TCP/IP Protocol Suite 1 Chapter 4 Objectives Upon completion you will be able to: IP Addresses: Classful Addressing Understand IPv4 addresses and classes Identify the class of an IP address Find the network address given an IP address Understand masks and how to use them Understand subnets and supernets

TCP/IP Protocol Suite 2 Figure 4.1 Dotted-decimal notation IPv4 uses 32-bit addresses Each connection has a unique address The address space is 2^32 = 4,294,967,296

TCP/IP Protocol Suite 3 Change the following IP addresses from binary notation to dotted-decimal notation. a b c d Example 1

TCP/IP Protocol Suite 4 Change the following IP addresses from binary notation to dotted-decimal notation. a b c d Example 1 Solution We replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation: a b c d

TCP/IP Protocol Suite 5 Change the following IP addresses from dotted-decimal notation to binary notation. a b c d Example 2

TCP/IP Protocol Suite 6 Change the following IP addresses from dotted-decimal notation to binary notation. a b c d Example 2 Solution We replace each decimal number with its binary equivalent: a b c d

TCP/IP Protocol Suite 7 Change the following IP addresses from binary notation to hexadecimal notation. a b Example 4

TCP/IP Protocol Suite 8 Change the following IP addresses from binary notation to hexadecimal notation. a b Example 4 Solution We replace each group of 4 bits with its hexadecimal equivalent (see Appendix B). Note that hexadecimal notation normally has no added spaces or dots; however, 0X (or 0x) is added at the beginning or the subscript 16 at the end to show that the number is in hexadecimal. a. 0X810B0BEF or 810B0BEF 16 b. 0XC1831BFF or C1831BFF 16

TCP/IP Protocol Suite CLASSFUL ADDRESSING IP addresses, when started a few decades ago, used the concept of classes. This architecture is called classful addressing. In the mid-1990s, a new architecture, called classless addressing, was introduced and will eventually supersede the original architecture. However, part of the Internet is still using classful addressing, but the migration is very fast. The topics discussed in this section include: Recognizing Classes Netid and Hostid Classes and Blocks Network Addresses Sufficient Information Mask CIDR Notation Address Depletion

TCP/IP Protocol Suite 10 Figure 4.2 Occupation of the address space Class A addresses cover ½ the address space!! Millions of class A addresses are wasted!

TCP/IP Protocol Suite 11 Table 4.1 Addresses per class

TCP/IP Protocol Suite 12 Figure 4.3 Finding the class in binary notation

TCP/IP Protocol Suite 13 Figure 4.4 Finding the address class

TCP/IP Protocol Suite 14 How can we prove that we have 2,147,483,648 addresses in class A? Example 5 Solution In class A, only 1 bit defines the class. The remaining 31 bits are available for the address. With 31 bits, we can have 2 31 or 2,147,483,648 addresses.

TCP/IP Protocol Suite 15 Find the class of each address: a b c d Example 6

TCP/IP Protocol Suite 16 Find the class of each address: a b c d Example 6 Solution See the procedure in Figure 4.4. a. The first bit is 0. This is a class A address. b. The first 2 bits are 1; the third bit is 0. This is a class C address. c. The first bit is 0; the second bit is 1. This is a class B address. d. The first 4 bits are 1s. This is a class E address..

TCP/IP Protocol Suite 17 Figure 4.5 Finding the class in decimal notation

TCP/IP Protocol Suite 18 Find the class of each address: a b c d e Example 7

TCP/IP Protocol Suite 19 Find the class of each address: a b c d e Example 7 Solution a. The first byte is 227 (between 224 and 239); the class is D. b. The first byte is 193 (between 192 and 223); the class is C. c. The first byte is 14 (between 0 and 127); the class is A. d. The first byte is 252 (between 240 and 255); the class is E. e. The first byte is 134 (between 128 and 191); the class is B.

TCP/IP Protocol Suite 20 Figure 4.6 Netid and hostid Class A, B and C addresses are divided into 2 parts: Netid and Hostid.

TCP/IP Protocol Suite 21 Figure 4.7 Blocks in class A

TCP/IP Protocol Suite 22 Figure 4.8 Blocks in class B Many class B addresses are wasted too.

TCP/IP Protocol Suite 23 Figure 4.9 Blocks in class C Class C blocks are too small for most businesses.

TCP/IP Protocol Suite 24 In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization. The range of addresses can automatically be inferred from the network address. Note:

TCP/IP Protocol Suite 25 Given the network address , find the class, the block, and the range of the addresses. Example 9

TCP/IP Protocol Suite 26 Given the network address , find the class, the block, and the range of the addresses. Example 9 Solution The class is A because the first byte is between 0 and 127. The block has a netid of 17. The addresses range from to

TCP/IP Protocol Suite 27 Example 10 Given the network address , find the class, the block, and the range of addresses.

TCP/IP Protocol Suite 28 Example 10 Given the network address , find the class, the block, and the range of addresses. The class is B, the block is , and the range is to

TCP/IP Protocol Suite 29 Example 11 Given the network address , find the class, the block, and the range of addresses

TCP/IP Protocol Suite 30 Example 11 Given the network address , find the class, the block, and the range of addresses

TCP/IP Protocol Suite 31 Example 11 Given the network address , find the class, the block, and the range of addresses The class is C, the block is , and the range of addresses is to

TCP/IP Protocol Suite 32 Figure 4.10 Masking concept Given an address from a block of addresses, we can find the network address by ANDing with a mask.

TCP/IP Protocol Suite 33 Figure 4.11 AND operation

TCP/IP Protocol Suite 34 Table 4.2 Default masks

TCP/IP Protocol Suite 35 The 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. Note:

TCP/IP Protocol Suite 36 Given the address , find the beginning address (network address). Example 12

TCP/IP Protocol Suite 37 Given the address , find the beginning address (network address). Example 12 Solution The default mask is , which means that only the first byte is preserved and the other 3 bytes are set to 0s. The network address is

TCP/IP Protocol Suite 38 Given the address , find the beginning address (network address). Example 13

TCP/IP Protocol Suite 39 Given the address , find the beginning address (network address). Example 13 Solution The default mask is , which means that the first 2 bytes are preserved and the other 2 bytes are set to 0s. The network address is

TCP/IP Protocol Suite 40 Given the address , find the beginning address (network address). Example 14

TCP/IP Protocol Suite 41 Given the address , find the beginning address (network address). Example 14 Solution The default mask is , which means that the first 3 bytes are preserved and the last byte is set to 0. The network address is

TCP/IP Protocol Suite 42 Note that we must not apply the default mask of one class to an address belonging to another class. Note:

TCP/IP Protocol Suite OTHER ISSUES In this section, we discuss some other issues that are related to addressing in general and classful addressing in particular. The topics discussed in this section include: Multihomed Devices Location, Not Names Special Addresses Private Addresses Unicast, Multicast, and Broadcast Addresses

TCP/IP Protocol Suite 44 Figure 4.12 Multihomed devices A computer that is connected to different networks is called a multihomed computer and will have more than one address, each possibly belonging to a different class. Routers are multihomed too. Recall- an IP address identifies a connection, not a device.

TCP/IP Protocol Suite 45 Table 4.3 Special addresses

TCP/IP Protocol Suite 46 Figure 4.13 Network address

TCP/IP Protocol Suite 47 Figure 4.14 Example of direct broadcast address

TCP/IP Protocol Suite 48 Figure 4.15 Example of limited broadcast address

TCP/IP Protocol Suite 49 Figure 4.16 Examples of “this host on this network” Example: starting a dial-up connection with DHCP.

TCP/IP Protocol Suite 50 Figure 4.17 Example of “specific host on this network”

TCP/IP Protocol Suite 51 Figure 4.18 Example of loopback address This address used to test the software. Packet never leaves the machine. A client process can send a message to a server process on the same machine.

TCP/IP Protocol Suite 52 Table 4.5 Addresses for private networks Often used in NAT.

TCP/IP Protocol Suite 53 Multicast addressing is from one to many. These are class D addresses. Multicasting works on the local level as well as the global level. Multicast delivery will be discussed in depth in Chapter 15.

TCP/IP Protocol Suite 54 Table 4.5 Category addresses

TCP/IP Protocol Suite 55 Table 4.6 Addresses for conferencing

TCP/IP Protocol Suite 56 Figure 4.19 Sample internet

TCP/IP Protocol Suite SUBNETTING AND SUPERNETTING In the previous sections we discussed the problems associated with classful addressing. Specifically, the network addresses available for assignment to organizations are close to depletion. This is coupled with the ever-increasing demand for addresses from organizations that want connection to the Internet. In this section we briefly discuss two solutions: subnetting and supernetting. The topics discussed in this section include: SubnettingSupernetting Supernet Mask Obsolescence

TCP/IP Protocol Suite 58 Figure 4.20 A network with two levels of hierarchy (not subnetted) IP addresses are designed with two levels of hierarchy: A netid and a host id. This network ( ) is a class B and can have 2^16 hosts. There is only 1 network with a whole-lotta hosts!

TCP/IP Protocol Suite 59 Figure 4.21 A network with three levels of hierarchy (subnetted) What if we break the network into 4 subnets?

TCP/IP Protocol Suite 60 Figure 4.22 Addresses in a class B network with and without subnetting

TCP/IP Protocol Suite 61 Figure 4.24 Default mask and subnet mask The subnet mask tells us how to break up the Hostid portion of the address. For example, we know a class B address has a 16-bit Netid and a 16-bit Hostid. We are not going to touch The Netid, only the Hostid. Using the mask, place 1s in the position where you want a subnet address, 0s where you want a Hostid. As an example, consider the subnet mask: In binary, that is

TCP/IP Protocol Suite 62 Figure 4.24 Default mask and subnet mask

TCP/IP Protocol Suite 63 What is the subnetwork address if the destination address is and the subnet mask is ? Example 15 Solution We apply the AND operation on the address and the subnet mask. Address ➡ Subnet Mask ➡ Subnetwork Address ➡ Or,

TCP/IP Protocol Suite 64 Figure 4.25 Comparison of a default mask and a subnet mask With this subnet mask, you have 3 bits for the subnet address (the yellow portion) which equals 8 addresses, leaving 13 bits for the Hostid (the blue portion) which equals 2^13 hosts.

TCP/IP Protocol Suite 65 Figure 4.26 A supernetwork What if an organization needs 1000 addresses and no class A or class B addresses are available? You can give the organization four class C addresses. But now you have four different network addresses. Messy. So create a supernetwork. A supernetwork mask is the opposite of a subnetwork mask: It has fewer 1s.

TCP/IP Protocol Suite 66 Figure 4.26 A supernetwork

TCP/IP Protocol Suite 67 In subnetting, we need the first address of the subnet and the subnet mask to define the range of addresses. In supernetting, we need the first address of the supernet and the supernet mask to define the range of addresses. Note:

TCP/IP Protocol Suite 68 Figure 4.27 Comparison of subnet, default, and supernet masks

TCP/IP Protocol Suite 69 The idea of subnetting and supernetting of classful addresses is almost obsolete. Note: