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Wireshark shows TCP Window full, but actually it is not

asked 2018-01-10 05:23:49 +0000

MSARUL gravatar image

Hello All, My device TCP window size is 1024. I`m transmitting data to the device from PC application. PC is sending 536 bytes of data at a time, Most of the times device is able to send ack and new window value just after this 536 bytes data reception. But sometimes the device is not able to send ack, within that PC is transmitting the next block, but PC application is smart enough to calculate the window size and it is sending about 488 bytes only this time (536 + 488 = 1024). Wireshark exactly captures this and shows TCP Window Full, this is fine. But after this my device sends ack and new window value (1024.) Then the PC application sends next 535 bytes. Wireshark shows TCP Window full this time too. But here the TCP Window has not reached its maximum value(1024). Why wireshark shows "TCP Window Full" for this too? Can anyone explain me the reason?

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Which version of wireshark is this? You should really share the capture file itself with us.

Jaap gravatar imageJaap ( 2018-01-10 06:40:00 +0000 )edit

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answered 2018-01-10 08:44:38 +0000

MSARUL gravatar image

Hello Jaap, I have found the reason.

//But after this my device sends ack and new window value (1024.)// - This ack has not been sent for the 488 Byte block, but for the 536 byte block which had been sent before the 536 byte block. That`s why after getting the next 536 byte block wireshark shows "TCP Window is full".

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Asked: 2018-01-10 05:23:49 +0000

Seen: 674 times

Last updated: Jan 10 '18