Answer:
Segment.
Explanation:
In Computer Networking, encapsulation can be defined as the process of adding a header to a data unit received by a lower layer protocol from a higher layer protocol during data transmission. This ultimately implies that, the header (segment) of a higher layer protocol such as an application layer, is the data of a lower layer such as a transportation layer in the Transmission Control Protocol and Internet Protocol (TCP/IP).
The TCP/IP model comprises of four (4) layers;
1. Application layer: this is the fourth layer of the TCP/IP model. Here, the data unit is encapsulated into segments and sent to the transport layer.
2. Transport layer (layer 3): it receives the segment and encapsulates it into packets and sends to the internet layer.
3. Internet layer (layer 2): packets are encapsulated into frames.
4. Network layer (layer 1): frames are then converted into bits and sent across the network (LAN).
<em>Hence, the data unit encapsulated inside a packet is known as segment, which is typically referred to as packet segmentation. </em>
Additionally, these data, segments, packets, frames and bits transmitted across various layers are known as protocol data units (PDUs).
