SSD8
.doc20 new telephone lines and a 200 Kbps digital data channel
A single 1.1 Mbps data channel
25 new telephone lines
(a) I, II, and III
(b) none
(c) II only
(d) I and II only
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 1.2.1 of the course notes.
(a) When multiplexing several channels on a single medium, we need to allow for filter imperfections by allowing guard bands. Thus, while voice can be carried in a 3 KHz, we need to apportion a lot of bandwidth to guard bands and other overhead.
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5.
In contrast to message switching, packet switching
needs to find a "copper" path to the receiver before transmitting any data
offers a better upper bound on transmission delay
suffers from greater overhead at the endpoints
(a) I and III only
(b) II and III only
(c) II only
(d) I and II only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.2.3 of the course notes.
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6.
In contrast with wireless communication, "wired" communication
does not suffer from attenuation and interference
can use any frequencies without a license
always has more throughput
(a) I and III only
(b) none
(c) II only
(d) I, II, and III
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 1.2.1 of the course notes.
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7.
A fiber optic is found to be able to deliver light cleanly in a frequency range 25,000 GHz wide. This fiber can be used to create the following type of channel between two routers
a single 50 terabits per second (Tbps = 1,000 Gbps) data channel
5 2-Gbps data channels
one video channel but no data channels, because data cannot be encoded in light beams
(a) III only
(b) I only
(c) II only
(d) I and II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
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8.
A university has 20 computers in a laboratory that is currently served by several small 10 Base-T "Ethernet" hubs that are directly connected to each other. The network performance has been found to be lacking, and an upgrade is planned. The computers are identical and place a comparable load on the network that is relatively constant and modest for each computer (in the order of 500 Kbps). What would you suggest for the upgrade?
(a) Replace the hubs with 10 Base-T switches
(b) Replace the hubs with 100 Base-T hubs
(c) A small 10 Base-T switch to connect the existing hubs
(d) A new bank of dial-up modems
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 1.2.4 of the course notes.
(b) This is expensive and is not necessary because each computer never uses more than the capacity of a 10 Mbps network.
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9.
Radio stations are able to share the AM (Amplitude Modulation) spectrum by using _____ multiplexing
(a) phase shift
(b) time-division
(c) frequency-division
(d) wavelength-division
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
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10.
A cable is rated at 19200 baud. A 19200 baud cable is guaranteed to transmit a signal successfully that has the potential to change 19200 times per second. The maximum throughput of this cable, assuming a sensible encoding,
(a) is between 19200 and 38400 bits per second, depending on the bit pattern of the transmitted data
(b) can be any number greater than or equal to 19200 bits per second, depending on the way the data is encoded into signal voltages
(c) is exactly 19200 bits per second
(d) is less than 19200 bits per second
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
1.
A fiber optic is found to be able to deliver light cleanly in a frequency range 25,000 GHz wide. This fiber can be used to create the following type of channel between two routers
a single 50 terabits per second (Tbps = 1,000 Gbps) data channel
5 2-Gbps data channels
one video channel but no data channels, because data cannot be encoded in light beams
(a) I only
(b) II only
(c) III only
(d) I and II only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
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2.
A university has 20 computers in a laboratory that is currently served by several small 10 Base-T "Ethernet" hubs. The network performance has been found to be lacking, and an upgrade is planned. The computers usually have modest network needs (in the order of 500 Kbps), but one or two are occasionally used to receive high-quality remote video streams that require in the order of 10 Mbps. No more than two computers are used for this purpose at any given time, but any two may be used for this application. What would you suggest for the upgrade?
(a) A new bank of dial-up modems
(b) Replace the hubs with 10 Base-T switches
(c) A 10 Base-T bridge to connect several existing hubs
(d) Replace the hubs with 100 Base-T hubs
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.2.4 of the course notes.
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3.
When a student in Hong Kong uses her computer to have a voice conversation with a teacher in Pittsburgh, the application she uses requires that the network deliver bits at a modest but constant bit rate. This is because, even though voice can be faithfully encoded in less than 64 Kbps, the late arrival of a voice sample produces a noticeable and unpleasant sound effect. Which of the following switching options will give you better quality?
(a) Circuit-switched
(b) Packet-switched
(c) Space-switched
(d) Message-switched
Correct answer is (a)
Your score on this question is: 0.00
Feedback:
See section 1.2.3 of the course notes.
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4.
What is the type of an "8+1" parity code that outputs 100101011?
(a) Null Parity
(b) Cannot tell since we do not know which bit is the parity bit
(c) Odd Parity
(d) Even Parity
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.2 of the course notes.
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5.
Which of the following are responsibilities of the data link layer?
Noticing transmission errors
Regulating transmission speed when a receiver is overwhelmed
Regulating transmission speed when any of several IP routers in a network path are overwhelmed
(a) I, II, and III
(b) I only
(c) II and III only
(d) I and II only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.2.2 of the course notes.
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6.
If you have seen any mobile telephone antennas, you will have noticed that they have groups of radiating elements facing different directions. Most antennas we know are arranged in a triangle, so that each group spans a 120-degree arc of the horizon, but we have also seen squares in which each group spans a 90-degree arc instead. There is one such arrangement for each cell of a mobile phone system. This sort of base station is unsightly and expensive. A cell could instead use a single omnidirectional antenna that would be simple and inconspicuous. Why do you think the more complicated designs are used?
(a) To decrease frequency reuse without the need for time-division multiplexing
(b) To allow the use of switches based on space-division multiplexing
(c) To increase frequency reuse without having to build more antenna towers
(d) To decrease the number of times a call must be handed off from one base station to another.
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.6 of the course notes.
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7.
A parity code is a(n)
(a) error-correcting code
(b) error-detecting code
(c) fair resource allocation scheme
(d) duplex transmission technique
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.2.2 of the course notes.
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8.
After the phone company installs a T1 trunk to an office building, which of the following can it provide to the tenants of the building? Recall that a T1 trunk has a capacity of 1.544 Mbps, and that a voice channel requires an isolated 3 KHz channel.
20 new telephone lines and a 200 Kbps digital data channel
A single 1.1 Mbps data channel
25 new telephone lines
(a) none
(b) I, II, and III
(c) I and II only
(d) II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
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9.
The maximum binary data throughput of a cable that cleanly transmits a range of frequencies up to 100 MHz is
(a) currently 56 Kbps but more as modem technology improves
(b) exactly 200 megabytes per second
(c) within 80 and 120 megabits per second
(d) exactly 200 megabits per second
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 1.2.1 of the course notes.
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10.
A sender's data link layer uses "bit stuffing" to
(a) avoid confusing data bits with control bits
(b) force the receiver to enlarge its flow control window
(c) pad the data so that it has an even length for parity calculations
(d) mark the start and the end of a frame
Correct answer is (a)
Your score on this question is: 0.00
Feedback:
See section 1.2.2 of the course notes.
1.
The point-to-point (PPP) protocol
can only be used in analog dial-up connections
is a data-link protocol
can only be used to carry IP over serial lines
(a) II only
(b) II and III only
(c) III only
(d) I and II only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.2.5 of the course notes.
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2.
A specific CSMA-CD network such as 10-BASET "Ethernet"
(a) works best for an even number of nodes
(b) suffers performance degradation as nodes are added
(c) has higher cost per node as nodes are added
(d) can connect very distant nodes
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.2.4 of the course notes.
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3.
What is the type of an "8+1" parity code that outputs 100101011?
(a) Cannot tell since we do not know which bit is the parity bit
(b) Null Parity
(c) Odd Parity
(d) Even Parity
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.2 of the course notes.
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4.
Collision Detection improves the throughput of multiple access networks because
it can shorten the length of garbled frames
it can decrease the number of garbled frames
it delays by a random amount of time when a collision is detected
(a) I and II only
(b) II and III only
(c) I, II, and III
(d) I only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.2.4 of the course notes.
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5.
A packet-switched network uses switches that schedule packets using a first-in-first-out (FIFO) discipline. Several people want to carry out a conference over this network. The conference is carried out via typed text for the most part, but, occasionally, one of the parties has to send a large video. This happens very rarely. Which of the following switching approaches is most suitable for this application?
(a) Circuit-switched
(b) Message-switched
(c) Space-switched
(d) Packet-switched
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.2.3 of the course notes.
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6.
A university has 20 computers in a laboratory that is currently served by several small 10 Base-T "Ethernet" hubs that are directly connected to each other. The network performance has been found to be lacking, and an upgrade is planned. The computers are identical and place a comparable load on the network that is relatively constant and modest for each computer (in the order of 500 Kbps). What would you suggest for the upgrade?
(a) Replace the hubs with 10 Base-T switches
(b) A new bank of dial-up modems
(c) A small 10 Base-T switch to connect the existing hubs
(d) Replace the hubs with 100 Base-T hubs
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.4 of the course notes.
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7.
When a student in Hong Kong uses her computer to have a voice conversation with a teacher in Pittsburgh, the application she uses requires that the network deliver bits at a modest but constant bit rate. This is because, even though voice can be faithfully encoded in less than 64 Kbps, the late arrival of a voice sample produces a noticeable and unpleasant sound effect. Which of the following switching options will give you better quality?
(a) Circuit-switched
(b) Message-switched
(c) Space-switched
(d) Packet-switched
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.2.3 of the course notes.
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8.
Which of the following are responsibilities of the data link layer?
Noticing transmission errors
Regulating transmission speed when a receiver is overwhelmed
Regulating transmission speed when any of several IP routers in a network path are overwhelmed
(a) I and II only
(b) I, II, and III
(c) I only
(d) II and III only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.2.2 of the course notes.
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9.
The maximum binary data throughput of a cable that cleanly transmits a range of frequencies up to 100 MHz is
(a) within 80 and 120 megabits per second
(b) currently 56 Kbps but more as modem technology improves
(c) exactly 200 megabits per second
(d) exactly 200 megabytes per second
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.2.1 of the course notes.
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10.
In a broadcast-based network, longer propagation delays
(a) significantly decrease the benefit of sensing the carrier before transmitting
(b) do not affect the cost-benefit trade-off of carrier sensing
(c) make it all the more critical to sense the carrier before transmitting
(d) destroy the carrier, making it impossible to sense it before transmitting
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.2.6 of the course notes.
1.
The Internet Protocol (IP)
is the only network-layer protocol
is required of hosts on the Internet
is the body of standard protocols in use on the Internet
(a) I only
(b) II only
(c) II and III only
(d) I and II only
Correct answer is (b)
Your score on this question is: 0.00
Feedback:
See section 1.3.1 of the course notes.
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2.
The network interface card of a Web server that you manage has developed sporadic problems. You measure the packet loss rate from your desktop computer and immediately decide to replace the network card. After this simple operation, the Web server successfully rejoins the network, as confirmed by your officemate using her desktop computer. You eagerly go to your desktop to measure the improvement, but find instead that the Web server is not responding to any of your packets. What is your diagnosis?
(a) The Domain Name System (DNS) has not yet updated its entry for the Web server.
(b) The new network card does not work.
(c) Your desktop computer's network card does not work.
(d) Your desktop computer is still trying to contact the server's old network card.
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.3.5 of the course notes.
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3.
A network uses a routing algorithm that uses paths with the least number of hops. These paths are computed periodically using a shortest-path algorithm. In this network, datagrams
are routed around congested links
may traverse the same router twice
will always reach their destination
(a) I and II only
(b) III only
(c) I and III only
(d) none
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 1.3.2 of the course notes.
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4.
Which of the following routing algorithms is the most scalable?
(a) Distance vector routing
(b) Flooding
(c) Link state routing
(d) Datagram broadcast
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.3.2 of the course notes.
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5.
The Dynamic Host Configuration Protocol (DHCP) may be used to
configure the scheduling policy of a busy server
relieve the saturation of the IP address space
assign a fixed address to a Web server after a reboot
(a) I only
(b) III only
(c) II and III only
(d) II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.3.6 of the course notes.
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6.
A modification is proposed to the IP protocol that would eliminate the "Identification" and "Fragment Offset" fields from the IP header. This could result in nearly a 15% improvement in the throughput of a link used for short transactions. Which other effects would this proposal have?
The resulting internetwork would no longer be able to interconnect subnetworks of any kind.
The scalability of the routing protocol would improve.
Data delivery would be more robust in the presence of congestion.
(a) III only
(b) I and II only
(c) I only
(d) none
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 1.3.4 of the course notes.
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7.
Which of the following benefit from "tunneling" IP datagrams by conveying them inside other packets?
Mobile IP
Multicast
Roll-out of IPv6
(a) I, II and III
(b) II only
(c) none
(d) I and III only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 1.3.8 of the course notes.
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8.
The main network engineer of a large corporation is charged with designing and deploying the company's intranet. She has decided to use a connection-oriented network layer. Which of the following concerns do you think motivated her choice?
(a) Cost of short transactions—e.g., credit card charge approval.
(b) Ability to re-route traffic around congested links
(c) Ability to reserve bandwidth—e.g., for important presentations to the Board
(d) Cost of the routers as the network grows
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.3.1 of the course notes.
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9.
A router is installed to interconnect 4 subnetworks with MTUs of 1024, 2048, 576, and 1556 bytes respectively. Nodes A and B are connected to the first and second subnets, respectively. An application on node A sends a 4096-byte datagram (e.g., using UDP) to an application on node B. How many IP fragments will the router process as a result?
(a) 4
(b) 1
(c) 5
(d) 2
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 1.3.4 of the course notes.
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10.
A corporate information systems manager is interested in collecting statistics on the frequency of computer failures within the organization. Most failures result in an automatic reboot, so the failed computer is typically back on the network in less than a minute. The corporate network connects 1,500 computers in far-flung locations to which the average latency of a packet is 40 milliseconds. The manager asks you to write a tool that will collect the times at which failures occurred in which computers. She wants it by tomorrow, so the tool will have to be simple. On which protocol will you base your implementation?
(a) PLM
(b) TCP
(c) ICMP (ping)
(d) SNMP
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 1.3.6 of the course notes.
1.
Which of the following is the most credible threat to the continuing success of the Internet Protocol (IP) as currently deployed?
(a) Big multimedia files will no longer fit into IP datagrams.
(b) Widespread deployment of fiber optics will call for more than 8192 fragments per datagram.
(c) Router memory will become insufficient to keep track of an exponentially increasing number of circuits.
(d) The IP address space will be exhausted.
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.3.3 of the course notes.
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2.
Tired of inaccurate routing tables, Joe, the network engineer, devises what he thinks is surely the best of all routing algorithms, which calculates the shortest-delay path for each packet. The algorithm works as follows. A routing server periodically polls each router for its full routing table and link delay statistics. This information from all routers is amalgamated into a complete model of the state of the network topology. Using this model, Joe's program selects the shortest delay paths, for which he derives new routing tables and sends to each router. Joe wants to deploy his algorithm immediately, but critics envious of his intelligence have offered the following objections. Which of the objections, if any, deserve attention?
Joe's algorithm is not scalable
Joe's algorithm is not reliable
Joe's algorithm results in inaccurate routing tables
(a) II only
(b) I and II only
(c) III only
(d) I, II, and III
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.3.2 of the course notes.
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3.
The class B IP network 128.2.x.x has been assigned to Carnegie Mellon University. To relieve congestion in its internal LAN, Carnegie Mellon has decided to subnet this IP network. This will have which of the following consequences?
The configuration of the subnets will have to be announced to routers all over the world by notifying NIC and/or IANA.
A computer may need to change its IP address when moved from one office to another.
Some bridges, hubs, or switches will need to be replaced with routers.
(a) I and III only
(b) I, II, and III
(c) II and III only
(d) III only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.3.3 of the course notes.
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4.
At which of the following layers of the OSI protocol stack can the Internet Control Message Protocol be implemented?
Network
Transport
Data link
(a) I or II only
(b) I only
(c) II only
(d) III only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.3.6 of the course notes.
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5.
The IP address space is organized in a hierarchy
to make the routing task more scalable
to decrease inefficient fragmentation of the address space
to give institutions managing local-area networks autonomous control over the assignment of addresses to computers
(a) II only
(b) I and III only
(c) none
(d) I only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.3.3 of the course notes.
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6.
The Internet Protocol (IP)
is the only network-layer protocol
is required of hosts on the Internet
is the body of standard protocols in use on the Internet
(a) I and II only
(b) II only
(c) I only
(d) II and III only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.3.1 of the course notes.
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7.
A modification is proposed to the IP protocol that would eliminate the "Identification" and "Fragment Offset" fields from the IP header. This could result in nearly a 15% improvement in the throughput of a link used for short transactions. Which other effects would this proposal have?
The resulting internetwork would no longer be able to interconnect subnetworks of any kind.
The scalability of the routing protocol would improve.
Data delivery would be more robust in the presence of congestion.
(a) I and II only
(b) none
(c) III only
(d) I only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 1.3.4 of the course notes.
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8.
Which of the following routing algorithms is the most scalable?
(a) Link state routing
(b) Distance vector routing
(c) Datagram broadcast
(d) Flooding
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.3.2 of the course notes.
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9.
Which of the following benefit from "tunneling" IP datagrams by conveying them inside other packets?
Mobile IP
Multicast
Roll-out of IPv6
(a) I and III only
(b) none
(c) I, II and III
(d) II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 1.3.8 of the course notes.
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10.
The main network engineer of a large corporation is charged with designing and deploying the company's intranet. She has decided to use a connection-oriented network layer. Which of the following concerns do you think motivated her choice?
(a) Cost of the routers as the network grows
(b) Ability to reserve bandwidth—e.g., for important presentations to the Board
(c) Cost of short transactions—e.g., credit card charge approval.
(d) Ability to re-route traffic around congested links
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 1.3.1 of the course notes.