Overview

The Ethernet is now so pervasive that even embedded systems can no longer ignore it. Ethernet is a bit more complicated than simple RS-232 as a communication interface, but it is also priceless once you get it up and running.

The TCP/IP protocol stack is encapsulated into protocol layers. Each layer of the protocol considers the layer above it to be just a block of data (or payload). That s all the layer knows. The payload for Ethernet is IP or ARP, the payload for IP is ICMP, UDP or TCP (and others), and then UDP and TCP carry others (like TFTP, HTTP, and FTP). FTP rides on TCP, TCP rides on IP, and IP rides on Ethernet. You can think of the TCP/IP protocol stack as a line of dump trucks. Each truck is small enough to fit inside the one in front of it. The front dump truck doesn t care what is inside its cargo area, so the fact that it is another smaller dump truck makes no difference. Each truck transfers its payload from source to destination. What happens to the payload after the transfer is of no concern to the dump truck that just dumped it.