typically, the protocol calls for the receiver tosend back special（ ）frame bearing positive or negative（ ）about the incoming frames.if the sender receives a positive acknowledgement about a frame, it
typically, the protocol calls for the receiver tosend back special（ ）frame bearing positive or negative（ ）about the incoming frames.if the sender receives a positive acknowledgement about a frame, it knows the the frame has arrivedsafely.（2008年下半年网络工程师上午真题解析）
A、data
B、controll
C、request
D、session
A、application
B、connection
C、stream
D、acknowledgement
参考答案：B、D
参考解析：正在整理中,欢迎在文下评论区解答,谢谢！