computer networks

i need a pdf file 

pdf document should consists of name ,id,name of the institution mail

 questions are:

1.using the layer models in figure 2.15 .describle the ordering and delivery of a pizza ,indicating the interacation at each level.

2.why is UDP needed ?why cant a user program directly access ?

3.find the period of the function f(t) = ( 10 cost)2

4.list the major disadvantages with the layered approach to protocols

5.a signal has a fundamental frequency of 1000Hz.what is its period?