Homework
Updated January 2007
CHAPTER 7
Wide Area Networks (WANs)
Last Name: ____________________________________________________
First Name: ____________________________________________________
Due Date: __________________________________
Test Your Understanding
1.
a) How are telephony and wide area networking related?
b) What are the three main purposes for WANs?
c) Compare LAN and WAN transmission speeds.
d) Why are they different?
e) What are carriers, and why must they be used?
f) How are prices and costs related in carrier WAN services?
2.
Distinguish between the technologies of leased line voice networks and data networks.
3.
a) What is the advantage of a full mesh leased line network?
b) What is the disadvantage?
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?
4.
a) Below what speed are there different leased line standards in different parts of the
world?
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 and Japan?
e) Why are fractional T1 and E1 speeds desirable?
Chapter 7-1
5.
6.
7.
8.
9.
10.
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?
i) All SONET and SDH lines are multiples of what speed?
a) How do leased lines and DSL lines differ in terms of transmission media?
b) Describe HDSL and HDSL2 in terms of speed.
c) Describe SHDSL in terms of speed.
d) Which DSL services usually offer performance guarantees?
a) Describe the physical components of PSDN technology.
b) Do customers need leased lines if they use PSDNs?
c) Compare leased line costs for leased line networks and PSDNs.
d) Which usually is less expensive overall—leased line data networks or PSDN
transmission?
e) Why is the PSDN transport core drawn as a cloud?
f) Why do PSDNs tend to cost less than leased line networks?
g) What things do SLAs guarantee?
h) Why would an SLA guarantee maximum latency rather than minimum latency?
a) Why are virtual circuits used?
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?
a) List the technical components in a Frame Relay network.
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?
a) What is the name of the Frame Relay virtual circuit number?
b) How long is it usually?
c) How many virtual circuits does this number of bits allow?
d) Distinguish between PVCs and SVCs.
e) Which are more expensive?
a) Compare Frame Relay and ATM speed ranges.
b) Are Frame Relay and ATM competitors? Explain.
c) In ATM, what is a cell?
d) How long are ATM headers and payloads?
e) Why does ATM use short cells? Explain your answer.
f) Compare what ATM has to offer to voice and data service.
g) Why does ATM have strong management tools?
h) Why is ATM’s sophistication good?
Chapter 7-2
11.
12.
13.
14.
15.
i) Why is it problematic?
j) Why is ATM usage likely to grow in the future?
a) What is metropolitan area Ethernet?
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?
a) What is a VPN?
b) Why are VPNs attractive?
c) Why are managed VPNs attractive?
d) What is a remote access VPN?
e) What are site-to-site VPNs?
f) Why are site-to-site VPNs likely to become the largest corporate use for VPNs?
g) What are host-to-host VPNs?
a) At what layer does IPsec operate?
b) What layers does it 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) Describe IPsec authentication in transport mode. In which IPsec mode do clients and
servers need digital certificates?
j) Is IPsec used for remote access or site-to-site VPNs?
a) How is SSL/TLS limited?
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?
a) Of the two VPN security technologies in this section, which provides transparent
security to higher layers?
b) Which tends to require the installation of software on many client PCs?
c) Which has the strongest 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.
Chapter 7-3
Thought Question
1.
Several Internet access systems are asymmetric, with higher downstream speeds than
upstream speeds. a) Is this good for client PC access to webservers? Explain.
b) Does it matter for client access to e-mail servers? Explain.
c) Is it good for a file server? Explain.
d) Is it good for videoconferencing? Explain.
Projects
1.
Getting Current. Go to the book website’s New Information and Errors pages for this
chapter to get new information since this book went to press and to correct any errors in
the text.
Chapter 7-4