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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8.16 For the “Additive Increase Multiplicative Decrease (AIMD)” mechanism used in TCP congestion control, how to determine the value for “CongestionWindow” ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，如何決定其壅塞視窗“CongestionWindow”值 ?
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| (a) The receiving side of TCP will send a suitable CongestionWindow to the sending side of TCP. TCP接收端會送一個合適的CongestionWindow值給TCP傳送端. | |
| (b) No one will send a suitable CongestionWindow to the sending side of TCP. 沒有任何程式或設備會送合適的CongestionWindow值給TCP傳送端 | |
| (c) TCP source sets the CongestionWindow based on the congestion level it observed. TCP 傳送端根據它觀察到的網路壅塞程度來設定CongestionWindow 值 | |
| (d) TCP source increasing the CongestionWindow when the level of congestion goes up 當網路壅塞程度增加時, TCP傳送端會增加其CongestionWindow 值 | |
| (e) TCP source decreasing the CongestionWindow when the level of congestion goes down. 當壅塞程度下降時, TCP 傳送端會減少其CongestionWindow 值 |
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8.17 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, how does the TCP source determine that the network is congested ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，TCP 傳送端如何判定網路已經發生壅塞 ?
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| (a) TCP interprets“packet lose” as a sign of congestion. TCP 將“封包遺失”視為壅塞訊號 | |
| (b) The receiving side of TCP will send a“congested notification”packet to the sending side of TCP. TCP接收端會發送一個“壅塞通知”的封包給TCP傳送端. | |
| (c) The routers in the Internet who dropped packets will send a“congested notification”packet to the sending side of TCP. 那些丟棄封包的路由器將會發送“壅塞通知”的封包給TCP傳送端 | |
| (d) When the TCP source receives 3-duplicate ACKs 當 TCP傳送端收到三個”重複回覆”時 | |
| (e) When“timeout event”happens in the TCP source. 當 TCP 傳送端發生“逾時事件”時 |
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8.18 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, what is the action when the TCP source receives 3-duplicate ACKs ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，當TCP 傳送端收到 三個”重複回覆”時, 會採取什麼行動 ?
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| (a) Set CongestionWindow to 1/2 of its previous value. 將CongestionWindow 減至原先的1/2 | |
| (b) Set CongestionWindow to 1/3 of its previous value. 將CongestionWindow減至原先的1/3 | |
| (c) Set CongestionWindow to 1/4 of its previous value. 將 CongestionWindow減至原先的1/4 | |
| (d) Set CongestionWindow to 1/5 of its previous value. 將CongestionWindow減至原先的1/5 | |
| (e) Set CongestionWindow to 1 MSS (maximum segment size). 將CongestionWindow減至 1 個 MSS (maximum segment size) 值. |
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8.19 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, the TCP source increases the congestion window when the newly capacity of network is available. Which of the following statements are correct ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，當有新的網路容量可利用時, TCP 傳送端會增加其壅塞視窗。下列哪些敘述是正確的 ?
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| (a) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds 1 MSS to the CongestionWindow. 每當傳送端成功送出數量等於 CongestionWindow 值的封包 (所有在上一個 RTT 期間傳送的封包都成功收到回覆)，便將CongestionWindow 值加上MSS值 | |
| (b) Every time the source successfully sends a packet (the sent packet has been ACKed), it adds 1 MSS to the CongestionWindow. 每當傳送端成功送出一個封包(該封包已收到回覆)，便將CongestionWindow 值加上MSS值 | |
| (c) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds 1/2 MSS to CongestionWindow. 每當傳送端成功送出數量等於 CongestionWindow 值的封包 (所有在上一個 RTT 期間傳送的封包都成功收到回覆)，便將CongestionWindow 值加上1/2 MSS值 | |
| (d) Every time the source successfully sends a packet (the sent packet has been ACKed), it adds 1/2 MSS to CongestionWindow. 每當傳送端成功送出一個封包(該封包已收到回覆)，便將CongestionWindow 值加上1/2 MSS 值 | |
| (e) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds 2 MSS to the CongestionWindow. 每當傳送端成功送出數量等於 CongestionWindow 值的封包 (所有在上一個 RTT 期間傳送的封包都成功收到回覆)，便將CongestionWindow 值加上2xMSS值 |
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8.20 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, TCP does not wait for an entire window’s worth of ACKs to add MSS to the congestion window, but instead increments CongestionWindow by a little (denoted as increment) for each ACK. Which of the following is correct for this increment ?
對於TCP壅塞控制採用的”線性增加倍數減少(AIMD)” 機制，TCP不會等在上一個 RTT 期間傳送的封包都成功收到回覆後才將Congestion Window 加上 MSS值，取而代之的是，每收到一個 ACK 就將Congestion Window 加上一個”增值” (increment)。請問此增值 (increment) 的值為何 ?
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| (a) Increment =1/CongestionWindow | |
| (b) Increment = 1/MSS | |
| (c) Increment = MSS/CongestionWindow | |
| (d) Increment = MSS (MSS/CongestionWindow) | |
| (e) Increment = MSS/(CongestionWindow+MSS); |
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