Hello and thanks for waiting. Welcome to our course titled Networks

Illustrated, Principles without Calculus. My name is Chris Brinton.

I'm a third year PHD candidate at Princeton University and I'll be teaching

this course along with my adviser, Professor Mung Chiang of Electrical

Engineering at Princeton University. In this lecture I want to give an

overview of what we will be learning in this course and how we will go about

learning. So the first thing that probably comes to

your mind is What is a network? Well, if you look that in the dictionary,

you come up with some pretty complicated definition.

For instance, an openware fabric or structure in which cords, threads or

wires cross at regular intervals. So, we would have some wires [SOUND]

maybe that are crossing [SOUND] at some regular intervals.

Or another one, a group of interconnected via cable and/or wireless, computers and

peripherals that is capable of sharing software and hardware resources between

many users. So there are many complicated terms

there, we heard, you know, users Like you or me, that are connected over maybe

wireless, or long cables. So those two definitions are pretty

complicated, and they probably leave you with a big question mark.

So now let;s discuss something simpler. What about a group of people like you and

me or things like smartphones, laptops, desktops, or tablets that are all

connected in some way. Now those connections might be over

wireless or cables or they might be overt the air over a wireless interface or they

could be social connections, for instance on Facebook.

Facebook if you and I are connected and become friends.

[SOUND] So, hopefully this makes a little more sense.

[SOUND] You may have a nice light bulb on your head right now.

So, these definitions on the left-hand side will become clearer to you as we go

throughout this course but we'll stick to this definition for now.

Now, where are these networks? Well, simply put, they're everywhere.

We have social networks like Facebook, Twitter or YouTube.

Now Facebook we have networks of friends, friend relationships.

On Twitter we have networks of following relationships, who you're following, who

is following you. Now, on YouTube, we have networks of

people who are talking, or we have networks of movies, videos.

We also have technological networks like cellular or 3G, maybe 4G that you might

use on your smartphone. We have WiFi, for instance, on your

smartphone or on your laptop device. And we also have the internet, which is

basically where all of these tasks run on top of.

So, you see Here we have a wide variety of of technological networks, starting

off with 3G, Wi-Fi or the Internet just being three examples.

And we also have economic networks, which is basically how we're priced for all the

services that we use and we have to pay for the Internet.

And that determines how we pay and how much we have to pay.

So if you think about it, our lives would be a lot different if we didn't have all

of these networks. So what do you need to know for this

course? You probably saw a similar course, which

is called, Networks, Friends, Money, and Bytes, that we have had on course to us

already. In that one we had a prerequisite of

calculus and linear algebra, where we're dealing with a lot of matrices.

So we may have written some complicated equation that looked something like this.

Pi of T, sequence of gamma I over SIR i of t times pi of t minus 1.

So we have a lot of symbols, for instance this p here.

We have a lot of subscripts, for instance that i, and things like sir and t for

time, which make it mathematically convenient to write down, but it doesn't

help the fact that it's pretty confusing. So in this course, we thought a lot about

how to present the material. And now we have two different

prerequisites. The first one is chalkboard math if you

will, like addition, multiplication, subtraction and division.

And the second one is just a desire to learn.

So we realized we can take this equation right here and write it in its English

form, a lot simpler. So we have, here, the next power, which

your cellphone will transmit it at is equal to this thing called the ratio

times the current power. So now all we need to do is multiply

these two things and we'll get the next power.

That looks a lot simpler than this equation right here, so we'll be using

chalkboard math rather than calculus and linear algebra [SOUND] and hopefully that

makes a lot more sense. Now how are these lectures presented?

Well we thought about what the best teaching style would be, or, pedagogy, if

you will, is for this type of material. And we summarize that in three As.

The first one, is analogies. Networks lend themselves very well to

analogies, things like transportation networks or the postal system.

For instance, we can relate congestion in the internet to what happens when you sit

in a traffic jam. And we can relate how Pieces of data get

through the internet. So, what happens when you send email to

someone and how it goes to all intermediate post offices along the way.

The second A is anecdotes. So, a lot of times best way to explain

some of these networking concepts is to tell stories and history about how they

came to be in the first place. And the third A is animations.

That's probably the most important. So Indeed, they say that a picture is

worth a thousand words and networks are no exception to that.

So, we'll be using a lot pictures to explain a lot of these tools.

So, now, each of these lectures revolves around a few key principles, namely we

have eight of them, which we call 8P. And these principles are simple phrases

that could probably fit within these two quotation marks right here.

So they're three or four words each, and they summarize a vast amount of network

ideas. And so we'll go through some of these

principles. Specifically we'll go through five out of

the eight of them. And we'll go through some of the topics

involved in them. The reason we're only going to do five is

because we only have six weeks together. So we'll just do as much as we can.

Now the question is, what are these principles.

So let's briefly go through them