David A. Ranch wrote:
> The typical reason why MASQ users get "failed TCP/UDP checksum"
> errors is that somewhere in their upstream network connection,
> packets are getting corrupted. Now while most TCP/IP stacks
> like Windows95, OS/2, etc will silently drop these packets,
> MASQ will report them.
>
> I've found the typical culprit for this corruption is either
> a crappy or overloaded terminal server that are performing
> VJ-header compression.
Haven't fixed this yet, but...when you say "packets are getting corrupted" it
feels like pppd crashes, since the only way out of this is to restart pppd.
> Follow these steps (in order) to try fixing your problem:
>
> 1) Make sure your COMM port on the Linux box is running at 115200
> or better:
>
> /etc/rc.d/rc.local or in /etc/rc.d/rc.serial (when it's
> enabled in the /etc/rc.d/rc.S file
> --
> setserial /dev/ttyS1 spd_vhi
> --
>
> - If you have an ISDN connection, you can lose data because
> of the serial rate bottleneck (115200 vs. 128000 x 4-times
> compression). I would recommend an accelerated serial port
> (say a Hayes ESP or something like that) for 230 or 460Kb/s
> serial rates.
Nope, it's just at 28.8 US Robotics FaxModem. setserial /dev/ttyS1 spd_vhi
gives me
Cannot get serial info: Invalid argument
I haven't figured out what to do next. I am running MkLinux on a PPC, Kernel
2.0.36, Generic #7 (yeah, kinda old in the 2.2 era, but it is the latest
kernel available for my (IP Masq) machine).
> 2) Make sure you have a good connection to your modem (externals)
>
> - If you have one of those ribbon-to-9or25 pin motherboard
> adapters, make sure it's in good condition. I personally
> have a ferrite coil around each of mine.
>
> - Check your serial cable quality and length.
Hmmm... I'm considering buying new cables, although I'm not convinced this is
the culprit.
> 3) The usual, but unfortunate, fix for the "failed checksum"
> error is to disable VJ-header compression. To do this,
> edit the /etc/ppp/options file and add:
>
> "-vj"
I don't think this option was recognized, so I commented it out a while ago.
The kernel that I'm using supports ppp version 2.2.0, but the version of ppp
installed is 2.3.5. I think this will be fixed soon, and hopefully this will
fix the problems I've been having.
Thanks for the suggestions!
Taro Fukunaga
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