1 kyung hee university prof. choong seon hong ip addressing : classful addressing

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Kyung Hee University

Prof. Choong Seon HONG

IP Addressing : IP Addressing : Classful AddresClassful Addres

singsing

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4.1 Introduction4.1 Introduction

For a host to communicate with any other host

Need a universal identification system

Need to name each host

Internet address or IP address is a 32-bit address that

uniquely defines a host or a router on the internet

The IP addresses are unique in the sense that two

devices can never have the same address. However, a

device can have more one address.

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NotationNotation

Binary notation

01110101 10010101 00011101 11101010

32 bit address, or a 4 octet address or a 4-byte address

Decimal point notation

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Notation (cont’d)Notation (cont’d)

Hexadecimal NotationHexadecimal Notation

- 8 hexadecimal digits- 8 hexadecimal digits

- Used in network programming- Used in network programming

0111 0101 1001 0101 0001 1101 1110 1010

75 95 1D EA

0x75951DEA

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4.2 Classful Addressing4.2 Classful Addressing Occupation of address space

In classful addressing, the address space is divided into five classes: A, B, C, D, and E.

Finding the class in binary notation

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Classful Addressing (cont’d)Classful Addressing (cont’d)

Finding the address class

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Classful Addressing (cont’d)Classful Addressing (cont’d)

Finding the class in decimal notation

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Netid and HostidNetid and Hostid

Each IP address is made of two parts; netid and hostid.

Netid defines a network; hostid identifies a host on that network.

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Netid and Hostid (cont’d)Netid and Hostid (cont’d)

IP addresses are divided into five different classes: A, B, C, D, and E

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Classes and Blocks Blocks in class A

Class A is divided into 128 blocks with each block having a different netid.

Millions of class A addresses Millions of class A addresses are wasted.are wasted.

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Classes and Blocks (cont’d) Class B is divided into 16,384 blocks with each block having a diffe

rent netid

Many class B addresses Many class B addresses are wasted.are wasted.

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Classes and Blocks (cont’d)

Class C is divided into 2,097,152 blocks with each block having a diff

erent netid.

The number of addresses in The number of addresses in a class C block a class C block is smaller than is smaller than the needs of most organizationthe needs of most organizationss

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Classes and Blocks (cont’d)

Class D addresses are used for multicasting;

there is only one block in this class.

Class E addresses are reserved for special purposes;

most of the block is wasted.

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Network AddressNetwork Address

The network address is the first address.

The network address defines the network to the rest of the I

nternet.

Given the network address, we can find the class of the ad

dress, the block, and the range of the addresses in the bloc

k

In classful addressing, the network address

(the first address in the block) is the one that is assigned to

the organization.

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Mask Mask

A mask is a 32-bit binary number that gives the first address in the bloc

k (the network address) when bitwise ANDed with an address in the blo

ck.

Masking concept

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Mask (cont’d)Mask (cont’d)

AND Operation

The network address is the beginning address of each block. It ca

n be found by applying the default mask to any of the addresses i

n the block (including itself). It retains the netid of the block and s

ets the hostid to zero. (refer table 4.2)(refer table 4.2)

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4.3 Others Issues4.3 Others Issues

Multihomed devices (computers, or routers)

A computer that is connected to different networks

Having more than one address

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Special AddressesSpecial Addresses

Some parts of the address space in class A, B, C for special addresses

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Special AddressesSpecial Addresses

Network address : an address with the hostid all set to 0s

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Special Addresses (cont’d)Special Addresses (cont’d) Direct Broadcast Address : Used by a router to send a packet to all

hosts in a specific network

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Special Addresses (cont’d)Special Addresses (cont’d) Limited Broadcast Address : all 1s for the netid and hostid (32bits)

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Special Addresses (cont’d)Special Addresses (cont’d) This Host on This Network : used by a host at bootstrap time when

it does not know its IP address

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Special Addresses (cont’d)Special Addresses (cont’d) Specific Host on This Network : used by a host to send a message

to another on the same network

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Special Addresses (cont’d)Special Addresses (cont’d) Loopback Address :

IP address of the first byte : 127Used to test the software on a machine Used by a client process to send a message to a server process on the same machine“Ping”

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Private AddressesPrivate Addresses

A number of blocks in each class are assigned for priv

ate use. They are not recognized globally. These blocks

are depicted in Table 4.4

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Unicast, Multicast, and Broadcast AddressesUnicast, Multicast, and Broadcast Addresses

Unicast communication is one-to-one.

Multicast communication is one-to-many.

Broadcast communication is one-to-all.

Multicast delivery will be discussed in depth in Chapter

14.

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Unicast, Multicast, and Broadcast Addresses (cont’d)Unicast, Multicast, and Broadcast Addresses (cont’d)

Assigned Multicast addresses : starting with a 224.0.0 prefix

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Unicast, Multicast, and Broadcast Addresses (cont’d)Unicast, Multicast, and Broadcast Addresses (cont’d)

Unicast Addresses : one-to-one

Multicast addresses : one-to-many; class D address

Used as a destination address

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Unicast, Multicast, and Broadcast Addresses (cont’d)Unicast, Multicast, and Broadcast Addresses (cont’d)

Multicast address for conferencing : starting with a 224.0.1 prefix

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Unicast, Multicast, and Broadcast Addresses (cont’d)Unicast, Multicast, and Broadcast Addresses (cont’d)

Broadcast addresses : one-to-all

Allowed only at the local level

Limited broadcast address (all 1s) Direct broadcast address (netid: specific, hostid: all)

No broadcasting is allowed at the global level

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4.4 A Sample Internet with Classful Address4.4 A Sample Internet with Classful Address

Token Ring LAN (Class C), Ethernet LAN (Class B), Ethernet LAN (Class A) ,

Point-to-point WAN, A Switched WAN