Solution Manual for Computer Networking,8th
Edition by James Kurose
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,Computer Networking: A Top-Down Approach,
8th Edition
Solutions to Review Questions and Problems
Version Date: August 2025
This document contains the solutions to review questions and problems for the 8th edition
of Computer Networking: A Top-Down Approach by Jim Kurose and Keith Ross. These
solutions are being made available to instructors ONLY. Please do NOT copy or distribute
this document to others (even other instructors). Please do not post any solutions on a
publicly-available Web site. We’ll be happy to provide a copy (up-to-date) of this solution
manual ourselves to anyone who asks.
Acknowledgments: Over the years, several students and colleagues have helped us prepare
this solutions manual. Special thanks goes to Honggang Zhang, Rakesh Kumar, Prithula
Dhungel, Vijay Annapureddy, Yifan Zhou. Also thanks to all the readers who have made
suggestions and corrected errors.
All material © copyright 1996-2025 by J.F. Kurose and K.W. Ross. All rights reserved
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end system”
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
are used interchangeably. End systems include PCs, workstations, Web servers,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
mail servers, PDAs, Internet-connected game consoles, etc.
v5 v5 v5 v5 v5 v5 v5
2. From Wikipedia: Diplomatic protocol is commonly described as a set of
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
international courtesy rules. These well-established and time-honored rules have
v5 v5 v5 v5 v5 v5 v5 v5 v5
made it easier for nations and people to live and work together. Part of protocol
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
has always been the acknowledgment of the hierarchical standing of all present.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Protocol rules are based on the principles of civility.
v5 v5 v5 v5 v5 v5 v5 v5 v5
3. Standards are important for protocols so that people can create networking systems
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
and products that interoperate.
v5 v5 v5 v5
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line: home
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
or small office; 3. Cable to HFC: home; 4. 100 Mbps switched Ethernet:
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
enterprise.
v5
5. HFC bandwidth is shared among the users. On the downstream channel, all
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
packets emanate from a single source, namely, the head end. Thus, there are no
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
collisions in the downstream channel.
v5 v5 v5 v5 v5
6. In most American cities, the current possibilities include: dial-up; DSL; cable
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
modem; fiber-to-the-home.
v5 v5
7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can run
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
over fibers optic links.
v5 v5 v5 v5
9. ADSL: up v5 to 24 Mbps downstream and 2.5 Mbps upstream, bandwidth is
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
dedicated;
v5 v5 HFC, rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth
v5 is shared. FTTH: 2-10Mbps upload; 10-20 Mbps download;
v5 v5 v5 v5 v5 v5 v5 v5
bandwidth
v5 v5 is not shared.
v5 v5
10. There are two popular wireless Internet access technologies today:
v5 v5 v5 v5 v5 v5 v5 v5
a. Wifi (802.11) In a wireless LAN, wireless users transmit/receive packets
v5 v5 v5 v5 v5 v5 v5 v5 v5
to/from an base station (i.e., wireless access point) within a radius of few
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
tens of meters. The base station is typically connected to the wired Internet
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
and thus serves to connect wireless users to the wired network.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
b. 3G and 4G wide-area wireless access networks. In these systems, packets
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
are transmitted over the same wireless infrastructure used for cellular
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
telephony, with the base station thus being managed by a
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
telecommunications provider. This provides wireless access to users
v5 v5 v5 v5 v5 v5 v5 v5
within a radius of tens of kilometers of the base station.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
11. At time t0 the sending host begins to transmit. At time t1 = L/R1, the sending
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
host completes transmission and the entire packet is received at the router (no
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
propagation delay). Because the router has the entire packet at time t1, it can
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
begin to transmit the
v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
, packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
completes transmission and the entire packet is received at the receiving host
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
(again, no propagation delay). Thus, the end-to-end delay is L/R1 + L/R2.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v 5 v5
12. A circuit-switched network can guarantee a certain amount of end-to-end
v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth for the duration of a call. Most packet-switched networks today
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
(including the Internet) cannot make any end-to-end guarantees for bandwidth.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
FDM requires sophisticated analog hardware to shift signal into appropriate
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
frequency bands.
v5 v5
13. a) 2 users can be supported because each user requires half of the link bandwidth.
v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
b) Since each user requires 1Mbps when transmitting, if two or fewer users
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
transmit simultaneously, a maximum of 2Mbps will be required. Since the
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
available bandwidth of the shared link is 2Mbps, there will be no queuing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
delay before the link. Whereas, if three users transmit simultaneously,
v5 v5 v5 v5 v 5 v 5 v 5 v 5 v 5 v 5
the bandwidth required will be 3Mbps which is more than the available
v 5 v 5 v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth of the shared link. In this case, there will be queuing delay
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
before the link.
v5 v5 v5
c) Probability that a given user is transmitting = 0.2 v5 v5 v5 v5 v5 v5 v5 v5
d) Probability that all three users are transmitting simultaneously =
v5 v5 v5 v5 v5 v5 v5 v5 v5
3
= (0.2) = 0.008. Since the queue grows when all the users are
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
transmitting, the fraction of time during which the queue grows (which
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
is equal to the probability
v5 v5 v5 v5 v5
that all three users are transmitting simultaneously) is 0.008.
v5 v5 v5 v5 v5 v5 v5 v5
14. If the two ISPs do not peer with each other, then when they send traffic to each
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5other they have to send the traffic through a provider ISP (intermediary), to
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5which they have to pay for carrying the traffic. By peering with each other
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5directly, the two ISPs can reduce their payments to their provider ISPs. An
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5Internet Exchange Points (IXP) (typically in a standalone building with its own
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5switches) is a meeting point where multiple ISPs can connect and/or peer
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5together. An ISP earns its money by charging each of the the ISPs that connect
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5to the IXP a relatively small fee, which may depend on the amount of traffic
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5sent to or received from the IXP.
v5 v5 v5 v5 v5 v5
15. Google's private network connects together all its data centers, big and small.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Traffic between the Google data centers passes over its private network rather
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
than over the public Internet. Many of these data centers are located in, or close
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
to, lower tier ISPs. Therefore, when Google delivers content to a user, it often
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
can bypass higher tier ISPs. What motivates content providers to create these
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
networks? First, the content provider has more control over the user experience,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
since it has to use few intermediary ISPs. Second, it can save money by sending
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
less traffic into provider networks. Third, if ISPs decide to charge more money to
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
highly profitable content providers (in countries where net neutrality doesn't
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
apply), the content providers can avoid these extra payments.
v5 v5 v5 v5 v5 v5 v5 v5 v5
16. The delay components are processing delays, transmission delays, propagation
v5 v5 v5 v5 v5 v5 v5 v5
delays, and queuing delays. All of these delays are fixed, except for the queuing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
Edition by James Kurose
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,Computer Networking: A Top-Down Approach,
8th Edition
Solutions to Review Questions and Problems
Version Date: August 2025
This document contains the solutions to review questions and problems for the 8th edition
of Computer Networking: A Top-Down Approach by Jim Kurose and Keith Ross. These
solutions are being made available to instructors ONLY. Please do NOT copy or distribute
this document to others (even other instructors). Please do not post any solutions on a
publicly-available Web site. We’ll be happy to provide a copy (up-to-date) of this solution
manual ourselves to anyone who asks.
Acknowledgments: Over the years, several students and colleagues have helped us prepare
this solutions manual. Special thanks goes to Honggang Zhang, Rakesh Kumar, Prithula
Dhungel, Vijay Annapureddy, Yifan Zhou. Also thanks to all the readers who have made
suggestions and corrected errors.
All material © copyright 1996-2025 by J.F. Kurose and K.W. Ross. All rights reserved
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end system”
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
are used interchangeably. End systems include PCs, workstations, Web servers,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
mail servers, PDAs, Internet-connected game consoles, etc.
v5 v5 v5 v5 v5 v5 v5
2. From Wikipedia: Diplomatic protocol is commonly described as a set of
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
international courtesy rules. These well-established and time-honored rules have
v5 v5 v5 v5 v5 v5 v5 v5 v5
made it easier for nations and people to live and work together. Part of protocol
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
has always been the acknowledgment of the hierarchical standing of all present.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Protocol rules are based on the principles of civility.
v5 v5 v5 v5 v5 v5 v5 v5 v5
3. Standards are important for protocols so that people can create networking systems
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
and products that interoperate.
v5 v5 v5 v5
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line: home
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
or small office; 3. Cable to HFC: home; 4. 100 Mbps switched Ethernet:
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
enterprise.
v5
5. HFC bandwidth is shared among the users. On the downstream channel, all
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
packets emanate from a single source, namely, the head end. Thus, there are no
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
collisions in the downstream channel.
v5 v5 v5 v5 v5
6. In most American cities, the current possibilities include: dial-up; DSL; cable
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
modem; fiber-to-the-home.
v5 v5
7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can run
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
over fibers optic links.
v5 v5 v5 v5
9. ADSL: up v5 to 24 Mbps downstream and 2.5 Mbps upstream, bandwidth is
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
dedicated;
v5 v5 HFC, rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth
v5 is shared. FTTH: 2-10Mbps upload; 10-20 Mbps download;
v5 v5 v5 v5 v5 v5 v5 v5
bandwidth
v5 v5 is not shared.
v5 v5
10. There are two popular wireless Internet access technologies today:
v5 v5 v5 v5 v5 v5 v5 v5
a. Wifi (802.11) In a wireless LAN, wireless users transmit/receive packets
v5 v5 v5 v5 v5 v5 v5 v5 v5
to/from an base station (i.e., wireless access point) within a radius of few
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
tens of meters. The base station is typically connected to the wired Internet
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
and thus serves to connect wireless users to the wired network.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
b. 3G and 4G wide-area wireless access networks. In these systems, packets
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
are transmitted over the same wireless infrastructure used for cellular
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
telephony, with the base station thus being managed by a
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
telecommunications provider. This provides wireless access to users
v5 v5 v5 v5 v5 v5 v5 v5
within a radius of tens of kilometers of the base station.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
11. At time t0 the sending host begins to transmit. At time t1 = L/R1, the sending
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
host completes transmission and the entire packet is received at the router (no
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
propagation delay). Because the router has the entire packet at time t1, it can
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
begin to transmit the
v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
, packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
completes transmission and the entire packet is received at the receiving host
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
(again, no propagation delay). Thus, the end-to-end delay is L/R1 + L/R2.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v 5 v5
12. A circuit-switched network can guarantee a certain amount of end-to-end
v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth for the duration of a call. Most packet-switched networks today
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
(including the Internet) cannot make any end-to-end guarantees for bandwidth.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
FDM requires sophisticated analog hardware to shift signal into appropriate
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
frequency bands.
v5 v5
13. a) 2 users can be supported because each user requires half of the link bandwidth.
v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
b) Since each user requires 1Mbps when transmitting, if two or fewer users
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
transmit simultaneously, a maximum of 2Mbps will be required. Since the
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
available bandwidth of the shared link is 2Mbps, there will be no queuing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
delay before the link. Whereas, if three users transmit simultaneously,
v5 v5 v5 v5 v 5 v 5 v 5 v 5 v 5 v 5
the bandwidth required will be 3Mbps which is more than the available
v 5 v 5 v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth of the shared link. In this case, there will be queuing delay
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
before the link.
v5 v5 v5
c) Probability that a given user is transmitting = 0.2 v5 v5 v5 v5 v5 v5 v5 v5
d) Probability that all three users are transmitting simultaneously =
v5 v5 v5 v5 v5 v5 v5 v5 v5
3
= (0.2) = 0.008. Since the queue grows when all the users are
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
transmitting, the fraction of time during which the queue grows (which
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
is equal to the probability
v5 v5 v5 v5 v5
that all three users are transmitting simultaneously) is 0.008.
v5 v5 v5 v5 v5 v5 v5 v5
14. If the two ISPs do not peer with each other, then when they send traffic to each
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5other they have to send the traffic through a provider ISP (intermediary), to
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5which they have to pay for carrying the traffic. By peering with each other
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5directly, the two ISPs can reduce their payments to their provider ISPs. An
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5Internet Exchange Points (IXP) (typically in a standalone building with its own
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5switches) is a meeting point where multiple ISPs can connect and/or peer
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5together. An ISP earns its money by charging each of the the ISPs that connect
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5to the IXP a relatively small fee, which may depend on the amount of traffic
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5sent to or received from the IXP.
v5 v5 v5 v5 v5 v5
15. Google's private network connects together all its data centers, big and small.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Traffic between the Google data centers passes over its private network rather
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
than over the public Internet. Many of these data centers are located in, or close
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
to, lower tier ISPs. Therefore, when Google delivers content to a user, it often
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
can bypass higher tier ISPs. What motivates content providers to create these
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
networks? First, the content provider has more control over the user experience,
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
since it has to use few intermediary ISPs. Second, it can save money by sending
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
less traffic into provider networks. Third, if ISPs decide to charge more money to
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
highly profitable content providers (in countries where net neutrality doesn't
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
apply), the content providers can avoid these extra payments.
v5 v5 v5 v5 v5 v5 v5 v5 v5
16. The delay components are processing delays, transmission delays, propagation
v5 v5 v5 v5 v5 v5 v5 v5
delays, and queuing delays. All of these delays are fixed, except for the queuing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
