1. Sub Topic : IP Addressing Concepts
Teaching Aids : Diagrams, Animations
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2. Recap
In the previous class, you have learnt about
• Leased line, DSL and Cable MODEM
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3. Objectives
On completion of this period, you will be able to know
about
• What is an IP Address?
• What is network prefix and host number?
• What is Internet address?
• What is sub-netting and no sub-netting?
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4. What is an IP Address?
• Internet identifier including information about how to
reach a network location (via the Internet routing
system)
• IPv4: 32-bit number. Written in Dotted Decimal
Notation 205.150.58.7.
– 4 billion different host addresses
• IPv6: 128-bit number. Written in Hex Decimal
Notation
2001:0503:0C27:0000:0000:0000:0000:0000
– 16 billion network addresses
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5. IP Addresses
32 bits
version header Type of Service/TOS Total Length (in bytes)
(4 bits) length (8 bits) (16 bits)
flags
Identification (16 bits) Fragment Offset (13 bits)
(3 bits)
TTL Time-to-Live Protocol
Header Checksum (16 bits)
(8 bits) (8 bits)
Source IP address (32 bits)
Destination IP address (32 bits)
Ethernet Header IP Header TCP Header Application data Ethernet Trailer
Ethernet frame
Fig .1 -- 5

6. Network Prefix and Host Number
•The network prefix identifies a network and the host
number identifies a specific host (actually, interface on the
network)
network prefix host number
•How do we know how long the network prefix is?
–Before 1993: The network prefix is implicitly defined
(see class-based addressing)
–After 1993: The network prefix is indicated by a net
mask
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7. Dotted Decimal Notation
• IP addresses are written in a so-called dotted
decimal notation
• Each byte is identified by a decimal number in the
range [0..255]:
10000000 10001111 10001001 10010000
1st Byte 2nd Byte 3rd Byte 4th Byte
= 128 = 143 = 137 = 144
Fig.2 128.143.137.144
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8. IP Address
• Every interface have a unique Internet address (IP address)
• Consist of 2 parts – network id and host id
• 32-bit address
• 5 Classes
–A – 0.0.0.0 to 127.255.255.255 (224 nodes)
–B – 128.0.0.0 to 191.255.255.255 (216 nodes)
–C – 192.0.0.0 to 223.255.255.255 (28 nodes)
–D – 224.0.0.0 to 239.255.255.255
–E – 240.0.0.0 to 247.255.255.255
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9. IP Address contd….
• When Internet addresses were standardized (early
1980s), the Internet address space was divided up into
classes
• Class A: Network prefix is 8 bits long
• Class B: Network prefix is 16 bits long
• Class C: Network prefix is 24 bits long
• Each IP address contained a key which identifies the
class
• Class A: IP address starts with “0”
• Class B: IP address starts with “10”
• Class C: IP address starts with “110”
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10. IP address contd…
bit # 0 1 7 8 31
Class A 0
Network Prefix Host Number
8 bits 24 bits
bit # 0 1 2 15 16 31
Class B 10 network id host
Network Prefix Host Number
16 bits 16 bits
bit # 0 1 2 3 23 24 31
Class C 110 network id host
Network Prefix Host Number
24 bits 8 bits
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11. IP Address contd…
bit # 0 1 2 3 4 31
Clas D 1110 multicast group id
bit # 0 1 2 3 4 5 31
Clas E 11110 (reserved for future use)
Fig .4 -- 11

12. Special IP Address
•All 0’s is reserved to refer to a network number
•All 1’s is reserved to refer to a broadcast
address
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13. Sub-netting
• Class A and B has too many nodes
• Network is divided to sub-network
• Improve network performance
• Indicate by subnet mask
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14. No Sub-netting
• All hosts think that the other hosts are on the same network
128.143.137.32/16 128.143.137.144/16 128.143.71.21/16 128.143.71.201/16
subnetmask: 255.255.0.0 subnetmask: 255.255.0.0 subnetmask: 255.255.0.0 subnetmask: 255.255.0.0
128.143.70.0/16
Fig .5
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15. With Sub-netting
• Hosts with same extended network prefix belong to the
same network
128.143.137.32/24 128.143.137.144/24 128.143.71.21/24 128.143.71.201/24
subnetmask: 255.255.255.0 subnetmask: 255.255.255.0 subnetmask: 255.255.255.0 subnetmask: 255.255.255.0
128.143.137.0/24 128.143.71.0/24
Subnet Subnet
128.143.0.0/16
Fig .6
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16. Summary
In this class, you have learnt about
• At the network layer, a global identification system that
uniquely identifies every host and router is necessary for
delivery of packet from host –to-host
• An IP v4 address is 32 bit long and uniquely and
universally define a host or router on the Internet
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17. Summary contd……
• In classfull adressing,the portion of IP address that
identifies the network is called netid
• In classfull adressing,the portion of IP address that
identifies the host or router on the network is called
the hostid
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18. Summary contd..
• An IP address defines a device’s connection to a
network
• There are five classes in IPv4 addresses
• Classes A, B and C differ in the no. of host allowed
per network
• Class D is for multicasting and class E is reserved
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19. Quiz
1. IP version 4 is of ______ bits
(a) 32
(b) 48
(c) 24
(d) None of the above
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20. Quiz
2. In IP addressing there are ___ classes
(a) 5
(b) 4
(c) 6
(d) None of the above
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21. Frequently Asked Questions
1. Discuss the concepts of IP addressing
2. Describe the classes of IP version 4 addressing
3. Write a short note on default gate ways
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