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Re: Why is my gigabit ethernet so slow?

    Date:        Tue, 26 Jan 2010 23:59:19 -0500
    From:        Thor Lancelot Simon <>
    Message-ID:  <>

  | Why the automatic socket buffer sizing code isn't bringing the socket
  | buffer size and thus the window size up to 128K by itself over the course
  | of a 10GB test is not obvious to me.

Is that still used if the application explicitly sets a buffer size?

And, if the -b option is not used, does ttcp just use whatever is the
default socket buffer size, or does it have its own default (perhaps 32KB)
that it explicitly sets?

If the combination of those answers is "no" and "always sets the buffer size"
then that would explain the observed behaviour, I believe - without 
postulating bugs (which doesn't mean they don't exist of course).

Testing with a less formal benchmark (seeing how fast ftp transfers a big
file) might determine better whether the auto window sizing is working or not
(but it would need to be a BIG file, and going to /dev/null on the receiver).


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