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