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TCP Window size

Hi

I captured some TCP comunication because there is a issue with long respons of some application.

I see in some TCP packets using Wireshark:

window size value:593

{Calculated window size: 151808}

{Window size scaling factor: 256}

Can this values indicate some issue?

Or is it correct?

I have other capture when respons of application is OK and there is still the same value "window size value" and "Calculated window size"

Thanks

Peter

1 REPLY
Cisco Employee

TCP Window size

Hi Peter,

The Calculated window size: 151808 as shown above should be fine.

As per RFC 1323:

The TCP header uses a 16 bit field to report the receive

window size to the sender.  Therefore, the largest window

that can be used is 2**16 = 65K bytes.

To circumvent this problem, Section 2 of this memo defines a

new TCP option, "Window Scale", to allow windows larger than

2**16.  This option defines an implicit scale factor, which

is used to multiply the window size value found in a TCP

header to obtain the true window size.

Hope this helps.

Thanks,

Rajesh.

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