Re: [6lo] draft-ietf-6lo-fragment-recovery: Send a FULL bitmap when datagram is complete?
Martine Lenders <m.lenders@fu-berlin.de> Wed, 23 October 2019 13:14 UTC
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From: Martine Lenders <m.lenders@fu-berlin.de>
Date: Wed, 23 Oct 2019 15:13:24 +0200
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To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
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Subject: Re: [6lo] draft-ietf-6lo-fragment-recovery: Send a FULL bitmap when datagram is complete?
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Hi Pascal, Sorry, I noticed this in your original mail, but forgot to mention it, now it is also in the draft: > […] Acknowledgment on the reverse path with a FULL bitmap, and harms a > short timer to absorb packets that are still in flight for that […] Do you mean "arms a short timer"? Best regards, Martine Am Mi., 23. Okt. 2019 um 14:52 Uhr schrieb Pascal Thubert (pthubert) < pthubert@cisco.com>: > Cool : ) > > > > I published 07, please see the diffs. > > > > All the best; > > > > Pascal > > > > *From:* 6lo <6lo-bounces@ietf.org> *On Behalf Of *Martine Lenders > *Sent:* mercredi 23 octobre 2019 14:46 > *To:* Pascal Thubert (pthubert) <pthubert@cisco.com> > *Cc:* 6lo@ietf.org > *Subject:* Re: [6lo] draft-ietf-6lo-fragment-recovery: Send a FULL bitmap > when datagram is complete? > > > > Hi, > > > > Am Mi., 23. Okt. 2019 um 14:43 Uhr schrieb Pascal Thubert (pthubert) < > pthubert@cisco.com>: > > Hello Martine > > > > I meant fragments. It can be expected that a few fragments are still in > flight after everything is received because of end to end fragment retries > or L2 ARQ. So the receiver must keep a state to drop them silently. But is > it gets “too much “ of that it may be an error and the receiver should > abort the flow. > > > > That “too much” decision is left to implementation. > > > > Thank, now it is clearer! > > > > Regards, > > Martine > > > > > > > > Regards, > > > > Pascal > > > > Le 23 oct. 2019 à 14:29, Martine Lenders <m.lenders@fu-berlin.de> a > écrit : > > > > Hi Pascal, > > > > Am Mo., 21. Okt. 2019 um 18:14 Uhr schrieb Pascal Thubert (pthubert) < > pthubert@cisco.com>: > > Hello Again > > > > I reread the text and it appears that the receiver operation is too > implicit. I suggest to add this in the last fragment processing: > > > > When all the fragments are received, the receiving endpoint > reconstructs > > the packet, passes it to the upper layer, sends a RFRAG Acknowledgment > on > > the reverse path with a FULL bitmap, and harms a short timer to absorb > > packets that are still in flight for that datagram without creating a > new > > state and abort the communication if it keeps going. > > > > Does that help? > > > > If this goes somewhere in section 6, yes I think that makes it far more > understandable. > > > > Note that there’s room for an implementation to decide if it absorbs > silently a few packets and for how long, and when it decides to reset the > flow. The all 1 (to be renamed throughout to FULL) does not help more than > the reset. > > > > By packets you mean fragments or reassembled datagrams. I don't really > understand what you mean by that. > > > > Best regards, > > Martine > > > > > > Pascal > > > > > > *From:* Pascal Thubert (pthubert) > *Sent:* lundi 21 octobre 2019 17:29 > *To:* Martine Lenders <m.lenders@fu-berlin.de>; 6lo@ietf.org > *Subject:* RE: [6lo] draft-ietf-6lo-fragment-recovery: Send a FULL bitmap > when datagram is complete? > > > > Sorry I missed that Martine! > > > > The ALL 1s was already sent when the last fragment was received. This text > happens later. > > > > It is supposed to have been processed along the way back. The receiving > end node maintains a state for a “short” time after the message processing > to absorb packets that may still be in flight. During that “short” time it > is capable to recognize redundant packets and drop them as opposed to > create a new state and expect the full fragment. For legitimate packets > still in flight the good thing would be to stay silent. If the Ack with a > FULL (All 1s) bitmap was lost then sending it again would be OK as you > point out. > > > > But there might also be error conditions, like a weird situation that the > FULL bitmap did not fix on its way back where the sender keeps sending. If > the FULL bitmap failed then retrying it may fail again. The reset is a > clearer indication to drop everything regardless and move to the next. > > > > Works? Should we massage text? > > > > All the best > > > > Pascal > > > > Am Di., 1. Okt. 2019 um 16:31 Uhr schrieb Martine Lenders < > m.lenders@fu-berlin.de>: > > Hi, > > > > draft-ietf-6lo-fragment-recovery states in section 6.3 > > > > [the] might need to abort the process of a fragmented packet for internal > reasons, for instance if it […] considers that this packet is already fully > reassembled and passed to the upper layer. In that case, the receiver > SHOULD indicate so to the sender with a NULL bitmap in a RFRAG > Acknowledgment. > > > > The given example seems to me the perfect instance to set a FULL bitmap > instead. There is no other instance were a FULL bitmap is specified to be > sent, except for the case that the datagram incidentally fills out the > whole value space of the sequence number field. > > > > Or am I missing something? > > > > Kind regards, > > Martine > >
- [6lo] draft-ietf-6lo-fragment-recovery: Send a FU… Martine Lenders
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Martine Lenders
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Pascal Thubert (pthubert)
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Pascal Thubert (pthubert)
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Martine Lenders
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Pascal Thubert (pthubert)
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Martine Lenders
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Pascal Thubert (pthubert)
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Martine Lenders
- Re: [6lo] draft-ietf-6lo-fragment-recovery: Send … Pascal Thubert (pthubert)