[工學(xué)]07-datalinkcontrol(編輯修改稿)
2025-02-15 10:31 本頁面
【文章內(nèi)容簡介】 nce number, the maximum window size is limited to 2k123Sliding Window Diagram P213發(fā)送窗口接收窗口Example Sliding Window滑動(dòng)窗口流量控制z發(fā)送窗口y每 發(fā)送 一幀，窗口從左側(cè) 縮小 一格y每收到一幀的 確認(rèn) ，窗口向右側(cè) 增大 一格y窗口最大值 W初始時(shí)刻設(shè)置，不能超過 2k1z接收窗口y每 接收 一幀，窗口從左側(cè) 縮小 一格y每發(fā)送一幀的 確認(rèn) ，窗口向右側(cè) 增大 一格y窗口的最大值根據(jù)不同的協(xié)議，初始值不同。xGobackn ARQ ， 接收窗口 W=1zVertical Bary左側(cè)為確認(rèn)過的幀，右側(cè)為尚未確認(rèn)的幀肯定確認(rèn)與否定確認(rèn)zRR 3yReady to receive frame number 3yAll frames up to frame number 2 were receivedzRNR 5yReceive not readyyAll frames up to number 4 were receivedyBut unable to accept any more27Piggybacking （捎帶確認(rèn)） P214zIf duplex（全雙工通信） , two station exchange data, use piggybacking。zEach data frame includes the number of the frame and the number used for acknowledgement. 數(shù)據(jù)幀攜帶要確認(rèn)的幀序號(hào)，不需要單獨(dú)發(fā)送確認(rèn)幀。28zWindow size is WzCase 1: 即： W≥1+2a the sender can transmit continuouslyzCase 2: 即： W1+2a the sender exhausts its window and wait until the acknowledge arrived Link utilization of sliding window flow control 采用滑動(dòng)窗口流量控制時(shí)鏈路的 利用率 P234，忽略 ack的傳輸時(shí)間W ≥ 1+2a， that is Wt f tTA BACK傳播時(shí)延 tp傳輸時(shí)延 tf傳輸時(shí)延 tAcktT時(shí)間往返時(shí)間Wtf F0F1F2傳播時(shí)延 tpF3F4F5F0F1……W1+2a ， that is W tf tTA BACK傳播時(shí)延 tp傳輸時(shí)延 tf傳輸時(shí)延 tAcktT時(shí)間往返時(shí)間wtf F0F1F2傳播時(shí)延 tpF0F1F231z忽略 ACK幀的傳輸時(shí)間 Link utilization of sliding window flow control 采用滑動(dòng)窗口流量控制時(shí)鏈路的 利用率 P23432Link utilization of sliding window flow controlz采用捎帶確認(rèn) piggyback acknowledgementz數(shù)據(jù)幀雙向發(fā)送z返回方向的 數(shù)據(jù)幀攜帶 相反方向數(shù)據(jù)幀的 確認(rèn) 信息。33 Error ControlzRefers to mechanisms to detect and correct errorszTwo types of errors: Lost frames； Damaged frameszTechniques for error controlyError detection（ Chapter 6)yPositive acknowledgmentyRetransmission after timeoutyNegative acknowledgement and retransmissionzThese techniques are all referred to as automatic repeat request (ARQ) 自動(dòng)重發(fā)請(qǐng)求zStop and wait ARQ； G
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