idnits 2.17.1 draft-templin-6man-omni-interface-35.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == The 'Updates: ' line in the draft header should list only the _numbers_ of the RFCs which will be updated by this document (if approved); it should not include the word 'RFC' in the list. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 18, 2020) is 1316 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '00' on line 1079 -- Looks like a reference, but probably isn't: '03' on line 1062 -- Looks like a reference, but probably isn't: '04' on line 1063 -- Looks like a reference, but probably isn't: '07' on line 1063 -- Looks like a reference, but probably isn't: '28' on line 1064 -- Looks like a reference, but probably isn't: '31' on line 1064 -- Looks like a reference, but probably isn't: '63' on line 1079 -- Looks like a reference, but probably isn't: '64' on line 1081 -- Looks like a reference, but probably isn't: '65' on line 1081 -- Looks like a reference, but probably isn't: '66' on line 1081 -- Looks like a reference, but probably isn't: '1' on line 1147 -- Looks like a reference, but probably isn't: '2' on line 1149 -- Looks like a reference, but probably isn't: '3' on line 1149 == Missing Reference: 'RFCXXXX' is mentioned on line 1836, but not defined -- Looks like a reference, but probably isn't: '67' on line 2198 -- Looks like a reference, but probably isn't: '70' on line 2199 -- Looks like a reference, but probably isn't: '76' on line 2199 == Unused Reference: 'RFC2225' is defined on line 2029, but no explicit reference was found in the text == Unused Reference: 'RFC4389' is defined on line 2083, but no explicit reference was found in the text == Unused Reference: 'RFC5175' is defined on line 2104, but no explicit reference was found in the text == Unused Reference: 'RFC7421' is defined on line 2150, but no explicit reference was found in the text == Unused Reference: 'RFC8754' is defined on line 2179, but no explicit reference was found in the text == Outdated reference: A later version (-13) exists of draft-ietf-intarea-tunnels-10 == Outdated reference: A later version (-11) exists of draft-templin-6man-dhcpv6-ndopt-10 == Outdated reference: A later version (-99) exists of draft-templin-intarea-6706bis-60 Summary: 0 errors (**), 0 flaws (~~), 11 warnings (==), 17 comments (--). 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 18, 2020 7 Expires: March 22, 2021 9 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-35 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 22, 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. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 11 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 14 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 14 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 15 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 16 67 9. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 17 68 9.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 19 69 9.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 20 70 9.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 20 71 9.1.3. Interface Attributes . . . . . . . . . . . . . . . . 20 72 9.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 24 73 9.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . . 25 74 9.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 25 75 9.1.7. Network Access Identifier (NAI) . . . . . . . . . . . 26 76 9.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . . 27 77 9.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . . 27 78 10. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 28 79 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 28 80 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 28 81 12. Router Discovery and Prefix Registration . . . . . . . . . . 29 82 12.1. Router Discovery in IP Multihop and IPv4-Only Access 83 Networks . . . . . . . . . . . . . . . . . . . . . . . . 33 84 12.2. MS-Register and MS-Release List Processing . . . . . . . 34 85 13. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 36 86 14. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 36 87 15. Detecting and Responding to MSE Failures . . . . . . . . . . 37 88 16. Transition Considerations . . . . . . . . . . . . . . . . . . 37 89 17. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 38 90 18. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 39 91 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 92 20. Security Considerations . . . . . . . . . . . . . . . . . . . 40 93 21. Implementation Status . . . . . . . . . . . . . . . . . . . . 41 94 22. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41 95 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 96 23.1. Normative References . . . . . . . . . . . . . . . . . . 42 97 23.2. Informative References . . . . . . . . . . . . . . . . . 44 98 Appendix A. Interface Attribute Heuristic Bitmap Encoding . . . 48 99 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 49 100 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 50 101 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 104 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 Adaptation Layer (OAL) 248 an OMNI interface process whereby packets admitted into the 249 interface are wrapped in a mid-layer IPv6 header and fragmented/ 250 reassembled if necessary to support the OMNI link Maximum 251 Transmission Unit (MTU). The OAL is also responsible for 252 generating MTU-related control messages as necessary, and for 253 providing addressing context for spanning multiple segments of a 254 bridged OMNI link. 256 OMNI Link-Local Address (LLA) 257 a link local IPv6 address per [RFC4291] constructed as specified 258 in Section 7. 260 OMNI Unique-Local Address (ULA) 261 a unique local IPv6 address per [RFC4193] constructed as specified 262 in Section 8. OMNI ULAs are statelessly derived from OMNI LLAs, 263 and vice-versa. 265 OMNI Option 266 an IPv6 Neighbor Discovery option providing multilink parameters 267 for the OMNI interface as specified in Section 9. 269 Multilink 270 an OMNI interface's manner of managing diverse underlying data 271 link interfaces as a single logical unit. The OMNI interface 272 provides a single unified interface to upper layers, while 273 underlying data link selections are performed on a per-packet 274 basis considering factors such as DSCP, flow label, application 275 policy, signal quality, cost, etc. Multilinking decisions are 276 coordinated in both the outbound (i.e. MN to correspondent) and 277 inbound (i.e., correspondent to MN) directions. 279 L2 280 The second layer in the OSI network model. Also known as "layer- 281 2", "link-layer", "sub-IP layer", "data link layer", etc. 283 L3 284 The third layer in the OSI network model. Also known as "layer- 285 3", "network-layer", "IPv6 layer", etc. 287 underlying interface 288 an ANET/INET interface over which an OMNI interface is configured. 289 The OMNI interface is seen as a L3 interface by the IP layer, and 290 each underlying interface is seen as a L2 interface by the OMNI 291 interface. 293 Mobility Service Identification (MSID) 294 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 295 as specified in Section 7. 297 Safety-Based Multilink (SBM) 298 A means for ensuring fault tolerance through redundancy by 299 connecting multiple independent OMNI interfaces to independent 300 routing topologies (i.e., multiple independent OMNI links). 302 Performance Based Multilink (PBM) 303 A means for selecting underlying interface(s) for packet 304 trasnmission and reception within a single OMNI interface. 306 3. Requirements 308 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 309 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 310 "OPTIONAL" in this document are to be interpreted as described in BCP 311 14 [RFC2119][RFC8174] when, and only when, they appear in all 312 capitals, as shown here. 314 OMNI links maintain a constant value "MAX_MSID" selected to provide 315 MNs with an acceptable level of MSE redundancy while minimizing 316 control message amplificaiton. It is RECOMMENDED that MAX_MSID be 317 set to the default value 5; if a different value is chosen, it should 318 be set uniformly by all nodes on the OMNI link. 320 An implementation is not required to internally use the architectural 321 constructs described here so long as its external behavior is 322 consistent with that described in this document. 324 4. Overlay Multilink Network (OMNI) Interface Model 326 An OMNI interface is a MN virtual interface configured over one or 327 more underlying interfaces, which may be physical (e.g., an 328 aeronautical radio link) or virtual (e.g., an Internet or higher- 329 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 330 with the MS through IPv6 ND message exchanges. The MN uses the MNP 331 to construct a unique OMNI LLA through the algorithmic derivation 332 specified in Section 7 and assigns the LLA to the OMNI interface. 334 The OMNI interface architectural layering model is the same as in 335 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 336 therefore sees the OMNI interface as a single L3 interface with 337 multiple underlying interfaces that appear as L2 communication 338 channels in the architecture. 340 +----------------------------+ 341 | Upper Layer Protocol | 342 Session-to-IP +---->| | 343 Address Binding | +----------------------------+ 344 +---->| IP (L3) | 345 IP Address +---->| | 346 Binding | +----------------------------+ 347 +---->| OMNI Interface | 348 Logical-to- +---->| (OMNI LLA) | 349 Physical | +----------------------------+ 350 Interface +---->| L2 | L2 | | L2 | 351 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 352 +------+------+ +------+ 353 | L1 | L1 | | L1 | 354 | | | | | 355 +------+------+ +------+ 357 Figure 1: OMNI Interface Architectural Layering Model 359 The OMNI virtual interface model gives rise to a number of 360 opportunities: 362 o since OMNI LLAs are uniquely derived from an MNP, no Duplicate 363 Address Detection (DAD) or Muticast Listener Discovery (MLD) 364 messaging is necessary. 366 o ANET interfaces do not require any L3 addresses (i.e., not even 367 link-local) in environments where communications are coordinated 368 entirely over the OMNI interface. (An alternative would be to 369 also assign the same OMNI LLA to all ANET interfaces.) 371 o as ANET interface properties change (e.g., link quality, cost, 372 availability, etc.), any active ANET interface can be used to 373 update the profiles of multiple additional ANET interfaces in a 374 single message. This allows for timely adaptation and service 375 continuity under dynamically changing conditions. 377 o coordinating ANET interfaces in this way allows them to be 378 represented in a unified MS profile with provisions for mobility 379 and multilink operations. 381 o exposing a single virtual interface abstraction to the IPv6 layer 382 allows for multilink operation (including QoS based link 383 selection, packet replication, load balancing, etc.) at L2 while 384 still permitting L3 traffic shaping based on, e.g., DSCP, flow 385 label, etc. 387 o L3 sees the OMNI interface as a point of connection to the OMNI 388 link; if there are multiple OMNI links (i.e., multiple MS's), L3 389 will see multiple OMNI interfaces. 391 o Multiple independent OMNI interfaces can be used for increased 392 fault tolerance through Safety-Based Multilink (SBM), with 393 Performance-Based Multilink (PBM) applied within each interface. 395 Other opportunities are discussed in [RFC7847]. 397 Figure 2 depicts the architectural model for a MN connecting to the 398 MS via multiple independent ANETs. When an underlying interface 399 becomes active, the MN's OMNI interface sends native (i.e., 400 unencapsulated) IPv6 ND messages via the underlying interface. IPv6 401 ND messages traverse the ground domain ANETs until they reach an 402 Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a 403 Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and 404 returns an IPv6 ND message response to the MN. IPv6 ND messages 405 traverse the ANET at layer 2; hence, the Hop Limit is not 406 decremented. 408 +--------------+ 409 | MN | 410 +--------------+ 411 |OMNI interface| 412 +----+----+----+ 413 +--------|IF#1|IF#2|IF#n|------ + 414 / +----+----+----+ \ 415 / | \ 416 / <---- Native | IP ----> \ 417 v v v 418 (:::)-. (:::)-. (:::)-. 419 .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) 420 `-(::::)-' `-(::::)-' `-(::::)-' 421 +----+ +----+ +----+ 422 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 423 . +-|--+ +-|--+ +-|--+ . 424 . | | | 425 . v v v . 426 . <----- Encapsulation -----> . 427 . . 428 . +-----+ (:::)-. . 429 . |MSE#2| .-(::::::::) +-----+ . 430 . +-----+ .-(::: INET :::)-. |MSE#m| . 431 . (::::: Routing ::::) +-----+ . 432 . `-(::: System :::)-' . 433 . +-----+ `-(:::::::-' . 434 . |MSE#1| +-----+ +-----+ . 435 . +-----+ |MSE#3| |MSE#4| . 436 . +-----+ +-----+ . 437 . . 438 . . 439 . <----- Worldwide Connected Internetwork ----> . 440 ........................................................... 442 Figure 2: MN/MS Coordination via Multiple ANETs 444 After the initial IPv6 ND message exchange, the MN can send and 445 receive unencapsulated IPv6 data packets over the OMNI interface. 446 OMNI interface multilink services will forward the packets via ARs in 447 the correct underlying ANETs. The AR encapsulates the packets 448 according to the capabilities provided by the MS and forwards them to 449 the next hop within the worldwide connected Internetwork via optimal 450 routes. 452 OMNI links span one or more underlying Internetwork via the OMNI 453 Adaptation Layer (OAL) which is based on a mid-layer overlay 454 encapsulation using [RFC2473] with [RFC4193] addressing. Each OMNI 455 link corresponds to a different overlay (differentiated by an address 456 codepoint) which may be carried over a completely separate underlying 457 topology. Each MN can facilitate SBM by connecting to multiple OMNI 458 links using a distinct OMNI interface for each link. 460 5. The OMNI Adaptation Layer (OAL) 462 The OMNI interface observes the link nature of tunnels, including the 463 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 464 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 465 The OMNI interface is configured over one or more underlying 466 interfaces that may have diverse MTUs. OMNI interfaces accommodate 467 MTU diversity through the use of the OMNI Adpatation Layer (OAL) as 468 discussed in this section. 470 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 471 1280 bytes and a minimum MRU of 1500 bytes [RFC8200], meaning that 472 the minimum IPv6 path MTU is 1280 bytes since routers on the path are 473 not permitted to perform network fragmentation even though the 474 destination is required to reassemble more. The network therefore 475 MUST forward packets of at least 1280 bytes without generating an 476 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 477 [RFC8201]. (Note: the source can apply IPv6 fragmentation for 478 locally-generated IPv6 packets up to 1500 bytes and larger still if 479 it if has a way to determine that the destination configures a larger 480 MRU, but this does not affect the minimum IPv6 path MTU.) 482 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 483 68 bytes and a minimum MRU of 576 bytes [RFC1122]. Therefore, when 484 the Don't Fragment (DF) bit in the IPv4 header is set to 0 the 485 minimum IPv4 path MTU is 576 bytes since routers on the path support 486 network fragmentation and the destination is required to reassemble 487 at least that much. The DF bit in the IPv4 encapsulation headers of 488 packets sent over IPv4 underlying interfaces therefore MUST be set to 489 0. (Note: even if the encapsulation source has a way to determine 490 that the encapsulation destination configures an MRU larger than 576 491 bytes, a larger minimum IPv4 path MTU should not be assumed without 492 careful consderation of the issues discussed in Section 5.1.) 494 The OMNI interface configures both an MTU and MRU of 9180 bytes 495 [RFC2492]; the size is therefore not a reflection of the underlying 496 interface MTUs, but rather determines the largest packet the OMNI 497 interface can forward or reassemble. The OMNI interface uses the 498 OMNI Adaptation Layer (OAL) to admit packets from the network layer 499 that are no larger than the OMNI interface MTU while generating IPv6 500 Path MTU Discovery (PMTUD) Packet Too Big (PTB) messages [RFC8201] as 501 necessary. For locally-generated IPv6 packets and IPv4 packets with 502 DF=0, the network layer performs IP fragmentation according to the 503 OMNI interface MTU if necessary then admits the fragments into the 504 interface; the OAL may then internally apply further IP fragmentation 505 prior to encapsulation. These fragments will be reassembled by the 506 final destination. (Note: Implementations normally apply 507 fragmentation prior to encapsulation according to the minimum IPv4/ 508 IPv6 path MTU in order to avoid further fragmentation in the network, 509 however they can optionally apply a larger size according to the 510 underlying interface MTU if the node that will reassemble is an on- 511 link neighbor on the underlying interface.) 513 Following any fragmentation of the original packet, OMNI interfaces 514 internally employ the OAL by either inserting or omitting a mid-layer 515 IPv6 header between the inner IP packet and any outer IP 516 encapsulation headers per [RFC2473], then performing fragmentation on 517 the mid-layer IPv6 packet when necessary. The OAL can also return 518 internally-generated PTB messages for packets admitted into the 519 interface that it deems too large (e.g., according to link 520 performance characteristics, reassembly congestion, etc.) while 521 either dropping or forwarding the packet. The OAL performs PMTUD 522 even if the destination appears to be on the same link since an OMNI 523 link node on the path may return a PTB. This ensures that the path 524 MTU is adaptive and reflects the current path used for a given data 525 flow. 527 The OAL operates with respect to both the minimum IPv6 and IPv4 path 528 MTUs as follows: 530 o When an OMNI interface sends a packet toward a final destination 531 via an ANET peer, it sends without OAL encapsulation if the packet 532 (including any outer-layer ANET encapsulations) is no larger than 533 the underlying interface MTU for on-link ANET peers or the minimum 534 ANET path MTU for peers separated by multiple IP hops. Otherwise, 535 the OAL inserts an IPv6 header with source address set to the 536 node's own OMNI Unique Local Address (ULA) (see: Section 8) and 537 destination set to the OMNI ULA of the ANET peer. The OAL then 538 uses IPv6 fragmentation to break the packet into a minimum number 539 of non-overlapping fragments, where the largest fragment size 540 (including both the OMNI and any outer-layer ANET encapsulations) 541 is determined by the (path) MTU for the ANET peer. The OAL then 542 encapsulates the fragements in any ANET headers and sends them to 543 the ANET peer, which reassembles before forwarding toward the 544 final destination. 546 o When an OMNI interface sends a packet toward a final destination 547 via an INET interface, it sends packets (including any outer-layer 548 INET encapsulations) no larger than the minimum INET path MTU 549 without OAL encapsulation if the destination is reached via an 550 INET address within the same OMNI link segment. Otherwise, the 551 OAL inserts an IPv6 header with source address set to the node's 552 OMNI ULA, destination set to the ULA of the next hop OMNI node 553 toward the final destination and (if necessary) with a Segment 554 Routing Header with the remaining Segment IDs on the path to the 555 final destination. The OAL then uses IPv6 fragmentation to break 556 the packet into a minimum number of non-overlapping fragments, 557 where the largest fragment size (including both the OMNI and 558 outer-layer INET encapsulations) is the minimum INET path MTU, and 559 the smallest fragment size is no smaller than 256 bytes (i.e., 560 slightly less than half the minimum IPv4 path MTU). The OAL then 561 encapsulates the fragments in any INET headers and sends them to 562 the OMNI link neighbor, which reassembles before forwarding toward 563 the final destination. 565 The OAL unconditionally drops all OAL fragments received from an INET 566 peer that are smaller than 256 bytes (note that no minimum fragment 567 size is specified for ANET peers since the underlying ANET is secured 568 against tiny fragment attacks). In order to set the correct context 569 for reassembly, the OAL of the OMNI interface that inserts the IPv6 570 header MUST also be the one that inserts the IPv6 Fragment Header 571 Identification value. While not strictly required, sending all 572 fragments of the same fragmented OAL packet consecutively over the 573 same underlying interface with minimal inter-fragment delay may 574 increase the likelihood of successful reassembly. 576 Note that the OAL can forward large packets via encapsulation and 577 fragmentation while at the same time returning "advisory" PTB 578 messages (subject to rate limiting). The receiving node that 579 performs reassembly can also send advisory PTB messages if reassembly 580 conditions become unfavorable. The OMNI interface can therefore 581 continuously forward large packets without loss while returning 582 advisory PTB messages recommending a smaller size. 584 The OAL sets the ICMPv6 message header Code field to the value 1 in 585 advisory PTB messages. Receiving nodes that recognize the code 586 reduce their estimate of the path MTU the same as for ordinary 587 "diagnistic" PTBs but do not regard the message as a loss indication. 588 Nodes that do not recognize the code treat the message the same as a 589 diagnostic PTB, but should heed the retransmission advice given in 590 [RFC8201]. This document therefore updates [RFC4443] and [RFC8201]. 592 Note: In networks where IPv6/IPv4 protocol translation may be 593 prevalent, it may be prudent for the OAL to always assume the IPv4 594 minimum path MTU (i.e., 576 bytes) regardless of the underlying 595 interface IP protocol version. Always assuming the IPv4 minimum path 596 MTU even for IPv6 networks may produce more fragments and additional 597 header overhead, but will always interoperate and never run the risk 598 of presenting an IPv4 node with a packet that exceeds its MRU. 600 5.1. Fragmentation Security Implications 602 As discussed in Section 3.7 of [RFC8900], there are four basic 603 threats concerning IPv6 fragmentation; each of which is addressed by 604 effective mitigations as follows: 606 1. Overlapping fragment attacks - reassembly of overlapping 607 fragments is forbidden by [RFC8200]; therefore, this threat does 608 not apply to the OAL. 610 2. Resource exhaustion attacks - this threat is mitigated by 611 providing a sufficiently large OAL reassembly cache and 612 instituting "fast discard" of incomplete reassemblies that may be 613 part of a buffer exhaustion attack. The reassembly cache should 614 be sufficiently large so that a sustained attack does not cause 615 excessive loss of good reassemblies but not so large that (timer- 616 based) data structure management becomes computationally 617 expensive. 619 3. Attacks based on predictable fragment identification values - 620 this threat is mitigated by selecting a suitably random ID value 621 per [RFC7739]. 623 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 624 threat is mitigated by disallowing "tiny fragments" per the OAL 625 fragmentation procedures specified above. 627 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 628 ID) field with only 65535 unique values such that at high data rates 629 the field could wrap and apply to new packets while the fragments of 630 old packets using the same ID are still alive in the network 631 [RFC4963]. However, since the largest OAL fragment that will be sent 632 via an IPv4 INET path is 576 bytes any IPv4 fragmentation would occur 633 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 634 recommendations suggest that such links will have low data rates. 635 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 636 at high data rates is not a concern for IPv6 fragmentation. 638 6. Frame Format 640 The OMNI interface transmits IPv6 packets according to the native 641 frame format of each underlying interface. For example, for 642 Ethernet-compatible interfaces the frame format is specified in 643 [RFC2464], for aeronautical radio interfaces the frame format is 644 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 645 Manual), for tunnels over IPv6 the frame format is specified in 646 [RFC2473], etc. 648 7. Link-Local Addresses (LLAs) 650 OMNI interfaces construct IPv6 Link-Local Addresses (i.e., "OMNI 651 LLAs") as follows: 653 o IPv6 MN OMNI LLAs encode the most-significant 112 bits of a MNP 654 within the least-significant 112 bits of the IPv6 link-local 655 prefix fe80::/16. The Prefix Length is determined by adding 16 to 656 the length of the embedded MNP. For example, for the MNP 657 2001:db8:1000:2000::/56 the corresponding MN OMNI LLA is 658 fe80:2001:db8:1000:2000::/72. This specification updates the IPv6 659 link-local address format specified in Section 2.5.6 of [RFC4291] 660 by defining a use for bits 11 - 63. 662 o IPv4-compatible MN OMNI LLAs are constructed as fe80::ffff:[IPv4], 663 i.e., the most significant 16 bits of the prefix fe80::/16, 664 followed by 64 '0' bits, followed by 16 '1' bits, followed by a 665 32bit IPv4 address/prefix. The Prefix Length is determined by 666 adding 96 to the length of the embedded IPv4 address/prefix. For 667 example, the IPv4-Compatible MN OMNI LLA for 192.0.2.0/24 is 668 fe80::ffff:192.0.2.0/120 (also written as 669 fe80::ffff:c000:0200/120). 671 o MS OMNI LLAs are assigned to ARs and MSEs from the range 672 fe80::/96, and MUST be managed for uniqueness. The lower 32 bits 673 of the LLA includes a unique integer "MSID" value between 674 0x00000001 and 0xfeffffff, e.g., as in fe80::1, fe80::2, fe80::3, 675 etc., fe80::feff:ffff. The MS OMNI LLA Prefix Length is 676 determined by adding 96 to the MSID prefix length. For example, 677 if the MSID '0x10002000' prefix length is 16 then the MS OMNI LLA 678 Prefix Length is set to 112 and the LLA is written as 679 fe80::1000:2000/112. Finally, the MSID 0x00000000 is the 680 "Anycast" MSID and corresponds to the link-local Subnet-Router 681 anycast address (fe80::) [RFC4291]; the MSID range 0xff000000 682 through 0xffffffff is reserved for future use. 684 o The OMNI LLA range fe80::/32 is used as the service prefix for the 685 address format specified in Section 4 of [RFC4380] (see Section 17 686 for further discussion). 688 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 689 MNPs can be allocated from that block ensuring that there is no 690 possibility for overlap between the above OMNI LLA constructs. 692 Since MN OMNI LLAs are based on the distribution of administratively 693 assured unique MNPs, and since MS OMNI LLAs are guaranteed unique 694 through administrative assignment, OMNI interfaces set the 695 autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 697 8. Unique-Local Addresses (ULAs) 699 OMNI links use IPv6 Unique Local Addresses (i.e., "OMNI ULAs") 700 [RFC4193] as the source and destination addresses in OAL IPv6 701 encapsulation headers. This document currently assumes use of the 702 ULA prefix fc80::/10 for mapping OMNI LLAs to routable OMNI ULAs 703 (however, see the note at the end of this section). 705 Each OMNI link instance is identified by bits 10-15 of the OMNI 706 service prefix fc80::/10. For example, OMNI ULAs associated with 707 instance 0 are configured from the prefix fc80::/16, instance 1 from 708 fc81::/16, etc., up to instance 63 from fcbf::/16. OMNI ULAs and 709 their associated prefix lengths are configured in one-to-one 710 correspondence with OMNI LLAs through stateless prefix translation. 711 For example, for OMNI link instance fc80::/16: 713 o the OMNI ULA corresponding to fe80:2001:db8:1:2::/80 is simply 714 fc80:2001:db8:1:2::/80 716 o the OMNI ULA corresponding to fe80::ffff:192.0.2.0/120 is simply 717 fc80::ffff:192.0.2.0/120 719 o the OMNI ULA corresponding to fe80::1000/112 is simply 720 fc80::1000/112 722 o the OMNI ULA corresponding to fe80::/128 is simply fc80:/128. 724 Each OMNI interface assigns the Anycast OMNI ULA specific to the OMNI 725 link instance, e.g., the OMNI interface connected to instance 3 726 assigns the Anycast OMNI ULA fc83:. Routers that configure OMNI 727 interfaces advertise the OMNI service prefix (e.g., fc83::/16) into 728 the local routing system so that applications can direct traffic 729 according to SBM requirements. 731 The OMNI ULA presents an IPv6 address format that is routable within 732 the OMNI link routing system and can be used to convey link-scoped 733 messages across multiple hops using IPv6 encapsulation [RFC2473]. 734 The OMNI link extends across one or more underling Internetworks to 735 include all ARs and MSEs. All MNs are also considered to be 736 connected to the OMNI link, however OAL encapsulation is omitted over 737 ANET links when possible to conserve bandwidth (see: Section 11). 739 The OMNI link can be subdivided into "segments" that often correspond 740 to different administrative domains or physical partitions. OMNI 741 nodes can use IPv6 Segment Routing [RFC8402] when necessary to 742 support efficient packet forwarding to destinations located in other 743 OMNI link segments. A full discussion of Segment Routing over the 744 OMNI link appears in [I-D.templin-intarea-6706bis]. 746 NOTE: An alternative to the application of ULAs as discussed in this 747 document would be to re-purpose the deprectated IPv6 Site-Local 748 Address (SLA) range fec0::/10 [RFC3879]. In many ways, re-purposing 749 SLAs would be a more natural fit since both LLA and SLA prefix 750 lengths are ::/10, the prefixes fe80:: and fec0:: differ only in a 751 single bit setting, and LLAs and SLAs can be unambiguously allocated 752 in one-to-one correspondence with one another. Re-purposing SLAs 753 would also make good use of an otherwise-wasted address range that 754 has been "parked" since the 2004 deprecation. However, moving from 755 ULAs to SLAs would require an IETF standards action acknowledging 756 this document as obsoleting [RFC3879] and updating [RFC4291]. The 757 authors therefore defer to IETF consensus as to the proper way 758 forward. 760 9. Address Mapping - Unicast 762 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 763 state and use the link-local address format specified in Section 7. 764 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 765 over physical underlying interfaces without encapsulation observe the 766 native underlying interface Source/Target Link-Layer Address Option 767 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 768 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 769 interfaces via encapsulation do not include S/TLLAOs which were 770 intended for encoding physical L2 media address formats and not 771 encapsulation IP addresses. Furthermore S/TLLAOs are not intended 772 for encoding additional interface attributes. Hence, this document 773 does not define an S/TLLAO format but instead defines a new option 774 type termed the "OMNI option" designed for these purposes. 776 MNs such as aircraft typically have many wireless data link types 777 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 778 etc.) with diverse performance, cost and availability properties. 779 The OMNI interface would therefore appear to have multiple L2 780 connections, and may include information for multiple underlying 781 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 782 an IPv6 ND option called the OMNI option formatted as shown in 783 Figure 3: 785 0 1 2 3 786 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 1 787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 788 | Type | Length | Prefix Length | S/T-ifIndex | 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 | | 791 ~ Sub-Options ~ 792 | | 793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 795 Figure 3: OMNI Option Format 797 In this format: 799 o Type is set to TBD. If multiple OMNI option instances appear in 800 the same IPv6 ND message, the first instance is processed and all 801 other instances are ignored. 803 o Length is set to the number of 8 octet blocks in the option. 805 o Prefix Length is determines the length of prefix to be applied to 806 an OMNI MN LLA/ULA. For IPv6 ND messages sent from a MN to the 807 MS, Prefix Length is the length that the MN is requesting or 808 asserting to the MS. For IPv6 ND messages sent from the MS to the 809 MN, Prefix Length indicates the length that the MS is granting to 810 the MN. For IPv6 ND messages sent between MS endpoints, Prefix 811 Length indicates the length associated with the target MN that is 812 subject of the ND message. 814 o S/T-ifIndex corresponds to the ifIndex value for source or target 815 underlying interface used to convey this IPv6 ND message. OMNI 816 interfaces MUST number each distinct underlying interface with an 817 ifIndex value between '1' and '255' that represents a MN-specific 818 8-bit mapping for the actual ifIndex value assigned by network 819 management [RFC2863] (the ifIndex value '0' is reserved for use by 820 the MS). For RS and NS messages,S/T-ifIndex corresponds to the 821 source underlying interface the message originated from. For RA 822 and NA messages, S/T-ifIndex corresponds to the target underlying 823 interface that the message is destined to. 825 o Sub-Options is a Variable-length field, of length such that the 826 complete OMNI Option is an integer multiple of 8 octets long. 827 Contains one or more Sub-Options, as described in Section 9.1. 829 9.1. Sub-Options 831 The OMNI option includes zero or more Sub-Options. Each consecutive 832 Sub-Option is concatenated immediately after its predecessor. All 833 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 834 encoded in the following format: 836 0 1 2 837 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 5 838 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 839 | Sub-Type | Sub-length | Sub-Option Data ... 840 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 842 Figure 4: Sub-Option Format 844 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 845 Sub-Options defined in this document are: 847 Option Name Sub-Type 848 Pad1 0 849 PadN 1 850 Interface Attributes 2 851 Traffic Selector 3 852 MS-Register 4 853 MS-Release 5 854 Network Access Identifier 6 855 Geo Coordinates 7 856 DHCP Unique Identifier (DUID) 8 858 Figure 5 860 Sub-Types 253 and 254 are reserved for experimentation, as 861 recommended in [RFC3692]. 863 o Sub-Length is a 1-octet field that encodes the length of the Sub- 864 Option Data (i.e., ranging from 0 to 255 octets). 866 o Sub-Option Data is a block of data with format determined by Sub- 867 Type. 869 During processing, unrecognized Sub-Options are ignored and the next 870 Sub-Option processed until the end of the OMNI option is reached. 872 The following Sub-Option types and formats are defined in this 873 document: 875 9.1.1. Pad1 877 0 878 0 1 2 3 4 5 6 7 879 +-+-+-+-+-+-+-+-+ 880 | Sub-Type=0 | 881 +-+-+-+-+-+-+-+-+ 883 Figure 6: Pad1 885 o Sub-Type is set to 0. If multiple instances appear in the same 886 OMNI option all are processed. 888 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 889 consists of a single zero octet). 891 9.1.2. PadN 893 0 1 2 894 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 5 895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 896 | Sub-Type=1 | Sub-length=N | N padding octets ... 897 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 899 Figure 7: PadN 901 o Sub-Type is set to 1. If multiple instances appear in the same 902 OMNI option all are processed. 904 o Sub-Length is set to N (from 0 to 255) being the number of padding 905 octets that follow. 907 o Sub-Option Data consists of N zero-valued octets. 909 9.1.3. Interface Attributes 910 0 1 2 3 911 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 1 912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 913 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 914 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 915 | Provider ID | Link |R| APS | SRT | FMT | LHS (0 - 7) | 916 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 917 | LHS (bits 8 - 31) | ~ 918 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 919 ~ ~ 920 ~ Link Layer Address (L2ADDR) ~ 921 ~ ~ 922 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 923 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 924 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 925 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 926 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 927 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 928 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 930 Figure 8: Interface Attributes 932 o Sub-Type is set to 2. If multiple instances with different 933 ifIndex values appear in the same OMNI option all are processed; 934 if multiple instances with the same ifIndex value appear, the 935 first is processed and all others are ignored. 937 o Sub-Length is set to N (from 4 to 255) that encodes the number of 938 Sub-Option Data octets that follow. 940 o Sub-Option Data contains an "Interface Attribute" option encoded 941 as follows (note that the first four octets must be present): 943 * ifIndex is set to an 8-bit integer value corresponding to a 944 specific underlying interface the same as specified above for 945 the OMNI option header S/T-ifIndex. An OMNI option may include 946 multiple Interface Attributes Sub-Options, with each distinct 947 ifIndex value pertaining to a different underlying interface. 948 The OMNI option will often include an Interface Attributes Sub- 949 Option with the same ifIndex value that appears in the S/ 950 T-ifIndex. In that case, the actual encapsulation address of 951 the received IPv6 ND message should be compared with the L2ADDR 952 encoded in the Sub-Option (see below); if the addresses are 953 different (or, if L2ADDR absent) the presence of a Network 954 Address Translator (NAT) is indicated. 956 * ifType is set to an 8-bit integer value corresponding to the 957 underlying interface identified by ifIndex. The value 958 represents an OMNI interface-specific 8-bit mapping for the 959 actual IANA ifType value registered in the 'IANAifType-MIB' 960 registry [http://www.iana.org]. 962 * Provider ID is set to an OMNI interface-specific 8-bit ID value 963 for the network service provider associated with this ifIndex. 965 * Link encodes a 4-bit link metric. The value '0' means the link 966 is DOWN, and the remaining values mean the link is UP with 967 metric ranging from '1' ("lowest") to '15' ("highest"). 969 * R is reserved for future use. 971 * APS - a 3-bit "Address/Preferences/Simplex" code that 972 determines the contents of the remainder of the sub-option as 973 follows: 975 + When the most significant bit (i.e., "Address") is set to 1, 976 the SRT, FMT, LHS and L2ADDR fields are included immediately 977 following the APS code; else, they are omitted. 979 + When the next most significant bit (i.e., "Preferences") is 980 set to 1, a preferences block is included next; else, it is 981 omitted. (Note that if "Address" is set the preferences 982 block immediately follows L2ADDR; else, it immediately 983 follows the APS code.) 985 + When a preferences block is present and the least 986 significant bit (i.e., "Simplex") is set to 1, the block is 987 encoded in "Simplex" form as shown in Figure 8; else it is 988 encoded in "Indexed" form as discussed below. 990 * When APS indicates that an "Address" is included, the following 991 fields appear in consecutive order (else, they are omitted): 993 + SRT - a 5-bit Segment Routing Topology prefix length value 994 that (when added to 96) determines the prefix length to 995 apply to the ULA formed from concatenating fc*::/96 with the 996 32 bit LHS MSID value that follows. For example, the value 997 16 corresponds to the prefix length 112. 999 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1000 the included Link Layer Address as follows: 1002 - When the most significant bit (i.e., "Framework") is set 1003 to 0, L2ADDR is the INET encapsulation address of a 1004 Proxy/Server; otherwise, it is the addresss for the 1005 Source/Target itself 1007 - When the next most significant bit (i.e., "Mode") is set 1008 to 0, the Source/Target L2ADDR is on the open INET; 1009 otherwise, it is (likely) located behind a Network 1010 Address Translator (NAT). 1012 - When the least significant bit (i.e., "Type") is set to 1013 0, L2ADDR includes a UDP Port Number followed by an IPv4 1014 address; else, a UDP Port Number followed by an IPv6 1015 address. 1017 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1018 path to the target. When SRT and LHS are both set to 0, the 1019 LHS is considered unspecified in this IPv6 ND message. When 1020 SRT is set to 0 and LHS is non-zero, the prefix length is 1021 set to 128. SRT and LHS provide guidance to the OMNI 1022 interface forwarding algorithm. Specifically, if SRT/LHS is 1023 located in the local OMNI link segment then the OMNI 1024 interface can encapsulate according to FMT/L2ADDR; else, it 1025 must forward according to the OMNI link spanning tree. See 1026 [I-D.templin-intarea-6706bis] for further discussion. 1028 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1029 and identifies the link-layer address (i.e., the 1030 encapsulation address) of the source/target. The UDP Port 1031 Number appears in the first two octets and the IP address 1032 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1033 The Port Number and IP address are recorded in ones- 1034 compliment "obfuscated" form per [RFC4380]. The OMNI 1035 interface forwarding algoritherm uses FMT/L2ADDR to 1036 determine the encapsulation address for forwarding when SRT/ 1037 LHS is located in the local OMNI link segment. 1039 * When APS indicates that "Preferences" are included, a 1040 preferences block appears as the remainder of the Sub-Option as 1041 a series of Bitmaps and P[*] values. In "Simplex" form, the 1042 index for each singleton Bitmap octet is inferred from its 1043 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1044 In "Indexed" form, each Bitmap is preceded by an Index octet 1045 that encodes a value "i" = (0 - 255) as the index for its 1046 companion Bitmap as follows: 1048 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1049 | Index=i | Bitmap(i) |P[*] values ... 1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1052 Figure 9 1054 * The preferences consist of a first (simplex/indexed) Bitmap 1055 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1056 2-bit P[*] values, followed by a second Bitmap (i), followed by 1057 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1058 the bits of each Bitmap(i) that are set to '1'' indicate the 1059 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1060 that follow; if any Bitmap(i) bits are '0', then the 1061 corresponding P[*] block is instead omitted. For example, if 1062 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1063 followed by the block with P[04]-P[07], etc., and ending with 1064 the block with P[28]-P[31] are included (as shown in Figure 8). 1065 The next Bitmap(i) is then consulted with its bits indicating 1066 which P[*] blocks follow, etc. out to the end of the Sub- 1067 Option. 1069 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1070 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1071 preference for underlying interface selection purposes. Not 1072 all P[*] values need to be included in the OMNI option of each 1073 IPv6 ND message received. Any P[*] values represented in an 1074 earlier OMNI option but omitted in the current OMNI option 1075 remain unchanged. Any P[*] values not yet represented in any 1076 OMNI option default to "medium". 1078 * The first 16 P[*] blocks correspond to the 64 Differentiated 1079 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1080 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1081 traffic classifier values P[64], P[65], P[66], etc. See 1082 Appendix A for further discussion and examples. 1084 9.1.4. Traffic Selector 1086 0 1 2 3 1087 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 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1090 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1091 ~ ~ 1092 ~ RFC 6088 Format Traffic Selector ~ 1093 ~ ~ 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 Figure 10: Traffic Selector 1098 o Sub-Type is set to 3. If multiple instances appear in the same 1099 OMNI option all are processed, i.e., even if the same ifIndex 1100 value appears multiple times. 1102 o Sub-Length is set to N (the number of Sub-Option Data octets that 1103 follow). 1105 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1106 specified in Section 9.1.3, followed by an N-1 octet traffic 1107 selector formatted per [RFC6088] beginning with the "TS Format" 1108 field. The largest traffic selector for a given ifIndex is 1109 therefore 254 octets. 1111 9.1.5. MS-Register 1113 0 1 2 3 1114 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 1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1118 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1122 ... ... ... ... ... ... 1123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1124 | MSID [n] (bits 16 - 32) | 1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1127 Figure 11: MS-Register Sub-option 1129 o Sub-Type is set to 4. If multiple instances appear in the same 1130 OMNI option all are processed. Only the first MAX_MSID values 1131 processed (whether in a single instance or multiple) are retained 1132 and all other MSIDs are ignored. 1134 o Sub-Length is set to 4n. 1136 o A list of n 4-octet MSIDs is included in the following 4n octets. 1137 The Anycast MSID value '0' in an RS message MS-Register sub-option 1138 requests the recipient to return the MSID of a nearby MSE in a 1139 corresponding RA response. 1141 9.1.6. MS-Release 1142 0 1 2 3 1143 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 1144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1145 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1147 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1149 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1151 ... ... ... ... ... ... 1152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1153 | MSID [n] (bits 16 - 32) | 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1156 Figure 12: MS-Release Sub-option 1158 o Sub-Type is set to 5. If multiple instances appear in the same 1159 IPv6 OMNI option all are processed. Only the first MAX_MSID 1160 values processed (whether in a single instance or multiple) are 1161 retained and all other MSIDs are ignored. 1163 o Sub-Length is set to 4n. 1165 o A list of n 4 octet MSIDs is included in the following 4n octets. 1166 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1167 i.e., only non-zero values are processed. 1169 9.1.7. Network Access Identifier (NAI) 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=6 | Sub-length=N |Network Access Identifier (NAI) 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1177 Figure 13: Network Access Identifier (NAI) Sub-option 1179 o Sub-Type is set to 6. If multiple instances appear in the same 1180 OMNI option the first is processed and all others are ignored. 1182 o Sub-Length is set to N. 1184 o A Network Access Identifier (NAI) up to 255 octets in length is 1185 coded per [RFC7542]. 1187 9.1.8. Geo Coordinates 1189 0 1 2 3 1190 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 1191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1192 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1195 Figure 14: Geo Coordinates Sub-option 1197 o Sub-Type is set to 7. If multiple instances appear in the same 1198 OMNI option the first is processed and all others are ignored. 1200 o Sub-Length is set to N. 1202 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1203 Includes Latitude/Longitude at a minimum; may also include 1204 additional attributes such as altitude, heading, speed, etc.). 1206 9.1.9. DHCP Unique Identifier (DUID) 1208 0 1 2 3 1209 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 1210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1211 | Sub-Type=8 | Sub-length=N | DUID-Type | 1212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1213 . . 1214 . type-specific DUID body (variable length) . 1215 . . 1216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1218 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1220 o Sub-Type is set to 8. If multiple instances appear in the same 1221 OMNI option the first is processed and all others are ignored. 1223 o Sub-Length is set to N (i.e., the length of the option beginning 1224 with the DUID-Type and continuing to the end of the type-specifc 1225 body). 1227 o DUID-Type is a two-octet field coded in network byte order that 1228 determines the format and contents of the type-specific body 1229 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1230 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1231 which will occur in common operational practice. 1233 o A type-specific DUID body up to 253 octets in length follows, 1234 formatted according to DUID-type. For example, for type 4 the 1235 body consists of a 128-bit UUID selected according to [RFC6355]. 1237 10. Address Mapping - Multicast 1239 The multicast address mapping of the native underlying interface 1240 applies. The mobile router on board the MN also serves as an IGMP/ 1241 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1242 using the L2 address of the AR as the L2 address for all multicast 1243 packets. 1245 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1246 coordinate with the AR, and ANET L2 elements use MLD snooping 1247 [RFC4541]. 1249 11. Conceptual Sending Algorithm 1251 The MN's IPv6 layer selects the outbound OMNI interface according to 1252 SBM considerations when forwarding data packets from local or EUN 1253 applications to external correspondents. Each OMNI interface 1254 maintains a neighbor cache the same as for any IPv6 interface, but 1255 with additional state for multilink coordination. 1257 After a packet enters the OMNI interface, an outbound underlying 1258 interface is selected based on PBM traffic attributes such as DSCP, 1259 application port number, cost, performance, message size, etc. OMNI 1260 interface multilink selections could also be configured to perform 1261 replication across multiple underlying interfaces for increased 1262 reliability at the expense of packet duplication. 1264 When the OMNI interface sends a packet over a selected outbound 1265 underlying interface, the OAL includes or omits a mid-layer 1266 encapsulation header as necessary as discussed in Section 5. The OAL 1267 also performs encapsulation when the nearest AR is located multiple 1268 hops away as discussed in Section 12.1. 1270 OMNI interface multilink service designers MUST observe the BCP 1271 guidance in Section 15 [RFC3819] in terms of implications for 1272 reordering when packets from the same flow may be spread across 1273 multiple underlying interfaces having diverse properties. 1275 11.1. Multiple OMNI Interfaces 1277 MNs may connect to multiple independent OMNI links concurrently in 1278 support of SBM. Each OMNI interface is distinguished by its Anycast 1279 OMNI ULA (e.g., fc80::, fc81::, fc82::). The MN configures a 1280 separate OMNI interface for each link so that multiple interfaces 1281 (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. A 1282 different Anycast OMNI ULA is assigned to each interface, and the MN 1283 injects the service prefixes for the OMNI link instances into the EUN 1284 routing system. 1286 Applications in EUNs can use Segment Routing to select the desired 1287 OMNI interface based on SBM considerations. The Anycast OMNI ULA is 1288 written into the IPv6 destination address, and the actual destination 1289 (along with any additional intermediate hops) is written into the 1290 Segment Routing Header. Standard IP routing directs the packets to 1291 the MN's mobile router entity, and the Anycast OMNI ULA identifies 1292 the OMNI interface to be used for transmission to the next hop. When 1293 the MN receives the message, it replaces the IPv6 destination address 1294 with the next hop found in the routing header and transmits the 1295 message over the OMNI interface identified by the Anycast OMNI ULA. 1297 Multiple distinct OMNI links can therefore be used to support fault 1298 tolerance, load balancing, reliability, etc. The architectural model 1299 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1301 12. Router Discovery and Prefix Registration 1303 MNs interface with the MS by sending RS messages with OMNI options 1304 under the assumption that one or more AR on the ANET will process the 1305 message and respond. The manner in which the ANET ensures AR 1306 coordination is link-specific and outside the scope of this document 1307 (however, considerations for ANETs that do not provide ARs that 1308 recognize the OMNI option are discussed in Section 17). 1310 For each underlying interface, the MN sends an RS message with an 1311 OMNI option to coordinate with MSEs identified by MSID values. 1312 Example MSID discovery methods are given in [RFC5214] and include 1313 data link login parameters, name service lookups, static 1314 configuration, a static "hosts" file, etc. The MN can also send an 1315 RS with an MS-Register suboption that includes the Anycast MSID value 1316 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1317 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1318 be itself) and returns an RA with the selected MSID in an MS-Register 1319 suboption. The AR selects only a single wildcard MSE (i.e., even if 1320 the RS MS-Register suboption included multiple '0' MSIDs) while also 1321 soliciting the MSEs corresponding to any non-zero MSIDs. 1323 MNs configure OMNI interfaces that observe the properties discussed 1324 in the previous section. The OMNI interface and its underlying 1325 interfaces are said to be in either the "UP" or "DOWN" state 1326 according to administrative actions in conjunction with the interface 1327 connectivity status. An OMNI interface transitions to UP or DOWN 1328 through administrative action and/or through state transitions of the 1329 underlying interfaces. When a first underlying interface transitions 1330 to UP, the OMNI interface also transitions to UP. When all 1331 underlying interfaces transition to DOWN, the OMNI interface also 1332 transitions to DOWN. 1334 When an OMNI interface transitions to UP, the MN sends RS messages to 1335 register its MNP and an initial set of underlying interfaces that are 1336 also UP. The MN sends additional RS messages to refresh lifetimes 1337 and to register/deregister underlying interfaces as they transition 1338 to UP or DOWN. The MN sends initial RS messages over an UP 1339 underlying interface with its OMNI LLA as the source and with 1340 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1341 messages include an OMNI option per Section 9 with valid prefix 1342 registration information, Interface Attributes appropriate for 1343 underlying interfaces, MS-Register/Release sub-options containing 1344 MSID values, and with any other necessary OMNI sub-options. The S/ 1345 T-ifIndex field is set to the index of the underlying interface over 1346 which the RS message is sent. 1348 ARs process IPv6 ND messages with OMNI options and act as an MSE 1349 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1350 and create a neighbor cache entry for the MN, then coordinate with 1351 any MSEs named in the Register/Release lists in a manner outside the 1352 scope of this document. When an MSE processes the OMNI information, 1353 it first validates the prefix registration information then injects/ 1354 withdraws the MNP in the routing/mapping system and caches/discards 1355 the new Prefix Length, MNP and Interface Attributes. The MSE then 1356 informs the AR of registration success/failure, and the AR returns an 1357 RA message to the MN with an OMNI option per Section 9. 1359 The AR returns the RA message via the same underlying interface of 1360 the MN over which the RS was received, and with destination address 1361 set to the MN OMNI LLA (i.e., unicast), with source address set to 1362 its own OMNI LLA, and with an OMNI option with S/T-ifIndex set to the 1363 value included in the RS. The OMNI option also includes valid prefix 1364 registration information, Interface Attributes, MS-Register/Release 1365 and any other necessary OMNI sub-options. The RA also includes any 1366 information for the link, including RA Cur Hop Limit, M and O flags, 1367 Router Lifetime, Reachable Time and Retrans Timer values, and 1368 includes any necessary options such as: 1370 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1372 o RIOs [RFC4191] with more-specific routes. 1374 o an MTU option that specifies the maximum acceptable packet size 1375 for this ANET interface. 1377 The AR MAY also send periodic and/or event-driven unsolicited RA 1378 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1379 OMNI header of the unsolicited RA message identifies the target 1380 underlying interface of the destination MN. 1382 The AR can combine the information from multiple MSEs into one or 1383 more "aggregate" RAs sent to the MN in order conserve ANET bandwidth. 1384 Each aggregate RA includes an OMNI option with MS-Register/Release 1385 sub-options with the MSEs represented by the aggregate. If an 1386 aggregate is sent, the RA message contents must consistently 1387 represent the combined information advertised by all represented 1388 MSEs. Note that since the AR uses its own OMNI LLA as the RA source 1389 address, the MN determines the addresses of the represented MSEs by 1390 examining the MS-Register/Release OMNI sub-options. 1392 When the MN receives the RA message, it creates an OMNI interface 1393 neighbor cache entry for each MSID that has confirmed MNP 1394 registration via the L2 address of this AR. If the MN connects to 1395 multiple ANETs, it records the additional L2 AR addresses in each 1396 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1397 then manages its underlying interfaces according to their states as 1398 follows: 1400 o When an underlying interface transitions to UP, the MN sends an RS 1401 over the underlying interface with an OMNI option. The OMNI 1402 option contains at least one Interface Attribute sub-option with 1403 values specific to this underlying interface, and may contain 1404 additional Interface Attributes specific to other underlying 1405 interfaces. The option also includes any MS-Register/Release sub- 1406 options. 1408 o When an underlying interface transitions to DOWN, the MN sends an 1409 RS or unsolicited NA message over any UP underlying interface with 1410 an OMNI option containing an Interface Attribute sub-option for 1411 the DOWN underlying interface with Link set to '0'. The MN sends 1412 an RS when an acknowledgement is required, or an unsolicited NA 1413 when reliability is not thought to be a concern (e.g., if 1414 redundant transmissions are sent on multiple underlying 1415 interfaces). 1417 o When the Router Lifetime for a specific AR nears expiration, the 1418 MN sends an RS over the underlying interface to receive a fresh 1419 RA. If no RA is received, the MN can send RS messages to an 1420 alternate MSID in case the current MSID has failed. If no RS 1421 messages are received even after trying to contact alternate 1422 MSIDs, the MN marks the underlying interface as DOWN. 1424 o When a MN wishes to release from one or more current MSIDs, it 1425 sends an RS or unsolicited NA message over any UP underlying 1426 interfaces with an OMNI option with a Release MSID. Each MSID 1427 then withdraws the MNP from the routing/mapping system and informs 1428 the AR that the release was successful. 1430 o When all of a MNs underlying interfaces have transitioned to DOWN 1431 (or if the prefix registration lifetime expires), any associated 1432 MSEs withdraw the MNP the same as if they had received a message 1433 with a release indication. 1435 The MN is responsible for retrying each RS exchange up to 1436 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1437 seconds until an RA is received. If no RA is received over a an UP 1438 underlying interface (i.e., even after attempting to contact 1439 alternate MSEs), the MN declares this underlying interface as DOWN. 1441 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1442 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1443 returns an internally-generated RA message as though the message 1444 originated from an IPv6 router. The internally-generated RA message 1445 contains configuration information that is consistent with the 1446 information received from the RAs generated by the MS. Whether the 1447 OMNI interface IPv6 ND messaging process is initiated from the 1448 receipt of an RS message from the IPv6 layer is an implementation 1449 matter. Some implementations may elect to defer the IPv6 ND 1450 messaging process until an RS is received from the IPv6 layer, while 1451 others may elect to initiate the process proactively. Still other 1452 deployments may elect to administratively disable the ordinary RS/RA 1453 messaging used by the IPv6 layer over the OMNI interface, since they 1454 are not required to drive the internal RS/RA processing. 1456 Note: The Router Lifetime value in RA messages indicates the time 1457 before which the MN must send another RS message over this underlying 1458 interface (e.g., 600 seconds), however that timescale may be 1459 significantly longer than the lifetime the MS has committed to retain 1460 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1461 therefore responsible for keeping MS state alive on a shorter 1462 timescale than the MN is required to do on its own behalf. 1464 Note: On multicast-capable underlying interfaces, MNs should send 1465 periodic unsolicited multicast NA messages and ARs should send 1466 periodic unsolicited multicast RA messages as "beacons" that can be 1467 heard by other nodes on the link. If a node fails to receive a 1468 beacon after a timeout value specific to the link, it can initiate a 1469 unicast exchange to test reachability. 1471 12.1. Router Discovery in IP Multihop and IPv4-Only Access Networks 1473 On some ANET types a MN may be located multiple IP hops away from the 1474 nearest AR. Forwarding through IP multihop ANETs is conducted 1475 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1476 Network (MANET) routing protocol over omni-directional wireless 1477 interfaces, an inter-domain routing protocol in an enterprise 1478 network, etc.). These ANETs could be either IPv6-enabled or 1479 IPv4-only, while IPv4-only ANETs could be either multicast-capable or 1480 unicast-only (note that for IPv4-only ANETs the following procedures 1481 apply for both single-hop and multhop cases). 1483 A MN located potentially multiple ANET hops away from the nearst AR 1484 prepares an RS message with source address set to its OMNI LLA and 1485 with destination set to link-scoped All-Routers multicast the same as 1486 discussed above. For IPv6-enabled ANETs, the MN then encapsulates 1487 the message in an IPv6 header with source address set to the ULA 1488 corresponding to the LLA source address and with destination set to 1489 site-scoped All-Routers multicast (ff05::2)[RFC4291]. For IPv4-only 1490 ANETs, the MN instead encapsulates the RS message in an IPv4 header 1491 with source address set to the node's own IPv4 address. For 1492 multicast-capable IPv4-only ANETs, the MN then sets the destination 1493 address to the site-scoped IPv4 multicast address corresponding to 1494 link-scoped IPv6 All-Routers multicast [RFC2529]; for unicast-only 1495 IPv4-only ANETs, the MN instead sets the destination address to the 1496 unicast IPv4 adddress of an AR [RFC5214]. The MN then sends the 1497 encapsulated RS message via the ANET interface, where it will be 1498 forwarded by zero or more intermediate ANET hops. 1500 When an intermediate ANET hop that particpates in the routing 1501 protocol receives the encapsulated RS, it forwards the message 1502 according to its routing tables (note that an intermediate node could 1503 be a fixed infrastructure element or another MN). This process 1504 repeats iteratively until the RS message is received by a penultimate 1505 ANET hop within single-hop communications range of an AR, which 1506 forwards the message to the AR. 1508 When the AR receives the message, it decapsulates the RS and 1509 coordinates with the MS the same as for an ordinary link-local RS, 1510 since the inner Hop Limit will not have been decremented by the 1511 multihop forwarding process. The AR then prepares an RA message with 1512 source address set to its own LLA and destination address set to the 1513 LLA of the original MN, then encapsulates the message in an IPv4/IPv6 1514 header with source address set to its own IPv4/ULA address and with 1515 destination set to the encapsulation source of the RS. 1517 The AR then forwards the message to an ANET node within 1518 communications range, which forwards the message according to its 1519 routing tables to an intermediate node. The multihop forwarding 1520 process within the ANET continues repetitively until the message is 1521 delivered to the original MN, which decapsulates the message and 1522 performs autoconfiguration the same as if it had received the RA 1523 directly from the AR as an on-link neighbor. 1525 Note: An alternate approach to multihop forwarding via IPv6 1526 encapsulation would be to statelessly translate the IPv6 LLAs into 1527 ULAs and forward the messages without encapsulation. This would 1528 violate the [RFC4861] requirement that certain IPv6 ND messages must 1529 use link-local addresses and must not be accepted if received with 1530 Hop Limit less than 255. This document therefore advocates 1531 encapsulation since the overhead is nominal considering the 1532 infrequent nature and small size of IPv6 ND messages. Future 1533 documents may consider encapsulation avoidance through translation 1534 while updating [RFC4861]. 1536 Note: An alternate approach to multihop forwarding via IPv4 1537 encapsulation would be to employ IPv6/IPv4 protocol translation. 1538 However, for IPv6 ND messages the OMNI LLA addresses would be 1539 truncated due to translation and the OMNI Router and Prefix Discovery 1540 services would not be able to function. The use of IPv4 1541 encapsulation is therefore indicated. 1543 12.2. MS-Register and MS-Release List Processing 1545 When a MN sends an RS message with an OMNI option via an underlying 1546 interface to an AR, the MN must convey its knowledge of its 1547 currently-associated MSEs. Initially, the MN will have no associated 1548 MSEs and should therefore include an MS-Register sub-option with the 1549 single MSID value 0 which requests the AR to select and assign an 1550 MSE. The AR will then return an RA message with source address set 1551 to the OMNI LLA containing the MSE of the selected MSE. 1553 As the MN activates additional underlying interfaces, it can 1554 optionally include an MS-Register sub-option with MSID value 0, or 1555 with non-zero MSIDs for MSEs discovered from previous RS/RA 1556 exchanges. The MN will thus eventually begin to learn and manage its 1557 currently active set of MSEs, and can register with new MSEs or 1558 release from former MSEs with each successive RS/RA exchange. As the 1559 MN's MSE constituency grows, it alone is responsible for including or 1560 omitting MSIDs in the MS-Register/Release lists it sends in RS 1561 messages. The inclusion or omission of MSIDs determines the MN's 1562 interface to the MS and defines the manner in which MSEs will 1563 respond. The only limiting factor is that the MN should include no 1564 more than MAX_MSID values in each list per each IPv6 ND message, and 1565 should avoid duplication of entries in each list unless it wants to 1566 increase likelihood of control message delivery. 1568 When an AR receives an RS message sent by a MN with an OMNI option, 1569 the option will contain zero or more MS-Register and MS-Release sub- 1570 options containing MSIDs. After processing the OMNI option, the AR 1571 will have a list of zero or more MS-Register MSIDs and a list of zero 1572 or more of MS-Release MSIDs. The AR then processes the lists as 1573 follows: 1575 o For each list, retain the first MAX_MSID values in the list and 1576 discard any additional MSIDs (i.e., even if there are duplicates 1577 within a list). 1579 o Next, for each MSID in the MS-Register list, remove all matching 1580 MSIDs from the MS-Release list. 1582 o Next, proceed according to whether the AR's own MSID or the value 1583 0 appears in the MS-Register list as folllows: 1585 * If yes, send an RA message directly back to the MN and send a 1586 proxy copy of the RS message to each additional MSID in the MS- 1587 Register list with the MS-Register/Release lists omitted. 1588 Then, send a uNA message to each MSID in the MS-Release list 1589 with the MS-Register/Release lists omitted and with an OMNI 1590 header with S/T-ifIndex set to 0. 1592 * If no, send a proxy copy of the RS message to each additional 1593 MSID in the MS-Register list with the MS-Register list omitted. 1594 For the first MSID, include the original MS-Release list; for 1595 all other MSIDs, omit the MS-Release list. 1597 Each proxy copy of the RS message will include an OMNI option and 1598 encapsulation header with the ULA of the AR as the source and the ULA 1599 of the Register MSE as the destination. When the Register MSE 1600 receives the proxy RS message, if the message includes an MS-Release 1601 list the MSE sends a uNA message to each additional MSID in the 1602 Release list. The Register MSE then sends an RA message back to the 1603 (Proxy) AR wrapped in an OMNI encapsulation header with source and 1604 destination addresses reversed, and with RA destination set to the 1605 LLA of the MN. When the AR receives this RA message, it sends a 1606 proxy copy of the RA to the MN. 1608 Each uNA message (whether send by the first-hop AR or by a Register 1609 MSE) will include an OMNI option and an encapsulation header with the 1610 ULA of the Register MSE as the source and the ULA of the Release ME 1611 as the destination. The uNA informs the Release MSE that its 1612 previous relationship with the MN has been released and that the 1613 source of the uNA message is now registered. The Release MSE must 1614 then note that the subject MN of the uNA message is now "departed", 1615 and forward any subsequent packets destined to the MN to the Register 1616 MSE. 1618 Note that it is not an error for the MS-Register/Release lists to 1619 include duplicate entries. If duplicates occur within a list, the 1620 the AR will generate multiple proxy RS and/or uNA messages - one for 1621 each copy of the duplicate entries. 1623 13. Secure Redirection 1625 If the ANET link model is multiple access, the AR is responsible for 1626 assuring that address duplication cannot corrupt the neighbor caches 1627 of other nodes on the link. When the MN sends an RS message on a 1628 multiple access ANET link, the AR verifies that the MN is authorized 1629 to use the address and returns an RA with a non-zero Router Lifetime 1630 only if the MN is authorized. 1632 After verifying MN authorization and returning an RA, the AR MAY 1633 return IPv6 ND Redirect messages to direct MNs located on the same 1634 ANET link to exchange packets directly without transiting the AR. In 1635 that case, the MNs can exchange packets according to their unicast L2 1636 addresses discovered from the Redirect message instead of using the 1637 dogleg path through the AR. In some ANET links, however, such direct 1638 communications may be undesirable and continued use of the dogleg 1639 path through the AR may provide better performance. In that case, 1640 the AR can refrain from sending Redirects, and/or MNs can ignore 1641 them. 1643 14. AR and MSE Resilience 1645 ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 1646 [RFC5798] configurations so that service continuity is maintained 1647 even if one or more ARs fail. Using VRRP, the MN is unaware which of 1648 the (redundant) ARs is currently providing service, and any service 1649 discontinuity will be limited to the failover time supported by VRRP. 1650 Widely deployed public domain implementations of VRRP are available. 1652 MSEs SHOULD use high availability clustering services so that 1653 multiple redundant systems can provide coordinated response to 1654 failures. As with VRRP, widely deployed public domain 1655 implementations of high availability clustering services are 1656 available. Note that special-purpose and expensive dedicated 1657 hardware is not necessary, and public domain implementations can be 1658 used even between lightweight virtual machines in cloud deployments. 1660 15. Detecting and Responding to MSE Failures 1662 In environments where fast recovery from MSE failure is required, ARs 1663 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 1664 manner that parallels Bidirectional Forwarding Detection (BFD) 1665 [RFC5880] to track MSE reachability. ARs can then quickly detect and 1666 react to failures so that cached information is re-established 1667 through alternate paths. Proactive NUD control messaging is carried 1668 only over well-connected ground domain networks (i.e., and not low- 1669 end ANET links such as aeronautical radios) and can therefore be 1670 tuned for rapid response. 1672 ARs perform proactive NUD for MSEs for which there are currently 1673 active MNs on the ANET. If an MSE fails, ARs can quickly inform MNs 1674 of the outage by sending multicast RA messages on the ANET interface. 1675 The AR sends RA messages to MNs via the ANET interface with an OMNI 1676 option with a Release ID for the failed MSE, and with destination 1677 address set to All-Nodes multicast (ff02::1) [RFC4291]. 1679 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 1680 by small delays [RFC4861]. Any MNs on the ANET interface that have 1681 been using the (now defunct) MSE will receive the RA messages and 1682 associate with a new MSE. 1684 16. Transition Considerations 1686 When a MN connects to an ANET link for the first time, it sends an RS 1687 message with an OMNI option. If the first hop AR recognizes the 1688 option, it returns an RA with its MS OMNI LLA as the source, the MN 1689 OMNI LLA as the destination and with an OMNI option included. The MN 1690 then engages the AR according to the OMNI link model specified above. 1691 If the first hop AR is a legacy IPv6 router, however, it instead 1692 returns an RA message with no OMNI option and with a non-OMNI unicast 1693 source LLA as specified in [RFC4861]. In that case, the MN engages 1694 the ANET according to the legacy IPv6 link model and without the OMNI 1695 extensions specified in this document. 1697 If the ANET link model is multiple access, there must be assurance 1698 that address duplication cannot corrupt the neighbor caches of other 1699 nodes on the link. When the MN sends an RS message on a multiple 1700 access ANET link with an OMNI LLA source address and an OMNI option, 1701 ARs that recognize the option ensure that the MN is authorized to use 1702 the address and return an RA with a non-zero Router Lifetime only if 1703 the MN is authorized. ARs that do not recognize the option instead 1704 return an RA that makes no statement about the MN's authorization to 1705 use the source address. In that case, the MN should perform 1706 Duplicate Address Detection to ensure that it does not interfere with 1707 other nodes on the link. 1709 An alternative approach for multiple access ANET links to ensure 1710 isolation for MN / AR communications is through L2 address mappings 1711 as discussed in Appendix C. This arrangement imparts a (virtual) 1712 point-to-point link model over the (physical) multiple access link. 1714 17. OMNI Interfaces on the Open Internet 1716 OMNI interfaces configured over IPv6-enabled underlying interfaces on 1717 the open Internet without an OMNI-aware first-hop AR receive RA 1718 messages that do not include an OMNI option, while OMNI interfaces 1719 configured over IPv4-only underlying interfaces do not receive any 1720 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 1721 without an OMNI option configure addresses, on-link prefxies, etc. on 1722 the underlying interface that received the RA according to standard 1723 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 1724 interfaces configured over IPv4-only underlying interfaces configure 1725 IPv4 address information on the underlying interfaces using 1726 mechanisms such as DHCPv4 [RFC2131]. 1728 OMNI interfaces configured over underlying interfaces that connect to 1729 the open Internet can apply security services such as VPNs to connect 1730 to an MSE or establish a direct link to an MSE through some other 1731 means. In environments where an explicit VPN or direct link may be 1732 impractical, OMNI interfaces can instead use UDP/IP encapsulation per 1733 [RFC6081][RFC4380]. (SEcure Neighbor Discovery (SEND) and 1734 Cryptographically Generated Addresses (CGA) [RFC3971][RFC3972] or 1735 other protocol-specific security services can can also be used if 1736 additional authentication is necessary.) 1738 After estabishing a VPN or preparing for UDP/IP encapsulation, OMNI 1739 interfaces send control plane messages to interface with the MS. The 1740 control plane messages must be authenticated while data plane 1741 messages are delivered the same as for ordinary best-effort Internet 1742 traffic with basic source address-based data origin verification. 1743 Data plane communications via OMNI interfaces that connect over the 1744 open Internet without an explicit VPN should therefore employ 1745 transport- or higher-layer security to ensure integrity and/or 1746 confidentiality. 1748 When SEND/CGA are used over an open Internet underlying interfaces, 1749 each OMNI node configures a link-local CGA for use as the source 1750 address of IPv6 ND messages. The node then employs OMNI link 1751 encapsualation and sets the IPv6 source address of the OMNI header to 1752 the ULA corresponding to its OMNI LLA. Any Prefix Length values in 1753 the IPv6 ND message OMNI option then apply to the ULA found in the 1754 OMNI header, i.e., and not to the CGA found in the IPv6 ND source 1755 address. 1757 OMNI interfaces in the open Internet are often located behind Network 1758 Address Translators (NATs). The OMNI interface accommodates NAT 1759 traversal using UDP/IP encapsulation and the mechanisms discussed in 1760 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 1762 18. Time-Varying MNPs 1764 In some use cases, it is desirable, beneficial and efficient for the 1765 MN to receive a constant MNP that travels with the MN wherever it 1766 moves. For example, this would allow air traffic controllers to 1767 easily track aircraft, etc. In other cases, however (e.g., 1768 intelligent transportation systems), the MN may be willing to 1769 sacrifice a modicum of efficiency in order to have time-varying MNPs 1770 that can be changed every so often to defeat adversarial tracking. 1772 Prefix delegation services such as those discussed in 1773 [I-D.templin-6man-dhcpv6-ndopt] and [I-D.templin-intarea-6706bis] 1774 allow OMNI MNs that desire time-varying MNPs to obtain short-lived 1775 prefixes. In that case, the identity of the MN can be used as a 1776 prefix delegation seed (e.g., a DHCPv6 Device Unique IDentifier 1777 (DUID) [RFC8415]). The MN would then be obligated to renumber its 1778 internal networks whenever its MNP (and therefore also its OMNI 1779 address) changes. This should not present a challenge for MNs with 1780 automated network renumbering services, however presents limits for 1781 the durations of ongoing sessions that would prefer to use a constant 1782 address. 1784 When a MN wishes to invoke DHCPv6 Prefix Delegation (PD) services, it 1785 sets the source address of an RS message to fe80:: and includes a 1786 DUID sub-option and a desired Prefix Length value in the RS message 1787 OMNI option. When the first-hop AR receives the RS message, it 1788 performs a PD exchange with the DHCPv6 service to obtain an IPv6 MNP 1789 of the requested length then returns an RA message with the OMNI LLA 1790 corresponding to the MNP as the destination address. When the MN 1791 receives the RA message, it provisons the PD to its downstream- 1792 attached networks and begins using the OMNI LLA in subsequent IPv6 ND 1793 messaging. 1795 19. IANA Considerations 1797 The IANA is instructed to allocate an official Type number TBD from 1798 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 1799 option. Implementations set Type to 253 as an interim value 1800 [RFC4727]. 1802 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 1803 Code Fields: Type 2 - Packet Too Big" registry. The registry should 1804 read as follows: 1806 Code Name Reference 1807 --- ---- --------- 1808 0 Diagnostic Packet Too Big [RFC4443] 1809 1 Advisory Packet Too Big [RFCXXXX] 1811 Figure 16: OMNI Option Sub-Type Values 1813 The IANA is instructed to allocate one Ethernet unicast address TBD2 1814 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 1815 Address Block - Unicast Use". 1817 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 1818 is instructed to create and maintain a new registry entitled "OMNI 1819 option Sub-Type values". Initial values for the OMNI option Sub-Type 1820 values registry are given below; future assignments are to be made 1821 through Expert Review [RFC8126]. 1823 Value Sub-Type name Reference 1824 ----- ------------- ---------- 1825 0 Pad1 [RFCXXXX] 1826 1 PadN [RFCXXXX] 1827 2 Interface Attributes [RFCXXXX] 1828 3 Traffic Selector [RFCXXXX] 1829 4 MS-Register [RFCXXXX] 1830 5 MS-Release [RFCXXXX] 1831 6 Network Acceess Identifier [RFCXXXX] 1832 7 Geo Coordinates [RFCXXXX] 1833 8 DHCP Unique Identifier (DUID) [RFCXXXX] 1834 9-252 Unassigned 1835 253-254 Experimental [RFCXXXX] 1836 255 Reserved [RFCXXXX] 1838 Figure 17: OMNI Option Sub-Type Values 1840 20. Security Considerations 1842 Security considerations for IPv6 [RFC8200] and IPv6 Neighbor 1843 Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD 1844 include Nonce and Timestamp options [RFC3971] when transaction 1845 confirmation and/or time synchronization is needed. 1847 OMNI interfaces configured over secured ANET interfaces inherit the 1848 physical and/or link-layer security properties of the connected 1849 ANETs. OMNI interfaces configured over open INET interfaces can use 1850 symmetric securing services such as VPNs or can by some other means 1851 establish a direct link. When a VPN or direct link may be 1852 impractical, however, an asymmetric security service such as SEcure 1853 Neighbor Discovery (SEND) [RFC3971] with Cryptographically Generated 1854 Addresses (CGAs) [RFC3972], the authentication option specified in 1855 [RFC4380] or other protocol control message security mechanisms may 1856 be necessary. While the OMNI link protects control plane messaging, 1857 applications must still employ end-to-end transport- or higher-layer 1858 security services to protect the data plane. 1860 The Mobility Service MUST provide strong network layer security for 1861 control plane messages and forwading path integrity for data plane 1862 messages. In one example, the AERO service 1863 [I-D.templin-intarea-6706bis] constructs a spanning tree between 1864 mobility service elements and secures the links in the spanning tree 1865 with network layer security mechanisms such as IPsec [RFC4301] or 1866 Wireguard. Control plane messages are then constrained to travel 1867 only over the secured spanning tree paths and are therefore protected 1868 from attack or eavesdropping. Since data plane messages can travel 1869 over route optimized paths that do not strictly follow the spanning 1870 tree, however, end-to-end transport- or higher-layer security 1871 services are still required. 1873 Security considerations for specific access network interface types 1874 are covered under the corresponding IP-over-(foo) specification 1875 (e.g., [RFC2464], [RFC2492], etc.). 1877 Security considerations for IPv6 fragmentation and reassembly are 1878 discussed in Section 5.1. 1880 21. Implementation Status 1882 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 1883 internal release, while Draft -30 is scheduled for implementation in 1884 the soon-to-be-tagged AERO/OMNI 3.0.1 internal release. First public 1885 release expected before the end of 2020. 1887 22. Acknowledgements 1889 The first version of this document was prepared per the consensus 1890 decision at the 7th Conference of the International Civil Aviation 1891 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 1892 2019. Consensus to take the document forward to the IETF was reached 1893 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 1894 Attendees and contributors included: Guray Acar, Danny Bharj, 1895 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 1896 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 1897 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 1898 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 1899 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 1900 Fryderyk Wrobel and Dongsong Zeng. 1902 The following individuals are acknowledged for their useful comments: 1903 Michael Matyas, Madhu Niraula, Michael Richardson, Greg Saccone, 1904 Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal 1905 Skorepa are recognized for their many helpful ideas and suggestions. 1906 Madhuri Madhava Badgandi, Katherine Tran, and Vijayasarathy 1907 Rajagopalan are acknowledged for their hard work on the 1908 implementation and insights that led to improvements to the spec. 1910 This work is aligned with the NASA Safe Autonomous Systems Operation 1911 (SASO) program under NASA contract number NNA16BD84C. 1913 This work is aligned with the FAA as per the SE2025 contract number 1914 DTFAWA-15-D-00030. 1916 23. References 1918 23.1. Normative References 1920 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1921 Requirement Levels", BCP 14, RFC 2119, 1922 DOI 10.17487/RFC2119, March 1997, 1923 . 1925 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1926 "Definition of the Differentiated Services Field (DS 1927 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1928 DOI 10.17487/RFC2474, December 1998, 1929 . 1931 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1932 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1933 DOI 10.17487/RFC3971, March 2005, 1934 . 1936 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1937 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1938 . 1940 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1941 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1942 November 2005, . 1944 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1945 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 1946 . 1948 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1949 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1950 2006, . 1952 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1953 Control Message Protocol (ICMPv6) for the Internet 1954 Protocol Version 6 (IPv6) Specification", STD 89, 1955 RFC 4443, DOI 10.17487/RFC4443, March 2006, 1956 . 1958 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 1959 ICMPv6, UDP, and TCP Headers", RFC 4727, 1960 DOI 10.17487/RFC4727, November 2006, 1961 . 1963 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1964 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1965 DOI 10.17487/RFC4861, September 2007, 1966 . 1968 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1969 Address Autoconfiguration", RFC 4862, 1970 DOI 10.17487/RFC4862, September 2007, 1971 . 1973 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 1974 "Traffic Selectors for Flow Bindings", RFC 6088, 1975 DOI 10.17487/RFC6088, January 2011, 1976 . 1978 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1979 Hosts in a Multi-Prefix Network", RFC 8028, 1980 DOI 10.17487/RFC8028, November 2016, 1981 . 1983 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1984 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1985 May 2017, . 1987 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1988 (IPv6) Specification", STD 86, RFC 8200, 1989 DOI 10.17487/RFC8200, July 2017, 1990 . 1992 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 1993 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 1994 DOI 10.17487/RFC8201, July 2017, 1995 . 1997 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1998 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1999 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2000 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2001 . 2003 23.2. Informative References 2005 [I-D.ietf-intarea-tunnels] 2006 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2007 Architecture", draft-ietf-intarea-tunnels-10 (work in 2008 progress), September 2019. 2010 [I-D.templin-6man-dhcpv6-ndopt] 2011 Templin, F., "A Unified Stateful/Stateless Configuration 2012 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2013 (work in progress), June 2020. 2015 [I-D.templin-intarea-6706bis] 2016 Templin, F., "Asymmetric Extended Route Optimization 2017 (AERO)", draft-templin-intarea-6706bis-60 (work in 2018 progress), September 2020. 2020 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2021 Communication Layers", STD 3, RFC 1122, 2022 DOI 10.17487/RFC1122, October 1989, 2023 . 2025 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2026 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2027 . 2029 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2030 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2031 . 2033 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2034 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2035 . 2037 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2038 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2039 December 1998, . 2041 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2042 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2043 . 2045 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2046 Domains without Explicit Tunnels", RFC 2529, 2047 DOI 10.17487/RFC2529, March 1999, 2048 . 2050 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2051 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2052 . 2054 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2055 Considered Useful", BCP 82, RFC 3692, 2056 DOI 10.17487/RFC3692, January 2004, 2057 . 2059 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2060 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2061 DOI 10.17487/RFC3810, June 2004, 2062 . 2064 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2065 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2066 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2067 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2068 . 2070 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2071 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2072 2004, . 2074 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2075 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2076 December 2005, . 2078 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2079 Network Address Translations (NATs)", RFC 4380, 2080 DOI 10.17487/RFC4380, February 2006, 2081 . 2083 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2084 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2085 2006, . 2087 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2088 "Considerations for Internet Group Management Protocol 2089 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2090 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2091 . 2093 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2094 "Internet Group Management Protocol (IGMP) / Multicast 2095 Listener Discovery (MLD)-Based Multicast Forwarding 2096 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2097 August 2006, . 2099 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2100 Errors at High Data Rates", RFC 4963, 2101 DOI 10.17487/RFC4963, July 2007, 2102 . 2104 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2105 Advertisement Flags Option", RFC 5175, 2106 DOI 10.17487/RFC5175, March 2008, 2107 . 2109 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2110 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2111 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2112 . 2114 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2115 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2116 DOI 10.17487/RFC5214, March 2008, 2117 . 2119 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2120 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2121 . 2123 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2124 Version 3 for IPv4 and IPv6", RFC 5798, 2125 DOI 10.17487/RFC5798, March 2010, 2126 . 2128 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2129 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2130 . 2132 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2133 DOI 10.17487/RFC6081, January 2011, 2134 . 2136 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2137 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2138 DOI 10.17487/RFC6355, August 2011, 2139 . 2141 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2142 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2143 2012, . 2145 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2146 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2147 DOI 10.17487/RFC7084, November 2013, 2148 . 2150 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2151 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2152 Boundary in IPv6 Addressing", RFC 7421, 2153 DOI 10.17487/RFC7421, January 2015, 2154 . 2156 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2157 DOI 10.17487/RFC7542, May 2015, 2158 . 2160 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2161 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2162 February 2016, . 2164 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2165 Support for IP Hosts with Multi-Access Support", RFC 7847, 2166 DOI 10.17487/RFC7847, May 2016, 2167 . 2169 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2170 Writing an IANA Considerations Section in RFCs", BCP 26, 2171 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2172 . 2174 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2175 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2176 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2177 July 2018, . 2179 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2180 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2181 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2182 . 2184 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2185 and F. Gont, "IP Fragmentation Considered Fragile", 2186 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2187 . 2189 Appendix A. Interface Attribute Heuristic Bitmap Encoding 2191 Adaptation of the OMNI option Interface Attributes Heuristic Bitmap 2192 encoding to specific Internetworks such as the Aeronautical 2193 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2194 may include link selection preferences based on other traffic 2195 classifiers (e.g., transport port numbers, etc.) in addition to the 2196 existing DSCP-based preferences. Nodes on specific Internetworks 2197 maintain a map of traffic classifiers to additional P[*] preference 2198 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2199 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2201 Implementations use Simplex or Indexed encoding formats for P[*] 2202 encoding in order to encode a given set of traffic classifiers in the 2203 most efficient way. Some use cases may be more efficiently coded 2204 using Simplex form, while others may be more efficient using Indexed. 2205 Once a format is selected for preparation of a single Interface 2206 Attribute the same format must be used for the entire Interface 2207 Attribute sub-option. Different sub-options may use different 2208 formats. 2210 The following figures show coding examples for various Simplex and 2211 Indexed formats: 2213 0 1 2 3 2214 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 2215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2216 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2218 | Provider ID | Link |R| APS | Bitmap(0)=0xff|P00|P01|P02|P03| 2219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2220 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2222 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2224 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2226 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2228 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2231 Figure 18: Example 1: Dense Simplex Encoding 2233 0 1 2 3 2234 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 2235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2236 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2238 | Provider ID | Link |R| APS | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2240 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2242 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2244 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2246 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2248 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2250 |Bitmap(10)=0x00| ... 2251 +-+-+-+-+-+-+-+-+-+-+- 2253 Figure 19: Example 2: Sparse Simplex Encoding 2255 0 1 2 3 2256 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 2257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2258 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2260 | Provider ID | Link |R| APS | Index = 0x00 | Bitmap = 0x80 | 2261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2262 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2264 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2266 | Bitmap = 0x01 |796|797|798|799| ... 2267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2269 Figure 20: Example 3: Indexed Encoding 2271 Appendix B. VDL Mode 2 Considerations 2273 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2274 (VDLM2) that specifies an essential radio frequency data link service 2275 for aircraft and ground stations in worldwide civil aviation air 2276 traffic management. The VDLM2 link type is "multicast capable" 2277 [RFC4861], but with considerable differences from common multicast 2278 links such as Ethernet and IEEE 802.11. 2280 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2281 magnitude less than most modern wireless networking gear. Second, 2282 due to the low available link bandwidth only VDLM2 ground stations 2283 (i.e., and not aircraft) are permitted to send broadcasts, and even 2284 so only as compact layer 2 "beacons". Third, aircraft employ the 2285 services of ground stations by performing unicast RS/RA exchanges 2286 upon receipt of beacons instead of listening for multicast RA 2287 messages and/or sending multicast RS messages. 2289 This beacon-oriented unicast RS/RA approach is necessary to conserve 2290 the already-scarce available link bandwidth. Moreover, since the 2291 numbers of beaconing ground stations operating within a given spatial 2292 range must be kept as sparse as possible, it would not be feasible to 2293 have different classes of ground stations within the same region 2294 observing different protocols. It is therefore highly desirable that 2295 all ground stations observe a common language of RS/RA as specified 2296 in this document. 2298 Note that links of this nature may benefit from compression 2299 techniques that reduce the bandwidth necessary for conveying the same 2300 amount of data. The IETF lpwan working group is considering possible 2301 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2303 Appendix C. MN / AR Isolation Through L2 Address Mapping 2305 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2306 unicast link-scoped IPv6 destination address. However, IPv6 ND 2307 messaging should be coordinated between the MN and AR only without 2308 invoking other nodes on the ANET. This implies that MN / AR control 2309 messaging should be isolated and not overheard by other nodes on the 2310 link. 2312 To support MN / AR isolation on some ANET links, ARs can maintain an 2313 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2314 ANETs, this specification reserves one Ethernet unicast address TBD2 2315 (see: Section 19). For non-Ethernet statically-addressed ANETs, 2316 MSADDR is reserved per the assigned numbers authority for the ANET 2317 addressing space. For still other ANETs, MSADDR may be dynamically 2318 discovered through other means, e.g., L2 beacons. 2320 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2321 both multicast and unicast) to MSADDR instead of to an ordinary 2322 unicast or multicast L2 address. In this way, all of the MN's IPv6 2323 ND messages will be received by ARs that are configured to accept 2324 packets destined to MSADDR. Note that multiple ARs on the link could 2325 be configured to accept packets destined to MSADDR, e.g., as a basis 2326 for supporting redundancy. 2328 Therefore, ARs must accept and process packets destined to MSADDR, 2329 while all other devices must not process packets destined to MSADDR. 2330 This model has well-established operational experience in Proxy 2331 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2333 Appendix D. Change Log 2335 << RFC Editor - remove prior to publication >> 2337 Differences from draft-templin-6man-omni-interface-31 to draft- 2338 templin-6man-omni-interface-32: 2340 o MTU 2342 o Support for multi-hop ANETS such as ISATAP. 2344 Differences from draft-templin-6man-omni-interface-29 to draft- 2345 templin-6man-omni-interface-30: 2347 o Moved link-layer addressing information into the OMNI option on a 2348 per-ifIndex basis 2350 o Renamed "ifIndex-tuple" to "Interface Attributes" 2352 Differences from draft-templin-6man-omni-interface-27 to draft- 2353 templin-6man-omni-interface-28: 2355 o Updates based on implementation expereince. 2357 Differences from draft-templin-6man-omni-interface-25 to draft- 2358 templin-6man-omni-interface-26: 2360 o Further clarification on "aggregate" RA messages. 2362 o Expanded Security Considerations to discuss expectations for 2363 security in the Mobility Service. 2365 Differences from draft-templin-6man-omni-interface-20 to draft- 2366 templin-6man-omni-interface-21: 2368 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2369 (PBM). 2371 Differences from draft-templin-6man-omni-interface-18 to draft- 2372 templin-6man-omni-interface-19: 2374 o SEND/CGA. 2376 Differences from draft-templin-6man-omni-interface-17 to draft- 2377 templin-6man-omni-interface-18: 2379 o Teredo 2381 Differences from draft-templin-6man-omni-interface-14 to draft- 2382 templin-6man-omni-interface-15: 2384 o Prefix length discussions removed. 2386 Differences from draft-templin-6man-omni-interface-12 to draft- 2387 templin-6man-omni-interface-13: 2389 o Teredo 2391 Differences from draft-templin-6man-omni-interface-11 to draft- 2392 templin-6man-omni-interface-12: 2394 o Major simplifications and clarifications on MTU and fragmentation. 2396 o Document now updates RFC4443 and RFC8201. 2398 Differences from draft-templin-6man-omni-interface-10 to draft- 2399 templin-6man-omni-interface-11: 2401 o Removed /64 assumption, resulting in new OMNI address format. 2403 Differences from draft-templin-6man-omni-interface-07 to draft- 2404 templin-6man-omni-interface-08: 2406 o OMNI MNs in the open Internet 2408 Differences from draft-templin-6man-omni-interface-06 to draft- 2409 templin-6man-omni-interface-07: 2411 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2412 L2 addressing. 2414 o Expanded "Transition Considerations". 2416 Differences from draft-templin-6man-omni-interface-05 to draft- 2417 templin-6man-omni-interface-06: 2419 o Brought back OMNI option "R" flag, and discussed its use. 2421 Differences from draft-templin-6man-omni-interface-04 to draft- 2422 templin-6man-omni-interface-05: 2424 o Transition considerations, and overhaul of RS/RA addressing with 2425 the inclusion of MSE addresses within the OMNI option instead of 2426 as RS/RA addresses (developed under FAA SE2025 contract number 2427 DTFAWA-15-D-00030). 2429 Differences from draft-templin-6man-omni-interface-02 to draft- 2430 templin-6man-omni-interface-03: 2432 o Added "advisory PTB messages" under FAA SE2025 contract number 2433 DTFAWA-15-D-00030. 2435 Differences from draft-templin-6man-omni-interface-01 to draft- 2436 templin-6man-omni-interface-02: 2438 o Removed "Primary" flag and supporting text. 2440 o Clarified that "Router Lifetime" applies to each ANET interface 2441 independently, and that the union of all ANET interface Router 2442 Lifetimes determines MSE lifetime. 2444 Differences from draft-templin-6man-omni-interface-00 to draft- 2445 templin-6man-omni-interface-01: 2447 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2448 for future use (most likely as "pseudo-multicast"). 2450 o Non-normative discussion of alternate OMNI LLA construction form 2451 made possible if the 64-bit assumption were relaxed. 2453 First draft version (draft-templin-atn-aero-interface-00): 2455 o Draft based on consensus decision of ICAO Working Group I Mobility 2456 Subgroup March 22, 2019. 2458 Authors' Addresses 2460 Fred L. Templin (editor) 2461 The Boeing Company 2462 P.O. Box 3707 2463 Seattle, WA 98124 2464 USA 2466 Email: fltemplin@acm.org 2467 Tony Whyman 2468 MWA Ltd c/o Inmarsat Global Ltd 2469 99 City Road 2470 London EC1Y 1AX 2471 England 2473 Email: tony.whyman@mccallumwhyman.com