Layered Models: Knowledge Checks
6.1 What This Check Covers
This assessment checks the distinctions established by the earlier addressing and Layered Models chapters. It treats models as reasoning tools, preserves the nesting of protocol data units, and keeps each observation at the boundary it actually exercises.
The questions do not assume that every gateway is a simple router, that every packet path uses the same link framing, or that one successful diagnostic proves the entire application path.
An overhead percentage is meaningful only when the measurement boundary is named. The number changes if a calculation includes only protocol headers, the complete data-link frame, or additional on-medium timing such as a preamble and inter-frame gap.
6.2 Compare the Models
6.3 Preserve Encapsulation
6.4 Check Addressing Boundaries
6.5 Check Evidence Limits
6.6 Review and Continue
You are ready to continue when you can choose the right model for a review question, name the outermost visible PDU while preserving its contents, state the boundary of an overhead calculation, and separate local, routed, gateway, and service evidence.
Continue to Data Representation in Networks, where the bytes inside the wrappers receive units, scale, schema, version, and meaning.