Hi Martine and Thomas, Martine, actually when I wrote the question I did not mean to imply that the 6LoWPAN standard has "lost fragment recovery". I did a quick search on it and I see no RFCs. Thanks for pointing it out.
Thomas, I agree that whether we do it on L2 or on the application layer depends on the problem scope. We are working on a prototype and would like to get things running with a decent performance in time. Hence the questions about what RIOT supports and what not. Perhaps we need to do some loss recovery implementation at the application layer to not have a poorly performing prototype. /Adeel > -----Original Message----- > From: devel [mailto:[email protected]] On Behalf Of Thomas C. > Schmidt > Sent: Friday, August 19, 2016 10:16 AM > To: RIOT OS kernel developers > Cc: Börje Ohlman; Joakim Borgh > Subject: Re: [riot-devel] Fragmentation support in IP > > 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" > > <[email protected] > > <mailto:[email protected]>>: > > > > 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" <[email protected] > > <mailto:[email protected]>> > > Date: 8/18/2016 23:27 (GMT+01:00) > > To: RIOT OS kernel developers <[email protected] > > <mailto:[email protected]>> > > Cc: Börje Ohlman <[email protected] > > <mailto:[email protected]>>, Joakim Borgh > > <[email protected] <mailto:[email protected]>> > > 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" <[email protected] > <mailto:[email protected]>> > > >> Date: 8/18/2016 18:11 (GMT+01:00) > > >> To: [email protected] <mailto:[email protected]> > > >> 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> ° > > >> _______________________________________________ > > >> devel mailing list > > >> [email protected] <mailto:[email protected]> > > >> https://lists.riot-os.org/mailman/listinfo/devel > > <https://lists.riot-os.org/mailman/listinfo/devel> > > >> > > >> _______________________________________________ > > >> devel mailing list > > >> [email protected] <mailto:[email protected]> > > >> https://lists.riot-os.org/mailman/listinfo/devel > > <https://lists.riot-os.org/mailman/listinfo/devel> > > > _______________________________________________ > > > devel mailing list > > > [email protected] <mailto:[email protected]> > > > https://lists.riot-os.org/mailman/listinfo/devel > > <https://lists.riot-os.org/mailman/listinfo/devel> > > > > > > > -- > > > > 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> ° > > _______________________________________________ > > devel mailing list > > [email protected] <mailto:[email protected]> > > https://lists.riot-os.org/mailman/listinfo/devel > > <https://lists.riot-os.org/mailman/listinfo/devel> > > > > _______________________________________________ > > devel mailing list > > [email protected] <mailto:[email protected]> > > https://lists.riot-os.org/mailman/listinfo/devel > > <https://lists.riot-os.org/mailman/listinfo/devel> > > > > -- > > 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 ° > ° http://www.informatik.haw-hamburg.de/~schmidt Fax: +49-40-42875- > 8409 ° > _______________________________________________ > devel mailing list > [email protected] > https://lists.riot-os.org/mailman/listinfo/devel _______________________________________________ devel mailing list [email protected] https://lists.riot-os.org/mailman/listinfo/devel
