Back in 1994, I had the opportunity
of working at Paramount Pictures.
And I realized there's a lot of actors,
and some have specialized skills,
and some are better than others.
And sometimes it depends on the role
that the actor is supposed to play in that determines
how well they do at it.
Well, in the world of our protocols suite--
specifically in the world of the TCP/IP protocol suite that we
use today--
we also have several actors or players that
are part of the protocol suite.
And what I'd like to do is focus on a few of the core TCP/IP
protocols, and I want to start right at this point
and going below it-- the transport layer
and working down.
And at the transport layer, although there
are several protocols that operate at that layer,
there are two primary protocols that are used most of the time.
One of them is connection-oriented and
reliable, and the other is connectionless and unreliable.
Of these two main protocols, the reliable one
is called Transmission Control Protocol, or as its friends
call him, TCP.
So the middle manager at layer 4 at the transport layer,
if it's using TCP, it's guarantying
reliable delivery of the messages-- or if you will,
the segments that are going to be sent from this computer
or from this device on the network.
And the way that TCP pulls off this feat--
it does something like this.
OK.
I'm going to go ahead and establish
a session with this other device I'm talking to, says TCP.
And I'm going to send requests and get acknowledgments.
And because I'm getting acknowledgments, says TCP,
I know that these segments that I'm sending
are being received by the other side.
And that's how the middle manager
role here at the transport layer, if it's using TCP,
can have reliable transmissions of those segments
by maintaining a connection-oriented
relationship between the local computer and the device
that we're talking to.
Now, what's one of the negatives of using TCP?
It sounds great.
It's reliable.
Well, there is some additional overhead,
including acknowledgments that are going to be sent
and additional setup for the communications.
So that's the negative side of TCP.
It's a little more heavy, if you will.
But it is reliable.
Now, on the other hand, the other major protocol
in the TCP/IP protocol suite at layer 4, the transport layer,
is User Datagram Protocol, or UDP.
And UDP, at the transport layer, if it's
being used by the middle manager,
it is not set up as a connection-oriented
relationship.
There are no acknowledgments from the other side.
So it's more like setting the segment of data
and just hoping, from the transport layer's perspective--
just hoping that it makes it.
Because the transport layer itself
is not expecting any acknowledgments
if it's using UDP as the transport protocol.
And a really good question that comes up
is, hey, how does the middle manager, the transport layer,
know if it should use TCP--
reliable, connection-oriented communications-- or UDP--
connectionless, unreliable?
And the answer is it depends on the application that
is at the upper layers that's being used.
So some applications are requiring TCP.
Other applications are requesting UDP.
And that's how the transport layer knows what to use.
And in either case, whether it's TCP or UDP that's
being used at the transport layer,
as those segments get passed down to the network
layer, layer 3, in the world of TCP/IP,
the one major protocol operating at the network layer
is a protocol called IP, which is short for Internet Protocol.
And down here at the network layer--
or in our analogy of the kings, that's the mailroom--
they're adding address information.
Specifically in the world of internet protocol,
they're adding IP addresses.
And that's true whether we're using IPv4 or IPv6.
The logic is the same.
This is the part where we would be adding the correct IP
addresses-- both source address and destination address--
on each of the packets before we hand them down to layer 2,
which is going to be responsible for the framing.
And as we consider the protocol suite
and we learn more about it, we're
going to have additional protocols that are also at play
and working.
But because we're calling this protocol suite something,
we've chosen to name it TCP/IP.
So when we see TCP/IP, it represents
all the possible protocols that we
might be using in this suite of protocols which may include
TCP or UDP as well as other common protocols
in the TCP/IP protocol suite, which
leads us to another question.
What is another protocol, or what
is an example of another protocol in the TCP/IP Protocol
Suite?
Another example is ICMP, which is an acronym for the Internet
Control Message Protocol.
And if we use the analogy of actors in the world of TCP/IP,
like movie actors, ICMP would be a really good supporting role.
It does a lot of support services for other IP
functionality.
For example, if a user at Computer A
did a ping, typed in ping and the IP address of Computer B,
behind the scenes, it's actually using ICMP as the mechanism
to say, hey, are you there.
That would be a ping request.
And if the other party is playing ball,
the ICMP can also be used as part
of the reply to that request, just
to confirm there's reachability between point A and point B.
And behind the scenes, ICMP is being used.
In this Nugget, we've identified some core protocols
in the world of TCP/IP, including
TCP and UDP at the transport layer,
IEP at the network layer, as well as a utility protocol
called ICMP that's also part of the TCP/IP protocol suite.
I hope this has been informative for you,
and I'd like to thank you for viewing.