Re: [quicwg/base-drafts] compensation of ack_delay is fragile against errors (#2060)

janaiyengar <> Thu, 29 November 2018 03:39 UTC

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Subject: Re: [quicwg/base-drafts] compensation of ack_delay is fragile against errors (#2060)
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@kazuho @martinthomson : Mathematically, yes, but I wanted to protect against overflow.

@kazuho: I'm concerned that if the ack_delay being reported is too large, I don't know how much of that is in error and how much of that is accurate. The patch assumes that exactly latest_rtt - min_rtt is the correct ack_delay, but there's no evidence of it. The problem with the proposed patch is that a client that reports an ack_delay that is too large will automatically cause the sender to always believe that the RTT is not growing at all. (Imagine the case where ack_delay is always reported as MAX_INT. This means that the sender will always end up with latest_rtt = min_rtt.)

I'm suggesting that if there's an indication that the peer is feeding in values that are too large for ack_delay (which should not happen consistently or all the time), then we should ignore ack_delay.

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