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.
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.
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.
Kind regards,
Alexander
Cheers,
Carles
Dear Carles,
On 17.10.19 18:16, Carles Gomez Montenegro wrote:
> Thanks for your new Internet Draft submission!
Thanks for the quick feedback.
> I have a few clarifying questions:
>
> - What type of power sources can we expect for CAN devices?
They are usually mains-powered. In the automotive domain, it could be
that nodes are battery-powered, but the battery is not a constraining
factor.
> - What bit rate/rates is/are typical in CAN?
The bit rate depends on the used cables, cable length, environment, ...
125 kbaud should work for long lines, 1 Mbaud for classic CAN and short
lines, and up to 8 Mbaud for CAN-FD.
> - What kind of errors (e.g. due to BER) can we expect? Would CAN be
> categorized as a lossy technology, or rather as a very low error rate
> technology (e.g. Ethernet-like)?
Bit errors may occur, but that heavily depends on the wiring and
environment. Usually, we can expect a low BER [1]. Errors during
transmission are detected, and the frame is retransmitted automatically.
All nodes have an error counter and disconnect from the bus when the
counter exceeds the limit. The bus is hard-wired, and nodes do not
disappear.
Kind regards,
Alexander
[1]
https://pdfs.semanticscholar.org/c16e/1c68ddfe5e525d3e4cc9c3478250f5ad36df.pdf
--
Alexander Wachter, BSc
Student of Information and Computer Engineering
Graz University of Technology
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