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Packet Loss Tests

Packet loss test

(After completeing this test the results can be used to initiate an official BT packet loss test on your line; if the test is approved then you will need to leave your equipment switch on and allow ICMP ping packets through your firewall for testing purposes.)

  • If you know how to change the MTU setting in your router please set it at 1492 to begin this test. 
  • Do not use a wireless connection for this test, rather please conect via an ethernet (network) cable. Also, make sure only one computer is turned on durig the test; turn everything else off.
  • Boot up the computer in "Safe Mode with Networking" by tapping the "F8" key as the computer turns on; this is a diagnostic mode ideal for testing netwokring issues.
  • Disconnect (unplug) any other equipment connected to the line. For example: fax machine, telephone, Sky TV, other computer devices, etc.
  • Close any applications that pass traffic across the Internet (File sharing, game servers, chat programs, VoIP, security updates, Windows Update, BBC iPlayer, anti-virus, email, etc.)
  • Open a command prompt
    • Click [Start],[Run] and type cmd (press [Enter])
  • Now we will send various sized packets to the Google and note the replies; type the following 'ping' commands:

    Note: If the command results show any packets lost (Lost = 1 or higher) then proceed to the next command until there are no packets lost.
    • ping google.com -n 10 -l 1480 (Press [Enter])
    • ping google.com -n 10 -l 1470 (Press [Enter])
    • ping google.com -n 10 -l 1460 (Press [Enter])
    • ping google.com -n 10 -l 1450 (Press [Enter])
    • ping google.com -n 10 -l 1400 (Press [Enter])
    • ping google.com -n 10 -l 1350 (Press [Enter])
    • ping google.com -n 10 -l 1200 (Press [Enter])
    • ping google.com -n 10 -l 1100 (Press [Enter])
    • ping google.com -n 10 -l 100 (Press [Enter])
  • Ideally please repeat the above tests using lower and lower MTU settings. We suggest starting with an MTU of 1492 (highest), then 1480, 1472, 1456, 1440, 1408,1400. If you are unable to modify your MTU or do not know what it is then say so, you're not alone as it is an advanced setting!
  • Next, run pathping 8.8.8.8
  • Finally, run the following command:
    • pathping 8.8.8.8 -R -P -T (Press [Enter])
  • Send the results back to support for analysis together with the time and date of the test and also the MTU setting if known.
    • To copy results within a Command Prompt window right-click the title bar ("Command Prompt") and select [Edit], [Select all], [Edit],[Copy]. Now paste into an email and sent to support.

Article ID: 3, Created On: 4/25/2008, Modified: 1/24/2014

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