CISCO (EXPLORATION 1) CHAPTER 8

OSI PHYSICAL LAYER

            The last layer of the OSI model is the Physical layer. It is where the signals are represented as bits in every frame, and also read the data that arrive, into a bit representation and pass it to the Data Link Layer for the purpose of framing the arrived data. The physical layer composed of hardware or electronic circuitry that helps to transmit and read binary representation. _­­­­­This layer functions as the physical components, data encoder, and also performs signaling, when we say encoding task this layer coverts the bits into code that is helpful in identifying the end and the beginning of the frame. In terms of signaling the physical layer will generate signals in wireless or other forms into binary representations 0 and 1, the signal will now then travel to media and it can occupy the media in an amount of time that is called bit time. Signals are characterize as amplitude, frequency, and phrase. The data transfer can be measured also in three ways by bandwidth that which measures the amount of information that can flow to another place in given time, by throughput that enables the measurement of bits transferred across the media in a given amount of time, and by goodput that measure the usable data transferred over a given period of time.

            In order to deliver and send the data to the receiver we need cabling that uses copper wires to control bits between the devices, UTP or Unshielded Twisted Pair was one of the copper media used commonly on Ethernet LAN’s and it minimize the signal degradation due to electronic noise or interface. The fiber optics on the other hand consists of jacket, aramid yarn, buffer, cladding and core. The purpose of cladding is to prevent the light loss from the fiber. Another way of transmitting data is through wireless media which compose of    wi-fi, Bluetooth, WiMax and GSM. Wi-fi is a wireless LAN technology, while Bluetooth is a kind of WPAN or Wireless Personal Area Network that communicate over distances from 1 to 100meters . The Worldwide Interoperability for Microwave Access, while the GSM enable the implementation of GPRS or General Packet Radio Services.