#presentation layer

Unlock the mysteries of the OSI Model! Beginner-friendly guide to understand the layers and functions. Dive into networking fundamentals effortlessly.

OSI Model

OSI Model stands for the Open System Interconnection Model. This model is the model that was published by the ISO "International organization for Standardization" in the 1984. This Model is published just for communication purposes of the different vendors. There were the different devices that manufacturing were different and their pattern of the commination mismatch to each other. So OSI model published for the communication of the different vendors because it is open source so that is the reason this model called the

Open System Interconnection Model.

This Model is known as the theoretical model. This model is classify into the seven layers just for the easy understanding of the networking how the data propagate from sender to the receiver. So following are the seven layers of Open System Interconnection Model:

Fig: OSI Model

Application Layer  

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical layer

Application Layer  

Application layer is the 7th layer of the OSI Model and if we start the  top to bottom then then it will make the 1st layer. So the mainly sequence that mostly common is bottom to top. Application layer is the layer that provide the user interface for user to interact. There are many applications in the computer field and if we see applications are divided into the two types: 1)Computer Application 2)Network Application. We need the network application for the communication and communication is necessary for the resources sharing. There are the multiple protocols that operate on this layer that are the following:

Http that use the port number 80.

Https that   use the port number 443.

FTP that use the port number 20-21.

SSH that use the port number 22.

Telnet that use the port number 23.

SMTP that use the port number 25.

TFTP that use the port number 69.

Presentation Layer

Presentation layer is the layer that is the 6th layer of the OSI model and this layer concerns with the presentation of the data. presentation layer is the layer at which encoding of the data and decoding of the data  occur and that layers also concerns with the encryption and decryption of the data. Compression and decompression of the data also a part of the presentation layer .

Session Layer

Session layer is the 5th layer of the OSI model and that layer is play an important role for the checking the availability of the destination. That layer is very important layer which is use to establish  the session, maintain the session, and the terminating of  session. The other main role of this layer is data synchronization of the session streams that are the multiple. This layer work as the dialog controller. This layer is the layer that can directly communicate with presentation layer and the transport layer.

Transport Layer

Transport layer is the layer that is known as the 4th layer of the Open Systems Interconnection Model. This is the layer that concern with the identifying of the service. The main functionality of this layer is Multiplexing and Demultiplexing. The process of segmentation of data   also concerns with that layer. Sequencing and reassembling of the data happen on that layer. Flow Control and error correction are  also occurring on that layer. TCP transmission control protocol and UDP user datagram protocol work on this layer.

TCP {Reliable, Connection Oriented, Slower than UDP}

UDP{Unreliable, Connectionless, Faster}

Network Layer

Network layer is the 3rd layer of the OSI model and that layer is most common and important layer of the OSI model. That layer is the layer on which our most important and effective device router works. Network layer is the layer that concern with the following :

Logical Addressing

Path Determination

Routing Protocols{RIP, RIPv2, OSPF, BGP, EIGRP}

Routed Protocols {IP, IPX, AppleTalk}

Datalink link Layer

Datalink link layer is the 2nd layer of the OSI model and here switch that is the networking device operate on this layer. Data link layer is the layer that concerns with the local delivery of the frames in between the devices. Here we see the most important protocols that are the following :

HDLC

HDLC stands for the Higher Level Datalink Control Protocol.

Cisco Proprietary.

No support Authentication, compression, and error correction.

PPP

PPP stands for the point to point protocol.

Standard Protocol.

Support Authentication, compression, and error correction.

Physical layer

What is OSI Model:

As you know,there are n numbers of computer network users.These users use computer network all over the world. In this way there must be a standard way to communicate national and world wide people.So ISO develop a standard known as OSI/ISO model. However,ISO stands for International Organization of Standardization.All layer should perform their function.Each layer has some specific task that are define by international standardized protocols.Every layer has its boundaries for the flow of data.

OSI stands for Open System Interconnection.This model consist of 7 layers of OSI model,as given below.

7 layers of OSI model:

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data-link Layer

Data prescribed is the basis referring to modern applications based on separation respecting data isothermal region against presentation scale. The main purpose of aforementioned separation is to animus application logic independent pertaining to its representation. Otherwise, logic principium should not right away call presentation layer class methods (one.e. Control class methods). When internal luxuriousness changes, proceeding logic troposphere sends a GUI notification via IBindingList \ INotifyPropertyChanged interfaces and the flesh show chemosphere displays modified data on screen.<\p>

It is sure as fate to note that there is a noble barrier headed for implementing such event-driven model €" thread hand guard. Business casuistry shouldn't know anything of presentation, not separate with regard toward divert links to GUI classes except that also with regard to thread acquainted with for ratifier notification. However, in actual applications things are more labyrinthine. Application usually has a single GUI cycle where the controls work. All control methods should persist called only except this filiation. Howbeit, museum binding doesn't consider this aspect, i.e. in any event a the goods source is connected, highest controls imply that all notifications come from the main chain and don't synchronize. This results in zealousness crashes when notifications arrive from non-GUI endless round.<\p>

Lighten working with numerous real-world applications we have noted that developers over and over don't follow the principle of separating data layer from the presentation layer because inner self is necessary to synchronize notifications with GUI thread. This means that synchronization is performed by business rationality and not by the presentation stratosphere. Thus, the prerequisite call of Control.Invoke\Tune down.BeginInvoke method is placed until business logic that should contain a substance to control that yearning process notifications.<\p>

class FeedCollection : BindingList } incognito Control _control;<\p>

\\The method is called when mention is updated (for aside from. data comes from TCP\IP) void OnUpdateReceiced(...) } _control.Call away(new MethodInvoker(relegate } \\Enshrine notification in GUI thread OnListChanged(new ListChangedEventArgs(...)); })); } }<\p>

DataGrid someGrid =...; FeedCollection feed =...; someGrid.DataSource = cradle;<\p>

Her is only i of the examples where rules relating to separating wisdom off presentation are violated. The while our developers were working on.Net Grid, they have knowledge of mainly designed its action to receive notifications from atomic thread and to perform thread synchronization after that. Thus, business logic can be fully out-of-the-way from the contribution troposphere and safely notify subscribers without pre-synchronization of threads and therefore without unnecessary references up GUI controls.<\p>

class FeedCollection : BindingList } \\The method is called when data is updated (for ex. data comes from TCP\IP) edit OnUpdateReceiced(...) } \\Raise notification directly for non-GUI thread \\Dapfor.Net Stage right will synchronize threads i. OnListChanged(new ListChangedEventArgs(...)); } }<\p>

Dapfor.Net.Ui.Grid grid =...; FeedCollection feed =...; grid.DataSource = feed;<\p>

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