Subject: Re: Hardware IPv4/TCP/UDP checksumming support
To: =?iso-8859-1?Q?P=E5l_Halvorsen?= <paalh@unik.no>
From: Ignatios Souvatzis <ignatios@theory.cs.uni-bonn.de>
List: tech-net
Date: 09/06/2001 12:39:04
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On Thu, Sep 06, 2001 at 10:59:58AM +0200, P=E5l Halvorsen wrote:
=20
> Is the packet transmitted to the NIC memory or can the NIC CPU access the
> main memory?

This depends on the NIC and the machine it is plugged into.

Modern NICs can do DMA, so yes, they do access (some of) the main machines
memory. Depending on PCI bus implementation, this might be any memory the=
=20
packet happens to be in, or just some specialized memory accessible to the
bus, and some copy might happen later. The details of this are hidden from
the NIC and the NIC driver by the NetBSD bus_dma abstraction. Read more abo=
ut
it with "man bus_dma".

	-is

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