Download Fitz and Dennis TB ch08 File

Chapter 8
Backbone Networks
True-False Questions
The following are possible True/False questions for tests. The statement is given and the answer
is provided . The level of difficulty (easy, moderate, 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
2.
Answer: True
Difficulty: Easy
Reference: p. 265
Backbone networks typically use lower speed circuits to interconnect a series of LANs and
provide connections to other backbone networks.
3.
Answer: False
Difficulty: Easy
Reference: p. 265
A backbone network that connects many backbone networks spanning several buildings at a
single location is often called an Internet backbone.
4.
Answer: False
Difficulty: Easy
Reference: p. 265
One basic component of a backbone network is the hardware device that connects other
networks to the backbone.
5.
Answer: True
Difficulty: Easy
Reference: p. 265
Switches, routers, and gateways devices that can connect networks to the BN.
6.
Answer: True
Difficulty: Easy
The cable to connect BNs is usually twisted pair.
7.
Answer: False
Difficulty: Easy
Reference: p. 265
A hardware device that operates at the application layer is a router.
8.
Answer: False
Difficulty: Moderate
Routers can only connect the same type of cable.
9.
Answer: False
Difficulty: Easy
Reference: p. 266
Routers use network layer address to forward packets between network segments.
10.
Answer: True
Difficulty: Moderate
Routers operate at the application layer
Reference: p. 265
Reference: p. 266
Reference: p. 266
11.
Answer: False
Difficulty: Moderate
Reference: p. 266
Routers connect two or more network segments that use the same or different data link
protocols, but the same network protocol.
12.
Answer: True
Difficulty: Moderate
Reference: p. 266
One advantage of a router is that it can choose the “best” route between networks when there
is a choice.
Answer: True
Difficulty: Easy
Reference: p. 267
13.
14.
One difference between a switch and a bridge is that a router will only process messages
addressed to the router, while a switch processes all messages..
Answer: True
Difficulty: Easy
Gateways are simpler than routers.
Reference: p. 267
15.
Answer: False
Difficulty: Easy
Reference: p. 268
Gateways connect two or more networks that use the same or different data link and the same
or different network protocols.
16.
Answer: True
Difficulty: Moderate
Reference: p. 268
One of the least common uses of gateways is to enable LANs that use TCP/IP and Ethernet
to communicate with mainframes that use other protocols.
17.
Answer: False
Difficulty: Moderate
Reference: p. 268
The terms for hardware devices, such as routers and gateways, are interchangeable among
vendors.
18.
Answer: False
Difficulty: Moderate
Reference: p. 269
Layer-3 switches switch messages based on their data link layer address.
19.
Answer: False
Difficulty: Easy
Reference: p. 269
Routed backbones are switches that move packets based on data link layer addresses.
20.
Answer: False
Difficulty: Moderate
The distribution layer of a backbone connects the LANs together
21.
Reference: p. 271
Answer: True
Difficulty: Easy
Reference: p. 270
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.
22.
Answer: True
Difficulty: Moderate
Reference: p. 272
One advantage of a routed backbone is that is requires little management.
23.
Answer: False
Difficulty: Easy
Reference: p. 273
A routed backbone tends to be used more for large networks than VLANs.
24.
Answer: False
Difficulty: Easy
A collapsed backbone uses a bus topology
25.
26.
Reference: p. 280
Answer: False
Difficulty: Easy
Reference: p. 274
A room that contains a rack of equipment for a rack-based collapsed backbone is also called
the main distribution facility (MDF) or central distribution facility (CDF).
Answer: True
Difficulty: Easy
Reference:
A key advantage of a chassis-based collapsed backbone is its flexibility.
Answer: True
Difficulty: Easy
Reference:
p. 275
p.279
27.
A VLAN network assigns computers to LAN segments by hardware.
28.
Answer: False
Difficulty: Easy
Reference: p. 280-281
A VLAN requires the computer manager to reconfigure the physical cables to the switch if a
computer is moved from one port to another port on a switch.
29.
Answer: False
Difficulty: Moderate
Reference: p. 280
VLANs provide faster performance compared to switched, collapsed or routed backbone
architectures.
30.
Answer: True
Difficulty: Easy
Reference: p. 280
With respect to high-speed networks, the acronym, ATM, refers to Automatic Teller
Machines
31.
Answer: False
Difficulty: Easy
Reference: p. 285
ATM is a layer 3 technology that also includes layer 2 and layer 1 technologies as part of its
specification
Answer: True
Difficulty: Moderate
ATM uses variable length cells.
Reference: p. 285
32.
Reference: p. 286
33.
Answer: False
Difficulty: Easy
ATM is connection oriented.
Answer: True
Difficulty: Easy
ATM uses permanent addresses.
Reference: p. 286
34.
35.
Answer: False
Difficulty: Easy
Reference: p. 286
A switched virtual circuit once defined is used for the current and future transmissions
between two computers.
Answer: False
Difficulty: Easy
Reference: p. 286
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 the
page number(s) relevant to the topic is also furnished.
1.
2.
3.
4.
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
Difficulty: Moderate
Reference: p. 265
Which of the following is not a type of hardware device that can be used to interconnect
networks?
a. switches
b. routers
c. multiprotocol routers
d. ‘dumb’ terminals
e. gateways
Answer: D
Difficulty: Moderate
Reference: p. 265-269
Switches:
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
Difficulty: Moderate
Reference: p. 266
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
Difficulty: Moderate
Reference: p. 66
5.
6.
7.
8.
9.
10.
Which of the following is not a way that a router differs from a switch?
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 switch
e. routers can choose the “best” route between networks for forwarding a packet
Answer:A
Difficulty: Difficult
Reference: p. 266
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
Difficulty: Moderate
Reference: 268
____________ routers can understand different network layer protocols.
a. Multiprotocol
b. 3270 emulation
c. ASCII/EBCDIC
d. Asynchronous
e. BridgeAnswer: A
Difficulty: Easy
Reference: p. 269
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
Difficulty: Moderate
Which of the following devices is the most complex?
a. Gateway
b. Router
c. Layer 3 switches
d. Switch
e. Multiprotocol router
Reference: p. 269
Answer: A
Difficulty: Moderate
Reference: p. 267
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
Difficulty: Easy
Reference: p. 270
11.
12.
13.
14.
15.
__________ refers to the way in which backbone interconnects the network attached to it and
how it manages the way in which packets from one network move though the backbone to
other networks.
a. Traffic architecture
b. Network design
c. Backbone architecture
d. Distribution layer
e. Core layer
Answer: C
Difficulty: Moderate
Reference: p. 270
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
Difficulty: Moderate
A subnetted or hierarchical backbone can also be called:
a. Bridged backbone
b. Virtual LAN
c. Hubbed backbone
d. Collapsed backbone
e. Routed backbone
Reference: p. 270
Answer: E
Difficulty: Moderate
Reference: p. 271
_________ 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
Difficulty: Moderate
Reference: p. 271
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
Difficulty: Moderate
Reference: p. 273
16.
17.
18.
19.
20.
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
Difficulty: Moderate
Reference: p. 271-273
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
Difficulty: Easy
_________ have no backbone cable.
a. Collapsed backbones
b. Cloud routed backbones
c. Hubbed backbones
d. Bridged backbones
e. Multistation access unit backbones
Answer: A
Difficulty: Easy
Collapsed backbone networks:
a. always use a ring topology
b. are the least common type of BN used in one building
c. use a star topology with one device, usually a switch
d. have a great deal of cable in their backbones
e. tend to have less cable, but more network devices
Reference: p. 274
Reference: p. 274-275
Answer: C
Difficulty: Moderate
Reference: p. 274
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
Difficulty: Moderate
Reference: p. 275
21.
22.
23.
24.
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
Difficulty: Moderate
Reference: p. 274-275
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
Difficulty: Moderate
Reference: p. 275
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
Difficulty: Moderate
Reference: p. 275
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
Difficulty: Easy
Reference: p. 280
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
Difficulty: Easy
Reference: p. 282
26.
27.
28.
29.
30.
31.
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
Difficulty: Easy
Reference: p. 282
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
Difficulty: Easy
Reference: p. 282
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
Difficulty: Easy
Which of the following can be used for network capacity allocation?
a. port-based VLANs
b. MAC-based VLANs
c. IP-based VLANs
d. application based VLANs
e. FDDI
Reference: p. 282
Answer: D
Difficulty: Moderate
Reference: p. 282
Which IEEE standard inserts a 16-byte VLAN tag into a normal Ethernet packet?
a. 802.11
b. 802.5
c. 803.3
d. 802.1q
e. 802.11g
Answer: D
Difficulty: Moderate
Reference: p. 283
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
Difficulty: Moderate
Reference: p. 280-283
32.
33.
34.
35.
36.
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
Difficulty: Moderate
Reference: p. 283
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
Difficulty: Moderate
ATM uses _______ -byte cells.
a. 39
b. 44
c. 48
d. 53
e. 34
Reference: p. 286
Answer: D
Difficulty: Moderate
Reference: p. 286
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
Difficulty: Moderate
Reference: p. 286
With ATM, The path defined between sender and receiver, which is used for communication
is called a ____________.
a. route
b. virtual circuit
c. ATM path
d. VLAN
e. ATM LANE
Answer: B
Difficulty: Easy
Reference: p. 286
37.
38.
39.
40.
41.
42.
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
Difficulty: Easy
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
Reference: p. 286
Answer: D
Difficulty: Moderate
Reference: p. 286
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
Difficulty: Easy
Reference: p. 287
______ means that the data transmission rate in the circuit will vary and the application is
tolerant of delays.
a. Variable bit rate-real time
b. Variable bit rate-nonreal time
c. Available bit rate
d. Unspecified bit rate
e. Constant bit rate
Answer: B
Difficulty: Moderate
Reference: p. 289
__________ means that the circuit must provide a constant, predefined data rate at all times.
a. Variable bit rate-real time
b. Variable bit rate-nonreal time
c. Available bit rate
d. Unspecified bit rate
e. Constant bit rate
Answer: E
Difficulty: Easy
________ means that the circuit has no guaranteed data rate.
a. Variable bit rate-real time
b. Variable bit rate-nonreal time
c. Available bit rate
d. Unspecified bit rate
e. Constant bit rate
Answer: D
Difficulty: Easy
Reference: p. 282
Reference: 289
43.
44.
45.
46.
47.
48.
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
Difficulty: Moderate
Reference: p. 288
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
Difficulty: Moderate
Reference: p. 293
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
Difficulty: Moderate
Reference: p. 294
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
Difficulty: Moderate
Reference: p. 294
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: C
Difficulty: Moderate
Gigabit Ethernet is not:
a. the newest technology used in LANs and backbones
b. rarely found in backbones at the present time
c. usually run over fiber
d. found in 1 GbE, 10 GbE and 40GbE formats
Reference: p. 294
e. likely to replace ATM in the backbone
Answer: B
Difficulty: Moderate
Reference: p. 284
49.
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
Difficulty: Moderate
Reference: p. 294-295
Short Answer and Essay Questions:
1. What is a backbone network? What is typical of this kind of network? What are
some business trends which we are seeing in backbone networks? What are three
major technologies which are commonly seen in backbone networks?
2. Given network devices such as routers, switches and gateways, discuss three
major technological trends that are helpful in explaining the differences between
these devices. When might a router be useful? When might a gateway be more
appropriate?
3. Describe the difference between backbone level shared media technologies and
backbone level switched media technologies. Using a chart, describe two forms of
shared media high speed networks and two forms of switched media technologies
for high speed networks.
4. Describe and draw the topology of ATM. What are the strengths of ATM, why
might ATM be slipping somewhat in the marketplace to fast ethernet?
5. List then describe 5 managerial factors to consider when selecting best practices
for a backbone network design. What are six actions that you might undertake as
a network manager to improve backbone performance?