Title: Review For Final
1Review For Final
2Network Architecture Models
3OSI 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
Application
Data transport
4Summary Questions
- (a) Name the 7 layers of the OSI model, (b) Name
OSI layers that deal with application issues ?
(b) Name the OSI layer that deal with data
transport issue ? - Answer See previous slide
- Application programs used at the application
layer of the OSI Model include word processing.
T / F - Upper layers of the OSI Model are usually
implemented in hardware devices. T / F
5Internetworking
6Summary Questions
- 1. The local area network shown in Figure 8-18
(p. 261) has two hubs (X and Y) interconnecting
the workstations and servers. What workstations
and servers will receive a copy of a packet if
the following workstations/servers transmit a
message - Workstation 1 sends a message to workstation 3
- Workstation 2 sends a message to Server 1
- Server 1 sends a message to workstation 3
- 2. Replace hub Y with a switch. Now, what
workstations and servers will receive a copy of a
packet if the following workstations/servers
transmit a message - Workstation 1 sends a message to workstation 3
- Workstation 2 sends a message to Server 1
- Server 1 sends a message to workstation 3
7Summary Questions
- 3. Do Internetworking Exercise 2
- The exercise is available in the Notes section.
Check the link next to the Internetworking II ppt
notes (posted on Mon 9/16)
8Fundamentals of Data Signals
9Summary Questions
- Distinguish between digital and analog signals
- Answer (see class notes for details if needed)
- Analog Continuous waveform, State of signal
(voltage level, etc.) varies continuously among
an infinite number of states - Digital Discrete (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 (2-64
states) - Binary 2 states
10Attenuation
- 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. - dB 10 log10 (P2 / P1)
- dB 10 log10 (5/10)
- dB 10 log10 (0.5)
- dB 10 (-0.3)
- 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 ?
11Frequency, Bandwidth(See Fundamentals of Data
Signals Continued ppt notes for details if
needed)
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
12Conducted and WirelessMedia
13Summary Questions
- 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.
14Local Area NetworksLAN Management
School of Business Eastern Illinois University
15Print Service
- A Print Server device is basically NIC a
parallel or USB port Random Access Memory
Intelligence to receive data and commands from
print queue manager program.
- Note Possible to connect printer directly to
file server, but people might have to walk far to
get their printout.
16Summary Questions
- To what two devices does a print server device
usually connect? - Answer To a printer via a parallel or USB cable,
and to a hub/switch via UTP or other transmission
media. - In print service with a print server device,
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.
17Summary Questions
Answers are in Week8SummaryQuest.doc (Review
section of course Website - Check Exam 2 Review
link)
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.
18Ethernet standards
19Automatic Inheritance of Access Rights
- Assigning rights to users or group in a directory
- Rights automatically inherited in lower
directories - Simplifies rights assignment
Inherits Browse And Read Rights
Assigned Browse And Read Rights
Application
Word Processing
Database
Inherits Browse And Read Rights
Oracle
QuickDB
20Automatic Inheritance of Access Rights
- Blocking of Inheritance
- If rights explicitly assigned in subdirectory,
inheritance is blocked - Only assigned rights are effective
Assigned Browse And Read Rights
Inherit Browse And Read Rights
Application
Word Processing
Database
Assigned Browse And Execute Rights
QuickDB
Oracle
(Browse and Execute Only)
21Summary Questions
- 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.
(Dont 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.
22Summary Questions (answers)
- R, S, T
- Explanation These rights are explicitly assigned
to the Outer group in the Applications directory.
And Lee is member of the Outer group which means
he will automatically have those access rights. - S, U, V
- Explanation These rights are explicitly assigned
to the Outer in the Databases directory. And Lee
is member of the Outer group which means he will
automatically have those access rights. - R, S, T
- Explanation These rights are automatically
inherited from the upper level i.e. from the
Applications directory in which they were
explicitly assigned to the Outer group to which
Lee belongs.
23The Internet
School of Business Eastern Illinois University
24The Internet
Network
Webserver Software
Browser
Packet
Packet
Route
Router
Webserver (Host) Operating System TCP/IP IP
Address139.67.14.54 Host name eiu.edu
User PC (Host) Operating System TCP/IP IP Address
128.150.50.9
25IP address
- 32-bits and Dotted Decimal Notation
- IP addresses are really strings of 32 bits (1s
and 0s) - 10000000101010100001000100001101
- To convert this to dotted decimal notation,
first, divide them into four bytes (also called
octets) - 10000000 10101010 00010001 00001101
- (Both octets and bytes are collections of eight
bits) - Convert each binary (Base 2) octet into decimal
(Base 10)
26IP address
Place Value (2N)
Bit
Decimal
Position (N)
Binary10100011 Decimal163
128
1
128
7
64
0
0
6
32
1
32
5
16
0
0
4
8
0
0
3
4
0
0
2
2
1
2
1
Note Starts with 0
1
1
1
0
163
27IP Address structure
- Each IP Address has two main parts
- Each Organization is given the Network Part by an
IP address Registrar (e.g www.arin.net) - For Eastern Illinois University, this is 139.67
- All IP Addresses for Easterns computers begin
with that Network Part
Network Part
Local Part
IP Address
139.67
American Registry for Internet Numbers
Check EIUs IP registration info
28IP Address structure
- Network Parts is 8 to 24 bits long
- For Eastern, it is 16 bits long
- 16 bits is only an example
- Local Part
- Total address is 32 bits, so if the network part
is 8 bits, the local part is 24 bits - Common way to refer to IP address structure
- x.x.x.x/ (where is the number of bits in the
network part) - e.g. 139.67.0.0/16
Network Part (8 to 24 bits)
29Network classes
- The value of the bits in the first octet of an IP
address determines the Network class
Class
Address range
Leftmost bits
Network Part Length
Class A
0.x.x.x to 127.x.x.x
0xxx
8 bits
128.0.x.x to 191.255.x.x
Class B
10xx
16 bits
192.0.0.x to 223.255.255.x
Class C
110x
24 bits
- For each of the following IP addresses, give the
class and the network bits. - 10101010111110000101010100000001
- 01010100111110000101010100000001
- What class does Easterns network belong to?
(Net. Part 139.67)
30Host name
- Host Names
- Like nicknames
- Not official addresses
- Each host must have an IP address
- But only some hosts have host names
- If you give it a host name, your browser must
look up IP address of host
eiu.edu
31Domain Name System (DNS)
32Autoconfiguration
- User PCs do not need permanent IP addresses
- They only need to be found within a use session
- They usually are given temporary IP addresses to
use on the Internet for a couple of days - The duration of temporary address is usually a
few days. When the lease expired another
temporary address is a given.
Autoconfiguration service provides clients
computers with temporary IP addresses to use for
communication with other computers on the
Internet.
33Autoconfiguration
- Request-Response Cycle
- User software requests IP address for the user PC
in Autoconfiguration Request message - Autoconfiguration Response message contains
temporary IP address to use in current session
34Autoconfiguration
- Most popular autoconfiguration protocol is DHCP
- Dynamic Host Configuration Protocol
- Built into Windows after Win 3.1
- Supplies host with temporary IP address
- DHCP can give more information too
- Usually gives IP address of a default gateway
(Microsoft terminology for router) - Can give IP address of a local DNS host
- Can give other information
35Summary Questions
- 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? - Using the conversion system in slide 26, convert
the following IP address to dotted decimal
notation 10101010 11110000 11001100 01010101.
(spaces are included to facilitate reading.) - Using the conversion system in slide 26, convert
the following dotted decimal IP address into a
32-bit IP address 192.128.2.4 -
36Summary Questions
- What are the two parts in IP addresses?
- a) Who assigns the Network part? b) The Local
part? - a) When do we need DNS? b) What information do
you send in a DNS request message? c) What
information do you receive in a DNS response
message? - a) What is autoconfiguration? b) What information
do we get back, at a minimum, in an
autoconfiguration response message? c) What other
information may we get back?