Design And Simulating Implementation Of A Load Balance Solution For DNS

Domain name system (DNS) is a core service provided by the Internet. It performs as a distributed database which maps the domain names into the corresponding IP addressdes. There are two types of Servers in DNS system—the Authority Server(or Name Server) and the Cache Server. The Authority Server shouders the responsbility of maintaining the information of an authorized domain, while the Cache Server is used as a proxy; it receives DNS requests, and take the action of requesting the domain information from the DNS authority server and sends the result back to the client.Currently used DNS systems are usually configured with many DNS Cache Servers, which are devided into several geomatical domains. Together with Anycast technology, the system provides a unique DNS service IP address. But the system cannot dispatch the DNS request according to the DNS Cache Servers'processing capability. Current implementaion is to send the DNS request to the lowest costed Cache Server. But these will result in some of the Cache Server very busy, while others got little DNS request to processing.In order to shorter the DNS request processing time and dispatch the DNS requests according to each DNS Cache Server's current load, a dynamic load-balanced DNS system is needed, which is introduced in this paper.The system has many Controllers, each of which deployed on a separate DNS Cache Server, and collects its current work load. The controller establishes a priority queue according to the caculated load, which is considered with the CPU usage, Memory usage and the disk usage. These can avoid the case that all Controllers choose one DNS Cache Server at the same time. Nevertheless, the system has been optimized in initializing the priority queue, the sorting work is done in linear time. The system's portability is also considered here, for the users can configure the monitored UDP port, in order to provide the load balance service to other UDP protocols. The simulating system is developed to verify the crorrentness of this solution. The designation and developing method is also introduced in this paper. The simulating system's development is based on the Netfilter API, which is used to catch the DNS request, and modify its destination address according to the rules defined, in order to redirect the DNS request to a lower-loaded DNS cache server. This DNS cache server sends back the result directly to the client.