Re: TCPv4 bad checksums

Stephen Clark (seclark@ix.netcom.com)
Tue, 22 Dec 1998 09:04:04 -0500

Mike Jagdis wrote:
>
> On Mon, 21 Dec 1998, Jack wrote:
>
> > Our specific symptom is the plethora of TCPv4 bad checksum
> > messages, sometimes resulting in stalled connections
> > [1]. Approximately 2-5% of all ip-packets over ppp0 are
> > TCPv4 bad checksums. The numbers are roughly 150k packets,
> > 3k bad checksums per day. [2]
>
> If it helps anyone I have seen TCPv4 checksum errors on a
> relatively simple network connected by ippp (ISDN):
>
> SCO 3.2v5 -- 100BaseTx -- Linux 2.0
> |
> ippp
> |
> Linux 2.0 -- 100BaseTx -- Linux 2.1.131
>
> The errors only appear to be logged by the 2.1.131 box for packets
> from the SCO box. (The lower 2.0 box doesn't appear to be logging
> debug messages to a file but the upper one is).
>
> The commonality with ippp, ppp and slip would be slhc. However
> I _only_ seem to see it on routed packets (I'm not masquerading).
>
> At home I see it on my PC talking directly via PPP to the Internet
> (via Demon) - but I've only noticed it when talking to RedHat sites.
> Could the commonality be whether the packets go through a Linux
> router or not?
>
> Mike
>
> --
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I get periodic burst of TCPv4 checksums. This usually happens when
retrieving mail. I am connected on a 10baset internal network. The
internal network has an ISDN connection to the internet thru an Ascend
Pipe 130.

Steve

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unix is user friendly. It's just selective about who its friends are.
Good programmers know what to write. Great ones know what to rewrite(and
reuse)


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