IO Graphs in Wireshark-TCP Spurious Retransmission events

TCP Spurious Retransmissions may be seen from time to time when using Wireshark.  How do you see them?  Capture some data with Wireshark on your workstation or server.  Click on Statistics, IO Graphs and click throughout the graph on the color that indicates TCP errors.  You’ll see the Wireshark main screen change to the point in time you are clicking.

Analyze the content and look for Spurious Retransmission.  These packets may indicate that the sender sent a retransmission for data that was already acknowledged.

Wireshark IO Graphs

Zoom on Picture

TCP will show some packet loss, so these are normal events.  If these are common, they may start to impact application and/or performance across your network.  Here’s what you can do.

  • Look at the path between devices and your server.
    • Look for ethernet errors, discards, possible high utilization.
      • This may indicate wireless or cabling issues.

How can you correct too many of these?

  • Disable everything on the server network card with the exception of flow control – under the Advanced tab.
  • Disable LLMNR (Multicast).
  • Look at driver updates on hardware (remember, if you update drivers, your network card advanced properties will reset).
  • Upgrade your NIC card or wireless card
  • Look at your switch utilization.
  • Look at adding a second card on your server.
  • Look for crowded wireless APs
  • Look for wireless channel overlap
  • Look at interference (wireless)

 

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About TCAT Shelbyville IT Department

The Tennessee College of Applied Technology - is one of 46 institutions in the Tennessee Board of Regents System, the seventh largest system of higher education in the nation. This system comprises six universities, fourteen community colleges, and twenty-six Applied Technology Colleges.
This entry was posted in computer troubleshooting, Home Networking, Information Technology, network, Networking, Technology, troubleshooting, Wireless and tagged , , . Bookmark the permalink.

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