An architecture of data center network to support virtual machines as workhorses and standard Ethernet as layer-2 with flat-addressing. Load-balancing is provided by Valiant Load Balancing (i.e. OSPF ECMP), and the multipath capability of the network is exploited by modifying the OS of hosts — so that different MAC addresses are used to correspond to different paths. The move of VM from one hardware host to another is done by tricking the MAC address. A centralised server is used as the MAC address directory system.

The topology mentioned in the paper is interesting: It claims as a Clos network but it is not a fat-tree, which is commonly called the folded Clos. The network presented is as follows: The core layer (called intermediate switches) are forming a complete bipartite graph with aggregation layer. That is, any aggregation switch connects to every core switch. The top-of-rack switch (edge) spans only two connections to two different aggregation switches.

Bibliographic data

   title = "VL2: A Scalable and Flexible Data Center Network",
   author = "Albert Greenberg and Srikanth Kandula and David A. Maltz and James R. Hamilton and Changhoon Kim and Parveen Patel and Navendu Jain and Parantap Lahiri and Sudipta Sengupta",
   booktitle = "Proc. SIGCOMM’09",
   month = "August 17–21",
   year = "2009",
   address = "Barcelona, Spain",