This RFC also presents an example of correct implementation. The two items in this RFC of the most interest to implementors are 1. Section 7 of this RFC shows by example a working method of avoiding loops. An implementor who uses the procedures given in that example need not worry about compliance with this RFC or with a large chunk of RFC 854. Rules marked MAY are optional.
Options are in almost all cases negotiated separately for each side of the connection.
The option on one side is separate from the option on the other side. Each sentence could be split into two, one with the words before the slash and one with the words after the slash. An implementor should be able to implement option negotiation machinery compliant with both this RFC and RFC 854 using just the information in Section 7. 2. Where RFC 854 implies that the other side may reject a request to enable an option, it means that you must accept such a rejection. During the negotiation state, any effects of having the option enabled MUST NOT be used.