Research And Design Of Link Layer Of Localized Embedded OS Network Protocol Stack

With the continuous development of operating systems,various mobile operating systems and home smart operating systems have been widely used.The network protocol stack of embedded operating systems needs to adapt to different application environments.In the traditional embedded operating system network protocol stack,the data frame processing method in the data link layer is too simple to meet some load conditions.Aiming at a localized embedded operating system developed by AVIC Research Institute,this topic designs the data link layer of the network protocol stack that meets the requirements,improves the ARP protocol function,and adds an adaptation layer to better handle data frames.In connection with the network card,a more suitable data structure and data frame queuing mechanism are designed for the limited and real-time nature of embedded operating system resources.This thesis first analyzes the domestic and foreign status quo of operating systems and network protocol stacks,and comprehensively sorts out the architecture and functions of a domestically produced embedded operating system.Research is carried out,focusing on the network layer technology and design of the connection part with the data link layer,as well as the theory of the ARP protocol and the data transmission and reception adaptation layer that need to be used in the data link layer.Secondly,the overall design of the ARP protocol in the data link layer is carried out.In order to meet the streamlined requirements of a localized embedded operating system,the ARP protocol is combined into four major functions,and the small functions in the large functional modules are connected as a whole,so that the entire protocol can cooperate with each other and be more perfect,and is designed for the overall process.A more suitable data structure and state field have been developed to make the cooperation between functions more convenient and stable.In order to better handle the connection between the Ethernet data frame and the network card,the design of the adaptation layer is added to the data link layer.In the adaptation layer,it is not only necessary to complete the encapsulation and receiving and offloading of Ethernet data frames,but also to add a queuing mechanism and a data packet receiving strategy before and after the network card processing,which improves the traditional simple mode of sending and receiving packets.A priority transmission queue mechanism is designed to improve the overall transmission quality,and a polling reception strategy is added to make the processing,reception and transmission of Ethernet data frames more stable and reliable.Finally,all designed functions are tested,the feasibility of each module is tested,and some special cases of sending failure are tested,which ensures the integrity,systematicness and reliability of the realization function of this project,and the CPU occupancy rate is also tested.And the network performance indicators of packet loss rate are tested.To sum up,this thesis implements the functional modules of the data link layer under the theoretical specification of the data link layer,and simplifies or optimizes its overall functional design according to its application environment,and adds some strategy algorithms to ensure its performance.stability.Experiments show that all links of the data link layer designed and implemented in this project are running normally and have achieved the corresponding performance indicators.