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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin, Ed. 3 Internet-Draft The Boeing Company 4 Updates: rfc1191, rfc4443, rfc8201 (if A. Whyman 5 approved) MWA Ltd c/o Inmarsat Global Ltd 6 Intended status: Standards Track December 28, 2020 7 Expires: July 1, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-65 13 Abstract 15 Mobile nodes (e.g., aircraft of various configurations, terrestrial 16 vehicles, seagoing vessels, enterprise wireless devices, etc.) 17 communicate with networked correspondents over multiple access 18 network data links and configure mobile routers to connect end user 19 networks. A multilink interface specification is therefore needed 20 for coordination with the network-based mobility service. This 21 document specifies the transmission of IP packets over Overlay 22 Multilink Network (OMNI) Interfaces. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on July 1, 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 13 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 18 64 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 19 65 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 19 66 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 21 67 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 22 68 10. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 23 69 10.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 24 70 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 25 71 10.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 26 72 10.1.3. Interface Attributes . . . . . . . . . . . . . . . . 26 73 10.1.4. Traffic Selector . . . . . . . . . . . . . . . . . . 30 74 10.1.5. MS-Register . . . . . . . . . . . . . . . . . . . . 31 75 10.1.6. MS-Release . . . . . . . . . . . . . . . . . . . . . 31 76 10.1.7. Network Access Identifier (NAI) . . . . . . . . . . 32 77 10.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 33 78 10.1.9. DHCP Unique Identifier (DUID) . . . . . . . . . . . 33 79 10.1.10. DHCPv6 Message . . . . . . . . . . . . . . . . . . . 34 80 11. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 34 81 12. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 35 82 12.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 35 83 12.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 36 84 13. Router Discovery and Prefix Registration . . . . . . . . . . 36 85 13.1. Router Discovery in IP Multihop and IPv4-Only Networks . 40 86 13.2. MS-Register and MS-Release List Processing . . . . . . . 42 87 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 43 88 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 44 89 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 45 90 16. Detecting and Responding to MSE Failures . . . . . . . . . . 45 91 17. Transition Considerations . . . . . . . . . . . . . . . . . . 46 92 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 46 93 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 47 94 20. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 95 21. Security Considerations . . . . . . . . . . . . . . . . . . . 49 96 22. Implementation Status . . . . . . . . . . . . . . . . . . . . 49 97 23. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50 98 24. References . . . . . . . . . . . . . . . . . . . . . . . . . 50 99 24.1. Normative References . . . . . . . . . . . . . . . . . . 50 100 24.2. Informative References . . . . . . . . . . . . . . . . . 52 101 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 58 102 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 60 103 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 61 104 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 61 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 64 107 1. Introduction 109 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 110 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 111 pedestrians with cellphones, etc.) often have multiple interface 112 connections to wireless and/or wired-link data links used for 113 communicating with networked correspondents. These data links may 114 have diverse performance, cost and availability properties that can 115 change dynamically according to mobility patterns, flight phases, 116 proximity to infrastructure, etc. MNs coordinate their data links in 117 a discipline known as "multilink", in which a single virtual 118 interface is configured over the node's underlying interface 119 connections to the data links. 121 The MN configures a virtual interface (termed the "Overlay Multilink 122 Network (OMNI) interface") as a thin layer over the underlying 123 interfaces. The OMNI interface is therefore the only interface 124 abstraction exposed to the IP layer and behaves according to the Non- 125 Broadcast, Multiple Access (NBMA) interface principle, while 126 underlying interfaces appear as link layer communication channels in 127 the architecture. The OMNI interface connects to a virtual overlay 128 service known as the "OMNI link". The OMNI link spans one or more 129 Internetworks that may include private-use infrastructures and/or the 130 global public Internet itself. 132 Each MN receives a Mobile Network Prefix (MNP) for numbering 133 downstream-attached End User Networks (EUNs) independently of the 134 access network data links selected for data transport. The MN 135 performs router discovery over the OMNI interface (i.e., similar to 136 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 137 behalf of its EUNs. The router discovery process is iterated over 138 each of the OMNI interface's underlying interfaces in order to 139 register per-link parameters (see Section 13). 141 The OMNI interface provides a multilink nexus for exchanging inbound 142 and outbound traffic via the correct underlying interface(s). The IP 143 layer sees the OMNI interface as a point of connection to the OMNI 144 link. Each OMNI link has one or more associated Mobility Service 145 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 146 prefixes from which OMNI link MNPs are derived. If there are 147 multiple OMNI links, the IPv6 layer will see multiple OMNI 148 interfaces. 150 MNs may connect to multiple distinct OMNI links by configuring 151 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 152 interface is configured over a set of underlying interfaces and 153 provides a nexus for Safety-Based Multilink (SBM) operation. Each 154 OMNI SBM "domain" configures a common ULA prefix [ULA]::/48, and each 155 OMNI link within the domain configures a unique 16-bit Subnet ID '*' 156 to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 157 layer applies SBM routing to select an OMNI interface, which then 158 applies Performance-Based Multilink (PBM) to select the correct 159 underlying interface. Applications can apply Segment Routing 160 [RFC8402] to select independent SBM topologies for fault tolerance. 162 The OMNI interface interacts with a network-based Mobility Service 163 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 164 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 165 track MN movements and represent their MNPs in a global routing or 166 mapping system. 168 Many OMNI use cases are currently under active consideration. In 169 particular, the International Civil Aviation Organization (ICAO) 170 Working Group-I Mobility Subgroup is developing a future Aeronautical 171 Telecommunications Network with Internet Protocol Services (ATN/IPS) 172 and has issued a liaison statement requesting IETF adoption [ATN] in 173 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 174 in Vehicular Environments (ipwave) working group has further included 175 problem statement and use case analysis for OMNI in a document now in 176 AD evaluation for RFC publication 177 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 178 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 179 programs that examine commercial aviation, Urban Air Mobility (UAM) 180 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 181 represent another large class of potential OMNI users. 183 This document specifies the transmission of IP packets and MN/MS 184 control messages over OMNI interfaces. The OMNI interface supports 185 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 186 as the network layer in the data plane, while using IPv6 ND messaging 187 as the control plane independently of the data plane IP protocol(s). 188 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 189 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 190 discussed in the following sections. 192 2. Terminology 194 The terminology in the normative references applies; especially, the 195 terms "link" and "interface" are the same as defined in the IPv6 196 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 197 Additionally, this document assumes the following IPv6 ND message 198 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 199 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 201 The Protocol Constants defined in Section 10 of [RFC4861] are used in 202 their same format and meaning in this document. The terms "All- 203 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 204 are the same as defined in [RFC4291] (with Link-Local scope assumed). 206 The term "IP" is used to refer collectively to either Internet 207 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 208 specification at the layer in question applies equally to either 209 version. 211 The following terms are defined within the scope of this document: 213 Mobile Node (MN) 214 an end system with a mobile router having multiple distinct 215 upstream data link connections that are grouped together in one or 216 more logical units. The MN's data link connection parameters can 217 change over time due to, e.g., node mobility, link quality, etc. 218 The MN further connects a downstream-attached End User Network 219 (EUN). The term MN used here is distinct from uses in other 220 documents, and does not imply a particular mobility protocol. 222 End User Network (EUN) 223 a simple or complex downstream-attached mobile network that 224 travels with the MN as a single logical unit. The IP addresses 225 assigned to EUN devices remain stable even if the MN's upstream 226 data link connections change. 228 Mobility Service (MS) 229 a mobile routing service that tracks MN movements and ensures that 230 MNs remain continuously reachable even across mobility events. 231 Specific MS details are out of scope for this document. 233 Mobility Service Endpoint (MSE) 234 an entity in the MS (either singular or aggregate) that 235 coordinates the mobility events of one or more MN. 237 Mobility Service Prefix (MSP) 238 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 239 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 240 from which more-specific Mobile Network Prefixes (MNPs) are 241 delegated. OMNI link administrators typically obtain MSPs from an 242 Internet address registry, however private-use prefixes can 243 alternatively be used subject to certain limitations (see: 244 Section 9). OMNI links that connect to the global Internet 245 advertise their MSPs to their interdomain routing peers. 247 Mobile Network Prefix (MNP) 248 a longer IP prefix delegated from an MSP (e.g., 249 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 250 MNs sub-delegate the MNP to devices located in EUNs. 252 Access Network (ANET) 253 a data link service network (e.g., an aviation radio access 254 network, satellite service provider network, cellular operator 255 network, wifi network, etc.) that connects MNs. Physical and/or 256 data link level security is assumed, and sometimes referred to as 257 "protected spectrum". Private enterprise networks and ground 258 domain aviation service networks may provide multiple secured IP 259 hops between the MN's point of connection and the nearest Access 260 Router. 262 Access Router (AR) 263 a router in the ANET for connecting MNs to correspondents in 264 outside Internetworks. The AR may be located on the same physical 265 link as the MN, or may be located multiple IP hops away. In the 266 latter case, the MN uses encapsulation to communicate with the AR 267 as though it were on the same physical link. 269 ANET interface 270 a MN's attachment to a link in an ANET. 272 Internetwork (INET) 273 a connected network region with a coherent IP addressing plan that 274 provides transit forwarding services between ANETs and nodes that 275 connect directly to the open INET via unprotected media. No 276 physical and/or data link level security is assumed, therefore 277 security must be applied by upper layers. The global public 278 Internet itself is an example. 280 INET interface 281 a node's attachment to a link in an INET. 283 *NET 284 a "wildcard" term used when a given specification applies equally 285 to both ANET and INET cases. 287 OMNI link 288 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 289 over one or more INETs and their connected ANETs. An OMNI link 290 can comprise multiple INET segments joined by bridges the same as 291 for any link; the addressing plans in each segment may be mutually 292 exclusive and managed by different administrative entities. 294 OMNI interface 295 a node's attachment to an OMNI link, and configured over one or 296 more underlying *NET interfaces. If there are multiple OMNI links 297 in an OMNI domain, a separate OMNI interface is configured for 298 each link. 300 OMNI Adaptation Layer (OAL) 301 an OMNI interface process whereby packets admitted into the 302 interface are wrapped in a mid-layer IPv6 header and fragmented/ 303 reassembled if necessary to support the OMNI link Maximum 304 Transmission Unit (MTU). The OAL is also responsible for 305 generating MTU-related control messages as necessary, and for 306 providing addressing context for spanning multiple segments of a 307 bridged OMNI link. 309 OMNI Option 310 an IPv6 Neighbor Discovery option providing multilink parameters 311 for the OMNI interface as specified in Section 10. 313 Mobile Network Prefix Link Local Address (MNP-LLA) 314 an IPv6 Link Local Address that embeds the most significant 64 315 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 316 Section 7. 318 Mobile Network Prefix Unique Local Address (MNP-ULA) 319 an IPv6 Unique-Local Address derived from an MNP-LLA. 321 Administrative Link Local Address (ADM-LLA) 322 an IPv6 Link Local Address that embeds a 32-bit administratively- 323 assigned identification value in the lower 32 bits of fe80::/96, 324 as specified in Section 7. 326 Administrative Unique Local Address (ADM-ULA) 327 an IPv6 Unique-Local Address derived from an ADM-LLA. 329 Multilink 330 an OMNI interface's manner of managing diverse underlying 331 interface connections to data links as a single logical unit. The 332 OMNI interface provides a single unified interface to upper 333 layers, while underlying interface selections are performed on a 334 per-packet basis considering factors such as DSCP, flow label, 335 application policy, signal quality, cost, etc. Multilinking 336 decisions are coordinated in both the outbound (i.e. MN to 337 correspondent) and inbound (i.e., correspondent to MN) directions. 339 L2 340 The second layer in the OSI network model. Also known as "layer- 341 2", "link-layer", "sub-IP layer", "data link layer", etc. 343 L3 344 The third layer in the OSI network model. Also known as "layer- 345 3", "network-layer", "IP layer", etc. 347 underlying interface 348 a *NET interface over which an OMNI interface is configured. The 349 OMNI interface is seen as a L3 interface by the IP layer, and each 350 underlying interface is seen as a L2 interface by the OMNI 351 interface. The underlying interface either connects directly to 352 the physical communications media or coordinates with another node 353 where the physical media is hosted. 355 Mobility Service Identification (MSID) 356 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 357 (see: Section 7). IDs are assigned according to MS-specific 358 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 360 Safety-Based Multilink (SBM) 361 A means for ensuring fault tolerance through redundancy by 362 connecting multiple affiliated OMNI interfaces to independent 363 routing topologies (i.e., multiple independent OMNI links). 365 Performance Based Multilink (PBM) 366 A means for selecting underlying interface(s) for packet 367 transmission and reception within a single OMNI interface. 369 OMNI Domain 370 The set of all SBM/PBM OMNI links that collectively provides 371 services for a common set of MSPs. Each OMNI domain consists of a 372 set of affiliated OMNI links that all configure the same ::/48 ULA 373 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 375 3. Requirements 377 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 378 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 379 "OPTIONAL" in this document are to be interpreted as described in BCP 380 14 [RFC2119][RFC8174] when, and only when, they appear in all 381 capitals, as shown here. 383 OMNI links maintain a constant value "MAX_MSID" selected to provide 384 MNs with an acceptable level of MSE redundancy while minimizing 385 control message amplification. It is RECOMMENDED that MAX_MSID be 386 set to the default value 5; if a different value is chosen, it should 387 be set uniformly by all nodes on the OMNI link. 389 An implementation is not required to internally use the architectural 390 constructs described here so long as its external behavior is 391 consistent with that described in this document. 393 4. Overlay Multilink Network (OMNI) Interface Model 395 An OMNI interface is a MN virtual interface configured over one or 396 more underlying interfaces, which may be physical (e.g., an 397 aeronautical radio link) or virtual (e.g., an Internet or higher- 398 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 399 with the MS through IPv6 ND message exchanges. The MN uses the MNP 400 to construct a unique Link-Local Address (MNP-LLA) through the 401 algorithmic derivation specified in Section 7 and assigns the LLA to 402 the OMNI interface. 404 The OMNI interface architectural layering model is the same as in 405 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 406 therefore sees the OMNI interface as a single L3 interface with 407 multiple underlying interfaces that appear as L2 communication 408 channels in the architecture. 410 +----------------------------+ 411 | Upper Layer Protocol | 412 Session-to-IP +---->| | 413 Address Binding | +----------------------------+ 414 +---->| IP (L3) | 415 IP Address +---->| | 416 Binding | +----------------------------+ 417 +---->| OMNI Interface | 418 Logical-to- +---->| (LLA) | 419 Physical | +----------------------------+ 420 Interface +---->| L2 | L2 | | L2 | 421 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 422 +------+------+ +------+ 423 | L1 | L1 | | L1 | 424 | | | | | 425 +------+------+ +------+ 427 Figure 1: OMNI Interface Architectural Layering Model 429 Each underlying interface provides an L2/L1 abstraction according to 430 one of the following models: 432 o INET interfaces connect to an INET either natively or through one 433 or several IPv4 Network Address Translators (NATs). Native INET 434 interfaces have global IP addresses that are reachable from any 435 INET correspondent. NATed INET interfaces typically have private 436 IP addresses and connect to a private network behind one or more 437 NATs that provide INET access. 439 o ANET interfaces connect to a protected ANET that is separated from 440 the open INET by an AR acting as a proxy. The ANET interface may 441 be either on the same L2 link segment as the AR, or separated from 442 the AR by multiple IP hops. 444 o VPNed interfaces use security encapsulation over a *NET to a 445 Virtual Private Network (VPN) gateway. Other than the link-layer 446 encapsulation format, VPNed interfaces behave the same as for 447 Direct interfaces. 449 o Direct (aka "point-to-point") interfaces connect directly to a 450 peer without crossing any *NET paths. An example is a line-of- 451 sight link between a remote pilot and an unmanned aircraft. 453 The OMNI virtual interface model gives rise to a number of 454 opportunities: 456 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 457 Address Detection (DAD) or Multicast Listener Discovery (MLD) 458 messaging is necessary. 460 o since Temporary LLAs are statistically unique, they can be used 461 without DAD for short-term purposes, e.g. until an MNP-LLA is 462 obtained. 464 o *NET interfaces on the same L2 link segment as an AR do not 465 require any L3 addresses (i.e., not even link-local) in 466 environments where communications are coordinated entirely over 467 the OMNI interface. (An alternative would be to also assign the 468 same LLA to all *NET interfaces.) 470 o as underlying interface properties change (e.g., link quality, 471 cost, availability, etc.), any active interface can be used to 472 update the profiles of multiple additional interfaces in a single 473 message. This allows for timely adaptation and service continuity 474 under dynamically changing conditions. 476 o coordinating underlying interfaces in this way allows them to be 477 represented in a unified MS profile with provisions for mobility 478 and multilink operations. 480 o exposing a single virtual interface abstraction to the IPv6 layer 481 allows for multilink operation (including QoS based link 482 selection, packet replication, load balancing, etc.) at L2 while 483 still permitting L3 traffic shaping based on, e.g., DSCP, flow 484 label, etc. 486 o the OMNI interface allows inter-INET traversal when nodes located 487 in different INETs need to communicate with one another. This 488 mode of operation would not be possible via direct communications 489 over the underlying interfaces themselves. 491 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 492 lossless and adaptive path MTU mitigations not available for 493 communications directly over the underlying interfaces themselves. 495 o L3 sees the OMNI interface as a point of connection to the OMNI 496 link; if there are multiple OMNI links (i.e., multiple MS's), L3 497 will see multiple OMNI interfaces. 499 o Multiple independent OMNI interfaces can be used for increased 500 fault tolerance through Safety-Based Multilink (SBM), with 501 Performance-Based Multilink (PBM) applied within each interface. 503 Other opportunities are discussed in [RFC7847]. Note that even when 504 the OMNI virtual interface is present, applications can still access 505 underlying interfaces either through the network protocol stack using 506 an Internet socket or directly using a raw socket. This allows for 507 intra-network (or point-to-point) communications without invoking the 508 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 509 is configured over an underlying IPv4 interface, applications can 510 still invoke IPv4 intra-network communications as long as the 511 communicating endpoints are not subject to mobility dynamics. 512 However, the opportunities discussed above are not available when the 513 architectural layering is bypassed in this way. 515 Figure 2 depicts the architectural model for a MN with an attached 516 EUN connecting to the MS via multiple independent *NETs. When an 517 underlying interface becomes active, the MN's OMNI interface sends 518 IPv6 ND messages without encapsulation if the first-hop Access Router 519 (AR) is on the same underlying link; otherwise, the interface uses 520 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 521 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 522 then coordinates with an INET Mobility Service Endpoint (MSE#1, 523 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 524 The Hop Limit in IPv6 ND messages is not decremented due to 525 encapsulation; hence, the OMNI interface appears to be attached to an 526 ordinary link. 528 +--------------+ (:::)-. 529 | MN |<-->.-(::EUN:::) 530 +--------------+ `-(::::)-' 531 |OMNI interface| 532 +----+----+----+ 533 +--------|IF#1|IF#2|IF#n|------ + 534 / +----+----+----+ \ 535 / | \ 536 / | \ 537 v v v 538 (:::)-. (:::)-. (:::)-. 539 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 540 `-(::::)-' `-(::::)-' `-(::::)-' 541 +----+ +----+ +----+ 542 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 543 . +-|--+ +-|--+ +-|--+ . 544 . | | | 545 . v v v . 546 . <----- INET Encapsulation -----> . 547 . . 548 . +-----+ (:::)-. . 549 . |MSE#2| .-(::::::::) +-----+ . 550 . +-----+ .-(::: INET :::)-. |MSE#m| . 551 . (::::: Routing ::::) +-----+ . 552 . `-(::: System :::)-' . 553 . +-----+ `-(:::::::-' . 554 . |MSE#1| +-----+ +-----+ . 555 . +-----+ |MSE#3| |MSE#4| . 556 . +-----+ +-----+ . 557 . . 558 . . 559 . <----- Worldwide Connected Internetwork ----> . 560 ........................................................... 562 Figure 2: MN/MS Coordination via Multiple *NETs 564 After the initial IPv6 ND message exchange, the MN (and/or any nodes 565 on its attached EUNs) can send and receive IP data packets over the 566 OMNI interface. OMNI interface multilink services will forward the 567 packets via ARs in the correct underlying *NETs. The AR encapsulates 568 the packets according to the capabilities provided by the MS and 569 forwards them to the next hop within the worldwide connected 570 Internetwork via optimal routes. 572 OMNI links span one or more underlying Internetwork via the OMNI 573 Adaptation Layer (OAL) which is based on a mid-layer overlay 574 encapsulation using [RFC2473]. Each OMNI link corresponds to a 575 different overlay (differentiated by an address codepoint) which may 576 be carried over a completely separate underlying topology. Each MN 577 can facilitate SBM by connecting to multiple OMNI links using a 578 distinct OMNI interface for each link. 580 Note: OMNI interface underlying interfaces often connect directly to 581 physical media on the local platform (e.g., a laptop computer with 582 WiFi, etc.), but in some configurations the physical media may be 583 hosted on a separate Local Area Network (LAN) node. In that case, 584 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 585 tunnel (at a layer below the underlying interface) to the node 586 hosting the physical media. The OMNI interface may also apply 587 encapsulation at a layer above the underlying interface such that 588 packets would appear "double-encapsulated" on the LAN; the node 589 hosting the physical media in turn removes the LAN encapsulation 590 prior to transmission or inserts it following reception. Finally, 591 the underlying interface must monitor the node hosting the physical 592 media (e.g., through periodic keepalives) so that it can convey 593 up/down/status information to the OMNI interface. 595 5. The OMNI Adaptation Layer (OAL) 597 The OMNI interface observes the link nature of tunnels, including the 598 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 599 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 600 The OMNI interface is configured over one or more underlying 601 interfaces that may have diverse MTUs. OMNI interfaces accommodate 602 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 603 discussed in this section. 605 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 606 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 607 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 608 permitted to perform network fragmentation even though the 609 destination is required to reassemble more. The network therefore 610 MUST forward packets of at least 1280 bytes without generating an 611 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 612 [RFC8201]. (Note: the source can apply "source fragmentation" for 613 locally-generated IPv6 packets up to 1500 bytes and larger still if 614 it if has a way to determine that the destination configures a larger 615 MRU, but this does not affect the minimum IPv6 path MTU.) 617 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 618 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 619 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 620 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 621 support network fragmentation and the destination is required to 622 reassemble at least that much. The "Don't Fragment" (DF) bit in the 623 IPv4 encapsulation headers of packets sent over IPv4 underlying 624 interfaces therefore MUST be set to 0. (Note: even if the 625 encapsulation source has a way to determine that the encapsulation 626 destination configures an MRU larger than 576 bytes, it should not 627 assume a larger minimum IPv4 path MTU without careful consideration 628 of the issues discussed in Section 5.1.) 630 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 631 encapsulation may be prevalent, it may be prudent for the OAL to 632 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 633 of the underlying interface IP protocol version. Always assuming the 634 IPv4 minimum path MTU even for IPv6 underlying interfaces may produce 635 more fragments and additional header overhead, but will always 636 interoperate and never run the risk of presenting an IPv4 interface 637 with a packet that exceeds its MRU. 639 The OMNI interface configures both an MTU and MRU of 9180 bytes 640 [RFC2492]; the size is therefore not a reflection of the underlying 641 interface MTUs, but rather determines the largest packet the OMNI 642 interface can forward or reassemble. The OMNI interface uses the 643 OMNI Adaptation Layer (OAL) to admit packets from the network layer 644 that are no larger than the OMNI interface MTU while generating 645 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 646 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 647 document refers to both of these ICMPv4/ICMPv6 message types simply 648 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 649 errors as discussed below. 651 For IPv4 packets with DF=0, the network layer performs IPv4 652 fragmentation if necessary then admits the packets/fragments into the 653 OMNI interface; these fragments will be reassembled by the final 654 destination. For IPv4 packets with DF=1 and IPv6 packets, the 655 network layer admits the packet if it is no larger than the OMNI 656 interface MTU; otherwise, it drops the packet and returns a PTB hard 657 error message to the source. 659 For each admitted IP packet/fragment, the OMNI interface internally 660 employs the OAL when necessary by encapsulating the inner IP packet/ 661 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 662 outer IP encapsulations. (The OAL does not decrement the inner IP 663 Hop Limit/TTL during encapsulation since the insertion occurs at a 664 layer below IP forwarding.) The OAL then calculates the 32-bit CRC 665 over the entire mid-layer packet and writes the value in a trailing 666 4-octet field at the end of the packet. Next, the OAL fragments this 667 mid-layer IPv6 packet, forwards the fragments (using *NET 668 encapsulation if necessary), and returns an internally-generated PTB 669 soft error message (subject to rate limiting) if it deems the packet 670 too large according to factors such as link performance 671 characteristics, reassembly congestion, etc. This ensures that the 672 path MTU is adaptive and reflects the current path used for a given 673 data flow. 675 The OAL operates with respect to both the minimum IPv6 and IPv4 path 676 MTUs as follows: 678 o When an OMNI interface sends a packet toward a final destination 679 via an ANET peer, it sends without OAL encapsulation if the packet 680 (including any outer-layer ANET encapsulations) is no larger than 681 the underlying interface MTU for on-link ANET peers or the minimum 682 ANET path MTU for peers separated by multiple IP hops. Otherwise, 683 the OAL inserts an IPv6 header per [RFC2473] with source address 684 set to the node's own Unique-Local Address (ULA) (see: Section 8) 685 and destination set to either the Administrative ULA (ADM-ULA) of 686 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 687 corresponding to the final destination (see below). The OAL then 688 calculates and appends the trailing 32-bit CRC, then uses IPv6 689 fragmentation to break the packet into a minimum number of non- 690 overlapping fragments where the size of each non-final fragment 691 (including both the OMNI and any outer-layer ANET encapsulations) 692 is determined by the underlying interface MTU for on-link ANET 693 peers or the minimum ANET path MTU for peers separated by multiple 694 IP hops. The OAL then encapsulates the fragments in any ANET 695 headers and sends them to the ANET peer, which either reassembles 696 before forwarding if the OAL destination is its own ADM-ULA or 697 forwards the fragments toward the final destination without first 698 reassembling otherwise. 700 o When an OMNI interface sends a packet toward a final destination 701 via an INET interface, it sends packets (including any outer-layer 702 INET encapsulations) no larger than the minimum INET path MTU 703 without OAL encapsulation if the destination is reached via an 704 INET address within the same OMNI link segment. Otherwise, the 705 OAL inserts an IPv6 header per [RFC2473] with source address set 706 to the node's ULA, destination set to the ULA of the next hop OMNI 707 node toward the final destination and (if necessary) with an OMNI 708 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 709 final segment addressing information. The OAL then calculates and 710 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 711 break the packet into a minimum number of non-overlapping 712 fragments where the size of each non-final fragment (including 713 both the OMNI and outer-layer INET encapsulations) is determined 714 by the minimum INET path MTU. The OAL then encapsulates the 715 fragments in any INET headers and sends them to the OMNI link 716 neighbor, which reassembles before forwarding toward the final 717 destination. 719 In light of the above considerations, the OAL should assume a minimum 720 path MTU of 576 bytes for the purpose of generating OAL fragments. 721 Each OAL fragment will undergo *NET encapsulation including either a 722 20 byte IPv4 or 40 byte IPv6 header plus an 8 byte UDP header, 723 leaving a minimum of 528 bytes for each fragment. Each OAL fragment 724 must accommodate 48 bytes for the OAL IPv6 header plus fragment 725 header, with the remaining space available for a portion of the inner 726 IP packet while reserving 40 additional bytes in case a maximum- 727 length ORH is added due to re-encapsulation. OAL fragmentation 728 algorithms must therefore produce non-final fragments that are 488 729 bytes in length (i.e., not including the ORH length), while the final 730 fragment may be smaller. OAL fragmentation algorithms may produce 731 larger non-final fragments if better path MTU information is 732 available, but must not produce smaller non-final fragments. 734 Note that when two ANET peers share a common physical or virtual link 735 with a larger MTU such as 1500 bytes or larger, OAL fragmentation may 736 use this larger MTU size as long as the receiving ANET peer 737 reassembles (and possibly also refragments) before forwarding. This 738 is important for accommodating links where performance is highly 739 dependent on maximum use of the available link MTU, e.g. for wireless 740 aviation data links. Additionally, in order to set the correct 741 context for reassembly, the OMNI interface that inserts the OAL 742 header MUST also be the one that inserts the IPv6 fragment header 743 Identification value. While not strictly required, sending all 744 fragments of the same fragmented OAL packet consecutively over the 745 same underlying interface with minimal inter-fragment delay may 746 increase the likelihood of successful reassembly. 748 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 749 header Code field value 0 are hard errors that always indicate that a 750 packet has been dropped due to a real MTU restriction. However, the 751 OAL can also forward large packets via encapsulation and 752 fragmentation while at the same time returning PTB soft error 753 messages (subject to rate limiting) indicating that a forwarded 754 packet was uncomfortably large. The OMNI interface can therefore 755 continuously forward large packets without loss while returning PTB 756 soft error messages recommending a smaller size. Original sources 757 that receive the soft errors in turn reduce the size of the packets 758 they send, i.e., the same as for hard errors. 760 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 761 field to the value 1 in PTB soft error messages. The OAL sets the 762 PTB destination address to the source address of the original packet, 763 and sets the source address to the MNP Subnet Router Anycast address 764 of the MN (i.e., whether the MN was the source or target of the 765 original packet). The OAL then sets the MTU field to a value no 766 smaller than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB 767 soft error to the original source. 769 When the original source receives the PTB, it reduces its path MTU 770 estimate the same as for hard errors but does not regard the message 771 as a loss indication. (If the original source does not recognize the 772 soft error code, it regards the PTB the same as a hard error but 773 should heed the retransmission advice given in [RFC8201] suggesting 774 retransmission based on normal packetization layer retransmission 775 timers.) This document therefore updates [RFC1191][RFC4443] and 776 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 777 that PTB hard or soft errors may arrive at any time even if after a 778 successful MTU probe (this is the same consideration as for an 779 ordinary path fluctuation following a successful probe). 781 In summary, the OAL supports continuous transmission and reception of 782 packets of various sizes in the face of dynamically changing network 783 conditions. Moreover, since PTB soft errors do not indicate loss, 784 original sources that receive soft errors can quickly scan for path 785 MTU increases without waiting for the minimum 10 minutes specified 786 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 787 therefore provides a lossless and adaptive service that accommodates 788 MTU diversity especially well-suited for dynamic multilink 789 environments. 791 Note: An OMNI interface that reassembles OAL fragments may experience 792 congestion-oriented loss in its reassembly cache and can optionally 793 send PTB soft errors to the original source and/or ICMP "Time 794 Exceeded" messages to the source of the OAL fragments. In 795 environments where the messages may contribute to unacceptable 796 additional congestion, however, the OMNI interface can simply regard 797 the loss as an ordinary unreported congestion event for which the 798 original source will eventually compensate. 800 Note: When the network layer forwards an IPv4 packet/fragment with 801 DF=0 into the OMNI interface, the interface can optionally perform 802 (further) IPv4 fragmentation before invoking the OAL so that the 803 fragments will be reassembled by the final destination. When the 804 network layer performs IPv6 fragmentation for locally-generated IPv6 805 packets, the OMNI interface typically invokes the OAL without first 806 applying (further) IPv6 fragmentation; the network layer should 807 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 808 push the reassembly burden to the final destination and avoid 809 receiving PTB soft errors from the OMNI interface. Aside from these 810 non-normative guidelines, the manner in which any IP fragmentation is 811 invoked prior to OAL encapsulation/fragmentation is an implementation 812 matter. 814 Note: Inclusion of the 32-bit CRC prior to fragmentation assumes that 815 the receiving OAL will discard any packets with incorrect CRC values 816 following reassembly. The 32-bit CRC is sufficient to detect 817 reassembly misassociations for packet sizes up to the OMNI interface 818 MTU 9180 but may not be sufficient to detect errors for larger sizes 819 [CRC]. 821 Note: Some underlying interface types (e.g., VPNs) may already 822 provide their own robust fragmentation and reassembly services even 823 without OAL encapsulation. In those cases, the OAL can invoke the 824 inherent underlying interface schemes instead while employing PTB 825 soft errors in the same fashion as described above. Other underlying 826 interface properties such as header/message compression can also be 827 harnessed in a similar fashion. 829 Note: Applications can dynamically tune the size of the packets they 830 to send to produce the best possible throughput and latency, with the 831 understanding that these parameters may change over time due to 832 factors such as congestion, mobility, network path changes, etc. The 833 receipt or absence of soft errors should be seen as hints of when 834 increasing or decreasing packet sizes may be beneficial. 836 5.1. Fragmentation Security Implications 838 As discussed in Section 3.7 of [RFC8900], there are four basic 839 threats concerning IPv6 fragmentation; each of which is addressed by 840 effective mitigations as follows: 842 1. Overlapping fragment attacks - reassembly of overlapping 843 fragments is forbidden by [RFC8200]; therefore, this threat does 844 not apply to the OAL. 846 2. Resource exhaustion attacks - this threat is mitigated by 847 providing a sufficiently large OAL reassembly cache and 848 instituting "fast discard" of incomplete reassemblies that may be 849 part of a buffer exhaustion attack. The reassembly cache should 850 be sufficiently large so that a sustained attack does not cause 851 excessive loss of good reassemblies but not so large that (timer- 852 based) data structure management becomes computationally 853 expensive. The cache should also be indexed based on the arrival 854 underlying interface such that congestion experienced over a 855 first underlying interface does not cause discard of incomplete 856 reassemblies for uncongested underlying interfaces. 858 3. Attacks based on predictable fragment identification values - 859 this threat is mitigated by selecting a suitably random ID value 860 per [RFC7739]. 862 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 863 threat is mitigated by disallowing "tiny fragments" per the OAL 864 fragmentation procedures specified above. 866 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 867 ID) field with only 65535 unique values such that at high data rates 868 the field could wrap and apply to new packets while the fragments of 869 old packets using the same ID are still alive in the network 870 [RFC4963]. However, since the largest OAL fragment that will be sent 871 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 872 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 873 recommendations suggest that such links will have low data rates. 874 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 875 at high data rates is not a concern for IPv6 fragmentation. 877 6. Frame Format 879 The OMNI interface transmits IPv6 packets according to the native 880 frame format of each underlying interface. For example, for 881 Ethernet-compatible interfaces the frame format is specified in 882 [RFC2464], for aeronautical radio interfaces the frame format is 883 specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical 884 Manual), for tunnels over IPv6 the frame format is specified in 885 [RFC2473], etc. 887 7. Link-Local Addresses (LLAs) 889 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 890 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 891 the MNP assigned to the mobile node, while "ADM-LLAs" include an 892 administratively-unique ID that is guaranteed to be unique on the 893 link. LLAs are configured as follows: 895 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 896 the least-significant 64 bits of the IPv6 link-local prefix 897 fe80::/64, i.e., in the LLA "interface identifier" portion. The 898 prefix length for the LLA is determined by adding 64 to the MNP 899 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 900 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 902 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 903 i.e., the interface identifier consists of 16 '0' bits, followed 904 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 905 prefix length for the LLA is determined by adding 96 to the MNP 906 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 907 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 908 fe80::ffff:c000:0200/120). 910 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 911 uniqueness. The lower 32 bits of the LLA includes a unique 912 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 913 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 914 prefix length is determined by adding 96 to the MSID prefix 915 length. For example, if the prefix length for MSID 0x10012001 is 916 16 then the ADM-LLA prefix length is set to 112 and the LLA is 917 written as fe80::1001:2001/112. The "zero" address for each ADM- 918 LLA prefix is the Subnet-Router anycast address for that prefix 919 [RFC4291]; for example, the Subnet-Router anycast address for 920 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 921 0xff000000 through 0xffffffff is reserved for future use. 923 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 924 used by MNs for the short-term purpose of procuring an actual MNP- 925 LLA upon startup or (re)connecting to the network. MNs may use 926 Temporary LLAs as the IPv6 source address of an RS message in 927 order to request a MNP-LLA from the MS. 929 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 930 MNPs can be allocated from that block ensuring that there is no 931 possibility for overlap between the various LLA constructs discussed 932 above. 934 Since MNP-LLAs are based on the distribution of administratively 935 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 936 administrative assignment, OMNI interfaces set the autoconfiguration 937 variable DupAddrDetectTransmits to 0 [RFC4862]. 939 Temporary LLAs employ optimistic DAD principles [RFC4429] since they 940 are probabilistically unique and their use is short-duration in 941 nature. 943 Note: If future protocol extensions relax the 64-bit boundary in IPv6 944 addressing, the additional prefix bits of an MNP could be encoded in 945 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 946 would therefore still be in bits 64-127, and the remaining bits would 947 appear in bits 16 through 48.) However, the analysis provided in 948 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 949 architecture for the forseeable future. 951 Note: Even though this document honors the 64-bit boundary in IPv6 952 addressing per [RFC7421], it suggests prefix lengths longer than /64 953 for routing purposes. This effectively extends IPv6 routing 954 determination into the interface identifier portion of the IPv6 955 address, but it does not redefine the 64-bit boundary. 957 8. Unique-Local Addresses (ULAs) 959 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 960 destination addresses in OAL IPv6 encapsulation headers. ULAs are 961 only routable within the scope of a an OMNI domain, and are derived 962 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 963 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 964 Global ID to produce the prefix [ULA]::/48, which is then followed by 965 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 966 specified in Section 3 of [RFC4193]. The statistic uniqueness of the 967 40-bit pseudo-random Global ID allows different OMNI domains to be 968 joined together in the future without requiring OMNI link 969 renumbering. 971 Each OMNI link instance is identified by a value between 0x0000 and 972 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xffff 973 are reserved for future use). For example, OMNI ULAs associated with 974 instance 0 are configured from the prefix [ULA]:0000::/64, instance 1 975 from [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 976 their associated prefix lengths are configured in correspondence with 977 LLAs through stateless prefix translation where "MNP-ULAs" are 978 assigned in correspondence to MNP-LLAs and "ADM-ULAs" are assigned in 979 correspondence to ADM-LLAs. For example, for OMNI link instance 980 [ULA]:1010::/64: 982 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 983 56-bit MNP length is derived by copying the lower 64 bits of the 984 LLA into the lower 64 bits of the ULA as 985 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 986 64 plus the IPv6 MNP length). 988 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 989 MNP length is derived by simply writing the LLA interface ID into 990 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 991 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 993 o the ADM-ULA corresponding to fe80::1000/112 is simply 994 [ULA]:1010::1000/112. 996 o the ADM-ULA corresponding to fe80::/128 is simply 997 [ULA]:1010::/128. 999 o the Temporary ULA corresponding to a Temporary LLA is simply 1000 [ULA]:1010:[64-bit Temporary Interface ID]/128. 1002 o etc. 1004 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1005 link instance. For example, the OMNI interface connected to instance 1006 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1007 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1008 [ULA]:0003::/64) into the local routing system so that applications 1009 can direct traffic according to SBM requirements. 1011 The ULA presents an IPv6 address format that is routable within the 1012 OMNI routing system and can be used to convey link-scoped IPv6 ND 1013 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1014 The OMNI link extends across one or more underling Internetworks to 1015 include all ARs and MSEs. All MNs are also considered to be 1016 connected to the OMNI link, however OAL encapsulation is omitted 1017 whenever possible to conserve bandwidth (see: Section 12). 1019 Each OMNI link can be subdivided into "segments" that often 1020 correspond to different administrative domains or physical 1021 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1022 necessary to support efficient packet forwarding to destinations 1023 located in other OMNI link segments. A full discussion of Segment 1024 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1026 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1027 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1028 however the range could be used for MSP and MNP addressing under 1029 certain limiting conditions (see: Section 9). 1031 9. Global Unicast Addresses (GUAs) 1033 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1034 as Mobility Service Prefixes (MSPs) from which Mobile Network 1035 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1037 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1038 associated regional assigned numbers authority such that the OMNI 1039 domain can be interconnected to the global IPv6 Internet without 1040 causing inconsistencies in the routing system. An OMNI domain could 1041 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1042 fc00::/8)[RFC4193], however this would require IPv6 Network Address 1043 Translation (NAT) if the domain were ever connected to the global 1044 IPv6 Internet. 1046 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1047 associated regional assigned numbers authority such that the OMNI 1048 domain can be interconnected to the global IPv4 Internet without 1049 causing routing inconsistencies. An OMNI domain could instead use 1050 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1051 this would require IPv4 NAT if the domain were ever connected to the 1052 global IPv4 Internet. 1054 10. Address Mapping - Unicast 1056 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1057 state and use the link-local address format specified in Section 7. 1058 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1059 over physical underlying interfaces without encapsulation observe the 1060 native underlying interface Source/Target Link-Layer Address Option 1061 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1062 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1063 interfaces via encapsulation do not include S/TLLAOs which were 1064 intended for encoding physical L2 media address formats and not 1065 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1066 for encoding additional interface attributes needed for multilink 1067 coordination. Hence, this document does not define an S/TLLAO format 1068 but instead defines a new option type termed the "OMNI option" 1069 designed for these purposes. 1071 MNs such as aircraft typically have many wireless data link types 1072 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1073 etc.) with diverse performance, cost and availability properties. 1074 The OMNI interface would therefore appear to have multiple L2 1075 connections, and may include information for multiple underlying 1076 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1077 an IPv6 ND option called the OMNI option formatted as shown in 1078 Figure 3: 1080 0 1 2 3 1081 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 1082 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1083 | Type | Length |T| Preflen | S/T-ifIndex | 1084 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1085 | | 1086 ~ Sub-Options ~ 1087 | | 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1090 Figure 3: OMNI Option Format 1092 In this format: 1094 o Type is set to TBD. If multiple OMNI option instances appear in 1095 the same IPv6 ND message, the first instance is processed and all 1096 other instances are ignored. 1098 o Length is set to the number of 8 octet blocks in the option. 1100 o T is a 1-bit flag set to 1 for Temporary LLAs (otherwise, set to 1101 0) and Preflen is a 7 bit field that determines the length of 1102 prefix associated with an LLA. Values 1 through 127 specify a 1103 prefix length, while the value 0 indicates "unspecified". For 1104 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1105 the IPv6 source LLA and provide the length that the MN is 1106 requesting or asserting to the MS. For IPv6 ND messages sent from 1107 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1108 and indicate the length that the MS is granting to the MN. For 1109 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1110 Preflen provides the length associated with the source/target MN 1111 that is subject of the ND message. 1113 o S/T-ifIndex corresponds to the ifIndex value for source or target 1114 underlying interface used to convey this IPv6 ND message. OMNI 1115 interfaces MUST number each distinct underlying interface with an 1116 ifIndex value between '1' and '255' that represents a MN-specific 1117 8-bit mapping for the actual ifIndex value assigned by network 1118 management [RFC2863] (the ifIndex value '0' is reserved for use by 1119 the MS). For RS and NS messages, S/T-ifIndex corresponds to the 1120 source underlying interface the message originated from. For RA 1121 and NA messages, S/T-ifIndex corresponds to the target underlying 1122 interface that the message is destined to. 1124 o Sub-Options is a Variable-length field, of length such that the 1125 complete OMNI Option is an integer multiple of 8 octets long. 1126 Contains one or more Sub-Options, as described in Section 10.1. 1128 10.1. Sub-Options 1130 The OMNI option includes zero or more Sub-Options. Each consecutive 1131 Sub-Option is concatenated immediately after its predecessor. All 1132 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1133 encoded in the following format: 1135 0 1 2 1136 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 1137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1138 | Sub-Type | Sub-length | Sub-Option Data ... 1139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1141 Figure 4: Sub-Option Format 1143 o Sub-Type is a 1-octet field that encodes the Sub-Option type. 1144 Sub-Options defined in this document are: 1146 Option Name Sub-Type 1147 Pad1 0 1148 PadN 1 1149 Interface Attributes 2 1150 Traffic Selector 3 1151 MS-Register 4 1152 MS-Release 5 1153 Network Access Identifier 6 1154 Geo Coordinates 7 1155 DHCP Unique Identifier (DUID) 8 1156 DHCPv6 Message 9 1158 Figure 5 1160 Sub-Types 253 and 254 are reserved for experimentation, as 1161 recommended in [RFC3692]. 1163 o Sub-Length is a 1-octet field that encodes the length of the Sub- 1164 Option Data (i.e., ranging from 0 to 255 octets). 1166 o Sub-Option Data is a block of data with format determined by Sub- 1167 Type. 1169 During processing, unrecognized Sub-Options are ignored and the next 1170 Sub-Option processed until the end of the OMNI option is reached. 1172 The following Sub-Option types and formats are defined in this 1173 document: 1175 10.1.1. Pad1 1177 0 1178 0 1 2 3 4 5 6 7 1179 +-+-+-+-+-+-+-+-+ 1180 | Sub-Type=0 | 1181 +-+-+-+-+-+-+-+-+ 1183 Figure 6: Pad1 1185 o Sub-Type is set to 0. If multiple instances appear in the same 1186 OMNI option all are processed. 1188 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" 1189 consists of a single zero octet). 1191 10.1.2. PadN 1193 0 1 2 1194 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 1195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1196 | Sub-Type=1 | Sub-length=N | N padding octets ... 1197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1199 Figure 7: PadN 1201 o Sub-Type is set to 1. If multiple instances appear in the same 1202 OMNI option all are processed. 1204 o Sub-Length is set to N (from 0 to 255) being the number of padding 1205 octets that follow. 1207 o Sub-Option Data consists of N zero-valued octets. 1209 10.1.3. Interface Attributes 1211 The Interface Attributes sub-option provides L2 forwarding 1212 information for the multilink conceptual sending algorithm discussed 1213 in Section 12. The L2 information is used for selecting among 1214 potentially multiple candidate underlying interfaces that can be used 1215 to forward packets to the neighbor based on factors such as DSCP 1216 preferences and link quality. Interface Attributes further include 1217 link-layer address information to be used for either OAL 1218 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1219 can be avoided). The Interface Attributes format and contents are 1220 given in Figure 8 below: 1222 0 1 2 3 1223 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 1224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1225 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 1226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1227 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1229 | LHS (bits 8 - 31) | ~ 1230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1231 ~ ~ 1232 ~ Link Layer Address (L2ADDR) ~ 1233 ~ ~ 1234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1235 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1237 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1239 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1242 Figure 8: Interface Attributes 1244 o Sub-Type is set to 2. If multiple instances with different 1245 ifIndex values appear in the same OMNI option all are processed; 1246 if multiple instances with the same ifIndex value appear, the 1247 first is processed and all others are ignored. 1249 o Sub-Length is set to N (from 4 to 255) that encodes the number of 1250 Sub-Option Data octets that follow. 1252 o Sub-Option Data contains an "Interface Attribute" option encoded 1253 as follows (note that the first four octets must be present): 1255 * ifIndex is set to an 8-bit integer value corresponding to a 1256 specific underlying interface the same as specified above for 1257 the OMNI option header S/T-ifIndex. An OMNI option may include 1258 multiple Interface Attributes Sub-Options, with each distinct 1259 ifIndex value pertaining to a different underlying interface. 1260 The OMNI option will often include an Interface Attributes Sub- 1261 Option with the same ifIndex value that appears in the S/ 1262 T-ifIndex. In that case, the actual encapsulation address of 1263 the received IPv6 ND message should be compared with the L2ADDR 1264 encoded in the Sub-Option (see below); if the addresses are 1265 different (or, if L2ADDR absent) the presence of a Network 1266 Address Translator (NAT) is indicated. 1268 * ifType is set to an 8-bit integer value corresponding to the 1269 underlying interface identified by ifIndex. The value 1270 represents an OMNI interface-specific 8-bit mapping for the 1271 actual IANA ifType value registered in the 'IANAifType-MIB' 1272 registry [http://www.iana.org]. 1274 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1275 for the network service provider associated with this ifIndex. 1277 * Link encodes a 4-bit link metric. The value '0' means the link 1278 is DOWN, and the remaining values mean the link is UP with 1279 metric ranging from '1' ("lowest") to '15' ("highest"). 1281 * R is reserved for future use. 1283 * API - a 3-bit "Address/Preferences/Indexed" code that 1284 determines the contents of the remainder of the sub-option as 1285 follows: 1287 + When the most significant bit (i.e., "Address") is set to 1, 1288 the SRT, FMT, LHS and L2ADDR fields are included immediately 1289 following the API code; else, they are omitted. 1291 + When the next most significant bit (i.e., "Preferences") is 1292 set to 1, a preferences block is included next; else, it is 1293 omitted. (Note that if "Address" is set the preferences 1294 block immediately follows L2ADDR; else, it immediately 1295 follows the API code.) 1297 + When a preferences block is present and the least 1298 significant bit (i.e., "Indexed") is set to 0, the block is 1299 encoded in "Simplex" form as shown in Figure 8; else it is 1300 encoded in "Indexed" form as discussed below. 1302 * When API indicates that an "Address" is included, the following 1303 fields appear in consecutive order (else, they are omitted): 1305 + SRT - a 5-bit Segment Routing Topology prefix length value 1306 that (when added to 96) determines the prefix length to 1307 apply to the ULA formed from concatenating [ULA*]::/96 with 1308 the 32 bit LHS MSID value that follows. For example, the 1309 value 16 corresponds to the prefix length 112. 1311 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1312 the included Link Layer Address as follows: 1314 - When the most significant bit (i.e., "Framework") is set 1315 to 0, L2ADDR is the INET encapsulation address of a 1316 Proxy/Server; otherwise, it is the address for the 1317 Source/Target itself 1319 - When the next most significant bit (i.e., "Mode") is set 1320 to 0, the Source/Target L2ADDR is on the open INET; 1321 otherwise, it is (likely) located behind a Network 1322 Address Translator (NAT). 1324 - When the least significant bit (i.e., "Type") is set to 1325 0, L2ADDR includes a UDP Port Number followed by an IPv4 1326 address; else, a UDP Port Number followed by an IPv6 1327 address. 1329 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1330 path to the target. When SRT and LHS are both set to 0, the 1331 LHS is considered unspecified in this IPv6 ND message. When 1332 SRT is set to 0 and LHS is non-zero, the prefix length is 1333 set to 128. SRT and LHS together provide guidance to the 1334 OMNI interface forwarding algorithm. Specifically, if SRT/ 1335 LHS is located in the local OMNI link segment then the OMNI 1336 interface can encapsulate according to FMT/L2ADDR; else, it 1337 must forward according to the OMNI link spanning tree. See 1338 [I-D.templin-intarea-6706bis] for further discussion. 1340 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1341 and identifies the link-layer address (i.e., the 1342 encapsulation address) of the source/target. The UDP Port 1343 Number appears in the first two octets and the IP address 1344 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1345 The Port Number and IP address are recorded in ones- 1346 compliment "obfuscated" form per [RFC4380]. The OMNI 1347 interface forwarding algorithm uses FMT/L2ADDR to determine 1348 the encapsulation address for forwarding when SRT/LHS is 1349 located in the local OMNI link segment. 1351 * When API indicates that "Preferences" are included, a 1352 preferences block appears as the remainder of the Sub-Option as 1353 a series of Bitmaps and P[*] values. In "Simplex" form, the 1354 index for each singleton Bitmap octet is inferred from its 1355 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 8. 1356 In "Indexed" form, each Bitmap is preceded by an Index octet 1357 that encodes a value "i" = (0 - 255) as the index for its 1358 companion Bitmap as follows: 1360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1361 | Index=i | Bitmap(i) |P[*] values ... 1362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1364 Figure 9 1366 * The preferences consist of a first (simplex/indexed) Bitmap 1367 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1368 2-bit P[*] values, followed by a second Bitmap (i), followed by 1369 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1370 the bits of each Bitmap(i) that are set to '1'' indicate the 1371 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1372 that follow; if any Bitmap(i) bits are '0', then the 1373 corresponding P[*] block is instead omitted. For example, if 1374 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1375 followed by the block with P[04]-P[07], etc., and ending with 1376 the block with P[28]-P[31] are included (as shown in Figure 8). 1377 The next Bitmap(i) is then consulted with its bits indicating 1378 which P[*] blocks follow, etc. out to the end of the Sub- 1379 Option. 1381 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1382 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1383 preference for underlying interface selection purposes. Not 1384 all P[*] values need to be included in the OMNI option of each 1385 IPv6 ND message received. Any P[*] values represented in an 1386 earlier OMNI option but omitted in the current OMNI option 1387 remain unchanged. Any P[*] values not yet represented in any 1388 OMNI option default to "medium". 1390 * The first 16 P[*] blocks correspond to the 64 Differentiated 1391 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1392 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1393 traffic classifier values P[64], P[65], P[66], etc. See 1394 Appendix A for further discussion and examples. 1396 10.1.4. Traffic Selector 1398 0 1 2 3 1399 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 1400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1401 | Sub-Type=3 | Sub-length=N | ifIndex | ~ 1402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1403 ~ ~ 1404 ~ RFC 6088 Format Traffic Selector ~ 1405 ~ ~ 1406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1408 Figure 10: Traffic Selector 1410 o Sub-Type is set to 3. If multiple instances appear in the same 1411 OMNI option all are processed, i.e., even if the same ifIndex 1412 value appears multiple times. 1414 o Sub-Length is set to N (the number of Sub-Option Data octets that 1415 follow). 1417 o Sub-Option Data contains a 1-octet ifIndex encoded exactly as 1418 specified in Section 10.1.3, followed by an N-1 octet traffic 1419 selector formatted per [RFC6088] beginning with the "TS Format" 1420 field. The largest traffic selector for a given ifIndex is 1421 therefore 254 octets. 1423 10.1.5. MS-Register 1425 0 1 2 3 1426 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 1427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1428 | Sub-Type=4 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1430 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1432 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1434 ... ... ... ... ... ... 1435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1436 | MSID [n] (bits 16 - 32) | 1437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1439 Figure 11: MS-Register Sub-option 1441 o Sub-Type is set to 4. If multiple instances appear in the same 1442 OMNI option all are processed. Only the first MAX_MSID values 1443 processed (whether in a single instance or multiple) are retained 1444 and all other MSIDs are ignored. 1446 o Sub-Length is set to 4n. 1448 o A list of n 4-octet MSIDs is included in the following 4n octets. 1449 The Anycast MSID value '0' in an RS message MS-Register sub-option 1450 requests the recipient to return the MSID of a nearby MSE in a 1451 corresponding RA response. 1453 10.1.6. MS-Release 1454 0 1 2 3 1455 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 1456 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1457 | Sub-Type=5 | Sub-length=4n | MSID[1] (bits 0 - 15) | 1458 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1459 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1461 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1463 ... ... ... ... ... ... 1464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1465 | MSID [n] (bits 16 - 32) | 1466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1468 Figure 12: MS-Release Sub-option 1470 o Sub-Type is set to 5. If multiple instances appear in the same 1471 IPv6 OMNI option all are processed. Only the first MAX_MSID 1472 values processed (whether in a single instance or multiple) are 1473 retained and all other MSIDs are ignored. 1475 o Sub-Length is set to 4n. 1477 o A list of n 4 octet MSIDs is included in the following 4n octets. 1478 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1479 i.e., only non-zero values are processed. 1481 10.1.7. Network Access Identifier (NAI) 1483 0 1 2 3 1484 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 1485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1486 | Sub-Type=6 | Sub-length=N |Network Access Identifier (NAI) 1487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1489 Figure 13: Network Access Identifier (NAI) Sub-option 1491 o Sub-Type is set to 6. If multiple instances appear in the same 1492 OMNI option the first is processed and all others are ignored. 1494 o Sub-Length is set to N (i.e., the length of the encoded Network 1495 Access Identifier (NAI)). 1497 o An NAI up to 255 octets in length is coded per [RFC7542]. 1499 10.1.8. Geo Coordinates 1501 0 1 2 3 1502 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 1503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1504 | Sub-Type=7 | Sub-length=N | Geo Coordinates 1505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1507 Figure 14: Geo Coordinates Sub-option 1509 o Sub-Type is set to 7. If multiple instances appear in the same 1510 OMNI option the first is processed and all others are ignored. 1512 o Sub-Length is set to N (i.e., the length of the encoded Geo 1513 Coordinates). 1515 o A set of Geo Coordinates up to 255 octets in length (format TBD). 1516 Includes Latitude/Longitude at a minimum; may also include 1517 additional attributes such as altitude, heading, speed, etc.). 1519 10.1.9. DHCP Unique Identifier (DUID) 1521 0 1 2 3 1522 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 1523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1524 | Sub-Type=8 | Sub-length=N | DUID-Type | 1525 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1526 . . 1527 . type-specific DUID body (variable length) . 1528 . . 1529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1531 Figure 15: DHCP Unique Identifier (DUID) Sub-option 1533 o Sub-Type is set to 8. If multiple instances appear in the same 1534 OMNI option the first is processed and all others are ignored. 1536 o Sub-Length is set to N (i.e., the length of the option beginning 1537 with the DUID-Type and continuing to the end of the type-specific 1538 body). 1540 o DUID-Type is a two-octet field coded in network byte order that 1541 determines the format and contents of the type-specific body 1542 according to Section 11 of [RFC8415]. DUID-Type 4 in particular 1543 corresponds to the Universally Unique Identifier (UUID) [RFC6355] 1544 which will occur in common operational practice. 1546 o A type-specific DUID body up to 253 octets in length follows, 1547 formatted according to DUID-type. For example, for type 4 the 1548 body consists of a 128-bit UUID selected according to [RFC6355]. 1550 10.1.10. DHCPv6 Message 1552 0 1 2 3 1553 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 1554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1555 | Sub-Type=9 | Sub-length=N | msg-type | id (octet 0) | 1556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1557 | transaction-id (octets 1-2) | | 1558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1559 | | 1560 . DHCPv6 options . 1561 . (variable number and length) . 1562 | | 1563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1565 Figure 16: DHCPv6 Message Sub-option 1567 o Sub-Type is set to 9. If multiple instances appear in the same 1568 OMNI option the first is processed and all others are ignored. 1570 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1571 beginning with 'msg-type' and continuing to the end of the DHCPv6 1572 options). The length of the entire DHCPv6 message is therefore 1573 restricted to 255 octets. 1575 o 'msg-type' and 'transaction-id' are coded according to Section 8 1576 of [RFC8415]. 1578 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1579 follows. 1581 11. Address Mapping - Multicast 1583 The multicast address mapping of the native underlying interface 1584 applies. The mobile router on board the MN also serves as an IGMP/ 1585 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1586 using the L2 address of the AR as the L2 address for all multicast 1587 packets. 1589 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1590 coordinate with the AR, and *NET L2 elements use MLD snooping 1591 [RFC4541]. 1593 12. Multilink Conceptual Sending Algorithm 1595 The MN's IPv6 layer selects the outbound OMNI interface according to 1596 SBM considerations when forwarding data packets from local or EUN 1597 applications to external correspondents. Each OMNI interface 1598 maintains a neighbor cache the same as for any IPv6 interface, but 1599 with additional state for multilink coordination. Each OMNI 1600 interface maintains default routes via ARs discovered as discussed in 1601 Section 13, and may configure more-specific routes discovered through 1602 means outside the scope of this specification. 1604 After a packet enters the OMNI interface, one or more outbound 1605 underlying interfaces are selected based on PBM traffic attributes, 1606 and one or more neighbor underlying interfaces are selected based on 1607 the receipt of Interface Attributes sub-options in IPv6 ND messages 1608 (see: Figure 8). Underlying interface selection for the nodes own 1609 local interfaces are based on attributes such as DSCP, application 1610 port number, cost, performance, message size, etc. OMNI interface 1611 multilink selections could also be configured to perform replication 1612 across multiple underlying interfaces for increased reliability at 1613 the expense of packet duplication. The set of all Interface 1614 Attributes received in IPv6 ND messages determine the multilink 1615 forwarding profile for selecting the neighbor's underlying 1616 interfaces. 1618 When the OMNI interface sends a packet over a selected outbound 1619 underlying interface, the OAL includes or omits a mid-layer 1620 encapsulation header as necessary as discussed in Section 5 and as 1621 determined by the L2 address information received in Interface 1622 Attributes. The OAL also performs encapsulation when the nearest AR 1623 is located multiple hops away as discussed in Section 13.1. 1625 OMNI interface multilink service designers MUST observe the BCP 1626 guidance in Section 15 [RFC3819] in terms of implications for 1627 reordering when packets from the same flow may be spread across 1628 multiple underlying interfaces having diverse properties. 1630 12.1. Multiple OMNI Interfaces 1632 MNs may connect to multiple independent OMNI links concurrently in 1633 support of SBM. Each OMNI interface is distinguished by its Anycast 1634 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1635 configures a separate OMNI interface for each link so that multiple 1636 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1637 layer. A different Anycast ULA is assigned to each interface, and 1638 the MN injects the service prefixes for the OMNI link instances into 1639 the EUN routing system. 1641 Applications in EUNs can use Segment Routing to select the desired 1642 OMNI interface based on SBM considerations. The Anycast ULA is 1643 written into the IPv6 destination address, and the actual destination 1644 (along with any additional intermediate hops) is written into the 1645 Segment Routing Header. Standard IP routing directs the packets to 1646 the MN's mobile router entity, and the Anycast ULA identifies the 1647 OMNI interface to be used for transmission to the next hop. When the 1648 MN receives the message, it replaces the IPv6 destination address 1649 with the next hop found in the routing header and transmits the 1650 message over the OMNI interface identified by the Anycast ULA. 1652 Multiple distinct OMNI links can therefore be used to support fault 1653 tolerance, load balancing, reliability, etc. The architectural model 1654 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1656 12.2. MN<->AR Traffic Loop Prevention 1658 After an AR has registered an MNP for a MN (see: Section 13), the AR 1659 will forward packets destined to an address within the MNP to the MN. 1660 The MN will under normal circumstances then forward the packet to the 1661 correct destination within its internal networks. 1663 If at some later time the MN loses state (e.g., after a reboot), it 1664 may begin returning packets destined to an MNP address to the AR as 1665 its default router. The AR therefore must drop any packets 1666 originating from the MN and destined to an address within the MN's 1667 registered MNP. To do so, the AR institutes the following check: 1669 o if the IP destination address belongs to a neighbor on the same 1670 OMNI interface, and if the link-layer source address is the same 1671 as one of the neighbor's link-layer addresses, drop the packet. 1673 13. Router Discovery and Prefix Registration 1675 MNs interface with the MS by sending RS messages with OMNI options 1676 under the assumption that one or more AR on the *NET will process the 1677 message and respond. The MN then configures default routes for the 1678 OMNI interface via the discovered ARs as the next hop. The manner in 1679 which the *NET ensures AR coordination is link-specific and outside 1680 the scope of this document (however, considerations for *NETs that do 1681 not provide ARs that recognize the OMNI option are discussed in 1682 Section 18). 1684 For each underlying interface, the MN sends an RS message with an 1685 OMNI option to coordinate with MSEs identified by MSID values. 1686 Example MSID discovery methods are given in [RFC5214] and include 1687 data link login parameters, name service lookups, static 1688 configuration, a static "hosts" file, etc. The MN can also send an 1689 RS with an MS-Register suboption that includes the Anycast MSID value 1690 '0', i.e., instead of or in addition to any non-zero MSIDs. When the 1691 AR receives an RS with a MSID '0', it selects a nearby MSE (which may 1692 be itself) and returns an RA with the selected MSID in an MS-Register 1693 suboption. The AR selects only a single wildcard MSE (i.e., even if 1694 the RS MS-Register suboption included multiple '0' MSIDs) while also 1695 soliciting the MSEs corresponding to any non-zero MSIDs. 1697 MNs configure OMNI interfaces that observe the properties discussed 1698 in the previous section. The OMNI interface and its underlying 1699 interfaces are said to be in either the "UP" or "DOWN" state 1700 according to administrative actions in conjunction with the interface 1701 connectivity status. An OMNI interface transitions to UP or DOWN 1702 through administrative action and/or through state transitions of the 1703 underlying interfaces. When a first underlying interface transitions 1704 to UP, the OMNI interface also transitions to UP. When all 1705 underlying interfaces transition to DOWN, the OMNI interface also 1706 transitions to DOWN. 1708 When an OMNI interface transitions to UP, the MN sends RS messages to 1709 register its MNP and an initial set of underlying interfaces that are 1710 also UP. The MN sends additional RS messages to refresh lifetimes 1711 and to register/deregister underlying interfaces as they transition 1712 to UP or DOWN. The MN sends initial RS messages over an UP 1713 underlying interface with its MNP-LLA as the source and with 1714 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1715 messages include an OMNI option per Section 10 with a Preflen 1716 assertion, Interface Attributes appropriate for underlying 1717 interfaces, MS-Register/Release sub-options containing MSID values, 1718 and with any other necessary OMNI sub-options (e.g., a DUID suboption 1719 as an identity for the MN). The S/T-ifIndex field is set to the 1720 index of the underlying interface over which the RS message is sent. 1722 ARs process IPv6 ND messages with OMNI options and act as an MSE 1723 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1724 and create a neighbor cache entry for the MN, then coordinate with 1725 any MSEs named in the Register/Release lists in a manner outside the 1726 scope of this document. When an MSE processes the OMNI information, 1727 it first validates the prefix registration information then injects/ 1728 withdraws the MNP in the routing/mapping system and caches/discards 1729 the new Preflen, MNP and Interface Attributes. The MSE then informs 1730 the AR of registration success/failure, and the AR returns an RA 1731 message to the MN with an OMNI option per Section 10. 1733 The AR returns the RA message via the same underlying interface of 1734 the MN over which the RS was received, and with destination address 1735 set to the MNP-LLA (i.e., unicast), with source address set to its 1736 own LLA, and with an OMNI option with S/T-ifIndex set to the value 1737 included in the RS. The OMNI option also includes a Preflen 1738 confirmation, Interface Attributes, MS-Register/Release and any other 1739 necessary OMNI sub-options (e.g., a DUID suboption as an identity for 1740 the AR). The RA also includes any information for the link, 1741 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 1742 Time and Retrans Timer values, and includes any necessary options 1743 such as: 1745 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 1747 o RIOs [RFC4191] with more-specific routes. 1749 o an MTU option that specifies the maximum acceptable packet size 1750 for this underlying interface. 1752 The AR MAY also send periodic and/or event-driven unsolicited RA 1753 messages per [RFC4861]. In that case, the S/T-ifIndex field in the 1754 OMNI header of the unsolicited RA message identifies the target 1755 underlying interface of the destination MN. 1757 The AR can combine the information from multiple MSEs into one or 1758 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 1759 Each aggregate RA includes an OMNI option with MS-Register/Release 1760 sub-options with the MSEs represented by the aggregate. If an 1761 aggregate is sent, the RA message contents must consistently 1762 represent the combined information advertised by all represented 1763 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 1764 address, the MN determines the addresses of the represented MSEs by 1765 examining the MS-Register/Release OMNI sub-options. 1767 When the MN receives the RA message, it creates an OMNI interface 1768 neighbor cache entry for each MSID that has confirmed MNP 1769 registration via the L2 address of this AR. If the MN connects to 1770 multiple *NETs, it records the additional L2 AR addresses in each 1771 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 1772 then configures a default route via the MSE that returned the RA 1773 message, and assigns the Subnet Router Anycast address corresponding 1774 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 1775 manages its underlying interfaces according to their states as 1776 follows: 1778 o When an underlying interface transitions to UP, the MN sends an RS 1779 over the underlying interface with an OMNI option. The OMNI 1780 option contains at least one Interface Attribute sub-option with 1781 values specific to this underlying interface, and may contain 1782 additional Interface Attributes specific to other underlying 1783 interfaces. The option also includes any MS-Register/Release sub- 1784 options. 1786 o When an underlying interface transitions to DOWN, the MN sends an 1787 RS or unsolicited NA message over any UP underlying interface with 1788 an OMNI option containing an Interface Attribute sub-option for 1789 the DOWN underlying interface with Link set to '0'. The MN sends 1790 an RS when an acknowledgement is required, or an unsolicited NA 1791 when reliability is not thought to be a concern (e.g., if 1792 redundant transmissions are sent on multiple underlying 1793 interfaces). 1795 o When the Router Lifetime for a specific AR nears expiration, the 1796 MN sends an RS over the underlying interface to receive a fresh 1797 RA. If no RA is received, the MN can send RS messages to an 1798 alternate MSID in case the current MSID has failed. If no RS 1799 messages are received even after trying to contact alternate 1800 MSIDs, the MN marks the underlying interface as DOWN. 1802 o When a MN wishes to release from one or more current MSIDs, it 1803 sends an RS or unsolicited NA message over any UP underlying 1804 interfaces with an OMNI option with a Release MSID. Each MSID 1805 then withdraws the MNP from the routing/mapping system and informs 1806 the AR that the release was successful. 1808 o When all of a MNs underlying interfaces have transitioned to DOWN 1809 (or if the prefix registration lifetime expires), any associated 1810 MSEs withdraw the MNP the same as if they had received a message 1811 with a release indication. 1813 The MN is responsible for retrying each RS exchange up to 1814 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 1815 seconds until an RA is received. If no RA is received over an UP 1816 underlying interface (i.e., even after attempting to contact 1817 alternate MSEs), the MN declares this underlying interface as DOWN. 1819 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 1820 Therefore, when the IPv6 layer sends an RS message the OMNI interface 1821 returns an internally-generated RA message as though the message 1822 originated from an IPv6 router. The internally-generated RA message 1823 contains configuration information that is consistent with the 1824 information received from the RAs generated by the MS. Whether the 1825 OMNI interface IPv6 ND messaging process is initiated from the 1826 receipt of an RS message from the IPv6 layer is an implementation 1827 matter. Some implementations may elect to defer the IPv6 ND 1828 messaging process until an RS is received from the IPv6 layer, while 1829 others may elect to initiate the process proactively. Still other 1830 deployments may elect to administratively disable the ordinary RS/RA 1831 messaging used by the IPv6 layer over the OMNI interface, since they 1832 are not required to drive the internal RS/RA processing. (Note that 1833 this same logic applies to IPv4 implementations that employ ICMP- 1834 based Router Discovery per [RFC1256].) 1836 Note: The Router Lifetime value in RA messages indicates the time 1837 before which the MN must send another RS message over this underlying 1838 interface (e.g., 600 seconds), however that timescale may be 1839 significantly longer than the lifetime the MS has committed to retain 1840 the prefix registration (e.g., REACHABLETIME seconds). ARs are 1841 therefore responsible for keeping MS state alive on a shorter 1842 timescale than the MN is required to do on its own behalf. 1844 Note: On multicast-capable underlying interfaces, MNs should send 1845 periodic unsolicited multicast NA messages and ARs should send 1846 periodic unsolicited multicast RA messages as "beacons" that can be 1847 heard by other nodes on the link. If a node fails to receive a 1848 beacon after a timeout value specific to the link, it can initiate a 1849 unicast exchange to test reachability. 1851 Note: if an AR acting as a proxy forwards a MN's RS message to 1852 another node acting as an MSE using UDP/IP encapsulation, it must use 1853 a distinct UDP source port number for each MN. This allows the MSE 1854 to distinguish different MNs behind the same AR at the link-layer, 1855 whereas the link-layer addresses would otherwise be 1856 indistinguishable. 1858 13.1. Router Discovery in IP Multihop and IPv4-Only Networks 1860 On some *NETs, a MN may be located multiple IP hops away from the 1861 nearest AR. Forwarding through IP multihop *NETs is conducted 1862 through the application of a routing protocol (e.g., a Mobile Ad-hoc 1863 Network (MANET) routing protocol over omni-directional wireless 1864 interfaces, an inter-domain routing protocol in an enterprise 1865 network, etc.). These *NETs could be either IPv6-enabled or 1866 IPv4-only, while IPv4-only *NETs could be either multicast-capable or 1867 unicast-only (note that for IPv4-only *NETs the following procedures 1868 apply for both single-hop and multihop cases). 1870 A MN located potentially multiple *NET hops away from the nearest AR 1871 prepares an RS message with source address set to either its MNP-LLA 1872 or a Temporary LLA, and with destination set to link-scoped All- 1873 Routers multicast the same as discussed above. For IPv6-enabled 1874 *NETs, the MN then encapsulates the message in an IPv6 header with 1875 source address set to the ULA corresponding to the LLA source address 1876 and with destination set to either a unicast or anycast ADM-ULA. For 1877 IPv4-only *NETs, the MN instead encapsulates the RS message in an 1878 IPv4 header with source address set to the node's own IPv4 address 1879 and with destination address set to either the unicast IPv4 address 1880 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 1881 MN then sends the encapsulated RS message via the *NET interface, 1882 where it will be forwarded by zero or more intermediate *NET hops. 1884 When an intermediate *NET hop that participates in the routing 1885 protocol receives the encapsulated RS, it forwards the message 1886 according to its routing tables (note that an intermediate node could 1887 be a fixed infrastructure element or another MN). This process 1888 repeats iteratively until the RS message is received by a penultimate 1889 *NET hop within single-hop communications range of an AR, which 1890 forwards the message to the AR. 1892 When the AR receives the message, it decapsulates the RS and 1893 coordinates with the MS the same as for an ordinary link-local RS, 1894 since the inner Hop Limit will not have been decremented by the 1895 multihop forwarding process. The AR then prepares an RA message with 1896 source address set to its own ADM-LLA and destination address set to 1897 the LLA of the original MN, then encapsulates the message in an IPv4/ 1898 IPv6 header with source address set to its own IPv4/ULA address and 1899 with destination set to the encapsulation source of the RS. 1901 The AR then forwards the message to an *NET node within 1902 communications range, which forwards the message according to its 1903 routing tables to an intermediate node. The multihop forwarding 1904 process within the *NET continues repetitively until the message is 1905 delivered to the original MN, which decapsulates the message and 1906 performs autoconfiguration the same as if it had received the RA 1907 directly from the AR as an on-link neighbor. 1909 Note: An alternate approach to multihop forwarding via IPv6 1910 encapsulation would be to statelessly translate the IPv6 LLAs into 1911 ULAs and forward the messages without encapsulation. This would 1912 violate the [RFC4861] requirement that certain IPv6 ND messages must 1913 use link-local addresses and must not be accepted if received with 1914 Hop Limit less than 255. This document therefore advocates 1915 encapsulation since the overhead is nominal considering the 1916 infrequent nature and small size of IPv6 ND messages. Future 1917 documents may consider encapsulation avoidance through translation 1918 while updating [RFC4861]. 1920 Note: An alternate approach to multihop forwarding via IPv4 1921 encapsulation would be to employ IPv6/IPv4 protocol translation. 1922 However, for IPv6 ND messages the LLAs would be truncated due to 1923 translation and the OMNI Router and Prefix Discovery services would 1924 not be able to function. The use of IPv4 encapsulation is therefore 1925 indicated. 1927 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 1928 of a new IPv4 /24 prefix allocation, but this may be difficult to 1929 obtain given IPv4 address exhaustion. An alternative would be to re- 1930 purpose the prefix 192.88.99.0 which has been set aside from its 1931 former use by [RFC7526]. 1933 13.2. MS-Register and MS-Release List Processing 1935 When a MN sends an RS message with an OMNI option via an underlying 1936 interface to an AR, the MN must convey its knowledge of its 1937 currently-associated MSEs. Initially, the MN will have no associated 1938 MSEs and should therefore include an MS-Register sub-option with the 1939 single MSID value 0 which requests the AR to select and assign an 1940 MSE. The AR will then return an RA message with source address set 1941 to the ADM-LLA of the selected MSE. 1943 As the MN activates additional underlying interfaces, it can 1944 optionally include an MS-Register sub-option with MSID value 0, or 1945 with non-zero MSIDs for MSEs discovered from previous RS/RA 1946 exchanges. The MN will thus eventually begin to learn and manage its 1947 currently active set of MSEs, and can register with new MSEs or 1948 release from former MSEs with each successive RS/RA exchange. As the 1949 MN's MSE constituency grows, it alone is responsible for including or 1950 omitting MSIDs in the MS-Register/Release lists it sends in RS 1951 messages. The inclusion or omission of MSIDs determines the MN's 1952 interface to the MS and defines the manner in which MSEs will 1953 respond. The only limiting factor is that the MN should include no 1954 more than MAX_MSID values in each list per each IPv6 ND message, and 1955 should avoid duplication of entries in each list unless it wants to 1956 increase likelihood of control message delivery. 1958 When an AR receives an RS message sent by a MN with an OMNI option, 1959 the option will contain zero or more MS-Register and MS-Release sub- 1960 options containing MSIDs. After processing the OMNI option, the AR 1961 will have a list of zero or more MS-Register MSIDs and a list of zero 1962 or more of MS-Release MSIDs. The AR then processes the lists as 1963 follows: 1965 o For each list, retain the first MAX_MSID values in the list and 1966 discard any additional MSIDs (i.e., even if there are duplicates 1967 within a list). 1969 o Next, for each MSID in the MS-Register list, remove all matching 1970 MSIDs from the MS-Release list. 1972 o Next, proceed according to whether the AR's own MSID or the value 1973 0 appears in the MS-Register list as follows: 1975 * If yes, send an RA message directly back to the MN and send a 1976 proxy copy of the RS message to each additional MSID in the MS- 1977 Register list with the MS-Register/Release lists omitted. 1978 Then, send a uNA message to each MSID in the MS-Release list 1979 with the MS-Register/Release lists omitted and with an OMNI 1980 header with S/T-ifIndex set to 0. 1982 * If no, send a proxy copy of the RS message to each additional 1983 MSID in the MS-Register list with the MS-Register list omitted. 1984 For the first MSID, include the original MS-Release list; for 1985 all other MSIDs, omit the MS-Release list. 1987 Each proxy copy of the RS message will include an OMNI option and 1988 encapsulation header with the ADM-ULA of the AR as the source and the 1989 ADM-ULA of the Register MSE as the destination. When the Register 1990 MSE receives the proxy RS message, if the message includes an MS- 1991 Release list the MSE sends a uNA message to each additional MSID in 1992 the Release list. The Register MSE then sends an RA message back to 1993 the (Proxy) AR wrapped in an OMNI encapsulation header with source 1994 and destination addresses reversed, and with RA destination set to 1995 the MNP-LLA of the MN. When the AR receives this RA message, it 1996 sends a proxy copy of the RA to the MN. 1998 Each uNA message (whether send by the first-hop AR or by a Register 1999 MSE) will include an OMNI option and an encapsulation header with the 2000 ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2001 Release ME as the destination. The uNA informs the Release MSE that 2002 its previous relationship with the MN has been released and that the 2003 source of the uNA message is now registered. The Release MSE must 2004 then note that the subject MN of the uNA message is now "departed", 2005 and forward any subsequent packets destined to the MN to the Register 2006 MSE. 2008 Note that it is not an error for the MS-Register/Release lists to 2009 include duplicate entries. If duplicates occur within a list, the AR 2010 will generate multiple proxy RS and/or uNA messages - one for each 2011 copy of the duplicate entries. 2013 13.3. DHCPv6-based Prefix Registration 2015 When a MN is not pre-provisioned with an MNP-LLA (or, when multiple 2016 MNPs are needed), it will require the AR to select MNPs on its behalf 2017 and set up the correct routing state within the MS. The DHCPv6 2018 service [RFC8415] supports this requirement. 2020 When an MN needs to have the AR select MNPs, it sends an RS message 2021 with a Temporary LLA as the source and with DHCPv6 Message suboption 2022 containing a Client Identifier, one or more IA_PD options and a Rapid 2023 Commit option. The MN also sets the 'msg-type' field to "Solicit", 2024 and includes a 3-octet 'transaction-id'. 2026 When the AR receives the RS message, it extracts the DHCPv6 message 2027 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 2028 a message exchange with the locally-resident DHCPv6 server, which 2029 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2030 (If the AR wishes to defer creation of MN state until the DHCPv6 2031 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2032 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2033 forward/reply exchange with Relay Message and Interface ID options.) 2035 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2036 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2037 sends an RA back to the MN with the DHCPv6 Reply message included in 2038 an OMNI DHCPv6 message sub-option. If the RS message source address 2039 was a Temporary address, the AR includes one of the (newly-created) 2040 MNP-LLAs as the RA destination address. The MN then creates a 2041 default route, assigns Subnet Router Anycast addresses and uses the 2042 RA destination address as its primary MNP-LLA. The MN will then use 2043 this primary MNP-LLA as the source address of any IPv6 ND messages it 2044 sends as long as it retains ownership of the MNP. 2046 Note: The single-octet OMNI sub-option length field restricts the 2047 DHCPv6 Message sub-option to a maximum of 255 octets for both the RS 2048 and RA messages. This provides sufficient room for the DHCPv6 2049 message header, a Client/Server Identifier option, a Rapid Commit 2050 option, at least 3 Identity Association for Prefix Delegation (IA_PD) 2051 options and any other supporting DHCPv6 options. A MN requiring more 2052 DHCPv6-based configuration information than this can either perform 2053 multiple independent RS/RA exchanges (with each exchange providing a 2054 subset of the total configuration information) or simply perform an 2055 actual DHCPv6 message exchange in addition to any RS/RA exchanges. 2057 Note: After a MN performs a DHCPv6-based prefix registration exchange 2058 with a first AR, it would need to repeat the exchange with each 2059 additional MSE it registers with. In that case, the MN supplies the 2060 MNP delegations received from the first AR in the IA_PD fields of a 2061 DHCPv6 message when it engages the additional MSEs. 2063 14. Secure Redirection 2065 If the *NET link model is multiple access, the AR is responsible for 2066 assuring that address duplication cannot corrupt the neighbor caches 2067 of other nodes on the link. When the MN sends an RS message on a 2068 multiple access *NET link, the AR verifies that the MN is authorized 2069 to use the address and returns an RA with a non-zero Router Lifetime 2070 only if the MN is authorized. 2072 After verifying MN authorization and returning an RA, the AR MAY 2073 return IPv6 ND Redirect messages to direct MNs located on the same 2074 *NET link to exchange packets directly without transiting the AR. In 2075 that case, the MNs can exchange packets according to their unicast L2 2076 addresses discovered from the Redirect message instead of using the 2077 dogleg path through the AR. In some *NET links, however, such direct 2078 communications may be undesirable and continued use of the dogleg 2079 path through the AR may provide better performance. In that case, 2080 the AR can refrain from sending Redirects, and/or MNs can ignore 2081 them. 2083 15. AR and MSE Resilience 2085 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2086 [RFC5798] configurations so that service continuity is maintained 2087 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2088 the (redundant) ARs is currently providing service, and any service 2089 discontinuity will be limited to the failover time supported by VRRP. 2090 Widely deployed public domain implementations of VRRP are available. 2092 MSEs SHOULD use high availability clustering services so that 2093 multiple redundant systems can provide coordinated response to 2094 failures. As with VRRP, widely deployed public domain 2095 implementations of high availability clustering services are 2096 available. Note that special-purpose and expensive dedicated 2097 hardware is not necessary, and public domain implementations can be 2098 used even between lightweight virtual machines in cloud deployments. 2100 16. Detecting and Responding to MSE Failures 2102 In environments where fast recovery from MSE failure is required, ARs 2103 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2104 manner that parallels Bidirectional Forwarding Detection (BFD) 2105 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2106 react to failures so that cached information is re-established 2107 through alternate paths. Proactive NUD control messaging is carried 2108 only over well-connected ground domain networks (i.e., and not low- 2109 end *NET links such as aeronautical radios) and can therefore be 2110 tuned for rapid response. 2112 ARs perform proactive NUD for MSEs for which there are currently 2113 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2114 of the outage by sending multicast RA messages on the *NET interface. 2115 The AR sends RA messages to MNs via the *NET interface with an OMNI 2116 option with a Release ID for the failed MSE, and with destination 2117 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2119 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2120 by small delays [RFC4861]. Any MNs on the *NET interface that have 2121 been using the (now defunct) MSE will receive the RA messages and 2122 associate with a new MSE. 2124 17. Transition Considerations 2126 When a MN connects to an *NET link for the first time, it sends an RS 2127 message with an OMNI option. If the first hop AR recognizes the 2128 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2129 as the destination and with an OMNI option included. The MN then 2130 engages the AR according to the OMNI link model specified above. If 2131 the first hop AR is a legacy IPv6 router, however, it instead returns 2132 an RA message with no OMNI option and with a non-OMNI unicast source 2133 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2134 according to the legacy IPv6 link model and without the OMNI 2135 extensions specified in this document. 2137 If the *NET link model is multiple access, there must be assurance 2138 that address duplication cannot corrupt the neighbor caches of other 2139 nodes on the link. When the MN sends an RS message on a multiple 2140 access *NET link with an LLA source address and an OMNI option, ARs 2141 that recognize the option ensure that the MN is authorized to use the 2142 address and return an RA with a non-zero Router Lifetime only if the 2143 MN is authorized. ARs that do not recognize the option instead 2144 return an RA that makes no statement about the MN's authorization to 2145 use the source address. In that case, the MN should perform 2146 Duplicate Address Detection to ensure that it does not interfere with 2147 other nodes on the link. 2149 An alternative approach for multiple access *NET links to ensure 2150 isolation for MN / AR communications is through L2 address mappings 2151 as discussed in Appendix C. This arrangement imparts a (virtual) 2152 point-to-point link model over the (physical) multiple access link. 2154 18. OMNI Interfaces on the Open Internet 2156 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2157 the open Internet without an OMNI-aware first-hop AR receive RA 2158 messages that do not include an OMNI option, while OMNI interfaces 2159 configured over IPv4-only underlying interfaces do not receive any 2160 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2161 without an OMNI option configure addresses, on-link prefixes, etc. on 2162 the underlying interface that received the RA according to standard 2163 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2164 interfaces configured over IPv4-only underlying interfaces configure 2165 IPv4 address information on the underlying interfaces using 2166 mechanisms such as DHCPv4 [RFC2131]. 2168 OMNI interfaces configured over underlying interfaces that connect to 2169 the open Internet can apply security services such as VPNs to connect 2170 to an MSE, or can establish a direct link to an MSE through some 2171 other means (see Section 4). In environments where an explicit VPN 2172 or direct link may be impractical, OMNI interfaces can instead use 2173 UDP/IP encapsulation and HMAC-based message authentication per 2174 [RFC6081][RFC4380]. 2176 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2177 interfaces send control plane messages to interface with the MS, 2178 including RS/RA messages used according to Section 13 and Neighbor 2179 Solicitation (NS) and Neighbor Advertisement (NA) messages used for 2180 address resolution / route optimization (see: 2181 [I-D.templin-intarea-6706bis]). The control plane messages must be 2182 authenticated while data plane messages are delivered the same as for 2183 ordinary best-effort Internet traffic with basic source address-based 2184 data origin verification. Data plane communications via OMNI 2185 interfaces that connect over the open Internet without an explicit 2186 VPN should therefore employ transport- or higher-layer security to 2187 ensure integrity and/or confidentiality. 2189 OMNI interfaces in the open Internet are often located behind Network 2190 Address Translators (NATs). The OMNI interface accommodates NAT 2191 traversal using UDP/IP encapsulation and the mechanisms discussed in 2192 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2194 19. Time-Varying MNPs 2196 In some use cases, it is desirable, beneficial and efficient for the 2197 MN to receive a constant MNP that travels with the MN wherever it 2198 moves. For example, this would allow air traffic controllers to 2199 easily track aircraft, etc. In other cases, however (e.g., 2200 intelligent transportation systems), the MN may be willing to 2201 sacrifice a modicum of efficiency in order to have time-varying MNPs 2202 that can be changed every so often to defeat adversarial tracking. 2204 The prefix delegation services discussed in Section 13.3 allows OMNI 2205 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2206 use a Temporary LLA as the source address of an RS message with an 2207 OMNI option with DHCPv6 Option sub-options. The MN would then be 2208 obligated to renumber its internal networks whenever its MNP (and 2209 therefore also its OMNI address) changes. This should not present a 2210 challenge for MNs with automated network renumbering services, 2211 however presents limits for the durations of ongoing sessions that 2212 would prefer to use a constant address. 2214 20. IANA Considerations 2216 The IANA is instructed to allocate an official Type number TBD from 2217 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2218 option. Implementations set Type to 253 as an interim value 2219 [RFC4727]. 2221 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2222 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2223 read as follows: 2225 Code Name Reference 2226 --- ---- --------- 2227 0 Diagnostic Packet Too Big [RFC4443] 2228 1 Advisory Packet Too Big [RFCXXXX] 2230 Figure 17: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2232 The IANA is instructed to allocate one Ethernet unicast address TBD2 2233 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2234 Address Block - Unicast Use". 2236 The OMNI option also defines an 8-bit Sub-Type field, for which IANA 2237 is instructed to create and maintain a new registry entitled "OMNI 2238 option Sub-Type values". Initial values for the OMNI option Sub-Type 2239 values registry are given below; future assignments are to be made 2240 through Expert Review [RFC8126]. 2242 Value Sub-Type name Reference 2243 ----- ------------- ---------- 2244 0 Pad1 [RFCXXXX] 2245 1 PadN [RFCXXXX] 2246 2 Interface Attributes [RFCXXXX] 2247 3 Traffic Selector [RFCXXXX] 2248 4 MS-Register [RFCXXXX] 2249 5 MS-Release [RFCXXXX] 2250 6 Network Access Identifier [RFCXXXX] 2251 7 Geo Coordinates [RFCXXXX] 2252 8 DHCP Unique Identifier (DUID) [RFCXXXX] 2253 9 DHCPv6 Message [RFCXXXX] 2254 10-252 Unassigned 2255 253-254 Experimental [RFCXXXX] 2256 255 Reserved [RFCXXXX] 2258 Figure 18: OMNI Option Sub-Type Values 2260 21. Security Considerations 2262 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2263 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2264 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2265 confirmation and/or time synchronization is needed. 2267 OMNI interfaces configured over secured ANET interfaces inherit the 2268 physical and/or link-layer security properties (i.e., "protected 2269 spectrum") of the connected ANETs. OMNI interfaces configured over 2270 open INET interfaces can use symmetric securing services such as VPNs 2271 or can by some other means establish a direct link. When a VPN or 2272 direct link may be impractical, however, an asymmetric security 2273 service such as the authentication option specified in [RFC4380] or 2274 other protocol control message security mechanisms may be necessary. 2275 While the OMNI link protects control plane messaging, applications 2276 must still employ end-to-end transport- or higher-layer security 2277 services to protect the data plane. 2279 The Mobility Service MUST provide strong network layer security for 2280 control plane messages and forwarding path integrity for data plane 2281 messages. In one example, the AERO service 2282 [I-D.templin-intarea-6706bis] constructs a spanning tree between 2283 mobility service elements and secures the links in the spanning tree 2284 with network layer security mechanisms such as IPsec [RFC4301] or 2285 Wireguard. Control plane messages are then constrained to travel 2286 only over the secured spanning tree paths and are therefore protected 2287 from attack or eavesdropping. Since data plane messages can travel 2288 over route optimized paths that do not strictly follow the spanning 2289 tree, however, end-to-end transport- or higher-layer security 2290 services are still required. 2292 Security considerations for specific access network interface types 2293 are covered under the corresponding IP-over-(foo) specification 2294 (e.g., [RFC2464], [RFC2492], etc.). 2296 Security considerations for IPv6 fragmentation and reassembly are 2297 discussed in Section 5.1. 2299 22. Implementation Status 2301 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2302 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2303 Newer specification versions will be tagged in upcoming releases. 2304 First public release expected before the end of 2020. 2306 23. Acknowledgements 2308 The first version of this document was prepared per the consensus 2309 decision at the 7th Conference of the International Civil Aviation 2310 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2311 2019. Consensus to take the document forward to the IETF was reached 2312 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2313 Attendees and contributors included: Guray Acar, Danny Bharj, 2314 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2315 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2316 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2317 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2318 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2319 Fryderyk Wrobel and Dongsong Zeng. 2321 The following individuals are acknowledged for their useful comments: 2322 Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric 2323 Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized 2324 for their many helpful ideas and suggestions. Madhuri Madhava 2325 Badgandi, Katherine Tran, and Vijayasarathy Rajagopalan are 2326 acknowledged for their hard work on the implementation and insights 2327 that led to improvements to the spec. 2329 Discussions on the IETF 6man and atn mailing lists during the fall of 2330 2020 suggested additional points to consider. The authors gratefully 2331 acknowledge the list members who contributed valuable insights 2332 through those discussions. Eric Vyncke and Erik Kline were the 2333 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2334 at the time the document was developed; they are all gratefully 2335 acknowledged for their many helpful insights. 2337 This work is aligned with the NASA Safe Autonomous Systems Operation 2338 (SASO) program under NASA contract number NNA16BD84C. 2340 This work is aligned with the FAA as per the SE2025 contract number 2341 DTFAWA-15-D-00030. 2343 24. References 2345 24.1. Normative References 2347 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2348 DOI 10.17487/RFC0791, September 1981, 2349 . 2351 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2352 Requirement Levels", BCP 14, RFC 2119, 2353 DOI 10.17487/RFC2119, March 1997, 2354 . 2356 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2357 "Definition of the Differentiated Services Field (DS 2358 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2359 DOI 10.17487/RFC2474, December 1998, 2360 . 2362 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2363 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2364 DOI 10.17487/RFC3971, March 2005, 2365 . 2367 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2368 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2369 November 2005, . 2371 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2372 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2373 . 2375 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2376 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2377 2006, . 2379 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2380 Control Message Protocol (ICMPv6) for the Internet 2381 Protocol Version 6 (IPv6) Specification", STD 89, 2382 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2383 . 2385 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2386 ICMPv6, UDP, and TCP Headers", RFC 4727, 2387 DOI 10.17487/RFC4727, November 2006, 2388 . 2390 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2391 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2392 DOI 10.17487/RFC4861, September 2007, 2393 . 2395 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2396 Address Autoconfiguration", RFC 4862, 2397 DOI 10.17487/RFC4862, September 2007, 2398 . 2400 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2401 "Traffic Selectors for Flow Bindings", RFC 6088, 2402 DOI 10.17487/RFC6088, January 2011, 2403 . 2405 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2406 Hosts in a Multi-Prefix Network", RFC 8028, 2407 DOI 10.17487/RFC8028, November 2016, 2408 . 2410 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2411 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2412 May 2017, . 2414 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2415 (IPv6) Specification", STD 86, RFC 8200, 2416 DOI 10.17487/RFC8200, July 2017, 2417 . 2419 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2420 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2421 DOI 10.17487/RFC8201, July 2017, 2422 . 2424 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2425 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2426 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2427 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2428 . 2430 24.2. Informative References 2432 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2433 Interface for Civil Aviation, IETF Liaison Statement 2434 #1676, https://datatracker.ietf.org/liaison/1676/", March 2435 2020. 2437 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2438 Aeronautical Telecommunication Network (ATN) using 2439 Internet Protocol Suite (IPS) Standards and Protocol), 2440 Draft Edition 3 (work-in-progress)", December 2020. 2442 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2443 Interface (FDDI), IEEE Transactions on Communications", 2444 August 1990. 2446 [I-D.ietf-6man-rfc4941bis] 2447 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2448 "Temporary Address Extensions for Stateless Address 2449 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2450 (work in progress), November 2020. 2452 [I-D.ietf-intarea-tunnels] 2453 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2454 Architecture", draft-ietf-intarea-tunnels-10 (work in 2455 progress), September 2019. 2457 [I-D.ietf-ipwave-vehicular-networking] 2458 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2459 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2460 ipwave-vehicular-networking-19 (work in progress), July 2461 2020. 2463 [I-D.templin-6man-dhcpv6-ndopt] 2464 Templin, F., "A Unified Stateful/Stateless Configuration 2465 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-10 2466 (work in progress), June 2020. 2468 [I-D.templin-6man-lla-type] 2469 Templin, F., "The IPv6 Link-Local Address Type Field", 2470 draft-templin-6man-lla-type-02 (work in progress), 2471 November 2020. 2473 [I-D.templin-intarea-6706bis] 2474 Templin, F., "Asymmetric Extended Route Optimization 2475 (AERO)", draft-templin-intarea-6706bis-83 (work in 2476 progress), December 2020. 2478 [IPV4-GUA] 2479 Postel, J., "IPv4 Address Space Registry, 2480 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2481 address-space.xhtml", December 2020. 2483 [IPV6-GUA] 2484 Postel, J., "IPv6 Global Unicast Address Assignments, 2485 https://www.iana.org/assignments/ipv6-unicast-address- 2486 assignments/ipv6-unicast-address-assignments.xhtml", 2487 December 2020. 2489 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2490 Communication Layers", STD 3, RFC 1122, 2491 DOI 10.17487/RFC1122, October 1989, 2492 . 2494 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2495 DOI 10.17487/RFC1191, November 1990, 2496 . 2498 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2499 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2500 . 2502 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2503 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2504 . 2506 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2507 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2508 . 2510 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2511 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2512 . 2514 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2515 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2516 December 1998, . 2518 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2519 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2520 . 2522 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2523 Domains without Explicit Tunnels", RFC 2529, 2524 DOI 10.17487/RFC2529, March 1999, 2525 . 2527 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2528 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2529 . 2531 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2532 DOI 10.17487/RFC3330, September 2002, 2533 . 2535 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2536 Considered Useful", BCP 82, RFC 3692, 2537 DOI 10.17487/RFC3692, January 2004, 2538 . 2540 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2541 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2542 DOI 10.17487/RFC3810, June 2004, 2543 . 2545 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2546 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2547 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2548 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2549 . 2551 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2552 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2553 2004, . 2555 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2556 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2557 DOI 10.17487/RFC4271, January 2006, 2558 . 2560 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2561 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2562 December 2005, . 2564 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2565 Network Address Translations (NATs)", RFC 4380, 2566 DOI 10.17487/RFC4380, February 2006, 2567 . 2569 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2570 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2571 2006, . 2573 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2574 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2575 . 2577 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2578 "Considerations for Internet Group Management Protocol 2579 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2580 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2581 . 2583 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2584 "Internet Group Management Protocol (IGMP) / Multicast 2585 Listener Discovery (MLD)-Based Multicast Forwarding 2586 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2587 August 2006, . 2589 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2590 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2591 . 2593 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2594 Errors at High Data Rates", RFC 4963, 2595 DOI 10.17487/RFC4963, July 2007, 2596 . 2598 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2599 Advertisement Flags Option", RFC 5175, 2600 DOI 10.17487/RFC5175, March 2008, 2601 . 2603 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2604 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2605 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2606 . 2608 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2609 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2610 DOI 10.17487/RFC5214, March 2008, 2611 . 2613 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2614 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2615 . 2617 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2618 Version 3 for IPv4 and IPv6", RFC 5798, 2619 DOI 10.17487/RFC5798, March 2010, 2620 . 2622 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2623 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2624 . 2626 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2627 DOI 10.17487/RFC6081, January 2011, 2628 . 2630 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2631 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2632 DOI 10.17487/RFC6221, May 2011, 2633 . 2635 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2636 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2637 DOI 10.17487/RFC6355, August 2011, 2638 . 2640 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 2641 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2642 2012, . 2644 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2645 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2646 DOI 10.17487/RFC7084, November 2013, 2647 . 2649 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 2650 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 2651 Boundary in IPv6 Addressing", RFC 7421, 2652 DOI 10.17487/RFC7421, January 2015, 2653 . 2655 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 2656 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 2657 DOI 10.17487/RFC7526, May 2015, 2658 . 2660 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 2661 DOI 10.17487/RFC7542, May 2015, 2662 . 2664 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 2665 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 2666 February 2016, . 2668 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 2669 Support for IP Hosts with Multi-Access Support", RFC 7847, 2670 DOI 10.17487/RFC7847, May 2016, 2671 . 2673 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2674 Writing an IANA Considerations Section in RFCs", BCP 26, 2675 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2676 . 2678 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 2679 Decraene, B., Litkowski, S., and R. Shakir, "Segment 2680 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 2681 July 2018, . 2683 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 2684 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 2685 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 2686 . 2688 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 2689 and F. Gont, "IP Fragmentation Considered Fragile", 2690 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 2691 . 2693 Appendix A. Interface Attribute Preferences Bitmap Encoding 2695 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 2696 encoding to specific Internetworks such as the Aeronautical 2697 Telecommunications Network with Internet Protocol Services (ATN/IPS) 2698 may include link selection preferences based on other traffic 2699 classifiers (e.g., transport port numbers, etc.) in addition to the 2700 existing DSCP-based preferences. Nodes on specific Internetworks 2701 maintain a map of traffic classifiers to additional P[*] preference 2702 fields beyond the first 64. For example, TCP port 22 maps to P[67], 2703 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 2705 Implementations use Simplex or Indexed encoding formats for P[*] 2706 encoding in order to encode a given set of traffic classifiers in the 2707 most efficient way. Some use cases may be more efficiently coded 2708 using Simplex form, while others may be more efficient using Indexed. 2709 Once a format is selected for preparation of a single Interface 2710 Attribute the same format must be used for the entire Interface 2711 Attribute sub-option. Different sub-options may use different 2712 formats. 2714 The following figures show coding examples for various Simplex and 2715 Indexed formats: 2717 0 1 2 3 2718 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 2719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2720 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2722 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 2723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2724 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 2725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2726 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 2727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2728 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 2729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2730 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2731 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2732 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 2733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2735 Figure 19: Example 1: Dense Simplex Encoding 2737 0 1 2 3 2738 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 2739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2740 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2742 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 2743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2744 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 2745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2746 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 2747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2748 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 2749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2750 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 2751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2752 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 2753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2754 |Bitmap(10)=0x00| ... 2755 +-+-+-+-+-+-+-+-+-+-+- 2757 Figure 20: Example 2: Sparse Simplex Encoding 2759 0 1 2 3 2760 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 2761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2762 | Sub-Type=2 | Sub-length=N | ifIndex | ifType | 2763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2764 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 2765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2766 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 2767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2768 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 2769 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2770 | Bitmap = 0x01 |796|797|798|799| ... 2771 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2773 Figure 21: Example 3: Indexed Encoding 2775 Appendix B. VDL Mode 2 Considerations 2777 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 2778 (VDLM2) that specifies an essential radio frequency data link service 2779 for aircraft and ground stations in worldwide civil aviation air 2780 traffic management. The VDLM2 link type is "multicast capable" 2781 [RFC4861], but with considerable differences from common multicast 2782 links such as Ethernet and IEEE 802.11. 2784 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 2785 magnitude less than most modern wireless networking gear. Second, 2786 due to the low available link bandwidth only VDLM2 ground stations 2787 (i.e., and not aircraft) are permitted to send broadcasts, and even 2788 so only as compact layer 2 "beacons". Third, aircraft employ the 2789 services of ground stations by performing unicast RS/RA exchanges 2790 upon receipt of beacons instead of listening for multicast RA 2791 messages and/or sending multicast RS messages. 2793 This beacon-oriented unicast RS/RA approach is necessary to conserve 2794 the already-scarce available link bandwidth. Moreover, since the 2795 numbers of beaconing ground stations operating within a given spatial 2796 range must be kept as sparse as possible, it would not be feasible to 2797 have different classes of ground stations within the same region 2798 observing different protocols. It is therefore highly desirable that 2799 all ground stations observe a common language of RS/RA as specified 2800 in this document. 2802 Note that links of this nature may benefit from compression 2803 techniques that reduce the bandwidth necessary for conveying the same 2804 amount of data. The IETF lpwan working group is considering possible 2805 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 2807 Appendix C. MN / AR Isolation Through L2 Address Mapping 2809 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 2810 unicast link-scoped IPv6 destination address. However, IPv6 ND 2811 messaging should be coordinated between the MN and AR only without 2812 invoking other nodes on the *NET. This implies that MN / AR control 2813 messaging should be isolated and not overheard by other nodes on the 2814 link. 2816 To support MN / AR isolation on some *NET links, ARs can maintain an 2817 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 2818 *NETs, this specification reserves one Ethernet unicast address TBD2 2819 (see: Section 20). For non-Ethernet statically-addressed *NETs, 2820 MSADDR is reserved per the assigned numbers authority for the *NET 2821 addressing space. For still other *NETs, MSADDR may be dynamically 2822 discovered through other means, e.g., L2 beacons. 2824 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 2825 both multicast and unicast) to MSADDR instead of to an ordinary 2826 unicast or multicast L2 address. In this way, all of the MN's IPv6 2827 ND messages will be received by ARs that are configured to accept 2828 packets destined to MSADDR. Note that multiple ARs on the link could 2829 be configured to accept packets destined to MSADDR, e.g., as a basis 2830 for supporting redundancy. 2832 Therefore, ARs must accept and process packets destined to MSADDR, 2833 while all other devices must not process packets destined to MSADDR. 2834 This model has well-established operational experience in Proxy 2835 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 2837 Appendix D. Change Log 2839 << RFC Editor - remove prior to publication >> 2841 Differences from draft-templin-6man-omni-interface-35 to draft- 2842 templin-6man-omni-interface-36: 2844 o Major clarifications on aspects such as "hard/soft" PTB error 2845 messages 2847 o Made generic so that either IP protocol version (IPv4 or IPv6) can 2848 be used in the data plane. 2850 Differences from draft-templin-6man-omni-interface-31 to draft- 2851 templin-6man-omni-interface-32: 2853 o MTU 2854 o Support for multi-hop ANETS such as ISATAP. 2856 Differences from draft-templin-6man-omni-interface-29 to draft- 2857 templin-6man-omni-interface-30: 2859 o Moved link-layer addressing information into the OMNI option on a 2860 per-ifIndex basis 2862 o Renamed "ifIndex-tuple" to "Interface Attributes" 2864 Differences from draft-templin-6man-omni-interface-27 to draft- 2865 templin-6man-omni-interface-28: 2867 o Updates based on implementation experience. 2869 Differences from draft-templin-6man-omni-interface-25 to draft- 2870 templin-6man-omni-interface-26: 2872 o Further clarification on "aggregate" RA messages. 2874 o Expanded Security Considerations to discuss expectations for 2875 security in the Mobility Service. 2877 Differences from draft-templin-6man-omni-interface-20 to draft- 2878 templin-6man-omni-interface-21: 2880 o Safety-Based Multilink (SBM) and Performance-Based Multilink 2881 (PBM). 2883 Differences from draft-templin-6man-omni-interface-18 to draft- 2884 templin-6man-omni-interface-19: 2886 o SEND/CGA. 2888 Differences from draft-templin-6man-omni-interface-17 to draft- 2889 templin-6man-omni-interface-18: 2891 o Teredo 2893 Differences from draft-templin-6man-omni-interface-14 to draft- 2894 templin-6man-omni-interface-15: 2896 o Prefix length discussions removed. 2898 Differences from draft-templin-6man-omni-interface-12 to draft- 2899 templin-6man-omni-interface-13: 2901 o Teredo 2902 Differences from draft-templin-6man-omni-interface-11 to draft- 2903 templin-6man-omni-interface-12: 2905 o Major simplifications and clarifications on MTU and fragmentation. 2907 o Document now updates RFC4443 and RFC8201. 2909 Differences from draft-templin-6man-omni-interface-10 to draft- 2910 templin-6man-omni-interface-11: 2912 o Removed /64 assumption, resulting in new OMNI address format. 2914 Differences from draft-templin-6man-omni-interface-07 to draft- 2915 templin-6man-omni-interface-08: 2917 o OMNI MNs in the open Internet 2919 Differences from draft-templin-6man-omni-interface-06 to draft- 2920 templin-6man-omni-interface-07: 2922 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 2923 L2 addressing. 2925 o Expanded "Transition Considerations". 2927 Differences from draft-templin-6man-omni-interface-05 to draft- 2928 templin-6man-omni-interface-06: 2930 o Brought back OMNI option "R" flag, and discussed its use. 2932 Differences from draft-templin-6man-omni-interface-04 to draft- 2933 templin-6man-omni-interface-05: 2935 o Transition considerations, and overhaul of RS/RA addressing with 2936 the inclusion of MSE addresses within the OMNI option instead of 2937 as RS/RA addresses (developed under FAA SE2025 contract number 2938 DTFAWA-15-D-00030). 2940 Differences from draft-templin-6man-omni-interface-02 to draft- 2941 templin-6man-omni-interface-03: 2943 o Added "advisory PTB messages" under FAA SE2025 contract number 2944 DTFAWA-15-D-00030. 2946 Differences from draft-templin-6man-omni-interface-01 to draft- 2947 templin-6man-omni-interface-02: 2949 o Removed "Primary" flag and supporting text. 2951 o Clarified that "Router Lifetime" applies to each ANET interface 2952 independently, and that the union of all ANET interface Router 2953 Lifetimes determines MSE lifetime. 2955 Differences from draft-templin-6man-omni-interface-00 to draft- 2956 templin-6man-omni-interface-01: 2958 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 2959 for future use (most likely as "pseudo-multicast"). 2961 o Non-normative discussion of alternate OMNI LLA construction form 2962 made possible if the 64-bit assumption were relaxed. 2964 First draft version (draft-templin-atn-aero-interface-00): 2966 o Draft based on consensus decision of ICAO Working Group I Mobility 2967 Subgroup March 22, 2019. 2969 Authors' Addresses 2971 Fred L. Templin (editor) 2972 The Boeing Company 2973 P.O. Box 3707 2974 Seattle, WA 98124 2975 USA 2977 Email: fltemplin@acm.org 2979 Tony Whyman 2980 MWA Ltd c/o Inmarsat Global Ltd 2981 99 City Road 2982 London EC1Y 1AX 2983 England 2985 Email: tony.whyman@mccallumwhyman.com