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SubjectRe: The ultimate TOE design
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@felter.org - http://felter.org/wesley/
>
> -
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*Red Hat, Inc.
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