• LAN (Local Area Net) and NetWork

  ◆什麼是區網?
  就是指涵蓋 OSI的 layer1(Physical Layer) 和 layer2(Data LinK Layer) 範圍。
  (不能用距離來分、比如SoftEther可以是全球性的)
  ehternet(乙太網路)、token ring、token bus 等等的網路技術，統統是在講 layer1 和 layer2。

  ◆區域網路的重點︰
  1.Share Medium
  2.topology

  ◆CSMA/CD AND CSMA/CA
  Ethernet的MAC

Pack(封包) and Frame(結構) and Error Detection (錯誤偵查)

◆電話與網路的差別︰
電話網路 circuit switching
電腦網路 Packet switching

◆Pack(封包)︰分封之意
layer1 封包的單位是 bit
layer2 封包的單位是 Frame
layer3 封包的單位是 Datagram
layer4 封包的單位是 segmemt
layer5 以上封包的單位是 Message

◆網路的基本概念就是Pack switching
其對

Who is wise and understanding among you? Let him show it by his good life, by deeds done in the humility that comes from wisdom. But if you harbor bitter envy and selfish ambition in your hearts, do not boast about it or deny the truth. Such 'wisdom' does not come down from heaven but is earthly, unspiritual, of the devil. For where you have envy and selfish ambition, there you find disorder and e

• 目前的網路大多是 client server 主從式架構、
  Server本身會先啟動Application (如︰Web Service、FTP、Telnet等)
  並會開啟其相對應的Port、
  然後listen 該 port 上 等 client 提 request
  也就是 which computer？ which application to access？ which service？
  
  其中、Server會有其 IP、還會有 domain name 去對應其IP Address
  所以Client在尋找Server

◆傳遞訊號時、為什麼短距離和長距離不一樣?
Local 訊號衰減、但也不至於衰減到難以辨認。
遠端的話、就會因為傳遞的物質有阻抗而衰減到無法辨認。
(即使光纖也會有、需用repeater)

◆電腦傳送的資料上都是Bit為單位、
但是實體上常用︰電流(wire)、電磁波(wireless)、光(wire & wireless)

◆傳輸介質的進步

◆調變和解調
訊號是encode在carrier(載波)裡面的、利用調變和解調達成
目的︰1.訊號傳更遠、2.多工方式增加Data傳輸量

◆需要一個Modem來達成(Modem = Modulation + Demodulation)

◆將訊號放入"連續性震盪訊號"中 (連續性震盪訊號稱為載波)
可用以下三種方法做調變、把Data載入載波上面
1.振幅 (EX: 1/2A是零 1/4A是

'Do not store up for yourselves treasures on earth, where moth and rust destroy, and where thieves break in and steal. But store up for yourselves treasures in heaven, where moth and rust do not destroy, and where thieves do not break in and steal. For where your treasure is, there your heart will be also. 'The eye is the lamp of the body. If your eyes are good, your whole body will be full of lig

Therefore, as God's chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience. Bear with each other and forgiver whatever grievances you may have against one another. Forgive as load forgave you. And over all these virtues put on love, which binds them all together in perfect unity.



◎ 我最喜歡吃的點心 曾加恩

我最喜歡吃的點心就是起司熱狗了，它的味道美極了！這種熱狗裡面有著濃濃的起司，味道很鮮美，所以我喜歡吃熱狗。每當我和爸爸到便利商店的時候，內心總是盼望著爸爸能買熱狗給我，但是爸爸卻為了省錢而不買給我，讓我只能流著口水，默默的望著起司熱狗



作者 李家同 2008.09.28

我雖然已離開了清華大學，但我仍有一個「合聘教授」的頭銜，所以在清大，仍有一間研究室。這間研究室的窗子對著一個非常迷人的廣場，廣場中種了很多丰姿綽約的欖仁樹。我離開清大的時候，這些欖仁樹和我差不多高，現在這些欖仁樹都有六層樓高了。每年，當我發現欖仁樹



JS. sat down opposite the place where the offerings were put and watched the crowd putting their money into the temple treasury. Many rich people threw in large amounts. But a poor widow came and put in two very small copper coins, worth only a fraction of a penny.

Calling his disciples to him, Jesus said, "I tell you the truth, this poor widow has put

美國華盛頓大學正在研發的高科技隱形鏡片, 不但可以幫你瀏覽網際網路, 還可以幫你服藥. 競片中的聚合物(polymers)可以收納藥物, 依照病人的指令釋放. 其他可能的用途包括: 汽車或飛機駕駛人可以看到速度"投射"在視野內; 電玩玩家可以恍如"置身"虛擬實境中, 上市時間五年後. (讀者文摘)

&

VOIP

PC <--> PC (Cyber)

PC <--> PSTN (電話)

PSTN <-->VOIP <--> PSTN (從local上車, 走VOIP, 下車走Local); 找最近的點下車走local

Ch4 Transmission Media
可分 有線和無線

網路七層中的最底層 實體層
傳輸介質、編碼。

傳輸介質一直在改進 (如光通訊、有抗雜訊、速度快等優點)、所以技術、品質越來越好
編碼(Da



峰後的平原 ◎ 曾智義



My goal is that they may be encouraged in heart and united in love, so that they may have the full riches of complete understanding.



And over all these virtues put on love, which binds them all together in perfect unity.

In humility, consider others better than yourselves. Each of you should look not only to your only to your own interests, but also to the interests of others.

1. Only let us live up to what we have already attained.

2. I can do everything through him who gives me strength.

3. Forgetting what is behind and straining toward what is ahead.

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Ph.D, Student Chih-Yi Tseng
Department of Information Management, National Sun Yat-sen University,
Taiwan