Solution Manual for Computer Networking, 8th Edition
Author:James F. Kurose|ISBN:9780135928615| All Chapters
Covered| A+ GRADED LATEST VERSION
FULL TEST BANK!!!
1|Page
, th
Computer Networking: A Top-Down Approach, 8 Edition
Solutions to Review Questions and Problems
Version Date: August 2020
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 1996-2020 by J.F. Kurose and K.W. Ross. All rights reserved
2|Page
, 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.
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
3|Page
, 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.
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 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.
4|Page
Author:James F. Kurose|ISBN:9780135928615| All Chapters
Covered| A+ GRADED LATEST VERSION
FULL TEST BANK!!!
1|Page
, th
Computer Networking: A Top-Down Approach, 8 Edition
Solutions to Review Questions and Problems
Version Date: August 2020
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 1996-2020 by J.F. Kurose and K.W. Ross. All rights reserved
2|Page
, 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.
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
3|Page
, 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.
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 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.
4|Page
