A. includes all modules needed to meet any network design
B. defines flexible boundaries between modules for scalability requirements
C. clearly defines module boundaries and demarcation points to identify where traffic is
D. requires specific core， distribution， and access layer requirements to match the model

A. determine types of protocols to be supported
B. determine the environment in which the router will be used
C. select the number of WAN ports required
D. select the number of LAN ports required