Computer Science 4630

Spring 2001

Practice Questions for Quiz 5

True/False. Write a clearly legible T to the left of each of the following that is true, and a clearly legible F to the left of each that is false.

1. One desirable characteristic of broadcast networks such as ethernet is the ease of adding new computers to the network.

2. Process migration is common in network operating systems.

3. Network operating systems tend to be more resilient to failures than distributed operating systems.

4. Sockets are useful for communicating among different processes on one computer, but cannot be used to communicate between two different computers.

Multiple choice. Circle the letter of the best answer to each question.

5. The TCP protocol is responsible (among other things) for

(a) Routing packets through the network.

(b) Reliable delivery of packets between directly connected machines.

(c) Reliable delivery of large (multi-packet) messages between machines that are not necessarily directly connected.

(d) Dealing with differences among operating system architectures.

6. The IP protocol is primarily concerned with

(a) Routing packets through the network.

(b) Reliable delivery of packets between directly connected machines.

(c) Reliable delivery of large (multi-packet) messages between machines that are not necessarily directly connected.

(d) Dealing with differences among operating system architectures.

7. The main difference between a network operating system and a distributed operating system is that

(a) A network operating system hides the existence of many machines from the user, but a distributed operating system makes the existence of many machines visible.

(b) A distributed operating system hides the existence of many machines from the user, but a network operating system makes the existence of many machines visible.

(c) A network operating system uses a local-area network, while a distributed operating system uses a wide-area network.

(d) A distributed operating system uses a local-area network, while a network operating system uses a wide-area network.

8. A distributed file system exhibits location transparency if

(a) The name of a file indicates exactly where the file can be found.

(b) The name of a file does not indicate where the file can be found.

(c) The name of a file does not need to be changed when the location of the file changes.

(d) The name of a file is not adequate for finding the file.

9. A file server provides stateless service if

(a) The files that it provides are not stored physically on that server.

(b) The files that it provides are stored physically on that server.

(c) The server keeps track of information about open files on client machines

(d) The server does not keep track of information about open files on client machines.

10. Local caching of files is common in distributed file systems, but it has the disadvantage that

(a) Temporary inconsistencies among views of a file by different machines can result.

(b) The file system is likely to be corrupted when a computer crashes.

(c) A much higher amount of network traffic results.

(d) Caching makes file migration impossible.

11. A message is directed to a particular well-known service such as ftp or http on a remote computer by

(a) Including the name of the service in each message.

(b) Including the port number of the service in each message.

(c) Including the process id of the service daemon process in each message.

(d) Bypassing the transport layer and making direct use of the network layer.

12. Suppose that somebody replaces the system encryption executable program by one that encrypts, but that also mails a copy of the cleartext of the document to himself. The modified program is called a

(a) virus

(b) worm

(c) Trojan horse

(d) trap door

13. If a malicious process is granted temporary administrator-level access to a system,

(a) the threat is over as soon as the process is killed.

(b) the threat is over after the operating system is rebooted.

(c) the thread is over after rebooting the machine and replacing files that show a virus infection.

(d) the threat is often permanent until the entire disk is wiped clean.

14. The access matrix approach to protection has the difficulty that

(a) the matrix, if stored directly, is large and can be clumsy to manage.

(b) it is not capable of expressing complex protection requirements.

(c) deciding whether a process has access to a resource is undecidable.

(d) there is no way to express who has rights to change the access matrix itself.