Research And Realization Of High Speed Data Transmission For TOE Network Card

With the devolvement of technology, the bandwidth of network grows nearly three times every year, and now the 10G network is being deployed. As the actual stand of the internet protocol stack, the TCP/IP protocol usually works as software at the host system. Normally one bit data must cost 1HZ CPU capacity to deal with it, so in a high speed network environment such as 10G network, the CPU's capacity becomes the bottle-neck of the system.To reduce the cost to the system caused by protocol dealing in a high speed network environment, the technology TOE (TCP/IP Offload Engine) is proposed and coming to use. In this paper, the TOE technology is introduced first, which offloads the protocol from the host system to the hardware. Complete offload and incomplete offload are the two ways of protocol offloading. A TOE can be implemented with a network processor and firmware, specialized Asics, or a combination of both. And we use the third method to implement the incomplete protocol offload.TOE software must be compatible with the existing applications, and it should supply high speed data transmission mechanism for the new application. To deal with it, the course of the message being disposed in the LINUX system is analyzed. It's mainly about how is the TCP link set up and closed down, and the course about the data being transmitted with one copy from the NIC buffer to the system kernel and one copy from the kernel to the application. Based on this, the TOE software architecture is analyzed, which is divided into two kinds, one is encapsulated architecture and the other is inbuilt architecture. The data transmission mechanism with the protocol offloaded is discussed. The course about how is the link downloaded to and released from the hardware is analyzed also.Right now, the TOE software must do the transmission with one copy, which affects the system performance. In this paper, the influence of data copying to system is analyzed, and it shows that the data copying has more influence to the system performance than other facts. Then, various zero-copy technologies are introduced with their advantages and disadvantages. RDMA is a zero-copy technology base on protocol offload engineer, but it isn't compatible with the existing applications and can't communicate with the normal NIC. So a TOE-based approach for zero-copy data transmission is proposed in this paper, which transmits data between NIC and the user space with the assistance of the terminal. It doesn't change the application interface and can communicate with the normal NIC.At last, it introduces the main implementation of the TOE software and the zero-copy technology. The inbuilt software architecture just modifies the original internet protocol to add the function of link management and data transmission with the protocol offloaded. The interactive events between the software and the hardware include the data transmission using the DMA buffer, the setup and the management of the descriptor events, and the management of hardware link. Three different paths to deal with the various messages are introduced, and the data transmission with protocol offloaded only needs one data copy. The implementation of the terminal assisted zero-copy technology includes the page mapping to locate the data, the missing data processing to load the pages, and the setting of the page attributes.