Wireshark mailing list archives

Re: Window scaling


From: Lee <ler762 () gmail com>
Date: Mon, 6 Jun 2016 19:11:34 -0400

On 6/6/16, Robert Dahlem <Robert.Dahlem () gmx net> wrote:


On 06.06.2016 17:37, ronnie sahlberg wrote:

I do not agree with the statement that packets with the SYN bit set are
never scaled.

The standard is pretty clear for this case.

The Window field in a SYN (i.e., a <SYN> or <SYN,ACK>) segment
itself is never scaled.

Maybe my English is not good enough for the proper definition of
"scaled". To clarify this for me: I have a SYN/ACK packet with Window
size 8192 and Window scale 8 (multiply by 256): is the client allowed to
send 8192 or 2G bytes without seeing the first ACK without SYN from the
server?

You're supposed to start out in 'slow start', so unless the MTU is
4KB it's probably allowed to send two packets.  See
https://tools.ietf.org/html/rfc5681
  3.1.  Slow Start and Congestion Avoidance

Regards,
Lee
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