RELENG-7 tcp connectivity problems with certain clients

[Mike Silbersack]

On Sun, 9 Mar 2008, Jake Rizzo wrote:

> The patch didn't work, but doing this:
>
> sysctl net.inet.tcp.tso=0
> sysctl net.inet.tcp.sack.enable=0
>
> Allows the client to connect again. Since my ifconfig doesn't show that my
> nic supports TSO then I presume it's the sack sysctl that's making it work.
>
> The machine's a webserver serving almost exclusively dynamic content - with
> sack disabled is it likely to affect performance much?
>
> Thanks,
> Jake

SACK makes retransmission more effective in some circumstances when packet 
loss occurs.  So, you're probably not going to notice it being disabled at 
all.  In fact. FreeBSD 4.x didn't have any SACK support whatsoever.

-Mike