As quoted from Curtis Villamizar:
> Microsoft does not implement RFC-1323 window scaling option that would
> allow windows greater than 64K.
>
> So Windoze and NT users *are* out of luck if they want to do even
> moderate performance TCP over satellite.
!!!THIS JUST IN!!!
A friend of mine has the Windows 98 (a.k.a. Memphis) Beta 2 CD, and just
pulled this from the documentation upon my request.
As usual, Microsoft gives no guarantees that any of this functionality
will end up in the final version of Memphis...
TCP/IP Stack
Support for TCP Large Windows (TCPLW)
Memphis TCP/IP supports TCP large windows as documented in RFC 1323.
TCP large windows can be used for networks that have large bandwidth
delay products such as high-speed trans-continental connections or
satellite links. Large windows support is controlled by a registry key
value in:
HKLM\system\currentcontrolset\services\VXD\MSTCP\Parameters
The registry key Tcp1323Opts is a string value type. The values for
Tcp1323Opt are
0 - No Windowscaling and Timestamp Options
1 - Window scaling but no Timestamp options
3 - Window scaling and Time stamp options.
The default value for Tcp1323Opts is 3: Window Scaling and Time stamp
options. Large window support is enabled if an application requests a
Winsock socket to use buffer sizes greater than 64K. The current
default value for TCP receive window size in Memphis TCP is 8196 bytes.
In previous implementations the TCP window size was limited to 64K, this
limit is raised to 2**30 through the use of TCP large window support.
Support for Selective Acknowledgements (SACK)
Memphis TCP supports Selective Acknowledgements as documented in RFC
2018. Selective acknowledgements allow TCP to recover from IP packet
loss without resending packets that were already received by the
receiver. Selective Acknowledgements is most useful when employed with
TCP large windows. SACK support is controlled by a registry key value
in:
HKLM\system\currentcontrolset\services\VXD\MSTCP\Parameters
The registry key SackOpts is a string value type. The values for
SackOpts are
0 - No Sack options
1 - Sack Option enabled.
Support for Fast Retransmission and Fast Recovery
Memphis TCP/IP supports Fast Retransmission and Fast Recovery of TCP
connections that are encountering IP packet loss in the network. These
mechanisms allow a TCP sender to quickly infer a single packet loss by
reception of duplicate acknowledgements for a previously sent and
acknowledged TCP/IP packet. This mechanism is useful when the network
is intermittently congested. The reception of 3 (default value)
successive duplicate acknowledgements indicates to the TCP sender that
it can resend the last unacknowledged TCP/IP packet (fast retransmit)
and not go into TCP slow start due to a single packet loss (fast
recovery). Fast Retransmission and Recovery support is controlled by a
registry key value in:
HKLM\system\currentcontrolset\services\VXD\MSTCP\Parameters
The registry key MaxDupAcks is DWORD taking integer values from 2 to N.
If MaxDupAcks is not defined, the default value is 3.
Regards,
--
-- Gertjan van Oosten, [email protected], West Consulting B.V.
--
KAS-Netbank: <URL:http://www.kasnetbank.com/>, winnaar van de
!!! COMPUTABLE IT AWARD 1997: <URL:http://www.computable.nl/cptita1.htm> !!!
en de Computable Innovatieprijs 1997
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