Chapter 4 - Network layer. After reading this chapter, the reader should be able to: Understand the position of the network layer in the Internet model, understand the rationale for the existence of the network layer, understand the concept of host-to-host delivery,. | Chapter 4 Network Layer Understand the position of the network layer in the Internet model. Understand the rationale for the existence of the network layer. Understand the concept of host-to-host delivery. Understand the duties of the network layer: packetizing, addressing, and routing. After reading this chapter, the reader should be able to: OBJECTIVES Know which upper-layer protocol can use the services of IP. Understand the network layer protocol, IP, used in the Internet. INTRODUCTION Figure 4-1 Network layer in the Internet model Figure 4-2 Duties of the network layer ADDRESSING The network addresses must be unique. Note: Technical Focus: Binary Notation of IP Addresses An IP address is stored as a binary number in the computer. A 4-part dotted-decimal address can be converted to binary if we replace each part by its binary equivalent. The following shows the IP address in dotted-decimal and binary notation: 00001010 00100010 11100000 00001000 | Chapter 4 Network Layer Understand the position of the network layer in the Internet model. Understand the rationale for the existence of the network layer. Understand the concept of host-to-host delivery. Understand the duties of the network layer: packetizing, addressing, and routing. After reading this chapter, the reader should be able to: OBJECTIVES Know which upper-layer protocol can use the services of IP. Understand the network layer protocol, IP, used in the Internet. INTRODUCTION Figure 4-1 Network layer in the Internet model Figure 4-2 Duties of the network layer ADDRESSING The network addresses must be unique. Note: Technical Focus: Binary Notation of IP Addresses An IP address is stored as a binary number in the computer. A 4-part dotted-decimal address can be converted to binary if we replace each part by its binary equivalent. The following shows the IP address in dotted-decimal and binary notation: 00001010 00100010 11100000 00001000 Technical Focus: Address Space A protocol such as IP that defines addresses has an address space. An address space is the total number of addresses available to the protocol. If a protocol uses N bits to define an address, the address space is 2N because each bit can have two different values (0 and 1); N bits can have 2N values. The Internet uses 32-bit addresses, which means that the address space is 232 or 4,294,967,296 (more than 4 billion). This means that theoretically, if there were no restrictions, more than 4 billion devices could be connected to the Internet. Figure 4-3 Two levels of hierarchy When using two levels of address hierarchy, the common part is referred to as the netid or prefix and the variable part is referred to as the hostid, or suffix. Note: Figure 4-4 Three levels of hierarchy With three levels of address hierarchy, the common part is referred to as the netid. The part common to all computers connected to the same subnet is referred to as the subnetid. The .
