Title: Development of Weighted Round-Robin with Variable TTL to Improve of Load Balancing Mechanism in a Distributed Web System Using DNS

Issue Number: Vol. 7, No. 3
Year of Publication: Sep - 2017
Page Numbers: 153-160
Authors: Kota MORIGAKI, Keizo SAISHO
Journal Name: International Journal of Digital Information and Wireless Communications (IJDIWC)
- Hong Kong
DOI:  http://dx.doi.org/10.17781/P002322


Progress of virtualization technology in recent years made it easy to build virtual servers on Cloud. They can be used as cache server for load balancing. However, expected responsiveness cannot be gained with insufficient cache servers against load. In contrast, costs will increase by surplus cache servers against load. Therefore, we have been developing a distributed Web system that adjust the number of cache servers according to load of them to reduce running cost. In this study, a load balancing method using DNS round-robin is under development. However, load imbalance occurs among the servers with this method and responsiveness decreases because it is difficult to distribute the load uniformly using DNS roundrobin. Therefore, we implement a function to suspend the allocation of requests to the overloaded server. From results of experiments, we confirm that improved function is possible to prevent lowering responsiveness with smaller TTL value. Small TTL, however, increases network traffic and DNS request. Therefore, we implement weighted round-robin with variable TTL to change the TTL value according to load of servers and increase request to the low load server. This paper describes development of suspending function and weighted round-robin with variable TTL and evaluation of them. By the experiments, it is possible to improve performance with optimal parameters.