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6.22. Consider an example that we have eight available sequence numbers: 0, 1, 2, 3, 4, 5, 6, and 7. Assume that RWS = SWS = 7. Now, we have the following steps:

• Step 1. Sender sends frames 0, 1, …, 6
• Step 2. Receiver receives frames 0, 1, … ,6, and acknowledges 0, 1, …, 6.
• Step 3. All ACKs (0, 1, …, 6) are lost
• Step 4. Sender finally timeouts and retransmits frames 0, 1, …, 6

假設有 8 個可使用的序號: 0, 1, 2, 3, 4, 5, 6, 7 且 RWS = SWS = 7. 經過以下步驟:

• 步驟 1. 傳送端送出訊框 0, 1, …, 6
• 步驟 2. 接收端收到訊框 0, 1, … ,6, 且肯定回覆 0, 1, …, 6.
• 步驟 3 所有肯定回覆 (0, 1, …, 6) 皆遺失
• 步驟 4. 傳送端等待逾時且重送訊框 0, 1, …, 6

Then, how many frames retransmitted in Step 4 will be accepted by receiver ?  則有多少在步驟 4 重送的訊框會被接收端接受 ?

Ans :___a____

How many frames retransmitted in Step 4 will be discarded by receiver ?有多少在步驟 4 重送的訊框會被接收端丟棄 ?

Ans:____b____

6.23  Consider an example that we have eight available sequence numbers: 0, 1, 2, 3, 4, 5, 6, and 7. Assume that RWS = SWS = 5. Now, we have the following steps:

• Step 1. Sender sends frames 0, 1, …, 4
• Step 2. Receiver receives frames 0, 1, … ,4, and acknowledges 0, 1, …, 4.
• Step 3. All ACKs (0, 1, …, 4) are lost
• Step 4. Sender finally timeouts and retransmits frames 0, 1, …,4

假設有 8 個可使用的序號: 0, 1, 2, 3, 4, 5, 6, 7. 假設 RWS = SWS = 5. 經過下列步驟:

• 步驟 1. 傳送端送出訊框 0, 1, …, 4
• 步驟 2. 接收端收到訊框 0, 1, … ,4, 且肯定回覆 0, 1, …, 4.
• 步驟 3 所有肯定回覆 (0, 1, …, 4) 皆遺失
• 步驟 4. 傳送端等待逾時且重新傳送訊框 0, 1, …,4

Then, how many frames retransmitted in Step 4 will be accepted by receiver ? 則有多少在步驟 4 重送的訊框會被皆端接受?

Ans: ____a______

How many frames retransmitted in Step 4 will be discarded by receiver ? 有多少在步驟 4 重送的訊框會被接收端丟棄?

Ans: ____b____

6.24. Consider an example that we have eight available sequence numbers: 0, 1, 2, 3, 4, 5, 6, and 7. Assume that RWS = SWS = 4. Now, we have the following steps:

• Step 1. Sender sends frames 0, 1, 2,3
• Step 2. Receiver receives frames 0, 1, 2, 3 and acknowledges 0, 1, 2,3.
• Step 3. All ACKs (0, 1, 2, 3) are lost
• Step 4. Sender finally timeouts and retransmits frames 0, 1, 2, 3

假設有 8 個可使用的序號: 0, 1, 2, 3, 4, 5, 6, 7. 且 RWS = SWS = 4. 經過以下步驟:

• 步驟 1. 傳送端送出訊框 0, 1, 2, 3
• 步驟 2. 接收端收到訊框 0, 1, 2, 3 且肯定回覆 0, 1, 2, 3.
• 步驟 3. 所有肯定回覆 (0, 1, 2, 3) 皆遺失
• 步驟 4. 傳送端等待逾時且重送訊框 0, 1, 2, 3

Then, how many frames retransmitted in Step 4 will be accepted by receiver ? 則有多少在步驟 4 重送的封包會被接收端接受 ?

Ans:  ____(a)______

How many frames retransmitted in Step 4 will be discarded by receiver ?有多少在步驟 4 重送的封包會被接收端丟棄 ?

Ans: ____(b)____

6.25 Let MaxSeqNum be the total number of available sequence numbers. Assume RWS = SWS, then which of the following relationship is sufficient to distinguish between different frames of the same sequence number ?
令 MaxSeqNum 表示可使用的序號的總數. 假設 RWS = SWS, 則下列哪組關係可以分辨出擁有相同序號的不同訊框 ?

6.26  Consider an example that we have seven available sequence numbers: 0, 1, 2, 3, 4, 5, and 6. Assume that RWS = SWS = 4. Now, we have the following steps:

• Step 1. Sender sends frames 0, 1, 2, 3
• Step 2. Receiver receives frames 0, 1, 2, 3 and acknowledges 0, 1, 2, 3.
• Step 3. All ACKs (0, 1, 2, 3) are lost
• Step 4. Sender finally timeouts and retransmits frames 0, 1, 2, 3

考慮有 7 個可使用的序號: 0, 1, 2, 3, 4, 5, 6. 假設 RWS = SWS = 4. 我們進行以下步驟:

• 步驟 1. 傳送端送出訊框 0, 1, 2, 3
• 步驟 2. 接收端收到訊框 0, 1, 2, 3 和肯定回覆 0, 1, 2, 3.
• 步驟 3. 所有肯定回覆 (0, 1, 2, 3) 都遺失
• 步驟 4. 傳送端等待逾時且重傳訊框 0, 1, 2, 3

Then, how many frames retransmitted in Step 4 will be accepted by receiver ? 則有多少在步驟 4 重送的訊框會被接收端接受 ?

Ans: ____(a)______

How many frames retransmitted in Step 4 will be discarded by receiver ? 有多少在步驟 4 重送的訊框會被接收端丟棄 ?

Ans: ____(b)______

6.27  Which of the following are the major features of the sliding window protocol ? 下列哪些是滑動視窗協議的主要特性?