Institute of Electrical & Electronic Engineers
Cloud computing coordinates a lot of collocated servers to provide versatile applications. The issues of networking these collocated servers are different from those in the current Wide Area Networks (WAN). Thus, many cloud datacenters develop new layer-2 routing topologies, while WAN considers the layer-3 routing. Basically, the layer-2 routing can have faster packet forwarding speed compared to the layer-3 routing topology because lower overhead. However, the layer-2 routing schemes may not be scalable when the number of servers increases. Many newly proposed topologies for cloud datacenters emphasize on the scalability issue, including VL2, PortLand, and BCube, etc. VL2 can achieve low cost in high-speed hardware implementations, but its Equal Cost Multi-Path (ECMP) scheme faces the problem of arriving packets with incorrect orders.