Ethernet physical layer
The classic Ethernet can be operated on coaxial cables, as well as on twisted lines or on optical fibers. The two coaxial cable variants, the classic thick coaxial cable (Yellow Cable) and the thin RG-58 cable, are specified as transmission media in the IEEE 802.3 10Base-5 and IEEE 802.3 10Base-2 standards. In Ethernet networks with higher speeds - Fast Ethernet, Gigabit Ethernet and 10 Gigabit Ethernet - only TP cables and optical fibers are specified.
The Ethernet variants with TP cables and fiber optics have essentially the same access techniques as the classic 10 Mbit/s Ethernet, but they differ in the Attachment Unit Interface( AUI).
In classic Ethernet, the physical layer is divided into three parts: the physical layer signaling( PLS) sublayer, the access unit interface (AUI), and the medium attachment unit ( MAU). The Physical Layer Signalling supports the exchange of data between two MAC layers. It is used to control the access procedure and signals collisions or the free state on the transmission medium. The functionality of physical layer signaling is implemented in the medium attachment unit (MAU). The Medium Attachment Unit (MAU) has a Physical Media Attachment( PMA) and Media Dependent Interface( MDI) adapted to the changed medium.
The Access Unit Interface corresponds to the transceiver cable with which the transceiver, formed by the Medium Attachment Unit, is connected to the physical layer signaling. The Medium Attachment Unit itself makes it possible to systematically qualify encodings, drop cables, transceivers, voltages, frequencies, data plugs, etc.
In the other Ethernet variants, the physical layer is subdivided into further layers. For example, Fast Ethernet and the faster variants have the Reconciliation Sublayer, the Physical Coding Sublayer( PCS), the Physical Media Attachment (PMA) and the Physical Medium Dependent( PMD). Similar sublayers use Gigabit Ethernet and 10 Gigabit Ethernet.