> I don't think that we should make this extensible via IANA registry.
> Any update will mostly have to Amend this document, probably it will have to
> obsolete it.
I don't have a strong preference here. Relying on a future follow-up document
to Amend it, or Obsolete it in a responsible way, seems fine. So we have to
decide whether to keep the registry or remove it - topic for the call today!
> Of these, I have a slight preference for (2) over (3).
> I don't like (1) at all.
For using the current single-array structure, my preference is (3). Doing (2)
seems risky from an implementation perspective. In today's Agile SW world,
people don't consider tomorrow's change so much in today's code. Because
they're supposed to only consider that in tomorrow's code. But as we know
today's code isn't always maintained anymore when tomorrow comes ;)
Identifying the particular risk here is left as an exercise to the reader.
> If we really need extensibility, then I would suggest we consider instead:
On your CDDL proposal: using a map here doesn't seem necessary. We need to
limit the overhead of the JPY message to the absolute minimum - it may be
transported over 6lowpan links, where the DTLS packet size may be near the 1280
byte limit. Then there's hardly any space to add more JPY header...
If we really want a clear separation of Header and Content, which isn't the
case in the current draft, then we could use 2 arrays:
[
[
ip : bstr,
port : int,
family : int,
index : int
payload : bstr
],
payload : bstr
]
Only the embedded array (Header field) is extendible in length. Doing this
approach adds only 1 byte to the JPY message size; examples:
[h'FE800000000000000000FFFFC0A801C8', 48551, 6, 0, h'0011'] --- 26
bytes ; what's currently specified
[[h'FE800000000000000000FFFFC0A801C8', 48551, 6, 0], h'0011'] --- 27
bytes ; above dual array proposal
[{0:h'FE800000000000000000FFFFC0A801C8', 1:48551, 2:6, 3:0}, h'0011'] --- 31
bytes ; the smallest possible 'map' approach.
But I'm also ok with a single-array structure if we choose the approach (3)
i.e. any extensions come *after* the payload element.
Esko
-----Original Message-----
From: Anima <anima-boun...@ietf.org> On Behalf Of Michael Richardson
Sent: Wednesday, December 1, 2021 19:32
To: anima@ietf.org
Subject: Re: [Anima] I-D Action: draft-ietf-anima-constrained-join-proxy-05.txt
/ Section 9 proposed text
Esko Dijk <esko.d...@iotconsultancy.nl> wrote:
> Good point; these are not CBOR map keys because it's not a map but an
> array. But still, for an array, the indices could be managed in an IANA
> registry for the JPY protocol. This allows future documents to add new
> map indices to the registry. An alternative is not to create a registry
> at all but just allow an RFC to update the array with 1 or more
> indices. I don't have a preference for one of these solutions.
Arrays are not as easily extensible as maps.
Receivers can't just ignore keys that they don't know.
Fortunately, it's CBOR, so things that the receiver doesn't know about can be
skipped, assuming they implement enough of CBOR.
{Right now, we have bstr, and int. The enclosing array can be open-coded as
a test for 0x85. Or processed as an array. No map, tstr, etc. code needed}
I don't think that we should make this extensible via IANA registry.
Any update will mostly have to Amend this document, probably it will have to
obsolete it. I don't think we can easily accomodate multiple documents
asking for a code.
There are three ways we can extend this array:
1) receiver can see that new array has 6+ elements, and then
can assume the "new" format. That could involve completely
changing the order of what is there.
2) receiver can process first four items as they are, and then
process the last element as the payload.
Anything between the fourth element and the payload would be
ignored in this version, but future versions put new things there.
3) receiver can process first five items as they are, and new items
can be placed after the payload, which older receivers are told
to ignore.
Of these, I have a slight preference for (2) over (3).
I don't like (1) at all.
Just remind other readers:
[
ip : bstr,
port : int,
family : int,
index : int
payload : bstr
]
If we really need extensibility, then I would suggest we consider instead:
JPY_message =
[
details : { ip : bstr,
port : int,
family : int,
index : int },
payload : bstr
]
{please forgive my poor CDDL here}
--
Michael Richardson <mcr+i...@sandelman.ca>, Sandelman Software Works
-= IPv6 IoT consulting =-
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