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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: rfc4193, rfc4291, rfc4443, A. Whyman 5 rfc8201 (if approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track September 16, 2020 7 Expires: March 20, 2021 9 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-32 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 IPv6 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 March 20, 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 . . . . . . 7 62 5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 11 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 13 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 14 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 14 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 16 67 9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 17 68 9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 18 69 9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 19 70 9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 20 71 9.1.3. Interface Attributes . . . . . . . . . . . . . . . . 20 72 9.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 23 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 24 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 25 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 25 76 9.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . . 26 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 26 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 27 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 27 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 28 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 28 82 12.1. Router Discovery in IP Multihop and IPv4-Only Access 83 Networks . . . . . . . . . . . . . . . . . . . . . . . . 32 84 12.2. MS-Register and MS-Release List Processing . . . . . . . 33 85 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 35 86 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 35 87 15. Detecting and Responding to MSE Failures . . . . . . . . . . 36 88 16. Transition Considerations . . . . . . . . . . . . . . . . . . 36 89 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 37 90 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 38 91 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 92 20. Security Considerations . . . . . . . . . . . . . . . . . . . 39 93 21. Implementation Status . . . . . . . . . . . . . . . . . . . . 40 94 22. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 40 95 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 41 96 23.1. Normative References . . . . . . . . . . . . . . . . . . 41 97 23.2. Informative References . . . . . . . . . . . . . . . . . 43 98 Appendix A. Interface Attribute Heuristic Bitmap Encoding . . . 47 99 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 48 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 49 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 50 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 104 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 IPv6 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 138 IPv6 layer sees the OMNI interface as a point of connection to the 139 OMNI link. Each OMNI link has one or more associated Mobility 140 Service Prefixes (MSPs) from which OMNI link MNPs are derived. If 141 there are 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 IPv6 packets [RFC8200] 161 and MN/MS control messaging over OMNI interfaces. 163 2. Terminology 165 The terminology in the normative references applies; especially, the 166 terms "link" and "interface" are the same as defined in the IPv6 167 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 168 Additionally, this document assumes the following IPv6 ND message 169 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 170 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 172 The Protocol Constants defined in Section 10 of [RFC4861] are used in 173 their same format and meaning in this document. The terms "All- 174 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 175 are the same as defined in [RFC4291] (with Link-Local scope assumed). 177 The following terms are defined within the scope of this document: 179 Mobile Node (MN) 180 an end system with a mobile router having multiple distinct 181 upstream data link connections that are grouped together in one or 182 more logical units. The MN's data link connection parameters can 183 change over time due to, e.g., node mobility, link quality, etc. 184 The MN further connects a downstream-attached End User Network 185 (EUN). The term MN used here is distinct from uses in other 186 documents, and does not imply a particular mobility protocol. 188 End User Network (EUN) 189 a simple or complex downstream-attached mobile network that 190 travels with the MN as a single logical unit. The IPv6 addresses 191 assigned to EUN devices remain stable even if the MN's upstream 192 data link connections change. 194 Mobility Service (MS) 195 a mobile routing service that tracks MN movements and ensures that 196 MNs remain continuously reachable even across mobility events. 197 Specific MS details are out of scope for this document. 199 Mobility Service Endpoint (MSE) 200 an entity in the MS (either singular or aggregate) that 201 coordinates the mobility events of one or more MN. 203 Mobility Service Prefix (MSP) 204 an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the 205 rest of the Internetwork by the MS, and from which more-specific 206 Mobile Network Prefixes (MNPs) are derived. 208 Mobile Network Prefix (MNP) 209 a longer IPv6 prefix taken from an MSP (e.g., 210 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate 211 the MNP to devices located in EUNs. 213 Access Network (ANET) 214 a data link service network (e.g., an aviation radio access 215 network, satellite service provider network, cellular operator 216 network, wifi network, etc.) that connects MNs. Physical and/or 217 data link level security between the MN and ANET are assumed. 219 Access Router (AR) 220 a first-hop router in the ANET for connecting MNs to 221 correspondents in outside Internetworks. 223 ANET interface 224 a MN's attachment to a link in an ANET. 226 Internetwork (INET) 227 a connected network region with a coherent IP addressing plan that 228 provides transit forwarding services for ANET MNs and INET 229 correspondents. Examples include private enterprise networks, 230 ground domain aviation service networks and the global public 231 Internet itself. 233 INET interface 234 a node's attachment to a link in an INET. 236 OMNI link 237 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 238 over one or more INETs and their connected ANETs. An OMNI link 239 can comprise multiple INET segments joined by bridges the same as 240 for any link; the addressing plans in each segment may be mutually 241 exclusive and managed by different administrative entities. 243 OMNI interface 244 a node's attachment to an OMNI link, and configured over one or 245 more underlying ANET/INET interfaces. 247 OMNI Link-Local Address (LLA) 248 a link local IPv6 address per [RFC4291] constructed as specified 249 in Section 7. 251 OMNI Unique-Local Address (ULA) 252 a unique local IPv6 address per [RFC4193] constructed as specified 253 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 254 and vice-versa. 256 OMNI Option 257 an IPv6 Neighbor Discovery option providing multilink parameters 258 for the OMNI interface as specified in Section 9. 260 Multilink 261 an OMNI interface's manner of managing diverse underlying data 262 link interfaces as a single logical unit. The OMNI interface 263 provides a single unified interface to upper layers, while 264 underlying data link selections are performed on a per-packet 265 basis considering factors such as DSCP, flow label, application 266 policy, signal quality, cost, etc. Multilinking decisions are 267 coordinated in both the outbound (i.e. MN to correspondent) and 268 inbound (i.e., correspondent to MN) directions. 270 L2 271 The second layer in the OSI network model. Also known as "layer- 272 2", "link-layer", "sub-IP layer", "data link layer", etc. 274 L3 275 The third layer in the OSI network model. Also known as "layer- 276 3", "network-layer", "IPv6 layer", etc. 278 underlying interface 279 an ANET/INET interface over which an OMNI interface is configured. 280 The OMNI interface is seen as a L3 interface by the IP layer, and 281 each underlying interface is seen as a L2 interface by the OMNI 282 interface. 284 Mobility Service Identification (MSID) 285 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 286 as specified in Section 7. 288 Safety-Based Multilink (SBM) 289 A means for ensuring fault tolerance through redundancy by 290 connecting multiple independent OMNI interfaces to independent 291 routing topologies (i.e., multiple independent OMNI links). 293 Performance Based Multilink (PBM) 294 A means for selecting underlying interface(s) for packet 295 trasnmission and reception within a single OMNI interface. 297 3. Requirements 299 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 300 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 301 "OPTIONAL" in this document are to be interpreted as described in BCP 302 14 [RFC2119][RFC8174] when, and only when, they appear in all 303 capitals, as shown here. 305 OMNI links maintain a constant value "MAX_MSID" selected to provide 306 MNs with an acceptable level of MSE redundancy while minimizing 307 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 308 set to the default value 5; if a different value is chosen, it should 309 be set uniformly by all nodes on the OMNI link. 311 An implementation is not required to internally use the architectural 312 constructs described here so long as its external behavior is 313 consistent with that described in this document. 315 4. Overlay Multilink Network (OMNI) Interface Model 317 An OMNI interface is a MN virtual interface configured over one or 318 more underlying interfaces, which may be physical (e.g., an 319 aeronautical radio link) or virtual (e.g., an Internet or higher- 320 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 321 with the MS through IPv6 ND message exchanges. The MN uses the MNP 322 to construct a unique OMNI LLA through the algorithmic derivation 323 specified in Section 7 and assigns the LLA to the OMNI interface. 325 The OMNI interface architectural layering model is the same as in 326 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 327 therefore sees the OMNI interface as a single L3 interface with 328 multiple underlying interfaces that appear as L2 communication 329 channels in the architecture. 331 +----------------------------+ 332 | Upper Layer Protocol | 333 Session-to-IP +---->| | 334 Address Binding | +----------------------------+ 335 +---->| IP (L3) | 336 IP Address +---->| | 337 Binding | +----------------------------+ 338 +---->| OMNI Interface | 339 Logical-to- +---->| (OMNI LLA) | 340 Physical | +----------------------------+ 341 Interface +---->| L2 | L2 | | L2 | 342 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 343 +------+------+ +------+ 344 | L1 | L1 | | L1 | 345 | | | | | 346 +------+------+ +------+ 348 Figure 1: OMNI Interface Architectural Layering Model 350 The OMNI virtual interface model gives rise to a number of 351 opportunities: 353 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 354 Address Detection (DAD) or Muticast Listener Discovery (MLD) 355 messaging is necessary. 357 o ANET interfaces do not require any L3 addresses (i.e., not even 358 link-local) in environments where communications are coordinated 359 entirely over the OMNI interface. (An alternative would be to 360 also assign the same OMNI LLA to all ANET interfaces.) 362 o as ANET interface properties change (e.g., link quality, cost, 363 availability, etc.), any active ANET interface can be used to 364 update the profiles of multiple additional ANET interfaces in a 365 single message. This allows for timely adaptation and service 366 continuity under dynamically changing conditions. 368 o coordinating ANET interfaces in this way allows them to be 369 represented in a unified MS profile with provisions for mobility 370 and multilink operations. 372 o exposing a single virtual interface abstraction to the IPv6 layer 373 allows for multilink operation (including QoS based link 374 selection, packet replication, load balancing, etc.) at L2 while 375 still permitting L3 traffic shaping based on, e.g., DSCP, flow 376 label, etc. 378 o L3 sees the OMNI interface as a point of connection to the OMNI 379 link; if there are multiple OMNI links (i.e., multiple MS's), L3 380 will see multiple OMNI interfaces. 382 o Multiple independent OMNI interfaces can be used for increased 383 fault tolerance through Safety-Based Multilink (SBM), with 384 Performance-Based Multilink (PBM) applied within each interface. 386 Other opportunities are discussed in [RFC7847]. 388 Figure 2 depicts the architectural model for a MN connecting to the 389 MS via multiple independent ANETs. When an underlying interface 390 becomes active, the MN's OMNI interface sends native (i.e., 391 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 392 ND messages traverse the ground domain ANETs until they reach an 393 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 394 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 395 returns an IPv6 ND message response to the MN. IPv6 ND messages 396 traverse the ANET at layer 2; hence, the Hop Limit is not 397 decremented. 399 +--------------+ 400 | MN | 401 +--------------+ 402 |OMNI interface| 403 +----+----+----+ 404 +--------|IF#1|IF#2|IF#n|------ + 405 / +----+----+----+ \ 406 / | \ 407 / <---- Native | IP ----> \ 408 v v v 409 (:::)-. (:::)-. (:::)-. 410 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 411 `-(::::)-' `-(::::)-' `-(::::)-' 412 +----+ +----+ +----+ 413 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 414 . +-|--+ +-|--+ +-|--+ . 415 . | | | 416 . v v v . 417 . <----- Encapsulation -----> . 418 . . 419 . +-----+ (:::)-. . 420 . |MSE#2| .-(::::::::) +-----+ . 421 . +-----+ .-(::: INET :::)-. |MSE#m| . 422 . (::::: Routing ::::) +-----+ . 423 . `-(::: System :::)-' . 424 . +-----+ `-(:::::::-' . 425 . |MSE#1| +-----+ +-----+ . 426 . +-----+ |MSE#3| |MSE#4| . 427 . +-----+ +-----+ . 428 . . 429 . . 430 . <----- Worldwide Connected Internetwork ----> . 431 ........................................................... 433 Figure 2: MN/MS Coordination via Multiple ANETs 435 After the initial IPv6 ND message exchange, the MN can send and 436 receive unencapsulated IPv6 data packets over the OMNI interface. 437 OMNI interface multilink services will forward the packets via ARs in 438 the correct underlying ANETs. The AR encapsulates the packets 439 according to the capabilities provided by the MS and forwards them to 440 the next hop within the worldwide connected Internetwork via optimal 441 routes. 443 OMNI links span one or more underlying Internetwork via a mid-layer 444 overlay encapsulation based on [RFC2473] and using [RFC4193] 445 addressing. Each OMNI link corresponds to a different overlay 446 (differentiated by an address codepoint) which may be carried over a 447 completely separate underlying topology. Each MN can facilitate SBM 448 by connecting to multiple OMNI links using a distinct OMNI interface 449 for each link. 451 5. Maximum Transmission Unit (MTU) and Fragmentation 453 The OMNI interface observes the link nature of tunnels, including the 454 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 455 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 456 The OMNI interface is configured over one or more underlying 457 interfaces that may have diverse MTUs. 459 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 460 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 461 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 462 not permitted to perform fragmentation even though the destination is 463 required to reassemble more. The network therefore MUST forward 464 packets of at least 1280 bytes without generating an IPv6 Path MTU 465 Discovery (PMTUD) Packet Too Big (PTB) message [RFC8201]. (Note: if 466 the encapsulation source has a way to determine that the 467 encapsulation destination configures a larger MRU, it can apply 468 source fragmentation for larger packet sizes. But, this does not 469 affect the minimum IPv6 path MTU as stated above.) 471 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 472 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 473 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 474 minimum IPv4 path MTU is 576 bytes since routers on the path are 475 permitted to perform fragmentation and the destination is required to 476 reassemble at least that much. The DF bit in the IPv4 encapsulation 477 headers of packets sent over IPv4 underlying interfaces therefore 478 MUST be set to 0. (Note: even if the encapsulation source has a way 479 to determine that the encapsulation destination configures a larger 480 MRU, a larger minimum IPv4 path MTU can only be assumed after careful 481 consderation of the issues discussed in Section 5.1.) 483 The OMNI interface configures both an MTU and MRU of 9180 bytes 484 [RFC2492]; the size is therefore not a reflection of the underlying 485 interface MTUs, but rather determines the largest packet the OMNI 486 interface can forward or reassemble. The OMNI interface admits 487 packets from the network layer that are no larger than the OMNI 488 interface MTU while generating IPv6 Path MTU Discovery (PMTUD) Packet 489 Too Big (PTB) messages [RFC8201] as necessary. For IPv4 packets with 490 DF=0, the IP layer performs IPv4 fragmentation according to the OMNI 491 interface MTU if necessary then admits the fragments into the 492 interface; the OMNI interface may then internally apply further IPv4 493 fragmentation prior to encapsulation if the fragments are larger than 494 the underlying interface MTU. For IPv6 packets originating from the 495 local system admitted into the OMNI interface that are larger than 496 the underlying interface MTU but no larger than the destination IPv6 497 MRU, the OMNI interface applies IPv6 fragmentation prior to 498 encapsulation. These (source) fragments will be reassembled by the 499 final destination. (Note: an implementation can optionally apply 500 source fragmentation according to the minimum IPv4/IPv6 path MTU 501 instead of the underlying interface MTU in order to avoid further 502 fragmentation in the network.) 504 Following any source fragmentation, OMNI interfaces internally employ 505 link adaptation when necessary by inserting a mid-layer IPv6 header 506 between the inner IP packet and any outer IP encapsulation headers 507 per [RFC2473] then performing fragmentation on the mid-layer IPv6 508 packet. The OMNI interface can instead return internally-generated 509 PTB messages for packets admitted into the interface that it deems 510 too large (e.g., according to link performance characteristics, 511 reassembly congestion, etc.) while either dropping or forwarding the 512 packet. The OMNI interface performs PMTUD even if the destination 513 appears to be on the same link since an OMNI link node on the path 514 may return a PTB. This ensures that the path MTU is adaptive and 515 reflects the current path used for a given data flow. 517 OMNI interfaces perform encapsulation and fragmentation/reassembly 518 with respect to both the minimum IPv6 and IPv4 path MTUs as follows: 520 o When an OMNI interface sends a packet toward a final destination 521 via an ANET peer, it sends without OMNI link encapsulation if the 522 packet (including any outer-layer ANET encapsulations) is no 523 larger than the underlying interface MTU for directly-connected 524 ANET peers or the minimum ANET path MTU for peers separated by 525 multiple IP hops. Otherwise, it inserts an IPv6 header with 526 source address set to the node's own OMNI Unique Local Address 527 (ULA) (see: Section 8) and destination set to the OMNI ULA of the 528 ANET peer. The OMNI interface then uses IPv6 fragmentation to 529 break the packet into a minimum number of non-overlapping 530 fragments, where the largest fragment size (including both the 531 OMNI and any outer-layer ANET encapsulations) is determined by the 532 (path) MTU for the ANET peer. The OMNI interface then 533 encapsulates the fragements in any ANET headers and sends them to 534 the ANET peer, which reassembles before forwarding toward the 535 final destination. 537 o When an OMNI interface sends a packet toward a final destination 538 via an INET interface, it sends packets (including any outer-layer 539 INET encapsulations) no larger than the minimum INET path MTU 540 without OMNI link adaptation if the destination is reached via an 541 INET address within the same OMNI link segment. Otherwise, it 542 inserts an IPv6 header with source address set to the node's OMNI 543 ULA, destination set to the ULA of the next hop OMNI node toward 544 the final destination and (if necessary) with a Segment Routing 545 Header with the remaining Segment IDs on the path to the final 546 destination. The OMNI interface then uses IPv6 fragmentation to 547 break the encapsulated packet into a minimum number of non- 548 overlapping fragments, where the largest fragment size (including 549 both the OMNI and outer-layer INET encapsulations) is the minimum 550 INET path MTU, and the smallest fragment size is no smaller than 551 256 bytes (i.e., slightly less than half the minimum IPv4 path 552 MTU). The OMNI interface then encapsulates the fragments in any 553 INET headers and sends them to the OMNI link neighbor, which 554 reassembles before forwarding toward the final destination. 556 OMNI interfaces unconditionally drop all OMNI link fragments received 557 from an INET peer that are smaller than 256 bytes (note that no 558 minimum fragment size is specified for ANET peers since the 559 underlying ANET is secured.) In order to set the correct context for 560 reassembly, the OMNI interface that inserts the IPv6 header MUST also 561 be the one that inserts the IPv6 Fragment Header Identification 562 value. While not strictly required, sending all fragments of the 563 same fragmented OMNI-encapsulated packet consecutively over the same 564 underlying interface with minimal inter-fragment delay may increase 565 the likelihood of successful reassembly. 567 Note that the OMNI interface can forward large packets via 568 encapsulation and fragmentation while at the same time returning 569 "advisory" PTB messages (subject to rate limiting). The receiving 570 node that performs reassembly can also send advisory PTB messages if 571 reassembly conditions become unfavorable. The OMNI interface can 572 therefore continuously forward large packets without loss while 573 returning advisory PTB messages recommending a smaller size. 575 OMNI interfaces that send advisory PTB messages set the ICMPv6 576 message header Code field to the value 1. Receiving nodes that 577 recognize the code reduce their estimate of the path MTU the same as 578 for ordinary "diagnistic" PTBs but do not regard the message as a 579 loss indication. Nodes that do not recognize the code treat the 580 message the same as a diagnostic PTB, but should heed the 581 retransmission advice given in [RFC8201]. This document therefore 582 updates [RFC4443] and [RFC8201]. 584 5.1. Fragmentation Security Implications 586 As discussed in Section 3.7 of [RFC8900], there are four basic 587 threats concerning IPv6 fragmentation; each of which is addressed by 588 effective mitigations as follows: 590 1. Overlapping fragment attacks - reassembly of overlapping 591 fragments is forbidden by [RFC8200]; therefore, this threat does 592 not apply to OMNI interfaces. 594 2. Resource exhaustion attacks - this threat is mitigated by 595 providing a sufficiently large OMNI interface reassembly cache 596 and instituting "fast discard" of incomplete reassemblies that 597 may be part of a buffer exhaustion attack. The reassembly cache 598 should be sufficiently large so that a sustained attack does not 599 cause excessive loss of good reassemblies but not so large that 600 (timer-based) data structure management becomes computationally 601 expensive. 603 3. Attacks based on predictable fragment identification values - 604 this threat is mitigated by selecting a suitably random ID value 605 per [RFC7739]. 607 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 608 threat is mitigated by disallowing "tiny fragments" per the OMNI 609 interface fragmentation procedures specified above. 611 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 612 ID) field with only 65535 unique values such that at high data rates 613 the field could wrap and apply to new packets while the fragments of 614 old packets using the same ID are still alive in the network 615 [RFC4963]. However, since the largest OMNI fragment that will be 616 sent via an IPv4 INET path is 576 bytes any IPv4 fragmentation would 617 occur only on links with an IPv4 MTU smaller than this size, and 618 [RFC3819] recommendations suggest that such links will have low data 619 rates. Since IPv6 provides a 32-bit Identification value, IP ID 620 wraparound at high data rates is not a concern for IPv6 621 fragmentation. 623 6. Frame Format 625 The OMNI interface transmits IPv6 packets according to the native 626 frame format of each underlying interface. For example, for 627 Ethernet-compatible interfaces the frame format is specified in 628 [RFC2464], for aeronautical radio interfaces the frame format is 629 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 630 Manual), for tunnels over IPv6 the frame format is specified in 631 [RFC2473], etc. 633 7. Link-Local Addresses (LLAs) 635 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 636 LLAs") as follows: 638 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 639 within the least-significant 112 bits of the IPv6 link-local 640 prefix fe80::/16. The Prefix Length is determined by adding 16 to 641 the length of the embedded MNP. For example, for the MNP 642 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 643 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 644 link-local address format specified in Section 2.5.6 of [RFC4291] 645 by defining a use for bits 11 - 63. 647 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 648 i.e., the most significant 16 bits of the prefix fe80::/16, 649 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 650 32bit IPv4 address/prefix. The Prefix Length is determined by 651 adding 96 to the length of the embedded IPv4 address/prefix. For 652 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 653 fe80::ffff:192.0.2.0/120 (also written as 654 fe80::ffff:c000:0200/120). 656 o MS OMNI LLAs are assigned to ARs and MSEs from the range 657 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 658 of the LLA includes a unique integer "MSID" value between 659 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 660 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 661 determined by adding 96 to the MSID prefix length. For example, 662 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 663 Prefix Length is set to 112 and the LLA is written as 664 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 665 "Anycast" MSID and corresponds to the link-local Subnet-Router 666 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 667 through 0xffffffff is reserved for future use. 669 o The OMNI LLA range fe80::/32 is used as the service prefix for the 670 address format specified in Section 4 of [RFC4380] (see Section 17 671 for further discussion). 673 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 674 MNPs can be allocated from that block ensuring that there is no 675 possibility for overlap between the above OMNI LLA constructs. 677 Since MN OMNI LLAs are based on the distribution of administratively 678 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 679 through administrative assignment, OMNI interfaces set the 680 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 682 8. Unique-Local Addresses (ULAs) 684 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 685 [RFC4193] as the source and destination addresses in OMNI link IPv6 686 encapsulation headers. This document currently assumes use of the 687 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 688 (however, see the note at the end of this section). 690 Each OMNI link instance is identified by bits 10-15 of the OMNI 691 service prefix fc80::/10. For example, OMNI ULAs associated with 692 instance 0 are configured from the prefix fc80::/16, instance 1 from 693 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 694 their associated prefix lengths are configured in one-to-one 695 correspondence with OMNI LLAs through stateless prefix translation. 696 For example, for OMNI link instance fc80::/16: 698 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 699 fc80:2001:db8:1:2::/80 701 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 702 fc80::ffff:192.0.2.0/120 704 o the OMNI ULA corresponding to fe80::1000/112 is simply 705 fc80::1000/112 707 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 709 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 710 link instance, e.g., the OMNI interface connected to instance 3 711 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 712 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 713 the local routing system so that applications can direct traffic 714 according to SBM requirements. 716 The OMNI ULA presents an IPv6 address format that is routable within 717 the OMNI link routing system and can be used to convey link-scoped 718 messages across multiple hops using IPv6 encapsulation [RFC2473]. 719 The OMNI link extends across one or more underling Internetworks to 720 include all ARs and MSEs. All MNs are also considered to be 721 connected to the OMNI link, however OMNI link encapsulation is 722 omitted over ANET links when possible to conserve bandwidth (see: 723 Section 11). 725 The OMNI link can be subdivided into "segments" that often correspond 726 to different administrative domains or physical partitions. OMNI 727 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 728 support efficient packet forwarding to destinations located in other 729 OMNI link segments. A full discussion of Segment Routing over the 730 OMNI link appears in [I-D.templin-intarea-6706bis]. 732 NOTE: An alternative to the application of ULAs as discussed in this 733 document would be to re-purpose the deprectated IPv6 Site-Local 734 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 735 SLAs would be a more natural fit since both LLA and SLA prefix 736 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 737 single bit setting, and LLAs and SLAs can be unambiguously allocated 738 in one-to-one correspondence with one another. Re-purposing SLAs 739 would also make good use of an otherwise-wasted address range that 740 has been "parked" since the 2004 deprecation. However, moving from 741 ULAs to SLAs would require an IETF standards action acknowledging 742 this document as obsoleting [RFC3879] and updating [RFC4291]. The 743 authors therefore defer to IETF consensus as to the proper way 744 forward. 746 9. Address Mapping - Unicast 748 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 749 state and use the link-local address format specified in Section 7. 750 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 751 over physical underlying interfaces without encapsulation observe the 752 native underlying interface Source/Target Link-Layer Address Option 753 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 754 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 755 interfaces via encapsulation do not include S/TLLAOs which were 756 intended for encoding physical L2 media address formats and not 757 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 758 for encoding additional interface attributes. Hence, this document 759 does not define an S/TLLAO format but instead defines a new option 760 type termed the "OMNI option" designed for these purposes. 762 MNs such as aircraft typically have many wireless data link types 763 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 764 etc.) with diverse performance, cost and availability properties. 765 The OMNI interface would therefore appear to have multiple L2 766 connections, and may include information for multiple underlying 767 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 768 an IPv6 ND option called the OMNI option formatted as shown in 769 Figure 3: 771 0 1 2 3 772 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 1 773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 | Type | Length | Prefix Length | ifIndex | 775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 776 | | 777 ~ Sub-Options ~ 778 | | 779 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 781 Figure 3: OMNI Option Format 783 In this format: 785 o Type is set to TBD. If multiple OMNI option instances appear in 786 the same IPv6 ND message, the first instance is processed and all 787 other instances are ignored. 789 o Length is set to the number of 8 octet blocks in the option. 791 o Prefix Length is determines the length of prefix to be applied to 792 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 793 MS, Prefix Length is the length that the MN is requesting or 794 asserting to the MS. For IPv6 ND messages sent from the MS to the 795 MN, Prefix Length indicates the length that the MS is granting to 796 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 797 Length indicates the length associated with the target MN that is 798 subject of the ND message. 800 o ifIndex corresponds to the source or target underlying interface 801 for this IPv6 ND message, with a value between 0 and 255 encoded 802 as specified in Section 9.1.3. For RS and NS messages, ifIndex 803 corresponds to the source underlying interface over which the 804 message originated. For RA and NA messages, ifIndex corresponds 805 to the target underlying interface that the message is destined 806 to. 808 o Sub-Options is a Variable-length field, of length such that the 809 complete OMNI Option is an integer multiple of 8 octets long. 810 Contains one or more options, as described in Section 9.1. 812 9.1. Sub-Options 814 The OMNI option includes zero or more Sub-Options. Each consecutive 815 Sub-Option is concatenated immediately after its predecessor. All 816 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 817 encoded in the following format: 819 0 1 2 820 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 5 821 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 822 | Sub-Type | Sub-length | Sub-Option Data ... 823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 825 Figure 4: Sub-Option Format 827 o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub- 828 Options defined in this document are: 830 Option Name Sub-Type 831 Pad1 0 832 PadN 1 833 Interface Attributes 2 834 Traffic Selector 3 835 MS-Register 4 836 MS-Release 5 837 Network Access Identifier 6 838 Geo Coordinates 7 839 DHCP Unique Identifier (DUID) 8 841 Figure 5 843 Sub-Types 253 and 254 are reserved for experimentation, as 844 recommended in [RFC3692]. 846 o Sub-Length is a 1-byte field that encodes the length of the Sub- 847 Option Data, in bytes (I.e., ranging from 0 to 255). 849 o Sub-Option Data is a byte string with format determined by Sub- 850 Type. 852 During processing, unrecognized Sub-Options are ignored and the next 853 Sub-Option processed until the end of the OMNI option is reached. 855 The following Sub-Option types and formats are defined in this 856 document: 858 9.1.1. Pad1 860 0 861 0 1 2 3 4 5 6 7 862 +-+-+-+-+-+-+-+-+ 863 | Sub-Type=0 | 864 +-+-+-+-+-+-+-+-+ 866 Figure 6: Pad1 868 o Sub-Type is set to 0. If multiple instances appear in the same 869 OMNI option all are processed. 871 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 872 consists of a single zero octet). 874 9.1.2. PadN 876 0 1 2 877 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 5 878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 879 | Sub-Type=1 | Sub-length=N | N padding bytes ... 880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 882 Figure 7: PadN 884 o Sub-Type is set to 1. If multiple instances appear in the same 885 OMNI option all are processed. 887 o Sub-Length is set to N (from 0 to 255) being the number of padding 888 bytes that follow. 890 o Sub-Option Data consists of N zero-valued octets. 892 9.1.3. Interface Attributes 894 0 1 2 3 895 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 1 896 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 897 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 898 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 899 | Provider ID | Link |R| LHS | SRT | FMT | MSID (0 - 7) | 900 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 901 | MSID (bits 8 - 31) | ~ 902 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 903 ~ ~ 904 ~ Link Layer Address (L2ADDR) ~ 905 ~ ~ 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 907 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 909 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 911 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 914 Figure 8: Interface Attributes 916 o Sub-Type is set to 2. If multiple instances with different 917 ifIndex values appear in the same OMNI option all are processed; 918 if multiple instances with the same ifIndex value appear, the 919 first is processed and all others are ignored. 921 o Sub-Length is set to N (from 4 to 255) that encodes the number of 922 Sub-Option Data bytes that follow. 924 o Sub-Option Data contains an "Interface Attribute" option encoded 925 as follows (note that the first four octets must be present): 927 * ifIndex is set to an 8-bit integer value corresponding to a 928 specific underlying interface. OMNI interfaces MUST number 929 each distinct underlying interface with an ifIndex value 930 between '1' and '255' that represents a MN-specific 8-bit 931 mapping for the actual ifIndex value assigned by network 932 management [RFC2863] (the ifIndex value '0' is reserved for use 933 by the MS). 935 * ifType is set to an 8-bit integer value corresponding to the 936 underlying interface identified by ifIndex. The value 937 represents an OMNI interface-specific 8-bit mapping for the 938 actual IANA ifType value registered in the 'IANAifType-MIB' 939 registry [http://www.iana.org]. 941 * Provider ID is set to an OMNI interface-specific 8-bit ID value 942 for the network service provider associated with this ifIndex. 944 * Link encodes a 4-bit link metric. The value '0' means the link 945 is DOWN, and the remaining values mean the link is UP with 946 metric ranging from '1' ("lowest") to '15' ("highest"). 948 * R is reserved for future use. 950 * LHS - a 3-bit "Link-Address/Heuristics/Simplex" code that 951 indicates which other fields appear in the sub-option as 952 follows: 954 + When the most significant bit (i.e., "Link-Address") is set 955 to 1, the SRT, FMT, MSID and L2ADDR fields are included 956 immediately following the LHS code; else, they are omitted. 958 + When the next most significant bit (i.e., "Heuristics") is 959 set to 1, a trailing Heuristics Bitmap is included next; 960 else, it is omitted. (Note that if "Link-Address" is set 961 the Bitmap immediately follows L2ADDR; else, it immediately 962 follows LHS.) 964 + When the Heuristics Bitmap is present and the least 965 significant bit (i.e., "Simplex") is set to 1, the Bitmap is 966 encoded in Simplex form as shown in Figure 8; else it is 967 encoded in Indexed form as discussed below. 969 * SRT - a 5-bit Segment Routing Topology prefix length value that 970 (when added to 96) determines the prefix length to apply to the 971 ULA formed from concatenating fc*::/96 with the 32 bit MSID 972 value that follows. For example, the value 16 corresponds to 973 the prefix length 112. 975 * FMT - a 3-bit "Framework/Mode/Type" code corresponding to the 976 included Link Layer Address as follows: 978 + When the most significant bit (i.e., "Framework") is set to 979 0, L2ADDR is the INET encapsulation address of a Proxy/ 980 Server; otherwise, it is the addresss for the Source/Target 981 itself 983 + When the next most significant bit (i.e., "Mode") is set to 984 0, the Source/Target L2ADDR is on the open INET; otherwise, 985 it is (likely) located behind a NAT. 987 + When the least significant bit (i.e., "Type") is set to 0, 988 L2ADDR is an IPv4 address; else, it is an IPv6 address. 990 * MSID includes the 32 bit ID of the last hop Proxy/Server ULA on 991 the path to the target according to LHS. When SRT and LHS are 992 both set to 0, the last hop Proxy/Server ULA is considered 993 unspecified in this IPv6 ND message. When SRT is set to 0 and 994 LHS is non-zero, the prefix length is set to 128. 996 * Link Layer Address (L2ADDR) - Included according to FMT, and 997 identifies the link-layer address (i.e., the encapsulation 998 address) of the source/target. The Port Number and IP address 999 are recorded in ones-compliment "obfuscated" form per 1000 [RFC4380]. 1002 * When LHS indicates that a Hueristics Bitmap is present, the 1003 Bitmap appears as the remainder of the suboption. In "Simplex" 1004 form, the index for each singleton Bitmap byte is inferred from 1005 its sequential position (i.e., 0, 1, 2, ...) as shown in 1006 Figure 8. In "Indexed" form, each Bitmap is preceded by an 1007 Index byte that encodes a value "i" = (0 - 255) as the index 1008 for its companion Bitmap as follows: 1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1011 | Index=i | Bitmap(i) |P[*] values ... 1012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1014 Figure 9 1016 * The remainder of the Sub-Option Data contains traffic 1017 classifier heuristics consisting of a first (simplex/indexed) 1018 Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte blocks of 1019 2-bit P[*] values, followed by a second Bitmap (i), followed by 1020 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1021 the bits of each Bitmap(i) that are set to '1'' indicate the 1022 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1023 that follow; if any Bitmap(i) bits are '0', then the 1024 corresponding P[*] block is instead omitted. For example, if 1025 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1026 followed by the block with P[04]-P[07], etc., and ending with 1027 the block with P[28]-P[31] are included (as shown in Figure 8). 1028 The next Bitmap(i) is then consulted with its bits indicating 1029 which P[*] blocks follow, etc. out to the end of the Sub- 1030 Option. 1032 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1033 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1034 heuristics preference for underlying interface selection 1035 purposes. Not all P[*] values need to be included in the OMNI 1036 option of each IPv6 ND message received. Any P[*] values 1037 represented in an earlier OMNI option but omitted in the 1038 current OMNI option remain unchanged. Any P[*] values not yet 1039 represented in any OMNI option default to "medium". 1041 * The first 16 P[*] blocks correspond to the 64 Differentiated 1042 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1043 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1044 traffic classifier values P[64], P[65], P[66], etc. See 1045 Appendix A for further discussion and examples. 1047 9.1.4. Traffic Selector 1048 0 1 2 3 1049 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 1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1051 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1052 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1053 ~ ~ 1054 ~ RFC 6088 Format Traffic Selector ~ 1055 ~ ~ 1056 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1058 Figure 10: Traffic Selector 1060 o Sub-Type is set to 3. If multiple instances appear in the same 1061 OMNI option all are processed, i.e., even if the same ifIndex 1062 value appears multiple times. 1064 o Sub-Length is set to N (the number of Sub-Option Data bytes that 1065 follow). 1067 o Sub-Option Data contains a 1 byte ifIndex encoded exactly as 1068 specified in Section 9.1.3, followed by an N-1 byte traffic 1069 selector formatted per [RFC6088] beginning with the "TS Format" 1070 field. The largest traffic selector for a given ifIndex is 1071 therefore 254 bytes. 1073 9.1.5. MS-Register 1075 0 1 2 3 1076 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 1077 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1078 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1079 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1080 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1081 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1082 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1083 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1084 ... ... ... ... ... ... 1085 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1086 | MSID [n] (bits 16 - 32) | 1087 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 Figure 11: MS-Register Sub-option 1091 o Sub-Type is set to 4. If multiple instances appear in the same 1092 OMNI option all are processed. Only the first MAX_MSID values 1093 processed (whether in a single instance or multiple) are retained 1094 and all other MSIDs are ignored. 1096 o Sub-Length is set to 4n. 1098 o A list of n 4-octet MSIDs is included in the following 4n octets. 1099 The Anycast MSID value '0' in an RS message MS-Register sub-option 1100 requests the recipient to return the MSID of a nearby MSE in a 1101 corresponding RA response. 1103 9.1.6. MS-Release 1105 0 1 2 3 1106 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 1107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1108 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1110 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1112 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1114 ... ... ... ... ... ... 1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 | MSID [n] (bits 16 - 32) | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1119 Figure 12: MS-Release Sub-option 1121 o Sub-Type is set to 5. If multiple instances appear in the same 1122 IPv6 OMNI option all are processed. Only the first MAX_MSID 1123 values processed (whether in a single instance or multiple) are 1124 retained and all other MSIDs are ignored. 1126 o Sub-Length is set to 4n. 1128 o A list of n 4 octet MSIDs is included in the following 4n octets. 1129 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1130 i.e., only non-zero values are processed. 1132 9.1.7. Network Access Identifier (NAI) 1134 0 1 2 3 1135 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 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1140 Figure 13: Network Access Identifier (NAI) Sub-option 1142 o Sub-Type is set to 6. If multiple instances appear in the same 1143 OMNI option the first is processed and all others are ignored. 1145 o Sub-Length is set to N. 1147 o A Network Access Identifier (NAI) up to 255 bytes in length is 1148 coded per [RFC7542]. 1150 9.1.8. Geo Coordinates 1152 0 1 2 3 1153 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 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1155 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1158 Figure 14: Geo Coordinates Sub-option 1160 o Sub-Type is set to 7. If multiple instances appear in the same 1161 OMNI option the first is processed and all others are ignored. 1163 o Sub-Length is set to N. 1165 o A set of Geo Coordinates up to 255 bytes in length (format TBD). 1166 Includes Latitude/Longitude at a minimum; may also include 1167 additional attributes such as altitude, heading, speed, etc.). 1169 9.1.9. DHCP Unique Identifier (DUID) 1171 0 1 2 3 1172 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 1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1174 | Sub-Type=8 | Sub-length=N | DUID-Type | 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1176 . . 1177 . type-specific DUID body (variable length) . 1178 . . 1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1181 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1183 o Sub-Type is set to 8. If multiple instances appear in the same 1184 OMNI option the first is processed and all others are ignored. 1186 o Sub-Length is set to N (i.e., the length of the option beginning 1187 with the DUID-Type and continuing to the end of the type-specifc 1188 body). 1190 o DUID-Type is a two-octet field coded in network byte order that 1191 determines the format and contents of the type-specific body 1192 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1193 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1194 which will occur in common operational practice. 1196 o A type-specific DUID body up to 253 bytes in length follows, 1197 formatted according to DUID-type. For example, for type 4 the 1198 body consists of a 128-bit UUID selected according to [RFC6355]. 1200 10. Address Mapping - Multicast 1202 The multicast address mapping of the native underlying interface 1203 applies. The mobile router on board the MN also serves as an IGMP/ 1204 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1205 using the L2 address of the AR as the L2 address for all multicast 1206 packets. 1208 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1209 coordinate with the AR, and ANET L2 elements use MLD snooping 1210 [RFC4541]. 1212 11. Conceptual Sending Algorithm 1214 The MN's IPv6 layer selects the outbound OMNI interface according to 1215 SBM considerations when forwarding data packets from local or EUN 1216 applications to external correspondents. Each OMNI interface 1217 maintains a neighbor cache the same as for any IPv6 interface, but 1218 with additional state for multilink coordination. 1220 After a packet enters the OMNI interface, an outbound underlying 1221 interface is selected based on PBM traffic attributes such as DSCP, 1222 application port number, cost, performance, message size, etc. OMNI 1223 interface multilink selections could also be configured to perform 1224 replication across multiple underlying interfaces for increased 1225 reliability at the expense of packet duplication. 1227 When an OMNI interface sends a packet over a selected outbound 1228 underlying interface, it omits or employs OMNI link adaptation as 1229 necessary as discussed in Section 5. The OMNI interface also 1230 performs encapsulation when the nearest AR is located multiple hops 1231 away as discussed in Section 12.1. 1233 OMNI interface multilink service designers MUST observe the BCP 1234 guidance in Section 15 [RFC3819] in terms of implications for 1235 reordering when packets from the same flow may be spread across 1236 multiple underlying interfaces having diverse properties. 1238 11.1. Multiple OMNI Interfaces 1240 MNs may connect to multiple independent OMNI links concurrently in 1241 support of SBM. Each OMNI interface is distinguished by its Anycast 1242 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1243 separate OMNI interface for each link so that multiple interfaces 1244 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1245 different Anycast OMNI ULA is assigned to each interface, and the MN 1246 injects the service prefixes for the OMNI link instances into the EUN 1247 routing system. 1249 Applications in EUNs can use Segment Routing to select the desired 1250 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1251 written into the IPv6 destination address, and the actual destination 1252 (along with any additional intermediate hops) is written into the 1253 Segment Routing Header. Standard IP routing directs the packets to 1254 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1255 the OMNI interface to be used for transmission to the next hop. When 1256 the MN receives the message, it replaces the IPv6 destination address 1257 with the next hop found in the routing header and transmits the 1258 message over the OMNI interface identified by the Anycast OMNI ULA. 1260 Multiple distinct OMNI links can therefore be used to support fault 1261 tolerance, load balancing, reliability, etc. The architectural model 1262 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1264 12. Router Discovery and Prefix Registration 1266 MNs interface with the MS by sending RS messages with OMNI options 1267 under the assumption that one or more AR on the ANET will process the 1268 message and respond. The manner in which the ANET ensures AR 1269 coordination is link-specific and outside the scope of this document 1270 (however, considerations for ANETs that do not provide ARs that 1271 recognize the OMNI option are discussed in Section 17). 1273 For each underlying interface, the MN sends an RS message with an 1274 OMNI option to coordinate with MSEs identified by MSID values. 1275 Example MSID discovery methods are given in [RFC5214] and include 1276 data link login parameters, name service lookups, static 1277 configuration, a static "hosts" file, etc. The MN can also send an 1278 RS with an MS-Register suboption that includes the Anycast MSID value 1279 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1280 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1281 be itself) and returns an RA with the selected MSID in an MS-Register 1282 suboption. The AR selects only a single wildcard MSE (i.e., even if 1283 the RS MS-Register suboption included multiple '0' MSIDs) while also 1284 soliciting the MSEs corresponding to any non-zero MSIDs. 1286 MNs configure OMNI interfaces that observe the properties discussed 1287 in the previous section. The OMNI interface and its underlying 1288 interfaces are said to be in either the "UP" or "DOWN" state 1289 according to administrative actions in conjunction with the interface 1290 connectivity status. An OMNI interface transitions to UP or DOWN 1291 through administrative action and/or through state transitions of the 1292 underlying interfaces. When a first underlying interface transitions 1293 to UP, the OMNI interface also transitions to UP. When all 1294 underlying interfaces transition to DOWN, the OMNI interface also 1295 transitions to DOWN. 1297 When an OMNI interface transitions to UP, the MN sends RS messages to 1298 register its MNP and an initial set of underlying interfaces that are 1299 also UP. The MN sends additional RS messages to refresh lifetimes 1300 and to register/deregister underlying interfaces as they transition 1301 to UP or DOWN. The MN sends initial RS messages over an UP 1302 underlying interface with its OMNI LLA as the source and with 1303 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1304 messages include an OMNI option per Section 9 with valid prefix 1305 registration information, Interface Attributes appropriate for 1306 underlying interfaces, MS-Register/Release sub-options containing 1307 MSID values, and with any other necessary OMNI sub-options. The OMNI 1308 header ifIndex field is set to the index of the underlying interface 1309 over which the RS message is sent. 1311 ARs process IPv6 ND messages with OMNI options and act as an MSE 1312 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1313 and create a neighbor cache entry for the MN, then coordinate with 1314 any MSEs named in the Register/Release lists in a manner outside the 1315 scope of this document. When an MSE processes the OMNI information, 1316 it first validates the prefix registration information then injects/ 1317 withdraws the MNP in the routing/mapping system and caches/discards 1318 the new Prefix Length, MNP and Interface Attributes. The MSE then 1319 informs the AR of registration success/failure, and the AR returns an 1320 RA message to the MN with an OMNI option per Section 9. 1322 The AR returns the RA message via the same underlying interface of 1323 the MN over which the RS was received, and with destination address 1324 set to the MN OMNI LLA (i.e., unicast), with source address set to 1325 its own OMNI LLA, and with an OMNI option with ifIndex set to the 1326 value included in the RS. The OMNI option also includes valid prefix 1327 registration information, Interface Attributes, MS-Register/Release 1328 and any other necessary OMNI sub-options. The RA also includes any 1329 information for the link, including RA Cur Hop Limit, M and O flags, 1330 Router Lifetime, Reachable Time and Retrans Timer values, and 1331 includes any necessary options such as: 1333 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1335 o RIOs [RFC4191] with more-specific routes. 1337 o an MTU option that specifies the maximum acceptable packet size 1338 for this ANET interface. 1340 The AR MAY also send periodic and/or event-driven unsolicited RA 1341 messages per [RFC4861]. In that case, the ifIndex field in the OMNI 1342 header of the unsolicited RA message identifies the target underlying 1343 interface of the destination MN. 1345 The AR can combine the information from multiple MSEs into one or 1346 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1347 Each aggregate RA includes an OMNI option with MS-Register/Release 1348 sub-options with the MSEs represented by the aggregate. If an 1349 aggregate is sent, the RA message contents must consistently 1350 represent the combined information advertised by all represented 1351 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1352 address, the MN determines the addresses of the represented MSEs by 1353 examining the MS-Register/Release OMNI sub-options. 1355 When the MN receives the RA message, it creates an OMNI interface 1356 neighbor cache entry for each MSID that has confirmed MNP 1357 registration via the L2 address of this AR. If the MN connects to 1358 multiple ANETs, it records the additional L2 AR addresses in each 1359 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1360 then manages its underlying interfaces according to their states as 1361 follows: 1363 o When an underlying interface transitions to UP, the MN sends an RS 1364 over the underlying interface with an OMNI option. The OMNI 1365 option contains at least one Interface Attribute sub-option with 1366 values specific to this underlying interface, and may contain 1367 additional Interface Attributes specific to other underlying 1368 interfaces. The option also includes any MS-Register/Release sub- 1369 options. 1371 o When an underlying interface transitions to DOWN, the MN sends an 1372 RS or unsolicited NA message over any UP underlying interface with 1373 an OMNI option containing an Interface Attribute sub-option for 1374 the DOWN underlying interface with Link set to '0'. The MN sends 1375 an RS when an acknowledgement is required, or an unsolicited NA 1376 when reliability is not thought to be a concern (e.g., if 1377 redundant transmissions are sent on multiple underlying 1378 interfaces). 1380 o When the Router Lifetime for a specific AR nears expiration, the 1381 MN sends an RS over the underlying interface to receive a fresh 1382 RA. If no RA is received, the MN can send RS messages to an 1383 alternate MSID in case the current MSID has failed. If no RS 1384 messages are received even after trying to contact alternate 1385 MSIDs, the MN marks the underlying interface as DOWN. 1387 o When a MN wishes to release from one or more current MSIDs, it 1388 sends an RS or unsolicited NA message over any UP underlying 1389 interfaces with an OMNI option with a Release MSID. Each MSID 1390 then withdraws the MNP from the routing/mapping system and informs 1391 the AR that the release was successful. 1393 o When all of a MNs underlying interfaces have transitioned to DOWN 1394 (or if the prefix registration lifetime expires), any associated 1395 MSEs withdraw the MNP the same as if they had received a message 1396 with a release indication. 1398 The MN is responsible for retrying each RS exchange up to 1399 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1400 seconds until an RA is received. If no RA is received over a an UP 1401 underlying interface (i.e., even after attempting to contact 1402 alternate MSEs), the MN declares this underlying interface as DOWN. 1404 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1405 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1406 returns an internally-generated RA message as though the message 1407 originated from an IPv6 router. The internally-generated RA message 1408 contains configuration information that is consistent with the 1409 information received from the RAs generated by the MS. Whether the 1410 OMNI interface IPv6 ND messaging process is initiated from the 1411 receipt of an RS message from the IPv6 layer is an implementation 1412 matter. Some implementations may elect to defer the IPv6 ND 1413 messaging process until an RS is received from the IPv6 layer, while 1414 others may elect to initiate the process proactively. Still other 1415 deployments may elect to administratively disable the ordinary RS/RA 1416 messaging used by the IPv6 layer over the OMNI interface, since they 1417 are not required to drive the internal RS/RA processing. 1419 Note: The Router Lifetime value in RA messages indicates the time 1420 before which the MN must send another RS message over this underlying 1421 interface (e.g., 600 seconds), however that timescale may be 1422 significantly longer than the lifetime the MS has committed to retain 1423 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1424 therefore responsible for keeping MS state alive on a shorter 1425 timescale than the MN is required to do on its own behalf. 1427 Note: On multicast-capable underlying interfaces, MNs should send 1428 periodic unsolicited multicast NA messages and ARs should send 1429 periodic unsolicited multicast RA messages as "beacons" that can be 1430 heard by other nodes on the link. If a node fails to receive a 1431 beacon after a timeout value specific to the link, it can initiate a 1432 unicast exchange to test reachability. 1434 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1436 On some ANET types a MN may be located multiple IP hops away from the 1437 nearest AR. Forwarding through IP multihop ANETs is conducted 1438 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1439 Network (MANET) routing protocol over omni-directional wireless 1440 interfaces, an inter-domain routing protocol in an enterprise 1441 network, etc.). These ANETs could be either IPv6-enabled or 1442 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1443 unicast-only (note that for IPv4-only ANETs the following procedures 1444 apply for both single-hop and multhop cases). 1446 A MN located potentially multiple ANET hops away from the nearst AR 1447 prepares an RS message with source address set to its OMNI LLA and 1448 with destination set to link-scoped All-Routers multicast the same as 1449 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1450 the message in an IPv6 header with source address set to the ULA 1451 corresponding to the LLA source address and with destination set to 1452 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1453 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1454 with source address set to the node's own IPv4 address. For 1455 multicast-capable IPv4-only ANETs, the MN then sets the destination 1456 address to the site-scoped IPv4 multicast address corresponding to 1457 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1458 IPv4-only ANETs, the MN instead sets the destination address to the 1459 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1460 encapsulated RS message via the ANET interface, where it will be 1461 forwarded by zero or more intermediate ANET hops. 1463 When an intermediate ANET hop that particpates in the routing 1464 protocol receives the encapsulated RS, it forwards the message 1465 according to its routing tables (note that an intermediate node could 1466 be a fixed infrastructure element or another MN). This process 1467 repeats iteratively until the RS message is received by a penultimate 1468 ANET hop within single-hop communications range of an AR, which 1469 forwards the message to the AR. 1471 When the AR receives the message, it decapsulates the RS and 1472 coordinates with the MS the same as for an ordinary link-local RS, 1473 since the inner Hop Limit will not have been decremented by the 1474 multihop forwarding process. The AR then prepares an RA message with 1475 source address set to its own LLA and destination address set to the 1476 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1477 header with source address set to its own IPv4/ULA address and with 1478 destination set to the encapsulation source of the RS. 1480 The AR then forwards the message to an ANET node within 1481 communications range, which forwards the message according to its 1482 routing tables to an intermediate node. The multihop forwarding 1483 process within the ANET continues repetitively until the message is 1484 delivered to the original MN, which decapsulates the message and 1485 performs autoconfiguration the same as if it had received the RA 1486 directly from the AR as an on-link neighbor. 1488 Note: An alternate approach to multihop forwarding via IPv6 1489 encapsulation would be to statelessly translate the IPv6 LLAs into 1490 ULAs and forward the messages without encapsulation. This would 1491 violate the [RFC4861] requirement that certain IPv6 ND messages must 1492 use link-local addresses and must not be accepted if received with 1493 Hop Limit less than 255. This document therefore advocates 1494 encapsulation since the overhead is nominal considering the 1495 infrequent nature and small size of IPv6 ND messages. Future 1496 documents may consider encapsulation avoidance through translation 1497 while updating [RFC4861]. 1499 Note: An alternate approach to multihop forwarding via IPv4 1500 encapsulation would be to employ IPv6/IPv4 protocol translation. 1501 However, for IPv6 ND messages the OMNI LLA addresses would be 1502 truncated due to translation and the OMNI Router and Prefix Discovery 1503 services would not be able to function. The use of IPv4 1504 encapsulation is therefore indicated. 1506 12.2. MS-Register and MS-Release List Processing 1508 When a MN sends an RS message with an OMNI option via an underlying 1509 interface to an AR, the MN must convey its knowledge of its 1510 currently-associated MSEs. Initially, the MN will have no associated 1511 MSEs and should therefore include an MS-Register sub-option with the 1512 single MSID value 0 which requests the AR to select and assign an 1513 MSE. The AR will then return an RA message with source address set 1514 to the OMNI LLA containing the MSE of the selected MSE. 1516 As the MN activates additional underlying interfaces, it can 1517 optionally include an MS-Register sub-option with MSID value 0, or 1518 with non-zero MSIDs for MSEs discovered from previous RS/RA 1519 exchanges. The MN will thus eventually begin to learn and manage its 1520 currently active set of MSEs, and can register with new MSEs or 1521 release from former MSEs with each successive RS/RA exchange. As the 1522 MN's MSE constituency grows, it alone is responsible for including or 1523 omitting MSIDs in the MS-Register/Release lists it sends in RS 1524 messages. The inclusion or omission of MSIDs determines the MN's 1525 interface to the MS and defines the manner in which MSEs will 1526 respond. The only limiting factor is that the MN should include no 1527 more than MAX_MSID values in each list per each IPv6 ND message, and 1528 should avoid duplication of entries in each list unless it wants to 1529 increase likelihood of control message delivery. 1531 When an AR receives an RS message sent by a MN with an OMNI option, 1532 the option will contain zero or more MS-Register and MS-Release sub- 1533 options containing MSIDs. After processing the OMNI option, the AR 1534 will have a list of zero or more MS-Register MSIDs and a list of zero 1535 or more of MS-Release MSIDs. The AR then processes the lists as 1536 follows: 1538 o For each list, retain the first MAX_MSID values in the list and 1539 discard any additional MSIDs (i.e., even if there are duplicates 1540 within a list). 1542 o Next, for each MSID in the MS-Register list, remove all matching 1543 MSIDs from the MS-Release list. 1545 o Next, proceed according to whether the AR's own MSID or the value 1546 0 appears in the MS-Register list as folllows: 1548 * If yes, send an RA message directly back to the MN and send a 1549 proxy copy of the RS message to each additional MSID in the MS- 1550 Register list with the MS-Register/Release lists omitted. 1551 Then, send a uNA message to each MSID in the MS-Release list 1552 with the MS-Register/Release lists omitted and with an 1553 Interface Attributes sub-option with ifIndex set to 0. 1555 * If no, send a proxy copy of the RS message to each additional 1556 MSID in the MS-Register list with the MS-Register list omitted. 1557 For the first MSID, include the original MS-Release list; for 1558 all other MSIDs, omit the MS-Release list. 1560 Each proxy copy of the RS message will include an OMNI option and 1561 encapsulation header with the ULA of the AR as the source and the ULA 1562 of the Register MSE as the destination. When the Register MSE 1563 receives the proxy RS message, if the message includes an MS-Release 1564 list the MSE sends a uNA message to each additional MSID in the 1565 Release list. The Register MSE then sends an RA message back to the 1566 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1567 destination addresses reversed, and with RA destination set to the 1568 LLA of the MN. When the AR receives this RA message, it sends a 1569 proxy copy of the RA to the MN. 1571 Each uNA message (whether send by the first-hop AR or by a Register 1572 MSE) will include an OMNI option and an encapsulation header with the 1573 ULA of the Register MSE as the source and the ULA of the Release ME 1574 as the destination. The uNA informs the Release MSE that its 1575 previous relationship with the MN has been released and that the 1576 source of the uNA message is now registered. The Release MSE must 1577 then note that the subject MN of the uNA message is now "departed", 1578 and forward any subsequent packets destined to the MN to the Register 1579 MSE. 1581 Note that it is not an error for the MS-Register/Release lists to 1582 include duplicate entries. If duplicates occur within a list, the 1583 the AR will generate multiple proxy RS and/or uNA messages - one for 1584 each copy of the duplicate entries. 1586 13. Secure Redirection 1588 If the ANET link model is multiple access, the AR is responsible for 1589 assuring that address duplication cannot corrupt the neighbor caches 1590 of other nodes on the link. When the MN sends an RS message on a 1591 multiple access ANET link, the AR verifies that the MN is authorized 1592 to use the address and returns an RA with a non-zero Router Lifetime 1593 only if the MN is authorized. 1595 After verifying MN authorization and returning an RA, the AR MAY 1596 return IPv6 ND Redirect messages to direct MNs located on the same 1597 ANET link to exchange packets directly without transiting the AR. In 1598 that case, the MNs can exchange packets according to their unicast L2 1599 addresses discovered from the Redirect message instead of using the 1600 dogleg path through the AR. In some ANET links, however, such direct 1601 communications may be undesirable and continued use of the dogleg 1602 path through the AR may provide better performance. In that case, 1603 the AR can refrain from sending Redirects, and/or MNs can ignore 1604 them. 1606 14. AR and MSE Resilience 1608 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1609 [RFC5798] configurations so that service continuity is maintained 1610 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1611 the (redundant) ARs is currently providing service, and any service 1612 discontinuity will be limited to the failover time supported by VRRP. 1613 Widely deployed public domain implementations of VRRP are available. 1615 MSEs SHOULD use high availability clustering services so that 1616 multiple redundant systems can provide coordinated response to 1617 failures. As with VRRP, widely deployed public domain 1618 implementations of high availability clustering services are 1619 available. Note that special-purpose and expensive dedicated 1620 hardware is not necessary, and public domain implementations can be 1621 used even between lightweight virtual machines in cloud deployments. 1623 15. Detecting and Responding to MSE Failures 1625 In environments where fast recovery from MSE failure is required, ARs 1626 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1627 manner that parallels Bidirectional Forwarding Detection (BFD) 1628 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1629 react to failures so that cached information is re-established 1630 through alternate paths. Proactive NUD control messaging is carried 1631 only over well-connected ground domain networks (i.e., and not low- 1632 end ANET links such as aeronautical radios) and can therefore be 1633 tuned for rapid response. 1635 ARs perform proactive NUD for MSEs for which there are currently 1636 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1637 of the outage by sending multicast RA messages on the ANET interface. 1638 The AR sends RA messages to MNs via the ANET interface with an OMNI 1639 option with a Release ID for the failed MSE, and with destination 1640 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1642 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1643 by small delays [RFC4861]. Any MNs on the ANET interface that have 1644 been using the (now defunct) MSE will receive the RA messages and 1645 associate with a new MSE. 1647 16. Transition Considerations 1649 When a MN connects to an ANET link for the first time, it sends an RS 1650 message with an OMNI option. If the first hop AR recognizes the 1651 option, it returns an RA with its MS OMNI LLA as the source, the MN 1652 OMNI LLA as the destination and with an OMNI option included. The MN 1653 then engages the AR according to the OMNI link model specified above. 1654 If the first hop AR is a legacy IPv6 router, however, it instead 1655 returns an RA message with no OMNI option and with a non-OMNI unicast 1656 source LLA as specified in [RFC4861]. In that case, the MN engages 1657 the ANET according to the legacy IPv6 link model and without the OMNI 1658 extensions specified in this document. 1660 If the ANET link model is multiple access, there must be assurance 1661 that address duplication cannot corrupt the neighbor caches of other 1662 nodes on the link. When the MN sends an RS message on a multiple 1663 access ANET link with an OMNI LLA source address and an OMNI option, 1664 ARs that recognize the option ensure that the MN is authorized to use 1665 the address and return an RA with a non-zero Router Lifetime only if 1666 the MN is authorized. ARs that do not recognize the option instead 1667 return an RA that makes no statement about the MN's authorization to 1668 use the source address. In that case, the MN should perform 1669 Duplicate Address Detection to ensure that it does not interfere with 1670 other nodes on the link. 1672 An alternative approach for multiple access ANET links to ensure 1673 isolation for MN / AR communications is through L2 address mappings 1674 as discussed in Appendix C. This arrangement imparts a (virtual) 1675 point-to-point link model over the (physical) multiple access link. 1677 17. OMNI Interfaces on the Open Internet 1679 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1680 the open Internet without an OMNI-aware first-hop AR receive RA 1681 messages that do not include an OMNI option, while OMNI interfaces 1682 configured over IPv4-only underlying interfaces do not receive any 1683 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1684 without an OMNI option configure addresses, on-link prefxies, etc. on 1685 the underlying interface that received the RA according to standard 1686 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1687 interfaces configured over IPv4-only underlying interfaces configure 1688 IPv4 address information on the underlying interfaces using 1689 mechanisms such as DHCPv4 [RFC2131]. 1691 OMNI interfaces configured over underlying interfaces that connect to 1692 the open Internet can apply security services such as VPNs to connect 1693 to an MSE or establish a direct link to an MSE through some other 1694 means. In environments where an explicit VPN or direct link may be 1695 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1696 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1697 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1698 other protocol-specific security services can can also be used if 1699 additional authentication is necessary.) 1701 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1702 interfaces send control plane messages to interface with the MS. The 1703 control plane messages must be authenticated while data plane 1704 messages are delivered the same as for ordinary best-effort Internet 1705 traffic with basic source address-based data origin verification. 1706 Data plane communications via OMNI interfaces that connect over the 1707 open Internet without an explicit VPN should therefore employ 1708 transport- or higher-layer security to ensure integrity and/or 1709 confidentiality. 1711 When SEND/CGA are used over an open Internet underlying interfaces, 1712 each OMNI node configures a link-local CGA for use as the source 1713 address of IPv6 ND messages. The node then employs OMNI link 1714 encapsualation and sets the IPv6 source address of the OMNI header to 1715 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1716 the IPv6 ND message OMNI option then apply to the ULA found in the 1717 OMNI header, i.e., and not to the CGA found in the IPv6 ND source 1718 address. 1720 OMNI interfaces in the open Internet are often located behind Network 1721 Address Translators (NATs). The OMNI interface accommodates NAT 1722 traversal using UDP/IP encapsulation and the mechanisms discussed in 1723 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1725 18. Time-Varying MNPs 1727 In some use cases, it is desirable, beneficial and efficient for the 1728 MN to receive a constant MNP that travels with the MN wherever it 1729 moves. For example, this would allow air traffic controllers to 1730 easily track aircraft, etc. In other cases, however (e.g., 1731 intelligent transportation systems), the MN may be willing to 1732 sacrifice a modicum of efficiency in order to have time-varying MNPs 1733 that can be changed every so often to defeat adversarial tracking. 1735 Prefix delegation services such as those discussed in 1736 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1737 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1738 prefixes. In that case, the identity of the MN can be used as a 1739 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1740 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1741 internal networks whenever its MNP (and therefore also its OMNI 1742 address) changes. This should not present a challenge for MNs with 1743 automated network renumbering services, however presents limits for 1744 the durations of ongoing sessions that would prefer to use a constant 1745 address. 1747 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1748 sets the source address of an RS message to fe80:: and includes a 1749 DUID sub-option and a desired Prefix Length value in the RS message 1750 OMNI option. When the first-hop AR receives the RS message, it 1751 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1752 of the requested length then returns an RA message with the OMNI LLA 1753 corresponding to the MNP as the destination address. When the MN 1754 receives the RA message, it provisons the PD to its downstream- 1755 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1756 messaging. 1758 19. IANA Considerations 1760 The IANA is instructed to allocate an official Type number TBD from 1761 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1762 option. Implementations set Type to 253 as an interim value 1763 [RFC4727]. 1765 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1766 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1767 read as follows: 1769 Code Name Reference 1770 --- ---- --------- 1771 0 Diagnostic Packet Too Big [RFC4443] 1772 1 Advisory Packet Too Big [RFCXXXX] 1774 Figure 16: OMNI Option Sub-Type Values 1776 The IANA is instructed to allocate one Ethernet unicast address TBD2 1777 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1778 Address Block - Unicast Use". 1780 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1781 is instructed to create and maintain a new registry entitled "OMNI 1782 option Sub-Type values". Initial values for the OMNI option Sub-Type 1783 values registry are given below; future assignments are to be made 1784 through Expert Review [RFC8126]. 1786 Value Sub-Type name Reference 1787 ----- ------------- ---------- 1788 0 Pad1 [RFCXXXX] 1789 1 PadN [RFCXXXX] 1790 2 Interface Attributes [RFCXXXX] 1791 3 Traffic Selector [RFCXXXX] 1792 4 MS-Register [RFCXXXX] 1793 5 MS-Release [RFCXXXX] 1794 6 Network Acceess Identifier [RFCXXXX] 1795 7 Geo Coordinates [RFCXXXX] 1796 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1797 9-252 Unassigned 1798 253-254 Experimental [RFCXXXX] 1799 255 Reserved [RFCXXXX] 1801 Figure 17: OMNI Option Sub-Type Values 1803 20. Security Considerations 1805 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1806 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1807 include Nonce and Timestamp options [RFC3971] when transaction 1808 confirmation and/or time synchronization is needed. 1810 OMNI interfaces configured over secured ANET interfaces inherit the 1811 physical and/or link-layer security properties of the connected 1812 ANETs. OMNI interfaces configured over open INET interfaces can use 1813 symmetric securing services such as VPNs or can by some other means 1814 establish a direct link. When a VPN or direct link may be 1815 impractical, however, an asymmetric security service such as SEcure 1816 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1817 Addresses (CGAs) [RFC3972], the authentication option specified in 1818 [RFC4380] or other protocol control message security mechanisms may 1819 be necessary. While the OMNI link protects control plane messaging, 1820 applications must still employ end-to-end transport- or higher-layer 1821 security services to protect the data plane. 1823 The Mobility Service MUST provide strong network layer security for 1824 control plane messages and forwading path integrity for data plane 1825 messages. In one example, the AERO service 1826 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1827 mobility service elements and secures the links in the spanning tree 1828 with network layer security mechanisms such as IPsec [RFC4301] or 1829 Wireguard. Control plane messages are then constrained to travel 1830 only over the secured spanning tree paths and are therefore protected 1831 from attack or eavesdropping. Since data plane messages can travel 1832 over route optimized paths that do not strictly follow the spanning 1833 tree, however, end-to-end transport- or higher-layer security 1834 services are still required. 1836 Security considerations for specific access network interface types 1837 are covered under the corresponding IP-over-(foo) specification 1838 (e.g., [RFC2464], [RFC2492], etc.). 1840 Security considerations for IPv6 fragmentation and reassembly are 1841 discussed in Section 5.1. 1843 21. Implementation Status 1845 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 1846 internal release, while Draft -30 is scheduled for implementation in 1847 the soon-to-be-tagged AERO/OMNI 3.0.1 internal release. First public 1848 release expected before the end of 2020. 1850 22. Acknowledgements 1852 The first version of this document was prepared per the consensus 1853 decision at the 7th Conference of the International Civil Aviation 1854 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1855 2019. Consensus to take the document forward to the IETF was reached 1856 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1857 Attendees and contributors included: Guray Acar, Danny Bharj, 1858 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1859 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1860 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1861 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1862 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1863 Fryderyk Wrobel and Dongsong Zeng. 1865 The following individuals are acknowledged for their useful comments: 1866 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1867 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1868 Skorepa are recognized for their many helpful ideas and suggestions. 1869 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 1870 Rajagopalan are acknowledged for their hard work on the 1871 implementation and insights that led to improvements to the spec. 1873 This work is aligned with the NASA Safe Autonomous Systems Operation 1874 (SASO) program under NASA contract number NNA16BD84C. 1876 This work is aligned with the FAA as per the SE2025 contract number 1877 DTFAWA-15-D-00030. 1879 23. References 1881 23.1. Normative References 1883 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1884 Requirement Levels", BCP 14, RFC 2119, 1885 DOI 10.17487/RFC2119, March 1997, 1886 . 1888 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1889 "Definition of the Differentiated Services Field (DS 1890 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1891 DOI 10.17487/RFC2474, December 1998, 1892 . 1894 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1895 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1896 DOI 10.17487/RFC3971, March 2005, 1897 . 1899 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1900 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1901 . 1903 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1904 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1905 November 2005, . 1907 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1908 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1909 . 1911 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1912 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1913 2006, . 1915 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1916 Control Message Protocol (ICMPv6) for the Internet 1917 Protocol Version 6 (IPv6) Specification", STD 89, 1918 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1919 . 1921 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1922 ICMPv6, UDP, and TCP Headers", RFC 4727, 1923 DOI 10.17487/RFC4727, November 2006, 1924 . 1926 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1927 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1928 DOI 10.17487/RFC4861, September 2007, 1929 . 1931 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1932 Address Autoconfiguration", RFC 4862, 1933 DOI 10.17487/RFC4862, September 2007, 1934 . 1936 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1937 "Traffic Selectors for Flow Bindings", RFC 6088, 1938 DOI 10.17487/RFC6088, January 2011, 1939 . 1941 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1942 Hosts in a Multi-Prefix Network", RFC 8028, 1943 DOI 10.17487/RFC8028, November 2016, 1944 . 1946 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1947 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1948 May 2017, . 1950 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1951 (IPv6) Specification", STD 86, RFC 8200, 1952 DOI 10.17487/RFC8200, July 2017, 1953 . 1955 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 1956 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 1957 DOI 10.17487/RFC8201, July 2017, 1958 . 1960 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1961 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1962 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1963 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1964 . 1966 23.2. Informative References 1968 [I-D.ietf-intarea-tunnels] 1969 Touch, J. and M. Townsley, "IP Tunnels in the Internet 1970 Architecture", draft-ietf-intarea-tunnels-10 (work in 1971 progress), September 2019. 1973 [I-D.templin-6man-dhcpv6-ndopt] 1974 Templin, F., "A Unified Stateful/Stateless Configuration 1975 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 1976 (work in progress), June 2020. 1978 [I-D.templin-intarea-6706bis] 1979 Templin, F., "Asymmetric Extended Route Optimization 1980 (AERO)", draft-templin-intarea-6706bis-60 (work in 1981 progress), September 2020. 1983 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 1984 Communication Layers", STD 3, RFC 1122, 1985 DOI 10.17487/RFC1122, October 1989, 1986 . 1988 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1989 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1990 . 1992 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 1993 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 1994 . 1996 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 1997 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 1998 . 2000 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2001 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2002 December 1998, . 2004 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2005 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2006 . 2008 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2009 Domains without Explicit Tunnels", RFC 2529, 2010 DOI 10.17487/RFC2529, March 1999, 2011 . 2013 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2014 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2015 . 2017 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2018 Considered Useful", BCP 82, RFC 3692, 2019 DOI 10.17487/RFC3692, January 2004, 2020 . 2022 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2023 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2024 DOI 10.17487/RFC3810, June 2004, 2025 . 2027 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2028 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2029 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2030 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2031 . 2033 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2034 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2035 2004, . 2037 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2038 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2039 December 2005, . 2041 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2042 Network Address Translations (NATs)", RFC 4380, 2043 DOI 10.17487/RFC4380, February 2006, 2044 . 2046 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2047 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2048 2006, . 2050 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2051 "Considerations for Internet Group Management Protocol 2052 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2053 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2054 . 2056 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2057 "Internet Group Management Protocol (IGMP) / Multicast 2058 Listener Discovery (MLD)-Based Multicast Forwarding 2059 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2060 August 2006, . 2062 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2063 Errors at High Data Rates", RFC 4963, 2064 DOI 10.17487/RFC4963, July 2007, 2065 . 2067 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2068 Advertisement Flags Option", RFC 5175, 2069 DOI 10.17487/RFC5175, March 2008, 2070 . 2072 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2073 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2074 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2075 . 2077 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2078 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2079 DOI 10.17487/RFC5214, March 2008, 2080 . 2082 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2083 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2084 . 2086 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2087 Version 3 for IPv4 and IPv6", RFC 5798, 2088 DOI 10.17487/RFC5798, March 2010, 2089 . 2091 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2092 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2093 . 2095 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2096 DOI 10.17487/RFC6081, January 2011, 2097 . 2099 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2100 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2101 DOI 10.17487/RFC6355, August 2011, 2102 . 2104 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2105 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2106 2012, . 2108 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2109 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2110 DOI 10.17487/RFC7084, November 2013, 2111 . 2113 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2114 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2115 Boundary in IPv6 Addressing", RFC 7421, 2116 DOI 10.17487/RFC7421, January 2015, 2117 . 2119 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2120 DOI 10.17487/RFC7542, May 2015, 2121 . 2123 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2124 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2125 February 2016, . 2127 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2128 Support for IP Hosts with Multi-Access Support", RFC 7847, 2129 DOI 10.17487/RFC7847, May 2016, 2130 . 2132 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2133 Writing an IANA Considerations Section in RFCs", BCP 26, 2134 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2135 . 2137 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2138 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2139 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2140 July 2018, . 2142 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2143 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2144 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2145 . 2147 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2148 and F. Gont, "IP Fragmentation Considered Fragile", 2149 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2150 . 2152 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2154 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2155 encoding to specific Internetworks such as the Aeronautical 2156 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2157 may include link selection preferences based on other traffic 2158 classifiers (e.g., transport port numbers, etc.) in addition to the 2159 existing DSCP-based preferences. Nodes on specific Internetworks 2160 maintain a map of traffic classifiers to additional P[*] preference 2161 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2162 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2164 Implementations use Simplex or Indexed encoding formats for P[*] 2165 encoding in order to encode a given set of traffic classifiers in the 2166 most efficient way. Some use cases may be more efficiently coded 2167 using Simplex form, while others may be more efficient using Indexed. 2168 Once a format is selected for preparation of a single Interface 2169 Attribute the same format must be used for the entire Interface 2170 Attribute sub-option. Different sub-options may use different 2171 formats. 2173 The following figures show coding examples for various Simplex and 2174 Indexed formats: 2176 0 1 2 3 2177 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 2178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2179 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2181 | Provider ID | Link |R| LHS | Bitmap(0)=0xff|P00|P01|P02|P03| 2182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2183 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2185 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2187 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2189 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2191 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2194 Figure 18: Example 1: Dense Simplex Encoding 2196 0 1 2 3 2197 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 2198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2199 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2201 | Provider ID | Link |R| LHS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2203 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2205 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2207 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2209 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2211 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2213 |Bitmap(10)=0x00| ... 2214 +-+-+-+-+-+-+-+-+-+-+- 2216 Figure 19: Example 2: Sparse Simplex Encoding 2218 0 1 2 3 2219 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 2220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2221 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2223 | Provider ID | Link |R| LHS | Index = 0x00 | Bitmap = 0x80 | 2224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2225 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2227 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2229 | Bitmap = 0x01 |796|797|798|799| ... 2230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2232 Figure 20: Example 3: Indexed Encoding 2234 Appendix B. VDL Mode 2 Considerations 2236 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2237 (VDLM2) that specifies an essential radio frequency data link service 2238 for aircraft and ground stations in worldwide civil aviation air 2239 traffic management. The VDLM2 link type is "multicast capable" 2240 [RFC4861], but with considerable differences from common multicast 2241 links such as Ethernet and IEEE 802.11. 2243 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2244 magnitude less than most modern wireless networking gear. Second, 2245 due to the low available link bandwidth only VDLM2 ground stations 2246 (i.e., and not aircraft) are permitted to send broadcasts, and even 2247 so only as compact layer 2 "beacons". Third, aircraft employ the 2248 services of ground stations by performing unicast RS/RA exchanges 2249 upon receipt of beacons instead of listening for multicast RA 2250 messages and/or sending multicast RS messages. 2252 This beacon-oriented unicast RS/RA approach is necessary to conserve 2253 the already-scarce available link bandwidth. Moreover, since the 2254 numbers of beaconing ground stations operating within a given spatial 2255 range must be kept as sparse as possible, it would not be feasible to 2256 have different classes of ground stations within the same region 2257 observing different protocols. It is therefore highly desirable that 2258 all ground stations observe a common language of RS/RA as specified 2259 in this document. 2261 Note that links of this nature may benefit from compression 2262 techniques that reduce the bandwidth necessary for conveying the same 2263 amount of data. The IETF lpwan working group is considering possible 2264 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2266 Appendix C. MN / AR Isolation Through L2 Address Mapping 2268 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2269 unicast link-scoped IPv6 destination address. However, IPv6 ND 2270 messaging should be coordinated between the MN and AR only without 2271 invoking other nodes on the ANET. This implies that MN / AR control 2272 messaging should be isolated and not overheard by other nodes on the 2273 link. 2275 To support MN / AR isolation on some ANET links, ARs can maintain an 2276 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2277 ANETs, this specification reserves one Ethernet unicast address TBD2 2278 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2279 MSADDR is reserved per the assigned numbers authority for the ANET 2280 addressing space. For still other ANETs, MSADDR may be dynamically 2281 discovered through other means, e.g., L2 beacons. 2283 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2284 both multicast and unicast) to MSADDR instead of to an ordinary 2285 unicast or multicast L2 address. In this way, all of the MN's IPv6 2286 ND messages will be received by ARs that are configured to accept 2287 packets destined to MSADDR. Note that multiple ARs on the link could 2288 be configured to accept packets destined to MSADDR, e.g., as a basis 2289 for supporting redundancy. 2291 Therefore, ARs must accept and process packets destined to MSADDR, 2292 while all other devices must not process packets destined to MSADDR. 2293 This model has well-established operational experience in Proxy 2294 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2296 Appendix D. Change Log 2298 << RFC Editor - remove prior to publication >> 2300 Differences from draft-templin-6man-omni-interface-31 to draft- 2301 templin-6man-omni-interface-32: 2303 o MTU 2305 o Support for multi-hop ANETS such as ISATAP. 2307 Differences from draft-templin-6man-omni-interface-29 to draft- 2308 templin-6man-omni-interface-30: 2310 o Moved link-layer addressing information into the OMNI option on a 2311 per-ifIndex basis 2313 o Renamed "ifIndex-tuple" to "Interface Attributes" 2315 Differences from draft-templin-6man-omni-interface-27 to draft- 2316 templin-6man-omni-interface-28: 2318 o Updates based on implementation expereince. 2320 Differences from draft-templin-6man-omni-interface-25 to draft- 2321 templin-6man-omni-interface-26: 2323 o Further clarification on "aggregate" RA messages. 2325 o Expanded Security Considerations to discuss expectations for 2326 security in the Mobility Service. 2328 Differences from draft-templin-6man-omni-interface-20 to draft- 2329 templin-6man-omni-interface-21: 2331 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2332 (PBM). 2334 Differences from draft-templin-6man-omni-interface-18 to draft- 2335 templin-6man-omni-interface-19: 2337 o SEND/CGA. 2339 Differences from draft-templin-6man-omni-interface-17 to draft- 2340 templin-6man-omni-interface-18: 2342 o Teredo 2344 Differences from draft-templin-6man-omni-interface-14 to draft- 2345 templin-6man-omni-interface-15: 2347 o Prefix length discussions removed. 2349 Differences from draft-templin-6man-omni-interface-12 to draft- 2350 templin-6man-omni-interface-13: 2352 o Teredo 2354 Differences from draft-templin-6man-omni-interface-11 to draft- 2355 templin-6man-omni-interface-12: 2357 o Major simplifications and clarifications on MTU and fragmentation. 2359 o Document now updates RFC4443 and RFC8201. 2361 Differences from draft-templin-6man-omni-interface-10 to draft- 2362 templin-6man-omni-interface-11: 2364 o Removed /64 assumption, resulting in new OMNI address format. 2366 Differences from draft-templin-6man-omni-interface-07 to draft- 2367 templin-6man-omni-interface-08: 2369 o OMNI MNs in the open Internet 2371 Differences from draft-templin-6man-omni-interface-06 to draft- 2372 templin-6man-omni-interface-07: 2374 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2375 L2 addressing. 2377 o Expanded "Transition Considerations". 2379 Differences from draft-templin-6man-omni-interface-05 to draft- 2380 templin-6man-omni-interface-06: 2382 o Brought back OMNI option "R" flag, and discussed its use. 2384 Differences from draft-templin-6man-omni-interface-04 to draft- 2385 templin-6man-omni-interface-05: 2387 o Transition considerations, and overhaul of RS/RA addressing with 2388 the inclusion of MSE addresses within the OMNI option instead of 2389 as RS/RA addresses (developed under FAA SE2025 contract number 2390 DTFAWA-15-D-00030). 2392 Differences from draft-templin-6man-omni-interface-02 to draft- 2393 templin-6man-omni-interface-03: 2395 o Added "advisory PTB messages" under FAA SE2025 contract number 2396 DTFAWA-15-D-00030. 2398 Differences from draft-templin-6man-omni-interface-01 to draft- 2399 templin-6man-omni-interface-02: 2401 o Removed "Primary" flag and supporting text. 2403 o Clarified that "Router Lifetime" applies to each ANET interface 2404 independently, and that the union of all ANET interface Router 2405 Lifetimes determines MSE lifetime. 2407 Differences from draft-templin-6man-omni-interface-00 to draft- 2408 templin-6man-omni-interface-01: 2410 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2411 for future use (most likely as "pseudo-multicast"). 2413 o Non-normative discussion of alternate OMNI LLA construction form 2414 made possible if the 64-bit assumption were relaxed. 2416 First draft version (draft-templin-atn-aero-interface-00): 2418 o Draft based on consensus decision of ICAO Working Group I Mobility 2419 Subgroup March 22, 2019. 2421 Authors' Addresses 2423 Fred L. Templin (editor) 2424 The Boeing Company 2425 P.O. Box 3707 2426 Seattle, WA 98124 2427 USA 2429 Email: fltemplin@acm.org 2430 Tony Whyman 2431 MWA Ltd c/o Inmarsat Global Ltd 2432 99 City Road 2433 London EC1Y 1AX 2434 England 2436 Email: tony.whyman@mccallumwhyman.com