1. CS 447 Networks and Data Communication
IP Address Format, Classes
Sub-Networking and Class-less Inter Domain Routing
Department of Computer Science
Southern Illinois University Edwardsville
Fall, 2017
Dr. Hiroshi Fujinoki

2. CS 447 Networks and Data Communication
What is IP address?
IP address is the ID for each NIC at a host computer
Internet Backbone Carrier
(long distance carrier)
ISPs
NIC
NIC
Internet
Host Y
Host X
SIUE Domain
Internet core routers
IP_Address/001

3. CS 447 Networks and Data Communication
What is IP address?
Every IP address must be unique
Advantage in using IP addresses
You can use the same format of IP address no matter where your destination is.
Host Q
Internet
Host Y
Host X
SIUE Domain
Host S
IP_Address/002
Host Z

4. CS 447 Networks and Data Communication
What is IP address?
IP Addresses = the unique identifiers
for each host computer (NIC) in
the Internet (or intranets)
IP_Address/003

5. CS 447 Networks and Data Communication
CIDR (Class-less Inter-Domain Routing)
 Each IP address = a combination of “domain address” and “host address”
Domain Address
Host Address
? bits
32-bit IPv4 address
 Only the source and destination network domains perform CIDR
This is how it is called “inter-domain routing”.
The gateway routers in your transmitting host and the
destination host perform CIDR
IP_Address/004

6. CS 447 Networks and Data Communication
CIDR (Class-less Inter-Domain Routing)
/16
“CIDR Prefix”
= How many bits (from the top) are “network address”
146
163
170
Network Address Bits
Example
If we need only up to 4,000 hosts?
We can come up with
(24-1) more domains
of the same size!
Since 212 = 4,096, we need only 12 bits for host address filed.
/20
146
163
170
Network Address Bits
IP_Address/005

7. CS 447 Networks and Data Communication
Domain and host addresses
Destination
Host
Domain X
Transmitting
Host
Domain Y
Routing using
host address
Routing using
domain address
Gateway Router
in Domain Y
Gateway Router
in Domain X
Internet
IP_Address/006

8. CS 447 Networks and Data Communication
Example of IP address construction
“ ”
What are the bit patterns for “146”, “163” and “170”?
“146”
MSB
LSB 1 2 3 4 5 6 7 8
128 64 32 16 8 4 2 1
Weight 1 1 1
146  18  -
128 - 16 18 2
IP_Address/007

9. CS 447 Networks and Data Communication
Example of IP address construction
“163”
MSB 1 2 3 4 5 6 7 8
LSB
Weight
128 64 32 16 8 4 2 1 1 1 1 1
163  35   3 -
128 - 32 - 1 2 35 3
IP_Address/008

10. CS 447 Networks and Data Communication
Example of IP address construction
“170”
MSB 1 2 3 4 5 6 7 8
LSB
Weight
128 64 32 16 8 4 2 1 1 1 1 1   
170 42 10 -
128 - 32 - 8 42 10 2
IP_Address/009

11. CS 447 Networks and Data Communication
Two extensions in IP address formats
1. Subnet and Subnet Masks
2. CIDR (Class-less Inter Domain Routing)
Purpose
A mechanism to make managing IP addresses easier
Partitioning a network domain within a domain
Method
Purpose
A mechanism to increase the number of network domains
Partitioning a network domain into more than one
network domain
Method
IP_Address/010

12. CS 447 Networks and Data Communication
Subnet and Subnet Masks
The problem
Managing IP addresses in a large domain is not an easy job
SIUE domain has more than 1,000 host computers
IP address must be unique
You can’t assign an IP address to more than one NIC
SIUE Domain ( X.X)
Assigned
IP address
IP_Address/011

13. CS 447 Networks and Data Communication
Subnet and Subnet Masks
The problem
Managing IP addresses in a large domain is not an easy job
Your job is to assign, maintain and manage all available IP addresses
in SIUE domain.
You can not assign an IP address to more than one host (or NIC)
SIUE Domain ( X.X)
Assigned
IP address
IP_Address/012

14. CS 447 Networks and Data Communication
Subnet and Subnet Masks
Two solutions
 Dynamic address assignment (DHCP)
 Subnet working IP
MAC
1ABF
NULL
SIUE Domain ( X.X)
MAC Address
DHCP Query
DHCP Server
DHCP Reply
1ABF
MAC Address
IP Address
Problem in DHCP
Every time you starts your PC, your IP address
may be different
IP_Address/013

15. CS 447 Networks and Data Communication
Subnet and Subnet Masks
Partition the entire domain
Assign a group of IP addresses to each partition
Address range:
SIUE Domain ( X.X)
Address range:
Address range:
Each partition is called “subnet”
IP_Address/014

16. CS 447 Networks and Data Communication
Exception in IP addresses (#1)
• • •
Private IP addresses
NAT
Internet
IP Masquerade
IP_Address/015

17. CS 447 Networks and Data Communication
Exception in IP addresses (#2)
Multicast IP addresses
(Class-D IP addresses)
A transmitting host transmits once
Multiple hosts receives at once
Multiple
Receiving Hosts
Transmitting
Host
Internet
IP_Address/016

18. CS 447 Networks and Data Communication
Exception in IP addresses (#2)
Multicast IP addresses
(Class-D IP addresses)
All the receivers should receive messages
All the receivers should
have the same multicast
IP addresses
A sender should transmit only once
Transmitting
Host
Internet
IP_Address/017

19. CS 447 Networks and Data Communication
Global-Internet
Multicast
Transmitting
Host
Internet
Local-Domain
Multicast
SIUE Domain
First
Last
Categories
Global-Internet Reserved
Global-Internet Multicast
Local-Domain Multicast
We developed a UDP IP-multicast audio-streaming application
applications in CS490 (Fall 2005) (as SIUE’s local-domain multicast).
IP_Address/018

20. CS 447 Networks and Data Communication
CIDR (Class-less Inter-Domain Routing)
CIDR Block PreFix
# Equivalent Class-C
# of Host Addresses
25/28 = 1/23
/27
1/8 of a Class-C
2(32-27)
= 32
/26
/25
/24
/14
/15
/16
/17
1/4 of a Class-C
2(32-26)
2(32-25) 28
216
2(32-17)
217
218
= 64
= 128
= 256
= 32,768
= 65,536
= 131,072
= 262,144
1/2 of a Class-C
1 Class-C
128 Class-C
256 Class-C
(Class-B)
512 Class-C
1024 Class-C
IP_Address/000