Bug ID 930005: Recover previous QUIC cwnd value on spurious loss

Last Modified: Jul 12, 2021

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
15.1.0, 15.1.0.1, 15.1.0.2, 15.1.0.3, 15.1.0.4, 15.1.0.5, 15.1.1, 15.1.2, 15.1.2.1, 16.0.0, 16.0.0.1, 16.0.1

Fixed In:
16.1.0, 16.0.1.1, 15.1.3

Opened: Jul 22, 2020
Severity: 3-Major

Symptoms

If a QUIC packet is deemed lost, but an ACK for it is then received, the cwnd is halved despite there being no actual packet loss. Packet reordering can cause this situation to occur.

Impact

Inefficient use of bandwidth in the presence of packet reordering.

Conditions

A QUIC packet is deemed lost, and an ACK for it is received before the ACK of its retransmission.

Workaround

None.

Fix Information

QUIC congestion window is restored to its pre-recovery value on a spurious loss recovery.

Behavior Change

QUIC congestion window is restored to its pre-recovery value on a spurious loss recovery.