課程影片與練習
課程簡介
第1週：網路架構與七層參考模式簡介
第2週：IEEE 802.3 乙太網路 (Ethernet)
第3週：IEEE 802.11 無線區域網路 (Wireless LAN)
第4週：IEEE 802.1D 交換機的擴張樹演算法 (Spanning Tree Algorithm)
第5週：IEEE 802.1Q 虛擬區域網路 (Virtual LAN)
第6週：區域網路可靠傳輸技術 －－ 滑動視窗技術
第7週：路由器運作原理以及網路互連技術
第8週：TCP 與網路阻塞偵測與控制技術
※觀看影片請點擊影片名稱後方的"YOUTUBE"或"YOUKU"，
觀看YOUKU影片，請輸入密碼：mooc01004
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8.21 Which of the following statements are correct for “slow start” in TCP congestion control ?
下列哪些對於TCP壅塞控制中的“慢啟動”機制的敘述是正確的 ?
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| (a) Slow start effectively increases the congestion window linearly 慢啟動採用線性方式增加雍塞視窗的值 | |
| (b) Slow start is used to increase the congestion window rapidly from a cold start 慢啟動從cold start開始快速增加雍塞視窗的值 | |
| (c) When the ACK for a packet arrives TCP source, the TCP source adds MSS to CongestionWindow 當 TCP 傳送端收到一個封包的回覆時，將雍塞視窗的值加上 MSS 值 | |
| (d) When the ACK for a packet arrives TCP source, the TCP source doubles the size of CongestionWindow 當 TCP 傳送端收到一個封包的回覆時，將雍塞視窗的值加倍 | |
| (e) Slow start effectively doubles the number of packets the TCP source has in transit every RTT 慢啟動讓 TCP 傳送端每經過一個RTT 時間封包就傳送兩倍的封包數量 |
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8.22 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, what is the action when the TCP source happens “timeout” ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，當TCP 傳送端發生“逾時事件”時 ，會採取什麼行動 ?
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| (a) Set CongestionWindow to 1/2 of its previous value. 將 CongestionWindow 減半 | |
| (b) Set CongestionWindow to 1/3 of its previous value. 將CongestionWindow減至原先值的1/3 | |
| (c) Set CongestionWindow to 1/4 of its previous value. 將CongestionWindow減至原先值的1/4 | |
| (d) Set CongestionWindow to 1/5 of its previous value. 將CongestionWindow減至原先值的1/5 | |
| (e) Set CongestionWindow to 1 MSS (maximum segment size). 將CongestionWindow 減至1 MSS (maximum segment size) 值. |
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8.23 Which of the following statements are correct for a TCP source to handle the “packet lost” in congestion control ?
下列哪些對於 TCP 傳送端在壅塞控制中處裡“封包遺失”事件的敘述是正確的 ?
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| (a) After receives 3 duplicate ACKs, the CongestionWindow is cut in half and then grows linearly. 在收到三個重複回覆之後，CongestionWindow被減半，然後呈線性增長 | |
| (b) After receives 3 duplicate ACKs, the CongestionWindow is set to 1 MSS and then grows linearly. 在收到三個重複回覆之後，CongestionWindow被設為1 MSS，然後呈線性增長. | |
| (c) After timeout event happens, the CongestionWindow is set to 1 MSS; the window then grows exponentially to a threshold, and then grows linearly. 在逾時事件發生之後，CongestionWindow被設為1 MSS; 然後以指數方式成長到一個臨界值, 再以線性增長 | |
| (d) After timeout event happens, the CongestionWindow is set to 1 MSS; the window then grows linearly. 在逾時事件發生之後，CongestionWindow被設為1 MSS; 然後以線性方式成長 | |
| (e) After timeout event happens, the CongestionWindow is cut in half; the window then grows exponentially to a threshold, and then grows linearly. 在逾時事件發生之後， CongestionWindow被減半; 然後以指數方式成長到一個臨界值, 再以線性增長 |
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8.24 Which of the following statements are correct for the “Threshold” used in TCP congestion control ? Please note that we said sender is in “slow-start phase” when the CongestionWindow is below Threshold, and in “congestion-avoidance phase” when the CongestionWindow is above Threshold.
下列哪些關於TCP壅塞控制機制使用的 “臨界值”的敘述是正確的? 請注意我們說當CongestionWindow值低於臨界值時傳送端是處 “慢啟動階段”，當CongestionWindow值高於臨界值時傳送端是處於“壅塞預防階段”.
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| (a) When a sender is in slow-start phase, its window grows exponentially. 當傳送端處於慢啟動階段，它的壅塞視窗值呈指數成長 | |
| (b) When a sender is in congestion-avoidance phase, its window grows linearly. 當傳送端處於壅塞預防階段，它的壅塞視窗值呈線性成長. | |
| (c) When a triple duplicate ACK occurs, the Threshold is set to CongWin/2 and CongWin is set to Threshold. 當出現三個重複回覆，臨界值被設為 CongWin/2 而 CongWin 被設為臨界值. | |
| (d) When timeout occurs, the Threshold is set to CongWin/2 and CongWin is set to Threshold. 當逾時事件發生，臨界值被設為CongWin/2, 而CongWin被設為臨界值. | |
| (e) When timeout occurs, the Threshold is set to CongWin/2 and CongWin is set to 1 MSS. 當逾時事件發生，臨界值被設為 CongWin/2 而CongWin被設為1 MSS. |
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