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© N. Ganesan, All rights reserved.
Chapter
IP Addressing Format
Questions
• How many bits are there in a TCP/IP address?• Name the components of a typical TCP/IP
address?• What is the difference between the old IPv4 and
the new IPv6 addresses?• Explain the difference between network ID and
host ID.• Name the classes of IP addresses. What are the
purpose and function of each class of addressing • Compute the number of networks and hosts that
can be supported in each class of address.
Questions Cont.
• List the restrictions placed on the assignment of addresses.
• Choose a IP class as an example and list the valid range of network and host addresses for that class.
Chapter Modules
• IP Address Format and Components
• Classes of Addresses• Scope of Addresses and
Restrictions
© N. Ganesan, All rights reserved.
Module 1
IP Address Format
Overview
• The IP address format discussed in this presentation applies to IPv4
• An IP address is composed of 32 bits that is viewed as being divided into 4 octets– One octet is made up of 8 bits
IP Address Format
10101111 11001100 10000001 00110011
32 bits divided into 4 octets for convenience
175 204 129 51
Converted into decimals for easy representation and remembrance
An Example in Binary-to-Decimal Conversion
Binary 1 0 0 1
Factor 8 4 2 1
Decimal=Binary * Factor
8 0 0 1 8+1= 9
Binary 1001 = Decimal 9
IP Addressing Components
Network ID Host ID
32 bits
The New IP Address
• The new IP address known as IPv6 has 128 bits– www.whatis.com
IP Component Reference
Internet
Host ID
Host ID
Network ID
End of Module 1
© N. Ganesan, All rights reserved.
Module 2
Classes of IP Addresses
Classes of IP Addresses
• IP addresses have been divided into classes– They are namely Classes A, B C, D and
E• Classes A, B and C are used for
commercial purpose• Class D is used for multicasting • Class E is used for experimental
purpose
Commercial Classes
• Classes A, B and C • Class A is for very large organizations
– Few, if any, are available
• Class B is used in medium size organizations– A few may be still be available
• Class C is used in small organizations– Often further divided and issued to smaller
organizations and individuals
Subnetting
• There is no strict rule as to who may use a certain class of address
• An enterprise such as an ISP can own a large Class B address space and subnet it into smaller spaces for its customers
Class D
• Reserved for IP multicasting• The first four higher-order bits are
set to 1 1 1 0 respectively• Microsoft supports Class D
addresses for multicasting• Multicasting is the process of
delivering media over the Internet at reduced bandwidths
A Note on Multicasting
• Multicasting delivers a single stream of medial to a router and the receiving end
• The router then multiplies and delivers the stream to local clients
• As such, only one stream travels along the Internet thus saving bandwidth
• In the case of Unicasting, multiple streams travel along the Internet to reach each client separately
Unicasting
3 Streams
Multicasting
1 Stream onInternet
3 Streams Locally
Alternative Methods of Delivering Media
• Unicasting– Easy to implement– Higher bandwidth is required for
transmission• Multicasting
– More involved in setting up – Uses bandwidth more efficiently
• Broadcasting
Class E
• Experimental addresses reserved for possible future use
• The first four higher-order bits are set to 1 1 1 1 respectively
End of Module 2
© N. Ganesan, All rights reserved.
Module 3
IP Formats for Commercial Classes
Class A Assignment Format
8 bits 8 bits 8 bits 8 bits
Network ID (8 bits)
Host ID (24 bits)
Number of Class A Networks and Nodes
• The first higher-order bit is always set to 0
• Total number of networks supported is 126 = 27 - 2 – All zeros and all ones are not allowed
• Total number of hosts supported per network is 16,777,214 = 224 - 2– All zeros and all ones are not allowed
Restrictions on Zeros and Ones
• The initial RFC 950 forbade the use of zeros and ones– All zeros prevented some early
routing protocols from operating correctly
– All ones may result in a conflict with a special broadcast address known as the all-subnets directional broadcast address
Easing of Restrictions
• RFC 1812 now eases the restriction and allows the use of zeros and ones in a CIDR-compliant environment
• CIDR– Classless Inter-Domain Routing (CIDR)– Explained under subnets
Class B Assignment Format
8 bits 8 bits 8 bits 8 bits
Network ID (16 bits)
Host ID (16 bits)
Number of Class B Networks and Nodes
• The first two higher-order bits are always set to 1 and 0 respectively
• Total number of networks supported is 16384 = 214 - 2 – All zeros and all ones are not allowed
• Number of hosts supported per network is 65,534 = 216 - 2 – All zeros and all ones are not allowed
Class C Assignment Format
8 bits 8 bits 8 bits 8 bits
Network ID (24 bits)
Host ID (8 bits)
Number of Class C Networks and Nodes
• The first three higher order bits are always set to 1, 1 and 0 respectively
• Total number of networks supported is 2,097,152 = 221 - 2 – All zeros and all ones are not allowed
• Number of hosts supported per network is 254 = 28 - 2– All zeros and all ones are not allowed
Overcoming the Limited Number of IP Addresses
• By dynamically assigning IP addresses to the clients– DHCP– DHCP is also used for better management of
network
• Network Address Translation (NAT) – Assign fictitious IP addresses to the clients– Often, implemented with hardware firewalls– NAT provides security as well
End of Module 3
© N. Ganesan, All rights reserved.
Module 3
Scope and Restriction of IP Addresses
Restrictions on Network ID Assignments
• In class A, network ID 127 is reserved for loop back functions
• All bits of a network ID cannot be set to ones – Reserved for use as an IP broadcast address
• All bits of a network ID cannot be set to zeros– Reserved for a specific host on the local host – Packets destined to this specific address will
not be routed
Loop Back Function
• Loop back function simply tests itself– Eg: 127.0.0.1 performs a test on the
machine itself
• localhost is another way of testing the loopback function
Valid Network IDs for Classes
Class BeginningNetwork ID
Ending NetworkID
A 1.0.0.0 126.0.0.0
B 128.0.0.0 191.255.0.0
C 192.0.0.0 223.255.255.0
Restrictions on Host ID Assignments
• All the bits of a host ID cannot be set to ones– Reserved as the broadcast IP address
to send a packet to all the hosts
• All the bits of a host ID cannot be set to zeros either– Reserved to represent the IP network
address
Valid Host IDs for Classes
Class Beginning Host ID
Ending Host ID
A w.0.0.1 w.255.255.254
B w.x.0.1 w.x.255.254
C w.x.y.1 w.x.y.254
Summary of Networks and Hosts Supported in Each
Class
NetworkID Portion
AvailableNetworks
Hosts per Networks
A 126 16,777,214
B 16,384 65,534C 2,097,15
2254
End of Module
© N. Ganesan, All rights reserved.
Module 4
Private IP Addresses
End of Module 4
END OF MODULEEND OF MODULE
END OF CHAPTEREND OF CHAPTER