This section provides guidelines to router implementors so that they can ensure interoperability with other routers using PPP over either synchronous or asynchronous links.
It is critical that an implementor understand the semantics of the option negotiation mechanism. Options are a means for a local device to indicate to a remote peer what the local device will accept from the remote peer, not what it wishes to send. It is up to the remote peer to decide what is most convenient to send within the confines of the set of options that the local device has stated that it can accept. Therefore it is perfectly acceptable and normal for a remote peer to ACK all the options indicated in an LCP Configuration Request (CR) even if the remote peer does not support any of those options. Again, the options are simply a mechanism for either device to indicate to its peer what it will accept, not necessarily what it will send.