[c-nsp] do i *need* DFCs on the 6500?

[Matyas Koszik]

The PFC is capable of the same things as a DFC, just in a centralized
manner. So, for example, CoPP works just fine in hardware with a PFC - you
don't NEED to offload the QoS to the LCs. You need a DFC only if some
resources are close to exhaustion (like pps rates supported by centralized
forwarding, netflow entries, QoS entries and so on).



On Wed, 2 Sep 2009, Justin Shore wrote:

> You eluded to one of my strongest selling points on DFCs though I don't
> think you made that particular connection yet.  DFCs offload QoS to the
> LC as you said.  That also means that CoPP is also handled in hardware
> if you have DFCs in place since it requires MLS QoS on that platform.
> Ie, if your 6500/7600 is going to be publicly-accessible on the Internet
> in any capacity and you want it to be able to use CoPP to withstand a
> targeted DoS attack then DFCs are not optional, they're critical.
>
> The others on the list can probably give you much more in-depth views on
> the other aspects of the card but I found CoPP to be a big enough
> selling point.  It wouldn't be good is a simple little DoS attack took
> down my core 7600s.
>
> Justin
>
>
> Alan Buxey wrote:
> > hi,
> >
> > okay, from the background of I know what the DFC is and how it
> > operates etc... i know I want them - however, I need to justify
> > the upgrade/part cost to sort out a couple of 6500's.  in some of
> > our 6500's, the 10G blades have DFCs already...but several 6724's dont
> > (they just have CFC). ...as i said, I want them, but need to get
> > some management/funding buy-in - and they dont want the 'what it
> > does' information - they want some hard and fast facts that Cisco dont
> > sem to want to tell me ..... so, the question is
> >
> > 1) is there any way of showing the sup720 strain/utilisation...particularly
> > is there a way of showing DFC usage on the blades where we have them?
> >
> > 2) it offloads IPv6 and QoS - we're into both of those (and more so over the
> > next year) - any particular insights into QoS performance/issues without
> > DFC ? any throughput figures for IPv6 ?
> >
> > (i know that with CFC we're limited to the backplane (32mpps?) and we get ~ 48mpps
> > per blade with DFC)
> >
> > ...or could it be that DFC's are only really useful to a particular deployment
> > and I just *think* i need them?  ;-)
> >
> > alan
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