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From: Norman Wilson <norman@oclsc.org>
To: tuhs@tuhs.org
Subject: Re: [TUHS] [SPAM] Re:  SCCS
Date: Fri, 13 Sep 2019 18:01:14 -0400	[thread overview]
Message-ID: <1568412078.22454.for-standards-violators@oclsc.org> (raw)

Peter Jeremy:

> NFS ran much faster when you turned off the UDP checksums as well.
> (Though there was still the Ethernet CRC32).

Dave Horsfall:

  Blerk...  That just tells you that the packet came across the wire more or
  less OK.

=====

UDP (and TCP) checksums are nearly useless against
the sort of corruption Larry described.  Since they
are a simple addition with carry wraparound, you
can insert or remove any number of word-aligned pairs
of zero octets without the checksum changing.

I discovered this the hard way, while tracking down
a kernel bug that caused exactly that sort of corruption.

Does IPv6 require a meaningful checksum, or just the
useless old ritual one?

Norman Wilson
Toronto ON

             reply	other threads:[~2019-09-13 22:14 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-13 22:01 Norman Wilson [this message]
2019-09-13 22:30 ` Dave Horsfall
2019-09-16 10:59   ` Tony Finch
2019-09-16 12:11 ` Leah Neukirchen
2019-09-16 21:45   ` Dave Horsfall
2019-09-16 22:21     ` George Michaelson
  -- strict thread matches above, loose matches on Subject: below --
2019-09-09  6:25 [TUHS] PWB vs Unix/TS Warner Losh
2019-09-10 15:16 ` Clem Cole
2019-09-11  3:53   ` Warner Losh
2019-09-11 15:36     ` Clem Cole
2019-09-11 18:11       ` Larry McVoy
2019-09-11 22:49         ` Dave Horsfall
2019-09-12  3:43           ` [TUHS] SCCS Larry McVoy
2019-09-12  4:20             ` George Michaelson
2019-09-12  4:31               ` [TUHS] [SPAM] SCCS Larry McVoy
2019-09-12 13:44                 ` Tony Finch
2019-09-13  4:11                   ` Larry McVoy
2019-09-13  5:54                     ` Dave Horsfall
2019-09-13  8:00                       ` Peter Jeremy
2019-09-13 15:23                         ` Larry McVoy
2019-09-13 21:36                         ` Dave Horsfall
2019-09-12  4:28             ` [TUHS] SCCS Jon Forrest
2019-09-12 16:45               ` Eric Allman
2019-09-12 17:29                 ` Clem Cole
2019-09-13  8:12                   ` emanuel stiebler
2019-09-13 21:11                     ` Steffen Nurpmeso
2019-09-13 21:17                       ` Larry McVoy
2019-09-13 23:03                         ` Steffen Nurpmeso
2019-09-14  1:55                           ` [TUHS] [SPAM] SCCS Larry McVoy

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