Re: NDIS - asymmetric link speed

From: Alireza Dabagh [MS] (alid_at_online.microsoft.com)
Date: 01/19/05 

Date: Tue, 18 Jan 2005 16:21:50 -0800

TCP/IP has no way of knowing that duplex has changed (not today). If you
change any advanced property of a NIC, you will cause the NIC to get halted
and restarted again in which case all TCP connections will be lost. The
change that you in TCP window size might be more related to reestablishing
the connection than anything else.
Even if you could change the effective link speed of the network without
restarting the NIC, (unplug from a 100meg switch, plug to a 10 Meg switch)
and you noticed a change in TCP window size, you can not assume that TCP
window size change is due to stack dynamically (=after the bind process)
"directly" monitoring the reported link speed from the NIC. Any "dynamic"
changes here -could- be the result of the self regulating algorithm in the
stack more than anything else.

NDIS 6.0 will support asymmetric link speed.By then, hopefully how link
speeds will be used for what purpose (routing table metrics, TCP initial
window size/connection time out determination, etc.) will be documented
somewhere.

-ali 

-- 
This posting is provided "AS IS" with no warranties, and confers no rights.
"Arkady Frenkel" <arkadyf@hotmailxdotxcom> wrote in message 
news:exXT%23U0%23EHA.2596@tk2msftngp13.phx.gbl...
> You can check that in any modern Os ( including XP SP2 ) : set half-duplex
> and you'll see the change in TCPWindowSize by any sniffer ( netmon ,
> ethereal... ). Unless Intel still continue to produce serialized drivers 
> :)
> Arkady
>
> "Maxim S. Shatskih" <maxim@storagecraft.com> wrote in message
> news:#FujTev#EHA.3472@TK2MSFTNGP14.phx.gbl...
>>     Alireza already told us that the "full-duplex" mode is a no-op in
> modern
>> Windows, since the real deserialized miniports are out here.
>>
>> --
>> Maxim Shatskih, Windows DDK MVP
>> StorageCraft Corporation
>> maxim@storagecraft.com
>> http://www.storagecraft.com
>>
>> "Pavel A." <pavel_a@NOwritemeNO.com> wrote in message
>> news:%23CSP5Xq%23EHA.600@TK2MSFTNGP09.phx.gbl...
>> > ?? Where that duplex mode is set in the registry?
>> > All device specific options like duplex, media type etc are not 
>> > relevant
> for
>> me.
>> >
>> >
>> > "Arkady Frenkel" <arkadyf@hotmailxdotxcom> wrote in message
>> news:umET6gj#EHA.2584@TK2MSFTNGP09.phx.gbl...
>> > > Forgot to mention. That you have to take radio/line speed not current
>> > > up/down.
>> > > There are a lot for 802.11 for sure
>> > > Arkady
>> > >
>> > > "Arkady Frenkel" <arkadyf@hotmailxdotxcom> wrote in message
>> > > news:OsyISBj#EHA.3472@TK2MSFTNGP14.phx.gbl...
>> > > > Pavel !
>> > > > Be aware that speed changed due to duplex mode set from/in registry
> too
>> > > > Arkady
>> > > >
>> > > > "Pavel A." <pavel_a@NOwritemeNO.com> wrote in message
>> > > > news:eq1tQre#EHA.3708@TK2MSFTNGP14.phx.gbl...
>> > > > > Dear NDIS gurus,
>> > > > > Now I have adapter with asymmetric send/receive speed ( uplink
> speed
>> > > about
>> > > > 1/3... 1/4 of downlink).
>> > > > > The media type is ethernet (generic or, possibly, 802.11
> emulated).
>> > > > > How TCPIP relies on link speed value reported by driver? which
> link
>> > > speed
>> > > > the driver should report?
>> > > > > And same question, if  the device does throttling and
> prioritizing -
>> the
>> > > > actual link speed
>> > > > > is different for different payload types.
>> > > > >
>> > > > > The marketing, sure enough, wants to display the biggest speed
> value...
>> > > > >
>> > > > > Thanks,
>> > > > > Pavel
>> > > > >
>> > > > >
>> > > > >
>> > > > >
>> > > >
>> > > >
>> > >
>> > >
>> >
>> >
>>
>>
>
>

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