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