[c-nsp] Nexus 5596 architecture

[Garry]

On 27.01.2012 02:30, Jiri Prochazka wrote:
> Hi,
> 
> we are considering investment in a few Nexus 5596 switches. All Cisco
> documents say it has 96 non-blocking 10G ports (for L2). Is it _really_
> true? Can the switch reach throughput of 960 Gbps regardless the traffic
> distribution? Is't there some hidden limitaion, which is not presented
> by Cisco? :-) I've heard some rumors about this, but nothing particular.
> 
> First thig which comes to my mind is a doubt, if all three expansion
> modules really do have 160 Gbps connection to the fabric..

Actually, the 5596 is rated at 1920 Gbps (5548: 960 Gbps) IIRC, so one
would assume it is non-blocking ... Please do note that any L3
forwarding without the L3 card will be blindingly slow and prone to
packetloss ...

Maybe this document can shed some additional light on the issue ...
description of the 5500 architecture ...

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/ps11215/white_paper_c11-622479.html

"The UPC manages eight ports of 1 and 10 Gigabit Ethernet or eight ports
of 1/2/4/8-Gbps Fibre Channel. It is responsible for all packet
processing and forwarding on ingress and egress ports. Each port in the
UPC has a dedicated data path. Each data path connects to UCF through a
dedicated fabric interface at 12 Gbps. This 20 percent over-speed rate
helps ensure line-rate throughput regardless of the internal packet
headers imposed by the ASICs."

"The UCF is a single-stage, high-performance 100-by-100 nonblocking
crossbar with an integrated scheduler (Figure 9). The single-stage
fabric allows a single crossbar fabric scheduler to have full visibility
into the entire system and therefore make optimal scheduling decisions
without building congestion within the switch."

Of course this is a (somewhat aged - still speaking of "upcoming 5596"
and "1G Support in Q1CY11") tech doc from Cisco, so I suppose they would
not divulge any "hidden issues" ...

We have a customer with a 5548 and 4 FEXes, no issues to date, though
they're not really pushing the system ...

-garry