Understanding the network.pdf - Back to Home

The transport layer as a whole represents the gateway of the host
level communication process. The transport bridges the internal data
communication process and the network data communication process.
This is evident in the fact that the process of encapsulating the
application layer data into and out of wrappers occurs at this level.
Figure 2.14 shows the relationship between the layers and the
wrapping of the data.
Figure 2.14. ULP data handling.
This wrapping of ULP data is an outbound/inbound process. The ULP
data follows this passthrough process on leaving the source host and
then follows the reverse on its arrival at the destination host:
1. Data stream is handed to the transport layer.
2. ULP data is wrapped in the transport packet, which consists of a
header and the data.
3. The transport packet is handed to the network layer.
4. At the network layer, the transport packet is wrapped in the
network packet, which consists of the network header and the
transport packet.