Networking Fundamentals

Network Models

There are two network models called, TCP/IP and OSI (Open System Interconnection).

TCP/IP model is known as a practical model while, OSI model is more likely to be theoretical. Four layers in TCP/IP model and the seven layers in OSI model will be discussed in the upcoming chapter.

TCP/IP Model

Network Access layer, Internet layer, Transport layer and Application layer are the four layers in this model. When sending, the sender can see application layer at first. At the other end, the receiver, receives the network access layer first.

Application Layer:

This layer provides network services to the applications. HTTP/HTTPS/FTP....are some of the protocols used in this layer.

Transport Layer:

This determines the transmission of data. UDP/TCP are the protocols used in this layer.

Internet Layer:

This layer handles the delivery of data and also, forms the data packets with source and destination IP's along with data. IP is the protocol used in this layer.

Network Access Layer:

Establishes the physical connection at transmission level and also, maps the IP addresses with MAC addresses vice versa.

OSI (Open System Interconnection)

Physical layer, Data link layer, Network layer, Transport layer, Session layer, Presentation layer and Application layer are the seven layers in this model.

Physical Layer:

This layer uses bit as its data unit. This is the interface between the network medium and the devices.

Data Link Layer:

This layer uses frames as its data unit. Since this layer has error detection codes, detecting errors is done by data link layer. Packets into bits and bits into packets, conversion is done at this layer.

Network Layer:

Packets are the data unit. Routing is done at this layer. Routing means determining the most efficient path to send data from source to a given destination.

Transport Layer:

This layer uses segments as its data unit. Error handling part is done at this layer. Unlike in TCP/IP model, in this model, transport layer uses only TCP as the protocol (is not using UDP). Therefore, always provides acknowledgment of data transmission.

Session Layer:

Uses data. This layer manages who can transmit data and for how long. Basically it is a virtual boundary between certain devices. Therefore, it is responsible for identifying the devices in a particular session.

Presentation Layer:

Responsible for protocol conversions, character conversions, data encryption as well as decryption etc.

Application Layer:

This layer is what user sees or does This layer interacts with software applications that implement a communicating component.