linux TCPIP stack design

[Andrew Hammond]

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Lennart Sorensen wrote:
> On Tue, May 17, 2005 at 12:40:38PM -0700, Joseph Kubik wrote:
> 
>>Sometimes:
>>nfs boot, I would argue, is a kernel talking at the application layer.
>>Can someone confirm this?
> 
> True, but NFS only uses tcp/udp packets, I don't think it really
> abstracts out any of the top 3 layers.  Almost nothing does.

The Linux kernel handles OSI layer 3 (network) through OSI layer 6
(presentation). Layer 1 is the actual copper/fiber/rf/pigeon. Layer 2
(data link) is mostly handled in hardware ASICs these days, although
configured by the kernel. In terms of the old model, that's layers 2 and
3 (network and transport).

As to which model the kernel "adheres" to, I don't really understand the
question. If you're trying to get an idea of how the kernel's networking
   works, there's a summary of the design the Linux netfilter stuff over
here. Old, but pretty readable.

http://www.gnumonks.org/ftp/pub/doc/packet-journey-2.4.html

If you're looking for wierdo edge cases where the kernel operates in
"application" layer, then the integrated web accelerator back in 2.4 was
pretty "application". I'm sure there are plenty more. Some of the load
balancing stuff feels kind of application like too.

Flipping things around, http://www.doxpara.com/paketto has a linkcat
application, which allows direct read/write at L2.

- --
Andrew Hammond    416-673-4138    ahammond-swQf4SbcV9C7WVzo/KQ3Mw at public.gmane.org
Database Administrator, Afilias Canada Corp.
CB83 2838 4B67 D40F D086 3568 81FC E7E5 27AF 4A9A
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