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COSC 2670 – Telecommunications
Week 5 Homework
Chap 7
1.
a) How are telephony and wide area networking related? [Question 1, page 274]
b) What are the three main purposes for WANs?
c) What are carriers, and why must they be used?
d) How are prices and costs related in carrier WAN services?
e) Does a company have more service options with LANs or with WANs?
f) Are service options and prices similar around the world?
g) List the three generations of carrier LAN technology.
h) Compare LAN and WAN transmission speeds.
i) Why are they different?
2.
a) What is the advantage of a full mesh leased line network? [Question 3, page 277]
b) What is the disadvantage of a full mesh leased line network?
c) What is the advantage of a pure hub-and-spoke leased line network?
d) What is the disadvantage?
e) Do most leased line networks use a full mesh or a pure hub-and-spoke topology?
Explain.
3.
a) Below what speed are there different leased line standards in different parts of the
world? [Question 5, page 279]
b) At what speeds do the slowest leased lines run?
c) What is the exact speed of a T1 line?
d) What are the speeds of comparable leased lines in Europe?
e) Why are fractional T1 and E1 speeds desirable?
f) List common fractional T1 speeds.
g) What are the most widely used leased lines?
h) What leased line standards are used above 50 Mbps?
4.
a) How do the lowest-speed leased lines and DSL lines differ in terms of transmission
media? [Question 7, page 282]
b) Describe HDSL and HDSL2 in terms of speed.
c) Describe SHDSL in terms of speed.
d) Which DSL services usually offer QoS guarantees?
5.
a) Why are virtual circuits used? [Question 9, page 285]
b) With virtual circuits, on what does a switch base its forwarding decision when a frame
arrives?
c) Do PSDN frames have destination addresses or virtual circuit numbers in their
headers?
6.
a) List the technical components in a Frame Relay network. [Question 10, page 288]
b) Briefly explain the purpose of each.
c) Which usually is the most expensive component in Frame Relay pricing?
d) Which usually is the second most expensive component in Frame Relay pricing?
e) What is managed Frame Relay service?
7.
a) What is metropolitan area Ethernet? [Question 13, page 292]
b) Distinguish between e-line and e-LAN service.
c) Why is metro Ethernet attractive?
d) Why are companies hesitant to create large metro Ethernet MANs?
8.
a) At what layer does IPsec operate? [Question 17, page 298]
b) What layers does IPsec protect?
c) Describe IPsec tunnel mode.
d) What is the main advantage of tunnel mode?
e) What is the main disadvantage of tunnel mode?
f) Describe IPsec transport mode.
g) What is the main advantage of transport mode?
h) What is the main disadvantage of transport mode?
i) In which IPsec mode are clients and servers required to have digital certificates?
j) Which IPsec mode does not require clients and servers to have digital certificates?
k) Is IPsec used for remote access or site-to-site VPNs?
9.
a) How is SSL/TLS limited? [Question 18, page 300]
b) Why is it attractive?
c) Without an SSL/TLS gateway, under what circumstances is SSL/TLS likely to be
used?
d) When an SSL/TLS gateway is used, how many SSL/TLS connections does the client
have?
e) What is webification?
f) What is webification’s benefit?
g) Why are downloads for SSL/TLS gateway service not likely to be useful on public
PCs?
10.
a) Of the two VPN security technologies discussed in this section, which provides
transparent security to higher layers? [Question 19, page 300]
b) Which tends to require the installation of software on many client PCs?
c) Which has stronger security?
d) Which would you use for an intranet that gives employees remote access to a highly
sensitive webserver via the Internet? (This is not a trivial question.) Justify your answer.
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