On Sun, Oct 21, 2007 at 09:23:39PM -0400, Brian A Seklecki (Mobile) wrote:
> On Mon, 2007-10-22 at 00:12 +0100, Tony Sarendal wrote:
> > On 10/21/07, Henning Brauer <[EMAIL PROTECTED]> wrote:
>
> I'll throw this out there since its been something on my mind for a
> while:
>
> Hardware VLAN tagging, TOE offload, IP/UDP/TCP Checksum offload,
> interface polling are all ways to accelerate packet forwarding. How
> about a standards-based hardware-software API equivalent to Cisco's
> "CEF" or "MLS"?
>
We have hardware VLAN tagging support on many interfaces.
TOE helps not a single bit on routers and I don't trust TOE just think
about it. TOE is a TCP/IP stack in HW. With every network card generation
we get new features. DMA, IP checksumming, TCP checksumming and each and
every of these much simpler functions where cursed with tons of bugs.
I think there are probably 2 network cards that do the checksumming right,
all others have some more or less noticable bugs in them. So do you think
that the HW designers will create a correct TOE engine?
How about a standards-based hardware-software API equivalent to Cisco's
"CEF" or "MLS"?
standards-based? with cisco? Cisco is not even able to follow standards
for easy stuff like VLAN etc.
CEF is a pure software gimmick. MLS needs a Layer-3 capable switch chip
which does all the work with its CAM. If you get me a PCI card with a L3
switching chip on it including a 500k entries CAM plus docu I will write a
driver for it.
> The basics:
> - layer 3 or layer 4 state ("flow") is identified and established using
> software IP-forwarding.
> - the software dynamically programs the switching hardware backplane
> ASIC to accelerate forwarding the "flow" w/o software further
> inspection (Including Fragment Reassembly, etc.)
>
Fragment Reassembly does not happen in the forwarding plane, it happens on
the end system. By doing "flow" based forwarding on the router you're no
longer able to do all the additional checks that pf(4) is doing in its
stateful forwarding path.
> There is probably a huge market out there for a commodity standards
> based hardware (if it could be done)
>
I doubt it, the necessary HW is just to expensive and complex.
--
:wq Claudio
