We have to remember that the TCP IP is a suite of protocols and there are two very famous protocols
that exist at the transport layer.
Now, admittedly, one is much more famous, and that's transmission control protocol.
Now it's much more famous than its brother, UDP.
And this is because the transmission control protocol, of course, makes its way into the name of the
suite.
That's how popular it is.
But let's talk about these two options.
Remember at the transport layer for encapsulating our data.
The transmission control protocol option is so incredibly popular because it's reliable.
So reliable transport means that when we send a segment to another system, it's going to acknowledge
it's going to let us know that that segment has been received.
The way we classically like to describe transmission control protocol is like two people communicating
via a phone call.
Think about how that works.
You will say, Are you there when you haven't heard anyone speaking for a while?
And you'll say things like Hello at the beginning and goodbye at the end.
This is much like the reliable mechanisms of a transmission control protocol session.
We like to say that it's connection oriented, just like that phone call, that there's going to be
a start, a duration of time where data is transmitted and then a conclusion to that connection.
There's flow control mechanisms.
So we have things like the window size, and we have mechanisms to ensure that we are sending as much
data as we can without overwhelming the recipient.
And of course, if something should be lost or damaged, there's re transmissions in the reliable world
of transmission control protocol.
Now there is a cost.
Of course, all these great features always seem to come at some kind of a cost.
And of course, with transmission control protocol, it's no surprise to us that this is going to be
a lot more overhead.
So that's why there is user data.
Graham Protocol.
You see, we may want to be sending data in an unreliable fashion.
And I think that's one of the toughest things for new students to networking, to really embrace and
wrap their head around.
They just can't seem to make sense of the fact that we would ever want to send something over an entire
network.
Unreliable.
But what they're forgetting is that the lack of overhead can make for real, efficient communications.
There is no connection that needs to be maintained.
There is no flow control to worry about.
There typically is not going to be transmissions.
In fact, we say no re transmissions here and that really is true in the fact that it is unreliable.
Where we see re transmissions with UDP is when we're doing things like UDP scans of course, where we
are trying to determine what ports are available.
But in the normal flow of UDP, we are not going to be dealing with any of that overhead stuff of transmission
control protocol.
Where might UDP show up?
Well, it shows up when we want to do something like stream information, right?
Kind of broadcast information out there in a stream and UDP frames in packets and segments will be great
for this because it is that lower overhead that we would be looking for in a situation like that.
Also keep in mind that a lot of times when we send UDP transmissions, we have some other protocol that
will go ahead and give us the reliability.
One of the things that is surprising to students as well when it comes to UDP is the fact that it is
the protocol of choice when it comes to carrying voice frames.
So now you realize, yeah, reliability can be provided by something else.
So and it would have to be in the case of voice traffic.
So the low overhead user data Graham protocol works out great for the tiny little voice packets, but
the reliability will have to be built in to other protocols in the stack, and that's exactly what happens
with voice over IP.
Now keep in mind that various protocols are going to call upon either TCP or UDP or both.
An example of one that can do both is DNS.
We can have DNS utilize UDP or if we want to enhance security, we'll do a transmission control protocol
based DNS implementation.
But here are some of just some of the well-known port numbers and whether it's TCP or UDP that is typically
utilized.
Information like this is great to commit to memory and that will help you with dozens and dozens, maybe
even hundreds of it.
Certification, exams and yes, you guessed it will be making some flashcards for you on this list.
So enjoy.