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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 February 1, 2021 7 Expires: August 5, 2021 9 Transmission of IP Packets over Overlay Multilink Network (OMNI) 10 Interfaces 11 draft-templin-6man-omni-interface-73 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 August 5, 2021. 41 Copyright Notice 43 Copyright (c) 2021 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 . . . . . . . . . . . . . . . . . . . . . . . . 9 61 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 9 62 5. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 14 63 5.1. Fragmentation Security Implications . . . . . . . . . . . 19 64 5.2. OAL "Super-Packet" Packing . . . . . . . . . . . . . . . 20 65 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 22 66 7. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 22 67 8. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 23 68 9. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 25 69 10. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 25 70 10.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 27 71 10.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 29 72 10.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 29 73 10.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 29 74 10.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 31 75 10.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 35 76 10.1.6. Origin Indication . . . . . . . . . . . . . . . . . 35 77 10.1.7. MS-Register . . . . . . . . . . . . . . . . . . . . 36 78 10.1.8. MS-Release . . . . . . . . . . . . . . . . . . . . . 36 79 10.1.9. Geo Coordinates . . . . . . . . . . . . . . . . . . 37 80 10.1.10. Dynamic Host Configuration Protocol for IPv6 81 (DHCPv6) Message . . . . . . . . . . . . . . . . . . 38 82 10.1.11. Host Identity Protocol (HIP) Message . . . . . . . . 38 83 10.1.12. Node Identification . . . . . . . . . . . . . . . . 39 84 11. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 41 85 12. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 41 86 12.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 42 87 12.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 42 88 13. Router Discovery and Prefix Registration . . . . . . . . . . 43 89 13.1. Router Discovery in IP Multihop and IPv4-Only Networks . 47 90 13.2. MS-Register and MS-Release List Processing . . . . . . . 48 91 13.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 50 92 14. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 51 93 15. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 51 94 16. Detecting and Responding to MSE Failures . . . . . . . . . . 51 95 17. Transition Considerations . . . . . . . . . . . . . . . . . . 52 96 18. OMNI Interfaces on the Open Internet . . . . . . . . . . . . 53 97 19. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 54 98 20. Node Identification . . . . . . . . . . . . . . . . . . . . . 54 99 21. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55 100 22. Security Considerations . . . . . . . . . . . . . . . . . . . 56 101 23. Implementation Status . . . . . . . . . . . . . . . . . . . . 57 102 24. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57 103 25. References . . . . . . . . . . . . . . . . . . . . . . . . . 58 104 25.1. Normative References . . . . . . . . . . . . . . . . . . 58 105 25.2. Informative References . . . . . . . . . . . . . . . . . 60 106 Appendix A. Interface Attribute Preferences Bitmap Encoding . . 66 107 Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 68 108 Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 69 109 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 70 110 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 72 112 1. Introduction 114 Mobile Nodes (MNs) (e.g., aircraft of various configurations, 115 terrestrial vehicles, seagoing vessels, enterprise wireless devices, 116 pedestrians with cellphones, etc.) often have multiple interface 117 connections to wireless and/or wired-link data links used for 118 communicating with networked correspondents. These data links may 119 have diverse performance, cost and availability properties that can 120 change dynamically according to mobility patterns, flight phases, 121 proximity to infrastructure, etc. MNs coordinate their data links in 122 a discipline known as "multilink", in which a single virtual 123 interface is configured over the node's underlying interface 124 connections to the data links. 126 The MN configures a virtual interface (termed the "Overlay Multilink 127 Network (OMNI) interface") as a thin layer over the underlying 128 interfaces. The OMNI interface is therefore the only interface 129 abstraction exposed to the IP layer and behaves according to the Non- 130 Broadcast, Multiple Access (NBMA) interface principle, while 131 underlying interfaces appear as link layer communication channels in 132 the architecture. The OMNI interface connects to a virtual overlay 133 service known as the "OMNI link". The OMNI link spans one or more 134 Internetworks that may include private-use infrastructures and/or the 135 global public Internet itself. 137 Each MN receives a Mobile Network Prefix (MNP) for numbering 138 downstream-attached End User Networks (EUNs) independently of the 139 access network data links selected for data transport. The MN 140 performs router discovery over the OMNI interface (i.e., similar to 141 IPv6 customer edge routers [RFC7084]) and acts as a mobile router on 142 behalf of its EUNs. The router discovery process is iterated over 143 each of the OMNI interface's underlying interfaces in order to 144 register per-link parameters (see Section 13). 146 The OMNI interface provides a multilink nexus for exchanging inbound 147 and outbound traffic via the correct underlying interface(s). The IP 148 layer sees the OMNI interface as a point of connection to the OMNI 149 link. Each OMNI link has one or more associated Mobility Service 150 Prefixes (MSPs), which are typically IP Global Unicast Address (GUA) 151 prefixes from which OMNI link MNPs are derived. If there are 152 multiple OMNI links, the IPv6 layer will see multiple OMNI 153 interfaces. 155 MNs may connect to multiple distinct OMNI links by configuring 156 multiple OMNI interfaces, e.g., omni0, omni1, omni2, etc. Each OMNI 157 interface is configured over a set of underlying interfaces and 158 provides a nexus for Safety-Based Multilink (SBM) operation. Each 159 OMNI SBM "domain" configures a common ULA prefix [ULA]::/48, and each 160 OMNI link within the domain configures a unique 16-bit Subnet ID '*' 161 to construct the sub-prefix [ULA*]::/64 (see: Section 8). The IP 162 layer applies SBM routing to select an OMNI interface, which then 163 applies Performance-Based Multilink (PBM) to select the correct 164 underlying interface. Applications can apply Segment Routing 165 [RFC8402] to select independent SBM topologies for fault tolerance. 167 The OMNI interface interacts with a network-based Mobility Service 168 (MS) through IPv6 Neighbor Discovery (ND) control message exchanges 169 [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that 170 track MN movements and represent their MNPs in a global routing or 171 mapping system. 173 Many OMNI use cases are currently under active consideration. In 174 particular, the International Civil Aviation Organization (ICAO) 175 Working Group-I Mobility Subgroup is developing a future Aeronautical 176 Telecommunications Network with Internet Protocol Services (ATN/IPS) 177 and has issued a liaison statement requesting IETF adoption [ATN] in 178 support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access 179 in Vehicular Environments (ipwave) working group has further included 180 problem statement and use case analysis for OMNI in a document now in 181 AD evaluation for RFC publication 182 [I-D.ietf-ipwave-vehicular-networking]. Still other communities of 183 interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA 184 programs that examine commercial aviation, Urban Air Mobility (UAM) 185 and Unmanned Air Systems (UAS). Pedestrians with handheld devices 186 represent another large class of potential OMNI users. 188 This document specifies the transmission of IP packets and MN/MS 189 control messages over OMNI interfaces. The OMNI interface supports 190 either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) 191 as the network layer in the data plane, while using IPv6 ND messaging 192 as the control plane independently of the data plane IP protocol(s). 193 The OMNI Adaptation Layer (OAL) which operates as a mid-layer between 194 L3 and L2 is based on IP-in-IPv6 encapsulation per [RFC2473] as 195 discussed in the following sections. Provisions are included for 196 both Vehicle-to-Infrastructure (V2I) communications and Vehicle-to- 197 Vehicle (V2V) communications outside the context of infrastructure. 199 2. Terminology 201 The terminology in the normative references applies; especially, the 202 terms "link" and "interface" are the same as defined in the IPv6 203 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. 204 Additionally, this document assumes the following IPv6 ND message 205 types: Router Solicitation (RS), Router Advertisement (RA), Neighbor 206 Solicitation (NS), Neighbor Advertisement (NA) and Redirect. 208 The Protocol Constants defined in Section 10 of [RFC4861] are used in 209 their same format and meaning in this document. The terms "All- 210 Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" 211 are the same as defined in [RFC4291] (with Link-Local scope assumed). 213 The term "IP" is used to refer collectively to either Internet 214 Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a 215 specification at the layer in question applies equally to either 216 version. 218 The following terms are defined within the scope of this document: 220 Mobile Node (MN) 221 an end system with a mobile router having multiple distinct 222 upstream data link connections that are grouped together in one or 223 more logical units. The MN's data link connection parameters can 224 change over time due to, e.g., node mobility, link quality, etc. 225 The MN further connects a downstream-attached End User Network 226 (EUN). The term MN used here is distinct from uses in other 227 documents, and does not imply a particular mobility protocol. 229 End User Network (EUN) 230 a simple or complex downstream-attached mobile network that 231 travels with the MN as a single logical unit. The IP addresses 232 assigned to EUN devices remain stable even if the MN's upstream 233 data link connections change. 235 Mobility Service (MS) 236 a mobile routing service that tracks MN movements and ensures that 237 MNs remain continuously reachable even across mobility events. 238 Specific MS details are out of scope for this document. 240 Mobility Service Endpoint (MSE) 241 an entity in the MS (either singular or aggregate) that 242 coordinates the mobility events of one or more MN. 244 Mobility Service Prefix (MSP) 245 an aggregated IP Global Unicast Address (GUA) prefix (e.g., 246 2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and 247 from which more-specific Mobile Network Prefixes (MNPs) are 248 delegated. OMNI link administrators typically obtain MSPs from an 249 Internet address registry, however private-use prefixes can 250 alternatively be used subject to certain limitations (see: 251 Section 9). OMNI links that connect to the global Internet 252 advertise their MSPs to their interdomain routing peers. 254 Mobile Network Prefix (MNP) 255 a longer IP prefix delegated from an MSP (e.g., 256 2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN. 257 MNs sub-delegate the MNP to devices located in EUNs. 259 Access Network (ANET) 260 a data link service network (e.g., an aviation radio access 261 network, satellite service provider network, cellular operator 262 network, wifi network, etc.) that connects MNs. Physical and/or 263 data link level security is assumed, and sometimes referred to as 264 "protected spectrum". Private enterprise networks and ground 265 domain aviation service networks may provide multiple secured IP 266 hops between the MN's point of connection and the nearest Access 267 Router. 269 Access Router (AR) 270 a router in the ANET for connecting MNs to correspondents in 271 outside Internetworks. The AR may be located on the same physical 272 link as the MN, or may be located multiple IP hops away. In the 273 latter case, the MN uses encapsulation to communicate with the AR 274 as though it were on the same physical link. 276 ANET interface 277 a MN's attachment to a link in an ANET. 279 Internetwork (INET) 280 a connected network region with a coherent IP addressing plan that 281 provides transit forwarding services between ANETs and nodes that 282 connect directly to the open INET via unprotected media. No 283 physical and/or data link level security is assumed, therefore 284 security must be applied by upper layers. The global public 285 Internet itself is an example. 287 INET interface 288 a node's attachment to a link in an INET. 290 *NET 291 a "wildcard" term used when a given specification applies equally 292 to both ANET and INET cases. 294 OMNI link 295 a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured 296 over one or more INETs and their connected ANETs. An OMNI link 297 can comprise multiple INET segments joined by bridges the same as 298 for any link; the addressing plans in each segment may be mutually 299 exclusive and managed by different administrative entities. 301 OMNI interface 302 a node's attachment to an OMNI link, and configured over one or 303 more underlying *NET interfaces. If there are multiple OMNI links 304 in an OMNI domain, a separate OMNI interface is configured for 305 each link. 307 OMNI Adaptation Layer (OAL) 308 an OMNI interface process whereby packets admitted into the 309 interface are wrapped in a mid-layer IPv6 header and fragmented/ 310 reassembled if necessary to support the OMNI link Maximum 311 Transmission Unit (MTU). The OAL is also responsible for 312 generating MTU-related control messages as necessary, and for 313 providing addressing context for spanning multiple segments of a 314 bridged OMNI link. 316 OMNI Option 317 an IPv6 Neighbor Discovery option providing multilink parameters 318 for the OMNI interface as specified in Section 10. 320 Mobile Network Prefix Link Local Address (MNP-LLA) 321 an IPv6 Link Local Address that embeds the most significant 64 322 bits of an MNP in the lower 64 bits of fe80::/64, as specified in 323 Section 7. 325 Mobile Network Prefix Unique Local Address (MNP-ULA) 326 an IPv6 Unique-Local Address derived from an MNP-LLA. 328 Administrative Link Local Address (ADM-LLA) 329 an IPv6 Link Local Address that embeds a 32-bit administratively- 330 assigned identification value in the lower 32 bits of fe80::/96, 331 as specified in Section 7. 333 Administrative Unique Local Address (ADM-ULA) 334 an IPv6 Unique-Local Address derived from an ADM-LLA. 336 Multilink 337 an OMNI interface's manner of managing diverse underlying 338 interface connections to data links as a single logical unit. The 339 OMNI interface provides a single unified interface to upper 340 layers, while underlying interface selections are performed on a 341 per-packet basis considering factors such as DSCP, flow label, 342 application policy, signal quality, cost, etc. Multilinking 343 decisions are coordinated in both the outbound (i.e. MN to 344 correspondent) and inbound (i.e., correspondent to MN) directions. 346 L2 347 The second layer in the OSI network model. Also known as "layer- 348 2", "link-layer", "sub-IP layer", "data link layer", etc. 350 L3 351 The third layer in the OSI network model. Also known as "layer- 352 3", "network-layer", "IP layer", etc. 354 underlying interface 355 a *NET interface over which an OMNI interface is configured. The 356 OMNI interface is seen as a L3 interface by the IP layer, and each 357 underlying interface is seen as a L2 interface by the OMNI 358 interface. The underlying interface either connects directly to 359 the physical communications media or coordinates with another node 360 where the physical media is hosted. 362 Mobility Service Identification (MSID) 363 Each MSE and AR is assigned a unique 32-bit Identification (MSID) 364 (see: Section 7). IDs are assigned according to MS-specific 365 guidelines (e.g., see: [I-D.templin-intarea-6706bis]). 367 Safety-Based Multilink (SBM) 368 A means for ensuring fault tolerance through redundancy by 369 connecting multiple affiliated OMNI interfaces to independent 370 routing topologies (i.e., multiple independent OMNI links). 372 Performance Based Multilink (PBM) 373 A means for selecting underlying interface(s) for packet 374 transmission and reception within a single OMNI interface. 376 OMNI Domain 377 The set of all SBM/PBM OMNI links that collectively provides 378 services for a common set of MSPs. Each OMNI domain consists of a 379 set of affiliated OMNI links that all configure the same ::/48 ULA 380 prefix with a unique 16-bit Subnet ID as discussed in Section 8. 382 3. Requirements 384 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 385 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 386 "OPTIONAL" in this document are to be interpreted as described in BCP 387 14 [RFC2119][RFC8174] when, and only when, they appear in all 388 capitals, as shown here. 390 OMNI links maintain a constant value "MAX_MSID" selected to provide 391 MNs with an acceptable level of MSE redundancy while minimizing 392 control message amplification. It is RECOMMENDED that MAX_MSID be 393 set to the default value 5; if a different value is chosen, it should 394 be set uniformly by all nodes on the OMNI link. 396 An implementation is not required to internally use the architectural 397 constructs described here so long as its external behavior is 398 consistent with that described in this document. 400 4. Overlay Multilink Network (OMNI) Interface Model 402 An OMNI interface is a MN virtual interface configured over one or 403 more underlying interfaces, which may be physical (e.g., an 404 aeronautical radio link) or virtual (e.g., an Internet or higher- 405 layer "tunnel"). The MN receives a MNP from the MS, and coordinates 406 with the MS through IPv6 ND message exchanges. The MN uses the MNP 407 to construct a unique Link-Local Address (MNP-LLA) through the 408 algorithmic derivation specified in Section 7 and assigns the LLA to 409 the OMNI interface. 411 The OMNI interface architectural layering model is the same as in 412 [RFC5558][RFC7847], and augmented as shown in Figure 1. The IP layer 413 therefore sees the OMNI interface as a single L3 interface with 414 multiple underlying interfaces that appear as L2 communication 415 channels in the architecture. 417 +----------------------------+ 418 | Upper Layer Protocol | 419 Session-to-IP +---->| | 420 Address Binding | +----------------------------+ 421 +---->| IP (L3) | 422 IP Address +---->| | 423 Binding | +----------------------------+ 424 +---->| OMNI Interface | 425 Logical-to- +---->| (LLA) | 426 Physical | +----------------------------+ 427 Interface +---->| L2 | L2 | | L2 | 428 Binding |(IF#1)|(IF#2)| ..... |(IF#n)| 429 +------+------+ +------+ 430 | L1 | L1 | | L1 | 431 | | | | | 432 +------+------+ +------+ 434 Figure 1: OMNI Interface Architectural Layering Model 436 Each underlying interface provides an L2/L1 abstraction according to 437 one of the following models: 439 o INET interfaces connect to an INET either natively or through one 440 or several IPv4 Network Address Translators (NATs). Native INET 441 interfaces have global IP addresses that are reachable from any 442 INET correspondent. NATed INET interfaces typically have private 443 IP addresses and connect to a private network behind one or more 444 NATs that provide INET access. 446 o ANET interfaces connect to a protected ANET that is separated from 447 the open INET by an AR acting as a proxy. The ANET interface may 448 be either on the same L2 link segment as the AR, or separated from 449 the AR by multiple IP hops. 451 o VPNed interfaces use security encapsulation over a *NET to a 452 Virtual Private Network (VPN) gateway. Other than the link-layer 453 encapsulation format, VPNed interfaces behave the same as for 454 Direct interfaces. 456 o Direct (aka "point-to-point") interfaces connect directly to a 457 peer without crossing any *NET paths. An example is a line-of- 458 sight link between a remote pilot and an unmanned aircraft. 460 The OMNI virtual interface model gives rise to a number of 461 opportunities: 463 o since MNP-LLAs are uniquely derived from an MNP, no Duplicate 464 Address Detection (DAD) or Multicast Listener Discovery (MLD) 465 messaging is necessary. 467 o since Temporary LLAs are statistically unique, they can be used 468 without DAD for short-term purposes, e.g. until an MNP-LLA is 469 obtained. 471 o *NET interfaces on the same L2 link segment as an AR do not 472 require any L3 addresses (i.e., not even link-local) in 473 environments where communications are coordinated entirely over 474 the OMNI interface. (An alternative would be to also assign the 475 same LLA to all *NET interfaces.) 477 o as underlying interface properties change (e.g., link quality, 478 cost, availability, etc.), any active interface can be used to 479 update the profiles of multiple additional interfaces in a single 480 message. This allows for timely adaptation and service continuity 481 under dynamically changing conditions. 483 o coordinating underlying interfaces in this way allows them to be 484 represented in a unified MS profile with provisions for mobility 485 and multilink operations. 487 o exposing a single virtual interface abstraction to the IPv6 layer 488 allows for multilink operation (including QoS based link 489 selection, packet replication, load balancing, etc.) at L2 while 490 still permitting L3 traffic shaping based on, e.g., DSCP, flow 491 label, etc. 493 o the OMNI interface allows inter-INET traversal when nodes located 494 in different INETs need to communicate with one another. This 495 mode of operation would not be possible via direct communications 496 over the underlying interfaces themselves. 498 o the OMNI Adaptation Layer (OAL) within the OMNI interface supports 499 lossless and adaptive path MTU mitigations not available for 500 communications directly over the underlying interfaces themselves. 502 o L3 sees the OMNI interface as a point of connection to the OMNI 503 link; if there are multiple OMNI links (i.e., multiple MS's), L3 504 will see multiple OMNI interfaces. 506 o Multiple independent OMNI interfaces can be used for increased 507 fault tolerance through Safety-Based Multilink (SBM), with 508 Performance-Based Multilink (PBM) applied within each interface. 510 Other opportunities are discussed in [RFC7847]. Note that even when 511 the OMNI virtual interface is present, applications can still access 512 underlying interfaces either through the network protocol stack using 513 an Internet socket or directly using a raw socket. This allows for 514 intra-network (or point-to-point) communications without invoking the 515 OMNI interface and/or OAL. For example, when an IPv6 OMNI interface 516 is configured over an underlying IPv4 interface, applications can 517 still invoke IPv4 intra-network communications as long as the 518 communicating endpoints are not subject to mobility dynamics. 519 However, the opportunities discussed above are not available when the 520 architectural layering is bypassed in this way. 522 Figure 2 depicts the architectural model for a MN with an attached 523 EUN connecting to the MS via multiple independent *NETs. When an 524 underlying interface becomes active, the MN's OMNI interface sends 525 IPv6 ND messages without encapsulation if the first-hop Access Router 526 (AR) is on the same underlying link; otherwise, the interface uses 527 IP-in-IP encapsulation. The IPv6 ND messages traverse the ground 528 domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which 529 then coordinates with an INET Mobility Service Endpoint (MSE#1, 530 MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN. 531 The Hop Limit in IPv6 ND messages is not decremented due to 532 encapsulation; hence, the OMNI interface appears to be attached to an 533 ordinary link. 535 +--------------+ (:::)-. 536 | MN |<-->.-(::EUN:::) 537 +--------------+ `-(::::)-' 538 |OMNI interface| 539 +----+----+----+ 540 +--------|IF#1|IF#2|IF#n|------ + 541 / +----+----+----+ \ 542 / | \ 543 / | \ 544 v v v 545 (:::)-. (:::)-. (:::)-. 546 .-(::*NET:::) .-(::*NET:::) .-(::*NET:::) 547 `-(::::)-' `-(::::)-' `-(::::)-' 548 +----+ +----+ +----+ 549 ... |AR#1| .......... |AR#2| ......... |AR#n| ... 550 . +-|--+ +-|--+ +-|--+ . 551 . | | | 552 . v v v . 553 . <----- INET Encapsulation -----> . 554 . . 555 . +-----+ (:::)-. . 556 . |MSE#2| .-(::::::::) +-----+ . 557 . +-----+ .-(::: INET :::)-. |MSE#m| . 558 . (::::: Routing ::::) +-----+ . 559 . `-(::: System :::)-' . 560 . +-----+ `-(:::::::-' . 561 . |MSE#1| +-----+ +-----+ . 562 . +-----+ |MSE#3| |MSE#4| . 563 . +-----+ +-----+ . 564 . . 565 . . 566 . <----- Worldwide Connected Internetwork ----> . 567 ........................................................... 569 Figure 2: MN/MS Coordination via Multiple *NETs 571 After the initial IPv6 ND message exchange, the MN (and/or any nodes 572 on its attached EUNs) can send and receive IP data packets over the 573 OMNI interface. OMNI interface multilink services will forward the 574 packets via ARs in the correct underlying *NETs. The AR encapsulates 575 the packets according to the capabilities provided by the MS and 576 forwards them to the next hop within the worldwide connected 577 Internetwork via optimal routes. 579 OMNI links span one or more underlying Internetwork via the OMNI 580 Adaptation Layer (OAL) which is based on a mid-layer overlay 581 encapsulation using [RFC2473]. Each OMNI link corresponds to a 582 different overlay (differentiated by an address codepoint) which may 583 be carried over a completely separate underlying topology. Each MN 584 can facilitate SBM by connecting to multiple OMNI links using a 585 distinct OMNI interface for each link. 587 Note: OMNI interface underlying interfaces often connect directly to 588 physical media on the local platform (e.g., a laptop computer with 589 WiFi, etc.), but in some configurations the physical media may be 590 hosted on a separate Local Area Network (LAN) node. In that case, 591 the OMNI interface can establish a Layer-2 VLAN or a point-to-point 592 tunnel (at a layer below the underlying interface) to the node 593 hosting the physical media. The OMNI interface may also apply 594 encapsulation at a layer above the underlying interface such that 595 packets would appear "double-encapsulated" on the LAN; the node 596 hosting the physical media in turn removes the LAN encapsulation 597 prior to transmission or inserts it following reception. Finally, 598 the underlying interface must monitor the node hosting the physical 599 media (e.g., through periodic keepalives) so that it can convey 600 up/down/status information to the OMNI interface. 602 5. The OMNI Adaptation Layer (OAL) 604 The OMNI interface observes the link nature of tunnels, including the 605 Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and 606 the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels]. 607 The OMNI interface is configured over one or more underlying 608 interfaces that may have diverse MTUs. OMNI interfaces accommodate 609 MTU diversity through the use of the OMNI Adaptation Layer (OAL) as 610 discussed in this section. 612 IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of 613 1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the 614 minimum IPv6 path MTU is 1280 bytes since routers on the path are not 615 permitted to perform network fragmentation even though the 616 destination is required to reassemble more. The network therefore 617 MUST forward packets of at least 1280 bytes without generating an 618 IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message 619 [RFC8201]. (Note: the source can apply "source fragmentation" for 620 locally-generated IPv6 packets up to 1500 bytes and larger still if 621 it if has a way to determine that the destination configures a larger 622 MRU, but this does not affect the minimum IPv6 path MTU.) 624 IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of 625 68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122]. 626 Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set 627 to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path 628 support network fragmentation and the destination is required to 629 reassemble at least that much. The "Don't Fragment" (DF) bit in the 630 IPv4 encapsulation headers of packets sent over IPv4 underlying 631 interfaces therefore MUST be set to 0. (Note: even if the 632 encapsulation source has a way to determine that the encapsulation 633 destination configures an MRU larger than 576 bytes, it should not 634 assume a larger minimum IPv4 path MTU without careful consideration 635 of the issues discussed in Section 5.1.) 637 In network paths where IPv6/IPv4 protocol translation or IPv6-in-IPv4 638 encapsulation may be prevalent, it may be prudent for the OAL to 639 always assume the IPv4 minimum path MTU (i.e., 576 bytes) regardless 640 of the underlying interface IP protocol version. Always assuming the 641 IPv4 minimum path MTU even for IPv6 underlying interfaces may produce 642 more fragments and additional header overhead, but will always 643 interoperate and never run the risk of presenting an IPv4 interface 644 with a packet that exceeds its MRU. 646 The OMNI interface configures both an MTU and MRU of 9180 bytes 647 [RFC2492]; the size is therefore not a reflection of the underlying 648 interface MTUs, but rather determines the largest packet the OMNI 649 interface can forward or reassemble. The OMNI interface uses the 650 OMNI Adaptation Layer (OAL) to admit packets from the network layer 651 that are no larger than the OMNI interface MTU while generating 652 ICMPv4 Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery 653 (PMTUD) Packet Too Big (PTB) [RFC8201] messages as necessary. This 654 document refers to both of these ICMPv4/ICMPv6 message types simply 655 as "PTBs", and introduces a distinction between PTB "hard" and "soft" 656 errors as discussed below. 658 For IPv4 packets with DF=0, the network layer performs IPv4 659 fragmentation if necessary then admits the packets/fragments into the 660 OMNI interface; these fragments will be reassembled by the final 661 destination. For IPv4 packets with DF=1 and IPv6 packets, the 662 network layer admits the packet if it is no larger than the OMNI 663 interface MTU; otherwise, it drops the packet and returns a PTB hard 664 error message to the source. 666 For each admitted IP packet/fragment, the OMNI interface internally 667 employs the OAL when necessary by encapsulating the inner IP packet/ 668 fragment in a mid-layer IPv6 header per [RFC2473] before adding any 669 outer IP encapsulations. (The OAL does not decrement the inner IP 670 Hop Limit/TTL during encapsulation since the insertion occurs at a 671 layer below IP forwarding.) If the OAL packet will itself require 672 fragmentation, the OMNI interface then calculates the 32-bit CRC over 673 the entire mid-layer packet and writes the value in a trailing field 674 at the end of the packet. Next, the OAL fragments this mid-layer 675 IPv6 packet, forwards the fragments (using *NET encapsulation if 676 necessary), and returns an internally-generated PTB soft error 677 message (subject to rate limiting) if it deems the packet too large 678 according to factors such as link performance characteristics, 679 reassembly congestion, etc. This ensures that the path MTU is 680 adaptive and reflects the current path used for a given data flow. 682 The OAL operates with respect to both the minimum IPv6 and IPv4 path 683 MTUs as follows: 685 o When an OMNI interface sends a packet toward a final destination 686 via an ANET peer, it sends without OAL encapsulation if the packet 687 (including any outer-layer ANET encapsulations) is no larger than 688 the underlying interface MTU for on-link ANET peers or the minimum 689 ANET path MTU for peers separated by multiple IP hops. Otherwise, 690 the OAL inserts an IPv6 header per [RFC2473] with source address 691 set to the node's own Unique-Local Address (ULA) (see: Section 8) 692 and destination set to either the Administrative ULA (ADM-ULA) of 693 the ANET peer or the Mobile Network Prefix ULA (MNP-ULA) 694 corresponding to the final destination (see below). The OAL then 695 calculates and appends the trailing 32-bit CRC, then uses IPv6 696 fragmentation to break the packet into a minimum number of non- 697 overlapping fragments where the size of each non-final fragment 698 (including both the OMNI and any outer-layer ANET encapsulations) 699 is determined by the underlying interface MTU for on-link ANET 700 peers or the minimum ANET path MTU for peers separated by multiple 701 IP hops. The OAL then encapsulates the fragments in any ANET 702 headers and sends them to the ANET peer, which either reassembles 703 before forwarding if the OAL destination is its own ADM-ULA or 704 forwards the fragments toward the final destination without first 705 reassembling otherwise. 707 o When an OMNI interface sends a packet toward a final destination 708 via an INET interface, it sends packets (including any outer-layer 709 INET encapsulations) no larger than the minimum INET path MTU 710 without OAL encapsulation if the destination is reached via an 711 INET address within the same OMNI link segment. Otherwise, the 712 OAL inserts an IPv6 header per [RFC2473] with source address set 713 to the node's ULA, destination set to the ULA of the next hop OMNI 714 node toward the final destination and (if necessary) with an OMNI 715 Routing Header (ORH) (see: [I-D.templin-intarea-6706bis]) with 716 final segment addressing information. The OAL then calculates and 717 appends the trailing 32-bit CRC, then uses IPv6 fragmentation to 718 break the packet into a minimum number of non-overlapping 719 fragments where the size of each non-final fragment (including 720 both the OMNI and outer-layer INET encapsulations) is determined 721 by the minimum INET path MTU. The OAL then encapsulates the 722 fragments in any INET headers and sends them to the OMNI link 723 neighbor, which reassembles before forwarding toward the final 724 destination. 726 In light of the above considerations, the OAL should assume a minimum 727 path MTU of 576 bytes for the purpose of generating OAL fragments. 728 Each OAL fragment will undergo *NET encapsulation including either a 729 20 byte IPv4 or 40 byte IPv6 header plus an 8 byte UDP header, 730 leaving a minimum of 528 bytes for each fragment. Each OAL fragment 731 must accommodate 40 bytes for the OAL IPv6 header plus 8 bytes for 732 the fragment header (while reserving 40 additional bytes in case a 733 maximum-length ORH is inserted during re-encapsulation), leaving 440 734 bytes to accommodate the actual inner IP packet fragment. OAL 735 fragmentation algorithms therefore MUST produce non-final fragments 736 with the OAL IPv6 header Payload Length set to no less than 448 bytes 737 (8 bytes for the fragment header plus 440 bytes for the inner packet 738 fragment), while the Payload Length of the final fragment may be 739 smaller. OAL reassembly algorithms MUST drop any non-final fragments 740 with Payload Length less than 448 bytes. 742 Note that OAL fragmentation algorithms MAY produce larger non-final 743 OAL fragments if better path MTU information is available. For 744 example, if it is known that no ORH will be inserted in the path the 745 algorithm may produce non-final fragments with a 488 byte Payload 746 Length. In a second example, when two ANET peers share a common 747 physical or virtual link with a larger MTU (e.g., 1280 bytes or 748 larger), OAL fragmentation may use this larger MTU size as long as 749 the receiving ANET peer reassembles (and possibly also refragments) 750 before forwarding. This is important for accommodating links where 751 performance is highly dependent on maximum use of the available link 752 MTU, e.g. for wireless aviation data links. Additionally, in order 753 to set the correct context for reassembly, the OMNI interface that 754 inserts the OAL header MUST also be the one that inserts the IPv6 755 fragment header Identification value. While not strictly required, 756 sending all fragments of the same fragmented OAL packet consecutively 757 over the same underlying interface with minimal inter-fragment delay 758 may increase the likelihood of successful reassembly. 760 Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6 761 header Code field value 0 are hard errors that always indicate that a 762 packet has been dropped due to a real MTU restriction. However, the 763 OAL can also forward large packets via encapsulation and 764 fragmentation while at the same time returning PTB soft error 765 messages (subject to rate limiting) indicating that a forwarded 766 packet was uncomfortably large. The OMNI interface can therefore 767 continuously forward large packets without loss while returning PTB 768 soft error messages recommending a smaller size. Original sources 769 that receive the soft errors in turn reduce the size of the packets 770 they send, i.e., the same as for hard errors. 772 The OAL sets the ICMPv4 header "unused" field or ICMPv6 header Code 773 field to the value 1 in PTB soft error messages. The OAL sets the 774 PTB destination address to the source address of the original packet, 775 and sets the source address to the MNP Subnet Router Anycast address 776 of the MN. The OAL then sets the MTU field to a value no smaller 777 than 576 for ICMPv4 or 1280 for ICMPv6, and returns the PTB soft 778 error to the original source. 780 When the original source receives the PTB, it reduces its path MTU 781 estimate the same as for hard errors but does not regard the message 782 as a loss indication. (If the original source does not recognize the 783 soft error code, it regards the PTB the same as a hard error but 784 should heed the retransmission advice given in [RFC8201] suggesting 785 retransmission based on normal packetization layer retransmission 786 timers.) This document therefore updates [RFC1191][RFC4443] and 787 [RFC8201]. Furthermore, implementations of [RFC4821] must be aware 788 that PTB hard or soft errors may arrive at any time even if after a 789 successful MTU probe (this is the same consideration as for an 790 ordinary path fluctuation following a successful probe). 792 In summary, the OAL supports continuous transmission and reception of 793 packets of various sizes in the face of dynamically changing network 794 conditions. Moreover, since PTB soft errors do not indicate loss, 795 original sources that receive soft errors can quickly scan for path 796 MTU increases without waiting for the minimum 10 minutes specified 797 for loss-oriented PTB hard errors [RFC1191][RFC8201]. The OAL 798 therefore provides a lossless and adaptive service that accommodates 799 MTU diversity especially well-suited for dynamic multilink 800 environments. 802 Note: An OMNI interface that reassembles OAL fragments may experience 803 congestion-oriented loss in its reassembly cache and can optionally 804 send PTB soft errors to the original source and/or ICMP "Time 805 Exceeded" messages to the source of the OAL fragments. In 806 environments where the messages may contribute to unacceptable 807 additional congestion, however, the OMNI interface can refrain from 808 sending PTB soft errors and simply regard the loss as an ordinary 809 unreported congestion event for which the original source will 810 eventually compensate. 812 Note: When the network layer forwards an IPv4 packet/fragment with 813 DF=0 into the OMNI interface, the interface can optionally perform 814 (further) IPv4 fragmentation before invoking the OAL so that the 815 fragments will be reassembled by the final destination. When the 816 network layer performs IPv6 fragmentation for locally-generated IPv6 817 packets, the OMNI interface typically invokes the OAL without first 818 applying (further) IPv6 fragmentation; the network layer should 819 therefore fragment to the minimum IPv6 path MTU (or smaller still) to 820 push the reassembly burden to the final destination and avoid 821 receiving PTB soft errors from the OMNI interface. Aside from these 822 non-normative guidelines, the manner in which any IP fragmentation is 823 invoked prior to OAL encapsulation/fragmentation is an implementation 824 matter. 826 Note: The source OAL includes a trailing 32-bit CRC only for OAL 827 packets that require fragmentation, and the destination OAL discards 828 any OAL packets with incorrect CRC values following reassembly. (The 829 source OAL calculates the CRC over the entire packet, then appends 830 the CRC to the end of the packet and adds the CRC length to the OAL 831 Payload Length prior to fragmentation. The destination OAL subtracts 832 the CRC length from the OAL Payload Length and verifies the CRC 833 following reassembly.) A 32-bit CRC is sufficient for detecting 834 reassembly misassociations for packet sizes no larger than the OMNI 835 interface MTU but may not be sufficient to detect errors for larger 836 sizes [CRC]. 838 Note: Some underlying interface types (e.g., VPNs) may already 839 provide their own robust fragmentation and reassembly services even 840 without OAL encapsulation. In those cases, the OAL can invoke the 841 inherent underlying interface schemes instead while employing PTB 842 soft errors in the same fashion as described above. Other underlying 843 interface facilities such as header/message compression can also be 844 harnessed in a similar fashion. 846 Note: Applications can dynamically tune the size of the packets they 847 to send to produce the best possible throughput and latency, with the 848 understanding that these parameters may change over time due to 849 factors such as congestion, mobility, network path changes, etc. The 850 receipt or absence of soft errors should be seen as hints of when 851 increasing or decreasing packet sizes may be beneficial. 853 5.1. Fragmentation Security Implications 855 As discussed in Section 3.7 of [RFC8900], there are four basic 856 threats concerning IPv6 fragmentation; each of which is addressed by 857 effective mitigations as follows: 859 1. Overlapping fragment attacks - reassembly of overlapping 860 fragments is forbidden by [RFC8200]; therefore, this threat does 861 not apply to the OAL. 863 2. Resource exhaustion attacks - this threat is mitigated by 864 providing a sufficiently large OAL reassembly cache and 865 instituting "fast discard" of incomplete reassemblies that may be 866 part of a buffer exhaustion attack. The reassembly cache should 867 be sufficiently large so that a sustained attack does not cause 868 excessive loss of good reassemblies but not so large that (timer- 869 based) data structure management becomes computationally 870 expensive. The cache should also be indexed based on the arrival 871 underlying interface such that congestion experienced over a 872 first underlying interface does not cause discard of incomplete 873 reassemblies for uncongested underlying interfaces. 875 3. Attacks based on predictable fragment identification values - 876 this threat is mitigated by selecting a suitably random ID value 877 per [RFC7739]. 879 4. Evasion of Network Intrusion Detection Systems (NIDS) - this 880 threat is mitigated by disallowing "tiny fragments" per the OAL 881 fragmentation procedures specified above. 883 Additionally, IPv4 fragmentation includes a 16-bit Identification (IP 884 ID) field with only 65535 unique values such that at high data rates 885 the field could wrap and apply to new packets while the fragments of 886 old packets using the same ID are still alive in the network 887 [RFC4963]. However, since the largest OAL fragment that will be sent 888 via an IPv4 *NET path is 576 bytes any IPv4 fragmentation would occur 889 only on links with an IPv4 MTU smaller than this size, and [RFC3819] 890 recommendations suggest that such links will have low data rates. 891 Since IPv6 provides a 32-bit Identification value, IP ID wraparound 892 at high data rates is not a concern for IPv6 fragmentation. 894 Finally, [RFC6980] documents fragmentation security concerns for 895 large IPv6 ND messages. These concerns are addressed when the OMNI 896 interface employs the OAL instead of directly fragmenting the IPv6 ND 897 message itself. For this reason, OMNI interfaces MUST NOT admit IPv6 898 ND messages larger than the OMNI interface MTU, and MUST employ the 899 OAL for IPv6 ND messages admitted into the OMNI interface the same as 900 discussed above. 902 5.2. OAL "Super-Packet" Packing 904 By default, the source OAL includes a 40-byte IPv6 encapsulation 905 header for each inner IP payload packet during OAL encapsulation. 906 When fragmentation is needed, the source OAL also calculates and 907 includes a 32-bit trailing CRC for the entire packet then performs 908 fragmentation such that a copy of the 40-byte IPv6 header plus an 909 8-byte IPv6 Fragment Header is included in each fragment. However, 910 these encapsulations may represent excessive overhead in some 911 environments. A technique known as "packing" discussed in 912 [I-D.ietf-intarea-tunnels] is therefore supported so that multiple 913 inner IP payload packets can be included within a single OAL packet 914 known as a "super-packet". 916 When the source OAL has multiple inner IP payload packets with total 917 length no larger than the OMNI interface MTU to send to the same 918 destination, it can optionally concatenate them into a super-packet 919 encapsulated in a single OAL header. Within the super-packet, the IP 920 header of the first inner packet (iHa) followed by its data (iDa) is 921 concatenated immediately following the OAL header, then the inner IP 922 header of the next packet (iHb) followed by its data (iDb) is 923 concatenated immediately following the first packet, etc. The super- 924 packet format is transposed from [I-D.ietf-intarea-tunnels] and shown 925 in Figure 3: 927 <-- Multiple inner IP payload packets to be "packed" --> 928 +-----+-----+ 929 | iHa | iDa | 930 +-----+-----+ 931 | 932 | +-----+-----+ 933 | | iHb | iDb | 934 | +-----+-----+ 935 | | 936 | | +-----+-----+ 937 | | | iHc | iDc | 938 | | +-----+-----+ 939 | | | 940 v v v 941 +----------+-----+-----+-----+-----+-----+-----+ 942 | OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc | 943 +----------+-----+-----+-----+-----+-----+-----+ 944 <-- OMNI "Super-Packet" with single OAL hdr --> 946 Figure 3: OAL Super-Packet Format 948 When the source OAL sends a super-packet, it calculates a CRC and 949 applies OAL fragmentation if necessary then sends the packet or 950 fragments to the destination OAL. When the destination OAL receives 951 the super-packet as a whole packet or as fragments, it reassembles 952 and verifies the CRC if necessary then regards the OAL header Payload 953 Length as the sum of the lengths of all payload packets. The 954 destination OAL then selectively extracts each individual payload 955 packet (e.g., by setting pointers into the buffer containing the 956 super-packet and maintaining a reference count, by copying each 957 payload packet into its own buffer, etc.) and forwards each payload 958 packet or processes it locally as appropriate. During extraction, 959 the OAL determines the IP protocol version of each successive inner 960 payload packet 'j' by examining the first four bits of iH(j), and 961 determines the length of the inner packet by examining the rest of 962 iH(j) according to the IP protocol version. 964 Note: OMNI interfaces must take care to avoid processing super-packet 965 payload elements that would subvert security. Specifically, if a 966 super-packet contains a mix of data and control payload packets 967 (which could include critical security codes), the node MUST NOT 968 process the data packets before processing the control packets. 970 6. Frame Format 972 The OMNI interface transmits IP packets according to the native frame 973 format of each underlying interface. For example, for Ethernet- 974 compatible interfaces the frame format is specified in [RFC2464], for 975 aeronautical radio interfaces the frame format is specified in 976 standards such as ICAO Doc 9776 (VDL Mode 2 Technical Manual), for 977 tunnels over IPv6 the frame format is specified in [RFC2473], etc. 979 7. Link-Local Addresses (LLAs) 981 OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses 982 (LLAs) through pre-service administrative actions. "MNP-LLAs" embed 983 the MNP assigned to the mobile node, while "ADM-LLAs" include an 984 administratively-unique ID that is guaranteed to be unique on the 985 link. LLAs are configured as follows: 987 o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within 988 the least-significant 64 bits of the IPv6 link-local prefix 989 fe80::/64, i.e., in the LLA "interface identifier" portion. The 990 prefix length for the LLA is determined by adding 64 to the MNP 991 prefix length. For example, for the MNP 2001:db8:1000:2000::/56 992 the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. 994 o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4], 995 i.e., the interface identifier consists of 16 '0' bits, followed 996 by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The 997 prefix length for the LLA is determined by adding 96 to the MNP 998 prefix length. For example, the IPv4-Compatible MN OMNI LLA for 999 192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as 1000 fe80::ffff:c000:0200/120). 1002 o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for 1003 uniqueness. The lower 32 bits of the LLA includes a unique 1004 integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as 1005 in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA 1006 prefix length is determined by adding 96 to the MSID prefix 1007 length. For example, if the prefix length for MSID 0x10012001 is 1008 16 then the ADM-LLA prefix length is set to 112 and the LLA is 1009 written as fe80::1001:2001/112. The "zero" address for each ADM- 1010 LLA prefix is the Subnet-Router anycast address for that prefix 1011 [RFC4291]; for example, the Subnet-Router anycast address for 1012 fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range 1013 0xff000000 through 0xffffffff is reserved for future use. 1015 o Temporary LLAs are constructed per [I-D.ietf-6man-rfc4941bis] and 1016 used by MNs for the short-term purpose of procuring an actual MNP- 1017 LLA upon startup or (re)connecting to the network. MNs may use 1018 Temporary LLAs as the IPv6 source address of an RS message in 1019 order to request a MNP-LLA from the MS. 1021 Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no 1022 MNPs can be allocated from that block ensuring that there is no 1023 possibility for overlap between the various LLA constructs discussed 1024 above. 1026 Since MNP-LLAs are based on the distribution of administratively 1027 assured unique MNPs, and since ADM-LLAs are guaranteed unique through 1028 administrative assignment, OMNI interfaces set the autoconfiguration 1029 variable DupAddrDetectTransmits to 0 [RFC4862]. 1031 Temporary LLAs employ optimistic DAD principles [RFC4429] since they 1032 are probabilistically unique and their use is short-duration in 1033 nature. 1035 Note: If future protocol extensions relax the 64-bit boundary in IPv6 1036 addressing, the additional prefix bits of an MNP could be encoded in 1037 bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits 1038 would therefore still be in bits 64-127, and the remaining bits would 1039 appear in bits 16 through 48.) However, the analysis provided in 1040 [RFC7421] suggests that the 64-bit boundary will remain in the IPv6 1041 architecture for the foreseeable future. 1043 Note: Even though this document honors the 64-bit boundary in IPv6 1044 addressing per [RFC7421], it suggests prefix lengths longer than /64 1045 for routing purposes. This effectively extends IPv6 routing 1046 determination into the interface identifier portion of the IPv6 1047 address, but it does not redefine the 64-bit boundary. 1049 8. Unique-Local Addresses (ULAs) 1051 OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and 1052 destination addresses in OAL IPv6 encapsulation headers. ULAs are 1053 only routable within the scope of a an OMNI domain, and are derived 1054 from the IPv6 Unique Local Address prefix fc00::/7 followed by the L 1055 bit set to 1 (i.e., as fd00::/8) followed by a 40-bit pseudo-random 1056 Global ID to produce the prefix [ULA]::/48, which is then followed by 1057 a 16-bit Subnet ID then finally followed by a 64 bit Interface ID as 1058 specified in Section 3 of [RFC4193]. The statistic uniqueness of the 1059 40-bit pseudo-random Global ID allows different OMNI domains to be 1060 joined together in the future without requiring OMNI link 1061 renumbering. 1063 Each OMNI link instance is identified by a value between 0x0000 and 1064 0xfeff in bits 48-63 of [ULA]::/48 (the values 0xff00 through 0xffff 1065 are reserved for future use). For example, OMNI ULAs associated with 1066 instance 0 are configured from the prefix [ULA]:0000::/64, instance 1 1067 from [ULA]:0001::/64, instance 2 from [ULA]:0002::/64, etc. ULAs and 1068 their associated prefix lengths are configured in correspondence with 1069 LLAs through stateless prefix translation where "MNP-ULAs" are 1070 assigned in correspondence to MNP-LLAs and "ADM-ULAs" are assigned in 1071 correspondence to ADM-LLAs. For example, for OMNI link instance 1072 [ULA]:1010::/64: 1074 o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a 1075 56-bit MNP length is derived by copying the lower 64 bits of the 1076 LLA into the lower 64 bits of the ULA as 1077 [ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes 1078 64 plus the IPv6 MNP length). 1080 o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit 1081 MNP length is derived by simply writing the LLA interface ID into 1082 the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the 1083 ULA prefix length is 64 plus 32 plus the IPv4 MNP length). 1085 o the ADM-ULA corresponding to fe80::1000/112 is simply 1086 [ULA]:1010::1000/112. 1088 o the ADM-ULA corresponding to fe80::/128 is simply 1089 [ULA]:1010::/128. 1091 o the Temporary ULA corresponding to a Temporary LLA is simply 1092 [ULA]:1010:[64-bit Temporary Interface ID]/128. 1094 o etc. 1096 Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI 1097 link instance. For example, the OMNI interface connected to instance 1098 3 assigns the Anycast address [ULA]:0003::/128. Routers that 1099 configure OMNI interfaces advertise the OMNI service prefix (e.g., 1100 [ULA]:0003::/64) into the local routing system so that applications 1101 can direct traffic according to SBM requirements. 1103 The ULA presents an IPv6 address format that is routable within the 1104 OMNI routing system and can be used to convey link-scoped IPv6 ND 1105 messages across multiple hops using IPv6 encapsulation [RFC2473]. 1106 The OMNI link extends across one or more underling Internetworks to 1107 include all ARs and MSEs. All MNs are also considered to be 1108 connected to the OMNI link, however OAL encapsulation is omitted 1109 whenever possible to conserve bandwidth (see: Section 12). 1111 Each OMNI link can be subdivided into "segments" that often 1112 correspond to different administrative domains or physical 1113 partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when 1114 necessary to support efficient packet forwarding to destinations 1115 located in other OMNI link segments. A full discussion of Segment 1116 Routing over the OMNI link appears in [I-D.templin-intarea-6706bis]. 1118 Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit 1119 set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing, 1120 however the range could be used for MSP and MNP addressing under 1121 certain limiting conditions (see: Section 9). 1123 9. Global Unicast Addresses (GUAs) 1125 OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291] 1126 as Mobility Service Prefixes (MSPs) from which Mobile Network 1127 Prefixes (MNP) are delegated to Mobile Nodes (MNs). 1129 For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an 1130 associated regional assigned numbers authority such that the OMNI 1131 domain can be interconnected to the global IPv6 Internet without 1132 causing inconsistencies in the routing system. An OMNI domain could 1133 instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix 1134 fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain 1135 were ever connected to the global IPv6 Internet. 1137 For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an 1138 associated regional assigned numbers authority such that the OMNI 1139 domain can be interconnected to the global IPv4 Internet without 1140 causing routing inconsistencies. An OMNI domain could instead use 1141 private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however 1142 this would require IPv4 NAT if the domain were ever connected to the 1143 global IPv4 Internet. 1145 10. Address Mapping - Unicast 1147 OMNI interfaces maintain a neighbor cache for tracking per-neighbor 1148 state and use the link-local address format specified in Section 7. 1149 OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent 1150 over physical underlying interfaces without encapsulation observe the 1151 native underlying interface Source/Target Link-Layer Address Option 1152 (S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in 1153 [RFC2464]). OMNI interface IPv6 ND messages sent over underlying 1154 interfaces via encapsulation do not include S/TLLAOs which were 1155 intended for encoding physical L2 media address formats and not 1156 encapsulation IP addresses. Furthermore, S/TLLAOs are not intended 1157 for encoding additional interface attributes needed for multilink 1158 coordination. Hence, this document does not define an S/TLLAO format 1159 but instead defines a new option type termed the "OMNI option" 1160 designed for these purposes. 1162 MNs such as aircraft typically have many wireless data link types 1163 (e.g. satellite-based, cellular, terrestrial, air-to-air directional, 1164 etc.) with diverse performance, cost and availability properties. 1165 The OMNI interface would therefore appear to have multiple L2 1166 connections, and may include information for multiple underlying 1167 interfaces in a single IPv6 ND message exchange. OMNI interfaces use 1168 an IPv6 ND option called the OMNI option formatted as shown in 1169 Figure 4: 1171 0 1 2 3 1172 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1174 | Type | Length |T| Preflen | S/T-omIndex | 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1176 | | 1177 ~ Sub-Options ~ 1178 | | 1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1181 Figure 4: OMNI Option Format 1183 In this format: 1185 o Type is set to TBD1. 1187 o Length is set to the number of 8 octet blocks in the option. The 1188 value 0 is invalid, while the values 1 through 255 (i.e., 8 1189 through 2040 octets, respectively) indicate the total length of 1190 the OMNI option. 1192 o T is a 1-bit flag set to 1 for Temporary LLAs (otherwise, set to 1193 0) and Preflen is a 7 bit field that determines the length of 1194 prefix associated with an LLA. Values 1 through 127 specify a 1195 prefix length, while the value 0 indicates "unspecified". For 1196 IPv6 ND messages sent from a MN to the MS, T and Preflen apply to 1197 the IPv6 source LLA and provide the length that the MN is 1198 requesting or asserting to the MS. For IPv6 ND messages sent from 1199 the MS to the MN, T and Preflen apply to the IPv6 destination LLA 1200 and indicate the length that the MS is granting to the MN. For 1201 IPv6 ND messages sent between MS endpoints, T is set to 0 and 1202 Preflen provides the length associated with the source/target MN 1203 that is subject of the ND message. 1205 o S/T-omIndex corresponds to the omIndex value for source or target 1206 underlying interface used to convey this IPv6 ND message. OMNI 1207 interfaces MUST number each distinct underlying interface with an 1208 omIndex value between '1' and '255' that represents a MN-specific 1209 8-bit mapping for the actual ifIndex value assigned by network 1210 management [RFC2863] (the omIndex value '0' is reserved for use by 1211 the MS). For RS and NS messages, S/T-omIndex corresponds to the 1212 source underlying interface the message originated from. For RA 1213 and NA messages, S/T-omIndex corresponds to the target underlying 1214 interface that the message is destined to. (For NS messages used 1215 for Neighbor Unreachability Detection (NUD), S/T-omIndex instead 1216 identifies the neighbor's underlying interface to be used as the 1217 target interface to return the NA.) 1219 o Sub-Options is a Variable-length field, of length such that the 1220 complete OMNI Option is an integer multiple of 8 octets long. 1221 Contains one or more Sub-Options, as described in Section 10.1. 1223 The OMNI option may appear in any IPv6 ND message type; it is 1224 processed by interfaces that recognize the option and ignored by all 1225 other interfaces. If multiple OMNI option instances appear in the 1226 same IPv6 ND message, the interface processes the T, Preflen and S/ 1227 T-omIndex fields in the first instance and ignores those fields in 1228 all other instances. The interface processes the Sub-Options of all 1229 OMNI option instances in the consecutive order in which they appear 1230 in the IPv6 ND message, beginning with the first instance and 1231 continuing consecutively through any additional instances to the end 1232 of the message. 1234 The OMNI option(s) in each IPv6 ND message may include full or 1235 partial information for the neighbor. The union of the information 1236 in the most recently received OMNI options is therefore retained, and 1237 the information is aged/removed in conjunction with the corresponding 1238 neighbor cache entry. 1240 10.1. Sub-Options 1242 The OMNI option includes zero or more Sub-Options. Each consecutive 1243 Sub-Option is concatenated immediately after its predecessor. All 1244 Sub-Options except Pad1 (see below) are in type-length-value (TLV) 1245 encoded in the following format: 1247 0 1 2 1248 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 1249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1250 | Sub-Type| Sub-length | Sub-Option Data ... 1251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1253 Figure 5: Sub-Option Format 1255 o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub- 1256 Options defined in this document are: 1258 Option Name Sub-Type 1259 Pad1 0 1260 PadN 1 1261 Interface Attributes (Type 1) 2 1262 Interface Attributes (Type 2) 3 1263 Traffic Selector 4 1264 Origin Indication 5 1265 MS-Register 6 1266 MS-Release 7 1267 Geo Coordinates 8 1268 DHCPv6 Message 9 1269 HIP Message 10 1270 Node Identification 11 1272 Figure 6 1274 Sub-Types 12-29 are available for future assignment. Sub-Type 30 1275 is reserved for experimentation, as recommended in [RFC3692]. 1276 Sub-Type 31 is reserved by IANA. 1278 o Sub-Length is an 11-bit field that encodes the length of the Sub- 1279 Option Data ranging from 0 to 2034 octets (the values 2035 through 1280 2047 are invalid, since each OMNI option is limited to 2040 1281 octets). 1283 o Sub-Option Data is a block of data with format determined by Sub- 1284 Type and length determined by Sub-Length. 1286 Note that Sub-Type and Sub-Length are coded together in network byte 1287 order in two consecutive octets. Note also that Sub-Option Data may 1288 be up to 2034 octets in length. This allows ample space for encoding 1289 large objects (e.g., ascii character strings, protocol messages, 1290 security codes, etc.), while a single OMNI option is limited to 2040 1291 octets the same as for any IPv6 ND option. If the Sub-Options to be 1292 coded would cause an OMNI option to exceed 2040 octets, any remaining 1293 Sub-Options are encoded in additional OMNI options in the consecutive 1294 order of intended processing. Implementations must therefore be 1295 mindful of size limitations, and must refrain from sending IPv6 ND 1296 messages larger than the OMNI interface MTU. 1298 During processing, unrecognized Sub-Options are ignored and the next 1299 Sub-Option processed until the end of the OMNI option is reached. 1301 The following Sub-Option types and formats are defined in this 1302 document: 1304 10.1.1. Pad1 1306 0 1307 0 1 2 3 4 5 6 7 1308 +-+-+-+-+-+-+-+-+ 1309 | S-Type=0|x|x|x| 1310 +-+-+-+-+-+-+-+-+ 1312 Figure 7: Pad1 1314 o Sub-Type is set to 0. If multiple instances appear in OMNI 1315 options of the same message all are processed. 1317 o Sub-Type is followed by three 'x' bits, set randomly on 1318 transmission and ignored on receipt. Pad1 therefore consists of a 1319 whole single octet with the most significant 5 bits set to 0, and 1320 with no Sub-Length or Sub-Option Data fields following. 1322 10.1.2. PadN 1324 0 1 2 1325 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 1326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1327 | S-Type=1| Sub-length=N | N padding octets ... 1328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1330 Figure 8: PadN 1332 o Sub-Type is set to 1. If multiple instances appear in OMNI 1333 options of the same message all are processed. 1335 o Sub-Length is set to N (from 0 to 2034 being the number of padding 1336 octets that follow. 1338 o Sub-Option Data consists of N zero-valued octets. 1340 10.1.3. Interface Attributes (Type 1) 1342 The Interface Attributes (Type 1) sub-option provides a basic set of 1343 attributes for underlying interfaces. Interface Attributes (Type 1) 1344 is deprecated throughout the rest of this specification, and 1345 Interface Attributes (Type 2) (see: Section 10.1.4) are indicated 1346 wherever the term "Interface Attributes" appears without an 1347 associated Type designation. 1349 Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in 1350 IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages 1351 they receive. If an Interface Attributes (Type 1) is included, it 1352 must have the following format: 1354 0 1 2 3 1355 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 1356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1357 | Sub-Type=2| Sub-length=N | omIndex | omType | 1358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1359 | Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07| 1360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1361 |P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23| 1362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1363 |P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39| 1364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1365 |P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55| 1366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1367 |P56|P57|P58|P59|P60|P61|P62|P63| 1368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1370 Figure 9: Interface Attributes (Type 1) 1372 o Sub-Type is set to 2. If multiple instances with different 1373 omIndex values appear in OMNI option of the same message all are 1374 processed; if multiple instances with the same omIndex value 1375 appear, the first is processed and all others are ignored 1377 o Sub-Length is set to N (from 4 to 2034 that encodes the number of 1378 Sub-Option Data octets that follow. 1380 o omIndex is a 1-octet field containing a value from 0 to 255 1381 identifying the underlying interface for which the attributes 1382 apply. 1384 o omType is a 1-octet field containing a value from 0 to 255 1385 corresponding to the underlying interface identified by omIndex. 1387 o Provider ID is a 1-octet field containing a value from 0 to 255 1388 corresponding to the underlying interface identified by omIndex. 1390 o Link encodes a 4-bit link metric. The value '0' means the link is 1391 DOWN, and the remaining values mean the link is UP with metric 1392 ranging from '1' ("lowest") to '15' ("highest"). 1394 o Resvd is reserved for future use. 1396 o A 16-octet ""Preferences" field immediately follows 'Resvd', with 1397 values P[00] through P[63] corresponding to the 64 Differentiated 1398 Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field 1399 is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") 1400 or '3' ("high") to indicate a QoS preference for underlying 1401 interface selection purposes. 1403 10.1.4. Interface Attributes (Type 2) 1405 The Interface Attributes (Type 2) sub-option provides L2 forwarding 1406 information for the multilink conceptual sending algorithm discussed 1407 in Section 12. The L2 information is used for selecting among 1408 potentially multiple candidate underlying interfaces that can be used 1409 to forward packets to the neighbor based on factors such as DSCP 1410 preferences and link quality. Interface Attributes (Type 2) further 1411 includes link-layer address information to be used for either OAL 1412 encapsulation or direct UDP/IP encapsulation (when OAL encapsulation 1413 can be avoided). 1415 Interface Attributes (Type 2) are the sole Interface Attributes 1416 format in this specification that all OMNI nodes must honor. 1417 Wherever the term "Interface Attributes" occurs throughout this 1418 specification without a "Type" designation, the format given below is 1419 indicated: 1421 0 1 2 3 1422 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 1423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1424 | S-Type=3| Sub-length=N | omIndex | omType | 1425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1426 | Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) | 1427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1428 | LHS (bits 8 - 31) | ~ 1429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1430 ~ ~ 1431 ~ Link Layer Address (L2ADDR) ~ 1432 ~ ~ 1433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1434 | Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11| 1435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1436 |P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27| 1437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1438 |P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ... 1439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1441 Figure 10: Interface Attributes (Type 2) 1443 o Sub-Type is set to 3. If multiple instances with different 1444 omIndex values appear in OMNI options of the same message all are 1445 processed; if multiple instances with the same omIndex value 1446 appear, the first is processed and all others are ignored. 1448 o Sub-Length is set to N (from 4 to 2034) that encodes the number of 1449 Sub-Option Data octets that follow. 1451 o Sub-Option Data contains an "Interface Attributes (Type 2)" option 1452 encoded as follows (note that the first four octets must be 1453 present): 1455 * omIndex is set to an 8-bit integer value corresponding to a 1456 specific underlying interface the same as specified above for 1457 the OMNI option header S/T-omIndex. The OMNI options of a same 1458 message may include multiple Interface Attributes Sub-Options, 1459 with each distinct omIndex value pertaining to a different 1460 underlying interface. The OMNI option will often include an 1461 Interface Attributes Sub-Option with the same omIndex value 1462 that appears in the S/T-omIndex. In that case, the actual 1463 encapsulation address of the received IPv6 ND message should be 1464 compared with the L2ADDR encoded in the Sub-Option (see below); 1465 if the addresses are different (or, if L2ADDR is absent) the 1466 presence of a NAT is assumed. 1468 * omType is set to an 8-bit integer value corresponding to the 1469 underlying interface identified by omIndex. The value 1470 represents an OMNI interface-specific 8-bit mapping for the 1471 actual IANA ifType value registered in the 'IANAifType-MIB' 1472 registry [http://www.iana.org]. 1474 * Provider ID is set to an OMNI interface-specific 8-bit ID value 1475 for the network service provider associated with this omIndex. 1477 * Link encodes a 4-bit link metric. The value '0' means the link 1478 is DOWN, and the remaining values mean the link is UP with 1479 metric ranging from '1' ("lowest") to '15' ("highest"). 1481 * R is reserved for future use. 1483 * API - a 3-bit "Address/Preferences/Indexed" code that 1484 determines the contents of the remainder of the sub-option as 1485 follows: 1487 + When the most significant bit (i.e., "Address") is set to 1, 1488 the SRT, FMT, LHS and L2ADDR fields are included immediately 1489 following the API code; else, they are omitted. 1491 + When the next most significant bit (i.e., "Preferences") is 1492 set to 1, a preferences block is included next; else, it is 1493 omitted. (Note that if "Address" is set the preferences 1494 block immediately follows L2ADDR; else, it immediately 1495 follows the API code.) 1497 + When a preferences block is present and the least 1498 significant bit (i.e., "Indexed") is set to 0, the block is 1499 encoded in "Simplex" form as shown in Figure 9; else it is 1500 encoded in "Indexed" form as discussed below. 1502 * When API indicates that an "Address" is included, the following 1503 fields appear in consecutive order (else, they are omitted): 1505 + SRT - a 5-bit Segment Routing Topology prefix length value 1506 that (when added to 96) determines the prefix length to 1507 apply to the ULA formed from concatenating [ULA*]::/96 with 1508 the 32 bit LHS MSID value that follows. For example, the 1509 value 16 corresponds to the prefix length 112. 1511 + FMT - a 3-bit "Framework/Mode/Type" code corresponding to 1512 the included Link Layer Address as follows: 1514 - When the most significant bit (i.e., "Framework") is set 1515 to 0, L2ADDR is the INET encapsulation address of a 1516 Proxy/Server; otherwise, it is the address for the 1517 Source/Target itself 1519 - When the next most significant bit (i.e., "Mode") is set 1520 to 0, the Source/Target L2ADDR is on the open INET; 1521 otherwise, it is (likely) located behind one or more 1522 NATs. 1524 - When the least significant bit (i.e., "Type") is set to 1525 0, L2ADDR includes a UDP Port Number followed by an IPv4 1526 address; else, a UDP Port Number followed by an IPv6 1527 address. 1529 + LHS - the 32 bit MSID of the Last Hop Server/Proxy on the 1530 path to the target. When SRT and LHS are both set to 0, the 1531 LHS is considered unspecified in this IPv6 ND message. When 1532 SRT is set to 0 and LHS is non-zero, the prefix length is 1533 set to 128. SRT and LHS together provide guidance to the 1534 OMNI interface forwarding algorithm. Specifically, if SRT/ 1535 LHS is located in the local OMNI link segment then the OMNI 1536 interface can encapsulate according to FMT/L2ADDR (following 1537 any necessary NAT traversal messaging); else, it must 1538 forward according to the OMNI link spanning tree. See 1539 [I-D.templin-intarea-6706bis] for further discussion. 1541 + Link Layer Address (L2ADDR) - Formatted according to FMT, 1542 and identifies the link-layer address (i.e., the 1543 encapsulation address) of the source/target. The UDP Port 1544 Number appears in the first two octets and the IP address 1545 appears in the next 4 octets for IPv4 or 16 octets for IPv6. 1546 The Port Number and IP address are recorded in ones- 1547 compliment "obfuscated" form per [RFC4380]. The OMNI 1548 interface forwarding algorithm uses FMT/L2ADDR to determine 1549 the encapsulation address for forwarding when SRT/LHS is 1550 located in the local OMNI link segment. Note that if the 1551 target is behind a NAT, L2ADDR will contain the mapped INET 1552 address stored in the NAT; otherwise, L2ADDR will contain 1553 the native INET information of the target itself. 1555 * When API indicates that "Preferences" are included, a 1556 preferences block appears as the remainder of the Sub-Option as 1557 a series of Bitmaps and P[*] values. In "Simplex" form, the 1558 index for each singleton Bitmap octet is inferred from its 1559 sequential position (i.e., 0, 1, 2, ...) as shown in Figure 9. 1560 In "Indexed" form, each Bitmap is preceded by an Index octet 1561 that encodes a value "i" = (0 - 255) as the index for its 1562 companion Bitmap as follows: 1564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1565 | Index=i | Bitmap(i) |P[*] values ... 1566 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1568 Figure 11 1570 * The preferences consist of a first (simplex/indexed) Bitmap 1571 (i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of 1572 2-bit P[*] values, followed by a second Bitmap (i), followed by 1573 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, 1574 the bits of each Bitmap(i) that are set to '1'' indicate the 1575 P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] 1576 that follow; if any Bitmap(i) bits are '0', then the 1577 corresponding P[*] block is instead omitted. For example, if 1578 Bitmap(0) contains 0xff then the block with P[00]-P[03], 1579 followed by the block with P[04]-P[07], etc., and ending with 1580 the block with P[28]-P[31] are included (as shown in Figure 9). 1581 The next Bitmap(i) is then consulted with its bits indicating 1582 which P[*] blocks follow, etc. out to the end of the Sub- 1583 Option. 1585 * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' 1586 ("low"), '2' ("medium") or '3' ("high") to indicate a QoS 1587 preference for underlying interface selection purposes. Not 1588 all P[*] values need to be included in the OMNI option of each 1589 IPv6 ND message received. Any P[*] values represented in an 1590 earlier OMNI option but omitted in the current OMNI option 1591 remain unchanged. Any P[*] values not yet represented in any 1592 OMNI option default to "medium". 1594 * The first 16 P[*] blocks correspond to the 64 Differentiated 1595 Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any 1596 additional P[*] blocks that follow correspond to "pseudo-DSCP" 1597 traffic classifier values P[64], P[65], P[66], etc. See 1598 Appendix A for further discussion and examples. 1600 10.1.5. Traffic Selector 1602 0 1 2 3 1603 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 1604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1605 | S-Type=4| Sub-length=N | omIndex | ~ 1606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1607 ~ ~ 1608 ~ RFC 6088 Format Traffic Selector ~ 1609 ~ ~ 1610 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1612 Figure 12: Traffic Selector 1614 o Sub-Type is set to 4. If multiple instances appear in OMNI 1615 options of the same message all are processed, i.e., even if the 1616 same omIndex value appears multiple times. 1618 o Sub-Length is set to N (the number of Sub-Option Data octets that 1619 follow). 1621 o Sub-Option Data contains a 1-octet omIndex encoded exactly as 1622 specified in Section 10.1.3, followed by an N-1 octet traffic 1623 selector formatted per [RFC6088] beginning with the "TS Format" 1624 field. The largest traffic selector for a given omIndex is 1625 therefore 2033 octets. 1627 10.1.6. Origin Indication 1629 0 1 2 3 1630 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 1631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1632 | S-Type=5| Sub-length=6/18 | Origin Port Number | 1633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1634 ~ Origin IPv4/IPv6 Address ~ 1635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1637 Figure 13: Origin Indication 1639 o Sub-Type is set to 5. If multiple instances appear in OMNI 1640 options of the same message the first instance is processed and 1641 all others are ignored. 1643 o Sub-Length is set to either 6 or 18; if Sub-Length encodes any 1644 other value, the Sub-Option is ignored. 1646 o Sub-Option Data contains a 2-octet Port Number followed by a 1647 4-octet IPv4 address if Sub-Length encodes 6 or a 16-octet IPv6 1648 address if Sub-Length encodes 18. 1650 10.1.7. MS-Register 1652 0 1 2 3 1653 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 1654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1655 | S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) | 1656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1657 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1659 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1661 ... ... ... ... ... ... 1662 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1663 | MSID [n] (bits 16 - 32) | 1664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1666 Figure 14: MS-Register Sub-option 1668 o Sub-Type is set to 6. If multiple instances appear in OMNI 1669 options of the same message all are processed. Only the first 1670 MAX_MSID values processed (whether in a single instance or 1671 multiple) are retained and all other MSIDs are ignored. 1673 o Sub-Length is set to 4n, with 508 as the maximum value for n. 1675 o A list of n 4-octet MSIDs is included in the following 4n octets. 1676 The Anycast MSID value '0' in an RS message MS-Register sub-option 1677 requests the recipient to return the MSID of a nearby MSE in a 1678 corresponding RA response. 1680 10.1.8. MS-Release 1681 0 1 2 3 1682 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 1683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1684 | S-Type=7| Sub-length=4n | MSID[1] (bits 0 - 15) | 1685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1686 | MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) | 1687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1688 | MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) | 1689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1690 ... ... ... ... ... ... 1691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1692 | MSID [n] (bits 16 - 32) | 1693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1695 Figure 15: MS-Release Sub-option 1697 o Sub-Type is set to 7. If multiple instances appear in OMNI 1698 options of the same message all are processed. Only the first 1699 MAX_MSID values processed (whether in a single instance or 1700 multiple) are retained and all other MSIDs are ignored. 1702 o Sub-Length is set to 4n, with 508 as the maximum value for n. 1704 o A list of n 4 octet MSIDs is included in the following 4n octets. 1705 The Anycast MSID value '0' is ignored in MS-Release sub-options, 1706 i.e., only non-zero values are processed. 1708 10.1.9. Geo Coordinates 1710 0 1 2 3 1711 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 1712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1713 | S-Type=8| Sub-length=N | Geo Coordinates 1714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 1716 Figure 16: Geo Coordinates Sub-option 1718 o Sub-Type is set to 8. If multiple instances appear in OMNI 1719 options of the same message the first is processed and all others 1720 are ignored. 1722 o Sub-Length is set to N (i.e., the length of the encoded Geo 1723 Coordinates up to a maximum of 2034 octets). 1725 o A set of Geo Coordinates. Format(s) to be specified in future 1726 documents; should include Latitude/Longitude, plus any additional 1727 attributes such as altitude, heading, speed, etc. 1729 10.1.10. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message 1731 0 1 2 3 1732 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 1733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1734 | S-Type=9| Sub-length=N | msg-type | id (octet 0) | 1735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1736 | transaction-id (octets 1-2) | | 1737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1738 | | 1739 . DHCPv6 options . 1740 . (variable number and length) . 1741 | | 1742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1744 Figure 17: DHCPv6 Message Sub-option 1746 o Sub-Type is set to 9. If multiple instances appear in OMNI 1747 options of the same message the first is processed and all others 1748 are ignored. 1750 o Sub-Length is set to N (i.e., the length of the DHCPv6 message 1751 beginning with 'msg-type' and continuing to the end of the DHCPv6 1752 options). The length of the entire DHCPv6 message is therefore 1753 restricted to 2034 octets. 1755 o 'msg-type' and 'transaction-id' are coded according to Section 8 1756 of [RFC8415]. 1758 o A set of DHCPv6 options coded according to Section 21 of [RFC8415] 1759 follows. 1761 10.1.11. Host Identity Protocol (HIP) Message 1762 0 1 2 3 1763 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 1764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1765 |S-Type=10| Sub-length=N |0| Packet Type |Version| RES.|1| 1766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1767 | Checksum | Controls | 1768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1769 | Sender's Host Identity Tag (HIT) | 1770 | | 1771 | | 1772 | | 1773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1774 | Receiver's Host Identity Tag (HIT) | 1775 | | 1776 | | 1777 | | 1778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1779 | | 1780 / HIP Parameters / 1781 / / 1782 | | 1783 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1785 Figure 18: HIP Message Sub-option 1787 o Sub-Type is set to 10. If multiple instances appear in OMNI 1788 options of the same message the first is processed and all others 1789 are ignored. 1791 o Sub-Length is set to N, i.e., the length of the option in octets 1792 beginning immediately following the Sub-Length field and extending 1793 to the end of the HIP parameters. The length of the entire HIP 1794 message is therefore restricted to 2034 octets. 1796 o The HIP message is coded exactly as specified in Section 5 of 1797 [RFC7401], with the exception that the OMNI "Sub-Type" and "Sub- 1798 Length" fields replace the first two header octets of the HIP 1799 message (i.e., the Next Header and Header Length fields). 1801 10.1.12. Node Identification 1802 0 1 2 3 1803 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 1804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1805 |S-Type=11| Sub-length=N | ID-Type | ~ 1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 1807 ~ Node Identification Value (N-1 octets) ~ 1808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1810 Figure 19: Node Identification 1812 o Sub-Type is set to 11. If multiple instances appear in OMNI 1813 options of the same IPv6 ND message the first instance of a 1814 specific ID-Type is processed and all other instances of the same 1815 ID-Type are ignored. (Note therefore that it is possible for a 1816 single IPv6 ND message to convey multiple Node Identifications - 1817 each having a different ID-Type.) 1819 o Sub-Length is set to N, i.e., the combined length of the ID-Type 1820 and Node Identification Value fields. The maximum Node 1821 Identification Value length is therefore 2033 octets. 1823 o ID-Type is a one-octet field that encodes the type of the Node 1824 Identification Value. The following ID-Type values are currently 1825 defined: 1827 * 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates 1828 that Node Identification Value contains a 16 octet UUID. 1830 * 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node 1831 Identification Value contains a 16 octet HIT. 1833 * 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates 1834 that Node Identification Value contains a 16 octet HHIT. 1836 * 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that 1837 Node Identification Value contains an N-1 octet NAI. 1839 * 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicated 1840 that Node Identification Value contains an N-1 octet FQDN. 1842 * 5 - 255 - Reserved. 1844 o Node Identification Value is an (N - 1)-octet field encoded 1845 according to the appropriate the "ID-Type" reference above. 1847 11. Address Mapping - Multicast 1849 The multicast address mapping of the native underlying interface 1850 applies. The mobile router on board the MN also serves as an IGMP/ 1851 MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while 1852 using the L2 address of the AR as the L2 address for all multicast 1853 packets. 1855 The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to 1856 coordinate with the AR, and *NET L2 elements use MLD snooping 1857 [RFC4541]. 1859 12. Multilink Conceptual Sending Algorithm 1861 The MN's IPv6 layer selects the outbound OMNI interface according to 1862 SBM considerations when forwarding data packets from local or EUN 1863 applications to external correspondents. Each OMNI interface 1864 maintains a neighbor cache the same as for any IPv6 interface, but 1865 with additional state for multilink coordination. Each OMNI 1866 interface maintains default routes via ARs discovered as discussed in 1867 Section 13, and may configure more-specific routes discovered through 1868 means outside the scope of this specification. 1870 After a packet enters the OMNI interface, one or more outbound 1871 underlying interfaces are selected based on PBM traffic attributes, 1872 and one or more neighbor underlying interfaces are selected based on 1873 the receipt of Interface Attributes sub-options in IPv6 ND messages 1874 (see: Figure 9). Underlying interface selection for the nodes own 1875 local interfaces are based on attributes such as DSCP, application 1876 port number, cost, performance, message size, etc. OMNI interface 1877 multilink selections could also be configured to perform replication 1878 across multiple underlying interfaces for increased reliability at 1879 the expense of packet duplication. The set of all Interface 1880 Attributes received in IPv6 ND messages determines the multilink 1881 forwarding profile for selecting the neighbor's underlying 1882 interfaces. 1884 When the OMNI interface sends a packet over a selected outbound 1885 underlying interface, the OAL includes or omits a mid-layer 1886 encapsulation header as necessary as discussed in Section 5 and as 1887 determined by the L2 address information received in Interface 1888 Attributes. The OAL also performs encapsulation when the nearest AR 1889 is located multiple hops away as discussed in Section 13.1. (Note 1890 that the OAL MAY employ packing when multiple packets are available 1891 for forwarding to the same destination.) 1893 OMNI interface multilink service designers MUST observe the BCP 1894 guidance in Section 15 [RFC3819] in terms of implications for 1895 reordering when packets from the same flow may be spread across 1896 multiple underlying interfaces having diverse properties. 1898 12.1. Multiple OMNI Interfaces 1900 MNs may connect to multiple independent OMNI links concurrently in 1901 support of SBM. Each OMNI interface is distinguished by its Anycast 1902 ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN 1903 configures a separate OMNI interface for each link so that multiple 1904 interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 1905 layer. A different Anycast ULA is assigned to each interface, and 1906 the MN injects the service prefixes for the OMNI link instances into 1907 the EUN routing system. 1909 Applications in EUNs can use Segment Routing to select the desired 1910 OMNI interface based on SBM considerations. The Anycast ULA is 1911 written into the IPv6 destination address, and the actual destination 1912 (along with any additional intermediate hops) is written into the 1913 Segment Routing Header. Standard IP routing directs the packets to 1914 the MN's mobile router entity, and the Anycast ULA identifies the 1915 OMNI interface to be used for transmission to the next hop. When the 1916 MN receives the message, it replaces the IPv6 destination address 1917 with the next hop found in the routing header and transmits the 1918 message over the OMNI interface identified by the Anycast ULA. 1920 Multiple distinct OMNI links can therefore be used to support fault 1921 tolerance, load balancing, reliability, etc. The architectural model 1922 is similar to Layer 2 Virtual Local Area Networks (VLANs). 1924 12.2. MN<->AR Traffic Loop Prevention 1926 After an AR has registered an MNP for a MN (see: Section 13), the AR 1927 will forward packets destined to an address within the MNP to the MN. 1928 The MN will under normal circumstances then forward the packet to the 1929 correct destination within its internal networks. 1931 If at some later time the MN loses state (e.g., after a reboot), it 1932 may begin returning packets destined to an MNP address to the AR as 1933 its default router. The AR therefore must drop any packets 1934 originating from the MN and destined to an address within the MN's 1935 registered MNP. To do so, the AR institutes the following check: 1937 o if the IP destination address belongs to a neighbor on the same 1938 OMNI interface, and if the link-layer source address is the same 1939 as one of the neighbor's link-layer addresses, drop the packet. 1941 13. Router Discovery and Prefix Registration 1943 MNs interface with the MS by sending RS messages with OMNI options 1944 under the assumption that one or more AR on the *NET will process the 1945 message and respond. The MN then configures default routes for the 1946 OMNI interface via the discovered ARs as the next hop. The manner in 1947 which the *NET ensures AR coordination is link-specific and outside 1948 the scope of this document (however, considerations for *NETs that do 1949 not provide ARs that recognize the OMNI option are discussed in 1950 Section 18). 1952 For each underlying interface, the MN sends an RS message with an 1953 OMNI option to coordinate with MSEs identified by MSID values. 1954 Example MSID discovery methods are given in [RFC5214] and include 1955 data link login parameters, name service lookups, static 1956 configuration, a static "hosts" file, etc. The MN can also send an 1957 RS with an MS-Register sub-option that includes the Anycast MSID 1958 value '0', i.e., instead of or in addition to any non-zero MSIDs. 1959 When the AR receives an RS with a MSID '0', it selects a nearby MSE 1960 (which may be itself) and returns an RA with the selected MSID in an 1961 MS-Register sub-option. The AR selects only a single wildcard MSE 1962 (i.e., even if the RS MS-Register sub-option included multiple '0' 1963 MSIDs) while also soliciting the MSEs corresponding to any non-zero 1964 MSIDs. 1966 MNs configure OMNI interfaces that observe the properties discussed 1967 in the previous section. The OMNI interface and its underlying 1968 interfaces are said to be in either the "UP" or "DOWN" state 1969 according to administrative actions in conjunction with the interface 1970 connectivity status. An OMNI interface transitions to UP or DOWN 1971 through administrative action and/or through state transitions of the 1972 underlying interfaces. When a first underlying interface transitions 1973 to UP, the OMNI interface also transitions to UP. When all 1974 underlying interfaces transition to DOWN, the OMNI interface also 1975 transitions to DOWN. 1977 When an OMNI interface transitions to UP, the MN sends RS messages to 1978 register its MNP and an initial set of underlying interfaces that are 1979 also UP. The MN sends additional RS messages to refresh lifetimes 1980 and to register/deregister underlying interfaces as they transition 1981 to UP or DOWN. The MN sends initial RS messages over an UP 1982 underlying interface with its MNP-LLA as the source and with 1983 destination set to All-Routers multicast (ff02::2) [RFC4291]. The RS 1984 messages include an OMNI option per Section 10 with a Preflen 1985 assertion, Interface Attributes appropriate for underlying 1986 interfaces, MS-Register/Release sub-options containing MSID values, 1987 and with any other necessary OMNI sub-options (e.g., a DUID sub- 1988 option as an identity for the MN). The S/T-omIndex field is set to 1989 the index of the underlying interface over which the RS message is 1990 sent. 1992 ARs process IPv6 ND messages with OMNI options and act as an MSE 1993 themselves and/or as a proxy for other MSEs. ARs receive RS messages 1994 and create a neighbor cache entry for the MN, then coordinate with 1995 any MSEs named in the Register/Release lists in a manner outside the 1996 scope of this document. When an MSE processes the OMNI information, 1997 it first validates the prefix registration information then injects/ 1998 withdraws the MNP in the routing/mapping system and caches/discards 1999 the new Preflen, MNP and Interface Attributes. The MSE then informs 2000 the AR of registration success/failure, and the AR returns an RA 2001 message to the MN with an OMNI option per Section 10. 2003 The AR returns the RA message via the same underlying interface of 2004 the MN over which the RS was received, and with destination address 2005 set to the MNP-LLA (i.e., unicast), with source address set to its 2006 own LLA, and with an OMNI option with S/T-omIndex set to the value 2007 included in the RS. The OMNI option also includes a Preflen 2008 confirmation, Interface Attributes, MS-Register/Release and any other 2009 necessary OMNI sub-options (e.g., a DUID sub-option as an identity 2010 for the AR). The RA also includes any information for the link, 2011 including RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable 2012 Time and Retrans Timer values, and includes any necessary options 2013 such as: 2015 o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. 2017 o RIOs [RFC4191] with more-specific routes. 2019 o an MTU option that specifies the maximum acceptable packet size 2020 for this underlying interface. 2022 The AR MAY also send periodic and/or event-driven unsolicited RA 2023 messages per [RFC4861]. In that case, the S/T-omIndex field in the 2024 OMNI header of the unsolicited RA message identifies the target 2025 underlying interface of the destination MN. 2027 The AR can combine the information from multiple MSEs into one or 2028 more "aggregate" RAs sent to the MN in order conserve *NET bandwidth. 2029 Each aggregate RA includes an OMNI option with MS-Register/Release 2030 sub-options with the MSEs represented by the aggregate. If an 2031 aggregate is sent, the RA message contents must consistently 2032 represent the combined information advertised by all represented 2033 MSEs. Note that since the AR uses its own ADM-LLA as the RA source 2034 address, the MN determines the addresses of the represented MSEs by 2035 examining the MS-Register/Release OMNI sub-options. 2037 When the MN receives the RA message, it creates an OMNI interface 2038 neighbor cache entry for each MSID that has confirmed MNP 2039 registration via the L2 address of this AR. If the MN connects to 2040 multiple *NETs, it records the additional L2 AR addresses in each 2041 MSID neighbor cache entry (i.e., as multilink neighbors). The MN 2042 then configures a default route via the MSE that returned the RA 2043 message, and assigns the Subnet Router Anycast address corresponding 2044 to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then 2045 manages its underlying interfaces according to their states as 2046 follows: 2048 o When an underlying interface transitions to UP, the MN sends an RS 2049 over the underlying interface with an OMNI option. The OMNI 2050 option contains at least one Interface Attribute sub-option with 2051 values specific to this underlying interface, and may contain 2052 additional Interface Attributes specific to other underlying 2053 interfaces. The option also includes any MS-Register/Release sub- 2054 options. 2056 o When an underlying interface transitions to DOWN, the MN sends an 2057 RS or unsolicited NA message over any UP underlying interface with 2058 an OMNI option containing an Interface Attribute sub-option for 2059 the DOWN underlying interface with Link set to '0'. The MN sends 2060 an RS when an acknowledgement is required, or an unsolicited NA 2061 when reliability is not thought to be a concern (e.g., if 2062 redundant transmissions are sent on multiple underlying 2063 interfaces). 2065 o When the Router Lifetime for a specific AR nears expiration, the 2066 MN sends an RS over the underlying interface to receive a fresh 2067 RA. If no RA is received, the MN can send RS messages to an 2068 alternate MSID in case the current MSID has failed. If no RS 2069 messages are received even after trying to contact alternate 2070 MSIDs, the MN marks the underlying interface as DOWN. 2072 o When a MN wishes to release from one or more current MSIDs, it 2073 sends an RS or unsolicited NA message over any UP underlying 2074 interfaces with an OMNI option with a Release MSID. Each MSID 2075 then withdraws the MNP from the routing/mapping system and informs 2076 the AR that the release was successful. 2078 o When all of a MNs underlying interfaces have transitioned to DOWN 2079 (or if the prefix registration lifetime expires), any associated 2080 MSEs withdraw the MNP the same as if they had received a message 2081 with a release indication. 2083 The MN is responsible for retrying each RS exchange up to 2084 MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL 2085 seconds until an RA is received. If no RA is received over an UP 2086 underlying interface (i.e., even after attempting to contact 2087 alternate MSEs), the MN declares this underlying interface as DOWN. 2089 The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. 2090 Therefore, when the IPv6 layer sends an RS message the OMNI interface 2091 returns an internally-generated RA message as though the message 2092 originated from an IPv6 router. The internally-generated RA message 2093 contains configuration information that is consistent with the 2094 information received from the RAs generated by the MS. Whether the 2095 OMNI interface IPv6 ND messaging process is initiated from the 2096 receipt of an RS message from the IPv6 layer is an implementation 2097 matter. Some implementations may elect to defer the IPv6 ND 2098 messaging process until an RS is received from the IPv6 layer, while 2099 others may elect to initiate the process proactively. Still other 2100 deployments may elect to administratively disable the ordinary RS/RA 2101 messaging used by the IPv6 layer over the OMNI interface, since they 2102 are not required to drive the internal RS/RA processing. (Note that 2103 this same logic applies to IPv4 implementations that employ ICMP- 2104 based Router Discovery per [RFC1256].) 2106 Note: The Router Lifetime value in RA messages indicates the time 2107 before which the MN must send another RS message over this underlying 2108 interface (e.g., 600 seconds), however that timescale may be 2109 significantly longer than the lifetime the MS has committed to retain 2110 the prefix registration (e.g., REACHABLETIME seconds). ARs are 2111 therefore responsible for keeping MS state alive on a shorter 2112 timescale than the MN is required to do on its own behalf. 2114 Note: On multicast-capable underlying interfaces, MNs should send 2115 periodic unsolicited multicast NA messages and ARs should send 2116 periodic unsolicited multicast RA messages as "beacons" that can be 2117 heard by other nodes on the link. If a node fails to receive a 2118 beacon after a timeout value specific to the link, it can initiate a 2119 unicast exchange to test reachability. 2121 Note: if an AR acting as a proxy forwards a MN's RS message to 2122 another node acting as an MSE using UDP/IP encapsulation, it must use 2123 a distinct UDP source port number for each MN. This allows the MSE 2124 to distinguish different MNs behind the same AR at the link-layer, 2125 whereas the link-layer addresses would otherwise be 2126 indistinguishable. 2128 Note: when an AR acting as an MSE returns an RA to an INET Client, it 2129 includes an OMNI option with an Interface Attributes sub-option with 2130 omIndex set to 0 and with SRT, FMT, LHS and L2ADDR information for 2131 its INET interface. This provides the Client with partition prefix 2132 context regarding the local OMNI link segment. 2134 13.1. Router Discovery in IP Multihop and IPv4-Only Networks 2136 On some *NETs, a MN may be located multiple IP hops away from the 2137 nearest AR. Forwarding through IP multihop *NETs is conducted 2138 through the application of a routing protocol (e.g., a Mobile Ad-hoc 2139 Network (MANET) routing protocol over omni-directional wireless 2140 interfaces, an inter-domain routing protocol in an enterprise 2141 network, etc.). These *NETs could be either IPv6-enabled or 2142 IPv4-only, while IPv4-only *NETs could be either multicast-capable or 2143 unicast-only (note that for IPv4-only *NETs the following procedures 2144 apply for both single-hop and multihop cases). 2146 A MN located potentially multiple *NET hops away from the nearest AR 2147 prepares an RS message with source address set to either its MNP-LLA 2148 or a Temporary LLA, and with destination set to link-scoped All- 2149 Routers multicast the same as discussed above. For IPv6-enabled 2150 *NETs, the MN then encapsulates the message in an IPv6 header with 2151 source address set to the ULA corresponding to the LLA source address 2152 and with destination set to either a unicast or anycast ADM-ULA. For 2153 IPv4-only *NETs, the MN instead encapsulates the RS message in an 2154 IPv4 header with source address set to the node's own IPv4 address 2155 and with destination address set to either the unicast IPv4 address 2156 of an AR [RFC5214] or an IPv4 anycast address reserved for OMNI. The 2157 MN then sends the encapsulated RS message via the *NET interface, 2158 where it will be forwarded by zero or more intermediate *NET hops. 2160 When an intermediate *NET hop that participates in the routing 2161 protocol receives the encapsulated RS, it forwards the message 2162 according to its routing tables (note that an intermediate node could 2163 be a fixed infrastructure element or another MN). This process 2164 repeats iteratively until the RS message is received by a penultimate 2165 *NET hop within single-hop communications range of an AR, which 2166 forwards the message to the AR. 2168 When the AR receives the message, it decapsulates the RS and 2169 coordinates with the MS the same as for an ordinary link-local RS, 2170 since the inner Hop Limit will not have been decremented by the 2171 multihop forwarding process. The AR then prepares an RA message with 2172 source address set to its own ADM-LLA and destination address set to 2173 the LLA of the original MN, then encapsulates the message in an IPv4/ 2174 IPv6 header with source address set to its own IPv4/ULA address and 2175 with destination set to the encapsulation source of the RS. 2177 The AR then forwards the message to an *NET node within 2178 communications range, which forwards the message according to its 2179 routing tables to an intermediate node. The multihop forwarding 2180 process within the *NET continues repetitively until the message is 2181 delivered to the original MN, which decapsulates the message and 2182 performs autoconfiguration the same as if it had received the RA 2183 directly from the AR as an on-link neighbor. 2185 Note: An alternate approach to multihop forwarding via IPv6 2186 encapsulation would be to statelessly translate the IPv6 LLAs into 2187 ULAs and forward the messages without encapsulation. This would 2188 violate the [RFC4861] requirement that certain IPv6 ND messages must 2189 use link-local addresses and must not be accepted if received with 2190 Hop Limit less than 255. This document therefore advocates 2191 encapsulation since the overhead is nominal considering the 2192 infrequent nature and small size of IPv6 ND messages. Future 2193 documents may consider encapsulation avoidance through translation 2194 while updating [RFC4861]. 2196 Note: An alternate approach to multihop forwarding via IPv4 2197 encapsulation would be to employ IPv6/IPv4 protocol translation. 2198 However, for IPv6 ND messages the LLAs would be truncated due to 2199 translation and the OMNI Router and Prefix Discovery services would 2200 not be able to function. The use of IPv4 encapsulation is therefore 2201 indicated. 2203 Note: An IPv4 anycast address for OMNI in IPv4 networks could be part 2204 of a new IPv4 /24 prefix allocation, but this may be difficult to 2205 obtain given IPv4 address exhaustion. An alternative would be to re- 2206 purpose the prefix 192.88.99.0 which has been set aside from its 2207 former use by [RFC7526]. 2209 13.2. MS-Register and MS-Release List Processing 2211 When a MN sends an RS message with an OMNI option via an underlying 2212 interface to an AR, the MN must convey its knowledge of its 2213 currently-associated MSEs. Initially, the MN will have no associated 2214 MSEs and should therefore include an MS-Register sub-option with the 2215 single MSID value 0 which requests the AR to select and assign an 2216 MSE. The AR will then return an RA message with source address set 2217 to the ADM-LLA of the selected MSE. 2219 As the MN activates additional underlying interfaces, it can 2220 optionally include an MS-Register sub-option with MSID value 0, or 2221 with non-zero MSIDs for MSEs discovered from previous RS/RA 2222 exchanges. The MN will thus eventually begin to learn and manage its 2223 currently active set of MSEs, and can register with new MSEs or 2224 release from former MSEs with each successive RS/RA exchange. As the 2225 MN's MSE constituency grows, it alone is responsible for including or 2226 omitting MSIDs in the MS-Register/Release lists it sends in RS 2227 messages. The inclusion or omission of MSIDs determines the MN's 2228 interface to the MS and defines the manner in which MSEs will 2229 respond. The only limiting factor is that the MN should include no 2230 more than MAX_MSID values in each list per each IPv6 ND message, and 2231 should avoid duplication of entries in each list unless it wants to 2232 increase likelihood of control message delivery. 2234 When an AR receives an RS message sent by a MN with an OMNI option, 2235 the option will contain zero or more MS-Register and MS-Release sub- 2236 options containing MSIDs. After processing the OMNI option, the AR 2237 will have a list of zero or more MS-Register MSIDs and a list of zero 2238 or more of MS-Release MSIDs. The AR then processes the lists as 2239 follows: 2241 o For each list, retain the first MAX_MSID values in the list and 2242 discard any additional MSIDs (i.e., even if there are duplicates 2243 within a list). 2245 o Next, for each MSID in the MS-Register list, remove all matching 2246 MSIDs from the MS-Release list. 2248 o Next, proceed according to whether the AR's own MSID or the value 2249 0 appears in the MS-Register list as follows: 2251 * If yes, send an RA message directly back to the MN and send a 2252 proxy copy of the RS message to each additional MSID in the MS- 2253 Register list with the MS-Register/Release lists omitted. 2254 Then, send a uNA message to each MSID in the MS-Release list 2255 with the MS-Register/Release lists omitted and with an OMNI 2256 header with S/T-omIndex set to 0. 2258 * If no, send a proxy copy of the RS message to each additional 2259 MSID in the MS-Register list with the MS-Register list omitted. 2260 For the first MSID, include the original MS-Release list; for 2261 all other MSIDs, omit the MS-Release list. 2263 Each proxy copy of the RS message will include an OMNI option and 2264 encapsulation header with the ADM-ULA of the AR as the source and the 2265 ADM-ULA of the Register MSE as the destination. When the Register 2266 MSE receives the proxy RS message, if the message includes an MS- 2267 Release list the MSE sends a uNA message to each additional MSID in 2268 the Release list. The Register MSE then sends an RA message back to 2269 the (Proxy) AR wrapped in an OMNI encapsulation header with source 2270 and destination addresses reversed, and with RA destination set to 2271 the MNP-LLA of the MN. When the AR receives this RA message, it 2272 sends a proxy copy of the RA to the MN. 2274 Each uNA message (whether send by the first-hop AR or by a Register 2275 MSE) will include an OMNI option and an encapsulation header with the 2276 ADM-ULA of the Register MSE as the source and the ADM-ULA of the 2277 Release ME as the destination. The uNA informs the Release MSE that 2278 its previous relationship with the MN has been released and that the 2279 source of the uNA message is now registered. The Release MSE must 2280 then note that the subject MN of the uNA message is now "departed", 2281 and forward any subsequent packets destined to the MN to the Register 2282 MSE. 2284 Note that it is not an error for the MS-Register/Release lists to 2285 include duplicate entries. If duplicates occur within a list, the AR 2286 will generate multiple proxy RS and/or uNA messages - one for each 2287 copy of the duplicate entries. 2289 13.3. DHCPv6-based Prefix Registration 2291 When a MN is not pre-provisioned with an MNP-LLA (or, when multiple 2292 MNPs are needed), it will require the AR to select MNPs on its behalf 2293 and set up the correct routing state within the MS. The DHCPv6 2294 service [RFC8415] supports this requirement. 2296 When an MN needs to have the AR select MNPs, it sends an RS message 2297 with a Temporary LLA as the source and with DHCPv6 Message sub-option 2298 containing a Client Identifier, one or more IA_PD options and a Rapid 2299 Commit option. The MN also sets the 'msg-type' field to "Solicit", 2300 and includes a 3-octet 'transaction-id'. 2302 When the AR receives the RS message, it extracts the DHCPv6 message 2303 from the OMNI option. The AR then acts as a "Proxy DHCPv6 Client" in 2304 a message exchange with the locally-resident DHCPv6 server, which 2305 delegates MNPs and returns a DHCPv6 Reply message with PD parameters. 2306 (If the AR wishes to defer creation of MN state until the DHCPv6 2307 Reply is received, it can instead act as a Lightweight DHCPv6 Relay 2308 Agent per [RFC6221] by encapsulating the DHCPv6 message in a Relay- 2309 forward/reply exchange with Relay Message and Interface ID options.) 2311 When the AR receives the DHCPv6 Reply, it adds routes to the routing 2312 system and creates MNP-LLAs based on the delegated MNPs. The AR then 2313 sends an RA back to the MN with the DHCPv6 Reply message included in 2314 an OMNI DHCPv6 message sub-option. If the RS message source address 2315 was a Temporary address, the AR includes one of the (newly-created) 2316 MNP-LLAs as the RA destination address. The MN then creates a 2317 default route, assigns Subnet Router Anycast addresses and uses the 2318 RA destination address as its primary MNP-LLA. The MN will then use 2319 this primary MNP-LLA as the source address of any IPv6 ND messages it 2320 sends as long as it retains ownership of the MNP. 2322 Note: After a MN performs a DHCPv6-based prefix registration exchange 2323 with a first AR, it would need to repeat the exchange with each 2324 additional MSE it registers with. In that case, the MN supplies the 2325 MNP delegations received from the first AR in the IA_PD fields of a 2326 DHCPv6 message when it engages the additional MSEs. 2328 14. Secure Redirection 2330 If the *NET link model is multiple access, the AR is responsible for 2331 assuring that address duplication cannot corrupt the neighbor caches 2332 of other nodes on the link. When the MN sends an RS message on a 2333 multiple access *NET link, the AR verifies that the MN is authorized 2334 to use the address and returns an RA with a non-zero Router Lifetime 2335 only if the MN is authorized. 2337 After verifying MN authorization and returning an RA, the AR MAY 2338 return IPv6 ND Redirect messages to direct MNs located on the same 2339 *NET link to exchange packets directly without transiting the AR. In 2340 that case, the MNs can exchange packets according to their unicast L2 2341 addresses discovered from the Redirect message instead of using the 2342 dogleg path through the AR. In some *NET links, however, such direct 2343 communications may be undesirable and continued use of the dogleg 2344 path through the AR may provide better performance. In that case, 2345 the AR can refrain from sending Redirects, and/or MNs can ignore 2346 them. 2348 15. AR and MSE Resilience 2350 *NETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) 2351 [RFC5798] configurations so that service continuity is maintained 2352 even if one or more ARs fail. Using VRRP, the MN is unaware which of 2353 the (redundant) ARs is currently providing service, and any service 2354 discontinuity will be limited to the failover time supported by VRRP. 2355 Widely deployed public domain implementations of VRRP are available. 2357 MSEs SHOULD use high availability clustering services so that 2358 multiple redundant systems can provide coordinated response to 2359 failures. As with VRRP, widely deployed public domain 2360 implementations of high availability clustering services are 2361 available. Note that special-purpose and expensive dedicated 2362 hardware is not necessary, and public domain implementations can be 2363 used even between lightweight virtual machines in cloud deployments. 2365 16. Detecting and Responding to MSE Failures 2367 In environments where fast recovery from MSE failure is required, ARs 2368 SHOULD use proactive Neighbor Unreachability Detection (NUD) in a 2369 manner that parallels Bidirectional Forwarding Detection (BFD) 2370 [RFC5880] to track MSE reachability. ARs can then quickly detect and 2371 react to failures so that cached information is re-established 2372 through alternate paths. Proactive NUD control messaging is carried 2373 only over well-connected ground domain networks (i.e., and not low- 2374 end *NET links such as aeronautical radios) and can therefore be 2375 tuned for rapid response. 2377 ARs perform proactive NUD for MSEs for which there are currently 2378 active MNs on the *NET. If an MSE fails, ARs can quickly inform MNs 2379 of the outage by sending multicast RA messages on the *NET interface. 2380 The AR sends RA messages to MNs via the *NET interface with an OMNI 2381 option with a Release ID for the failed MSE, and with destination 2382 address set to All-Nodes multicast (ff02::1) [RFC4291]. 2384 The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated 2385 by small delays [RFC4861]. Any MNs on the *NET interface that have 2386 been using the (now defunct) MSE will receive the RA messages and 2387 associate with a new MSE. 2389 17. Transition Considerations 2391 When a MN connects to an *NET link for the first time, it sends an RS 2392 message with an OMNI option. If the first hop AR recognizes the 2393 option, it returns an RA with its ADM-LLA as the source, the MNP-LLA 2394 as the destination and with an OMNI option included. The MN then 2395 engages the AR according to the OMNI link model specified above. If 2396 the first hop AR is a legacy IPv6 router, however, it instead returns 2397 an RA message with no OMNI option and with a non-OMNI unicast source 2398 LLA as specified in [RFC4861]. In that case, the MN engages the *NET 2399 according to the legacy IPv6 link model and without the OMNI 2400 extensions specified in this document. 2402 If the *NET link model is multiple access, there must be assurance 2403 that address duplication cannot corrupt the neighbor caches of other 2404 nodes on the link. When the MN sends an RS message on a multiple 2405 access *NET link with an LLA source address and an OMNI option, ARs 2406 that recognize the option ensure that the MN is authorized to use the 2407 address and return an RA with a non-zero Router Lifetime only if the 2408 MN is authorized. ARs that do not recognize the option instead 2409 return an RA that makes no statement about the MN's authorization to 2410 use the source address. In that case, the MN should perform 2411 Duplicate Address Detection to ensure that it does not interfere with 2412 other nodes on the link. 2414 An alternative approach for multiple access *NET links to ensure 2415 isolation for MN / AR communications is through L2 address mappings 2416 as discussed in Appendix C. This arrangement imparts a (virtual) 2417 point-to-point link model over the (physical) multiple access link. 2419 18. OMNI Interfaces on the Open Internet 2421 OMNI interfaces configured over IPv6-enabled underlying interfaces on 2422 the open Internet without an OMNI-aware first-hop AR receive RA 2423 messages that do not include an OMNI option, while OMNI interfaces 2424 configured over IPv4-only underlying interfaces do not receive any 2425 (IPv6) RA messages at all. OMNI interfaces that receive RA messages 2426 without an OMNI option configure addresses, on-link prefixes, etc. on 2427 the underlying interface that received the RA according to standard 2428 IPv6 ND and address resolution conventions [RFC4861] [RFC4862]. OMNI 2429 interfaces configured over IPv4-only underlying interfaces configure 2430 IPv4 address information on the underlying interfaces using 2431 mechanisms such as DHCPv4 [RFC2131]. 2433 OMNI interfaces configured over underlying interfaces that connect to 2434 the open Internet can apply security services such as VPNs to connect 2435 to an MSE, or can establish a direct link to an MSE through some 2436 other means (see Section 4). In environments where an explicit VPN 2437 or direct link may be impractical, OMNI interfaces can instead use 2438 UDP/IP encapsulation per [RFC6081][RFC4380] and HIP-based message 2439 authentication per [RFC7401]. 2441 For "Vehicle-to-Infrastructure (V2I)" coordination, the MN codes the 2442 HIP messages in an OMNI option of an IPv6 RS message and the MSE 2443 responds with HIP messages coded in an OMNI option of an IPv6 RA 2444 message. The standard HIP security services are applied per 2445 [RFC7401], using the RS/RA messages as simple "shipping containers" 2446 to convey the HIP parameters. In that case, a "two-message HIP 2447 exchange" through a single RS/RA exchange may be sufficient for 2448 mutual authentication. For "Vehicle-to-Vehicle (V2V)" coordination, 2449 two MNs can coordinate directly with one another with HIP messages 2450 coded in OMNI options of IPv6 NS/NA messages. In that case, a four- 2451 message HIP exchange (i.e., two back-to-back NS/NA exchanges) may be 2452 necessary for the two MNs to attain mutual authentication. 2454 After establishing a VPN or preparing for UDP/IP encapsulation, OMNI 2455 interfaces send control plane messages to interface with the MS, 2456 including RS/RA messages used according to Section 13 and Neighbor 2457 Solicitation (NS) and Neighbor Advertisement (NA) messages used for 2458 address resolution / route optimization (see: 2459 [I-D.templin-intarea-6706bis]). The control plane messages must be 2460 authenticated while data plane messages are delivered the same as for 2461 ordinary best-effort Internet traffic with basic source address-based 2462 data origin verification. Data plane communications via OMNI 2463 interfaces that connect over the open Internet without an explicit 2464 VPN should therefore employ transport- or higher-layer security to 2465 ensure integrity and/or confidentiality. 2467 OMNI interfaces in the open Internet are often located behind NATs. 2468 The OMNI interface accommodates NAT traversal using UDP/IP 2469 encapsulation and the mechanisms discussed in 2470 [RFC6081][RFC4380][I-D.templin-intarea-6706bis]. 2472 19. Time-Varying MNPs 2474 In some use cases, it is desirable, beneficial and efficient for the 2475 MN to receive a constant MNP that travels with the MN wherever it 2476 moves. For example, this would allow air traffic controllers to 2477 easily track aircraft, etc. In other cases, however (e.g., 2478 intelligent transportation systems), the MN may be willing to 2479 sacrifice a modicum of efficiency in order to have time-varying MNPs 2480 that can be changed every so often to defeat adversarial tracking. 2482 The prefix delegation services discussed in Section 13.3 allows OMNI 2483 MNs that desire time-varying MNPs to obtain short-lived prefixes to 2484 use a Temporary LLA as the source address of an RS message with an 2485 OMNI option with DHCPv6 Option sub-options. The MN would then be 2486 obligated to renumber its internal networks whenever its MNP (and 2487 therefore also its OMNI address) changes. This should not present a 2488 challenge for MNs with automated network renumbering services, 2489 however presents limits for the durations of ongoing sessions that 2490 would prefer to use a constant address. 2492 20. Node Identification 2494 MNs and MSEs that connect over the open Internet generate a Host 2495 Identity Tag (HIT) using the procedures specified in [RFC7401] and 2496 use the value as a robust general-purpose node ID. Emerging work on 2497 Hierarchical HITs (HHITs) [I-D.ietf-drip-rid] may also produce node 2498 IDs for use in specific domains such as the Unmanned (Air) Traffic 2499 Management (UTM) service for Unmanned Air Systems (UAS). 2501 After generating a (H)HIT, the node may use it in both HIP and DHCPv6 2502 protocol message exchanges. In the latter case, the (H)HIT is coded 2503 as a DHCP Unique IDentifier (DUID) using the DUID-EN format with 2504 enterprise number 45282 (see: Section 21). The DUID-EN has the 2505 following format: 2507 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 2508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2509 | DUID-Type (2) | EN (high bits == 0) | 2510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2511 | EN (low bits = 45282) | | 2512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 2513 . (Hierarchical) Host Identity Tag (128 bits) . 2514 . . 2515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2517 Figure 20: DUID-EN for (H)HIT Format 2519 This document therefore permanently associates Private Enterprise 2520 Number 45282 with the (H)HIT DUID format shown in Figure 20. 2522 When a MN is truly outside the context of any infrastructure, it may 2523 have no MNP information at all. In that case, it may be able to use 2524 its (H)HIT as the IPv6 source address in packets used for ongoing 2525 communications with other vehicles in V2V scenarios. The (H)HIT 2526 could also be propagated into the multihop routing protocol tables of 2527 (collective) Vehicular Ad-hoc Networks (VANETs) using only the 2528 vehicles themselves as communications relays. 2530 Note: In environments with strong link-layer and physical-layer 2531 security, a node may be able to include an administratively-assigned 2532 identifier (e.g., a MAC address, serial number, airframe ID, VIN, 2533 etc.) in message exchanges where a (H)HIT may not be necessary. In 2534 that case, a (H)HIT SHOULD still be generated and maintained both on 2535 the node and in a network-wide database in one-to-one correspondence 2536 with the (non-cryptographic) administrative identifier. The node can 2537 then include the (H)HIT in an OMNI "Node Identification" sub-option 2538 should the need to transmit it over the network ever arise. 2540 21. IANA Considerations 2542 The IANA has assigned a 4-octet Private Enterprise Number (PEN) code 2543 "45282" in the "enterprise-numbers" registry. This document is the 2544 normative reference for using this code in DHCP Unique IDentifiers 2545 based on Enterprise Numbers (DUID-EN) for (Hierarchical) Host 2546 Identity Tags ((H)HITs) (see: Section 20). 2548 The IANA is instructed to allocate an official Type number TBD1 from 2549 the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI 2550 option. Implementations set Type to 253 as an interim value 2551 [RFC4727]. 2553 The IANA is instructed to assign a new Code value "1" in the "ICMPv6 2554 Code Fields: Type 2 - Packet Too Big" registry. The registry should 2555 read as follows: 2557 Code Name Reference 2558 --- ---- --------- 2559 0 Diagnostic Packet Too Big [RFC4443] 2560 1 Advisory Packet Too Big [RFCXXXX] 2562 Figure 21: ICMPv6 Code Fields: Type 2 - Packet Too Big Values 2564 The IANA is instructed to allocate one Ethernet unicast address TBD2 2565 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet 2566 Address Block - Unicast Use". 2568 The OMNI option defines a 5-bit Sub-Type field, for which IANA is 2569 instructed to create and maintain a new registry entitled "OMNI 2570 option Sub-Type values". Initial values for the OMNI option Sub-Type 2571 values registry are given below; future assignments are to be made 2572 through Expert Review [RFC8126]. 2574 Value Sub-Type name Reference 2575 ----- ------------- ---------- 2576 0 Pad1 [RFCXXXX] 2577 1 PadN [RFCXXXX] 2578 2 Interface Attributes (Type 1) [RFCXXXX] 2579 3 Interface Attributes (Type 2) [RFCXXXX] 2580 4 Traffic Selector [RFCXXXX] 2581 5 Origin Indication [RFCXXXX] 2582 6 MS-Register [RFCXXXX] 2583 7 MS-Release [RFCXXXX] 2584 8 Geo Coordinates [RFCXXXX] 2585 9 DHCPv6 Message [RFCXXXX] 2586 10 HIP Message [RFCXXXX] 2587 11 Node Identification [RFCXXXX] 2588 12-29 Unassigned 2589 30 Experimental [RFCXXXX] 2590 31 Reserved [RFCXXXX] 2592 Figure 22: OMNI Option Sub-Type Values 2594 22. Security Considerations 2596 Security considerations for IPv4 [RFC0791], IPv6 [RFC8200] and IPv6 2597 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages 2598 SHOULD include Nonce and Timestamp options [RFC3971] when transaction 2599 confirmation and/or time synchronization is needed. 2601 MN OMNI interfaces configured over secured ANET interfaces inherit 2602 the physical and/or link-layer security properties (i.e., "protected 2603 spectrum") of the connected ANETs. MN OMNI interfaces configured 2604 over open INET interfaces can use symmetric securing services such as 2605 VPNs or can by some other means establish a direct link. When a VPN 2606 or direct link may be impractical, however, the security services 2607 specified in [RFC7401] can be employed. While the OMNI link protects 2608 control plane messaging, applications must still employ end-to-end 2609 transport- or higher-layer security services to protect the data 2610 plane. 2612 Strong network layer security for control plane messages and 2613 forwarding path integrity for data plane messages between MSEs MUST 2614 be supported. In one example, the AERO service 2615 [I-D.templin-intarea-6706bis] constructs a spanning tree between MSEs 2616 and secures the links in the spanning tree with network layer 2617 security mechanisms such as IPsec [RFC4301] or Wireguard. Control 2618 plane messages are then constrained to travel only over the secured 2619 spanning tree paths and are therefore protected from attack or 2620 eavesdropping. Since data plane messages can travel over route 2621 optimized paths that do not strictly follow the spanning tree, 2622 however, end-to-end transport- or higher-layer security services are 2623 still required. 2625 Identity-based key verification infrastructure services such as iPSK 2626 may be necessary for verifying the identities claimed by MNs. This 2627 requirement should be harmonized with the manner in which (H)HITs are 2628 attested in a given operational environment. 2630 Security considerations for specific access network interface types 2631 are covered under the corresponding IP-over-(foo) specification 2632 (e.g., [RFC2464], [RFC2492], etc.). 2634 Security considerations for IPv6 fragmentation and reassembly are 2635 discussed in Section 5.1. 2637 23. Implementation Status 2639 Draft -29 is implemented in the recently tagged AERO/OMNI 3.0.0 2640 internal release, and Draft -30 is now tagged as the AERO/OMNI 3.0.1. 2641 Newer specification versions will be tagged in upcoming releases. 2642 First public release expected before the end of 2020. 2644 24. Acknowledgements 2646 The first version of this document was prepared per the consensus 2647 decision at the 7th Conference of the International Civil Aviation 2648 Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2649 2019. Consensus to take the document forward to the IETF was reached 2650 at the 9th Conference of the Mobility Subgroup on November 22, 2019. 2651 Attendees and contributors included: Guray Acar, Danny Bharj, 2652 Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, 2653 Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu 2654 Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg 2655 Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane 2656 Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, 2657 Fryderyk Wrobel and Dongsong Zeng. 2659 The following individuals are acknowledged for their useful comments: 2660 Stuart Card, Michael Matyas, Robert Moskowitz, Madhu Niraula, Greg 2661 Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron 2662 and Michal Skorepa are especially recognized for their many helpful 2663 ideas and suggestions. Madhuri Madhava Badgandi, Sean Dickson, Don 2664 Dillenburg, Joe Dudkowski, Vijayasarathy Rajagopalan, Ron Sackman and 2665 Katherine Tran are acknowledged for their hard work on the 2666 implementation and technical insights that led to improvements for 2667 the spec. 2669 Discussions on the IETF 6man and atn mailing lists during the fall of 2670 2020 suggested additional points to consider. The authors gratefully 2671 acknowledge the list members who contributed valuable insights 2672 through those discussions. Eric Vyncke and Erik Kline were the 2673 intarea ADs, while Bob Hinden and Ole Troan were the 6man WG chairs 2674 at the time the document was developed; they are all gratefully 2675 acknowledged for their many helpful insights. 2677 This work is aligned with the NASA Safe Autonomous Systems Operation 2678 (SASO) program under NASA contract number NNA16BD84C. 2680 This work is aligned with the FAA as per the SE2025 contract number 2681 DTFAWA-15-D-00030. 2683 This work is aligned with the Boeing Information Technology (BIT) 2684 Mobility Vision Lab (MVL) program. 2686 25. References 2688 25.1. Normative References 2690 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2691 DOI 10.17487/RFC0791, September 1981, 2692 . 2694 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2695 Requirement Levels", BCP 14, RFC 2119, 2696 DOI 10.17487/RFC2119, March 1997, 2697 . 2699 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2700 "Definition of the Differentiated Services Field (DS 2701 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2702 DOI 10.17487/RFC2474, December 1998, 2703 . 2705 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 2706 "SEcure Neighbor Discovery (SEND)", RFC 3971, 2707 DOI 10.17487/RFC3971, March 2005, 2708 . 2710 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2711 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 2712 November 2005, . 2714 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 2715 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 2716 . 2718 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 2719 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2720 2006, . 2722 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 2723 Control Message Protocol (ICMPv6) for the Internet 2724 Protocol Version 6 (IPv6) Specification", STD 89, 2725 RFC 4443, DOI 10.17487/RFC4443, March 2006, 2726 . 2728 [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, 2729 ICMPv6, UDP, and TCP Headers", RFC 4727, 2730 DOI 10.17487/RFC4727, November 2006, 2731 . 2733 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2734 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2735 DOI 10.17487/RFC4861, September 2007, 2736 . 2738 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2739 Address Autoconfiguration", RFC 4862, 2740 DOI 10.17487/RFC4862, September 2007, 2741 . 2743 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, 2744 "Traffic Selectors for Flow Bindings", RFC 6088, 2745 DOI 10.17487/RFC6088, January 2011, 2746 . 2748 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 2749 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 2750 RFC 7401, DOI 10.17487/RFC7401, April 2015, 2751 . 2753 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 2754 Hosts in a Multi-Prefix Network", RFC 8028, 2755 DOI 10.17487/RFC8028, November 2016, 2756 . 2758 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2759 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2760 May 2017, . 2762 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2763 (IPv6) Specification", STD 86, RFC 8200, 2764 DOI 10.17487/RFC8200, July 2017, 2765 . 2767 [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., 2768 "Path MTU Discovery for IP version 6", STD 87, RFC 8201, 2769 DOI 10.17487/RFC8201, July 2017, 2770 . 2772 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 2773 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 2774 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 2775 RFC 8415, DOI 10.17487/RFC8415, November 2018, 2776 . 2778 25.2. Informative References 2780 [ATN] Maiolla, V., "The OMNI Interface - An IPv6 Air/Ground 2781 Interface for Civil Aviation, IETF Liaison Statement 2782 #1676, https://datatracker.ietf.org/liaison/1676/", March 2783 2020. 2785 [ATN-IPS] WG-I, ICAO., "ICAO Document 9896 (Manual on the 2786 Aeronautical Telecommunication Network (ATN) using 2787 Internet Protocol Suite (IPS) Standards and Protocol), 2788 Draft Edition 3 (work-in-progress)", December 2020. 2790 [CRC] Jain, R., "Error Characteristics of Fiber Distributed Data 2791 Interface (FDDI), IEEE Transactions on Communications", 2792 August 1990. 2794 [I-D.ietf-6man-rfc4941bis] 2795 Gont, F., Krishnan, S., Narten, T., and R. Draves, 2796 "Temporary Address Extensions for Stateless Address 2797 Autoconfiguration in IPv6", draft-ietf-6man-rfc4941bis-12 2798 (work in progress), November 2020. 2800 [I-D.ietf-drip-rid] 2801 Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, 2802 "UAS Remote ID", draft-ietf-drip-rid-06 (work in 2803 progress), December 2020. 2805 [I-D.ietf-intarea-tunnels] 2806 Touch, J. and M. Townsley, "IP Tunnels in the Internet 2807 Architecture", draft-ietf-intarea-tunnels-10 (work in 2808 progress), September 2019. 2810 [I-D.ietf-ipwave-vehicular-networking] 2811 Jeong, J., "IPv6 Wireless Access in Vehicular Environments 2812 (IPWAVE): Problem Statement and Use Cases", draft-ietf- 2813 ipwave-vehicular-networking-19 (work in progress), July 2814 2020. 2816 [I-D.templin-6man-dhcpv6-ndopt] 2817 Templin, F., "A Unified Stateful/Stateless Configuration 2818 Service for IPv6", draft-templin-6man-dhcpv6-ndopt-11 2819 (work in progress), January 2021. 2821 [I-D.templin-6man-lla-type] 2822 Templin, F., "The IPv6 Link-Local Address Type Field", 2823 draft-templin-6man-lla-type-02 (work in progress), 2824 November 2020. 2826 [I-D.templin-intarea-6706bis] 2827 Templin, F., "Asymmetric Extended Route Optimization 2828 (AERO)", draft-templin-intarea-6706bis-87 (work in 2829 progress), January 2021. 2831 [IPV4-GUA] 2832 Postel, J., "IPv4 Address Space Registry, 2833 https://www.iana.org/assignments/ipv4-address-space/ipv4- 2834 address-space.xhtml", December 2020. 2836 [IPV6-GUA] 2837 Postel, J., "IPv6 Global Unicast Address Assignments, 2838 https://www.iana.org/assignments/ipv6-unicast-address- 2839 assignments/ipv6-unicast-address-assignments.xhtml", 2840 December 2020. 2842 [RFC1035] Mockapetris, P., "Domain names - implementation and 2843 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 2844 November 1987, . 2846 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2847 Communication Layers", STD 3, RFC 1122, 2848 DOI 10.17487/RFC1122, October 1989, 2849 . 2851 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 2852 DOI 10.17487/RFC1191, November 1990, 2853 . 2855 [RFC1256] Deering, S., Ed., "ICMP Router Discovery Messages", 2856 RFC 1256, DOI 10.17487/RFC1256, September 1991, 2857 . 2859 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 2860 RFC 2131, DOI 10.17487/RFC2131, March 1997, 2861 . 2863 [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over 2864 ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, 2865 . 2867 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 2868 Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, 2869 . 2871 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in 2872 IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, 2873 December 1998, . 2875 [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM 2876 Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, 2877 . 2879 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 2880 Domains without Explicit Tunnels", RFC 2529, 2881 DOI 10.17487/RFC2529, March 1999, 2882 . 2884 [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group 2885 MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, 2886 . 2888 [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, 2889 DOI 10.17487/RFC3330, September 2002, 2890 . 2892 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers 2893 Considered Useful", BCP 82, RFC 3692, 2894 DOI 10.17487/RFC3692, January 2004, 2895 . 2897 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener 2898 Discovery Version 2 (MLDv2) for IPv6", RFC 3810, 2899 DOI 10.17487/RFC3810, June 2004, 2900 . 2902 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 2903 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 2904 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 2905 RFC 3819, DOI 10.17487/RFC3819, July 2004, 2906 . 2908 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 2909 Addresses", RFC 3879, DOI 10.17487/RFC3879, September 2910 2004, . 2912 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 2913 Unique IDentifier (UUID) URN Namespace", RFC 4122, 2914 DOI 10.17487/RFC4122, July 2005, 2915 . 2917 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2918 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2919 DOI 10.17487/RFC4271, January 2006, 2920 . 2922 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2923 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2924 December 2005, . 2926 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 2927 Network Address Translations (NATs)", RFC 4380, 2928 DOI 10.17487/RFC4380, February 2006, 2929 . 2931 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 2932 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 2933 2006, . 2935 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) 2936 for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, 2937 . 2939 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 2940 "Considerations for Internet Group Management Protocol 2941 (IGMP) and Multicast Listener Discovery (MLD) Snooping 2942 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 2943 . 2945 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 2946 "Internet Group Management Protocol (IGMP) / Multicast 2947 Listener Discovery (MLD)-Based Multicast Forwarding 2948 ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, 2949 August 2006, . 2951 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 2952 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 2953 . 2955 [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly 2956 Errors at High Data Rates", RFC 4963, 2957 DOI 10.17487/RFC4963, July 2007, 2958 . 2960 [RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router 2961 Advertisement Flags Option", RFC 5175, 2962 DOI 10.17487/RFC5175, March 2008, 2963 . 2965 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 2966 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 2967 RFC 5213, DOI 10.17487/RFC5213, August 2008, 2968 . 2970 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 2971 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 2972 DOI 10.17487/RFC5214, March 2008, 2973 . 2975 [RFC5558] Templin, F., Ed., "Virtual Enterprise Traversal (VET)", 2976 RFC 5558, DOI 10.17487/RFC5558, February 2010, 2977 . 2979 [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) 2980 Version 3 for IPv4 and IPv6", RFC 5798, 2981 DOI 10.17487/RFC5798, March 2010, 2982 . 2984 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2985 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2986 . 2988 [RFC6081] Thaler, D., "Teredo Extensions", RFC 6081, 2989 DOI 10.17487/RFC6081, January 2011, 2990 . 2992 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 2993 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 2994 DOI 10.17487/RFC6221, May 2011, 2995 . 2997 [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based 2998 DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, 2999 DOI 10.17487/RFC6355, August 2011, 3000 . 3002 [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for 3003 Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 3004 2012, . 3006 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 3007 with IPv6 Neighbor Discovery", RFC 6980, 3008 DOI 10.17487/RFC6980, August 2013, 3009 . 3011 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 3012 Requirements for IPv6 Customer Edge Routers", RFC 7084, 3013 DOI 10.17487/RFC7084, November 2013, 3014 . 3016 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 3017 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 3018 Boundary in IPv6 Addressing", RFC 7421, 3019 DOI 10.17487/RFC7421, January 2015, 3020 . 3022 [RFC7526] Troan, O. and B. Carpenter, Ed., "Deprecating the Anycast 3023 Prefix for 6to4 Relay Routers", BCP 196, RFC 7526, 3024 DOI 10.17487/RFC7526, May 2015, 3025 . 3027 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542, 3028 DOI 10.17487/RFC7542, May 2015, 3029 . 3031 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 3032 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 3033 February 2016, . 3035 [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface 3036 Support for IP Hosts with Multi-Access Support", RFC 7847, 3037 DOI 10.17487/RFC7847, May 2016, 3038 . 3040 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 3041 Writing an IANA Considerations Section in RFCs", BCP 26, 3042 RFC 8126, DOI 10.17487/RFC8126, June 2017, 3043 . 3045 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 3046 Decraene, B., Litkowski, S., and R. Shakir, "Segment 3047 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 3048 July 2018, . 3050 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 3051 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 3052 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 3053 . 3055 [RFC8900] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., 3056 and F. Gont, "IP Fragmentation Considered Fragile", 3057 BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020, 3058 . 3060 Appendix A. Interface Attribute Preferences Bitmap Encoding 3062 Adaptation of the OMNI option Interface Attributes Preferences Bitmap 3063 encoding to specific Internetworks such as the Aeronautical 3064 Telecommunications Network with Internet Protocol Services (ATN/IPS) 3065 may include link selection preferences based on other traffic 3066 classifiers (e.g., transport port numbers, etc.) in addition to the 3067 existing DSCP-based preferences. Nodes on specific Internetworks 3068 maintain a map of traffic classifiers to additional P[*] preference 3069 fields beyond the first 64. For example, TCP port 22 maps to P[67], 3070 TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. 3072 Implementations use Simplex or Indexed encoding formats for P[*] 3073 encoding in order to encode a given set of traffic classifiers in the 3074 most efficient way. Some use cases may be more efficiently coded 3075 using Simplex form, while others may be more efficient using Indexed. 3076 Once a format is selected for preparation of a single Interface 3077 Attribute the same format must be used for the entire Interface 3078 Attribute sub-option. Different sub-options may use different 3079 formats. 3081 The following figures show coding examples for various Simplex and 3082 Indexed formats: 3084 0 1 2 3 3085 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 3086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3087 | Sub-Type=3| Sub-length=N | omIndex | omType | 3088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3089 | Provider ID | Link |R| API | Bitmap(0)=0xff|P00|P01|P02|P03| 3090 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3091 |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| 3092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3093 |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| 3094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3095 |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| 3096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3097 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3099 | Bitmap(2)=0xff|P64|P65|P67|P68| ... 3100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3102 Figure 23: Example 1: Dense Simplex Encoding 3104 0 1 2 3 3105 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 3106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3107 | Sub-Type=3| Sub-length=N | omIndex | omType | 3108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3109 | Provider ID | Link |R| API | Bitmap(0)=0x00| Bitmap(1)=0x0f| 3110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3111 |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| 3112 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3113 | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| 3114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3115 | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| 3116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3117 |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| 3118 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3119 |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| 3120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3121 |Bitmap(10)=0x00| ... 3122 +-+-+-+-+-+-+-+-+-+-+- 3124 Figure 24: Example 2: Sparse Simplex Encoding 3126 0 1 2 3 3127 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 3128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3129 | Sub-Type=3| Sub-length=N | omIndex | omType | 3130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3131 | Provider ID | Link |R| API | Index = 0x00 | Bitmap = 0x80 | 3132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3133 |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| 3134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3135 | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | 3136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3137 | Bitmap = 0x01 |796|797|798|799| ... 3138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 3140 Figure 25: Example 3: Indexed Encoding 3142 Appendix B. VDL Mode 2 Considerations 3144 ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" 3145 (VDLM2) that specifies an essential radio frequency data link service 3146 for aircraft and ground stations in worldwide civil aviation air 3147 traffic management. The VDLM2 link type is "multicast capable" 3148 [RFC4861], but with considerable differences from common multicast 3149 links such as Ethernet and IEEE 802.11. 3151 First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of 3152 magnitude less than most modern wireless networking gear. Second, 3153 due to the low available link bandwidth only VDLM2 ground stations 3154 (i.e., and not aircraft) are permitted to send broadcasts, and even 3155 so only as compact layer 2 "beacons". Third, aircraft employ the 3156 services of ground stations by performing unicast RS/RA exchanges 3157 upon receipt of beacons instead of listening for multicast RA 3158 messages and/or sending multicast RS messages. 3160 This beacon-oriented unicast RS/RA approach is necessary to conserve 3161 the already-scarce available link bandwidth. Moreover, since the 3162 numbers of beaconing ground stations operating within a given spatial 3163 range must be kept as sparse as possible, it would not be feasible to 3164 have different classes of ground stations within the same region 3165 observing different protocols. It is therefore highly desirable that 3166 all ground stations observe a common language of RS/RA as specified 3167 in this document. 3169 Note that links of this nature may benefit from compression 3170 techniques that reduce the bandwidth necessary for conveying the same 3171 amount of data. The IETF lpwan working group is considering possible 3172 alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. 3174 Appendix C. MN / AR Isolation Through L2 Address Mapping 3176 Per [RFC4861], IPv6 ND messages may be sent to either a multicast or 3177 unicast link-scoped IPv6 destination address. However, IPv6 ND 3178 messaging should be coordinated between the MN and AR only without 3179 invoking other nodes on the *NET. This implies that MN / AR control 3180 messaging should be isolated and not overheard by other nodes on the 3181 link. 3183 To support MN / AR isolation on some *NET links, ARs can maintain an 3184 OMNI-specific unicast L2 address ("MSADDR"). For Ethernet-compatible 3185 *NETs, this specification reserves one Ethernet unicast address TBD2 3186 (see: Section 21). For non-Ethernet statically-addressed *NETs, 3187 MSADDR is reserved per the assigned numbers authority for the *NET 3188 addressing space. For still other *NETs, MSADDR may be dynamically 3189 discovered through other means, e.g., L2 beacons. 3191 MNs map the L3 addresses of all IPv6 ND messages they send (i.e., 3192 both multicast and unicast) to MSADDR instead of to an ordinary 3193 unicast or multicast L2 address. In this way, all of the MN's IPv6 3194 ND messages will be received by ARs that are configured to accept 3195 packets destined to MSADDR. Note that multiple ARs on the link could 3196 be configured to accept packets destined to MSADDR, e.g., as a basis 3197 for supporting redundancy. 3199 Therefore, ARs must accept and process packets destined to MSADDR, 3200 while all other devices must not process packets destined to MSADDR. 3201 This model has well-established operational experience in Proxy 3202 Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 3204 Appendix D. Change Log 3206 << RFC Editor - remove prior to publication >> 3208 Differences from draft-templin-6man-omni-interface-35 to draft- 3209 templin-6man-omni-interface-36: 3211 o Major clarifications on aspects such as "hard/soft" PTB error 3212 messages 3214 o Made generic so that either IP protocol version (IPv4 or IPv6) can 3215 be used in the data plane. 3217 Differences from draft-templin-6man-omni-interface-31 to draft- 3218 templin-6man-omni-interface-32: 3220 o MTU 3222 o Support for multi-hop ANETS such as ISATAP. 3224 Differences from draft-templin-6man-omni-interface-29 to draft- 3225 templin-6man-omni-interface-30: 3227 o Moved link-layer addressing information into the OMNI option on a 3228 per-ifIndex basis 3230 o Renamed "ifIndex-tuple" to "Interface Attributes" 3232 Differences from draft-templin-6man-omni-interface-27 to draft- 3233 templin-6man-omni-interface-28: 3235 o Updates based on implementation experience. 3237 Differences from draft-templin-6man-omni-interface-25 to draft- 3238 templin-6man-omni-interface-26: 3240 o Further clarification on "aggregate" RA messages. 3242 o Expanded Security Considerations to discuss expectations for 3243 security in the Mobility Service. 3245 Differences from draft-templin-6man-omni-interface-20 to draft- 3246 templin-6man-omni-interface-21: 3248 o Safety-Based Multilink (SBM) and Performance-Based Multilink 3249 (PBM). 3251 Differences from draft-templin-6man-omni-interface-18 to draft- 3252 templin-6man-omni-interface-19: 3254 o SEND/CGA. 3256 Differences from draft-templin-6man-omni-interface-17 to draft- 3257 templin-6man-omni-interface-18: 3259 o Teredo 3261 Differences from draft-templin-6man-omni-interface-14 to draft- 3262 templin-6man-omni-interface-15: 3264 o Prefix length discussions removed. 3266 Differences from draft-templin-6man-omni-interface-12 to draft- 3267 templin-6man-omni-interface-13: 3269 o Teredo 3271 Differences from draft-templin-6man-omni-interface-11 to draft- 3272 templin-6man-omni-interface-12: 3274 o Major simplifications and clarifications on MTU and fragmentation. 3276 o Document now updates RFC4443 and RFC8201. 3278 Differences from draft-templin-6man-omni-interface-10 to draft- 3279 templin-6man-omni-interface-11: 3281 o Removed /64 assumption, resulting in new OMNI address format. 3283 Differences from draft-templin-6man-omni-interface-07 to draft- 3284 templin-6man-omni-interface-08: 3286 o OMNI MNs in the open Internet 3288 Differences from draft-templin-6man-omni-interface-06 to draft- 3289 templin-6man-omni-interface-07: 3291 o Brought back L2 MSADDR mapping text for MN / AR isolation based on 3292 L2 addressing. 3294 o Expanded "Transition Considerations". 3296 Differences from draft-templin-6man-omni-interface-05 to draft- 3297 templin-6man-omni-interface-06: 3299 o Brought back OMNI option "R" flag, and discussed its use. 3301 Differences from draft-templin-6man-omni-interface-04 to draft- 3302 templin-6man-omni-interface-05: 3304 o Transition considerations, and overhaul of RS/RA addressing with 3305 the inclusion of MSE addresses within the OMNI option instead of 3306 as RS/RA addresses (developed under FAA SE2025 contract number 3307 DTFAWA-15-D-00030). 3309 Differences from draft-templin-6man-omni-interface-02 to draft- 3310 templin-6man-omni-interface-03: 3312 o Added "advisory PTB messages" under FAA SE2025 contract number 3313 DTFAWA-15-D-00030. 3315 Differences from draft-templin-6man-omni-interface-01 to draft- 3316 templin-6man-omni-interface-02: 3318 o Removed "Primary" flag and supporting text. 3320 o Clarified that "Router Lifetime" applies to each ANET interface 3321 independently, and that the union of all ANET interface Router 3322 Lifetimes determines MSE lifetime. 3324 Differences from draft-templin-6man-omni-interface-00 to draft- 3325 templin-6man-omni-interface-01: 3327 o "All-MSEs" OMNI LLA defined. Also reserved fe80::ff00:0000/104 3328 for future use (most likely as "pseudo-multicast"). 3330 o Non-normative discussion of alternate OMNI LLA construction form 3331 made possible if the 64-bit assumption were relaxed. 3333 First draft version (draft-templin-atn-aero-interface-00): 3335 o Draft based on consensus decision of ICAO Working Group I Mobility 3336 Subgroup March 22, 2019. 3338 Authors' Addresses 3339 Fred L. Templin (editor) 3340 The Boeing Company 3341 P.O. Box 3707 3342 Seattle, WA 98124 3343 USA 3345 Email: fltemplin@acm.org 3347 Tony Whyman 3348 MWA Ltd c/o Inmarsat Global Ltd 3349 99 City Road 3350 London EC1Y 1AX 3351 England 3353 Email: tony.whyman@mccallumwhyman.com