Figure shows two OSI models side by side.  One for the source node, on the left and one for the destination node, on the right.  Between the upper three layers is a box with the words Application Data in it.  Between the transport layers are 3 boxes with the word Data in each one.  This shows how the Application Data is segmented.  Between the network layers is the Data from the transport layer with a header attached to the front if it.  Between the data link layers is the Data and Header from the network layer with a frame header attached to the front and a frame trailer attached to the end. Between the physical layers is a string of ones and zeros that are the bits that make up the frame. Below the models is a digital signal representing how the bits are sent to the destination over the media. Between each layer on the left, the source, there is an arrow pointing down to the next layer as the data flows down the OSI model. Between each layer on the right, the destination, there is an arrow pointing up to the next layer as the data flows back up the OSI model.