It is quite common to connect to IP network for embedded systems such as consumer electronics appliances, automobile electronics devices, security communication devices, etc. in recent years. These systems need a single-chip microcomputer with internal RAM and don't have usually external RAM to reduce hardware cost. Quite a few TCP/IP protocol stacks including open source software have been developed for usage of a small size RAM. We investigated the RAM usage in detail by using "lwIP" named for a lightweight TCP/IP protocol stack, an embedded real time ITRON-based OS, and evaluation boards for a 32-bit ARM Cortex M3 microprocessor. We recognized that their RAM usage has a very large proportion of storing buffer for packet data and the buffer space increases more than a twofold by congested network. And we are researching buffer management mechanism among an IP network interface and other interfaces, based on the evaluation data of IP network congestion and stagnant data among such interfaces.
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