Subject: [core] DNS over CoAP: OBSERVE needed?

From: Martine Sophie Lenders <[email-masked]>
Date: Fri, 25 Mar 2022 13:08:12 +0100

Hi,

during today's meeting, I was asked to put the four discussion points I 
presented in my talk on DoC [1] on the list. Here is the discussion 
point on OBSERVE/Server push (slides 13 of [2]).

Our current version (-03) of the draft has a TBD section on OBSERVE 
(section 5.3). That came from considerations put forward in DoH, RFC 
8484, section 4.3 which discusses the delivery of further HTTP responses 
with the queried name, e.g., the index.html at the root of the name 
requested. The question is: do we need or want this in CoRE? A use case 
could be to also deliver the resource directories entries, when a node 
requests its name. If we want this, some extension to CoAP would be 
required to deliver the "intended request" with the unsolicited response 
(or OBSERVE notification?), so it can be properly cached at the client.

For OBSERVE specifically, there were also some more use cases put 
forward, such as RFC 8490 (DNS Stateful Operations) and RFC 8765 (DNS 
Push Notifications), which might be less constructed and less HTTP-ey 
use cases to include considerations on OBSERVE in DoC.

Cheers,
Martine

[1] https://datatracker.ietf.org/doc/draft-lenders-dns-over-coap/
[2] 
https://datatracker.ietf.org/meeting/113/materials/slides-113-core-dns-queries-over-coap-doc-00