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tlswg / dtls13-spec

Repo for DTLS 1.3
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Retransmissions #236

Closed hannestschofenig closed 3 years ago

hannestschofenig commented 3 years ago

Bernard writes:

[BA] Is it always possible to distinguish a retransmission from a late arrival of an original packet? This seems like it could result in wrongly resetting the timer in some situations.

[BA] How does the implementation know how much of the flight to send?

[BA] For the fatal alert case, it does seem like retransmission would be a good idea; otherwise the peer can be left hanging.

Section 7.1
"Disruptions" such as reordering do not affect timers, correct? ACKs SHOULD NOT be sent for these flights unless generating the
responding flight takes significant time. What is "significant time"?

ekr commented 3 years ago

[BA] Is it always possible to distinguish a retransmission from a late arrival of an original packet? This seems like it could result in wrongly resetting the timer in some situations.

No, because if there are any retransmissions you shouldn't reset.

[BA] How does the implementation know how much of the flight to send?

We just give some guidance and let them sort it out. There's no really good answer.

[BA] For the fatal alert case, it does seem like retransmission would

be a good idea; otherwise the peer can be left hanging.

DTLS has been this way for some time, and there's no really obvious way to deal with it, so i think we leave as-is.

Section 7.1
"Disruptions" such as reordering do not affect timers, correct?

Yes. How could they.

ACKs SHOULD NOT be sent for these flights unless generating the
responding flight takes significant time. What is "significant time"?

Changed this to "immediate"

hannestschofenig commented 3 years ago

Regarding:

[BA] How does the implementation know how much of the flight to send?

I guess the question is about whether one or multiple handshake messages are packed in single underlying datagram.

I would say it depends a bit on the use case and the PMTU size. If there is enough space (PMTU-wise) then it may be good in some cases to wait until a number of messages are ready for transmission. In other cases, it may be better to transmit the messages right away individually without packing.

ekr commented 3 years ago

@chris-wood I propose we just close this.

chris-wood commented 3 years ago

That seems reasonable. @ekr, please feel free to close with no action (beyond "immediate" above).