Hi Martine, Adeel,
there had been proposals in 6LowPan + Roll by Pascal Thubert for adding
reliability to 6LowPan (recovering fragments) ... but if I see things
correctly, they have never gotten anywhere -> Carsten?
In any case, the design discussion seems a bit out of focus: Whether to
design a L2 protocol or an application layer (on top of CoAP) should be
sorted out first. I guess these things depend on the problem scope and
the objectives.
Cheers,
Thomas
On 19.08.2016 09:56, Martine Lenders wrote:
Hi Adeel,
What do you mean by "lost fragment recovery"? To my knowledge there is
no such thing in 6LoWPAN fragmentation.
Regards,
Martine
Am 19.08.2016 12:59 vorm. schrieb "Adeel Mohammad Malik"
<adeel.mohammad.ma...@ericsson.com
<mailto:adeel.mohammad.ma...@ericsson.com>>:
Hi again Thomas,
Do you mean that 6LoWPAN in RIOT does not support lost fragment
recovery? Assuming it does, what I had in mind was that we could
segment data in the application to the IP MTU and leverage the lost
fragment recovery feature in 6LoWPAN to get a decent performance.
This way we may not need to implement lost segment recovery in the
application. But if 6LoWPAN in RIOT does not support recovery of
lost fragments we might as well run our application direclty on link
layer (since we dont need IP routing).
/Adeel
-------- Original message --------
From: "Thomas C. Schmidt" <t.schm...@haw-hamburg.de
<mailto:t.schm...@haw-hamburg.de>>
Date: 8/18/2016 23:27 (GMT+01:00)
To: RIOT OS kernel developers <devel@riot-os.org
<mailto:devel@riot-os.org>>
Cc: Börje Ohlman <borje.ohl...@ericsson.com
<mailto:borje.ohl...@ericsson.com>>, Joakim Borgh
<joakim.bo...@ericsson.com <mailto:joakim.bo...@ericsson.com>>
Subject: Re: [riot-devel] Fragmentation support in IP
Hi Adeel,
adding to this: you should keep in mind that in LowPANs you may easily
trigger multiple layers of fragmentation (loosing one fragment is
loosing all!) ... and that receivers may not be ready to handle UDP
datagrams of 'arbitrary' sizes.
So if you really want to stay away from upper layer protocols like
CoAP,
you should process data segmentation in your application (not sure this
is the best idea, though).
Cheers,
Thomas
On 18.08.2016 22:54, Carsten Bormann wrote:
> Hi Adeel,
>
> IP fragmentation is usually a bad idea*), and more so on a constrained
> network. If you need to transfer payloads beyond a kilobyte or so,
> maybe CoAP (RFC 7252) with the block-wise transfer protocol (currently
> being published as RFC-to-be 7959) solves your problem.
>
> Which encryption expands a few bytes of plaintext to kilobytes of
> ciphertext? (You may be thinking about signatures; e.g., hash-based
> signatures can be 3-6 KiB or even more. These might occur in firmware
> updates and are covered quite well by CoAP + block-wise.)
>
> Grüße, Carsten
>
> *)
> https://tools.ietf.org/html/draft-mathis-frag-harmful-00
<https://tools.ietf.org/html/draft-mathis-frag-harmful-00>
> http://www.hpl.hp.com/techreports/Compaq-DEC/WRL-87-3.pdf
<http://www.hpl.hp.com/techreports/Compaq-DEC/WRL-87-3.pdf>
>
> Adeel Mohammad Malik wrote:
>> Hi Thomas,
>>
>> I agree that IP fragmentation is not an equivalent for data streaming.
>> However it still facilitates transporting data that exceeds the MTU. The
>> use case we are looking at is encryption of IoT data that may result in
>> a few bytes of plaintext being converted to a few kilobytes of
>> ciphertext. Had IP supported fragmentation in RIOT it would have been
>> possible for us to send such data.
>>
>> /Adeel
>>
>>
>> -------- Original message --------
>> From: "Thomas C. Schmidt" <t.schm...@haw-hamburg.de
<mailto:t.schm...@haw-hamburg.de>>
>> Date: 8/18/2016 18:11 (GMT+01:00)
>> To: devel@riot-os.org <mailto:devel@riot-os.org>
>> Subject: Re: [riot-devel] Fragmentation support in IP
>>
>> Hi Adeel,
>>
>> GNRC in RIOT supports fragmentation, e.g. in the context of 6LowPAN.
>>
>> However, you seem to be interested in sending UDP datagrams that exceed
>> the MTU payload size. I don't think this is common use ... and I don't
>> think this is clever, either. IP fragmentation is not an equivalent for
>> data streaming.
>>
>> Cheers,
>> Thomas
>>
>> On 18.08.2016 18:04, Adeel Mohammad Malik wrote:
>>> Hi all,
>>>
>>>
>>>
>>> My question is about fragmentation support in IP in RIOT. Does IP in
>>> RIOT support fragmentation? The use case I am after is transferring a
>>> large blob of data (let’s say 5 kilobytes) on the UDP/IP stack in RIOT.
>>> Is that possible?
>>>
>>>
>>>
>>> I know that 6LoWPAN supports fragmentation but that is below the IP
>>> layer. I am interested in fragmentation at the IP layer so that
>>> application running over it in RIOT can send large data.
>>>
>>>
>>>
>>> Regards,
>>>
>>> Adeel
>>>
>>
>> --
>>
>> Prof. Dr. Thomas C. Schmidt
>> ° Hamburg University of Applied Sciences Berliner Tor
7 °
>> ° Dept. Informatik, Internet Technologies Group 20099 Hamburg,
Germany °
>> ° http://www.haw-hamburg.de/inet Fon:
+49-40-42875-8452 <tel:%2B49-40-42875-8452> °
>> ° http://www.informatik.haw-hamburg.de/~schmidt
<http://www.informatik.haw-hamburg.de/~schmidt> Fax:
+49-40-42875-8409 <tel:%2B49-40-42875-8409> °
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--
Prof. Dr. Thomas C. Schmidt
° Hamburg University of Applied Sciences Berliner
Tor 7 °
° Dept. Informatik, Internet Technologies Group 20099 Hamburg,
Germany °
° http://www.haw-hamburg.de/inet Fon:
+49-40-42875-8452 <tel:%2B49-40-42875-8452> °
° http://www.informatik.haw-hamburg.de/~schmidt
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° Hamburg University of Applied Sciences Berliner Tor 7 °
° Dept. Informatik, Internet Technologies Group 20099 Hamburg, Germany °
° http://www.haw-hamburg.de/inet Fon: +49-40-42875-8452 °
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