Business Data Communications and Networking 7th Edition Test Bank - Chapter 07 (400 Level Course)

Business Data Communications and Networking 7th Edition Test Bank - Chapter 07 (400 Level Course)

TRUE/FALSE

The following are possible True/False questions for tests. The statement is given and the answer is provided in square brackets. The level of difficulty (easy, moderate, or difficult) and the page number(s) relevant to the topic are also furnished.

1. A backbone network is a high-speed network that connects many networks. [True; p. 204]
Easy

2. A backbone network that connects many backbone networks spanning several buildings at a single location is often called an Internet backbone. [False, it is called a campus network; p. 204]
Moderate

3. One basic component of a backbone network is the hardware device that connects other networks to the backbone. [True, p. 204]
Easy

4. The cable to connect BNs is usually twisted pair. [False, it is generally fiber optic to provide higher data rates; p. 204]
Moderate

5. A hardware device that operates at the application layer is a bridge. [False, a bridge operates at the data link layer; p. 205]
Moderate

6. Bridges can only connect the same type of cable. [False, they can connect the same or different types of cable; p. 205]
Easy

7. Bridges use network layer address to forward packets between network segments. [False, they use data link layer addresses; p. 205]
Moderate

8. Routers operate at the application layer. [False, they operate at the network layer; p. 205]
Easy

9. Routers connect two or more network segments that use the same or different data link protocols, but the same network protocol. [True; p. 205]
Moderate

10. One advantage of a router over a bridge is that it can choose the “best” route between networks when there is a choice. [True; p. 206]
Moderate

11. Gateways are simpler than routers. [False, they are more complex; p. 207]
Easy

12. Gateways connect two or more networks that use the same or different data link and the same or different network protocols. [True; p. 207]
Moderate

13. One of the least common uses of gateways is to enable LANs that use TCP/IP and Ethernet to communicate with IBM mainframes that use SNA. [False, it is one of the most common uses of gateways; p. 207]
Moderate

14. The terms for hardware devices, such as routers and bridges, are interchangeable among vendors. [False, there is a great deal of confusion about the terminology for internetworking hardware devices; p. 208]
Moderate

15. Brouters are devices that combine the functions of backbones and routers. [False, they combine the functions of bridges and routers; p. 208]
Moderate

16. Bridged backbones are switches that move packets based on data link layer addresses. [False, they are bridges; p. 208]
Moderate

17. The distribution layer of a backbone connects the LANs together. [True; p. 209]
Easy

18. The most common form of routed backbone uses a ring topology. [False, it uses a bus topology; p. 210]
Moderate

19. The primary advantage of a routed backbone is that it clearly segments each part of the network connected to the backbone because each segment has its own subnet addresses that can be managed separately. [True; p. 210]
Moderate

20. One advantage of a routed backbone is that is requires little management. [False, it requires a lot of management; p. 210]
Easy

21. A bridged backbone tends to be more expensive than routed backbones. [False, they are cheaper; p. 212]
Easy

22. A collapsed backbone uses a bus topology. [False, they use a star topology; p. 213]
Easy

23. A room that contains a rack of equipment for a rack-based collapsed backbone is the main distribution facility (MDF) or central distribution facility (CDF). [True; p. 216]
Easy

24. A key advantage of a chassis-based collapsed backbone is its flexibility. [True; p. 216]
Easy

25. A VLAN network assigns computers to LAN segments by hardware. [False, they are assigned by software; p. 218]
Easy

26. FDDI (fiber distributed data interface) is a ring network that operates at 100 Mbps over a fiber optic cable. [True; p. 224]
Easy

27. FDDI uses contention approach media access control with a token passing system. [False, it is a controlled access media access control; p. 225]
Moderate

28. With respect to high-speed networks, the acronym, ATM, refers to Automatic Teller Machines. [False, it refers to Asynchronous Transfer Mode; p. 225]
Moderate

29. ATM uses variable length cells. [False, they are fixed-length cells; p. 226]
Easy

30. ATM provides no error detection/correction on the user data except at the source and destination. [True; p. 226]
Difficult

31. Instead of using permanent data link or network layer addresses, ATM defines a virtual channel, or virtual circuit, (VC) instead between each sender and receiver. [True; p. 226]
Moderate

32. Translating from Ethernet into ATM (and vice versa) is very easy. [False, it is not simple; p. 228]
Easy
MULTIPLE CHOICE

The following are possible multiple-choice questions for tests. The question is posed and the answer is provided under the choices. The level of difficulty (easy, moderate, difficult) and page number(s) relevant to the topic are also furnished.

1. The shift to ___________ is the driving force behind enterprise networking.
a. an industrial production society
b. an atomic energy-based economy
c. a conservation-oriented society
d. an information-based business economy
e. an agrarian-based economy
Answer: d, Easy, p. 204

2. Which of the following is not true about backbone networks?
a. They may also be called enterprise networks if they connect all networks within an organization.
b. They typically connect many networks, including LANs.
c. They typically provide connections to other BNs, WANs, MANs, and the Internet.
d. They may also be called campus networks if they connect many BNs spanning several buildings as a single location.
e. They tend to use lower speed circuits than LANs.
Answer: e, Moderate, p. 204

3. Which of the following is not a type of hardware device that can be used to interconnect networks?
a. brouters
b. routers
c. bridges
d. ‘dumb’ terminals
e. gateways
Answer: d, Moderate, p. 205-208

4. Bridges:
a. learn addresses by reading the source and destination addresses
b. operate at the physical layer only
c. connect two ore more network segments that use different data link protocols
d. connect two or more network segments that use different network protocols
e. have become more popular than layer 2 switches
Answer: a, Moderate, p. 205

5. Routers:
a. operate at the application layer
b. operate only at the physical layer
c. cannot connect two or more networks that use the same type of cable
d. may also be called TCP/IP gateways
e. operate only at the data link layer
Answer: d, Moderate, p. 205-206

6. Which of the following is not a way that a router differs from a bridge?
a. routers can connect two or more networks that use the same data link protocol
b. routers only process messages that are specifically addressed to it
c. routers operate at the network layer
d. routers perform more processing on each message than bridges
e. routers can choose the “best” route between networks for forwarding a packet
Answer: a, Difficult, p. 205-206

7. Gateways:
a. process all messages, even if the messages are not explicitly addressed to them
b. can translate one network protocol into another
c. are less complex than bridges
d. are most often used as the interface between two or more networks that have similar data link and network layer protocols
e. cannot perform a routing function
Answer: b, Moderate, p. 207

8. One common use of gateways is to enable TCP/IP and Ethernet LANs to communicate with IBM mainframe-based networks that use ______ network protocol.
a. ATM
b. FDDI
c. SNA
d. ISDN
e. SMTP
Answer: c, Easy, p. 207

9. ____________ routers can understand different network layer protocols.
a. Multiprotocol
b. 3270 emulation
c. ASCII/EBCDIC
d. Asynchronous
e. Bridge-
Answer: a, Easy, p. 208

10. Brouters:
a. can connect different data link type segments
b. only operate at the physical layer
c. only operate at the application layer
d. cannot route messages that are explicitly addressed to it
e. always operate slower than routers for any type of network
Answer: a, Moderate, p. 208

11. Which of the following is not true about Layer-3 switches?
a. They switch messages based on their IP address.
b. They can be used in place of routers.
c. They function faster than routers.
d. They have more simultaneously active ports than routers.
e. They can only switch messages based on their data link layer addresses.
Answer: e, Moderate, p. 208

12. Which of the following devices is the most complex?
a. Gateway
b. Router
c. Hub
d. Bridge
e. Brouter
Answer: a, Moderate, p. 205-208

13. Which of the following is not a fundamental backbone network architecture?
a. Bridged backbone
b. Virtual LAN
c. Hubbed backbone
d. Collapsed backbone
e. Routed backbone
Answer: c, Easy, p. 208

14. Which of the following is not a technology layer that is considered when designing backbone networks?
a. access layer
b. distribution layer
c. decentralized layer
d. core layer
e. none of the above
Answer: c, Moderate, p. 209

15. A subnetted or hierarchical backbone can also be called:
a. Bridged backbone
b. Virtual LAN
c. Hubbed backbone
d. Collapsed backbone
e. Routed backbone
Answer: e, Moderate, p. 210

16. _________ move packets along the backbone based on their network layer address.
a. Bridged backbones
b. Hubbed backbones
c. Multistation access unit backbones
d. Routed backbones
e. NIC backbones
Answer: d, Easy; p. 210

17. Routed backbones:
a. require a lot of management
b. are not susceptible to time delays
c. use data link layer addresses to move packets that leave the subnet
d. require only a few set of TCP/IP addresses
e. don’t need much time to establish separate subnet addresses for each LAN
Answer: a, Moderate; p. 210

18. A _____________ type of BN segments (each of which has a special set of subnet addresses that can be managed by different network managers) each part of the network connected to the backbone.
a. bridged backbone
b. virtual LAN
c. hubbed backbone
d. collapsed backbone
e. routed backbone
Answer e, Moderate, p. 210

19. A _____________ type of BN moves packets along the backbone based on their data link layer addresses.
a. bridged backbone
b. virtual LAN
c. hubbed backbone
d. collapsed backbone
e. routed backbone
Answer: a, Easy, p. 210

20. Bridged backbones:
a. tend to be more expensive than routed backbones
b. are set up with many different subnets, just like a routed backbone
c. are slower than routed backbones for large networks
d. do not have significant performance problems for large networks
e. use network layer addresses to move packets
Answer: c, Moderate, p. 210-213

21. A __________ type of BN has a star topology with one device, such as a switch, at its center.
a. Bridged backbone
b. Virtual LAN
c. Hubbed backbone
d. Collapsed backbone
e. Routed backbone
Answer: d, Easy, p. 213

22. _________ have no backbone cable.
a. Collapsed backbones
b. Cloud routed backbones
c. Hubbed backbones
d. Bridged backbones
e. Multistation access unit backbones
Answer: a, Easy, p. 213

23. Collapsed backbone networks:
a. always use a ring topology
b. are the least common type of BN used in one building
c. are a switched backbone design with improved performance over traditional BNs
d. have a great deal of cable in their backbones
e. tend to have less cable, but more network devices
Answer: c, Moderate, p. 213-214
24. Which of the following is an advantage of the traditional BN approach over collapsed backbone design?
a. throughput is much higher in a traditional design BN
b. traditional design BNs require far fewer networking devices
c. traditional design BNs have much simpler network management
d. much more cable is used in traditional design backbone networks
e. if one networking device fails, the entire BN does not fail
Answer: e, Moderate, p. 214

25. Which of the following is not true about collapsed backbones?
a. performance is improved over traditional (bridged or routed) backbone networks
b. each connection into the switch is a separate point-to-point circuit which supports simultaneous access by the LANs connected to the switch
c. there are many more networking devices in a collapsed backbone network
d. if the switch fails, so does the entire backbone network
e. the backbone essentially exists in the switch; there is no backbone cable
Answer: c, Moderate, p. 213-214

26. A rack-based collapsed backbone:
a. places all network devices for one part of the building physically in the same room, often in a rack of equipment
b. has an advantage of requiring less cable
c. makes it more difficult to move computers from one LAN to another
d. means that network capacity is always tied to the physical location of the computers
e. is harder to maintain and upgrade than a BN that is not rack-based
Answer: a, Moderate, p. 215-216

27. Associated with a rack-based collapsed backbone, MDF is an acronym for:
a. multi-station device foundation
b. main distribution facility
c. manual data frequency
d. multiplexer downstream flow
e. maximum data facility
Answer: b, Moderate, p. 216

28. A _____________ type of BN is a new type of LAN/BN architecture made possible by intelligent, high speed switches that assign computers to LAN segments via software, rather than by hardware.
a. Bridged backbone
b. Virtual LAN
c. Hubbed backbone
d. Collapsed backbone
e. Routed backbone
Answer: b, Easy, p. 218-222

29. Port-based VLANs use the __________ layer port number to form the VLAN groups.
a. physical
b. data link
c. network
d. transport
e. application
Answer: a, Easy, p. 219

30. MAC-based VLANs use the _________ layer address to form the VLAN groups.
a. physical
b. data link
c. network
d. transport
e. application
Answer: b, Easy, p. 220

31. IP-based VLANs use the _______ layer address to form the VLAN groups.
a. Physical
b. data link
c. network
d. transport
e. application
Answer: c, Easy, p. 221

32. Policy-based VLANs use the _______ layer address to form the VLAN groups.
a. physical
b. data link
c. network
d. transport
e. application
Answer: e, Moderate, p. 221

33. Which of the following is not a way in which computers attached to a VLAN switch can be assigned to the specific virtual LANs inside them?
a. IP-based
b. Port-based
c. MAC-based
d. ATM-based
e. Application-based
Answer: d, Moderate, p. 220-221

34. Which of the following is not true about multi-switch VLANs?
a. Several switches are used to build a VLAN
b. The switches in the VLAN can send packets among themselves in a way that identifies the VLAN to which the packet belongs.
c. In some multi-switch VLANs, the Ethernet packet is modified based on the emerging IEE 802.1q standard.
d. In some multi-switch VLANs, a new VLAN packet encapsulates the Ethernet packet.
e. All of the above are true statements.
Answer: e, Moderate, p. 221-222

35. Which of the following is not true about FDDI?
a. It uses a variation of token passing as a media access control method.
b. It was originally designed in the 1980s for use in MANs.
c. It uses two counter-rotating rings called the primary ring and the secondary rings
d. All computers on a FDDI network are connected to the secondary ring.
e. It is self-healing because it can still operate in a limited fashion even if the cable is broken.
Answer: d, Moderate, p. 224-225

36. _________ is a type of FDDI that uses twisted pair cable instead of fiber.
a. TDDI
b. TPDDI
c. CDDI
d. TwistedDDI
e. Cat5DDI
Answer: c, Moderate, p. 225

37. Which of the following is not true with respect to ATM?
a. It uses fixed length packets, or cells.
b. It is also known as Cell Relay.
c. It provides no error correction to user data. (that is left to software at the source and destination)
d. It is not a switched network.
e. It uses a different type of addressing from traditional data link protocols because it uses virtual circuit identifiers.
Answer: d, Moderate, p. 225-227

38. ATM uses _______ -byte cells.
a. 39
b. 44
c. 48
d. 53
e. 34
Answer: d, Easy, p. 226

39. The header of an ATM cell is comprised of _____ bytes of address and control information, such as Quality of Service.
a. 3
b. 5
c. 35
d. 48
e. 53
Answer: b, Easy, p. 226

40. ATM is __________ so that all packets travel in order through the virtual circuit.
a. synchronous
b. connection-oriented
c. sequence multiplexed
d. time multiplexed
e. connectionless
Answer: b, Moderate, p. 226

41. Which of the following is not an ATM class of service?
a. variable bit rate – real time
b. variable bit rate – non-real time
c. unspecified bit rate
d. iso-synchronous bit rate
e. available bit rate
Answer: d, Moderate, p. 228

42. ATM defines _________ service classes (for Quality of Service routing/switching) that enable the network to prioritize transmissions.
a. three
b. four
c. five
d. seven
e. nine
Answer: c, Easy, p. 228

43. Which of the following is an approach that can be used to translate Ethernet LAN packets to flow over ATM networks?
a. QoS
b. LAN encapsulation
c. Time division multiplexing
d. Connectionless transmission
e. Variable length packets
Answer: b, Easy, p. 227-229

44. Used with ATM networks, MPOA is an acronym for:
a. Multi-Point Overhaul Asynchronous
b. Multiprocessing on Access
c. Multiprotocol over ATM
d. Multiplexing over Address
e. Multiplexing on Asynchronous
Answer: c, Moderate, p. 229

45. Which of the following would be least effective in improving backbone performance?
a. improving the computers in the network
b. changing the demand placed on the network
c. adding new keyboards to the client computers
d. upgrading the circuits between computers
e. improving devices in the network
Answer: c, Moderate, p. 229-231

46. ___________ is not usually a helpful way to speed up routing in backbone networks because they have only a few routes through the network.
a. Dynamic routing
b. Passive routing
c. Guided routing
d. Static routing
e. Radiated routing
Answer: a, Moderate, p. 230

47. Device performance on a backbone network will not be improved by:
a. using the same protocols in the backbone and the LANs
b. using static routing in low to moderate traffic conditions
c. ensuring that backbone devices have sufficient memory so that packets do not have to be retransmitted by the sender
d. translating packets from one protocol to another as they enter the BN
e. none of the above
Answer: d, Moderate, p. 230

48. Circuit capacity on a backbone network will not be improved by:
a. going from 100Base-T Ethernet to 10Base-T Ethernet
b. going from 100Base-T Ethernet to gigabit Ethernet
c. adding additional circuits alongside heavily used ones
d. replacing a shared circuit backbone with a switched circuit backbone
e. providing a faster circuit to the server
Answer: a, Moderate, p. 230-231

49. Network demand will not be reduced by:
a. restricting (or moving) applications such as desktop videoconferencing
b. using network devices to ensure that broadcast messages do not go to other networks
c. restricting (or moving) applications such as medical imaging
d. sending status information to all computers on all LANs in the backbone network
e. restricting (or moving) applications such as multimedia
Answer: d, Moderate, p. 231

50. Which of the following would not be part of an “ideal” backbone design for the future?
a. access layer composed of 10/100 layer 2 Ethernet switches
b. distribution layer composed of layer 3 Ethernet switches of 100 (or 1000) Base-T
c. redundant switches
d. core layer composed of layer 3 Ethernet switches running 10 (or 40) GbE over fiber
e. coax cabling throughout LANs and BN
Answer: e, Moderate, p. 231-232

Short Answer Questions

1. How does a bridge differ from a hub?
Answer: Hubs are very simple devices that pass all traffic in both directions between the LAN sections they link. Hubs operate at the physical layer only.
Bridges operate at the data link layer. They connect two or more network segments that use the same data link and network protocol. They understand only data link layer protocols and addresses. They may connect the same or different types of cable. They learn addresses by reading the source and destination addresses.
2. Describe two ways in which a router differs from a bridge.
Answer: Bridges operate at the data link layer. They connect two or more network segments that use the same data link and network protocol. They understand only data link layer protocols and addresses. They may connect the same or different types of cable.
Routers operate at the network layer. Routers connect two or more networks that use the same or different data link protocols, but the same network protocol. They may connect the same or different types of cable. One major feature of a router is that it can choose the “best” route between networks when there are several possible routes between them. Because a router knows its own location, as well as the packet's final destination, it looks in a routing table to identify the best route or path. One other important difference between a router and a bridge is that router only processes messages that are specifically addressed to it. Bridges process all messages that appear on the network and forward them to the appropriate network based on their data link layer address. Bridges simply forward the message unchanged onto the other network.
3. Under what circumstances would you want to use a brouter?
Answer: Brouters combine the functions of both bridges and routers. These operate at both the data link and network layers. A brouter connects same data link type network segments and different data link type network segments. For similar segments, the brouter will function as fast as a bridge; for different data link type network segments, the brouter will be slower, but will be flexible enough to connect these different segments. A brouter would be useful when an organization needs to connect several types of data link segments.
4. What are the three technology layers that are important in backbone design?
Answer: The layer closest to the user is the access layer, the technology used in the LANs attached to the backbone. The second layer is the distribution layer that contains the TCP/IP gateway to connect LANs together. The core layer is the part of the backbone that connects the different backbone networks together, often from building to building.
5. Which backbone architecture is the most flexible? Why?
Answer: A chassis-based collapsed backbone switch is extremely flexible. It is simple to add new modules with additional ports as the LAN grows, and to upgrade the switch to new technologies.
6. How can broadcast messages be handled on a backbone network and why is that important?
Answer: Some bridges, switches, bridges, and routers can be set to filter broadcast messages so that they do not go to other networks. This reduces network traffic and improves performance. On a LAN, broadcast messages go to all computers in the LAN; as a result, these broadcast messages do not place any “extra” demand on the network. However, switched LANs or LANs connected to backbone networks normally don’t get broadcast messages; therefore, unanticipated broadcast messages can consume a fair amount of BN network capacity. These messages usually don’t have much value outside their ‘home’ LAN so it is best to use a device that can filter out these messages.
7. How does ATM work?
Answer: ATM (asynchronous transfer mode) is a packet-switched technology originally designed for use in wide area networks. ATM used 53-byte fixed length packets with no error control of full duplex 155 Mbps point-to-point circuits. ATM enables QoS, and uses virtual circuits rather than permanently assigning addresses to devices. In order to use ATM in a backbone network that connects LANs, some conversion must be done on the LAN packets to enable them to flow over the ATM backbone.
8. Describe how LAN Encapsulation (LANE) enables ATM backbones to connect Ethernet networks.
Answer: With LANE, an ATM edge switch encapsulates the Ethernet packet, leaving the existing data link layer packet intact and transmits it based on data link layer addresses.
9. How does ATM LANE differ from MPOA?
Answer: With LANE, an ATM edge switch encapsulates the Ethernet (or token ring) packet, leaving the existing data link layer packet intact and transmits it based on data link layer addresses. MPOA is an alternative that can use network layer addresses for transmission.
10. Suppose a 10Base-T backbone network is having performance problems. Describe two specific steps you could take to improve performance.
Answer: Network performance can be improved by upgrading the computers and other devices in the network, by using static rather than dynamic routing if there are few routes through the network, by reducing switch-to-switch traffic in networks without standard protocols, by using the same protocols in the backbone network as in the attached LANs, by encapsulating rather than translating between different protocols, and by increasing the memory in backbone devices. Performance can also be improved by adding additional circuits to increase capacity, by changing to controlled access rather than contention protocols, by going to a switched network, and by increasing the circuits on high traffic circuits. In addition, performance can be enhanced by reducing demand or by restricting applications that use lots of network capacity, and by using switches that filter broadcast messages.
11. Some experts believe Ethernet will be the dominant backbone technology in three years time. Other experts believe ATM will win. Explain two reasons why Ethernet is likely to win. Explain two reasons why ATM is likely to win.
Answer: Reasons for ATM to dominate:
• ATM is a dominant technology in the WAN, and versions of ATM are available to the desktop (One group of industry experts therefore predicts that ATM will become common in the backbone because it enables a complete end-to-end solution (LAN to BN to WAN)).
• ATM’s small fixed-length packet and built-in quality of service (QoS) capability makes it more suitable for voice and video transmission; small fixed length packets make routing and packetizing easier and minimize the effects of lost packets, while QoS enables the network to give higher priority to time-sensitive voice and video transmissions
Reasons for Ethernet to dominate:
• in general, newer technologies such as switched Ethernet and ATM are harder to manage than older, more established ones such as Ethernet or FDDI
• there are no formal standardized management protocols for backbone ATM switches
• the response to ATM-25 has been rather poor; the dominant LAN technology is Ethernet (Therefore, another group of industry experts predicts that fast Ethernet and gigabit Ethernet will dominate the backbone.)
• ATMs QoS advantage may change, however, once QoS routing is implemented in TCP/IP
• network costs for Ethernet is relatively cheaper than ATM
12. Thought question: What are the two most important considerations in selecting a backbone network. Justify your choices.
Answer: Five factors to consider in selecting a backbone network are throughput, cost, type of application, ease of network management, and compatibility with current and future technologies.
Network cost is always a critical issue. Costs change rapidly in the marketplace, based on competition and demand. The management of backbone networks can be extremely costly and challenging, and therefore, the quality of the network management tools available in each type of network is very important. Compatibility with current and future technologies is also important in the management of networks. Most network managers strive to have similar technologies throughout their networks to reduce management costs.