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 PPPoE/LLC over PPPoA is 50% extra data sent. PPPoEoA + VC-MUX would be fine though: with 32 or 36 byte overhead, our IP packet still fits in two cells. In all cases the most efficient option for ATM-based ADSL internet access is to choose PPPoA (RFC2364) VC-MUX. However if PPPoEoA is required, then the best choice is always to use VC-MUX (as opposed to LLC) with no Ethernet FCS, giving an ATM payload overhead of 32 bytes = 2 bytes (for PPP) + 6 (for PPPoE) + 14 (Ethernet MAC, no FCS) + 2 (RFC 2684 VC-MUX) + 8 (AAL5