Re: [quicwg/base-drafts] Encoding of blocksize in ACK frames. (#679)

Igor Lubashev <notifications@github.com> Wed, 04 October 2017 09:16 UTC

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Subject: Re: [quicwg/base-drafts] Encoding of blocksize in ACK frames. (#679)
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Does Gap = 0 ever make sense?  I do not think so.
We could do one of two things:

1. Define the actual gap to be Gap+1 (and keep the semantics of "ACK Block Length" unchanged), or

2. If Gap=0, the following `(("ACK Block Length" << 8) | "Following Gap")` actually defines the length of the gap. In this case, the semantics of the regular "ACK Block Length" can be made to match "First ACK Block Length", and chances are excellent that multiple ACK frames will not be needed.

Option 2 has a few special cases in it: (a) If "ACK Block Length" is 64 bit, `(("ACK Block Length" << 8) | "Following Gap")` is too large; (b) the last Gap=0 still does not make sense (unless someone is willing to assign semantics to it).

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