Subject: [tcpm] CUBIC Bug fix

From: "Agarwal, Anil" <[email-masked]>
Date: Mon, 28 Sep 2015 13:35:02 +0000

(Fixed subject line)

Just saw a bug fix for CUBIC in the Linux kernel code, contributed by Google -
https://github.com/torvalds/linux/commit/30927520dbae297182990bb21d08762bcc35ce1d<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_torvalds_linux_commit_30927520dbae297182990bb21d08762bcc35ce1d&d=BQMGaQ&c=jcv3orpCsv7C4ly8-ubDob57ycZ4jvhoYZNDBA06fPk&r=FyvaklKYrHaSCPjbBTdviWIW9uSbnxdNSheSGz1Jvq4&m=IMhCBSi7dMsf7MzSG8LnZE-n9Ogt7SH74_bRPB0SPB0&s=0vvm71Jyb-SFOxHOHeQ8bi-kH072c8RI3voU4bqc0io&e=>

It appears that CUBIC does not specify any special rules for handling TCP cwnd increase after an idle period. There is no feedback (packet losses or ECN) during the idle period which makes the cwnd increase algorithm unnecessarily aggressive after an idle period, especially if cwnd is not reset during the idle period.

Question - where is the CUBIC specification documented? How will it be updated? Is there an RFC on CUBIC?

Anil