Concerning the high complexity of multiple controller placement model in existing works, several metrics to improve network service quality were defined and an approach to partition network domain and implement controller placement for large scale Software Defined Network (SDN) was proposed. The network was partitioned into several domains based on Label Propagation Algorithm (LPA) and then the controllers in the small domains were deployed separately, which makes the model complexity be linear with the network size on consideration of control path average latency, reliability and the load balance. Simulation results show that our strategy improves the load balance dramatically compared with the original LPA, decreases the model complexity and enhances network service quality compared with CCP. In Internet2, the average control path latency decreases by 9% and the reliability increases by 10% at most.

In multi-controller Software Defined Network (SDN), since the existed switch migration strategies always have low efficiency and need to migrate many times which only consider single migration factor, a mechanism of switches migration based on progressive auction named PASMM (Progressive Auction based Switches Migration Mechanism) was proposed. To improve network benefit, the switch migration problem was optimized by auctioning controllers' remaining resources in the mechanism. By increasing the trading price of the over-demanded controllers' resources, PASMM completed the auction and redeployed the controllers and switches. The simulation results show that, compared with some typical switch migration policies, PASMM achieves good load balancing of controllers, reduces the response time of the PACKET_IN messages by an average of 13.5%, and spends the least migration time with the increasing of switches flow requests.

The vertex shader needs an extra generating pattern and the calculation of subdivision level is complicated when subdividing terrain grid. A Level of Detail (LOD) terrain rendering algorithm using subdivision shader was put forward for the insufficiency. The proposed method used block quad tree organization to build a rough terrain grid hierarchical structure, and filtrated the activity terrain blocks by LOD discrimination function. A subdivision factor calculation method was proposed based on viewpoint in a three-dimensional continuous distance in tessellation control shader and cracks of the external factor segment was eliminated. As a result, displacement mapping on tessellation evaluation shader and displacement of height component in fine grid blocks were achieved. Meanwhile, the quadtree was saved to vertex buffer, and the exchange of resource between Central Processing Unit (CPU) and Graphic Processing Unit (GPU) was decreased. The subdivision process was accelerated by bringing in subdivision queue. The experimental results show that the proposed algorithm has a smooth detail level transition and good subdivision effect, and it can increase the utilization ratio of GPU and terrain rendering efficiency.