Physical Layer Of Osi Model :: Networks Telecommunications

AbstractThe Physical Layer is the lowest seam of the Open Source Interconnect Model (OSI). It is the layer that deals with altogether the measurable, material entities associated with the network. At this layer it is specified how much bandwidth (Baseband or Broadband) will be used in the transmission of data on the network. This layer too includes the strong-arm topology ( corporeal lay out) of the network such as Bus, Star, Ring or Mesh. The Physical Layer includes these devices Network Interface Cards (NICs), Transceivers, Hubs, Multistation Access Units (MAUs), Repeaters and Cables. It is at this layer that frames received from the Data Link layer are converted to bits for transmission over the network media to the receiving machines Physical Layer.The Physical Layer defines all electrical and physical specifications for devices. This includes the layout of pins, voltages, and cable specifications. The major functions and services performed by the Physical Layer are e stablishment and termination of a connection to a communications medium, participation in the process whereby the communication resources are effectively shared among multiple users, modulation, or conversion between the representation of digital data in user equipment and the alike signals transmitted over a communications channel. These are signals operating over the physical cabling copper and fiber optic. (OSI Model, 2005)The Physical Layer is special compared to the otherwise layers of the model, because it is the only unity where data is physically moved across the network interface. All of the other layers perform useful functions to create messages to be sent, but they essential all be transmitted down the protocol stack to the Physical Layer, where they are actually sent out over the network.(Kozierok, 2004)Physical Layer also specifies how much of the media will be used during the data transmission referred to as Baseband or Broadband signaling. 1. Baseband Signa ling Technology in which a network uses all available signal frequencies or the entire bandwidth i.e., Most LAN technologies like Ethernet. 2. Broadband Signaling Technology in which a network uses only one frequency or a part of the entire bandwidth i.e., multiple signals can be transmitted over a media simultaneously like TV signals, where you piss various channels like CNBC, MTV, BBC, each on a different frequency and hence each occupies a part of the bandwidth. (Chandrasekaran, 2002)The Physical Layer also deals with the way a network is laid out which is referred to as the topology of a network.