Look at this post from someone on slash-dot (btw, what does "it was
slash-dotted" mean!?):


           The smallest MTU allowed by RFC 1122 is 576 bytes.

           The 12C509 processor has 41 bytes of RAM.

           You can write up to 64 bytes to the 24LC256 EEPROM, with the write
cycle                   taking
           5 ms.

           In 5 ms, 66 bytes arrive on the serial link at 115200 bps.

           I suppose with heavy use of flow control on the serial link, you
could buffer a       packet to the EEPROM.

           But I'm still skeptical of an IP stack in 256 instructions.