NetworkingTCP/IP

The OSI Reference Model:

OSI Reference Model
As many networking tutorials do, this one begins with an
introduction to the Open Systems Interconnection (OSI)
Reference Model (OSI Model). The OSI model is a layered,
abstract description for communication and computer network
protocol design, developed as part of the Open Systems
Interconnection initiative. It is also called the OSI 7-layer model.

Purpose
The OSI model divides the functions of a protocol into a series of
layers. Each layer has the property that it only uses the functions
of the layer directly below, and only exports functionality to the
layer directly above. A system that implements protocol behavior
consisting of a series of these layers is known as a protocol stack
or simply stack. Protocol stacks can be implemented either in
hardware or software, or a mixture of both. Typically, only the
lower layers are implemented in hardware, with the higher layers
being implemented in software.

Application Layer
The application layer provides a means for the user to access
information on the network through an application. This layer is
the main interface for users to interact with the application and
therefore the network.

Presentation Layer
The presentation layer transforms data to provide a standard
interface for the application layer. Encoding, data compression,
data encryption and similar manipulation of the presentation is
done at this layer to present the data as a service or protocol
developer sees fit.

Session Layer
The session layer controls the connections (sessions) between
computers. It establishes, manages and terminates the
connections between the local and remote application.

Transport Layer
The transport layer provides transparent transfer of data between
end users, thus relieving the upper layers from transfer concerns
while providing reliable data transfer. The transport layer controls
the reliability of a given link through flow control, segmentation/
desegmentation, and error control.

Network Layer
The network layer provides the means of transferring data
sequences from a source to a destination by using one or more
networks while maintaining the quality of service requested by
the Transport layer. The Network layer performs network routing
functions, and might also perform segmentation/desegmentation,
and report delivery errors.

Data Link Layer
The data link layer provides the means to transfer data between
network entities and to detect and possibly correct errors that
may occur in the Physical layer. It arranges bits from the physical
layer into logical chunks of data, known as frames.

Physical Layer
The physical layer defines all the electrical and physical
specifications for devices. This includes the layout of pins,
voltages, and cable specifications.

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4 Comments

  1. I am curious to find out what blog platform you have been working with? I’m experiencing some small security issues with my latest site and I would like to find something more safe. Do you have any solutions?

  2. WordPress is great blog if you know how to secure it & secure you Apache for Example :
    1.FILE PERMISSIONS
    It’s wise to lock down your files and directories as much as possible. All files except wp-config.php and the wp-content directory should only be writable by you.
    CHMOD – All files to 644
    CHMOD – All directories to 755
    CHMOD – wpconfig.php to 750
    CHMOD – wp-content/ varies. If your users or plugins require to upload, edit or otherwise change anything in that folder, you will need to manually assign a proper numerical value to each file/directory. Ideally you would use 644 here too if your cirumstances allow it. Note that while your permissions are at 644, some things may not work correctly like updating plugins. If you need to modify something change it to 777, but as soon as you’re done with your modifications revert it back to 644.
    2.MYSQL DATABASE
    If you have multiple wordpress installations on the same hosting server, it’s wise to keep your database username and password unique for every wordpress installation. If a reverse engineer obtained user access to one of your websites, and your login credentials are all the same for your other websites, you may potentially experience damage on a much bigger scale. Keep your login details separate.

    3.Login Lock
    Login Lock provides a number of security enhancing features:
    Enforces strong password selection policies.
    Monitors login attempts.
    Blocks IP addresses for too many failed login attempts.
    Lets you manually unblock IP addresses at any time.
    Lets you forcibly log out all users immediately and require that they all change their passwords before logging back in.
    Lets you forcibly log out idle users after a configurable number of minutes.

    4.CREATE AN .htaccess FILE IN “wp-admin/”
    # BEGIN WordPress
    RewriteEngine On
    RewriteBase /
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . /index.php [L]
    # END WordPress
    Save the file as .htaccess and upload it to your “wp-admin/” folder

    And More
    Let me know if you need more info
    Thanks,
    Diab

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