Research On Resource Discovery And Location Technology For Constrained Applications

With the rapid development of the Internet of Things,more and more nodes will access the Internet of Things.These nodes have low processing power,rely on battery power and have small storage space,and are collectively referred as constrained nodes.The network which is composed of constrained nodes is called as constrained network.Due to the constrained feature of the Internet of things,its resource communication mechanism is different from the existing resource communication services in the Internet,the traditional Internet resource discovery method can not be applied to a constrained network,and the Internet of Things urgently needs a new resource discovery and location mechanism.In this case,how to design and realize resource discovery and location mechanism under constrained network has became an important research topic.Based on the constrained network,this dissertation proposes solutions and verifies how to realize resource discovery and location mechanism in constrained environment.The core work is divided into two parts:the research and implementation of Resource Directory Server under CoAP protocol and the research on DNS Service Discovery in constrained environment.In order to meet IoT or M2M communication requirements,the IETF CoRE Working Group defines a constrained network communication architecture and a constrained environment application protocol(CoAP).Based on the CoAP protocol,this paper proposes Resource Directory Server to realize resource discovery and location.Based on the OMA resource discovery and the IETF CoRE Working Group constrained network resource discovery draft,the server has been designed and implemented in detail.In addition,resource can also be regarded as a kind of service.As a widely used form of service discovery,the DNS service discovery mechanism in the Internet has good stability and scalability.Based on this,the paper proposes to use DNS Service discovery mechanism to discover and locate resources.Through the reference service found at home and abroad related information,this issue is studied and analyzed in detail.Aimed at the impact of node dormancy on DNS service discovery in constrained environment,a proxy server solution is proposed.Finally,the dissertation makes a theoretical comparison between the resource directory server and the traditional centralized resource discovery scheme and verifies with the Cf framework and the Copper plug-in.The analysis shows that compared with the centralized resource discovery scheme,Resource Directory Server has obvious advantages in response speed,throughput rate and response success rate.At the same time,a detailed comparison of the proxy server solution and the caching solution proposed in the constrained environment to solve the node dormancy problem is carried out,and the performance test of IOT simulation environment is conducted.The results show that the proxy solutions are about 20%more responsive than caching solutions in hibernation.