Homework
Chapter 10: Wide Area Networks
Last Name: ______
First Name: ______
Due Date: ______
Directions
Place your cursor at the end of a question and hit Enter. This will place you in the Answer style. This has already been done for Part a) of Question 1.
Test Your Understanding Questions
1.a) Distinguish between LANs and WANs. [373]
b) What are rights of way?[374]
c) What are carriers?[374]
d) Why do you have more flexibility with LAN service than with WAN service? Why?[374]
2.a) Why are typical WAN speeds slower than typical LAN speeds? Give a clear and complete argument. [375]
b) Why are future WAN prices difficult to predict?[375]
c) Compare the diversity of technologies in LANs and WANs.[375]
3.a) Why do MANs have higher typical speeds than broader-scope WANs?[376]
b) Are LANs single networks or internets? [376]
c) Are WANs single networks or internets?[376]
d) Is the Internet a WAN?[376]
4.a) List the three basic components of wide area networks.[376]
b) Are access links wired or wireless?[376]
c) What is CPE?(Do not just spell out the abbreviation.) [376]
5.a) What two technologies are used in business local loops?[377-379]
b) What two technologies are used in residential local loops?[379]
c) Compare the two local loop UTP technologies in terms of number of pairs and voice-grade versus data-grade wiring quality.[377-379]
d) Compare the types of UTP used in corporate buildings and in low-speed PSTN leased lines. {5, 19}[377-379]
e) Is all UTP wiring limited to 100 meters? Explain. {5, 19}[379]
6.a) Explain the difference between access lines and leased lines. [380]
b) Compare dial- up connections with leased line connections along the dimensions shown in Figure 10-7.[380]
7.a) Below what speed are there different leased line standards in different parts of the world? {6,21} [381]
b) What is the exact speed of a T1 line?[381]
c) What are the speeds of comparable leased lines in Europe?[381]
d) What access link transmission media do T1 and E1 lines use?{6,21}[381]
e) What access link transmission medium do all higher-speed leased lines require? {6,21}[381]
f) Why are fractional T1 and E1 speeds desirable?{6,21}[381]
g) List common fractional T1 speeds.{6,21}[381]
h) What is T1/E1 bonding, and why is it attractive?
i) What are the most widely used leased lines?[381]
8.a) What leased line standards are used above 50 Mbps?[382]
b) What is the lowest-speed SONET/SDH leased line?[382]
c) Why does 10 Gbps Ethernet use a speed of 9,953.28 Mbps on “10 Gbps” WAN links?[383]
9.a) Why are DSL connections likely to be less expensive than traditional leased line connections? [383]
b) Are business DSL service speeds symmetric or asymmetric? Explain.[383]
c) What are the downstream and upstream speeds of HDSL, HDSL2, and SHDSL?[384]
d) Do business, residential, or both DSL services offer quality-of- service guarantees?[384]
e) What is the fastest DSL standard?[384]
f) Why is VDSL difficult to compare to the other standards?[384]
10.a) Why is asymmetric speed acceptable in residential DSL service? [385]
b) What is the benefit of not providing quality-of-service guarantees to residential DSL customers?[385]
c) Does residential DSL offer simultaneous voice and data service?[386]
d) What equipment does the customer have to add to his or her home?[386]
e) What is the purpose of the DSL access multiplexer?[386]
f) Compare rated downstream speeds for ADSL initially and today.[386]
g) Compare rated upstream speeds for ADSL initially and today.[386]
h) What three factors reduce actual user throughput?[386]
i) Why is fiber to the home attractive?[386]
j) Compare fiber to the home installation with pulling optical fiber to firms for high-speed leased lines.[386]
11.a) What transmission media do cable television companies use? {5, 21} [388]
b) Why is coaxial cable called “coaxial”?[388]
c) Distinguish between the coaxial trunk cable and drop cable.[388]
d) What types of amplifiers are needed for cable data service?[388]
e) What device do customers need for cable modem service?[388]
12.a) What two technologies are needed for leased line switched WANs? [390]
b) What are the cost elements in networks of leased lines?[390]
13.a) List the physical components of PSDN technology. {6, 23} [391]
b) Do customers need leased lines if they use PSDNs?[391]
c) What is a POP?[391]
d) Why do you want a WAN with many POPs? (The answer is not in the text. It requires you to think about POPs.)[391]
e) If a company has seven sites, how many leased lines will it need if it uses a PSDN?[391]
f) Why are PSDNs fairly inexpensive?[391]
g) Why is the PSDN transport core drawn as a cloud?[391]
14.a) What is the speed range of Frame Relay? {6, 24} [392]
b) Why is this speed range attractive?[392]
c) Why has ATM not been popular?[392]
d) What is metro Ethernet?[392]
e) For what reasons is it attractive?[392]
f) What PSDN service is growing?[392]
*15.a) Why are virtual circuits used? {6, 25} [393]
b) With virtual circuits, on what does a switch base its forwarding decision when a frame arrives?[394]
c) Do PSDN frames have destination addresses or virtual circuit numbers in their headers?[394]
d) What is the name of the Frame Relay virtual circuit number?[394]
e) How long, typically, is a DLCI?[394]
f) How many virtual circuits does this number of bits allow? (The answer is not specifically in the text.)[393-394]
16.a) What are the two attractions of using the Internet as a WAN? [395]
b) What are the two issues that companies must overcome to do so?[395]
17.a) List the three protections that can be used to address the lack of security on the Internet.[395]
b) Based on what you learned in the first chapter, how can the second approach make the first approach less effective?[395]
18.a) How may connecting all of a company’s sites to a single ISP mitigate quality-of-service issues for traffic flowing over the Internet? [396]
b) What technology do ISPs use to provide quality-of-service guarantees?[396]
c) Do these guarantees work for site-to-site traffic within a firm, for traffic with other firms, or both? [396]
19.a) In cellular technology, what is a cell? {8,14} [397]
b) What is a cellsite? [397]
c) What are the two functions of the MTSO? [398]
20.a) Why does cellular telephony use cells?{8,15} [398-399]
b) What is the benefit of channel reuse?[398-399]
c) In Figure 10-19, assume thatchannels cannot be reused in adjacent cells, and Channel 47 is being used in Cells A, D, and F. What other cells can it be used in? [399]
d) Continuing, how many times is Channel 47 used?[399]
e) If a city has a hundred cells, how many times can a channel be used without channel reuse?[399]
f) Repeat the last two parts if channel reuse is possible in adjacent cells.[399]
21.a) Distinguish between handoffs and roaming in cellular telephony. {8,16}[400]
b) Distinguish between handoffs and roaming in 802.11 wireless LANs. [400]
22.a) List the required download speeds for each of the four generations of service.[402]
b) With what generation did web surfing become attractive?[402]
c) Compare 3G required download speeds with initial 3G actual throughput.[402]
d) What throughput do the best 3G services provide today?[402]
e) What applications that are difficult or impossible to use with 3G will be easy to use in 4G?[403]
f) What are the technical advances required in 4G systems?[402]
g) What 4G technology is likely to dominate in the future?[403]
23.a) What generation is HSPA+? [402-403]
b) What generation is LTE in terms of current speed?[402-403]
c) What generation does the ITU allow LTE to be called? Why?[402-403]
d) What is the designation of the version of LTE that will fully meet 4G performance requirements?[402-403]
e) Toward what standards are carriers converging?[402-403]
24.a) List the general categories of conditions that may limit user throughput. [403-404]
b) Which can the carrier do something about?[403-404]
c) What can the vendor do for each of these?[403-404]
d) What category is beyond the vendor’s control?[403-404]
25.a) Why is it attractive to a laptop user to have WLAN access? (This is a simple question.) [405]
b) Why is it attractive for a laptop user to have cellular data access?[405]
c) Why is it good for users that some smartphones can connect to WLAN access points?[405]
d) Why is it good for carriers?[405]
e) Why is it attractive to users that some smartphones can act as access points?[405]
f) Why is it attractive for a smartphone to act as an access point?[406]
g) Why should it be more attractive in the future?[406]
h) What is unattractive using a smartphone as an access point today?[406]
26.a) What technical problem does virtual WAN technology address? [406-407]
b) What must be added to create a corporate virtual WAN? [407]
c) What benefits can a virtual WAN system bring? [407]
End-of-Chapter Questions
Thought Questions
1.Why was this chapter so difficult?
Hands-On
1.If you have a smartphone, download an app to tell your data transmission throughput. What did you find?