Re: OID_TCP_TASK_OFFLOAD question

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From: Alex the 1'th (AlX_at_a)
Date: 07/12/04 

Date: Tue, 13 Jul 2004 01:07:35 +0300

That made everything clear, thankx.

Well, right, TCP packets will not fragment at sender because there is no
need to, you just send up to the MTU limit.
But, large UDP packes will fragment at sender (probabbly everything else
then TCP will fragment) so there should be an offloading option for IP
packes in general. me thinks...

"Stephan Wolf" <stewo68@hotmail.com> wrote in message
news:e006f0hduqmhs0tklt7b7opucnmmf3rpm1@4ax.com...
> You are mixing up IP *fragmentation* and TCP *segmentation*. They are
> completely different things.
>
> The API provided to user programs (usually WinSock) allows "large"
> blocks of data to be sent to the peer TCP socket, e.g. 64 KB (= max.
> for IPv4). The TCP protocol stack then breaks down the data block into
> segments that fit the MTU of the underlying network (including
> headers).
>
> That is, a TCP segment usually fits in a single network packet at the
> sender.
>
> Now when such a packet needs to traverse one or more routers and if
> the packet size exceeds the MTU of the connecting medium between two
> (or more) routers, then the router will break down the TCP *segment*
> (contained in the original packet) into several IP *fragments*. Each
> IP fragment makes up a new packet on the intermediate network(s).
>
> Note that IP fragments are always reassembled at the final destination
> (i.e. not by routers). So the IP stack at the receiver gathers IP
> fragments and rebuilds the TCP segments. TCP itself has no knowledge
> of all this (and does not need to know).
>
> See also
>
> "Windows Network Task Offload"
> http://www.microsoft.com/whdc/device/network/taskoffload.mspx
> -> "TCP Segmentation Offload"
>
> For the bigger picture see:
>
> http://www.microsoft.com/whdc/device/network/netintro.mspx
>
> Stephan
> ---
> On Mon, 12 Jul 2004 20:30:31 +0300, "Alex the 1'th" <AlX@a> wrote:
>
> >So, no fragmentation offload support for UDP packets?
> >
> >"Alex the 1'th" <AlX@a> wrote in message
> >news:%23MFnIz7ZEHA.2972@TK2MSFTNGP12.phx.gbl...
> >> NDIS_TASK_TCP_LARGE_SEND is refering to all IP packes or only TCP ones?
> >> If I am correct the packet fragmentation is related to the IP packes in
> >> general not TCP in particular, so this offload should applay to TCP and
> >UDP.
> >> Right? or I am missing something...

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