Final answer:
Data is broken up at the Transport layer of the OSI model. The Transport layer is responsible for the segmentation or fragmentation of data into packets for transmission, ensuring error-free and in-sequence delivery.
Step-by-step explanation:
On a sending machine, data gets broken up at the Transport layer of the OSI seven layer model. The OSI model, which stands for Open Systems Interconnection model, is a conceptual framework used to understand and standardize the functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is to allow different systems to communicate using standard protocols.
In the OSI model, the Transport layer is responsible for breaking down data into smaller packets that can be transmitted over the network and then reassembled into the original data at the destination. The Transport layer ensures that the packets arrive in sequence and without errors. The process of breaking data down into packets is known as segmentation in the case of TCP (Transmission Control Protocol) or fragmentation in the case of UDP (User Datagram Protocol).