Time flies, a week has passed, this week we came to the Internet History, Technology and Security (Week 2) learning, can be seen from the title, is born this week, mainly introduce "Internet" prototype. Supercomputers Justify a National Network "describes the background of the birth and development of the network of networks." The First 'Internet' "is from a different perspective to tell the story behind the birth of the early network by three well-known figure associated with
History Through Supercomputing
60 years ,, the communication between the city through a copper cable, every time someone calls between the two cities, we must find a wire in the United States and its audio link up this call will be by telephone line, transferred to the other side, this mode is called the Data transfer with Leased lines .
However, cost is also associated with distance and because of their prices are very high. Therefore, in order to reduce costs, Ever since we jointly lease a line, and the establishment of a node, this model known as Store and ForwardNetworking. May This mode also has a disadvantage in that network congestion problem, the information sent by the user at a computer node will queue messages waiting in front of the transponder and then transmits After completion, but the next one computer node, if also forwarded , will enter the waiting, so that the sender can not determine the state information, and a large delay.
And the same time, the United States Department of Defense believe that if only one centralized military command center, this center was destroyed in case the former Soviet Union's nuclear weapons, the country's military command will be paralyzed, the consequences would be disastrous, it is necessary to design such a decentralized command system - consisting of a decentralized command dots, when command points are partially destroyed other points still work, but these contact points scattered through some form of communication network, based on this situation US Department of Defense investment named ARPANET research network, and that this network is the predecessor of the Internet.
· Data Transfer with Leased Lines: leased line (referred to as green) is used to connect two areas symmetrical telecommunications lines. Different from traditional PSTN, leased line does not have a phone number, the end of the leased create a permanent connection. Line can be used in telephony, data and Internet services. The cost based on the distance, quite expensive .
· Store and Forward Networking: Use BITNET can reduce the cost of pay telephone line (using leased lines because the cost of communication too high). However, as demonstrated in the video as data transmission and the data needs to be sent by others queued in the network. The sender and the recipient is not established line two line (too expensive to do so), but between this set some nodes of the network to be forwarded.
The disadvantage is that if you send a large file to be forwarded at the time of transmission for a long time (because of continuous sections, the same time can only be transmitted over a link), which will affect the end of the file you want to send, that affect the efficiency . The following ARPANET considering the large file into a film, which can improve efficiency. The following figure demonstrates a simple video store and forward principle.
The ARPANET ·: (Wiki) Advanced Research Projects Agency Network (English: Advanced Research Projects Agency Network, abbreviated ARPAnet) in the United States DARPA developed the world's first operational packet switching network, it is the originator of the global Internet.
ARPANET uses a "packet-switching technology" (Packet switching technology). The so-called "packet switching theory" is to split the information into fixed-size blocks each "pack", are noted on each package come from, where the pass. I want to transmit, for example, "I have a good friend and I like him.", Which may be divided into two portions (packets), and indicate the sequence number, and then are respectively transmitted (transmission may be different links --- i.e. to the center, because you do not know these specific strike packages). Finally, and in accordance with the recipient we accept the number of these small portion of the splice, the final composition of the complete information.
There is also exemplified a question: What happens if your packet forwarding in the network is a "roundabout" way to conduct this solution.
Larry Smarr – NCSA
This section describes Larry Smarr, he is a trained astrophysicist relativity, you know, related to objects require extremely large computation, but it was the super computer is not open to the academic community. So he persuaded Congress to authorize the use of supercomputers, but also to persuade Congress to pay for the establishment of the National Science Foundation Network, and uses a TCP / IP network protocol of ARPANET. It can be said that it promoted the development of the network to a certain extent.
History Through NSFNet
这部分介绍了NSFnet诞生的历史， 这部分介绍了NSFnet诞生的历史，首先是密歇根大学原本也想建立一个超级计算机中心，但因为战略失误问题，没有得到，之后他们选择建立将各计算机中心连接在一起的网络。但在项目一开始就面临了资金短缺的问题，于是他们与IBM合作，由IBM提供硬件和软件来建立路由结构，此外，还邀请了MCI提供跨越美国国境的通讯设施，且得到州长的了预算。但是这项计划遭到了质疑，因为Merit没有在TCP/IP上有很强的背景，并且那时的IBM正在搞自己专有的网络协议。所幸后来审查顺利通过，这项计划才得以继续进行而后来，由于影响到了专有网络的开发，IBM放弃了对NSFNET开发路由器的努力，这使得Cisco成为了美国路由器的主导制作商。
Leonard Kleinrock – The First Two Packets on the Internet
当你来到Boelter Hall，你可能会注意到入口处有一种表面上随机的地砖图案。如果你花一点时间观察这个模式，你可能会发现这些瓷砖代表的是0和1，然后你甚至会发现这些瓷砖代表的是ASCII字符。，而这正是为了纪念互联网历史性的一刻。 L.Kleinrock 是一名计算机专家，在本节中他讲诉了当时在加州大学洛杉矶分校(UCLA)到斯坦福研究所(Stanford Research Institute)的ARPANET，“L”和“O”这两个数据包在这之间传送的详细过程。
Katie Hafner - Where Wizards Stay Up Late
Katie Hafner是纽约时报的主编，可以说见证了NSFnet和ARPAnet历史发展：她采访过许多计算机网络相关的知名人物，比如Ray Tomlinson（电子邮件的发明者），以及Jon Postel，IANA（互联网编号分配机构）创始人。这段视频主要就是她对这些人的一些简单回忆，通过这段视频，我了解到了这些大师级人物背后的一些轶事，也透过这些了解到了他们的为人。
Think after class
- 任何伟大的成就一开始都是简陋的，不完美的。互联网也正是这样慢慢发展起来的。
- 没有完美的人，只有完美的Team。强如密歇根大学校长这样的人，也是在IBM和MCI的帮助下实现了NSFnet的建设，单枪匹马终究比不上团结就是力量。
- PS:( 首先来说说这次学习遇到的挫折吧。这次听了老师的建议，用纯英文字幕看视频，才发现第一周用中文字幕看视频有多么偷懒了，用英文字幕和中文字幕看视频完全是一个天一个地。发现学习这门课程最难的不是去理解教授说的内容，而且如何去翻译教授所讲诉的内容。英文的阅读才是这门课对我来说最大的挑战。看视频第一遍下来，才发现花非花，雾非雾，整个人云里雾里的。没办法，一遍不行哪就来第二遍，第二遍看下来发现，教授有时候语速太快，字幕看不过来。于是我在网页下面看英文文本。这样下来，才对内容有了一个大概的认识。写完这周学习笔记，才发现自己其实对英文字幕这种挑战并没有多大的排斥，反而有一丝丝欣喜，虽然这样可能会使我在这门课上花费的时间翻了几番，但我相信未来会慢慢变好的，英语也会慢慢变好的。最后说一个小发现，终于明白为什么看英文文学要看原本了，因为有些翻译要自己去翻译才有哪个味道。哈哈哈哈，加油！)