Well you have a choice. You make a protocol extensible and live with the fact that people are eventually going to extend it. Otherwise you choose a different fi

Well you have a choice. You make a protocol extensible and live with the fact that people are eventually going to extend it. Otherwise you choose a different fixed protocol for each and every task and live with the fact that you will never get any level of interoperability at all. If one complains about extensible protocols, one should be willing to come up with some other approach that works.