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Are you a starter in Networking : OSI model

Well today we will discuss on the topic which is relevant to all the network engineers, It can be from Routing and Switching domain, Security domain, Service Provider domain, Collaboration domain or datacenter domain. OSI ( Open Systems interconnection model ) which actual shows the traffic flow from layer 1 till application layer. I hope you all guys know about the all layers which is described in the OSI model.

OSI model consists of the 7 layers and all layers define specific work around in the network. Lets talk about all the layers in detail. The layers are

  • Layer 1 : Physical Layer
  • Layer 2: Data Link Layer
  • Layer 3: Network Layer
  • Layer 4 : Transport Layer
  • Layer 5: Session Layer
  • Layer 6 : Presentation Layer
  • Layer 7 : Application Layer
Physical Layer : Physical Layer is called as Layer 1 in the networks and described all the physical media. The devices and the cables are in physical layers. All the ethernet cables, BNC connectors, Hub repeaters, network adapters are the part of the physical layers. When you connect the physical connectivities like connectivity to layer 2 switches, end hosts are in the Layer 1 connectivity.

Components: Hubs, Cables, Connectors, Repeaters, BNC connectors, Network adapters.

Datalink Layer : Data link layer called as Layer 2 in OSI model which includes the Switches which have frames, MAC addressing ( Devices hardware addresses ). this layer defines the framing, addressing and check summing of Ethernet packets. Data Link Layer divided in two sub layers:-Media Access Control (MAC) layer - responsible for controlling how computers in the network gain access to data and permission to transmit it. Logical Link Control (LLC) layer - control error checking and packet synchronization.  The Point-to-Point Protocol (PPP) is an example of a data link layer in the TCP/IP protocol stack

Components : Network Switches, Bridges, PPP protocol, Ethernet Technology

Network Layer : Network layer is also called as layer 3 in OSI model where routing information and layer 3 traffic includes. The devices like Router is the part of the Network Layer and various routing protocols such as RIP ( Routing information Protocol ), OSPF ( Open shortest path First ), IGRP ( Interior Gateway routing protocol ), EIGRP ( Enhanced IGRP ) , IS-IS ( Intermediate system-intermediate system ),  are the parts of the network layer

Components : Devices-router and Routing protocols except BGP are part of the Network Layer.

Transport Layer : Transport layer which is also called as layer 4 in the OSI model. Transport layer tells about the delivery of the packets in the network from source to destination. It ensures the transmission of the signals in the form of 0s and 1s in the network and acknowledge  about the delivery.

Fig 1.1 -OSI model in short


Session Layer : Session Layer is called as Layer 5 in the OSI model. this layer describes how request and reply packets are paired in a remote procedure call. The session layer or layer 5 establishes, manages and terminates the connections between the local and remote application. If we are talking about the layer 5 in the OSI model, this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol.

Presentation Layer : Presentation layer is also called as Layer 6 or the second last layer of the OSI model. The layers tells about floating point numbers can be exchanged between hosts with different math formats. The layer 5 called as presentation layer actually presentation service data units are encapsulated into session protocol data units, and passed down the TCP/IP stack.The layer 5 transforms data into the form that the application accepts.

Application layer : Application layer which is also called as 7th Layer in the OSI model is one of the most important layer where all the applications works.This layer interacts with software applications that implement a communicating component.Application-layer functions typically include identifying communication partners, determining resource availability, and synchronising communication.When determining resource availability, the application layer must decide whether sufficient network or the requested communication exists







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