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Review For Final
© Abdou Illia, Spring 2006
Network Architecture
Models
3
Data transport
Application
OSI Reference Model

7 layers

Each layer communicate
with its peer layer, and with
layer above and below it.

Different protocols at each
layer

Upper layer deal with
application issues, and are
implemented in software

Lower layers handle data
transport issues, and are
implemented in software and
hardware
Summary Questions
1.
(a) Name the OSI layers that deal with
application issues ? (b) Name the OSI layer
that deal with data transport issue ?
Answer: See previous slide
2)
Application programs used at the
application layer of the OSI Model include
word processing. T / F
3)
Upper layers of the OSI Model are usually
implemented in physical devices. T / F
4
Internetworking
Summary Questions
3. The local area network shown in Figure 8-18 (p. 269) has
two hubs (X and Y) interconnecting the workstations and
servers. What workstations and servers will receive the
message if the following workstations/servers transmit (not
counting the sender)?
Workstation 1 sends a message to workstation 3:
Workstation 2 sends a message to Server 1:
Server 1 sends a message to workstation 3:
4. Replace hub Y with a switch. Now workstations and servers
will receive the message if the following workstations/servers
transmit (not counting the sender)?
Workstation 1 sends a message to workstation 3:
Workstation 2 sends a message to Server 1:
Server 1 sends a message to workstation 3:
6
Fundamentals of Data &
Signals
Summary Questions
1.
Distinguish between digital and analog signals
Answer: (see class notes for details):


Analog: Continuous waveform, State of signal (voltage
level, etc.) varies continuously among an infinite
number of states
Digital: Non-continuous waveform, State of signal
remain constant during each clock-cycle, Few possible
states
2. Distinguish between digital and binary transmission
Answer: Digital: Few possible states
Binary: 2 states
8
Attenuation
9

A signal starts at a transmitter with 10 watts of power and
arrived at a receiver with 5 watts of power. Calculate the loss
of power in dB.
1.
dB = 10 log10 (P2 / P1)
2.
dB = 10 log10 (5/10)
3.
dB = 10 log10 (0.5)
4.
dB = 10 (-0.3)
5.
dB = -3
Q: What is the decibel loss of a signal that starts at 50 watts and experiences a 10-watt loss over a given section of cable ?
Q: What is the decibel loss of a signal that loses half its power during the course of transmission ?
Frequency, Bandwidth
10
(See Fundamentals of Data & Signals – Continued for details)
Q: What is the frequency (in Hz) of a signal that repeats
80000 times within one minute ?
Answer: 80000 / 60 = 1333.33 Hz
Q: What is the bandwidth of a signal composed of frequencies
from 50 Hz to 500 Hz ?
Answer: |500 Hz – 50 Hz | = 450 Hz
Conducted and Wireless
Media
Summary Questions

12
What does cross talk interference mean ? How can crosstalk interference be reduced ?
If transmission wires are placed side by side, electromagnetic radiation is emitted by one
wire and picked up by the other. Twisting pair of wire reduce crosstalk interference.

What categories of twisted pair are usually used in LANs ?
Categories 3, 4, 5, 6, 7, 8

What are the advantages and disadvantages of STP compared to UTP ?
Advantage: better level of isolation from interference. Disadvantage: cost

What is the main difference between Baseband coaxial cable and Broadband coaxial cable ?
Baseband transmit signals in a single channel, whereas broadband uses multiple channels.

What are the advantages of Optical fiber compared twisted pair and coaxial cable ?
Speed, No significant noise, No interference, Long distance

Can you transmit video signal over twisted pair wire ? Explain
Yes, you can (e.g. Digital Video Service or DVS). Noise used to be a limiting factor.
School of Business
Eastern Illinois University
Local Area Networks
14
Summary Questions

What are the four factors to take into account in deciding how many
servers to use to implement a LAN’s services?
Answer: Optimization, reliability, security, cost

To what two devices does a print server usually connect?
Answer: To a printer via a parallel or USB cable and to a hub/switch via UTP

Where does a print job go when it leaves the client PC (not counting the
hub or switch)?
Answer: The print job first goes to the computer where the print queue
manager program is installed, which puts it in a print queue.

Do you have to use special printers for print service?
Answer: You do not need special printers, because all printers come with a
parallel and/or USB port that could be used.
15
Summary Questions

Why does file sharing for programs make software
installation easier with File Server Access?
Answer: A program only has to be installed once,
on the file server, not on each client PC.

Why is storing program files on a file server
limiting?
Answer: Programs stored on file servers execute on
client PCs, which have limited processing power.
Servers

Single server Versus Multiple specialized Servers
–

Decision based on Cost, Optimization, Reliability, and Security
Optimization:
–
–
File servers need storage capacity and rapid access
Client/Server applications need very fast processors
16
17
Servers

Print Server: basically NIC + a parallel port + Random
Access Memory + Intelligence to receive data and
commands from print queue manager program.
Newer printers
have built-in NICs
& print server
hardware

Note: Possible to connect printer directly to file server, but
people might have to walk far to get their printout.
Servers

File Server: A server that acts like a very large hard disk
shared by many client PCs

Advantages: Single program installation, Sharing
programs and files with access rights.
18
19
File Server Program Access

For execution,
–
–
–
Program and data files are downloaded (copied) to the
Client PC
Processing on the client PC, not on the file server
File server merely stores programs and data files
Downloaded to
Client PC,
Executed There
Client PC
File Server
Summary Questions
20
Answers are in Week8SummaryQuestions.doc (Review
section of course Website)
Your organization has 12 employees, each with his
or her own stand-alone PC running Windows 98. a)
List all the additional hardware and software you
would have to buy to install a simple PC network.
Be very sure that you list all the things the
organization will have to buy. The organization
wishes to use electronic mail, word processing, file
sharing, and print sharing with four existing
printers. b) How many ports on the hub or switch
will your organization use? Explain.
c) Suppose that a decision have been made to
implement the 100BaseTX Ethernet standard. What
does it mean in terms of the characteristics of the
following components: Hub/Switch, NICs, Wiring.
Software and Support Systems
21
• [Individual] or standard Operating System on Client PCs
• Network Operating System on Servers
- [Individual] Operating System
- Utilities
- Network Operating System
- Application programs:
- Word processor
- Spreadsheets
- Accountability
- Utilities
Ethernet standards
22
Q: If a LAN is described as 10BaseT, list everything you know about
that network?
Summary Questions
23
Answers are in LAN-Management.doc (Review section of
course web site)
1. (a) What is LAN management ? (b)
Name some common management
activities.
2. a) What are access rights? b) How does
the use of groups simplify the
assignment of access rights? c) How
does automatic inheritance simplify the
assignment of access rights? d) How
does explicit assignment modify
automatic inheritance?
Summary Questions
Answers are in LAN-Management.doc (Review section of
course web site)
3. Directory Applications has Subdirectories Databases
and WordProcessings. The Network administrator
assigns user Lee to the group Outer. The
administrator assigns Outer the access rights R, S,
and T in Directory Applications. (Don’t worry about
the meaning of R, S, and T. They are simply types
of rights.) The administrator assigns Outer the
access rights S, U, and V in Subdirectory Databases.
a) What access rights does user Lee have in
Directory Applications? Explain. b) What access
rights does user Lee have in Directory Databases?
Explain. c) What access rights does user Lee have in
Directory WordProcessings? Explain.
Applications
Databases
WordProcessings
24
Automatic Inheritance of Access Rights



25
Assigning rights to users or group in a directory
Rights automatically inherited in lower directories
Simplifies rights assignment
Assigned Browse
And Read Rights
Application
Word Processing
Inherits Browse
And Read Rights
Inherits Browse
And Read Rights
Database
Oracle
QuickDB
Automatic Inheritance of Access Rights

26
Blocking of Inheritance
–
–
If rights explicitly assigned in subdirectory, inheritance is blocked
Only assigned rights are effective
Assigned Browse
And Read Rights
Application
Word Processing
Assigned Browse
And Execute Rights
Inherit Browse
And Read Rights
Database
Oracle
QuickDB
(Browse and Execute Only)
School of Business
Eastern Illinois University
Wide Area Networks
28
Summary Questions

What is the difference between a station and a node?
Answer: A station is the device that interfaces a user to the
network. A node is a transfer point for passing data through the
network. A node could be a computer, a router, or a telephone
switch.

What are the main characteristics of Circuit Switched
networks?
Answer: In Circuit Switched networks: (1) a dedicated circuit is
established between sender and receiver, (2) circuit capacity is
reserved during the duration of each communication, at each
node (switch) and on each transmission line; (3) no routing
decisions are necessary since circuit is dedicated.
29
Summary Questions

What are the main characteristics of Virtual Circuit Packet
Switching?
Answer: (1) Data sent in packets, (2) all packets follow the
same virtual circuit, (3) the virtual circuit may be shared
with packets from other conversions, (4) no routing
decisions except the first one that creates the circuit.

Name some criteria that routing decisions are based on
Answer: see slide #17 in appropriate class notes

Name two routing algorithms/techniques.
Answer: see slide #18 in appropriate class notes
School of Business
Eastern Illinois University
Telecommunications Systems
31
Summary Questions
1.
When a standard telephone line is used to connect to a network: (a)
What device limits the speed? (b) Where is this device located?
(a) The analog-to-digital converter (ADC).
(b) It is located at the telephone company’s switch at the end of your
local loop access line.
2.
(a) In using a V.90 modem, what does the ISP need? (b) What does the
telephone company need?
(a) A digital leased line to the telephone carrier (and some internal
equipment).
Note: The ISP does not have a V.90 modem. If it did, it could only
transmit at 33.6 kbps, and the receiver could only receive at 33.6 kbps.
(b) The telephone company does not have to do anything differently.
Note: the telephone company does not have to install ADCs. These are
already there. You use ADCs and DACs every time you make a voice
telephone call.
32
Summary Questions
3.
(a) How are 56K Leased lines and standard telephone
lines different in terms of operation? (b) How are they
different in terms of speed and cost? (c) How are 56K
leased lines different than T1 in terms of speed?
(a) With Standard telephone lines you need to dial a telephone
number to connect. The connection is not permanent (active
only during a call). With 56K Leased line, there is no need to
dial a telephone number, and the connection is always active.
(b) 56K Leased lines are faster and more expensive.
(c) T1, which operate at 1.54 Mbps are faster than 56K (56
Kbps)
Standard telephone line

ADC limits transmission speed

ADC needed because internal telephone system is digital
33
School of Business
Eastern Illinois University
The Internet
35
Review class notes titled “The
Internet”, (Slides #1-17)
Summary Questions
36
1.
a) Distinguish between IP address and host name. b)
Which is the official address of a host? c) Does a
server host need an IP address? d) Does your home
PC need an IP address when you are on the Internet?
e) Does a server host need a host name? f) Does
your home PC need a host name when you are on
the Internet?
2.
Using the conversion system on slide #10 (see class
notes), convert the following IP address to dotted
decimal notation: 10101010 11110000 11001100
01010101. (Spaces are included to facilitate
reading.)
37
Summary Questions
3.
a) What are the two parts in IP addresses?
4.
a) Who assigns the Network part? b) The Local
part?
5.
Check questions on slide #17 in class notes
School of Business
Eastern Illinois University
The Internet (part 2)
Security
Central Network Management
See Review For Exam 4