Most Important Layers for CCNA

1.Transport: provides reliable or unreliable delivery and error recovery and flow control.

2. Network: provides logical addressing used by routers for path determination. Logical addressing is used to identify a host on a network (for example, by its IP  address).

3. Data Link: combines packets into bytes and bytes into frames. Each frame has a header and a trailer. A header contains the source and destination MAC address. A trailer  contains the Frame Check Sequence field, used for errors detection. The Data Link layer is divided into two sublayers: 

Logical Link Control – used for flow control and error detection and 

Media Access Control – used for hardware addressing and controlling the access method.

4. Physical: defines how to move bits from one device to another. It deals with the physical characteristics of the transmission medium, describing connectors, pins, cables,  connectors, and network interface cards.

OSI MODEL

The Open Systems Interconnection (OSI) model was created by theInternational Organization for Standardization (ISO), the world's largest developer of voluntary international standards. It is a layered model that was created to enable different networks to communicate reliably between disparate systems. The OSI model provides a framework for creating and implementing networking standards and devices and describes how network applications on different computers can communicate through the network media.

The OSI model has seven hierarchical layers. Each layer describes a different network function. The layers are:

Application, Presentation, Session, Transport, Network, Data Link, Physical  Also.

Router

Which is used to transmitting data and observe incoming signals of service provider.

Switch

Switch is used to connect number of host and it can be work an broadcast.

Network concept

Network is the exchange of information or services among individuals, groups. Then we create some small network need some devices such as computer,switch and any one host. Then host means devises in network concept. Then let's we are going to see switch, router also.

Introduction

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