Python Programming

Physical layer is responsible for transmission of bits from one node to the next node.

Physical layer of OSI model

Physical layer is responsible for following:-

1. Physical layer is responsible for providing the interface between the device on which we are working and the transmission medium which we are using for data transfer.
2. Physical layer is responsible for representation of bits i.e. 0 and 1 in the form of signals. The bits 0 and 1 can not transfer though the physical medium which we are using. There is a need to convert these bits into the form of signal so that can be transferred.
3. Physical layer also define the data rate also i.e. number of bits transferred per second.
4. Physical layer is also responsible for Synchronization of bits at the bit level means to transfer the data clock pulse of the sender and receiver must be same.
5. Physical layer is responsible for line configuration. The line configuration will decide that whether there is a dedicated line between two systems or systems will share the transmission medium.
6. Physical layer is responsible for the physical topology. Physical topology means how the systems are connected to each other i.e. whether they are in ring topology, bus topology etc.
7. Physical layer is also responsible transmission mode. Transmission mode means the direction of transmission. There are three transmission mode i.e. simplex (there is a transmission in one direction only), half-duplex (the is a transmission in both directions but not simultaneously) and full- duplex (there is a transmission in both the direction and simultaneously). 
8. The Physical Layer receives data from the data link Layer, and transmits it to the wire. The physical layer controls the electrical and mechanical functions related to the transmission and receipt of a communications signal. It also manages the encoding and decoding of data contained within the modulated signal.
   
   
   Note that for two devices to communicate, they must beconnected to the same type of physical medium (wiring). 802.3 Ethernet to 802.3 Ethernet, FDDI to FDDI, serial to serial etc. Two end stations using different protocols can only communicate through a multi-protocol bridge or a router.
   The physical layer is responsible for:
   1. Communication with the data link layer above it.
   2. Fragmentation of data into frames
   3. Reassembly of frames into data link Protocol Data Units.
   4. Transmission to the physical media
   5. Receiving from the physical media
   It should be noted that in most modern network interface adaptors, the physical and data link functions are performed by the adaptor.
   Example Physical Protocols
   • CSMA/CD - Carrier Sense Multiple Access / Collision Detect
   • CSMA/CA - Carrier Sense Multiple Access / Collision Avoid
   • FDMA - Frequency Division Multiple Access
   • MSK - Minimum Shift Keying
   • GFMSK - Gaussian-Fitered Minimum Shift Keying
   • TDMA - Time Division Multiple Access
   • CDMA - Code Division Multiple Access
   • B8ZS - Binary 8 Zero Substitution
   • 2B1Q - 2 Binary 1 Quaternary
   • PCM - Pulse Code Modulation
   • QAM - Quadrature Amplitude Modulation
   • PSK - Phase Shift Keying
   SONET - Synchronous Optical NETworking