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In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium.
The link layer corresponds to the OSI data link layer and may include similar functions as the physical layer, as well as some protocols of the OSI's network layer. These comparisons are based on the original seven-layer protocol model as defined in ISO 7498, rather than refinements in the internal organization of the network layer.
IEEE 802.3 is a working group and a collection of standards defining the physical layer and data link layer's media access control (MAC) of wired Ethernet.The standards are produced by the working group of Institute of Electrical and Electronics Engineers (IEEE).
This layer deals with the physical plugs, sockets, electrical/optical specifications and the required line codes. The physical layer includes the medium over which the digital signals are transmitted. It can be twisted pair, coaxial cable, optical fiber, wireless, or other transmission media.
The physical-layer specifications of the Ethernet family of computer network standards are published by the Institute of Electrical and Electronics Engineers (IEEE), which defines the electrical or optical properties and the transfer speed of the physical connection between a device and the network or between network devices.
These responsibilities encompass bit timing, signal encoding, interacting with the physical medium, and the properties of the cable, optical fiber, or wire itself. Common examples are specifications for Fast Ethernet , Gigabit Ethernet and 10 Gigabit Ethernet defined by the Institute of Electrical and Electronics Engineers (IEEE).
This article lists protocols, categorized by the nearest layer in the Open Systems Interconnection model.This list is not exclusive to only the OSI protocol family.Many of these protocols are originally based on the Internet Protocol Suite (TCP/IP) and other models and they often do not fit neatly into OSI layers.
The channel access control mechanism relies on a physical layer multiplex scheme. The most widespread multiple access method is the contention-based CSMA/CD used in Ethernet networks. This mechanism is only utilized within a network collision domain, for example, an Ethernet bus network or a hub-based star topology network.