Review For Final

1
Review For Final
2
Network Architecture Models
3
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

Application
Data transport
4
Summary 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

5
Internetworking
6
Summary 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

7
Summary 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)

8
Fundamentals of Data Signals
9
Summary 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

10
Attenuation

• 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 ?
11
Frequency, 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
12
Conducted and WirelessMedia
13
Summary 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.

14
Local Area NetworksLAN Management
School of Business Eastern Illinois University
15
Print 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.

16
Summary 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.

17
Summary 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.

18
Ethernet standards
19
Automatic 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
20
Automatic 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)
21
Summary Questions

1. 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.

22
Summary 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.

23
The Internet
School of Business Eastern Illinois University
24
The 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
25
IP 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)

26
IP 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
27
IP 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
28
IP 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)
29
Network 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)

30
Host 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
31
Domain Name System (DNS)
32
Autoconfiguration

• 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.
33
Autoconfiguration

• 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

34
Autoconfiguration

• 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

35
Summary 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

36
Summary Questions

1. What are the two parts in IP addresses?
2. a) Who assigns the Network part? b) The Local
   part?
3. 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?
4. 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?