Download Introduction - Eastern Illinois University

School of Business
Eastern Illinois University
Review for Exam 3
© Abdou Illia, Spring 2007
School of Business
Eastern Illinois University
Local Area Networks
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
3
4
Print Server device

A Print Server is basically: NIC + a parallel or USB port
+ Random Access Memory + Intelligence to receive data
and commands from print queue manager program.
Network printers
have built-in NIC
& 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.
5
6
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
7
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 connect?
Answer: To a printer via a parallel or USB cable and to a hub/switch via
UTP (or fiber optic cable in some case).

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 a file server, 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 any printer with a
parallel or USB cable could be connected to a print server. Network
printers include integrated NIC. They can be used without a print
server device.
8
Summary Questions

Can anyone access shared files?
Answer: No. Only those who have access rights.

Why does file sharing for programs make software
installation easier?
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.
Software and Support Systems
9
• Workstation Operating System on Client PCs
• Network Operating System on Servers
- Workstation Operating System
- Client application programs
- Network Operating System
- Application programs:
- Word processor
- Spreadsheets
- Accountability
- Utility programs
Ethernet standards
10
Q: If a LAN is described as 10BaseT, list everything you know about
that network?
Summary Questions
11
Answers are in Week9SummaryQuestionsS07.doc (Review
section of course Website)
Your organization has 12 employees, each with his
or her own stand-alone PC running Windows 98.
Each computer has a 10 Mbps NIC that could work
with coaxial cable or twisted pair.
a) List all the additional hardware and software you
would have to buy to install a 100BaseTX LAN. 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 fed with
parallel ports.
b) How many ports should the hub or switch have?
Explain.
Automatic Inheritance of Access Rights



12
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

13
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)
Summary Questions
1.
14
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
School of Business
Eastern Illinois University
Wide Area Networks
Wide Area Networks basics

A station is a device that interfaces a user to a network

A station can be:
–
–
a computer (for Data networks)
a telephone (For Voice networks)
16
Wide Area Networks basics
17

Data is transferred from node to node through the network

A Node is a transfer point for passing data through the
network

A Node is often a computer, a router, or a telephone switch
Q: What is the difference between a station and a node?
Wide Area Networks basics
18

The subnet is the underlying physical connection of nodes
and communication lines that transfer data from one
location to another.

A Subnet is a collection of nodes and different types of
transmission media
Q: How does the subnet differ from the network?
Circuit Switching Subnet
19

Usually used for Voice networks

A subnet in which a dedicated circuit is established between
sender and receiver and all data passes over this circuit.
20
Virtual-Circuit Packet Switching Subnets

Amount of data broken into n packets

A virtual circuit (temporary path through the network) is
determined

Note: The virtual circuit is not dedicated (not reserved)

All n packets transmitted through the virtual circuit

When transfer completed, virtual circuit dissolved
Q:
21
Summary Questions

How does the subnet differ from the network?
Answer: The network include: the subnet(s), the stations, the OS & other
application software, and the other networking devices & transmission
medium needed to connect the stations to the subnet

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
transfer point for passing data through the network. A node can 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.
22
Summary Questions

What are the main characteristics of Virtual-Circuit Packet
Switched network?
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 ones that create 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 #18-19 in appropriate class notes
23
 Reviewing
Question #2 of Review
Exercise (WAN) available in the Notes’
section of the course web site will be
helpful.
School of Business
Eastern Illinois University
Telecommunications Systems
25
Review:
- Class notes titled “Telecommunications Systems, Part 1”)
- Class notes titled “Telecommunication Systems, Part 2”
26
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.
27
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?
(a) With Standard telephone lines you need to dial a
telephone number to connect. The connection is no
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.
28
Summary Questions
1. What is the difference between a T-1 Trunk line and T-1
Leased line?
Answer: A T-1 trunk line only runs between two
switches within the telephone network. T-1 Leased lines
extend T-1 trunk line speeds to end-to-end circuits
between 2 locations.
2. In T-1 Leased lines, what kind of twisted pair wire is
used to connect a customer to the 1st telephone switch?
Answer: Data-grade TP which is a category 2 TP.
29
Summary Questions
3) On the user end, what elements are needed to establish a DSL
connection?
A computer, a DSL modem, filter(s) to separate regular
telephone line from the DSL data line, tel. line, software (OS,
client application programs, TCP/IP), and an ISP
4) Several Internet access systems are asymmetric, with higher
downstream speeds than upstream speeds. (a) Is this good for
Webservice? (b) Is it good for videoconferencing?

a) Asymmetric speeds are good for Webservice because
requests tend to be small but downloaded pages large.

(b) It is not good for videoconferencing, which needs high
speed in both directions.
30
 Reviewing
Quiz 2 will also be helpful
Standard telephone line

ADC limits transmission speed

ADC needed because internal telephone system is digital
31
School of Business
Eastern Illinois University
Security
33

Review Questions in Security 1 and Security class
notes.
Review Questions
34
What is the difference between DoS and DDoS?
What kinds of tools/techniques could be used during the
scanning process by a hacker?
Are ping of death attacks and LAND attacks all example of
single-message DoS attacks
What kind of techniques or defense systems could be used to
protect a system against (a) intercepting messages, (b) malware
or content attack
What is the difference between a worm, a Trojan horse, and a
logic bomb
What kind of malware could harm a host computer by
consuming processor time and random access memory