In modern packet-switched networks, the source host segments long,application-layer messages (for example, an image or a music file) into smaller packets and sends the packets into the network. The receiver then reassembles the packets back into the original message. We refer to this process as message segmentation. Figure 1.28 illustrates the end-to-end transport of a message with and without message segmentation. Consider a message that is 7.5 · 106 bits long that is to be sent from source to destination in Figure 1.28. Suppose each link in the figure is 1.5 Mbps. Ignore propagation,queuing, and processing delays.
