So it's important to note that different network devices only process or really
understand up to different layers in this protocol stack as we call it.
So this layering right here is called a protocol stack.
For instance. A modem [SOUND] can only understand up to
the physical link layer. You have a modem in your house.
Now, a router can process up to the network layer, as we've said, it's
managing these hop by hop decisions. And your cell phone [SOUND] can
understand all the way up to the application layers since it runs things
like Facebook and Twitter. So what this means is that your phone can
understand everything and decode all of these layers, all the way directly down
to the physical layer, whereas the router can only understand up to the network
layer and the modem can only still understand up to the physical layer.
The eighth and final principle is not something we'll have time to cover in
this course unfortunately, but it is in the book and it's called Bigger and
Bigger. It revolves around the fact that the
internet keeps getting larger and sometimes its size can be hard to
comprehend. If you just look at the number of
connected devices as opposed to the world's population, sometime between 2003
and 2010 we actually had more connected devices than people and that ratio
continues to get larger and larger. By 2010 it was 1.8 which means that every
person on average has 1.8 connected or between 1 and 2 devices that connect to
the internet. And if you think that's cool, well by
2015, that's expected to go up to 3.5, and by 2020 it's expected to be between
six and seven, which means that every person in 2020 will have between six and
seven devices that can connect to the internet.
So there's many implications of the fact that the Internet keeps getting so large,
one of which we can just think about for a second.
So I'm imagine you on some social networking site.
And try to think about if you took some random person in the world, where ever
that person may be. How many steps it would take for you to
get to that person, and by step I mean that you can go to one of your friends,
who can go to one of their friends, who can go to one of their friends and so on.
And each one of those is the step so if you Found one of your friends, that would
be one step, who could then find one of their friends, which would be another
step, and so on. How many steps do you think it would take
to get to this random person, on average. You may think, well, probably a lot,
maybe like 50, or 60, or something, some really large number.
Well, it turns out that, on average, that it's been experimentally proven to be
around six. And that's where the notorious six
degrees of separation comes from. Even though there's so many people on the
Internet, that on average, it should take you about six steps to get to this
person. Something like this.
You find one of your friends, who then finds one of their friends, then one of
their friends, one of their friends, and so on.
And it'll take 1, 2, 3, 4, 5, 6 steps on average.
Now there's a lot to this because we didn't say anything about how you might
go about finding this path, for instance you have to choose your right friend in
order to make that the smallest number of people possible, then your friend has to
choose the right person and so on... And in the book we look at ways you can
go about describing such networks, and what properties these types of networks
have. Now another thing that we've seen from
day to day now is the idea of the cloud, which is this mysterious place where you
can put all of your data, and you can go back and access it.
And the idea is that rather than having to have external storage, you can
actually go and store all of your data or run processes within this cloud, and then
you can come back and request those at any time that you want.
But if you ever stop to think what's actually inside of that cloud, what is
that cloud actually doing, because it's pretty amazing that it can keep operating
as efficiently as it does. With the amount of people now that have
internet connected devices, and especially by 2020 the amount of people
that will have these devices and being able to keep cloud storage going.
Well, in order to do that we have to actually open up the cloud and see what's
inside of it. Well, the cloud actually consists of
physically a number of data centers. And within each of these data centers we
have a lot of servers, which store and perform these tasks that we need.
And so, the cloud keeps getting more and more servers as it needs to have more and
more users. But if you've ever heard of the concept,
you're only as strong as your weakest link, that definitely applies here.
And that every single component of this Cloud has to be strong or else we're
going to be limited by the capacity of one of those links.
And to really see how that's done, we have to go into understanding the
fundamental building blocks are behind the cloud.
And they come into things that are even smaller than these individual.
Servers, and to do that we can consider it an analogy to building a lego set for
instance, and each of these lego sets consists of one of these really small
building block legos, and without these small legos we can never build something
as big as this large house right here. Just like...
Without these devices called switches, which are very small, but there's very,
very many of them, we could never connect all these servers together, so that we
can operate and make best use of our available capacity on each of the
servers. And operate the cloud as efficiently as
possible.
