Hi Thomas, Hi Ekr, > > * Receiving ACKs: Upon receipt of an ACK, implementations should note > > which messages have been received and omit them from future > > retransmissions. It is up to the implementation to decide when to > > retransmit and what to retransmit, but it is recommended they > > retransmit after a period of time during which no further ACK messages > > have been received. They may also proactively retransmit parts of a > > flight early if an ACK message indicates a gap (note, though, that in > > this example one would only retransmit the gap, not the gap + tail as > > before). > > Looks like a sound proposal to me. The only problem I see with this is > that recovery from tail loss is not efficient, which might or might not > be a problem, depending on the loss pattern of your path. > > > By contrast. we do know that DTLS retransmission is too slow and given > > that small flights are common, losing the ability to indicate that you > > lost a tail seems undesirable. > > I agree this should be avoided if possible.
As far as I see, tail loss indication involves a timer in both cases: - As it stands, tail loss recovery is triggered by the ACK resulting from the 'lack of progress' indicator of disruption, described in the second bullet point of https://tools.ietf.org/html/draft- ietf-tls-dtls13-37#section-7.1<https://tools.ietf.org/html/draft-ietf-tls-dtls13-37#section-7.1> In particular, it only occurs after a 'short' timer triggered on the receiver, where by 'short' I mean that is has smaller threshold than the ordinary retransmission timer from DTLS 1.2, marking the bottom line recovery time we want to improve upon. - Likewise, there's short timer based recovery in the new proposal, but mirrored: The sender retransmits upon noticing a gap in the ACKs, which too can be detected by a short timer as in the current proposal. Best, Hanno IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
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