Created By: QuickNotesPro
Solution Manual for Computer Networking A Top-Down Approach,
8th Edition by James Kurose 2025 A Graded
Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end system” are used
interchangeably. End systems include PCs, workstations, Web servers, mail servers, PDAs,
Internet-connected game consoles, etc.
2. From Wikipedia: Diplomatic protocol is commonly described as a set of international
courtesy rules. These well-established and time-honored rules have made it easier for nations and
people to live and work together. Part of protocol has always been the acknowledgment of the
hierarchical standing of all present. Protocol rules are based on the principles of civility.
3. Standards are important for protocols so that people can create networking systems and
products that interoperate.
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line: home or small
office; 3. Cable to HFC: home; 4. 100 Mbps switched Ethernet: enterprise.
5. HFC bandwidth is shared among the users. On the downstream channel, all packets
emanate from a single source, namely, the head end. Thus, there are no collisions in the
downstream channel.
6. In most American cities, the current possibilities include: dial-up; DSL; cable modem;
fiber-to-the-home.
7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can run over
fibers optic links.
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9. ADSL: up to 24 Mbps downstream and 2.5 Mbps upstream, bandwidth is dedicated;
HFC, rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps, bandwidth is shared. FTTH:
2-10Mbps upload; 10-20 Mbps download; bandwidth is not shared.
10. There are two popular wireless Internet access technologies today:
a. Wifi (802.11) In a wireless LAN, wireless users transmit/receive packets to/from an base
station (i.e., wireless access point) within a radius of few tens of meters. The base station is
typically connected to the wired Internet and thus serves to connect wireless users to the wired
network.
b. 3G and 4G wide-area wireless access networks. In these systems, packets are transmitted
over the same wireless infrastructure used for cellular telephony, with the base station thus being
managed by a telecommunications provider. This provides wireless access to users within a
radius of tens of kilometers of the base station.
11. At time t0 the sending host begins to transmit. At time t1 = L/R1, the sending host
completes transmission and the entire packet is received at the router (no propagation delay).
Because the router has the entire packet at time t1, it can begin to transmit the
packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router completes transmission
and the entire packet is received at the receiving host (again, no propagation delay). Thus, the
end-to-end delay is L/R1 + L/R2.
12. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for
the duration of a call. Most packet-switched networks today (including the Internet) cannot make
any end-to-end guarantees for bandwidth. FDM requires sophisticated analog hardware to shift
signal into appropriate frequency bands.
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13. a) 2 users can be supported because each user requires half of the link bandwidth.
b) Since each user requires 1Mbps when transmitting, if two or fewer users transmit
simultaneously, a maximum of 2Mbps will be required. Since the available bandwidth of the
shared link is 2Mbps, there will be no queuing delay before the link. Whereas, if three users
transmit simultaneously, the bandwidth required will be 3Mbps which is more than the available
bandwidth of the shared link. In this case, there will be queuing delay before the link.
c) Probability that a given user is transmitting = 0.2
d) Probability that all three users are transmitting simultaneously =
= (0.2)3 = 0.008. Since the queue grows when all the users are transmitting, the fraction of time
during which the queue grows (which is equal to the probability
that all three users are transmitting simultaneously) is 0.008.
14. If the two ISPs do not peer with each other, then when they send traffic to each other they
have to send the traffic through a provider ISP (intermediary), to which they have to pay for
carrying the traffic. By peering with each other directly, the two ISPs can reduce their payments
to their provider ISPs. An Internet Exchange Points (IXP) (typically in a standalone building
with its own switches) is a meeting point where multiple ISPs can connect and/or peer together.
An ISP earns its money by charging each of the the ISPs that connect to the IXP a relatively
small fee, which may depend on the amount of traffic sent to or received from the IXP.
15. Google's private network connects together all its data centers, big and small. Traffic
between the Google data centers passes over its private network rather than over the public
Internet. Many of these data centers are located in, or close to, lower tier ISPs. Therefore, when
Google delivers content to a user, it often can bypass higher tier ISPs. What motivates content
providers to create these networks? First, the content provider has more control over the user
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experience, since it has to use few intermediary ISPs. Second, it can save money by sending less
traffic into provider networks. Third, if ISPs decide to charge more money to highly profitable
content providers (in countries where net neutrality doesn't apply), the content providers can
avoid these extra payments.
16. The delay components are processing delays, transmission delays, propagation delays,
and queuing delays. All of these delays are fixed, except for the queuing delays, which are
variable.
17. a) 1000 km, 1 Mbps, 100 bytes
b) 100 km, 1 Mbps, 100 bytes
18. 10msec; d/s; no; no
19. a) 500 kbps
b) 64 seconds
c) 100kbps; 320 seconds
20. End system A breaks the large file into chunks. It adds header to each chunk, thereby
generating multiple packets from the file. The header in each packet includes the IP address of
the destination (end system B). The packet switch uses the destination IP address in the packet to
determine the outgoing link. Asking which road to take is analogous to a packet asking which
outgoing link it should be forwarded on, given the packet’s destination address.
21. The maximum emission rate is 500 packets/sec and the maximum transmission rate is
350 packets/sec. The corresponding traffic intensity is 500/350 =1.43 > 1. Loss will eventually
occur for each experiment; but the time when loss first occurs will be different from one
experiment to the next due to the randomness in the emission process.
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Solution Manual for Computer Networking A Top-Down Approach,
8th Edition by James Kurose 2025 A Graded
Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end system” are used
interchangeably. End systems include PCs, workstations, Web servers, mail servers, PDAs,
Internet-connected game consoles, etc.
2. From Wikipedia: Diplomatic protocol is commonly described as a set of international
courtesy rules. These well-established and time-honored rules have made it easier for nations and
people to live and work together. Part of protocol has always been the acknowledgment of the
hierarchical standing of all present. Protocol rules are based on the principles of civility.
3. Standards are important for protocols so that people can create networking systems and
products that interoperate.
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line: home or small
office; 3. Cable to HFC: home; 4. 100 Mbps switched Ethernet: enterprise.
5. HFC bandwidth is shared among the users. On the downstream channel, all packets
emanate from a single source, namely, the head end. Thus, there are no collisions in the
downstream channel.
6. In most American cities, the current possibilities include: dial-up; DSL; cable modem;
fiber-to-the-home.
7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can run over
fibers optic links.
1
,Created By: QuickNotesPro
9. ADSL: up to 24 Mbps downstream and 2.5 Mbps upstream, bandwidth is dedicated;
HFC, rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps, bandwidth is shared. FTTH:
2-10Mbps upload; 10-20 Mbps download; bandwidth is not shared.
10. There are two popular wireless Internet access technologies today:
a. Wifi (802.11) In a wireless LAN, wireless users transmit/receive packets to/from an base
station (i.e., wireless access point) within a radius of few tens of meters. The base station is
typically connected to the wired Internet and thus serves to connect wireless users to the wired
network.
b. 3G and 4G wide-area wireless access networks. In these systems, packets are transmitted
over the same wireless infrastructure used for cellular telephony, with the base station thus being
managed by a telecommunications provider. This provides wireless access to users within a
radius of tens of kilometers of the base station.
11. At time t0 the sending host begins to transmit. At time t1 = L/R1, the sending host
completes transmission and the entire packet is received at the router (no propagation delay).
Because the router has the entire packet at time t1, it can begin to transmit the
packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router completes transmission
and the entire packet is received at the receiving host (again, no propagation delay). Thus, the
end-to-end delay is L/R1 + L/R2.
12. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for
the duration of a call. Most packet-switched networks today (including the Internet) cannot make
any end-to-end guarantees for bandwidth. FDM requires sophisticated analog hardware to shift
signal into appropriate frequency bands.
2
,Created By: QuickNotesPro
13. a) 2 users can be supported because each user requires half of the link bandwidth.
b) Since each user requires 1Mbps when transmitting, if two or fewer users transmit
simultaneously, a maximum of 2Mbps will be required. Since the available bandwidth of the
shared link is 2Mbps, there will be no queuing delay before the link. Whereas, if three users
transmit simultaneously, the bandwidth required will be 3Mbps which is more than the available
bandwidth of the shared link. In this case, there will be queuing delay before the link.
c) Probability that a given user is transmitting = 0.2
d) Probability that all three users are transmitting simultaneously =
= (0.2)3 = 0.008. Since the queue grows when all the users are transmitting, the fraction of time
during which the queue grows (which is equal to the probability
that all three users are transmitting simultaneously) is 0.008.
14. If the two ISPs do not peer with each other, then when they send traffic to each other they
have to send the traffic through a provider ISP (intermediary), to which they have to pay for
carrying the traffic. By peering with each other directly, the two ISPs can reduce their payments
to their provider ISPs. An Internet Exchange Points (IXP) (typically in a standalone building
with its own switches) is a meeting point where multiple ISPs can connect and/or peer together.
An ISP earns its money by charging each of the the ISPs that connect to the IXP a relatively
small fee, which may depend on the amount of traffic sent to or received from the IXP.
15. Google's private network connects together all its data centers, big and small. Traffic
between the Google data centers passes over its private network rather than over the public
Internet. Many of these data centers are located in, or close to, lower tier ISPs. Therefore, when
Google delivers content to a user, it often can bypass higher tier ISPs. What motivates content
providers to create these networks? First, the content provider has more control over the user
3
, Created By: QuickNotesPro
experience, since it has to use few intermediary ISPs. Second, it can save money by sending less
traffic into provider networks. Third, if ISPs decide to charge more money to highly profitable
content providers (in countries where net neutrality doesn't apply), the content providers can
avoid these extra payments.
16. The delay components are processing delays, transmission delays, propagation delays,
and queuing delays. All of these delays are fixed, except for the queuing delays, which are
variable.
17. a) 1000 km, 1 Mbps, 100 bytes
b) 100 km, 1 Mbps, 100 bytes
18. 10msec; d/s; no; no
19. a) 500 kbps
b) 64 seconds
c) 100kbps; 320 seconds
20. End system A breaks the large file into chunks. It adds header to each chunk, thereby
generating multiple packets from the file. The header in each packet includes the IP address of
the destination (end system B). The packet switch uses the destination IP address in the packet to
determine the outgoing link. Asking which road to take is analogous to a packet asking which
outgoing link it should be forwarded on, given the packet’s destination address.
21. The maximum emission rate is 500 packets/sec and the maximum transmission rate is
350 packets/sec. The corresponding traffic intensity is 500/350 =1.43 > 1. Loss will eventually
occur for each experiment; but the time when loss first occurs will be different from one
experiment to the next due to the randomness in the emission process.
4
