Answer each of the following questions briefly, i.e., in at most a few sentences. a). What is the major differences between TCP and UDP? Why an application developer might choose to run an application over UDP rather than TCP? b). According to layer structure adopted in this course, how many layers are included in the Internet (give their names too)? Give one example of application, or protocol, or device, that corresponding to each layer c). List at least three services offered by TCP d). Suppose a web server has 3 ongoing TCP connections. How many server-side sockets are used? How many server-side port numbers are used? e). What is the standard size of a TCP header? What is the standard size of a UDP header? What fields exist in both TCP header and UDP header? f