In layered systems, PDU represents a unit of data specified in the protocol of a given layer, which consists of protocol control information and user data. PDU is a significant term related to the initial four layers of the OSI model. In Layer 1, PDU is a bit, in Layer 2 it is a frame, in Layer 3 it is a packet and in Layer 4 it is a segment. In Layer 5 and above, PDU is referred to as data.
During Reconstruction, however, the conflict over labor resulted in the sharecropping system, in which black families would rent small plots of land in return for a portion of their crop, to be given to the landowner at the end of each year.nstead of receiving wages for working an ownerâs landâand having to submit to supervision and disciplineâmost freedmen preferred to rent land for a fixed payment rather than receive wages. By the early 1870s, the system known as sharecropping had come to dominate agriculture across the cotton-planting South.
Great achievements in science and technology in ancient Africa. Despite suffering through the horrific system of slavery, sharecropping and the Jim Crow era, early African-Americans made countless contributions to science and technology (1). This lineage and culture of achievement, though, emerged at least 40,000 years ago in Africa.