Internet Security Lesson Two, 20 April

April 20th, 2009
Packet:
1st 3 numbers are all the same in classroom 142.156.121.
Subnet mask determines network address
Because of subnet mask that allows you to be on certain network
Number can go from 0-255
32bit IP address, IPV4=32bit
Computers use binary language, 2 possible combinations, 0 or 1
How to convert binary to Decimal:
Create the chart
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
Add the 1’s not the 0’s
How to Convert Decimal to binary
Use the Chart
Example number **200
Find the last number that 200 is larger than, and start there…128
Take 200 and minus 128=72
If the next number is smaller than 72 open it=1
Then subtract 72 from 64-8 all numbers till 8 is closed then
8-8=0 so all numbers after 8 are closed
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
1 1 0 0 1 0 0 0
Use this to practice: 142, 65, 256, 33
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
29 28 27 26 25 24 23 22 21 20
512 256 128 64 32 16 8 4 2 1
How to Change IP Address:
Go to my network places
Go to view network connections
Right click local Area Connections and go to properties
You will see protocol stack
Highlight TCP/IP and right click and go to properties
Network ID on the same network, needs to have the same Network ID
If you do not have the same ID you do not belong to the ID
DHCP: server that assigns IP address
DHCP= Dynamic Host Configuration Protocol
Broadcast message, every computer will receive message
Multicast: Certain people will receive message
Unicast: just yourself or 1 computer
Routing Tables: list of routers each know…almost like a favourites list
Every time a message goes from one router to the other it’s called a hop
2 types of networks at any given time: Classful or Classless
5 classes if classfull
A: 1-126--------255.0.0.0
B 128-191------255.255.0.0
C 192-223------255.255.255.0
D 224-239------Does not exist
E 240-255-------Does not exist
Determined by 1st octet
127 is reserved for loopback address
If its classful you can determine what the subnet mask is
Class D and E do not have subnet masks as Class D is used for multitask and E is for Government use
In textbook pg 46/47
Need to know how Classfull and Classless work
OSI Model: Open Systems interconnect
7 A-Application—programs, email, network print etc
6 P-Presentation---- data compression and encryption
5 S-Session----dialog of communication, actual communication happens
4 T- Transport----End to end layout of conversation, packets are formed
3 N- Network----determines what network ID is
2 D- Data link----MAC-Media access control
LLC- Logical Link Control
1 P- Physical---- responsible for converting packets into binary form

Internet Security Lesson One, 13 April

April 13, 2009
Network:
A Network is 2 or more computers connected together to share data, resources (printers)
The benefits are reduced costs, to max. productivity, save time by communicating (protocols)
Internet:
A combination of many networks working together
Protocol:
Transmission control protocol, internet protocol, (TCP/IP) largest protocol in the world
Every operating system by default uses TCP/IP
The more popular an item is the more at risk it is for a hacker.
You can have a computer with a multi protocol.
Data flows to and from, from the network card
Protocol stack:
Where multiple protocols appear in order (1.TCP/IP 2.Gopher)
TCP/IP has a predictable response just by saying “hi” a hacker can tell there is a computer, what operating system etc.
Customer oriented means less security, and therefore more at risk, hackers get the reward
LAN: Local area network- anything less than 2km in size
CAN: Campus area network- designed for campuses
WAN: Wide Area Network, 2 or more LAN’s-Larger than 2km
MAN: Metropolitan area network- City’s
Intranet: internal internet- private use only
Extranet: External intranet- access through intranet externally
Type of network relationship:
2 styles of networks:
1st Peer to Peer network:
All workstations, no longer ask questions to be done, able to do them on own.
Still able to share info. Based on security levels…example Windows XP
Physically plugged into individual workstation
2nd Client server network:
Client servers have to ask permission, and server asks for codes
Requires NOS-Network operating system… example windows server, Linux
Host: is a Node on a TCI/IP network
NODE: Any device that communicates on a network is known as a Node (router etc.)
Backbone: Will be a high speed connection that connects all together
Segment: the Distance on the network…branch of a network..2 communicating devices linked together
Scalability: the ability for your network to grow
Transmission Media: the devices on the network (physical) example: Ethernet cable
Subnet mask: combined with the IP= net work ID and Host ID—very important to where packet goes
sdhanapala@rogers.com
sdhanapala@conestogac.on.ca