Original subtitles

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It all the job is also is to segment the data.

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It uses sequence numbers to do this and it also has an interesting thing to use between communication

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which is call port numbers

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that each one of these things has its own lesson to teach this means if the traffic is going to not

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be guaranteed it means I'm going to send the traffic down the wire and I don't really care if it gets

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there or not it's best.

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I mean I wanted to get there but I'm not going to make sure it does get there.

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TZP is a mess that is a method of being guarantying traffic and making sure that my traffic is being

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used.

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B I'm sorry being delivered and in order for me to get that guarantee guess what I'm going to use secret

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numbers to make sure that I'm getting the proper data back.

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And make sure the my date has been set let's see how that works so quick

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if I see a piece of data over the PC one now remember sequence numbers in TCAP or you know TCAP uses

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secret numbers to make sure we have guaranteed communication which means using TCAP you are expecting

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reliable transmission a transmission

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between poverty's buffer these devices p.s. one since the date over here is my data comes out here.

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PC to attached to this data up have a sequence of say seekers number one piece or two will come back

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and say look I have this data I got it.

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This is going to send what is called Room knowledge meant.

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And with that acknowledgement he's going to send a sequence number of to that sequence number two means

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to receive that piece of that demeans the PC one PC one gets this acknowledgment with the sequence number

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two.

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He knows pc 2 is expecting sequence number of two if PC to send this announcement back with a sequence

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number of one it's tell the pc that he's expecting a sequel number of one.

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And P.S. one knows that both of your spectrum 1 and already set one I need to resend one because you're

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not getting it.

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So I'll go ahead and send that and these sequent numbers of which used to guarantee those traffic back

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and forth.

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That's just the basics.

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We'll get a little bit more detail into it later on.

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Point numbers think of port numbers as a means of listening on a particular gateway Nasik gateway I'm

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talking Mollah hyperspace gateway not a gateway and networking think of them as what you can think of

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those tunnels.

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But then we have tunnel interfaces that may confuse you think of you actually going through a wormhole

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in space.

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If this PC want to sit in here

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and I'm trying to send data over to PC to and I want to send an out port number 23

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I'm going as soon as data

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through this nice little warm hole bending space and time excels are right.

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Going down port 23 over to this PC Now that's one way of looking at it.

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But then some people get confused with that as well.

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Because they think that this is 23 is automatically open and so on and so on.

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So let's think of it as another way I like explained it that way because a lot of people read it as

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as a warm hole and it kind of get kind of confused.

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I like to think of them also as this wall

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of Doris

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sitting on the PC

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and we've got lots of doors.

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OK here's our door handle for each one of these doors.

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Imagine

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that these doors have numbers on them.

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Now pc 2 is going to be listening

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and each one of these doors he's going to have his ear up to them.

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PC to just define what port number is or what doors he's allowed to listen on.

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So PC to say I'm going to listen on door 23 Orndorff 15 and on door 33 OK.

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So these are the only doors and I'm going to be listening on and that's it.

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So if PC one sends information over the PC to and he says I'm going to send this information to port

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25 and PC too is not listening on the port 25 you'll never be able to open one of these doors.

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He's not he's not going to open the door for traffic to come through.

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And in fact PC is going to say I'm not listening on 25 CJA and I'll drop the data.

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So these these so-called port numbers these doors PC to needs to be listening on that port number in

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order to allow the traffic to go in.

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Now if I communicate on port 23 when that's beautiful that's fantastic

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PC two will actually allow that traffic to come in.

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Open this door because he's listening on 23 and that traffic will be allowed to come in.

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This is the transport's job to make sure of this transformation so let's look at it like this

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I'm going to have my application Ababil my application and application I'm going to say I want this

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application to be Portland OR 1 1 1 1 1111 So what's going to happen is when ever this pc will say PC

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one is using this application in that PC goes it's building these layers of presentation layer session

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layer session layer remembered as such a layer actually goes out and tries to create the session once

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the session is created.

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Now we're going to get to the transport layer the transport layer is going to define whether it's going

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to be UDP or TZP

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ever GTP who cares it's just going to send it out with the port number and be done with it.

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If it's TZP we're going to set up a TCAP session first to to make sure we have this guarantee.

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Traffic communication going and once we get that TCAP session set up every time I go through and communicate

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to the other PC it's going to be with Pt. 1 1 1 1 that door

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so this is nice because if I have a PC sitting here you see one gone into this switch

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P.S. to receive three

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have a server sitting here this server could be listening

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on port 1111 and these PCs are not.

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So that's nice because I know if my traffic accidentally gets too PC to a PC 3 who cares.

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They're not listening on port.

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One one thousand one hundred eleven.

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So who cares.

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Two and Three would drop it and as long as the server gets it he guessed or ill allow the traffic to

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go through.

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Listening to the old read the traffic see what it's for.

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Whatever request that server has he will send it back out.

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Now this is pretty cool.

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Remember this is the basics we're going to get to get more detail later on so if it's not making all

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sense to you that's fine.

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For right now so the application will define whether he wants to do UDP traffic and TCAP traffic.

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And so I'm talking about the dual layer as worked with each other because the application would definitely

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tell the presentation how you know how it needs to be presented and a presentation to make sure that

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that happens the presentation will work with the session to make sure that the sessions up

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I want to see them work together.

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Really the presentation is really working with the application

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technically it's really working at the presentation after this part has been defined the session will

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start to be created through the transport system a kind of working together because the session is