CoRE C. Amsüss
Internet-Draft 2 November 2020
Intended status: Experimental
Expires: 6 May 2021
CoRE Resource Directory Extensions
draft-amsuess-core-resource-directory-extensions-04
Abstract
A collection of extensions to the Resource Directory
[I-D.ietf-core-resource-directory] that can stand on their own, and
have no clear future in specification yet.
Status of This Memo
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This Internet-Draft will expire on 6 May 2021.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Reverse Proxy requests . . . . . . . . . . . . . . . . . . . 3
2.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Registration . . . . . . . . . . . . . . . . . . . . . . 3
2.2.1. Registration updates . . . . . . . . . . . . . . . . 4
2.2.2. Proxy behavior . . . . . . . . . . . . . . . . . . . 4
2.2.3. On-Demand proxying . . . . . . . . . . . . . . . . . 5
2.2.4. Multiple upstreams . . . . . . . . . . . . . . . . . 5
2.2.5. Examples . . . . . . . . . . . . . . . . . . . . . . 5
2.2.6. Notes on stability and maturity . . . . . . . . . . . 7
2.2.7. Security considerations . . . . . . . . . . . . . . . 7
3. Infinite lifetime . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Lookup across link relations . . . . . . . . . . . . . . . . 8
4.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Lifetime Age . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Zone identifier introspection . . . . . . . . . . . . . . . . 9
6.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Proxying multicast requests . . . . . . . . . . . . . . . . . 10
7.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Opportunistic RD . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Applications . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 15
Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 16
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
This document pools some extensions to the Resource Directory
[I-D.ietf-core-resource-directory] that might be useful but have no
place in the original document.
They might become individual documents for IETF submission, simple
registrations in the RD Parameter Registry at IANA, or grow into a
shape where they can be submitted as a collection of tools.
At its current state, this draft is a collection of ideas.
[ This document is being developed at https://gitlab.com/chrysn/
resource-directory-extensions (https://gitlab.com/chrysn/resource-
directory-extensions). ]
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2. Reverse Proxy requests
When a registrant registers at a Resource Directory, it might not
have a suitable address it can use as a base address. Typical
reasons include being inside a NAT without control over port
forwarding, or only being able to open outgoing connections (as
program running inside a web browser utilizing CoAP over WebSocket
[RFC8323] might be).
[I-D.ietf-core-resource-directory] suggests (in the Cellular M2M use
case) that proxy access to such endpoints can be provided, it gives
no concrete mechanism to do that; this is such a mechanism.
This mechanism is intended to be a last-resort option to provide
connectivity. Where possible, direct connections are preferred.
Before registering for proxying, the registrant should attempt to
obtain a publicly available port, for example using PCP ([RFC6887]).
The same mechanism can also be employed by clients that want to
conceal their network address from its clients.
2.1. Discovery
An RD that provides proxying functionality advertises it by
announcing the additional resource type "TBD1" on its directory
resource.
2.2. Registration
A client passes the "proxy=yes" or "proxy=ondemand" query parameter
in addition to (but typically instead of) a "base" query parameter.
A server that receives a "proxy=yes" query parameter in a
registration (or receives "proxy=ondemand" and decides it needs to
proxy) MUST come up with a "Proxy URL" on which it accepts requests,
and which it uses as a Registration Base URI for lookups on the
present registration.
The Proxy URL SHOULD have no path component, as acting as a reverse
proxy in such a scenario means that any relative references in all
representations that are proxied must be recognized and possibly
rewritten.
The RD MAY mint several alternative Registration Base URIs using
different protocols to make the proxied content available;
[I-D.silverajan-core-coap-protocol-negotiation] can be used to
advertise them.
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The registrant is not informed of the chosen public name by the RD.
This mechanism is applicable to all transports that can be used to
register. If proxying is active, the restrictions on when the base
parameter needs to be present ([I-D.ietf-core-resource-directory]
Registration template) are relaxed: The base parameter may also be
absent if the connection originates from an ephemeral port, as long
as the underlying protocol supports role reversal, and link-local
IPv6 addresses may be used without any concerns of expressibility.
If the client uses the role reversal rule relaxation, it keeps that
connection open for as long as it wants to be reachable. When the
connection terminates, the RD SHOULD treat the registration as having
timed out (even if its lifetime has not been exceeded) and MAY
eventually remove the registration.
2.2.1. Registration updates
The "proxy" query parameter can not be changed or repeated in a
registration update; RD servers MUST answer 4.00 Bad Request to any
registration update that has a "proxy" query parameter.
As always, registration updates can explicitly or implicitly update
the Registration Base URI. In proxied registrations, those changes
are not propagated to lookup, but do change the forwarding address of
the proxy.
For example, if a registration is established over TCP, an update can
come along in a new TCP connection. Starting then, proxied requests
are forwarded along that new connection.
Note that transports can not be switched in a registration update, as
the protocol is part of the registration resource.
2.2.2. Proxy behavior
The RD operates as a reverse-proxy as described in [RFC7252]
Section 5.7.3 at the announced Proxy URL(s), where it decides based
on the requested host and port to which registrant endpoint to
forward the request.
The address the incoming request are forwarded to is the base address
of the registration. If an explicit "base" paremter is given, the RD
will forward requests to that location. Otherwise, it forwards to
the registration's source address (which is the implied base
parameter).
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2.2.3. On-Demand proxying
If an endpoint is deployed in an unknown network, it might not know
whether it is behind a NAT that would require it to configure an
explicit base address, and ask the RD to assist by proxying if
necessary by registering with the "proxy=ondemand" query parameter.
A server receiving that SHOULD use a different IP address to try to
access the registrant's .well-known/core file using a GET request
under the Registration Base URI. If that succeeds, it may assume
that no NAT is present, and ignore the proxying request. Otherwise,
it configures proxying as if "proxy=yes" were requested.
Note that this is only a heuristic [ and not tested in deployments
yet ].
2.2.4. Multiple upstreams
When a proxying RD is operating behind a router that has uplinks with
multiple provisioning domains (see [RFC7556]) or a similar setup, it
MAY mint multiple addresses that are reachable on the respective
provisioning domains. When possible, it is preferred to keep the
number of URIs handed out low (avoiding URI aliasing); this can be
achieved by announcing both the proxy's public addresses under the
same wildcard name.
If RDs are announced by the uplinks using RDAO, the proxy may use the
methods of [I-D.amsuess-core-rd-replication] to distribute its
registrations to all the announced upstream RDs.
In such setups, the router can forward the upstream RDs using the PvD
option ([RFC8801]) to PvD-aware hosts and only announce the local RD
to PvD-unaware ones (which then forwards their registrations). It
can be expected that PvD-aware endpoints are capable of registering
with multiple RDs simultaneously.
2.2.5. Examples
2.2.5.1. Registration through a firewall
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Req from [2001:db8:42::9876]:5683:
POST coap://rd.example.net/rd?ep=node9876&proxy=ondemand
</some-resource>;rt="example.x"
Req from other-address.rd.example.net:
GET coap://[2001:db8:42::9876]/.well-known/core
Request blocked by stateful firewall around [2001:db8:42::]
RD decides that proxying is necessary
Res: 2.04 Created
Location: /reg/abcd
Later, lookup of that registration might say:
Req: GET coap://rd.example.net/lookup/res?rt=example.x
Res: 2.05 Content
<coap://node987.rd.example.net/some-resource>;rt="example.x
A request to that resource will end up at an IP address of the RD,
which will forward it using its the IP and port on which the
registrant had registered as source port, thus reaching the
registrant through the stateful firewall.
2.2.5.2. Registration from a browser context
Req: POST coaps+ws://rd.example.net/rd?ep=node1234&proxy=yes
</gyroscope>;rt="core.s"
Res: 2.04 Created
Location: /reg/123
The gyroscope can now not only be looked up in the RD, but also be
reached:
Req: GET coap://rd.example.net/lookup/res?rt=core.s
Res: 2.05 Content
<coap://[2001:db8:1::1]:10123/gyroscope>;rt="core.s"
In this example, the RD has chosen to do port-based rather than host-
based virtual hosting and announces its literal IP address as that
allows clients to not send the lengthy Uri-Host option with all
requests.
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2.2.6. Notes on stability and maturity
Using this with UDP can be quite fragile; the author only draws on
own experience that this can work across cell-phone NATs and does not
claim that this will work over generic firewalls.
[ It may make sense to have the example as TCP right away. ]
2.2.7. Security considerations
An RD MAY impose additional restrictions on which endpoints can
register for proxying, and thus respond 4.01 Unauthorized to request
that would pass had they not requested proxying.
Attackers could do third party registrations with an attacked
device's address as base URI, though the RD would probably not
amplify any attacks in that case.
The RD MUST NOT reveal the address at which it reaches the registrant
except for adaequately authenticated and authorized debugging
purposes, as that address could reveal sensitive location data the
registrant may wish to hide by using a proxy.
Usual caveats for proxies apply.
3. Infinite lifetime
An RD can indicate support for infinite lifetimes by adding the
resoruce type "TBD2" to its list of resource types.
A registrant that wishes to keep its registration alive indefinitely
can set the lifetime value as "lt=inf".
Registrations with infinite lifetimes never time out.
Infinite lifetimes SHOULD only be used by commissioning tools, or for
proxy registrations over stateful connections.
3.1. Example
Had the example of Section 2.2.5.2 discovered support for infinite
lifetimes during lookup like this:
Req: GET coaps+ws://rd.example.net/.well-known/coer?rt=core.rd*
Res: 2.05 Content
</rd>;rt="core.rd TBD1 TBD2";ct=40
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it could register like that:
Req: POST coaps+ws://rd.example.net/rd?ep=node1234&proxy=yes<=inf
</gyroscope>;rt="core.s"
Res: 2.04 Created
Location: /reg/123
and never need to update the registration for as long as the
websocket connection is open.
(When it gets terminated, it could try renewing the registration, but
needs to be prepared for the RD to already have removed the original
registration.)
4. Lookup across link relations
Resource lookup occasionally needs execute multiple queries to follow
links.
An RD server (or any other server that supports [RFC6690] compatible
lookup), can announce support for following links in resource lookups
by announcing support for the TBD3 interface type on its resource
lookup.
A client can the query that server to not only provide the matched
links, but also links that are reachable over relations given in
"follow" query parameters.
4.1. Example
Assume a node presents the following data in its <.well-known/core>
resource (and submitted the same to the RD):
</temp>;if="core.s";rt="example.temperature",
</t-prot>;rel="calibration-protocol";anchor="/temp",
<http://vendor.example.com/temp9000>;rel="describedby";anchor="/temp",
</hum>;if="core.s";rt="example.humidity",
</h-prot>;rel="calibration-protocol";anchor="/hum",
A lookup client can, in one query, find the temperature sensor and
its relevant metadata:
Req: GET /rd-lookup/res?rt=example.temperature&follow=calibration-protocol&follow=describedby
<coap://node1/temp>;if="core.s";rt="example.temperature";anchor="coap://node1",
<coap://node1/t-prot>;rel="calibration-protocol";anchor="coap://node1/temp",
<http://vendor.example.com/temp9000>;rel="describedby";anchor="coap://node1/temp",
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[ There is a better example (https://github.com/ace-wg/ace-oauth/
issues/120#issuecomment-407997786) in an earlier stage of
[I-D.tiloca-core-oscore-discovery] ]
Given the likelihood of a CoRAL based successor to [RFC6690], this
lookup variant might easily be superseeded by a CoRAL FETCH format;
it might look like this there:
Req: FETCH /reef-lookup
Content-Format: application/template-coral+cbor
Payload:
#using core = <...>
#using reef = <...>
reef:content ?x {
core:rt "example.temperature"
calibration-protocol ?y {
core:describedby ?z
}
}
Res: 2.01 Content
Content-Format: aplication/coral+cbor
Payload:
reef:content <coap://node1/temp> {
core:rt "example.temperature"
calibration-protocol <coap://node1/t-prot> {
core:describedby <http://vendor.example.com/temp9000>
}
}
5. Lifetime Age
This extension is described in [I-D.amsuess-core-rd-replication]
Section 5.2.
The "provenance" extension in Section 5.1 of the same document should
probably be expressed differently to avoid using non-target link
attributes.
6. Zone identifier introspection
The 'split-horizon' mechanism introduced in
[I-D.ietf-core-resource-directory] (-19) (that registrations with
link-local bases can only be read from the zone they registered on)
reduces the usability of the endpoint lookup interface for debugging
purposes.
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To allow an administrator to read out the "show-zone-id" query
parameter for endpoint and resource lookup is introduced.
A Resource Directory that understands this parameter MUST NOT limit
lookup results to registrations from the lookup's zone, and MUST use
[RFC6874] zone identifiers to annotate which zone those registrations
are valid on.
The RD MUST limit such requests to authenticated and authorized
debugging requests, as registrants may rely on the RD to keep their
presence secret from other links.
6.1. Example
Req: GET /rd-lookup/ep?show-zone-id&et=printer
Res: 2.05 Content
</reg/1>;base="coap://[2001:db8::1]";et=printer;ep="bigprinter",
</reg/2>;base="coap://[fe80::99%wlan0]";et=printer;ep="localprinter-1234",
</reg/3>;base="coap://[fe80::99%eth2]";et=printer;ep="localprinter-5678",
7. Proxying multicast requests
Multicast requests are hard to forward at a proxy: Even if a media
type is used in which multiple responses can be aggregated
transparently, the proxy can not reliably know when all responses
have come in. [RFC7390] Section 2.9 destribes the difficulties in
more detail.
A proxy MAY expose an interface compatible with the RD lookup
interface, which SHOULD be advertised by a link to it that indicates
the resource types core.rd-lookup-res and TBD4.
The proxy sends multicast requests to All CoAP Nodes ([RFC7252]
Section 12.8) requesting their .well-known/core files either eagerly
(ie. in regular intervals independent of queries) or on demand (in
which case it SHOULD limit the results by applying [RFC6690] query
filtering; if it has received multiple query parameters it should
forward the one it deems most likely to limit the results, as .well-
known/core only supports a single query parameter).
In comparison to classical RD operation, this RD behaves roughly as
if it had received a simple registration with a All CoAP Nodes
address as the source address, if such behavior were specified. The
individual registrations that result from this neither have an
explicit registration resource nor an explicit endpoint name; given
that the endpoint lookup interface is not present on such proxies,
neither can be queried.
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Clients that would intend to do run a multicast discovery operation
behind the proxy can then instead query that resource lookup
interface. They SHOULD use observation on lookups, as an on-demand
implementation MAY return the first result before others have
arrived, or MAY even return an empty link set immediately.
7.1. Example
Req: GET coap+ws://gateway.example.com/.well-known/core?rt=TBD4
Res: 2.05 Content
</discover>;rt="core.rd-lookup-res TBD4";ct=40
Req: GET coap+ws://gateway.example.com/discover?rt=core.s
Observe: 0
Res: 2.05 Content
Observe: 0
Content-Format: 40
(empty payload)
At the same time, the proxy sends out multicast requests on its
interfaces:
Req: GET coap://ff05::fd/.well-known/core?rt=core.s
Res (from [2001:db8::1]:5683): 2.05 Content
</temp>;ct="0 112";rt="core.s"
Res (from [2001:db8::2]:5683): 2.05 Content
</light>;ct="0 112";rt="core.s"
upon receipt of which it sends out a notification to the websocket
client:
Res: 2.05 Content
Observe: 1
Content-Format: 40
<coap://[2001:db8::1]/temp>;ct="0 112";rt="core.s";anchor="coap://[2001:db8::1]",
<coap://[2001:db8::2]/light>;ct="0 112";rt="core.s";anchro="coap://[2001:db8::2]"
8. Opportunistic RD
An application that wants to advertise its resources in Resource
Directory can find itself in a network that has no RD deployed. It
may be able to start an RD on its own to fill in that gap until an
explicitly configured one gets installed.
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This bears the risk of having competing RDs on the same network,
where resources registered at one can not be discovered on the other.
To mitigate that, such Opportunistic Resource Directories should
follow those steps:
* The RD chooses its own Opportunistic Capability value. That
integer number is an estimate of number of target attributes it
expects to be able to store, where in absence of better estimates
one would assume that a registration contains 16 links, and each
links contains three target attributes each with an eight byte key
and a 16 byte value.
The Opportunistic Capability value is advertised as a TBD5-cap=
target attribute on the registration resource.
* The RD chooses its own Opportunistic Tie-Break value. That
integer number needs no other properties than being likely to be
different even for two instances of the same device being started;
numeric forms of MAC addresses or random numbers make good
candidates.
The Opportunistic Capability value is advertised as a TBD5-tie=
target attribute on the registration resource.
* The Opportunistic RD, before advertising its resources, performs
RD discovery itself, using at least all the discovery paths it may
become discoverable on itself.
* If the Opportunistic RD finds no other RD, or if the RD it finds
is less capable than itself, it can start advertising itself as a
Resource Directory.
An RD is called more capable than another if its TBD5-cap value is
greater than the other's, or if its TBD5-tie value is greater than
the other's if the former results in a tie. Absent or unparsable
attributes are considered greater than any present attribute.
In case an RD observes a tie even after evaluating the tie
breaker, it may change its Opportunistic Tie-Break value if that
was picked randomly, or reevaluate its life choices if it uses its
own MAC address.
* A running Opportunistic RD needs to perform discovery for other
RDs repeatedly. If it discovers a more capable RD, it stops
advertising its own resources. It should continue to serve lookup
requests, but refuse any new registration or registration updates
(which will trigger the registrant endpoints to look for a new
RD).
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An inactive Opportunistic RD will be notified of the highter
capability RD's shutdown by the expiry of whatever it may be
started to advertise that was now advertised there; see below for
possible improvements.
* An RD that discovers an Opportunistic RD of lower capability may
speed up the transition process by (not mutually exclusive) two
ways
- It can register its own (registration) resource(s) into the
lower capability directory. That RD can take that as having
discovered a higher capability RD and stop advertising.
- It can expose resources and registrations of the lower
capability directory using the methods described in
[I-D.amsuess-core-rd-replication].
* An Opportunistic RD that yields to a more capable RD may ease the
transition by attempting to register its active registrations at
the more capable RD, taking the role of a CT. The lifetimes
picked for those must not exceed the remaining lifetime of its
registrations, and it must not renew those registrations.
Future iterations of this document may want to cut down on the
possibilities listed above.
Some ideas are around for making the shutdown of a commissioned or
otherwise high-capability RD more graceful, but they still have some
problems
* Setting a commissioned or high-capability RD's Capability to zero
in preparation of the shutdown may create loops in any distributed
lookups.
* Asking the lower capability RD to register its registration
resource (even though not otherwise advertised) at the higher
capability RD still creates a situation where clients may find two
RDs running simultaneously, and we can't expect clients to make
any decisions based on TBD5 values.
* Asking the higher capability RD to register its registration
resource with the lower capability RD contradicts the current
recommendation for the passive Opportunistic RD to not accept
registrations / renewals. Also, the deployed RD may not know that
Opportunistic RDs are a thing.
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* Advertising an almost-but-not-quite rt= value on passive
registration resources may be an option, but needs to be thought
through thoroughly.
Installations of Opportunistic RDs are at special risk of resource
exhaustion because they are not sized with their actual deployment in
mind, but rely on defaults set by the application that starts the RD.
Opportunistic RDs should only be started if the application's
administrator can be informed in a timely fashion when the RD's
resources are nearing exhaustion; guidance towards installing a more
capable RD on the network should be provided in that case.
8.1. Applications
* Group managers using [I-D.tiloca-core-oscore-discovery] can ship
its own low-priority Opportunistic RD to announce its join
resources. This provides benefits over announcing them on
multicast discovery if the network can efficiently route requests
to the All CoAP Resource Directories multicast address (so group
members get a response back from an early focused request to all
RDs rather than falling back to multicasting All CoAP Nodes for
"?rt=osc.j&..."), or if discovery of the group's multicast address
is used.
* Administrative tools that try to provide a broad overview of a
network's CoAP devices could offer to open an Opportunistic RD if
they find no active RD on the network (but should ask the user in
interactive scenarios).
That allows them to see devices that newly join the network
quickly (by observing their own or the found RD), rather than
relying periodic multicasts.
9. References
9.1. Normative References
[I-D.amsuess-core-rd-replication]
Amsuess, C., "Resource Directory Replication", Work in
Progress, Internet-Draft, draft-amsuess-core-rd-
replication-02, 11 March 2019, <http://www.ietf.org/
internet-drafts/draft-amsuess-core-rd-replication-02.txt>.
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[I-D.ietf-core-resource-directory]
Amsuess, C., Shelby, Z., Koster, M., Bormann, C., and P.
Stok, "CoRE Resource Directory", Work in Progress,
Internet-Draft, draft-ietf-core-resource-directory-26, 2
November 2020, <http://www.ietf.org/internet-drafts/draft-
ietf-core-resource-directory-26.txt>.
[RFC6874] Carpenter, B., Cheshire, S., and R. Hinden, "Representing
IPv6 Zone Identifiers in Address Literals and Uniform
Resource Identifiers", RFC 6874, DOI 10.17487/RFC6874,
February 2013, <https://www.rfc-editor.org/info/rfc6874>.
[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/info/rfc7252>.
9.2. Informative References
[I-D.silverajan-core-coap-protocol-negotiation]
Silverajan, B. and M. Ocak, "CoAP Protocol Negotiation",
Work in Progress, Internet-Draft, draft-silverajan-core-
coap-protocol-negotiation-09, 2 July 2018,
<http://www.ietf.org/internet-drafts/draft-silverajan-
core-coap-protocol-negotiation-09.txt>.
[I-D.tiloca-core-oscore-discovery]
Tiloca, M., Amsuess, C., and P. Stok, "Discovery of OSCORE
Groups with the CoRE Resource Directory", Work in
Progress, Internet-Draft, draft-tiloca-core-oscore-
discovery-07, 2 November 2020, <http://www.ietf.org/
internet-drafts/draft-tiloca-core-oscore-discovery-
07.txt>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/info/rfc6690>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
the Constrained Application Protocol (CoAP)", RFC 7390,
DOI 10.17487/RFC7390, October 2014,
<https://www.rfc-editor.org/info/rfc7390>.
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[RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain
Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,
<https://www.rfc-editor.org/info/rfc7556>.
[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
RFC 8323, DOI 10.17487/RFC8323, February 2018,
<https://www.rfc-editor.org/info/rfc8323>.
[RFC8801] Pfister, P., Vyncke, É., Pauly, T., Schinazi, D., and W.
Shao, "Discovering Provisioning Domain Names and Data",
RFC 8801, DOI 10.17487/RFC8801, July 2020,
<https://www.rfc-editor.org/info/rfc8801>.
Appendix A. Change log
Since -03:
* Added interaction with PvD (Provisioning Domains)
Since -02:
* Added abstract
* Added example of CoRAL FETCH to Lookup across link relations
section
Since -01:
* Added section on Opportunistic RDs
Since -00:
* Add multicast proxy usage pattern
* ondemand proxying: Probing queries must be sent from a different
address
* proxying: Point to RFC7252 to describe how the actual proxying
happens
* proxying: Describe this as a last-resort options and suggest
attempting PCP first
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Appendix B. Acknowledgements
[ Reviews from: Jaime Jimenez ]
Author's Address
Christian Amsüss
Hollandstr. 12/4
1020
Austria
Phone: +43-664-9790639
Email: christian@amsuess.com
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