問題文
A design team has to settle what an answering gateway may do with the address ranges the opening side proposed, if one of the proposed selectors is of a kind the answering side has yet to learn. Which reading does the key exchange specification support, and what does it send when its policy leaves nothing?
選択肢
- The answering side may cut the proposed ranges down to a part of them so long as the result is left holding something, and a selector of a kind it has yet to learn is passed over so that the unlearned kind is left out of the narrowed set it sends back, and where its own policy leaves it no part of the proposal it can take, it answers with an empty pair of ranges and waits for a second proposal, in that narrowing-side choice.
- The answering side may widen the proposed ranges beyond what was asked so long as the result is left holding something, and a selector of a kind it has yet to learn is copied over so that the unlearned kind is carried into the set it sends back, and where its own policy leaves it no part of the proposal it can take, it answers with the notice that the ranges are unacceptable, in that narrowing-side choice.
- The answering side may widen the proposed ranges beyond what was asked so long as the result is left holding something, and a selector of a kind it has yet to learn is copied over so that the unlearned kind is carried into the set it sends back, and where its own policy leaves it no part of the proposal it can take, it answers with an empty pair of ranges and waits for a second proposal, in that narrowing-side choice.
- The answering side may cut the proposed ranges down to a part of them so long as the result is left holding something, and a selector of a kind it has yet to learn is passed over so that the unlearned kind is left out of the narrowed set it sends back, and where its own policy leaves it no part of the proposal it can take, it answers with the notice that the ranges are unacceptable, in that narrowing-side choice.