The International Standards Organization (ISO) developed the Open Systems Interconnection (OSI) Reference Model to define functional communications standards. This reference model is widely used by equipment manufacturers to assure their products will interoperate with products from other vendors. The OSI model describes the functions that are performed in data communications. The model architecture is seven layers those are listed below with each layer defining specific functions.
Read more »
osi layer, osi layer model, IOS model, Application Layers, osi architecture, osi layers, communication layers, osi model layers, layer model, ios layer
The Application layer provides three basic services to applications:
- It makes sure the resources needed to carry out a session are present.
- It matches the application to the appropriate communication protocol or service.
- It synchronizes the tgransmission of data between the application and its protocol.
The Application layer is used to support the following services:
- File services – store, move control access to, and retrieve files
- Print services – send data to local or network printers
- Message services – transfer text, graphics, audio, and video over a network
- Application services – process applications locally or through distributed processing
- Database services – allow a local computer to access network services
In addition, the Application layer advertises any services that are being offered and determines whether requests made by the client should be processed locally or remotely (through another network resource).
Read more »
application layer, 7 layers network, layer 7 application layer
The main function of the presentation layer is to define the data formats used to provide a number of services to the Application layer.
Included in these services the ones you need to know are:
Data encryption – coding data so that it is protected from unauthorizaed access
Data compression – reducing the number of packets required for transport
Conversions standards defined on the Presentation Layer for data conversion and formatting:
||ASCII, EBCDIC, encryption
||MIDI, MPEG, QuickTime, AVI
||GIF, JPEG, PICT, TIFF
Presentation layer, what is presentation layer, osi layer 6 presentation, presentation layer JPEG
Layer 5 of the OSI model is the Session Layer, which establishes, manages, and terminates sessions between applications.
Following are some of the communication tasks performed at this layer:
- Establishing connections
- Maintaining connections
- Synchronizing communications
- Controlling dialogues
- Terminating connections
When you create a connection, you authenticate the user account at the sending and receiving computers. Connection creation also involves determining the type of communication that will take place and the protocols that will be used by the lower layers.
Data transfer and dialogue control are used to determine which computer is making requests and which computer is making responses. This also determines whether acknowledgments are required for data transmission.
A session is a series of related connection-oriented transmissions between network nodes. Another way to look at it is that a session is the interrelated communications between two or more presentation entities, which emphasizes that the Session layer provides services to the Presentation layer.
Read more »
session layer, communication protocol layers, layers of communication protocol, communications protocols image, layer, Layer 5
The four main functions of the Transport layer are:
Segment and assemble upper-layer applications
Transport segments from one host to another host
Establish and manage end-to-end operations
In carrying out its duties, the Transport layer performs a range of support activities, including:
Maintaining data integrity through flow control techniques
Multiplexing the data from upper layer applications
Setting up and tearing down any virtual circuits established to transport the data over the network
Hiding any network-dependent information from the upper layers (which will only confuse them)
Breaking down Session layer (layer 5) datagrams into segments
Monitoring the error-free delivery of the data to its destination
Providing for general connection management and data transfer services
Providing for the reliable (but, not guaranteed) delivery of data
Read more »
frame packet segment datagram, frame packet segment, transport layer, packets frames and segments, segment frame packet, OSI Transport Layer study guide, packet datagram segment frame, frame packet datagram, segment packet frame, transport layer segment