17487/RFC2474, December 1998, 2054 . 2056 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2057 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2058 DOI 10.17487/RFC3971, March 2005, 2059 . 2061 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 2062 RFC 3972, DOI 10.17487/RFC3972, March 2005, 2063 . 2065 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2066 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2067 November 2005, . 2069 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2070 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2071 . 2073 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2074 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2075 2006, . 2077 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2078 Control Message Protocol (ICMPv6) for the Internet 2079 Protocol Version 6 (IPv6) Specification", STD 89, 2080 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2081 . 2083 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2084 ICMPv6, UDP, and TCP Headers", RFC 4727, 2085 DOI 10.17487/RFC4727, November 2006, 2086 . 2088 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2089 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2090 DOI 10.17487/RFC4861, September 2007, 2091 . 2093 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2094 Address Autoconfiguration", RFC 4862, 2095 DOI 10.17487/RFC4862, September 2007, 2096 . 2098 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2099 "Traffic Selectors for Flow Bindings", RFC 6088, 2100 DOI 10.17487/RFC6088, January 2011, 2101 . 2103 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2104 Hosts in a Multi-Prefix Network", RFC 8028, 2105 DOI 10.17487/RFC8028, November 2016, 2106 . 2108 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2109 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2110 May 2017, . 2112 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2113 (IPv6) Specification", STD 86, RFC 8200, 2114 DOI 10.17487/RFC8200, July 2017, 2115 . 2117 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2118 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2119 DOI 10.17487/RFC8201, July 2017, 2120 . 2122 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2123 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2124 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2125 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2126 . 2128 23.2. Informative References 2130 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2131 Interface (FDDI), IEEE Transactions on Communications", 2132 August 1990. 2134 [I-D.ietf-intarea-tunnels] 2135 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2136 Architecture", draft-ietf-intarea-tunnels-10 (work in 2137 progress), September 2019. 2139 [I-D.templin-6man-dhcpv6-ndopt] 2140 Templin, F., "A Unified Stateful/Stateless Configuration 2141 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2142 (work in progress), June 2020. 2144 [I-D.templin-intarea-6706bis] 2145 Templin, F., "Asymmetric Extended Route Optimization 2146 (AERO)", draft-templin-intarea-6706bis-65 (work in 2147 progress), September 2020. 2149 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2150 Communication Layers", STD 3, RFC 1122, 2151 DOI 10.17487/RFC1122, October 1989, 2152 . 2154 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2155 DOI 10.17487/RFC1191, November 1990, 2156 . 2158 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2159 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2160 . 2162 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2163 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2164 . 2166 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2167 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2168 . 2170 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2171 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2172 . 2174 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2175 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2176 December 1998, . 2178 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2179 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2180 . 2182 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2183 Domains without Explicit Tunnels", RFC 2529, 2184 DOI 10.17487/RFC2529, March 1999, 2185 . 2187 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2188 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2189 . 2191 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2192 Considered Useful", BCP 82, RFC 3692, 2193 DOI 10.17487/RFC3692, January 2004, 2194 . 2196 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2197 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2198 DOI 10.17487/RFC3810, June 2004, 2199 . 2201 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2202 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2203 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2204 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2205 . 2207 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2208 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2209 2004, . 2211 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2212 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2213 December 2005, . 2215 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2216 Network Address Translations (NATs)", RFC 4380, 2217 DOI 10.17487/RFC4380, February 2006, 2218 . 2220 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2221 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2222 2006, . 2224 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2225 "Considerations for Internet Group Management Protocol 2226 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2227 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2228 . 2230 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2231 "Internet Group Management Protocol (IGMP) / Multicast 2232 Listener Discovery (MLD)-Based Multicast Forwarding 2233 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2234 August 2006, . 2236 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2237 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2238 . 2240 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2241 Errors at High Data Rates", RFC 4963, 2242 DOI 10.17487/RFC4963, July 2007, 2243 . 2245 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2246 Advertisement Flags Option", RFC 5175, 2247 DOI 10.17487/RFC5175, March 2008, 2248 . 2250 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2251 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2252 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2253 . 2255 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2256 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2257 DOI 10.17487/RFC5214, March 2008, 2258 . 2260 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2261 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2262 . 2264 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2265 Version 3 for IPv4 and IPv6", RFC 5798, 2266 DOI 10.17487/RFC5798, March 2010, 2267 . 2269 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2270 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2271 . 2273 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2274 DOI 10.17487/RFC6081, January 2011, 2275 . 2277 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2278 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2279 DOI 10.17487/RFC6355, August 2011, 2280 . 2282 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2283 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2284 2012, . 2286 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2287 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2288 DOI 10.17487/RFC7084, November 2013, 2289 . 2291 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2292 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2293 Boundary in IPv6 Addressing", RFC 7421, 2294 DOI 10.17487/RFC7421, January 2015, 2295 . 2297 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2298 DOI 10.17487/RFC7542, May 2015, 2299 . 2301 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2302 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2303 February 2016, . 2305 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2306 Support for IP Hosts with Multi-Access Support", RFC 7847, 2307 DOI 10.17487/RFC7847, May 2016, 2308 . 2310 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2311 Writing an IANA Considerations Section in RFCs", BCP 26, 2312 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2313 . 2315 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2316 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2317 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2318 July 2018, . 2320 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2321 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2322 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2323 . 2325 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2326 and F. Gont, "IP Fragmentation Considered Fragile", 2327 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2328 . 2330 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2332 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2333 encoding to specific Internetworks such as the Aeronautical 2334 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2335 may include link selection preferences based on other traffic 2336 classifiers (e.g., transport port numbers, etc.) in addition to the 2337 existing DSCP-based preferences. Nodes on specific Internetworks 2338 maintain a map of traffic classifiers to additional P[*] preference 2339 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2340 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2342 Implementations use Simplex or Indexed encoding formats for P[*] 2343 encoding in order to encode a given set of traffic classifiers in the 2344 most efficient way. Some use cases may be more efficiently coded 2345 using Simplex form, while others may be more efficient using Indexed. 2346 Once a format is selected for preparation of a single Interface 2347 Attribute the same format must be used for the entire Interface 2348 Attribute sub-option. Different sub-options may use different 2349 formats. 2351 The following figures show coding examples for various Simplex and 2352 Indexed formats: 2354 0 1 2 3 2355 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 2356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2357 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2359 | Provider ID | Link |R| APS | Bitmap(0)=0xff|P00|P01|P02|P03| 2360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2361 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2363 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2365 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2367 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2369 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2372 Figure 18: Example 1: Dense Simplex Encoding 2374 0 1 2 3 2375 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 2376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2377 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2379 | Provider ID | Link |R| APS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2381 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2383 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2385 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2387 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2389 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2391 |Bitmap(10)=0x00| ... 2392 +-+-+-+-+-+-+-+-+-+-+- 2394 Figure 19: Example 2: Sparse Simplex Encoding 2396 0 1 2 3 2397 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 2398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2399 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2401 | Provider ID | Link |R| APS | Index = 0x00 | Bitmap = 0x80 | 2402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2403 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2405 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2407 | Bitmap = 0x01 |796|797|798|799| ... 2408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2410 Figure 20: Example 3: Indexed Encoding 2412 Appendix B. VDL Mode 2 Considerations 2414 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2415 (VDLM2) that specifies an essential radio frequency data link service 2416 for aircraft and ground stations in worldwide civil aviation air 2417 traffic management. The VDLM2 link type is "multicast capable" 2418 [RFC4861], but with considerable differences from common multicast 2419 links such as Ethernet and IEEE 802.11. 2421 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2422 magnitude less than most modern wireless networking gear. Second, 2423 due to the low available link bandwidth only VDLM2 ground stations 2424 (i.e., and not aircraft) are permitted to send broadcasts, and even 2425 so only as compact layer 2 "beacons". Third, aircraft employ the 2426 services of ground stations by performing unicast RS/RA exchanges 2427 upon receipt of beacons instead of listening for multicast RA 2428 messages and/or sending multicast RS messages. 2430 This beacon-oriented unicast RS/RA approach is necessary to conserve 2431 the already-scarce available link bandwidth. Moreover, since the 2432 numbers of beaconing ground stations operating within a given spatial 2433 range must be kept as sparse as possible, it would not be feasible to 2434 have different classes of ground stations within the same region 2435 observing different protocols. It is therefore highly desirable that 2436 all ground stations observe a common language of RS/RA as specified 2437 in this document. 2439 Note that links of this nature may benefit from compression 2440 techniques that reduce the bandwidth necessary for conveying the same 2441 amount of data. The IETF lpwan working group is considering possible 2442 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2444 Appendix C. MN / AR Isolation Through L2 Address Mapping 2446 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2447 unicast link-scoped IPv6 destination address. However, IPv6 ND 2448 messaging should be coordinated between the MN and AR only without 2449 invoking other nodes on the ANET. This implies that MN / AR control 2450 messaging should be isolated and not overheard by other nodes on the 2451 link. 2453 To support MN / AR isolation on some ANET links, ARs can maintain an 2454 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2455 ANETs, this specification reserves one Ethernet unicast address TBD2 2456 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2457 MSADDR is reserved per the assigned numbers authority for the ANET 2458 addressing space. For still other ANETs, MSADDR may be dynamically 2459 discovered through other means, e.g., L2 beacons. 2461 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2462 both multicast and unicast) to MSADDR instead of to an ordinary 2463 unicast or multicast L2 address. In this way, all of the MN's IPv6 2464 ND messages will be received by ARs that are configured to accept 2465 packets destined to MSADDR. Note that multiple ARs on the link could 2466 be configured to accept packets destined to MSADDR, e.g., as a basis 2467 for supporting redundancy. 2469 Therefore, ARs must accept and process packets destined to MSADDR, 2470 while all other devices must not process packets destined to MSADDR. 2471 This model has well-established operational experience in Proxy 2472 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2474 Appendix D. Change Log 2476 << RFC Editor - remove prior to publication >> 2478 Differences from draft-templin-6man-omni-interface-35 to draft- 2479 templin-6man-omni-interface-36: 2481 o Major clarifications on aspects such as "hard/soft" PTB error 2482 messages 2484 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2485 be used in the data plane. 2487 Differences from draft-templin-6man-omni-interface-31 to draft- 2488 templin-6man-omni-interface-32: 2490 o MTU 2491 o Support for multi-hop ANETS such as ISATAP. 2493 Differences from draft-templin-6man-omni-interface-29 to draft- 2494 templin-6man-omni-interface-30: 2496 o Moved link-layer addressing information into the OMNI option on a 2497 per-ifIndex basis 2499 o Renamed "ifIndex-tuple" to "Interface Attributes" 2501 Differences from draft-templin-6man-omni-interface-27 to draft- 2502 templin-6man-omni-interface-28: 2504 o Updates based on implementation expereince. 2506 Differences from draft-templin-6man-omni-interface-25 to draft- 2507 templin-6man-omni-interface-26: 2509 o Further clarification on "aggregate" RA messages. 2511 o Expanded Security Considerations to discuss expectations for 2512 security in the Mobility Service. 2514 Differences from draft-templin-6man-omni-interface-20 to draft- 2515 templin-6man-omni-interface-21: 2517 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2518 (PBM). 2520 Differences from draft-templin-6man-omni-interface-18 to draft- 2521 templin-6man-omni-interface-19: 2523 o SEND/CGA. 2525 Differences from draft-templin-6man-omni-interface-17 to draft- 2526 templin-6man-omni-interface-18: 2528 o Teredo 2530 Differences from draft-templin-6man-omni-interface-14 to draft- 2531 templin-6man-omni-interface-15: 2533 o Prefix length discussions removed. 2535 Differences from draft-templin-6man-omni-interface-12 to draft- 2536 templin-6man-omni-interface-13: 2538 o Teredo 2539 Differences from draft-templin-6man-omni-interface-11 to draft- 2540 templin-6man-omni-interface-12: 2542 o Major simplifications and clarifications on MTU and fragmentation. 2544 o Document now updates RFC4443 and RFC8201. 2546 Differences from draft-templin-6man-omni-interface-10 to draft- 2547 templin-6man-omni-interface-11: 2549 o Removed /64 assumption, resulting in new OMNI address format. 2551 Differences from draft-templin-6man-omni-interface-07 to draft- 2552 templin-6man-omni-interface-08: 2554 o OMNI MNs in the open Internet 2556 Differences from draft-templin-6man-omni-interface-06 to draft- 2557 templin-6man-omni-interface-07: 2559 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2560 L2 addressing. 2562 o Expanded "Transition Considerations". 2564 Differences from draft-templin-6man-omni-interface-05 to draft- 2565 templin-6man-omni-interface-06: 2567 o Brought back OMNI option "R" flag, and discussed its use. 2569 Differences from draft-templin-6man-omni-interface-04 to draft- 2570 templin-6man-omni-interface-05: 2572 o Transition considerations, and overhaul of RS/RA addressing with 2573 the inclusion of MSE addresses within the OMNI option instead of 2574 as RS/RA addresses (developed under FAA SE2025 contract number 2575 DTFAWA-15-D-00030). 2577 Differences from draft-templin-6man-omni-interface-02 to draft- 2578 templin-6man-omni-interface-03: 2580 o Added "advisory PTB messages" under FAA SE2025 contract number 2581 DTFAWA-15-D-00030. 2583 Differences from draft-templin-6man-omni-interface-01 to draft- 2584 templin-6man-omni-interface-02: 2586 o Removed "Primary" flag and supporting text. 2588 o Clarified that "Router Lifetime" applies to each ANET interface 2589 independently, and that the union of all ANET interface Router 2590 Lifetimes determines MSE lifetime. 2592 Differences from draft-templin-6man-omni-interface-00 to draft- 2593 templin-6man-omni-interface-01: 2595 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2596 for future use (most likely as "pseudo-multicast"). 2598 o Non-normative discussion of alternate OMNI LLA construction form 2599 made possible if the 64-bit assumption were relaxed. 2601 First draft version (draft-templin-atn-aero-interface-00): 2603 o Draft based on consensus decision of ICAO Working Group I Mobility 2604 Subgroup March 22, 2019. 2606 Authors' Addresses 2608 Fred L. Templin (editor) 2609 The Boeing Company 2610 P.O. Box 3707 2611 Seattle, WA 98124 2612 USA 2614 Email: fltemplin@acm.org 2616 Tony Whyman 2617 MWA Ltd c/o Inmarsat Global Ltd 2618 99 City Road 2619 London EC1Y 1AX 2620 England 2622 Email: tony.whyman@mccallumwhyman.com