why does not quic bbr use undo mechanism

[mingkun bian]

Hi,
I read quic's retransmission code implementation and rfc documentation， I  didn't find any logic about undo like linux kernel tcp stack.

I think quic may need undo logic because the losses whiic quic detect may be spurious.

Thanks.

[ians...@google.com]

Undo logic is relatively complex, and with BBR relying on bandwidth more than loss, I'd expect the value of undo to be much smaller, so it's never been implemented.

If we had a reason to believe it would meaningfully improve real world performance, we'd definitely consider adding it to QUIC BBR.

Thanks, Ian