Restarting Idle Connections

[Yongmin Cho]

I think, This implementation is right.
Thank you for the quick reply. :-)

On Fri, Jan 29, 2016 at 01:58:50PM -0800, hiren panchasara wrote:
> On 01/29/16 at 01:51P, hiren panchasara wrote:
> > On 01/29/16 at 01:38P, Yongmin Cho wrote:
> > > Hi, all.
> > > 
> > > I have an opinion about net.inet.tcp.initcwnd_segments.
> > > You know, snd_cwnd is restarted transmission after a long idle
> > > period(Current RTO).
> > > And, All of congestion control algorithm is using newreno_after_idle
> > > function after a long idle period.
> > > But, The newreno_after_idle function is not using initcwnd_segments.
> > > I think, The initcwnd_segments should be used in newreno_after_idle
> > > function, If the newreno_after_idle is called.
> > > I referred to rfc6928.
> > > 
> > > Please check my opinion.
> > 
> > You are absolutely right. We (FreeBSD) adopted initcwnd to be 10
> > segments but never bothered to update newreno_after_idle() function to
> > reflect that in calculating cwnd after idle period. Though the comments
> > in that function clearly says:
> > "The restart window is the initial window or the last CWND, whichever is
> > smaller."
> > 
> > I think we should make following change to accommodate it:
> > 
> > diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c
> > index 97ec35f..5210a45 100644
> > --- a/sys/netinet/cc/cc_newreno.c
> > +++ b/sys/netinet/cc/cc_newreno.c
> > @@ -166,6 +166,10 @@ newreno_after_idle(struct cc_var *ccv)
> >          *
> >          * See RFC5681 Section 4.1. "Restarting Idle Connections".
> >          */
> > +       if (V_tcp_initcwnd_segments)
> > +               rw = min(V_tcp_initcwnd_segments * CCV(ccv, t_maxseg),
> > +                   max(2 * CCV(ccv, t_maxseg),
> > +                       V_tcp_initcwnd_segments * 1460));
>  -       if (V_tcp_do_rfc3390)
>  +       else if (V_tcp_do_rfc3390) 
> 
> But you get the idea. :-)
> 
> Cheers,
> Hiren
> >                 rw = min(4 * CCV(ccv, t_maxseg),
> >                     max(2 * CCV(ccv, t_maxseg), 4380));
> > 
> > Any inputs?
> > 
> > Cheers,
> > Hiren
> 
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