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Old 11-02-2014, 12:05 PM   #1
Registered: Jun 2001
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More advanced testing than ping

When I try to download anything more than 30mb the connection breaks at some point and the download won't resume.

Ping shows no packet loss. Traceroute shows nothing abnormal... but then most hops are filtered these days.

How can I test in way more detail?
Old 11-02-2014, 01:18 PM   #2
Registered: Nov 2007
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You could have a look at nmap and wireshark.

The very popular nmap has plethora of options and scanning modes which may help.

The equally popular wireshark will allow you to snif the traffic and possibly assertain what's going on when the connection breaks.
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Old 11-02-2014, 04:03 PM   #3
Registered: Jun 2001
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I'm familiar with these tools for other uses. What would be a good server to nmap from behind the poor connection? Or should I nmap my own IP from a VPS?

I need to know the exact time that the download fails if I'm going to look at the packets at that exact point. To do this I see the --timestamping option in wget but that's no use since that requires the download to actually complete. Even if I am able to note the time of failure that time is not so much that time the conection breaks... but when the download times out. I need the time the download stops progressing... and I don't know how to achieve that. I guess I need some sort of script... but it needs to be concurrent with the download yet monitoring the download. So I guess I need to monitor when the file being cached to disk stops increasing in size? Then when I have that time I can go to this time in wireshark.

But what is wireshark really going to tell me? Will it give me an IP that most likely caused the problem? I don't think so? My gut feeling is that it's not our router but somewhere at the ISP... but I can't be sure as yet...
Old 11-03-2014, 09:12 PM   #4
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You would capture the traffic on your interface, and when your connection breaks, you stop the capture and download, and then review the packets to see *why* it happened.
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Old 11-04-2014, 03:35 PM   #5
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I generally say ping is bad. I agree that other tools may offer better clues.
Might also ping to test packet size for fragmentation. Possibly mtu off.
Could ping for a long time.

Sometimes cpu load may need to be looked at. See how bad CRC is on packets.

We have to assume you are using TCP/IP and not UDP or other means to download.

Might log into router/modem for clues.

Since you know it is downloads, do web pages also suffer issues?


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