One major difference between the TCP/IP protocol suite and the OSI protocol suite is that the former asks you to try to make sense of whatever you receive, one way or the other. OSI follows the principle that a protocol error is fatal, you cancel the connection. Disconnect is mandatory; if you continue operation trying to keep it going, then you are not conformant to the standard. Those sloppy, haphazard implementations are kicked out. If you want to exchange data, you better do it in the proper way! Of course it makes it more difficult to be an eager student who has not yet learnt proper behavior; before he goes out in the wide open world he must know what to do. The Internet lenient philosophy is fair enough while you are still playing in the sand pit, but not when you grow up. Programming languages are similar. They should define clearly what you can and cannot do. They should specify clearly all the issues that the compiler is required to detect, those that the generated code / runtime system is required to detect, and those that cannot reasonably be detected neither at compile time nor run time but is nevertheless an error. I know of one language specifications that includes all three, the Z.200 CHILL language. Unfortunately, CHILL never made it as a mainstream language (nobody really tried to make it!) - it was a language design of excellent quality. But I guess most programmers moving from C to CHILL would feel the strict discipline as a straightjacket.
