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I'm looking for some software to monitor packet loss or packet retries. Preferably something that continuously monitors vs. a testing approach and preferably free.

My server's OS is debian. I'm not sure if wireshark can do this since I don't have access to a graphical interface on my server, only text/SSH.

Any suggestion please ?

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What exactly do you mean by "packet loss"? –  Chris S Oct 19 '11 at 13:15
    
Errr I guess I'm going to give the bad answer but anyway this is what I mean : packet loss @ wikipedia –  Joel Oct 19 '11 at 13:23
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Yes, I know what a lost packet is. But which packets? Do you want to generate test packets directly, or are you more concerned with the packets applications on your server are supposed to be sending and receiving? Or are you testing a link, a route, any path between two endpoints? You can use tcpdump to generate a pcap file for Wireshark to read. –  Chris S Oct 19 '11 at 13:41
    
thks, it's for testing my dedicated server which i believe to be a bad one. –  Joel Oct 19 '11 at 17:37
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3 Answers

up vote 2 down vote accepted

You could use a tool that generates ICMP Echo requests and monitor their feedback.

But if you wanted to see how your actual applications are responding you can watch the output of netstat -s -p tcp, the section for "packets sent" should have a "retransmitted" counter, indicating dropped packets that needed to be retransmitted (it would also show packets unnecessarily retransmitted, but should have another counter for these exclusively as well, which would indicate latency problems rather than outright dropped packets).

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Take a look at SmokePing.

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Cool software, I'd never seen it before. One more tool for the batbelt! –  Matthew Oct 19 '11 at 13:38
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for a command-line, instant packet loss, take a look at mtr. –  Giovanni Toraldo Oct 19 '11 at 14:53
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Packet retransmits can be captured via SNMP if the application provides that information. You may be able to get to it using MIB-2 (the standard host mib), but looking at it now it looks like it only includes errors and discarded packets - I don't see anything indicating loss. The process itself would need to provide that information somehow, or give you a protocol that monitors a separate protocol (kind of how RTCP monitors RTP).

TCP retransmits can be monitored with OID 1.3.6.1.2.1.6.12, but that will be system wide for all interfaces.

What exactly are you trying to monitor? That may be helpful.

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