use of P2P technology. In contrast, BitTorrent uses P2P for
actual content sharing in the data plane. Later in lecture nineteen, we'll talk more
about control versus data plane. Roughly speaking, you can think of data
plane as where, the place where the actual transmission of data takes places,
Whereas, control plane is where the control signals take place.
For example, in Netflix, when you go online to put some movies in your queue,
that is the control plane, And it carries out itself over the
Internet. And the actual DVD in rental services
arrives by, say, US Mail service. That's a completely different network,
then the Internet, And that is the data point, that's where
the actual movie arrives. Okay.
So BitTorrent actually uses Internet, P2P, for content distribution, including file
sharing, including video sharing. Okay? To share chunks of files and we will come to
more details in a minute. In fact, Skype's actual operation remains
a commercial secret. There were a few papers trying to reverse
engineer Skype operations in the late 2000s.
But the BitTorrent was founded by graduate student, and there were quite a few papers
written by the founding team about the BitTorrent operation.
So we'd know quite a bit more about the BitTorrent and we will say quite a bit
more about it in this lecture. Before we go there, I want to highlight
that P2P really underlines the tremendous potential of positive network effect.
Going all the way back to lecture seven, for example, when we were examining the
popularity of a new product and we were looking at the impact of, knowing there
are many other users of the same technology and how they influence your
decision to acquire the technology or product or service.
Now there is the famous Metcalfe's Law. Okay? Named after the inventor of the
Ethernet that connects networks, computers in a local area network.
And, Metcalfe's law has, quite a few different versions and misinterpretation,
But, popular version says that the benefits of joining a network grows like
the square of, say n, Which is the number of nodes in the
network right now. Okay?
So the benefit grows like N^2 order. And the underlying assumption is that
every link, okay, are equally important, Which is a problematic assumption, because
we know some links are much more important than others.
And, furthermore, if I have, five nodes, Pretty much every node talk to every other
node. So it forms a full mesh network,
And therefore, if you look at the number of connections in the network with n
nodes, it is N^2, or, you know, N N - one, which is in the order of N^2.
And more generally speaking, we need the number of lengths coming from a node to
grow at least linear order of n in order to enjoy this n^2 benefits of Metcalfe's
law. And this has been invoked in so many
studies in social sciences and as well as engineering.