Re: [quicwg/base-drafts] kDefaultInitialRtt too large (#752)

[janaiyengar <[e-mail]>]

Finally getting to this. Note that the initial RTT only matters insofar as retransmissions are concerned. The handshake RTO is 2 x initialRTT, which means retransmissions should happen after 200ms, which is good enough for 90% of the cases.

Separately, on constants: the IETF has always been reluctant to change TCP's constants despite the fact that implementations have changed them a long time ago. Consider the min RTO, which is still recommended by RFC 6298 to be 1 second, is not used in practice. The minimum RTO in Linux is ~200 ms.

I agree with @mcmanus: I would put latency over bandwidth, or at least provide a knob to allow QUIC implementations to put latency over bandwidth. In this case, I would argue that a few extra retransmissions are really not a major cost, but waiting for a long time when you have just one packet outstanding in the network is a massive cost that browsers and server have repeatedly shown to be worth reducing.

It's all about latency. IMO a few extra retransmissions don't matter.

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