Re: 2.4 tcp very slow under certain circumstances (Re: netdev issues

Jordan Mendelson (jordy@napster.com)
Wed, 21 Feb 2001 14:30:37 -0800


"David S. Miller" wrote:
>
> Ookhoi writes:
> > We have exactly the same problem but in our case it depends on the
> > following three conditions: 1, kernel 2.4 (2.2 is fine), 2, windows ip
> > header compression turned on, 3, a free internet access provider in
> > Holland called 'Wish' (which seemes to stand for 'I Wish I had a faster
> > connection').
> > If we remove one of the three conditions, the connection is oke. It is
> > only tcp which is affected.
> > A packet on its way from linux server to windows client seems to get
> > dropped once and retransmitted. This makes the connection _very_ slow.
>
> :-( I hate these buggy systems.
>
> Does this patch below fix the performance problem and are the windows
> clients win2000 or win95?

I wanted to see if this would fix the problem I was seeing with Win9x
users on PPP w/ compression dialing up to Earthlink in the bay area
(there are others, but it's the only one I can reproduce).

I compiled 2.4.1 with this change and for some odd reason, the kernel
started dropping packets and became unusable (couldn't ssh in) after
around 4050 connections were opened. I tested it also with 2.4.1-ac20
and had the same problem right around 4050 connections.

This is on a VA Linux box with dual eepro100's (one used) connected to a
Cisco 6509.

> --- include/net/ip.h.~1~ Mon Feb 19 00:12:31 2001
> +++ include/net/ip.h Wed Feb 21 02:56:15 2001
> @@ -190,9 +190,11 @@
>
> static inline void ip_select_ident(struct iphdr *iph, struct dst_entry *dst)
> {
> +#if 0
> if (iph->frag_off&__constant_htons(IP_DF))
> iph->id = 0;
> else
> +#endif
> __ip_select_ident(iph, dst);
> }
>
> -
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