"congesting the crossbar fabric(sh fabric util) which is pretty unlikely when you are talking a 24G linecard on a 40G fabric connection"
Just a nitpick or two - the 6724 only has one channel of fabric, so it's a 24G linecard with a 20G fabric connection, thus a slight oversubscription. If you're extremely rigorous about line-rate, leave four of those ports unused. But the DFC issue is more about Mpps than Mbps. As Phil pointed out, you could run them well under their line-rate, but with small packets, and overwhelm the forwarding capacity of the PFC. -Geoff On Wed, Sep 2, 2009 at 5:59 PM, Ben Steele<[email protected]> wrote: > Unless you are hitting a cam limit on any of your resources on your SUP(very > possible if you are exporting netflow) OR you are congesting the crossbar > fabric(sh fabric util) which is pretty unlikely when you are talking a 24G > linecard on a 40G fabric connection then you probably won't see any > difference putting a DFC on a 6724 > > Remember these chassis are a hardware only based forwarding solution, so all > your doing with a DFC is moving cam/asic resources off the sup, so in > regards to your specific questions unless you have filled all your QoS > queues on the sup you are going to see nothing more on the DFC, also the sup > does (from memory) up to 100-200m pps in ipv6, I don't believe for a moment > you are even remotely close to this, and the global ipv6 routing table is no > where near the cam limit for that either, by the way is your SUP an XL? does > the DFC's on the 10G's match the sup or have they fallen back to the lowest > common configuration? > > "...or could it be that DFC's are only really useful to a particular > deployment > and I just *think* i need them? ;-)" - I think you might be on the money > here. > > If you give us the current utilization of your cam resources(from the sup) > and the 6724 linecard throughput and what its functions > are(netflow/qos/mac/acls etc) then we can tell you for sure. > > Ben > > > On Wed, Sep 2, 2009 at 9:16 PM, Alan Buxey <[email protected]> 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 >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
