Physical Layer
The Physical layer provides the electrical and mechanical interface to the network medium. This layer gives the data link layer its ability to transport a steam of serial data bits between two communication systems, it conveys the bits that move along with the cable. The Physical layer consists of simply the wire or media by which the network signal is conducted. Physical layer include hardware wire, plugs and sockets, signals generators etc.
This layer has no understanding of the meaning of the bits, but also deals with the electrical and mechanical characteristics of the signals and signaling methods. The Physical layer cover-
1. Physical characteristic of media and interface
The Physical layer defines the characteristics of the interface between the devices and the transmission medium. It also defines the types of transmission medium.
2. Representation of bits
The Physical layer data consists of a stream of bits without any interpretation. To be transmitted bit must be encoded into signal –electrical or optical. The physical layer defines the type of encoding.
3. Data rate
It is a transmission rate. The number of bits sends each second is also defined by the physical layer.
4. Synchronization of bits
The sender and the receiver must be synchronizing at the bits level. In the other word we can say that the sender and the receiver clock must be synchronized.
5. Line configuration
In point to point configuration two devices are connected together through a dedicated link.ln a multipoint configuration a line is shared between several devices.
6. Physical Topology
The Physical topology defines how devices are connected to make a network. Devices can be connected using mesh, bus, ring, star topology.
Transmission Mode-
The Physical layer also defines the direction of transmission between two devices simplex, half duplex and full duplex.
In the simplex mode, only one device can send and the other devices can receive. The simplex mode is one way communication .In the half duplex mode two devices can send and receive but not at the same time. In the full duplex mode two devices can send and receive at the same time.
We find the Physical layer does two things-it send bits and receive bits. The Physical layer communicates directly with the various type of actual communication media. This layer is also identifying the interface between the Data terminal equipment (DTE) and Data communication equipment (DCE).
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