1. One of the main objections to layered protocols arises from the apparent overhead  copying occurs at each layer. How can copying be eliminated? 
2. Layered protocols hide all underlying details from applications. Could application software be optimized if an application knew about the underlying networks being used? Explain.
3. Should the Internet protocols include a presentation layer that specifies standards for each data type (e.g., a graphic image type, a digital music type, etc)? Why or why not?
4. Build a case that TCP/IP is moving toward a six-layer protocol architecture that includes a presentation layer. (Hint: various programs use the XDR protocol, XML, and ASN.1.)
5. Find out how a UNIX system uses the mbuf structure to make layered protocol software efficient.