[erlang-questions] Intermittent failures connecting C hidden nodes

Per Hedeland per@REDACTED
Fri Jul 6 22:52:40 CEST 2007

Matthias Lang <matthias@REDACTED> wrote:
> Jeff >> * Double checking that the switches between the two machines are locks
> Jeff >> at the correct speed, eg 100Mps full-duplex.
> Matthias > Verifying that the interfaces are running as expected, e.g. that both
> Matthias > ends have the same idea about what they're doing, is good.
>Chasing possible ethernet problems is not the first thing I'd do if
>presented with the evidence Andy gave. 
>I posted because a small part of Jeff's advice (above) is prone to
>misinterpretation. And also because my calling in life is to prevent
>people from making that particular mistake.

I wouldn't consider it my calling in life:-), but it's a pet peeve for
me too (for a number of reasons) - and I think your "causes TCP to
behave erratically" is quite an understatement. The type of broken setup
you're describing can effectively kill a network segment when the
traffic load is high, while it seems to work just fine in light testing
- extremely nasty. And the amount of myth propagation or downright
misinformation is immense - just earlier today I happened to be googling
for how to configure speed/duplex on Solaris (it seems to be arguably
even more bizarre than Linux in this area), and on one of the first hits
I found this:

"Solaris is often unable to correctly auto-negotiate duplex settings
with a link partner (e.g. switch), especially when the switch is set to
100Mbit full-duplex."


--Per Hedeland

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