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Fast Failover for Control Traffic in Software-defined Networks Globecom 2012 Neda B. & Ying Z. Presented by: Szu-Ping Wang Introduction (1/2) Controller Control Plane Control Traffic Data Plane Network Device Traditional Switch SDN 2 / 11 Introduction (2/2) How to implement? - Adding new links? Cost increasing… Control Plane Control Traffic - Choose one node in original topology to be controller? Data Plane 3 / 11 Controller Placement (1/2) • How to choose the best placement on the original topology? - Fast Failover ? Backup Link Protected Switch Choose the best placement with minimum number of unprotected switch. 4 / 11 Controller Placement (2/2) • Define the Protected Switch: Unprotected! 1. Check the other nodes that is not in the same sub-tree. 2. Does there exist a link between target switch and the set of green circle? Protected! Special case: controller’s immediate children check the all other nodes except controller in step 1. 5 / 11 Algorithm overview (1/1) • Two algorithms for choosing the best location for the network controller. • One algorithm for improving the resiliency of shortest path routing tree. • The ideas are all about protected switches numbers. 6 / 11 Algorithm 1 Opt. algo. Unprotected! (1/1) Minimized the descendants number of unprotected switches. Unprotected! • Search through all switch and choose the one that minimized the descendants number of unprotected switches. 7 / 11 Algorithm 2 GREEDY algo. (1/1) • It’s non-practical if the size of the network is large! • Heuristic Algorithm. • Check only the neighbors of controller and choose the one that maximized the number of protected switches. • No need to find the routing tree first! Protected! Protected! Special case: controller’s immediate children check the all other nodes except controller in step 1. 8 / 11 Algorithm 3 routing. algo. (1/1) • Start from Shortest Path Tree. • Try to modify the tree by replacing the edge to the tree edge. 2 2 Switch ID Descendants number of unprotected switches Initial 2 a 0 b 2 c 0 0 a b c 9 / 11 SIMULATION (1/1) • 10 real network topologies. • Calculating the descendants number of unprotected switches. 10 / 11 Thanks !! Presented by: Szu-Ping Wang conclusion (1/1) • It’s practical for implement SDN on original topology. • The algorithm 1 and 3 are straightforward. • There is no analysis for Algorithm 2. 12 / 11