Re: UDP zero checksums and v4 to v6 translators

[David Malone <dwmalone at maths.tcd.ie>]

On Tue, Jul 28, 2009 at 05:00:22AM -0400, Christopher Morrow wrote:
> it's 10 years old, from a single network link, in what I suspect was
> VBNS+, so not even today's internet (scale or applications or users or
> traffic levels or uses)

People might want to check "netstat -s" - on some OSes it displays
the number of datagrams with no checksum. From some machines I have
access to:

	Datagrams	with no csum	Fraction
	1643918434	1660		~0.000001
	1780472220	233156		~0.00001
	1335609090	918129		~0.0007
	4157989		931		~0.0002
	122783361	43532		~0.0004

The second machine is a moderately busy DNS server. The third a
public NTP server. I don't think the counters have wrapped - I get
plausible looking pps numbers if I divide the datagrams by uptime.

Checking some other traces, I see about 21420/17253070 NTP packets
with no checksum. Of non-NTP, non-DNS traffic I see about half a
percent of UDP with no checksums. A lot of this looks like either
port scans or people trying to use obsolete services like port 37.

	David.