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
Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
system” are used interchangeably. End systems include PCs, workstations,
v5 v5 v5 v5 v5 v5 v5 v5 v5
Web servers, mail servers, PDAs, Internet-connected game consoles, etc.
v5 v5 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
v5 v5 v5 v5 v5 v5 v5 v5
have
v5
made it easier for nations and people to live and work together. Part of
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
protocol has always been the acknowledgment of the hierarchical standing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
of all present. Protocol rules are based on the principles of civility.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,3. Standards are important for protocols so that people can create networking
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
systems
v5
v5 and products that interoperate.
v5 v5 v5
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line:
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
home
v5
v5 or small office;
v5 3. Cable to HFC: home;
v5 4. 100 v5 v5 v5 v5 v5 v5 v5
Mbps switched
v5 Ethernet: enterprise.v5 v5 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
v5 packets emanate from a single source, namely, the head end. Thus, there are
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5 no 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Gbps.
v5
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
run
v5
v5 over fibers optic links.
v5 v5 v5
9. ADSL: up to 24 Mbps downstream and 2.5
v5 Mbps v5 v5 v5 v5 v5 v5 v5
upstream,
v5 bandwidth is v5 v5
v5 dedicated; 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 v5
v5 bandwidth is shared. FTTH: 2-10Mbps upload; 10-20 Mbps download;
v5 v5 v5 v5 v5 v5 v5 v5
v5 bandwidth is not shared. v5 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
few tens of meters. The base station is typically connected to the
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
wired Internet and thus serves to connect wireless users to the wired
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
network. v5
b. 3G and 4G wide-area wireless access networks. In these systems,
v5 v5 v5 v5 v5 v5 v5 v5 v5
packets 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
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
, begin to transmit the
v5 v5 v5 v5
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 v5 v5
12. A circuit-switched
v5 network can guarantee a certain v5 v5 v5 v5 v5
amount v5 of end-to-end 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
v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth. FDM requires sophisticated analog hardware to shift signal into
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
appropriate frequency bands.
v5 v5 v5
13. a) 2 users can be supported because each user requires half of the link
v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth.
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 v5 v5 v5 v5 v5 v5
the bandwidth required will be 3Mbps which is more than the available
v5 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 v 5
= (0.2)3 = 0.008. Since the queue grows when all the users are
v5 v5 v5 v 5 v5 v5 v5 v5 v 5 v 5 v 5 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
each other they have to send the traffic through a provider ISP (intermediary),
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
to v5
which 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 v5
directly, the two ISPs can reduce their payments to their provider ISPs. An
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Internet Exchange Points (IXP) (typically in a standalone building with its own
v5 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
together. 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 v5
to 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 v5
sent to or received from the IXP.
v5 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
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
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
Chapter 1 Review Questions
1. There is no difference. Throughout this text, the words “host” and “end
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
system” are used interchangeably. End systems include PCs, workstations,
v5 v5 v5 v5 v5 v5 v5 v5 v5
Web servers, mail servers, PDAs, Internet-connected game consoles, etc.
v5 v5 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
v5 v5 v5 v5 v5 v5 v5 v5
have
v5
made it easier for nations and people to live and work together. Part of
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
protocol has always been the acknowledgment of the hierarchical standing
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
of all present. Protocol rules are based on the principles of civility.
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
,3. Standards are important for protocols so that people can create networking
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
systems
v5
v5 and products that interoperate.
v5 v5 v5
4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line:
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
home
v5
v5 or small office;
v5 3. Cable to HFC: home;
v5 4. 100 v5 v5 v5 v5 v5 v5 v5
Mbps switched
v5 Ethernet: enterprise.v5 v5 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
v5 packets emanate from a single source, namely, the head end. Thus, there are
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
v5 no 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Gbps.
v5
8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
run
v5
v5 over fibers optic links.
v5 v5 v5
9. ADSL: up to 24 Mbps downstream and 2.5
v5 Mbps v5 v5 v5 v5 v5 v5 v5
upstream,
v5 bandwidth is v5 v5
v5 dedicated; 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 v5
v5 bandwidth is shared. FTTH: 2-10Mbps upload; 10-20 Mbps download;
v5 v5 v5 v5 v5 v5 v5 v5
v5 bandwidth is not shared. v5 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
few tens of meters. The base station is typically connected to the
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
wired Internet and thus serves to connect wireless users to the wired
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
network. v5
b. 3G and 4G wide-area wireless access networks. In these systems,
v5 v5 v5 v5 v5 v5 v5 v5 v5
packets 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
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
, begin to transmit the
v5 v5 v5 v5
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 v5 v5
12. A circuit-switched
v5 network can guarantee a certain v5 v5 v5 v5 v5
amount v5 of end-to-end 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
v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth. FDM requires sophisticated analog hardware to shift signal into
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
appropriate frequency bands.
v5 v5 v5
13. a) 2 users can be supported because each user requires half of the link
v 5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
bandwidth.
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 v5 v5 v5 v5 v5 v5
the bandwidth required will be 3Mbps which is more than the available
v5 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 v 5
= (0.2)3 = 0.008. Since the queue grows when all the users are
v5 v5 v5 v 5 v5 v5 v5 v5 v 5 v 5 v 5 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
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
each other they have to send the traffic through a provider ISP (intermediary),
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
to v5
which 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 v5
directly, the two ISPs can reduce their payments to their provider ISPs. An
v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5 v5
Internet Exchange Points (IXP) (typically in a standalone building with its own
v5 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
together. 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 v5
to 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 v5
sent to or received from the IXP.
v5 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
© 2026 Pearson Education, Hoboken, NJ. All rights reserved.
