問題文
A design review has to settle how many requests one end of a key negotiation may leave unanswered at each stage, if either end has announced that it can hold state for several at once. Which reading does RFC 7296 support, and what does it ask of an end that already has a request of its own outstanding?
選択肢
- The announced allowance is in force from the very first message onwards, and the end has to keep a stored copy of the requests it has left unanswered and turn away the rest, since the count carried in the header is what the sending end promises to hold, in that outstanding-request handling.
- The announced allowance is in force from the very first message onwards, and the end has to hold back and set aside an incoming request until a reply to its own has come in, since an end that worked through crossing requests would lose track of which stored reply belongs to which, in that outstanding-request handling.
- The announced allowance stays out of force until the opening exchanges have closed, and the end has to raise a fresh negotiation and drop the old one once its own request has gone unanswered, since a window is read as a ceiling on stored replies rather than on requests in flight, in that outstanding-request handling.
- The announced allowance stays out of force until the opening exchanges have closed, and the end has to be ready to take in and work through an incoming request while one of its own is still unanswered, since two ends that both sat waiting for a reply would come to a standstill, in that outstanding-request handling.