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DCTCP: update alpha only once after loss recovery.

Description

DCTCP: update alpha only once after loss recovery.

In mixed ECN marking and loss scenarios it was found, that
the alpha value of DCTCP is updated two times. The second
update happens with freshly initialized counters indicating
to ECN loss. Overall this leads to alpha not adjusting as
quickly as expected to ECN markings, and therefore lead to
excessive loss.

Reported by: Cheng Cui
Reviewed by: chengc_netapp.com, rrs, tuexen (mentor)
Approved by: tuexen (mentor)
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D24817

Details

Provenance
rscheffAuthored on
Reviewer
guest-ccui
Differential Revision
D24817: DCTCP: update alpha only once after loss recovery.
Parents
rS361347: With RFC3168 ECN, CWR SHOULD only be sent with new data
Branches
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Tags
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