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Is there a way to measure packet loss on a wifi network that is caused by bad reception or interference?

I would like to measure it from the client side without moving the computer or access point.

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    Do you mean frame loss, or actual packet loss? 802.11 does have a retransmission process. – YLearn Feb 10 '15 at 7:45
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 11 '17 at 4:10
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i experienced same problem in site with 40 AP are installed and controlled by wireless controller . they take photos in any place in the site and upload it on FTP server automatically ,some places are working good and other upload in big time . i used very useful android application called WiFi Speed Test which is simulating upload and download files between your phone and other remote PC and show you the upload and download speed of this file Transfer.

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regarding the problem of those APs it was the AP output power , which need to be adjusted on the controller it self

if you want to plot the shape of packet loss percentage you can use the great application ping plotter

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  • One option to test packet loss is to ping, e.g you can send a large number of pings to an IP address, this way you can find the failed responses and can estimate the packet loss. following example send a set of 40 pings to the address you specify.

Ping -n 40 (IP Address or domain name)

  • another option can be traceroute, although the output will not show you the packet loss but it will show the slow-responding routers along the path, this will help you find where the packet loss may occur.

  • or test some monitoring tools such as: IP-SLA or pingplotter (http://pingplotter.com/index.php)

  • Ok, so a slow ping to the first router can indicate that the packet loss is caused by congestion on that router? – Per Feb 9 '15 at 13:01
  • usually packet loss occurs when network is congested but it is not the only reason, it can also be depends on how far the router(access point) is from you. The distance is another important factor on a wifi network, you should give the highest strength signal to devices in order to prevent packet loss. – Maria Feb 10 '15 at 16:53
  • by distance I also mean there should not be many interferences or obstacles in the way which will degrade the transmission signal quality. – Maria Feb 10 '15 at 17:00
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As @YLearn has pointed out: you have to destinguish between frame loss (on wireless MAC layer) and packet loss (IP layer).

IEEE 802.11 has a retransmission scheme for the wireless link to compensate for the high frame loss rate compared to wire bound networks. Only if a frame has failed to be acknowledged on the wireless link for a number of times, the packet encapsulated in that frame gets lost. The number of retransmissions is adapted by a vendor specific algorithm.

On a linux system you can use e.g. iwconfig to obtain the number of lost packets caused by excessive retries on the wireless link:

$ /sbin/iwconfig wlan0
wlan0     IEEE 802.11abg  ESSID:"XXX"  
          Mode:Managed  Frequency:2.412 GHz  Access Point: aa:bb:cc:dd:ee:ff
          Bit Rate=54 Mb/s   Tx-Power=15 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=62/70  Signal level=-48 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:26  Invalid misc:1830   Missed beacon:0

So if you are interested in the number of IP packets that are lost on the uplink (laptop→access point) of the wireless link, then Tx excessive retries is what you are looking for.

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Since you want to measure packet loss from a client, I suggest to run ping IP_address -i 0.001 -M do -n -s 1472 and try to stress the link as much as possible.

  • The -i option drastically shortens the interval.
  • The -M do option sets the Don't Fragment bit which is a must for testing the MTU.
  • The -n option disables DNS resolution which is unnecessary for testing packet loss.
  • The -s option sets the packet size.

If a message containing Frag needed and DF set is printed, then either the MTU is less than 1500 bytes or there actually is packet loss.

Because ping -i 0.001 prints many lines, it comes in handy to use the -q option as well. So you'll get a summary when ping is stopped. Alternatively, you can use the -c option to limit the number of packets sent by ping.

By stressing the link, I mean that you should try to creates as much throughput as possible by using other tools than ping. This increases the round-trip time and allows you to test the network as if everyone in the office is working. Even the fastest ping test does not show performance issues. There could be a switch or a router which cannot handle a certain load and consequenly could cause an inacceptable latency or even packet loss.

  • @Per Side note: That's the most common ping tool on GNU/Linux and Mac. – user2964971 Sep 9 '15 at 19:42
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Signal levels can also help you figure out wireless interference, as can channel assignments of APs around you. For free, you can use vistumbler if on Windows, or InSSIDer (which isn't free anymore I don't think).

On Mac, you have some options in the App Store, but I prefer NetSpot which has a free version and also has some site surveying options included in it.

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