PAST-HOAS: Fast Setup of Per-Address Sink Routing Trees by Reverse Flooding

Scaling Ethernet switched networks to sizes of hundreds of thousands of hosts is a key requirement for data center networks. PAST is a simple and scalable OpenFlow-based layer-two architecture for data center Ethernet networks that outperforms Equal Cost Multipath Forwarding. PAST computes and configures one spanning tree for every MAC destination address. However, an important bottleneck of PAST is the time taken to perform the massive installation of rules at OpenFlow switches to set up the trees. PAST-HOAS aims to solve that obstacle, building trees instantly by path discovery, either triggered by the controller with a multicast probe frame from the edge destination switch or by the standard ARP Request frame; without flow installation and without tree computation. PASTHOAS is loop-free, and provides 100–400 times faster network initialization, lower forwarding delays and increased robustness and scalability.