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来自 Princeton University 的课程

Networks Illustrated: Principles without Calculus

39 个评分

Princeton University

Networks Illustrated: Principles without Calculus

39 个评分

What makes WiFi faster at home than at a coffee shop? How does Google order its search results from the trillions of webpages on the Internet? Why does Verizon charge $15 for every GB of data we use? Is it really true that we are connected in six social steps or less? These are just a few of the many intriguing questions we can ask about the social and technical networks that form integral parts of our daily lives. This course is about exploring the answers, using a language that anyone can understand. We will focus on fundamental principles like “sharing is hard”, “crowds are wise”, and “network of networks” that have guided the design and sustainability of today’s networks, and summarize the theories behind everything from the social connections we make on platforms like Facebook to the technology upon which these websites run. Unlike other networking courses, the mathematics included here are no more complicated than adding and multiplying numbers. While mathematical details are necessary to fully specify the algorithms and systems we investigate, they are not required to understand the main ideas. We use illustrations, analogies, and anecdotes about networks as pedagogical tools in lieu of detailed equations. Please note that per Princeton University policy, no certificates, credentials or reports are awarded in connection with this course.

从本节课中

Pricing Data

Data makes up a significant part of our cell phone bills. How do cellular providers set these price points? In this lesson, we will see how so-called usage-based pricing schemes can send better signals than flat- rate, “buffet” schemes, leading to better sharing of the network.

Our mobile data plans4:13

Demand for data8:04

Jobs' Inequality of Capacity6:27

Usage-based plans6:31

Comparing pricing schemes6:35

Demand curve & net utility5:25

The Tragedy of the Commons9:24

Flat rate creates waste & favors heavy users10:11

与讲师见面

Christopher Brinton
Lecturer
Electrical Engineering
Mung Chiang
Professor
Electrical Engineering

All right. So we've covered a lot in this lecture.

And let's just, summarize the key points that we've seen now.

we talked exclusively about data pricing. Where we, we saw how its originally

flat-rate pricing, and, with some of the, problems with that, and what made us

recently switch to usage-based pricing, to more properly landing sentence right

we. The ISPs couldn't really deal with those

excessive demands anymore. They came about with our Smartphones and

the ease at which we can access data, right.

And we even argue that the primary use of phones now maybe even switched to data

over voice and that's a possibility. we talked about the pros and the cons of

different methods, so we focused mostly on comparing usage base of flat rate and

showing how usage base is more efficient in many instances, but we've looked at

others as well. then we talked about economics and that

was a huge part of our analysis in comparing usage based to flat rate

pricing. we talked about utility and what utility

means is really users' happiness for a given quantity of their consuming of a

product. Alright, the utility is never going to

decrease, because whenever you get more of something, it's always a positive

thing, no matter how small, it may help. and the utility could be constant as you

go from one point to another. it could, but it's just, it's never going

to decrease, usually always going to increase.

the demand. We talk about the demand, which has the

opposite trend. That's looking at how the quantity they

will consume will change as the price, which is set by the network, is going to

change. Alright, so a higher price is going to

induce a lower demand. the demand will never increase.

It could, it could potentially the demand will never increase with a higher price.

There's a potential that it could stay the same.

Right? For instance, if you're putting gas in

your car, for instance. Something that's really, really

important. Even if someone charged you a little

more, you might still buy the same amount.

And then we also talked about a graphical interpretation of utility demand.

And that it's really important when comparing flat rate usage based pricing.

And understanding. Really, what this graph means here,

alright, so when we set our given price, what demand that induces, so if the price

is some amount per gigabyte, then that will tell us how many gigabytes we're

going to assume, based upon whoever the demand curve is, and

So it's really important to understand what these, what the implications are of

these graphs and how to read them. Then some major themes that we saw here.

first the idea of the negative externality.

Right so negative externality here in this case.

We saw it back in chapter one with interference.

But here it's in terms of any congestion through networks.

So every device, by being in the network, is going to come and pose some congestion

because they're drawing data from the network.

And we need to make the devices internalize the negative externalities

and the way that we do that is through feedback signals, right.

And here it's a negative feedback signal right, issued in the form of money,

right. So the more money that you have to pay,

the less you're going to want to take away from the network.

more incongestion because you're just going to have to be paying more and more

money. And overall, we just saw that networks

are expensive, right, and you know, that you can get charged $10 every gigabyte of

data that you use, right? So, taking data from a 3 or 4G plan isn't

cheap but now we understand why they're expensive and that's the main idea here

is. We know why they're expensive there

because of the demands and because we have to keep this supply per dollar.

we, we have to account for the fact that the supply per dollar can't keep up with

the demand, forever. Especially with our exorbitant demand

increases lately, in the recent years with the smartphones.

And there's a whole ecosystem out there, right.

The ISPs need to at least recover their costs, but they're also province seeking

organizations. then there's just a whole bunch of people

who get their hands on this ecosystem and they all need to have the share of it.

And that causes the networks to be expensive, but it's for very valid

reasons. Alright, so hope you've enjoyed this

lecture, I'll see you in the next one.

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