# Re: How does SACK or FACK determine the time to start fast retransmition?

- From: Eric Dumazet \<hidden\>
- Date: 2012-06-21 05:59:09 
- List: netdev
- Page: https://ratatoskr.run/netdev/2012/06/3882798
- Thread: https://ratatoskr.run/netdev/2012/06/3882344/t.md

```text
On Wed, 2012-06-20 at 22:31 +0800, LovelyLich wrote:
> HI all,
>     When tcp uses reno as its congestion control algothim, it uses
> tp->sacked_out as dup-ack. When the third dup-ack(under default
> condition) comes, tcp will initiate its fast retransmition.
>     But how about sack ?

Some tcp experts out there only catch tcp related stuff if Subject
includes TCP.

You might resend your mail on netdev (not sure lkml will really help)
with following subject :

[RFC] tcp: How does SACK or FACK determine the time to start fast
retransmission?

To get more traction.
```