Spin bit - semantics - rtt and loss

"Lubashev, Igor" <ilubashe@akamai.com> Fri, 23 March 2018 00:12 UTC

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From: "Lubashev, Igor" <ilubashe@akamai.com>
To: "quic@ietf.org" <quic@ietf.org>
Subject: Spin bit - semantics - rtt and loss
Thread-Topic: Spin bit - semantics - rtt and loss
Thread-Index: AQHTwjus7aoj5pwVoECWxZMvp9O9NQ==
Date: Fri, 23 Mar 2018 00:12:48 +0000
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Since we decided to put some work into spin bit, albeit in a separate document from V1, here are some thoughts.

It is nice that spin bit can be used to estimate rtt. I am sure that it is useful to many well-meaning people. It is not very useful to me, though.

When I debug network problems, they are much more likely to be about lost packets. And I like to be able to know packet loss frequency and pattern very accurately. (I am assuming an encrypted packet number, or the problem would be trivial.)

I would prefer, if we have a spin bit, for it to spin not every rtt but every, say, 10 packets that an endpoint sends. Client sends 10 packets with 0 and then 10 packets with 1, repeat. Sever does the same.

So maybe two spin bits -- one for rtt and one for loss? I would assume that loss bit would assist in rtt estimation in case of loss.

Thoughts?

- Igor