Time
3 hours 38 minutes
Difficulty
Beginner
CEU/CPE
2

Video Description

Transport Layer- Session multiplexing

  • Flow control
  • Reliability
  • Segmentation
  • Uses TCP or UDP
  • Adds port number
  • Socket to socket

What is Port Number?- Service identifier

  • Length: 16 bits
  • Ranges from 0 to 65,535
  • Well-known ports: 0-1024

    • HTTP: 80
    • FTP: 21
    • DNS: 53
    • SMTP: 25
  • Ephemeral ports > 1024

UDP Protocol- Best-effort delivery (unreliable)

  • Provides applications with access to the network layer
  • Saves the overhead of reliability mechanisms
  • Connectionless protocol
  • Limited error checking
  • Data loss due to:

    • Routing error
    • Dupliation
  • No data-recovery features

TCP Protocol- Reliable protocol

  • Provides access to the network layer for applications
  • Connection-oriented protocol
  • Error checking
  • Data-recovery features
  • Sequencing of data packets
  • Acknowledgement of receipt
  • More commonly used than UDP

Video Transcription

00:00
Now we will talk about the two main transport layer protocols in the TCP I p. Protocol,
00:08
the TCP Transmission Control protocol and do the Pee user data Graham Protocol.
00:15
The transport layer
00:17
in the eyes OS I model, of course, is layer for
00:22
and in the TCP I P implementation. It is implemented in two protocols. The TCP and the UDP. You either use this or use that. Use the TCP for reliable communication if needed.
00:37
Or do you use the UDP for unreliable communication? If this is the needed
00:42
mode
00:44
that
00:45
transport layer is responsible off session multiplexing
00:50
multiplexing means that several inputs leads only to one outward.
00:56
This is the responsibility off the transport layer
00:59
to let every service at the source
01:03
talk specifically, tow the corresponding service at the destination site.
01:07
It's responsible or flow control if needed. It's responsible. Adjusting the flew off the data, according tow. The slowest
01:18
side, either the sender or the receiver. It lets the festive side slows down. Toby
01:26
suitable for the slower side.
01:29
It's responsible for reliability if needed for lost detection,
01:34
for error recovery and to end.
01:38
It's responsible for dividing data into segments,
01:42
adding the port number and the port number is a very important identified toe. Identify the type of service requested from the client to the server or from the source through the destination. It is responsible for the communication socket toe socket and let's see what is a socket.
02:00
The socket is a combination, as we can see in the diagram is a combination between the I. P address that we have talked about and the fourth number that we need to talk about. Now.
02:09
What is a port number? It's the island. The fire for the service.
02:15
Each port number is associated with a certain service over the Internet, especially the port numbers ranging from 0 to 1024.
02:24
The lands off this sport number is 16 bits. That's why we can say that the port number can range from 0 to 65,535.
02:36
Among these port numbers, the port numbers, ranging from 0 to 1 24 are the well known ports. For example, port number eighties. For the http port number 21 is for FTP 53 for the Ennis
02:53
25 4 SMTP. Simple male transfer protocols
02:57
Port numbers larger than
03:00
1024 is called a fair Merrill Ports
03:05
Ephemeral ports means that they are not the well known ports, not associate ID toe very well known surfaces, but can be used for the communication from the client side to the server side. While the West known ports are
03:21
dedicated on the server side for each of the service's, such as http, f d P d, N s or SMTP,
03:30
here is the socket communication. Here we can see the socket Address I P address and port number forming a socket address. This socket address is at the source and a corresponding one is formed at the destination from the I P address off the distillation and the port number at the destination.
03:47
Here is a socket at the source, another one at the destination. They are communicating with each other
03:53
in socket toe socket communication. This is the responsibility off the transport layer layer for the responsibility off the TCP Protocol or the UDP Protocol. Let's compare between the reliable communication and the best effort communication there. A lot of communication is connection oriented.
04:12
No data transfer before connection establishment,
04:15
but in the best effort communication, it is connection less data can be transmitted without establishing a complete connection or a complete session complete circuit from the source to the destination. The protocol used for reliable communication is the TCP
04:33
the protocol used before the best effort delivery is the UDP Protocol.
04:39
There. A lot of communication provides a means off sequencing the sequence number in the TC people to cool in the best effort. The Love Delivery. You cannot
04:47
specify the sequence off the data, which is before which or witches after which
04:54
they use is off. The reliable protocol are for transferring email file sharing, downloading files. The best effort delivery
05:02
is for transferring voice or video.
05:06
In general, it is four really time data. It's for later that is delay sensitive and not lost sensitive, such as the voices screaming or the video streaming Where UDP is much more efficient than TCP,
05:24
the U. The people took over as the first protocol in the transport layer. It's disused in the best effort delivery. It is unreliable, but it provides application with access to the network clear. It saves the overhead of reliability mechanisms it saves. The acknowledgment saves the sequencing off later,
05:44
each off the acknowledgement and sequencing needs adding Heather's
05:47
and they do the people to call saves this heather and saves bend with for the data itself, the voice or the video being transmitted its connection. Less protocol. No connection establishment Before sending data, you send data, and you are not sure that the recipient is there. The recipient is up and running.
06:06
The recipient will receive the data in sequence.
06:10
It has a very limited error checking, and this checking does not include recovery off errors. If
06:16
existing
06:17
it is
06:19
they're not resilient. Toe day. Tell us, and it'll also scan bead youto routing errors or the application. The GDP protocol provides no data recovery features for such losses, so it is completely unreliable and therefore it is used with the delay sensitive data and not for the lost sensitive data.
06:40
The UDP heather. It's simple, and it does not provide any
06:44
form off better
06:46
recovery. So it is simply composed off
06:51
that sore sport registration Poor David appeal ends and there will be checks on their checks on the heather only it does not provide error. Recovery does not provide acknowledgement sequence number, as we will see later in the TCP Protocol,
07:08
the TC people took over is the reliable protocol. It's the reliable version off the protocols that are acting on the
07:16
transport layer. It provides access to the network layer for applications just like the UDP, but it is different, different in the way that it is connection or enter protocol before data transmission. There should be an establishment off connection complete circuit between the source and the destination.
07:33
It provides error checking. It provides data recovery features and to end
07:39
if there is data lost data application or any
07:44
change in the data from the source to the destination. The TC people took hold can detect this can detect the loss and the application
07:54
in the later and can recover this by resending the data itself. It provides sequencing off data through the sequence number Heather that existing in the header of the TCP. So if the arriving data is in the wrong order, the sequence number helps the receiver to reorder the data,
08:13
tow the right order.
08:15
It provides acknowledgement of receipt. So by this it can face the losses on the network and can detect that some data are lost and can be re sent by the source the TCP Protocol for the sake of such features.
08:30
The features of data recovery, sequencing and acknowledgement is more commonly used than you, Tippi,
08:35
because it is reliable because it is
08:39
more,
08:41
ah,
08:41
error resilient. So it is more commonly used than UDP, especially for Web transfer, male transfer and file transfer.
08:52
The TCP heather is off course more complex than they really p heather. We can see the source for the registration port. We can see the sequence number used for sequencing data. We can use the 32 bit acknowledgement number, which is used for acknowledging data being some. We can see the 16 between the size used for Flo control.
09:13
We can see the check some, which is the strike, some anywhere
09:16
used for checking errors across the heather and the data. We can see the 16 bit urgent pointer, which points on that
09:26
urgent data inside the data field. If this field, for example, contains the number 2000 this means that the by 2000 in the data field is urgent and needs to be processed before its turn comes.
09:41
So
09:43
this is the TCP Heather. We have some flags for the urgent feel for example for the acknowledgment for the push for the same for the things that are used for the three way handshaking used at the beginning off the session off
09:58
TCP communication and the four way handshaking used at the end off their session off
10:03
TCP communication.
10:07
If we try to map Layer four protocols to applications layer for protocols and the port number two the application protocols, we can see that the FTP Protocol use a sport number 21 uses the TCP as the transport layer
10:24
Communication protocol.
10:26
Tell not uses 23 esport number tell it is used for a remote administration. It is used by a client toe administrate a server remotely and act as if sitting on it, copying and pasting and formatting the machine
10:45
from another remote machine. And this is done through the port. Number 23 the http the hypertext transfer protocol use a sport number 80 and it uses the TCP Protocol so it is reliable so it can correct some errors. It is resilient to data losses
11:05
that the on us is a special case. It can use the TCP and can use the UDP.
11:09
In both cases, it uses the port number 53. It can act in a reliable form using the TCP Protocol. It can act as unreliable form using the UDP Protocol. If speed is more important than reliability,
11:26
the tea FTP or the Trivial File transfer protocol use a sport number 69.
11:31
It is just fund transfer without any user name or password or something like this. It is faster
11:39
file transfer than the normal FTP. That's an MP or the Simple Network Management Protocol, which is used for managing the network. It's used for communication between the routers. It is a protocol that is used to manage the network and make it faster and more robust.
11:58
It uses there would be people to call for the sake off the speed and the Sekoff being fester.
12:03
And it works on the port number 161.
12:09
By this we come toe the clear demonstration off both the TCP and they were the people to calls acting in the transport layer off the S. O S. I model and the transport layer off the TCP I people to call as well.
12:26
Thank you.

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