The physical layer is responsible for encoding and transmission of data over network communications media. It operates with data in the form of bits that are sent from the physical layer of the sending (source) device and received at the physical layer of the destination device. Ethernet, Token Ring, SCSI, hubs, repeaters, cables and connectors are standard network devices that function at the physical layer. The physical layer is also considered the domain of many hardware related network design issues such as LAN, WAN topologies and wireless technology.
Normally the application programmers and users use layer 5 protocols (application layer. Layer 3 and 4 protocols are services provided by the TCP/IP stack in operating system. Microcontroller firmware in the network adapter handles layer 2 issues. It is supported by driver software in the operating system. Non-programmable analog and digital electronics are normally in charge of the physical layer typically using an application specific integrated circuit (ASIC) chipset for each radio interface or other physical standards.
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