Re: 2.1.111 VM and low memory machines

Chris Wedgwood (
Tue, 28 Jul 1998 17:43:01 +1200

On Mon, Jul 27, 1998 at 03:35:56AM -0700, David S. Miller wrote:

> If you want large windows talk to a host who speaks window scaling,
> this is what it's there for.

And how many internet hosts actually support wscale? I suggest
somebody who can sniff a busy ethernet segment with lots of outbound
connections do something like:

tcpdump -n -s 128 'tcp[13] & 2 != 0 and not src net localnet and not dst net localnet'

and see just how many hosts support wscale.

In my tests, I find a little less than 7% of hosts support wscale.

> Otherwise all bets are off for >32k windows. (I have real life
> experience with the sign extension problems, I did try to enable
> 64k windows without scaling by default once and I hit too many
> machines which wouldn't talk to me properly)

I don't doubt your experience, but I've yet to find a single host
where this doesn't work! What stacks are broken in such a way?

It might be my testing methods here are insufficient.

> It's getting too close to the 2.2.x wire now for these sorts of itty
> bitty things, let's work on the higher priority problems instead so we
> can get a clean stable release out soon.

Fair 'nuf.

> (I'm soon going to be asking people to start reporting TCP performance
> and behavior anomalies to me again, I just submitted a sync-up patch
> to Linus with all my latest networking fixes etc. so when he releases
> a kernel with that stuff in there, fire away)

btw, I'm still seeing funnies with 2.1.112-pre2 and sucky

Oh, and when I sniff the interface, I get double packets for anything
out-bound - anyone else?


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