As the data packet moves from the upper to the lower layers, headers are _________________.
As the data packet moves from the upper to the lower layers, headers are Added.
Physical, data link and network layers are network support layers and session, presentation and application layers are user support layers. A Service Access Point (SAP) is an identifying label for network endpoints used in Open Systems Interconnection (OSI) networking. The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. ... This computer networking article is a stub. You can help Wikipedia by expanding it.
The Transport Layer. The Transport layer is the next layer and is typically related directly with the same named layer in the OSI model. Functions include message segmentation, acknowledgement, traffic control, session multiplexing, error detection and correction (resends), and message reordering.