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SubjectRe: Dreadful xfer rates and TCPv4 bad checksum in 2.1.1xx with PPP
On Thu, 5 Nov 1998, David G Hamblen wrote:

> kernels, I get lots of these messages and my ftp downloads drop from
> 1.8kb/s with 2.0.33 to 0.6Kb/s with 2.1.125 to 0.3Kb/s with 2.1.127-pre7.
> This is with my 14.4 modems on a 30K file on an unloaded ISP. The 2.0.33
> kernel runs consistently at 1.8Kb/s. This makes the 2.1.12x kernels
> pretty much unusable for email. The syslogd messages file will get a
> dozen or so TCPv4 bad checksum messages, while ifconfig shows maybe 3
> errors, and 3 frames. I've tried /dev/ttyS0? at 38400 and 19200 with no
> variation in performance. The line is connecting at 14,400 (usually -))

Responding to my own post, I've got a little more info. I borrowed a
Gateway Telepath xjack pcmcia 33.6 fax/modem, and it works fine at 33.6K.
Conclusion: something about my serial port (16450) and the serial driver
is garbling data. The internal modem on COM2 and the Hayes modem on COM1
both give lots of checksum errors and slow transfers at 14.4, while the
pcmcia modem works well.


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