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Re: The ultimate TOE design

To: Jeff Garzik <jgarzik@xxxxxxxxx>
Subject: Re: The ultimate TOE design
From: Neil Horman <nhorman@xxxxxxxxxx>
Date: Wed, 15 Sep 2004 16:54:30 -0400
Cc: David Stevens <dlstevens@xxxxxxxxxx>, Netdev <netdev@xxxxxxxxxxx>, leonid.grossman@xxxxxxxx, Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>
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Jeff Garzik wrote:
David Stevens wrote:

I've never understood why people are so interested in off-loading
networking. Isn't that just a multi-processor system where you can't
use any of the network processor cycles for anything else? And, of
course, to be cheap, the network processor will be slower, and much
harder to debug and update software.


Well I do agree there is a strong don't-bother-with-TOE argument: Moore's law, the CPUs (manufactured in vast quantities) will usually


However, there are companies are Just Gotta Do TOE... and I am not inclined to assist in any effort that compromises Linux's RFC compliancy or security. Current TOE efforts seem to be of the "shove your data through this black box" variety, which is rather disheartening.

Even non-TOE NICs these days have ever-more-complex firmwares. tg3 is a MIPS-based engine for example.


If the PCI bus is too slow, or MTU's too small, wouldn't
it be better to fix those directly and use a fast host processor that can
also do other things when not needed for networking? And why have
memory on a NIC that can't be used by other things?


PCI bus tends to be slower than DRAM<->CPU speed, and MTUs across the Internet will be small as long as ethernet enjoys continued success.

    Jeff

There is also something to be said for the embedded market here. offload chips are fairly usefull when building switches and routers. Dave M. in a thread just a few weeks ago provided some metrics for how much bandwidth a PCI-x bus and a some-odd-gigahertz processor could handle. It worked that a pc with the right componenets could theoretically handle about 4 gigahertz nics running traffic full duplex at line rate. Thats great, but it doesn't come close to what you need for a 24 port gigabit L3 switch, nor does it approach the correct price point. Most of these designs use a less expensive processor running at a slower speed, and an offload chip (that incorporates tx/rx logic and a switching fabric) to preform most of the routing and switching. For cost concious network equipment manufacturers, they are really the way to go. Unfortunately, many of them don't actaully run as a co-processor, and so don't enable Jeff's idea very well (yet :))

Neil

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