Network Models C01

Network Models/ Protocol.

A protocol is a collection of guidelines that controls how computers on a network communicate with one another.

Includes rules governing the following attributes of a network:

• Access method
• Allowed Physical Topologies
• Types of Cabling
• Speed of Data Transfer

Includes a number of layers, each of which completes a certain function.

Also includes two popular models:

• OSI Reference Model
• TCP/IP Model

The ideas of layering serve as the foundation for both models.

Layering

A process when a task is broken down into smaller tasks and each smaller task is solved separately.

1. Major advantages conclude:
2. Code Reuse
3. Engineering
4. Facilities Modular
5. Extensibility
6. Standardizes Interfaces
7. Simplifies Teaching and Learning

Introduction to OSI

Layered communications, computer network protocol and transmission design are described by the Open System Interconnection Reference Model (OSI Reference Model or OSI Model).

Divides the transportation of data into the following seven layers:

1. Application Layer
2. Presentation Layer
3. Session Layer
4. Transport Layer
5. Network Layer
6. Data Link Layer
7. Physical Layer
8. 

1. Physical Layer 

Specifies the physical and electrical requirements for devices.

Includes host bus adapters, network adapters, hubs, repeaters, voltages, cable specifications, and more.

Functions include:

1. Connection creation and disconnection from a communication channel.
2. Single 0s and 1s are being sent and received.
3. Conversion of bits into signals.
4. Bit synchronization.
5. Manages physical connection.
6. Bit rate control.
7. Line configuration.
8. Physical topology.
9. Transmission mode.
10. Multiplexing.
11. Switching.

2. Data Link Layer

To transfer data across network entities and to find and fix any mistakes that might happen in the physical layer, the data link layer offers the functional and procedural levels.

MAC address is used and switches function at this layer.

3. Network Layer

Utilizes one or more networks to move data from a source to a destination.

The network layer performs network routing of options.

Router operates at this layer.

4. Transport Layer

Delivers reliable data transmission services to the upper layer as well as transparent data transfer between end users.

Flow control, segmentation, and error control are used to manage the reliability of a specific link.

5. Session Layer

Controls the connection between computers.

Connects the local and remote applications, manages those connections, and terminates them.

6. Presentation Layer

Creates a context for entities in the Application Layer.

By converting from application to network format, and vice versa, it offers independence from variances in data representation.

Sometimes called the syntax layer.

7. Application Layer

The OSI layer closest to the end layer.

Function includes:

1. Identifies communication partners.
2. Determines resource availability.

Some examples of application layer implementation include:

1. HTTP (Hyper Text Protocol)
2. FTP (File Transfer Protocol)
3. SMTP (Simple Mail Transfer Protocol)

Packets and Frames

Computers send bursts of 1500 bytes of data across networks every seconds. 

TCP/IP Model

TCP/IP forms the base of present-day internet.

TCP and IP are two protocols of this model.

Initially used by APPANET

Includes 4 layers:

1. Host-to-Network
2. Internet
3. Transport
4. Application

Host to Network Layer

Bottom Layer of TCP/IP model also known as Network Interface Layer.

Connects the host to the network.

Internet Layer

Functionally comparable to the OSI model's network layer.

Accountable for sending IP packets to their intended location.

IP (Internet Protocol) is a significant protocol of this tier.

Internet Protocol (IP)

It is a connectionless protocol that is unreliable.

Datagrams are the packets used by IP to convey data.

The routes are not located by IP.

TCP

TCP is used for reliable connection services.

Functions include error control, low control and sequencing.

UPD

This protocol was used by the transport layer for unreliable connectionless services.

Useful for transferring big amounts of data quickly and in real time.

Application Layer

The OSI model's integration of the application, presentation, and session layers.

Offers a variety of services to various user apps.

Many high-level protocols are employed in a number of applications, including:

1. TELNET (Terminal Network): Used for remote login.
2. FTP (Transfer Protocol): For transfer of file from one system to another.
3. HTTP (Hyper Text Transfer Protocol): For fetching web pages on World Wide web (WWW).

Similarities between OSI and TCP/IP

Based on the idea of an autonomous protocol stack.

Up to network-oriented transport.