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.
