Nadir Nadir The nadir (, ; from / ALA-LC: "naẓīr", meaning "counterpart") is the direction pointing directly "below" a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there. Since the concept of "being below" is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location. The direction opposite the nadir is the zenith. Nadir is
Point-to-Point Protocol over Ethernet PPPoE payload "across the Ethernet link to a router" (or PPPoE-speaking single PC), PPP + PPPoE contributes an additional overhead of 8 bytes = 2 (PPP) + 6 (PPPoE) included within the payload of each Ethernet frame. This added overhead can mean that a reduced maximum length limit (so-called "‘MTU’" or "‘MRU’") of 1500 - 8 = 1492 bytes is imposed on (for example) IP packets sent or received, as opposed to the usual 1500-byte Ethernet frame payload length limit which applies to standard Ethernet networks. Some devices support RFC 4638, which allows negotiation for the use of non-standard Ethernet