EI内核中TCP状态机约简的研究

Reasearch on TCP State Machine Reduction in Embedded Internet Kernel

在嵌入式Internet(EI)环境中,可以利用的资源十分有限,而要在这种条件下实现Internet接口是很困难的,通常的做法就是扩充系统资源,但是这种方法增加了系统成本,大材小用。而且嵌入式Internet设备将要最终嵌入到设备中去,因此必须要在尽量小的空间内实现所需要的功能。本文提出一种TCP状态机的约简原则,减少状态机的处理流程,将复杂状态变换转化为简单变化,将状态机中的状态数和跳转条件进行约简与合并,提高了性能,减少实现代码。在不改变协议接口的前提下在原有的资源空间内实现通用的TCP/IP协议栈,并保证了协议功能上的完备性。根据这套约简原则,在一个8位单片机上实现了一个功能完善、体积微小的嵌入式Internet内核,使其可以嵌入到任何一个小型设备和家用电器中。

In Embedded Internet (EI) environment there are limited resources, so it is very difficult to realize a Internet in EI environment. In general some high performance processor and memory are used to solve the problem. It is clearly is the wrong way as it incurs additional development time, testing time and price. In this paper a proper method is presented which is based on TCP state machine reduction. In TCP/IP protocol suite TCP is the most complex protocol and consumed most resources. We delete unimportant and unnecessarily state in EI environment and simplify complex relations. All these reduction are complete transparent for user because the interfaces are untouched. According to the reduction principle proposed in paper we realize an mini EI kernel in a 8 bit processor, in this kernel there are full function Web Server and correlative protocols.