Define/allocate "same.arpa" ?
---
Semantic: May be used by any application where the recipient can deduce
a prior hostname (or in the absence of the hostname an IP/IPv6 address)
from the context in which it receives a URL with hostname "same.arpa".
That hostname should then be used to connect to this URL. URL responders are
assumed to recognize and accordingly react to a "same.arpa" URL.
"same.arpa" can have arbitrary, application specific subdomain.
---
The question really if in our use-case we will actually save significantly.
If the only benefit is saving bytes on the wire, it's a bit underhwlming.
The use of a generic hostname would be a lot more attractive if it would
help to solve other problems too.
Cheers
Toerless
On Mon, Oct 13, 2025 at 08:46:43PM +0200, Esko Dijk wrote:
> > RFC9031 uses 6tisch.arpa on the forward direction in Uri-Host.
>
> Ok! This is also an interesting type of special hostname. In cBRSKI,
> Uri-Host wouldn't be added to the request as we target the JP directly with
> the CoAPS request as if it were the final server and not a proxy.
> And unlike the 6TiSCH case the proxy can't inspect the CoAP request as it is
> hidden in DTLS encryption.
>
> In cBRSKI discovery the authority component that includes the host is in a
> link in the CoRE Link Format document and it cannot be elided from there.
>
> > I don't think foo.alt is going to fly...
>
> It was exactly the purpose to not make a client fly off somewhere ;-)
> Thinking about this: a ".alt" name might have some effect in a system that
> uses a non-IETF-defined resolution mechanism in the "alt" namespace.
> The domain ".invalid" is at least guaranteed to have non-resolvable names.
> But I didn't like using such a name on purpose. (You may have the same feel
> about "foo.alt")
>
> > Since then I wonder why we didn't just leave Uri-Host option out.
> > I think it's because we wanted to get out of .well-known, so Uri-Path
> could
> > be "j", ignoring RFC8820.
>
> Uri-Host is included because RFC 9031 uses the CoAP (forward/explicit) proxy
> mechanism which needs a target host definition, being the "host to forward
> the request to".
> The proxy resolves the hostname into an anycast IP address. Because this
> final host is by design a 6TiSCH Registrar the client already knows it
> supports the "j" resource.
> But I think according to RFC 8820 this would still not be allowed though:
>
> To avoid collisions, rigidity, and erroneous client assumptions,
> Specifications MUST NOT define a
> fixed prefix for their URI paths -- for example, "/myapp" -- unless
> allowed by the scheme definition.
>
> The scheme in this case is "coap" which doesn't define a specific allowance
> for fixed URI paths outside of ".well-known". But in practice it just works
> fine so I'm okay with that.
>
> Esko
>
> On 12-10-2025 20:28, Michael Richardson wrote:
> > Esko Dijk<[email protected]> wrote:
> > > An alternative to the string "::" would be a short hostname that's
> > guaranteed
> > > to be not resolved using the DNS, or using some local name
> > configuration, or
> > > other known methods.
> >
> > uhm, okay.
> >
> > > An even shorter version would be just "alt" for the hostname. Or
> > > "jp.brski.alt" if potential name clashes are a worry.
> >
> > RFC9031 uses 6tisch.arpa on the forward direction in Uri-Host.
> > I don't think foo.alt is going to fly...
> >
> > Since then I wonder why we didn't just leave Uri-Host option out.
> > I think it's because we wanted to get out of .well-known, so Uri-Path could
> > be "j", ignoring RFC8820.
> >
> > --
> > Michael Richardson<[email protected]> . o O ( IPv6 IøT consulting )
> > Sandelman Software Works Inc, Ottawa and Worldwide
> >
> >
> >
> >
> >
> > _______________________________________________
> > Anima mailing list [email protected]
> > To unsubscribe send an email [email protected]
>
> --
> *IoTconsultancy.nl* | Email/Teams: [email protected] | +31 6 2385
> 8339
--
---
[email protected]
_______________________________________________
Anima mailing list -- [email protected]
To unsubscribe send an email to [email protected]
