There were also some differences in design tastes. For example OSI went with ASN.1[1] for binary descriptions rather than plain and simple. TCP and IP just us

There were also some differences in design tastes. For example OSI went with ASN.1[1] for binary descriptions rather than plain and simple. TCP and IP just use 8/16/32 bit fields in a predefined byte ordering and that is it. That makes TCP/IP considerably easier to eyeball. In higher level protocols like email, the TCP/IP world tended towards ASCII based protocols which are far more flexible and future proof, while OSI again did ASN.1. I once worked on an X.400 (OSI Email) gateway and was highly amused that they defined a different error code for every possible reason an email could be refused. There were pages of them (including recipient is dead!) while SMTP allowed for arbitrary text and an overal numeric code to indicate the type of error. Again you can see which was easier to eyeball and diagnose. Practicality tends to be very effective. [1] http://en.wikipedia.org/wiki/Abstract_Syntax_Notation_One http://en.wikipedia.org/wiki/Abstract_Syntax_Notation_One