A full TCP/IP implementation on a cheap IC? Yes, it is available. The Korean company WIZnet produces an IC with the name W5100 that implements a full TCP/IP stack, easy to interface to a microcontroller as a peripheral or via SPI. Perfect for controllers from AVR for example. And the interface is also suitable for our beloved old microprocessors like the Z80 and the 6502.
WIZ810MJ is a simple module, a PCB with the W5100 IC and a RJ45, you get microcontroller and SPI Interface, Auto MDIX/MDIX network status indicator LEDs – FDX, TX, RX, LINK, Collision , and TCP, UDP, IP, ARP, ICMP, IGMP, PPPoE (good for ADSL!), MAC network protocols. With appropriate drivers it can do DNS, DHCP, enough examples are given. The IC is programmed via registers, and seems very powerful in built-in IP stack facilities.
The good news is: the module is very cheap, 12 dollar, in the WIZnet shop. The bad news, shipping costs 30 dollar…
Get a sample kit! WIZnet and Circuit Cellar run a competion, to find applications, with free samples.
Update october 31: My sample kit is on its way now, it has been approved!