| Summary: | 碩士 === 淡江大學 === 電機工程學系碩士班 === 104 === Software Defined Network(SDN) concept decouples the control plane and the data plane of network devices. SDN can implement programmable network through the strategy management of the control layer. It can be quickly and easily implemented in the data layer of the underlying system. SDN can implement flow control, load balancing, network security and innovative web applications. OpenFlow protocol is used to realize SDN concept. OpenFlow protocol defines the communication between the control plane device and the data plane device. The shortest path algorithm was used to find minimum hop counts between two endpoints in the traditional routing planning. In load-balancing, we find optimal routings by using the shortest path algorithm and adding the link utilization rate as the edge weight.
Network traffics are dynamic in the practical application. The initial path can’t be guaranteed load balancing during transmission. When the network is load imbalancing, routing paths need to be adjusted in order to achieve load balancing. In the current studies, the optimal path algorithm is used to find the optimal path in each routing so that the network can achieve load balancing. However, we found the shortage in the current individual adjustment strategy. The link load is changed after the paths are adjusted. Therefore, other routing paths need to be changed in order to become optimal paths. The individual adjustment strategy will spend more time to achieve balancing and become stable.
We propose the global adjustment strategy which solve the problem about spending too much time to achieve load balancing. Our strategy reschedules the optimal path just one time. Next, all the paths will be changed to achieve load balancing in the same time. All the routings are rearranged, therefore a lot of paths need to be changed so that a large number of packets become out of order.
We also propose the partial adjustment strategy which is improved from the global adjustment strategy. The partial adjustment adjusts part of routings, and then we determine whether the networks are load balancing. If the networks are not load balancing, more routings would be adjusted until the networks achieve load balancing. Then all paths will be changed in the same time. In partial adjustment strategy, the networks may achieve load balancing by using part of routings. Therefore, fewer paths are changed and the number of packets which are out of order decreases.
The experimental results confirm that the global adjustment and the partial adjustment can achieve load balancing in single period. But the individual adjustment spends more periods to achieve load balancing. Therefore, the global adjustment and the partial adjustment in the UDP packets can improve packets loss rate, out of order, delay jitter and throughput in shorter time. In addition, the partial adjustment just adjusts part of paths to achieve load balancing in some cases. Number of packets which are out of order caused by routing adjustment decrease. Finally, we compare average delay of TCP packets in these three strategies in a long time. Our strategies achieve load balancing efficiently.
|
|---|
