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Layer One of OSI ModelPhysical Layer
|by Deepak Chandrasekaran|
In the last article I explained in depth about the OSI and TCP/IP Models. Now in this layered protocol structure, we have to see what each layer does. Basically in the OSI Model, we have two layers:
1) Upper Layer – Comprising of Sessions, Presentation and Applications Layers.
Devices in this layer copy frames or data from one network to another, depending upon the device in operation like a Hub or a Repeater. This layer basically deals with the network components that you can touch. Any device or protocol that operates at the Physical Layer deals with the physical components of the network. It deals with medium like Copper Wires, UTP cables, Coaxial cables or Fiber Optic Cables. When a protocol at the physical layer receives information from the upper layers, it translates all the data into signals that can be transmitted on a transmission medium. This is called Signal Encoding. That is the ones and zeros of data are converted into electrical on –off’s by the physical layer protocols.
Physical Layer also specifies how much of the media will be used during the data transmission.
1. Base band Signaling: Technology in which a network uses all available signal frequencies or the entire bandwidth. Eg: Most LAN technologies like Ethernet.
Physical layer also specifies the topology or layout of the transmission media. There are four possible kinds of topologies:
Devices used in the Physical Layer are
Implementations in the Physical Layer :
Remember that the physical layer is the same for TCP/IP Model so all the above applies to TCP/IP Model too. I will cover all the subtopics like the devices, topologies, implementations and transmission media in the forthcoming articles. In the next article, lets have a look at the Data Link Layer and also some part of the Network Layer.
|More by : Deepak Chandrasekaran|
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08/20/2013 17:50 PM
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