I am currently attempting to test Microsoft Windows 98's (beta)
implementation of satellite friendly options (TCPLW, SACK, and Fast
Retransmission and Fast Recovery) using a simulated 128 Kbps forward link
and 4 Mbps return link with a 1.2 second round trip delay (two geo satellite
hops each way).
I am curious if anyone has tried to use/test these options on the Win98
beta, and if so, what they found.
Thanks,
Steve Rader - NASA Johnson Space Center
> ----------
> From: Gertjan van Oosten[SMTP:[email protected]]
> Sent: Wednesday, November 19, 1997 8:09 AM
> To: [email protected]
> Subject: Re: TCP over GEO < 512kbps
>
> !!!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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