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Re: [quicwg/base-drafts] varint packet numbers (#989)

martinduke <notifications@github.com> Wed, 06 December 2017 23:23 UTC

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Date: Wed, 06 Dec 2017 23:23:03 +0000
From: martinduke <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] varint packet numbers (#989)
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I'm not sure if this is a related issue or not, but the "Packet Numbers" section is very clear on how to size the packet number in the packet header, but there is no corresponding advice for sizing the largest_acknowledged field in the ACK frame. In general Varints refer to numbers that start at zero, so there is a natural occasion to truncate them. Packet numbers have 32 bits, so right away we're at 32.

To be specific, the packet header part requires enough bits to encode 2 * (max_pkt - lowest_pkt_unacked). This obviously doesn't work so well on the receiver side. We could just mandate a de facto min size of 4, tie it to the peer's packet number size, or something else.

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