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6.18 Let SeqNumToAck denote the largest sequence number not yet acknowledged, such that all frames with sequence number less than SeqNumToAck have been received. Which of the following statements are correct for the “cumulative acknowledgement” ? 令 SeqNumToAck 表示尚未回覆的訊框最大序號, 也就是所有序號小於SeqNumToAck 的訊框都已被接收.下列哪些有關“累積回覆”的敘述是正確的 ? |
| (a) The receiver acknowledges SeqNumToAck to sender if a frame with sequence number of SeqNumToAck + k, k > 0, is received. | |
| (b) The receiver acknowledges SeqNumToAck+k to sender if a frame with sequence number of SeqNumToAck + k, k > 0, is received. | |
| (c) The receiver then sets LFR = SeqNumToAck - 1 and LAF = LFR + RWS. 接收端會設定 LFR = SeqNumToAck - 1 與 LAF = LFR + RWS. | |
| (d) The receiver then sets LFR = SeqNumToAck and LAF = LFR + RWS.接收端會設定 LFR = SeqNumToAck 與 LAF = LFR + RWS. | |
| (e) The receiver then sets LFR = SeqNumToAck + 1 and LAF = LFR + RWS-1. 接收端會設定 LFR = SeqNumToAck + 1 與 LAF = LFR + RWS-1. |
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6.19 Consider the following communication sequence between sender and receiver. Assume the “cumulative acknowledgement” scheme is used and the frame with sequence number of 2 is lost. The lost frame is retransmitted again when the timer timeouts.
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