Re: [quicwg/base-drafts] pto_count should be reset when dropping a packet number space (#3272)

Jana Iyengar <notifications@github.com> Thu, 28 November 2019 18:23 UTC

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Date: Thu, 28 Nov 2019 10:23:00 -0800
From: Jana Iyengar <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] pto_count should be reset when dropping a packet number space (#3272)
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@kazuho: you make a good point. I don't think this is orthogonal to the original issue, I think it's very much related. In addition to what you note, you would also need to use the per-epoch counter for determining how long to set the timer.

This is going to be imperfect or ugly or both. If we use a single pto_count, we'll have duplicate counts. If we use separate pto_counts, we'll have to reconcile different epochs having varying counts.

I think the behavior we're looking for is (i) use a separate pto_count per epoch, (ii) use the max of all pto_counts when setting the timer for any PN space, (iii) reset all pto_counts when an ACK is received for any epoch. 

This isn't great, and it is imperfect -- you can end up being more aggressive than with a single count. But I think it's good enough.

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