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On Friday 22 Feb 2013 08:04:38 Helmut Jarausch wrote: |
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> Hi, |
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> |
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> I have no experiences in debugging a slow network. |
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> |
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> At home, I have a router which is connected to my telephone line via |
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> VDSL2. |
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> I have 2 PCs one of which is connected by an ethernet cable (i.e. |
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> wired) while the other |
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> one uses a wireless connection which is specified as 56 Mbit/s. |
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> |
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> When copying data from one machine to the other one I see varying |
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> speeds from only 0.5 Mbits/s up to |
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> more than 20 Mbits/s. I have no idea why it is so slow some times. |
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> There are no other wireless devices nearby. |
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Where do you see these transfer speeds? On the wired machine, or on the |
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wireless machine? |
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What do you use to check the transfer speed? |
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Do the speeds go up when you used a Cat5e cable at full duplex? |
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Have you scanned for access points to be absolutely sure that there are no |
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other wireless devices, or APs? |
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Do you use encryption? |
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What frequency and channel are you on and have you tried to change |
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channel/frequency? (some domestic devices like cordless phones, wireless |
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earphones, bluetooth, microwaves, perimeter sensors, etc. can cause co-channel |
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and adjacent channel interference and/or force sharing of the bandwidth). |
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Are both machines and the router's LAN on the same MTU? |
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> What tools and techniques can I use to debug this situation? |
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> |
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> Many thanks for a hint, |
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First use ifconfig to see how many dropped packets you get on both machines. |
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Then use iwconfig, or cat /proc/net/wireless on the PC running the wireless to |
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see how many discarded packets you get, fragmentation, etc. as well as nwid |
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packets from different networks on the same frequency. |
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Then check with e.g. iptraf-ng what network connections are running, their |
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rate(s) and if any of these should not be there. |
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The router stats may also be revealing in this respect, as well as dropped |
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packets on the WiFi. |
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I hope the above will give something to work with, others may have better |
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ideas and more specialised tools for troubleshooting this. |
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PS. I haven't mentioned spectrum analysers to keep this thread within the |
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realm of quick fixes, but if you do have EM interference and the source of it |
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is obscure, you may need more professional equipment to nail this problem. |
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-- |
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Regards, |
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Mick |
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