Download IS- 162 Final Exam Winter 2011

IS- 162 Final Exam Winter 2011
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Enter your answers in the spaces provided. If you feel the need to object to or comment upon
any question, put your discussion in blue ink.
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I will post the answers on the web site shortly after the final is over.
True/False (2 ea)
1. [ F ] (TF) 8 bit parallel ribbon cable is highly preferable to serial cable for connecting
devices further apart than fifty feet.
Parallel cables are subject to skew, so six feet or so is the limit for parallel cables.
2. [ T ] (TF) Any processing or transmission of analog signals will degrade the signals.
However, a well designed digital channel will deliver perfect data as long as design
parameters are not exceeded.
I think I said this about twenty times.
3. [ F ] (TF) RJ-45, Registered Jack 45, refers to the important job of documenting the
connections while wiring a building. This would be the 45th jack in a registered punchdown block.
RJ 11 and RJ 45 are designation for plugs and jacks
4. [ T ] (TF) Spread Spectrum is a transmission mode in which a broad band is used.
Normally the transmitter and receiver frequency hop, using a pseudo-random sequence.
Since the frequencies change constantly, a band can support many channels. Since the PN
sequence is complex, it is hard for anyone to listen in unless they have the code.
5. [ t ] (TF) A subnet mask of 255.255.255.0 allows for about 255 nodes in the local area
network. 0s in a subnet mask indentify bits that can change for each node in the subnet
6. [ T ] (TF) ADSL does not have the same uplink speed as downlink speed.
Stands for Asymetric DSL.
7. [ F ] (TF) Collapsed Backbone refers to a WAN that has crashed and no longer works.
Not broken, collapsed refers to a very small physical distance.
8. [ T ] (TF) Modulation is the imposition of information upon a carrier signal.
I’ve said this a few times in class. It’s also in the book.
9. [ T ] (TF) 66 blocks and 110 blocks are two versions of punch-down blocks on which
telecomm circuits are terminated.
66 blocks are older, used for telephone circuits. 110 blocks are often used for networks.
10. [ F ] (TF) Bluetooth has a longer range than 802.11 a.
11. [ T ] (TF) A two-ring Sonnet ring is self-healing in most cases.
A failure causes the system to go to the back-up ring without losing data.
12. [ F ] (TF) 10GBase-SW is used in Sonnet. It is one of the copper network standards
operating at the same 10 Gb/s transmission speed as fiber.
No. this is a fiber optic network designation
13. [ T ] (TF) VPNs provide private networking, often spanning thousands of miles, using
existing networks.
Virtual Private Lans
14. [ T ] (TF) Statistical multiplexing allows more flexible data transfer, usually resulting in a
higher information throughput rate than the nominal data throughput rate.
A statistical mux only transmits data that needs to be transmitted. A normal mux
transmits everything whether it is changing or not.
--------------------------------------------------------------------------------Mult. Choice (2 ea)
1. [ D ] (ABCD) Wireless 802.11 g is characterized as:
A Uses the 2.4 GHz band
B Max throughput of about 54 Mb/s
C Nominal range = 100 M
D All of the above
2. [ B ] (ABCD)Single mode fiber is:
A Thicker so it supports longer distance range than multi-mode fiber.
B Thinner and supports longer distance range than multi-mode fiber.
C Is not viable outside the protected environment of buildings.
D Came first. Multi-mode fiber is replacing single mode, since it can carry more signals
Single mode’s diameter is similar to wavelength of the light being transmitted, so it acts
like a waveguide. Multi-mode fiber transmits reflections that can soften the received
signal.
3. [ C ] (ABCD) Polar satellite orbits are used primarily for:
A Long distance communications
B Satellite TV
C Research, Weather, and GPS
D Geosynchronous links.
It has to be an equatorial orbit to be geosynchronous. Otherwise, it would wave north
and south and the satellite dishes would point to the wrong place several times a day.
4. [ A ] (ABCD) The radiation patterns for various kinds of antennas vary in the following
order: (Tightest pattern first, broadest pattern last)
A Dish -- multi-element -- Dipole
B multi-element -- Dish -- Dipole
C Dipole -- Dish -- multi-element
D None of the above. All antennas radiate the same pattern.
The standard for antennas is the quarter wave dipole. That’s what the quality of all
antennae are measured against. Add director and reflector elements to make it a multielement antenna like roof-top antennas. The dish has the tightest beam since its
parabolic shape directs all the energy in a forward direction. The larger the dish
antenna’s diameter with respect to wavelength, the tighter the beam.
5. [ C ] (ABCD) When installing a WI-FI wireless net in a building, you should consider the
following issues.
A Small metal items will scatter the signal
B Large metal items will reflect the signal
C Both A and B will reduce the integrity of the signal at different points.
D The signal cannot propagate through walls. Transmission is strictly line of sight.
Radio can propagate through walls, just not through metal or otherwise conductive
surfaces. Steel studs, large metal items, do reflect waves from their intended direction.
Small metal objects (small with respect to wavelength) aren’t big enough to reflect
reliably, so they scatter the waves in many directions. The point is, that if the waves are
scattered and reflected, they don’t get to the receiver all at once so they don’t deliver
all the power to the receiver.
6. [ D ] (ABCD)If many functional channels are to be carried over long distances, which
mode transmission is applicable?
A Time-Division Multiplexing
B Many individual channels
C Frequency division multiplexing
D All of the above.
7. [ C ] (ABCD) T – Carriers provide a variety of bandwidths (Thoughput rates) Which of
the following is correct?
A T- 1 – 64 Kb/s
B T – 5 -- about 274 Mb/s
C T-4 -- about 274 Mb/s
D T-3 -- 10 Mb/s
Look at the table. T1 is the basis. All the T carriers are derived therefrom.
8. [ D ] (ABCD) Some common modulation modes used in RF communications are:
A FM -- Frequency Modulation
B AM – Amplitude Modulation
C FSK – Frequency Shift Keying (for data)
D All of the above
We talked about AM and FM several times in class. FSK is sending one frequency for a
one and a different frequency for a zero.
9. [ D ] (ABCD) Remote Desktop, a standard Microsoft application layer process, uses
TCP/IP.
A Is standard on all Windows operating systems.
B Allows risk-free access to your desktop from any internet site
C Both of the above
D Neither of the above
Remote Desktop is not distributed with the home versions.
There is no such thing as risk-free communications.
10. [ D ] (ABCD) Of what use is the sequence number in the TCP header?
A Helps to re-assemble the data stream
B Identifies the sequence of the data in the packet
C Identifies the means of sequential data transmission, Async or synchronous
D essential to re-assembling the data stream
It’s not just useful. TCP needs these numbers to tell where to put each packet into the
data stream. If any are missing, it uses these numbers to ask for retransmission of any
missing packets.
11. [ C ] (ABCD) Digital Phase Modulation can be characterized as
A By changing the phase of signals to different parts of an antenna, the phase of the
antenna, (the pattern pointing direction) can be changed.
B Phase is a constant. It cannot be changed to modulate a carrier signal.
C A digital data modulation mode. A phase shift of specific angle indicates a
combination of bits for the Baud being sent.
D All of the above
A defines a synthetic aperture antenna.
Phase can be varied by the modulator. That’s what an FM modulator ends up doing.
QAM is an example of C.
12. [ C ] (ABCD) In the IP datagram, the Total-Length field occupies 16 bits. Which of the
following is an acceptable packet length
A 11 bytes
B 65536 bytes
C 25600 bits
D 524288 bits
Sixteen bits can select from 35536 items. The largest number specifiable in sixteen bits
is 35535. There are 8 bits in a byte.
Fill-in (3 ea)
1.
TCP occupies which layer in the OSI model?
Transport layer
2.
Ethernet occupies which two layers in the OSI model?
Physical and Data Link
3.
Two remote access protocols are: (Give the acronyms and the names)
SLIP, Serial Line Internet Protocol and PPP, Point-to-Point Protocol
4.
What do you call a LAN that segments different groups into subnetworks,
each with its own security, but they all use the physical network?
Virtual Network
5.
On which OSI layer(s) does each of the following operate?
Bridge Data Link -- MAC
Router Network
Switch Data Link Layer -- Sometimes Network or Transport layers
6.
A switch uses the destination address in the packet header to direct a packet
to its addressed destination. One switch mode reads the whole packet
before sending it. The other only needs to read the header before sending it
on. Name these two Modes.
Store and Forward and
Cut through right from the book.
Essay Questions (6 ea) Answer briefly, but succinctly
1. Identify three significant differences between IPv4 and IPv6.
1. A more efficient header, better security, better prioritization
2. Typically read out as colon separated Hex numbers
3. Multicast and any cast.
4. Many more IP addresses
2. Relate the 802.11 variants by carrier frequency, speed, and compatibility.
3. What role do IRQs (interrupts) play in communications between asynchronous devices,
especially devices that operate at significantly different speeds?
They allow the computer to be doing other things while communicating with another entity.
Whenever the data transfer needs service, it interrupts the background activity in the computer
to execute an Interrupt Service Request routine. Then the computer can return to the
background program where it left off. This allows more than one program to be running
concurrently.
4. When installing a new wireless network, what are the important decision points? What
do you have to set, and why, at these decision points?
Here are some issues
Distance to support -- Different models support different ranges
Intervening obstacles -- They can interfere with signals and significantly reduce range.
Open or private -- Unless you are installing a hot spot at a coffee shop, you probably won’t
install it without security.
Change the IP address of the wireless router from the factory standard
Enable DHCP
Establish a good WEP key
5. How can an Ethernet LAN be both bus and star topology?
The Ethernet is collapsed to a very short length of coax or UTP. Hubs, or switches distribute the
network to individual computers in a functional star topology.
6. In class, I briefly discussed the concept that interactions like those represented in the
Corning Glass video operate at a high level. What is the relationship between that highlevel intercommunications and the low-level networking of the individual items in the
house and workplace? Why did I try to separate the two levels? Limit your response to
two or three sentences.
Once your job as an IT person is done, that is, everything is connected and responsive, a
higher level program can be loaded that calls upon the nodes to work together, sharing
information as needed. The high level program(s) are written by sophisticated
programmers, but use the nitty-gritty networks that IT provides.