Re: [core] Using CoAP for P2P

Thomas Fossati <Thomas.Fossati@arm.com> Thu, 02 April 2020 10:45 UTC

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From: Thomas Fossati <Thomas.Fossati@arm.com>
To: Abhijan Bhattacharyya <abhijan.bhattacharyya@gmail.com>
CC: core <core@ietf.org>, Thomas Fossati <Thomas.Fossati@arm.com>
Thread-Topic: [core] Using CoAP for P2P
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Subject: Re: [core] Using CoAP for P2P
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Hi Abhijan,

On 02/04/2020, 09:04, "Abhijan Bhattacharyya"
<abhijan.bhattacharyya@gmail.com> wrote:
> What I am looking at is a situation where I have two nodes each having
> a time-varying resource. Both want to push the states of the
> respective resource to the other node within a common application
> context. However, these exchanges are naturally asynchronous.  May be
> I can think of it more like a chat. A typical client-server or observe
> relationship will not serve the purpose. Actually both should have a
> client and server instance running under a common application. Then
> either each can *observe* the other, or can *post* the other. That is
> how we can do that without a central server.

What you describe above is a perfectly reasonable implementation: each
node has both client and server endpoints where the former observe the
latter on the peer.  To share state across co-located endpoints one can
use an IPC of choice including shared memory between threads.

> If my understanding is right, according to CoAP specification, the
> nodes which can have both server and client (to the origin server) are
> "intermediary" nodes. The only example of "intermediary" considered in
> the spec is the proxy node. But, anyway the situation in this case
> does not concern with intermediary. Both are origin server and
> end-client together.

7252 says that an intermediary has both client and server endpoints, not
that any node with both client and server endpoints is an intermediary.

> Is there any standardized mechanism to handle this situation?

The design you've described above is a standardised (and logical) way to
handle your case.

cheers, t
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