IP Address

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From the course by Princeton University

Networks Illustrated: Principles without Calculus

43 ratings

Princeton University

Networks Illustrated: Principles without Calculus

43 ratings

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. All the features of this course are available for free. It does not offer a certificate upon completion.

From the lesson

Routing Traffic through the Internet

It is hard to overstate the impact that the Internet has had on society. In this lesson, we will overview the fundamental concepts behind the way the Internet is designed. We will also take a look at routing, which is the process of determining how packets of information are transported.

Meet the Instructors

Christopher Brinton
Lecturer
Electrical Engineering
Mung Chiang
Professor
Electrical Engineering

So the first part in routing is, is addressing.

So we need to give each network device a unique identifier.

Now that wasn't a problem when we were talking about circuit

switching, because just by the fact that we were dedicating a

network resource we would know how, what the message was test

for the receiver and we could filter it out that way.

Like you could listen on the specific frequency.

You listen just in on the specific times, your time slots.

You listen in just through that code.

That's how that works. But here we need

to actually give an identifier to each network

device so that we know where it's going.

And it's much like the way the mail system works where

these unique identifiers are very similar, for instance, to the address.

that's why they're called actually addresses as we'll see in a minute.

But, you know, when you send a letter to someone

you say, okay, I want this to got to Pat Prospect.

I want it and he's one, two, three any street in anywhere in America.

And his ZIP code is 09012.

We will look at how the ZIP code

really is analogous to one portion of internet addressing.

You have your center identifier and your recipient identifier, and that is

how the mail service can tell where to where to send it next.

And that's how, my routing is really analogous here, to this,

so it's a very good analogy when you consider the mail system.

So the, all the devices in the internet have an IP address.

All network devices

have IP addresses, and those are the, their unique identifiers.

IP stands for Internet Protocol.

So we said again we were going to look at IP in this section.

This is where we're doing it.

It's, this is the Internet Protocol address.

the IP addresses are decimal numbers separated by dots.

So we see these dots, and you've probably heard someone say an IP address before.

127.

12.5.88, right, so we have four decimal numbers right here.

No,

it doesn't have to be four decimal numbers, but we

have that separated by dots, and then each of the

decimal numbers is going to range between zero and 255,

right, so this is 127, it's like almost halfway there.

they, each one of these can go all the way up to 255.

And so just to give you an idea, not all devices are going to have IP addresses.

All network level devices, which we'll look at

in the next lecture, do have IP addresses.

But, here, so your modem for instance in your house does

not have an IP address, right, cause it doesn't understand IP.

It doesn't speak the IP protocol.

But any device that speaks and must understand

the IP protocol needs to have an IP address.

Routers have IP addresses.

so 127.12.5.87, but you see they're all different,

right, so 88 is for the desktop and 89

is for this laptop here, so that's how

they're identified, and how you know where it's going.

So now

let's look at IP address lengths a little bit.

We usually measure that in bits.

We'd say, we say bits, so, IP version four, okay, and

we've moved to IP version six now we're starting the migration there.

IPv4 is a 32 bit address.

so, remember bits, as we said, were zeros or ones.

And we looked at that back in the first lecture.

It's either a zero or a one so, each of these

numbers in here, there's four numbers, right IPv4

has four numbers, one, two, three, four, and

there's eight bits in each of those numbers

that's for a total of 32 bits total.

So each of these in here in an IP address, and you

have x dot x dot x dot x, whatever that may be.

Each of these is going to have eight bits, separated by those dots in there.

But what happened was we actually ran out of IP addresses back in like 2011.

Because there's so many internet connected devices.

So then we moved onto IPv6, and that actually increased the number of bits

in each address by a factor of 4, so we went up to 128.

So IPv4 we had 4 billion total IP addresses that we could possible use.

Now that mo, this is basically taking four billion and raising it to

the fourth power, multiplying it by four billion.

So it's four billion times four billion

times four billion times four billion addresses.

That may sound like a lot, but with the number

of internet-connected devices that are out there, and, the amount

that we're predicting to have we may, it may be

relatively soon that we run out of IPv6 addresses soon.

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