Re: [6lo] Call for feedback to draft-wachter-6lo-can-00

"Carles Gomez Montenegro" <carlesgo@entel.upc.edu> Sun, 20 October 2019 15:54 UTC

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Date: Sun, 20 Oct 2019 17:54:54 +0200
From: "Carles Gomez Montenegro" <carlesgo@entel.upc.edu>
To: "Alexander Wachter" <alexander@wachter.cloud>
Cc: 6lo@ietf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/6lo/1jfZtN-2G0WU7a8bMxwkqaXL9BU>
Subject: Re: [6lo] Call for feedback to draft-wachter-6lo-can-00
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Dear Alexander,

> Dear Carles,
>
>
> On 20.10.19 15:37, Carles Gomez Montenegro wrote:
>> Dear Alexander,
>>
>> Thanks for your responses.
>>
>> To some extent, I see similarities between the environment you are
>> considering (CAN) and MS/TP. Few years ago, the 6Lo WG produced RFC
>> 8163,
>> which specifies IPv6 over MS/TP.
>
> The main difference I see between CAN and MS/TP is the packet/frame
> size. MS/TP satisfies the minimal requirements of 1500 octets minimal
> MTU where CAN only has 8 octets of payload per frame. 6LoCAN therefore
> defines a fragmentation an reassembly.

Your draft proposes using a subset of ISO-TP for fragmentation and
reassembly.

Clarifying question: is ISO-TP part of the CAN protocol (stack)?

>> I understand that using header compression reduces the amount of IPv6
>> packets that will require fragmentation. Also, it provides a more
>> efficient use of the bus. Interesting!
>
> IPHC helps to reduce the number of frames needed to send an IPv6 packet.
> Nevertheless, sending an IPv6 packet in a single frame is only possible
> for CAN-FD (up to 64 bytes payload). Classical CAN always needs
> fragmentation and reassembly.

I see. Anyway, there is the need to comply with the 1280-byte IPv6 MTU
requirement, but it is already satisfied in your draft.

> In my opinion, 6LoCAN is the right WG because it defines a
> "6lo-adaption-layer". It specifies a fragmentation and reassembly as
> other 6lo technologies do.

I actually mentioned MS/TP and the (6Lo-produced) RFC 8163 to emphasize
the potential similarities with CAN (and 6LoCAN), since the 6Lo WG has
also dealt with technologies with somewhat different characteristics (e.g.
wireless, mesh topologies, energy-constrained devices, etc.).

Kind regards,

Carles


> Kind regards,
>
> Alexander