Assignment 2 (Replacement) Solution
Total of 50 marks. Two hours. Answer the following questions based on topics
covered in lectures 4-7. Show your work for any
calculations.
Treat this assignment as an open-book individual exam. You may consult any of
your class notes or other books or documents, paper or electronic. However, you
may NOT discuss questions or share answers with any other person until
after the assignment is due.
-
What is the advantage of modulating a combination of amplitude, frequency and
phase rather than just one of the three? [2]
- Increases the bandwidth (number of bits that can
be encoded in a given signal)
-
What method does broadband communication use to carry multiple signals
simultaneously? [2]
- frequency division multiplexing (each signal is
assigned a frequency range, separated by empty frequency bands)
-
What is an advantage of 5 bit/6 bit encoding over 4 bit/5 bit encoding? [2]
- The encoded signal must have 3 1's and 3 0's,
allowing an extra error check.
-
What bandwidth would be needed to send [3]
- uncompressed CD-quality sound (44 KHz, 16 bits per sample, two stereo
channels) in real time?
44K x 16 x 2 bits/sec = about 1.4 Mbits/sec.
- the same sound if it were compressed to 50% of its original size?
half the bandwidth or about 0.7 Mbits/sec.
-
What type of electromagnetic radiation is commonly used in [4]
- fibre optic cables?
visible light
- television broadcasts?
radio waves
- wireless LANs?
infrared
- wireless voice transmissions?
microwaves
-
Why are conducted media generally more secure and reliable than radiated
media? [4]
- radiated media can be received by anyone with a
receiver
- radiated media can be disturbed by various forms
of noise such as weather and interference
-
What factors should a company consider to decide whether to connect to the
Internet through a dial-up connection or a leased line? [4]
- peak, average and minimum bandwidth needed while
connected
- connection hours per day needed
- costs of each type of connection (equipment,
installation labour, per-hour and per-month)
-
What two types of cables and connectors are most commonly used by Ethernet
network cards? What type of media access does Ethernet use? [5]
- UTP cables with RJ-45 connectors or co-axial
cables with BNC connectors
- CSMA/CD (carrier sense multiple access with
collision detection)
-
Why do servers often have multiple [5]
- power supplies?
- reliability (backup if one fails)
- processors?
- performance (to divide up processing) in
multiprocessing systems
- hard disks? (two reasons)
- performance (faster reading and possibly
writing)
- reliability (backup or parity information in
case of disk failure)
- expansion slots?
- for multiple disks, network cards, and other
shared devices
-
Why do switches perform better than hubs? [2]
- hubs broadcast so only one computer can send data
at a time
- switches make a connection between sender and
receiver so that up to half of connected computers can send simultaneously
-
Some networks use a combination of collision detection and collision
avoidance. When would each technique be appropriate to use? [2]
- collision detection is appropriate for most
circumstances (few computers, small load, few collisions)
- collision avoidance is appropriate when the system
is overloaded and there are many collisions
-
What type of media access is used by large corporations like IBM and General
Motors who need a guaranteed level of performance? [1]
-
What computer component stores the address that can be used as a source or
destination address of an Ethernet frame? [1]
- Every NIC (network interface or adapter card) has
a MAC address to uniquely identify it
-
Which sub-layer of the OSI data link layer determines which computer can send
data at what time? [1]
- MAC (media access control) layer
-
What factors determine how often backups should be performed and which type of
backups (e.g. full, differential and/or incremental) should be used? [4]
- importance/value/cost of the data
- amount of data to back up
- speed and costs of backup media
- labour time and costs of performing backups and
restores
-
What is software piracy? Why does it harm software companies? [3]
- Software piracy is the duplication and
distribution of software illegally, in violation of the license agreement.
- Piracy reduces the profits a company would have
gained by selling the software.
-
What are some of the most important features of LAN server software? [5]
- object-oriented global database of network
resources
- access control and authentication mechanisms (e.g.
users, groups, passwords, access rights)
- compatibility with various client operating
systems
- support for popular LAN and WAN protocols and
standards (e.g. TCP/IP)
- scalability (support for many users, printers, and
interconnected LANs)
- performance (I/O optimisation techniques) and
reliability (fault tolerance and data redundancy)
- administration and management tools (e.g. remote
management, performance monitoring, log files for auditing)
- user-friendly user interface for ease of use and
administration (e.g. graphical, wizards)