The Funkschau special edition „Datacenter 2011“ features an article about *server access technologies* (network design) within datacenters. The author elaborates on pros/cons of ToR vs EoR/MoR designs. Having read a couple of papers about this topic, to me, Top-or-Rack (ToR) seemed to be de-facto industry standard. Apparently, this is not the case.
Browsing the Web for some additional info I came across an excellent source on the overall topic (networks/datacenters/cloud computing/etc). Check, for instance, ToR vs EoR for a lengthy discussion on datacenter network design choices.
Another good source on the same / a similar topic