1 Kyung Hee University Prof. Choong Seon HONG IP Addressing : Classful Addressing

2 Kyung Hee University 4.1 Introduction oFor a host to communicate with any other host Need a universal identification system Need to name each host oInternet address or IP address is a 32-bit address that uniquely defines a host or a router on the internet oThe IP addresses are unique in the sense that two devices can never have the same address. However, a device can have more one address.

3 Kyung Hee University Notation o Binary notation bit address, or a 4 octet address or a 4-byte address oDecimal point notation

4 Kyung Hee University Notation (cont’d) Hexadecimal Notation o Hexadecimal Notation - 8 hexadecimal digits - Used in network programming D EA 0x75951DEA

5 Kyung Hee University 4.2 Classful Addressing oOccupation 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

6 Kyung Hee University Classful Addressing (cont’d) Finding the address class

7 Kyung Hee University Classful Addressing (cont’d) Finding the class in decimal notation

8 Kyung Hee University Netid and Hostid oEach IP address is made of two parts; netid and hostid. oNetid defines a network; hostid identifies a host on that network.

9 Kyung Hee University Netid and Hostid (cont’d) oIP addresses are divided into five different classes: A, B, C, D, and E

10 Kyung Hee University Classes and Blocks oBlocks in class A Class A is divided into 128 blocks with each block having a different netid. Millions of class A addresses are wasted.

11 Kyung Hee University Classes and Blocks (cont’d) o Class B is divided into 16,384 blocks with each block having a different netid Many class B addresses are wasted.

12 Kyung Hee University Classes and Blocks (cont’d) o Class C is divided into 2,097,152 blocks with each block having a different netid. The number of addresses in a class C block is smaller than the needs of most organizations

13 Kyung Hee University Classes and Blocks (cont’d) o Class D addresses are used for multicasting; there is only one block in this class. o Class E addresses are reserved for special purposes; most of the block is wasted.

14 Kyung Hee University Network Address o The network address is the first address. oThe network address defines the network to the rest of the Internet. o Given the network address, we can find the class of the address, the block, and the range of the addresses in the block o In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization.

15 Kyung Hee University Mask o A mask is a 32-bit binary number that gives the first address in the block (the network address) when bitwise ANDed with an address in the block. o Masking concept

16 Kyung Hee University Mask (cont’d) o AND Operation (refer table 4.2) oThe network address is the beginning address of each block. It can be found by applying the default mask to any of the addresses in the block (including itself). It retains the netid of the block and sets the hostid to zero. (refer table 4.2)

17 Kyung Hee University 4.3 Others Issues oMultihomed devices (computers, or routers) A computer that is connected to different networks Having more than one address

18 Kyung Hee University Special Addresses Special Addresses oSome parts of the address space in class A, B, C for special addresses

19 Kyung Hee University Special Addresses oNetwork address : an address with the hostid all set to 0s

20 Kyung Hee University Special Addresses (cont’d) oDirect Broadcast Address : Used by a router to send a packet to all hosts in a specific network

21 Kyung Hee University Special Addresses (cont’d) oLimited Broadcast Address : all 1s for the netid and hostid (32bits)

22 Kyung Hee University Special Addresses (cont’d) oThis Host on This Network : used by a host at bootstrap time when it does not know its IP address

23 Kyung Hee University Special Addresses (cont’d) oSpecific Host on This Network : used by a host to send a message to another on the same network

24 Kyung Hee University Special Addresses (cont’d) oLoopback Address : IP address of the first byte : 127 Used 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”

25 Kyung Hee University Private Addresses o A number of blocks in each class are assigned for private use. They are not recognized globally. These blocks are depicted in Table 4.4

26 Kyung Hee University Unicast, Multicast, and Broadcast Addresses o Unicast communication is one-to-one. o Multicast communication is one-to-many. o Broadcast communication is one-to-all. o Multicast delivery will be discussed in depth in Chapter 14.

27 Kyung Hee University Unicast, Multicast, and Broadcast Addresses (cont’d) oAssigned Multicast addresses : starting with a prefix

28 Kyung Hee University Unicast, Multicast, and Broadcast Addresses (cont’d) oUnicast Addresses : one-to-one oMulticast addresses : one-to-many; class D address Used as a destination address

29 Kyung Hee University Unicast, Multicast, and Broadcast Addresses (cont’d) oMulticast address for conferencing : starting with a prefix

30 Kyung Hee University Unicast, Multicast, and Broadcast Addresses (cont’d) oBroadcast addresses : one-to-all Allowed only at the local level l Limited broadcast address (all 1s) l Direct broadcast address (netid: specific, hostid: all) No broadcasting is allowed at the global level

31 Kyung Hee University 4.4 A Sample Internet with Classful Address oToken Ring LAN (Class C), Ethernet LAN (Class B), Ethernet LAN (Class A), Point-to-point WAN, A Switched WAN