© 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 an 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 bits divided into 4 octets for convenience Converted into decimals for easy representation and remembrance

An Example in Binary-to- Decimal Conversion Binary1001 Factor8421 Decimal= Binary * Factor = 9 Binary 1001 = Decimal 9

IP Addressing Components Network IDHost ID 32 bits

The New IP Address The new IP address known as IPv6 has 128 bits –

IP Component Reference Internet Host ID Network ID

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© N. Ganesan, All rights reserved. Module 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 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 on Internet 3 Streams Locally

Broadcasting One stream is sent to the destination The stream is then multiplied and sent to the hosts regardless of the fact that the hosts do or do not request to receive the broadcast

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 –More involved in setting up –Uses bandwidth more efficiently from host to the local router –However, the bandwidth usage within the local network may be higher

Class E Experimental addresses reserved for possible future use The first four higher-order bits are set to respectively

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© N. Ganesan, All rights reserved. Module IP Formats for Commercial Classes

Class A Assignment Format 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 = –All zeros and all ones are not allowed Total number of hosts supported per network is 16,777,214 = –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 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 = –All zeros and all ones are not allowed Number of hosts supported per network is 65,534 = –All zeros and all ones are not allowed

Class C Assignment Format 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 = –All zeros and all ones are not allowed Number of hosts supported per network is 254 = –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

Increasing IP Address Space IPv6 would increase the address space as it is 128 bits long whereas IPv4 is only 32 bits long

End of Module

© N. Ganesan, All rights reserved. Module 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: performs a test on the machine itself localhost is another way of testing the loopback function

Valid Network IDs for Classes ClassBeginning Network ID Ending Network ID A B C

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 ClassBeginning Host ID Ending Host ID Aw.0.0.1w Bw.x.0.1w.x Cw.x.y.1w.x.y.254

Summary of Networks and Hosts Supported in Each Class Network ID Portion Available Networks Hosts per Networks A 12616,777,214 B16,38465,534 C2,097,152254

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© N. Ganesan, All rights reserved. Module Private IP Addresses

Addresses that cannot be accessed from the Internet An important application is in setting up firewalls –IP addresses are used for clients on the user side of the network May also be used in setting up local networks that do not need access to the Internet

Firewall IP Configuration What are private IP addresses? –The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets (local networks): – Also, IP addresses in the range of are reserved for Automatic Private IP Addressing. Automatic Private IP Addressing Source:

Private IP Addresses

End of Module

END OF MODULE END OF CHAPTER