Re: [core] coap discovery

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 17 August 2021 16:28 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Christian =?us-ascii?Q?=3D=3Fiso-8859-1=3FQ=3FAms=3DFCss=3F=3D?= <christian@amsuess.com>, Peter van der Stok <stokcons@bbhmail.nl>, core@ietf.org
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Date: Tue, 17 Aug 2021 12:27:54 -0400
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Subject: Re: [core] coap discovery
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Christian Amsüss <christian@amsuess.com> wrote:
    > However, just to get a better understanding, why is the protocol
    > through which the CoAP messages are forwarded between the join-proxy
    > and the registrar neither CoAP nor a new CoAP transport? (Just sounds
    > like it'd be working around the very shortcomics of CoAP proxies that
    > RFC8974 resolved). Is this protocol described anywhere so far?

Because, it is CoAP in DTLS in stuff.

Between Pledge and Register, it is supposed to look like CoAP-in-DTLS.

Between Pledge and Join Proxy, it's CoAP-in-DTLS (over IPv6-LL)
Between Join Proxy and Register, it's CoAP-in-DTLS-in-"CBORUDP" (over ULA/GUA).

The "CBORUDP" provides for a stateless (i.e. stored in the network) record
of where the packets come from.

In RFC9031, which uses OSCORE, and therefore has security *above* CoAP,
rather than security *below* CoAP, we use the CoAP (extended) token for the state.
(RFC8974).

--
Michael Richardson <mcr+IETF@sandelman.ca>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide