Re: [quicwg/base-drafts] Retaining the largest received packet number (#3541)

Mike Bishop <notifications@github.com> Wed, 01 April 2020 14:47 UTC

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Date: Wed, 01 Apr 2020 07:47:43 -0700
From: Mike Bishop <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Retaining the largest received packet number (#3541)
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> Given you need to track largest acknowledged locally(ie: not only in the in-flight ACK frame), I don't think there are any problems there.
> 
> I have two cases in mind where the largest acked could validly decrease:

Perhaps it's a naive model, but I had envisioned an implementation remembering a chain of ranges of packet numbers it had received or not.  The implementation would save space by forgetting the earliest packet numbers when the chain got too long, and would construct an ACK frame out of the latest set of these ranges it had room for.

In that mental model, at least, there's not really room for the idea that you might drop the largest-acked frame number from your memory because it's too old -- it's always at the most-recent end of your chain, even if you currently happen to be receiving packets that fill in the middle for some implementation-specific reason.  (Implementation-specific *to the peer*, which you obviously can't know about or code for!)

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