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“Everyone today. I m going to talk about the tftp protocol. The ftp is an an application layer protocol. It stands for trivial file transfer protocol and it is used transfer files between computers now the tftp protocol is quite it does the same thing as ftp transfer files.
However the mechanism is different first thing here. Ftp relies on tcp at the transport layer on the other side tftp. Relies on udp at the transport layer ftp uses port 21 and 20 okay for the active ftp the tftp protocol uses port udp port 69. Another difference is that ftp needs username and password ftp requires authentication requires authentication so if you want to if you want to access an ftp server.
You should have user name and password with tftp. There is no need for a complication no need for a complication. You don t need authentication. So you just have to know the name of the file that you want to download and you send a command for to request that particular file now i m going to describe things how they work first the tftp protocols follow the client server paradigm.
So we have the client server paradigm. Which means that you have a t ftp client in one side. Then you have you will have a tftp you need a tftp server on the other side okay as we said the tftp server is always listening it s always listening at port 669 for any incoming request so there is a port 69. Here for any incoming requests from the tftp client.
So whenever the ftp client wants to send a particular request download the file from the tftp server. It s going to create a process here process we need a port to communicate for the network. So the part number will be assigned by the operating system let s say more example 50000. And then this process is going to send udp datagram containing the command to the tftp server.
Which is listening at 469 waiting for a command to service once the tftp server receives this command from the ftp client then the tftp server is going to send the data to the tftp client now since tftp is using udp. A transport layer and we know that udp is not reliable. How things works. What is the mechanism used by the ftp is that the data that the tftp server is going to handle or to send to the clients or the data that the client will upload to tftp server.
This data assumed that we have something like this assume that i have a large large chunk of data ok i assume that the tftp server is going to download that the ftp client wants to download some files from tftp server. So tftp server prepares this the file as data and then we divide it into small blocks smaller blocks like this this is block. 0. Or let s say block.
1. Block. 2. Block.
3. O clock. 4. O clock.
5. Now the th. The tftp server will take each block encapsulated. The inside encapsulated inside udp datagram.
An ip packet and then send it to the t. Ftp client. Now the t ftp client. Once it receives block.
1. For example block number 1. It s going to generate an acknowledgment. It will generate an acknowledgement to the tftp server.
Acknowledge that block 1. Has been received so for example tftp server has sent block 1 to 30p client. Then t. Ftp client will generate an acknowledgement saying that block man has been received only after that acknowledgement is received by tftp server.
Then the tftp server will proceed sending the next block here the next block. Which is block 2. So now the tftp server is going to send block. 2 of data to the tftp client now the tftp client is going to receive the second block and then it will send the acknowledgement to the tftp server saying that i receive at block number two so number two in the acknowledgment.
Meaning that the second block has been received and so on so each time two fcb server will send block of data to the client. It waits until the client will send the acknowledgement in order to proceed so this is kind of stop and wait protocol stopping away the protocol where the server does not proceed until it receives. I can alternate from the client in order to send the next block of data and we know stop and wait protocol is very slow this is what makes the completely ftp protocol very slow compared to ftp this is very important to understand the concept here is very important so remember each each data or each file will be sent will be divided into blocks each block will be sent in of course. Data.
Each block of data will be encapsulated inside so for example. If i can do this representation. Okay. I have block 1 all right block.
1. Like this block. One will be encapsulated inside udp datagram. So we will have the udp header and then this udp datagram will be encapsulated inside an ip header inside an ip packet.
Sorry ip will be encapsulated inside ethernet frame ok. It s not here we have an ethernet header and the trailer okay a trailer and then this frame is going to be sent to the clients now once the client will receive this frame. The uncaps allayed fund this block here block number one that moment. It s going to send another acknowledgment and acknowledgement saying that yes i receive it block number one to the tftp server then tftp server will not proceed until the second hodgman is receive it then it will continue sending block.
2 block. Three block. 4 block. Five each time.
It sends the next block until it it waits to receive acknowledgement in order to send the next block. Now. Let s see the mechanism. How all these things work.
So there are two case. Two situations here so the first one. I will describe the mechanism of tftp at the download. When the file when the file is downloaded okay.
So here we have a tftp. The client. This is one thing and on the other side. I have a tftp server so as we said earlier so the server is always listening at port 69.
Okay and then the client will create a process here let s say the process is opening part 50000. Who s choosing this number on the client side of course is the operating system. And then it will send udp datagram containing the command to download a particular file. Which is available on the tftp server assume this is a file available on the ftp server once the ftp server receives this file then what it does is going to create another process here okay.
It s another process this process will open let s say a port 5 4. 3. 2. And then it will use this process to send the file.
The data actually using udp datagram to the tftp file. But wait here you have to notice that the destination part will be the same port used to send the command to the tftp. Server so it s something like this. 50000 is a source port for the commenter the tftp server 50000.
Is also a destination part for receiving the data requests from the tftp server. However the data when not will be sent from a different port number which means that another process will be created by the tftp server just to service. The tftp client. So this is the way things will work with the tftp client in the download situation so here tftp server will take this file divided into blocks.
It will send the first block here block. 1. And then it will not it waits once block. 1.
Is sent the ftp server will wait to receive the acknowledgement about block. 1 lab by i received block 1. Once the acknowledgement about block 1. Is received by dhcp server then that the ftp server will proceed sending the second block block to and then it waits until it receives acknowledgement for block 2 in order to proceed until and so on until the file is completely downloaded from the tftp server to the tftp client.
This is the first scenario now in the second scenario. I m going to explain the upload situation so in the upload ok in the upload again i have a t ftp client like this and i have a tftp server. I have a tftp server as we said again i repeat the tftp server is always listening at port 69 for any requests to be received from the t ftp client. So assume here.
There is a process. Which is going to be instantiated and started and this. Process. Listening at 4.
50. Opening part 50000 for sending the command to the tftp server like this using udp data. Grams. All right now here the t ftp clients will tell the tftp server that is going to upload a file.
So the data will go in this direction. So in this case. The tftp server. Understand for the command receive from the tftp line that the tftp client wants to upload something what it will do the tftp server will create another process here and this process will open port 5 4.
3. 2. Just as an example and through this process is going to send acknowledgement acknowledgement 0. To the tftp client say ok i receive it your requests now what is the purpose of this acknowledgement.
This acknowledgement. Which is sent to part 50000. Which was used earlier to send a command to the tftp server. The purpose of this acknowledgement is to convey the port number used by the tftp server to receive the material to be uploaded from the tftp client in other words.
How can t ftp client. Know about this port number here. How does it know about it if it is not that the tftp server will send udp datagram to the tftp client to inform it about it so implicitly here. The ftp client will receive acknowledgement from the tftp server and through this acknowledgement is going to pick the port number which has been prepared by the open by dt ftp server to receive the data at that time now the ftp client is aware about the port used by dhcp server to receive the file.
And then the t ftp client will start sending the file as blocks. So it will send the first block of the file to the tftp server and then it will not proceed until it receives the acknowledgement for block. 1. At that time t ftp client will generate a second block block.
And then it waits for acknowledgement that block. 2. Was received and then it will send a third block and so on so each time. The ftp client sends block of data it will not send the next one until it receives the key knowledge meant for that particular block.
That was transmitted earlier in order to send the next one. So. This is the mechanism. Which is used by the tftp protocol.
So let s just summarize here in the download situation in the download situation as you see the tftp client is instructing. The tftp server to get to download the file to send a file. So the tftp server is going to open a process here as you see this process here which would be listening at specific part 5 4. 3.
2. This is just an example because parts will vary. After that so it s going to open this process and start sending the data to the same part used by the tftp client to send a comment. Ok so like this that you have to become.
And we know exactly about this. Part 5 4. 3. 2.
In order to send the acknowledgement in the other situation if the tftp client wants to upload something to the tftp server definitely the tftp client needs to know the port used by the tftp server to receive the material to be uploaded so in this situation. The tftp server will send an acknowledgement to the jtp client. Saying. Yeah.
I received your order yes. I received your request and the purpose of this acknowledgement is to implicitly provide the port number to be used by the tftp server to receive uploaded material from the tftp client. So this is all about the tftp protocol. And it s very important to notice the difference between tftp and the ftp protocol and the purpose of understanding the mechanism of this application layer protocol is to be aware about them how they work in order to successfully implement access control.
Lists. Acls. Either either either standard icl. Or extended.
Hope. This video was useful. ” ..
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