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Homework
Updated January 2007
CHAPTER 1
An Introduction to Networking
Learning Objectives:
Last Name: ____________________________________________________
First Name: ____________________________________________________
Due Date: __________________________________
Directions
You must do all Test Your Understanding questions in italics.
You are responsible for all other TYA questions that are now crossed out.
You must do all end-of-chapter questions.
Test Your Understanding
1.
a) Distinguish between the Internet and the World Wide Web.
b) Distinguish between the Internet and e-mail.
c) Describe client/server applications.
d) Distinguish between the Internet and corporate networks.
e) What are the characteristics of transaction processing applications?
f) Describe VoIP.
g) Distinguish between data communications and telecommunications.
2.
List the nine elements of a network.
3.
a) Distinguish between client and server computers. (Yes, this repeats an earlier
question.)
b) Which element of single networks do users care about?
4.
a) What are messages called in single networks?
b) What is packet switching?
Chapter 1-1
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a) Distinguish between switches and routers.
b) On what do Ethernet switches base switching decisions?
a) Distinguish between the two types of transmission lines.
b) Which type of line has higher speed? Why?
c) What type of line is the connection between the server computer and Switch 3 in
Figure 1-3?
d) What type of line is the connection between Switch 1 and Switch 4 in Figure 1-3?
e) What is multiplexing?
f) What is the benefit of multiplexing?
g) Why is packet switching useful in multiplexing?
What is the purpose of wireless access points?
When you discuss network costs, what should you mention?
a) In what units is transmission speed normally measured?
b) Is speed measured as bits per second or bytes per second?
c) Give the names and abbreviations for speeds in increasing factors of 1,000.
d) What is 55,000,000,000 bits per second in metric notation?
e) What is 100 kbps in bits per second?
f) Write the following speeds properly: 0.067 Mbps, 23,000 kbps, and 45.62 Gbps.
a) Distinguish between rated speed and throughput.
b) Distinguish between individual and aggregate throughput.
a) List the First Bank of Paradise’s sites.
b) Explain the functions of the bank’s three main buildings.
a) What is a WAN?
b) Does FBP use a single WAN or several?
a) What are LANs?
b) Distinguish between core and workgroup switches.
c) In Figure 1-9, how many workgroup switches are there?
d) How many core switches?
e) Suppose that there is a server connected to Workgroup Switch 2. Through what
switches will frames travel when the client connected to Workgroup Switch 1 sends
frames to the server?
a) For what is SOHO an abbreviation?
b) What are campus LANs?
a) Compare typical LAN and WAN speeds.
b) Why are typical LAN speeds faster than typical WAN speeds? Give a complete and
logical answer.
When are carriers needed?
a) What is an internet?
b) What are messages in internets called?
Chapter 1-2
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a) In an internet, what are hosts?
b) Is a client PC connected to an internet called a host?
a) What is a host’s official address on the Internet or an internet?
b) What is a host’s address on an Ethernet network?
c) How many bits long is an IP address?
d) How many bits long is an Ethernet address?
e) How are IP addresses presented for human reading?
f) How are Ethernet addresses presented for human reading?
g) What kind of address is 10.215.47.88?
h) What kind of address is AA-11-BF-47-3C-A9?
In an internet, what device connects networks together?
a) Distinguish between frames and packets.
b) In a certain internet, the source and destination hosts are separated by five networks
(including their own networks). When the source host transmits, how many packets will
travel through the internet?
c) How many frames?
a) For Frame X in Figure 1-12, list the source and destination Ethernet addresses and
the source and destination IP addresses of the packet contained in the frame.
b) Repeat for Frame Y.
c) Repeat for Frame Z.
a) Distinguish between internets and the Internet.
b) Is a home PC connected to the Internet a host?
c) Is the Internet a single network?
d) What are the three basic functions of ISPs on the Internet?
e) What are NAPs?
f) Why are NAPs crucial to universal connectivity on the Internet?
g) What standards allow ISPs and hosts to communicate with one another?
a) What is redundancy?
b) What is the benefit of redundancy?
c) Why does FBP use two ISPs?
a) What are subnets?
b) What are single networks called by single-network professionals?
c) What are single networks called by internet professionals?
d) What are internets called by single-network professionals?
e) What are internets called by internet professionals?
f) How do single-network professionals and internet professionals differ in their use of
the term network? (Yes, this question repeats material in some earlier questions.)
a) What is an intranet?
b) What is an extranet?
Chapter 1-3
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c) Can intranets and extranets use the Internet for transmission?
d) What standards do intranets and extranets use?
a) What is a host’s official address on the Internet?
b) What kind of IP addresses do server hosts normally receive?
c) What kind of IP addresses do client hosts normally receive?
d) How does a host get a dynamic IP address?
a) You know the host name of a server host you are attempting to reach. What kind of
server will you need to use before you can send messages to the server you are
attempting to reach?
b) If you know the IP address of the host you wish to send packets to, do you need to use
a DNS server?
c) In DHCP, the IP address the client PC receives is the address of which host?
d) In DNS, the IP address the client PC receives is the address of which host?
a) Why is the bank especially concerned about security?
b) What is the function of a firewall?
c) What benefits do cryptographic protections provide?
Thought Questions
1.
2.
Is efficiency more important in LANs or WANs? Justify your answer.
Your DSL line has a listed speed of 500 kbps. However, when your make downloads, a
speed counter tells you that you are only receiving 50 kBps. Can you explain this
apparent inconsistency?
Troubleshooting Questions
Troubleshooting is identifying and fixing problems. Troubleshooting is an important skill, and
we will see troubleshooting questions throughout this textbook. Research has shown that people
often make fundamental mistakes when they do troubleshooting. Most fundamentally, they
usually only consider one or two possible causes for their problem. Often, the one or two
possible causes they consider are incorrect. Consequently, they often waste time trying to solve
the wrong problem. Only later do they realize that they need to consider additional possibilities.
Premature focusing on one or two possible causes tends to extend downtime needlessly and
sometimes leads to “solutions” that fail to fix the real problem.
In troubleshooting questions, you will be expected to create multiple hypotheses, not just
one or two. It is almost always best to draw a diagram of all of the components of a system to
broaden your perspective. After you develop multiple possible causes for the problem, you can
then use logic or experimentation to prioritize them and eliminate false causes.
1.
Here is a sample troubleshooting problem for you to solve. You have been using a
telephone modem to access the Internet. Its rated download speed is 56 kbps. You switch
to a cable modem, which should allow you to receive at 500 kbps. In general, your
download speed for webpages is faster than it was with your modem; however, your
actual download rates usually vary from only 128 kbps to 256 kbps.
Chapter 1-4
2.
a) List likely reasons for your not being able to get a full 500 kbps. Do NOT just come
up with one or two possible explanations. Hint: Consider Figure 1-17, which shows the
Internet.
b) Assess the likelihood of each alternative given the facts in the problem description and
any other analysis you can consider.
In your browser, you enter the URL of a website you use daily. After some delay, you
receive a DNS error message that the host does not exist. What may have happened?
Again, do NOT just come up with one or two possible explanations.
Hands-On Exercises
Binary and Decimal Conversions
As noted Chapter 1, it is relatively easy to convert 32-bit IP addresses in dotted decimal notation.
The one thing that is hard to do is converting each group of eight bits into a decimal
number. If you have Microsoft Windows, the Calculator accessory shown as Figure 1-25 can
convert between binary and dotted decimal notations. Go to the Start button, then to Programs or
All Programs, then to Accessories, and then click on Calculator. The Windows Calculator will
then pop up.
Binary to Decimal
To convert eight binary bits to decimal, first choose View and click on Scientific to make the
Calculator a more advanced scientific calculator. Click on the Bin (binary) radio button and type
in the 8-bit binary sequence you wish to convert. Then click on the Dec (decimal) radio button.
The decimal value for that segment will appear.
Decimal to Binary
To convert decimal to binary, go to View and choose Scientific if you have not already done so.
Click on Dec to indicate that you are entering a decimal number. Type the number. Now click on
Bin to convert this number to binary.
One additional subtlety is that Calculator drops initial zeros. So if you convert 17, you get
10001. You must add three initial zeros to make this an 8-bit segment: 00010001.
Another subtlety is that you can only convert one 8-bit segment at a time.
1.
a) What is the binary number 11001010 in decimal?
b) Express the following IP address in binary: 128.171.17.13. Hint: The number 128 is
10000000 in binary. Put spaces between each group of eight bits.
c) Convert the following address in binary to dotted decimal notation: 11110000
10101010 00001111 11100011. (Spaces are added between bytes to make reading
easier.) Hint: The binary number 11110000 is 240 in decimal.
Binary to Hex
The same process can be used to convert 48-bit Ethernet addresses into hexadecimal notation
(hex). First, divide the address into bytes. In the Windows Calculator, click on bin (binary) and
enter the byte 10101010. Now click on hex. You will see AA. This is correct.
2.
a) What is 11000011 in hexadecimal?
b) What is 0F in binary? Remember that you will get a one-byte answer.
Chapter 1-5
Test Your Download Speed
How fast is your Internet connection? Test your download speed at
http://www.pcpitstop.com/internet/bandwidth.asp or
http://webservices.zdnet.com/zdnet/bandwidth. If you can, test your bandwidth during periods of
light and heavy use.
3.
a) What kind of connection do you have (telephone modem, cable modem, LAN, etc.)?
b) What was your download speed during the test?
Working with the Windows Command Line
Windows offers a number of tools from its command line prompt. Network professionals need to
learn to work with these commands.
Getting to the Command Line
To get to the command line, click on the Start button and choose Run. Type either cmd and hit
OK or command and then OK, depending on your version of Windows.
Command Line Rules
At the command line, you need to type everything exactly. You also need to hit Enter at the end
of each line. It is also good to know that you can clear the command line screen by typing
cls[Enter].
Your Configuration
In Windows, you can find information about your own computer with ipconfig or winipconfig.
In newer versions of Windows, type the command ipconfig/all[Enter]. Older versions of
Windows require you to type the command winipconfig[Enter]. This will give you your IP
address, your physical address (your Ethernet address), the IP addresses of your organization’s or
ISP’s DNS hosts, and other information—some of which we will see in Chapter 8.
4.
Use ipconfig/all or winipconfig. a) What is your computer’s IP address?
b) What is its Ethernet address?
c) What are the IP addresses of your DNS hosts?
DNS Lookup
In this chapter we saw that if you know the host name of the host to which you want to
communicate, then your computer must look up the host’s IP address by sending a DNS request
message to your local DNS server. You can also do this yourself from the command line, using
the nslookup command (DNS servers are also called name servers). For instance, type nslookup
www.google.com[Enter] to find Google’s IP address.
5.
a) Do an nslookup DNS lookup on a host whose name you know and that you use
frequently. What is its IP address?
b) Now do an nslookup on that IP address. Do you get the host name?
Ping
To find out if you can reach a host, and to see how much latency there is when you contact a
host, use the ping command. You ping an IP address or host name much as a submarine pings a
target to see if it exists and to see how many router hops away it is. To use the command, type
ping hostname[Enter] or ping IPaddress[Enter]. Ping may not work if the host is behind a
firewall, because firewalls typically block pings.
Chapter 1-6
6.
Ping a host whose name you know and that you use frequently. What is the latency? If
this does not work because the host is behind a firewall, do other hosts until you succeed.
Ping 127.0.0.1 (PC, Call Home)
Ping the address 127.0.0.1. This is your computer’s loopback address. In effect, the computer’s
network program sends a ping to itself. If your PC seems to be having trouble communicating
over the Internet, type ping 127.0.0.1[Enter]. If the ping fails, you know that the problem is
internal, and you need to focus on your network software’s configuration. If the ping succeeds,
then your computer is talking to the outside world at least.
7.
Ping 127.0.0.1. Did it succeed?
Tracert
The Windows tracert program is like a super ping. It lists latency not only to a target host but
also lists each router along the way and lists latency to that router. Actually, it shows three
latencies because it tests each router three times. To use tracert, type tracert hostname[Enter] or
tracert IPaddress[Enter]. Again, hosts (and routers) behind firewalls will not respond.
8.
Do a tracert on a host whose name you know and that you use frequently. You can stop
the tracert process by hitting Control-C. a) What is the destination host?
b) How many routers are there between you and the destination host? If this does not
work because the host is behind a firewall, do other hosts until you succeed.
9.
Distinguish between the information that ping provides and the information that tracert
provides.
To Get Your IP and Ethernet Addresses with Windows XP
Do the following if you have an XP computer. This exercise will give you configuration
information without your having to go to the command line. Choose Start, then Control Panel,
then Network and Internet Connections, then Network Connections. In the window that appears,
click on a network connection icon to select it. Choose File, Status. You will see the Connection
Status dialog box for that connection. Select the Support tab to see your IP address. Click on
Details while in the Support tab to see more information, including the physical (Ethernet)
address of your Network Interface Card (NIC).
10.
If you have a Windows XP computer, find your IP address and the physical (Ethernet)
address of your computer.
Chapter 1-7