Re: The ultimate TOE design

[Neil Horman]

Wes Felter wrote:
> Neil Horman wrote:
>
> > Paul Jakma wrote:
> >
> > > On Wed, 15 Sep 2004, Jeff Garzik wrote:
> > >
> > > > Put simply, the "ultimate TOE card" would be a card with network 
> > > > ports, a generic CPU (arm, mips, whatever.), some RAM, and some 
> > > > flash.  This card's "firmware" is the Linux kernel, configured to 
> > > > run as a _totally indepenent network node_, with IP address(es) all 
> > > > its own.
> > > >
> > > > Then, your host system OS will communicate with the Linux kernel 
> > > > running on the card across the PCI bus, using IP packets (64K fixed 
> > > > MTU).
>
>
> > > The intel IXP's are like the above, XScale+extra-bits host-on-a-PCI 
> > > card running Linux. Or is that what you were referring to with 
> > > "<cards exist> but they are all fairly expensive."?
>
>
> > IBM's PowerNP chip was also very simmilar (a powerpc core with lots of 
> > hardware assists for DMA and packet inspection in the extended 
> > register area).  Don't know if they still sell it, but at one time I 
> > had heard they had booted linux on it.
>
>
> An IXP or PowerNP wouldn't work for Jeff's idea. The IXP's XScale core 
> and PowerNP's PowerPC core are way too slow to do any significant 
> processing; they are intended for control tasks like updating the 
> routing tables. All the work in the IXP or PowerNP is done by the 
> microengines, which have weird, non-Linux-compatible architectures.
I didn't say the assist hardware wouldn't need an extra driver.  Its not 
100% free, as Jeff proposes, but the CPU portion of these designs is 
_sufficient_ to run linux, and a driver can be written to drive the 
remainder of these chips.  Its the combination that network device 
manufacturers design to today: A specialized chip to do L3/L2 forwarding 
at line rate over a large number of ports, and just enough general 
purpose CPU to manage the user interface, the forwarding hardware and 
any overflow forwarding that the forwarding hardware can't deal with 
quickly.
> To do 10 Gbps Ethernet with Jeff's approach, wouldn't you need a 5-10 
> GHz processor on the card? Sounds expensive.
To handle port densities that are competing in the market today?  Yes, 
which as I mentioned earlier would price designs like this out of the 
market.  Jeffs idea is a nice one, but it doesn't really fit well with 
the hardware that networking equipment manufacturers are building today. 
 Take a look at Broadcoms StrataSwitch/StrataXGS lines, or Switchcores 
Xpeedium processors.  These are the sorts of things we have to work with 
.  They provide network stack offload in competitive port densities, but 
they aren't also general purpose processors.  They need a driver to 
massage their behavior into something more linux friendly.  If we could 
develop an infrastrucutre that made these chips easy to integrate into a 
 platform running linux, linux could quickly come to dominate a large 
portion of the network device space.

Neil

> Wes Felter - wesley@xxxxxxxxxx - http://felter.org/wesley/
>
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