Re: [core] coap discovery

Christian Amsüss <> Wed, 18 August 2021 08:35 UTC

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Date: Wed, 18 Aug 2021 10:35:32 +0200
From: Christian =?iso-8859-1?Q?Ams=FCss?= <>
To: Michael Richardson <>
Cc: Peter van der Stok <>,
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Subject: Re: [core] coap discovery
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Ok, then I misunderstood; next attempt. Would it look roughly like this,

| IP header | UDP header  | CBORUDP | DTLS containing CoAP |

where CBORUDP is some self-delimited prefix in which the proxy encodes
the pledge's address (probably opaque to the register), and by itself
doesn't care what precisely is encapsulated in it.

In that case, I'd advertise it either as


which just announces that there is some service of that kind without
saying what can be done with it (although a more precise rel or rt may
say that), or as


which'd indicate that coaps can be transported through that and that
there is a /j resource available. This'd help the proxy to advertise an
own `<coaps://[fe80::...]/j>;rt=some..join` resource which it doesn't on
its own control, but still provides for in its reverse proxy capacity.
(Given that resource is probably not discovered, that may be of little

For me, either would work; announcing a <coaps://[ip]:port/j> would IMO
be misleading if no requests really arrive there through CoAP on DTLS
directly on UDP.


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  -- Terry Pratchett (attributed)