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Templin, Ed. 3 Internet-Draft The Boeing Company 4 Intended status: Standards Track A. Whyman 5 Expires: August 10, 2020 MWA Ltd c/o Inmarsat Global Ltd 6 February 7, 2020 8 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 9 Interfaces 10 draft-templin-atn-aero-interface-20 12 Abstract 14 Mobile nodes (e.g., aircraft of various configurations, terrestrial 15 vehicles, seagoing vessels, mobile enterprise devices, etc.) 16 communicate with networked correspondents over multiple access 17 network data links and configure mobile routers to connect end user 18 networks. A multilink interface specification is therefore needed 19 for coordination with the network-based mobility service. This 20 document specifies the transmission of IPv6 packets over Overlay 21 Multilink Network (OMNI) Interfaces. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on August 10, 2020. 40 Copyright Notice 42 Copyright (c) 2020 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 60 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 5 61 5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 9 62 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 10 63 7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . 10 64 8. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 11 65 9. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 14 66 10. Address Mapping for IPv6 Neighbor Discovery Messages . . . . 14 67 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 15 68 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 15 69 12. Router Discovery and Prefix Registration . . . . . . . . . . 16 70 13. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 19 71 14. Detecting and Responding to MSE Failures . . . . . . . . . . 19 72 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 73 16. Security Considerations . . . . . . . . . . . . . . . . . . . 20 74 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 75 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 76 18.1. Normative References . . . . . . . . . . . . . . . . . . 21 77 18.2. Informative References . . . . . . . . . . . . . . . . . 22 78 Appendix A. OMNI Option Extensions for Pseudo-DSCP Mappings . . 24 79 Appendix B. Prefix Length Considerations . . . . . . . . . . . . 24 80 Appendix C. VDL Mode 2 Considerations . . . . . . . . . . . . . 25 81 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 26 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 84 1. Introduction 86 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 87 terrestrial vehicles, seagoing vessels, mobile enterprise devices, 88 etc.) often have multiple data links for communicating with networked 89 correspondents. These data links may have diverse performance, cost 90 and availability properties that can change dynamically according to 91 mobility patterns, flight phases, proximity to infrastructure, etc. 92 MNs coordinate their data links in a discipline known as "multilink", 93 in which a single virtual interface is configured over the underlying 94 data link interfaces. 96 The MN configures a virtual interface (termed the "Overlay Multilink 97 Network (OMNI) interface") as a thin layer over the underlying access 98 network interfaces. The OMNI interface is therefore the only 99 interface abstraction exposed to the IPv6 layer and behaves according 100 to the Non-Broadcast, Multiple Access (NBMA) interface principle, 101 while underlying access network interfaces appear as link layer 102 communication channels in the architecture. The OMNI interface 103 connects to a virtual overlay service known as the "OMNI link". The 104 OMNI link spans a worldwide Internetwork that may include private-use 105 infrastructures and/or the global public Internet itself. 107 Each MN receives a Mobile Network Prefix (MNP) for numbering 108 downstream-attached End User Networks (EUNs) independently of the 109 access network data links selected for data transport. The MN 110 performs router discovery over the OMNI interface (i.e., similar to 111 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 112 behalf of its EUNs. The router discovery process is iterated over 113 each of the OMNI interface's underlying access network data links in 114 order to register per-link parameters (see Section 12). 116 The OMNI interface provides a multilink nexus for exchanging inbound 117 and outbound traffic via the correct underlying Access Network (ANET) 118 interface(s). The IPv6 layer sees the OMNI interface as a point of 119 connection to the OMNI link. Each OMNI link has one or more 120 associated Mobility Service Prefixes (MSPs) from which OMNI link MNPs 121 are derived. If there are multiple OMNI links, the IPv6 layer will 122 see multiple OMNI interfaces. 124 The OMNI interface interacts with a network-based Mobility Service 125 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 126 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 127 track MN movements and represent their MNPs in a global routing or 128 mapping system. 130 This document specifies the transmission of IPv6 packets [RFC8200] 131 and MN/MS control messaging over OMNI interfaces. 133 2. Terminology 135 The terminology in the normative references applies; especially, the 136 terms "link" and "interface" are the same as defined in the IPv6 137 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 138 Also, the Protocol Constants defined in Section 10 of [RFC4861] are 139 used in their same format and meaning in this document. The terms 140 "All-Routers multicast", "All-Nodes multicast" and "Subnet-Router 141 anycast" are defined in [RFC4291] (with Link-Local scope assumed). 143 The following terms are defined within the scope of this document: 145 Mobile Node (MN) 146 an end system with multiple distinct upstream data link 147 connections that are managed together as a single logical unit. 148 The MN's data link connection parameters can change over time due 149 to, e.g., node mobility, link quality, etc. The MN further 150 connects a downstream-attached End User Network (EUN). The term 151 MN used here is distinct from uses in other documents, and does 152 not imply a particular mobility protocol. 154 End User Network (EUN) 155 a simple or complex downstream-attached mobile network that 156 travels with the MN as a single logical unit. The IPv6 addresses 157 assigned to EUN devices remain stable even if the MN's upstream 158 data link connections change. 160 Mobility Service (MS) 161 a mobile routing service that tracks MN movements and ensures that 162 MNs remain continuously reachable even across mobility events. 163 Specific MS details are out of scope for this document. 165 Mobility Service Prefix (MSP) 166 an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the 167 rest of the Internetwork by the MS, and from which more-specific 168 Mobile Network Prefixes (MNPs) are derived. 170 Mobile Network Prefix (MNP) 171 a longer IPv6 prefix taken from the MSP (e.g., 172 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate 173 the MNP to devices located in EUNs. 175 Access Network (ANET) 176 a data link service network (e.g., an aviation radio access 177 network, satellite service provider network, cellular operator 178 network, etc.) that provides an Access Router (AR) for connecting 179 MNs to correspondents in outside Internetworks. Physical and/or 180 data link level security between the MN and AR are assumed. 182 ANET interface 183 a MN's attachment to a link in an ANET. 185 Internetwork (INET) 186 a connected network region with a coherent IP addressing plan that 187 provides transit forwarding services for ANET MNs and INET 188 correspondents. Examples include private enterprise networks, 189 ground domain aviation service networks and the global public 190 Internet itself. 192 INET interface 193 a node's attachment to a link in an INET. 195 OMNI link 196 a virtual overlay configured over one or more INETs and their 197 connected ANETs. An OMNI link can comprise multiple INET segments 198 joined by bridges the same as for any link; the addressing plans 199 in each segment may be mutually exclusive and managed by different 200 administrative entities. 202 OMNI interface 203 a node's attachment to an OMNI link, and configured over one or 204 more underlying ANET/INET interfaces. 206 OMNI link local address (LLA) 207 an IPv6 link-local address constructed as specified in Section 7, 208 and assigned to an OMNI interface. 210 Multilink 211 an OMNI interface's manner of managing diverse underlying data 212 link interfaces as a single logical unit. The OMNI interface 213 provides a single unified interface to upper layers, while 214 underlying data link selections are performed on a per-packet 215 basis considering factors such as DSCP, flow label, application 216 policy, signal quality, cost, etc. Multilinking decisions are 217 coordinated in both the outbound (i.e. MN to correspondent) and 218 inbound (i.e., correspondent to MN) directions. 220 L2 221 The second layer in the OSI network model. Also known as "layer- 222 2", "link-layer", "sub-IP layer", "data link layer", etc. 224 L3 225 The third layer in the OSI network model. Also known as "layer- 226 3", "network-layer", "IPv6 layer", etc. 228 3. Requirements 230 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 231 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 232 "OPTIONAL" in this document are to be interpreted as described in BCP 233 14 [RFC2119][RFC8174] when, and only when, they appear in all 234 capitals, as shown here. 236 4. Overlay Multilink Network (OMNI) Interface Model 238 An OMNI interface is a MN virtual interface configured over one or 239 more ANET interfaces, which may be physical (e.g., an aeronautical 240 radio link) or virtual (e.g., an Internet or higher-layer "tunnel"). 242 The MN receives a MNP from the MS, and coordinates with the MS 243 through IPv6 ND message exchanges. The MN uses the MNP to construct 244 a unique OMNI LLA through the algorithmic derivation specified in 245 Section 7 and assigns the LLA to the OMNI interface. 247 The OMNI interface architectural layering model is the same as in 248 [RFC7847], and augmented as shown in Figure 1. The IP layer (L3) 249 therefore sees the OMNI interface as a single network layer interface 250 with multiple underlying ANET interfaces that appear as L2 251 communication channels in the architecture. 253 +----------------------------+ 254 | Upper Layer Protocol | 255 Session-to-IP +---->| | 256 Address Binding | +----------------------------+ 257 +---->| IP (L3) | 258 IP Address +---->| | 259 Binding | +----------------------------+ 260 +---->| OMNI Interface | 261 Logical-to- +---->| (OMNI LLA) | 262 Physical | +----------------------------+ 263 Interface +---->| L2 | L2 | | L2 | 264 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 265 +------+------+ +------+ 266 | L1 | L1 | | L1 | 267 | | | | | 268 +------+------+ +------+ 270 Figure 1: OMNI Interface Architectural Layering Model 272 The OMNI virtual interface model gives rise to a number of 273 opportunities: 275 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 276 Address Detection (DAD) messaging is necessary over the OMNI 277 interface. 279 o ANET interfaces do not require any L3 addresses (i.e., not even 280 link-local) in environments where communications are coordinated 281 entirely over the OMNI interface. 283 o as ANET interface properties change (e.g., link quality, cost, 284 availability, etc.), any active ANET interface can be used to 285 update the profiles of multiple additional ANET interfaces in a 286 single message. This allows for timely adaptation and service 287 continuity under dynamically changing conditions. 289 o coordinating ANET interfaces in this way allows them to be 290 represented in a unified MS profile with provisions for mobility 291 and multilink operations. 293 o exposing a single virtual interface abstraction to the IPv6 layer 294 allows for multilink operation (including QoS based link 295 selection, packet replication, load balancing, etc.) at L2 while 296 still permitting queuing at the L3 based on, e.g., DSCP, flow 297 label, etc. 299 o L3 sees the OMNI interface as a point of connection to the OMNI 300 link; if there are multiple OMNI links (i.e., multiple MS's), L3 301 will see multiple OMNI interfaces. 303 Other opportunities are discussed in [RFC7847]. 305 Figure 2 depicts the architectural model for a MN connecting to the 306 MS via multiple independent ANETs. When an ANET interface becomes 307 active, the MN's OMNI interface sends native (i.e., unencapsulated) 308 IPv6 ND messages via the underlying ANET interface. IPv6 ND messages 309 traverse the ground domain ANETs until they reach an Access Router 310 (AR#1, AR#2, .., AR#n). The AR then coordinates with a Mobility 311 Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and returns 312 an IPv6 ND message response to the MN. IPv6 ND messages traverse the 313 ANET at layer 2; hence, the Hop Limit is not decremented. 315 +--------------+ 316 | MN | 317 +--------------+ 318 |OMNI interface| 319 +----+----+----+ 320 +--------|IF#1|IF#2|IF#n|------ + 321 / +----+----+----+ \ 322 / | \ 323 / <---- Native | IP ----> \ 324 v v v 325 (:::)-. (:::)-. (:::)-. 326 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 327 `-(::::)-' `-(::::)-' `-(::::)-' 328 +----+ +----+ +----+ 329 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 330 . +-|--+ +-|--+ +-|--+ . 331 . | | | 332 . v v v . 333 . <----- Encapsulation -----> . 334 . . 335 . +-----+ (:::)-. . 336 . |MSE#2| .-(::::::::) +-----+ . 337 . +-----+ .-(::: INET :::)-. |MSE#m| . 338 . (::::: Routing ::::) +-----+ . 339 . `-(::: System :::)-' . 340 . +-----+ `-(:::::::-' . 341 . |MSE#1| +-----+ +-----+ . 342 . +-----+ |MSE#3| |MSE#4| . 343 . +-----+ +-----+ . 344 . . 345 . . 346 . <----- Worldwide Connected Internetwork ----> . 347 ........................................................... 349 Figure 2: MN/MS Coordination via Multiple ANETs 351 After the initial IPv6 ND message exchange, the MN can send and 352 receive unencapsulated IPv6 data packets over the OMNI interface. 353 OMNI interface multilink services will forward the packets via ARs in 354 the correct underlying ANETs. The AR encapsulates the packets 355 according to the capabilities provided by the MS and forwards them to 356 the next hop within the worldwide connected Internetwork via optimal 357 routes. 359 5. Maximum Transmission Unit (MTU) and Fragmentation 361 All IPv6 interfaces are REQUIRED to configure a minimum Maximum 362 Transmission Unit (MTU) of 1280 bytes [RFC8200]. The network 363 therefore MUST forward packets of at least 1280 bytes without 364 generating an IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) 365 message [RFC8200]. 367 The OMNI interface configures an MTU of 9180 bytes [RFC2492]; the 368 size is therefore not a reflection of the underlying ANET interface 369 MTUs, but rather determines the largest packet the OMNI interface 370 will forward or reassemble. 372 The OMNI interface returns internally-generated PTB messages for 373 packets admitted into the interface that it deems too large for the 374 outbound underlying ANET interface. For all other packets, the OMNI 375 interface performs PMTUD even if the destination appears to be on the 376 same link since a proxy on the path could return a PTB message. This 377 ensures that the path MTU is adaptive and reflects the current path 378 used for a given data flow. 380 When the OMNI interface sends a packet that is no larger than the MTU 381 of the selected underlying ANET interface, it sends according to the 382 ANET L2 frame format. When the OMNI interface sends a packet that is 383 larger than the ANET interface MTU, it first encapsulates the packet 384 in a new IPv6 header per [RFC2473] with source address set to the 385 MN's link-local address and destination address set to the link-local 386 address of the MSE (see: Section 7). The OMNI interface then uses 387 IPv6 fragmentation to break the encapsulated packet into fragments 388 that are no larger than the ANET interface MTU and sends the 389 fragments over the ANET where they will be intercepted by the AR. 390 The AR then performs re-encapsulation and further fragmentation if 391 necessary, then conveys the packets toward the final destination. 393 When an AR receives a fragmented or whole packet from the INET 394 destined to an ANET MN, it must determine whether to forward or drop 395 and return a PTB (e.g., according to ANET performance 396 characteristics, MTU, etc). If the AR deems the packet to be of 397 acceptable size, it first reassembles locally (if necessary) then 398 forwards the packet to the MN. If the (reassembled) packet is no 399 larger than the ANET MTU, the AR forwards according to the ANET L2 400 frame format. If the packet is larger than the ANET MTU, the AR 401 instead uses IPv6 encapsulation and fragmentation as above. The MN 402 then reassembles and discards the encapsulation header, then forwards 403 the whole packet to the final destination. 405 Applications that cannot tolerate loss due to MTU restrictions SHOULD 406 avoid sending packets larger than 1280 bytes, since dynamic path 407 changes can reduce the path MTU at any time. Applications that may 408 benefit from sending larger packets even though the path MTU may 409 change dynamically MAY use larger sizes (i.e., up to the OMNI 410 interface MTU). 412 Note that when the AR forwards a fragmented packet received from the 413 INET, it is imperative that the AR reassembles locally first instead 414 of blindly forwarding fragments directly to the MN to avoid attacks 415 such as tiny fragments, overlapping fragments, etc. 417 6. Frame Format 419 The OMNI interface transmits IPv6 packets according to the native 420 frame format of each underlying ANET interface. For example, for 421 Ethernet-compatible interfaces the frame format is specified in 422 [RFC2464], for aeronautical radio interfaces the frame format is 423 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 424 Manual), for tunnels over IPv6 the frame format is specified in 425 [RFC2473], etc. 427 7. Link-Local Addresses 429 OMNI interfaces assign IPv6 Link-Local Addresses (i.e., "OMNI LLAs") 430 using the following constructs: 432 o IPv6 MN OMNI LLAs encode the most-significant 64 bits of a MNP 433 within the least-significant 64 bits (i.e., the interface ID) of a 434 Link-Local IPv6 Unicast Address (see: [RFC4291], Section 2.5.6). 435 For example, for the MNP 2001:db8:1000:2000::/56 the corresponding 436 LLA is fe80::2001:db8:1000:2000. 438 o IPv4-compatible MN OMNI LLAs are assigned as fe80::ffff:[v4addr], 439 i.e., the most significant 10 bits of the prefix fe80::/10, 440 followed by 70 '0' bits, followed by 16 '1' bits, followed by a 441 32bit IPv4 address. For example, the IPv4-Compatible MN OMNI LLA 442 for 192.0.2.1 is fe80::ffff:192.0.2.1 (also written as 443 fe80::ffff:c000:0201). 445 o MSE OMNI LLAs are assigned from the range fe80::/96, and MUST be 446 managed for uniqueness. The lower 32 bits of the LLA includes a 447 unique integer value between '1' and 'fffffffe', e.g., as in 448 fe80::1, fe80::2, fe80::3, etc., fe80::ffff:fffe. The address 449 fe80:: is the link-local Subnet-Router anycast address [RFC4291] 450 and the address fe80::ffff:ffff is reserved. (Note that distinct 451 OMNI link segments can avoid overlap by assignig MSE OMNI LLAs 452 from unique fe80::/96 sub-prefixes. For example, a first segment 453 could assign from fe80::1000/116, a second from fe80::2000/116, a 454 third from fe80::3000/116, etc.) 456 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 457 MNPs can be allocated from that block ensuring that there is no 458 possibility for overlap between the above OMNI LLA constructs. 460 Since MN OMNI LLAs are based on the distribution of administratively 461 assured unique MNPs, and since MSE OMNI LLAs are guaranteed unique 462 through administrative assignment, OMNI interfaces set the 463 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 465 8. Address Mapping - Unicast 467 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 468 state and use the link-local address format specified in Section 7. 469 IPv6 Neighbor Discovery (ND) [RFC4861] messages on MN OMNI interfaces 470 observe the native Source/Target Link-Layer Address Option (S/TLLAO) 471 formats of the underlying ANET interfaces (e.g., for Ethernet the S/ 472 TLLAO is specified in [RFC2464]). 474 MNs such as aircraft typically have many wireless data link types 475 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 476 etc.) with diverse performance, cost and availability properties. 477 The OMNI interface would therefore appear to have multiple L2 478 connections, and may include information for multiple ANET interfaces 479 in a single IPv6 ND message exchange. 481 OMNI interfaces use an IPv6 ND option called the "OMNI option" 482 formatted as shown in Figure 3: 484 0 1 2 3 485 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 1 486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 487 | Type | Length | Prefix Length |R|N|P| Reservd | 488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 | ifIndex[1] | ifType[1] | Reserved [1] |Link[1]|QoS[1] | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15| 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 497 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 | ifIndex[2] | ifType[2] | Reserved [2] |Link[2]|QoS[2] | 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 501 |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15| 502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 503 |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 ... ... ... 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | ifIndex[N] | ifType[N] | Reserved [N] |Link[N]|QoS[N] | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15| 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 | zero-padding (if necessary) | 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 523 | Notification ID (present only if N=1) | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 Figure 3: OMNI Option Format 528 In this format: 530 o Type is set to TBD. 532 o Length is set to the number of 8 octet blocks in the option. 534 o Prefix Length is set according to the IPv6 source LLA type. For 535 MN OMNI LLAs, the value is set to the length of the embedded MNP. 536 For MSE OMNI LLAs, the value is set to 128. 538 o R (the "Register/Release" bit) is set to '1' to register an MNP or 539 set to '0' to release a registration. 541 o N (the "Notify" bit) is set to '1' if the option includes a 542 trailing 4 byte "Notification ID" (see below). Valid only in MN 543 RS messages, and ignored in all other ND messages. 545 o P (the "Primary" bit) is set to '1' in a MN RS message to request 546 an AR to serve as primary, and set to '1' in the AR's RA message 547 to accept the primary role. Set to '0' in all other RS/RA 548 messages, and ignored in all other ND messages. 550 o Reservd is set to the value '0' on transmission and ignored on 551 reception. 553 o A set of N ANET interface "ifIndex-tuples" are included as 554 follows: 556 * ifIndex[i] is set to an 8-bit integer value corresponding to a 557 specific underlying ANET interface. The first ifIndex-tuple 558 MUST correspond to the ANET interface over which the message is 559 sent. IPv6 ND messages originating from a MN may include 560 multiple ifIndex-tuples, and MUST number each with a distinct 561 ifIndex value between '1' and '255' that represents a MN- 562 specific 8-bit mapping for the actual ifIndex value assigned to 563 the ANET interface by network management [RFC2863]. IPv6 ND 564 messages originating from the MS include a single ifIndex-tuple 565 with ifIndex set to the value '0'. 567 * ifType[i] is set to an 8-bit integer value corresponding to the 568 underlying ANET interface identified by ifIndex. The value 569 represents an OMNI interface-specific 8-bit mapping for the 570 actual IANA ifType value registered in the 'IANAifType-MIB' 571 registry [http://www.iana.org]. 573 * Reserved[i] is set to the value '0' on transmission and ignored 574 on reception. 576 * Link[i] encodes a 4-bit link metric. The value '0' means the 577 link is DOWN, and the remaining values mean the link is UP with 578 metric ranging from '1' ("lowest") to '15' ("highest"). 580 * QoS[i] encodes the number of 4-byte blocks (between '0' and 581 '15') of two-bit P[*] values that follow. The first 4 blocks 582 correspond to the 64 Differentiated Service Code Point (DSCP) 583 values P00 - P63 [RFC2474]. If additional 4-byte P[i] blocks 584 follow, their values correspond to "pseudo-DSCP" values P64, 585 P65, P66, etc. numbered consecutively. The pseudo-DSCP values 586 correspond to ancillary QoS information defined for the 587 specific OMNI interface (e.g., see Appendix A). 589 * P[*] includes zero or more per-ifIndex 4-byte blocks of two-bit 590 Preferences. Each P[*] field is set to the value '0' 591 ("disabled"), '1' ("low"), '2' ("medium") or '3' ("high") to 592 indicate a QoS preference level for ANET interface selection 593 purposes. The first four blocks always correspond to the 64 594 DSCP values in consecutive order. If one or more of the blocks 595 are absent (e.g., for QoS values 0,1,2,3) the P[*] values for 596 the missing blocks default to "medium". 598 o Zero-padding added if necessary to produce an integral number of 8 599 octet blocks. 601 o Notification ID (present only if N = '1') contains the least- 602 significant 32 bits of an MSE OMNI LLA to notify (e.g., for the 603 LLA fe80::face:cafe the field contains 0xfacecafe). Valid only in 604 MN RS messages, and ignored in all other ND messages. 606 9. Address Mapping - Multicast 608 The multicast address mapping of the native underlying ANET interface 609 applies. The mobile router on board the aircraft also serves as an 610 IGMP/MLD Proxy for its EUNs and/or hosted applications per [RFC4605] 611 while using the L2 address of the router as the L2 address for all 612 multicast packets. 614 10. Address Mapping for IPv6 Neighbor Discovery Messages 616 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 617 unicast link-scoped IPv6 destination address. However, IPv6 ND 618 messaging is coordinated between the MN and MS only without invoking 619 other nodes on the ANET. 621 For this reason, ANET links maintain unicast L2 addresses ("MSADDR") 622 for the purpose of supporting MN/MS IPv6 ND messaging. For Ethernet- 623 compatible ANETs, this specification reserves one Ethernet unicast 624 address TBD2. For non-Ethernet statically-addressed ANETs, MSADDR is 625 reserved per the assigned numbers authority for the ANET addressing 626 space. For still other ANETs, MSADDR may be dynamically discovered 627 through other means, e.g., L2 beacons. 629 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 630 both multicast and unicast) to an MSADDR instead of to an ordinary 631 unicast or multicast L2 address. In this way, all of the MN's IPv6 632 ND messages will be received by MS devices that are configured to 633 accept packets destined to MSADDR. Note that multiple MS devices on 634 the link could be configured to accept packets destined to MSADDR, 635 e.g., as a basis for supporting redundancy. 637 Therefore, ARs MUST accept and process packets destined to MSADDR, 638 while all other devices MUST NOT process packets destined to MSADDR. 639 This model has well-established operational experience in Proxy 640 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 642 11. Conceptual Sending Algorithm 644 The MN's IPv6 layer selects the outbound OMNI interface according to 645 standard IPv6 requirements when forwarding data packets from local or 646 EUN applications to external correspondents. The OMNI interface 647 maintains default routes and neighbor cache entries for MSEs, and may 648 also include additional neighbor cache entries created through other 649 means (e.g., Address Resolution, static configuration, etc.). 651 After a packet enters the OMNI interface, an outbound ANET interface 652 is selected based on multilink parameters such as DSCP, application 653 port number, cost, performance, message size, etc. OMNI interface 654 multilink selections could also be configured to perform replication 655 across multiple ANET interfaces for increased reliability at the 656 expense of packet duplication. 658 OMNI interface multilink service designers MUST observe the BCP 659 guidance in Section 15 [RFC3819] in terms of implications for 660 reordering when packets from the same flow may be spread across 661 multiple ANET interfaces having diverse properties. 663 11.1. Multiple OMNI Interfaces 665 MNs may associate with multiple MS instances concurrently. Each MS 666 instance represents a distinct OMNI link distinguished by its 667 associated MSPs. The MN configures a separate OMNI interface for 668 each link so that multiple interfaces (e.g., omni0, omni1, omni2, 669 etc.) are exposed to the IPv6 layer. 671 Depending on local policy and configuration, an MN may choose between 672 alternative active OMNI interfaces using a packet's DSCP, routing 673 information or static configuration. Interface selection based on 674 per-packet source addresses is also enabled when the MSPs for each 675 OMNI interface are known (e.g., discovered through Prefix Information 676 Options (PIOs) and/or Route Information Options (RIOs)). 678 Each OMNI interface can be configured over the same or different sets 679 of ANET interfaces. Each ANET distinguishes between the different 680 OMNI links based on the MSPs represented in per-packet IPv6 681 addresses. 683 Multiple distinct OMNI links can therefore be used to support fault 684 tolerance, load balancing, reliability, etc. The architectural model 685 parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs 686 serve as (virtual) VLAN tags. 688 12. Router Discovery and Prefix Registration 690 ARs process IPv6 ND messages destined to All-Routers multicast 691 (ff02::2), Subnet-Router anycast (fe80::) and unicast IPv6 LLAs 692 [RFC4291]. ARs configure the L2 address MSADDR (see: Section 10) and 693 act as a proxy for MSE OMNI LLAs. 695 MNs interface with the MS by sending RS messages with OMNI options. 696 For each ANET interface, the MN sends an RS message with an OMNI 697 option, with L2 destination address set to MSADDR and with L3 698 destination address set to either a specific MSE OMNI LLA, link-local 699 Subnet-Router anycast, or All-Routers multicast. The MN discovers 700 MSE OMNI LLAs either through an RA message response to an initial 701 anycast/multicast RS or before sending an initial RS message. 702 [RFC5214] provides example MSE address discovery methods, including 703 information conveyed during data link login, name service lookups, 704 static configuration, etc. 706 The AR receives the RS messages and coordinates with the 707 corresponding MSE in a manner outside the scope of this document. 708 The AR returns an RA message with source address set to the MSE OMNI 709 LLA, with an OMNI option and with any information for the link that 710 would normally be delivered in a solicited RA message. (Note that if 711 all MSEs share common state, the AR can instead return an RA with 712 source address set to link-local Subnet-Router anycast.) 714 MNs configure OMNI interfaces that observe the properties discussed 715 in the previous section. The OMNI interface and its underlying 716 interfaces are said to be in either the "UP" or "DOWN" state 717 according to administrative actions in conjunction with the interface 718 connectivity status. An OMNI interface transitions to UP or DOWN 719 through administrative action and/or through state transitions of the 720 underlying interfaces. When a first underlying interface transitions 721 to UP, the OMNI interface also transitions to UP. When all 722 underlying interfaces transition to DOWN, the OMNI interface also 723 transitions to DOWN. 725 When an OMNI interface transitions to UP, the MN sends initial RS 726 messages to register its MNP and an initial set of underlying ANET 727 interfaces that are also UP. The MN sends additional RS messages to 728 refresh lifetimes and to register/deregister underlying ANET 729 interfaces as they transition to UP or DOWN. 731 ARs return RA messages with configuration information in response to 732 a MN's RS messages. The AR sets the RA Cur Hop Limit, M and O flags, 733 Router Lifetime, Reachable Time and Retrans Timer values as directed 734 by the MSE, and includes any necessary options such as: 736 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 738 o RIOs [RFC4191] with more-specific routes. 740 o an MTU option that specifies the maximum acceptable packet size 741 for this ANET interface. 743 The AR coordinates with the MSE and sends immediate unicast RA 744 responses without delay; therefore, the IPv6 ND MAX_RA_DELAY_TIME and 745 MIN_DELAY_BETWEEN_RAS constants for multicast RAs do not apply. The 746 AR MAY send periodic and/or event-driven unsolicited RA messages, but 747 is not required to do so for unicast advertisements [RFC4861]. 749 The MN sends RS messages from within the OMNI interface while using 750 an UP underlying ANET interface as the outbound interface. Each RS 751 message is formatted as though it originated from the IPv6 layer, but 752 the process is coordinated wholly from within the OMNI interface and 753 is therefore opaque to the IPv6 layer. The MN sends initial RS 754 messages over an UP underlying interface with its OMNI LLA as the 755 source and with destination set as discussed above. The RS messages 756 include an OMNI option per Section 8 with a valid Prefix Length, 757 (R,N,P) flags, and with ifIndex-tuples appropriate for underlying 758 ANET interfaces. The AR processes RS message and conveys the OMNI 759 option information to the MSE. 761 When the MSE processes the OMNI information, it first validates the 762 prefix registration information. If the prefix registration was 763 valid, the MSE injects the MNP into the routing/mapping system then 764 caches the new Prefix Length, MNP and ifIndex-tuples. If the MN's 765 OMNI option included a Notification ID, the new MSE also notifies the 766 former MSE. The MSE then directs the AR to return an RA message to 767 the MN with an OMNI option per Section 8 and with a non-zero Router 768 Lifetime if the prefix registration was successful; otherwise, with a 769 zero Router Lifetime. 771 When the MN receives the RA message, it creates a default route with 772 L3 next hop address set to the address found in the RA source address 773 and with L2 address set to MSADDR. The AR will then forward packets 774 between the MN and the MS. 776 The MN then manages its underlying ANET interfaces according to their 777 states as follows: 779 o When an underlying ANET interface transitions to UP, the MN sends 780 an RS over the ANET interface with an OMNI option. The OMNI 781 option contains a first ifIndex-tuple with values specific to this 782 ANET interface, and may contain additional ifIndex-tuples specific 783 to other ANET interfaces. 785 o When an underlying ANET interface transitions to DOWN, the MN 786 sends an RS or unsolicited NA message over any UP ANET interface 787 with an OMNI option containing an ifIndex-tuple for the DOWN ANET 788 interface with Link(i) set to '0'. The MN sends an RS when an 789 acknowledgement is required, or an unsolicited NA when reliability 790 is not thought to be a concern (e.g., if redundant transmissions 791 are sent on multiple ANET interfaces). 793 o When a MN wishes to release from a current MSE, it sends an RS or 794 unsolicited NA message over any UP ANET interfaces with an OMNI 795 option with R set to 0. The corresponding MSE then withdraws the 796 MNP from the routing/mapping system and (for RS responses) directs 797 the AR to return an RA message with an OMNI option and with Router 798 Lifetime set to 0. 800 o When a MN wishes to transition to a new MSE, it sends an RS or 801 unsolicited NA message over any UP ANET interfaces with an OMNI 802 option with R set to 1, with the new MSE OMNI LLA set in the 803 destination address, and (optionally) with N set to 1 and a 804 Notification ID included for the former MSE. 806 o When all of a MNs underlying interfaces have transitioned to DOWN 807 (or if the prefix registration lifetime expires) the MSE withdraws 808 the MNP the same as if it had received a message with an OMNI 809 option with R set to 0. 811 The MN is responsible for retrying each RS exchange up to 812 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 813 seconds until an RA is received. If no RA is received over multiple 814 UP ANET interfaces, the MN declares this MSE unreachable and tries a 815 different MSE. 817 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 818 Therefore, when the IPv6 layer sends an RS message the OMNI interface 819 returns an internally-generated RA message as though the message 820 originated from an IPv6 router. The internally-generated RA message 821 contains configuration information that is consistent with the 822 information received from the RAs generated by the MS. 824 Whether the OMNI interface IPv6 ND messaging process is initiated 825 from the receipt of an RS message from the IPv6 layer is an 826 implementation matter. Some implementations may elect to defer the 827 IPv6 ND messaging process until an RS is received from the IPv6 828 layer, while others may elect to initiate the process proactively. 830 Note: The Router Lifetime value in RA messages indicates the time 831 before which the MN must send another RS message over this underlying 832 interface (e.g., 600 seconds), however that timescale may be 833 significantly longer than the lifetime the MS has committed to retain 834 the prefix registration (e.g., REACHABLETIME seconds). For this 835 reason, the MN should select a primary AR, which is responsible for 836 keeping the MS prefix registration alive on the MN's behalf. If the 837 MN does not select a primary, then it must perform more frequent RS/ 838 RA exchanges on its own behalf to refresh the MS prefix registration 839 lifetime. 841 13. AR and MSE Resilience 843 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 844 [RFC5798] configurations so that service continuity is maintained 845 even if one or more ARs fail. Using VRRP, the MN is unaware which of 846 the (redundant) ARs is currently providing service, and any service 847 discontinuity will be limited to the failover time supported by VRRP. 848 Widely deployed public domain implementations of VRRP are available. 850 MSEs SHOULD use high availability clustering services so that 851 multiple redundant systems can provide coordinated response to 852 failures. As with VRRP, widely deployed public domain 853 implementations of high availability clustering services are 854 available. Note that special-purpose and expensive dedicated 855 hardware is not necessary, and public domain implementations can be 856 used even between lightweight virtual machines in cloud deployments. 858 14. Detecting and Responding to MSE Failures 860 In environments where fast recovery from MSE failure is required, ARs 861 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 862 manner that parallels Bidirectional Forwarding Detection (BFD) 863 [RFC5880] to track MSE reachability. ARs can then quickly detect and 864 react to failures so that cached information is re-established 865 through alternate paths. Proactive NUD control messaging is carried 866 only over well-connected ground domain networks (i.e., and not low- 867 end aeronautical radio links) and can therefore be tuned for rapid 868 response. 870 ARs perform proactive NUD for MSEs for which there are currently 871 active ANET MNs. If an MSE fails, ARs can quickly inform MNs of the 872 outage by sending multicast RA messages on the ANET interface. The 873 AR sends RA messages to the MN via the ANET interface with source 874 address set to the MSEs OMNI LLA, destination address set to All- 875 Nodes multicast (ff02::1) [RFC4291], and Router Lifetime set to 0. 877 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 878 by small delays [RFC4861]. Any MNs on the ANET interface that have 879 been using the (now defunct) MSE will receive the RA messages and 880 associate with a new MSE. 882 15. IANA Considerations 884 The IANA is instructed to allocate an official Type number TBD from 885 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 886 option. Implementations set Type to 253 as an interim value 887 [RFC4727]. 889 The IANA is instructed to allocate one Ethernet unicast address TBD2 890 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 891 Address Block - Unicast Use". 893 16. Security Considerations 895 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 896 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 897 include Nonce and Timestamp options [RFC3971] when synchronized 898 transaction confirmation is needed. 900 Security considerations for specific access network interface types 901 are covered under the corresponding IP-over-(foo) specification 902 (e.g., [RFC2464], [RFC2492], etc.). 904 17. Acknowledgements 906 The first version of this document was prepared per the consensus 907 decision at the 7th Conference of the International Civil Aviation 908 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 909 2019. Consensus to take the document forward to the IETF was reached 910 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 911 Attendees and contributors included: Guray Acar, Danny Bharj, 912 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 913 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 914 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 915 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 916 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 917 Fryderyk Wrobel and Dongsong Zeng. 919 The following individuals are acknowledged for their useful comments: 920 Pavel Drasil, Zdenek Jaron, Michael Matyas, Madhu Niraula, Greg 921 Saccone, Stephane Tamalet, Eric Vyncke. Naming of the IPv6 ND option 922 was discussed on the 6man mailing list. 924 This work is aligned with the NASA Safe Autonomous Systems Operation 925 (SASO) program under NASA contract number NNA16BD84C. 927 This work is aligned with the FAA as per the SE2025 contract number 928 DTFAWA-15-D-00030. 930 18. References 932 18.1. Normative References 934 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 935 Requirement Levels", BCP 14, RFC 2119, 936 DOI 10.17487/RFC2119, March 1997, 937 . 939 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 940 "Definition of the Differentiated Services Field (DS 941 Field) in the IPv4 and IPv6 Headers", RFC 2474, 942 DOI 10.17487/RFC2474, December 1998, 943 . 945 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 946 "SEcure Neighbor Discovery (SEND)", RFC 3971, 947 DOI 10.17487/RFC3971, March 2005, 948 . 950 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 951 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 952 November 2005, . 954 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 955 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 956 2006, . 958 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 959 ICMPv6, UDP, and TCP Headers", RFC 4727, 960 DOI 10.17487/RFC4727, November 2006, 961 . 963 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 964 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 965 DOI 10.17487/RFC4861, September 2007, 966 . 968 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 969 Address Autoconfiguration", RFC 4862, 970 DOI 10.17487/RFC4862, September 2007, 971 . 973 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 974 Hosts in a Multi-Prefix Network", RFC 8028, 975 DOI 10.17487/RFC8028, November 2016, 976 . 978 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 979 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 980 May 2017, . 982 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 983 (IPv6) Specification", STD 86, RFC 8200, 984 DOI 10.17487/RFC8200, July 2017, 985 . 987 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 988 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 989 DOI 10.17487/RFC8201, July 2017, 990 . 992 18.2. Informative References 994 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 995 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 996 . 998 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 999 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 1000 . 1002 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 1003 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 1004 December 1998, . 1006 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 1007 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 1008 . 1010 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 1011 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 1012 . 1014 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 1015 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 1016 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 1017 RFC 3819, DOI 10.17487/RFC3819, July 2004, 1018 . 1020 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 1021 "Internet Group Management Protocol (IGMP) / Multicast 1022 Listener Discovery (MLD)-Based Multicast Forwarding 1023 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 1024 August 2006, . 1026 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1027 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1028 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1029 . 1031 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 1032 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 1033 DOI 10.17487/RFC5214, March 2008, 1034 . 1036 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 1037 Version 3 for IPv4 and IPv6", RFC 5798, 1038 DOI 10.17487/RFC5798, March 2010, 1039 . 1041 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1042 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 1043 . 1045 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 1046 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 1047 2012, . 1049 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 1050 Requirements for IPv6 Customer Edge Routers", RFC 7084, 1051 DOI 10.17487/RFC7084, November 2013, 1052 . 1054 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 1055 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 1056 Boundary in IPv6 Addressing", RFC 7421, 1057 DOI 10.17487/RFC7421, January 2015, 1058 . 1060 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 1061 Support for IP Hosts with Multi-Access Support", RFC 7847, 1062 DOI 10.17487/RFC7847, May 2016, 1063 . 1065 Appendix A. OMNI Option Extensions for Pseudo-DSCP Mappings 1067 Adaptation of the OMNI interface to specific Internetworks such as 1068 the Aeronautical Telecommunications Network with Internet Protocol 1069 Services (ATN/IPS) includes link selection preferences based on 1070 transport port numbers in addition to the existing DSCP-based 1071 preferences. ATN/IPS nodes maintain a map of transport port numbers 1072 to additional "pseudo-DSCP" P[*] preference fields beyond the first 1073 64. For example, TCP port 22 maps to pseudo-DSCP value P67, TCP port 1074 443 maps to P70, UDP port 8060 maps to P76, etc. Figure 4 shows an 1075 example OMNI option with extended P[*] values beyond the base 64 used 1076 for DSCP mapping (i.e., for QoS values 5 or greater): 1078 0 1 2 3 1079 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 1080 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1081 | Type | Length | Prefix Length |R|N|P| Reservd | 1082 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1083 | ifIndex | ifType | Flags | Link |QoS=5+ | 1084 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1085 |P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15| 1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1087 |P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 1090 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1091 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 1092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1093 |P64|P65|P66|P67|P68|P69|P70|P71|P72|P73|P74|P75|P76|P77|P78|P79| 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1095 ... 1097 Figure 4: ATN/IPS Extended OMNI Option Format 1099 Appendix B. Prefix Length Considerations 1101 The 64-bit boundary in IPv6 addresses [RFC7421] determines the MN 1102 OMNI LLA format for encoding the most-significant 64 MNP bits into 1103 the least-significant 64 bits of the prefix fe80::/64 as discussed in 1104 Section 7. 1106 [RFC4291] defines the link-local address format as the most 1107 significant 10 bits of the prefix fe80::/10, followed by 54 unused 1108 bits, followed by the least-significant 64 bits of the address. If 1109 the 64-bit boundary is relaxed through future standards activity, 1110 then the 54 unused bits can be employed for extended coding of MNPs 1111 of length /65 up to /118. 1113 The extended coding format would continue to encode MNP bits 0-63 in 1114 bits 64-127 of the OMNI LLA, while including MNP bits 64-117 in bits 1115 10-63. For example, the OMNI LLA corresponding to the MNP 1116 2001:db8:1111:2222:3333:4444:5555::/112 would be 1117 fe8c:ccd1:1115:5540:2001:db8:1111:2222, and would still be a valid 1118 IPv6 LLA per [RFC4291]. 1120 Appendix C. VDL Mode 2 Considerations 1122 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 1123 (VDLM2) that specifies an essential radio frequency data link service 1124 for aircraft and ground stations in worldwide civil aviation air 1125 traffic management. The VDLM2 link type is "multicast capable" 1126 [RFC4861], but with considerable differences from common multicast 1127 links such as Ethernet and IEEE 802.11. 1129 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 1130 magnitude less than most modern wireless networking gear. Second, 1131 due to the low available link bandwidth only VDLM2 ground stations 1132 (i.e., and not aircraft) are permitted to send broadcasts, and even 1133 so only as compact layer 2 "beacons". Third, aircraft employ the 1134 services of ground stations by performing unicast RS/RA exchanges 1135 upon receipt of beacons instead of listening for multicast RA 1136 messages and/or sending multicast RS messages. 1138 This beacon-oriented unicast RS/RA approach is necessary to conserve 1139 the already-scarce available link bandwidth. Moreover, since the 1140 numbers of beaconing ground stations operating within a given spatial 1141 range must be kept as sparse as possible, it would not be feasible to 1142 have different classes of ground stations within the same region 1143 observing different protocols. It is therefore highly desirable that 1144 all ground stations observe a common language of RS/RA as specified 1145 in this document. 1147 Note that links of this nature may benefit from compression 1148 techniques that reduce the bandwidth necessary for conveying the same 1149 amount of data. The IETF lpwan working group is considering possible 1150 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 1152 Appendix D. Change Log 1154 << RFC Editor - remove prior to publication >> 1156 Differences from draft-templin-atn-aero-interface-19 to draft- 1157 templin-atn-aero-interface-20: 1159 o MTU 1161 Differences from draft-templin-atn-aero-interface-18 to draft- 1162 templin-atn-aero-interface-19: 1164 o MTU 1166 Differences from draft-templin-atn-aero-interface-17 to draft- 1167 templin-atn-aero-interface-18: 1169 o MTU and RA configuration information updated. 1171 Differences from draft-templin-atn-aero-interface-16 to draft- 1172 templin-atn-aero-interface-17: 1174 o New "Primary" flag in OMNI option. 1176 Differences from draft-templin-atn-aero-interface-15 to draft- 1177 templin-atn-aero-interface-16: 1179 o New note on MSE OMNI LLA uniqueness assurance. 1181 o General cleanup. 1183 Differences from draft-templin-atn-aero-interface-14 to draft- 1184 templin-atn-aero-interface-15: 1186 o General cleanup. 1188 Differences from draft-templin-atn-aero-interface-13 to draft- 1189 templin-atn-aero-interface-14: 1191 o General cleanup. 1193 Differences from draft-templin-atn-aero-interface-12 to draft- 1194 templin-atn-aero-interface-13: 1196 o Minor re-work on "Notify-MSE" (changed to Notification ID). 1198 Differences from draft-templin-atn-aero-interface-11 to draft- 1199 templin-atn-aero-interface-12: 1201 o Removed "Request/Response" OMNI option formats. Now, there is 1202 only one OMNI option format that applies to all ND messages. 1204 o Added new OMNI option field and supporting text for "Notify-MSE". 1206 Differences from draft-templin-atn-aero-interface-10 to draft- 1207 templin-atn-aero-interface-11: 1209 o Changed name from "aero" to "OMNI" 1211 o Resolved AD review comments from Eric Vyncke (posted to atn list) 1213 Differences from draft-templin-atn-aero-interface-09 to draft- 1214 templin-atn-aero-interface-10: 1216 o Renamed ARO option to AERO option 1218 o Re-worked Section 13 text to discuss proactive NUD. 1220 Differences from draft-templin-atn-aero-interface-08 to draft- 1221 templin-atn-aero-interface-09: 1223 o Version and reference update 1225 Differences from draft-templin-atn-aero-interface-07 to draft- 1226 templin-atn-aero-interface-08: 1228 o Removed "Classic" and "MS-enabled" link model discussion 1230 o Added new figure for MN/AR/MSE model. 1232 o New Section on "Detecting and responding to MSE failure". 1234 Differences from draft-templin-atn-aero-interface-06 to draft- 1235 templin-atn-aero-interface-07: 1237 o Removed "nonce" field from AR option format. Applications that 1238 require a nonce can include a standard nonce option if they want 1239 to. 1241 o Various editorial cleanups. 1243 Differences from draft-templin-atn-aero-interface-05 to draft- 1244 templin-atn-aero-interface-06: 1246 o New Appendix C on "VDL Mode 2 Considerations" 1248 o New Appendix D on "RS/RA Messaging as a Single Standard API" 1249 o Various significant updates in Section 5, 10 and 12. 1251 Differences from draft-templin-atn-aero-interface-04 to draft- 1252 templin-atn-aero-interface-05: 1254 o Introduced RFC6543 precedent for focusing IPv6 ND messaging to a 1255 reserved unicast link-layer address 1257 o Introduced new IPv6 ND option for Aero Registration 1259 o Specification of MN-to-MSE message exchanges via the ANET access 1260 router as a proxy 1262 o IANA Considerations updated to include registration requests and 1263 set interim RFC4727 option type value. 1265 Differences from draft-templin-atn-aero-interface-03 to draft- 1266 templin-atn-aero-interface-04: 1268 o Removed MNP from aero option format - we already have RIOs and 1269 PIOs, and so do not need another option type to include a Prefix. 1271 o Clarified that the RA message response must include an aero option 1272 to indicate to the MN that the ANET provides a MS. 1274 o MTU interactions with link adaptation clarified. 1276 Differences from draft-templin-atn-aero-interface-02 to draft- 1277 templin-atn-aero-interface-03: 1279 o Sections re-arranged to match RFC4861 structure. 1281 o Multiple aero interfaces 1283 o Conceptual sending algorithm 1285 Differences from draft-templin-atn-aero-interface-01 to draft- 1286 templin-atn-aero-interface-02: 1288 o Removed discussion of encapsulation (out of scope) 1290 o Simplified MTU section 1292 o Changed to use a new IPv6 ND option (the "aero option") instead of 1293 S/TLLAO 1295 o Explained the nature of the interaction between the mobility 1296 management service and the air interface 1298 Differences from draft-templin-atn-aero-interface-00 to draft- 1299 templin-atn-aero-interface-01: 1301 o Updates based on list review comments on IETF 'atn' list from 1302 4/29/2019 through 5/7/2019 (issue tracker established) 1304 o added list of opportunities afforded by the single virtual link 1305 model 1307 o added discussion of encapsulation considerations to Section 6 1309 o noted that DupAddrDetectTransmits is set to 0 1311 o removed discussion of IPv6 ND options for prefix assertions. The 1312 aero address already includes the MNP, and there are many good 1313 reasons for it to continue to do so. Therefore, also including 1314 the MNP in an IPv6 ND option would be redundant. 1316 o Significant re-work of "Router Discovery" section. 1318 o New Appendix B on Prefix Length considerations 1320 First draft version (draft-templin-atn-aero-interface-00): 1322 o Draft based on consensus decision of ICAO Working Group I Mobility 1323 Subgroup March 22, 2019. 1325 Authors' Addresses 1327 Fred L. Templin (editor) 1328 The Boeing Company 1329 P.O. Box 3707 1330 Seattle, WA 98124 1331 USA 1333 Email: fltemplin@acm.org 1335 Tony Whyman 1336 MWA Ltd c/o Inmarsat Global Ltd 1337 99 City Road 1338 London EC1Y 1AX 1339 England 1341 Email: tony.whyman@mccallumwhyman.com