[CentOS] tool for packet detection

nate centos at linuxpowered.net
Thu Apr 30 15:19:52 UTC 2009


Agnello George wrote:
> Hi
> I have small query, all our server are centos based 5 and 5.2 . We are
> looking ofr a tool to that measure packet loss. we have servers in two IDC's
> bothin the US  and we are trying  to download a 2gb file from the internet.
> Some server are able to download the file at a higher  b/w rate in one IDC
> ...while servers at he the other  IDC download the same file at a lowe b/w
> rate . Is ther any tool to measure packet losses.
> Thanks a lot  !

ping.

Also latency is much more likey a culprit of your bandwidth issues
rather than packet loss. Use ping or traceroute to measure the latency
from the sources to the destination(s). I have one of my sites upload
roughly 550GB of data per day to another site that is on the other side
of the country, fortunately the data comes from 40+ servers so running
them all in parallel I can get the data pretty fast(about 350Mbit).
Running each server one at a time I tend to get roughly 7Mbit/s a pop(each
side has a gigabit internet link).

In order to improve throughput I'm using rsync over HPNSSH, which does
some basic TCP magic to improve throughput over higher latency
connections -
http://www.psc.edu/networking/projects/hpn-ssh/

Interestingly enough on downloads I get higher performance, with 10
connections I can get 250Mbit, whereas on uploads I get about 70mbit,
just came across that a couple of days ago. Perhaps for some reason
HPNSSH is not as optimized for uploads(?). In any case I work around
it with multiple threads/processes since I'm dealing with roughly
150k files of various sizes per day.

Worst case split the file up on the other side and transfer it in
parallel and reconstruct it locally.

nate



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