| Summary: | 碩士 === 國立暨南國際大學 === 資訊管理學系 === 93 === As the explosion of Internet, adding Internet connectivity is required for embedded systems. TCP/IP protocol is the core technology for Internet connectivity. However, TCP/IP codes developed for general-purpose operating systems may not be suitable for operating in embedded environments, especially embedded systems are usually resource limited in terms of processing power, memory, and power consumption. Therefore, embedded TCP/IP should be designed to be efficient in the usage of limited resource.
Zero-copy is a mechanism in which data from network card is directly received in the user buffer and data from user buffer is directly sent to network card. No data copying between user buffers and kernel buffers is needed. Through the zero-copy implementation in TCP/IP protocol stack for embedded systems, CPU processing time and memory usage for data transmission can be reduced. As a result, power consumption can be reduced too.
In this thesis, we present the design and implementation of zero-copy mechanisms in the target embedded TCP/IP component, LyraNET. Two mechanisms named “Simple Copy Elimination” and “Enhanced Copy Elimination” are developed to eliminate data copying in TCP/IP transmission. We also present the modifications of the related data structures and TCP/IP protocol stack codes for incorporating these mechanisms. Because of these modifications, network card drivers should also be modified to work with these new mechanisms. In summary, the main tasks of this study include (1) analyzing overheads in TCP/IP transmission, (2) developing zero-copy mechanisms for LyraNET, (3) modifying network drivers to work with new mechanisms.
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