Network Working Group F. Templin, Ed. Internet-Draft The Boeing Company Intended status: Standards Track A. Whyman Expires: August 29, 2020 MWA Ltd c/o Inmarsat Global Ltd February 26, 2020 Transmission of IPv6 Packets over Overlay Multilink Network (OMNI) Interfaces draft-templin-6man-omni-interface-02 Abstract Mobile nodes (e.g., aircraft of various configurations, terrestrial vehicles, seagoing vessels, mobile enterprise devices, etc.) communicate with networked correspondents over multiple access network data links and configure mobile routers to connect end user networks. A multilink interface specification is therefore needed for coordination with the network-based mobility service. This document specifies the transmission of IPv6 packets over Overlay Multilink Network (OMNI) Interfaces. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 29, 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Templin & Whyman Expires August 29, 2020 [Page 1] Internet-Draft IPv6 over OMNI Interfaces February 2020 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 6 5. Maximum Transmission Unit (MTU) and Fragmentation . . . . . . 10 6. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 11 7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . 11 8. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 12 8.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . . 13 8.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 14 8.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 15 8.1.3. ifIndex-tuple (Type 1) . . . . . . . . . . . . . . . 15 8.1.4. ifIndex-tuple (Type 2) . . . . . . . . . . . . . . . 17 8.1.5. Notification ID . . . . . . . . . . . . . . . . . . . 18 9. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 18 10. Address Mapping for IPv6 Neighbor Discovery Messages . . . . 18 11. Conceptual Sending Algorithm . . . . . . . . . . . . . . . . 19 11.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 19 12. Router Discovery and Prefix Registration . . . . . . . . . . 20 13. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 23 14. Detecting and Responding to MSE Failures . . . . . . . . . . 24 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 16. Security Considerations . . . . . . . . . . . . . . . . . . . 25 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 18.1. Normative References . . . . . . . . . . . . . . . . . . 26 18.2. Informative References . . . . . . . . . . . . . . . . . 27 Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference Encoding . . . . . . . . . . . . . . . . . . . . . . 29 Appendix B. Prefix Length Considerations . . . . . . . . . . . . 31 Appendix C. VDL Mode 2 Considerations . . . . . . . . . . . . . 32 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37 1. Introduction Mobile Nodes (MNs) (e.g., aircraft of various configurations, terrestrial vehicles, seagoing vessels, mobile enterprise devices, etc.) often have multiple data links for communicating with networked correspondents. These data links may have diverse performance, cost Templin & Whyman Expires August 29, 2020 [Page 2] Internet-Draft IPv6 over OMNI Interfaces February 2020 and availability properties that can change dynamically according to mobility patterns, flight phases, proximity to infrastructure, etc. MNs coordinate their data links in a discipline known as "multilink", in which a single virtual interface is configured over the underlying data link interfaces. The MN configures a virtual interface (termed the "Overlay Multilink Network (OMNI) interface") as a thin layer over the underlying access network interfaces. The OMNI interface is therefore the only interface abstraction exposed to the IPv6 layer and behaves according to the Non-Broadcast, Multiple Access (NBMA) interface principle, while underlying access network interfaces appear as link layer communication channels in the architecture. The OMNI interface connects to a virtual overlay service known as the "OMNI link". The OMNI link spans a worldwide Internetwork that may include private-use infrastructures and/or the global public Internet itself. Each MN receives a Mobile Network Prefix (MNP) for numbering downstream-attached End User Networks (EUNs) independently of the access network data links selected for data transport. The MN performs router discovery over the OMNI interface (i.e., similar to IPv6 customer edge routers [RFC7084]) and acts as a mobile router on behalf of its EUNs. The router discovery process is iterated over each of the OMNI interface's underlying access network data links in order to register per-link parameters (see Section 12). The OMNI interface provides a multilink nexus for exchanging inbound and outbound traffic via the correct underlying Access Network (ANET) interface(s). The IPv6 layer sees the OMNI interface as a point of connection to the OMNI link. Each OMNI link has one or more associated Mobility Service Prefixes (MSPs) from which OMNI link MNPs are derived. If there are multiple OMNI links, the IPv6 layer will see multiple OMNI interfaces. The OMNI interface interacts with a network-based Mobility Service (MS) through IPv6 Neighbor Discovery (ND) control message exchanges [RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that track MN movements and represent their MNPs in a global routing or mapping system. This document specifies the transmission of IPv6 packets [RFC8200] and MN/MS control messaging over OMNI interfaces. 2. Terminology The terminology in the normative references applies; especially, the terms "link" and "interface" are the same as defined in the IPv6 [RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications. Templin & Whyman Expires August 29, 2020 [Page 3] Internet-Draft IPv6 over OMNI Interfaces February 2020 Also, the Protocol Constants defined in Section 10 of [RFC4861] are used in their same format and meaning in this document. The terms "All-Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast" are defined in [RFC4291] (with Link-Local scope assumed). The following terms are defined within the scope of this document: Mobile Node (MN) an end system with multiple distinct upstream data link connections that are managed together as a single logical unit. The MN's data link connection parameters can change over time due to, e.g., node mobility, link quality, etc. The MN further connects a downstream-attached End User Network (EUN). The term MN used here is distinct from uses in other documents, and does not imply a particular mobility protocol. End User Network (EUN) a simple or complex downstream-attached mobile network that travels with the MN as a single logical unit. The IPv6 addresses assigned to EUN devices remain stable even if the MN's upstream data link connections change. Mobility Service (MS) a mobile routing service that tracks MN movements and ensures that MNs remain continuously reachable even across mobility events. Specific MS details are out of scope for this document. Mobility Service Endpoint (MSE) an entity in the MS (either singluar or aggregate) that coordinates the mobility events of one or more MN. Mobility Service Prefix (MSP) an aggregated IPv6 prefix (e.g., 2001:db8::/32) advertised to the rest of the Internetwork by the MS, and from which more-specific Mobile Network Prefixes (MNPs) are derived. Mobile Network Prefix (MNP) a longer IPv6 prefix taken from an MSP (e.g., 2001:db8:1000:2000::/56) and assigned to a MN. MNs sub-delegate the MNP to devices located in EUNs. Access Network (ANET) a data link service network (e.g., an aviation radio access network, satellite service provider network, cellular operator network, wifi network, etc.) that connects MNs. Physical and/or data link level security between the MN and ANET are assumed. Access Router (AR) Templin & Whyman Expires August 29, 2020 [Page 4] Internet-Draft IPv6 over OMNI Interfaces February 2020 a first-hop router in the ANET for connecting MNs to correspondents in outside Internetworks. ANET interface a MN's attachment to a link in an ANET. Internetwork (INET) a connected network region with a coherent IP addressing plan that provides transit forwarding services for ANET MNs and INET correspondents. Examples include private enterprise networks, ground domain aviation service networks and the global public Internet itself. INET interface a node's attachment to a link in an INET. OMNI link a virtual overlay configured over one or more INETs and their connected ANETs. An OMNI link can comprise multiple INET segments joined by bridges the same as for any link; the addressing plans in each segment may be mutually exclusive and managed by different administrative entities. OMNI interface a node's attachment to an OMNI link, and configured over one or more underlying ANET/INET interfaces. OMNI link local address (LLA) an IPv6 link-local address constructed as specified in Section 7, and assigned to an OMNI interface. OMNI Option an IPv6 Neighbor Discovery option providing multilink parameters for the OMNI interface as specified in Section 8. Multilink an OMNI interface's manner of managing diverse underlying data link interfaces as a single logical unit. The OMNI interface provides a single unified interface to upper layers, while underlying data link selections are performed on a per-packet basis considering factors such as DSCP, flow label, application policy, signal quality, cost, etc. Multilinking decisions are coordinated in both the outbound (i.e. MN to correspondent) and inbound (i.e., correspondent to MN) directions. L2 The second layer in the OSI network model. Also known as "layer- 2", "link-layer", "sub-IP layer", "data link layer", etc. Templin & Whyman Expires August 29, 2020 [Page 5] Internet-Draft IPv6 over OMNI Interfaces February 2020 L3 The third layer in the OSI network model. Also known as "layer- 3", "network-layer", "IPv6 layer", etc. 3. Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here. An implementation is not required to internally use the architectural constructs described here so long as its external behavior is consistent with that described in this document. 4. Overlay Multilink Network (OMNI) Interface Model An OMNI interface is a MN virtual interface configured over one or more ANET interfaces, which may be physical (e.g., an aeronautical radio link) or virtual (e.g., an Internet or higher-layer "tunnel"). The MN receives a MNP from the MS, and coordinates with the MS through IPv6 ND message exchanges. The MN uses the MNP to construct a unique OMNI LLA through the algorithmic derivation specified in Section 7 and assigns the LLA to the OMNI interface. The OMNI interface architectural layering model is the same as in [RFC7847], and augmented as shown in Figure 1. The IP layer (L3) therefore sees the OMNI interface as a single network layer interface with multiple underlying ANET interfaces that appear as L2 communication channels in the architecture. Templin & Whyman Expires August 29, 2020 [Page 6] Internet-Draft IPv6 over OMNI Interfaces February 2020 +----------------------------+ | Upper Layer Protocol | Session-to-IP +---->| | Address Binding | +----------------------------+ +---->| IP (L3) | IP Address +---->| | Binding | +----------------------------+ +---->| OMNI Interface | Logical-to- +---->| (OMNI LLA) | Physical | +----------------------------+ Interface +---->| L2 | L2 | | L2 | Binding |(IF#1)|(IF#2)| ..... |(IF#n)| +------+------+ +------+ | L1 | L1 | | L1 | | | | | | +------+------+ +------+ Figure 1: OMNI Interface Architectural Layering Model The OMNI virtual interface model gives rise to a number of opportunities: o since OMNI LLAs are uniquely derived from an MNP, no Duplicate Address Detection (DAD) messaging is necessary. o ANET interfaces do not require any L3 addresses (i.e., not even link-local) in environments where communications are coordinated entirely over the OMNI interface. (An alternative would be to also assign the same OMNI LLA to all ANET interfaces.) o as ANET interface properties change (e.g., link quality, cost, availability, etc.), any active ANET interface can be used to update the profiles of multiple additional ANET interfaces in a single message. This allows for timely adaptation and service continuity under dynamically changing conditions. o coordinating ANET interfaces in this way allows them to be represented in a unified MS profile with provisions for mobility and multilink operations. o exposing a single virtual interface abstraction to the IPv6 layer allows for multilink operation (including QoS based link selection, packet replication, load balancing, etc.) at L2 while still permitting L3 traffic shaping based on, e.g., DSCP, flow label, etc. Templin & Whyman Expires August 29, 2020 [Page 7] Internet-Draft IPv6 over OMNI Interfaces February 2020 o L3 sees the OMNI interface as a point of connection to the OMNI link; if there are multiple OMNI links (i.e., multiple MS's), L3 will see multiple OMNI interfaces. Other opportunities are discussed in [RFC7847]. Figure 2 depicts the architectural model for a MN connecting to the MS via multiple independent ANETs. When an ANET interface becomes active, the MN's OMNI interface sends native (i.e., unencapsulated) IPv6 ND messages via the underlying ANET interface. IPv6 ND messages traverse the ground domain ANETs until they reach an Access Router (AR#1, AR#2, .., AR#n). The AR then coordinates with a Mobility Service Endpoint (MSE#1, MSE#2, ..., MSE#m) in the INET and returns an IPv6 ND message response to the MN. IPv6 ND messages traverse the ANET at layer 2; hence, the Hop Limit is not decremented. Templin & Whyman Expires August 29, 2020 [Page 8] Internet-Draft IPv6 over OMNI Interfaces February 2020 +--------------+ | MN | +--------------+ |OMNI interface| +----+----+----+ +--------|IF#1|IF#2|IF#n|------ + / +----+----+----+ \ / | \ / <---- Native | IP ----> \ v v v (:::)-. (:::)-. (:::)-. .-(::ANET:::) .-(::ANET:::) .-(::ANET:::) `-(::::)-' `-(::::)-' `-(::::)-' +----+ +----+ +----+ ... |AR#1| .......... |AR#2| ......... |AR#n| ... . +-|--+ +-|--+ +-|--+ . . | | | . v v v . . <----- Encapsulation -----> . . . . +-----+ (:::)-. . . |MSE#2| .-(::::::::) +-----+ . . +-----+ .-(::: INET :::)-. |MSE#m| . . (::::: Routing ::::) +-----+ . . `-(::: System :::)-' . . +-----+ `-(:::::::-' . . |MSE#1| +-----+ +-----+ . . +-----+ |MSE#3| |MSE#4| . . +-----+ +-----+ . . . . . . <----- Worldwide Connected Internetwork ----> . ........................................................... Figure 2: MN/MS Coordination via Multiple ANETs After the initial IPv6 ND message exchange, the MN can send and receive unencapsulated IPv6 data packets over the OMNI interface. OMNI interface multilink services will forward the packets via ARs in the correct underlying ANETs. The AR encapsulates the packets according to the capabilities provided by the MS and forwards them to the next hop within the worldwide connected Internetwork via optimal routes. Templin & Whyman Expires August 29, 2020 [Page 9] Internet-Draft IPv6 over OMNI Interfaces February 2020 5. Maximum Transmission Unit (MTU) and Fragmentation All IPv6 interfaces are REQUIRED to configure a minimum Maximum Transmission Unit (MTU) of 1280 bytes [RFC8200]. The network therefore MUST forward packets of at least 1280 bytes without generating an IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB) message [RFC8201]. The OMNI interface configures an MTU of 9180 bytes [RFC2492]; the size is therefore not a reflection of the underlying ANET interface MTUs, but rather determines the largest packet the OMNI interface can forward or reassemble. The OMNI interface can employ link-layer IPv6 encapsulation and fragmentation/reassembly per [RFC2473], but its use is OPTIONAL since correct operation will result in either case. Implementations that omit link-layer IPv6 fragmentation/reassembly may be more prone to dropping large packets and returning a PTB, while those that include it may see improved performance at the expense of including additional code. In both cases, OMNI interface neighbors are responsible for advertising their willingness to reassemble. The OMNI interface returns internally-generated PTB messages for packets admitted into the interface that it deems too large for the outbound underlying ANET interface (e.g., according to ANET performance characteristics, MTU, etc). For all other packets, the OMNI interface performs PMTUD even if the destination appears to be on the same link since a proxy on the path could return a PTB message. This ensures that the path MTU is adaptive and reflects the current path used for a given data flow. The MN's OMNI interface forwards packets that are no larger than the MTU of the selected underlying ANET interface according to the ANET L2 frame format. When the OMNI interface forwards a packet that is larger than the ANET interface MTU, it drops the packet and returns a PTB if the AR is not willing to reassemble. Otherwise, the OMNI interface encapsulates the packet in an IPv6 header with source address set to the MN's link-local address and destination address set to the link-local address of the MSE (see: Section 7). The OMNI interface then uses IPv6 fragmentation to break the encapsulated packet into fragments that are no larger than the ANET interface MTU and sends the fragments over the ANET where they will be intercepted by the AR. The AR then reassembles and conveys the packet toward the final destination. When an AR receives a fragmented or whole packet from the INET destined to an ANET MN, it first determines whether to forward or Templin & Whyman Expires August 29, 2020 [Page 10] Internet-Draft IPv6 over OMNI Interfaces February 2020 drop and return a PTB. If the AR deems the packet to be of acceptable size, it first reassembles locally (if necessary) then forwards the packet to the MN. If the (reassembled) packet is no larger than the ANET MTU, the AR forwards according to the ANET L2 frame format. If the packet is larger than the ANET MTU, the AR instead uses link-layer IPv6 encapsulation and fragmentation as above if the MN accepts fragments or drops and returns a PTB otherwise. The MN then reassembles and discards the encapsulation header, then forwards the whole packet to the final destination. Applications that cannot tolerate loss due to MTU restrictions SHOULD avoid sending packets larger than 1280 bytes, since dynamic path changes can reduce the path MTU at any time. Applications that may benefit from sending larger packets even though the path MTU may change dynamically MAY use larger sizes (i.e., up to the OMNI interface MTU). Note that when the AR forwards a fragmented packet received from the INET, it is imperative that the AR reassembles locally first instead of blindly forwarding fragments directly to the MN to avoid attacks such as tiny fragments, overlapping fragments, etc. 6. Frame Format The OMNI interface transmits IPv6 packets according to the native frame format of each underlying ANET interface. For example, for Ethernet-compatible interfaces the frame format is specified in [RFC2464], for aeronautical radio interfaces the frame format is specified in standards such as ICAO Doc 9776 (VDL Mode 2 Technical Manual), for tunnels over IPv6 the frame format is specified in [RFC2473], etc. 7. Link-Local Addresses OMNI interfaces assign IPv6 Link-Local Addresses (i.e., "OMNI LLAs") using the following constructs: o IPv6 MN OMNI LLAs encode the most-significant 64 bits of a MNP within the least-significant 64 bits (i.e., the interface ID) of a Link-Local IPv6 Unicast Address (see: [RFC4291], Section 2.5.6). For example, for the MNP 2001:db8:1000:2000::/56 the corresponding LLA is fe80::2001:db8:1000:2000. o IPv4-compatible MN OMNI LLAs are assigned as fe80::ffff:[v4addr], i.e., the most significant 10 bits of the prefix fe80::/10, followed by 70 '0' bits, followed by 16 '1' bits, followed by a 32bit IPv4 address. For example, the IPv4-Compatible MN OMNI LLA Templin & Whyman Expires August 29, 2020 [Page 11] Internet-Draft IPv6 over OMNI Interfaces February 2020 for 192.0.2.1 is fe80::ffff:192.0.2.1 (also written as fe80::ffff:c000:0201). o MSE OMNI LLAs are assigned from the range fe80::/96, and MUST be managed for uniqueness. The lower 32 bits of the LLA includes a unique integer value between '1' and 'feffffff', e.g., as in fe80::1, fe80::2, fe80::3, etc., fe80::feff:ffff. The address fe80:: is the link-local Subnet-Router anycast address [RFC4291] and the address fe80::ffff:ffff is the "All-MSEs" address. The address range fe80::ff00:0000/104 is reserved for future use. (Note that distinct OMNI link segments can avoid overlap by assigning MSE OMNI LLAs from unique fe80::/96 sub-prefixes. For example, a first segment could assign from fe80::1000/116, a second from fe80::2000/116, a third from fe80::3000/116, etc.) Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no MNPs can be allocated from that block ensuring that there is no possibility for overlap between the above OMNI LLA constructs. Since MN OMNI LLAs are based on the distribution of administratively assured unique MNPs, and since MSE OMNI LLAs are guaranteed unique through administrative assignment, OMNI interfaces set the autoconfiguration variable DupAddrDetectTransmits to 0 [RFC4862]. 8. Address Mapping - Unicast OMNI interfaces maintain a neighbor cache for tracking per-neighbor state and use the link-local address format specified in Section 7. IPv6 Neighbor Discovery (ND) [RFC4861] messages on MN OMNI interfaces observe the native Source/Target Link-Layer Address Option (S/TLLAO) formats of the underlying ANET interfaces (e.g., for Ethernet the S/ TLLAO is specified in [RFC2464]). MNs such as aircraft typically have many wireless data link types (e.g. satellite-based, cellular, terrestrial, air-to-air directional, etc.) with diverse performance, cost and availability properties. The OMNI interface would therefore appear to have multiple L2 connections, and may include information for multiple ANET interfaces in a single IPv6 ND message exchange. OMNI interfaces use an IPv6 ND option called the "OMNI option" formatted as shown in Figure 3: Templin & Whyman Expires August 29, 2020 [Page 12] Internet-Draft IPv6 over OMNI Interfaces February 2020 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length |R|A| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Sub-Options ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: OMNI Option Format In this format: o Type is set to TBD. o Length is set to the number of 8 octet blocks in the option. o Prefix Length is set according to the IPv6 source address type. For MN OMNI LLAs, the value is set to the length of the embedded MNP. For IPv4-compatible MN OMNI LLAs, the value is set to 96 plus the length of the embedded IPv4 prefix. For MSE OMNI LLAs, the value is set to 128. o R (the "Register/Release" bit) is set to '1' to register an MNP or set to '0' to release a registration. o A (the "Accepts Fragments" bit) is set to '1' if the sender accepts OMNI interface link-local fragments (see: Section 5); otherwise, set to 0. o Reserved is set to the value '0' on transmission and ignored on reception. o Sub-Options is a Variable-length field, of length such that the complete OMNI Option is an integer multiple of 8 octets long. Contains one or more options, as described in Section 8.1. 8.1. Sub-Options The OMNI option includes zero or more Sub-Options, some of which may appear multiple times in the same message. Each consecutive Sub- Option is concatenated immediately after its predecessor. All Sub- Options except Pad1 (see below) are type-length-value (TLV) encoded in the following format: Templin & Whyman Expires August 29, 2020 [Page 13] Internet-Draft IPv6 over OMNI Interfaces February 2020 0 1 2 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | Sub-Type | Sub-length | Sub-Option Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 4: Sub-Option Format o Sub-Type is a 1-byte field that encodes the Sub-Option type. Sub- Options defined in this document are: Option Name Sub-Type Pad1 0 PadN 1 ifIndex-tuple (Type 1) 2 ifIndex-tuple (Type 2) 3 Notification ID 4 Figure 5 Sub-Types 253 and 254 are reserved for experimentation, as recommended in[RFC3692]]. o Sub-Length is a 1-byte field that encodes the length of the Sub- Option Data, in bytes o Sub-Option Data is a byte string with format determined by Sub- Type During processing, unrecognized Sub-Options are ignored and the next Sub-Option processed until the end of the OMNI option. The following Sub-Option types and formats are defined in this document: 8.1.1. Pad1 0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ | Sub-Type=0 | +-+-+-+-+-+-+-+-+ Figure 6: Pad1 o Sub-Type is set to 0. Templin & Whyman Expires August 29, 2020 [Page 14] Internet-Draft IPv6 over OMNI Interfaces February 2020 o No Sub-Length or Sub-Option Data follows (i.e., the "Sub-Option" consists of a single zero octet). 8.1.2. PadN 0 1 2 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | Sub-Type=1 |Sub-length=N-2 | N-2 padding bytes ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 7: PadN o Sub-Type is set to 1. o Sub-Length is set to N-2 being the number of padding bytes that follow. o Sub-Option Data consists of N-2 zero-valued octets. 8.1.3. ifIndex-tuple (Type 1) 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | Link |S|I|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P32|P33|P34|P35|P36|P37|P38|P39| ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 8: ifIndex-tuple (Type 1) o Sub-Type is set to 2. o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that follow). o Sub-Option Data contains an "ifIndex-tuple" (Type 1) encoded as follows (note that the first four bytes must be present): * ifIndex is set to an 8-bit integer value corresponding to a specific underlying ANET interface. OMNI options MAY include Templin & Whyman Expires August 29, 2020 [Page 15] Internet-Draft IPv6 over OMNI Interfaces February 2020 multiple ifIndex-tuples, and MUST number each with an ifIndex value between '1' and '255' that represents a MN-specific 8-bit mapping for the actual ifIndex value assigned to the ANET interface by network management [RFC2863] (the ifIndex value '0' is reserved for use by the MS). Multiple ifIndex-tuples with the same ifIndex value MAY appear in the same OMNI option. * ifType is set to an 8-bit integer value corresponding to the underlying ANET interface identified by ifIndex. The value represents an OMNI interface-specific 8-bit mapping for the actual IANA ifType value registered in the 'IANAifType-MIB' registry [http://www.iana.org]. * Provider ID is set to an OMNI interface-specific 8-bit ID value for the network service provider associated with this ifIndex. * Link encodes a 4-bit link metric. The value '0' means the link is DOWN, and the remaining values mean the link is UP with metric ranging from '1' ("lowest") to '15' ("highest"). * S is set to '1' if this ifIndex-tuple corresponds to the underlying ANET interface that is the source of the ND message. Set to '0' otherwise. * I is set to '0' ("Simplex") if the index for each singleton Bitmap byte in the Sub-Option Data is inferred from its sequential position (i.e., 0, 1, 2, ...), or set to '1' ("Indexed") if each Bitmap is preceded by an Index byte. Figure 8 shows the simplex case for I set to '0'. For I set to '1', each Bitmap is instead preceded by an Index byte that encodes a value "i" = (0 - 255) as the index for its companion Bitmap as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | Index=i | Bitmap(i) |P[*] values ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 9 * RSV is set to the value 0 on transmission and ignored on reception. * The remainder of the Sub-Option Data contains N = (0 - 251) bytes of traffic classifier preferences consisting of a first (indexed) Bitmap (i.e., "Bitmap(i)") followed by 0-8 1-byte blocks of 2-bit P[*] values, followed by a second Bitmap (i), followed by 0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7, the bits of each Bitmap(i) that are set to '1'' Templin & Whyman Expires August 29, 2020 [Page 16] Internet-Draft IPv6 over OMNI Interfaces February 2020 indicate the P[*] blocks from the range P[(i*32)] through P[(i*32) + 31] that follow; if any Bitmap(i) bits are '0', then the corresponding P[*] block is instead omitted. For example, if Bitmap(0) contains 0xff then the block with P[00]-P[03], followed by the block with P[04]-P[07], etc., and ending with the block with P[28]-P[31] are included (as showin in Figure 8). The next Bitmap(i) is then consulted with its bits indicating which P[*] blocks follow, etc. out to the end of the Sub-Option. The first 16 P[*] blocks correspond to the 64 Differentiated Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. If additional P[*] blocks follow, their values correspond to "pseudo-DSCP" traffic classifier values P[64], P[65], P[66], etc. See Appendix A for further discussion and examples. * Each 2-bit P[*] field is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium") or '3' ("high") to indicate a QoS preference level for ANET interface selection purposes. Not all P[*] values need to be included in all OMNI option instances of a given ifIndex-tuple. Any P[*] values represented in an earlier OMNI option but ommitted in the current OMNI option remain unchanged. Any P[*] values not yet represented in any OMNI option default to "medium". 8.1.4. ifIndex-tuple (Type 2) 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=3 | Sub-length=4+N| ifIndex | ifType | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | Link |S|Resvd| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ ~ RFC 6088 Format Traffic Selector ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: ifIndex-tuple (Type 2) o Sub-Type is set to 3. o Sub-Length is set to 4+N (the number of Sub-Option Data bytes that follow). o Sub-Option Data contains an "ifIndex-tuple" (Type 2) encoded as follows (note that the first four bytes must be present): Templin & Whyman Expires August 29, 2020 [Page 17] Internet-Draft IPv6 over OMNI Interfaces February 2020 * ifIndex, ifType, Provider ID, Link and S are set exactly as for Type 1 ifIndex-tuples as specified in Section 8.1.3. * the remainder of the Sub-Option body encodes a variable-length traffic selector formatted per [RFC6088], beginning with the "TS Format" field. 8.1.5. Notification ID 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=4 | Sub-length=4 | Notification ID (bits 0 - 15) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Notification ID (bits 16 - 32)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: Notification ID o Sub-Type is set to 4. o Sub-Length is set to 4. o Notification ID contains the least-significant 32 bits of an MSE OMNI LLA to notify (e.g., for the LLA fe80::face:cafe the field contains 0xfacecafe). Valid only in MN RS messages, and ignored in all other ND messages. OMNI options contain zero or more Notification IDs. 9. Address Mapping - Multicast The multicast address mapping of the native underlying ANET interface applies. The mobile router on board the aircraft also serves as an IGMP/MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while using the L2 address of the router as the L2 address for all multicast packets. 10. Address Mapping for IPv6 Neighbor Discovery Messages Per [RFC4861], IPv6 ND messages may be sent to either a multicast or unicast link-scoped IPv6 destination address. However, IPv6 ND messaging is coordinated between the MN and MS only without invoking other nodes on the ANET. For this reason, ANET links maintain unicast L2 addresses ("MSADDR") for the purpose of supporting MN/MS IPv6 ND messaging. For Ethernet- compatible ANETs, this specification reserves one Ethernet unicast address TBD2. For non-Ethernet statically-addressed ANETs, MSADDR is Templin & Whyman Expires August 29, 2020 [Page 18] Internet-Draft IPv6 over OMNI Interfaces February 2020 reserved per the assigned numbers authority for the ANET addressing space. For still other ANETs, MSADDR may be dynamically discovered through other means, e.g., L2 beacons. MNs map the L3 addresses of all IPv6 ND messages they send (i.e., both multicast and unicast) to an MSADDR instead of to an ordinary unicast or multicast L2 address. In this way, all of the MN's IPv6 ND messages will be received by MS devices that are configured to accept packets destined to MSADDR. Note that multiple MS devices on the link could be configured to accept packets destined to MSADDR, e.g., as a basis for supporting redundancy. Therefore, ARs MUST accept and process packets destined to MSADDR, while all other devices MUST NOT process packets destined to MSADDR. This model has well-established operational experience in Proxy Mobile IPv6 (PMIP) [RFC5213][RFC6543]. 11. Conceptual Sending Algorithm The MN's IPv6 layer selects the outbound OMNI interface according to standard IPv6 requirements when forwarding data packets from local or EUN applications to external correspondents. The OMNI interface maintains default routes and neighbor cache entries for MSEs, and may also include additional neighbor cache entries created through other means (e.g., Address Resolution, static configuration, etc.). After a packet enters the OMNI interface, an outbound ANET interface is selected based on multilink parameters such as DSCP, application port number, cost, performance, message size, etc. OMNI interface multilink selections could also be configured to perform replication across multiple ANET interfaces for increased reliability at the expense of packet duplication. OMNI interface multilink service designers MUST observe the BCP guidance in Section 15 [RFC3819] in terms of implications for reordering when packets from the same flow may be spread across multiple ANET interfaces having diverse properties. 11.1. Multiple OMNI Interfaces MNs may associate with multiple MS instances concurrently. Each MS instance represents a distinct OMNI link distinguished by its associated MSPs. The MN configures a separate OMNI interface for each link so that multiple interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6 layer. Depending on local policy and configuration, an MN may choose between alternative active OMNI interfaces using a packet's DSCP, routing Templin & Whyman Expires August 29, 2020 [Page 19] Internet-Draft IPv6 over OMNI Interfaces February 2020 information or static configuration. Interface selection based on per-packet source addresses is also enabled when the MSPs for each OMNI interface are known (e.g., discovered through Prefix Information Options (PIOs) and/or Route Information Options (RIOs)). Each OMNI interface can be configured over the same or different sets of ANET interfaces. Each ANET distinguishes between the different OMNI links based on the MSPs represented in per-packet IPv6 addresses. Multiple distinct OMNI links can therefore be used to support fault tolerance, load balancing, reliability, etc. The architectural model parallels Layer 2 Virtual Local Area Networks (VLANs), where the MSPs serve as (virtual) VLAN tags. 12. Router Discovery and Prefix Registration ARs process IPv6 ND messages destined to All-Routers multicast (ff02::2), Subnet-Router anycast (fe80::) and unicast IPv6 LLAs [RFC4291]. ARs configure the L2 address MSADDR (see: Section 10) and act as a proxy for MSE OMNI LLAs. MNs interface with the MS by sending RS messages with OMNI options. For each ANET interface, the MN sends an RS message with an OMNI option, with L2 destination address set to MSADDR and with L3 destination address set to either a specific MSE OMNI LLA, link-local Subnet-Router anycast, or All-Routers multicast. The MN discovers MSE OMNI LLAs either through an RA message response to an initial anycast/multicast RS or before sending an initial RS message. [RFC5214] provides example MSE address discovery methods, including information conveyed during data link login, name service lookups, static configuration, etc. The AR receives the RS messages and coordinates with the corresponding MSE in a manner outside the scope of this document. The AR returns an RA message with source address set to the MSE OMNI LLA, with an OMNI option and with any information for the link that would normally be delivered in a solicited RA message. (Note that if all MSEs share common state, the AR can instead return an RA with source address set to link-local Subnet-Router anycast.) MNs configure OMNI interfaces that observe the properties discussed in the previous section. The OMNI interface and its underlying interfaces are said to be in either the "UP" or "DOWN" state according to administrative actions in conjunction with the interface connectivity status. An OMNI interface transitions to UP or DOWN through administrative action and/or through state transitions of the underlying interfaces. When a first underlying interface transitions Templin & Whyman Expires August 29, 2020 [Page 20] Internet-Draft IPv6 over OMNI Interfaces February 2020 to UP, the OMNI interface also transitions to UP. When all underlying interfaces transition to DOWN, the OMNI interface also transitions to DOWN. When an OMNI interface transitions to UP, the MN sends initial RS messages to register its MNP and an initial set of underlying ANET interfaces that are also UP. The MN sends additional RS messages to refresh lifetimes and to register/deregister underlying ANET interfaces as they transition to UP or DOWN. ARs return RA messages with configuration information in response to a MN's RS messages. The AR sets the RA Cur Hop Limit, M and O flags, Router Lifetime, Reachable Time and Retrans Timer values as directed by the MSE, and includes any necessary options such as: o PIOs with (A; L=0) that include MSPs for the link [RFC8028]. o RIOs [RFC4191] with more-specific routes. o an MTU option that specifies the maximum acceptable packet size for this ANET interface. The AR coordinates with the MSE and sends immediate unicast RA responses without delay; therefore, the IPv6 ND MAX_RA_DELAY_TIME and MIN_DELAY_BETWEEN_RAS constants for multicast RAs do not apply. The AR MAY send periodic and/or event-driven unsolicited RA messages, but is not required to do so for unicast advertisements [RFC4861]. The MN sends RS messages from within the OMNI interface while using an UP underlying ANET interface as the outbound interface. Each RS message is formatted as though it originated from the IPv6 layer, but the process is coordinated wholly from within the OMNI interface and is therefore opaque to the IPv6 layer. The MN sends initial RS messages over an UP underlying interface with its OMNI LLA as the source and with destination set as discussed above. The RS messages include an OMNI option per Section 8 with a valid Prefix Length, (R,P,A) flags, and with ifIndex-tuples appropriate for underlying ANET interfaces. The AR processes RS message and conveys the OMNI option information to the MSE. When the MSE processes the OMNI information, it first validates the prefix registration information. If the prefix registration was valid, the MSE injects the MNP into the routing/mapping system then caches the new Prefix Length, MNP and ifIndex-tuples. If the MN's OMNI option included one or more Notification IDs, the new MSE also notifies the former MSE(s). The MSE then directs the AR to return an RA message to the MN with an OMNI option per Section 8 and with a Templin & Whyman Expires August 29, 2020 [Page 21] Internet-Draft IPv6 over OMNI Interfaces February 2020 non-zero Router Lifetime if the prefix registration was successful; otherwise, with a zero Router Lifetime. When the MN receives the RA message, it creates a default route with L3 next hop address set to the address found in the RA source address and with L2 address set to MSADDR. The AR will then forward packets between the MN and the MS. The MN then manages its underlying ANET interfaces according to their states as follows: o When an underlying ANET interface transitions to UP, the MN sends an RS over the ANET interface with an OMNI option. The OMNI option contains at least one ifIndex-tuple with values specific to this ANET interface, and may contain additional ifIndex-tuples specific to this and/or other ANET interfaces. o When an underlying ANET interface transitions to DOWN, the MN sends an RS or unsolicited NA message over any UP ANET interface with an OMNI option containing an ifIndex-tuple for the DOWN ANET interface with Link set to '0'. The MN sends an RS when an acknowledgement is required, or an unsolicited NA when reliability is not thought to be a concern (e.g., if redundant transmissions are sent on multiple ANET interfaces). o When the Router Lifetime for a specific ANET interface nears expiration, the MN sends an RS over the ANET interface to receive a fresh RA. If no RA is received, the MN marks the ANET interface as DOWN. o When a MN wishes to release from a current MSE, it sends an RS or unsolicited NA message over any UP ANET interfaces with an OMNI option with R set to 0. The corresponding MSE then withdraws the MNP from the routing/mapping system and (for RS responses) directs the AR to return an RA message with an OMNI option and with Router Lifetime set to 0. o When a MN wishes to transition to a new MSE, it sends an RS or unsolicited NA message over any UP ANET interfaces with an OMNI option with R set to 1, with the new MSE OMNI LLA set in the destination address, and (optionally) with a Notification ID included for the former MSE. o When all of a MNs underlying interfaces have transitioned to DOWN (or if the prefix registration lifetime expires) the MSE withdraws the MNP the same as if it had received a message with an OMNI option with R set to 0. Templin & Whyman Expires August 29, 2020 [Page 22] Internet-Draft IPv6 over OMNI Interfaces February 2020 The MN is responsible for retrying each RS exchange up to MAX_RTR_SOLICITATIONS times separated by RTR_SOLICITATION_INTERVAL seconds until an RA is received. If no RA is received over a single UP ANET interface, the MN declares this ANET interface as DOWN. If no RA is received over multiple UP ANET interfaces, the MN declares this MSE unreachable and tries a different MSE. The IPv6 layer sees the OMNI interface as an ordinary IPv6 interface. Therefore, when the IPv6 layer sends an RS message the OMNI interface returns an internally-generated RA message as though the message originated from an IPv6 router. The internally-generated RA message contains configuration information that is consistent with the information received from the RAs generated by the MS. Whether the OMNI interface IPv6 ND messaging process is initiated from the receipt of an RS message from the IPv6 layer is an implementation matter. Some implementations may elect to defer the IPv6 ND messaging process until an RS is received from the IPv6 layer, while others may elect to initiate the process proactively. Note: The Router Lifetime value in RA messages indicates the time before which the MN must send another RS message over this ANET interface (e.g., 600 seconds), however that timescale may be significantly longer than the lifetime the MS has committed to retain the prefix registration (e.g., REACHABLETIME seconds). ARs are therefore responsible for keeping MS state alive on a finer-grained timescale than the MN is required to do on its own behalf. 13. AR and MSE Resilience ANETs SHOULD deploy ARs in Virtual Router Redundancy Protocol (VRRP) [RFC5798] configurations so that service continuity is maintained even if one or more ARs fail. Using VRRP, the MN is unaware which of the (redundant) ARs is currently providing service, and any service discontinuity will be limited to the failover time supported by VRRP. Widely deployed public domain implementations of VRRP are available. MSEs SHOULD use high availability clustering services so that multiple redundant systems can provide coordinated response to failures. As with VRRP, widely deployed public domain implementations of high availability clustering services are available. Note that special-purpose and expensive dedicated hardware is not necessary, and public domain implementations can be used even between lightweight virtual machines in cloud deployments. Templin & Whyman Expires August 29, 2020 [Page 23] Internet-Draft IPv6 over OMNI Interfaces February 2020 14. Detecting and Responding to MSE Failures In environments where fast recovery from MSE failure is required, ARs SHOULD use proactive Neighbor Unreachability Detection (NUD) in a manner that parallels Bidirectional Forwarding Detection (BFD) [RFC5880] to track MSE reachability. ARs can then quickly detect and react to failures so that cached information is re-established through alternate paths. Proactive NUD control messaging is carried only over well-connected ground domain networks (i.e., and not low- end ANET links such as aeronautical radios) and can therefore be tuned for rapid response. ARs perform proactive NUD for MSEs for which there are currently active ANET MNs. If an MSE fails, ARs can quickly inform MNs of the outage by sending multicast RA messages on the ANET interface. The AR sends RA messages to the MN via the ANET interface with source address set to the MSEs OMNI LLA, destination address set to All- Nodes multicast (ff02::1) [RFC4291], and Router Lifetime set to 0. The AR SHOULD send MAX_FINAL_RTR_ADVERTISEMENTS RA messages separated by small delays [RFC4861]. Any MNs on the ANET interface that have been using the (now defunct) MSE will receive the RA messages and associate with a new MSE. 15. IANA Considerations The IANA is instructed to allocate an official Type number TBD from the registry "IPv6 Neighbor Discovery Option Formats" for the OMNI option. Implementations set Type to 253 as an interim value [RFC4727]. The OMNI option also defines an 8-bit Sub-Type field, for which IANA is instructed to create and maintain a new registry entitled "OMNI option Sub-Type values". Initial values for the OMNI option Sub-Type values registry are given below; future assignments are to be made through Expert Review [RFC8126]. Templin & Whyman Expires August 29, 2020 [Page 24] Internet-Draft IPv6 over OMNI Interfaces February 2020 Value Sub-Type name Reference ----- ------------- ---------- 0 Pad1 [RFCXXXX] 1 PadN [RFCXXXX] 2 ifIndex-tuple (Type 1) [RFCXXXX] 3 ifIndex-tuple (Type 2) [RFCXXXX] 4 Notification ID [RFCXXXX] 5-252 Unassigned 253-254 Experimental [RFCXXXX] 255 Reserved [RFCXXXX] Figure 12: OMNI Option Sub-Type Values The IANA is instructed to allocate one Ethernet unicast address TBD2 (suggest 00-00-5E-00-52-14 [RFC5214]) in the registry "IANA Ethernet Address Block - Unicast Use". 16. Security Considerations Security considerations for IPv6 [RFC8200] and IPv6 Neighbor Discovery [RFC4861] apply. OMNI interface IPv6 ND messages SHOULD include Nonce and Timestamp options [RFC3971] when synchronized transaction confirmation is needed. Security considerations for specific access network interface types are covered under the corresponding IP-over-(foo) specification (e.g., [RFC2464], [RFC2492], etc.). 17. Acknowledgements The first version of this document was prepared per the consensus decision at the 7th Conference of the International Civil Aviation Organization (ICAO) Working Group-I Mobility Subgroup on March 22, 2019. Consensus to take the document forward to the IETF was reached at the 9th Conference of the Mobility Subgroup on November 22, 2019. Attendees and contributors included: Guray Acar, Danny Bharj, Francois D'Humieres, Pavel Drasil, Nikos Fistas, Giovanni Garofolo, Bernhard Haindl, Vaughn Maiolla, Tom McParland, Victor Moreno, Madhu Niraula, Brent Phillips, Liviu Popescu, Jacky Pouzet, Aloke Roy, Greg Saccone, Robert Segers, Michal Skorepa, Michel Solery, Stephane Tamalet, Fred Templin, Jean-Marc Vacher, Bela Varkonyi, Tony Whyman, Fryderyk Wrobel and Dongsong Zeng. The following individuals are acknowledged for their useful comments: Michael Matyas, Madhu Niraula, Greg Saccone, Stephane Tamalet, Eric Vyncke. Pavel Drasil, Zdenek Jaron and Michal Skorepa are recognized for their many helpful ideas and suggestions. Templin & Whyman Expires August 29, 2020 [Page 25] Internet-Draft IPv6 over OMNI Interfaces February 2020 This work is aligned with the NASA Safe Autonomous Systems Operation (SASO) program under NASA contract number NNA16BD84C. This work is aligned with the FAA as per the SE2025 contract number DTFAWA-15-D-00030. 18. References 18.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, . [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, DOI 10.17487/RFC3971, March 2005, . [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, November 2005, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers", RFC 4727, DOI 10.17487/RFC4727, November 2006, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . Templin & Whyman Expires August 29, 2020 [Page 26] Internet-Draft IPv6 over OMNI Interfaces February 2020 [RFC6088] Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont, "Traffic Selectors for Flow Bindings", RFC 6088, DOI 10.17487/RFC6088, January 2011, . [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by Hosts in a Multi-Prefix Network", RFC 8028, DOI 10.17487/RFC8028, November 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., "Path MTU Discovery for IP version 6", STD 87, RFC 8201, DOI 10.17487/RFC8201, July 2017, . 18.2. Informative References [RFC2225] Laubach, M. and J. Halpern, "Classical IP and ARP over ATM", RFC 2225, DOI 10.17487/RFC2225, April 1998, . [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, . [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, December 1998, . [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, . [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, . Templin & Whyman Expires August 29, 2020 [Page 27] Internet-Draft IPv6 over OMNI Interfaces February 2020 [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", BCP 82, RFC 3692, DOI 10.17487/RFC3692, January 2004, . [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. Wood, "Advice for Internet Subnetwork Designers", BCP 89, RFC 3819, DOI 10.17487/RFC3819, July 2004, . [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605, August 2006, . [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, DOI 10.17487/RFC5213, August 2008, . [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, DOI 10.17487/RFC5214, March 2008, . [RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP) Version 3 for IPv4 and IPv6", RFC 5798, DOI 10.17487/RFC5798, March 2010, . [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, . [RFC6543] Gundavelli, S., "Reserved IPv6 Interface Identifier for Proxy Mobile IPv6", RFC 6543, DOI 10.17487/RFC6543, May 2012, . [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic Requirements for IPv6 Customer Edge Routers", RFC 7084, DOI 10.17487/RFC7084, November 2013, . Templin & Whyman Expires August 29, 2020 [Page 28] Internet-Draft IPv6 over OMNI Interfaces February 2020 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit Boundary in IPv6 Addressing", RFC 7421, DOI 10.17487/RFC7421, January 2015, . [RFC7847] Melia, T., Ed. and S. Gundavelli, Ed., "Logical-Interface Support for IP Hosts with Multi-Access Support", RFC 7847, DOI 10.17487/RFC7847, May 2016, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . Appendix A. Type 1 ifIndex-tuple Traffic Classifier Preference Encoding Adaptation of the OMNI option Type 1 ifIndex-tuple's traffic classifier Bitmap to specific Internetworks such as the Aeronautical Telecommunications Network with Internet Protocol Services (ATN/IPS) may include link selection preferences based on other traffic classifiers (e.g., transport port numbers, etc.) in addition to the existing DSCP-based preferences. Nodes on specific Internetworks maintain a map of traffic classifiers to additional P[*] preference fields beyond the first 64. For example, TCP port 22 maps to P[67], TCP port 443 maps to P[70], UDP port 8060 maps to P[76], etc. Implementations use Simplex or Indexed encoding formats for P[*] encoding in order to encode a given set of traffic classifiers in the most efficient way. Some use cases may be more efficiently coded using Simplex form, while others may be more efficient using Indexed. Once a format is selected for preparation of a single ifIndex-tuple the same format must be used for the entire Sub-Option. Different Sub-Options may use different formats. The following figures show coding examples for various Simplex and Indexed formats: Templin & Whyman Expires August 29, 2020 [Page 29] Internet-Draft IPv6 over OMNI Interfaces February 2020 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | Link |S|0|RSV| Bitmap(0)=0xff|P00|P01|P02|P03| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P04|P05|P06|P07|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P20|P21|P22|P23|P24|P25|P26|P27|P28|P29|P30|P31| Bitmap(1)=0xff| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P32|P33|P34|P35|P36|P37|P38|P39|P40|P41|P42|P43|P44|P45|P46|P47| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bitmap(2)=0xff|P64|P65|P67|P68| ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 13: Example 1: Dense Simplex Encoding 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | Link |S|0|RSV| Bitmap(0)=0x00| Bitmap(1)=0x0f| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P48|P49|P50|P51|P52|P53|P54|P55|P56|P57|P58|P59|P60|P61|P62|P63| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bitmap(2)=0x00| Bitmap(3)=0x00| Bitmap(4)=0x00| Bitmap(5)=0x00| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bitmap(6)=0xf0|192|193|194|195|196|197|198|199|200|201|202|203| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |204|205|206|207| Bitmap(7)=0x00| Bitmap(8)=0x0f|272|273|274|275| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |276|277|278|279|280|281|282|283|284|285|286|287| Bitmap(9)=0x00| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap(10)=0x00| ... +-+-+-+-+-+-+-+-+-+-+- Figure 14: Example 2: Sparse Simplex Encoding Templin & Whyman Expires August 29, 2020 [Page 30] Internet-Draft IPv6 over OMNI Interfaces February 2020 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type=2 | Sub-length=4+N| ifIndex | ifType | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | Link |S|1|RSV| Index = 0x00 | Bitmap = 0x80 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P00|P01|P02|P03| Index = 0x01 | Bitmap = 0x01 |P60|P61|P62|P63| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Index = 0x10 | Bitmap = 0x80 |512|513|514|515| Index = 0x18 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bitmap = 0x01 |796|797|798|799| ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 15: Example 3: Indexed Encoding Appendix B. Prefix Length Considerations The 64-bit boundary in IPv6 addresses [RFC7421] determines the MN OMNI LLA format for encoding the most-significant 64 MNP bits into the least-significant 64 bits of the prefix fe80::/64 as discussed in Section 7. [RFC4291] defines the link-local address format as the most significant 10 bits of the prefix fe80::/10, followed by 54 unused bits, followed by the least-significant 64 bits of the address. If the 64-bit boundary is relaxed through future standards activity, then the 54 unused bits can be employed for extended coding of MNPs of length /65 up to /118. The extended coding format would continue to encode MNP bits 0-63 in bits 64-127 of the OMNI LLA, while including MNP bits 64-117 in bits 10-63. For example, the OMNI LLA corresponding to the MNP 2001:db8:1111:2222:3333:4444:5555::/112 would be fe8c:ccd1:1115:5540:2001:db8:1111:2222/128, and would still be a valid IPv6 LLA per [RFC4291]. However, a prefix length shorter than /128 cannot be applied due to the non-sequential byte ordering. Note that if the 64-bit boundary were relaxed an alternate form of OMNI LLA construction could be employed by embedding the MNP beginning with the most significant bit immediately following bit 10 of the prefix fe80::/10. For example, the OMNI LLA corresponding to the MNP 2001:db8:1111:2222:3333:4444:5555::/112 would be written as fe88:0043:6e04:4448:888c:ccd1:1115:5540/122. This alternate form may provide a more natural coding for the MS along with the ability to apply a fully-qualified prefix length. It has the disadvantages of requiring an unweildy 10-bit right-shift of a 16byte address, as well as presenting a non-human-readable form. Templin & Whyman Expires August 29, 2020 [Page 31] Internet-Draft IPv6 over OMNI Interfaces February 2020 Appendix C. VDL Mode 2 Considerations ICAO Doc 9776 is the "Technical Manual for VHF Data Link Mode 2" (VDLM2) that specifies an essential radio frequency data link service for aircraft and ground stations in worldwide civil aviation air traffic management. The VDLM2 link type is "multicast capable" [RFC4861], but with considerable differences from common multicast links such as Ethernet and IEEE 802.11. First, the VDLM2 link data rate is only 31.5Kbps - multiple orders of magnitude less than most modern wireless networking gear. Second, due to the low available link bandwidth only VDLM2 ground stations (i.e., and not aircraft) are permitted to send broadcasts, and even so only as compact layer 2 "beacons". Third, aircraft employ the services of ground stations by performing unicast RS/RA exchanges upon receipt of beacons instead of listening for multicast RA messages and/or sending multicast RS messages. This beacon-oriented unicast RS/RA approach is necessary to conserve the already-scarce available link bandwidth. Moreover, since the numbers of beaconing ground stations operating within a given spatial range must be kept as sparse as possible, it would not be feasible to have different classes of ground stations within the same region observing different protocols. It is therefore highly desirable that all ground stations observe a common language of RS/RA as specified in this document. Note that links of this nature may benefit from compression techniques that reduce the bandwidth necessary for conveying the same amount of data. The IETF lpwan working group is considering possible alternatives: [https://datatracker.ietf.org/wg/lpwan/documents]. Appendix D. Change Log << RFC Editor - remove prior to publication >> Differences from draft-templin-6man-omni-interface-01 to draft- templin-6man-omni-interface-02: o Removed "Primary" flag and supporting text. o Clarified that "Router Lifetime" applies to each ANET interface independently, and that the union of all ANET interface Router Lifetimes determines MSE lifetime. Differences from draft-templin-6man-omni-interface-00 to draft- templin-6man-omni-interface-01: Templin & Whyman Expires August 29, 2020 [Page 32] Internet-Draft IPv6 over OMNI Interfaces February 2020 o "All-MSEs" OMNI LLA defined. Also reserverd fe80::ff00:0000/104 for future use (most likely as "pseudo-multicast"). o Non-normative discussion of alternate OMNI LLA construction form made possible if the 64-bit assumption were relaxed. Differences from draft-templin-atn-aero-interface-21 to draft- templin-6man-omni-interface-00: o Minor clarification on Type-2 ifIndex-tuple encoding. o Draft filename change (replaces draft-templin-atn-aero-interface). Differences from draft-templin-atn-aero-interface-20 to draft- templin-atn-aero-interface-21: o OMNI option format o MTU Differences from draft-templin-atn-aero-interface-19 to draft- templin-atn-aero-interface-20: o MTU Differences from draft-templin-atn-aero-interface-18 to draft- templin-atn-aero-interface-19: o MTU Differences from draft-templin-atn-aero-interface-17 to draft- templin-atn-aero-interface-18: o MTU and RA configuration information updated. Differences from draft-templin-atn-aero-interface-16 to draft- templin-atn-aero-interface-17: o New "Primary" flag in OMNI option. Differences from draft-templin-atn-aero-interface-15 to draft- templin-atn-aero-interface-16: o New note on MSE OMNI LLA uniqueness assurance. o General cleanup. Templin & Whyman Expires August 29, 2020 [Page 33] Internet-Draft IPv6 over OMNI Interfaces February 2020 Differences from draft-templin-atn-aero-interface-14 to draft- templin-atn-aero-interface-15: o General cleanup. Differences from draft-templin-atn-aero-interface-13 to draft- templin-atn-aero-interface-14: o General cleanup. Differences from draft-templin-atn-aero-interface-12 to draft- templin-atn-aero-interface-13: o Minor re-work on "Notify-MSE" (changed to Notification ID). Differences from draft-templin-atn-aero-interface-11 to draft- templin-atn-aero-interface-12: o Removed "Request/Response" OMNI option formats. Now, there is only one OMNI option format that applies to all ND messages. o Added new OMNI option field and supporting text for "Notify-MSE". Differences from draft-templin-atn-aero-interface-10 to draft- templin-atn-aero-interface-11: o Changed name from "aero" to "OMNI" o Resolved AD review comments from Eric Vyncke (posted to atn list) Differences from draft-templin-atn-aero-interface-09 to draft- templin-atn-aero-interface-10: o Renamed ARO option to AERO option o Re-worked Section 13 text to discuss proactive NUD. Differences from draft-templin-atn-aero-interface-08 to draft- templin-atn-aero-interface-09: o Version and reference update Differences from draft-templin-atn-aero-interface-07 to draft- templin-atn-aero-interface-08: o Removed "Classic" and "MS-enabled" link model discussion o Added new figure for MN/AR/MSE model. Templin & Whyman Expires August 29, 2020 [Page 34] Internet-Draft IPv6 over OMNI Interfaces February 2020 o New Section on "Detecting and responding to MSE failure". Differences from draft-templin-atn-aero-interface-06 to draft- templin-atn-aero-interface-07: o Removed "nonce" field from AR option format. Applications that require a nonce can include a standard nonce option if they want to. o Various editorial cleanups. Differences from draft-templin-atn-aero-interface-05 to draft- templin-atn-aero-interface-06: o New Appendix C on "VDL Mode 2 Considerations" o New Appendix D on "RS/RA Messaging as a Single Standard API" o Various significant updates in Section 5, 10 and 12. Differences from draft-templin-atn-aero-interface-04 to draft- templin-atn-aero-interface-05: o Introduced RFC6543 precedent for focusing IPv6 ND messaging to a reserved unicast link-layer address o Introduced new IPv6 ND option for Aero Registration o Specification of MN-to-MSE message exchanges via the ANET access router as a proxy o IANA Considerations updated to include registration requests and set interim RFC4727 option type value. Differences from draft-templin-atn-aero-interface-03 to draft- templin-atn-aero-interface-04: o Removed MNP from aero option format - we already have RIOs and PIOs, and so do not need another option type to include a Prefix. o Clarified that the RA message response must include an aero option to indicate to the MN that the ANET provides a MS. o MTU interactions with link adaptation clarified. Differences from draft-templin-atn-aero-interface-02 to draft- templin-atn-aero-interface-03: Templin & Whyman Expires August 29, 2020 [Page 35] Internet-Draft IPv6 over OMNI Interfaces February 2020 o Sections re-arranged to match RFC4861 structure. o Multiple aero interfaces o Conceptual sending algorithm Differences from draft-templin-atn-aero-interface-01 to draft- templin-atn-aero-interface-02: o Removed discussion of encapsulation (out of scope) o Simplified MTU section o Changed to use a new IPv6 ND option (the "aero option") instead of S/TLLAO o Explained the nature of the interaction between the mobility management service and the air interface Differences from draft-templin-atn-aero-interface-00 to draft- templin-atn-aero-interface-01: o Updates based on list review comments on IETF 'atn' list from 4/29/2019 through 5/7/2019 (issue tracker established) o added list of opportunities afforded by the single virtual link model o added discussion of encapsulation considerations to Section 6 o noted that DupAddrDetectTransmits is set to 0 o removed discussion of IPv6 ND options for prefix assertions. The aero address already includes the MNP, and there are many good reasons for it to continue to do so. Therefore, also including the MNP in an IPv6 ND option would be redundant. o Significant re-work of "Router Discovery" section. o New Appendix B on Prefix Length considerations First draft version (draft-templin-atn-aero-interface-00): o Draft based on consensus decision of ICAO Working Group I Mobility Subgroup March 22, 2019. Templin & Whyman Expires August 29, 2020 [Page 36] Internet-Draft IPv6 over OMNI Interfaces February 2020 Authors' Addresses Fred L. Templin (editor) The Boeing Company P.O. Box 3707 Seattle, WA 98124 USA Email: fltemplin@acm.org Tony Whyman MWA Ltd c/o Inmarsat Global Ltd 99 City Road London EC1Y 1AX England Email: tony.whyman@mccallumwhyman.com Templin & Whyman Expires August 29, 2020 [Page 37]