Join Proxy for Bootstrapping of Constrained Network Elements
draft-ietf-anima-constrained-join-proxy-17
| Document | Type | Active Internet-Draft (anima WG) | |
|---|---|---|---|
| Authors | Michael Richardson , Peter Van der Stok , Panos Kampanakis , Esko Dijk | ||
| Last updated | 2025-07-05 | ||
| Replaces | draft-vanderstok-anima-constrained-join-proxy | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews |
GENART IETF Last Call review
(of
-14)
by Ines Robles
Almost ready
ARTART IETF Last Call review
(of
-10)
by Rich Salz
Ready w/nits
GENART IETF Last Call review
(of
-09)
by Ines Robles
On the right track
OPSDIR IETF Last Call review
(of
-09)
by Jürgen Schönwälder
Serious issues
IOTDIR IETF Last Call review
(of
-05)
by Russ Housley
On the right track
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Sheng Jiang | ||
| Shepherd write-up | Show Last changed 2022-02-24 | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Mahesh Jethanandani | ||
| Send notices to | jiangsheng@huawei.com, shengjiang@bupt.edu.cn | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA expert review state | Issues identified | ||
| IANA expert review comments | From the designated expert for Resource Type (rt=) Link Target Attribute Values: I looked at the registration requests in the draft. They use somewhat unusual language about discovering ports - resource discovery is understood to discover resources. For brski.jp, this appears to be about discovering a CoAP or CoAPs entry point (without describing how exactly that is then used, e.g., what happens if that has a different IP address in the authority than the request address). For brski.rjp, this appears to be about discovering an entry point for a protocol that I don’t seem to fully understand the description for. I didn’t try to obtain a deep understanding of the protocol before writing this, but I would prefer if the language used for the description were understandable for other registrants in this registry, i.e., discussing resources, not ports (port numbers?). All the other criteria for a registration appear to be fulfilled. |
draft-ietf-anima-constrained-join-proxy-17
anima M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Standards Track P. van der Stok
Expires: 6 January 2026 vanderstok consultancy
P. Kampanakis
Cisco Systems
E. Dijk
IoTconsultancy.nl
5 July 2025
Join Proxy for Bootstrapping of Constrained Network Elements
draft-ietf-anima-constrained-join-proxy-17
Abstract
This document extends the constrained Bootstrapping Remote Secure Key
Infrastructures (cBRSKI) onboarding protocol by adding a new network
function, the constrained Join Proxy. This function can be
implemented on a constrained node. The goal of the Join Proxy is to
help new constrained nodes ("Pledges") securely onboard into a new IP
network using the cBRSKI protocol. It acts as a circuit proxy for
User Datagram Protocol (UDP) packets that carry the onboarding
messages. The solution is extensible to support other UDP-based
onboarding protocols as well. The Join Proxy functionality is
designed for use in constrained networks, including IPv6 over Low-
Power Wireless Personal Area Networks (6LoWPAN) based networks in
which the onboarding authority server ("Registrar") may be multiple
IP hops away from a Pledge. Despite this distance, the Pledge only
needs to use link-local communication to complete cBRSKI onboarding.
Two modes of Join Proxy operation are defined, stateless and
stateful, to allow different trade-offs regarding resource usage,
implementation complexity and security.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-anima-constrained-join-
proxy/.
Discussion of this document takes place on the anima Working Group
mailing list (mailto:anima@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/anima/. Subscribe at
https://www.ietf.org/mailman/listinfo/anima/.
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Source for this draft and an issue tracker can be found at
https://github.com/anima-wg/constrained-join-proxy.
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 6 January 2026.
Copyright Notice
Copyright (c) 2025 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
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Join Proxy Problem Statement and Solution . . . . . . . . . . 6
3.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 6
3.2. Solution . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Solution for Multiple Registrars . . . . . . . . . . . . 8
3.4. Forming 6LoWPAN Mesh Networks with cBRSKI . . . . . . . . 8
4. Join Proxy Specification . . . . . . . . . . . . . . . . . . 10
4.1. Mode Implementation and Configuration Requirements . . . 10
4.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3. Stateful Join Proxy . . . . . . . . . . . . . . . . . . . 12
4.4. Stateless Join Proxy . . . . . . . . . . . . . . . . . . 14
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4.5. JPY Protocol and Messages . . . . . . . . . . . . . . . . 16
4.5.1. JPY Message Structure . . . . . . . . . . . . . . . . 17
4.5.2. JPY Message Port Usage . . . . . . . . . . . . . . . 17
4.5.3. JPY Message Overhead and MTU Size . . . . . . . . . . 18
4.5.4. JPY Message Security . . . . . . . . . . . . . . . . 18
4.5.5. Example Format for JPY Header Data . . . . . . . . . 19
4.5.6. Processing by Registrar . . . . . . . . . . . . . . . 20
4.6. Handling Multiple Registrars . . . . . . . . . . . . . . 21
5. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1. Join Proxy Discovers Registrar . . . . . . . . . . . . . 22
5.1.1. Stateless Case . . . . . . . . . . . . . . . . . . . 22
5.1.2. Stateful Case . . . . . . . . . . . . . . . . . . . . 23
5.1.3. Examples . . . . . . . . . . . . . . . . . . . . . . 24
5.2. Pledge Discovers Join Proxy . . . . . . . . . . . . . . . 24
5.3. Pledge Discovers Multiple Join Ports . . . . . . . . . . 25
6. Comparison of Stateless and Stateful Modes . . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
8.1. Resource Type Attributes Registry . . . . . . . . . . . . 31
8.2. coaps+jpy Scheme Registration . . . . . . . . . . . . . . 31
8.3. Service Name and Transport Protocol Port Number
Registry . . . . . . . . . . . . . . . . . . . . . . . . 32
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.1. Normative References . . . . . . . . . . . . . . . . . . 32
9.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Stateless Join Proxy JPY Message Examples . . . . . 36
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 38
Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction
The Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol
described in [RFC8995] provides a solution for a secure zero-touch
(automated) onboarding of new, unconfigured devices. In the context
of BRSKI, new devices, called "Pledges", are equipped with a factory-
installed Initial Device Identifier (IDevID) [ieee802-1AR], and are
enrolled into a network. BRSKI makes use of Enrollment over Secure
Transport (EST) [RFC7030] with [RFC8366bis] signed vouchers to
securely enroll devices. A Registrar provides the trust anchor of
the network domain to which a Pledge enrolls.
[cBRSKI] defines a version of BRSKI that is suitable for constrained
nodes ([RFC7228]) and for operation on constrained networks
([RFC7228]) including Low-Power and Lossy Networks (LLN) [RFC7102].
It uses Constrained Application Protocol (CoAP) [RFC7252] messages
secured by Datagram Transport Layer Security (DTLS) [RFC9147] to
implement the BRSKI functions defined by [RFC8995].
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In this document, cBRSKI is extended such that a cBRSKI Pledge can
connect to a Registrar via a constrained Join Proxy. In particular,
this solution is intended to support IPv6 over Low-Power Wireless
Personal Area Networks (6LoWPAN) [RFC4944] mesh networks. 6TiSCH
networks are not in scope of this document since these use the CoJP
[RFC9031] proxy mechanism.
The Join Proxy as specified in this document is one of the Join Proxy
options referred to in Section 2.5.2 of [RFC8995] as future work.
However, in IP networks that require node authentication, such as
those using 6LoWPAN [RFC4944], data to and from the Pledge will not
be routable over the IP network before it is properly authenticated
to the network. A new Pledge can initially only use a link-local
IPv6 address to communicate with a mesh neighbor [RFC6775] until it
receives the necessary network configuration parameters.
Before it can receive these parameters, the Pledge needs to be
authenticated and authorized to onboard the network. This is done in
cBRSKI through an end-to-end encrypted DTLS session with a domain
Registrar.
When this Registrar is not a direct (link-local) neighbor of the
Pledge but several hops away, the Pledge needs to discover a link-
local neighbor that is operating as a constrained Join Proxy, which
helps forward the DTLS messages of the session between Pledge and
Registrar.
Because the Join Proxy is a regular network node that has already
been onboarded onto the network, it can send IP packets to the
Registrar which are then routed over one or more hops over the mesh
network -- and potentially over other IP networks too, before
reaching the Registrar. Likewise, the Registrar sends its response
IP packets which are routed back to the Join Proxy over the mesh
network.
Once a Pledge has enrolled onto the network in this manner, it can
optionally be configured itself as a new constrained Join Proxy. In
this role it can help other Pledges perform the cBRSKI onboarding
process.
Two modes of operation for a constrained Join Proxy are specified:
1. A stateful Join Proxy that locally stores UDP connection state
per Pledge.
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2. A stateless Join Proxy that does not locally store UDP connection
state, but stores it in the header of a message that is exchanged
between the Join Proxy and the Registrar.
Similar to the difference between storing and non-storing Modes of
Operations (MOP) in RPL [RFC6550], the stateful and stateless modes
differ in the way that they store the state required to forward
return UDP packets from the Registrar back to the Pledge.
2. 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 here.
The following terms are defined in [RFC8366bis] and [RFC8995], and
are used identically in this document: artifact, Circuit Proxy, Join
Proxy, domain, imprint, Registrar, Pledge, and Voucher.
The term "installation" refers to all devices in the network and
their interconnections, including Registrar, enrolled nodes (with and
without constrained Join Proxy functionality) and Pledges (not yet
enrolled).
(Installation) IP addresses are assumed to be routable over the whole
installation network, except for link-local IP addresses.
The term "Join Proxy" is used in this document with the same
definition as in [RFC8995]. However, in this document it refers
specifically to a Join Proxy that can support Pledges to onboard
using a UDP-based protocol, such as the cBRSKI protocol [cBRSKI].
This protocol operates over an end-to-end secured DTLS session
between a Pledge and a cBRSKI Registrar.
The acronym "JPY" is used to refer to a new protocol and JPY message
format defined by this document. The message can be seen as a "Join
Proxy Yoke": connecting two data items and letting these travel
together over a network.
Because UDP does not have the notion of a connection, the term "UDP
connection" in this document refers to a pseudo-connection, whose
establishment on the Join Proxy is triggered by receipt of a first
UDP packet from a new Pledge source.
The term "endpoint" is used as defined in [RFC7252].
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The terms "6LoWPAN Router" (6LR), "6LoWPAN Border Router" (6LBR) and
"6LoWPAN link" are used as defined in [RFC6775].
Details of the IP address and port notation used in the Join Proxy
specification are provided in Section 4.2.
3. Join Proxy Problem Statement and Solution
3.1. Problem Statement
As depicted in Figure 1, the Pledge (P), in a network such as a
6LoWPAN [RFC4944] mesh network can be more than one hop away from the
Registrar (R) and it is not yet authenticated to the network. Also,
the Pledge does not possess any key material to encrypt or decrypt
link-layer data transmissions.
In this situation, the Pledge can only communicate one-hop to its
neighbors, such as the constrained Join Proxy (J), using link-local
IPv6 addresses and using no link-layer encryption. However, the
Pledge needs to communicate with end-to-end security with a Registrar
to authenticate and obtain its domain identity/credentials. In the
case of cBRSKI, the domain identity is an X.509 certificate. Domain
credentials may include key material for network access.
multi-hop mesh
.---. IPv6
| R +---. +-----+ +---+ link-local +---+
| | \ | 6LR +----+ J |..............| P |
'---' `--+ | | | | |
+-----+ +---+ +---+
Registrar Join Proxy Pledge
Figure 1: Multi-hop cBRSKI onboarding scenario in a 6LoWPAN mesh
network
So one problem is that there is no IP routability between the Pledge
and the Registrar, via intermediate nodes such as 6LoWPAN Routers
(6LRs), despite the need for an end-to-end secured session between
both.
Furthermore, the Pledge is not be able to discover the IP address of
the Registrar because it is not yet allowed onto the network.
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3.2. Solution
To overcome these problems, the constrained Join Proxy is introduced.
This is specific functionality that all, or a specific subset of,
authenticated nodes in an IP network can implement. When the Join
Proxy functionality is enabled in a node, it can help a neighboring
Pledge securely onboard the network.
The Join Proxy performs relaying of UDP packets from the Pledge to
the intended Registrar, and relaying of the subsequent return
packets. An authenticated Join Proxy can either be configured with
the routable IP address of the Registrar, or it can discover this
address as specified in this document. Other methods of Registrar
discovery (not yet specified in this document) can also be easily
added.
The Join Proxy acts as a packet-by-packet proxy for UDP packets
between Pledge and Registrar. The cBRSKI protocol between Pledge and
Registrar [cBRSKI] which this Join Proxy supports uses UDP messages
with DTLS-encrypted CoAP payloads, but the Join Proxy as described
here is unaware of these payloads. The Join Proxy solution can
therefore be easily extended to work for other UDP-based protocols,
as long as these protocols are agnostic to (or can be made to work
with) the change of the IP and UDP headers performed by the Join
Proxy.
In summary, the following steps are typically taken for the
onboarding process of a Pledge:
1. Join Proxies in the network learn the IP address and UDP port of
the Registrar.
2. A new Pledge arrives: it discovers one or more Join Proxies and
selects one.
3. The Pledge sends a link-local UDP message to the selected Join
Proxy.
4. The Join Proxy relays the message to the Registrar (and port) of
step 1.
5. The Registrar sends a response UDP message back to the Join
Proxy.
6. The Join Proxy relays the message back to the Pledge.
7. Step 3 to 6 repeat as needed, for multiple messages, to complete
the onboarding protocol.
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8. The Pledge uses its obtained domain identity/credentials to join
the domain network.
To reach the Registrar in step 4, the Join Proxy needs to be either
configured with a Registrar address or needs to dynamically discover
a Registrar as detailed in Section 5.1. This configuration/discovery
is specified here as step 1. Alternatively, in case of automated
discovery it can also happen on-demand in step 4, at the moment that
the Join Proxy has data to send to the Registrar.
3.3. Solution for Multiple Registrars
The solution description in Section 3.2 assumes there is only one
Registrar service configured or discovered by a Join Proxy, defined
by a single IP address and single UDP port.
However, there may be multiple Registrars present in a network
deployment. There may be multiple Registrars supporting the exact
same onboarding protocol, or multiple Registrars supporting different
onboarding protocols, or a combination of both. Such cases are all
supported by this specification, to enable redundancy, backward-
compatibility, and introduction of new variants of onboarding
protocols over time. Further information about the "BRSKI variants"
concept can be found in [I-D.ietf-anima-brski-discovery].
See Section 4.6 for the specific requirements on the Join Proxy for
supporting multiple Registrars or multiple onboarding protocol
variants.
3.4. Forming 6LoWPAN Mesh Networks with cBRSKI
The Join Proxy has been specifically designed to set up an entire
6LoWPAN mesh network using cBRSKI onboarding. This section outlines
how this process works and highlights the role that the Join Proxy
plays in forming the mesh network.
Typically, the first node to be set up is a 6LoWPAN Border Router
(6LBR) which will form the new mesh network and decide on the
network's configuration. The 6LBR may be configured using for
example one of the below methods. Note that multiple methods may be
used within the scope of a single installation.
1. Manual administrative configuration
2. Use non-constrained BRSKI [RFC8995] to automatically onboard over
its high-speed network interface when it gets powered on.
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3. Use cBRSKI [cBRSKI] to automatically onboard over its high-speed
network interface when it gets powered on.
Once the 6LBR is enabled, it requires an active Registrar reachable
via IP communication to onboard any Pledges. Once cBRSKI onboarding
is enabled (either administratively, or automatically) on the 6BLR,
it can support the onboarding of 6LoWPAN-enabled Pledges, via its
6LoWPAN network interface. This 6LBR may host the cBRSKI Registrar
itself, but the Registrar may also be hosted elsewhere on the
installation network.
At the time the Registrar and the 6LBR are enabled, there may be zero
Pledges, or there may be already one or more installed and powered
Pledges waiting - periodically attempting to discover a Join Proxy
over their 6LoWPAN network interface.
A Registrar hosted on the 6LBR will, per [cBRSKI], make itself
discoverable as a Join Proxy so that Pledges can use it for cBRSKI
onboarding over a 6LoWPAN link (one hop). Note that only some of
Pledges waiting to onboard may be direct neighbors of the
Registrar/6LBR. Other Pledges would need their traffic to be relayed
by Join Proxies across one or more enrolled mesh devices (6LR, see
Figure 1) in order to reach the Registrar/6LBR. For this purpose,
all or a subset of the enrolled Pledges start to act as Join Proxies
themselves. Which subset is selected, and when the Join Proxy
function is enabled by a node, is out of scope of this document.
The desired end state of the installation includes a network with a
Registrar and all Pledges successfully enrolled in the network domain
and connected to one of the 6LoWPAN mesh networks that are part of
the installation. New Pledges may also be added by future network
maintenance work on the installation.
Pledges employ link-local communication until they are enrolled, at
which point they stop being a "Pledge". A Pledge will periodically
try to discover a Join Proxy using for example link-local discovery
requests, as defined in [cBRSKI]. Pledges that are neighbors of the
Registrar will discover the Registrar itself (which is posing as a
Join Proxy) and will be enrolled first, using cBRSKI. The Pledges
that are not a neighbor of the Registrar will at first fail to find a
Join Proxy. Later on, they will eventually discover a Join Proxy so
that they can be enrolled with cBRSKI too. While this continues,
more and more Join Proxies with a larger hop distance to the
Registrar will emerge. The mesh network auto-configures in this way,
such that at the end of the onboarding process, all Pledges are
enrolled into the network domain and connected to the mesh network.
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4. Join Proxy Specification
A Join Proxy can operate in two modes:
1. Stateful mode
2. Stateless mode
The advantages and disadvantages of the two modes are presented in
Section 6.
4.1. Mode Implementation and Configuration Requirements
For a Join Proxy implementation on a node, there are three possible
scenarios:
1. Both stateful and stateless modes are implemented. The Join
Proxy can switch between these modes, depending on configuration
and/or auto-discovery of Registrar(s) for each option.
2. Only stateful mode is implemented.
3. Only stateless mode is implemented.
Option 2 and 3 have the advantage of reducing code size, testing
efforts and deployment complexity, but requires all devices in the
deployment to standardize on the same choice.
A standard for a network-wide application or ecosystem profile, that
integrates the Join Proxy functionality as defined in this document,
MAY specify the use of any of these three options. It is expected
that most deployments of constrained Join Proxies will be in the
context of such standards and that these standards will be able to
pick either option 2 or 3 based on considerations such as those in
Section 6.
A Join Proxy that is not adhering to such an additional standard MUST
implement both modes (option 1). A Join Proxy or Registrar not
adhering to such additional standards is called "generic".
If a Join Proxy implements both modes but does not implement methods
to discover available Registrars (for either method), then it MUST
use only the mode that is currently configured for the network, or
configured individually for the device. The method or profile that
defines such a configuration is outside the scope of this document.
If the mode is not configured and also can not be discovered
automatically, then the device MUST NOT operate as a Join Proxy.
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For a Join Proxy to be operational, the node on which it is running
has to be able to communicate with a Registrar (that is, exchange UDP
messages with it). Establishing this connectivity can happen fully
automatically if the Join Proxy node first enrolls itself as a
Pledge, and then discovers the Registrar IP address/port, and if
applicable its desired mode of operation (stateful or stateless),
through a discovery mechanism (see Section 5). Other methods, such
as provisioning the Join Proxy are out of scope for this document but
equally feasible. Such methods would typically be defined by a
standard or ecosystem profile that integrates Join Proxy
functionality. Such provisioning can also be fully automated, for
example if the Registrar IP address/port are included in the network
configuration parameters that are disseminated to each trusted
network node.
Independent of the mode of the Join Proxy or its discovery/
configuration methods, the Pledge first discovers (see Section 5.2)
and selects the most appropriate Join Proxy. From the discovery
result, the Pledge learns a Join Proxy's link-local IP address and
UDP join-port. Details of this discovery are defined by the
onboarding protocol and are not in scope of this document. For
cBRSKI, this is defined in Section 10 of [cBRSKI].
A generic cBRSKI Registrar by design necessarily implements the
stateful mode, and it SHOULD implement support for Join Proxies
operating in the stateless mode. Support for only the stateless mode
is considered not to bring significant simplifications to a generic
cBRSKI Registrar implementation. However, the generic cBRSKI
Registrar MAY offer a configuration option to disable either the
stateful or stateless mode, which can be useful in a particular
deployment. A cBRSKI Registrar that is only implemented to support
an aforementioned network-wide application or ecosystem profile MAY
implement either stateful and/or stateless mode.
4.2. Notation
The following notation is used in this section in both text and
figures:
* The colon (:) separates IP address and port number (<IP>:<port>).
* IP_P denotes the link-local IP address of the Pledge. For
simplicity, it is assumed here that the Pledge only has one
network interface.
* IP_R denotes the routable IP address of the Registrar.
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* IP_Jl denotes the link-local IP address of the Join Proxy on the
interface that connects it to the Pledge.
* IP_Jr denotes the routable IP address of the Join Proxy.
* p_P denotes the UDP port used by the Pledge for its onboarding/
joining protocol, which may be cBRSKI. The Pledge acts in a UDP
client role, specifically as a DTLS client for the case of cBRSKI.
* p_Jl denotes the join-port of the Join Proxy.
* p_Jr denotes the client port of the Join Proxy that it uses to
forward packets to the Registrar.
* p_R denotes the server port of the Registrar on which it serves
the onboarding protocol, such as cBRSKI.
* p_Rj denotes the server port of the Registrar on which it serves
the JPY protocol.
* JPY[H( ),C( )] denotes a JPY message, as defined by the JPY
protocol, with header H and content C indicated in between the
parentheses.
4.3. Stateful Join Proxy
In stateful mode, the Join Proxy acts as a UDP circuit proxy that
does not change the UDP payload (called "data octets" in [RFC768])
but only rewrites the IP and UDP headers of each UDP packet it
forwards between a Pledge and a Registrar.
The UDP flow mapping state maintained by the Join Proxy can be
represented as a list of tuples, one for each active Pledge, as
follows:
Local UDP state Routable UDP state Time state
(IP_P:p_P, IP_Jl:p_Jl) <===> (IP_Jr:p_Jr, IP_R:p_R) (Exp-timer)
In case a Join Proxy has multiple network interfaces that accept
Pledges, an interface identifier needs to be added on the leftmost
tuple component. If a Join Proxy has multiple network interfaces to
connect to (one or more) Registrars, an interface identifier needs to
be added to the rightmost tuple component. Both of these are not
shown further in this section, for better readability.
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The establishment of the UDP connection state on the Join Proxy is
solely triggered by receipt of a UDP packet from a Pledge with an
IP_P:p_P link-local source and IP_Jl:p_Jl link-local destination for
which no mapping state exists, and that is terminated by a connection
expiry timer.
Figure 2 depicts an example DTLS session via the Join Proxy, to show
how this state is used in practice. In this case the Join Proxy
knows the IP address of the Registrar (IP_R) and the default CoAPS
port (P_R = 5684) on the Registrar is used to access cBRSKI
resources.
+------------+------------+-------------+--------------------------+
| Pledge | Join Proxy | Registrar | UDP Message |
| (P) | (J) | (R) | Src_IP:port | Dst_IP:port|
+------------+------------+-------------+-------------+------------+
| ---ClientHello--> | IP_P:p_P | IP_Jl:p_Jl |
| ---ClientHello--> | IP_Jr:p_Jr| IP_R:5684 |
| | | |
| <--ServerHello--- | IP_R:5684 | IP_Jr:p_Jr |
| : | | |
| <--ServerHello--- : | IP_Jl:p_Jl| IP_P:p_P |
| : : | : | : |
| [DTLS messages] | : | : |
| : : | : | : |
| ---Finished--> : | IP_P:p_P | IP_Jl:p_Jl |
| ---Finished--> | IP_Jr:p_Jr| IP_R:5684 |
| | | |
| <--Finished--- | IP_R:5684 | IP_Jr:p_Jr |
| <--Finished--- | IP_Jl:p_Jl| IP_P:p_P |
| : : | : | : |
+---------------------------------------+-------------+------------+
Figure 2: Example of the message flow of a DTLS session via a
stateful Join Proxy.
The Join Proxy MUST allocate a unique IP_Jr:p_Jr for every unique
Pledge that it serves. This is typically done by selecting a unique
available port P_Jr for each Pledge. Doing so enables the Join Proxy
to correctly map the UDP packets received from the Registrar back to
the corresponding Pledges. Also, it enables the Registrar to
correctly distinguish multiple DTLS clients by means of IP address/
port tuples.
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The default timeout for clearing the state for a Pledge MUST be 30
seconds after the last relayed packet was sent on a UDP connection
associated to that Pledge, in either direction. The default timeout
MAY be overridden by another value that is either configured, or
discovered in some way out of scope of this document.
When a Join Proxy receives an ICMP [RFC792] / ICMPv6 [RFC4443] error
from the Registrar, this may signal a permanent change of the
Registrar's IP address and/or port, or it may signal a temporary
disruption of the network. In such case, the Join Proxy SHOULD send
an equivalent ICMP error message (with same Type and Code) to the
Pledge. The specific Pledge can be determined from the IP/UDP header
information that is contained in the ICMP error message body, if
included. In case the ICMP message body is empty, or insufficient
information is included there, the Join Proxy does not send the ICMP
error message to the Pledge because the intended recipient cannot be
determined.
To protect itself and the Registrar against malfunctioning Pledges
and/or denial of service (DoS) attacks, the Join Proxy SHOULD limit
the number of simultaneous state tuples for a given IP_p to at most
2, and it SHOULD limit the number of simultaneous state tuples per
network interface to at most 10.
When a new Pledge connection is received and the Join Proxy is unable
to build new mapping state for it, for example due to the above
limits, the Join Proxy SHOULD return an ICMP Type 1 "Destination
Unreachable" error message with Code 1, "Communication with
destination administratively prohibited".
4.4. Stateless Join Proxy
Stateless Join Proxy operation eliminates the need and complexity to
maintain per-Pledge UDP connection mapping state on the proxy and the
machinery to build, maintain and remove this mapping state. It also
removes the need to protect this mapping state against DoS attacks
and may also reduce memory and CPU requirements on the proxy.
Stateless Join Proxy operations work by introducing a new JPY message
used in communication between Proxy and Registrar. This message will
store the state "in the network". It consists of two parts:
* Header (H) field: contains state information about the Pledge (P)
such as the link-local IP address and UDP port.
* Contents (C) field: the original UDP payload (data octets
according to [RFC768]) received from the Pledge, or destined to
the Pledge.
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When the join proxy receives a UDP message from a Pledge, it encodes
the Pledge's link-local IP address, interface ID and UDP (source)
port of the UDP packet into the Header field and the UDP payload into
the Contents field and sends the packet to the Registrar from a fixed
source UDP port. When the Registrar sends packets for the Pledge, it
MUST return the Header field unchanged, so that the join proxy can
decode the Header to reconstruct the Pledge's link-local IP address,
interace and UDP (destination) port for the return UDP packet.
Figure 3 shows this per-packet mapping on the join proxy for a DTLS
session.
The Registrar transiently stores the Header field information. The
Registrar uses the Contents field to execute the Registrar
functionality. When the Registrar replies, it wraps its DTLS message
in a JPY message and sends it back to the Join Proxy. The Registrar
SHOULD NOT assume that it can decode the Header Field of a received
JPY message, it MUST simply replicate it when responding. The Header
of a reply JPY message contains the original source link-local
address and port of the Pledge from the transient state stored
earlier and the Contents field contains the DTLS payload created by
the Registrar.
On receiving the JPY message, the Join Proxy retrieves the two parts.
It uses the Header field information to send a link-local UDP message
containing the (DTLS) payload retrieved from the Contents field to a
particular Pledge.
When the Registrar receives such a JPY message, it MUST treat the
Header H as a single additional opaque identifier of all packets
associated to a UDP connection with a Pledge. Whereas in the
stateful proxy case, all packets with the same 4-tuple (IP_Jr:p_Jr,
IP_R:p_R) belong to a single Pledge's UDP connection, in the
stateless proxy case only the packets with the same 5-tuple
(IP_Jr:p_Jr, IP_R:p_Rj, H) belong to a single Pledge's UDP
connection. The JPY message Contents field contains the UDP payload
of the packet for that Pledge's UDP connection. Packets with
different header H belong to different Pledge's UDP connections.
In the stateless mode, the Registrar MUST offer the JPY protocol on a
discoverable UDP port (p_Rj). There is no default port number
available for the JPY protocol, unlike in the stateful mode where the
Registrar can host all its services on the CoAPS default port (5684).
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+--------------+------------+---------------+-----------------------+
| Pledge | Join Proxy | Registrar | UDP Message |
| (P) | (J) | (R) |Src_IP:port|Dst_IP:port|
+--------------+------------+---------------+-----------+-----------+
| ---ClientHello---> | IP_P:p_P |IP_Jl:p_Jl |
| ---JPY[H(IP_P:p_P), --> | IP_Jr:p_Jr|IP_R:p_Rj |
| C(ClientHello)] | | |
| <--JPY[H(IP_P:p_P), --- | IP_R:p_Rj |IP_Jr:p_Jr |
| C(ServerHello)] | | |
| <---ServerHello--- | IP_Jl:p_Jl|IP_P:p_P |
| : | : | : |
| [ DTLS messages ] | : | : |
| : | : | : |
| ---Finished---> | IP_P:p_P |IP_Jr:p_Jr |
| ---JPY[H(IP_P:p_P), --> | IP_Jl:p_Jl|IP_R:p_Rj |
| C(Finished)] | | |
| <--JPY[H(IP_P:p_P), --- | IP_R:p_Rj |IP_Jr:p_Jr |
| C(Finished)] | | |
| <---Finished-- | IP_Jl:p_Jl|IP_P:p_P |
| : | : | : |
+-------------------------------------------+-----------+-----------+
Figure 3: Example of the message flow of a DTLS session via a
stateless Join Proxy.
When a Join Proxy receives an ICMP [RFC792] / ICMPv6 [RFC4443] error
from the Registrar, this may signal a permanent change of the
Registrar's IP address and/or port, or it may signal a temporary
disruption of the network.
Unlike a stateful Join Proxy, the stateless Join Proxy cannot
determine the Pledge to which this ICMP error should be mapped,
because the JPY header containing this information is not included in
the ICMP error message. Therefore, it cannot inform the Pledge of
the specific error that occurred.
4.5. JPY Protocol and Messages
JPY messages are used by a stateless Join Proxy to carry required
state information in the relayed UDP messages, such that it does not
need to store this state in memory. JPY messages are carried
directly over the UDP layer. So, there is no CoAP or DTLS layer used
between the JPY messages and the UDP layer.
A Registrar that supports the JPY protocol also uses JPY message to
return relayed UDP messages to the stateless Join Proxy, including
the state information that it needs.
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4.5.1. JPY Message Structure
Each JPY message consists of one CBOR [RFC8949] array with 2
elements:
1. The Header (H) with the Join Proxy's per-message state data:
wrapped in a CBOR byte string. The state data SHOULD be at most
32 bytes.
2. The Content (C) field: the binary (DTLS) payload being relayed,
wrapped in a CBOR byte string. The payload is encrypted. The
Join Proxy cannot decrypt it and therefore has no knowledge of
any transported (CoAP) messages, or the URI paths or media types
within the CoAP messages.
Using CDDL [RFC8610], the CBOR array that constitutes the JPY message
can be formally defined as:
jpy_message =
[
jpy_header : bstr,
jpy_content : bstr,
]
Figure 4: CDDL representation of a JPY message
The jpy_header state data is to be reflected (unmodified) by the
Registrar when sending return JPY messages to the Join Proxy. The
header's internal representation is not standardized: it can be
constructed by the Join Proxy in whatever way. It is to be used by
the Join Proxy to record state for the included jpy_content field,
which includes the information which Pledge the data in jpy_content
came from.
This state data stored in the JPY message is similar to the "state
object" mechanism described in Section 7.1 of [RFC9031]. However,
since the CoAP protocol layer (if any) is inside the DTLS layer, so
end-to-end encrypted between the Pledge and the Registrar, it is not
possible for the Join Proxy to act as a CoAP proxy per Section 5.7 of
[RFC7252].
Detailed examples of a complete JPY message are shown in Appendix A.
4.5.2. JPY Message Port Usage
For the JPY messages sent to the Registrar, the Join Proxy SHOULD use
the same UDP source port and IP source address for the JPY messages
sent on behalf of all Pledges.
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Although a Join Proxy MAY vary the UDP source port, doing so creates
more local state. A Join Proxy with multiple CPUs (unlikely in a
constrained system, but possible) could, for instance, use different
UDP source port numbers to demultiplex connections across CPUs.
4.5.3. JPY Message Overhead and MTU Size
The use of the JPY message CBOR encoding adds a 3-6 byte overhead on
top of the data carried within the Header and Contents fields. The
Header state data itself (up to 32 bytes) also adds an overhead on
each UDP message exchanged between Join Proxy and Registrar.
Therefore, a protocol using the stateless Join Proxy MUST use (UDP)
payloads that are bounded in size, such that the maximum payload
length used minus the maximum overhead size (38 bytes) stays below
the MTU size of the network. cBRSKI is designed to work even for the
minimum IPv6 MTU of 1280 bytes, by configuring the DTLS maximum
fragment length and using CoAP blockwise transfer for large resource
transfers [cBRSKI].
At the CoAP level, using the cBRSKI [cBRSKI] and the EST-CoAPS
[RFC9148] protocols, the CoAP blockwise options [RFC7959] are often
used to split large payloads into multiple data blocks. The
Registrar and the Pledge MUST select a block size that would allow
the addition of the JPY message structure without violating MTU
sizes.
4.5.4. JPY Message Security
Application or ecosystem standards adopting the stateless Join Proxy
need to determine if there is the potential for attacks originating
from the trusted network side of the Join Proxy. Such attacks would
involve senders other than a trustworthy Registrar sending packets to
the Join Proxy, impersonating the trusted Registrar by using its
source address and port. In many well-designed solutions, this
attack vector can be excluded because IP source addresses are
verified. For example, in Autonomic Networking Infrastructure (ANI)
networks, the Autonomic Control Plane (ACP) ([RFC8994]) ensures that
only trustworthy nodes can communicate amongst each other. In an
ACP, compromising an ACP node may be as hard as compromising the
Registrar itself. Likewise, in many Wi-Fi mesh networks and 6LoWPAN
mesh networks, link-layer security is applied and claimed to achieve
similar levels of secure and trusted communication within the scope
of the mesh.
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For stateless Join Proxies that only operate in such secured network
environments, it can be sufficient to only accept JPY messages
originating from a Registrar's IP address and port, and not use any
additional encryption or integrity protection of the JPY header. The
Registrar's IP address and port are configured on the Join Proxy, or
discovered by the Join Proxy, for sending JPY messages.
Generic stateless Join Proxies on the other hand can not assume any
such additional security measures for the network that connects the
Proxy to the Registrar. For example, a generic Join Proxy's network
connection to a Registrar may pass through a lightly protected
enterprise network, such as a university or campus network, without
additional security. Therefore, a generic stateless Join Proxy
SHOULD encrypt and integrity-protect the state data prior to wrapping
it in a CBOR byte string in jpy_header.
It SHOULD be encrypted with a symmetric key known only to the Join
Proxy itself. When the Join Proxy attempts to decrypt a receiver
jpy_header byte string, and either the decryption or the integrity
check fails, it MUST silently discard the JPY message.
The symmetric key need not persist on a long-term basis, and MAY be
changed periodically. Because a key change during an onboarding
attempt of a Pledge could lead to DTLS retransmissions, or even
failure of the onboarding attempt, it is RECOMMENDED to change the
key infrequently: for example every 24 hours.
4.5.5. Example Format for JPY Header Data
A typical JPY message header format, prior to encryption, could be
constructed using the following binary data structure (expressed in C
style notation):
struct jpy_header_plaintext {
uint8_t family; // Only valid in the range 0...1
uint8_t ifindex; // Only valid in the range 0...MAX_INTERFACES
uint16_t srcport; // Only valid > 0
uint8_t iid[8];
uint32_t zero; // Only valid == 0
};
This is illustrative only: the format of the data inside jpy_header
is not subject to standardization and may vary across Pledges. It
may for example use a CBOR array encoding, formally defined and
constrained using CDDL [RFC8610].
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The data structure stores the Pledge's UDP source port (srcport), the
IID bits of the Pledge's originating IPv6 link-Local address (iid),
the IPv4/IPv6 family (as a uint8 value 0 or 1) and an interface index
(ifindex) to provide the link-local scope for the case that the Join
Proxy has multiple network interfaces. The zero field is both for
integrity protection and padding. It is always value zero (before
encryption) on sending and MUST be zero after decryption on
reception.
The resulting plaintext size is 16 bytes. This size fits into a
single AES128 CBC block for instance, resulting in a 16 byte block of
encrypted state data, jpy_header_ciphertext. Due to the way that CBC
encryption mixes all the contents of a block together, an attacker
that modifies any bit of this block will most likely change one of
the zero bits in the family and/or zero fields as well.
This jpy_header_ciphertext data is then wrapped in a CBOR byte string
to form the jpy_header element. This results in a jpy_header CBOR
element of 17 bytes which includes a 1-byte overhead to encode the
data as a CBOR byte string of length 16.
Note: when IPv6 is used only the lower 64-bits of the source IPv6
address need to be recorded, because they must be by design all IPv6
link-Local addresses, so the upper 64-bits are just "fe80::" and can
be elided. For IPv4, a link-Local IPv4 address [RFC3927] would be
used, and it would always fit into the 64 bits of the iid field. On
link types where the Interface IDentifier (IID) is not 64-bits, a
different field size for iid will be necessary.
Replay protection is not included in this example security solution,
because the regular transport layers of cBRSKI and BRSKI,
respectively UDP and TCP, also do not provide replay protection.
Rather, replay protection is handled by the higher layer protocol,
respectively DTLS and TLS. If replay attack protection is desired,
AES with GCM [RFC5288] SHOULD be used.
Detailed examples of a complete JPY message are shown in Appendix A.
4.5.6. Processing by Registrar
On reception of a JPY message by the Registrar, the Registrar MUST
verify that the number of CBOR array elements is 2 or more. To
implement this specification, only the first two elements are used.
The data in the jpy_content field must be provided as input to a DTLS
library [RFC9147], which along with the 5-tuple defined in
Section 4.4 provides enough information for the Registrar to pick an
appropriate (active) client context. Note that the same UDP socket
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will need to be used for multiple DTLS flows, which is atypical for
how DTLS usually uses sockets. The jpy_context field can be used to
select an appropriate DTLS context, as DTLS headers do not contain
any kind of per-session context. The jpy_context field needs to be
linked to the DTLS context, and when a DTLS message need to be sent
back to the client, the jpy_context needs to be included in a JPY
message along with the DTLS message in the jpy_content field.
4.6. Handling Multiple Registrars
In a network deployment there MAY be multiple Registrar hosts
present, each host operating one or more Registrar service(s).
Regardless of the number of (physical or logical) hosts, each of
these Registrar services is considered a separate Registrar. One or
more of these Registrars MAY be configured in a Join Proxy, by a
method out of scope of this specification. Also one or more of these
Registrars MAY be found by a Join Proxy using its discovery
method(s).
The Join Proxy is not necessarily aware of all onboarding protocol
variants that are enabled in its network. Specifically, it may not
be aware of the expected communication timing characteristics for the
onboarding protocol that it is providing its proxy function for.
Therefore, the final selection of onboarding protocol and Registrar
is left to the Pledge and not to the Join Proxy. Also the
determination of "onboarding progress" and whether the Registrar is
considered responsive or not is left to the Pledge performing the
onboarding protocol. This is consistent with Section 4.1 of
[RFC8995] which defines how a BRSKI Pledge attempts onboarding via
multiple Join Proxies and defines the related retry and switching
behaviors.
If a Join Proxy discovers more Registrars than it can simultaneously
offer to Pledges, given its resource limits or implementation-defined
limits, then the Join Proxy MUST select from the discovered
Registrars in an implementation-defined manner. Future work such as
[I-D.ietf-anima-brski-discovery] may define a selection process for
this case.
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As an example, a network deployment might include a single Registrar
host that offers two Registrar services: cBRSKI and a hypothetical
"future BRSKI" (fuBRSKI). Both services are hosted on different UDP
ports. Each Join Proxy is configured with these two Registrar
services, and when a Pledge is sending CoAP discovery requests each
Join Proxy in range will respond with both services in a CoAP
discovery response. The Join Proxy is able to distinguish the
properties of the two Registrar services by the differences in the
CoRE Link Format parameters included in the two responded onboarding
service descriptions.
5. Discovery
5.1. Join Proxy Discovers Registrar
In order to accommodate automatic configuration of the Join Proxy, it
MUST discover the location and capabilities of the Registrar, in case
this information is not configured already.
In BRSKI [RFC8995] the GeneRic Autonomic Signaling Protocol (GRASP)
[RFC8990] protocol is supported for discovery of a BRSKI Registrar in
an Autonomic Control Plane (ACP). However, this document does not
target the ACP context of use. Therefore, the definition of how to
use GRASP for discovering a cBRSKI Registrar in an ACP is left to
future work such as [I-D.ietf-anima-brski-discovery].
Although multiple discovery methods can be supported in principle by
a single Join Proxy, this document only defines one default method
for a Join Proxy to discover a Registrar: using CoAP resource
discovery queries [RFC6690] [RFC7252].
The CoAP discovery query to use depends on the intended mode of
operation of the Join Proxy: stateless or stateful. A stateless Join
Proxy needs to discover a UDP endpoint (address and port) that can
accept JPY messages, supporting the coaps+jpy scheme. On the other
hand, a stateful Join Proxy needs to discover a single CoAPS endpoint
supporting the coaps scheme that offers the full set of cBRSKI
Registrar resources.
5.1.1. Stateless Case
The stateless Join Proxy can discover the JPY protocol endpoint of
the Registrar by sending a multicast CoAP GET discovery query to the
"/.well-known/core" resource including a resource type (rt) query
parameter "brski.rjp". The latter CoAP resource type is defined in
Section 8.1.
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Upon success, the return payload will contain the port of the
Registrar on which the JPY protocol handler is hosted. This exchange
is shown below:
REQ: GET coap://[ff05::fd]/.well-known/core?rt=brski.rjp
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps+jpy://[ipv6_address]:port>;rt=brski.rjp
In this case, the multicast CoAP request is sent to the site-local
"All CoAP Nodes" multicast IPv6 address ff05::fd. In some
deployments, a smaller scope than site-local is more appropriate to
reduce the network load due to this CoAP discovery traffic. For
example, in a 6LoWPAN mesh network where a JPY protocol endpoint is
always hosted on a 6LoWPAN Border Router (6LBR), the realm-local
scope "All CoAP Nodes" address ff03::fd can be used.
The reason that the IPv6 address (field ipv6_address) is always
included in the link-format result is that in the [RFC6690] link
format, and per Section 3.2 of [RFC3986], the authority component
cannot include only a port number but has to include also the IP
address.
The returned port is expected to process the encapsulated JPY
messages described in Section 4.5. The scheme is coaps+jpy,
described in Section 8.2, and not regular coaps because the JPY
messages effectively form a new protocol that encapsulates CoAPS.
5.1.2. Stateful Case
The stateful Join Proxy can discover the Registrar's cBRSKI resource
set by sending a multicast CoAP GET discovery query to the "/.well-
known/core" resource including a resource type (rt) query parameter
"brski". The latter CoAP resource type is defined in [cBRSKI].
Upon success, the return payload will contain the URI path and port
of the Registrar on which the cBRSKI resources are hosted. This
exchange is shown below:
REQ: GET coap://[ff05::fd]/.well-known/core?rt=brski
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps://[ipv6_address]:port/uri_path>;rt=brski
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The port field and its preceding colon are optionally included: if
elided, the default CoAPS port 5684 is implied. The uri_path field
may be a single CoAP URI path resource label, or it may be a
hierarchy of resources. For efficiency, it is RECOMMENDED for the
Registrar to configure the URI path as short as possible, for example
b.
Note that the Join Proxy does not use the returned uri_path
information, while it uses the ipv6_address and port information for
its relaying operations.
5.1.3. Examples
A Registrar with address 2001:db8:0:abcd::52, with the JPY protocol
hosted on port 7634, and the CoAPS resources hosted on default port
5684 could for example reply to a multicast CoAP query of a stateful
Join Proxy as follows:
REQ: GET coap://[ff05::fd]/.well-known/core?rt=brski
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps://[2001:db8:0:abcd::52]/b>;rt=brski
The same Registrar could for example reply to a multicast CoAP query
of a stateless Join Proxy as follows:
REQ: GET coap://[ff05::fd]/.well-known/core?rt=brski.rjp
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps+jpy://[2001:db8:0:abcd::52]:7634>;rt=brski.rjp
In these examples, the Join Proxy in a specific mode of operation
(stateful or stateless) only queries for those cBRSKI services that
it minimally needs to perform the Join Proxy function in that mode.
For this reason, wildcard queries (such as rt=brski*) are not sent.
5.2. Pledge Discovers Join Proxy
Regardless of whether the Join Proxy operates in stateful or
stateless mode, it is discovered by the Pledge identically.
Section 10 of [cBRSKI] defines the details of the CoAP discovery
request sent by the Pledge.
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A Join Proxy implementation by default MUST support this discovery
method. If there is another method configured, by some means outside
of the scope of this document, the default method MAY be deactivated.
The join-port of the Join Proxy is discovered by sending a multicast
GET request to "/.well-known/core" including a resource type (rt)
parameter with the value "brski.jp". This value is defined in
Section 8.1. Upon success, the return payload will contain the join-
port.
The meta-example below shows the discovery of the join-port (field
join_port) of the Join Proxy:
REQ: GET coap://[ff02::fd]/.well-known/core?rt=brski.jp
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps://[IP_address]:join_port>;rt=brski.jp
In actual examples based on this, the field IP_address would contain
the link-local IP address of the Join Proxy and the field join_port
would contain the join-port value as a decimal number.
Note that the join_port field and preceding colon MAY be absent in
the discovery response: this indicates that the join-port is the
default CoAPS port 5684.
In the returned CoRE link format document, discoverable port numbers
are usually returned for the Join Proxy resource in the <URI-
Reference> of the link (see Section 5.1 of [RFC6690] for details).
5.3. Pledge Discovers Multiple Join Ports
A Pledge MUST be able to handle multiple join-ports being returned in
a discovery response sent by a Join Proxy. This can happen if the
network supports multiple Registrars and/or multiple Registrar-
services as defined in Section 4.6. Then, each Registrar gets
assigned its own join-port (up to a limit imposed by Join Proxy
implementation) so that a Pledge is enabled to failover to another
Registrar if a prior onboarding attempt fails.
How the Pledge selects between the onboarding services matching its
query, is implementation-specific and out of scope of this document.
Discovery of multiple Registrars works in the same way as discovery
of a single Registrar as defined in Section 5.2, except that multiple
links are returned in the CoRE Link Format document.
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The meta-example below shows the discovery of two join-ports (fields
join_port1 and join_port2) on a Join Proxy, each associated to a
different cBRSKI protocol variant, defined by two CoRE Link Format
links:
REQ: GET coap://[ff02::fd]/.well-known/core?rt=brski.jp
RES: 2.05 Content
Content-Format: 40
Payload:
<coaps://[IP_address]:join_port1>;rt=brski.jp,
<coaps://[IP_address]:join_port2>;rt=brski.jp;
param1=value1;param2=value2
In actual examples based on this, the field IP_address would contain
the link-local IP address of the Join Proxy and the fields join_port1
and join_port2 would contain distinct decimal port number values.
The parameter values (param1 and param2) are included for
illustrative purposes. In a real example, these would contain Link
Format parameters specifically defined for the brski.jp resource
type. Such parameters may be defined in future work
([I-D.ietf-anima-brski-discovery]). These parameters, if understood
by the Pledge, help in selecting the optimal matching onboarding
protocol variant of cBRSKI. If the Pledge does not understand these
parameters, it can select any one of the two join-ports for cBRSKI
onboarding. If the attempt subsequently fails, the Pledge repeats
the attempt using the other discovered join-port as defined by
[cBRSKI].
6. Comparison of Stateless and Stateful Modes
The stateful and stateless mode of operation for the Join Proxy each
have their advantages and disadvantages. This section helps
operators and/or profile-specifiers to make a choice between the two
modes based on the available device resources and network bandwidth.
Stateful mode introduces the complexity of maintaining per-connection
state, which can increase processing and memory requirements on the
proxy compared to the stateless mode under ideal conditions.
Additionally, it opens up a wider range of potential implementation
challenges in the presence of misbehaving or malicious Pledges. For
example: How can state be effectively limited? How can malicious
Pledges be detected—or at least prevented from negatively impacting
non-malicious nodes? And so on.
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If the proxy is deployed on nodes that support frequent and reliable
software updates, then tailoring software enhancements based on the
observed attack profile(s) in the deployment scenario is an effective
way to improve and harden the implementation. However, many
constrained devices either lack this software agility or
intentionally avoid it. In such environments, stateless mode becomes
advantageous, as it offloads most of the complex hardening
responsibilities to the Registrar, allowing the proxy implementation
to remain as lightweight as possible. Ultimately, a stateless proxy
requires no more protective mechanisms than a basic packet-forwarding
router.
The main concern for a stateless Join Proxy is the risk of forwarding
an excessive number of packets to the Registrar, particularly over
low-bandwidth connections such as 6LoWPAN links. Rate-limiting
forwarded packets is the primary defense mechanism in such cases.
All other Pledge-specific protections can be delegated to the
Registrar, which is expected to have the necessary software agility
to handle these.
The following table summarizes more comparison details.
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+=============+=============================+=======================+
| Properties | Stateful mode | Stateless mode |
+=============+=============================+=======================+
| State | The Join Proxy needs | No information is |
| Information | additional storage to | maintained by the |
| | maintain mappings between | Join Proxy. |
| | the address and port | Registrar transiently |
| | number of the Pledge and | stores the JPY |
| | those of the Registrar. | message header. |
+-------------+-----------------------------+-----------------------+
| Packet size | The size of a relayed | Size of a relayed |
| | message is the same as the | message is up to 38 |
| | original message. | bytes larger than the |
| | | original: due to |
| | | additional context |
| | | data. |
+-------------+-----------------------------+-----------------------+
| Technical | The Join Proxy needs | Requires new JPY |
| complexity | additional functions to | message structure |
| | maintain state | (CBOR) in Join Proxy. |
| | information, and specify | The Registrar |
| | the source and destination | requires a function |
| | addresses and ports of | to process JPY |
| | relayed messages. | messages. |
+-------------+-----------------------------+-----------------------+
| Join Proxy | Join Proxy needs | Join Proxy needs |
| Ports | discoverable join-port | discoverable join- |
| | | port |
+-------------+-----------------------------+-----------------------+
| Registrar | Registrar can host on a | Registrar must host |
| Ports | single UDP port. | on two UDP ports: one |
| | | for DTLS, one for JPY |
| | | messages. |
+-------------+-----------------------------+-----------------------+
Table 1: Comparison between stateful and stateless Join Proxy mode
7. Security Considerations
For a Pledge using a Join Proxy, all the security considerations and
requirements in Section 4.1 of [RFC8995] apply. While doing
discovery of Join Proxies, the Pledge can be deceived by malicious
Join Proxy announcements.
The subsequent communication of a Pledge with a Registrar that flows
via the Join Proxy is end-to-end protected by DTLS.
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A malicious Join Proxy has a number of relay/routing options for
messages sent by a Pledge:
* It relays messages to a malicious Registrar. This is the same
case as the presence of a "malicious Registrar" discussed in
[RFC8995].
* It does not relay messages, or does not return the responses from
the Registrar to the Pledge. This is equivalent to the case of a
non-responding Registrar discussed in Section 4.1 of [RFC8995] and
Section 5.1 of [RFC8995].
* It uses the returned responses of the Registrar for its own
(attack) purposes. This is very unlikely due to the DTLS
security.
* It uses the request from the Pledge to take the Pledge certificate
and impersonate the Pledge. This is very unlikely because that
requires it to acquire the private key of the Pledge, for an
attack to be effective.
A malicious Pledge may also craft and send messages to a Join Proxy:
* It can construct an invalid DTLS or UDP message and send it to the
open join-port of the Join Proxy. A Join Proxy will accept the
message and relay to the Registrar without checking the payload.
The Registrar will now parse the invalid message as DTLS protocol
payload. Due to the security properties of DTLS, it is highly
unlikely that this malicious payload will lead to message
acceptance or to the Registrar's malfunctioning. The Registrar of
course MUST be prepared to receive invalid and/or non-DTLS
payloads in this way. If the Pledge uses large UDP payloads, the
attacker is able to misuse network resources. This way, a DoS
attack could be performed by using multiple malicious Pledges, or
using a single device posing as multiple Pledges.
For a malicious node that is either a neighbor of a Join Proxy, or is
a router on the network path to the Registrar, and the node is part
of the trusted network:
* It may sniff the messages routed by the Join Proxy. It is very
unlikely that the malicious node can decrypt the DTLS payload.
The malicious node may be able to read the inner data structure in
the JPY Header field, if that is not encrypted. This does expose
some information about the Pledge attempting to join, but this can
be mitigated by the Pledge using a new (random) link-local address
for each onboarding attempt.
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In case the JPY Header is not encrypted, a malicious node has a
number of options to craft a JPY message and send it to a stateless
Join Proxy:
* It can craft a JPY message with header fields of its choice based
on earlier observed contents of JPY messages sent by a stateless
Join Proxy. In that case, the Join Proxy would accept the message
and send the Content field data to a Pledge as a UDP message.
Such a message could disrupt an ongoing DTLS session. It could
also allow the attacker to access an unsecured UDP port that a
Pledge may have exposed. For this reason, a Pledge MUST NOT
accept messages on other UDP ports than its port used for
onboarding while an onboarding attempt is ongoing.
It should be noted here that the JPY message CBOR array and the JPY
Header field are not DTLS protected. When the communication between
stateless Join Proxy and Registrar passes over an unsecure network,
an attacker can change the CBOR array, and change the Header field if
no encryption is used there. These concerns are also expressed in
[RFC8974]. It is also pointed out here that the encryption by the
source of the JPY Header, the Join Proxy, is a local matter. Similar
to [RFC8974], the use of AES-CCM [RFC3610] with a 64-bit tag is
recommended, combined with a sequence number and a replay window.
A "malicious Registrar" (see [RFC8995]) may also be unknowingly
selected by a genuine (non-compromised) Join Proxy. This may happen
when the malicious Registrar either modifies the network's Registrar
address configuration or presents itself as a Registrar using the
discovery method used in the network. If the discovery of Registrars
is performed in an unsecured manner within the trusted network, it
would allow the malicious Registrar to present itself as a Registrar
candidate. CoAP discovery defined in Section 5) is, for example,
defined without any transport-layer or application-layer security. A
trusted Join Proxy may therefore relay a Pledge's messages to it.
It is the responsibility of a Pledge to monitor if an onboarding
attempt with the selected Join Proxy and selected join-port on this
Proxy (in case of multiple) is proceeding sufficiently quickly. If
this is not the case, the Pledge needs to switch to another join-port
and/or another Join Proxy to retry its onboarding attempt. See
Section 4.6 for specification details on this.
In some installations, layer 2 (link layer) security is provided
between all node pairs of a mesh network. In such an environment, in
case all mesh nodes are trusted, and the Registrar is also located on
the mesh network, and on-mesh attackers are not considered, then
encryption of the JPY Header field as specified in this document is
not necessary because the layer 2 security already protects it.
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8. IANA Considerations
8.1. Resource Type Attributes Registry
This specification registers two new Resource Type (rt=) Link Target
Attributes in the "Resource Type (rt=) Link Target Attribute Values"
registry under the "Constrained RESTful Environments (CoRE)
Parameters" registry group, per the [RFC6690] procedure.
Attribute Value: brski.jp
Description: Constrained Join Proxy for cBRSKI onboarding protocol.
Reference: [This RFC]
Attribute Value: brski.rjp
Description: cBRSKI Registrar Join Proxy endpoint that supports the
JPY protocol.
Reference: [This RFC]
8.2. coaps+jpy Scheme Registration
This specification registers a new URI scheme per [RFC7595] under the
IANA "Uniform Resource Identifier (URI) Schemes" registry.
Scheme name: coaps+jpy
Status: permanent
Applications/protocols that use this scheme name:
cBRSKI, constrained Join Proxy
Contact: ANIMA WG
Change controller: IESG
References: [This RFC]
The scheme specification is provided below.
* Scheme syntax: identical to the "coaps" scheme defined in
[RFC7252].
* Scheme semantics: identical to the "coaps" scheme, except that the
JPY message encapsulation mechanism described in Section 4.5 of
[This RFC] is used to transport each CoAPS UDP datagram.
* Encoding considerations: identical to the "coaps" scheme.
* Interoperability considerations: identical to the "coaps" scheme.
* Security considerations: all of the security considerations of the
"coaps" scheme apply. Users of this scheme should be aware that
as part of the intended use, a UDP message that was formed using
the "coaps" scheme is embedded by a Join Proxy as defined by [This
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RFC] into a UDP message conforming to the "coaps+jpy" scheme
without the Join Proxy being able to parse/decode which CoAPS URI
was originally used by the sender, since that information is
stored as DTLS-protected data. The receiving server can transform
the "coaps+jpy" scheme back to the original "coaps" scheme by
decoding the JPY message payload. However, any CoAP-related
information not stored in the DTLS-protected data (such as in the
UDP/IP headers) may be changed by these scheme transforms.
8.3. Service Name and Transport Protocol Port Number Registry
This specification registers two service names under the IANA
"Service Name and Transport Protocol Port Number" registry.
Service Name: brski-jp
Transport Protocol(s): udp
Assignee: IESG <iesg@ietf.org>
Contact: IESG <iesg@ietf.org>
Description: Bootstrapping Remote Secure Key Infrastructure
constrained Join Proxy
Reference: [This RFC]
Service Name: brski-rjp
Transport Protocol(s): udp
Assignee: IESG <iesg@ietf.org>
Contact: IESG <iesg@ietf.org>
Description: Bootstrapping Remote Secure Key Infrastructure
Registrar join-port, supporting the coaps+jpy
scheme, used by stateless constrained Join Proxy
Reference: [This RFC]
9. References
9.1. Normative References
[cBRSKI] Richardson, M., Van der Stok, P., Kampanakis, P., and E.
Dijk, "Constrained Bootstrapping Remote Secure Key
Infrastructure (cBRSKI)", Work in Progress, Internet-
Draft, draft-ietf-anima-constrained-voucher-27, 3 March
2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-constrained-voucher-27>.
[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/rfc/rfc2119>.
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[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/rfc/rfc4443>.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
DOI 10.17487/RFC5288, August 2008,
<https://www.rfc-editor.org/rfc/rfc5288>.
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/rfc/rfc768>.
[RFC792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<https://www.rfc-editor.org/rfc/rfc792>.
[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/rfc/rfc8174>.
[RFC8366bis]
Watsen, K., Richardson, M., Pritikin, M., Eckert, T. T.,
and Q. Ma, "A Voucher Artifact for Bootstrapping
Protocols", Work in Progress, Internet-Draft, draft-ietf-
anima-rfc8366bis-14, 1 April 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-anima-
rfc8366bis-14>.
[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/rfc/rfc8949>.
[RFC8995] Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
May 2021, <https://www.rfc-editor.org/rfc/rfc8995>.
[RFC9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/rfc/rfc9147>.
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[RFC9148] van der Stok, P., Kampanakis, P., Richardson, M., and S.
Raza, "EST-coaps: Enrollment over Secure Transport with
the Secure Constrained Application Protocol", RFC 9148,
DOI 10.17487/RFC9148, April 2022,
<https://www.rfc-editor.org/rfc/rfc9148>.
9.2. Informative References
[I-D.ietf-anima-brski-discovery]
Eckert, T. T. and E. Dijk, "BRSKI discovery and
variations", Work in Progress, Internet-Draft, draft-ietf-
anima-brski-discovery-05, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-anima-
brski-discovery-05>.
[I-D.kumar-dice-dtls-relay]
Kumar, S. S., Keoh, S. L., and O. Garcia-Morchon, "DTLS
Relay for Constrained Environments", Work in Progress,
Internet-Draft, draft-kumar-dice-dtls-relay-02, 20 October
2014, <https://datatracker.ietf.org/doc/html/draft-kumar-
dice-dtls-relay-02>.
[I-D.richardson-anima-state-for-joinrouter]
Richardson, M., "Considerations for stateful vs stateless
join router in ANIMA bootstrap", Work in Progress,
Internet-Draft, draft-richardson-anima-state-for-
joinrouter-03, 22 September 2020,
<https://datatracker.ietf.org/doc/html/draft-richardson-
anima-state-for-joinrouter-03>.
[ieee802-1AR]
"IEEE 802.1AR Secure Device Identity", IEEE Standards
Association, 2018,
<https://standards.ieee.org/ieee/802.1AR/6995/>.
[RFC3610] Whiting, D., Housley, R., and N. Ferguson, "Counter with
CBC-MAC (CCM)", RFC 3610, DOI 10.17487/RFC3610, September
2003, <https://www.rfc-editor.org/rfc/rfc3610>.
[RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
Configuration of IPv4 Link-Local Addresses", RFC 3927,
DOI 10.17487/RFC3927, May 2005,
<https://www.rfc-editor.org/rfc/rfc3927>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/rfc/rfc3986>.
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[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/rfc/rfc4944>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/rfc/rfc6550>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/rfc/rfc6690>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/rfc/rfc6775>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/rfc/rfc7030>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/rfc/rfc7102>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/rfc/rfc7228>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
and Registration Procedures for URI Schemes", BCP 35,
RFC 7595, DOI 10.17487/RFC7595, June 2015,
<https://www.rfc-editor.org/rfc/rfc7595>.
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[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/rfc/rfc7959>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8974] Hartke, K. and M. Richardson, "Extended Tokens and
Stateless Clients in the Constrained Application Protocol
(CoAP)", RFC 8974, DOI 10.17487/RFC8974, January 2021,
<https://www.rfc-editor.org/rfc/rfc8974>.
[RFC8990] Bormann, C., Carpenter, B., Ed., and B. Liu, Ed., "GeneRic
Autonomic Signaling Protocol (GRASP)", RFC 8990,
DOI 10.17487/RFC8990, May 2021,
<https://www.rfc-editor.org/rfc/rfc8990>.
[RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
Autonomic Control Plane (ACP)", RFC 8994,
DOI 10.17487/RFC8994, May 2021,
<https://www.rfc-editor.org/rfc/rfc8994>.
[RFC9031] Vučinić, M., Ed., Simon, J., Pister, K., and M.
Richardson, "Constrained Join Protocol (CoJP) for 6TiSCH",
RFC 9031, DOI 10.17487/RFC9031, May 2021,
<https://www.rfc-editor.org/rfc/rfc9031>.
Appendix A. Stateless Join Proxy JPY Message Examples
This appendix shows an example of a JPY message, sent by a stateless
Join Proxy to a Registrar, and an example of the return JPY message
sent by the Registrar. The DTLS payload itself, carried in the
Content (C) field of the JPY message, is not shown in detail but
abbreviated.
First, assume that a Pledge creates a CoAP request to a Join Proxy
that it has just discovered and selected for performing [cBRSKI]
onboarding.
This request may be a Pledge Voucher Request (PVR) as follows:
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POST coaps://[fe80::1234:5678]:45965/.well-known/brski/rv
Content-Format: 836
Payload:
<bytes of the COSE-signed PVR>
Because a DTLS session is not yet established at this point, the
first step for the client is to send the DTLS Client Hello message to
the Join Proxy's join-port 45965. When the Join Proxy receives this
UDP packet, it creates a JPY message with the following UDP payload:
82 # array(2)
50 # bytes(16)
D01914BCC376A88FFECC50CA6017B0C1 #
59 01AB # bytes(427)
16FEFD0000000000000000019E ...
<further bytes of DTLS 1.2 Client Hello>
The same JPY message written in CBOR diagnostic notation [RFC8949]
is:
[ h'd01914bcc376a88ffecc50ca6017b0c1' ,
h'16fefd0000000000000000019e' ... '3d45' ]
Above, the ellipsis ("...") notation in a CBOR diagnostic byte string
denotes a further sequence of bytes that is not shown for brevity.
The first CBOR byte string wraps the 16 bytes of encrypted state
information of the Header (H) field. The second CBOR byte string
wraps the 427 bytes of the received DTLS message.
After the Registrar has processed the received JPY message, it sends
a DTLS 1.2 Hello Verify Request in response to the received Client
Hello message. This Hello Verify Request is wrapped in a new JPY
message that it sends back to the Join Proxy:
82 # array(2)
50 # bytes(16)
D01914BCC376A88FFECC50CA6017B0C1 #
58 3C # bytes(60)
16FEFD0000000000000000002F ...
<further bytes of DTLS 1.2 Hello Verify Request>
The same JPY message in CBOR diagnostic notation is:
[ h'd01914bcc376a88ffecc50ca6017b0c1' ,
h'16fefd0000000000000000002f' ... '66c1' ]
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Acknowledgements
[I-D.richardson-anima-state-for-joinrouter] outlined the various
options for building a constrained Join Proxy.
Many thanks for the comments by Bill Atwood, Carsten Bormann, Brian
Carpenter, Spencer Dawkins, Esko Dijk, Toerless Eckert, Russ Housley,
Ines Robles, Rich Salz, Jürgen Schönwälder, Mališa Vučinić, and Rob
Wilton.
This document is very much inspired by text published earlier in
[I-D.kumar-dice-dtls-relay]. Sandeep Kumar, Sye loong Keoh, and
Oscar Garcia-Morchon are the co-authors of this document. Their
draft text has served as a basis for this document.
Changelog
-16 to -17
* Added security consideration that a genuine Join Proxy may
relay to a malicious Registrar (#33, #77).
* Added solution and specification sections on the use of
multiple Registrars (#45, #65, #76).
* Added clarification that Registrar address(es) can be
configured, or discovered (#76).
* Define conditions for implementing only a single Join Proxy
mode - stateful or stateless (#69, #73)
* Improved JPY Header security by adding integrity protection
(#74).
* Fixed format definition of example JPY Header (#74).
* Editorial updates.
-15 to -16
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* Security considerations text reviewed and expanded with more
attack types.
* Define CoAP discovery as default, remove GRASP/6TiSCH (#68).
* Abstract updated to describe higher-level concepts (#47).
* Applied Spencer's TSVART review comment 2022-05-16 in an
improved manner.
* Applied Russ' review comments from IOTDIR review 2023-08-09.
* Rewrite Section 4.1 based on Russ' review (#48).
* Applied Toerless' review comments from WGLC (#63).
* Applied review comments of Bill Atwood of 2024-05-21.
* Clarify 'context payload' terminology (#49).
* Use shorter and consistent term for Join Proxy (#58).
* Appendix A corrected to use latest JPY message format.
* Author added.
* Update reference RFC8366 to RFC8366bis.
* Many editorial updates.
-13 to -15
* Various editorial updates and minor changes.
-12 to -13
* jpy message encrypted and no longer standardized
-11 to -12
* many typos fixed and text re-organized
* core of GRASP and CoAP discovery moved to constrained-voucher
document, only stateless extensions remain
-10 to -11
* Join Proxy and Registrar discovery merged
* GRASP discovery updated
* ARTART review
* TSVART review
-09 to -10
* OPSDIR review
* IANA review
* SECDIR review
* GENART review
-07 to -09
* typos
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-06 to -07
* AD review changes
-05 to -06
* RT value change to brski.jp and brski.rjp
* new registry values for IANA
* improved handling of jpy header array
-04 to -05
* Join Proxy and join-port consistent spelling
* some nits removed
* restructured discovery
* section
* rephrased parts of security section
-03 to -04
* mail address and reference
-02 to -03
* Terminology updated
* Several clarifications on discovery and routability
* DTLS payload introduced
-01 to -02
* Discovery of Join Proxy and Registrar ports
-00 to -01
* Registrar used throughout instead of EST server
* Emphasized Join Proxy port for Join Proxy and Registrar
* updated discovery accordingly
* updated stateless Join Proxy JPY header
* JPY header described with CDDL
* Example simplified and corrected
-00 to -00
* copied from vanderstok-anima-constrained-join-proxy-05
Authors' Addresses
Richardson, et al. Expires 6 January 2026 [Page 40]
Internet-Draft Join Proxy July 2025
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Peter van der Stok
vanderstok consultancy
Email: stokcons@kpnmail.nl
Panos Kampanakis
Cisco Systems
Email: pkampana@cisco.com
Esko Dijk
IoTconsultancy.nl
Email: esko.dijk@iotconsultancy.nl
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