[c-nsp] IDSM load splitting with EC on C6k

[Peter Rathlev]

Hi,

Sorry if I keep "spamming" the list with data center related question.
Write me if you think this is the wrong place. :-)

I've been reading about IDSM load splitting with Etherchannels on
Cat6500/Sup720, and it seems really nice that you can scale away from
the 600 mbps per IDSM bottleneck. I still have a few worries though.

First, the load splitting uses the standard EC hashing to make sure all
packets from the same flow uses the same IDSM. What worries me is that
communication between two hosts, e.g. a TCP stream, is actually two
different flows. So I could have client->server traffic using one IDSM
and server->client traffic using another. Doesn't that mean that the
IDSM cannot identify bad streams, or do they work in a way that makes
this a non-issue?

Second, with DFC-enabled LAN cards and a Sup720, there shouldn't be any
performance issues for traffic switched between these LAN cards, even if
I put 6 IDSM classic bus modules in the chassis. But when using VLAN
capture or SPAN to send the traffic to the IDSM, do I defeat the DFC
advantages, ruining the decentralised concept? Or doesn't VLAN
capture/SPAN replication "disturb" the forwarding process? Am I
downgrading the system to 30 Mpps also for inter-DFC traffic?

Again, thanks for any comments. :-)

Regards,
Peter