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 4-byte Ethernet MAC FCS, which reduces the figure of 18 bytes above to 14, and (ii) by using the RFC 2684 VC-MUX option, which reduces the 10 byte LLC overhead down to 2 bytes. It turns out that this can be a very valuable efficiency improvement. Using VC-MUX instead of LLC, the ATM payload overhead would be either 32 bytes (without Ethernet FCS) or 36 bytes (with FCS). ATM AAL5 requires that an 8-byte long ‘CPCS’ trailer must always be present at the very end of the final cell (‘right justified’) of the run of ATM cells that make up