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I am currently facing an issue in my application where the TCP messages seem to be blocked until an acknowledgment received. Specifically, the subsequent messages wait for the acknowledgment of the first message before continuing transmission.

I ruled out the window size as the potential cause, as the window size is set to 29200, while the packet length remains at a comfortable 290. To provide more context and details, I have attached a screenshot of the pcap for your reference.

I would greatly appreciate any insights, suggestions, or guidance that the community can offer to help me identify and resolve the root cause of this delay.

Thank you in advance for your time and assistance.

Pcap

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  • What amount of delay are you talking about? Your pcap screenshot doesn't really show enough to understand your problem. If you aren't using the PSH option the TCP handler awaits more data before sending out a less-than-MSS segment.
    – Zac67
    Nov 28, 2023 at 18:03
  • "I am currently facing an issue in my application where the TCP messages seem to be blocked until an acknowledgment received." That is normal for the congestion window. "I ruled out the window size as the potential cause, as the window size is set to 29200" The congestion window cannot be set, and it continuously changes. Once there is a problem, the windows dramatically shrinks, and the sender will stop sending until it gets an ACK that the data have been received with no problem.
    – Ron Maupin
    Nov 28, 2023 at 18:52
  • So I need to change my congestion control algorithm, but couldn't find any that is suitable for me. I just need to send as many messages as window size allowed. Any recommendations? Nov 30, 2023 at 8:24
  • Your Wireshark picture appears to have redacted areas, plus omitted columns and rows. Plus, the entire screenshot covers 3/10 of a single millisecond, so I'm not sure what you expect to be happening in 300 microseconds. There's really not enough information here to be helpful. It sounds like you maybe wrote the app? You could explore switching to UDP instead of TCP, but you're going to have to add more software to handle your own acknowledgement mechanisms. yesterday

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