Non blocking data center switch

[jmprats]

Are data center switches non blocking? Is it an important feature in a data center switch? 

For example, Cisco Nexus C36180YC-R,

It has got:

- Switching capacity: 3.6 Tbps (48x25+6x100=1800 Gbps half duplex x2)

- Forwarding Rate: 1.67 Bpps

I calculate the forwarding rate as 1800x1.5= 2700 Mpps= 2.7Bpps, so I understand this switch is not Non-blocking, so it has got oversubscription in its ports

[Sergiu.Daniluk]

Hi,

The non-blocking line rate performance is usually needed in cloud computing data centers or for media and broadcasting providers. There are few Nexus switches which are capable of non-blocking traffic: Nexus 3548, Nexus 9200 series, different N9500 line cards.

For the rest of the Nexus families, the over-subscription ratio is low, and it can be reduced even more by having an optimized utilization of all available paths, through the use of CLOS topologies and data center specific protocols (vxlan, vpc etc).

For Nexus C36180YC-R, according to the data sheet, you have 1.8-Tbps switching capacity.

Reference: https://www.cisco.com/c/en/us/products/collateral/switches/nexus-3000-series-switches/datasheet-c78-739189.html 

Hope it helps,

Sergiu

[jmprats]

Thanks

I think 1.8 Tbps is one way. In another part of the data sheet it says " Wire-rate Layer 2 and 3 switching on all ports, with up to 3.6 Terabits per second (Tbps) and up to 1.67 billion packets per second (bpps)"

48ports x25G + 6x100 uplinks= 1800 Gbps (half duplex). So 1800x2 = 3.6 Tbps full duplex switching capacity

It is true that access switches 10G are normally non blocking, while data centers switches are not. Maybe the switch can not use all the ports at 25G and all the uplinks at 100G at the same time, but I think it would be important find out this information somewhere in order to know how to built a non blocking network with the switch.