Solution Manual For Computer Networking A Top-Down Approach, 8th Edition by James Kurose| Ultimate Guide A+

Computer Networking A Top-Down Approach, 8th Edition by James Kurose
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© 2020 Pearson Education, Hoboken, NJ. All rights reserved.
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,ComputerNetworking: A Top-Down Approach, 8th k k k k k




Edition
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Solutionsto Review Questions and Problems k k k k k




Version Date: August 2020 k k k




Chapter1ReviewQuestions k k k




1. There is no difference. Throughout this text, the words “host” and “end system” are used
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interchangeably. End systems include PCs, workstations, Web servers, mail servers,
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PDAs, Internet-connected game consoles, etc.
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2. From Wikipedia: Diplomatic protocol is commonly described as a set of international
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courtesy rules. These well-established and time-honored rules have made it easier for
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nations and people to live and work together. Part of protocol has always been the
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acknowledgment of the hierarchical standing of all present. Protocol rules are based on the
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principles of civility.
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3. Standards are important for protocols so that people can create networking systems and
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products that interoperate.
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4. 1. Dial-up modem over telephone line: home; 2. DSL over telephone line: home or small
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office; 3. Cable to HFC: home; 4. 100 Mbps switched Ethernet: enterprise.
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5. HFC bandwidth is shared among the users. On the downstream channel, all packets
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emanate from a single source, namely, the head end. Thus, there are no collisions in the
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downstream channel.
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6. In most American cities, the current possibilities include: dial-up; DSL; cable modem;
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fiber-to-the-home.
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© 2020 Pearson Education, Hoboken, NJ. All rights reserved.
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,7. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
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8. Today, Ethernet most commonly runs over twisted-pair copper wire. It also can run over
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kfibers optic links.
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9. ADSL: up to 24 Mbps downstream and 2.5 Mbps upstream, bandwidth is dedicated; HFC,
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rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps, bandwidth is shared. FTTH:
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2-10Mbps upload; 10-20 Mbps download; bandwidth is not shared.
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10. There are two popular wireless Internet access technologies today:
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a. Wifi (802.11) In a wireless LAN, wireless users transmit/receive packets to/from
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an base station (i.e., wireless access point) within a radius of few tens of meters.
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The base station is typically connected to the wired Internet and thus serves to
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connect wireless users to the wired network.
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b. 3G and 4G wide-area wireless access networks. In these systems, packets are
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transmitted over the same wireless infrastructure used for cellular telephony, with
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the base station thus being managed by a telecommunications provider. This
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provides wireless access to users within a radius of tens of kilometers of the base
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11. At time t0 the sending host begins to transmit. At time t1 = L/R1, the sending host
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kcompletes transmission and the entire packet is received at the router (no propagation
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kdelay). Because the router has the entire packet at time t1, it can begin to transmit the
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© 2020 Pearson Education, Hoboken, NJ. All rights reserved.
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, packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router completes
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transmission and the entire packet is received at the receiving host (again, no propagation
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delay). Thus, the end-to-end delay is L/R1 + L/R2.
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12. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for
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the duration of a call. Most packet-switched networks today (including the Internet) cannot
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make any end-to-end guarantees for bandwidth. FDM requires sophisticated analog
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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.
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b) Since each user requires 1Mbps when transmitting, if two or fewer users transmit
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simultaneously, a maximum of 2Mbps will be required. Since the available
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bandwidth of the shared link is 2Mbps, there will be no queuing delay before the link.
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Whereas, if three users transmit simultaneously, the bandwidth required will
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be 3Mbps which is more than the available bandwidth of the shared link. In this case,
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there will be queuing delay before the link.
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c) Probability that a given user is transmitting = 0.2 k k k k k k k k




d) Probability that all three users are transmitting simultaneously = k k k k k k k k k




3
= (0.2) = 0.008. Since the queue grows when all the users are transmitting, the
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fraction of time during which the queue grows (which is equal to the probability
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that all three users are transmitting simultaneously) is 0.008.
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14. If the two ISPs do not peer with each other, then when they send traffic to each other they
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have to send the traffic through a provider ISP (intermediary), to which they have to pay for
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carrying the traffic. By peering with each other directly, the two ISPs can reduce their
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payments to their provider ISPs. An Internet Exchange Points (IXP) (typically in a
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standalone building with its own switches) is a meeting point where multiple ISPs can
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connect and/or peer together. An ISP earns its money by charging each of the the ISPs that
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connect to the IXP a relatively small fee, which may depend on the amount of traffic sent
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to or received from the IXP.
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15. Google's private network connects together all its data centers, big and small. Traffic
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between the Google data centers passes over its private network rather than over the
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public Internet. Many of these data centers are located in, or close to, lower tier ISPs.
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Therefore, when Google delivers content to a user, it often can bypass higher tier ISPs.
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What motivates content providers to create these networks? First, the content provider has
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more control over the user experience, since it has to use few intermediary ISPs. Second, it
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can save money bysending less traffic into provider networks. Third, if ISPs decidetocharge
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more money to highly profitable content providers (in countries where net neutrality
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doesn't apply), the content providers can avoid these extra payments.
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16. The delay components are processing delays, transmission delays, propagation delays,
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and queuing delays. All of these delays are fixed, except for the queuing delays, which are
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variable.
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© 2020 Pearson Education, Hoboken, NJ. All rights reserved.
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