High volume of Zero Windows In & Zero Windows Out


Troubleshooting some web servers & JBoss servers… seeing high volumes of Zero Windows In/Outs and wanting to learn more about where to focus.

From the below numbers, it appears that the web server is both receiving and sending Zero Windows. But the web server is also receiving Zero Windows In from a bunch of different clients that are making the requests. So I feel like the web tier is in the middle (literally) of issues with clients making the requests… possibly delaying the performance of the web server, which in turn throw zero windows upstream to the application tier.

So where do I focus???

Web Server (24 hour period):
Zero Window In 5,514
Zero Window Out 3,345 (to Vert.X server)

Vert.X (24 hour period)
Zero Window In 3,298 (from web server)
Zero Window Out 7


Zero Window is something to investigate.

Troubleshooting a Zero Window For one reason or another, the machine alerting the Zero Window will not receive any more data from the host. It could be that the machine is running too many processes at that moment, and its processor is maxed. Or it could be that there is an error in the TCP receiver, like a Windows registry misconfiguration. Try to determine what the client was doing when the TCP Zero Window happened.

Source: https://wiki.wireshark.org/TCP%20ZeroWindow


Can you give me more information about what this server does… and OS type