NETWORKING concepts - Cyber Warriors

what is OSI model

The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers.

what is tcp/ip model

protocols and services run on each and every layers

Physical Layer – They Physical Layer converts data into streams of electric or analog pulses- commonly referred to as “1’s and 0’s.” Data is broke down into simple electric pulses, and rebuilt at the receiving end.

Data Link Layer – The Data Link layer provides an interface with the network adapter, and can also perform basic error checking. It also maintains logical links for subnets, so that subnets can communicate with other parts of the network without problem.

Network Layer – Much like the Transport Layer of the TCP/IP model, the Network Layer simply supports logical addressing and routing. The IP protocol operates on the Network Layer.

Transport Layer – Since we left out the error and flow control in the Network Layer, we introduce it into the Transport Layer. The Transport Layer is responsible for keeping a reliable end-to-end connection for the network.

Session Layer – The Session Layer establishes sessions between applications on a network. This may be useful for network monitoring, using a login system, and reporting. The Session Layer is actually not used a great deal over networks, although it does still serve good use in streaming video and audio, or web conferencing.

Presentation Layer – The Presentation Layer translates data into a standard format, while also being able to provide encryption and data compression. Encryption or data compression does not have to be done at the Presentation Layer, although it is commonly performed in this layer.

Application Layer – The Application Layer provides a network interface for applications and supports network applications. This is where many protocols such as FTP, SMTP, POP3, and many others operate. Telnet can be used at this layer to send a ping request- if it is successful, it means that each layer of the OSI model should be functioning properly.