课程概况
你在咖啡店排队的时候拿起你的iPhone，用谷歌搜索一个不怎么出名的演员，谷歌就会显示他的维基百科页面，上面有他演的电影和YouTube上的相关片段。你在亚马逊上看用户评价挑选了其中一部电影，在比特流上把它下载下来，或者转发到网飞公司（Netflix）。突然手机上的WiFi信号消失了，于是你开始使用3G网络。视频质量开始下降，但你不确定到底是服务器不堪重负，还是网络哪里卡了。这时候，你用掉一个1G就会花掉10美元，你决定不看电影了，干脆一边发推特一边用Skype和朋友聊天，同时有几首歌通过iCloud传到手机里。你对通话质量很满意，但同时又有点不高兴，因为看到推特上的粉丝没有增加。你可能会好奇这一切都是怎样运作的，为什么有时候他们会不好用。看看下面20个问题。选择这些问题不光是因为它们和我们生活息息相关，还因为问题的答案包含了网络领域的核心概念。这门课程的主要内容就是提出并回答这20个问题。
You pick up your iPhone while waiting in line at a coffee shop. You google a not-so-famous actor, get linked to a Wikipedia entry listing his recent movies and popular YouTube clips of several of them. You check out user reviews on Amazon and pick one, download that movie on BitTorrent or stream that in Netflix. But suddenly the WiFi logo on your phone is gone and you’re on 3G. Video quality starts to degrade, but you don’t know if it’s the server getting crowded or the Internet is congested somewhere. In any case, it costs you $10 per Gigabyte, and you decide to stop watching the movie, and instead multitask between sending tweets and calling your friend on Skype, while songs stream from iCloud to your phone. You’re happy with the call quality, but get a little irritated when you see there’re no new followers on Twitter. You may wonder how they all kind of work, and why sometimes they don’t. Take a look at the list of 20 questions below. Each question is selected not just for its relevance to our daily lives, but also for the core concepts in the field of networking illustrated by its answers. This course is about formulating and answering these 20 questions.
All the features of this course are available for free. It does not offer a certificate upon completion.
课程大纲
周1
完成时间为 2 小时
Introduction
An introduction to what we will explore in this course: 20 practical questions and their answers, about your networked life.
5 个视频 （总计 94 分钟）, 3 个阅读材料
完成时间为 2 小时
What Makes CDMA Work for My Smartphone?
We study cellular network technology, the air interface between end-user devices and base stations, and an important algorithm which has
been developed to manage interference between our devices as they share this medium: Distributed Power Control.
6 个视频 （总计 99 分钟）, 2 个阅读材料
周2
完成时间为 1 小时
How Does Google Sell Ad Spaces?
How does Google sells the ads that appear on its search results page through auctions? We learn about different types of auction mechanisms, including those for single and multiple items. QUESTION 3: We explore PageRank, the famous algorithm that underlies how Google orders its list of search results whenever we type in a query.
5 个视频 （总计 80 分钟）
完成时间为 2 小时
How Does Google Rank Webpages?
In this lecture, we will explore PageRank, the famous algorithm that underlies how Google orders its list of search results whenever we type in a
query.
5 个视频 （总计 81 分钟）, 2 个阅读材料
周3
完成时间为 2 小时
How Does Netflix Recommend Movies?
As a user of Netflix, you may have had movies recommended for you to watch. Behind the scenes, Netflix is leveraging powerful machine learning to determine which will be recommended to you specifically. In this lecture, we will study some of the fundamental algorithms that have been used for this purpose.
5 个视频 （总计 116 分钟）
完成时间为 2 小时
When Can I Trust an Average Rating on Amazon?
The decision of whether or not to make an online purchase is often driven by feedback that has been left by past customers, commonly in the form of star ratings. In this lecture, we will study Amazon's review system. In doing so, we will explore some of the methods for, and challenges behind, rating aggregation.
5 个视频 （总计 72 分钟）, 2 个阅读材料
周4
完成时间为 1 小时
Why Does Wikipedia Even Work?
In this lecture, we focus on the concepts of crowdsourcing and consensus formation, which are two of the mechanisms allowing Wikipedia to be both a scalable and (reasonably) accurate encyclopedia. In particular, we will look at different voting systems, which are ways of determining consensus from a collection of individual preferences.
5 个视频 （总计 68 分钟）
完成时间为 2 小时
How Do I Viralize a Youtube Video?
In this lecture, we will study models that have been developed for the popularity of products over time, motivated by the phenomenon of videos going "viral" on YouTube. Overall, the theme will be the dependence of opinions, as opposed to the wisdom of crowds discussed in the previous two lectures.
5 个视频 （总计 75 分钟）, 2 个阅读材料
周5
完成时间为 1 小时
How Do I Influence People on Facebook?
In this lecture, we continue with the theme of information spread in networks, turning to the effect of graph topology. In particular, we will
discuss influence models for social networks like Facebook, and how to measure importance.
5 个视频 （总计 85 分钟）
完成时间为 2 小时
Can I Really Reach Anyone in 6 Steps?
Six degrees of separation, or the small world phenomenon, has become one of the most widely told stories in popular science. In this lecture, we will study different models to explain both how short paths can exist in realistic networks, and how they can be discovered by people in the networks.
4 个视频 （总计 78 分钟）, 2 个阅读材料, 1 个测验
周6
完成时间为 1 小时
Does the Internet Have an Achilles' Heel?
At one time, there were rumors that the Internet has an Achilles' Heel, or a few center points which if attacked would completely disconnect the Internet. In this lecture, we debunk this myth, by showing that the fact the Internet is a "scale-free" network does imply it comes from a network model which would have such center points.
4 个视频 （总计 62 分钟）
完成时间为 2 小时
Why Do Mobile Carriers Charge Me $10/GB?
In recent years, mobile carriers have introduced a usage-based component to their data plans, where you are charged proportionally to the amount of data you consume. In this lecture, we will look at the reasons behind the switch to usage-based pricing, in terms of fundamental economic principles.
5 个视频 （总计 87 分钟）, 2 个阅读材料
周7
完成时间为 1 小时
How Do I Save on Each GB?
In the last lecture, we studied flat-rate and usage-based pricing schemes for mobile carriers. What these both fail to model is the time varying aspect of demand: consumption varies throughout the day, leading to peaks and troughs in usage. In this lecture, we will look at methods of Smart Data Pricing for taking this into account.
4 个视频 （总计 67 分钟）
完成时间为 2 小时
How Does Traffic Go Through the Internet?
It is hard to overestimate the impact that the Internet has had on society. In this lecture, we will overview the layered architecture on which the
Internet was designed, and will dive into the process of determining how packets of information are transported, known as routing.
5 个视频 （总计 102 分钟）, 2 个阅读材料
周8
完成时间为 2 小时
Why Doesn't the Internet Collapse Under Congestion?
When the demand for capacity on the Internet exceeds the available supply on the network links, we have congestion. In this lecture, we will
discuss the principles of distributed congestion control, and will detail protocols that have been designed to regulate demand for the Internet.
5 个视频 （总计 90 分钟）
完成时间为 1 小时
How can Skype and BitTorrent be free?
The amount of content on the Internet continues to grow at a rapid pace. One of the ways that content distribution at such massive scale is made possible is through peer to peer (P2P) protocols. In this lecture, we will study P2P applications like Skype and BitTorrent. In doing so, we will see how peers in a network can share the workload of distributing content throughout a network.
4 个视频 （总计 67 分钟）, 2 个阅读材料
周9
完成时间为 1 小时
What's Inside the Cloud?
The Cloud is another rapidly growing Internet service, allowing users to rent storage and computation resources inside the network. In this
lecture, we will see how the large data centers operated by Cloud providers can be constructed from a multitude of small switches.
5 个视频 （总计 71 分钟）
完成时间为 2 小时
Which Way to Watch Video on the Internet?
We have seen that the Internet provides a "best effort" service. In this lecture, we will look at how it supports video distribution, which often
imposes stringent demands on throughput and delay.
4 个视频 （总计 75 分钟）, 2 个阅读材料
周10
完成时间为 1 小时
Why is WiFi Faster at Home Than at Hotspot?
WiFi hotspots have become an essential feature of our wireless lifestyle. In this lecture, we will study WiFi, and focus specifically on common link layer protocols that are used to manage interference. In doing so, we will see why WiFi does not scale well beyond several devices sharing one access point.
4 个视频 （总计 73 分钟）
完成时间为 1 小时
Why Am I Only Getting 3% of the Cellular Speed?
Advertised network speeds are typically only those that can be obtained at the physical layer under ideal channel conditions. In this lecture, we
will study various factors that impact the actual speeds we obtain at the application layer under realistic channel conditions.
4 个视频 （总计 59 分钟）, 2 个阅读材料
周11
完成时间为 1 小时
Is It Fair that My Neighbor’s iPad Downloads Faster?
In this final lecture of the course, we will study a subject that we touched upon many times previously and forms an essential part of both social
choice theory and technology network design: quantifying fairness of resource allocation.
4 个视频 （总计 73 分钟）
完成时间为 1 小时
Course Summary
Here, we will summarize the important points of what we have learned in this course.
2 个视频 （总计 22 分钟）, 1 个测验
周12
完成时间为 4 小时
Guest Lectures
This contains various guest lectures from renowned members of academia and industry who are experts across the topics covered in this
course.
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