> If the application layer is required to take notice of what is going on at the lower levels its because the layering was botched. > no, it just means that all lower-level network services weren't designed to provide exactly the same set of services and semantics to higher layers. in the IP stack, we expect link layers to be diverse, we expect IP service to be fairly uniform, precisely so that things layered on top of IP don't have to worry about it. expecting all applications to support multiple transport protocols adds complexity where it is almost never needed. _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf