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 longer packets are allowed. Using PPPoEoA with the RFC2684 VC-MUX header option is always much more efficient than the LLC option, since the ATM overhead, as mentioned earlier, is only 32 or 36 bytes (depending on whether this is without or with the ethernet FCS option in PPPoEoA) so that a 1500 byte long packet including all overheads of PPP + PPPoEoA using VC-MUX equates to a total 1500 + 36 = 1536 bytes ATM payload if the FCS is present = 32 ATM cells exactly, thus saving an entire ATM cell. With short packets, the longer the header overheads