[CentOS] tool for packet detection

John R Pierce pierce at hogranch.com
Thu Apr 30 05:17:31 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. 

# netstat -s
    4192230 active connections openings
    12120496 passive connection openings
    117185 failed connection attempts
    129707 connection resets received
    69 connections established
    980405402 segments received
    1087064944 segments send out
    1572505 segments retransmited
    11611 bad segments received.
    91074 resets sent

(the ..... are because it shows a lot more stats than just tcp).  your 
'dropped packets' are represented by 'segments retransmitted'.

the only other way to measure dropped packets is to send test packets 
like via the PING command, and measure the responses.     this, of 
course, can interfere with your normal traffic if the links are near 

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