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 !
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.
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.
From: Agnello George agnello.dsouza@gmail.com
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 !
In the mean time, ifconfig shows you the values for errors/dropped/collisions... You can also see them in /proc/net/dev
JD
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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nate