Hi, I am trying to get a better understanding of the Nexus 5K/2K with respect to how packet forwarding occurs and comparing it to the 6Ks. The Nexus 2K is a Fabric extender and it is documented that we need to treat the 2K as a line card. In addition it also seems that when traffic needs to go from east to west or from 1 port on the 2K to another port on the same 2K than the entire packet (header + data) is forwarded to the Nexus 5K.
Would this operation be similar to how a 6K chassis works with classic line cards in Flow-through mode where the header + data is forwarded to the Supervisor?
If that is the case above than won't this affect the forwarding performance and latency on the Nexus 5K and in such traffic patterns (east to west) won't the 6K give better performance from a forwarding and latency perspective if you are using a 6K with classic/fabric enabled cards in truncated mode or fabric enabled only in compact mode and if your egress port is on the same line card as your ingress port?
if you are using a 6K with DFC enabled line cards than won't the 6K give even better performance since the 6K with DFC modules will perform a local lookup and if the egress port is on the same line card than it won't have to send the data across the crossbar fabric at all hence achieving better numbers for latency and throughput?
I guess the nexus does makeup some of this by being a cut-through box but still just thinking about how the entire header+data needs to be sent to the N5K and than sent back down to the same fex would be a lot higher than doing it locally.
In addition won't the distance also come into play now since the Fex can be placed anywhere in the DC and if this happens to be a lot further away from the N5K than propogation delay will also be a factor?
I apologize for asking so many questions but am trying to understand the architecture better as compared to the 6Ks and the benefits/disadvantages. Appreciate any feedback and corrections if the above is incorrect. Thx for your help.
