Zenith Zenith The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the nadir. The zenith is the "highest" point on the celestial sphere. The word "zenith" derives from an inaccurate reading of the Arabic expression (), meaning "direction of the head" or "path above the head", by Medieval Latin scribes in the Middle Ages (during the 14th century), possibly through Old Spanish. It was reduced to 'samt'
Point-to-Point Protocol over Ethernet computer or from the DSL-AC. PPPoE is used to connect a PC or a router to a modem via an Ethernet link and it can also be used in Internet access over DSL on a telephone line in the "PPPoE over ATM" (PPPoEoA) over ADSL protocol stack. PPPoE over ATM has the highest overhead of the popular DSL delivery methods, when compared with for example PPPoA (RFC 2364). The amount of overhead added by PPPoEoA on a DSL link depends on the packet size because of (i) the absorbing effect of ATM cell-padding (discussed below), which completely cancels out additional