$1)$ List five nonproprietary Internet applications and the application$-$layer protocols that they use.

$2)$ What information is used by a process running on one host to identify a process running on another host?

$3)$ In this problem, we consider sending real$-$time voice from Host A to Host B over a packet$-$switched network $($VoIP$).$ Host A converts analog voice to a digital $64$ kbps bit stream on the fly. Host A then groups the bits into $56-$byte packets. There is one link between Hosts A and B; its transmission rate is $10$ Mbps and its propagation delay is $10$ msec. As soon as Host A gathers a packet, it sends it to Host B$.$ As soon as Host B receives an entire packet, it converts the packet$$s bits to an analog signal. How much time elapses from the time a bit is created $($from the original analog signal at Host A$)$ until the bit is decoded $($as part of the analog signal at Host B$)?$

$4)$ Consider an application that transmits data at a steady rate $($for example, the sender generates an N$-$bit unit of data every k time units, where k is small and fixed$).$ Also, when such an application starts, it will continue running for a relatively long period of time. Answer the following questions, briefly justifying your answer:

a$.$ Would a packet$-$switched network or a circuit$-$switched network be more appropriate for this application? Why?

b$.$ Suppose that a packet$-$switched network is used and the only traffic in this network comes from such applications as described above. Furthermore, assume that the sum of the application data rates is less than the capacities of each and every link. Is some form of congestion control needed? Why?

$5)$ Review the car$-$caravan analogy in Section $1\mathrm{.}4.$ Assume a propagation speed of $100$ km$/$hour$.$

a$.$ Suppose the caravan travels $175$ km$,$ beginning in front of one tollbooth, passing through a second tollbooth, and finishing just after a third tollbooth. What is the end$-$to$-$end delay?

Ans:

b$.$ Repeat $($a$),$ now assuming that there are eight cars in the caravan instead of ten.