Wireshark-users: Re: [Wireshark-users] TCP Question - Retransmissions vs. Window
Michael,
I agree with you, that the window size should not be the problem. Retransmissions
occur for the following reasons:
- A TCP segment or returning ACK is dropped by a switch or router.
- The packet is dropped during transmission (CRC error)
- The data portion of the packet is corrupt (TCP checksum error)
- The recipient cannot buffer the packet (the sender is basically
ignoring the window size)
- The TCP segment gets fragmented and a fragment is dropped or corrupt.
- The ACK is slow to return and the sender retransmits the data.
I hope this helps.
Bill Baltas
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Hello.
This may not be a Wireshark question - it is really a TCP
question. To
that end, if there is a good TCP forum to which I should post this, and
similar questions, please let me know.
Recently, there have been 2 occasions where colleagues have seen
retransmissions occurring, and they have been blaming this on the TCP
Window Size being too small, and want to increase it. My response is:
- If the TCP Window size was too small, they would see conditions
where the receiver's window size goes to zero (or very small), and the
sender stops sending until a window update is received showing a bigger
window size. They are NOT seeing this.
- I cannot think of a scenario where a too-small TCP Window size
would cause retransmissions. (Can anyone in this forum???)
Can anyone comment on my assertions? And, can you point me to a good
TCP forum?
Thx much!
Michael Feeny
Merrill Lynch
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