(HotOS'03 Note)TCP Offload is a Dumb Idea Whose Time Has Come

TCP Offload is a Dumb Idea Whose Time Has Come
Jeffrey C. Mogul
HotOS 2003

关于在NIC上实现TCP或者其它传输层协议的分析，即TOE（TCP Offload Engine）问题。

作者分析了TOE在实践中不成功的原因。认为，对于HTTP这样常见的应用，存在大量短时间的链接，从TOE中获得的收益有限，尤其是在当前通用CPU速度快速提高的情形之下。

作者认为对于网络存储等数据吞吐量特别大的应用，TOE还是有用武之地的。作者提出针对RDMA（Remote Direct Memory Access）应用TOE。

RDMA是一个引起我关注的点，似乎和设备/总线映射问题相关。其中有一段话如下。Although much of the network on RDMA has focused on storage systems, high-bandwidth graphics applications (e.g. streaming HDTV videos) have similar characteristic. A video-on-demand connection might use RDMA both at the server (for access to the stored video) and at the client (for rendering the video).

另外，文章中对于协议栈中single-copy technique也进行了总结，有兴趣可以作为一个起点进行检索。例如：Dalton et al. (1995):　NIC Supporting a Single-copy Host OS Implementation of TCP