Re: Linux 2.2.2 TCP delays every 41st small packet by 10-20 ms

Donald Becker (becker@cesdis1.gsfc.nasa.gov)
Fri, 26 Feb 1999 02:02:40 -0500 (EST)


On 25 Feb 1999, Ben Gertzfield wrote:

> I ran into something suspiciously similar to this today; the tulip.c
> driver (version 0.90) in 100BaseT full-duplex mode would often deal
> extremely poorly with the collisions that full-duplex mode brings
> about. I would get runts, giants, and all sorts of nasty packet errors.

Ackkk!
Full duplex mode never has collisions.
You were likely trying to use full duplex mode on a CSMA/CD Ethernet.
Full duplex can only be used on host-to-host and host-to-switch links, and
only when both endpoints are configured or negotiate full duplex.

Full duplex can never be used when there is a repeater (aka hub) in the
network. Spank yourself if you configured FDX in that case.

> Forcing half-duplex mode solved the problem. I don't know if it's
> a driver or hardware problem at this point, but I've never had
> luck with any DEC-related ethernet cards. :)

Donald Becker becker@cesdis.gsfc.nasa.gov
USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
Code 930.5, Goddard Space Flight Center, Greenbelt, MD. 20771
301-286-0882 http://cesdis.gsfc.nasa.gov/people/becker/whoiam.html

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