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1. What are the differences between client/server model and peer-to-peer mode?

Client server model č˘ŤĺŽšçžŠç‚şä¸€ĺ€‹é›†ä¸­çš„ç’°ĺ˘ƒä¸‹ďźŒć‰€ćœ‰ç”¨ćˆśă€ ç‰Šäťśă€ čł‡ćş?ç­‰éƒ˝č˘Ťé›†ä¸­ĺœ¨ä¸€čľˇçŽĄç?†ă€‚ Peer to peer model ć˜Żä¸€ç¨Žäž?賴眲衯中ĺ?ƒčˆ‡č€…çš„č¨ˆçŽ—čƒ˝ĺŠ›ĺ’Œé ťĺŻŹçš„ćŠ€čĄ“ďźŒč€Œä¸?ć˜ŻćŠŠč™•ç?†čƒ˝ĺŠ›éƒ˝č š

é›†ĺœ¨čźƒĺ°‘çš„ĺšžĺ?°äźşćœ?器上。 2. What are the flow control and the congestion control?

Flow control ď§ŠďĽžćŽ§ĺˆść˜ŻčŚ čŽ“ĺ‚łé€ čł‡ďŚžč€…ďĽ§čŚ ĺ‚łé€ ĺ¤ŞĺżŤč€Œčś…é ŽďŚşćŽĽć”śč€…čƒ˝č™•ď§¤çš„é€&#x;ď¨ ă€‚ congestion control ĺŁ…ďĽŹćŽ§ĺˆść˜ŻčŚ ç•śçś˛čˇŻç™źç”&#x;é›?ĺĄžĺžŒďźŒé™?ä˝Žĺ‚łé€ č€…ĺ‚łé€ é€&#x;ĺşŚďźŒčŽ“çś˛čˇŻčƒ˝ĺ¤ ćśˆĺŒ–ćŽ‰ĺ¤§é‡?ĺ° ĺŒ…äťĽć”šĺ–„é›?ĺĄžćƒ… 形。 3. What are the full name and major function of the following network protocols? (a) DNS

DomainNameSystem : ĺ?ŻäťĽç”¨ domain name ć‰žĺˆ°ç›¸ĺ°?çš„ IP addressďźŒć˜Żç?žĺœ¨çś˛čˇŻä¸­ä¸?ĺ?Żçźşĺ°‘çš„ĺŠ&#x;čƒ˝äš‹ä¸€ă€‚ (b) SMTP

Simple Mail Transfer Protocol ďźŒĺ‚łé€ Email 的標準ĺ?”厚。 (c) TCP

Transmission Control Protocol ďźŒ 一税連掼導ĺ?‘的〠ĺ?Żé? 的〠ĺ&#x;şć–źä˝?ĺ…ƒçľ„ćľ çš„é ‹čź¸ĺą¤ďźˆTransport layer 通訊ĺ?”議。 (d) UDP

User Datagram Protocol ďźŒç”¨ UDP 傳蟸資料的兊獯ä¸?ĺťşçŤ‹é€ŁçˇšďźŒĺ‚łé€ çŤŻĺ?Şć šć“š IP čˆ‡ port number ĺ‚łĺ‡şĺ° ĺŒ…ĺžŒĺ°ąä¸?ćœƒçŽĄĺ…śäť–çš„äş‹ă€‚ 4. Suppose that all links are 1.536 Mbps, and each link uses TDM with 12 slots. The time of end-to-end circuit established is 500msec. How long does it take to send a file of 640,000 byte from host A to host B over a circuit-switched network?

500msec + 640000byte*8 / (1.536 Mbps / 12) = 40.5 sec 5. Suppose that the link speed is 8 Mbps, the demand bandwidth of each active user is 1OOKBps. The active probability of each user is 10%. How much user can support under the block probability is less than 0.0004?

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đ??ą ) (đ?&#x;&#x17D;. đ?&#x;?)đ?&#x;?đ?&#x;&#x17D; (đ?&#x;&#x17D;. đ?&#x;&#x2014;)đ??ąâ&#x2C6;&#x2019;đ?&#x;?đ?&#x;&#x17D; < đ?&#x;&#x17D;. đ?&#x;&#x17D;đ?&#x;&#x17D;đ?&#x;&#x17D;đ?&#x;&#x2019; đ?&#x;?đ?&#x;&#x17D; X= 35

6. What and why are the four sources of packet delay?

Processing delay : check bit error & determine output link Queuing delay : time waiting at output link for transmissionďź&#x152;ć&#x153;&#x192;袍 congestion 役é&#x;ż Transmission delay : ć&#x160;&#x160;ć&#x2022;´ĺ&#x20AC;&#x2039; packet ä¸&#x;ĺ&#x2021;şĺ&#x17D;ťç&#x161;&#x201E;ć&#x2122;&#x201A;é&#x2013;&#x201C;ďź&#x152;ć&#x153;&#x192;袍 packet é&#x2022;ˇĺşŚĺ˝ąé&#x;ż propagation delay : link ä¸&#x160;ç&#x161;&#x201E;ĺ&#x201A;łčź¸ć&#x2122;&#x201A;é&#x2013;&#x201C;ďź&#x152;蜨čż&#x2018;ć&#x2013;źé&#x203A;śă&#x20AC;&#x201A;


7. What are the differences between non-persistent HTTP and persistent HTTP? What is pipelining in HTTP?

nonpersistentHTTP : 一個 TCP 連線只能傳送一個物件 persistentHTTP : 一個 TCP 連線可以傳送多個物件 Pipelining : sender 一次送出多個封包在等待 ack,而不是送出一個封包後就要等一個 ack 8. How can TCP support reliable transmission over Internet?

Acknowledgements, retransmit, sequence number, timer 9. What are the differences between go-Back-N, and selective repeat?

再傳送一序列的封包時 Go-Back-N 的接收端如果有一個封包沒收到,他會要求傳送端從未收到的封包開始重送一序列的封包, 即使第一次接收時這些重送的封包有正確收到,傳送端將不會保留這些正確收到的封包。 selective repeat 則會要求傳送端重送這些沒收到的封包,而且會把所有正確收到的封包保留下來而不 用重送。 10. In TCP, how can we measure the Timeoutlnterval ?

a.要去估算每次封包的 RTT 時間 為 SampleRTT b.利用 EstimatedRTT = (1- α)*EstimatedRTT +α*SampleRTT 去計算新的 EstimatedRTT c.必須考慮容忍的寬限值 safety margin DevRTT = (1-β)*DevRTT +β*|SampleRTT-EstimatedRTT| d.產生 TimeoutInterval = EstimatedRTT + 4*DevRTT

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