Re: Version 2.1.92 -> 2.1.101 Ethernet

Richard B. Johnson (
Mon, 18 May 1998 19:58:43 -0400 (EDT)

On Tue, 19 May 1998, Alan Cox wrote:

> > If I ping a Linux machine with a packet length of the default (64 bytes?),
> > it works okay. As I increase the size up to the normal ~1460 bytes,
> > nothing gets through! The problems start at a packet size of about
> > 400 bytes. Tcpdump on the source machines show packets being transmitted,
> > Tcpdump on the destination machine shows no packets received.
> Check your cable quality is really cat5 and your hub is ok. Thats not a Linux
> problem by any way I can figure it since we dont execute any different code
> for long/short frames there.
> Alan
Right! It's a brand-new installation with all new high-quality stuff.
The new (latest 3COM stuff) gets fed to/from a fiber back-bone. Everybody
else thinks it's the greatest thing!
I first thought the hub was bad so I had the Network techs patch me
into another hub. Same problem.

Then a tech brought his "@#&^_@*^" windoze laptop to my office and
transferred a file at, what seemed like, a damned good speed, i.e.,
one mouse-click and it's done.

I know our network code should be good. I wonder about the checksum, not
that it's bad, but that 3COM's checksum may be bad (reversed high/low
bytes checksum okay until the carries have to be handled). I note that
Windoze packet-lengths out of the laptop are only 512+header length!!!

Dick Johnson
Penguin : Linux version 2.1.101 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

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