n the network topology on the left, click one of the envelopes on an intermediary device and investigate what is inside. Over the course of your CCNA studies, you will learn the meaning of most everything inside these envelopes. For now, see if you can answer the following questions:

o Under the OSI Model tab, how many In Layers and Out Layers have information?

o Under the Inbound PDU Details and Outbound PDU Details tabs$,$ what are the headings of the main sections?

o Click back and forth between the Inbound PDU Details and Outbound PDU Details tabs$.$ Do you see information changing? If so$,$ what?