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TCP-IP CRC calculation in PCs

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Michael Schuster

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Jan 9, 2008, 12:58:08 PM1/9/08
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Hi,
just a silly Q we are discussing here. The CRC calculation for TCP-IP
Protcols: Where is it calculated? In the CPU or the network-card?

Thanks
Michael
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Remove the sport from my address to obtain email
www.enertex.de - Innovative Systemlösungen der Energie- und Elektrotechnik

Arlet Ottens

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Jan 9, 2008, 1:11:54 PM1/9/08
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Michael Schuster wrote:
> Hi,
> just a silly Q we are discussing here. The CRC calculation for TCP-IP
> Protcols: Where is it calculated? In the CPU or the network-card?
>
> Thanks
> Michael

TCP/IP doesn't use CRC (Cyclic Redundancy Check), but a much easier to
calculate 1's complement checksum. It is often calculated by the CPU,
although there are also network cards that can do it. On common
architectures, the calculation takes < 1 cycle/byte.

The Ethernet level CRC-32 is (nearly) always done by the netword card.

richar...@gmail.com

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Jan 9, 2008, 5:32:21 PM1/9/08
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On Jan 9, 11:58 am, Michael Schuster <schusterSoc...@enertex.de>
wrote:

> Hi,
> just a silly Q we are discussing here. The CRC calculation for TCP-IP
> Protcols: Where is it calculated? In the CPU or the network-card?

Can be either, depending on the "checksum offload" setting of the
driver. Some NICs may not support checksum offload, but these now
seem to be in the minority.

>
> Thanks
> Michael
> --
> Remove the sport from my address to obtain emailwww.enertex.de- Innovative Systemlösungen der Energie- und Elektrotechnik

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