[CLUE-Tech] Network DD

[Keith Hellman]

I'm wondering if your accurately counting the actual bytes going across
the interface.  Your file may be X bytes big but your byte calculation
doesn't account for the tcp wrapper, ip wrapper, or link layer envelope.

I'm not even sure where to get these numbers, but I would suggest doing a 
  >/sbin/ifconfig ethX
  >dd if=/dev/random bs=4 count=4 |netcat target.ip.address target-port
  >/sbin/ifconfig ethX

And compare the total transferred bytes between the two ifconfig outputs. 
I think they should be more than 16 bytes...

Also keep in mind, IIRC, netcat is doing VERY dumb byte transfers: give it
a byte, it sends a byte.  The SSH tools, on the other hand, may (and this
is pure speculation) be more optimized (especially scp) to moving large
blocks of data, hence they do it with less protocol overhead, hence
faster.

Someone knowledgeable about this stuff should comment, I'm really just
thinking out loud...
 
--- "Timothy C. Klein" <teece at silverklein.net> wrote:
> * Jed S. Baer (thag at frii.com) wrote:
> > On Tue, 30 Apr 2002 21:31:58 -0600
> > "Timothy C. Klein" <teece at silverklein.net> wrote:
> > 
> > > Hey all,
> > > 
> > > I just made changes to the way I load my network module, and it
> > > supposedly will have improved my throughput.  A test with SSH seems
> to
> > > have confirmed this, but I want some kind of bandwidth test without
> all
> > > the overhead.  I want to see how close I am to saturating the 100
> Mb/S
> > > that I supposedly have.  What would be the network equivalent of dd?
> > > How do I send raw 0s across the wire?
> > 
> > Have you tried netcat?
> > 
> Ah, thanks.  I *knew* I had heard of something that would do this once.
> And as I supsected, my throughput doesn't seem all that great.
> 
> Anybody want to check my numbers?  100 Mb/s = 12.5 MB/s (in decimal
> megabytes, rather than 1024.  Than just complicates things).
> 
> When I transfer the kernel with the ncp script provided by netcat, it
> takes 6.295 seconds of real time (as reported by time), and the file is:
> 23,841,012 bytes / 6.295 s = 3,787,293 bytes / second.  This seems to be
> about one quarter of max.  On both ends I have a 3com 3c59x card.  Seems
> low to me.  Also, ssh didn't have nearly the overhead I expected.  It
> does the same file in 6.444 seconds.  
> 
> Any ideas?
> Tim
> --
> ==============================================
> == Timothy Klein || teece at silverklein.net   ==
> == ---------------------------------------- ==
> == "Hello, World" 17 Errors, 31 Warnings... ==
> ==============================================
> _______________________________________________
> CLUE-Tech mailing list
> CLUE-Tech at clue.denver.co.us
> http://clue.denver.co.us/mailman/listinfo/clue-tech


__________________________________________________
Do You Yahoo!?
Yahoo! Health - your guide to health and wellness
http://health.yahoo.com