Nexus 7K 10G Line Rate Ports (?)

[visitor68]

It was my contention that, according to Cisco data sheets, the Nexus 7018 can deliver 768 10G ports at wire rate (non-blocking - no oversubscription), when deployed with 16 F2 48-port 10G line cards and 5 Fabric 2 modules.

Someone answered me by saying:

Cisco claims that the Nexus7018 can support 768 10GbE interfaces with 16 - 48x10GbE cards. In reality, with 64 byte packets, each line card can only support 8 ports out of 48 at line rate.

Nexus 7018 Total packets supported (with F2 series modules) = 1.92 Bpps for 16 slots

Max PPS per slot = 1.92B/16 = 120Mpps

Number of 64 byte packets per 10GbE = 10 x 1000/672 = 15 Mpps

Hence, the number of line rate 10GbE per slot = 120 /15 = 8

So, the total number of ports that a Nexus7018 can support is 128. This is exactly the same as the Z9000.

Does this make any sense at all? Not sure where he got his numbers, especially the 1.92 Bpps. The Cisco data sheet says 11.5 Bpps per 7018 system. And how does he know that these are 64-byte packets? I'm also confused as to what that line in red means.

Can anyone from Cisco answer this please?

[Leo Laohoo]

It was my contention that, according to Cisco data sheets, the Nexus 7018 can deliver 768 10G ports at wire rate (non-blocking - no oversubscription), when deployed with 16 F2 48-port 10G line cards and 5 Fabric 2 modules.

Firstly, Fabric 2 cards have a bandwidth speed of 110 Gbps per slot.

The current generation of F2 card, N7K-F248XP-25, can push up to 480 Gbps.  So in reality, you need at least four Fab 2 cards and one for redundancy.

"Powered by the Cisco Nexus 7000 F2-Series SoC architecture, the module delivers 720 million packets per second (mpps) of distributed Layer 2 and 3 forwarding and up to 480 Gbps of data throughput. A Cisco Nexus 7000 18-Slot Switch fully populated with the Cisco Nexus 7000 F2-Series module has the capability to deliver up to 11.5 billion packets per second and 15.4 Tbps of switching performance,"

[visitor68]

Secondly, we are assuming that all 5 fabric modules are populating the chassis. This is a given and it is not the question. I didnt ask how many fabric 2 modules I need. So, with 5 Fabric 2 modules, you get 550Gbps per slot.

You didnt answer my question at all. What is this guy talking about? Is he correct? What do those numbers on the red line mean? "672"? what is he getting at?

[Leo Laohoo]

672 / 8 = 84

Ok so far?

Now go here:  Bandwidth, Packets Per Second, and Other Network Performance Metrics

Please don't ask me to explain because this is one topic I can't get my thick skull around.

Look at Table 1.

[visitor68]

:-) OK, but what does the 672 number mean??

I think his numbers are wrong. its not 1.92 Bpps per 7018 system. Its 11.5 Bpps.

[nkarpysh]

Hello,

So 672 means how many bits in 84 bytes (minimum frame size) -> 672 =84*8. Speed on interface is in bits and packet size was in bytes thus we need to bring all to bits and then make the math. So 15Mps is correct.

But the values of 1.92Bpps is not correct. 11.5 Bpps is the right one.

I guess 1.92Bpps is the rate of Juniper EX (not sure but found it here  http://www.scribd.com/doc/84062573/Cisco-Nexus-vs-Juniper-EX-Series)

Nik