Research And Optimization Of DTLS Protocol Based On SMS

The constrained application protocol CoAP and the default protocol stack CoAP/DTLS/UDP with security capabilities had been defined by the CoRE working group of IETF,in the lightweight machine-to-machine communication architecture proposed by the open mobile alliance,short messages are defined as a means of transmission and form a CoAP/DTLS/SMS stack.Since the characteristics of SMS affect the performance of DTLS protocol,it has become an important in the standardization process of CoAP/DTLS/SMS to study the characteristics of DTLS/SMS stack and improve its performance.In this paper,the CoAPs over SMS protocol stack is realized through the extended development of C.f CoAP in MI Android system,the work includes:1)CoAPs/UDP/SMS software was designed to realize the function of message reuse;the performance of DTLS/SMS was tested by data transmission experiment,Based on experimental data analysis,it was pointed out that the handshake message delay existed in DTLS,especially the poor performance caused by error retransmission.2)A mechanism based on selective repeat is proposed to solve the retransmission of DTLS handshake message with flight,so as to reduce the amount of retransmission data and improve the performance of handshaking message exchange.3)A cross-layer approach is studied,that is,a reliable datagram protocol(RUDP)mechanism is introduced between UDP and DTLS to improve DTLS performance.Because RUDP guarantees the reliable transmission of DTLS records in the CoAP/DTLS/RUDP/SMS stack,DTLS handshake message retransmission is avoided,thus improving the performance of DTLS handshake message transmission.4)In order to improve the performance of DTLS/SMS,a false start mechanism of message transmission is studied.In this paper,the selective repeat and the RUDP and the false start are realized,through theoretical analysis and communication experiments,DTLS data interaction time before and after optimization is compared.The results show that the optimization mechanism improves the performance of DTLS protocol effectively.