OSI Model and TCP/IP Model

OSI Model

                     The Open System Interconnection (OSI) Model provides an abstract description of the network communication process. International Organization for Standard (ISO) develops it to provide a road map for non-proprietary protocol development. The OSI model is just a reference model and many of OSI protocols are no longer in use. There are seven layers in OSI Model. Those are as follows:

Layer 7 -  Application

                        Performs services for the application used by the end users.

Layer 6 -  Presentation

                       Provides data format information to the application.

Layer 5 -  Session

                      Manages session between users.

Layer 4 -  Transport

                     Defines data segments and numbers them at the source, transfers the data, and reassembles the data at the destination.

Layer 3 -  Network

                    Creates and addresses packets for end-to-end delivery through intermediary devices in other network.

Layer 2 - Data Link

                    Creates and addresses frames for host-to-host delivery on the local LANs and between WAN devices.

Layer 1 - Physical

                    Transmits binary data over media between devices. Physical layer protocols define media specifications.

Network Protocols

Network Protocols are machine languages used to communicate the devices on the network. For devices to communicate on a network, they must follow different protocols that perform the many tasks to be complicated. The protocols define the followings:

Ø  The format of the message, such as how much data to put into each segment

Ø  The way intermediary devices share information about the path to the destination

Ø  The method to handle update messages between intermediary devices

Ø  The process to initiate and terminate communications between hosts
The examples of Network Protocols are as follows:

Hypertext Transfer Protocol (HTTP):  HTTP is a common protocol that controls the wa that a web server and web client interact.

Transport Protocol: Transmission Control Protocol (TCP) is the transport protocol that manages the individual conversions between a web server and web client. TCP divides the HTTP messages into smaller pieces, called segment, to be sent to the destination client. It also controls the size and rate of messages exchanged between the server and the client.

      Internet Protocol (IP): IP takes the formatted segments from TCP, encapsulates them into packets, assign the appropriate addresses, and select the best path to the destination client.

Network Access Protocols: Network access protocols describe two primary functions: data-link management and the physical transmission of data on the media. Data-link management protocols take the packets from IP and format them to be transmitted over the media. The physical media controls how the signals are sent over the media and how they are interpreted by the receiving clients.

Short Description of Networking Devices

Desktop Computer

A common computer used in a home or offices.

Laptop

A portable computer.

IP Phone

A digital telephone that carries voice at data over networks instead of analog phone lines.

LAN Media

Local-area network media, usually copper cable.

Wireless Media

Depicts local-area network wireless access.

Switch

The most common devices for interconnecting local-area networks

Router

A device that helps direct message between networks

Firewall

A device that provides security network.

Server

A common computer dedicated to provide application services to end users on a network. Server stores information to share with its clients.

The things we need to check when buying computers

- System Model and Generation
- Processor
- RAM
 - Graphic
- Network Interface Card (NIC)
- Hard Disk
 - And the most important is price.

How to check system information in computer with windows os

We need to check the system information when we buy new computers or old computers.

 To check the system

1. Press Windows + R key together.

2. Type dxdiag or msinfo32 in the run box and click ok.

Then you will see the system information about the computer.

LAN and WAN

LAN (Local Area Network)

LAN is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building and has its network equipment and interconnects locally managed.

WAN (Wide Area Network)

WAN is the network that is interconnected by two or more LANs. WAN is not only defined by a larger geographic distance, but also generally defined by leased telecommunication circuits.

Sample Network Diagram for Small Office

Access Point

Normally, the access points allow the users to connect the Internet through the Wired Network(Switch, Router, Modem, etc....).

Switches

The switch (layer 2) normally receive the packets, process it and forward data to the destination.

Routers

Normally, the router is used to connect the different networks. But there are so many router functions if detailed.

Modem

The Modem is the common networking device that turns the digital data of an electronic device into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

Internet

The Internet is the global system of interconnected computer networks that use the Internet Protocol Suite (TCP/IP) to link billions of devices worldwide.

VPN (Virtual Private Network)

I want to explain about VPN because some of my friends are confusing about VPN.

The big companies use VPN to get secured network connection to connect offices, industries, etc... from different locations through the Internet. (for example, most of the banks use VPN).

Generally, there are two types of VPN.(More than two if detailed)

1. Side-to-Side VPN.

2. Remote Access VPN.