Self Test

The following questions will help you measure your understanding of the material presented in this chapter. Read all the choices carefully because there might be more than one correct answer. Choose all correct answers for each question.

1.	Which of the layers is responsible for establishing end-to-end communication between two machines? Network layer Transport layer Data link layer Application layer
2.	What other terms are used for an Ethernet address of a machine? Hardware address Physical address MAC Internet address
3.	Which of the following protocols provide reliable end-to-end communication? TCP UDP IP RELIABLE
4.	At which TCP/IP layer does a router operate? Physical Network interface Internet Transport
5.	Which of the following statements are true about a MAC address? A computer can have only one MAC address. When an Ethernet card of a computer is replaced, its MAC address changes. A MAC address is a 32-bit number. An IP datagram contains the source and destination MAC addresses in its header.
6.	Which of the following files would you look into to find out the IP address associated with a host name on your machine? /etc/hostname.<interface> /etc/hostname /etc/nodename /etc/inet/hosts
7.	Which of the following devices forwards data packets called IP datagrams from one network to another? Router Bridge Switch Hub
8.	An Internet service—for example, rlogin—was started when you booted your Solaris 10 system. After the boot, you disabled the service with the svcadm command. Now when you reboot the machine, you will need to manually enable the service by using the svcadm command. True False
9.	Which command would you use to check whether a remote host is reachable? ping snoop ifconfig netstat
10.	Which command would you use to check what kind of information is being exchanged between two systems? ping snoop ifconfig netstat

Answers

1.	þ. B. The transport layer provides protocols to establish end-to-end communication by defining port number to uniquely identify an application on a machine. ý A is incorrect because the network layer defines the IP address of a machine but not the port number; therefore, you cannot uniquely identify the communicating application on the machine. C is incorrect because the data link layer defines hardware addresses; it's not even aware of IP addresses. D is incorrect because the application layer is responsible for specifying the application functionality and does not concern itself with establishing connections.
2.	þ A, B, and C. A machine on a LAN is uniquely identified by its Media Access (MAC) address, which is called a physical address or a hardware address. A MAC address on an Ethernet LAN is also called an Ethernet address. ý D is incorrect because an Internet address is an IP address, not the MAC address.
3.	þ A. TCP offers reliable end-to-end communication by creating a virtual connection between the two communicating machines and by providing a mechanism for acknowledgment and retransmission. ý B is incorrect because UDP provides only ports but nothing for reliability or creating virtual connection. C is incorrect because IP offers unreliable data delivery service. Furthermore, it cannot even identify the correct communication application on the machine and it takes time to calculate parity information. D is incorrect because there is no protocol called RELIABLE.
4.	þ C. A router deals with IP addresses, so it has to operate at the Internet layer, because that's where IP addresses are defined. ý A and B are incorrect because the physical layer and the network interface layer are not aware of IP addresses. D is incorrect because a router does not need to know what is in the data portion of an IP datagram.
5.	þ B. A MAC address is burned into an Ethernet card, which is a NIC for an Ethernet network. ý A is incorrect because a computer can have more than one interface card and each interface card has its own MAC address. However, remember that multiple interfaces on a SPARC system have the same MAC address because it is derived from the NVRAM chip. C is incorrect because an Ethernet address is a 48-bit number, not a 32-bit number. An IP address (IPv4) is a 32-bit number. D is incorrect because a MAC source and a destination MAC address are in the frame header and IP addresses are in the IP datagram header.
6.	þ D. An entry in the /etc/inet/hosts file on your system contains the following information about a host name associated with your machine: the host name, the corresponding IP address, and an alias for the host name, if any. ý A is incorrect because the /etc/hostname.<interface> file contains only the host name associated with the interface specified by <interface>. B is incorrect because there is no such file as /etc/hostname, and C is incorrect because the /etc/nodename contains only the node name of your machine.
7.	þ A. A router receives a frame from one network, retrieves the IP datagram from the frame, encapsulate it in another frame, and delivers the frame on the other network. ý B is incorrect because a bridge is not aware of IP addresses; therefore, it cannot deliver data packets across networks. C is incorrect because in its original functionality, a switch is not aware of IP addresses; therefore, it can only deliver frames over the same network, not IP datagrams across networks. However, layer-3 switches are available from some vendors that have the functionality of a router. D is incorrect because a hub operates only in the physical layer and simply provides electrical connection between different physical ports. It's not aware of hardware addresses or IP addresses.
8.	þ A. Once you enable or disable an SMF service, the status change information goes into a configuration repository and persists across multiple boots. ý B is incorrect because, according to the configuration repository, the rlogin service is disabled; therefore, it will not be automatically started at boot time until you change its status by enabling it again.
9.	þ A. You use the ping command to test the reachability of another host on the same network or on another network. ý B is incorrect because the snoop command is used to view the packet headers at various layer levels coming in or going out of an interface. C is incorrect because the ifconfig command is used to configure the network interfaces. D is incorrect because the netstat command is used to view the packet statistics on inbound/outbound connections.
10.	þ B. The snoop command is used to view the packet headers at various layer levels coming in or going out of an interface. ý A is incorrect because you use the ping command to test the reachability of another host on the same network or on another network. C is incorrect because the ifconfig command is used to configure the network interfaces. D is incorrect because the netstat command is used to view the packet statistics on inbound/outbound connections.