Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-18
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9434.
|
|
|---|---|---|---|
| Authors | Stuart W. Card , Adam Wiethuechter , Robert Moskowitz , Shuai Zhao , Andrei Gurtov | ||
| Last updated | 2021-12-15 | ||
| Replaces | draft-card-drip-arch | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
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by Dave Thaler
Ready w/issues
IOTDIR IETF Last Call review
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Associated WG milestones |
|
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| Document shepherd | Daniel Migault | ||
| IESG | IESG state | Became RFC 9434 (Informational) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Éric Vyncke | ||
| Send notices to | daniel.migault@ericsson.com |
draft-ietf-drip-arch-18
drip S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 17 June 2022 R. Moskowitz
HTT Consulting
S. Zhao (Editor)
Tencent
A. Gurtov
Linköping University
14 December 2021
Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-18
Abstract
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), plus RID-related communications. This architecture
adheres to the requirements listed in the DRIP Requirements document.
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
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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 17 June 2022.
Copyright Notice
Copyright (c) 2021 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 carefully, as they describe your rights
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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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID)
and Standardization . . . . . . . . . . . . . . . . . . . 3
1.2. Overview of Types of UAS Remote ID . . . . . . . . . . . 4
1.2.1. Broadcast RID . . . . . . . . . . . . . . . . . . . . 4
1.2.2. Network RID . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview of USS Interoperability . . . . . . . . . . . . 7
1.4. Overview of DRIP Architecture . . . . . . . . . . . . . . 8
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 10
2.1. Architecture Terminology . . . . . . . . . . . . . . . . 10
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 10
2.3. Claims, Assertions, Attestations, and Certificates . . . 10
2.4. Additional Definitions . . . . . . . . . . . . . . . . . 11
3. HHIT as the DRIP Entity Identifier . . . . . . . . . . . . . 11
3.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 12
3.2. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 12
3.3. HHIT for DRIP Identifier Registration and Lookup . . . . 14
3.4. HHIT as a Cryptographic Identifier . . . . . . . . . . . 14
4. DRIP Identifier Registration and Registries . . . . . . . . . 14
4.1. Public Information Registry . . . . . . . . . . . . . . . 15
4.1.1. Background . . . . . . . . . . . . . . . . . . . . . 15
4.1.2. DNS as the Public DRIP Identifier Registry . . . . . 15
4.2. Private Information Registry . . . . . . . . . . . . . . 15
4.2.1. Background . . . . . . . . . . . . . . . . . . . . . 15
4.2.2. EPP and RDAP as the Private DRIP Identifier
Registry . . . . . . . . . . . . . . . . . . . . . . 16
4.2.3. Alternative Private DRIP Registry methods . . . . . . 16
5. DRIP Identifier Trust . . . . . . . . . . . . . . . . . . . . 16
6. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 17
6.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 18
6.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 18
7. DRIP Contact . . . . . . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. Privacy & Transparency Considerations . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.1. Normative References . . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM) . . . . . . . . . . . . . . . . . . . . 23
A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 23
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A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 24
A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 24
Appendix B. Automatic Dependent Surveillance Broadcast
(ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 25
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), plus RID-related communications. The architecture takes
into account both current (including proposed) regulations and non-
IETF technical standards.
The architecture adheres to the requirements listed in the DRIP
Requirements document [I-D.ietf-drip-reqs]. The requirements
document provides an extended introduction to the problem space and
use cases.
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID) and
Standardization
UAS Remote Identification (RID) is an application enabler for a UAS
to be identified by Unmanned Aircraft Systems Traffic Management
(UTM) and UAS Service Supplier (USS) (Appendix A) or third parties
entities such as law enforcement. Many considerations (e.g., safety)
dictate that UAS be remotely identifiable.
Civil Aviation Authorities (CAAs) worldwide are mandating UAS RID.
CAAs currently promulgate performance-based regulations that do not
specify techniques, but rather cite industry consensus technical
standards as acceptable means of compliance.
Federal Aviation Administration (FAA)
The FAA published a Notice of Proposed Rule Making [NPRM] in 2019
and thereafter published a "Final Rule" in 2021 [FAA_RID],
imposing requirements on UAS manufacturers and operators, both
commercial and recreational. The rule clearly states that
Automatic Dependent Surveillance Broadcast (ADS-B) Out and
transponders cannot be used to satisfy the RID requirements on UAS
to which the rule applies (see Appendix B).
European Union Aviation Safety Agency (EASA)
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The EASA published a [Delegated] regulation in 2019 imposing
requirements on UAS manufacturers and third-country operators,
including but not limited to RID requirements. The EASA also
published in 2019 an [Implementing] regulation laying down
detailed rules and procedures for UAS operations and operating
personnel.
American Society for Testing and Materials (ASTM)
ASTM International, Technical Committee F38 (UAS), Subcommittee
F38.02 (Aircraft Operations), Work Item WK65041, developed the
ASTM [F3411] Standard Specification for Remote ID and Tracking.
ASTM defines one set of RID information and two means, MAC-layer
broadcast and IP-layer network, of communicating it. If an UAS
uses both communication methods, the same information must be
provided via both means. [F3411] is cited by FAA in its RID final
rule [FAA_RID] as "a potential means of compliance" to a Remote ID
rule.
The 3rd Generation Partnership Project (3GPP)
With release 16, the 3GPP completed the UAS RID requirement study
[TS-22.825] and proposed a set of use cases in the mobile network
and the services that can be offered based on RID. Release 17
specification focuses on enhanced UAS service requirements and
provides the protocol and application architecture support that
will be applicable for both 4G and 5G networks. The study of
Further Architecture Enhancement for Uncrewed Aerial Vehicles
(UAV) and Urban Air Mobility (UAM) [FS_AEUA] in release 18 further
enhances the communication mechanism between UAS and USS/UTM. The
RID discussed in Section 3 may be used as the 3GPP CAA-level ID
for Remote Identification purposes.
1.2. Overview of Types of UAS Remote ID
1.2.1. Broadcast RID
[F3411] defines a set of RID messages for direct, one-way, broadcast
transmissions from the UA over Bluetooth or Wi-Fi. These are
currently defined as MAC-Layer messages. Internet (or other Wide
Area Network) connectivity is only needed for UAS registry
information lookup by Observers using the directly received UAS ID.
Broadcast RID should be functionally usable in situations with no
Internet connectivity.
The minimum Broadcast RID data flow is illustrated in Figure 1.
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+------------------------+
| Unmanned Aircraft (UA) |
+-----------o------------+
|
|
|
| app messages directly over
| one-way RF data link (no IP)
|
|
v
+------------------o-------------------+
| Observer's device (e.g., smartphone) |
+--------------------------------------+
Figure 1
Broadcast RID provides information only about unmanned aircraft (UA)
within direct RF LOS, typically similar to visual Light-Of-Sight
(LOS), with a range up to approximately 1 km. This information may
be 'harvested' from received broadcasts and made available via the
Internet, enabling surveillance of areas too large for local direct
visual observation or direct RF link based ID (see Section 6).
1.2.2. Network RID
[F3411], using the same data dictionary that is the basis of
Broadcast RID messages, defines a Network Remote Identification (Net-
RID) data flow as follows.
* The information to be reported via RID is generated by the UAS
(typically some by the UA and some by the GCS, e.g. their
respective GNSS derived locations).
* The information is sent by the UAS (UA or GCS) via unspecified
means to the cognizant Network Remote Identification Service
Provider (Net-RID SP), typically the USS under which the UAS is
operating if participating in UTM.
* The Net-RID SP publishes via the Discovery and Synchronization
Service (DSS) over the Internet that it has operations in various
4-D airspace volumes, describing the volumes but not the
operations.
* An Observer's device, expected typically but not specified to be
web based, queries a Network Remote Identification Display
Provider (Net-RID DP), typically also a USS, about any operations
in a specific 4-D airspace volume.
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* Using fully specified web based methods over the Internet, the
Net-RID DP queries all Net-RID SP that have operations in volumes
intersecting that of the Observer's query for details on all such
operations.
* The Net-RID DP aggregates information received from all such Net-
RID SP and responds to the Observer's query.
The minimum Net-RID data flow is illustrated in Figure 2:
+-------------+ ******************
| UA | * Internet *
+--o-------o--+ * *
| | * *
| | * * +------------+
| '--------*--(+)-----------*-----o |
| * | * | |
| .--------*--(+)-----------*-----o NET-RID SP |
| | * * | |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
| | * '------*-----o |
| | * * | NET-RID DP |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
+--o-------o--+ * '------*-----o Observer's |
| GCS | * * | Device |
+-------------+ ****************** +------------+
Figure 2
Command and Control (C2) must flow from the GCS to the UA via some
path, currently (in the year of 2021) typically a direct RF link, but
with increasing beyond Visual Line of Sight (BVLOS) operations
expected often to be wireless links at either end with the Internet
between.
Telemetry (at least UA's position and heading) flows from the UA to
the GCS via some path, typically the reverse of the C2 path. Thus,
RID information pertaining to both the GCS and the UA can be sent, by
whichever has Internet connectivity, to the Net-RID SP, typically the
USS managing the UAS operation.
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The Net-RID SP forwards RID information via the Internet to
subscribed Net-RID DP, typically USS. Subscribed Net-RID DP forward
RID information via the Internet to subscribed Observer devices.
Regulations require and [F3411] describes RID data elements that must
be transported end-to-end from the UAS to the subscribed Observer
devices.
[F3411] prescribes the protocols between the Net-RID SP, Net-RID DP,
and the Discovery and Synchronization Service (DSS). It also
prescribes data elements (in JSON) between Observer and Net-RID DP.
DRIP could address standardization of secure protocols between the UA
and GCS (over direct wireless and Internet connection), between the
UAS and the Net-RID SP, and/or between the Net-RID DP and Observer
devices.
Informative note: Neither link layer protocols nor the use of
links (e.g., the link often existing between the GCS and the
UA) for any purpose other than carriage of RID information is
in the scope of [F3411] Network RID.
1.3. Overview of USS Interoperability
With Net-RID, there is direct communication between each UAS and its
USS. Multiple USS exchange information with the assistance of a
Discovery and Synchronization Service (DSS) so all USS collectively
have knowledge about all activities in a 4D airspace.
The interactions among an Observer, multiple UAS, and their USS are
shown in Figure 3.
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+------+ +----------+ +------+
| UAS1 | | Observer | | UAS2 |
+----o-+ +-----o----+ +-o----+
| | |
| | |
******|*************|************|******
* | | | *
* | +---o--+ | *
* | .------o USS3 o------. | *
* | | +--o---+ | | *
* | | | | | *
* +-o--o-+ +--o--+ +-o--o-+ *
* | o----o DSS o-----o | *
* | USS1 | +-----+ | USS2 | *
* | o----------------o | *
* +------+ +------+ *
* *
* Internet *
****************************************
Figure 3
1.4. Overview of DRIP Architecture
Figure 4 illustrates the general UAS RID usage scenario. Broadcast
RID links are not shown as they reach from any UA to any listening
receiver in range and thus would obscure the intent of the figure.
Figure 4 shows, as context, some entities and interfaces beyond the
scope of DRIP (as currently (2022) chartered).
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*************** ***************
* UAS1 * * UAS2 *
* * * *
* +--------+ * DAA/V2V * +--------+ *
* | UA o--*----------------------------------------*--o UA | *
* +--o--o--+ * * +--o--o--+ *
* | | * +------+ Lookups +------+ * | | *
* | | * | GPOD o------. .------o PSOD | * | | *
* | | * +------+ | | +------+ * | | *
* | | * | | * | | *
* C2 | | * V2I ************ V2I * | | C2 *
* | '-----*--------------* *--------------*-----' | *
* | * * * * | *
* | o====NetRID====* *====NetRID====o | *
* +--o--+ * * Internet * * +--o--+ *
* | GCS o-----*--------------* *--------------*-----o GCS | *
* +-----+ * Registration * * Registration * +-----+ *
* * (and UTM) * * (and UTM) * *
*************** ************ ***************
| | |
+----------+ | | | +----------+
| Public o---' | '---o Private |
| Registry | | | Registry |
+----------+ | +----------+
+--o--+
| DNS |
+-----+
GPOD: General Public Observer Device (for brevity in this figure)
PSOD: Public Safety Observer Device (for brevity in this figure)
Figure 4
DRIP is meant to leverage existing Internet resources (standard
protocols, services, infrastructures, and business models) to meet
UAS RID and closely related needs. DRIP will specify how to apply
IETF standards, complementing [F3411] and other external standards,
to satisfy UAS RID requirements.
This document outlines the DRIP architecture in the context of the
UAS RID architecture. This includes presenting the gaps between the
CAAs' Concepts of Operations and [F3411] as it relates to the use of
Internet technologies and UA direct RF communications. Issues
include, but are not limited to:
o Design of trustworthy remote identifiers (Section 3).
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- Mechanisms to leverage Domain Name System (DNS [RFC1034]),
Extensible Provisioning Protocol (EPP [RFC5731]) and
Registration Data Access Protocol (RDAP) ([RFC7482]) for
publishing public and private information (see Section 4.1 and
Section 4.2).
- Specific authentication methods and message payload formats to
enable verification that Broadcast RID messages were sent by
the claimed sender (Section 5) and that sender is in the
claimed registry (Section 4 and Section 5).
- Harvesting broadcast RID messages for UTM inclusion
(Section 6).
- Methods for instantly establishing secure communications
between an Observer and the pilot of an observed UAS
(Section 7).
- Privacy in RID messages (PII protection) (Section 10).
2. Terms and Definitions
2.1. Architecture Terminology
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 above.
2.2. Abbreviations
EdDSA: Edwards-Curve Digital Signature Algorithm
HHIT: Hierarchical HIT
HIP: Host Identity Protocol
HIT: Host Identity Tag
2.3. Claims, Assertions, Attestations, and Certificates
This section introduces the terms "Claims", "Assertions",
"Attestations", and "Certificates" as used in DRIP. DRIP certificate
has a different context compared with security certificates and
Public Key Infrastructure used in X.509.
Claims:
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A claim in DRIP is a predicate (e.g., "X is Y", "X has property
Y", and most importantly "X owns Y" or "X is owned by Y").
Assertions:
An assertion in DRIP is a set of claims. This definition is
borrowed from JWT [RFC7519] and CWT [RFC8392].
Attestations:
An attestation in DRIP is a signed assertion. The signer may be
the claimant or a related party with stake in the assertion(s).
Under DRIP this is normally used when an entity asserts a
relationship with another entity, along with other information,
and the asserting entity signs the assertion, thereby making it an
attestation.
Certificates:
A certificate in DRIP is an attestation, strictly over identity
information, signed by a third party. This third party should be
one with no stake in the attestation(s) its signing over.
2.4. Additional Definitions
This document uses terms defined in [I-D.ietf-drip-reqs].
3. HHIT as the DRIP Entity Identifier
This section describes the DRIP architectural approach to meeting the
basic requirements of a DRIP entity identifier within external
technical standard ASTM [F3411] and regulatory constraints. It
justifies and explains the use of Hierarchical Host Identity Tags
(HHITs) as self-asserting IPv6 addresses suitable as a UAS ID type
and more generally as trustworthy multipurpose remote identifiers.
Self-asserting in this usage is given the Host Identity (HI), the
HHIT ORCHID construction and a signature of the HHIT by the HI can
both be validated. The explicit registration hierarchy within the
HHIT provides registry discovery (managed by a Registrar) to either
yield the HI for 3rd-party (who is looking for ID attestation)
validation or prove the HHIT and HI have uniquely been registered.
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3.1. UAS Remote Identifiers Problem Space
A DRIP entity identifier needs to be "Trustworthy" (See DRIP
Requirement GEN-1, ID-4 and ID-5 in [I-D.ietf-drip-reqs]). This
means that given a sufficient collection of RID messages, an Observer
can establish that the identifier claimed therein uniquely belongs to
the claimant: that the only way for any other entity to prove
ownership of that identifier would be to obtain information that
ought to be available only to the legitimate owner of the identifier
(e.g., a cryptographic private key).
To satisfy DRIP requirements and maintain important security
properties, the DRIP identifier should be self-generated by the
entity it names (e.g., a UAS) and registered (e.g., with a USS, see
Requirements GEN-3 and ID-2).
Broadcast RID, especially its support for Bluetooth 4, imposes severe
constraints. ASTM RID [F3411] allows a UAS ID of types 1, 2 and 3 of
20 bytes; a revision to [F3411], currently in balloting (as of Oct
2021), adds type 4, Session IDs, to be standardized by IETF and other
standard development organizations (SDOs) as extensions to ASTM RID,
consumes one of those bytes to index the sub-type, leaving only 19
for the identifier (see DRIP Requirement ID-1). Likewise, the
maximum ASTM RID [F3411] Authentication Message payload is 201 bytes
for most authentication types, but for type 5, also added in this
revision, for IETF and other SDOs to develop Specific Authentication
Methods as extensions to ASTM RID, one byte is consumed to index the
sub-type, leaving only 200 for DRIP authentication payloads,
including one or more DRIP entity identifiers and associated
authentication data.
3.2. HHIT as A Trustworthy DRIP Entity Identifier
A Remote ID that can be trustworthily used in the RID Broadcast mode
can be built from an asymmetric keypair. Rather than using a key
signing operation to claim ownership of an ID that does not guarantee
name uniqueness, in this method the ID is cryptographically derived
directly from the public key. The proof of ID ownership (verifiable
attestation, versus mere claim) is guaranteed by signing this
cryptographic ID with the associated private key. The association
between the ID and the private key is ensured by cryptographically
binding the public key with the ID, more specifically the ID results
from the hash of the public key. It is statistically hard for
another entity to create a public key that would generate (spoof) the
ID.
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The basic HIT is designed statistically unique through the
cryptographic hash feature of second-preimage resistance. The
cryptographically-bound addition of the Hierarchy and an HHIT
registration process (e.g. based on Extensible Provisioning Protocol,
[RFC5730]) provide complete, global HHIT uniqueness. This
registration forces the attacker to generate the same public key
rather than a public key that generates the same HHIT. This is in
contrast to general IDs (e.g. a UUID or device serial number) as the
subject in an X.509 certificate.
A DRIP identifier can be assigned to a UAS as a static HHIT by its
manufacturer, such as a single HI and derived HHIT encoded as a
hardware serial number per [CTA2063A]. Such a static HHIT SHOULD
only be used to bind one-time use DRIP identifiers to the unique UA.
Depending upon implementation, this may leave a HI private key in the
possession of the manufacturer (more details in Section 9).
A UA equipped for Broadcast RID SHOULD be provisioned not only with
its HHIT but also with the HI public key from which the HHIT was
derived and the corresponding private key, to enable message
signature. A UAS equipped for Network RID SHOULD be provisioned
likewise; the private key resides only in the ultimate source of
Network RID messages (i.e. on the UA itself if the GCS is merely
relaying rather than sourcing Network RID messages). Each Observer
device SHOULD be provisioned either with public keys of the DRIP
identifier root registries or certificates for subordinate
registries.
HHITs can also be used throughout the USS/UTM system. The Operators,
Private Information Registries, as well as other UTM entities, can
use HHITs for their IDs. Such HHITs can facilitate DRIP security
functions such as used with HIP to strongly mutually authenticate and
encrypt communications.
A self-attestation of a HHIT used as a UAS ID can be done in as
little as 84 bytes, by avoiding an explicit encoding technology like
ASN.1 or Concise Binary Object Representation (CBOR [RFC8949]). This
attestation consists of only the HHIT, a timestamp, and the EdDSA
signature on them.
In general, Internet access may be needed to validate Attestations or
Certificates. This may be obviated in the most common cases (e.g.
attestation of the UAS ID), even in disconnected environments, by
prepopulating small caches on Observer devices with Registry public
keys and a chain of Attestations or Certificates (tracing a path
through the Registry tree). This is assuming all parties on the
trust path also use HHITs for their identities.
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3.3. HHIT for DRIP Identifier Registration and Lookup
Remote ID needs a deterministic lookup mechanism that rapidly
provides actionable information about the identified UA. Given the
size constraints imposed by the Bluetooth 4 broadcast media, the UAS
ID itself needs to be a non-spoofable inquiry input into the lookup.
A DRIP registration process based on the explicit hierarchy within a
HHIT provides manageable uniqueness of the HI for the HHIT. This is
the defense against a cryptographic hash second pre-image attack on
the HHIT (e.g. multiple HIs yielding the same HHIT, see Requirement
ID-3). A lookup of the HHIT into this registration data provides the
registered HI for HHIT proof. A first-come-first-serve registration
for a HHIT provides deterministic access to any other needed
actionable information based on inquiry access authority (more
details in Section 4.2).
3.4. HHIT as a Cryptographic Identifier
The only (known to the authors at the time of this writing) extant
types of IP address compatible identifiers cryptographically derived
from the public keys of the identified entities are Cryptographically
Generated Addresses (CGAs) [RFC3972] and Host Identity Tags (HITs)
[RFC7401]. CGAs and HITs lack registration/retrieval capability. To
provide this, each HHIT embeds plaintext information designating the
hierarchy within which is registered and a cryptographic hash of that
information concatenated with the entity's public key, etc. Although
hash collisions may occur, the registrar can detect them and reject
registration requests rather than issue credentials, e.g., by
enforcing a first-claimed, first-attested policy. Pre-image hash
attacks are also mitigated through this registration process, locking
the HHIT to a specific HI
4. DRIP Identifier Registration and Registries
DRIP registries hold both public and private UAS information
resulting from the DRIP identifier registration process. Given these
different uses, and to improve scalability, security, and simplicity
of administration, the public and private information can be stored
in different registries. This section introduces the public and
private information registries for DRIP identifiers. This DRIP
Identifier registration process satisfies the following DRIP
requirements defined in [I-D.ietf-drip-reqs]: GEN-3, GEN-4, ID-2, ID-
4, ID-6, PRIV-3, PRIV-4, REG-1, PRG-2, REG-3 and REG-4.
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4.1. Public Information Registry
4.1.1. Background
The public registry provides trustable information such as
attestations of RID ownership and registration with the HDA
(Hierarchical HIT Domain Authority). Optionally, pointers to the
registries for the HDA and RAA (Registered Assigning
Authority)implicit in the RID can be included (e.g., for HDA and RAA
HHIT|HI used in attestation signing operations). This public
information will be principally used by Observers of Broadcast RID
messages. Data on UAS that only use Network RID, is available via an
Observer's Net-RID DP that would tend to directly provide all public
registry information. The Observer may visually "see" these Net-RID
UAS, but they may be silent to the Observer. The Net-RID DP is the
only source of information based on a query for an airspace volume.
4.1.2. DNS as the Public DRIP Identifier Registry
A DRIP identifier SHOULD be registered as an Internet domain name (at
an arbitrary level in the hierarchy, e.g. in .ip6.arpa). Thus DNS
can provide all the needed public DRIP information. A standardized
HHIT FQDN (Fully Qualified Domain Name) can deliver the HI via a HIP
RR (Resource Record) [RFC8005] and other public information (e.g.,
RRA and HDA PTRs, and HIP RVS (Rendezvous Servers) [RFC8004]). These
public information registries can use secure DNS transport (e.g. DNS
over TLS) to deliver public information that is not inherently
trustable (e.g. everything other than attestations).
4.2. Private Information Registry
4.2.1. Background
The private information required for DRIP identifiers is similar to
that required for Internet domain name registration. A DRIP
identifier solution can leverage existing Internet resources:
registration protocols, infrastructure, and business models, by
fitting into an ID structure compatible with DNS names. The HHIT
hierarchy can provide the needed scalability and management
structure. It is expected that the private registry function will be
provided by the same organizations that run a USS, and likely
integrated with a USS. The lookup function may be implemented by the
Net-RID DPs.
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4.2.2. EPP and RDAP as the Private DRIP Identifier Registry
A DRIP private information registry supports essential registry
operations (e.g. add, delete, update, query) using interoperable open
standard protocols. It can accomplish this by using the Extensible
Provisioning Protocol (EPP [RFC5730]) and the Registry Data Access
Protocol (RDAP RFC7480] [RFC7482] [RFC7483]). The DRIP private
information registry in which a given UAS is registered needs to be
findable, starting from the UAS ID, using the methods specified in
[RFC7484].
4.2.3. Alternative Private DRIP Registry methods
A DRIP private information registry might be an access controlled DNS
(e.g. via DNS over TLS). Additionally, WebFinger [RFC7033] can be
deployed. These alternative methods may be used by Net-RID DP with
specific customers.
5. DRIP Identifier Trust
While the DRIP entity identifier is self-asserting, it alone does not
provide the "trustworthiness" specified in [I-D.ietf-drip-reqs]. For
that it MUST be registered (under DRIP Registries) and be actively
used by the party (in most cases the UA). For Broadcast RID this is
a challenge to balance the original requirements of Broadcast RID and
the efforts needed to satisfy the DRIP requirements all under severe
constraints.
From received Broadcast RID messages and information that can be
looked up using the received UAS ID in online registries or local
caches, it is possible to establish levels of trust in the asserted
information and the Operator.
An optimization of different DRIP Authentication Messages allows an
Observer, without Internet connection (offline) or with (online), to
be able to validate a UAS DRIP ID in real-time. First is the sending
of Broadcast Attestations (over DRIP Link Authentication Messages)
containing the relevant registration of the UA's DRIP ID in the
claimed Registry. Next is sending DRIP Wrapper Authentication
Messages that sign over both static (e.g. above registration) and
dynamically changing data (such as UA location data). Combining
these two sets of information an Observer can piece together a chain
of trust and real-time evidence to make their determination of the
UAs claims.
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This process (combining the DRIP entity identifier, Registries and
Authentication Formats for Broadcast RID) can satisfy the following
DRIP requirement defined in [I-D.ietf-drip-reqs]: GEN-1, GEN-2, GEN-
3, ID-2, ID-3, ID-4 and ID-5.
6. Harvesting Broadcast Remote ID messages for UTM Inclusion
ASTM anticipated that regulators would require both Broadcast RID and
Network RID for large UAS, but allow RID requirements for small UAS
to be satisfied with the operator's choice of either Broadcast RID or
Network RID. The EASA initially specified Broadcast RID for UAS of
essentially all UAS and is now also considering Network RID. The FAA
RID Final Rules [FAA_RID] permit only Broadcast RID for rule
compliance, but still encourage Network RID for complementary
functionality, especially in support of UTM.
One obvious opportunity is to enhance the architecture with gateways
from Broadcast RID to Network RID. This provides the best of both
and gives regulators and operators flexibility. It offers advantages
over either form of RID alone: greater fidelity than Network RID
reporting of planned area operations; surveillance of areas too large
for local direct visual observation and direct RF-LOS link based
Broadcast RID (e.g., a city or a national forest).
These gateways could be pre-positioned (e.g. around airports, public
gatherings, and other sensitive areas) and/or crowd-sourced (as
nothing more than a smartphone with a suitable app is needed). As
Broadcast RID media have limited range, gateways receiving messages
claiming locations far from the gateway can alert authorities or a
SDSP to the failed sanity check possibly indicating intent to
deceive. Surveillance SDSPs can use messages with precise date/time/
position stamps from the gateways to multilaterate UA location,
independent of the locations claimed in the messages, which are
entirely operator self-reported in UAS RID and UTM, and thus are
subject not only to natural time lag and error but also operator
misconfiguration or intentional deception.
Further, gateways with additional sensors (e.g. smartphones with
cameras) can provide independent information on the UA type and size,
confirming or refuting those claims made in the RID messages. This
Crowd Sourced Remote ID (CS-RID) would be a significant enhancement,
beyond baseline DRIP functionality; if implemented, it adds two more
entity types.
This approach satisfies the following DRIP requirements defined in
[I-D.ietf-drip-reqs]: GEN-5, GEN-11, and REG-1.
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6.1. The CS-RID Finder
A CS-RID Finder is the gateway for Broadcast Remote ID Messages into
the UTM. It performs this gateway function via a CS-RID SDSP. A CS-
RID Finder could implement, integrate, or accept outputs from, a
Broadcast RID receiver. However, it should not depend upon a direct
interface with a GCS, Net-RID SP, Net-RID DP or Network RID client.
It would present a TBD interface to a CS-RID SDSP, similar to but
readily distinguishable from that between a GCS and a Net-RID SP.
6.2. The CS-RID SDSP
A CS-RID SDSP aggregates and processes (e.g., estimates UA location
using including using multilateration when possible) information
collected by CS-RID Finders. A CS-RID SDSP should appear (i.e.
present the same interface) to a Net-RID SP as a Net-RID DP.
7. DRIP Contact
One of the ways in which DRIP can enhance [F3411] with immediately
actionable information is by enabling an Observer to instantly
initiate secure communications with the UAS remote pilot, Pilot In
Command, operator, USS under which the operation is being flown, or
other entity potentially able to furnish further information
regarding the operation and its intent and/or to immediately
influence further conduct or termination of the operation (e.g., land
or otherwise exit an airspace volume). Such potentially distracting
communications demand strong "AAA" (Authentication, Attestation,
Authorization, Access Control, Accounting, Attribution, Audit) per
applicable policies (e.g., of the cognizant CAA).
A DRIP entity identifier based on a HHIT as outlined in Section 3
embeds an identifier of the registry in which it can be found
(expected typically to be the USS under which the UAS is flying) and
the procedures outlined in Section 5 enable Observer verification of
that relationship. A DRIP entity identifier with suitable records in
public and private registries as outlined in Section 5 can enable
lookup not only of information regarding the UAS but also identities
of and pointers to information regarding the various associated
entities (e.g., the USS under which the UAS is flying an operation),
including means of contacting those associated entities (i.e.,
locators, typically IP addresses). An Observer equipped with HIP can
initiate a Base Exchange (BEX) and establish a Bound End to End
Tunnel (BEET) protected by IPsec Encapsulating Security Payload (ESP)
encryption to a likewise equipped and identified entity: the UA
itself, if operating autonomously; the GCS, if the UA is remotely
piloted and the necessary records have been populated in DNS;
likewise the USS, etc. Certain preconditions are necessary: each
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party to the communication needs a currently usable means (typically
DNS) of resolving the other party's DRIP entity identifier to a
currently usable locator (IP address); and there must be currently
usable bidirectional IP (not necessarily Internet) connectivity
between the parties. Given a BEET, arbitrary standard higher layer
protocols can then be used for Observer to Pilot (O2P) communications
(e.g., SIP [RFC3261] et seq), V2X communications (e.g., [MAVLink]),
etc. This approach satisfies DRIP requirement GEN-6 Contact,
supports satisfaction of requirements [I-D.ietf-drip-reqs] GEN-8,
GEN-9, PRIV-2, PRIV-5 and REG-3, and is compatible with all other
DRIP requirements.
8. IANA Considerations
This document does not make any IANA request.
9. Security Considerations
The security provided by asymmetric cryptographic techniques depends
upon protection of the private keys. A manufacturer that embeds a
private key in an UA may have retained a copy. A manufacturer whose
UA are configured by a closed source application on the GCS which
communicates over the Internet with the factory may be sending a copy
of a UA or GCS self-generated key back to the factory. Keys may be
extracted from a GCS or UA. The RID sender of a small harmless UA
(or the entire UA) could be carried by a larger dangerous UA as a
"false flag." Compromise of a registry private key could do
widespread harm. Key revocation procedures are as yet to be
determined. These risks are in addition to those involving Operator
key management practices.
10. Privacy & Transparency Considerations
Broadcast RID messages can contain Personally Identifiable
Information (PII). A viable architecture for PII protection would be
symmetric encryption of the PII using a session key known to the UAS
and its USS. Authorized Observers could obtain plaintext in either
of two ways. An Observer can send the UAS ID and the cyphertext to a
server that offers decryption as a service. An Observer can send the
UAS ID only to a server that returns the session key, so that
Observer can directly locally decrypt all cyphertext sent by that UA
during that session (UAS operation). In either case, the server can
be: a Public Safety USS; the Observer's own USS; or the UA's USS if
the latter can be determined (which under DRIP it can be, from the
UAS ID itself). PII can be protected unless the UAS is informed
otherwise. This could come as part of UTM operation authorization.
It can be special instructions at the start or during an operation.
PII protection MUST not be used if the UAS loses connectivity to the
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USS. The UAS always has the option to abort the operation if PII
protection is disallowed.
11. References
11.1. Normative References
[I-D.ietf-drip-reqs]
Card, S. W., Wiethuechter, A., Moskowitz, R., and A.
Gurtov, "Drone Remote Identification Protocol (DRIP)
Requirements", Work in Progress, Internet-Draft, draft-
ietf-drip-reqs-18, 8 September 2021,
<https://www.ietf.org/archive/id/draft-ietf-drip-reqs-
18.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References
[CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers",
2019.
[Delegated]
European Union Aviation Safety Agency (EASA), "EU
Commission Delegated Regulation 2019/945 of 12 March 2019
on unmanned aircraft systems and on third-country
operators of unmanned aircraft systems", 2019.
[F3411] ASTM International, "Standard Specification for Remote ID
and Tracking", February 2020,
<http://www.astm.org/cgi-bin/resolver.cgi?F3411>.
[FAA_RID] United States Federal Aviation Administration (FAA),
"Remote Identification of Unmanned Aircraft", 2021,
<https://www.govinfo.gov/content/pkg/FR-2021-01-15/
pdf/2020-28948.pdf>.
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[FAA_UAS_Concept_Of_Ops]
United States Federal Aviation Administration (FAA),
"Unmanned Aircraft System (UAS) Traffic Management (UTM)
Concept of Operations (V2.0)", 2020,
<https://www.faa.gov/uas/research_development/
traffic_management/media/UTM_ConOps_v2.pdf>.
[FS_AEUA] "Study of Further Architecture Enhancement for UAV and
UAM", 2021, <https://www.3gpp.org/ftp/tsg_sa/WG2_Arch/
TSGS2_147E_Electronic_2021-10/Docs/S2-2107092.zip>.
[Implementing]
European Union Aviation Safety Agency (EASA), "EU
Commission Implementing Regulation 2019/947 of 24 May 2019
on the rules and procedures for the operation of unmanned
aircraft", 2019.
[LAANC] United States Federal Aviation Administration (FAA), "Low
Altitude Authorization and Notification Capability", n.d.,
<https://www.faa.gov/uas/programs_partnerships/
data_exchange/>.
[MAVLink] "Micro Air Vehicle Communication Protocol", 2021,
<http://mavlink.io/>.
[NPRM] United States Federal Aviation Administration (FAA),
"Notice of Proposed Rule Making on Remote Identification
of Unmanned Aircraft Systems", 2019.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
<https://www.rfc-editor.org/info/rfc5730>.
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[RFC5731] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Domain Name Mapping", STD 69, RFC 5731,
DOI 10.17487/RFC5731, August 2009,
<https://www.rfc-editor.org/info/rfc5731>.
[RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr,
"WebFinger", RFC 7033, DOI 10.17487/RFC7033, September
2013, <https://www.rfc-editor.org/info/rfc7033>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<https://www.rfc-editor.org/info/rfc7401>.
[RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
Protocol (RDAP) Query Format", RFC 7482,
DOI 10.17487/RFC7482, March 2015,
<https://www.rfc-editor.org/info/rfc7482>.
[RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
Registration Data Access Protocol (RDAP)", RFC 7483,
DOI 10.17487/RFC7483, March 2015,
<https://www.rfc-editor.org/info/rfc7483>.
[RFC7484] Blanchet, M., "Finding the Authoritative Registration Data
(RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March
2015, <https://www.rfc-editor.org/info/rfc7484>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <https://www.rfc-editor.org/info/rfc8004>.
[RFC8005] Laganier, J., "Host Identity Protocol (HIP) Domain Name
System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005,
October 2016, <https://www.rfc-editor.org/info/rfc8005>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
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[TS-22.825]
3GPP, "Study on Remote Identification of Unmanned Aerial
Systems (UAS)", n.d.,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3527>.
[U-Space] European Organization for the Safety of Air Navigation
(EUROCONTROL), "U-space Concept of Operations", 2019,
<https://www.sesarju.eu/sites/default/files/documents/u-
space/CORUS%20ConOps%20vol2.pdf>.
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM)
A.1. Operation Concept
The National Aeronautics and Space Administration (NASA) and FAA's
effort of integrating UAS's operation into the national airspace
system (NAS) led to the development of the concept of UTM and the
ecosystem around it. The UTM concept was initially presented in 2013
and version 2.0 was published in 2020 [FAA_UAS_Concept_Of_Ops].
The eventual concept refinement, initial prototype implementation,
and testing were conducted by the UTM research transition team which
is the joint workforce by FAA and NASA. World efforts took place
afterward. The Single European Sky ATM Research (SESAR) started the
CORUS project to research its UTM counterpart concept, namely
[U-Space]. This effort is led by the European Organization for the
Safety of Air Navigation (Eurocontrol).
Both NASA and SESAR have published the UTM concept of operations to
guide the development of their future air traffic management (ATM)
system and ensure safe and efficient integration of manned and
unmanned aircraft into the national airspace.
The UTM comprises UAS operation infrastructure, procedures and local
regulation compliance policies to guarantee safe UAS integration and
operation. The main functionality of a UTM includes, but is not
limited to, providing means of communication between UAS operators
and service providers and a platform to facilitate communication
among UAS service providers.
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A.2. UAS Service Supplier (USS)
A USS plays an important role to fulfill the key performance
indicators (KPIs) that a UTM has to offer. Such an Entity acts as a
proxy between UAS operators and UTM service providers. It provides
services like real-time UAS traffic monitoring and planning,
aeronautical data archiving, airspace and violation control,
interacting with other third-party control entities, etc. A USS can
coexist with other USS to build a large service coverage map that can
load-balance, relay, and share UAS traffic information.
The FAA works with UAS industry shareholders and promotes the Low
Altitude Authorization and Notification Capability [LAANC] program
which is the first system to realize some of the UTM envisioned
functionality. The LAANC program can automate the UAS operational
intent (flight plan) submission and application for airspace
authorization in real-time by checking against multiple aeronautical
databases such as airspace classification and operating rules
associated with it, FAA UAS facility map, special use airspace,
Notice to Airmen (NOTAM), and Temporary Flight Restriction (TFR).
A.3. UTM Use Cases for UAS Operations
This section illustrates a couple of use case scenarios where UAS
participation in UTM has significant safety improvement.
1. For a UAS participating in UTM and taking off or landing in a
controlled airspace (e.g., Class Bravo, Charlie, Delta, and Echo
in the United States), the USS under which the UAS is operating
is responsible for verifying UA registration, authenticating the
UAS operational intent (flight plan) by checking against
designated UAS facility map database, obtaining the air traffic
control (ATC) authorization, and monitoring the UAS flight path
in order to maintain safe margins and follow the pre-authorized
sequence of authorized 4-D volumes (route).
2. For a UAS participating in UTM and taking off or landing in
uncontrolled airspace (ex. Class Golf in the United States),
pre-flight authorization must be obtained from a USS when
operating beyond-visual-of-sight (BVLOS). The USS either accepts
or rejects the received operational intent (flight plan) from the
UAS. Accepted UAS operation may share its current flight data
such as GPS position and altitude to USS. The USS may keep the
UAS operation status near real-time and may keep it as a record
for overall airspace air traffic monitoring.
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Appendix B. Automatic Dependent Surveillance Broadcast (ADS-B)
The ADS-B is the de jure technology used in manned aviation for
sharing location information, from the aircraft to ground and
satellite-based systems, designed in the early 2000s. Broadcast RID
is conceptually similar to ADS-B, but with the receiver target being
the general public on generally available devices (e.g. smartphones).
For numerous technical reasons, ADS-B itself is not suitable for low-
flying small UA. Technical reasons include but not limited to the
following:
1. Lack of support for the 1090 MHz ADS-B channel on any consumer
handheld devices
2. Weight and cost of ADS-B transponders on CSWaP constrained UA
3. Limited bandwidth of both uplink and downlink, which would likely
be saturated by large numbers of UAS, endangering manned aviation
Understanding these technical shortcomings, regulators worldwide have
ruled out the use of ADS-B for the small UAS for which UAS RID and
DRIP are intended.
Acknowledgements
The work of the FAA's UAS Identification and Tracking (UAS ID)
Aviation Rulemaking Committee (ARC) is the foundation of later ASTM
and proposed IETF DRIP WG efforts. The work of ASTM F38.02 in
balancing the interests of diverse stakeholders is essential to the
necessary rapid and widespread deployment of UAS RID. Thanks to
Alexandre Petrescu and Stephan Wenger for the helpful and positive
comments. Thanks to chairs Daniel Migault and Mohamed Boucadair for
direction of our team of authors and editor, some of whom are
newcomers to writing IETF documents. Thanks especially to Internet
Area Director Eric Vyncke for guidance and support.
Authors' Addresses
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY, 13495
United States of America
Email: stu.card@axenterprize.com
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Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY, 13495
United States of America
Email: adam.wiethuechter@axenterprize.com
Robert Moskowitz
HTT Consulting
Oak Park, MI, 48237
United States of America
Email: rgm@labs.htt-consult.com
Shuai Zhao
Tencent
2747 Park Blvd
Palo Alto, 94588
United States of America
Email: shuai.zhao@ieee.org
Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping Linköping
Sweden
Email: gurtov@acm.org
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