A network system for a data center is described in which a switch fabric provides full mesh interconnectivity such that any servers may communicate packet data to any other of the servers using any of a number of parallel data paths. Moreover, according to the techniques described herein, edge-positioned access nodes, optical permutation devices and core switches of the switch fabric may be configured and arranged in a way such that the parallel data paths provide single L2/L3 hop, full mesh interconnections between any pairwise combination of the access nodes, even in massive data centers having tens of thousands of servers.