01/11/12

1. 要解决的问题
2. 现行方法缺陷
3. 创新之处，为什么新方法能解决问题
4. 新方法的应用前景

Paul Baran

The chances are you've never heard of him, but without his pioneering work in the 1960s, you wouldn't be reading this web page, because there wouldn't be a web for you to read it on.

His name is Paul Baran, and he died March 26, aged 84. Baran, a Polish-born engineer at the RAND corporation, invented one of the most fundamental aspects of internet technology, the concept that later became known as "packet switching".

Put simply, packet switching is the way data is chopped up into smaller chunks, and each chunk is sent across a distributed network to end up at its destination.

The chunks, or packets, might not all take the same route. The whole point is that there are many different routes available to them. Each packet has something called a header — a summary of metadata, information about the packet and its contents.

As the packets arrive at their destination, the packet headers tell the computer there how to re-assemble them in the right order.

Baran shares some of the credit for packet switching with researchers Donald Davies and Leonard Kleinrock, who were working independently along similar lines; before they came up with the idea, information had to go from point A to point B using what's called circuit switching. (Think of old footage of manual telephone exchanges, where operators plugged wires to connect one circuit with another.) With packet switching, a single circuit could be used more efficiently, to send more data between more people.

Baran's pioneering work in this field was a direct precursor to the creation of the government-sponsored network Arpanet, which itself was one of the first building blocks of the internet as we know it today.

A version of this text originally appeared on TIME.com on March 28, 2011.

Read more: http://www.time.com/time/specials/packages/article/0,28804,2101745_2102136_2102369,00.html #ixzz1iY27cuxm

纽约Day14

起来以后到星巴克吃了早餐，然后去Path站门口的UPS店打印了帝国大厦的票和rent的票，打印要50美分一张，真是贵，唉。然后直奔中央公园，在湖边转了小半圈以后做公车到39街的草堂小餐吃午饭，点了干煸四季豆，干烧鱼片，和春笋排骨汤。午饭后已经三点左右了，走路到42街看了一下中央车站 Grand Central Station，昊爷在那儿花了不到2分钟时间买了一个iPad。然后继续走到33街的帝国大厦，排队过安检，再排队上电梯，再排队爬楼梯到86层，看了落日，然后看了夜景，又走回草堂小餐要了碗酸辣粉，还点了钵钵鸡和肉末酸豆角，然后奔去50街看Rent，中间还在一家店里买了一小碗冰淇凌。Off-broadway的阵容果然不够强大，Mimi除了出场的一首歌唱的还行，其他的solo嗓音都不亮，有点失望。不过Maureen很给力，又能演又能唱，Angel也是，竟然是个高中生，不知道是不是真的gay。

纽约Day13

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