1、精選優質文檔-傾情為你奉上網絡實驗報告一數據鏈路層協議的設計與實現 計 83 班 同志強 實驗目的計算機網絡的數據鏈路層協議保證通信雙方在有差錯的通信線路上進行無差錯的數據傳輸，是計算機網絡各層協議中通信控制功能最典型的一種協議。本實驗實現一個數據鏈路層協議的數據傳送部分，目的在于使學生更好地理解數據鏈路層協議中的“滑動窗口”技術的基本工作原理，掌握計算機網絡協議的基本實現技術。實驗內容在一個數據鏈路層的模擬實現環境中，用C 語言實現下面兩個數據鏈路層協議。（1）“退回到N 重發”的滑動窗口協議（參考文獻1第四章的協議5）；（2）“選擇重發”的滑動滑動窗口協議（參考文獻1第四章的協議6）；實驗

2、原理，過程以及分析 首先，我們來分析一下試驗原理和所得到的數據，從以下的數據我們不難分析出以下的結論：Protocol 5. Events: 10000 Parameters: 100 20 30Process 1: Total data frames sent: 802 Data frames lost: 162 Data frames not lost: 640 Frames retransmitted: 679 Good ack frames rec'd: 0 Bad ack frames rec'd: 0 Good data frames rec'd: 429

3、Bad data frames rec'd: 201 Payloads accepted: 129 Total ack frames sent: 0 Ack frames lost: 0 Ack frames not lost: 0 Timeouts: 97 Ack timeouts: 0Process 0: Total data frames sent: 807 Data frames lost: 177 Data frames not lost: 630 Frames retransmitted: 672 Good ack frames rec'd: 0 Bad ack f

4、rames rec'd: 0 Good data frames rec'd: 444 Bad data frames rec'd: 193 Payloads accepted: 117 Total ack frames sent: 0 Ack frames lost: 0 Ack frames not lost: 0 Timeouts: 96 Ack timeouts: 0Efficiency (payloads accepted/data pkts sent) = 15%End of simulation. Time=10000Protocol 6. Events:

5、10000 Parameters: 100 20 30Process 1: Total data frames sent: 539 Data frames lost: 119 Data frames not lost: 420 Frames retransmitted: 296 Good ack frames rec'd: 13 Bad ack frames rec'd: 8 Good data frames rec'd: 302 Bad data frames rec'd: 132 Payloads accepted: 202 Total ack frames

6、 sent: 34 Ack frames lost: 6 Ack frames not lost: 28 Timeouts: 296 Ack timeouts: 34Process 0: Total data frames sent: 557 Data frames lost: 123 Data frames not lost: 434 Frames retransmitted: 315 Good ack frames rec'd: 20 Bad ack frames rec'd: 8 Good data frames rec'd: 300 Bad data frame

7、s rec'd: 120 Payloads accepted: 206 Total ack frames sent: 25 Ack frames lost: 4 Ack frames not lost: 21 Timeouts: 315 Ack timeouts: 25Efficiency (payloads accepted/data pkts sent) = 37%End of simulation. Time=10000Protocol 5. Events: 10000 Parameters: 200 20 30Process 1: Total data frames sent:

8、 415 Data frames lost: 89 Data frames not lost: 326 Frames retransmitted: 343 Good ack frames rec'd: 0 Bad ack frames rec'd: 0 Good data frames rec'd: 237 Bad data frames rec'd: 101 Payloads accepted: 73 Total ack frames sent: 0 Ack frames lost: 0 Ack frames not lost: 0 Timeouts: 49

9、Ack timeouts: 0Process 0: Total data frames sent: 415 Data frames lost: 77 Data frames not lost: 338 Frames retransmitted: 336 Good ack frames rec'd: 0 Bad ack frames rec'd: 0 Good data frames rec'd: 218 Bad data frames rec'd: 108 Payloads accepted: 65 Total ack frames sent: 0 Ack fr

10、ames lost: 0 Ack frames not lost: 0 Timeouts: 48 Ack timeouts: 0Efficiency (payloads accepted/data pkts sent) = 16%End of simulation. Time=10000Protocol 5. Events: 10000 Parameters: 200 20 30Process 1: Total data frames sent: 415 Data frames lost: 89 Data frames not lost: 326 Frames retransmitted: 3

11、43 Good ack frames rec'd: 0 Bad ack frames rec'd: 0 Good data frames rec'd: 237 Bad data frames rec'd: 101 Payloads accepted: 73 Total ack frames sent: 0 Ack frames lost: 0 Ack frames not lost: 0 Timeouts: 49 Ack timeouts: 0Process 0: Total data frames sent: 415 Data frames lost: 77

12、Data frames not lost: 338 Frames retransmitted: 336 Good ack frames rec'd: 0 Bad ack frames rec'd: 0 Good data frames rec'd: 218 Bad data frames rec'd: 108 Payloads accepted: 65 Total ack frames sent: 0 Ack frames lost: 0 Ack frames not lost: 0 Timeouts: 48 Ack timeouts: 0Efficiency

13、(payloads accepted/data pkts sent) = 16%End of simulation. Time=10000Protocol 6. Events: 10000 Parameters: 200 40 30Process 1: Total data frames sent: 253 Data frames lost: 115 Data frames not lost: 138 Frames retransmitted: 171 Good ack frames rec'd: 7 Bad ack frames rec'd: 6 Good data fram

14、es rec'd: 116 Bad data frames rec'd: 38 Payloads accepted: 80 Total ack frames sent: 7 Ack frames lost: 2 Ack frames not lost: 5 Timeouts: 171 Ack timeouts: 7Process 0: Total data frames sent: 262 Data frames lost: 108 Data frames not lost: 154 Frames retransmitted: 170 Good ack frames rec&#

15、39;d: 5 Bad ack frames rec'd: 0 Good data frames rec'd: 97 Bad data frames rec'd: 41 Payloads accepted: 69 Total ack frames sent: 19 Ack frames lost: 6 Ack frames not lost: 13 Timeouts: 170 Ack timeouts: 19Efficiency (payloads accepted/data pkts sent) = 28%End of simulation. Time=10000Pr

16、otocol 6. Events: 10000 Parameters: 200 20 70Process 0: Total data frames sent: 217 Data frames lost: 44 Data frames not lost: 173 Frames retransmitted: 190 Good ack frames rec'd: 2 Bad ack frames rec'd: 10 Good data frames rec'd: 46 Bad data frames rec'd: 131 Payloads accepted: 27 T

17、otal ack frames sent: 13 Ack frames lost: 1 Ack frames not lost: 12 Timeouts: 190 Ack timeouts: 13Process 1: Total data frames sent: 218 Data frames lost: 41 Data frames not lost: 177 Frames retransmitted: 186 Good ack frames rec'd: 4 Bad ack frames rec'd: 8 Good data frames rec'd: 44 Ba

18、d data frames rec'd: 129 Payloads accepted: 22 Total ack frames sent: 14 Ack frames lost: 2 Ack frames not lost: 12 Timeouts: 186 Ack timeouts: 14Efficiency (payloads accepted/data pkts sent) = 11%End of simulation. Time=100001 由兩協議的原理我們也可分析出不同之處：1)由于協議6要存儲后續的幀，所以它要用的buffer也就要多一些。2)協議5的接受窗口為1，而協議6的窗口則為：（max_seq+1）/2.2 在一般的情況下，協議6的效率要比協議5的效率高。這個我們可以從原理上來分得到此結論：1）對于協議5，當出現錯誤時，接受過程直接拋棄所有后續的幀,當發送過程時間到，在重發后續的未經確認的幀；但是對于協議6，當出現錯誤時，接受方的數據連路層存儲后續所有正確的幀，第二次之重發出現錯誤的幀。重發的幀就少了，所以效率也就上去了。2） 協議6多了一個輔助計時器，當一個按序列號發的數據幀到達后，啟動它，如當超時前無反向的通訊后