Subject is data communication and computer networking

a. Suppose we have Marketing, Accounts and HR departments and all these departments are connected locally that is they are in one local area network. Now we want that HR department users can not directly access data of Accounts and Marketing departments and similary Marketing department user can not directly access HR and Accounts departments data. So in this case what will be the simple and feasible solution and also write the names and role of the hardware devices use in the solution. b. Why Cyclic Redundancy Check (CRC) technique is used in the world of networking? Also show the CRC calculation process at the sender end and the verification process at the receiver end for the given data 10111010 by using Generator Ploynomial X4+X3+1.

Answer it wit details and examples also