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 running directly over Ethernet or other IEEE 802 networks or over Ethernet bridged over ATM, in order to distinguish it from PPPoEoA (PPPoE over ATM), which is PPPoE running over an ATM virtual circuit using RFC 2684 and SNAP encapsulation of PPPoE. (PPPoEoA is not the same as Point-to-Point Protocol over ATM (PPPoA), which doesn't use SNAP). According to a Cisco document "PPPoEoE is a variant of PPPoE where the Layer 2 transport protocol is now Ethernet or 802.1q VLAN instead of ATM. This encapsulation method is generally found in Metro Ethernet or Ethernet digital subscriber line access multiplexer