| From: | Greg Stark <stark(at)mit(dot)edu> |
|---|---|
| To: | Florian Weimer <fw(at)deneb(dot)enyo(dot)de> |
| Cc: | Greg Smith <greg(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Daniel Farina <daniel(at)heroku(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Jim Nasby <jim(at)nasby(dot)net> |
| Subject: | Re: Enabling Checksums |
| Date: | 2013-04-18 21:20:08 |
| Message-ID: | CAM-w4HPSivQU9Reyk4aH0YSroMU=fpQd0QjvJNkWfK_O0tWgdw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Apr 18, 2013 at 6:04 PM, Florian Weimer <fw(at)deneb(dot)enyo(dot)de> wrote:
> The TCP checksum is too weak to be practical. Every now an then, I
> see data transfers where the checksum is valid, but the content
> contains bit flips.
Well of course, it's only a 16-bit checksum. 64k packets isn't very
many so if you're not counting checksum failures it won't take very
long before one gets through. The purpose of the checksum is to notify
you that you have a problem, not to block bad packets from getting
through.
> Anything that flips bits randomly at intervals
> which are multiples of 16 bits is quite likely to pass through
> checksum detection.
I'm not sure about this
--
greg
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