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    Cisco Hierarchical Model for Datacenters, outdated?


      So I recently came across an article reposted by a popular internet blogger (pointing to http://www.theregister.co.uk/2011/09/21/flatter_networks/  ). This article basically asserts that Cisco's Hierarchical Model for Datacenters is not well-suited for high-performance virtualized datacenters. To my understanding, the position taken is that as hardware platforms continue to increase in the quantity and performance of their processor cores, the system performance of server nodes (hypervising shared VMs) will outpace the performance of the route/switch hardware infrastructure; ipso facto, the server nodes processors will be waiting on the network to move packets between the nodes. The arguement appears to be that replacing the hierarchy with a flat network is more efficient and suitable for the datacenter.


      So while I follow the basic logic of this arguement, I'm failing to see where the specific functions delegated to the different layers (such as filtering and security functions in the aggregation layer) will be relocated. In other words, how might you implement such things as ACLs or inter-vlan routing typically found in the distribution layer? I mean wouldn't the nanonsecond/microsecond latency incurred to support such tasks simply be shifted elsewhere? Maybe I'm misunderstanding the strategies of the competing models proposed within the articles and how it is overall superior? Thanks in advance for all your input.

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