[CentOS] tool for packet detection

Les Mikesell lesmikesell at gmail.com
Thu Apr 30 05:26:47 UTC 2009

John R Pierce wrote:
> 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
> ......
> Tcp:
>     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 
> saturated.

Or you can use wireshark to capture and decode a session (set a filter 
on the target host address) and it will show the timing and 
retransmitted packets.

    Les Mikesell
     lesmikesell at gmail.com

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